Towards Digitally Addressable Delay Synthesis: GHZ Low-Loss Acoustic Delay Elements from 20 NS to 900 NS

We present the first group of GHz S0 mode low-loss acoustic delay lines covering a wide range of delays from 20 ns to 900 ns for digitally addressable delay synthesis. The fabricated miniature acoustic delay lines show a fractional bandwidth of 4%, a minimum insertion loss of 3.2 dB, outperforming the incumbent surface acoustic wave counterparts. Multiple acoustic delay lines with center frequencies from 0.9 to 2 GHz have been demonstrated, underscoring their great frequency scalability. The acoustic delay lines use single-phase unidirectional transducers design to launch and propagate the S0 mode in an X-cut lithium niobate thin film with large electromechanical coupling and low damping. The demonstrated acoustic delay lines can enable wide-range and high-resolution delay synthesis that is highly sought-after for the self-interference cancellation in full-duplex radios.