Randomly Jittered Under-Sampling for Low-Power Digital Metering
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Solution Overview
Problem
Modern electronic circuit breakers and digital meters face challenges in achieving high-frequency ground fault detection due to constraints on CPU utilization and power consumption, which limit the sampling rate below the required Nyquist rate, making it difficult to accurately estimate high-frequency signal amplitudes.
Innovation Solution
The implementation of randomly jittered under-sampling techniques reduces the sampling rate required for estimating high-frequency signal amplitudes by introducing aperiodicity in the sampling process, allowing for efficient data acquisition and analysis while maintaining accurate waveform representation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a periodic sampling rate of 10 times higher than the highest frequency component is used to ensure accurate signal representation, then measurement precision is improved, but CPU utilization and power consumption increase significantly
Solution Approach 1:
The patent applies periodic action by using a periodic sampling clock that is intentionally run at a lower frequency than the Nyquist rate. By combining this periodic sampling with random jitter injection, the system achieves accurate high-frequency signal representation without requiring the traditional high periodic sampling rate, thus reducing power consumption while maintaining measurement precision
Solution Approach 2:
The patent changes the sampling rate parameter from the conventional high rate (10x signal frequency) to a lower rate that satisfies a different mathematical relationship (involving signal frequency divided by an integer N). This parameter change, combined with random jitter, allows accurate amplitude estimation at reduced sampling rates, directly addressing the power consumption vs. precision contradiction
2Measurement precision
If a periodic sampling rate of 10 times higher than the highest frequency component is used to ensure accurate signal representation, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent uses a periodic sampling clock running at a lower frequency combined with random jitter injection. This approach simplifies the controller design by reducing the required sampling rate while maintaining measurement accuracy through the mathematical relationship involving signal frequency divided by integer N, rather than requiring complex high-speed periodic sampling hardware
Solution Approach 2:
The patent introduces random jitter as an intermediary element that mediates between the low periodic sampling rate and the high-frequency signal. This intermediary random variation in sampling timing allows accurate amplitude estimation without requiring the controller to operate at high speeds, thus reducing device complexity while maintaining precision
3Use of energy by moving object
If the sampling rate is reduced below the Nyquist rate to reduce power consumption and CPU utilization, then energy efficiency is improved, but measurement precision deteriorates due to aliasing errors
Solution Approach 1:
The patent fundamentally changes the sampling rate parameter from being based on the Nyquist criterion (2x signal frequency) to a new criterion where the sampling frequency is related to the signal frequency divided by an integer N. This parameter change enables sub-Nyquist sampling while avoiding aliasing through the combination of random jitter and specific mathematical relationships in the sampling timing
Solution Approach 2:
The patent employs periodic sampling at a reduced rate combined with random jitter injection. The periodic nature provides structure while the random jitter prevents aliasing by ensuring that samples are taken at varied phases of the signal cycle, enabling accurate amplitude estimation even when sampling below the Nyquist rate, thus improving energy efficiency without sacrificing precision
4Measurement precision
If a high periodic sampling rate is used to detect high-frequency ground fault signals, then measurement precision is improved, but loss of energy increases
Solution Approach 1:
The patent changes the sampling rate parameter from high frequency to a lower frequency that satisfies the relationship involving signal frequency divided by integer N. This parameter change enables accurate high-frequency ground fault detection while significantly reducing the energy consumption associated with high-speed periodic sampling operations
Solution Approach 2:
The patent uses periodic sampling at a reduced rate with random jitter injection to detect high-frequency ground fault signals. The periodic structure combined with random timing variations allows accurate detection of high-frequency transients while minimizing the energy loss inherent in continuous high-rate periodic sampling
Data Source
AI summary
Methods/systems employ randomly jittered under-sampling to reduce a sampling rate required to estimate the amplitude of high-frequency signals in circuit breakers, power meters, and other digital signal processing applications. The methods/systems can greatly reduce the nominal sampling rate for applications where RMS, peak and mean estimates of the signal are desired for both the entire band-limited signal and separate estimates for each frequency component. This can in turn result in large cost savings, as less complex and thus less expensive controllers and related components may be used to perform the sampling. As well, the methods/systems herein can provide reasonably accurate waveform estimates that allow additional cost savings in bill of materials (BOM) and printed circuit board assembly (PCBA) footprint and real-estate by eliminating the need for certain analog components, such as signal conditioning components.