Time and frequency domain analysis and design of circularly-polarized spiral antenna arrays

A circularly polarized metal-backed hexagonal array operating over multi-octave bandwidth is presented. A four-arm spiral antenna designed to have simultaneously good time (TD)-and frequency-domain (FD) performances and a simple mode-former is used as a unit cell. The antenna arms are resistively loaded to improve its VSWR and reduce interaction with the ground plane. Experiments verify excellent TD/FD performances with fidelity factor > 90%, VSWR<; 2:1, axial ratio <; 1dB, side lobe level (SLL) <; -10dB, and high efficiency.