Compensated Demodulator for MEMS Gyroscope Quadrature Errors
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Solution Overview
Problem
MEMS gyroscopes face measurement errors due to quadrature errors caused by phase and amplitude variations in the quadrature component, which are not accurately compensated by existing realignment methods in the digital domain.
Innovation Solution
A demodulator and demodulation method that includes a register for phase calibration, a temperature sensor, and a compensation stage to generate samples based on temperature differences, producing a demodulating signal that maintains phase coherence with the input signal, thereby compensating for phase and amplitude variations in the quadrature component.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If realignment methods are used in the digital domain to compensate for quadrature errors, then some compensation is achieved, but the compensation is not accurate enough due to phase and amplitude variations
Solution Approach 1:
The patent applies preliminary action by performing phase calibration and generating compensation samples before the actual measurement process. The system pre-characterizes the phase relationship between driving and sensing signals at different temperatures, storing these compensation samples for later use during operation, thereby eliminating the need for complex real-time digital domain compensation.
Solution Approach 2:
The patent utilizes parameter changes by measuring and compensating for phase variations as a function of temperature. The system characterizes how the phase difference between driving and sensing signals changes with temperature, and uses these characterized parameters to generate temperature-dependent compensation samples that accurately correct quadrature errors under varying thermal conditions.
2Temperature
If temperature variations occur, then phase and amplitude variations in the quadrature component increase, but existing methods cannot accurately compensate for these variations
Solution Approach 1:
The system performs preliminary temperature characterization during a calibration phase, measuring the phase relationship between driving and sensing signals at multiple temperature points. These measurements are stored as compensation samples that will be used during actual operation, allowing the system to handle temperature variations without requiring complex real-time adjustments.
Solution Approach 2:
The patent implements feedback by continuously monitoring temperature and selecting appropriate compensation samples based on the current temperature condition. The system uses the temperature sensor output to index into pre-characterized compensation data, automatically applying the correct compensation for the current thermal state, thereby maintaining measurement accuracy across varying temperatures.
3Measurement precision
If complex digital domain realignment methods are used to compensate for quadrature errors, then measurement accuracy improves, but device complexity increases
Solution Approach 1:
The patent moves the complex processing to a preliminary calibration phase where phase relationships are characterized and compensation samples are generated offline. During actual operation, the system simply retrieves and applies these pre-computed compensation samples based on temperature, replacing complex real-time digital domain realignment with simple table lookup and application, thereby significantly reducing operational complexity.
Solution Approach 2:
The patent replaces complex mechanical/digital signal processing operations with a simpler system based on pre-characterized data tables. Instead of performing complex digital domain realignment calculations during operation, the system substitutes this with straightforward temperature-based indexing and application of pre-computed compensation factors, reducing computational complexity while maintaining accuracy.
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 solution effectively annuls the projection of the quadrature component onto the Coriolis axis, improving the accuracy and stability of angular velocity measurements by maintaining phase coherence and reducing measurement errors caused by temperature changes.
Implementation Method 1
a temperature sensor (51) are present in the second die (8)
Implementation Method 2
generating a demodulating signal phase locked with the input signal, the demodulating signal having a phase which depends on the second samples
Implementation Method 3
A compensation stage (63) is configured to generate a corresponding first sample for each temperature sensed, on the basis of the difference between the detected temperature and a calibration temperature and a compensation function indicative of a relationship existing between the phase of the input signal and temperature
Data Source
AI summary
A demodulator for demodulating the in-phase component of an input signal which is in-phase and quadrature modulated. The demodulator includes a register storing a phase calibration value and a temperature sensor that performs a plurality of temperature sensings. A compensating stage generates for each temperature sensed a corresponding first sample on the basis of the difference between the sensed temperature and a calibration temperature and a compensation function indicative of a relationship existing between the phase of the input signal and the temperature. A combination stage generates a plurality of second samples, each second sample being a function of the phase calibration value and a corresponding first sample. A generating stage generates a demodulating signal having a phase which depends on the second samples and a demodulating stage demodulates the input signal by means of the demodulating signal.