Abstract: A multistage radio frequency (RF) signal power amplifier is described that utilizes microstrip transmission line techniques for realizing essentially all of the matching circuitry for each stage of amplification. The power amplifier includes a variable gain predriver, a driver amplifier and a pair of paralleled final amplifiers, all of which are intercoupled by microstrip coupling circuitry. A power detector senses the magnitude of the final amplifier output and provides a forward power signal having a magnitude proportional thereto. A power output regulator is responsive to the forward power signal for providing a drive signal for varying the gain of the predriver amplifier to maintain the magnitude of the final amplifier output at a preset magnitude. The RF signal power amplifier further includes spurious signal suppression circuitry coupled to the output of the driver amplifier and final amplifiers for suppressing spurious signals generated by regenerative modes of oscillation occurring therein.

Abstract: Impedance matching circuitry is described that utilizes a plurality of series coupled microstrip transmission lines of different characteristic impedances for matching a radio frequency (RF) signal power amplifier to a predetermined output impedance, such as, for example, 50 ohms. Each of the microstrip transmission lines are successively coupled to the relatively low impedance output of a transistor of the power amplifier that is desired to be matched to the predetermined output impedance. Each of the successively coupled microstrip transmission lines has a greater characteristic impedance than the previously coupled microstrip transmission line for achieving the desired impedance match. The series coupled microstrip transmission lines not only match the power amplifier transistor to the predetermined output impedance, but also suppress regenerative oscillations which may occur when the power amplifier transistor is subjected to impedance mismatches.