High Efficiency J Band Read IMPATT Amplifiers

This paper describes the development of an efficient, compact amplifier with a gain of 20 dB and an output of 2 W in J Band. An overall efficiency of greater than 10% was achieved using GaAs Read IMPATT diodes with Schottky barrier contacts in a three stage reflection amplifier. The severe gain compression that usually occurs with IMPATT amplifiers can present a considerable problem in that owing to the presence of a small-signal oscillation, there will be an output signal in the absence of an input signal. It is shown that by operating the IMPATT diode at a constant voltage and by appropriate selection of the Schottky barrier metal, the diode bias current will increase with increasing rf signal level thus achieving a more linear input-output characteristic. This allows higher gain at large signal levels together with stability at small signal levels.