Adaptive feedforward amplifier using digital controller

We designed and implemented a feedforward amplifier for WCDMA base station. The feedforward amplifier has the capability of adjusting the center frequency of linearization loops to get the better cancellation performance in the interesting frequency band. The controller detects the power of the pilot signal and the frequency of the pilot signal can be changed for the better cancellation performance in the interesting frequency band. The principles of control algorithm and the cancellation performance of the implemented feedforward amplifier are presented in this paper. The cancellation performance of the 1st loop is about 20 dB over 2110 MHz ∼ 2170 MHz and 20 dB for the 2nd loop over 2090 MHz ∼ 2190 MHz. For two-tone test the IMD cancellation performance is about 25 dB. For WCDMA signal, the cancellation performance is about 14 dB.