A Broadband and Low-Loss Linear-to-Circular Polarization Converter for K-/Ka-Band Satellite Communications

A broadband linear-to-circular polarization converter (LCPC) with low insertion loss is proposed and implemented for K/Ka band satellite communications. The proposed converter comprises three equal-spaced dielectric substrates, where each layer has four asymmetric sectors together with two short strips printed in its top copper foil and a long metal grid printed in its bottom copper foil. The proposed structure introduces a stable phase difference of around 90° to two orthogonal components of the incident wave over a broad frequency band, resulting in a conversion from linear to circular polarization. A prototype is fabricated and measured, whose size is 286 mm × 286 mm × 6.762 mm. The measured results agree well with simulations, showing that a successful conversion is achieved over 18.0 GHz to 30.9 GHz (52.8%) with a low insertion loss of less than 1.65 dB. The axial ratio remains less than 3 dB when the oblique incidence angle increases to 25°. The proposed polarization converter is promising for K-/Ka-band satellite applications.