A 40-80 GHz quasi-optical balanced doubler using nested ring-slot antennas

A 40-80 GHz ring-slot antenna doubler has been designed for use as a local oscillator source for heterodyne receivers. The doubler is a quasi-optical design that has the potential for high efficiency operation and scaling for use at submillimeter-wave frequencies. Simulation results indicate that the multiplier can perform at 82% efficiency with 11 mW of available input power and 9 mW of output power. Design considerations and initial measurements on a prototype ring-slot doubler are presented and discussed. The prototype operates at an estimated 13% efficiency, and produces 0.53 mW of output power. This output power and efficiency are far less than the optimum predicted by simulation and we believe this is due primarily to inadequate input pump power being provided to the doubler.