Low-phase-noise surface-acoustic-wave oscillator using an edge mode of a phononic band gap

Low-phase-noise microwave-frequency integrated oscillators provide compact solutions for various applications in signal processing, communications, and sensing. Surface acoustic waves (SAWs), featuring orders-of-magnitude shorter wavelength than electromagnetic waves at the same frequency, enable integrated microwave-frequency systems with much smaller footprint on chip. SAW devices also allow higher-quality () factors than electronic components at room temperature. Here, we demonstrate a low-phase-noise gigahertz-frequency SAW oscillator on 128°-cut lithium niobate, where the SAW resonator occupies a footprint of <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"><a:mn>0.05</a:mn><a:mspace width="0.1em"/><a:msup><a:mi>mm</a:mi><a:mn>2</a:mn></a:msup></a:math>. Leveraging phononic crystal band-gap-edge modes to balance between factors and insertion losses, our 1-GHz SAW oscillator features a low phase noise of −132.5 dBc/Hz at a 10-kHz offset frequency and an overlapping Hadamard deviation of 6.5 × <e:math xmlns:e="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"><e:msup><e:mn>10</e:mn><e:mrow><e:mo>−</e:mo><e:mn>10</e:mn></e:mrow></e:msup></e:math> at an analysis time of 64 ms. The SAW resonator-based oscillator holds high potential in developing low-noise sensors and acousto-optic integrated circuits.