Linearization of RF Power Amplifiers in Wideband Communication Systems by Adaptive Indirect Learning Using RPEM Algorith
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Linearization of RF Power Amplifiers in Wideband Communication Systems by Adaptive Indirect Learning Using RPEM Algorithm Duc Han Le1 · Van-Phuc Hoang1 · Minh Hong Nguyen1 · Hien M. Nguyen2 · Duc Minh Nguyen3
© Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract This paper proposes a new approach of digital predistortion (DPD) technique based on the adaptive indirect learning architecture (ILA) by using a recursive prediction error minimization (RPEM) algorithm for linearizing radio frequency (RF) power amplifiers (PAs) in emerging wideband communication systems. In the proposed RPEM-based linearization approach, the forgetting factor varies with time and is less sensitive to noise. Therefore, the predistorter (PD) parameter estimates become more consistent and accurate in steady state so that the mean square errors can be reduced. Both the error vector magnitude (EVM) and the adjacent channel power ratio (ACPR) are used to evaluate the DPD technique in RF PAs employing the proposed linearization. The efficiency validation of the proposed method is based on a simulated PA Wiener model. The simulation results have clarified the improvement of the proposed adaptive ILA-based DPD with RPEM algorithm in terms of both EVM and ACPR. Keywords RPEM · Digital predistortion · RF power amplifiers · Linearization · Adaptive indirect learning architecture · Predistorter
1 Introduction The development of future wireless communication systems, such as the fifth generation (5G) and beyond [1, 2], continuously demands higher data rates and larger user capacities, which faces significant challenges in both system performance and energy efficiency. It requires not only wideband transceiver architecture, but also higherorder modulation schemes. The signals of these systems are characterized by non-constant envelopes and high peak-toaverage power ratio (PAPR), leading to stringent linearity requirements for signal amplification. In the meantime, the power dissipation must be remained as low as possible. To cope with these challenges, high efficiency and linear radio frequency (RF) power amplifiers (PAs) are indispensable components. Unfortunately, due to the inherent nonlinear This paper has been submitted in part to the 5th EAI International Conference on Industrial Networks and Intelligent Systems (INISCOM 2019). The corresponding and the first authors are the main authors contributing equally to the paper. Van-Phuc Hoang
[email protected]
Extended author information available on the last page of the article.
behavior of PAs, efficiency and linearity requirements often conflict each other. In order to provide highly-efficient power conversion, PAs should be driven into the saturation region. However, the saturated PAs produce not only inband distortion but also result in spectral regrowth that interferes the adjacent frequency band channels. Consequently, the spectra utilization efficiency is reduced. In contrast, the nonlinear distortion can be mitigated by a traditional backoff approach, but this ge
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