Compensation of delay within an analog predistortion module used to linearize a dual-band RF transmitter

摘要

Analog predistortion (APD) is used to linearize a power amplifier (PA) whose input is composed of two radio frequency (RF) signals that are modulated onto separate carriers. The APD has two processing paths: a RF path for the linear signal and a baseband (BB) path for the signal that compensates for intermodulation distortion (IMD) generated by the nonlinear PA. Time misalignment between the RF and BB paths degrades the effectiveness of the APD. The conventional solution adds a bulk delay to the RF path, but it is expensive to implement in a RFIC. It is proposed that the degradation be reduced using memory basis waveforms within the APD model and introducing a phase shift between the two input signals prior to entering the BB path.