Ultra-Wideband Tapered Transducers in Thin-Film Lithium Niobate on Silicon Carbide

TL;DR

This paper introduces an ultra-wideband transducer design on a lithium niobate on silicon carbide platform, using tapered electrodes and shear-horizontal modes to significantly expand bandwidth for RF signal processing.

Contribution

It presents a novel tapered electrode transducer design that achieves ultra-wideband response on a LN on SiC platform, surpassing traditional bandwidth limitations.

Findings

Achieved 55% fractional bandwidth at 2.23 GHz with 26 dB insertion loss.

Potential to improve bandwidth to 79% with impedance matching.

Design scalable for better bandwidth and loss trade-offs.

Abstract

Acoustic devices offer significant advantages in size and loss, making them ubiquitous for mobile radio frequency signal processing. However, the usable bandwidth is often limited to the achievable electromechanical coupling, setting a hard limit using typical transducer designs. In this work, we present an ultra-wideband transducer design utilizing a tapered electrode configuration to overcome this limitation. The design is realized on a lithium niobate (LN) on silicon carbide platform, utilizing a combination of first and higher order shear-horizontal modes to generate the ultra-wideband response. The implementation shows a fractional bandwidth (FBW) of 55% at 2.23 GHz with an associated insertion loss (IL) of 26 dB for the measured 50 ohm case. Upon improved impedance matching, this performance could be improved to 79% FBW and an IL of 16.5 dB. Upon further development, this ultra-wideband design could be reasonably scaled towards improved FBW and IL trade off to enable improved usability for cases where bandwidth should be prioritized.