MEMS Acceleration Sensor Binarization Noise Reduction
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Solution Overview
Problem
MEMS capacitive acceleration sensors used in seismic reflection surveys face challenges in reducing noise levels, particularly due to errors generated during the binarization of servo control signals near high-order resonance frequencies, which increase noise levels within the signal band.
Innovation Solution
Incorporating a delta-sigma modulation function in the binarization process of the servo control signal, along with a digital PID control unit and a binarizer configured with integrators and an encoder, to reduce the spectral density of quantization errors near high-order resonance frequencies, thereby suppressing low-frequency noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If binarization of servo control signal is performed near high-order resonance frequencies, then the control precision is improved, but quantization errors are generated that convert to low-frequency noise and increase noise levels within the signal band
Solution Approach 1:
The binarization process is segmented into multiple stages: first, delta-sigma modulation is applied to distribute quantization errors across a wide frequency range, then digital filtering selectively removes the harmful high-frequency error components that would otherwise convert to low-frequency noise, while preserving the useful control signal
Solution Approach 2:
A digital filter is introduced as an intermediary between the binarization process and the final control signal application. This filter acts as a mediator that selectively eliminates harmful quantization error components (particularly those near high-order resonance frequencies) while allowing the useful control signal to pass through, thereby preventing the conversion of high-frequency errors to low-frequency noise
2Device complexity
If time division processing is used to alternately perform acceleration signal detection and servo control, then the MEMS capacitive element can be shared, but each operation period is halved requiring faster internal circuit operation or higher voltage which increases power consumption
Solution Approach 1:
The patent merges the acceleration signal detection and servo control operations into a single simultaneous process by providing independent MEMS devices for each function. This allows both operations to occur in parallel without time-division multiplexing, eliminating the need for faster circuit operation or higher voltages, thereby reducing power consumption while maintaining structural simplicity
3Use of energy by moving object
If independent MEMS are provided for acceleration signal detection and servo force application to perform operations in parallel, then power consumption is reduced, but the MEMS structure becomes more complicated
Solution Approach 1:
The system is segmented into functionally independent modules: a dedicated acceleration sensing MEMS and a separate servo control MEMS. This segmentation allows each module to be optimized for its specific function and enables parallel operation, reducing power consumption while keeping each individual MEMS structure relatively simple
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 effectively reduces the conversion of high-frequency quantization errors to low-frequency noise, thereby lowering the noise level within the signal band and improving the sensitivity of the MEMS capacitive acceleration sensors.
Implementation Method 1
a capacitive MEMS 11; a C/V amplifier 12
Implementation Method 2
an acceleration signal detection unit 101 that detects an acceleration signal in a measurement direction
Data Source
AI summary
A servo control signal is binarized using a digital delta-sigma modulator. The digital delta-sigma modulator forms a feedback loop including a digital adder/subtractor, a digital integrator, and a one-bit quantizer to perform pulse-density modulation of the input servo control signal and output the signal as a binary value of +1 or −1.