What is the DC component in frequency analysis?

・In Japanese
＜Premise knowledge＞
・How to analyze frequency

If the signal to be frequency-analyzed contains an offset element, it will be difficult to understand the original frequency band even if frequency analysis is performed. This offset element is called the direct current (DC) component. While the original frequency behaves like an alternating current, the offset is like a direct current, so it is called a direct current component. When doing frequency analysis, it may be better to remove the DC component (this depends on the purpose of the frequency analysis).

As an example, the results of frequency analysis with and without a DC component in the 5Hz frequency signal are as follows.



As mentioned above, the amplitude of the original frequency band becomes relatively small when there is a DC component (however, the absolute value of the amplitude is almost the same as when there is no DC component).

■How to remove DC component

A common way to remove the DC component is to subtract the mean of the signal from the original signal.



If the DC component is uniformly offset as described above, if the average value is subtracted, the DC component may not be uniformly offset and may change with time. In that case, you need to do another method instead of subtracting the average value. Click here.

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