POWER AMPLIFIER LINEARIZATION USING DIGITAL PREDISTORTION

Predistortion may be employed to avoid distortion in the output of a power amplifier (PA) in a transmitter, while maintaining transmit power. An active transmission signal, instead of test tones, may be used for training a predistorter for the PA, and for the entire analog transmit path of the transmitter, via a loopback path from the output of the PA to the input of a receiver path. The transmitter may include an upconverter, and the receive path may include a downconverter, which may therefore both be included in the loopback path, helping eliminate phase noise. The predistortion training may incorporate fractional timing correction, to properly align the amplified version of the original TX signal received via the loopback path with the original TX signal. The transfer function of the PA may be estimated as a polynomial function, obtaining the coefficients of the polynomial function using adaptation techniques according to one of a number of possible different methods, e.g. through curve fitting using a least mean square (LMS) algorithm.