Feedforward amplifier using power sensors for the loop balancing

Adaptively controlled feedforward amplifiers are discussed in a large number of publications over the past years. So far, for the control of the distortion cancellation loop it seemed inevitable to implement a baseband processing unit at the output of the amplifier if the use of a pilot carrier should be avoided. This paper analyzes a modified feedforward structure, in which power sensors are used to provide the input signals for the loop controllers. The limits of this approach are discussed and measurement results for a 40 W GSM2+ (EDGE) power amplifier are presented.