The use of Baritt diodes in self-oscillating mixers

Baritt diodes were used to construct single sideband X and C-band waveguide mixers which gave conversion gain up to an IF frequency of 200 MHz. Within this band gain variation of 4 to 6 dB and noise figures of 11 to 14 dB were measured. The microwave circuit could also be used as a reflection amplifier and gave gains greater than 8 dB over a 300 MHz bandwidth, with noise figures in the range 8-10 dB. It was clear that in the mixer the Baritt diode was functioning as a small signal amplifier, mixer and large signal oscillator. A model for the Baritt diode was developed which considered the effects of space charge, a variable plane for charge injection and velocity modulation in the drift region. In particular the effects of the temperature were studied and a thermovision microscope was used to measure the temperature of the diode.