fft and windowing

Started by heavyfranz in comp.dsp6 years ago 1 reply

Hi, I'm doing a spectrum analyzer. i collect 4096 samples of data from codec then I stop interrupt and begin fft. The algoritm that I use ( in...

Hi, I'm doing a spectrum analyzer. i collect 4096 samples of data from codec then I stop interrupt and begin fft. The algoritm that I use ( in the ti's dsplib) does not provide a windowing, so I don't understand if would be ok to do some "by-hand weighted windowing" multiplying a window with the frame of data, without implementing an overlap-add function. And secondarily, is right to do a "fake o...


Adaptive windowing to improve FFT resolution and side lobes rejection

Started by boon chun in comp.dsp10 years ago 2 replies

Hi, I come accross a patent found by Russell. The below is the link. http://www.freepatentsonline.com/6298363.html I try to find more...

Hi, I come accross a patent found by Russell. The below is the link. http://www.freepatentsonline.com/6298363.html I try to find more information on the Adaptive windowing method but did got any luck. May I know does any one has any opinion or information about the Adapative Windowing method? Regards, BC


Windowing problem before LPC

Started by hyeewang in comp.dsp8 years ago 4 replies

Why window the signal before computing LPC coefficients? What is the whys of windowing? I know windowing can prevent spectrum leakage,but...

Why window the signal before computing LPC coefficients? What is the whys of windowing? I know windowing can prevent spectrum leakage,but LPC is none of business of FFT, so it has no spectrum leakage. Any comments would be appreciated!


Inverse windowing

Started by Anonymous in comp.dsp12 years ago 4 replies

Hi All, I am taking FFT of incoming signal and then windowing (convolving H(f) with the signal) it in frequency domain. After that I perform...

Hi All, I am taking FFT of incoming signal and then windowing (convolving H(f) with the signal) it in frequency domain. After that I perform filtering of the signal. Now before taking the the IFFT, I want to do inverse windowing. What should be my H(f) for this?


windowing and zero-padding

Started by Anonymous in comp.dsp10 years ago 26 replies

Suppose I have a sequence of n samples where n is not a power of 2 and I zero-pad that sequence up to the next power of 2 number of samples...

Suppose I have a sequence of n samples where n is not a power of 2 and I zero-pad that sequence up to the next power of 2 number of samples before computing the FFT of the resulting padded sequence. If I want to apply windowing (e.g. Hamming) before computing the FFT, should the window width used to compute the windowing weights be n (the original number of samples) or should it be the ...


What purpose is for a sliding FFT on windowing data?

Started by fl in comp.dsp3 years ago 1 reply

Hi, I read some codes from some formal demonstration sample project. It is found that there are 4 data blocks (one is the present data...

Hi, I read some codes from some formal demonstration sample project. It is found that there are 4 data blocks (one is the present data block). After the 4 block data windowing, it is sent to an FFT function. The interesting thing is that the FFT function is not the same with the windowing block. In fact, the FFT is cycled with a fixed data block position (as one data block is getting...


How are windowing functions' coefficients extracted?

Started by Vahid Raissi in comp.dsp14 years ago 3 replies

Hi all, I just wonder why for example Hamming has chosen 'that' special set of coefficient for his windowing function, or any other guy such...

Hi all, I just wonder why for example Hamming has chosen 'that' special set of coefficient for his windowing function, or any other guy such as Kaiser, Van Haan etc. Is there any mathematical reasoning behind these coefficients or are they just 'discovered' by performing several tests? Vahid


Matched filters via cross-correlation

Started by Larry Gadallah in comp.dsp2 years ago 3 replies

Hi all: I am working on a tone receiver that uses cross-correlation to implement a matched filter for the tone. I have frames of samples that I...

Hi all: I am working on a tone receiver that uses cross-correlation to implement a matched filter for the tone. I have frames of samples that I cross-correlate with a frame containing samples of a pure reference tone. My question involves windowing: Should I use a windowing function on each frame? Should the windowing function apply both to the signal frame and the reference frame


Why is Dolph-Chebychev windowing relatively obscure?

Started by Eric in comp.dsp7 months ago 22 replies

Most software seems to focus on Hann, Hamming, and Blackman windowing. From the graphs I've seen, Dolph-Chebychev appears to outperform...

Most software seems to focus on Hann, Hamming, and Blackman windowing. From the graphs I've seen, Dolph-Chebychev appears to outperform them: https://en.wikipedia.org/wiki/Window_function#Dolph.E2.80.93Chebyshev_window Anyone know why it isn't featured in DSP texts to the extent of the other windows above? Are there drawbacks?


How much do Windowing procedures harm the signal?

Started by Pygmalion in comp.dsp10 years ago 24 replies

Hello experts, I was cruising on Internet for faily long time and I could not get the answer to my questions regarding windowgin...

Hello experts, I was cruising on Internet for faily long time and I could not get the answer to my questions regarding windowgin procedure. 1. Everybody are writing how good windowing is for supressing leakage (amplitudes at frequencies higher and lower than the signal frequency). However nobody says how much it supresses amplitude at signal frequency itself. It surely must suppress ...


Windowing effect on spectral leakage and phase after FFT

Started by shinchan75034 in comp.dsp8 years ago 4 replies

Hi, This is a great forum. I am learning a lot about DSP here. But I am puzzled by the effect of windowing in the code below. (P.S., this is not...

Hi, This is a great forum. I am learning a lot about DSP here. But I am puzzled by the effect of windowing in the code below. (P.S., this is not a homework problem. I am trying to learn how to do spectral analysis on random signals). I am much obliged to your help. 1. Why did spectral leakage and gain loss occurred in when I windowed the sinusoid? (I think I coded it correctly). 2. My time ...


About windowing question.

Started by HyeeWang in comp.dsp9 years ago 8 replies

Assume a digital signal x,let us call its true spectrum X.then we apply a window w with x,we get y = x.*w. let us call y's true...

Assume a digital signal x,let us call its true spectrum X.then we apply a window w with x,we get y = x.*w. let us call y's true spectrum Y. Then my question is : Are X and Y the same? 1. If they,X and Y, are same, how to account for that they are different in time domain obviously? 2. If they,X and Y,are different,but we always analysis the spectrum of X by using windowing the original ...


Windowing in the Frequency Domain

Started by OldUncleSilas in comp.dsp9 years ago 50 replies

Hello there, I'm currently working on a pitch identification program in MATLAB. It uses the Sliding DFT so I need to apply windowing functions...

Hello there, I'm currently working on a pitch identification program in MATLAB. It uses the Sliding DFT so I need to apply windowing functions in the frequency domain. I understand this is done by convolution and have managed to find the kernel for the von Hann window: [-0.25 0.5 -0.25], but am struggling to find a concrete answer for other windows like the Hamming and Blackman window. Anyon...


DFT spectrum and coefficient insight

Started by Blocher's spokesman in comp.dsp10 years ago 10 replies

Hi, I have created a new flash program that gives further insight into the DFT. it is located...

Hi, I have created a new flash program that gives further insight into the DFT. it is located here. http://www.fourier-series.com/fourierseries2/DFT_tutorial.html I have the new program highlighted on the page. This program explains the DFT coeffiecients and also gives insight into why windowing is needed. I intended to do a program on windowing, but got sidetracked and did this ...


FIR notch filters using the Windowing method

Started by Greer in comp.dsp13 years ago 41 replies

Hi, I am trying to obtain a FIR notch filter which is very narrow. For example, a 50 Hz notch filter to remove mains noise from a 1250Hz...

Hi, I am trying to obtain a FIR notch filter which is very narrow. For example, a 50 Hz notch filter to remove mains noise from a 1250Hz signal say. Doing this with an IIR filter was easy, I could specify my "notch region" as small as [49 51]Hz. I am now trying to do the same with a FIR filter. I am using Intel Peformance Primative functions to generate the taps. These use the windowing ...


FFT windowing and deconvolution

Started by Arrigo Benedetti in comp.dsp13 years ago 7 replies

I would like to get some feedback on this idea. Multiplying a signal in the time domain by a window before computing its FFT is equivalent to...

I would like to get some feedback on this idea. Multiplying a signal in the time domain by a window before computing its FFT is equivalent to the convolution of the transform of the signal with the transform of the window. It seems therefore that one could "undo" the effect of a square window (i.e. FFT with no windowing at all) by applying a complex deconvolution algorithm in the frequency d...


Frequency resolution of FFT after windowing

Started by spaz in comp.dsp11 years ago 11 replies

When I normally do a FFT, the frequency resolution = sampling frequency/number of samples. When I use windowing (like BH4) to prevent smearing,...

When I normally do a FFT, the frequency resolution = sampling frequency/number of samples. When I use windowing (like BH4) to prevent smearing, this should increase the frequency resolution of the FFT, because of the convolution in the frequency domain. I have seen tables which show the frequency resolution increases by a factor of 1.9 for a Blackman Harris window, so if the frequency resoluti...


How do apply window in the Frequency Domain for a signal that was zero padded before FFT?

Started by Anonymous in comp.dsp4 years ago 10 replies

I can window in the frequency domain without zero padding by following this article...

I can window in the frequency domain without zero padding by following this article here: http://www.embedded.com/design/configurable-systems/4008835/DSP-Tricks-Frequency-Domain-Windowin g However I need to Zero pad the input signal for a particular size but I'm not sure how to then do frequency domain windowing on this signal.


DFT output signal power

Started by jungledmnc in comp.dsp9 years ago 1 reply

Hi there, yet another question about DFT/IDFT processing. Here's what I do (assuming 80% overlap): 1) Take let's say 4096 source samples. 2)...

Hi there, yet another question about DFT/IDFT processing. Here's what I do (assuming 80% overlap): 1) Take let's say 4096 source samples. 2) Perform windowing (using Hann). 3) DFT the result. 4) Here should be some spectral processing, but now it is not. 5) IDFT the result. 6) Perform windowing again (could this be omitted?) 7) Multiple each resulting sample by 2.0 / 4096. I don't remember...


advice for choosing FFT window function

Started by ggk in comp.dsp10 years ago 3 replies

Hello, I was hoping I could get some advice to help me decide which FFT windowing function (or no windowing function) would be...

Hello, I was hoping I could get some advice to help me decide which FFT windowing function (or no windowing function) would be most appropriate for my application. I have a (1xN) array of sampled data. For reference, the sampled data is IC clock jitter (each data point is a measurement of the difference between a clock's measured rising edge and its ideal location). The noise spectrum i...