Proximity-coupled microstrip reflectarray

In this paper, a microstrip reflectarray on a two-layer substrate is presented. The delay lines were proximity-coupled to corners of patches. Compared with delay lines in a single-layer reflectarray, the delay lines used here play two important roles: phase delay and impedance match. As it is a two-layer structure, we can get more design flexibilities. For linear polarized waves, -3 dB gain bandwidth can be achieved to 22%. Antenna patterns with -15 dB side-lobe and -30 dB cross-polarization level can also be obtained. It is demonstrated that simple design formula used in a single-layer reflectarray can also be used for the present case.