MEMS Gyroscope Sense Amplifier Filtering for Linear Noise Rejection
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Solution Overview
Problem
Conventional sense amplifiers used in MEMS gyroscopes suffer from poor noise rejection capabilities and non-linear responses, which impair the accurate detection of angular motion, especially at low angular rates, due to their direct current (DC) discharge paths.
Innovation Solution
The development of sense amplifiers that utilize low-pass filters and anti-aliasing filters in the discharge path to attenuate alternating current (AC) signals, ensuring the discharge circuits operate in a linear region and providing high noise rejection capabilities, with low-pass comb filters specifically designed to attenuate signals at the gyroscope's resonant frequency and its integer multiples.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional sense amplifiers with DC discharge paths are used, then the discharge function is provided, but noise rejection capability deteriorates and linearity is poor
Solution Approach 1:
The feedback circuit is segmented into multiple parallel paths: a first feedback circuit with low-pass frequency response and a second feedback circuit with high-pass frequency response. This segmentation allows each path to handle specific frequency components, with the low-pass path providing DC discharge while the high-pass path handles AC signals, thereby improving both noise rejection and linearity simultaneously
Solution Approach 2:
The low-pass filter is introduced as an intermediary element in the DC discharge path. This intermediary component allows DC signals to pass through for discharge while blocking AC noise signals, thus improving noise rejection capability without compromising the linearity of the sense amplifier's response
2Measurement precision
If DC discharge path is provided without filtering, then discharge function is achieved, but thermal noise increases and saturation occurs
Solution Approach 1:
The low-pass filter converts the potentially harmful AC noise signals into benefit by selectively blocking them while allowing DC discharge. The filter transforms the discharge path from a noise-conducting path into a noise-rejecting path, improving detection accuracy while maintaining the necessary DC discharge function
Solution Approach 2:
The harmful AC noise components are extracted and removed from the discharge path using the low-pass filter. By taking out the unwanted frequency components while retaining the DC discharge path, the system achieves better detection accuracy without the detrimental effects of thermal noise
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 proposed sense amplifiers enhance the linearity and noise rejection of MEMS gyroscope signals, allowing for more accurate detection of angular motion by preventing saturation and reducing thermal noise, thereby improving the sensitivity of angular rate measurements.
Implementation Method 1
The anti-aliasing filter may be designed with a frequency response such that discrete frequency sub-bands are blocked or at least attenuated. The frequency sub-bands may be tuned to substantially match the gyroscope's resonant frequency and its integer multiples.
Implementation Method 2
The sense amplifier may further provide a DC discharge path allowing for discharge of the DC component of the output signal. The anti-aliasing filter may filter the output signal to maintain the resistive circuit in the linear region.
Implementation Method 3
A sense amplifier may be configured to change the level of a gyroscope signal, the signal produced by a gyroscope in response to angular motion, to a level suitable for processing circuitry
Implementation Method 4
The DC discharge path may include an anti-aliasing filter and a resistive circuit.
Implementation Method 5
MEMS gyroscopes detect angular motion by sensing accelerations produced by Coriolis forces. Coriolis forces arise when a resonant mass of a MEMS gyroscope is subjected to angular motion.
Data Source
AI summary
Sense amplifiers for use in connection with microelectromechanical system (MEMS) gyroscopes are described. The sense amplifiers may be configured to change the level of a gyroscope signal, i.e., the signal produced by a gyroscope in response to angular motion, to a level suitable for processing circuitry arranged to infer the angular velocity. The sense amplifier may further provide a DC discharge path allowing for discharge of the DC component of the output signal. The DC discharge path may include an anti-aliasing filter and a resistive circuit. The anti-aliasing filter may filter the output signal to maintain the resistive circuit in the linear region. The anti-aliasing filter may be designed with a frequency response such that discrete frequency sub-bands are blocked or at least attenuated. The frequency sub-bands may be tuned to substantially match the gyroscope's resonant frequency and its integer multiples.