MEMS Sensor Array Dithered Sampling Clock Ringing Noise Reduction
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Solution Overview
Problem
MEMS-based pressure sensors face measurement errors due to underdamped responses caused by mechanical resonances, leading to ringing noise in output signals, which affects accuracy.
Innovation Solution
The solution involves reducing the slope of the excitation signal to attenuate harmonics, using a dithered sampling clock to average out underdamped components, and implementing an array of MEMS sensors with varying dimensions to reduce ringing through destructive interference, as well as employing an oversampled ADC with a dithered clock to alleviate idle tones.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a standard excitation signal is applied to the MEMS sensor, then the sensor responds with a measurable signal, but mechanical resonances cause ringing noise and measurement errors
Solution Approach 1:
The patent applies a preliminary action by using a dithered sampling clock before the measurement is taken. The sampling clock is intentionally modulated with a dither signal that matches the resonant frequency, causing the resonant oscillations to be spread across multiple frequency components. This preliminary modulation prevents the buildup of coherent ringing noise that would otherwise corrupt the measurement signal.
Solution Approach 2:
The patent converts the harmful resonant oscillations into a beneficial effect by using the dithered sampling clock to deliberately excite the resonant frequency. This transforms the harmful ringing into a controlled modulation that can be easily filtered out in the digital domain, converting the harmful resonance into a distinguishable signal component that aids in identifying and removing the noise.
2Object-generated harmful factors
If the excitation signal slope is reduced to attenuate harmonics, then ringing noise is minimized, but the measurement response time increases
Solution Approach 1:
The patent employs periodic action by using a dithered sampling clock that periodically modulates the sampling instants at the resonant frequency. This periodic modulation creates a systematic pattern in the sampling process that allows resonant components to be consistently separated from the measurement signal through digital filtering, enabling fast response without the need for slow excitation signals.
3Object-generated harmful factors
If an array of MEMS sensors with varying dimensions is used, then destructive interference reduces ringing noise, but device complexity increases
Solution Approach 1:
The patent applies segmentation by dividing the sensing function across multiple MEMS sensors with different resonant frequencies. Each sensor in the array has slightly different dimensions, causing them to resonate at different frequencies. When excited simultaneously, their resonant responses interfere destructively, reducing the overall ringing noise. This segmentation approach distributes the complexity across identical circuitry handling multiple simple sensor elements.
4Stability of the object's composition
If a dithered sampling clock is used to average out underdamped components, then measurement stability improves, but the system complexity increases
Solution Approach 1:
The patent replaces the mechanical approach of physically damping resonant oscillations with an electrical/digital approach. Instead of modifying the mechanical MEMS structure to reduce Q-factor, the system uses a dithered sampling clock to modulate the sampling process, and digital signal processing to filter out the resonant components. This substitution of mechanical damping with electronic modulation and digital filtering achieves the same stability improvement with greater flexibility and less physical complexity.
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
These methods effectively reduce measurement errors by minimizing ringing noise, improving accuracy and stability in MEMS pressure sensor measurements.
Implementation Method 1
mechanical resonances of the MEMS device may also be considered. In some systems, such mechanical resonances may generate oscillations in response to an excitation signal
Implementation Method 2
using a dithered sampling clock to average out underdamped components
Implementation Method 3
implementing an array of MEMS sensors with varying dimensions to reduce ringing through destructive interference
Data Source
AI summary
An embodiment includes a method of performing a measurement using a micro-electro-mechanical system (MEMS) device that includes a plurality of MEMS sensors having different resonant frequencies. The method includes applying an excitation signal to a first port of the MEMS device such that each of the plurality of the MEMS sensors is stimulated by the excitation signal. The method further includes measuring a signal at a second port of the MEMS device and determining a measured value based on the measuring the signal.