Signal Trend Separation Using Smoothed Extreme Envelopes
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Solution Overview
Problem
Conventional signal processing methods, such as FFT, struggle to accurately separate trend components from physiological signals due to contamination in the spectrum, leading to interference and distortion, especially when dealing with non-periodic signals and incorrect periodic lengths, which affects energy estimation and recognition of specific wave patterns.
Innovation Solution
A signal processing method and apparatus that establishes upper and lower extreme envelopes, calculates a mean envelope, and smooths it to determine a trend component, allowing for effective separation of trend and non-trend components, thereby reducing spectral contamination and distortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional FFT method is used for spectrum calculation, then frequency analysis can be performed, but spectral contamination occurs due to aperiodic trend lines affecting the entire spectrum
Solution Approach 1:
The patent extracts the aperiodic trend component from the original signal using envelope detection and smoothing operations. By separating the trend component from the fluctuation components, the method removes the source of spectral contamination before performing FFT analysis, thereby improving spectrum accuracy without requiring complex filtering in the frequency domain.
Solution Approach 2:
The patent performs preliminary trend removal by establishing extreme envelopes and calculating smoothed mean envelopes before conducting spectrum analysis. This preliminary action of separating the trend component prevents spectral contamination from occurring in the first place, rather than attempting to correct it after FFT transformation.
2Object-affected harmful factors
If conventional filtering methods are applied to remove trend components, then low-frequency interference can be reduced, but distortion of specific wave patterns occurs affecting recognition
Solution Approach 1:
The patent introduces an intermediary approach by using envelope detection and smoothing operations to estimate and remove the trend component. This intermediary method avoids direct filtering of the original signal, thereby preventing distortion of specific wave patterns while still effectively removing low-frequency interference through the calculated trend component.
3Reliability
If window functions are used to mitigate boundary condition leakage, then spectral leakage is reduced, but low-frequency diffusion interference still occurs and energy estimation is affected
Solution Approach 1:
The patent extracts and removes the aperiodic trend component before performing FFT with window functions. By taking out the source of low-frequency diffusion interference beforehand, the method prevents both spectral leakage and energy estimation errors, allowing window functions to effectively handle boundary conditions without the additional problem of low-frequency diffusion.
Data Source
AI summary
An apparatus and a method for processing signal are provided. The signal processing apparatus comprises an input interface and a processing unit. The input interface receives smoothing parameters and a to-be-separated signal. The processing unit establishes an upper extreme envelope and a lower extreme envelope of the to-be-separated signal, and calculates a mean envelope between the upper extreme envelope and the lower extreme envelope. The processing unit performs smoothing according to the smoothing parameters and the mean envelope to generate a smoothed mean envelope, and determines a trend component or a non-trend component according to the smoothed mean envelope.