**5. Polarization and pattern reconfigurable FPC antenna**

#### **5.1 Design of the reconfigurable PRS**

In the last section, we design an FPC antenna with large beam steering angle. However, it can only realize beam tilting in one plane. In practice application, we prefer the antenna to be able to steer the beam in two directions. So in this Section, we will design a configurable PRS to realize two-dimensional beam steering of the FPC antenna [17].

The unit cell of the PRS is shown in **Figure 17**. It is also printed on the substrate of FR4. Each unit cell consists of four square patches. Four PIN diodes are inserted between two adjacent patches. The four diodes are controlled simultaneously, and the

**4.3 Fabrication and measurement of the antenna**

**Figure 15.**

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The photograph of the fabricated antenna is shown in **Figure 14**. After simulation, we find that the antenna can work in at kinds of states. We measured the S11 and radiation patterns of the antenna in these 11 states. **Table 3** gives the detail performance of the antenna in different states, including the states of the diodes, beam directions, and maximum gain. Because the antenna structure at state 2 (4, 6, 8, 10) is completely symmetrical to that at state 3 (5, 7, 9, 11), so they have same the S11. For simplicity, we just show the simulated and measured S11 in states of 1, 2, 4, 6, 8, and 10 in **Figure 15**. The measured results agree well with the simulated ones. The measured impedance bandwidth of the antenna is 4.92–5.08 GHz (3.2%). The

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

S11 of the antenna only has little difference between different states.

*Simulated and measured S11: (a) states 1, 2, and 4 and (b) states 6, 8, and 10.*

The radiation patterns of the antenna are measured in anechoic chamber. The simulated and measured radiation patterns of the antenna are presented in **Figure 16**. Good agreement is obtained between the measured results and the simulated ones. We know that the main beam of the antenna tilts in *xoz* plane,

unit cell can present two states. The unit cell has different reflection coefficients in different states. The reflection coefficients of the unit cell are simulated by the CST, and the results are shown in **Figure 18**. We can see that the unit cell has the same reflection coefficients for both polarization waves. The reflection phases of the unit cell in two states at 5.5 GHz are 187° and 217°, respectively. And the reflection magnitude is always larger than 0.75. This suggests that the unit cell remains to have high reflectivity when tuning the reflection phase through controlling the state of the diodes. The high reflectivity ensures the high gain of the antenna.

We compose a PRS with 6 6 unit cells by the unit cell shown in **Figure 17**. The top view of the PRS is shown in **Figure 19**. The PRS is divided into four parts. The diodes in different parts can be controlled independently. Through tuning the state of the diodes in different parts, the PRS presents different reflection phase distributions. A DC biasing circuit is designed on the PRS to realize independent control of the diodes in different parts. Two patches of each unit cell are connected to the biasing lines on the bottom side of the PRS through metalized via holes. By reasonably arranging the orientation of the diodes in each unit cell, the diodes can be controlled simultaneously. The biasing lines on the bottom of the PRS are shown in **Figure 20b**. The biasing point V1, V2, V3, and V4 are connected to the anode of the

> DC source, and the Gnd is connected to the cathode. The width of the biasing line is 0.2 mm, and the diameter of the metalized via holes is 0.3 mm to reduce the

> 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.

influence of biasing lines on the RF signal.

*The structure of the PRS: (a) top view and (b) bottom view.*

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

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

**Figure 19.**

**Figure 20.**

**237**

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

*Polarization configurable feeder antenna: (a) top view and (b) side view.*

**Figure 18.** *The reflection coefficients of the unit cell.*

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

**Figure 19.** *The structure of the PRS: (a) top view and (b) bottom view.*

**Figure 20.**

unit cell can present two states. The unit cell has different reflection coefficients in different states. The reflection coefficients of the unit cell are simulated by the CST, and the results are shown in **Figure 18**. We can see that the unit cell has the same reflection coefficients for both polarization waves. The reflection phases of the unit cell in two states at 5.5 GHz are 187° and 217°, respectively. And the reflection magnitude is always larger than 0.75. This suggests that the unit cell remains to have high reflectivity when tuning the reflection phase through controlling the state of the

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

We compose a PRS with 6 6 unit cells by the unit cell shown in **Figure 17**. The top view of the PRS is shown in **Figure 19**. The PRS is divided into four parts. The diodes in different parts can be controlled independently. Through tuning the state of the diodes in different parts, the PRS presents different reflection phase distributions. A DC biasing circuit is designed on the PRS to realize independent control of the diodes in different parts. Two patches of each unit cell are connected to the biasing lines on the bottom side of the PRS through metalized via holes. By reasonably arranging the orientation of the diodes in each unit cell, the diodes can be controlled simultaneously. The biasing lines on the bottom of the PRS are shown in **Figure 20b**. The biasing point V1, V2, V3, and V4 are connected to the anode of the

diodes. The high reflectivity ensures the high gain of the antenna.

**Figure 17.**

**Figure 18.**

**236**

*The reflection coefficients of the unit cell.*

*The unit cell of the PRS.*

*Polarization configurable feeder antenna: (a) top view and (b) side view.*

DC source, and the Gnd is connected to the cathode. The width of the biasing line is 0.2 mm, and the diameter of the metalized via holes is 0.3 mm to reduce the influence of biasing lines on the RF signal.
