A hybrid ring coupler quasi-optical antenna-mixer

This paper proposes a hybrid ring coupler quasi-optical antenna-mixer for mitigating local oscillator retransmission. By demonstrating at K-band, the antenna element consists of back-to-back aperture coupled inverted square patch antenna to couple the RF signal at 18.8 GHz to the sigma port of a hybrid ring mixer while the LO signal at 17.5 GHz is coupled to the delta port. The HSCH-9101 Schottky diodes are used to transform the RF signal to the intermediate frequency signal at 1.3 GHz. The results show that the RF/LO isolation is better than 29 dB at 18.19 GHz, and the isotropic conversion loss of the down converted signal is better than 16 dB at 19.25 GHz. The application of the interest is an inverse measurement technique for dielectric property determination.