Low Phase Noise RF Oscillators Based on Thin-Film Lithium Niobate Acoustic Delay Lines

Abstract

An RF oscillator has been demonstrated using a wideband SH0 mode lithium niobate acoustic delay line (ADL). The design space of the ADL-based oscillators is theoretically investigated using the classical linear time-invariant (LTI) phase noise model. The analysis reveals that the key to low phase noise is low insertion loss (IL), large delay ( ${\tau }_{\mathbf {G}}$ ), and high carrier frequency ( $\mathbf {f}_{\mathbf {o}}$ ). Two SH0 ADL oscillators based on a single SH0 ADL ( $\mathbf {f}_{\mathbf {o}}= 157$ MHz, IL = 3.2 dB, ${\tau }_{\mathbf {G}} = 270$ ns) but with different loop amplifiers have been measured, showing low phase noise of −114 dBc/Hz and −127 dBc/Hz at 10-kHz offset with a carrier power level of −8 dBm and 0.5 dBm, respectively. These oscillators not only have surpassed other Lamb wave delay oscillators but also compete favorably with surface acoustic wave (SAW) delay line oscillators in performance. [2019-0223]