Slow Waves in Metamaterial Two-Dimensional-Resonant-Rods (2DRRs) Delay Lines

This paper presents a new class of Aluminum Nitride (AlN) delay-lines (DLs) for Ultra- and Super-High-Frequency (U/SHF) radio-frequency (RF) applications, enabled by the excitation of rod-modes in microacoustic resonant devices. These DLs are formed by a novel acoustic metamaterial structure, namely the Two-Dimensional-Resonant-Rods(2DRRs), formed by a profiled AlN thin film. Just recently, 2DRRs with superior electromechanical coupling coefficient (k
_t
²
> 7.2% ) were demonstrated. Such feature, in addition to the 2DRRs' unique dispersive characteristics, renders AlN 2DRRs promising components to form next-generation acoustic DLs for wideband RF applications. In this work, we designed a 2DRR-based DL operating at 700MHz and we studied the performance of this device in terms of bandwidth-delay-product (BDP), a useful metric to benchmark any DLs. We show that the designed DL allows a 5dB-fractional bandwidth (BW%) exceeding 12% and an average in-band group delay (GD) surpassing 32ns, thus resulting into a record-high BDP for AlN DLs, exceeding 3.8.