MEMS Switch Enabled Spatiotemporally Modulated Isolators

Authors: Connor Devitt, Graduate Student Member, IEEE, Yong-Bok Lee, Member, IEEE, Pavitra Jain, Graduate Student Member, IEEE, Sunil Ashok Bhave,
Senior Member, IEEE, Xu Zhu, Senior Member, IEEE, Nicholas Yost, Member, IEEE, and Yabei Gu, Member, IEEE

ABSTRACT

This work reports the simulation, design, and implementation of a compact MEMS switch based spatiotemporally modulated (STM) bandpass filtering isolator to improve self-interference cancellation (SIC) in underwater acoustic communication networks.

Conventional ferrite circulators are unavailable in ultrasonic frequency ranges limiting SIC to techniques such as spatial cancellation and adaptive digital cancellation. This study details a sub-megahertz electronic non-magnetic filtering isolator.

Compact and reliable MEMS switches in hermetically sealed glass packaging enable the periodically time varying filter circuit to be non-reciprocal.

A printed circuit board (PCB) implementation shows strong agreement with spectral admittance matrix simulations with a maximum measured isolation of 15.99 dB. In conjunction with digital SIC methods, this isolator can enable in-band full duplex underwater communication, environmental sensing, and imaging.

INDEX TERMS

Spatiotemporal modulation (STM), MEMS switches, non-reciprocity, bandpass filter (BPF), underwater communication.

I. INTRODUCTION

NON-RECIPROCAL radio-frequency (RF) components such as circulators and isolators are essential for a wide range of systems.

Circulators are frequently used in RF front-end modules for both half-duplex and full-duplex communication systems providing isolation between the transmit (Tx) and receive (Rx) signal paths [1], [2], [3], [4].

They are also critical components in quantum non-demolition superconducting qubit readout [5], [6], [7], [8], [9].

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