A Switchable Linear to Circular Polarization Converter Using PIN Diodes

In this paper, we present a method to design a switchable polarizer using p-i-n diodes. An antenna-filter-antenna architecture with four metal layers (receiving and transmitting radiating elements, ground plane, and bias lines) is implemented to convert an impinging linearly-polarized electromagnetic wave to a circularly-polarized one. Furthermore, by controlling opportunely the bias current flowing on the two pi-n diodes flip chipped on the transmitting radiating element, the transmission wave can be switched to either left-handed circular polarization (LHCP) or right-handed circular polarization (RHCP). Full-wave electromagnetic simulations of a single element show a transmission loss < 0.8 dB for both polarization (LHCP/RHCP) and 180° phase difference in the frequency band (27 - 31 GHz).