Undersampling Reference Receiver For LNA Distortions Compensation Direct RF Digitization Receiver

Abstract

The paper analyzes the effect of the nonlinear distortion of Low Noise Amplifier (LNA) in multichannel direct RF digitization receivers (DRF-RX). A novel distortion compensation approach has been proposed, where the compensation is performed entirely in the digital domain at baseband after the digital down-converter (DDC). Distortion information is extracted from the signals of the main receiver and a linear reference receiver. The reproduced information is used for distortion compensation using a nonlinear model and an adaptive Least Mean Square (LMS) algorithm. As the major advantage, processing at baseband with a low sampling rate significantly reduces the cost, the design complexity and the energy consumption of the receiver. The proposed undersampling reference receiver structure exhibits additional benefit in terms of hardware usage and energy consumption by using a low-cost and large dynamic range ADC. To verify the scheme's efficiency, an Ultra High Frequency (UHF) DRX with four QPSK channels is simulated by Matlab Simulink. The simulation results show that the method improves the Spurious-free dynamic range (SFDR) with an increase of about 20 dB, compared to the results of RX without distortion compensation.