Multi-carrier high power amplifier using digital pre-distortion

Abstract

A distortion correction technique for use with a high power amplifier (HPA) in a multi-carrier radio signaling system such as a cellular base station. Distortion correction is implemented by making use of a broadband digital composite signal input to the high power amplifier as a reference signal in a form of intermediate frequency (IF) distortion correction circuit. A multichannel synthesizer provides the broadband composite signal to a broadband digital radio which in turn provides an input to the (HPA). A portion of the output signal from the HPA is fed back through a radio frequency (RF) and intermediate frequency (IF) down-conversion stage that uses the same IF and RF local oscillators that were used to generate the input signal to the HPA. This feedback signal is fed to a predistortion processor together with a version of the composite digital signal. The predistortion processor may perform a first crude amplitude correction procedure by finding a difference between the HPA feedback signal and the composite signal, to provide an offset to be loaded into a look-up table which is disposed between the broadband digital synthesizer and the broadband digital radio,. Subsequent precise correction and distortion correction procedures are performed using the offset value.