Oscillator Feedback Circuit for Stable MEMS Gyroscope Drive Amplitude
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Solution Overview
Problem
Conventional oscillator circuits for MEMS gyroscopes require additional electrodes, such as a monitor electrode, which increase complexity and error sources due to limited space, especially when maintaining a constant amplitude of the driving signal.
Innovation Solution
An oscillator circuit comprising a driver circuit with a first amplifier producing an oscillation voltage signal and a current detector generating a drive voltage signal, along with a feedback circuit using a second amplifier to produce a feedback voltage signal, eliminating the need for a monitor electrode by maintaining the amplitude through an oscillation loop.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a monitor electrode is added to maintain constant amplitude of the driving signal, then the amplitude stability is improved, but the device complexity increases
Solution Approach 1:
The patent combines the monitor electrode and drive electrode into a single integrated electrode structure. The electrode serves dual functions: driving the bulk acoustic resonator and monitoring the oscillation amplitude. This merging eliminates the need for separate monitor electrodes while maintaining amplitude stability through feedback control.
Solution Approach 2:
The drive electrode is designed to perform multiple functions simultaneously: it acts as both the driving electrode for exciting the resonator and the monitor electrode for detecting oscillation amplitude. This multi-functionality reduces the total electrode count while ensuring reliable amplitude control for constant output.
2Reliability
If multiple electrodes are used to maintain constant amplitude, then the amplitude control is improved, but the manufacturing precision requirements increase
Solution Approach 1:
By merging the monitor and drive electrodes into one integrated structure, the patent eliminates positioning errors that would arise from misalignment between separate electrodes. The single electrode design removes the manufacturing precision challenge of co-locating multiple electrodes while maintaining effective amplitude control.
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 configuration reduces system complexity and error sources by maintaining the amplitude of the driving signal without a monitor electrode, enhancing the stability and accuracy of the MEMS gyroscope's operation.
Implementation Method 1
a bulk acoustic wave gyroscope generally requires at least one drive electrode coupled to a bulk acoustic resonator and positioned to excite vibration of the bulk acoustic resonator
Implementation Method 2
The AGC amplifier applies signal gain and low-pass filtering to the detected signal to produce a control signal. The linear multiplier combines the amplified oscillation signal with the control signal to produce and feed a driving signal to the second electrode of the crystal element where the amplitude of the driving signal is maintained at a constant level.
Data Source
AI summary
An aspect of the present disclosure concerns an oscillator circuit including a driver circuit that includes a first amplifier and a current detector where the first amplifier produces an oscillation voltage signal, where the current detector detects an oscillation current signal and produces a drive voltage signal, and where the oscillation current signal corresponds to difference in voltage between the oscillation voltage signal and the drive voltage signal; a feedback circuit that includes a second amplifier receiving the oscillation voltage signal and the drive voltage signal, to produce a feedback voltage signal to the driver circuit; and an oscillator that oscillates at a frequency determined in accordance with the drive voltage signal.