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Adaptive windowing to improve FFT resolution and side lobes rejection

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? ...

Inverse windowing

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? ...

DFT spectrum and coefficient insight

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...

How much do Windowing procedures harm the signal?

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). Howeve...

How are windowing functions' coefficients extracted?

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? Vah...

How spectral leakage changes the phase spectrum?

Hello All, I want to understand how spectral leakage changes the phase spectrum of a sine wave? Also when I apply window (blackman harris 11 Term or chebyshev window with 300db attenuation), I see a significant amount of reduction in spectral leakage in ...

Re: Phase of FFT compared to phase of Sinusoid

Stan Pawlukiewicz wrote: > robert bristow-johnson wrote: > > Ron N. wrote: > > > robert bristow-johnson wrote: > > > > in article 1143525055.696028.32790@u72g2000cwu.googlegroups.com, Ron N. at > > > > rhnlogic@yahoo.com wrote on 03/28/2006 00:50: > > > > > Within the DFT window, ...

Frequency resolution of FFT after windowing

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 frequenc...

thx for clay and julius, 'Still mathetical problem, but for AM demodulation with FIR filter"

Clay, thanks for your opinion... my problem is the mathematical equation for how the FIR filter to process demodulation for AM. oya, bout the windowing method, u tell me...i found the equation for bandpass filter ideal. i read a book, and i got the equation for unideal filter. is it h=w.hd? h...

Re: Need help for some simple questions

doggie wrote: ... > 4) What is the purpose of the overlap add method? Why are we doing it? To avoid circular convolution, also called time-domain aliasing. Spectral leakage of the FFT has nothing to do with this. Indeed, if you perform frame windowing and frequency-domain filtering (as in...

Re: short-term energy

"ciskusz" wrote in message news:1gcyc83.a13c3txqo280N%hotaru@alinet.it... > Jerry Avins wrote: > > > Normalizing or not doesn't affect ratios. Why bother? > > Because later I could need the energy for other purpose, hence I have to > window anyway, isn't it? ciskusz, Jerr...

seeking formula for Fourier xform of Hamming family of windowing functions

Can someone please post a closed form *formula* for (not just a plot of) the Fourier transform of windowing functions in the Hamming family of such functions, or at least post link(s) to web page(s) containing such a formula. Thanks in advance, -Michael ...

Windowed FFT power and amplitude spectrum

Here is another fascinating question on FFT spectrum!! I am trying to find how to incorporate the normalisation factors when windowing is applied to the time series before FFT is applied. When windowing (eg Hanning, flat top etc.) is applied to the time series, the amplitude of the time series...

Re: Blackman Window

Sorry for being late... Already solved it... i've decided not to use windowing. What i'm doing is the following.... As a final university project, i've written a software based on neural networks, able to distortion guitar-digitalized-audio-signals, in offline mode. In order to do so, yo...

FFT windowing and deconvolution

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 (...

Increasing Notch depth using windowing

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 ...

Re: FFT with discontinuities...

Hello, Fourier theory doesn't like discontinuities... it's optimal in a least-squares sense, since it minimizes the integral over the error squared. But that says little about the -peak- amplitude of the error itself. Or, taking an alternative view, the FT result is correct, under the bandwid...

six DFT window functions applied to a 64 point DFT

Hi, I have created a new flash program that shows how windowing is used to reduce leakage in a DFT. The program also discussed magnitude and power representation of the DFT coefficients. The program allows you to run a 64 point DFT. The DFT allows two frequency inputs with variable g...

coherent sampling and I/Q demod

(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...

Re: Finding phase and mag at particular freq

Hi, Conceptually: a) Multiply your first stream with the complex sequence exp(-j*2*pi*f*t) The purpose is to downconvert your "f" of interest to 0 Hz b) Do the same for the other stream c) low-pass filter both results. This is the tricky part, unless your signal is cyclic - for example one ...

Re: Autocorrelation

> My question was for a more general case... A lot of people says that > the autocorrelation is dominated by a cardinal sinus (ie something > like sin(A)/A), Which people say that and under what context?? Once again, the autocoreleation description that you mentioned above is what I would...

Re: Unusual Impulse Resp. from Parks-McClellan

"Jerry Avins" wrote in message news:bklsqc$j53$1@bob.news.rcn.net... I learned here recently that other optimizations -- least square error, for example -- often yield more desirable impulse responses. With a few extra taps and a nice window like Blackman, the problem doesn't arise. Does t...

Re: formula for hanning (sic) filter

Perhaps it really should be called the "von Hann" window? Does it really matter? We could call it the "cosine-squared" window, as I believe some physicists like to do, and cut Herr von Hann out completely. "Can't we all just get along?" - Rodney King Note that the relationsh...

Re: A little question about THD+N

It can be done without windowing, as Randy said. It can also be done with windowing, but why make it more complicated. I've got an example on my web page, that does a similar job. If you like, have a look (below). The method is a bit more complicated, but you could copy the general approach: -...

FIR notch filters using the Windowing method

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 fi...

Re: PitchShift using STFT

How are the clicks suppresed? Is it because of the windowing being done? I am still not able to correlate the two? Help. Regards --Himanshu ...

FFTW Accuracy vs Matlab Accuracy

Hi, i'm using FFTW to computer determine the SNR of a recorded sinusoidal signal. (1khz sinus for 5seconds @ 48khz) I'm experiencing a strange behaviour: if i compute the fft with FFTW i obtain really different values from what matlab compute. To be more specific: i compute a real 2 rea...

Re: Hamming window

Hi, You can think of windowing in general as a convolution in frequency domain (you are multiplying both functions in the time domain). The result of this convolution on frequency domain is that samples outside one frequency affect the amplitude value at that frequency ! Ideally you would wan...

Seeking Free Frequency analysis toolkit or examples

Hi, I'm currently a 17-year-old student trying to do a project, involving embedding data within an audio file. Hopefully, it will survive MP3 compression... so I've come to the conclusion I will have to convert all the samples to the freq. domain to do any analysis. I downloaded FFTW and I ...

Re: filter with arbitrary and variable rolloff

"banton" wrote in message news:lr-dnWVG__V5xfTZnZ2dnUVZ_tSdnZ2d@giganews.com... > > That is a straight forward way. I'll try it. > What do you think is a good way to design the tables of coefficients > for the fir filters. Ifft and windowing? Either the windowing method of filter...

Re: Suggestion for tapered sinc

robert bristow-johnson wrote in message news: ... > > > > > > maybe use a Kaiser window? > > > > OK. Any reason? > > > > I just read somewhere that Hamming is supposed to give the smallest > > side lobes, so I was thinking of using that. > > Hamming is easier to calcu...

Re: time difference between two acoustic sine waves

> (dbd) > The data in your referenced article should be easy to measure the > delay in. Try using the same time window on the shifted signal as on > the original signal. That is: generate the delayed signal and then > window both signals the same. That's the problem in the real world, > not wi...

Re: Low pass filter

PS: > > Not at all. On your website, you write something similar: .. and thanks for the comment. Yes, this clashes with what was discussed above. I had mostly windowing in mind. I removed that sentence. The site should get an overhaul anyway. -Markus ...

Re: DFT of a Fourier summation

I am going to admit that I didn't read your formulas carefully, but here is my understanding of it: You have a signal f(t) that is a sum of discrete tones, as given by your formula. You then want to take the Fourier transform of f(t) and do some comparison? First of all, f(t) is a finite...

Re: Recovering Phase of different frequency tones

Hi Ron, I agree fully. I started with a more complete answer, including windowing and padding with zeros to minimize some of these problems. It just got too long. Thanks, Steve ...

windowing DFT vs FFT (newbie)

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 i...

Re: Problem with FFT

On 2=A4=EB9=A4=E9, =A4W=A4=C81=AE=C901=A4=C0, patrick.me...@dmradiocom.fr w= rote: > Hi, > > I use a FFT and when I send a pure 1 MHz sinus in my 1024 pts FFT > sampled at 10 MHz, I have a lot of amplitude variation in the output > visualization.. 20% variation > > I send to the compl...

MFCC

Hey people, Im new to this group and in serious need of help.... currently doing my final yr BE... Im doing a project on Speech Recognition... I have considered an ideal case dat is a noise free enviroment and speaker dependent... only 1 speaker... ...

spectral estimation question

OK, here's one of those "This should be simple..." questions. We know that many (all?) methods of spectral estimation of discrete-time data rely fundamentally on the DFT (the N-point DFT). However, the output of a specific bin of the DFT can be viewed as a bandpass filter. This DFT bandpass ...

Re: proper terminology for one bin of an fft/dft?

Ron N. wrote: > What is the proper or most common term for computing or > describing only one bin of an fft or dft? I wish there were. Bin intimates that some kind of collection is occurring there when it is really a sample of the underlying continuous frequency domain function evalua...