**2.2. Electric and magnetic antennas**

Planar UWB and SWB antennas which geometrically resemble its counterpart (wire) monopole antennas are widely called monopole. However, this topological naming for the planar radiators is incorrect and confused, because the radiation pattern of all the so-called (planar)-monopole antennas have not the shaped of the monopole but of the dipole antenna i.e., having the shape of the full-doughnut.

To avoid ambiguities, formal definitions for planar antennas are hereafter provided.

The definitions planar-magnetic antenna and planar-electric antenna were constructed by means of an analogy to the wire-loop antenna and the wire-electric dipole which are documented in (IEEE std, op. cit.; Schantz et al., 2003, 2004; and Tanyer et al. 2009a), to keep this chapter self-content and avoid cross-reference, we summarize them here:

As a first step, let the base plane *B*, be the plane comprises the antenna's effective radiating/ receiving aperture, and let **n** be the unit normal vector to this plane, with reference to Figure 5 , *B* can be assimilated into *xOy*, while n = iz.

Assume that the field has a transverse electromagnetic (TEM) distribution propagating along the base plane. Then the following cases can be distinguished:


The above definitions are strictly applied to structures that support propagating-and-nonzero TEM- field distributions only, so that the waveguide case is automatically excluded by this TEM regard. We note here that the above definition have not taken in to account the diffraction effects at the edges/vertexes/corners of the metallic/dielectric material that constituent the transmitting/receiving aperture.

#### **2.3. Quasi-electric and quasi-magnetic antennas**

Most of the cases, particularly in planar antenna configuration, the topology of the radiating apertures may prevent the above-indicated conditions from being rigorously satisfied. Even in such cases, either one or the other of the two situations may prevail, thus correctly determine the type of the antenna. For instant, a radiator for which the magnetic field strength H(r) or the electric field strength **E**(**r**) is parallel to **n** over most of the effective aperture will be denoted as *quasi-magnetic* antenna, or *quasi-electric* antenna, respectively.

Obviously, planar antennas fed by microstrip-line or co-planar-waveguide can be classified as quasi-electric or quasi-magnetic antennas, respectively.

As will be demonstrated hereby, our prototypes fall in the class of quasi-magnetic antennas, whilst for all patch antennas fed by micro-strip line, as an example, the RAD-NAV antenna (Tran et al., 2010) belongs to the class of quasi-electric antennas.

#### **2.4. Bandwidth definitions**

There are several definitions of bandwidth circulated among our antennas and propagation society; those frequently met are octave-, decade-, ratio-, fractional-, percent-, and ratiobandwidths. The two definitions, that most frequently used, are the percent bandwidth and the ratio bandwidth. They are defined respectively as follows:

$$BW\_p \triangleq 100\% \times BW \;/\; f\_c \tag{1}$$

$$BW \triangleq f\_H - f\_L \tag{2}$$

$$BW\_{\text{LINB}} = \begin{cases} BW\_{\text{LINB}, \text{DATA}} \triangleq BW\_p \ge 25\% \\ BW\_{\text{LINB}, \text{FCC}} \quad \triangleq BW\_p \ge 20\% \end{cases} \tag{3}$$

$$BW\_{R:1} \triangleq BW \;/\; f\_{L'} \; \text{ when } BW\_p \geq 100\% \tag{4}$$

Where:

156 Ultra Wideband – Current Status and Future Trends

figure-eight (Balanis op. cit. p.163).

while its length is one half of the dipole.

**2.2. Electric and magnetic antennas** 

i.e., having the shape of the full-doughnut.

5 , *B* can be assimilated into *xOy*, while n = iz.

radiator is referred as *magnetic antenna*.

radiator is referred as *electric antenna*.

constituent the transmitting/receiving aperture.

second is for those resembling of thin wire linear antennas.

patterns are also well-known [ibis., p.154]. The antenna first used by Hertz in his early RF experiments in the late 19th century, as an example, was a half-wave dipole (Krauss, op. cit.) and the shapes of its 3D-radiation pattern had a similar appearance to a full-doughnut or

The Monopole antenna is formed by replacing one half of the dipole antenna with the ground plane, when the ground plane is large enough the monopole behaves like the dipole, except that its radiation pattern is just one half of the dipole, its gain approaches twice,

Magnetic dipole and electric dipole are standardized and well documented in [IEEE STD 145-1983, p.11-16]. The terms magnetic antenna and electric antenna were logically defined but occasionally used in literature, the first term used to describe radiators which possess radiation properties resembling those of thin wire loop (Balanis, op. cit., p.217), while the

Planar UWB and SWB antennas which geometrically resemble its counterpart (wire) monopole antennas are widely called monopole. However, this topological naming for the planar radiators is incorrect and confused, because the radiation pattern of all the so-called (planar)-monopole antennas have not the shaped of the monopole but of the dipole antenna

The definitions planar-magnetic antenna and planar-electric antenna were constructed by means of an analogy to the wire-loop antenna and the wire-electric dipole which are documented in (IEEE std, op. cit.; Schantz et al., 2003, 2004; and Tanyer et al. 2009a), to keep

As a first step, let the base plane *B*, be the plane comprises the antenna's effective radiating/ receiving aperture, and let **n** be the unit normal vector to this plane, with reference to Figure

Assume that the field has a transverse electromagnetic (TEM) distribution propagating

• In the case when the base plane magnetic field **H**(**r**), with r ∊ *B*, is directed along **n**, the

• In the case when the base plane electric field **E**(**r**), with **r** ∊ *B*, is directed along **n**, the

The above definitions are strictly applied to structures that support propagating-and-nonzero TEM- field distributions only, so that the waveguide case is automatically excluded by this TEM regard. We note here that the above definition have not taken in to account the diffraction effects at the edges/vertexes/corners of the metallic/dielectric material that

To avoid ambiguities, formal definitions for planar antennas are hereafter provided.

this chapter self-content and avoid cross-reference, we summarize them here:

along the base plane. Then the following cases can be distinguished:

*f*H, *f*L are the maximum and minimum frequency at -10 dB, respectively.

*BW* is the nominal bandwidth defined by *BW* = *f*H - *f*L

*fC* is the central frequency defined by *fC* = (*f*H + *f*L )/2

*BP* is the percent bandwidth and,

*BWR:1* is the *Ratio bandwidth*, commonly read as *R-over-1 bandwidth*, in which *R* is the normalized ratio of *f*H to *f*L defined as R= *f*H/*f*L. ,( *f*<sup>L</sup> *≠ 0*)

The *percent bandwidth* (1) has originally been used to describe the narrow-bandwidth of conventional antennas and microwave-devices. Its usage is quite popular and often considered as a standard in many textbooks, nevertheless, it is mathematically not a solid definition because it possesses a defect when *f*L approaching zero. For example, suppose that the nominal bandwidth of antennas #1 is 2GHz (0-2GHz), and antenna #2 is 20GHz (0-

20GHz). It is clearly that the nominal bandwidth *BW* of the second antenna is 10 times wider than the first one; however, formula (1) indicates that both antennas have the same percent bandwidth. Another weak point is the percent bandwidth of formula (1) is always less than or equal to 200% irrespective of how wide the antenna's nominal bandwidth was. Note also that formula (1) is often mistakenly called as *fractional bandwidth*, indeed the formula (1) consolidates its meaning "fractional bandwidth" only when the factor 100% is removed.

Architecture and Design Procedure of a Generic SWB Antenna with Superb Performances for Tactical Commands and Ubiquitous Communications 159

(2002). Close inspection the patterns displayed in fig. 1 (and in all referenced work above) we discovered a **remarkable** general property that pattern dispersion became lesser as the

antenna's sharp corners becoming more rounded. So our generic radiator

**Figure 1.** Distortion of radiation patterns of common planar UWB/SWB radiators

**Figure 2.** Typical extremely large impedance bandwidth of planar dipole antennas

There are countless numbers of UWB/SWB monopole antennas have been developed in the last 20 years, the variety in shapes and architectures vary enormous. **Figure 3** represents the

**3.2. Planar monopole antennas** 

Alternatively, the *ratio bandwidth* (2) can also be used for expressing the bandwidth of UWB and SWB antennas and devices. The defect at zero- frequency point still lurks there but the 200%-limit is lifted. The use of the ratio bandwidth is more adequate to envision the wideband characteristics of devices under investigation. We choose for the second formula (2) for describing the bandwidth for the SWB-prototype discussed in this chapter.

How to choose two formulas, although no official consent however, the first formula is often used for cases that the bandwidths are less than 100%, whilst the second is for UWB and SWB antennas/devices.

Traditional communications systems typically used signals having a percent bandwidth of less than 1%, while standard CDMA has an approximately of 2%. Early definition in the radar and communications fields considered signals with percent bandwidth of 25% or greater (measured at the -3 dB points) to be ultra-wideband. The recent FCC regulations (FCC,2004), which will be used as a standard throughout this text, defined UWB devices/signals as having an nominal bandwidth which exceeds 500 MHz or percent bandwidth of over 20%, measured at -10 dB points.

The term SWB has been often used to indicate bandwidth, which is greater than a decade bandwidth. Since the percent bandwidth confused and failed to envision the SWB property adequately as discussed in §2.4, the "ratio bandwidth" is more suitable and often be used for describing bandwidth of 10:1 or larger, we adopt this convention throughout this report.

The proposed antenna possesses
