A Voltage-Controlled Surface Acoustic Wave Oscillator based on Lithium Niobate on Sapphire Low-Loss Acoustic Delay Line

In this work, we investigate, for the first time, a low-phase noise and wide-tuning range voltage-controlled surface acoustic wave oscillator (VCSO) based on a lithium niobate on sapphire (LNOS) low-loss acoustic delay line (ADL). The thin-film LN/SiO
₂
bilayer acoustic waveguide, together with the single-phase unidirectional transducer (SPUDT) design, is key to attaining low insertion loss (IL) by enhancing the energy confinement and directionality. Based on a high performance ADL with an IL of only 5.2 dB, a fractional bandwidth (FBW) of 5.38%, and a group delay of 110 ns, the VCSO is implemented by commercially available circuit components using a series-resonant topology. The LNOS ADL oscillator operates at 888 MHz, showcasing a low phase noise of -94.1 dBc/Hz at 1-kHz offset and a root-mean-square (RMS) jitter of only 30.26 fs (integrated from 12 kHz to 20 MHz) while only consuming 16 mA of supply current. Featuring a wide frequency tuning range of 6,630 ppm, the proposed VCSO is a promising low-noise, low-power, high-frequency timing device for emerging applications.