THERMISTOR CONTROLLED GUNN OSCILLATOR AT KA-BAND

Frequency drift of Gunn oscillators is a major cause of concern in mos t of the Millimeter wave communication systems. This paper describes a simple and cost effective technique to arrest the frequency drift of a Ka band Gunn oscillator within 15 MHz for the operating temperature range of 0 degrees C to 60 degrees C as against a typical drift of abo ut 50 to 100 MHz for free running Gunn oscillator for the same tempera ture range. At the ambient, the oscillator remains within +/-1 MHz fro m switching on to stabilization. The temperature variation is sensed w ith a small thermistor bead placed close to the diode and a correction voltage is applied to the bias to compensate for the frequency drift. This compensation circuit also takes into account the non-linear beha viour of the thermistor and the Gunn oscillator with the temperature.