Fourier Transform existed, but I never had intuitive understanding until now
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Fourier Transform existed, but I never had intuitive understanding until now
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Re: Fourier Transform existed, but I never had intuitive understanding until now
#2Hmmmm i am still missing something. Are you analysing in real time or testing chunks of the wave? It would seem like chunks
Re: Fourier Transform existed, but I never had intuitive understanding until now
#3Hmmmm i am still missing something. Are you analysing in real time or testing chunks of the wave? It would seem like chunks
Real time with DFT is a bit sketchy.
Just view it as a matrix vector multiplication.
The vector is the sampled signal at discrete time steps of equal spacing, the matrix is the DFT of fixed size.
You need to fill your vector before the multiplication. This time needs to pass. You might shift it by just one value in time to create a sliding DFT, but nonetheless you will need to sample your time vector first.
The length of each chunk is fixed by the size of the DFT.
Let's say it is 1 millisecond long, each sample is 1 microsecond spaced, so it has a length of 1000. You may then create a spectrogram that captures 1 millisecond and then advances by 1 microsecond every step and this will be as close as real time as you can get.
The initial delay of your analysis vector, then advancing by one sample, plus all the time you need for the calculations included cause a delay. Although this is sometimes called real time DFT. Since you may observe the change in the signal basically in real time, but after some delay.
It is always done in chunks. Hope this helps.
Re: Fourier Transform existed, but I never had intuitive understanding until now
#4Hmmmm i am still missing something. Are you analysing in real time or testing chunks of the wave? It would seem like chunks
Real time with DFT is a bit sketchy. Just view it as a matrix vector multiplication. The vector is the sampled signal at discrete time steps of equal spacing, the matrix is the DFT of fixed size. You need to fill your vector before the multiplication. This time needs to pass. You might shift it by just one value in time to create a sliding DFT, but nonetheless you will need to sample your time vector first. The lengt…
Its helps thanks.
Re: Fourier Transform existed, but I never had intuitive understanding until now
#5Multiplication is used because when a frequency is present and in phase (meaning peaks are aligned), it would result in more 'positive curves' sitting above the x-axis than negative curves below.
This is also the principle behind DSSS modulation ( https://en.wikipedia.org/wiki/Direct-sequence_spread_spectru... ), which is used in numerous communications systems.
Re: Fourier Transform existed, but I never had intuitive understanding until now
#6https://www.dspguide.com/ is a great, general introduction to digital signal processing and includes coverage of the Fourier Transform. I'd recommend checking it out for anyone struggling to grok DSP concepts.
This article seems to have the right intent, but I felt the quality of the writing would need to improve for it to become truly useful for learners.
Re: Fourier Transform existed, but I never had intuitive understanding until now
#7Hmmmm i am still missing something. Are you analysing in real time or testing chunks of the wave? It would seem like chunks
short loops made from single chunks, actually. since frequencies are in a limited band, signal must be infinite and repeating. That is the reason analysis usually multiplies signal by window function before FFT, to "fade out" discontinuity at the loop point
Re: Fourier Transform existed, but I never had intuitive understanding until now
#8https://www.dspguide.com/ is a great, general introduction to digital signal processing and includes coverage of the Fourier Transform. I'd recommend checking it out for anyone struggling to grok DSP concepts. This article seems to have the right intent, but I felt the quality of the writing would need to improve for it to become truly useful for learners.
I think the writing was poor, but also there are some things that are just wrong. Like most of the time people sample at 10x Nyquist. That would be a huge waste of processing given that it doesn't give you any more information about the signal than just Nyquist.
Re: Fourier Transform existed, but I never had intuitive understanding until now
#9https://www.dspguide.com/ is a great, general introduction to digital signal processing and includes coverage of the Fourier Transform. I'd recommend checking it out for anyone struggling to grok DSP concepts. This article seems to have the right intent, but I felt the quality of the writing would need to improve for it to become truly useful for learners.
I think the writing was poor, but also there are some things that are just wrong. Like most of the time people sample at 10x Nyquist. That would be a huge waste of processing given that it doesn't give you any more information about the signal than just Nyquist.
Almost by definition, it does give you more information about the signal than sampling at the Nyquist frequency though?
If you have any noise at all, oversampling will be very helpful to improve the signal to noise ratio.
Re: Fourier Transform existed, but I never had intuitive understanding until now
#10For me this produced more confusion than it explained anything.