Adaptive compensation for microwave linearizer

This paper presents a new adaptive microwave linearizer compensation system against temperature drifts and operating frequency variations (1). The main principle rests on the fact that for a QAM modulated RF carrier the signal envelope exhibits a fixed peak value to average value ratio which depends only on the constellation and on the roll-off factor. It follows that the peak to average value ratio of the SSPA output signal envelope has to be constant when the SSPA operates in the linear amplitude region. Moreover the peak to average ratio decreases or increases as the amplifier goes through a gain compression or gain expansion due to a change in temperature, operating frequency or in any other parameter. Therefore it can be used as a criterion on which to base the amount of AM/AM compensation to be introduced by the linearizer. This method exhibits good performance in a wide range of temperatures and frequencies while employing easy to implement low cost hardware.