Analog Least Mean Square Loop with I/Q Imbalance for Self-Interference Cancellation in Full-Duplex Radios

Authors

Anh Tuyen Le, University of Technology SydneyFollow
Le Chung Tran, University of WollongongFollow
Xiaojing Huang, University of Technology SydneyFollow
Y J. Guo, University of Technology Sydney

RIS ID

137912

Publication Details

A. Tuyen. Le, L. Chung. Tran, X. Huang & Y. Jay. Guo, "Analog Least Mean Square Loop with I/Q Imbalance for Self-Interference Cancellation in Full-Duplex Radios," IEEE Transactions on Vehicular Technology, vol. 68, (10) pp. 9848-9860, 2019.

Abstract

Analog least mean square (ALMS) loop is a promising structure for self-interference (SI) mitigation in full-duplex radios due to its simplicity and adaptive capability. However, being constructed from in-phase/quadrature (I/Q) demodulators and modulators to process complex signals, the ALMS loop may face I/Q imbalance problems. Thus, in this paper, the effects of I/Q imbalance in the ALMS loop are investigated. It is revealed that I/Q imbalance affects the loop gain and the level of SI cancellation. The loop gain can be easily compensated by adjusting the gain at other stages of the ALMS loop. Meanwhile, the degradation on cancellation performance is proved to be insignificant even under severe conditions of I/Q imbalance. In addition, an upper bound of the degradation factor is derived to provide an essential reference for the system design. Simulations are conducted to confirm the theoretical analyses.