Comprehensive Analysis of Quantization Effects on Digital-Controlled Adaptive Self-Interference Cancellation System

Jinling Xing,Songhu Ge,Jin Meng,Zhongpu Cui,Yongcai Liu

doi:10.1109/access.2020.2989001

Abstract

A digital-controlled adaptive self-interference cancellation system with capabilities of high interference cancellation ratio and strong environmental applicability is presented. The key part - analog-to-digital converter (ADC) / digital-to-analog converter (DAC) quantization effect, is analysed comprehensively. Specially, the analytical relation between the quantization noise and the interference cancellation ratio is derived, which can provide important guidance for system implementation and performance optimization. The theoretical deductions are validated firstly by Simulink simulation and then by practical experimental measurements. Both the analysis and experiments show that the system stability and convergence property are not affected by ADC/DAC. The magnification of the conditioning circuit in front of the error-sampled ADC plays an important role in the cancellation ratio improvement. The practical space channel measurements presented an average interference cancellation ratio of 59 dB for the single-tone interference waveform and 50 dB for the amplitude-modulated (AM) interference waveform, rendering the system as a powerful tool for solving the in-band self-interference problem.

Highlights

The growth in wireless communications necessitates more efficient utilization of spectrum, especially for the spacelimited ship, vehicle, aircraft environments [1]–[3], where multiple type and multiple frequency band of communication systems are co-site placed
The interference cancellation ratio (ICR) is introduced as an important performance assessment criteria for adaptive interference cancellation system (AICS), which is defined as the power difference in dB of the spurious signals falling into the receiver passband before and after cancellation in the stable state
Wn(t) is a wideband signal compared to the interference carrier frequency fc, it can still be regarded as the narrowband bandpass signal within the receiver band pass filter (BPF) passband [fc − B/2, fc + B/2], providing the possibility to calculate the power of the digital-to-analog converter (DAC) noise in the equivalent baseband domain

Summary

INTRODUCTION

The growth in wireless communications necessitates more efficient utilization of spectrum, especially for the spacelimited ship, vehicle, aircraft environments [1]–[3], where multiple type and multiple frequency band of communication systems are co-site placed. Considering the importance of the ADC/DAC noise analysis, this paper provides a comprehensive theoretical analysis of the quantization effects on the self-interference cancellation system. Contributions of this paper are summarized as follows: (1) it provides an analytical mean to investigate the impact of the converter quantization noise on the performance of the AICS in terms of convergence property, stability, interference cancellation ratio. As shown in Fig., two one-order low pass filters (LPFs) are introduced to implement the correlation process between the reference signals and the error signal in order to obtain the weight coefficients for the electrically tuned attenuators. The interference cancellation ratio (ICR) is introduced as an important performance assessment criteria for AICS, which is defined as the power difference in dB of the spurious signals falling into the receiver passband before and after cancellation in the stable state.

PERFORMANCE ANALYSIS WITH ADC QUANTIZATION NOISE

PERFORMANCE ANALYSIS WITH BOTH ADC AND DAC QUANTIZATION NOISE

CONCLUSION