To 'sinc' or not to 'sink'

Started by Richard Owlett in comp.dsp16 years ago 23 replies

What is 'sinc' function and why is it important. First response of "google" is "Sisters in Crime Internet Chapter" ;{ OK, I did find a site...

What is 'sinc' function and why is it important. First response of "google" is "Sisters in Crime Internet Chapter" ;{ OK, I did find a site with plot of 'sinc' which resembled a 'cosine with decreasing amplitude' -- The amplitude at 0 WAS 1 and decreased from there ;] Actually I suspect I need to know more about "windowing". Any references besides a book coming out in March ;> ...


windowing DFT vs FFT (newbie)

Started by Thomas Magma in comp.dsp17 years ago 1 reply

Hello, I wrote a program in Java that does a DFT on raw 8bit samples stored in memory from a RF ADC (Post processing). This allows me to...

Hello, I wrote a program in Java that does a DFT on raw 8bit samples stored in memory from a RF ADC (Post processing). This allows me to easily adjust the span (zoom) when I'm viewing the spectrum. Works great, but slow as hell. So I'm now trying an FFT with a Chirp Z-Transform so I can zoom in on the desired frequency and look for subtle modulation characteristics. I borrowed this code fr...


FFT, windowing & hop

Started by Rolf Keller in comp.dsp15 years ago 1 reply

Hi, I' m using an FFT with a Kaiser window and a hop of 50 %. 50 percent seemed to be theoretically optimal to me. But recently I read...

Hi, I' m using an FFT with a Kaiser window and a hop of 50 %. 50 percent seemed to be theoretically optimal to me. But recently I read that my idea is wrong and that the optimal hop depends on the shape of the window. The goal is that the contribution delivered by any individual sample to the final result does not depend on the random points of time where the window begins resp. en...


[NEWBIE] I need some advice

Started by Armand in comp.dsp16 years ago 1 reply

hi to everyone, I need to find WORKING dsp routines, that is, not vague or damned crypted or totaly wrong routines ( usually these are find...

hi to everyone, I need to find WORKING dsp routines, that is, not vague or damned crypted or totaly wrong routines ( usually these are find in most books). By the way , I want implement a simple ( for you,not for me) procedure to do FFT convolution of large signals ,so I think I must windowing segments of the signal , to make the convolution and to use some type of overlap in order to ...


Signals on FFT bins, and Windowing

Started by analog_fever in comp.dsp10 years ago 1 reply

I have an input signal that is generated using the following statements. Fs = 1.4287e6 (Sampling Frequency) Fbin = 32 (FFT Bin Number) N =...

I have an input signal that is generated using the following statements. Fs = 1.4287e6 (Sampling Frequency) Fbin = 32 (FFT Bin Number) N = 2^17 (FFT points) t = 0:N-1 input = A*Sin(2*pi*(Fbin/N)*t) I send this input through a Delta Sigma modulator. And then decimate it by 100 using a CIC decimation filter. Now the question is 1. I thought that the equation I use to generate the input,...


PSD-Frequency Bin?

Started by Kevin W in comp.dsp12 years ago 9 replies

I have a question about the PSD estimation and where exactly does the 'Hz' term come from on the unit denominator. After taking the 1024pt...

I have a question about the PSD estimation and where exactly does the 'Hz' term come from on the unit denominator. After taking the 1024pt FFT of a signal (let's say discrete vibration data sampled at 5kHz), we will get a plot of G vs Frequency (Hz)) with frequency resolution of 4.88Hz per data point. From my understanding of the PSD estimation (without windowing), we will square the ma...


Rectangular Window Advantage

Started by vasindagi in comp.dsp12 years ago 1 reply

Hi All, I read in this book DSP with Computer Applications that the rectangular window (used for windowing ) gives the best approximation to...

Hi All, I read in this book DSP with Computer Applications that the rectangular window (used for windowing ) gives the best approximation to the desired frequency response in a least square sense. That is, it gives the least squared, integrated, error between the Hd(W) and Ha(W) for a given number of impulse response terms. where Hd(W) is the ideal response of the filter. Ha(W) is the...


FIR filter design question

Started by Zeph80 in comp.dsp12 years ago 7 replies

In windowing method for FIR design, you specify the frequency response of the desired filter at sample points fs/N, and perform an IDFT to...

In windowing method for FIR design, you specify the frequency response of the desired filter at sample points fs/N, and perform an IDFT to obtain h(n). So doesnt this mean that you want fs to be as low as possible to specify better frequency resolution. But Fs is generally many times the cut-off frequency - more than the minimum of twice the cut off needed. Why is this?Isn't the frequency res...


Help required to use MFCC for speaker recognition

Started by AMIT kaul in comp.dsp15 years ago 5 replies

I want to use MFCC for the task of Speaker recognition but inspite of following the Steps given below i have not been able to...

I want to use MFCC for the task of Speaker recognition but inspite of following the Steps given below i have not been able to discriminate between the speakers 1)windowing 2)fft 3)power spectrum(p) 4)using melscaled filter bank f'*p(whether this is mel warping or it is something else) 5)log 6)DCT(mfccs) if there is any paper which explains which explains what exactly is melfrequency w...


Windowing and spectrum amplitude

Started by Alberto in comp.dsp15 years ago 16 replies

I have a program that does real time spectral analysis of audio signals. If I interactively change the window used before the FFT,...

I have a program that does real time spectral analysis of audio signals. If I interactively change the window used before the FFT, choosing between Hamming, Hann, Balckman, etc. etc I can of course see the widening or the narrowing of the peaks corresponding to steady frequencies, but I notice also a changing value for the amplitude of the peaks, depending on the window used. I compute the v...


FIR windowing design

Started by pinkisntwell in comp.dsp10 years ago 35 replies

Let's say I decide on a desired frequency response, for example a highpass filter with zero phase. I can then take the samples of that frequency...

Let's say I decide on a desired frequency response, for example a highpass filter with zero phase. I can then take the samples of that frequency response and take their inverse DFT to get the impulse response of a truncated IIR system, essentially windowed with the rectangular window. I can then calculate its frequency response and plot it: http://i47.tinypic.com/vrg941.png If I apply the ...


Illustrating concepts of FFT bin width and spectral leakage

Started by Richard Owlett in comp.dsp11 years ago

Recent discussion of bin width got me thinking about that and the how/why of windowing data before performing an FFT. As one who always did...

Recent discussion of bin width got me thinking about that and the how/why of windowing data before performing an FFT. As one who always did better in lab courses than theory, I decided to do some experiments. The attached program is my attempt to illustrate effects of window width and sampling frequency. I plan to add illustrations of effect of window type and numerical precision (emu...


Time Scaling using Phase Vocoder

Started by Rob Vermeulen in comp.dsp16 years ago 5 replies

Hello, I am pretty new to the topic of DSP. However, I do have some practical experience with FFT and windowing. Now what I like to have is...

Hello, I am pretty new to the topic of DSP. However, I do have some practical experience with FFT and windowing. Now what I like to have is some explanation of how to implement a phase vocoder to create a (real-time) time compress/expand algoritm. Ofcourse I've been wandering around google for quite some time and I did see some already-made implementations for the Windows platform. But th...


Questions about "windowing & bin width" and "DCT/DST & convolution"

Started by Richard Owlett in comp.dsp10 years ago 6 replies

CAVEAT - My formal coursework in "Signals and Systems" predates undergrads being introduced to Cooley, Tukey etc. I'm also such an antique...

CAVEAT - My formal coursework in "Signals and Systems" predates undergrads being introduced to Cooley, Tukey etc. I'm also such an antique that I visualize in terms of RLC tank circuits characterized by Q ~= F0/BW. (My father operated a legal land based spark gap transmitter and built his own capacitors in a fish tank obtaining ~ 1 ufd/gal {no idea what the insulation was} ;) BACKGROU...


Disperately seeking Hilbert filter coefficients

Started by Giuseppe Sbarra in comp.dsp15 years ago 11 replies

Hi everybody thanks to the support I received on a previous post I have been able to get working my implementation of a 90 degrees phase...

Hi everybody thanks to the support I received on a previous post I have been able to get working my implementation of a 90 degrees phase shifter, all I need now is a good guy which can calculate and post for me the coefficients for a 67 order Hilbert with Hamming windowing, because my tool just reach 35, or some reference to a free tool on the net for this job. ( I'm not planning to buy a 1K...


Audio output distorted with any FFT windowing other than rectangular

Started by tomb18 in comp.dsp5 years ago 18 replies

Hi, For an experiment i have a simple application that takes a quadrature signal from a radio and then does the following: Complex FFT -> ...

Hi, For an experiment i have a simple application that takes a quadrature signal from a radio and then does the following: Complex FFT -> Inverse FFT -> Cartesian to Polar -> audio out If I tune the radio to an AM signal I can demodulate it perfectly well by this but it depends on how the FFT is processed. In the FFT routine, I apply a window and if it is anything other than a rectangular wind


Peak Windowing for OFDM

Started by Crisanquito in comp.dsp11 years ago 8 replies

Hi I am trying to implement a program in Matlab in order to apply a window to the peaks of the envelope of an OFDM signal. The window I am...

Hi I am trying to implement a program in Matlab in order to apply a window to the peaks of the envelope of an OFDM signal. The window I am using is a Gaussian window, with factor gamma (exp(-gamma*t^2)) I have already implemented it, but I do not know if the results obtained are so satisfactory as they should be. My concern is on the proper choice of the value gamma: I make it inversely prop...


Increasing Notch depth using windowing

Started by ravash in comp.dsp12 years ago 3 replies

Hello everyone, Hope no introduction for why I am here (I have a problem.....) Presently i am working on a ofdm simulink implementation...

Hello everyone, Hope no introduction for why I am here (I have a problem.....) Presently i am working on a ofdm simulink implementation where I need to increase the single carrier notch depth (notch is created by putting some carriers to zero)which at present is 13dB(because of 'no window' or default 'rectangular' window implemented). I am using a raised cosine window for the same so as to ...


Picket fence effect or Scalloping

Started by rajgerman in comp.dsp14 years ago 1 reply

Hey Could anyone explain to me what the picket fence effect or scalloping is and how you would see such effects when doing fourier analysis...

Hey Could anyone explain to me what the picket fence effect or scalloping is and how you would see such effects when doing fourier analysis and using windowing? I would appreciate any help. Thanks Raj


coherent sampling and I/Q demod

Started by petethepop in comp.dsp15 years ago 1 reply

(how) does coherent sampling (used primarily in A/D testing?) differ from I/Q demodulation? Say for instance I'm using I/Q to close a PLL. In...

(how) does coherent sampling (used primarily in A/D testing?) differ from I/Q demodulation? Say for instance I'm using I/Q to close a PLL. In this case the 'sine wave' I'm locked to is being sampled at x4 the sine frequency. This would seem to satisfy the coherent sampling requirement that regarding the digitizer clock. next question - coherent sampling removes the need for windowing in FFT ap...