Digital linearizer for RF amplifiers

Abstract

Broadcast technology is at the beginning of a new era. It is characterized by the intensive use of the most advanced digital modulations formats (8VSB, QAM, OFDM) in combination with high power RF amplifiers. To date the linearity required for these digital formats has only been accomplished in cumbersome low efficiency class A amplifier or even more cumbersome feed-forward systems. A potentially more efficient and cost effective approach is the combination of non linear power amplifiers and a predistortion technique capable of compensating for the non linear amplifiers. Digital predistortion will provide a highly linear output and improved efficiency. Itelco has developed a digital adaptive base band predistorter to provide for improved performance and cost. The technique is independent of the modulation type, the output frequency, or the signal bandwidth. Furthermore the capability of automatic adaptive predistortion to compensate for the environment (temperature, power supply variations, aging ,and even operation during replacement of a faulty module) is highly desirable.

Adaptive Digital Predistortion for Wideband High Crest Factor Applications Based on the WACP Optimization Objective: A Conceptual Overview

“…Of all models, the Volterra Series is considered the most general and for this reason is used here. It is noted that the common AM-AM/AM-PM model [25] is not suitable in this situation due to the transmitter's wide bandwidth requirements. The discrete time, causal, complex baseband Volterra Series power amplifier model with maximum nonlinearity (odd) and memory is given by: (1) In this equation, and represent the input and output complex signal envelopes respectively and denotes complex conjugation.…”

Nonlinear Correction of Digital Predistortion with Maximum Power Amplification Efficiency in PAPR

“…This paper in order to reduce adjacent channel interference, we use a relatively high sampling rate. To improve linear region we use digital predistortion techniques [8][9][10] which is one of the most cost effective. The digital predistortion and HP A series are composed of a nonlinear correction system model that adds an expanding nonlinearity.…”

An enhanced Phase Shifted Transmitter based on 2^ndHT GaN-PAs with energy recovery circuit

“…To meet these contradictory requirements, non-linear PAs are usually used in combination with linearization techniques such as adaptive predistortion, feed-forward, etc. [2]. However, these methods increase the complexity of the overall transmitter, making them less attractive solutions.…”