A Novel Interdigital Capacitances (IDCs) Based Linear-Cross Reflective Type Polarization Converter for X- and Ku-Band Applications

A novel reflective type linear-cross polarizer is proposed in this article for X-and Ku-bands. This design consists of top FSS, including a dipole covered with Interdigital Capacitances (IDCs) on its periphery on a 2.6 mm thin FR-4 dielectric substrate. The structure exhibits Polarization Conversion Ratio (PCR) greater than 90% from 7.94 to 17.77 GHz (76.46% Fractional Bandwidth), with three resonant peaks approaching the PCR nearly 100%. For oblique incidence TE and TM, the response is stable up to 45° up to 80% PCR and slightly reduced bandwidth. Multiple plasmonic resonances are the reason behind the broadband polarization conversion, and it is investigated from the surface current profiles of top FSS and ground planes. The novelty of this design exists in the introduction of IDCs, enabling the highest resonant peak tuning without degrading the performance on the lowest side. It possesses the unitcell periodicity and thickness of 0.185 λL and 0.069λL, respectively, where λL is the lowest broadband frequency's free-space wavelength. The authors are confident in the design's compactness, low profile, and angular stability, making it well-suited for real-time applications that need broadband linear-cross polarization conversion.