An analog adaptive feedforward amplifier linearizer

Feedforward is a wideband linearization method capable for third generation mobile communication systems. However, it requires automatic adaptation of key parameters for reliable distortion cancellation as operating conditions vary. This paper presents a novel time-continuous adaptive compensation technique for the amplitude and phase imbalances of feedforward amplifiers. In contrast to algorithm-based digital techniques, the proposed method can be implemented entirely with analog circuitry and, consequently, enables a fully integrated low-cost analog adaptive feedforward linearizer. The functionality of the proposed analog adaptive feedforward amplifier is verified by means of simulations. Results for a WCDMA signal demonstrate that the adaptation is sufficiently fast and accurate with the out-of-hand power being suppressed to below -50 dBc.