Analysis of longitudinal leaky surface acoustic waves on quartz thin plate bonded to similar-material substrate

The propagation and resonance properties of longitudinal leaky surface acoustic waves (LLSAWs) on bonded structures consisting of a quartz (Qz) thin plate and a Qz support substrate with different Euler angles were investigated theoretically. By using both an X-cut Qz thin plate and a Qz support substrate with optimal Euler angles, we obtained LLSAWs with a larger coupling factor, a smaller attenuation, and a lower temperature coefficient of frequency than those on a single Qz substrate. Furthermore, from the resonance properties simulated by the finite element method, the bonded structures were found to exhibit a large admittance ratio and a high quality factor, which could not be obtained when using a single Qz substrate; the bandwidth however was as small as 0.016-0.086%.

Thermal compensation in quantum frequency standards based on the effect of coherent population trapping

The problem of developing a thermal compensation system in quantum frequency standards based on the effect of coherent population trapping is considered. The development of such a system significantly reduces the temperature coefficient of frequency, the value of which is an order of magnitude higher than in rubidium frequency standards. One of the ways to reduce the temperature coefficient of frequency is temperature compensation. A method of thermal compensation based on the Zeeman effect for the shift of the actual frequency is proposed. A method for determining the minimum value of the magnetic field at which there is no influence of magnetosensitive resonances on the reference resonance is considered. The results of the operation of the quantum frequency standard before and after switching on the thermal compensation system are presented.

A Laterally Vibrating Lithium Niobate MEMS Resonator Array Operating at 500 °C in Air

This paper reports the high-temperature characteristics of a laterally vibrating piezoelectric lithium niobate (LiNbO3; LN) MEMS resonator array up to 500 °C in air. After a high-temperature burn-in treatment, device quality factor (Q) was enhanced to 508 and the resonance shifted to a lower frequency and remained stable up to 500 °C. During subsequent in situ high-temperature testing, the resonant frequencies of two coupled shear horizontal (SH0) modes in the array were 87.36 MHz and 87.21 MHz at 25 °C and 84.56 MHz and 84.39 MHz at 500 °C, correspondingly, representing a −3% shift in frequency over the temperature range. Upon cooling to room temperature, the resonant frequency returned to 87.36 MHz, demonstrating the recoverability of device performance. The first- and second-order temperature coefficient of frequency (TCF) were found to be −95.27 ppm/°C and 57.5 ppb/°C2 for resonant mode A, and −95.43 ppm/°C and 55.8 ppb/°C2 for resonant mode B, respectively. The temperature-dependent quality factor and electromechanical coupling coefficient (kt2) were extracted and are reported. Device Q decreased to 334 and total kt2 increased to 12.40% after high-temperature exposure. This work supports the use of piezoelectric LN as a material platform for harsh environment radio-frequency (RF) resonant sensors (e.g., temperature and infrared) incorporated with high coupling acoustic readout.

Resistorless Frequency Locked On-Chip Oscillator with Proportional-to-Absolute Temperature References

A 36-kHz frequency locked on-chip oscillator is proposed, the proportional-to-absolute temperature (PTAT) current and voltage generator is presented to eliminate conventional temperature-compensated resistors. The resistorless approach reduces the process variation of frequency and the chip area. The oscillator is fabricated in 0.18-[Formula: see text]m standard CMOS process with an active area of 0.072[Formula: see text]mm2. The temperature coefficient of frequency is 48[Formula: see text]ppm/∘C at best and 82.5[Formula: see text]ppm/∘C on average over [Formula: see text]–70∘C and the frequency spread is 1.43% ([Formula: see text]/[Formula: see text] without calibration. The supply voltage sensitivity is 1.8%/V in the range from 0.65[Formula: see text]V to 1[Formula: see text]V and the power consumption is 95[Formula: see text]nW under the supply voltage of 0.65[Formula: see text]V.