An adaptive feedforward amplifier for WCDMA base stations using imperfect signal cancellation

Abstract

This article describes a new adaptive feedforward amplifier for a WCDMA system using an imperfect signal cancellation. Due to the complicated signal statistics, the distortion generated by the error amplifier is significantly reduced by an imperfect signal cancellation. Therefore, the performances of feedforward amplifiers are improved with this new adaptation technique, especially for modulated signals with a high peak-to-average ratio. For verification, a 2.14 GHz feedforward amplifier, with 80 W output power, has been implemented and tested with digital control circuits. The results, compared to a perfect signal cancellation, show more than 7 dB improvement of adjacent channel leakage ratio (ACLR) at 80 W output power. The amplifier efficiency is also improved from 7.5 to 9 percent for the same ACLR.