Resampling Circuit for Asynchronous IMU Data Noise Reduction
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Solution Overview
Problem
Existing inertial measurement units (IMUs) and physical quantity sensor units face issues with periodic noise in output data due to asynchronous sampling rates, leading to lower quality measurement data when converting analog to digital signals.
Innovation Solution
A resampling circuit that measures time intervals between clock signal edges using a high-frequency clock and calculates measurement data by linear approximation, incorporating a low-pass filter to reduce noise and synchronize data with an external trigger signal, thereby reducing periodic noise and improving data accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If interpolation with the lowest common multiple of two sampling rates is performed, then the sampling rate conversion is achieved, but periodic noise is generated in output data due to asynchronous sampling rates
Solution Approach 1:
The patent changes the fundamental parameter of time measurement by using a high-frequency clock to measure both the first time interval (between successive edges of the first clock signal) and the second time interval (between one of the plurality of edges of the first clock signal and an edge of the second clock signal). This parameter change enables precise timing measurement without relying on integer-based interpolation, thereby avoiding periodic noise while achieving accurate sampling rate conversion.
Solution Approach 2:
The patent replaces the traditional mechanical approach of integer-based interpolation (lowest common multiple method) with a time-measurement-based approach using high-frequency clock cycles. This substitution allows for non-integer resampling ratios and asynchronous clock synchronization, eliminating the periodic noise inherent in integer-based methods while maintaining accurate sampling rate conversion.
2Measurement precision
If a high-frequency clock is used to measure time intervals, then the band of measurement data is limited, but additional circuit complexity is introduced
Solution Approach 1:
The high-frequency clock serves multiple functions simultaneously: it measures the first time interval between successive edges of the first clock signal, measures the second time interval between an edge of the first clock signal and an edge of the second clock signal, and provides the timing basis for calculating the resampled data. This multi-functionality reduces the need for separate measurement circuits, thereby limiting the increase in circuit complexity while achieving high measurement precision.
3Productivity
If linear approximation is used to calculate the second data, then the calculation speed is improved, but approximation errors are introduced
Solution Approach 1:
The patent applies linear approximation as a partial solution that is sufficient for the specific application requirements. By using linear approximation between two measured points (the first data points at the measured time intervals), the patent achieves fast calculation speed while the approximation error remains within acceptable limits for the measurement application. This partial action approach balances calculation speed and accuracy without requiring more complex calculation methods.
Data Source
AI summary
A resampling circuit converts first data updated synchronously with a first clock signal into second data updated synchronously with a second clock signal asynchronous with the first clock signal and outputs the second data. The resampling circuit measures a first time interval between a plurality of successive edges of the first clock signal, and a second time interval between one of the plurality of edges of the first clock signal and an edge of the second clock signal, with a third clock signal having a higher frequency than the first clock signal and the second clock signal. The resampling circuit calculates and outputs the second data updated at the edge of the second clock signal, based on the first time interval and the second time interval, and a plurality of the first data updated at the plurality of edges of the first clock signal.