An FBAR Circulator

TL;DR

This paper demonstrates a novel FBAR-based circulator operating at 2.5 GHz, utilizing spatio-temporal modulation to achieve high isolation with a compact chip design, advancing non-reciprocal RF components.

Contribution

It introduces an experimental FBAR circulator with spatio-temporal modulation, achieving high isolation and low modulation requirements at microwave frequencies.

Findings

Achieved 76 dB isolation at 2.5 GHz.

Used a compact 0.25 mm² chip with three FBARs.

Realized non-reciprocity with a small modulation-to-RF frequency ratio.

Abstract

This letter presents the experimental demonstration of a film bulk acoustic resonator (FBAR) circulator at 2.5 GHz. The circulator is based on spatio-temporal modulation of the series resonant frequency of FBARs using varactors and exhibits a large isolation of 76 dB at 2.5 GHz. The FBAR chip (0.25 mm2) consists of three identical FBARs connected in wye configuration. The FBAR0s quality factor (Q) of 1250 and piezoelectric coupling coefficient kt 2 of 3% relaxes the modulation requirements, achieving non-reciprocity with small modulationto- RF frequency ratio bettter than 1:800 (3 MHz:2.5 GHz).