MEMS Accelerometer Servo Noise Cancellation Circuit
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Solution Overview
Problem
Next-generation high-accuracy seismic surveys require ultralow noise MEMS capacitive acceleration sensors, but existing technologies face challenges in reducing noise and power consumption due to servo signal leakage and limitations in variable capacitance circuits.
Innovation Solution
An electronic circuit configuration that includes an analog filter, A/D converter, digital filter, and adaptive control to cancel servo signal noise, allowing for parallel signal detection and servo control while reducing power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If time-division multiplexing is used to share the MEMS capacitive element for acceleration signal detection and servo control, then device complexity is reduced, but power consumption increases due to faster internal circuitry operation and higher voltage requirements
Solution Approach 1:
The patent divides the system into separate functional components: a dedicated acceleration signal detection capacitive element and a separate capacitive element for servo control. This segmentation allows both functions to operate simultaneously without time-division multiplexing, eliminating the need for high-speed switching and high-voltage generation while maintaining low power consumption.
Solution Approach 2:
The patent uses multiple capacitive elements that can serve their specific functions independently yet are part of the same MEMS structure. The separation allows each element to be optimized for its specific purpose while contributing to the overall system functionality, avoiding the power consumption penalties of shared resource time-division approaches.
2Use of energy by moving object
If parallel acceleration signal detection and servo control are performed simultaneously, then power consumption is reduced, but noise increases due to servo signal leakage superimposing on the detection signal
Solution Approach 1:
The patent extracts and removes the servo signal leakage component from the detection signal path by providing a dedicated cancellation path. The leakage cancellation circuit specifically targets and removes the servo signal interference, allowing parallel operation of detection and servo control without noise contamination.
Solution Approach 2:
The patent introduces a leakage cancellation circuit as an intermediary component that mediates between the servo control signal and the acceleration detection signal. This intermediary path generates an equal and opposite cancellation signal to neutralize the servo leakage, enabling clean simultaneous operation of both functions.
3Measurement precision
If variable capacitance circuits are used to cancel servo leakage signal with high accuracy, then measurement precision improves, but manufacturing becomes difficult due to process constraints on capacitance control
Solution Approach 1:
The patent changes the approach from requiring precise variable capacitance control to using fixed capacitance values that can be accurately controlled during standard semiconductor manufacturing. By adjusting other circuit parameters (resistances, gain settings) rather than relying on difficult-to-control variable capacitances, the system achieves high cancellation accuracy with manufacturable components.
Solution Approach 2:
The patent replaces complex, difficult-to-manufacture variable capacitance circuits with simpler, more manufacturable fixed capacitance components. This substitution uses standard semiconductor process capabilities to achieve the same functional goal with greater ease of manufacture and better process 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 achieves highly accurate sensor performance with reduced power consumption by effectively canceling servo signal noise and enabling simultaneous signal detection and servo control.
Implementation Method 1
a sensor element including a MEMS capacitive element
Implementation Method 2
MEMS (Micro Electro Mechanical System) capacitive acceleration sensor
Implementation Method 3
an electrostatic actuator including a movable electrode and a fixed electrode, and a capacitance between the movable electrode and the fixed electrode
Data Source
AI summary
Provided is a sensor that is highly accurate while ensuring reduced power consumption. A sensor is an electronic circuit that includes a sensor element, an analog filter, an A/D converter, and first and second electronic circuit. The analog filter filters a waveform that includes a sensor signal from the sensor element and noise based on a servo signal. The A/D converter converts the waveform filtered by the analog filter into a first digital signal. The first electronic circuit includes a digital filter and acquires a second digital signal by performing signal processing including at least a filtering process on the servo signal by using the digital filter. The second electronic circuit acquires a third digital signal by subtracting the second digital signal from the first digital signal. A setting for the signal processing for acquiring the second digital signal is changed on the basis of the third digital signal.