Patent ID: 7183843

Claim:
An electronically tuned power amplifier apparatus comprising: a main power amplifier circuit comprising: a first large signal amplifier; a second large signal amplifier; and a main power amplifier output quadrature hybrid circuit having an isolation port, an input port, and two output ports, wherein a first of the two output ports of the main power amplifier output quadrature hybrid circuit is coupled to an output of the first large signal amplifier of the main power amplifier circuit, and a second of the two output ports of the main power amplifier output quadrature hybrid circuit is coupled to an output of the second large signal amplifier of the main power amplifier circuit; and an injection power amplifier circuit configured to provide an injection signal into the isolation port of the main power amplifier output quadrature hybrid circuit, wherein the injection signal controls impedance seen by the first and second large signal amplifiers of the main power amplifier circuit.