Low voltage medium power class C power amplifier with precise gain control

Abstract

A non-linear power amplifier for amplifying a constant envelope phase modulation component of a modulation signal and combining an amplitude envelope component of the modulation signal into the amplified constant envelope phase modulation component and method for performing the same. The power amplifier receives a constant envelope phase modulation signal and transmits the signal through a pair of amplifier stages which are impedance matched together. The first amplifier stage has a fixed gain which drives an impedance load and, in turn, the second amplifier stage. A variable resistance device is connected between a base of an amplifying transistor in the second amplifier stage and electrical ground for variably controlling the gain of the second amplifier stage by variably controlling the base-to-ground resistance of the amplifying transistor in the second amplifier stage. By varying the base-to-ground resistance of the amplifying transistor, the pulse width, gain, and power output of the constant envelope phase modulation signal can be controlled. The amplitude envelope component of the modulation signal is then reintroduced into the amplified constant envelope phase modulation component at a low current point between the base of the amplifying transistor and the variable resistance device, which enables the power amplifier to be operated with a low current consumption.

Dependencies are inferred from the claim text.