IMU Sensor Multiplexer With Analog Notch Filtering for Vibration Noise
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Solution Overview
Problem
Inertial measurement units (IMUs) using round-robin sampling architectures are susceptible to vibrational noise interference due to their intrinsic sampled transfer function, which folds harmonics of the round-robin frequency into the baseband, leading to performance issues and increased power consumption when higher frequencies are used to mitigate noise.
Innovation Solution
Implementing a sensor signal multiplexer and digitizer with an analog notch filter and optimized sample frequency, utilizing a higher frequency for input channel multiplexing and a lower frequency for analog-to-digital conversion, which reduces vibrational noise sensitivity by employing a low-speed ADC and integrating samples to generate lower frequency outputs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by stationary object
If round-robin sampling is used to share hardware across sensing channels, then cost, power, and space efficiency is improved, but vibrational noise sensitivity increases due to harmonic folding into baseband
Solution Approach 1:
The patent changes the sampling frequency parameter to be significantly higher than the round-robin frequency (e.g., 10x or more). This parameter change ensures that harmonics fold into frequencies above the baseband of interest, effectively removing vibrational noise from the measurement band while maintaining the power-efficient shared hardware architecture
Solution Approach 2:
The patent converts the harmful effect of harmonic folding into a beneficial filtering mechanism. By intentionally allowing harmonics to fold at a higher sampling frequency, the system creates natural notches in the frequency response that eliminate vibrational noise, transforming what was previously a source of interference into a noise-rejection feature
2Object-affected harmful factors
If round-robin sampling frequency is increased to avoid vibrational noise, then vibrational noise sensitivity is reduced, but power consumption and design complexity increase
Solution Approach 1:
The patent segments the sampling process into two distinct stages: a high-frequency sampling stage that captures signals above vibrational noise frequencies, and a lower-frequency output stage that delivers processed results. This segmentation allows the system to benefit from high-frequency noise rejection while maintaining lower power consumption and complexity in the output processing stage
3Object-affected harmful factors
If high-speed ADC is used to increase sampling frequency, then vibrational noise sensitivity is reduced, but power consumption increases
Solution Approach 1:
The patent implements dynamic frequency multiplication where the effective sampling frequency is derived from a lower-frequency ADC through digital or analog frequency multiplication techniques. This dynamic approach allows the system to achieve high-frequency sampling performance without the continuous high power consumption of a native high-speed ADC, as the multiplication can be performed intermittently or with lower power requirements
Data Source
AI summary
The described technology is generally directed towards a sensor signal multiplexer and digitizer with analog notch filter and optimized sample frequency, and corresponding methods of use and manufacture. In some examples, the disclosed technologies can be used to reduce vibration sensitivity of an inertial measurement unit (IMU). The disclosed sensor signal multiplexer can sample sensor inputs on multiple input channels at a first, higher frequency, and integrate samples for each channel in order to generate lower frequency sensor outputs. The lower frequency sensor outputs can be converted to digital form.