Small Signal Gain Degradation and Its Correction by Feedforward Linearization

Abstract

In this paper we propose a new measure of amplifier nonlinearity; namely, the small signal gain degradation due to large signal capture of the amplifier power. This new criterion for linearity evaluation is specially important in repeaters where received signals are not a priory known. A 5 th order mathematical model is used to characterize this phenomenon. After a thorough comparison between different linearization techniques, we select the classical feed-forward linearization. We adapt the FF linearization circuit to the total input signal power at different conditions and simulate the small signal gain against a large input signal gain in each case. An interesting result was that the feed-forward linearization circuit adapted to the total input power, completely compensates the small signal gain degradation. Although the results are frequency dependent, we can find some average settings to correct the system performance within a certain frequency band. We propose the use of a general power detector and a set of look-up tables for system adaptation.