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Digital Predistortion of Wideband Signals with Reduced Complexity Based on Feedback Wiener System

Bouazza Tayeb H. C., Bachir Smail, Duvanaud Claude

Journal of Telecommunications and Information Technology

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2021

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nr 2

1--10

EN

Digital predistortion (DPD) using baseband signals is commonly used for power amplifier linearization. This paper is devoted to this subject and aims to reduce DPD complexity. In this study, we propose a structure that allows to decrease the number of DPD parameters by using multiple blocks, with each one of them dedicated to characterizing the non-linear behavior and/or memory effects. Such a structure is based on the feedback Wiener system, involving a FIR filter used as a feedback path to reproduce the PA inverse dynamics. A memory polynomial block (MP) is inserted as the final element to minimize the modeling errors. A relevant model identification method, based on an iterative algorithm, has been developed as well. The proposed architecture is used for the linearization of a commercial class-AB LDMOS RF PA by NXP Semiconductors, in wideband communication systems. Comparison of performance with the conventional generalized memory polynomial model (GMP) shows that the proposed model offers similar results, with its advantage consisting in the reduced number of parameters.

2

High power amplifiers chain nonlinearity influence on the acelerating beam stability in free electron laser (FLASH)

Cichalewski W., Jałmużna W.

International Journal of Microelectronics and Computer Science

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2010

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Vol. 1, nr 1

77-80

EN

The high power amplifiers transfer characteristics nonlinearities can have a negative influence on the overall system performance. This is also true for the TESLA superconducting cavities accelerating field parameters control systems. This Low Level Radio Frequency control systems uses microwave high power amplifiers (like 10 MW klystrons) as actuators in the mentioned feedback loops. The amplitude compression and phase deviations phenomena introduced to the control signals can reduce the feedback performance and cause electron beam energy instabilities. The transfer characteristics deviations in the Free Electron Laser in Hamburg experiment have been investigated. The outcome of this study together with the description of the developed linearization method based on the digital predistortion approach have been described in this paper. Additionally, the results from the linearization tool performance tests in the FLASH's RF systems have been placed.

3

FPGA Adaptive Predistorter Based on 64QAM Modulation

Pochmara J., Katarzyński P.

International Journal of Electronics and Telecommunications

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2010

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Vol. 56, No. 4

387-392

EN

This paper presents a predistortion technique compensating for nonlinear distortions caused by HPA (High Power Amplifier) in a QAM (Multilevel Quadrature Modulation) system. Investigations were held both with software and hardware tools. It is confirmed by computer simulation that proposed approach produces a faster convergence speed than traditional computer performed algorithms. Predistortion technique based on programmable logic device is a very attractive from the implementation point of view, because of a low amount of required RAM and rapid convergence from a blind start.