Extremely low phase noise UHF oscillators utilizing high-overtone, bulk-acoustic resonators

Abstract

High-overtone, bulk acoustic resonators (HBAR) have been designed that exhibit 9-dB insertion loss and loaded Q values of 80000 at 640 MHz with out-of-phase resonances occurring every 2.5 MHz. These resonators have been used as ovenized frequency-control elements in very low phase noise oscillators. The oscillator sustaining stage circuitry incorporates low-1/f noise modular RF amplifiers, Schottky-diode ALC, and a miniature 2-pole helical filter for suppression of HBAR adjacent resonant responses. Measurement of oscillator output signal flicker-of-frequency noise confirms that state-of-the-art levels of short-term frequency stability have been obtained. Sustaining stage circuit contribution to resulting oscillator flicker-of-frequency noise is 7-10 dB below that due to the resonators themselves. At 16-dBm resonator drive, an oscillator output signal white phase noise floor level of -175 dBc/Hz is achieved.

Frequency flicker of 2.3 GHz AlN-sapphire high-overtone bulk acoustic resonators

“…1-3) and making them well-suited for the development of ultra-low phase noise oscillators. [4][5][6] A HBAR, which can be seen as an acoustic analogy to the optical Fabry-Perot interferometer, is obtained by stacking a thin piezoelectric transducer above a thick low-loss acoustic substrate. The piezoelectric film generates acoustic waves that propagate in the whole material stack.…”

Resonance Spectrum Characteristics of Effective Electromechanical Coupling Coefficient of High-Overtone Bulk Acoustic Resonator

“…Besides, HBAR has a large quality factor ( Q ) due to the low acoustic attenuation substrate, and exhibits the largest Q -Frequency product of the crystal oscillators. Thus, it can also be applied in the low-phase noise microwave signal sources [2,3]. …”

Study of high-overtone bulk acoustic resonators based on the Me1/AlN/Me2/(100) diamond piezoelectric layered structure

“…The microwave HBARs belong to the class of composite acoustoelectronic devices, which differ from conven tional piezoelectric resonators by their miniature dimensions and high Q factor [1]. Owing to these advantages, HBARs can be used, e.g., in microwave generators with low phase noise level [4]. Usually, HBARs are fabricated using a layered structure con sisting of a thin film piezoelectric transducer depos ited onto a substrate (Fig.…”