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

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.

Keywords

• Band limited
• digital predistortion
• I/Q imbalance
• multi-band
• power amplifier
• sampling rate