**Active Compact Antenna for Broadband Applications**

Y. Taachouche, M. Abdallah, F. Colombel, G. Le Ray and M. Himdi

Additional information is available at the end of the chapter

http://dx.doi.org/10.5772/58839

#### **1. Introduction**

[37] Petosa, A.; Mongia, R.K.; Cuhaci, M.; Wight, J.S., "Magnetically tunable ferrite reso‐ nator antenna," *Electronics Letters*, vol.30, no.13, pp.1021,1022, 23 Jun 1994

[38] *Aeroflex Metelics datasheet*, Available: http://www.aeroflex.com/AMS/Metelics/pdfiles/

[39] Laur, V.; Costes, R.; Houndonougbo, F.; et al., "Microwave study of tunable planar capacitors using mn-doped ba0.6sr0.4tio3 ceramics," *Ultrasonics, Ferroelectrics and Fre‐ quency Control, IEEE Transactions on*, vol.56, no.11, pp.2363-2369, November 2009

MGV\_Series\_Hyperabrupt\_A17041.pdf

110 Progress in Compact Antennas

The recent development of wireless communication technology and the miniaturization of electronics components increase the demand for compact systems applications including small antennas. One of the major challenges is the integration of antennas inside devices in a limited area. The main characteristics of these antennas are large frequency bandwidth and small size.

Many passive antennas such as monopole, dipole and printed antenna have been largely studied to yield small size relatively to the wavelength or broadband behavior. Previous studies have shown that antenna miniaturization impacts negatively antenna bandwidth and impedance matching [1].

The active antennas have found a wide interest for industrial applications in last years. The terminology of the active antenna indicates that the passive antenna elements are combined with an active device on the same substrate to provide a non-separated device and to improve antenna performances, especially in the field of size reduction and frequency bandwidth. The ability to adjust the size reduction and the frequency bandwidth of an active antenna is also very suitable when the antenna is included inside devices with many components located in a limited area.

In this chapter, we are interested in the improvements brought by the active antennas towards size reduction and the covered bandwidth. We present our work on compacts actives antennas in which we develop new techniques to reduce the size of antennas with good performances. Our main works is carried on two solutions; the first one is a broadband antenna with a very important size reduction. This solution corresponds to an active printed monopole integrating a bipolar transistor directly on the antenna structure without matching circuit. The second solution is a tunable narrow frequency band antenna operating on a wide band based on a printed loop antenna associated to a varactor diode.

© 2014 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

#### **2. Active monopole antenna**

#### **2.1. Introduction**

Miniaturized and broadband antennas with ominidirectional coverage have attracted atten‐ tion for industrial applications. For example, today's mobile phones are innovative devices that provide a wide variety of services to users. One of the most attractive mobile phone services is the entertainment services, and especially the functionality that allows users to listen to FM radios through their mobile phones. This development induces a growing demand of FM antennas for mobile phones, and the necessity of innovative technologies to develop internal small FM antennas, which replace the external wire antennas that exhibit current mobile phones in the market. For automobile application, many radio systems as communi‐ cation system, FM radio reception are collocated on the top roof of the car, and the very low visual impact of the antenna is required. The goal of this section is to propose a compact antenna to replace the historical monopole to improve the integration capability of the antenna in VHF band applications systems.

the same height. The active antenna is very broadband and operates at very low frequencies besides its very small size. In [14], it has been explained that an active monopole fed by a microwave transistor provides a wider frequency bandwidth than a passive monopole.

In order to provide innovative designs, the growing interest for active antennas has required more accurate analysis method. A hybrid analysis including electromagnetic full wave and nonlinear circuit solver is used in [15] and accurate theoretical results validated with meas‐ urements on an oscillator active antenna are provided. In [16], the analysis method used in a circuit voltages generated by a CAD software as source distribution for a magnetic current radiation calculation to allow estimation of the integrated antenna is presented. In [17],

In this section, the problem of matching a short monopole antenna by including a transistor in the monopole structure is presented. We are interested in the influence of the transistor on the behavior of active antenna towards size reduction, bandwidth and gain. We investigate an active receiving antenna based on a printed monopole associated to a bipolar transistor. In the first part, we will present the antenna design working on the VHF/UHF bands and the theoretical approach. In the second part, we will exhibit results for two transistor configuration. Measurement results will be compared to the simulated ones and the influence of the transistor

The structure of the active receiving antenna is shown in Figure 2. The antenna is a combination of a monopole and a high frequency bipolar transistor (BFR182). The antenna has been printed on a Neltec NX9300 substrate (*εr*=3, *h*=0.786 mm, tanδ=0.0023) and is placed above a limited

to two parts and the bipolar transistor BFR 182 is directly integrated between these two parts of the monopole without matching circuit. The antenna is connected to a SMA connector

We separate the printed structure into two zones. The first one is the area on which the monopole is printed; the second region (Area 2) welcomes the elements of the bias circuit of the transistor. A printed line, called "parasite" is added to connect the third pin of the transistor

The active component used in our work is a bipolar PNP transistor BFR 182 used for low noise and high-gain broadband amplifier applications, and operates up to 8GHz. The transistor is located at *h2* over the ground plane and is used in two configurations. The first one is the common emitter configuration. In this case, the emitter of the transistor is grounded through the parasitic printed line, the transistor base and collector are respectively linked to the upper

The second one is the common collector configuration, the base of the transistor is connected to the upper part and the emitter of the transistor to the lower part of the monopole, the

). As shown in Figure 2, the monopole has been cut in

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theoretical or experimental methods are explained to study active antennas.

location on the monopole will be studied.

square reflector plane (500×500×4 mm3

through a 50 Ω microstrip line [18-19].

to ground in area 2 at a distance p from the monopole.

part and to the bottom part of the monopole.

collector is connected to ground via the parasite line.

**2.2. Design of the active monopole antenna**

The idea of using active antennas can be traced back to as early as 1928 [2]. A small antenna with electron tube was commonly used in radio broadcast receivers around 1MHz (Figure 1).

With the invention of high frequency transistor, the studies of active antennas have been performed in the years 60-70 [3-11].

Literature contribution on active antennas exhibits several advantages, the frequency band‐ width or signal to noise improvements compared to a passive antenna of the same size. In this contribution, we have started from the results given by Meinke [4] who have inserted the electronic components (tunnel diode and transistor) directly on the structure without matching network.

A combination of a resonance half wavelength dipole with a VHF transistor has been proposed in [4]. The size of the antenna related to the wavelength is λ/2. As it is mentioned in [12], an active antenna provides new opportunities for many applications including the increase of bandwidth or the size reduction. In [13], a loop dipole has been proposed as a transmitting antenna. A total height of λ/2000 has been built and compared to a passive dipole which has the same height. The active antenna is very broadband and operates at very low frequencies besides its very small size. In [14], it has been explained that an active monopole fed by a microwave transistor provides a wider frequency bandwidth than a passive monopole.

In order to provide innovative designs, the growing interest for active antennas has required more accurate analysis method. A hybrid analysis including electromagnetic full wave and nonlinear circuit solver is used in [15] and accurate theoretical results validated with meas‐ urements on an oscillator active antenna are provided. In [16], the analysis method used in a circuit voltages generated by a CAD software as source distribution for a magnetic current radiation calculation to allow estimation of the integrated antenna is presented. In [17], theoretical or experimental methods are explained to study active antennas.

In this section, the problem of matching a short monopole antenna by including a transistor in the monopole structure is presented. We are interested in the influence of the transistor on the behavior of active antenna towards size reduction, bandwidth and gain. We investigate an active receiving antenna based on a printed monopole associated to a bipolar transistor. In the first part, we will present the antenna design working on the VHF/UHF bands and the theoretical approach. In the second part, we will exhibit results for two transistor configuration. Measurement results will be compared to the simulated ones and the influence of the transistor location on the monopole will be studied.

#### **2.2. Design of the active monopole antenna**

**2. Active monopole antenna**

in VHF band applications systems.

performed in the years 60-70 [3-11].

**Figure 1.** Active receiving antenna

network.

Miniaturized and broadband antennas with ominidirectional coverage have attracted atten‐ tion for industrial applications. For example, today's mobile phones are innovative devices that provide a wide variety of services to users. One of the most attractive mobile phone services is the entertainment services, and especially the functionality that allows users to listen to FM radios through their mobile phones. This development induces a growing demand of FM antennas for mobile phones, and the necessity of innovative technologies to develop internal small FM antennas, which replace the external wire antennas that exhibit current mobile phones in the market. For automobile application, many radio systems as communi‐ cation system, FM radio reception are collocated on the top roof of the car, and the very low visual impact of the antenna is required. The goal of this section is to propose a compact antenna to replace the historical monopole to improve the integration capability of the antenna

The idea of using active antennas can be traced back to as early as 1928 [2]. A small antenna with electron tube was commonly used in radio broadcast receivers around 1MHz (Figure 1). With the invention of high frequency transistor, the studies of active antennas have been

Literature contribution on active antennas exhibits several advantages, the frequency band‐ width or signal to noise improvements compared to a passive antenna of the same size. In this contribution, we have started from the results given by Meinke [4] who have inserted the electronic components (tunnel diode and transistor) directly on the structure without matching

A combination of a resonance half wavelength dipole with a VHF transistor has been proposed in [4]. The size of the antenna related to the wavelength is λ/2. As it is mentioned in [12], an active antenna provides new opportunities for many applications including the increase of bandwidth or the size reduction. In [13], a loop dipole has been proposed as a transmitting antenna. A total height of λ/2000 has been built and compared to a passive dipole which has

**2.1. Introduction**

112 Progress in Compact Antennas

The structure of the active receiving antenna is shown in Figure 2. The antenna is a combination of a monopole and a high frequency bipolar transistor (BFR182). The antenna has been printed on a Neltec NX9300 substrate (*εr*=3, *h*=0.786 mm, tanδ=0.0023) and is placed above a limited square reflector plane (500×500×4 mm3 ). As shown in Figure 2, the monopole has been cut in to two parts and the bipolar transistor BFR 182 is directly integrated between these two parts of the monopole without matching circuit. The antenna is connected to a SMA connector through a 50 Ω microstrip line [18-19].

We separate the printed structure into two zones. The first one is the area on which the monopole is printed; the second region (Area 2) welcomes the elements of the bias circuit of the transistor. A printed line, called "parasite" is added to connect the third pin of the transistor to ground in area 2 at a distance p from the monopole.

The active component used in our work is a bipolar PNP transistor BFR 182 used for low noise and high-gain broadband amplifier applications, and operates up to 8GHz. The transistor is located at *h2* over the ground plane and is used in two configurations. The first one is the common emitter configuration. In this case, the emitter of the transistor is grounded through the parasitic printed line, the transistor base and collector are respectively linked to the upper part and to the bottom part of the monopole.

The second one is the common collector configuration, the base of the transistor is connected to the upper part and the emitter of the transistor to the lower part of the monopole, the collector is connected to ground via the parasite line.

*w1*=2mm, *w2*=1mm) **Figure 2.** Geometry of the proposed active receiving antenna

When *VCC*=18V and *VBB*=8.3V, the transistor is biased with *IC*=10mA and *VCE*=8V for common emitter configuration, *IC*=4.8mA and *VCE*=4.86V for common collector configuration. The resistances values (*R1*=1kΩ, *R2*=68kΩ) have been calculated in order to obtain the collector to emitter voltage (*Vce*) and collector current (*Ic)* required. The active component used in our work is a bipolar PNP transistor BFR 182 used for low noise and high-gain broadband amplifier applications, and operates up to 8GHz. The transistor is located at *h2* over the ground plane and is used in two configurations. The first one is the common emitter configuration. In this case, the emitter of the transistor is grounded through the parasitic printed line, the transistor base and collector are **Figure 3.** Two-port system proposed to calculate the active antenna performances.

**2.4. Theoretical results and measurements**

receiving antenna which operates in VHF band.

calculation of the *S21* (formula. 1) in both configurations.

input impedance, and the size reduction.

*2.4.1. Influence of the height of antenna*

Where *Gi* is the transmitter antenna gain, *Gr* the receiver antenna gain and D the distance between the two antennas. To ensure the validity of formula (1), the distance between the antennas (D) must satisfy the far field condition and the antennas are matched to 50Ω.

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Despite the difficulty to simulate an active antenna, we use CST software to achieve consistency between measurements and simulations. Several parameters, as the position of the transistor, the position of the parasite and the design of the antenna are investigated. All of these parameters allow us to vary the impedance of the active antenna and adjust the frequency band. In this section, we present theoretical and experimental results obtained on the active

The antenna presented is working on the FM band (88-108MHz). We investigate the influence of the integration of the transistor in the monopole without matching circuit, its impact on the

We start with the influence of the height of the active monopole antenna (*h1*) on its resonance frequency. Then, we investigate the influence of the transistor location on the monopole (*h2*) and the position of the parasitic line (*p*) both on the return loss and on the gain through the

In this section, we present the theorical results of the performance of the active receiving antenna versus the height of the monopole (*h1*), the transistor is positioned at *h2=h1/2* (Figure

The theoretical results of the return loss of the active monopole as function of *h1* for both

4). The heights of the active monopole (*h1*) vary between 355 mm and 30 mm.

configurations, common emitter and common collector are shown in Figure 5.

#### **2.3. Calculation methods** respectively linked to the upper part and to the bottom part of the monopole.

calculate methods.

We present here the theoretical and experimental methods of calculation used to evaluate the performance of the active monopole antenna. There are several methods to simulate and calculate the performance of an active antenna. Our choice is based on the method of combining the results of the electromagnetic calculation of the antenna structure with electrical model of the bipolar transistor. It conducts to a full analysis of the active antenna. This simulation was performed with CST Microwave Studio®. The second one is the common collector configuration, the base of the transistor is connected to the upper part and the emitter of the transistor to the lower part of the monopole, the collector is connected to ground via the parasite line. When *VCC* = 18V and *VBB* = 8.3V, the transistor is biased with *IC* = 10mA and *VCE* = 8V for

With this method, only the input impedance of the active receiving antenna is calculated, because the antenna operates only at the reception due to unilaterally of the transistor. Hence, it is impossible to calculate the radiation characteristics (pattern, gain) with the usual calculate methods. common emitter configuration, *IC* = 4.8mA and *VCE* = 4.86V for common collector configuration. The resistances values (*R1*=1kΩ, *R2*=68kΩ) have been calculated in order to obtain the collector to emitter voltage (*Vce*) and collector current (*Ic)* required.

To solve this problem, we calculate the gain of the active receiving antenna by using the Link Budget method explained in [17], the setup system is illustrated in the Figure 3. **2.3. Calculation methods**

We compute the transmission parameter between a transmitting reference antenna and the active receiving antenna separated by the distance D. We present here the theoretical and experimental methods of calculation used to evaluate the performance of the active monopole antenna. There are several methods to simulate and calculate the performance of an active antenna. Our choice is based on the method of

Then by using the FRIIS formula (1) and knowing *Gi* , the transmitter antenna gain (2.1dBi), we are able to deduce *Gr* the gain of the active antenna. combining the results of the electromagnetic calculation of the antenna structure with electrical model of the bipolar transistor. It conducts to a full analysis of the active antenna.

With this method, only the input impedance of the active receiving antenna is calculated, because the antenna operates only at the reception due to unilaterally of the transistor. Hence, it is impossible to calculate the radiation characteristics (pattern, gain) with the usual

This simulation was performed with CST Microwave Studio®.

$$S\_{21} = Gi + Gr + 20 \text{ log } \left(\mathcal{k} / 4\pi D\right) \tag{1}$$

**Figure 3.** Two-port system proposed to calculate the active antenna performances.

Where *Gi* is the transmitter antenna gain, *Gr* the receiver antenna gain and D the distance between the two antennas. To ensure the validity of formula (1), the distance between the antennas (D) must satisfy the far field condition and the antennas are matched to 50Ω.

#### **2.4. Theoretical results and measurements**

When *VCC*=18V and *VBB*=8.3V, the transistor is biased with *IC*=10mA and *VCE*=8V for common emitter configuration, *IC*=4.8mA and *VCE*=4.86V for common collector configuration. The resistances values (*R1*=1kΩ, *R2*=68kΩ) have been calculated in order to obtain the collector to

(a) Front view (b) Side view

Figure 2. Geometry of the proposed active receiving antenna ( *h1*=25mm, *h2*=5mm, *p*=20mm, *w*=4mm,

The active component used in our work is a bipolar PNP transistor BFR 182 used for low noise and high-gain broadband amplifier applications, and operates up to 8GHz. The transistor is located at *h2* over the ground plane and is used in two configurations. The first one is the common emitter configuration. In this case, the emitter of the transistor is grounded through the parasitic printed line, the transistor base and collector are

We present here the theoretical and experimental methods of calculation used to evaluate the performance of the active monopole antenna. There are several methods to simulate and calculate the performance of an active antenna. Our choice is based on the method of combining the results of the electromagnetic calculation of the antenna structure with electrical model of the bipolar transistor. It conducts to a full analysis of the active antenna. This simulation was

The second one is the common collector configuration, the base of the transistor is connected to the upper part and the emitter of the transistor to the lower part of the monopole, the

When *VCC* = 18V and *VBB* = 8.3V, the transistor is biased with *IC* = 10mA and *VCE* = 8V for common emitter configuration, *IC* = 4.8mA and *VCE* = 4.86V for common collector configuration. The resistances values (*R1*=1kΩ, *R2*=68kΩ) have been calculated in order to

respectively linked to the upper part and to the bottom part of the monopole.

With this method, only the input impedance of the active receiving antenna is calculated, because the antenna operates only at the reception due to unilaterally of the transistor. Hence, it is impossible to calculate the radiation characteristics (pattern, gain) with the usual calculate

To solve this problem, we calculate the gain of the active receiving antenna by using the Link

We compute the transmission parameter between a transmitting reference antenna and the

We present here the theoretical and experimental methods of calculation used to evaluate the performance of the active monopole antenna. There are several methods to simulate and calculate the performance of an active antenna. Our choice is based on the method of combining the results of the electromagnetic calculation of the antenna structure with electrical model of the bipolar transistor. It conducts to a full analysis of the active antenna.

> l p

With this method, only the input impedance of the active receiving antenna is calculated, because the antenna operates only at the reception due to unilaterally of the transistor. Hence, it is impossible to calculate the radiation characteristics (pattern, gain) with the usual

( ) <sup>21</sup> *S Gi Gr* =++ 20 log / 4

, the transmitter antenna gain (2.1dBi), we

*D* (1)

Budget method explained in [17], the setup system is illustrated in the Figure 3.

obtain the collector to emitter voltage (*Vce*) and collector current (*Ic)* required.

emitter voltage (*Vce*) and collector current (*Ic)* required.

(*h1*=25mm, *h2*=5mm, *p*=20mm, *w*=4mm, *w1*=2mm, *w2*=1mm)

**Figure 2.** Geometry of the proposed active receiving antenna

collector is connected to ground via the parasite line.

performed with CST Microwave Studio®.

**2.3. Calculation methods**

active receiving antenna separated by the distance D.

Then by using the FRIIS formula (1) and knowing *Gi*

are able to deduce *Gr* the gain of the active antenna.

This simulation was performed with CST Microwave Studio®.

**2.3. Calculation methods**

*w1*=2mm, *w2*=1mm)

114 Progress in Compact Antennas

methods.

calculate methods.

Despite the difficulty to simulate an active antenna, we use CST software to achieve consistency between measurements and simulations. Several parameters, as the position of the transistor, the position of the parasite and the design of the antenna are investigated. All of these parameters allow us to vary the impedance of the active antenna and adjust the frequency band. In this section, we present theoretical and experimental results obtained on the active receiving antenna which operates in VHF band.

The antenna presented is working on the FM band (88-108MHz). We investigate the influence of the integration of the transistor in the monopole without matching circuit, its impact on the input impedance, and the size reduction.

We start with the influence of the height of the active monopole antenna (*h1*) on its resonance frequency. Then, we investigate the influence of the transistor location on the monopole (*h2*) and the position of the parasitic line (*p*) both on the return loss and on the gain through the calculation of the *S21* (formula. 1) in both configurations.

#### *2.4.1. Influence of the height of antenna*

In this section, we present the theorical results of the performance of the active receiving antenna versus the height of the monopole (*h1*), the transistor is positioned at *h2=h1/2* (Figure 4). The heights of the active monopole (*h1*) vary between 355 mm and 30 mm.

The theoretical results of the return loss of the active monopole as function of *h1* for both configurations, common emitter and common collector are shown in Figure 5.

antenna versus the height of the monopole (*h1*), the transistor is positioned at *h2=h1/2* (Figure

*h1* **(mm)**

monopole (influence of height *h2*).

the two antennas is 4.7m.

*2.4.2. Influence of the position of the transistor*

**Figure 6.** Position of the transistor on the active receiving antenna

*2.4.2.1. Input impedance and gain*

**a. Common emitter configuration**

**Emitter common configuration collector common configuration Fr (MHz) Reduction ratio(λ/** *h1***) Fr (MHz) Reduction ratio(λ/** *h1***)**

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 25 34 20 42 45 38 40 42 65 52.5 70 48 94 72.5 100 68 109 92 120 83

**Table 1.** Matching frequencies of the active monopole and size reduction ratio as function of the height *h1*

This study provides the first results that we can suggest for reducing the active antennas size. In this first part, the transistor is placed at mid-height of the active monopole. To provide an accurate justification of the influence of the transistor on the miniaturization of the antenna, we will study in the next sub-section the influence of the position of the transistor on active

In this paragraph, we set the height of the active monopole antenna *h1* to 30 mm. We investigate the influence of the transistor location on the monopole (*h2*) both on the return loss and the gain through the calculation of the *S21*. We present the theoretical and experimental results for three different locations. The measurement process was performed in an anechoic chamber and the reference transmitting antenna was a telescopic dipole TR1722. The distance between

The theoretical results of the return loss of the active monopole as function of *h1* for both **Figure 4.** Geometry of the active monopole antenna.

configurations, common emitter and common collector are shown in Figure 5.

Figure 5. Return loss of the active receiving antenna as function of the *h1*. (a) Common emitter (⋅‧‧*h1*=355mm, – – –*h1*=177mm,-‧‧-*h1*=88mm, –––*h1*=44mm, –▫– *h1*=30mm)

configuration (b) Common collector configuration Figure 6. **Figure 5.** Return loss of the active receiving antenna as function of the *h1*. (a) Common emitter configuration, (b) Common collector configuration

(… *h1*=355mm, **– – –** *h1*=177mm, -·-·- *h1*=88mm, ––– *h1*=44mm, –▫– *h1*=30mm) As a result, we note a very low resonance frequency of active monopole. This resonance frequency depends on the height of the monopole and the configuration of the transistor used.

As a result, we note a very low resonance frequency of active monopole. This resonance frequency depends on the height of the monopole and the configuration of the transistor used. For the common-emitter configuration, the reduction factor is λ/34 for *h1* = 355 mm with a resonance frequency of 25 MHz and it is λ/92 for *h1* = 30mm with a resonance at 109 MHz. We also note that the resonance frequency of the active monopole does not vary linearly versus the length of the antenna as a liability for classical monopole. In our case, every time For the common-emitter configuration, the reduction factor is λ/34 for *h1*=355 mm with a resonance frequency of 25 MHz and it is λ/92 for *h1*=30mm with a resonance at 109 MHz. We also note that the resonance frequency of the active monopole does not vary linearly versus the length of the antenna as a liability for classical monopole. In our case, every time the height of the monopole is halved, the resonance frequency is multiplied by a coefficient which varies between 1.4 and 1.6. For the common collector configuration, we have a reduction factor of λ/ 42 for *h1*=355mm and λ/83 for *h1*=30mm.

We summarize in Table 1 the matching frequencies obtained for different heights of the active monopole for common emitter and common collector configurations.


**Table 1.** Matching frequencies of the active monopole and size reduction ratio as function of the height *h1*

This study provides the first results that we can suggest for reducing the active antennas size. In this first part, the transistor is placed at mid-height of the active monopole. To provide an accurate justification of the influence of the transistor on the miniaturization of the antenna, we will study in the next sub-section the influence of the position of the transistor on active monopole (influence of height *h2*).

#### *2.4.2. Influence of the position of the transistor*

In this section, we present the theorical results of the performance of the active receiving antenna versus the height of the monopole (*h1*), the transistor is positioned at *h2=h1/2* (Figure

The theoretical results of the return loss of the active monopole as function of *h1* for both

(a) (b)

Figure 5. Return loss of the active receiving antenna as function of the *h1*. (a) Common emitter

**Figure 5.** Return loss of the active receiving antenna as function of the *h1*. (a) Common emitter configuration, (b)

As a result, we note a very low resonance frequency of active monopole. This resonance frequency depends on the height of the monopole and the configuration of the transistor used.

As a result, we note a very low resonance frequency of active monopole. This resonance frequency depends on the height of the monopole and the configuration of the transistor

For the common-emitter configuration, the reduction factor is λ/34 for *h1*=355 mm with a resonance frequency of 25 MHz and it is λ/92 for *h1*=30mm with a resonance at 109 MHz. We also note that the resonance frequency of the active monopole does not vary linearly versus the length of the antenna as a liability for classical monopole. In our case, every time the height of the monopole is halved, the resonance frequency is multiplied by a coefficient which varies between 1.4 and 1.6. For the common collector configuration, we have a reduction factor of λ/

For the common-emitter configuration, the reduction factor is λ/34 for *h1* = 355 mm with a resonance frequency of 25 MHz and it is λ/92 for *h1* = 30mm with a resonance at 109 MHz. We also note that the resonance frequency of the active monopole does not vary linearly versus the length of the antenna as a liability for classical monopole. In our case, every time

We summarize in Table 1 the matching frequencies obtained for different heights of the active

(… *h1*=355mm, **– – –** *h1*=177mm, -·-·- *h1*=88mm, ––– *h1*=44mm, –▫– *h1*=30mm)

monopole for common emitter and common collector configurations.

configurations, common emitter and common collector are shown in Figure 5.

4). The heights of the active monopole (*h1*) vary between 355 mm and 30 mm.

Figure 4. Geometry of the active monopole antenna.

**Figure 4.** Geometry of the active monopole antenna.

116 Progress in Compact Antennas

configuration (b) Common collector configuration

42 for *h1*=355mm and λ/83 for *h1*=30mm.

(⋅‧‧*h1*=355mm, – – –*h1*=177mm,-‧‧-*h1*=88mm, –––*h1*=44mm, –▫– *h1*=30mm)

Figure 6.

Common collector configuration

used.

In this paragraph, we set the height of the active monopole antenna *h1* to 30 mm. We investigate the influence of the transistor location on the monopole (*h2*) both on the return loss and the gain through the calculation of the *S21*. We present the theoretical and experimental results for three different locations. The measurement process was performed in an anechoic chamber and the reference transmitting antenna was a telescopic dipole TR1722. The distance between the two antennas is 4.7m.

**Figure 6.** Position of the transistor on the active receiving antenna

#### *2.4.2.1. Input impedance and gain*

#### **a. Common emitter configuration**

simulation)

The adaptation of the active antenna could be evaluated by the reflection coefficient at the output (*S22*) of the two-port system described in Figure 3.

noticed that the frequency bandwidth increases when the transistor is located close to the ground plane (*h2*=5mm). The measurements exhibit a -10dB bandwidth of 77% around 77MHz when the transistor is located 25mm over the ground plane and 94% around 107.5MHz when the transistor is placed 5mm over the ground plane. In the first case (*h2*=25mm) the height of the active antenna is close to λ/212 at the lowest operating

Figure 7. |S22| of the active receiving antenna an common emitter configuration (— measurement, ---

We summarized the simulated and the measured frequency bandwidth results of the active

For the gain of the active receiving antenna, we present the simulated and measured results of the transmission coefficient between the transmitting antenna and the active antenna for three location of the transistor (*h2*=5mm, *h2*=15mm and *h2*=25mm). These results are plotted in Figure 8. The global shape of the |*S21*| for different transistor locations is well predicted and the theoretical results are in agreement with the measurements as a function of frequency From this results, at 130MHz, the measured transmission coefficient |*S21*| are close to -52dB

**Location of the transistor Simulated bandwidth (MHz) Measured bandwidth (MHz)**  *h2*=25mm 69-162 (80%) 47-107 (78%) *h2*=15mm 70-165 (81%) 53-128 (83%) *h2*=5mm 78-190 (83%) 57-158 (94%)

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119

*h2*=25mm *h2*=15mm *h2*=5mm

Figure 8. Transmission coefficients |*S21*| between reference antenna and active receiving antenna **Figure 8.** Transmission coefficients |*S21*| between reference antenna and active receiving antenna

provided by an equivalent passive antenna with the same height (-49dBi).

provided by an equivalent passive antenna with the same height (-49dBi).

From the FRIIS formula, we can estimate the measured and theoretical gain of the active receiving antenna at 130MHz. We measured a gain of-25.7dBi for *h1*=25mm and-21.8dBi for *h2*=5mm. The difference between these gains is closed to 3.9 dB and is due to the position of transistor on monopole. We notice that the highest gain is obtained when the transistor is very close from the ground plane (*h2*=5mm). This gain level should be compared to the gain

In this second part, we present the same simulated and measured results of the active antenna as function of location of the transistor (*h2*) for the common collector configuration. The results

In this second part, we present the same simulated and measured results of the active antenna as function of location of the transistor (*h2*) for the common collector configuration.

very close from the ground plane (*h2*=5mm). This gain level should be compared to the gain

Figure 9. There is a central resonance frequency around 100 MHz as in the common emitter configuration. Matching is always better in simulation and the bandwidth increases when the

Figure 9. There is a central resonance frequency around 100 MHz as in the common emitter configuration. Matching is always better in simulation and the bandwidth increases when

*h2*=25mm *h2*=15mm *h2*=5mm

Figure 9. |S22| of the active receiving antenna in common collector configuration (—measurement, ---

**Location of the transistor Simulated bandwidth (MHz) Measured bandwidth (MHz)**  *h2*=25mm 58-182 (103%) 29-198 (148%) *h2*=15mm 60-210 (111%) 28-272 (162%) *h2*=5mm 70-260 (115%) 27-426 (176%)

Figure 10 presents the transmission coefficient |*S21*| as a function of the position of the transistor in common collector configuration for a height *h1* = 30mm. The results are presented from 50 MHz to 1 GHz frequency band to compare the behavior of the receiving active antenna as a function of frequency between simulations and measurements in order to validate the simulation methods. Agreements between the measured and simulated results are obtained. At 130 MHz, we obtained a transmission coefficient |*S21*| of -54.3 dB for a transistor positioned at *h2* = 25mm over to the reflector plane, of -53.8 dB for *h2* = 15mm and

Table 3. Simulated and measured bandwidth versus transistor location on the active antenna in

We reported in the Table 3 the simulated and measured results.

**Figure 9.** |*S22*| of the active receiving antenna in common collector configuration

We reported in the Table 3 the simulated and measured results.

Table 2. Simulated and measured bandwidth versus transistor location on the active antenna in

frequency and when *h2*=5mm the height of the monopole is λ/175.

and -48.17dB respectively for *h2*=25mm and for *h2*=5mm.

simulation)

receiving antenna in the Table 2.

common emitter configuration

**b. Common collector configuration**

b. Common collector configuration

transistor is close to the reflector plane.

common collector configuration


the transistor is close to the reflector plane.

The results of |*S22*| are plotted in

of |*S22*| are plotted in

simulation)

(—measurement,---simulation)

In Figure 7, the simulated and the measured |*S22*| are plotted for three transistor locations (*h2*). Even if there is a shift between theories and measurements, the results are still in good agreement. These discrepancies are probably due to the difference between the theoretical parameters of the transistor provided by the PSPICE model and the real one. It can be no‐ ticed that the frequency bandwidth increases when the transistor is located close to the ground plane (*h2*=5mm). The measurements exhibit a-10dB bandwidth of 77% around 77MHz when the transistor is located 25mm over the ground plane and 94% around 107.5MHz when the transistor is placed 5mm over the ground plane. In the first case (*h2*=25mm) the height of the active antenna is close to λ/212 at the lowest operating frequen‐ cy and when *h2*=5mm the height of the monopole is λ/175. noticed that the frequency bandwidth increases when the transistor is located close to the ground plane (*h2*=5mm). The measurements exhibit a -10dB bandwidth of 77% around 77MHz when the transistor is located 25mm over the ground plane and 94% around 107.5MHz when the transistor is placed 5mm over the ground plane. In the first case (*h2*=25mm) the height of the active antenna is close to λ/212 at the lowest operating

frequency and when *h2*=5mm the height of the monopole is λ/175.

Figure 7. |S22| of the active receiving antenna an common emitter configuration (— measurement, --- **Figure 7.** |*S22*| of the active receiving antenna an common emitter configuration (— measurement,---simulation)

We summarized the simulated and the measured frequency bandwidth results of the active We summarized the simulated and the measured frequency bandwidth results of the active receiving antenna in the Table 2.

receiving antenna in the Table 2. For the gain of the active receiving antenna, we present the simulated and measured results of the transmission coefficient between the transmitting antenna and the active antenna for three location of the transistor (*h2*=5mm, *h2*=15mm and *h2*=25mm). These results are plotted in Figure 8. The global shape of the |*S21*| for different transistor locations is well predicted and the theoretical results are in agreement with the measurements as a function of frequency From this results, at 130MHz, the measured transmission coefficient |*S21*| are close to -52dB For the gain of the active receiving antenna, we present the simulated and measured results of the transmission coefficient between the transmitting antenna and the active antenna for three location of the transistor (*h2*=5mm, *h2*=15mm and *h2*=25mm). These results are plotted in Figure 8. The global shape of the |*S21*| for different transistor locations is well predicted and the theoretical results are in agreement with the measurements as a function of frequency From this results, at 130MHz, the measured transmission coefficient |*S21*| are close to-52dB and-48.17dB respectively for *h2*=25mm and for *h2*=5mm.


and -48.17dB respectively for *h2*=25mm and for *h2*=5mm.

Table 2. Simulated and measured bandwidth versus transistor location on the active antenna in common emitter configuration **Table 2.** Simulated and measured bandwidth versus transistor location on the active antenna in common emitter configuration

noticed that the frequency bandwidth increases when the transistor is located close to the ground plane (*h2*=5mm). The measurements exhibit a -10dB bandwidth of 77% around 77MHz when the transistor is located 25mm over the ground plane and 94% around 107.5MHz when the transistor is placed 5mm over the ground plane. In the first case (*h2*=25mm) the height of the active antenna is close to λ/212 at the lowest operating

Figure 7. |S22| of the active receiving antenna an common emitter configuration (— measurement, ---

We summarized the simulated and the measured frequency bandwidth results of the active

For the gain of the active receiving antenna, we present the simulated and measured results of the transmission coefficient between the transmitting antenna and the active antenna for three location of the transistor (*h2*=5mm, *h2*=15mm and *h2*=25mm). These results are plotted in Figure 8. The global shape of the |*S21*| for different transistor locations is well predicted and the theoretical results are in agreement with the measurements as a function of frequency From this results, at 130MHz, the measured transmission coefficient |*S21*| are close to -52dB

**Location of the transistor Simulated bandwidth (MHz) Measured bandwidth (MHz)**  *h2*=25mm 69-162 (80%) 47-107 (78%) *h2*=15mm 70-165 (81%) 53-128 (83%)

frequency and when *h2*=5mm the height of the monopole is λ/175.

and -48.17dB respectively for *h2*=25mm and for *h2*=5mm.

simulation)

receiving antenna in the Table 2.

common emitter configuration

Figure 8. Transmission coefficients |*S21*| between reference antenna and active receiving antenna **Figure 8.** Transmission coefficients |*S21*| between reference antenna and active receiving antenna

From the FRIIS formula, we can estimate the measured and theoretical gain of the active receiving antenna at 130MHz. We measured a gain of-25.7dBi for *h1*=25mm and-21.8dBi for *h2*=5mm. The difference between these gains is closed to 3.9 dB and is due to the position of transistor on monopole. We notice that the highest gain is obtained when the transistor is very close from the ground plane (*h2*=5mm). This gain level should be compared to the gain provided by an equivalent passive antenna with the same height (-49dBi). very close from the ground plane (*h2*=5mm). This gain level should be compared to the gain

#### **b. Common collector configuration** provided by an equivalent passive antenna with the same height (-49dBi).

the transistor is close to the reflector plane.

The adaptation of the active antenna could be evaluated by the reflection coefficient at the

In Figure 7, the simulated and the measured |*S22*| are plotted for three transistor locations (*h2*). Even if there is a shift between theories and measurements, the results are still in good agreement. These discrepancies are probably due to the difference between the theoretical parameters of the transistor provided by the PSPICE model and the real one. It can be no‐ ticed that the frequency bandwidth increases when the transistor is located close to the ground plane (*h2*=5mm). The measurements exhibit a-10dB bandwidth of 77% around 77MHz when the transistor is located 25mm over the ground plane and 94% around 107.5MHz when the transistor is placed 5mm over the ground plane. In the first case (*h2*=25mm) the height of the active antenna is close to λ/212 at the lowest operating frequen‐

noticed that the frequency bandwidth increases when the transistor is located close to the ground plane (*h2*=5mm). The measurements exhibit a -10dB bandwidth of 77% around 77MHz when the transistor is located 25mm over the ground plane and 94% around 107.5MHz when the transistor is placed 5mm over the ground plane. In the first case (*h2*=25mm) the height of the active antenna is close to λ/212 at the lowest operating

 *h2*=25mm *h2*=15mm *h2*=5mm

**Figure 7.** |*S22*| of the active receiving antenna an common emitter configuration (— measurement,---simulation)

Figure 7. |S22| of the active receiving antenna an common emitter configuration (— measurement, ---

We summarized the simulated and the measured frequency bandwidth results of the active

We summarized the simulated and the measured frequency bandwidth results of the active

For the gain of the active receiving antenna, we present the simulated and measured results of the transmission coefficient between the transmitting antenna and the active antenna for three location of the transistor (*h2*=5mm, *h2*=15mm and *h2*=25mm). These results are plotted in Figure 8. The global shape of the |*S21*| for different transistor locations is well predicted and the theoretical results are in agreement with the measurements as a function of frequency From this results, at 130MHz, the measured transmission coefficient |*S21*| are close to-52dB

For the gain of the active receiving antenna, we present the simulated and measured results of the transmission coefficient between the transmitting antenna and the active antenna for three location of the transistor (*h2*=5mm, *h2*=15mm and *h2*=25mm). These results are plotted in Figure 8. The global shape of the |*S21*| for different transistor locations is well predicted and the theoretical results are in agreement with the measurements as a function of frequency From this results, at 130MHz, the measured transmission coefficient |*S21*| are close to -52dB

**Location of the transistor Simulated bandwidth (MHz) Measured bandwidth (MHz)**  *h2*=25mm 69-162 (80%) 47-107 (78%) *h2*=15mm 70-165 (81%) 53-128 (83%) *h2*=5mm 78-190 (83%) 57-158 (94%)

**Location of the transistor Simulated bandwidth (MHz) Measured bandwidth (MHz)** *h2*=25mm 69-162 (80%) 47-107 (78%) *h2*=15mm 70-165 (81%) 53-128 (83%) *h2*=5mm 78-190 (83%) 57-158 (94%)

Table 2. Simulated and measured bandwidth versus transistor location on the active antenna in

**Table 2.** Simulated and measured bandwidth versus transistor location on the active antenna in common emitter

output (*S22*) of the two-port system described in Figure 3.

cy and when *h2*=5mm the height of the monopole is λ/175.

and -48.17dB respectively for *h2*=25mm and for *h2*=5mm.

and-48.17dB respectively for *h2*=25mm and for *h2*=5mm.

simulation)

118 Progress in Compact Antennas

configuration

receiving antenna in the Table 2.

receiving antenna in the Table 2.

common emitter configuration

frequency and when *h2*=5mm the height of the monopole is λ/175.

In this second part, we present the same simulated and measured results of the active antenna as function of location of the transistor (*h2*) for the common collector configuration. The results of |*S22*| are plotted in b. Common collector configuration In this second part, we present the same simulated and measured results of the active antenna as function of location of the transistor (*h2*) for the common collector configuration.

Figure 9. There is a central resonance frequency around 100 MHz as in the common emitter configuration. Matching is always better in simulation and the bandwidth increases when the transistor is close to the reflector plane. The results of |*S22*| are plotted in Figure 9. There is a central resonance frequency around 100 MHz as in the common emitter configuration. Matching is always better in simulation and the bandwidth increases when

Figure 9. |S22| of the active receiving antenna in common collector configuration (—measurement, ---

*h2*=15mm 60-210 (111%) 28-272 (162%) *h2*=5mm 70-260 (115%) 27-426 (176%)

Figure 10 presents the transmission coefficient |*S21*| as a function of the position of the transistor in common collector configuration for a height *h1* = 30mm. The results are presented from 50 MHz to 1 GHz frequency band to compare the behavior of the receiving active antenna as a function of frequency between simulations and measurements in order to validate the simulation methods. Agreements between the measured and simulated results are obtained. At 130 MHz, we obtained a transmission coefficient |*S21*| of -54.3 dB for a transistor positioned at *h2* = 25mm over to the reflector plane, of -53.8 dB for *h2* = 15mm and

Table 3. Simulated and measured bandwidth versus transistor location on the active antenna in

simulation) (—measurement,---simulation)


common collector configuration

We reported in the Table 3 the simulated and measured results. **Figure 9.** |*S22*| of the active receiving antenna in common collector configuration

**Location of the transistor Simulated bandwidth (MHz) Measured bandwidth (MHz)**  *h2*=25mm 58-182 (103%) 29-198 (148%) We reported in the Table 3 the simulated and measured results.


Figure 11 present the position of the active monopole over a reflector plane (500 mm x 500 mm)

To confirm our link budget calculation, we present in this part the measured radiation patterns of the active receiving antenna as function of the position of the transistor (*h2*). We

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Figure 10. Transmission coefficients |*S21*| between reference antenna and active receiving antenna

These measurement results are very interesting towards the size and frequency bandwidth of the active receiving antenna and we underline that we can adjust the antenna bandwidth and the size reduction of the active receiving antenna compared to the wavelength by

Figure 12 and Figure 13 show the radiation patterns of the active receiving monopole for both configurations, common emitter and common collector at several frequencies in FM band (88-108MHz). The radiation of the active antenna according to the frequency is similar to the

Figure 12 and Figure 13 show the radiation patterns of the active receiving monopole for both configurations, common emitter and common collector at several frequencies in FM band (88-108MHz). The radiation of the active antenna according to the frequency is similar

(a) (b)

(a) (b) Figure 11. (a) Geometry of the antenna (b) Photography of the antenna prototype on the ground plane

(a) (b) Figure 11. (a) Geometry of the antenna (b) Photography of the antenna prototype on the ground plane

E<sup>θ</sup> in XZ plane at 80 MHz E<sup>θ</sup> in XZ plane at 100 MHz Figure 12. Normalized measured radiation patterns of the active receiving antenna in common emitter configuration (── *h2*=5mm, - - - *h2*=25mm)

E<sup>θ</sup> in XZ plane at 80 MHz E<sup>θ</sup> in XZ plane at 100 MHz Figure 12. Normalized measured radiation patterns of the active receiving antenna in common emitter configuration (── *h2*=5mm, - - - *h2*=25mm)

**Figure 12.** Normalized measured radiation patterns of the active receiving antenna in common emitter configuration

E<sup>θ</sup> in XZ plane at 80 MHz E<sup>θ</sup> in XZ plane at 100 MHz Figure 13. Normalized measured radiation patterns of the active receiving antenna in common collector configuration (── *h2*=5mm, - - - *h2*=25mm)

As we have noticed above, the antenna gain depends on the transistor position. The gain variation between the two positions of the transistor is more important in common emitter than in common collector configuration. For example at 100 MHz, a gain of -22.6 dBi is measured for *h2* = 25mm and -19.6 dBi for *h2* = 5mm in common emitter configuration and -27.5 dBi for *h2* = 25mm and -27.3 dBi for *h2* = 5mm common collector configuration. Thus, there is a variation of 3 dB on

E<sup>θ</sup> in XZ plane at 80 MHz E<sup>θ</sup> in XZ plane at 100 MHz Figure 13. Normalized measured radiation patterns of the active receiving antenna in common collector configuration (── *h2*=5mm, - - - *h2*=25mm)

As we have noticed above, the antenna gain depends on the transistor position. The gain variation between the two positions of the transistor is more important in common emitter than in common collector configuration. For example at 100 MHz, a gain of -22.6 dBi is measured for *h2* = 25mm and -19.6 dBi for *h2* = 5mm in common emitter configuration and -27.5 dBi for *h2* = 25mm and -27.3 dBi for *h2* = 5mm common collector configuration. Thus, there is a variation of 3 dB on

**Figure 13.** Normalized measured radiation patterns of the active receiving antenna in common collector configura‐

The variations of transistor position provide the variation on the size reduction, bandwidth and the gain of active receiving antenna. The highest gain is obtained when the transistor is very close to the ground plane. For common emitter configuration, we have measured a gain of -19.6dBi at 100MHz and a bandwidth of 94% around 107.5MHz. In common collector configuration, the gain is equal to -27.3 dBi at 100MHz and the bandwidth is close to 176% around 226 MHz. The height of the active antenna is close to λ/175 and λ/370 in common emitter and common collector configuration

The variations of transistor position provide the variation on the size reduction, bandwidth and the gain of active receiving antenna. The highest gain is obtained when the transistor is very close to the ground plane. For common emitter configuration, we have measured a gain of -19.6dBi at 100MHz and a bandwidth of 94% around 107.5MHz. In common collector configuration, the gain is equal to -27.3 dBi at 100MHz and the bandwidth is close to 176% around 226 MHz. The height of the active antenna is close to λ/175 and λ/370 in common emitter and common collector configuration

common emitter and 0.2 dB common collector when *h2* varies from 25mm to 5mm.

common emitter and 0.2 dB common collector when *h2* varies from 25mm to 5mm.

respectively, where λ is the wavelength at the lowest operating frequency.

respectively, where λ is the wavelength at the lowest operating frequency.

11

11

Figure 11. (a) Geometry of the antenna (b) Photography of the antenna prototype on the ground plane **Figure 11.** (a) Geometry of the antenna (b) Photography of the antenna prototype on the ground plane

Figure 11 present the position of the active monopole over a reflector plane (500 mm x 500

radiation of a conventional monopole with vertical polarization.

to the radiation of a conventional monopole with vertical polarization.

present the results of two heights *h2* = 25mm and *h2* = 5mm.

and the radiation pattern reference.

(── *h2*=5mm, *h2*=25mm)

(── *h2*=5mm, *h2*=25mm)

tion

changing the position of the transistor.

mm) and the radiation pattern reference.

**2.4.2.2. Radiation patterns**

**Table 3.** Simulated and measured bandwidth versus transistor location on the active antenna in common collector configuration

Figure 10 presents the transmission coefficient |*S21*| as a function of the position of the transistor in common collector configuration for a height *h1*=30mm. The results are presented from 50 MHz to 1 GHz frequency band to compare the behavior of the receiving active antenna as a function of frequency between simulations and measurements in order to validate the simulation methods. Agreements between the measured and simulated results are obtained. At 130 MHz, we obtained a transmission coefficient |*S21*| of-54.3 dB for a transistor positioned at *h2*=25mm over to the reflector plane, of-53.8 dB for *h2*=15mm and-53.8 dB when *h2*=5mm.

Using the Friis formula, we calculates a gain of-28 dBi for the active receiving antenna when *h2*=25mm and-27.58 dBi for *h2*=5mm. The gain is almost identical between the two positions of the transistor.

Figure 10. Transmission coefficients |*S21*| between reference antenna and active receiving antenna **Figure 10.** Transmission coefficients |*S21*| between reference antenna and active receiving antenna

These measurement results are very interesting towards the size and frequency bandwidth of the active receiving antenna and we underline that we can adjust the antenna bandwidth and the size reduction of the active receiving antenna compared to the wavelength by changing the position of the transistor. These measurement results are very interesting towards the size and frequency bandwidth of the active receiving antenna and we underline that we can adjust the antenna bandwidth and the size reduction of the active receiving antenna compared to the wavelength by changing the position of the transistor.

#### **2.4.2.2. Radiation patterns** *2.4.2.2. Radiation patterns*

mm) and the radiation pattern reference.

patterns of the active receiving antenna as function of the position of the transistor (*h2*). We present the results of two heights *h2* = 25mm and *h2* = 5mm. To confirm our link budget calculation, we present in this part the measured radiation patterns of the active receiving antenna as function of the position of the transistor (*h2*). We present the results of two heights *h2*=25mm and *h2*=5mm.

Figure 11 present the position of the active monopole over a reflector plane (500 mm x 500

Figure 12 and Figure 13 show the radiation patterns of the active receiving monopole for both configurations, common emitter and common collector at several frequencies in FM band (88-108MHz). The radiation of the active antenna according to the frequency is similar

(a) (b) Figure 11. (a) Geometry of the antenna (b) Photography of the antenna prototype on the ground plane

to the radiation of a conventional monopole with vertical polarization.

To confirm our link budget calculation, we present in this part the measured radiation

Figure 11 present the position of the active monopole over a reflector plane (500 mm x 500 mm) and the radiation pattern reference. To confirm our link budget calculation, we present in this part the measured radiation patterns of the active receiving antenna as function of the position of the transistor (*h2*). We present the results of two heights *h2* = 25mm and *h2* = 5mm.

Figure 10. Transmission coefficients |*S21*| between reference antenna and active receiving antenna

changing the position of the transistor.

**2.4.2.2. Radiation patterns**

These measurement results are very interesting towards the size and frequency bandwidth of the active receiving antenna and we underline that we can adjust the antenna bandwidth and the size reduction of the active receiving antenna compared to the wavelength by

Figure 12 and Figure 13 show the radiation patterns of the active receiving monopole for both configurations, common emitter and common collector at several frequencies in FM band (88-108MHz). The radiation of the active antenna according to the frequency is similar to the radiation of a conventional monopole with vertical polarization. Figure 11 present the position of the active monopole over a reflector plane (500 mm x 500 mm) and the radiation pattern reference. Figure 12 and Figure 13 show the radiation patterns of the active receiving monopole for both configurations, common emitter and common collector at several frequencies in FM band (88-108MHz). The radiation of the active antenna according to the frequency is similar

Figure 11. (a) Geometry of the antenna (b) Photography of the antenna prototype on the ground plane

Figure 11. (a) Geometry of the antenna (b) Photography of the antenna prototype on the ground plane **Figure 11.** (a) Geometry of the antenna (b) Photography of the antenna prototype on the ground plane (a) (b)

to the radiation of a conventional monopole with vertical polarization.

(── *h2*=5mm, *h2*=25mm)

**Location of the transistor Simulated bandwidth (MHz) Measured bandwidth (MHz)** *h2*=25mm 58-182 (103%) 29-198 (148%) *h2*=15mm 60-210 (111%) 28-272 (162%) *h2*=5mm 70-260 (115%) 27-426 (176%)

**Table 3.** Simulated and measured bandwidth versus transistor location on the active antenna in common collector

Figure 10 presents the transmission coefficient |*S21*| as a function of the position of the transistor in common collector configuration for a height *h1*=30mm. The results are presented from 50 MHz to 1 GHz frequency band to compare the behavior of the receiving active antenna as a function of frequency between simulations and measurements in order to validate the simulation methods. Agreements between the measured and simulated results are obtained. At 130 MHz, we obtained a transmission coefficient |*S21*| of-54.3 dB for a transistor positioned at *h2*=25mm over to the reflector plane, of-53.8 dB for *h2*=15mm and-53.8 dB when *h2*=5mm.

Using the Friis formula, we calculates a gain of-28 dBi for the active receiving antenna when *h2*=25mm and-27.58 dBi for *h2*=5mm. The gain is almost identical between the two positions of

 *h2*=25mm *h2*=15mm *h2*=5mm

**Figure 10.** Transmission coefficients |*S21*| between reference antenna and active receiving antenna

Figure 10. Transmission coefficients |*S21*| between reference antenna and active receiving antenna

These measurement results are very interesting towards the size and frequency bandwidth of the active receiving antenna and we underline that we can adjust the antenna bandwidth and the size reduction of the active receiving antenna compared to the wavelength by

These measurement results are very interesting towards the size and frequency bandwidth of the active receiving antenna and we underline that we can adjust the antenna bandwidth and the size reduction of the active receiving antenna compared to the wavelength by changing

To confirm our link budget calculation, we present in this part the measured radiation patterns of the active receiving antenna as function of the position of the transistor (*h2*). We

To confirm our link budget calculation, we present in this part the measured radiation patterns of the active receiving antenna as function of the position of the transistor (*h2*). We present the

Figure 11 present the position of the active monopole over a reflector plane (500 mm x 500

Figure 12 and Figure 13 show the radiation patterns of the active receiving monopole for both configurations, common emitter and common collector at several frequencies in FM band (88-108MHz). The radiation of the active antenna according to the frequency is similar

(a) (b) Figure 11. (a) Geometry of the antenna (b) Photography of the antenna prototype on the ground plane

configuration

120 Progress in Compact Antennas

the transistor.

changing the position of the transistor.

mm) and the radiation pattern reference.

results of two heights *h2*=25mm and *h2*=5mm.

present the results of two heights *h2* = 25mm and *h2* = 5mm.

to the radiation of a conventional monopole with vertical polarization.

**2.4.2.2. Radiation patterns**

the position of the transistor.

*2.4.2.2. Radiation patterns*

E<sup>θ</sup> in XZ plane at 80 MHz E<sup>θ</sup> in XZ plane at 100 MHz

common emitter and 0.2 dB common collector when *h2* varies from 25mm to 5mm.

common emitter and 0.2 dB common collector when *h2* varies from 25mm to 5mm.

respectively, where λ is the wavelength at the lowest operating frequency.

respectively, where λ is the wavelength at the lowest operating frequency.

common collector configuration. For example at 100 MHz, a gain of -22.6 dBi is measured for *h2* = 25mm and -19.6 dBi for *h2* = 5mm in common emitter configuration and -27.5 dBi for *h2* = 25mm and -27.3 dBi for *h2* = 5mm common collector configuration. Thus, there is a variation of 3 dB on As we have noticed above, the antenna gain depends on the transistor position. The gain variation between the two positions of the transistor is more important in common emitter than in common collector configuration. For example at 100 MHz, a gain of -22.6 dBi is measured for *h2* = **Figure 13.** Normalized measured radiation patterns of the active receiving antenna in common collector configura‐ tion

25mm and -19.6 dBi for *h2* = 5mm in common emitter configuration and -27.5 dBi for *h2* = 25mm and -27.3 dBi for *h2* = 5mm common collector configuration. Thus, there is a variation of 3 dB on

The variations of transistor position provide the variation on the size reduction, bandwidth and the gain of active receiving antenna. The highest gain is obtained when the transistor is very close to the ground plane. For common emitter configuration, we have measured a gain of -19.6dBi at 100MHz and a bandwidth of 94% around 107.5MHz. In common collector configuration, the gain is equal to -27.3 dBi at 100MHz and the bandwidth is close to 176% around 226 MHz. The height of the active antenna is close to λ/175 and λ/370 in common emitter and common collector configuration

The variations of transistor position provide the variation on the size reduction, bandwidth and the gain of active receiving antenna. The highest gain is obtained when the transistor is very close to the ground plane. For common emitter configuration, we have measured a gain of -19.6dBi at 100MHz and a bandwidth of 94% around 107.5MHz. In common collector configuration, the gain is equal to -27.3 dBi at 100MHz and the bandwidth is close to 176% around 226 MHz. The height of the active antenna is close to λ/175 and λ/370 in common emitter and common collector configuration

11

11

As we have noticed above, the antenna gain depends on the transistor position. The gain variation between the two positions of the transistor is more important in common emitter than in common collector configuration. For example at 100 MHz, a gain of-22.6 dBi is measured for *h2*=25mm and-19.6 dBi for *h2*=5mm in common emitter configuration and-27.5 dBi for *h2*=25mm and-27.3 dBi for *h2*=5mm common collector configuration. Thus, there is a variation of 3 dB on common emitter and 0.2 dB common collector when *h2* varies from 25mm to 5mm.

Figure 14. Position of the parasite in active antenna

To observe the influence of the distance of (*p*) on the performances of the active antenna, this parameter has been sweep between 20 mm and 0.5 mm. The total length of the parasitic element varies from 25 mm to 5.5 mm. The simulation results of |*S11*| are shown in Figure

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 (a) (b) Common emitter configuration

 (a) (b) Common collector configuration Figure 15. (a) Theoretical impedances of the active monopole as function of the position of the parasite *p* 

It can be noticed that the bandwidth of the active antenna increases as *p* decreases, for the two configurations: common emitter and common collector. The results are summarized in

It can be noticed that the bandwidth of the active antenna increases as *p* decreases, for the two configurations: common emitter and common collector. The results are summarized in Table 4.

**Figure 15.** (a) Theoretical impedances of the active monopole as function of the position of the parasite *p* (b) Theoret‐

20 78-190 (83%) 70-260 (115%) 10 90-300 (107%) 82-385 (130%) 5 100-474 (130%) 90-550 (143%) 0.5 105-632 (143%) 96-741 (154%)

 78-190 (83%) 70-260 (115%) 90-300 (107%) 82-385 (130%) 100-474 (130%) 90-550 (143%) 0.5 105-632 (143%) 96-741 (154%)

**Common emitter Common collector** 

**Bandwidth (MHz) Common emitter Common collector**

(b) Theoretical return loss active monopole based on the position of the parasite *p*.

**Position of the parasite** *p* **(mm) Bandwidth (MHz)**

**Table 4.** Simulated bandwidth versus parasite position (*p*) on the active antenna

(── *p*=0.5mm, … *p*=5mm, -.- *p*=10mm, - - - *p*=20mm)

ical return loss active monopole based on the position of the parasite *p*.

(──*p*=0.5mm, ⋅‧‧ *p*=5mm,-‧-*p*=10mm,---*p*=20mm)

**Position of the parasite p (mm)**

**2.4.3.1. Parametric studies**

15.

Table 4.

The variations of transistor position provide the variation on the size reduction, bandwidth and the gain of active receiving antenna. The highest gain is obtained when the transistor is very close to the ground plane. For common emitter configuration, we have measured a gain of-19.6dBi at 100MHz and a bandwidth of 94% around 107.5MHz. In common collector configuration, the gain is equal to-27.3 dBi at 100MHz and the bandwidth is close to 176% around 226 MHz. The height of the active antenna is close to λ/175 and λ/370 in common emitter and common collector configuration respectively, where λ is the wavelength at the lowest operating frequency.

#### *2.4.3. Influence of the position of the parasite*

The study of active monopole is focused on two parameters: the height of the active receiving antenna (*h1*) and the position of the transistor (*h2*). In this part, the variation of the parasitic element position *p* is investigated (Figure 14). Indeed, the parasitic element is used to polarize the transistor and its length provides a variation of the input impedance of the active monopole.

**Figure 14.** Position of the parasite in active antenna

#### *2.4.3.1. Parametric studies*

To observe the influence of the distance of (*p*) on the performances of the active antenna, this parameter has been sweep between 20 mm and 0.5 mm. The total length of the parasitic element varies from 25 mm to 5.5 mm. The simulation results of |*S11*| are shown in Figure 15.

To observe the influence of the distance of (*p*) on the performances of the active antenna, this

Figure 15. (a) Theoretical impedances of the active monopole as function of the position of the parasite *p*  (──*p*=0.5mm, ⋅‧‧ *p*=5mm,-‧-*p*=10mm,---*p*=20mm)

Figure 14. Position of the parasite in active antenna

**2.4.3.1. Parametric studies**

15.

As we have noticed above, the antenna gain depends on the transistor position. The gain variation between the two positions of the transistor is more important in common emitter than in common collector configuration. For example at 100 MHz, a gain of-22.6 dBi is measured for *h2*=25mm and-19.6 dBi for *h2*=5mm in common emitter configuration and-27.5 dBi for *h2*=25mm and-27.3 dBi for *h2*=5mm common collector configuration. Thus, there is a variation of 3 dB on common emitter and 0.2 dB common collector when *h2* varies from 25mm

The variations of transistor position provide the variation on the size reduction, bandwidth and the gain of active receiving antenna. The highest gain is obtained when the transistor is very close to the ground plane. For common emitter configuration, we have measured a gain of-19.6dBi at 100MHz and a bandwidth of 94% around 107.5MHz. In common collector configuration, the gain is equal to-27.3 dBi at 100MHz and the bandwidth is close to 176% around 226 MHz. The height of the active antenna is close to λ/175 and λ/370 in common emitter and common collector configuration respectively, where λ is the wavelength at the

The study of active monopole is focused on two parameters: the height of the active receiving antenna (*h1*) and the position of the transistor (*h2*). In this part, the variation of the parasitic element position *p* is investigated (Figure 14). Indeed, the parasitic element is used to polarize the transistor and its length provides a variation of the input impedance of the active monopole.

To observe the influence of the distance of (*p*) on the performances of the active antenna, this parameter has been sweep between 20 mm and 0.5 mm. The total length of the parasitic element

varies from 25 mm to 5.5 mm. The simulation results of |*S11*| are shown in Figure 15.

to 5mm.

122 Progress in Compact Antennas

lowest operating frequency.

*2.4.3. Influence of the position of the parasite*

**Figure 14.** Position of the parasite in active antenna

*2.4.3.1. Parametric studies*

(b) Theoretical return loss active monopole based on the position of the parasite *p*. (── *p*=0.5mm, … *p*=5mm, -.- *p*=10mm, - - - *p*=20mm) **Figure 15.** (a) Theoretical impedances of the active monopole as function of the position of the parasite *p* (b) Theoret‐ ical return loss active monopole based on the position of the parasite *p*.

It can be noticed that the bandwidth of the active antenna increases as *p* decreases, for the two configurations: common emitter and common collector. The results are summarized in Table 4. It can be noticed that the bandwidth of the active antenna increases as *p* decreases, for the two configurations: common emitter and common collector. The results are summarized in Table 4.


**Table 4.** Simulated bandwidth versus parasite position (*p*) on the active antenna

#### *2.4.3.2. Experimental results*

To validate the theoretical studies of the influence of the position of the parasite on the impedance of the antenna, measurement results for two positions of the parasite in the common emitter and common collector configurations are presented. For the first one, *p* is equal to 20mm, for the second, *p*=0.5mm.

To improve the gain performance of the active monopole antenna, we change the geometry of the antenna, especially on the upper part of the monopole. The transistor is in common emitter

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To improve the gain performance of the active monopole antenna, we change the geometry of the antenna, especially on the upper part of the monopole. The transistor is in common

(── measured *p*=0.5mm, … measured *p*=20mm, -.-.- simulated *p*=20mm, - - - simulated

The variation of the parasitic element position can enhance the bandwidth of active receiving antenna as shown in Figure 16. For the common emitter configuration, we measured a bandwidth of 94% around 107 MHz for *p* = 20 mm and a bandwidth of 149.5% around 320 MHz for *p* = 0.5mm. For the common collector configuration, when *p* = 0.5mm, there is a -10 dB bandwidth of 175% around 521 MHz measurement (Table 5). For the two

*p*=20mm 78-190 57-158 70-260 27-426 *p*=0.5mm 105-636 81-560 96-741 65-978

Table 5. Simulated and measured bandwidth (MHz) versus parasite position (*p*) on the active antenna

In the first part of this chapter, we have presented the influence of different parameters on the performance of an active receiving monopole. The influence of the transistor position and the parasitic element position on the size reduction, on the bandwidth and on the gain

**Emitter common configuration Collector common configuration Simulated Measured Simulated Measured** 

configurations, the measurements and simulations are in good agreements.

*p*=0.5mm)

We calculated and measured two structures of active monopole antenna (Figure 17), the length

Prototype 1 Prototype 2

The theoretical and experimental return losses of the active antenna as a function of the length

(a) Prototype 1 (b) Prototype 2

There is a frequency shift between measurements and simulations. However, measurements and simulations are in a good agreement. We measured a bandwidth of 150% around 322 MHz for prototype 1 and 130 % around 228 MHz for prototype 2. These results are

There is a frequency shift between measurements and simulations. However, measurements and simulations are in a good agreement. We measured a bandwidth of 150% around 322 MHz for prototype 1 and 130 % around 228 MHz for prototype 2. These results are summarized in

Prototype 1 108-693 (146%) 81-563 (150%) Prototype 2 97-335(110%) 80-377(130%)

In Figure 19, we presented the measured radiation patterns of the proposed antenna at 80 MHz and 100MHz. Radiation patterns are in good agreement for the bending structure and the classical one. A maximum gain of -21.57 dBi at 100 MHz was measured for the prototype 1 and -15.11 dBi for prototype 2. We have a difference of 6 dB between the two prototypes.

For evaluate the performances of active antenna in FM radio reception, we have measured the received signal strength indicator and the signal to noise ratio in FM band using the FM

Figure 19. Measured normalized radiation patterns of the active antenna in the XZ and YZ plan

**simulated BW (MHz) measured BW (MHz)** 

We calculated and measured two structures of active monopole antenna (Figure 17), the

configuration positioned at *h2*=5mm (*h1*=30mm, *p*=0.5mm).

Figure 17. Geometry of the active monopole antenna **Figure 17.** Geometry of the active monopole antenna

Figure 18. return losses of active monopole antenna

**Figure 18.** return losses of active monopole antenna

Table 6. Simulated and measured bandwidth of the active antenna

receiver evaluation board of silicon labs (Si4706).

( - - - measured, ── simulated)

summarized in Table 6.

Table 6.

(---measured, ── simulated)

80MHz 100MHz

(- - - prototype 1, ── prototype 2)

emitter configuration positioned at *h2* = 5mm (*h1* = 30mm, *p* =0.5mm).

**2.4.4. Influence of the geometry of the monopole**

has been clearly underlined.

of the upper part of the monopole ranges from 25 mm to 106 mm.

of the upper part of the monopole are presented in Figure 18.

length of the upper part of the monopole ranges from 25 mm to 106 mm.

Figure 16. Measured return loss of the active monopole antenna based on the position of the parasite *p*. (── measured *p*=0.5mm, ⋅‧‧ measured *p*=20mm,-‧-‧-simulated *p*=20mm,---simulated *p*=0.5mm)

(── measured *p*=0.5mm, … measured *p*=20mm, -.-.- simulated *p*=20mm, - - - simulated **Figure 16.** Measured return loss of the active monopole antenna based on the position of the parasite *p*.

*p*=0.5mm) The variation of the parasitic element position can enhance the bandwidth of active receiving antenna as shown in Figure 16. For the common emitter configuration, we measured a bandwidth of 94% around 107 MHz for *p* = 20 mm and a bandwidth of 149.5% around 320 MHz for *p* = 0.5mm. For the common collector configuration, when *p* = 0.5mm, there is a -10 dB bandwidth of 175% around 521 MHz measurement (Table 5). For the two The variation of the parasitic element position can enhance the bandwidth of active receiving antenna as shown in Figure 16. For the common emitter configuration, we measured a bandwidth of 94% around 107 MHz for *p=*20 mm and a bandwidth of 149.5% around 320 MHz for *p=*0.5mm. For the common collector configuration, when *p*=0.5mm, there is a-10 dB bandwidth of 175% around 521 MHz measurement (Table 5). For the two configurations, the measurements and simulations are in good agreements.


Table 5. Simulated and measured bandwidth (MHz) versus parasite position (*p*) on the active antenna **Table 5.** Simulated and measured bandwidth (MHz) versus parasite position (*p*) on the active antenna

emitter configuration positioned at *h2* = 5mm (*h1* = 30mm, *p* =0.5mm).

length of the upper part of the monopole ranges from 25 mm to 106 mm.

#### **2.4.4. Influence of the geometry of the monopole** *2.4.4. Influence of the geometry of the monopole*

has been clearly underlined.

In the first part of this chapter, we have presented the influence of different parameters on the performance of an active receiving monopole. The influence of the transistor position and the parasitic element position on the size reduction, on the bandwidth and on the gain In the first part of this chapter, we have presented the influence of different parameters on the performance of an active receiving monopole. The influence of the transistor position and the parasitic element position on the size reduction, on the bandwidth and on the gain has been clearly underlined.

To improve the gain performance of the active monopole antenna, we change the geometry of the antenna, especially on the upper part of the monopole. The transistor is in common

We calculated and measured two structures of active monopole antenna (Figure 17), the

To improve the gain performance of the active monopole antenna, we change the geometry of the antenna, especially on the upper part of the monopole. The transistor is in common emitter configuration positioned at *h2*=5mm (*h1*=30mm, *p*=0.5mm). To improve the gain performance of the active monopole antenna, we change the geometry of the antenna, especially on the upper part of the monopole. The transistor is in common emitter configuration positioned at *h2* = 5mm (*h1* = 30mm, *p* =0.5mm).

(── measured *p*=0.5mm, … measured *p*=20mm, -.-.- simulated *p*=20mm, - - - simulated

The variation of the parasitic element position can enhance the bandwidth of active receiving antenna as shown in Figure 16. For the common emitter configuration, we measured a bandwidth of 94% around 107 MHz for *p* = 20 mm and a bandwidth of 149.5% around 320 MHz for *p* = 0.5mm. For the common collector configuration, when *p* = 0.5mm, there is a -10 dB bandwidth of 175% around 521 MHz measurement (Table 5). For the two

*p*=20mm 78-190 57-158 70-260 27-426 *p*=0.5mm 105-636 81-560 96-741 65-978

Table 5. Simulated and measured bandwidth (MHz) versus parasite position (*p*) on the active antenna

In the first part of this chapter, we have presented the influence of different parameters on the performance of an active receiving monopole. The influence of the transistor position and the parasitic element position on the size reduction, on the bandwidth and on the gain

**Emitter common configuration Collector common configuration Simulated Measured Simulated Measured** 

configurations, the measurements and simulations are in good agreements.

**2.4.4. Influence of the geometry of the monopole**

has been clearly underlined.

*p*=0.5mm)

We calculated and measured two structures of active monopole antenna (Figure 17), the length of the upper part of the monopole ranges from 25 mm to 106 mm. We calculated and measured two structures of active monopole antenna (Figure 17), the length of the upper part of the monopole ranges from 25 mm to 106 mm.

Prototype 1 Prototype 2

*2.4.3.2. Experimental results*

124 Progress in Compact Antennas

*p*=0.5mm)

equal to 20mm, for the second, *p*=0.5mm.

To validate the theoretical studies of the influence of the position of the parasite on the impedance of the antenna, measurement results for two positions of the parasite in the common emitter and common collector configurations are presented. For the first one, *p* is

Common emitter configuration Common collector configuration

Figure 16. Measured return loss of the active monopole antenna based on the position of the parasite *p*.

(── measured *p*=0.5mm, … measured *p*=20mm, -.-.- simulated *p*=20mm, - - - simulated

The variation of the parasitic element position can enhance the bandwidth of active receiving antenna as shown in Figure 16. For the common emitter configuration, we measured a bandwidth of 94% around 107 MHz for *p* = 20 mm and a bandwidth of 149.5% around 320 MHz for *p* = 0.5mm. For the common collector configuration, when *p* = 0.5mm, there is a -10 dB bandwidth of 175% around 521 MHz measurement (Table 5). For the two

The variation of the parasitic element position can enhance the bandwidth of active receiving antenna as shown in Figure 16. For the common emitter configuration, we measured a bandwidth of 94% around 107 MHz for *p=*20 mm and a bandwidth of 149.5% around 320 MHz for *p=*0.5mm. For the common collector configuration, when *p*=0.5mm, there is a-10 dB bandwidth of 175% around 521 MHz measurement (Table 5). For the two configurations, the

*p*=20mm 78-190 57-158 70-260 27-426 *p*=0.5mm 105-636 81-560 96-741 65-978 Table 5. Simulated and measured bandwidth (MHz) versus parasite position (*p*) on the active antenna

**Table 5.** Simulated and measured bandwidth (MHz) versus parasite position (*p*) on the active antenna

*p*=20mm 78-190 57-158 70-260 27-426 *p*=0.5mm 105-636 81-560 96-741 65-978

In the first part of this chapter, we have presented the influence of different parameters on the performance of an active receiving monopole. The influence of the transistor position and the parasitic element position on the size reduction, on the bandwidth and on the gain

In the first part of this chapter, we have presented the influence of different parameters on the performance of an active receiving monopole. The influence of the transistor position and the parasitic element position on the size reduction, on the bandwidth and on the gain has been

To improve the gain performance of the active monopole antenna, we change the geometry of the antenna, especially on the upper part of the monopole. The transistor is in common

We calculated and measured two structures of active monopole antenna (Figure 17), the

**Emitter common configuration Collector common configuration Simulated Measured Simulated Measured** 

**Emitter common configuration Collector common configuration Simulated Measured Simulated Measured**

configurations, the measurements and simulations are in good agreements.

(── measured *p*=0.5mm, ⋅‧‧ measured *p*=20mm,-‧-‧-simulated *p*=20mm,---simulated *p*=0.5mm)

**Figure 16.** Measured return loss of the active monopole antenna based on the position of the parasite *p*.

**2.4.4. Influence of the geometry of the monopole**

*2.4.4. Influence of the geometry of the monopole*

measurements and simulations are in good agreements.

emitter configuration positioned at *h2* = 5mm (*h1* = 30mm, *p* =0.5mm).

length of the upper part of the monopole ranges from 25 mm to 106 mm.

has been clearly underlined.

clearly underlined.

The theoretical and experimental return losses of the active antenna as a function of the length of the upper part of the monopole are presented in Figure 18.

Figure 18. return losses of active monopole antenna (---measured, ── simulated)

80MHz 100MHz

(- - - prototype 1, ── prototype 2)

( - - - measured, ── simulated) **Figure 18.** return losses of active monopole antenna

There is a frequency shift between measurements and simulations. However, measurements and simulations are in a good agreement. We measured a bandwidth of 150% around 322 MHz for prototype 1 and 130 % around 228 MHz for prototype 2. These results are summarized in Table 6. There is a frequency shift between measurements and simulations. However, measurements and simulations are in a good agreement. We measured a bandwidth of 150% around 322 MHz for prototype 1 and 130 % around 228 MHz for prototype 2. These results are summarized in Table 6.

In Figure 19, we presented the measured radiation patterns of the proposed antenna at 80 MHz and 100MHz. Radiation patterns are in good agreement for the bending structure and the classical one. A maximum gain of -21.57 dBi at 100 MHz was measured for the prototype 1 and -15.11 dBi for prototype 2. We have a difference of 6 dB between the two prototypes.

For evaluate the performances of active antenna in FM radio reception, we have measured the received signal strength indicator and the signal to noise ratio in FM band using the FM

Figure 19. Measured normalized radiation patterns of the active antenna in the XZ and YZ plan

Prototype 1 108-693 (146%) 81-563 (150%) Prototype 2 97-335(110%) 80-377(130%)

Table 6. Simulated and measured bandwidth of the active antenna

receiver evaluation board of silicon labs (Si4706).

**simulated BW (MHz) measured BW (MHz)** 


There is a frequency shift between measurements and simulations. However, measurements

**Table 6.** Simulated and measured bandwidth of the active antenna Prototype 1 108-693 (146%) 81-563 (150%) Prototype 2 97-335(110%) 80-377(130%)

receiver evaluation board of silicon labs (Si4706).

Figure 18. return losses of active monopole antenna

In Figure 19, we presented the measured radiation patterns of the proposed antenna at 80 MHz and 100MHz. Radiation patterns are in good agreement for the bending structure and the classical one. A maximum gain of-21.57 dBi at 100 MHz was measured for the prototype 1 and-15.11 dBi for prototype 2. We have a difference of 6 dB between the two prototypes. Table 6. Simulated and measured bandwidth of the active antenna In Figure 19, we presented the measured radiation patterns of the proposed antenna at 80 MHz and 100MHz. Radiation patterns are in good agreement for the bending structure and the classical one. A maximum gain of -21.57 dBi at 100 MHz was measured for the prototype

For evaluate the performances of active antenna in FM radio reception, we have measured the received signal strength indicator and the signal to noise ratio in FM band using the FM receiver evaluation board of silicon labs (Si4706). 1 and -15.11 dBi for prototype 2. We have a difference of 6 dB between the two prototypes. For evaluate the performances of active antenna in FM radio reception, we have measured the received signal strength indicator and the signal to noise ratio in FM band using the FM

(- - - prototype 1, ── prototype 2) **Figure 19.** Measured normalized radiation patterns of the active antenna in the XZ and YZ plan

The results are plotted for the active receiving antenna (prototype 2) and a reference monopole antenna of 60cm of height. The average power received by the reference λ/4 monopole antenna is 10dB higher than the power received by active receiving antenna. The results are plotted for the active receiving antenna (prototype 2) and a reference monopole antenna of 60cm of height. The average power received by the reference λ/4 monopole antenna is 10dB higher than the power received by active receiving antenna. Despite the reduction of the power level, we measured a good received signal quality for listen to FM radio without interference.

#### **2.5. Conclusion**

In this first section, we studied the influence of the integration of a transistor on a passive monopole antenna, including the miniaturization of the antenna and the increase of the frequency bandwidth. Our contribution is based on the results obtained by Meinke in 60-70th and we conducted a theoretical and experimental validation of the active receiving antennas.

We also studied two configurations of transistor, i.e. common emitter and common collector. It was found that each configuration provides different performances. The bandwidth is wider in common collector (176%) than common emitter (94%). The reduction size is equal to λ/370

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127

Concerning the gain, the common emitter configuration presents a gain of-19.6 dBi which is higher than the gain (-27.3 dBi) obtained with the common collector configuration. These gains must be compared to gain a classical monopole of the same height (30mm) which is-49dBi.

in common collector configuration and λ/175 in a common emitter.

**Figure 20.** Received Signal Strength Indicator in FM band.

**Figure 21.** Signal to Noise Ratio

Despite the difficulty to simulate an active antenna, we use CST software to achieve consistency between measurements and simulations. Several parameters, as the position of the transistor, the position of the parasite and the design of the antenna are investigated.

**Figure 20.** Received Signal Strength Indicator in FM band.

**simulated BW (MHz) measured BW (MHz)**

**simulated BW (MHz) measured BW (MHz)** 

Prototype 1 108-693 (146%) 81-563 (150%) Prototype 2 97-335(110%) 80-377(130%)

Prototype 1 108-693 (146%) 81-563 (150%) Prototype 2 97-335(110%) 80-377(130%)

There is a frequency shift between measurements and simulations. However, measurements and simulations are in a good agreement. We measured a bandwidth of 150% around 322 MHz for prototype 1 and 130 % around 228 MHz for prototype 2. These results are

In Figure 19, we presented the measured radiation patterns of the proposed antenna at 80 MHz and 100MHz. Radiation patterns are in good agreement for the bending structure and the classical one. A maximum gain of-21.57 dBi at 100 MHz was measured for the prototype 1 and-15.11 dBi for prototype 2. We have a difference of 6 dB between the two prototypes.

In Figure 19, we presented the measured radiation patterns of the proposed antenna at 80 MHz and 100MHz. Radiation patterns are in good agreement for the bending structure and the classical one. A maximum gain of -21.57 dBi at 100 MHz was measured for the prototype 1 and -15.11 dBi for prototype 2. We have a difference of 6 dB between the two prototypes.

For evaluate the performances of active antenna in FM radio reception, we have measured the received signal strength indicator and the signal to noise ratio in FM band using the FM receiver

For evaluate the performances of active antenna in FM radio reception, we have measured the received signal strength indicator and the signal to noise ratio in FM band using the FM

80MHz 100MHz

Figure 19. Measured normalized radiation patterns of the active antenna in the XZ and YZ plan

**Figure 19.** Measured normalized radiation patterns of the active antenna in the XZ and YZ plan

The results are plotted for the active receiving antenna (prototype 2) and a reference monopole antenna of 60cm of height. The average power received by the reference λ/4 monopole antenna is 10dB higher than the power received by active receiving antenna.

In this first section, we studied the influence of the integration of a transistor on a passive monopole antenna, including the miniaturization of the antenna and the increase of the frequency bandwidth. Our contribution is based on the results obtained by Meinke in 60-70th and we conducted a theoretical and experimental validation of the active receiving antennas.

Despite the difficulty to simulate an active antenna, we use CST software to achieve consistency between measurements and simulations. Several parameters, as the position of the transistor,

the position of the parasite and the design of the antenna are investigated.

The results are plotted for the active receiving antenna (prototype 2) and a reference monopole antenna of 60cm of height. The average power received by the reference λ/4 monopole antenna is 10dB higher than the power received by active receiving antenna. Despite the reduction of the power level, we measured a good received signal quality for listen to FM radio without

**Table 6.** Simulated and measured bandwidth of the active antenna

Table 6. Simulated and measured bandwidth of the active antenna

Figure 18. return losses of active monopole antenna

( - - - measured, ── simulated)

summarized in Table 6.

126 Progress in Compact Antennas

evaluation board of silicon labs (Si4706).

(- - - prototype 1, ── prototype 2)

(---prototype 1, ── prototype 2)

interference.

**2.5. Conclusion**

receiver evaluation board of silicon labs (Si4706).

**Figure 21.** Signal to Noise Ratio

We also studied two configurations of transistor, i.e. common emitter and common collector. It was found that each configuration provides different performances. The bandwidth is wider in common collector (176%) than common emitter (94%). The reduction size is equal to λ/370 in common collector configuration and λ/175 in a common emitter.

Concerning the gain, the common emitter configuration presents a gain of-19.6 dBi which is higher than the gain (-27.3 dBi) obtained with the common collector configuration. These gains must be compared to gain a classical monopole of the same height (30mm) which is-49dBi.

Finally, the change of active monopole geometries has allowed us to increase the gain of the active antenna. It led to the creation of a miniature active antenna with a bandwidth of 130% around 228 MHz, the height of the active antenna is λ/80 at the lowest frequency of the bandwidth. The measured gain is-15.1 dBi at 100 MHz. We have measured a good received signal quality.

computed with CST Microwave Studio Software and compared to measurements. Regarding this first part of the study, we propose a physical explanation of the antenna behavior. Thereafter, parametric studies give additional information and help us to increase our

X

w1

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R

short circuits feed

*R* and *r* are respectively the radii of the half loop and the arc monopole lines, *w1* and *w2* are their widths. *P* is the total length of the arc monopole line and *α* is the angle between its both

By an optimized choice of the lengths, the widths and the distance between the two lines, it is possible to achieve a broadband solution presented in Figure 23. The antenna has been printed on a Neltec NY9300 substrate (*εr*=3, *h*=0.786 mm, tanδ=0.0023) and above a limited square

In this case, *R*=100 mm, *r*=84 mm, *w1*=0.4 mm, *w2*=0.5 mm, *X*=220 mm, *Y*=110 mm, *α*=90° and *P*=132 mm. The return loss and the input impedance of the antenna have been computed. The

The Figure 23 shows a comparison between simulation and measurement with a very good agreement. The measured return loss bandwidth is close to 70MHz (≈15.3%). With this design,

On Figure 23.a, the shape of the return loss shows two resonances. The first resonance frequency depends of the λ/2 half loop radiator, whereas the second one has been created by the arc monopole considered as a quarter wavelength conventional monopole. As noticed in reference [26], the electromagnetic coupling between the two parts of the antenna affects the

To increase our understanding of this antenna, we proceed to theoretical parametric studies. We investigate the dimensions of the ground plane, the length, the width of the arc monopole line, the width of the half-loop line and the distance between the two microstrip lines and we will show the influence of these parameters on the input impedance. In this section, we present just two parameters, the length of the arc monopole and the distance between the two printed

extremities. The radius (thus the length) of the half loop line will remain constant.

simulation and measurement have been performed between 200MHz and 800MHz.

we increase three times the bandwidth of the antenna proposed in [25].

a

w r

2

Y

).

reflector plane

X

knowledge of this design.

Z

Y

**Figure 22.** Geometry of the proposed antenna

ground plane (300×300×4 mm3

impedance behavior.

lines.
