Spectrum Analysis Apparatus for EMI Noise Filtering
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Solution Overview
Problem
Conventional FFT-based spectrum analyzers fail to accurately determine conformity to EMI standards due to infrequent impulse noise masking frequently occurring noise, making it impossible to capture necessary noise for final evaluations.
Innovation Solution
A spectrum analysis method and apparatus that accumulate multiple FFT spectrums, apply a threshold to identify frequently occurring data, and perform Max Hold only on the selected maximum levels at each frequency point, excluding infrequent noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If Max Hold is performed using conventional FFT-based spectrum analyzer, then impulse noise can be captured, but frequently occurring noise is masked and hidden by infrequent impulse noise
Solution Approach 1:
The patent applies preliminary action by performing a preliminary sweep to identify infrequent impulse noise before conducting the main measurement. The system stores results from the preliminary sweep and uses them to exclude infrequent noise components from the final Max Hold calculation, ensuring that frequently occurring noise is not masked by transient impulses.
Solution Approach 2:
The patent extracts and separates infrequent impulse noise from the total noise spectrum by comparing preliminary sweep data with main measurement data. Frequency components that appear only in the preliminary sweep (indicating infrequent impulses) are identified and excluded from the final evaluation, leaving only frequently occurring noise for compliance determination.
2Ease of operation
If swept spectrum analyzer is used to sweep frequencies, then frequency scanning is performed, but noise at frequencies not swept is not obtained
Solution Approach 1:
The patent employs periodic action by performing multiple sweeps over the frequency range, including both preliminary and main sweeps. This periodic scanning ensures that impulsive noise occurring at different times is captured across multiple measurement cycles, improving the completeness of noise detection while maintaining the swept frequency operation.
3Measurement precision
If FFT-based spectrum analyzer measures radiated disturbances, then impulse noise is not missed, but infrequent emissions mask necessary noise for final evaluation
Solution Approach 1:
The patent uses feedback by continuously comparing noise levels detected in preliminary sweeps with those in main measurements. The system identifies frequency components that exceed thresholds during preliminary sweeps, feeds this information back into the measurement process, and uses it to selectively exclude those components from final evaluation, thereby preserving relevant noise data for compliance determination.
Data Source
AI summary
Provided is a spectrum analysis method including: accumulating n spectrums obtained by consecutively fast Fourier transforming an input signal n times; receiving a threshold; identifying, in the n spectrums accumulated in the accumulating, frequently occurring data that includes data whose number of occurrences exceeds the threshold received in the receiving, the number of occurrences being defined as a total number of items of data at a same frequency point that indicate levels that are close to each other, to within a predetermined range; selecting a maximum level at each of the frequency points from among only the identified frequently occurring data; and outputting a spectrum indicating the maximum levels selected at the frequency points.