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Re: Time-Limited Functions Represented as Periodic

"Clay S. Turner" wrote in message news:srzPa.2$Y_1.1@fe04.atl2.webusenet.com... > > "Fred Marshall" wrote in message > news:JBjPa.2522$Jk5.1647120@feed2.centurytel.net... > > We had a long discussion about time-limited functions, spectral > > representation, etc. > > > > I...

Re: Zero Padding in radix 2 FFT

Fred Marshall wrote: > I'm not sure why the FIR situation is any different. What is wrong with the > notion of "circular convolution"? It's only meaningful for circular signals. In general, convolution, as mathematically described, requires a result that's as long as the sum of t...

Re: closed form expression for the spectrum of a windowed sinusoid

banton wrote: > I am trying to find a closed form expression for > the spectrum of a hanning windowed sinusoid. Anton, I got that first sentence. Afterwards, you lost me. However, the von Hann window can easily be applied through circular convolution in the frequency domain. Here are t...

Re: numerical differentiation using FFT

"Hakuna M. C." wrote in message news:39e8436d.0312101151.10763b4c@posting.google.com... > Hi all, > I am using a frequency operator to act as a differentiator like > > i*w d/dt > here w is the frequency defined in fourier space. > > I have my code written in matlab as foll...

Re: My problem [was Emperor...]

"Walther Fledelius" wrote in message news:231220031625598959%-@-.dk... > In article , > Randy Yates wrote: > > > Walther, > > > > You're not listening. Multiplying using the FFT (which is just an > > efficient DFT) is performing *circular* convolution. Because of > > ...

Re: Large FFT --- NOT radix-2

"Richard Owlett" wrote in message news:vvar7epmfqmuee@corp.supernews.com... > Richard Owlett wrote: > > Fred Marshall wrote: > > > > > "Richard Owlett" wrote in message > > > news:vv9fams78p7438@corp.supernews.com... > > > > > > > Any pointers to doing non-radix 2 FFT's....

Re: Anthropomorphisms and the inherent periodicity of the DFT

On Wed, 11 Jan 2006 16:44:48 -0500, Stan Pawlukiewicz wrote: > robert bristow-johnson wrote: > > (big snip) > > s" that the data > > passed to it is one period of a discrete, infinite, and periodic > > sequence of numbers that has period length of N. > > > > i fail to see this ...

Circular Convolution Riddle / Error?

I've got myself befuddled here..... Start with a temporal cosine of peak amplitude 1.0 with an integral number of cycles in 256 seconds- period of some integer multiple "k" of 1/256Hz like 10/256. Window it (multiply it) with a rectangular window of length 256 and amplitude 1.0 - from t=0 to ...

Re: Recycling FFTs

> X(2k+1) = DFT( x1[n] w_2N[n]) - DFT( x2(n) w_2N[n]) (1). The DFT of the window w_2N[n] is equal to W_2N[k] := exp(-i pi (k-1/2)(1-1/N)) sin(pi(k-1/2))/sin(pi(k-1/2)/N). So DFT( x1[n] w_2N[n]) = X1[k] * W_2N[k], the circular convolution of X1 with the transform of the windo...

fast convolution overlap-scrap filtering with scrap at end

I recently implemented fast convolution filtering for the "tools" portion of KISS FFT ( http://sourceforge.net/projects/kissfft ) I've seen a few realizations of the overlap-scrap (aka overlap save) method. They all have the scrapped output samples at the beginning of the output buffer. Th...

Re: FIR Interpolation question

Hello Roger, I'm still not quite sure of what you are trying to do overall, but if I had a block of just 256 samples sampled at 48000 samples per second and I wanted to up the sampling rate by four for just this block, then I'd FFT the data and then prepend and postpend 384 zeroes to the FFT's...

Re: Convolution versus LPFiltering

XED wrote: > Hi everyone, > > I'm trying to implement a digital filter in c++ (assignment work, so I can't > just use one that someone else has written (--bummer)) and along the way > I've discovered that my knowledge of (low pass) filtering isn't quite what > it should be. I designed m...

Re: Convolution of 2 different sized arrays of data?

in article 1132671563.449008.35900@z14g2000cwz.googlegroups.com, dbell at dbell@niitek.com wrote on 11/22/2005 09:59: > Processing to be done real-time or off-line? actually, it shouldn't make much difference if the audio file is much, much larger than the impulse response. this is reall...

Re: help me find the bug in this program please :-??

Thank you very much for the attention. I wrote directly to the author, Prof V.Ingle and here is his question. Should any one face the problem as I do, plz read this :) -------------------------- Dear Prof. NGUYEN: Thanks for the feedback. Yes, there appears to be a bug. The function was or...

Re: Zero padding and Cross Correlations

"dspchick" wrote in message news:1100t92ljn6vdc0@news.supernews.com... > Just say I am using the FFT (in matlab) to compute the crosscorrelation of > 2 discrete time signals, each of length N. I've tried 2 cases > > 1) zero-padding to a length of 2N, in order to avoid circular convoluti...

Re: returning to the alleged periodic nature of the DFT

In article d61ab25b.0405011423.2a066928@posting.google.com, Mark Ovchain at mark_ovchain@yahoo.com wrote on 05/01/2004 18:23: > glen herrmannsfeldt wrote in message > news: ... > > > If the function is not periodic, then you should not use a DFT. ... > The example of fast convolut...

comp.dsp conference: Still need presenters? How about ...

TITLE:"Fast Convolution (FFT) Filtering: From Basics to Filter Banks". DESCRIPTION: Fast Convolution filtering is a powerful technique with which every DSP engineer should be familiar. All but the shortest FIR filters are more efficiently implemented with FFTs rather than direct forms. Th...

Re: mixing sine waves

"viswanath" wrote in message news:791e9679.0405111129.111fd12f@posting.google.com... > Hi, > I have a question regarding mixing discrete sine waves. If you have > two sine waves sin(w1*t) and sin(w2*t) and they are sampled at the > same rate. If you are mixing them in a receiver operat...

Re: A stupid question about FIR filter

"Jerry Avins" wrote in message news:410a60d9$0$2828$61fed72c@news.rcn.com... > Fred Marshall wrote: > > "Jerry Avins" wrote in message > > news:4107d474$0$2824$61fed72c@news.rcn.com... > > > > > Fred Marshall wrote: > > > > > > > > > > "phuture_project" wrote in mess...

Circular convolution to Linear convolution.

Hi, I am new to this programming world, and i really need some serious help. I have done a program in which i design a filter in frequency domain, then i take a CT image, which is a 3d image, read each voxel and make a 1d array. then i equal the number of samples for both the data set. so i have e...

Re: FIR facts: True or False.

On 2004-10-02 15:30:12 +0200, Jerry Avins said: > I was under the impression that ccnvolution was convolution, no matter > how implemented; that implemention via FFT/IFFT and via transversal > methods produce the same result. Was I wrong? > > Jerry The DFT produces circular convol...

Re: Fast cross correlation!

"Atmapuri" wrote in message news: ... > Hi! > > Thanks. Would you have any references to why > you have to XX=fft(X,1,2*L); > double length of FFT with zero padding? The key word is "circular convolution". Rune ...

Re: interesting Filtering problem

akashya@uncc.edu (Abhinav Kashyap) wrote in message news: ... > I am trying to compare two data sets with equal no. of points (it has > several peaks in it).I am using correlation technique .First I filter > the noise present in signal. > For that I first FFT the data, multiply low pass fil...

comp.dsp FAQ [1 of 4]

Archive-name: dsp-faq/part1 Last-modified: Tue Oct 19 2004 URL: http://www.bdti.com/faq/ FAQs (Frequently asked questions with answers) on Digital Signal Processing The world-wide web version of the comp.dsp FAQ is maintained and sponsored by Berkeley Design Technology, Inc....

Re: convolving noise with noise will get Gaussian? what does that imply?

"kiki" wrote in message news: ... > Suppose I have a segment of data, which is basically random numbers between > 0 and 1. I call it "f". > > Doing "f" -- the noise -- self convolution several times, the resultant > data, if plotted, is of Gaussian shape. Exactly what do you do, ...

Re: Is FFT Overlap-add needed here?

Shafik wrote: > If you dont mind me asking: > > How then, is the FFT used for filtering of images, where the FFT of an > image is taken, modified in the frequency domain, then converted back. > The same is done with time-domain signals as well. > Why is the issue of aliasing not consi...

Re: filtering in freq domain

Rune Allnor wrote: > Randy Yates wrote in message news: ... ... > > Note that frequency-domain filtering is only useful for FIR filters, i.e., > > filters in which the a vector above is 1. Butterworth filters are not > > FIR filters, so you won't be able to use frequency-domain filtering o...

Re: non uniform QMF bank

dear all, i am Rama Krishna jetty,let me tell thank to dirk for his valuable suggestion. i got output after putting equivalent delay in which channel is not decomposed. i am asking one more question. i am using linear convolution in qmf bank.due that ...

Re: Why not just filter directly in the frequency domain using the fft and ifft?

Jerry Avins wrote: > John Monro wrote: > > ... > > > > > Another consideration is that latency of the FFT / IFFT is much greater > > because to implement a n-point filter you have to read in 2N samples > > even before you start the FFT/IFFTcalculations, and then the N > > calcula...

Re: fir allpass filters for phase-alignment

Valdimir Vassilevsky wrote: > > Your message is all about process. What exactly are you trying to > accomplish as the result of that process? What are the problems? It's a sound synthesis process. It's about concatenating wave-segments and aligning the phases at the transitions from one se...

Problem with circular convolution in SC-FDE

Hi, I am simulating a single carrier system in which signals are equalized in frequency domain. The concept is similar to OFDM, except both FFT and IFFT are reside in receiver side. Prefix is also used to deal with dispersive channel response. I have implemented the rooted raised cosine filte...

Re: A question about Covariance??

VijaKhara, I'm by no means an expert on this material, just a grad student, but hopefully the following comments will help further your knowledge. It's difficult to do justice to these concepts quickly, so your best bet is to Google for detailed explanations with illustrations. Basic termin...

Re: Manipulate frequency data

robert bristow-johnson wrote: > in article 1107829665.001267.308890@c13g2000cwb.googlegroups.com, > yeti349@yahoo.com at yeti349@yahoo.com wrote on 02/07/2005 21:27: > > > > ok, well eventually I need to apply filters in the frequency domain. > > > your "need" is to do the filte...

OFDM cyclic extension related question

Hello group, It is my pleasure to be posting queries to this group again. My understanding of the presence of the cyclic prefix (CP) in an OFDM symbol is to: 1. Prevent inter-symbol interference in a FIR channel if the length of the CP is larger than the delay spread of channel. 2. Makes l...

Re: Convolution of two one-dimensional arrays

"katz" wrote in message news:qfCdnVdQhc4pn9XfRVn-pw@giganews.com... > hello everyone, > i just downloaded the FFTW library, and i read the tutorial (well..i > skimmed through it). > > i'm using dev-C++. in c++, i constructed 2 vectors, and i have to convolve > them using the FFTW ...

Re: downsampling -> FFT -> upsampling

On Wed, 06 Apr 2005 12:52:06 +0000, Fred T. Weiler wrote: > > Leaving aside the downsampling, if you are splitting your input into > > consecutive blocks of N samples, and assuming that the impulse > > response of your filter is less than N samples long, then zero pad both > > blocks of i...

Re: Do the mathematical inverse and identity elements exist for convolution?

in article R3vae.105239$cg1.65671@bgtnsc04-news.ops.worldnet.att.net, Charles Krug at cdkrug@worldnet.att.net wrote on 04/23/2005 12:53: > I'm brushing up the mathematical side of my DSP brain. It's a bit dusty > having spent the last few years doing implementation and device control > wit...

Re: Interpolated frequency sampling linear-phase FIR design

Fred, thanks for pitching in! Fred Marshall wrote: > > Assume I specify the desired magnitude response of a linear-phase FIR > > filter at N/2+1 evenly spaced points [H(n):N/2+1], starting with 0, > > ending at Fs/2, where Fs is the sampling rate. > > Unless you are going to do so...

first post - first trick

I don't see this anywhere on dspguru. So here it is. Feedback welcome. I used this durning my masters project. ============================================================ --- DSP Trick Submission Form --- ============================================================ TH...

Re: Relation between dynamic range and bandwidth?

wrote in message news:1116617006.771789.155470@g14g2000cwa.googlegroups.com... > Randy, first of all I want to thank you for spending some time on this > problem. > Yes, by random I mean random for t=0,...,N-1 then these values are > repeated periodically for t=-\infty...+\infty. > ...