## Circular Convolution Riddle / Error?

Started by in comp.dsp19 years ago 8 replies

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-...

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 t=255. This does nothing to the original samples within that time span. So, we have multiplied in ...

## Problem with circular convolution in SC-FDE

Started by in comp.dsp18 years ago 1 reply

Hi, I am simulating a single carrier system in which signals are equalized in frequency domain. The concept is similar to OFDM, except both...

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 filter(Alpha=0.2) in both transmitter and receiver. A static dispersive fading channel is used in each ...

## Zero padding and Cross Correlations

Started by in comp.dsp18 years ago 1 reply

Hi, 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...

Hi, 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 convolution (aliasing effects) 2) zero-padding to a length of 8N. I expected that case 2) would give me a better estimate on the lag, but it seems like the estimate is worse! Is t...

## OFDM cyclic extension related question

Started by in comp.dsp17 years ago 4 replies

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...

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 linear convolution "appear" as circular convolution over the duration of the useful period in the OF...

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

Started by in comp.dsp17 years ago 6 replies

This is a program I found in the book named: DSP using Matlab v4.0. I think it's quite popular since I can easily find in on the Internet using...

This is a program I found in the book named: DSP using Matlab v4.0. I think it's quite popular since I can easily find in on the Internet using google. Many website provide its source code It's about Circular convolution: ---------------------------------------------------- function y = circonvt(x1,x2,N) if length(x1) > N error('N must be > = the length of x1') end if length(x2) >

## fastest cyclic convolution algorithm

Started by in comp.dsp17 years ago 5 replies

Hello everyone: First of all, thanks to all those who have posted before and for saving the archives. As you know this is my first post here. ...

Hello everyone: First of all, thanks to all those who have posted before and for saving the archives. As you know this is my first post here. I searched the archives by terms and by circular convolution but did not find anything, hope I didn't miss a post. You see, I'm trying to implement a parallel cyclic convolution algorithm and was wondering if someone can point out the fastest cyclic con...

## circular convolution

Started by in comp.dsp16 years ago 20 replies

I'm perusing the web and I suspect worse case I'll grab a few texts to further assist me, nonetheless, given two sequences ( radar application )...

I'm perusing the web and I suspect worse case I'll grab a few texts to further assist me, nonetheless, given two sequences ( radar application ) - reference and receive of length 1024. It was explained to me that the for linear convolution, I'll pad the sequences with zeros, then compute the FFTs. For circular convolution there's no need for padding. None of this makes sense to me as a re...

## Convolution and cepstral mean subtraction

Started by in comp.dsp16 years ago 8 replies

It seems to me that cepstral mean subtraction (CMS), which is commonly performed in computer speech recognition system, corresponds to...

It seems to me that cepstral mean subtraction (CMS), which is commonly performed in computer speech recognition system, corresponds to a circular convolution. I am curious what people think about how I'm viewing this and about the possible effects of changing CMS to use a linear convolution. This post turned out very long, so if you're in a hurry please just read from the fourth paragraph...

## DFT circular convolution

Started by in comp.dsp15 years ago 2 replies

hello everybody!! can anyone tell me in calculating circular convolution using DFT what will happen if i use two different length...

hello everybody!! can anyone tell me in calculating circular convolution using DFT what will happen if i use two different length signal? suppose one is of 4 point and the other is of 3 point then what will be the system?i have to do both 4 point DFT?or 4+3-1 or 6 point DFT as like linear convolution... plz help me out.. shatila

## Why linear convolution in OFDM causes ICI;

Started by in comp.dsp15 years ago 2 replies

Hello group We know that the use of cyclic prefix (CP) in an OFDM turns the linear convolution (between the channel and the transmitted...

Hello group We know that the use of cyclic prefix (CP) in an OFDM turns the linear convolution (between the channel and the transmitted signal) into a circular convolution. This is efficient to do because then we can easily equalize the channel. In most books it is referred that CP combats ISI and ICI. With ISI i am fine. I know that a circular conv between the channel (L points ) and...

## Circular convolution to Linear convolution.

Started by in comp.dsp15 years ago 1 reply

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...

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 equal samples. then i do convolution using fftw3 library. but what happens is that i am doing circula...

## linear n circular convolution relation

Started by in comp.dsp15 years ago 6 replies

I have the knowledge of fourier transform of the circular convoluion of two vectors say h and s, ie i know FFT (s ** h) [saying ** stands for...

I have the knowledge of fourier transform of the circular convoluion of two vectors say h and s, ie i know FFT (s ** h) [saying ** stands for circular convolution]. I want to know FFT of linear convolution of s and h ie my target is to calculate FFT(s*h) [where * is the linear convolution]. I neither know s nor h. Is it possible and if yes then how?

Started by in comp.dsp14 years ago 12 replies

Here's my problem. I have an image to be processed (well, deconvolved pretty much), and a star-shaped impulse response I want to deconvolve it...

Here's my problem. I have an image to be processed (well, deconvolved pretty much), and a star-shaped impulse response I want to deconvolve it with. The impulse response is symmetric in both the vertical and horizontal axis and pretty much centred, but not very precisely. Of course both the image and the impulse response are appropriately zero- padded as to avoid any circular convolution. ...

Started by in comp.dsp14 years ago 35 replies

Hi everyone, I'm currently a student studying electrical engineering at University so I'm new to both these forums and the subject of DSP in...

Hi everyone, I'm currently a student studying electrical engineering at University so I'm new to both these forums and the subject of DSP in general. I would just like to ask how can I compute the circular convolution of the two sequences: {x(n)} = {4,3,2,1} and {h(n)} = {5,6,7} I know how to compute the linear convolution, but I am stuck as to how to do the circular convolution.. Co...

## circular convolution or matrix multiplication

Started by in comp.dsp14 years ago 6 replies

Hi, I'm currently doing project on OFDM based. I want to transmit my signal through a Rayleigh channel. assume that the received signal should...

Hi, I'm currently doing project on OFDM based. I want to transmit my signal through a Rayleigh channel. assume that the received signal should be y(t)=x(t)*h(t)+n(t) or Y(f)=X(f)H(f)+N(f). I understand that in order to get y(t), we need to do a convolution between x(t) and h(t). let say, after IFFT in OFDM part, then I change the signal into serial where the data is in time domain. Now, I don...

## circular convolution and wraparound error....

Started by in comp.dsp13 years ago 4 replies

Hello forum, another basic questions, but you experts are better than any book. Give two finite sequences X and Y of duration, respectively...

Hello forum, another basic questions, but you experts are better than any book. Give two finite sequences X and Y of duration, respectively N and M samples, the convolution will be a new sequence G of length M+N-1 samples. that said, what is the wraparound error? The discrete convolution assumes that both X and Y are periodic sequences. (That way we can approximate the convolution ...

## Circular convolution optimization

Started by in comp.dsp13 years ago 2 replies

Hi there. I'm going to implement circular convolution with zero latency, however here I'll simplify it to say 1024 points latency, because I need...

Hi there. I'm going to implement circular convolution with zero latency, however here I'll simplify it to say 1024 points latency, because I need to understand where is the problem. So let's say we have an extremely long kernel, like 1000 * 1024 points. Now this is the input: i1 i2 i3 .. i1000 (each 1024 points long). And this is the kernel: k1 k2 k3 .. k1000 (each 1024 points long). To...

## Circular convolution

Started by in comp.dsp12 years ago 19 replies

I want to write a Matlab code to convolve the two signals: x=[1 2 3 4]; y=[1 -1 3]. I want to do it through circular convolution. Please kindly...

I want to write a Matlab code to convolve the two signals: x=[1 2 3 4]; y=[1 -1 3]. I want to do it through circular convolution. Please kindly any body could help in guiding how to generate the code which should be in generic form that could be used for all signals. Thank you

## How to apply Bandstop IIR Digital filter to the 60Hz Noisy ECG Signal??

Started by in comp.dsp11 years ago 2 replies

Hi every one.. I has designed a bandstop IIR filter to removed 60 Hz Sinus Noise at ECG signal. The step of I have done are : 1. Designed a...

Hi every one.. I has designed a bandstop IIR filter to removed 60 Hz Sinus Noise at ECG signal. The step of I have done are : 1. Designed a bandpass filter (frequency domain) -> it will be H 2. Do FFT to the ECG Signal -> it will be X 3. Do the circular convolution -> Y = X.*H But my question is : the output of Y is WRONG, because the result of X by FFT is SYMMETRIC , but H is not symm

## DHT circular convolution

Started by in comp.dsp10 years ago

I'm looking to prove circular convolution using the Discrete Hartley Transform. I saw an old thread on this forum where someone had got it...

I'm looking to prove circular convolution using the Discrete Hartley Transform. I saw an old thread on this forum where someone had got it working: http://www.dsprelated.com/showmessage/130417/1.php I'm using the same formulations given by wiki: http://en.wikipedia.org/wiki/Discrete_Hartley_transform http://en.wikipedia.org/wiki/Hartley_transform (see the "properties" section in ea...