Mark Sitkowski (@MarkSitkowski)

I've been involved with DSP for more years than I can remember, since I wrote a SPICE post-processor which applied functions like FFT/IFT, Convolution/Deconvolution etc to simulation results. I still write on the subject in my ResearchGate account.

Re: Impulse response in OFDM system using IFFT

That's only half of the IFFT. The other half contained redundant information, so I cut it.The algorithm is the standard Cooley-Tukey, with no zero-filling. Interpolating...

Re: Impulse response in OFDM system using IFFT

I split your raw data into 10 separate files, then performed an IFFT on each, and got the expected results. Here are (a) Composite frequency domain plot of all 10...

Re: Impulse response in OFDM system using IFFT

Cool. So the channel data is <-Ch1 100 data points-><-Ch2 100 data points-><-ch3...-> etc

Re: Impulse response in OFDM system using IFFT

Thanks! I'll play with it over the weekend. Do I assume you have (magnitude,phase in radians) with a linear frequency axis, with 10 channels concatenated in a single...

Re: Impulse response in OFDM system using IFFT

Any chance of accessing your raw data? I'd be interested in running it through my IFFT algorithm to see what happens.

Re: Impulse response in OFDM system using IFFT

Your phase response is due to misinterpretation of (angle), (angle+360), (angle-360) etc.As for the amplitude, you should just throw away the second half of the...

Re: Measurement of frequency deviation in FM signals

If you can get the time domain samples into an ASCII file (or whatever) and load that into an analysis tool, all the information you need is in the FFT. Here's a...

Re: z-transform examples

This doesn't answer your question, but it might shorten the design time for a real system:https://www.researchgate.net/publication/343124231...

Re: hardware FFT coefficients .vs. np.numpy.fft.rfft

Are the phase differences regular? Is it possible that it's just a case of misinterpretation of what happens when the phase vector rotates past a multiple of 360...

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Re: SPI Signal

You might try these guys:https://www.signalogic.com/index.pl?page=obsolete(40 pins could be a 32 bit data bus with 5 address bits, plus R/W line, VCC and GND. If...

Re: Use cross-correlation for speech detection/verification and time delay measurement

All with thermionic valves. I suspect there were a few well-designed filters in there somewhere.It also had a push-button automatic transmission, but we'll ignore...

Re: Use cross-correlation for speech detection/verification and time delay measurement

The 1957 Plymouth Belvedere had a self-seeking radio, with buttons labelled 'Speech' and 'Music' It would accurately find radio stations with either type of program...

Re: FSK demodulation with Doppler correction

Yes, that's correct. (Pity about the pictures - they were quite good...)

Re: FSK demodulation with Doppler correction

Hmm... looks like you can't post pictures. Sorry about that!

Re: FSK demodulation with Doppler correction

If you need to see the effect of zero-filling, here's an FFT of a 512 point 1MHz sine wave:Here's the same thing, zero-filled to 8192 points:As you can see, all...

Re: Is there any relationship between the autocorrelation of the instantaneous phase extracted from signal and the autocorrelation of the signal in time domain

Not sure if this is what you want, but this is an impulse response magnitude (green) and phase (red). I've annotated a few values of phase, just for reference. Below...

Re: FFT of a sine wave signal

Perhaps visualisation might help?Here are the real/imaginary and the mag/phase FFT's of a single frequency sine wave

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