# Design of a 3-Bit Circularly Polarized Reconfigurable Reflectarray
## 3 Fabrication and Measurement Results
It is noted that the axial ratio and gain bandwidth in the measurement result are slightly shifted toward the high frequency, and the gain decreases compared with the simulation result. Combined with the measurement results of the feed antenna shown in Figures 7 and 12d, it can be seen that the feed antenna's axial ratio bandwidth is also shifted toward the high frequency, and the gain value of the low frequency in the measurement result is somewhat decreased compared with the simulation result. It is shown that the feed antenna is one of the important factors that causes the deviation between the simulation and measurement results. In addition, the machining and assembly errors of the array will also cause the deviation between the simulation and measurement results, but, in general, the antenna still has a good performance. Figures 13 and 14 show the measurement results of the antenna beam scanning direction pattern in the xoz plane and yoz plane at the four frequency points of 3.45 GHz, 3.5 GHz, 3.6 GHz, and 3.7 GHz, respectively. It can be seen that the designed antenna can achieve a \(\pm 60^{\circ}\) beam scanning range in these frequency points and two planes, and the sidelobe level is low. Figure 15 shows the comparison results of the axial ratio and gain obtained via the simulation and measurements at each scanning angle at 3.5 GHz. It can be seen that the measurement results are in good agreement with the simulation results. When scanning in two scanning planes, the axial ratio is less than 3 dB. When scanning in the xoz plane, the gain is reduced to less than 3 dB compared to the normal direction. When scanning in the yoz plane, the gain in the normal direction is reduced to less than 4 dB due to the effect of the feed and its support. Due to the decrease in the measured gain of the feed antenna, the error of machining and assembly, and the influence of the actual working environment of the PIN diode, the measured gain is slightly lower than the simulation, but the overall performance is in good agreement. Figure 11: Sample of the 3-bit circularly polarized reconfigurable reflectarray: (**a**) sample and (**b**) test scene. Figure 12: Diagram of antenna operating characteristics at 0\({}^{\circ}\) beam pointing. Radiation pattern: (a) xoz plane and (b) yoz plane. (c) Gain and axial ratio. (d) Gain of the feed antenna. Figure 13: Measurement results of antenna beam scanning at different frequencies (xoz plane): (a) 3.45 GHz, (b) 3.5 GHz, (c) 3.6 GHz, and (d) 3.7 GHz. The reflection phase of each element in the circularly polarized reconfigurable reflect-array proposed in this paper can be controlled independently. The designed antenna can not only realize the beam scanning performance shown above, but it can also realize the functions of multi-beam and beamforming. In order to verify this, a double-beam radiation pattern with beam directions of \(\pm 35^{\circ}\) in the xoz plane was designed using the method of aperture field superposition. A simulation and measurement analysis were carried out for the designed antenna. The comparison between simulation and measurement results is shown in Figure 16. It can be seen that the measurement results are in good agreement with the simulation results in the two orthogonal planes. The two beams are directed at \(-35^{\circ}\) and \(34^{\circ}\), respectively, and the gain is 12.4 dB and 13.2 dB, respectively. Since the cross-polarization component is more than 15 dB lower than the main polarization component, it can be seen that the axial ratio performance is also better. Figure 14: Measurement results of antenna beam scanning at different frequencies (yoz plane): (a) 3.45 GHz, (b) 3.5 GHz, (c) 3.6 GHz, and (d) 3.7 GHz. Figure 15: Comparison of simulation results and measurement results of gain and axial ratio at different scanning angles: (a) xoz plane and (b) yoz plane.