A systematic circuit-based approach to efficiently realize single- and dual-band circular polarizers

摘要

This paper describes a systematic circuit-based approach which streamlines the realization of linear-to-circular polarizers. Two demonstrative designs are presented and the related challenges and opportunities are discussed. The first design is a low-loss polarizer, composed of two identical frequency selective surfaces (FSSs). The reduced number of layers yields a total profile of one-tenth of a wavelength, while providing high polarization purity and high transparency. This design features axial ratio of less than 3 dB (1 dB) over 10% (4%) fractional bandwidth, with low insertion loss of 0.5 dB (0.36 dB). The second design is a dual-band polarizer comprised of five FSS layers, which demonstrates low insertion loss of 0.6 dB and 4 / 2.7% bandwidth at 20 / 30 GHz. The unit cell used to realize the equivalent circuit elements of the polarizers is based on a subwavelength FSS grid, the so-called modified Jerusalem cross, recently introduced in the literature. The low profile and compactness of this cell (0.17λ0×0.17λ0×0.11λ0) enhance the accuracy of the circuit-driven approach, relax the computational analysis, and could potentially reduce the sensitivity to the angle of incidence. In particular, the low insertion loss of such designs makes them appealing for a variety of terrestrial and satellite applications.