An SH0 Lithium Niobate dispersive delay line for chirp compression-enabled low power radios

Abstract

This paper presents the first demonstration of a shear-horizontal mode Lithium Niobate dispersive delay line, featuring a center frequency of 250 MHz, a delay-bandwidth (TB) product of 100, an electromechanical coupling (k2) in excess of 35%, and a low insertion loss of 10 dB. The high compression is attained via a large bandwidth of 125 MHz, centered at 250 MHz, and an extensive delay of 0.8 μS. The device shown herein has greatly outperformed the state of the art, namely surface acoustic wave delay lines which typically have an insertion loss over 25 dB for a comparable compression ratio. The attained performance can be attributed to the excellent piezoelectric coupling of lamb waves in a suspended Lithium Niobate X-cut thin film. A voltage gain of 3 has been demonstrated for instantaneously amplifying chirp-coded signals, a feature that can be harnessed to enhance signal to noise ratio in low power wake-up radios for Internet of Things (IoT) applications.