This study reports an evaluation of the maximum axial ratio (AR) bandwidth which is obtainable from a transmission type linear (LP) to circular polarization (CP) convertor working at normal incidence. The anisotropic bandpass FSS structure is composed of a thin metal surface perforated with an array of unequal length orthogonal slots. Full wave simulations are used to study the effect of changing the physical dimensions of the individual slot structural parameters by computing the amplitude and phase of the TE and TM transmitted waves at normal incidence over the frequency range 8‐12 GHz. The results are used to establish design guidelines which are employed to obtain the optimum topology for a single layer LP to CP convertor working at a center frequency of 10 GHz. The numerical results which are shown to be in close agreement with measurements, demonstrate that this class of periodic structure can be designed to give a 3 dB AR fractional bandwidth of 5.0%.

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In this article, we investigate the electromagnetic behavior of freestanding and dielectric embedded frequency selective surface (FSS) based linear to circular polarization convertors. The two structures were designed to operate in transmission mode at normal incidence and yield the lowest value for axial ratio (AR) at frequencies around 10 GHz. In addition to providing mechanical robustness, a 72% increase in the 3 dB AR bandwidth (BW) is achieved when the 140‐μm thick perforated FSS sheet is inserted between two 5‐mm thick polytetrafluoroethylene (PTFE) slabs. At oblique incidence a downward shift in frequency is observed, however the BW is still significantly larger than the results obtained for the freestanding periodic array within a field of view of ±30° in the cardinal planes. Spectral transmission measurements presented for both anisotropic media verify the simulated results.

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This paper describes a new design strategy which is used to obtain a fivefold increase in the 3 dB axial ratio bandwidth of linear to circular polarization convertors based on anisotropic frequency selective surfaces composed of single screens of cross slots. The performance improvement is obtained by employing stratified dielectric media to carefully tailor the shape of the TE and TM spectral transmission responses. We demonstrate that a bandwidth of 24.5% can be achieved at a center operating frequency of 10.6 GHz using an array of unequal length cross-slots embedded centrally between two 2.25 mm thick dielectric slabs (ε r = 9.0). Moreover it is shown that the inherent self-filtering behavior of the structure provides greater rejection of unwanted signals than designs embedded in lower permittivity material. Computed and experimental axial ratio results are compared to verify the new design methodology.