Retired Engineer working in Defence Electronics, and numerous other areas. BSc (first) in Applied Physics and Electronics, Durham University 1976.

Re: FFT question

Reply posted 2 months ago (06/23/2022)
I'm not familiar with 'liquid'. The fftw3 does work, but the user interfaces can make implicit assumptions that don't match what you expect (true for all implementations)One...

Re: FFT question

Reply posted 2 months ago (06/23/2022)
Are you using a full complex fft, or one that assumes symmetry of the positive and negative spectrums. Many FFTs make the assumption of real valued inputs, such...

Re: Applications for a new FFT algorithm

Reply posted 4 months ago (04/28/2022)
Vaguely sounds like the Lifted wavelet transforms, with the wavelet transform being seen as cascaded short ffts or FIR filters. Still sounds interesting. Definately...
In line with the other replies, try explaining the code to a video recording as if you'll be publishing the explanation of how to debug to YouTube (other platforms...
While it is true that oversampling doesn't add any more data, what it does provide is extra spaces for the smooth interpolation of the spectrum to better estimate...
Just thinking out loud here. If the matrix is split into a complex conjugate part and a residual part (which would be complex and could be off diagonal), does that...
As @krasin notes the missing signal frequencies appear in the second half of the signal. That will be because it's a chirp, so the frequency changes with time (=...
My impression is that 'gap' in the frequency band is, as you expect, caused by the undersampling of the signal. You will have a period where you have an almost fs/2...

Re: Phase brake in tonal signal and frequency estimation

Reply posted 8 months ago (12/09/2021)
Notice where the nulls stay aligned and ponder why is that? Also beware using the same analysis technique as used for generating the problem (i.e. digital sampling...

Re: Using noise to increase resolution of ADC

Reply posted 9 months ago (11/22/2021)
IIRC, I did my original calculation on a Sinclair QL to see what linearity was possible out of filtering sample noise on an ADC..A side fact is looking at the 'knee'...

Re: Using noise to increase resolution of ADC

Reply posted 9 months ago (11/22/2021)
With ideal Gaussian noise, with rms = 0.5 bits (of the ADC), then you can gain upto 8 extra bits by averaging a long sequence of results for a constant DC level...

Re: Modulation in laser satellite communication

Reply posted 10 months ago (09/29/2021)
Hi Adilko, It's not that it's impossible, rather it is just that you need either sneaky techniques or careful selection of the method. I don't think the laser...

Re: Modulation in laser satellite communication

Reply posted 11 months ago (09/28/2021)
Remember that "phase" is measured in metres (or millimetres, or microns) as it is 'fractions of a wavelength'.So shifting to optical frequencies, where the wavelength...

Re: Can you find the illegal step?

Reply posted 12 months ago (08/27/2021)
This is mathematics, not real world, isn't it? The error, if there is one ;-), is the last step where 'b' should be subtracted from both sides, resulting in the...

Re: Recent FFT benchmarking report

Reply posted 1 year ago (08/03/2021)
Thanks, looks useful. Always like stuff on FFTs and its derivatives.

Re: Digital IIR Parallel Implementation

Reply posted 1 year ago (06/26/2021)
Do make sure that if x[0...n] = 1, that you have stability, rather than an exponential 'explosion'. That is, don't forget the effective multiplier for the x[n]...

Re: Overdriven Sine Wave through DSP Filter

Reply posted 1 year ago (05/28/2021)
Some quick thoughts.There are two things to consider: the amount of overdrive, i.e. just a little clipping, or large overdrive giving a trapezoid shape, or the massive...

Re: Off by one windowing

Reply posted 1 year ago (05/04/2021)
Is there a typo here"0 2÷3 2÷3" ?Should it read"0 1÷3 2÷3", i.e. ~ "0 0.333333 0.666666" ?If not, maybe a slight expansion of the text to tease out more of the...

Re: Recover signal from the real part of IFFT

Reply posted 1 year ago (04/24/2021)
Also, ultimately, the transmitted signal is a purely real signal, sampled in the time domain, thus all those complex parts are mathematical artefacts with various...

Re: ADC can't perceive MLS (maximum length sequence)

Reply posted 1 year ago (04/06/2021)
Definitely start with a lower sequence rate, and lower them until you can see the sequence cleanly.Also consider doubling the 'sample/bit rate' in the sense that...

Re: Real Numbers

Reply posted 1 year ago (04/05/2021)
You forgot the distinctions around zero.Some number systems have no zero, such as Roman numerals (and no negative).We also have the subtle distinction between additive...

Re: phase error correction

Reply posted 1 year ago (03/18/2021)
Are you simply averaging the theta values, which have roll-over, as that roll over can cause a significant non-linearity. You could average the complex phase (i.e....
Just a quick thought, without any real 'thinking' - do those two delayed signals simply amount to a small phase shift that effectively increase the size of the signal,...

Re: How to test my FFT implementation?

Reply posted 1 year ago (03/07/2021)
Random noise can produce wildly random results (well, because..). It's a reasonable approximation but the statistics aren't always as good is hoped.You didn't say...
The maximum value is determined by the initial y[0] {aka y(1)} value copied from x[0] {x(1)}, so the randomised trial will get rather random results because the...
so, I think you have: y[n] = 0.98*y[n-1] + (x[n] - x[n-1])Assuming that y[-1] = 0, you have a 2% decay on any existing y[n-1] value, plus the difference between...
The Wikipedia 'Stability' section https://en.wikipedia.org/wiki/Infinite_impulse_res... maybe a useful place to start.Separating the variables will be part of the...

Re: Matlab Basic Functions Reference (pdf)

Reply posted 2 years ago (01/08/2021)
Maybe it needs    A=[1 2 3 4 5 6]; A(:)and    B = [1 2 3; 4 5 6]; B(:)to highlight the internal ordering. (Perhaps along with sum(A) and sum (B) just to clarify..)The...

Re: Matlab Basic Functions Reference (pdf)

Reply posted 2 years ago (01/07/2021)
It would be nice if they also included a note/clarification about the row/column, X-Y, angle conventions for 'row vectors' etc.The conventions can confuse many,...

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