Abstract
In this work, we present the low-loss acoustic delay lines (ADLs) at 5 GHz, using the first-order antisymmetric (A1) mode in 128° Y-cut lithium niobate thin films. The ADLs use a single-phase unidirectional transducer (SPUDT) design with a feature size of quarter acoustic wavelength. The design space is analytically explored and experimentally validated. The fabricated miniature A1 ADLs with a feature size of show a high operating frequency at 5.4 GHz, a minimum insertion loss (IL) of 3 dB, a fractional bandwidth (FBW) of 1.6%, and a small footprint of 0.0074 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . The low IL and high operating frequency have significantly surpassed the state-of-the-art performance of ADLs. The propagation characteristics of A1 acoustic waves have also been extracted. The demonstrated designs can lead to low-loss and high-frequency transversal filters for future 5G applications in the sub-6-GHz bands.
Highlights
T HE development of fifth-generation (5G) New Radio (NR) has been calling for unprecedented signal processing capabilities at radio frequency (RF) [1], [2]
Thanks to both unique features, thin-film bulk acoustic resonators (FBARs) and surface acoustic wave (SAW) devices have become ubiquitous in 4G filters [6]
We aim to demonstrate the first group of A1 acoustic delay lines (ADLs) with single-phase unidirectional transducer (SPUDT) for the transversal filter application
Summary
T HE development of fifth-generation (5G) New Radio (NR) has been calling for unprecedented signal processing capabilities at radio frequency (RF) [1], [2]. The enhanced mobile broadband (eMBB) [3] require new components at higher frequencies for the recently released bands [4], [5]. The shorter acoustic wavelengths [6] lead to orders of magnitude smaller resonant structures than their EM counterparts, while the low damping of acoustic waves enables efficient passives. Thanks to both unique features, thin-film bulk acoustic resonators (FBARs) and surface acoustic wave (SAW) devices have become ubiquitous in 4G filters [6]. It is challenging to scale the incumbent acoustic platforms to the 5G bands above 4 GHz, unless resorting to complex designs [9], [10], intrinsically high-damping modes [11], [12], or higher-cost substrates [13]–[15]
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