A 3-Port Circulator Based on Non-Reciprocal Acoustoelectric Delay Lines

Abstract

This work describes an approach to utilize acoustoelectric delay lines in an integrated non-magnetic RF circulator. Three adjacent delay lines are defined in X-cut lithium niobate, with a bonded thin film silicon layer in the path of the forward and reverse propagating surface acoustic waves. By applying uniform dc bias (30V) to the Si semiconductor, the delay lines each produce a non-reciprocal response, which is measured with a contrast of up to 20 dB in a single delay line. Through appropriate routing of ports, these delay lines can used to realize a 3-port circulator at 409 MHz with at least 13 dB of isolation simulated between ports. In contrast with previous works using switching or periodic modulation of acoustic wave delay lines, this work demonstrates the feasibility of using acoustoelectric effects to produce chip-scale circulators.