A Polarization Reconfigurable Patch Antenna in the Millimeter-Waves Domain Using Optical Control of Phase Change Materials

We present the integration of GeTe (Germanium Telluride), a phase change material (PCM), within the structure of an antenna operating in the millimeter wave domain (~ 30 GHz) in order to make it reconfigurable in three polarizations: a linear polarization (LP), a left hand circular polarization (LHCP) and a right hand circular polarization (RHCP). The device is based on a conventional patch antenna excited by a microstrip line with the GeTe material integrated into the four corners of the patch. The phase change between the insulating (OFF) and metallic (ON) states of this material is controlled by direct irradiation using ultraviolet (UV) short laser pulses and allows the reconfigurability of the antenna between an LP, an LHCP and an RHCP. The measured performances of the fabricated device show axial ratios of less than 3 dB over a 400 MHz of bandwidth around 29.5 GHz with total efficiencies up to 75 % for the circularly polarized configurations and a maximum gain up to 8.3 dBi for the linear polarization states.