Dual-Mode MEMS Resonator for Temperature-Compensated Frequency Output

Solution Overview

Problem

Microelectromechanical Systems (MEMS) resonators face challenges with temperature sensitivity, as silicon-based devices have a negative temperature coefficient of elasticity, leading to frequency deviations that are difficult to control, and the addition of external circuitry for temperature measurement consumes power and space while providing inaccurate measurements.

Innovation Solution

A dual-mode MEMS resonator operating in both in-plane and out-of-plane vibration modes, allowing for two frequencies to be generated within a single package, which can replace two separate resonators, and using these frequencies to determine temperature without external sensors, enabling more accurate temperature measurement and compensation for frequency drifts.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If external circuitry is added to the MEMS resonator for temperature measurement, then temperature compensation can be achieved, but power consumption increases and space requirements increase

Engineering Contradiction:

Improvefrequency stabilityVSAvoidpower consumption

Core Design Contradiction:

ReliabilityVSUse of energy by moving object

Solution Approach 1:

The patent combines temperature measurement and frequency reference functions into a single MEMS resonator device. The resonator operates in multiple vibration modes (e.g., flexural and longitudinal modes) that have different temperature dependencies, allowing temperature to be determined from frequency ratios without external sensors. This integration eliminates separate temperature measurement circuitry, reducing power consumption and device footprint while maintaining frequency stability through temperature compensation.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The MEMS resonator is designed to perform multiple functions simultaneously: it provides a stable frequency reference and inherently measures temperature through its multi-mode vibration characteristics. By utilizing the different temperature coefficients of various vibration modes, the device self-determines temperature and compensates for frequency drift without requiring external temperature sensors or additional power-consuming circuitry.

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Reliability

If external circuitry is added to the MEMS resonator for temperature measurement, then temperature compensation can be achieved, but device size increases

Engineering Contradiction:

Improvefrequency stabilityVSAvoiddevice footprint

Core Design Contradiction:

ReliabilityVSArea of stationary object

Solution Approach 1:

The patent combines temperature measurement and frequency reference functions into a single MEMS resonator device. The resonator operates in multiple vibration modes (e.g., flexural and longitudinal modes) that have different temperature dependencies, allowing temperature to be determined from frequency ratios without external sensors. This integration eliminates separate temperature measurement circuitry, reducing power consumption and device footprint while maintaining frequency stability through temperature compensation.

Inventive Principle:

Principle #5Merging (Combining)

3Device complexity

If conventional single-mode MEMS resonators are used, then device simplicity is maintained, but temperature sensitivity causes frequency deviations

Engineering Contradiction:

Improveresonator structureVSAvoidfrequency stability

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The patent changes the operational parameters of the MEMS resonator by utilizing multiple vibration modes (e.g., flexural mode with negative TCF and longitudinal mode with positive TCF) instead of a single mode. By measuring the frequency ratio between these modes, the system can determine temperature and compensate for frequency drift. This approach maintains relatively simple device structure while significantly improving frequency stability through temperature compensation.

Inventive Principle:

Principle #35Parameter changes

4Adaptability or versatility

If two separate resonators are used to provide different frequencies, then frequency requirements are met, but power consumption and space requirements increase

Engineering Contradiction:

Improvefrequency outputVSAvoidpower consumption

Core Design Contradiction:

Adaptability or versatilityVSUse of energy by moving object

Solution Approach 1:

The MEMS resonator is designed to perform multiple functions simultaneously: it provides a stable frequency reference and inherently measures temperature through its multi-mode vibration characteristics. By utilizing the different temperature coefficients of various vibration modes, the device self-determines temperature and compensates for frequency drift without requiring external temperature sensors or additional power-consuming circuitry.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The patent combines temperature measurement and frequency reference functions into a single MEMS resonator device. The resonator operates in multiple vibration modes (e.g., flexural and longitudinal modes) that have different temperature dependencies, allowing temperature to be determined from frequency ratios without external sensors. This integration eliminates separate temperature measurement circuitry, reducing power consumption and device footprint while maintaining frequency stability through temperature compensation.

Inventive Principle:

Principle #5Merging (Combining)

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

This approach reduces power consumption and space requirements while providing more accurate temperature measurements and frequency stability, suitable for applications like global navigation satellite systems, by using the dual frequencies to calculate temperature and adjust for temperature-induced frequency deviations.

Implementation Method 1

operating the MEMS resonator in an in-plane mode of vibration using a first oscillator, thereby obtaining a first electrical signal having a first frequency. The method comprises concurrently operating the MEMS resonator in an out-of-plane mode of vibration

Methodology Applied

Scientific EffectMechanical vibration: Vibration

Implementation Method 2

mixing the first and second electrical signals together, thereby obtaining a third electrical signal having a third frequency, the third frequency being proportional to a temperature of the MEMS resonator

Methodology Applied

Scientific EffectSignal mixing: Heterodyne

Data Source

PatentUS11932530B2Dual-output microelectromechanical resonator and method of manufacture and operation thereof

Publication Date: 2024.03.19 MICROSYST NXTSENS INC

AI summary

An example resonating structure comprises a substrate, a resonator body, and an anchoring body for anchoring the resonator body to the substrate. The resonator body includes a layer of base material and, deposited on top of the layer of base material, a layer of mismatch material having a mismatch in temperature coefficient of elasticity (TCE) relative to the base material. The base material is doped with a dopant having a concentration chosen so as to minimize a second order temperature coefficient of frequency for the resonator body. The thickness of the layer of the mismatch material is chosen so as to minimize a first order temperature coefficient of frequency for the resonator body.