A Single-Layer Broadband Linear-to-Circular Polarization Reflectarray With 45° Offset Feed for Ka-Band Communications

A millimeter-wave broadband circularly polarized reflectarray with a linearly polarized (LP) source at 45 degrees incidence/reflection based on a single-layer dielectric substrate is introduced. The array element consists of a Jerusalem cross and four straight strips with the end capacitive loading, which provides a 360 degrees phase range and shows a linear phase response in the wide frequency band. When TM and TE polarized waves are incident/reflected at large angles, the additional T-shaped and loop-shaped resonances are generated, respectively, causing the array performance to deteriorate. In this case, the influence of the T-shaped resonance is reduced by arranging elements with phase distortion as far away from the center of the reflectarray surface as possible. Meanwhile, the impact of the loop-shaped one is diminished by choosing the specific phase curve to average the phase compensation discrepancy. Then, the reflectarray with 24x24 cells is designed, fabricated, and measured. The measured results have a good agreement with the simulated ones. The measured 1 dB gain and 3 dB axial ratio bandwidths are 13.9% and 28.8%, respectively. The peak gain is 26.22 dBi at 37.5 GHzand the aperture efficiency is 32.1%, which is comparable to that of the excellent LP reflectarray at 45 degrees incidence/reflection.