Reflectarray Antenna Design With Arbitrary Incident and Reflection Beam Angle

Accurate unit-cell analysis and reflectarray synthesis are two key issues in reflectarray antennas design. In unit-cell analysis, forced linked boundary condition (FLBC) is proposed to emulate quasi-periodic reflectarray environment. We demonstrate that both incident and reflection angles affect the reflection phase of reflectarray elements. In reflectarray synthesis, a novel modes superposition synthesis method (MSSM) based on linear superposition of the unit TE and TM mode responses is proposed. The MSSM can take the real incident angles, polarizations of incident fields, and the quasi-periodic reflectarray environment into account. Two reflectarrays are designed to justify the proposed FLBC and MSSM. The first one is a low-profile broadside-radiating flat Cassegrain reflectarray featuring a 0.5 dB gain improvement after accounting for the effects of incident angle. The second is an offset-fed reflectarray achieving a 1.2 dB gain enhancement and lower sidelobes after taking the effects of both incident and reflection angles into account.