Abstract: A power amplification system and method for generating low power radio frequency signals. A coupler divides a received signal to be amplified into first and second components. First and second driver stages individually amplify the first and second components. During a low power operation the first and second components of the divided signal are combined in a coupler. In a high power operation, the first and second components are supplied to first and second output amplifiers. The output amplifiers are interconnected so that the amplified signals are combined in the second coupler. The output amplifiers may be output at peak efficiency, using a constant input signal level during the high power mode of operation. During the lower power operation, the driver stages produce the output signal levels.

Abstract: Apparatus and method for reducing reflected power in a radio frequency amplifier. A first directional coupler divides the radio frequency signal to first and second quadrature signals. First and second amplifiers amplify each of the quadrature signals. A second directional coupler combines signals from the amplifiers to produce a combined signal. A third directional coupler samples a portion of the reflected power received on the second directional coupler output. A control signal is derived from sampling the reflected power. A variable load impedance connected to the remaining output port of the second directional coupler has an impedance value which changes with respect to a control signal and the impedance is varied so as to substantially match the impedance received by the first output port.

Abstract: A re-entrant, low-pressure, electrodeless lamp apparatus includes two identical re-entrant center conductors driven in quadrature, resulting in a matched lamp input impedance in both the off and on states nearly independent of incident microwave power.