Adaptive Weight Gating: A Performance Enhancement Method for Analog-Digital Cascaded Self-Interference Cancellation

Abstract

With the high-density integration of electronic systems on modern integrated platforms, co-site high-power electromagnetic interference has become a critical bottleneck degrading electromagnetic compatibility of such platforms. Analog-digital cascaded self-interference cancellation (SIC) is widely recognized as a promising solution, but its performance is limited by the dynamic coupling between the analog and digital stages. In this paper, a unified time-domain model is constructed for the analog-digital cascaded SIC system consisting of the analog least mean square (ALMS) loop and digital multi-tap cancellation. Rigorous theoretical derivation demonstrates that the additional alternating current (AC) components induced by adaptive analog weight variation lead to irreducible residual interference and signal coupling, which fundamentally limit the overall performance of the cascaded system. To address this issue, an adaptive weight gating method is proposed, which accurately determines the enable timing of the digital stage, and adapts to time-varying multipath scenarios. By judging the power intensity of the input signal in the digital SIC circuit and the variation rate of analog weight, this method controls whether to enter the weight adaptation phase or the weight fixation phase, thereby eliminating extra AC components. Both simulation and experimental results demonstrate that the proposed method improves the overall interference cancellation ratio (ICR) by more than 30 dB in the fixation phase compared with the adaptation phase, under a typical co-site scenario with 20 MHz bandwidth, 20 dBm transmit power, and a multipath channel with four taps. This study provides a practical and high-performance solution for the deployment of cascaded SIC technology.