Clover polarimetric detector - a novel design of an ortho-mode transducer at 150 and 225 GHz

This paper presents the design of an ortho-mode transducer (OMT) to separate two orthogonal linearly polarized signals traveling in a circular waveguide with frequency channels at 150/255 GHz band. Simulations (in HFSS) are presented to determine the optimal probe geometry and feed impedance to achieve good coupling to the optimized probes over a wide bandwidth with corresponding feed impedances for telescopes operating at 150 and 225 GHz. The results show that at 150 GHz band, the return loss can reach below -20 dB from 126 GHz to 180 GHz with the cross polarization reach below -40 dB. At 225 GHz band, the return loss can reach below -20 dB from 190 GHz to 260 GHz with the polarization isolation more than 32 dB.