A feedback-loop oscillator stabilized using laterally-coupled-mode narrow-band HBAR filters

In this work, we investigate the use of laterally coupled filters based on thinned single crystal LiNbO₃ layers bonded on AT-Quartz substrates for the stabilization of feedback-loop oscillators operating near 1 GHz and above. The resonator exploits dispersion properties as well as the presence of a thick resonating structure (i.e. the substrate) to enhance the lateral coupling between two resonators placed very close to one another to favor their modal interaction. Design rules are reported to optimize the resonator temperature coefficient of frequency (TCF). Finally, a feed-back-loop-based oscillator is built near 1.6GHz, exhibiting a phase noise better than -130dBc/Hz at 10kHz from the carrier.