A Novel Multi-Band Reduced Sampling Rate and I/Q Compensation Technique for RF Power Amplifiers

Jingmei Zhao,Feng Yang,Linbo Zhai

doi:10.1109/access.2019.2958414

Jingmei Zhao, Feng Yang + Show 1 more

Open Access

https://doi.org/10.1109/access.2019.2958414

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Abstract

In this paper, a novel multi-band reduced sampling rate technique is proposed for power amplifier (PA) linearization system. It is used to enhance performance and reduce hardware costs in spectrum aggregation discontinuous broadband systems and compensate in-phase/quadrature (I/Q) imbalance in the multi-band case. During the feedback loop process of sampling rate, a band-limited filter is introduced, and the frequency band extrapolation is carried out so that the spectrum outside the limited band is compensated effectively. Theoretical analysis is performed to compare the proposed method and the conventional methods. To evaluate the performance of the proposed method, a broadband PA is excited by a tri-band signal composed of a 20 MHz long-term evolution (LTE) signal at 1.31 GHz, a 20 MHz 4-carrier wideband code division multiple access (WCDMA) signal at 2.49 GHz, and a 20 MHz 2-carrier WiMAX signal at 2.58 GHz respectively. The experimental results demonstrate that the normalized mean square error (NMSE) can get high accuracy less than −41 dB, with peak-to-average power ratio (PAPR) equaling 9 dB accompanied by a large reduction in sampling rate. Error vector magnitude (EVM) is 1% better than band-limited memory polynomial (MP) model and 2.3% better than conventional MP model.

Highlights

With the rapid development of wireless communication technology, the signal bandwidth becomes wider to support higher data rate under the limited spectrum resources
We propose a novel multi-band digital predistortion, which can achieve significant improvement of linearization property and reduce the sampling rate in the feed-back loop
I/Q COMPENSATION AND AMPLITUDE CHARACTERISTICS In view of the existence of I/Q imbalance, this paper proposed a multi-band I/Q compensation method, and ascendant compensation effect is obtained

Summary

INTRODUCTION

With the rapid development of wireless communication technology, the signal bandwidth becomes wider to support higher data rate under the limited spectrum resources. After PA amplification, harmonic components, intra-band intermodulation components, intermodulation components and cross-modulation components are generated in the output signal Some of these components such as 2ω1, ω2 + ω1 − ω3, 2ω3 − ω2, and 2ω2 − ω3 etc in the base band of interest will affect the linearization performance of PA or increase the modeling complexity. In order to ensure that all lower than 5-order harmonic products and cross-modulation products of tri-band signal away from the basic band, the non-overlapping conditions need to be satisfied, and these distortion components can be removed by the filter. If the system satisfies the condition that the multi-band does not overlap, we can verify whether the given tri-band signal can be properly linearized without considering the harmonic and cross-modulation distortion products. ACPR is 14 dB better than MP model, and 4dB better than BD model while no complexity increases

THE RESULTS OF NMSE AND EVM

Findings

CONCLUSION