MEMS Inertial Sensor Quadrature Error Cancellation
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Solution Overview
Problem
Conventional MEMS devices face challenges in increasing performance, reducing size, and decreasing cost, while also requiring more complex microsystems with greater computational power, which are not adequately addressed by existing technologies.
Innovation Solution
The integration of a MEMS inertial sensor device overlying a CMOS substrate with a drive frame, sense mass, sense electrode, and quadrature cancellation electrodes, where the torques caused by N-electrodes and P-electrodes are the same when the same electrical potential is applied, utilizing a drive circuit with a phase shifter and gain controller to provide DC or AC drive signals for quadrature error cancellation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional MEMS devices use traditional electrode configurations, then device structure is simple, but quadrature errors remain uncanceled reducing measurement precision
Solution Approach 1:
The electrode system is segmented into distinct quadrature cancellation electrodes separate from sense electrodes, allowing independent optimization of each function. The quadrature cancellation electrodes are positioned at specific locations around the proof mass to target quadrature error sources without interfering with primary sensing operations.
Solution Approach 2:
The quadrature cancellation electrodes are positioned asymmetrically relative to the proof mass and sense electrodes, with specific offset distances and angular positions designed to generate electrostatic forces that counteract quadrature errors. This asymmetric configuration enables selective cancellation of unwanted signal components while preserving desired measurement signals.
2Measurement precision
If AC drive signals with phase shifters are used for quadrature cancellation, then cancellation effectiveness is improved, but CMOS area and device complexity increase
Solution Approach 1:
The patent replaces traditional AC drive signal approaches requiring phase shifters and quadrature DAC elements with a DC electrostatic force-based cancellation system. This substitution eliminates the need for complex signal generation circuitry, significantly reducing CMOS area while maintaining quadrature error cancellation capability through direct electrostatic actuation.
Solution Approach 2:
The system transitions from time-varying AC signals requiring phase manipulation to steady DC electrostatic potentials. By changing the operational parameter from dynamic AC voltage with phase control to static DC voltage, the patent eliminates the need for phase shifters and reduces the complexity of drive circuitry while achieving effective quadrature error cancellation.
3Adaptability or versatility
If integrated MEMS devices incorporate more computational power and complex microsystems, then application versatility increases, but manufacturing complexity and cost increase
Solution Approach 1:
The patent combines MEMS sensing structures with CMOS electronics in a single integrated device, merging mechanical sensing elements with signal processing capabilities. This integration allows complex computational functions to be incorporated while maintaining manufacturing efficiency through compatible fabrication processes, thereby increasing application versatility without proportionally increasing manufacturing complexity.
Solution Approach 2:
The integrated MEMS device incorporates multiple functional elements including sense electrodes, quadrature cancellation electrodes, and CMOS circuitry that can serve various application requirements. The universal design allows the same basic structure to be applied across different sensing applications by adjusting electrode configurations and control algorithms, enhancing adaptability while leveraging standardized manufacturing processes.
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 approach reduces CMOS area requirements, eliminates phase shifter and quad DAC elements, and effectively cancels quadrature errors using AC or DC signals, enhancing the performance and efficiency of MEMS inertial sensors without substantial modifications to conventional semiconductor and MEMS processes.
Implementation Method 1
at least one pair of quadrature cancellation electrodes disposed within a vicinity of the sense electrode... The at least one pair of quadrature cancellation electrodes is configured such that the torques caused by the N-electrode and the P-electrode are the same when the same electrical potential is applied to them
Data Source
AI summary
An integrated MEMS inertial sensor device. The device includes a MEMS inertial sensor overlying a CMOS substrate. The MEMS inertial sensor includes a drive frame coupled to the surface region via at least one drive spring, a sense mass coupled to the drive frame via at least a sense spring, and a sense electrode disposed underlying the sense mass. The device also includes at least one pair of quadrature cancellation electrodes disposed within a vicinity of the sense electrode, wherein each pair includes an N-electrode and a P-electrode.