Analysis and Design of Commutation-Based Circulator-Receivers for Integrated Full-Duplex Wireless

TL;DR

This paper presents a detailed analysis, design, and experimental validation of a non-magnetic, commutation-based circulator-receiver for full-duplex wireless, achieving high isolation, low noise figure, and effective self-interference cancellation.

Contribution

It introduces a novel non-magnetic circulator-receiver architecture with comprehensive analysis, verified by a CMOS prototype demonstrating high power handling and SI suppression.

Findings

Achieves 8 dB noise figure and 40 dB isolation over 20 MHz bandwidth.

Handles up to +8 dBm TX power with 80 dB SI suppression.

Successfully recovers weak signals amidst strong self-interference.

Abstract

Previously, we presented a non-magnetic, nonreciprocal N-path-filter-based circulator-receiver (circ.-RX) architecture for full-duplex (FD) wireless which merges a commutation-based linear periodically-time-varying (LPTV) non-magnetic circulator with a down-converting mixer and directly provides the baseband (BB) receiver signals at its output, while suppressing the noise contribution of one set of the commutating switches. The architecture also incorporates an on-chip balance network to enhance the transmitter (TX)-receiver (RX) isolation. In this paper, we present a detailed analysis of the architecture, including a noise analysis and an analysis of the effect of the balance network. The analyses are verified by simulation and measurement results of a 65 nm CMOS 750 MHz circulator-receiver prototype. The circulator-receiver can handle up to +8 dBm of TX power, with 8 dB noise figure (NF) and 40 dB average isolation over 20 MHz RF bandwidth (BW). In conjunction with digital self-interference (SI) and its third-order intermodulation (IM3) cancellation, the FD circ.-RX demonstrates 80 dB overall SI suppression for up to +8 dBm TX average output power. The claims are also verified through an FD demonstration where a -50 dBm weak desired received signal is recovered while transmitting a 0 dBm average-power OFDM-like TX signal.