Oscillator Trim Circuit for MEMS Gyroscope Phase Calibration
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Solution Overview
Problem
The existing methods for calibrating the phase lag in vibratory MEMS gyroscopes are time-consuming, costly, and prone to errors due to the need for iterative testing and the introduction of noise from external test equipment.
Innovation Solution
A trim circuit is integrated into the oscillator drive circuit of the vibratory gyroscope, comprising comparators and a processing element that determines the phase lag between input and output signals and generates a trim code to adjust the phase shift component, allowing for phase calibration to be performed internally within the integrated circuit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If external test equipment is used to measure and adjust phase lag, then phase calibration can be performed, but test time increases and noise errors are introduced
Solution Approach 1:
The patent merges the phase calibration function directly into the oscillator drive circuit by integrating a trim circuit that includes comparators and a processing element. This eliminates the need for separate external test equipment, thereby reducing test time while maintaining calibration precision through internal signal measurement and adjustment.
Solution Approach 2:
The oscillator drive circuit performs its own phase calibration using the integrated trim circuit. The processing element measures the phase lag between drive signal and feedback signal, generates a trim code, and adjusts the phase shift circuit internally without requiring external intervention, thus eliminating test time loss and noise errors.
2Measurement precision
If external test equipment is used for phase calibration, then phase lag measurement is possible, but noise from external environment introduces errors
Solution Approach 1:
The patent extracts the phase calibration function from the external test environment and relocates it entirely within the oscillator drive circuit. By measuring phase lag internally using comparators and processing elements that operate within the same circuit, the system eliminates exposure to external noise sources while maintaining accurate measurement capability.
Solution Approach 2:
The trim circuit acts as an intermediary within the oscillator drive circuit, mediating the phase lag measurement between the drive signal and feedback signal. This internal intermediary structure isolates the measurement process from external noise while still enabling accurate phase calibration through the processing element that generates trim codes for adjustment.
3Manufacturing precision
If iterative testing is performed for phase calibration, then accurate phase alignment is achieved, but calibration process becomes time-consuming and costly
Solution Approach 1:
The patent implements preliminary action by integrating the trim circuit and processing element directly into the oscillator drive circuit during manufacturing. This allows phase calibration to be performed once during production without requiring subsequent iterative testing, thereby achieving accurate phase alignment while dramatically improving calibration efficiency and reducing costs.
Solution Approach 2:
The processing element uses feedback from the phase lag measurement between the drive signal and feedback signal to generate appropriate trim codes. This feedback mechanism enables accurate phase alignment to be achieved in a single calibration event rather than through iterative testing, thus improving productivity while maintaining manufacturing precision.
Data Source
AI summary
An oscillator drive circuit and a trim circuit are implemented inside an integrated circuit of a sensor. The drive circuit provides an oscillating drive signal at a resonant frequency to drive a movable mass of the sensor. The drive circuit includes a phase shift circuit having an input for receiving a first signal indicative of an oscillation of the movable mass and having an output. The phase shift circuit adds a phase shift component to the first signal and produces a second signal shifted in phase by the phase shift component. The trim circuit includes a first comparator for receiving the first signal, a second comparator for receiving the second signal, and a processing element. The processing element determines a phase lag between the first and second signals and produces trim code for use by the phase shift circuit, the trim code being configured to adjust the phase shift component.