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and lack of sleep can make us all think less clearly
Q1 The DFT is basically the DTFT of a periodic signal. As you say, in the real world we have limited time sequences and can't deal with nonperiodic signals that extend for all time. If we have a limited time-slice, we can't even know if the signal is periodic or zero for other time values. Hence, we can implement a DFT and just assume the signal is periodic, which leads to discrete frequencies, rather than a continuum, which is also efficient in practice. Then you can decide whether your sequence should be padded with zeros around it before making it periodic, and in this way approximate a nonperiodic signal.
You can choose that. It could be N, or you can pad the time domain signal with zero values and make the series longer. You can look up the Matlab help information for "fft" to get some more details.[/quote]... But what is the period of frequency spectrum of DFT?
steveB said:Q1 The DFT is basically the DTFT of a periodic signal. As you say, in the real world we have limited time sequences and can't deal with nonperiodic signals that extend for all time. If we have a limited time-slice, we can't even know if the signal is periodic or zero for other time values. Hence, we can implement a DFT and just assume the signal is periodic, which leads to discrete frequencies, rather than a continuum, which is also efficient in practice. Then you can decide whether your sequence should be padded with zeros around it before making it periodic, and in this way approximate a nonperiodic signal.
You can't pad an infinite number of zeros, so it won't become a continuum. But, in a sense, you can approximate a continuous spectrum by making the frequency resolution very fine.But if you are padding it with zeros and hence approximating a non-periodic signal, then don't you think you will have continuous frequency spectrum rather than discrete spectrum? Thank you.