When I sample a certain digital signal with increasing sampling frequency, the fast Fourier transform of the sampled signal becomes finer and finer. (the image follows) Previously I thought higher sampling frequency makes the sampled signal more similar to the original one, so the Fourier transform of a signal sampled at very high frequency would be the same as the FT of the original signal. But in fact the FT of the sampled signal is much narrower.(adsbygoogle = window.adsbygoogle || []).push({});

How to explain this phenomenon? As the FT is different in different sampling conditions, why the original signal can still be correctly reconstructed?

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# Sampling a signal and do the discrete Fourier transform

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