We present a quasi-optical frequency tripler with heterostructure barrier varactor (HBV) diodes soldered across two slot antennas and located at the focal plane of a dielectric lens. The slot antennas are fed from a WR-22 waveguide connected to a Gunn oscillator. A quasi-optical high-pass filter is used to tune the slot impedance and increase the conversion efficiency. The symmetric capacitance-voltage and asymmetric current-voltage characteristics of the HBV diodes only allows odd harmonics of the applied signal to be generated, and thus simplifies the frequency tripler design
