A LINEAR AMPLIFIER ARRANGEMENT

摘要

This invention relates to high power linear amplifiers. A high power linear amplifier is disclosed for communications such as CDMA communication systems. In accordan ce with the invention, there is provided a linear power amplifier comprising a power amplifier, a feedback circuit and a control element; wherein the architectur e proposed uses an envelope detector to generate a baseband signal representing the amplitude envelope of the system input RF signal. This is digitised and used to genera te phase and gain correction signals. The correction signals modulate the input signa l to create a pre-distorted signal: which is applied to the power amplifier for amplification. The pre-distortion is such as to cancel the AM-AM and AM-PM distortion of the power amplifier thus resulting in an amplified output of improved spectral purity. In order to achieve the very high levels of spectral purity required by 3G cellular and multi-carrie r 2G cellular systems, the correction coefficients in the lookup table need to be very precisely set. The method proposed incorporates an adaptation system whereby the pre- distorter can 'learn' the contents of the lookup table as it operates.