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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 $0.45~\mu \text{m}$ 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 mm2. 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. [ABSTRACT FROM AUTHOR]

In this work, we present a novel unidirectional transducer design for frequency scaling aluminum nitride (AlN)-based radio frequency (RF) microsystems. The proposed thickness-field-excited single-phase unidirectional transducers (TFE-SPUDT) adopt 5/16 wavelength electrodes and, thus, enable efficient piezoelectric transduction with better frequency scalability. The design space of the TFE-SPUDT is theoretically explored and validated using the acoustic delay line (ADL) testbeds. The ADL testbeds with a large feature size of ${3}~\mu \text{m}$ show a center frequency of 1 GHz, a minimum insertion loss (IL) of 4.9 dB, and a fractional bandwidth (FBW) of 5.3%, significantly surpassing the IL and frequency scalability of the previously reported AlN transducers. The design approach can potentially contribute to various AlN-based RF microsystems for signal processing, physical sensing, optomechanical interaction, and quantum acoustic applications, and are readily extendable to other piezoelectric platforms. [ABSTRACT FROM AUTHOR]

We present a group of low-loss Lamb mode acoustic delay lines in an aluminum nitride (AlN) thin film. The low-loss acoustic delay lines are enabled by the thickness-field-excited single-phase unidirectional transducers. The fabricated miniature acoustic delay lines show a fractional bandwidth of 4.5%, a minimum insertion loss of 5.9 dB, outperforming the previously reported aluminum nitride delay platforms. The demonstrated delay ranges from 105 ns to 165 ns with center frequencies from 175 MHz to 255 MHz. The design approach and the significantly lower insertion loss described herein are expected to open new horizons for hybridized signal processing based on AlN and CMOS. [2019-0094] [ABSTRACT FROM AUTHOR]