MEMS Gyroscope Calibration Circuit for Offset Error Cancellation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In MEMS gyroscopes, non-uniform gaps or asymmetry between the bulk acoustic resonator and sense electrodes can cause mismatched current signal amplitudes, leading to a non-zero voltage signal offset even when no angular velocity is detected, affecting the accuracy of navigation systems.
Innovation Solution
A calibration system comprising a test tone signal generator, a transimpedance amplifier, and a calibration circuit that uses a feedback loop to cancel error signals by applying a calibration signal, ensuring matched voltage signal amplitudes and reducing offset errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the gap between the bulk acoustic resonator and sense electrodes is non-uniform or there is asymmetry in electrode characteristics, then the manufacturing process is simpler, but the measurement precision deteriorates due to mismatched current signal amplitudes and offset errors
Solution Approach 1:
The patent applies preliminary action by introducing a calibration signal before actual measurement to pre-compensate for the amplitude mismatch caused by manufacturing variations. The calibration system measures the offset error and generates a correction signal that is added to the subsequent measurement signals, thereby eliminating the need for extremely precise manufacturing while maintaining high measurement accuracy.
Solution Approach 2:
The patent changes the electrical parameter (voltage signal) by introducing a calibration voltage signal that compensates for the amplitude mismatch. The calibration circuit adjusts the voltage level dynamically to match the signals from both sense electrodes, thereby correcting the underlying physical asymmetry without modifying the physical structure.
2Measurement precision
If a calibration circuit is added to cancel error signals, then the measurement precision is improved, but the device complexity increases
Solution Approach 1:
The patent implements feedback by using the output of the transimpedance amplifier to generate a calibration signal that is fed back to the calibration circuit. The calibration circuit continuously monitors the offset error and adjusts the calibration signal accordingly, creating a closed-loop system that automatically maintains signal balance without requiring complex external control mechanisms.
Solution Approach 2:
The calibration system is self-service in that it uses its own output signal to generate the necessary calibration correction. The transimpedance amplifier's output is directly used to create the calibration signal, eliminating the need for separate external calibration equipment or complex control systems.
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 calibration system effectively cancels error signals, ensuring accurate angular velocity detection by matching voltage signal amplitudes and reducing offset errors in MEMS gyroscopes, thereby enhancing navigation system reliability.
Implementation Method 1
at least one drive electrode coupled to a bulk acoustic resonator and positioned to excite vibration of the bulk acoustic resonator in a first bulk acoustic wave mode
Implementation Method 2
Plural electrodes including the at least one drive electrode and the two sense electrodes surround and are separated from the bulk acoustic resonator, generally having a disk shape, with predetermined capacitive gaps
Implementation Method 3
a later-stage amplifier (for example, transimpedance amplifier (TIA)) receives the two current signals and outputs a voltage signal corresponding to the difference between the two current signals
Data Source
AI summary
An aspect of the present disclosure concerns a calibration system including a test tone signal generator that produces a test tone; a transimpedance amplifier (TIA) that comprises two input terminals, receives two output signals from an external sensor device, the test tone, and a calibration signal at the two input terminals, and produces a voltage signal; and a calibration circuit that receives the voltage signal and the test tone to produce the calibration signal that causes the TIA to produce the voltage signal such that an error signal included in the voltage signal is canceled. The external sensor device may be a mode-matched vibratory micro-electro-mechanical systems (MEMS) gyroscope.