Wideband Self-Adaptive RF Cancellation Circuit for Full-Duplex Radio: Operating Principle and Measurements

TL;DR

This paper introduces a wideband, self-adaptive RF cancellation circuit for full-duplex radios, capable of automatically tracking and canceling self-interference over 100 MHz bandwidth, demonstrated with real measurements at 2.4 GHz.

Contribution

A novel RF cancellation architecture with wideband and self-adaptive features, enabling effective self-interference suppression in full-duplex transceivers.

Findings

41 dB cancellation at 100 MHz bandwidth

60 dB cancellation at 20 MHz bandwidth

Effective tracking in time-varying interference scenarios

Abstract

This paper presents a novel RF circuit architecture for self-interference cancellation in inband full-duplex radio transceivers. The developed canceller is able to provide wideband cancellation with waveform bandwidths in the order of 100 MHz or beyond and contains also self-adaptive or self-healing features enabling automatic tracking of time-varying self-interference channel characteristics. In addition to architecture and operating principle descriptions, we also provide actual RF measurements at 2.4 GHz ISM band demonstrating the achievable cancellation levels with different bandwidths and when operating in different antenna configurations and under low-cost highly nonlinear power amplifier. In a very challenging example with a 100 MHz waveform bandwidth, around 41 dB total cancellation is obtained while the corresponding cancellation figure is close to 60 dB with the more conventional 20 MHz carrier bandwidth. Also, efficient tracking in time-varying reflection scenarios is demonstrated.