A compact modulator circuit with high current protection for low chirp pulsed IMPATT oscillator

Abstract

A compact pulsed modulator circuit is presented which can drive pulsed IMPATT diode at Ka band with peak current of 18A and duty ratio of 0.04%. A TTL pulse generator circuit using solid state delay is developed for driving the bias circuit which has a good temperature stability. A protection circuit is also incorporated to prevent burn-out of the diode at high current. A Ka band pulsed IMPATT oscillator is designed and developed using the pulse modulator. Very low chirp is obtained using constant current source and varying the slope of the bias current pulse. A peak power of 12W has been realized with a chirp bandwidth of 150 MHz.