Design of a Dual-Polarized Broadband Single-Layer Reflectarray Based on Square Spiral Element

A dual-polarized broadband single-layer reflectarray antenna based on square spiral element is presented in this paper. Two designs with similar square spiral structures but different construction processes and transition patterns are investigated and compared. The comparison results show that the design varying the length of the first stub of one-arm square spiral is more suitable for building the reflectarray. Several 441-element reflectarray antennas fed by horn with different offset angles are also simulated and compared to show the broadband characteristic. A reflectarray with offset angle of 15 degrees is then fabricated and tested. The measured results show good radiation performances, and the 1-dB gain bandwidth of 34.7% is obtained. The measured gain is 27.1 dB at the center frequency of 15 GHz, which is equivalent to 45.6% aperture efficiency.