# Dual-Polarized Multi-Beam Fixed-Frequency Beam Scanning Leaky-Wave Antenna
## 3 Results and Discussion  
To verify the design, the antenna system prototype shown in Figure 7 is fabricated for the actual measurement. The prototype comprises three main components: a beam control board, a USB2 ANY module, and the proposed LWA array. The host computer connects to the beam control board via the USB2 ANY, while the six voltage output channels of the board are connected to the metal vias of the DC bias lines of the LWA array through Dupont wires. By using specialized control software, the beam control board can be commanded to adjust the voltage loaded on both sides of the varactor diode, thereby enabling flexible beam regulation. The results are presented in Figure 8, and it can be seen that the S-parameters perform well in the range of 3.3 to 3.8 GHz. Specifically, the reflection coefficients of X-polarized and Y-polarized antennas are below \(-10\) dB in the operating frequency band. Figure 6: Simulated far-field radiation of the antenna at 3.5 GHz. 3-D far-field radiation patterns (**a**) backward scanning, (**b**) forward scanning; X-polarized antenna with (**c**) small capacitance state and (**d**) large capacitance state; Y-polarized antenna with (**e**) small capacitance state and (**f**) large capacitance state. The beam sweep performance of the antenna at a fixed frequency is indicated in Figure 9. The LWA can provide three dual-polarized beams. Antenna 1 and antenna 2 are the same set of dual-polarized fixed frequency scanning antennas with a common scanning area of \(-16^{\circ}\) to \(19^{\circ}\) at 3.5 GHz. Antenna 3 and antenna 4 have a common scan area of \(-6^{\circ}\) to \(29^{\circ}\) at 3.5 GHz. From the results of the measured radiation patterns, although the maximum beam scan range of antenna 1 in the multi-beam state can cover \(-28^{\circ}\) to \(19^{\circ}\), considering the comprehensive dual-polarized performance, each group of dual-polarized antenna common beam scan range is about \(35^{\circ}\). Taking antenna 3 as an example to analyze the test results, when the bias voltage range varies from 0 V to 12.6 V, the capacitance of the varactor diode changes from 4.7 pF to 0.6 pF, and the antenna scans from \(29^{\circ}\) to \(-4^{\circ}\). The side beam level of the antenna is more than 10 dB lower than the main beam level during the entire scan. The differences between the measurement results and the simulation results may be due to the different parasitic parameters generated by the varactor diode when high and low voltages are applied, which cannot be accurately simulated by the simulation software. Next, we will investigate the single-beam mode and the multi-beam mode. The measured radiation patterns are displayed in Figure 10 when the different feeding ports of the antenna array are excited. The antenna array can produce multiple directional radiation beams when fed individually from different ports, which is a multi-beam operation. The X-polarized antenna gain ranges from 9.7 to 9.9 dBi with a 3 dB beam width of about \(9^{\circ}\), while the Y-polarized antenna gain ranges from 11.3 to 11.7 dBi with a 3 dB beam width of about \(11^{\circ}\). When multiple ports are fed simultaneously, the antenna array can generate  
Figure 8: Measured S-parameters of the LWA array. (**a**) X-polarized antenna, (**b**) Y-polarized antenna. Figure 7: Experimental sample of the dual-polarized multi-beam scanning antenna system. a wider beam, which is the single-beam working state. The X-polarized antennas have a beam width of about 31\({}^{\circ}\), and the Y-polarized antennas have a beam width of about 32\({}^{\circ}\) in the single-beam working state. The scanning range of the single beam can be flexibly adjusted by varying the voltage value of the varactor diode on the antenna, allowing for a total scanning range of approximately 55\({}^{\circ}\), with the ability to scan from \(-27^{\circ}\) to 28\({}^{\circ}\).