A Low-Profile Broadband Circularly Polarized Antenna Array for UAV Ground-to-Air Communication

A low-profile circularly polarized microstrip antenna array for the UAV communication system is presented in this paper. A broadband phase-shift network and two circular capacitive slots are both used to broad the bandwidth of the array element in S-band. The simulation results of the array element show that its relative bandwidth is 21.7% with AR <3dB, gain greater than 5 dBic and VSWR ≤1.25. A sunflower-shaped array layout applied to the UAV platform is proposed. This novel antenna array consists of 17 array elements whose height is 16mm (O.122o) respectively. Compared to antenna elements, the sunflowershaped antenna array performs better circularly polarization at all scanning angles. The simulation results of the sunflowershaped array show that its beam-scanning angles can be ±45° with AR <3dB. The active VSWR of this array is less than 1.6 and the gain is greater than 16dBic in the operating band.