Current Measurement Frequency Response Correction with Equalization
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Solution Overview
Problem
Current measurement systems face challenges with signal noise ratio (SNR) degradation and signal saturation due to the positioning of the corner frequency of analog filters outside the operating frequency range, leading to inaccurate measurements and increased costs for high dynamic range ADCs.
Innovation Solution
Analog filters with corner frequencies positioned within the operating frequency range, combined with digital equalizers to compensate for changes in group delay and magnitude response, ensuring a constant gain and linear phase response across the frequency range of interest.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the corner frequency of the analog filter is positioned outside the operating frequency range, then the filter provides stable frequency response, but the SNR degrades and measurement accuracy decreases
Solution Approach 1:
The patent introduces a digital equalizer as an intermediary component between the analog filter and the measurement system. This digital equalizer compensates for the frequency response distortions introduced by positioning the analog filter's corner frequency outside the operating range, thereby maintaining both stability and measurement accuracy simultaneously
Solution Approach 2:
The patent changes the parameter of corner frequency positioning from 'outside the operating frequency range' to 'within the operating frequency range', and compensates for the resulting response variations through digital equalization, achieving improved SNR while maintaining frequency response stability
2Measurement precision
If the corner frequency of the analog filter is positioned within the operating frequency range, then the SNR improves, but the group delay and magnitude response become non-constant
Solution Approach 1:
The patent employs digital equalization as a feedback mechanism that measures the actual frequency response and group delay variations caused by the analog filter positioning, then applies compensating adjustments to restore constant group delay and magnitude response across the operating frequency range
Solution Approach 2:
The digital equalizer acts as an intermediary that decouples the benefit of improved SNR from the penalty of non-constant group delay, allowing the analog filter to be positioned optimally while the digital equalizer restores the desired response characteristics
3Device complexity
If the corner frequency of the analog filter is positioned within the operating frequency range, then high dynamic range ADCs are not needed, but signal saturation may occur due to fast di/dt signals
Solution Approach 1:
The patent converts the potentially harmful effect of fast di/dt signals that could cause saturation into a benefit by using them to demonstrate the effectiveness of the digital equalizer in maintaining signal integrity without requiring high dynamic range ADCs, as the digital equalization compensates for the filter's response variations
Data Source
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AI summary
Various current measurement systems and methods of signal processing are disclosed. In one example, there is a current measurement system that includes a filter with a corner frequency within the operating frequency range of the current measurement system. This provides a system with good SNR, whilst also preventing or reducing the likelihood of output saturation during large di/dt spikes. The system further includes an equaliser arranged to compensate for the phase and/or magnitude response of the filter within the operating frequency range.