Evaluation of a Novel Topology for MEMS Programmable Reflectarray Antennas

This paper presents a programmable reflectarray topology for passive beamforming at millimeter-wave frequencies. This topology relies on reconfigurable antenna-filter-antenna (AFA) elements and has a multilayer structure that makes it suitable for implementation as a monolithic MEMS device. We address different aspects of design, modeling, and characterization of the AFA elements and the reflectarray. A 2-bit reflective AFA element is introduced and studied using full-wave and hybrid models. An approximate bistatic reflectance model is proposed and used in a ray-based formulation to predict the radiation pattern of the reflectarray. The principle of operation, scanning performance, and modeling approach are validated experimentally using proof-of-concept reflectarray prototypes designed for 35 GHz. Pattern measurements in offset-fed and folded center-fed configurations show that the proposed topology is capable of wide-angle scanning in two dimensions. The measured scan loss is less than 2 dB for up to 45° scan in both E - and H -planes. The cross-pol level is < -11 dB in all cases, and the worst case sidelobe level is -9 dB. A near-scan-blindness behavior is observed for 60° scan in the E-plane. These results are consistent with the simulations, indicating the effectiveness of the bistatic reflectance model.