Performance of feed‐forward linearizers of power amplifiers in OFDM systems under complex gain errors

Abstract

Adaptive feed-forward (FF) linearization schemes of power amplifiers provide high distortion cancelation and adjacent channel power ratio (ACPR) reduction. However, FF schemes are very sensitive to imbalances in the circuit parameters used to achieve signal cancelation. In this paper, an FF linearization circuit is analyzed using the orthogonalization of the nonlinear model and considering the effects of complex gain errors in the signal and distortion cancelation loops on the overall performance of the FF linearizer. The analysis enables the effective signal-to-distortion ratio (SDR) and ACPR to be estimated from FF circuit model. It is shown that complex gain errors in the distortion cancelation loop have a more significant effect on in-band distortion than out-of-band distortion, which means that the design of FF linearizers based on ACPR improvement is not optimal.

A low complexity pre‐distortion scheme for power amplifier linearization in wideband applications

“…This is due to its several advantages over feedforward linearization techniques [1] such as high flexibility, low cost, and high performance. This is due to its several advantages over feedforward linearization techniques [1] such as high flexibility, low cost, and high performance.…”

“…Many techniques proposed in the literature to linearize power amplifiers by employing digital pre-distortion techniques. This is due to its several advantages over feedforward linearization techniques [1] such as high flexibility, low cost, and high performance. Popular techniques which have been presented in the past include Volterra series techniques [2], Hammerstein [3], memory polynomial (MP) pre-distortion [4], and generalized memory polynomial (GMP) pre-distortion [5].…”