Design, Optimization and Verification of a Dual Band Circular Polarization Selective Structure

We present a non-resonant, dual band circular polarization selective structure (CPSS) for satellite communication applications in the K- and Ka-bands. The structure consists of multiple layers of cascaded anisotropic sheets, with printed meander lines, separated by low permittivity spacers. It reflects right handed circular polarization and transmits left handed circular polarization in the lower frequency band. In the upper frequency band the opposite polarization selectivity is achieved. The theory of dual band circular polarization selectivity from cascaded anisotropic sheets is presented. The separation between the frequency bands of operation is shown to be governed by the relative rotation between subsequent layers. An optimization routine for synthesizing dual band CPSSs from predefined design requirements is introduced, utilizing several different optimization algorithms. A simulated design is presented which fulfills the strict requirements of insertion loss and return loss less than 0.5 dB, and axial ratio less than 0.78 dB, in the frequency bands 17.7–20.2 GHz and 27.5–30.0 GHz. A prototype of the optimized design is fabricated and characterized experimentally, both in transmission and reflection. Good agreement is observed between simulated and experimental results. This type of structure is a potential candidate for implementation in dual band multiple spot beam systems utilizing frequency and polarization reuse schemes