Concept
If the data is not intercepted in the whole cycle, the truncation will cause sudden changes at both ends of the signal waveform. The intercepted signal is very different from the original signal. When the time-domain signal is subjected to spectrum analysis, the originally concentrated line spectrum will be scattered in the frequency band adjacent to the line spectrum, resulting in new frequency components that do not exist in the original signal. This effect is called leakage in spectrum analysis technology. . This means that the originally concentrated frequency information leaks into the adjacent frequency bands, which affects the accuracy of spectrum analysis and interferes with the identification of the spectrum.
Response
If the time domain signal is a random signal, the truncated result will have wrinkles on the original continuum, that is, the wrinkle effect, which will also affect the recognition of the spectrogram. The cause of leakage due to signal truncation is signal distortion. Because truncation is equivalent to multiplying the signal with a rectangular window function, according to the convolution theorem, the frequency spectrum is the convolution of the two time function spectra, that is, the frequency spectrum is multiplied at the corresponding frequency, because the frequency spectrum of the rectangular function is a band-side The spectrum of the infinite bandwidth of the lobe (the graph corresponding to the fundamental frequency is called the main lobe, and the harmonic frequency is called the side lobe), so the spectral lines are expanded into a rectangular signal spectral window (sinω(t) shape function) shape. In order to reduce the leakage error, besides adopting the whole cycle truncation, the main method is to add windows.
