Distortion Reducing Means for Single-Sideband Transmitters

The need for reduced levels of intermodulation distortion products from linear rf power amplifiers is increasing as the state of the art advances. Two basic means of reducing distortion to levels better than is obtainable from available tubes are shown. One is direct rf feedback and the other is envelope distortion cancelling modulation. Some of the problems and limitations as well as advantages and performance characteristics are presented to aid the reader in evaluating these methods. RF feedback is a superior method, although useful amounts of distortion reduction can be achieved using envelope distortion cancelling modulation. A circuit of an amplifier combining both methods is shown which produces better performance than using either alone.