Integrated Conductivity-Modulation-Based RF Magnetic-Free Non-Reciprocal Components: Recent Results and Benchmarking

TL;DR

This paper reviews recent advances in RF non-reciprocal components using conductivity modulation, highlighting their advantages over traditional magnetic methods, and introduces new benchmarking metrics for performance comparison.

Contribution

It provides a comprehensive review of recent conductivity-modulation-based non-reciprocal RF components and proposes a new figure of merit for antenna interface efficiency.

Findings

Four generations of non-reciprocal circulators are discussed.

Conductivity-modulation enables low-loss, wide-bandwidth RF non-reciprocal components.

A new antenna interface efficiency metric is introduced.

Abstract

Achieving non-reciprocity and building nonreciprocal components through spatio-temporal modulation of material properties has attracted a lot of attention in the recent past as an alternative to the more traditional approach of exploiting Faraday rotation in magnetic materials. In this letter, we review recent research on spatio-temporal conductivity-modulation, which enables low-loss, small-footprint, wide-bandwidth and high-power-handling non-reciprocal components operating from radio frequencies (RF) to millimeter-waves (mm-waves) and integrated in a CMOS platform. Four generations of non-reciprocal circulators and circulator-based systems will be reviewed. We will also discuss metrics of performance that are important for wireless applications and standards, and introduce a new antenna (ANT) interface efficiency figure of merit ($\eta_{ANT}$) to enable a fair comparison between various types of antenna interfaces.