**4.3 Return loss measurement**

This discontinuity can be a mismatch with the terminating load or with a device inserted in the line. It is usually expressed as a ratio in decibels (dB).

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**4.2 Return loss**

**4. Results**

**Figure 6.**

**4.1 VSWR**

get the optimum parameters.

shown in **Figure 7(a)** and **(b)**.

software for single cavity and double cavity respectively.

The numerical simulation of directional antenna is done using CST software. The performance of the antenna does not improve monotonically as the parameters of the antenna changes. It must be optimized through analysis during simulation to

*(a) Fabricated single cavity Vivaldi antenna and (b) fabricated double cavity Vivaldi antenna.*

The simulations for Vivaldi antenna operating in the band 8–18 GHz are done using CST. The obtained VSWR simulation results for the respective antenna are as

As shown in **Figure 7(a)** and **(b)**, the VSWR-frequency plot for the Vivaldi antenna without SMA connector seems to have a high VSWR, which means the reflection of power is more and the reflected wave amplitude is high from frequency 8 to 18 GHz. To lower the VSWR, a connector is attached to the antenna for the required band of frequencies. **Figure 8(a)** and **(b)** shows the VSWR with SMA connector in CST

The obtained return loss simulation results for the single cavity Vivaldi antenna and double cavity Vivaldi antenna are as shown in **Figure 9(a)** and **(b)**, respectively.

**Figure 8.**

*(a) Simulated VSWR for single cavity Vivaldi antenna with SMA connector and (b) simulated VSWR for double cavity Vivaldi antenna with SMA connector.*

#### **Figure 9.**

*(a) Simulated return loss for single cavity Vivaldi antenna and (b) simulated return loss for double cavity Vivaldi antenna.*

The steps involved for measuring the return loss using network analyzer are given below:

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**Figure 11.**

*Vivaldi antenna.*

**Figure 10.**

*antenna.*

*Characterization of Printed Podal Vivaldi Antenna (8–18 GHz) on RT Duroid with Single…*

4. calibrate the network analyzer by connecting the standard short circuit, open circuit and matched loads at the test port. Observe the trace on the display to

5. remove the standards and connect the antenna and observe the shift in the trace of the display. The display can be changed for obtaining the return loss, reflection coefficient, and impedance over the selected frequency band.

The measured return loss for single cavity Vivaldi antenna and double cavity

To provide a controlled environment, an all-weather capability, and security, and to minimize electromagnetic interference, indoor anechoic chambers have been developed as an alternative to outdoor testing. By this method, the testing is performed inside a chamber having walls that are covered with RF absorbers. The design of each is based on geometrical optics techniques, and each attempt to reduce or to minimize specular reflections. The phase difference between the

*(a) Measured VSWR for single cavity Vivaldi antenna and (b) measured VSWR for double cavity Vivaldi* 

*(a) Measured return loss for single cavity Vivaldi antenna and (b) measured return loss for double cavity* 

Return loss in dB = −20 log (ρ), where ρ is the reflection coefficient.

Vivaldi antenna are shown in **Figure 11(a)** and **(b)**, respectively.

*DOI: http://dx.doi.org/10.5772/intechopen.88727*

3. select log amplitude mode on display;

get a solid reference line; and

**4.4 Anechoic chamber**

2. select one port S11 for calibration measurement;

1. select sweep frequency range by selecting start and stop frequency;

*Characterization of Printed Podal Vivaldi Antenna (8–18 GHz) on RT Duroid with Single… DOI: http://dx.doi.org/10.5772/intechopen.88727*


Return loss in dB = −20 log (ρ), where ρ is the reflection coefficient. The measured return loss for single cavity Vivaldi antenna and double cavity Vivaldi antenna are shown in **Figure 11(a)** and **(b)**, respectively.

### **4.4 Anechoic chamber**

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given below:

*Vivaldi antenna.*

**Figure 9.**

**Figure 8.**

*double cavity Vivaldi antenna with SMA connector.*

The steps involved for measuring the return loss using network analyzer are

*(a) Simulated return loss for single cavity Vivaldi antenna and (b) simulated return loss for double cavity* 

*(a) Simulated VSWR for single cavity Vivaldi antenna with SMA connector and (b) simulated VSWR for* 

1. select sweep frequency range by selecting start and stop frequency;

To provide a controlled environment, an all-weather capability, and security, and to minimize electromagnetic interference, indoor anechoic chambers have been developed as an alternative to outdoor testing. By this method, the testing is performed inside a chamber having walls that are covered with RF absorbers. The design of each is based on geometrical optics techniques, and each attempt to reduce or to minimize specular reflections. The phase difference between the

#### **Figure 10.**

*(a) Measured VSWR for single cavity Vivaldi antenna and (b) measured VSWR for double cavity Vivaldi antenna.*

#### **Figure 11.**

*(a) Measured return loss for single cavity Vivaldi antenna and (b) measured return loss for double cavity Vivaldi antenna.*

**Figure 12.** *Anechoic chamber.*

#### **Figure 13.**

*(a) 3-D radiation pattern of single cavity Vivaldi antenna at 14 GHz and (b) 3-D radiation pattern of double cavity Vivaldi antenna at 14 GHz.*

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**Figure 14.**

*antenna.*

*Characterization of Printed Podal Vivaldi Antenna (8–18 GHz) on RT Duroid with Single…*

direct radiation and that reflected from the walls near the source can be made very small by properly locating the source antenna near the apex. Thus, the direct and reflected rays near the test antenna region add vectorially and provide a relatively smooth amplitude illumination taper. This can be illustrated by ray-tracing tech-

The simulated 3D radiation patterns of printed Vivaldi antenna for single cavity and double cavity at frequency of 14 GHz is shown in **Figure 13(a)** and **(b)**

The E-plane and H-plane are the reference planes for linearly polarized waveguides, antennas and other microwave devices. The E-plane and H-plane patterns

The plane containing the E aperture and the direction of maximum radiation results in a linearly polarized antenna and it determines the orientation of the radio

*(a) E plane patterns for single cavity Vivaldi antenna and (b) E plane patterns for double cavity Vivaldi* 

*DOI: http://dx.doi.org/10.5772/intechopen.88727*

are also called as the polar plots or gain plots.

niques (**Figure 12**).

respectively.

*4.6.1 E-plane*

**4.6 Plane patterns**

**4.5 Radiation pattern**

*Characterization of Printed Podal Vivaldi Antenna (8–18 GHz) on RT Duroid with Single… DOI: http://dx.doi.org/10.5772/intechopen.88727*

direct radiation and that reflected from the walls near the source can be made very small by properly locating the source antenna near the apex. Thus, the direct and reflected rays near the test antenna region add vectorially and provide a relatively smooth amplitude illumination taper. This can be illustrated by ray-tracing techniques (**Figure 12**).
