A wideband circularly polarized antenna array using phase-gradient and amplitude-tapered technique for UAV communication

This letter presents a wideband circularly polarized antenna array for communication with unmanned aerial vehicle (UAV). The antenna array is composed of three substrate layers. The bottom substrate features an amplitude-tapered phase-coherent feeding network designed to enhance the axial ratio (AR) bandwidth and reduce the side lobe level (SLL), thus adapting to the complex communication environment of UAV. The middle layer contains 8 $8$ 8 phase-gradient feeding rings of uniform amplitude to increase the impedance bandwidth and stabilize the AR bandwidth. The top layer consists of 32 $32$ 32 basic radiating patches. The simulation and measurement results show that the antenna array achieves approximately 87.6 percent sign $%$ % of minus 10 $-10$ − 10 dB impedance bandwidth in the frequency range of 2.39 tilde 7.47 2.39~7.47 2.39 ~ 7.47 GHz. A 3 $3$ 3 dB AR bandwidth of 16.0 percent sign $16.0%$ 16.0 % is obtained in the range of 5.1 tilde 6.0 5.1~6.0 5.1 ~ 6.0