Beam-steering antenna array based on a butler matrix feed network with CP capability for satellite application

In this paper, a broadband circularly polarized (CP) antenna array for beam-steering applications is presented. The antenna consists of a 2×2 antenna array of substrate integrated waveguide (SIW) CP slot elements fed by a Butler matrix network. Each SIW element is rotated sequentially with respect to each other to improve the array CP purity. To validate the performance of the proposed structure, a prototype is fabricated and measured. The measured results show an impedance bandwidth of 18% (9.15–10.92 GHz) for 0|S11|≤−1 dB and a minimum 3-dB axial ratio bandwidth from 9.4 to 10.1 GHz. The beam-steering antenna has about 25-degree scan angle with the peak gain of 14 dBi at 10 GHz.