MEMS Gyroscope Signal Demodulation Circuit
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Solution Overview
Problem
Existing MEMS-type gyroscope systems for measuring angular velocity face challenges in reducing electrical consumption and achieving precise measurements due to the use of phase-locked loops and VCO type oscillators, which result in high power consumption and complexity.
Innovation Solution
An electronic circuit that demodulates the angular speed signal by integrating a measurement signal based on the oscillation of the mass, using a timing signal phase-shifted by π/2, without relying on phase-locked loops, allowing for low-power operation and high-quality factor resonator maintenance, with a simplified circuit design that converts only the angular velocity data using a low-complexity analog-to-digital converter.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a phase-locked loop is used to maintain mass oscillation and measure rotational speed, then measurement precision is improved, but electrical consumption increases
Solution Approach 1:
The patent extracts the essential function of phase detection from the complex phase-locked loop system. By using a simplified approach where the oscillating mass itself generates the reference signal and a secondary resonator detects the Coriolis effect, the system achieves angular velocity measurement without requiring the full phase-locked loop infrastructure, thereby reducing electrical consumption while maintaining measurement capability
Solution Approach 2:
The system uses the oscillating mass's own motion to generate the reference signal for measurement, eliminating the need for external VCO type oscillators and complex phase-locked loop control circuits. The secondary resonator naturally detects the Coriolis force induced by rotation, providing self-contained operation that reduces power requirements
2Measurement precision
If a VCO type oscillator is used to force oscillation and servo-control phase and amplitude, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent removes the VCO type oscillator and servo-control infrastructure from the system. Instead of using complex phase and amplitude servo-control, the invention relies on the natural resonance of the primary and secondary resonators, where the oscillating mass provides its own timing reference and the secondary resonator naturally responds to Coriolis forces, achieving measurement without complex control circuits
Solution Approach 2:
Rather than using the secondary resonator's output to control the primary resonator's oscillation (as in conventional force-to-rebalance systems), the patent inverts the approach by using the primary resonator's natural oscillation to drive the system and having the secondary resonator passively detect the rotation-induced Coriolis effect, thereby simplifying the circuit architecture
3Measurement precision
If phase-locked loop and secondary resonator are used for measurement, then measurement precision is improved, but start-up time increases
Solution Approach 1:
The system pre-establishes the oscillation of the primary mass at its resonant frequency before measurement begins. By having the mass already oscillating with defined amplitude and frequency, the system eliminates the time required for phase-locked loop acquisition and oscillation build-up, enabling immediate measurement upon activation while maintaining precision through the sustained oscillation
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 solution enables efficient demodulation of the angular velocity signal, reducing power consumption and system complexity, while maintaining high precision in measuring angular velocity with a high-quality factor resonator, facilitating easier implementation and lower electrical costs.
Implementation Method 1
an electronic circuit connected to at least one resonator of a MEMS-type resonator device can also be used to measure an angular speed... a mass maintained by a structure in the form of a spring and capable of being electrically oscillated at a frequency determined by the constant of the spring
Implementation Method 2
An angular velocity can be determined based on an oscillation velocity of the mass and the generated force, which is perpendicular to the angular velocity and the oscillating displacement of the mass
Implementation Method 3
following an integration of a measurement signal dependent on the oscillation of the oscillating mass, it is possible to easily demodulate the angular speed signal. Demodulation in an integration unit is performed synchronously on the basis of a timing signal with a frequency equivalent to the oscillation frequency of the moving mass
Data Source
Figure 1~2
Figure 3
Figure 4
AI summary
An electronic circuit (1) for measuring angular velocity in a MEMS-type gyroscope, the gyroscope comprising a mass (m) connected to a spring (k) and a damping element (d), an activation capacitor (Cact) to activate the mass, and a detection capacitor (Cdet) to detect the movement of the mass. The electronic circuit includes a measuring resistor (4), which is connected to the moving mass and has a resistive variation equal to the oscillation frequency of the mass. The resistor is biased to provide a measurement signal (Sm), which comprises a carrier signal in phase with the oscillation of the mass and an angular velocity signal phase-shifted by π/2 with respect to the carrier signal. The measurement signal is supplied to an integrating unit (5) clocked by a timing signal (SCLK) phase-shifted by π/2 with respect to the carrier signal and originating from a mass drive circuit (3).The angular velocity signal is demodulated at the output of the integrating unit.