**5.2 Design of the polarization configurable feeder antenna**

In order to realize the polarization configuration of the antenna, a polarization configurable feeder antenna is needed. So we designed a polarization configurable slot coupled patch antenna, as shown in **Figure 20**. The feeder antenna is composed by two substrates with different thickness (1.6 mm for Sub1 and 0.8 mm for Sub2). Four identical patches are chosen as the radiators of the antenna. They are printed on the top side of the Sub1 and are symmetric with respect to the center of the antenna. Between the two substrates is a metal ground plane, and four slots are etched on the plane under four patches. The slots 1 and 3 are along the y direction, and the slots 2 and 4 are along the x direction. The feeding line is printed on the bottom side of the Sub2. The four stubs are used to feed four patches through slots.

## *Advanced Radio Frequency Antennas for Modern Communication and Medical Systems*

The lengths of the four stubs are properly designed to make the patches receive the excited with the same phase. Two PIN diodes K1 and K2 are inserted into the feeding line. The biasing points V1, V2, and Gnd are added near the microstrip line to bias the PIN diodes. These points are connected to the microstrip line through inductors. The inductors can allow DC to pass through and block the RF signals. When V1 connects the anode of the DC source, the K1 is turned ON, and when V2 connects the anode of the DC source, the K2 is turned ON. When K1 is ON and K2 is OFF, patches 1 and 3 are excited and the antenna radiates *x*-polarized wave. Whereas when K1 is OFF and K2 is ON, patches 2 and 4 are excited and the antenna radiates *y*-polarized wave. Besides, in order to prevent the DC from going into the RF sources, a slot is added in the microstrip line, and a capacitor is inserted into the

*Reconfigurable Fabry-Pérot Cavity Antenna Basing on Phase Controllable Metasurfaces*

slot. The capacitor can allow RF signal to pass through and block the DC.

Using the proposed configurable PRS and the polarization configurable patch antenna, a polarization and pattern reconfigurable FPC antenna are formed, as shown in **Figure 21**. The PRS is set above the feeder antenna with a distance of h. The antenna is designed to work at 5 GHz. The height of the cavity h is calculated

**5.3 Design of the antenna**

*DOI: http://dx.doi.org/10.5772/intechopen.91695*

**Figure 23.**

**239**

*Simulated and measured S11 of the antenna: (a) x-polarized and (b) y-polarized.*

**Figure 21.** *Geometry of the FPC antenna.*


#### **Table 4.**

*Detail information of the antenna at different states.*

**Figure 22.** *The photograph of the fabricated antenna.*

*Reconfigurable Fabry-Pérot Cavity Antenna Basing on Phase Controllable Metasurfaces DOI: http://dx.doi.org/10.5772/intechopen.91695*

The lengths of the four stubs are properly designed to make the patches receive the excited with the same phase. Two PIN diodes K1 and K2 are inserted into the feeding line. The biasing points V1, V2, and Gnd are added near the microstrip line to bias the PIN diodes. These points are connected to the microstrip line through inductors. The inductors can allow DC to pass through and block the RF signals. When V1 connects the anode of the DC source, the K1 is turned ON, and when V2 connects the anode of the DC source, the K2 is turned ON. When K1 is ON and K2 is OFF, patches 1 and 3 are excited and the antenna radiates *x*-polarized wave. Whereas when K1 is OFF and K2 is ON, patches 2 and 4 are excited and the antenna radiates *y*-polarized wave. Besides, in order to prevent the DC from going into the RF sources, a slot is added in the microstrip line, and a capacitor is inserted into the slot. The capacitor can allow RF signal to pass through and block the DC.

#### **5.3 Design of the antenna**

**Figure 21.**

**Table 4.**

**Figure 22.**

**238**

*The photograph of the fabricated antenna.*

*Detail information of the antenna at different states.*

*Geometry of the FPC antenna.*

**States Part 1 Part 2 Part 3 Part 4 Beam direction** OFF OFF OFF OFF Broadside ON OFF OFF ON *φ* = 0° ON OFF OFF OFF *φ* = 45° ON ON OFF OFF *φ* = 90° OFF ON OFF OFF *φ* = 135° OFF ON ON OFF *φ* = 180° OFF OFF ON OFF *φ* = 225° OFF OFF ON ON *φ* = 270° OFF OFF OFF ON *φ* = 315°

*Advanced Radio Frequency Antennas for Modern Communication and Medical Systems*

Using the proposed configurable PRS and the polarization configurable patch antenna, a polarization and pattern reconfigurable FPC antenna are formed, as shown in **Figure 21**. The PRS is set above the feeder antenna with a distance of h. The antenna is designed to work at 5 GHz. The height of the cavity h is calculated

**Figure 23.** *Simulated and measured S11 of the antenna: (a) x-polarized and (b) y-polarized.*

according to Eq. (9) with the reflection phase of the unit cell when diodes are OFF. After being optimized, the h is set to 28 mm.

**5.4 Fabrication and measurement of the antenna**

*DOI: http://dx.doi.org/10.5772/intechopen.91695*

the results in states 1, 2, 3, and 4.

well with the simulated ones.

**6. Conclusion**

**Abbreviations**

**241**

FP Fabry-Pérot FPC Fabry-Pérot cavity MS metasurface

PRS partially reflection surfaces

**Figure 22** shows the photograph of the fabricated antenna. We measured the reflection coefficients and the radiation patterns of the antenna. Because of the symmetry of the PRS, the simulated and measured results of the antenna in states 2 and 6 (states 4 and 8 and states 3, 5, 7, and 9) are almost the same. So we just show

**Figure 23** plots the simulated and measured S11 of the antenna at states 1, 2, 3,

and 4. **Figure 23a** is the result under *x*- polarization and **Figure 23b** is under *y*-polarization. The measured impedance bandwidth of the antenna is 5.4–5.6 GHz (3.6%). Because the feeder of the antenna remains constant in different states, the S11 of the antenna in different states varies very little. The measured results agree

*Reconfigurable Fabry-Pérot Cavity Antenna Basing on Phase Controllable Metasurfaces*

The radiation patterns of the antenna are measured in anechoic chamber. **Figure 24** plots the measured results of the antenna. **Figure 24a** is the radiation pattern of the antenna at states 1 and 3 in the plane of *φ* = 0°, **Figure 24b** is at states 1 and 3 in the plane of *φ* = 45°, and **Figure 24c** is at states 1 and 4 in the plane of *φ* = 90°. The results show that the main beam of the antenna is in the +*z* direction at state 1 and tilts in the plane of *φ* = 0°, *φ* = 45°, and *φ* = 90° at states 2, 3, and 4, respectively. The tilted angle at states 2 and 4 is 10° and that at state 3 is 8°. The maximum gains of the antenna at different states are also measured. The antenna achieves maximum gain of 9.7 dB at state 1, 8.9 dB at state 3, and 8.7 dB at states 2 and 4. Meanwhile, the antenna obtains stable gain at all states. The gain floating of the antenna at all states are less than 2.3% within the impedance bandwidth. **Table 5** summarizes the antenna performance. The beam tilted angle and gain are measured results and the directivity is simulated results. The aperture efficiency is calculated by the gain and size of the antenna, as shown in Eq. (12). And the radiation efficiency is calculated by the gain and direction, as shown in Eq. (13).

*<sup>η</sup>*<sup>1</sup> <sup>¼</sup> *<sup>G</sup> <sup>λ</sup>*<sup>0</sup>

In this chapter, we summarize our recent efforts in realizing reconfigurable FPC antenna basing on the reconfigurable MS. PIN diodes are added on the MS to realize the reflection phase control. Using the flexible phase control capability of the MS, it is easy to tune the frequency and radiation pattern of the FPC antenna, so as to realize reconfigurable FP antenna. The reconfigurable FPC antenna is a good way to improve the performance of antenna. This method can make the FPC antenna more

widely used in the field of wireless communication systems.

2

<sup>4</sup>*π<sup>A</sup>* (12)

*η*<sup>2</sup> ¼ *G=D* (13)

Through controlling the diodes in four parts of the PRS, the PRS can present nine different states, and the antenna obtains nine beam directions in both polarizations. **Table 4** gives the detailed information of the antenna at different states. Due to the PRS having the same function on different polarized waves, the antenna has the same beam direction at the same diode states for different polarizations.

**Figure 24.** *The radiation patterns of the antenna: (a)* φ *= 0°, (b)* φ *= 45°, and (c)* φ *= 90°.*


**Table 5.** *The antenna performance.*

### **5.4 Fabrication and measurement of the antenna**

according to Eq. (9) with the reflection phase of the unit cell when diodes are OFF.

*Advanced Radio Frequency Antennas for Modern Communication and Medical Systems*

Through controlling the diodes in four parts of the PRS, the PRS can present nine different states, and the antenna obtains nine beam directions in both polarizations. **Table 4** gives the detailed information of the antenna at different states. Due to the PRS having the same function on different polarized waves, the antenna has the same beam direction at the same diode states for different polarizations.

After being optimized, the h is set to 28 mm.

*The radiation patterns of the antenna: (a)* φ *= 0°, (b)* φ *= 45°, and (c)* φ *= 90°.*

**Direction (dBi)**

 0 9.7 12.5 27.3 52.5 10 8.7 12 21.7 46.8 8 8.9 11.9 22.7 50.1 10 8.7 12 21.7 46.8 8 8.9 11.9 22.7 50.1 10 8.7 12 21.7 46.8 8 8.9 11.9 22.7 50.1 10 8.7 12 21.7 46.8 8 8.9 11.9 22.7 50.1

**Aperture efficiency (%)**

**Radiation efficiency (%)**

**Gain (dB)**

**Figure 24.**

**Table 5.**

**240**

*The antenna performance.*

**States Beam tilted angle (°)**

**Figure 22** shows the photograph of the fabricated antenna. We measured the reflection coefficients and the radiation patterns of the antenna. Because of the symmetry of the PRS, the simulated and measured results of the antenna in states 2 and 6 (states 4 and 8 and states 3, 5, 7, and 9) are almost the same. So we just show the results in states 1, 2, 3, and 4.

**Figure 23** plots the simulated and measured S11 of the antenna at states 1, 2, 3, and 4. **Figure 23a** is the result under *x*- polarization and **Figure 23b** is under *y*-polarization. The measured impedance bandwidth of the antenna is 5.4–5.6 GHz (3.6%). Because the feeder of the antenna remains constant in different states, the S11 of the antenna in different states varies very little. The measured results agree well with the simulated ones.

The radiation patterns of the antenna are measured in anechoic chamber. **Figure 24** plots the measured results of the antenna. **Figure 24a** is the radiation pattern of the antenna at states 1 and 3 in the plane of *φ* = 0°, **Figure 24b** is at states 1 and 3 in the plane of *φ* = 45°, and **Figure 24c** is at states 1 and 4 in the plane of *φ* = 90°. The results show that the main beam of the antenna is in the +*z* direction at state 1 and tilts in the plane of *φ* = 0°, *φ* = 45°, and *φ* = 90° at states 2, 3, and 4, respectively. The tilted angle at states 2 and 4 is 10° and that at state 3 is 8°. The maximum gains of the antenna at different states are also measured. The antenna achieves maximum gain of 9.7 dB at state 1, 8.9 dB at state 3, and 8.7 dB at states 2 and 4. Meanwhile, the antenna obtains stable gain at all states. The gain floating of the antenna at all states are less than 2.3% within the impedance bandwidth. **Table 5** summarizes the antenna performance. The beam tilted angle and gain are measured results and the directivity is simulated results. The aperture efficiency is calculated by the gain and size of the antenna, as shown in Eq. (12). And the radiation efficiency is calculated by the gain and direction, as shown in Eq. (13).

$$
\eta\_1 = G \frac{{\lambda\_0}^2}{4\pi A} \tag{12}
$$

$$
\eta\_2 = \mathbf{G}/\mathbf{D} \tag{13}
$$
