METHOD AND APPARATUS FOR LINEAR TRANSMISSION BY DIRECT INVERSE MODELING

摘要

A system for linearly transmitting an amplified output signal using predistortion whereby a straight/direct inverse modeling scheme (503) is used to determined the inverse of the distortion caused by a power amplifier (103). The predistorter system (407) stores complex coefficients in a LUT (603), which are then used as tap weights of a digital filter (601) implementing the predistorter. The predistortion is done by a non-linear filter (601) which incorporates both instantaneous and average envelope power or magnitude effects thereby compensating for modulation envelope memory effects of the power amplifier (103). The LUT (603) is addressed as a function of the instantaneous power or magnitude of the current sample and a profile of the power or magnitude envelope of previous samples. The LUT (603) is updated with values that are indexed as a function of the powers or magnitudes of past samples and the power or magnitude of the current sample.