A Hammerstein predistortion linearization design based on the indirect learning architecture

Abstract

Power amplifiers (PAs) are inherently nonlinear devices and are used in virtually all communications systems. Digital baseband predistortion is a highly cost effective way to lin earize the PAs, but most existing architectures ass ume that the PA has a memory less nonlinearity. For wider bandwidth applications such as WCDMA, PA memory effects can no longer be ignored, and memoryless predistortion has limited effectiveness. In tHis paper, we model the PA as a Wiener system and construct a Hammerstein predistorter, obtained using an indirect learning architecture. Linearization per formance is demonstrated on a 3-carrier UMTS signal. 1.. INTRODUCTIONPower amplifiers �rAs) are indispensable components in a communication system and are inherently nonlinear. It is.well known that there is an approximate inverse relationship between the PA efficiency and its linearity. Hence, nonlinear PAs are desirable from an efficiency point of view. The price paid for higher efficiency is that nonlinearity causes spec tral regrowth (broadening) which leads to adjacent channel interference. It also causes in-band distortion which de grades the bit error rate (BER) performance . Newer trans 0-7803-7402-9/02/$17.00

An Efficient Scheme for Nonlinear Modeling and Predistortion in Mixed-Signal Systems

“…1 in order to either identify the amplifier and compute the inverse (predistorter) or identify immediately the predistorter [1], [5]. It is well known that the identification of a Volterra system can be accomplished at a sampling rate that is just twice the input signal bandwidth [6].…”

Optimized Low-Complexity Implementation of Least Squares Based Model Extraction for Digital Predistortion of RF Power Amplifiers

“…where the matrix X contains all of the linear and product terms ( ) x n  , ( 1) x n −  , … To extract the coefficients, the pth-order post-inverse [13] or the in-direct learning [17] can be employed, where the feedback signal, i.e., the output of the PA, ( ) y n  , is used as the input of the model, while the predistorted output signal, ( ) u n  , is used as the expected output. By employing the standard least squares algorithm, the coefficients vector C can be estimated from,…”

Generalized direct predistortion with adaptive crest factor reduction control

“…Referring to Fig. 3 and focussing on the cases in which CFR is not applied, we present three sets of results: standard indirect estimation [4] (brown), conventional direct estimation [15] (red) and our novel direct estimation algorithm (green) of Section 3.1. Observing Fig.…”

“…This tech nique, referred as signal predistortion (DPD) is usually performed on the baseband version of the signal and it is often based on polynomial functions [1,2,3,4,5] or look up tables (LUT) [6,7]. While liter ature mostly focuses on terrestrial applications, signal predistortion techniques are also becoming popular in satellite communications [8] partly due to the move towards amplification of multiple carriers (or multicarrier signals) in a single wideband HPA for reducing the payload mass and mission costs.…”