Performance Comparison of Loop Based Polarization Dependent/ Independent Reflectors for Microwave Frequency Bands

This paper presents performance analysis of Frequency selective reflecting surfaces (FSSs) based on rectangular, elliptical and rhombic loop unit elements respectively. Two orthogonally oriented configurations of polarization dependent (PD) arrays of rectangular loop, elliptical loop and rhombic loops are designed and their transmission characteristics under normal electromagnetic (EM) wave incidence are studied for comparison. These orthogonal PD arrays are first cascaded on both sides of the dielectric substrate as back-to-back (BTB) configurations and then merged and patterned on same side of the substrate. The transmission responses of both BTB and merged FSSs configurations are studied and compared. Later, all these FSSs are evaluated under oblique EM incidences. Although all FSSs maintain stable response even under oblique incidence in the microwave frequency bands, rectangular loop based FSSs provide excellent stability in their transmission responses. Merged FSSs outperform PD and BTB FSSs in the form of bandwidths (BWs) over which angular stable (AS) and polarization independent (PI) transmission responses are preserved. Merged rectangular loop (MRECT) FSS and Merged elliptical loop (MELIP) FSS remain AS and PI over 2.67 GHz and 1.65 GHz wide frequency bands respectively while Merged rhombic loop (MRL) FSS preserves AS and PI over 0.57 GHz wide frequency band.