Fork-Shaped Quartz Resonator Using Torsional Mode for Temperature Sensing
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Solution Overview
Problem
Existing quartz crystal oscillators face challenges in achieving high reliability and sensitivity for temperature sensing, particularly in miniaturized forms, due to limitations in frequency stability and power consumption.
Innovation Solution
A fork-shaped quartz crystal device configured for temperature sensing, featuring a pair of elongate tines with vertically protruding line structures and electrodes designed to vibrate in a torsional mode, enhancing sensitivity and linearity of frequency response to temperature changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If quartz crystal oscillators are miniaturized, then device size is reduced, but frequency stability and sensitivity deteriorate
Solution Approach 1:
The quartz crystal is divided into a fork-shaped structure with two separate tines instead of a single monolithic resonator. This segmentation allows each tine to vibrate independently in torsional mode, maintaining frequency stability while reducing overall device size. The segmented structure also enables better thermal isolation and reduced stress concentration.
Solution Approach 2:
The patent utilizes torsional mechanical vibration mode where each tine twists about its longitudinal axis when voltage is applied to the electrodes. This specific vibration mode provides higher frequency stability and sensitivity compared to traditional modes, enabling reliable operation in miniaturized devices. The torsional mode is excited by applying voltage between electrodes on opposite sides of each tine.
2Volume of moving object
If quartz crystal oscillators are miniaturized, then device size is reduced, but temperature sensing sensitivity deteriorates
Solution Approach 1:
The torsional vibration mode provides enhanced sensitivity to temperature changes because the resonant frequency of the fork-shaped structure exhibits a strong, linear dependence on temperature. The twisting motion of the tines creates a more pronounced frequency shift per degree temperature change compared to traditional oscillator modes, improving measurement precision in a compact form factor.
Solution Approach 2:
The patent exploits the change in resonant frequency parameter with temperature for sensing applications. The fork-shaped torsional mode provides a large frequency-temperature coefficient, allowing high sensitivity temperature measurement. By monitoring the shift in resonant frequency, the device can accurately sense temperature changes despite its miniaturized size.
3Device complexity
If traditional oscillator modes are used, then device structure is simple, but power consumption increases
Solution Approach 1:
The torsional vibration mode of the fork-shaped quartz crystal requires less drive energy to sustain oscillation compared to traditional modes. The electrodes apply voltage to induce twisting motion, which has lower mechanical losses and higher quality factor. This results in reduced power consumption while maintaining the relatively simple piezoelectric oscillator structure.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The device achieves high sensitivity and linearity in temperature sensing, with improved frequency stability and reduced power consumption, making it suitable for miniaturized applications.
Implementation Method 1
A quartz crystal oscillator vibrates at a stable frequency by being distorted by an electric field when voltage is applied to an electrode near or on the crystal. This property is known as electrostriction or inverse piezoelectricity.
Implementation Method 2
When the field is removed, the quartz, which oscillates in a precise frequency, generates an electric field as it returns to its previous shape, which in turn can generate a voltage.
Data Source
AI summary
The disclosed technology generally relates to quartz crystal devices and more particularly to quartz crystal devices configured to vibrate in torsional mode. In one aspect, a quartz crystal device configured for temperature sensing comprises a fork-shaped quartz crystal comprising a pair of elongate tines laterally extending from a base region in a horizontal lengthwise direction of the fork-shaped quartz crystal. Each of the tines has formed on one or both of opposing sides thereof a vertically protruding line structure laterally elongated in the horizontal lengthwise direction. The quartz crystal device further comprises a first electrode and a second electrode formed on the one or both of the opposing sides of each of the tines and configured such that, when an electrical bias is applied between the first and second electrodes, the fork-shaped quartz crystal vibrates in a torsional mode in which each of the tines twists about a respective axis extending in the horizontal lengthwise direction.