## FFT

Started by in Matlab DSP10 years ago

This is my Question: I am performing fast Fourier transform (matlab> fft) of a time series of a load (with a certain magnitude) converting it...

This is my Question: I am performing fast Fourier transform (matlab> fft) of a time series of a load (with a certain magnitude) converting it into a load spectrum (frequency dependent). How can I understand the spectrum amplitude....in respect to the time load... what is the relation.... Thanks in advance... best regards, Josif

## Non-Uniform Sampling

Started by in Matlab DSP18 years ago 1 reply

Hi all, My Question is: Is FFT applicable to a non-uniformly sampled signal?. I heard from one of my friends that we can...

Hi all, My Question is: Is FFT applicable to a non-uniformly sampled signal?. I heard from one of my friends that we can apply DFT to a N-US signal and not FFT. Is this correct? And also how is the nyquist rate defined for a non uniformly sampled sign

## SC-FDE

Started by in Matlab DSP14 years ago

Dear all, I am simulating Single Carrier Frequency Domain Equalizer in AWGN Channel.. I used the QPSK BER curve and modified that to make...

Dear all, I am simulating Single Carrier Frequency Domain Equalizer in AWGN Channel.. I used the QPSK BER curve and modified that to make the SC-FDE. I am using 512 fft size and guard interval of 56. As awgn channel is used ,there is no operation in between the fft & ifft at the receiver. Should I do the zero padding at the transmitter?. If anyone

## help for matlab implementation of DIT sr FFT

Started by in Matlab DSP13 years ago

Sir I am an Mtech student doing my project in Drowsiness estimation from EEG waves.I want to implement this in realtime . For that...

Sir I am an Mtech student doing my project in Drowsiness estimation from EEG waves.I want to implement this in realtime . For that purpose initially i have to implement DECIMATION IN TIME SPLIT RADIX FFT ALGORITHM in matlab for simulation purposes. I am new to matlab. hence I request your valuable help for this. please help me by providing some information THanking yo...

## FFT GUIDE

Started by in Matlab DSP14 years ago

Hi ! Looking in the newsgroup about FFT, I think that a useful starting point could be a Guide about fft present in the Matworks site: ...

Hi ! Looking in the newsgroup about FFT, I think that a useful starting point could be a Guide about fft present in the Matworks site: http://www.mathworks.com/matlabcentral/fileexchange/loadFile.do?objectId=5654&objec tType=file This is a script where is repo

## FFT and IFFT

Started by in Matlab DSP16 years ago

Hi, I want to ask if I FFT an image, how can I recover the image using IFFT. I try to use it directly, but turn out some a totally...

Hi, I want to ask if I FFT an image, how can I recover the image using IFFT. I try to use it directly, but turn out some a totally bright picture. However, when i change the image to a very simple one, say only black and whit region, ifft can receover the image. I find out from

## Power spectrum & FFT

Started by in Matlab DSP16 years ago 1 reply

Hi, I have a question on Power Specturm using fft . I am using ode45 to solve two second order Ordinary Differential Equations. A...

Hi, I have a question on Power Specturm using fft . I am using ode45 to solve two second order Ordinary Differential Equations. A part of my program is : N=14 Yo=[zeros(N,1);zeros(N,1);zeros(N,1);zeros(N,1)];% initial conditions options =odeset('RelTol', 1e-4, 'Abs

## Require info regarding Ridgelets

Started by in Matlab DSP15 years ago

Hi, friends , I wish to implement a matlab code to find ridgelet transforms.Which includes finding FFT and then Radon...

Hi, friends , I wish to implement a matlab code to find ridgelet transforms.Which includes finding FFT and then Radon transform. The radon transform is obtained from FFT of an image by using Pseudo polar grid . While using this one ,whether we have to take only magnitude of Obtained

## FFT of rectified signal

Started by in Matlab DSP13 years ago

Hello Dear All; I am just wondering how the fft of rectified signal is different from raw signal.In fact,I am getting the same result ,when I...

Hello Dear All; I am just wondering how the fft of rectified signal is different from raw signal.In fact,I am getting the same result ,when I pass the raw signal fron HP filter and when not.I appreciate so much your help. Regards; Nastaran

## FFT : How to plot...

Started by in Matlab DSP13 years ago 1 reply

I want some help regarding the plotting of the FFT in matlab...Here is the code : Fs=3D650; % Ts=3D1/Fs; % N=3D2000; % number of samples...

I want some help regarding the plotting of the FFT in matlab...Here is the code : Fs=3D650; % Ts=3D1/Fs; % N=3D2000; % number of samples wanted, vector length %( better N=3DFs; or N=3DFs*2 or N=3DFs/2...) why ???? Fo=3D1/(Ts*N) % frequency resolution Fx=3Dfft(x); % DFT of x Nx=3Dlength(x); % Fo=3D 1/(Ts*Nx); f=3D0:Fo:Fs-Fo; % frequency vector from 0 =96 ((N-1)/N) 2 pi =3D 0 =96 Fs-F= ...

## fftshift of the fft of the fftshift (x(t))

Started by in Matlab DSP11 years ago 4 replies

Hi everyone, could somebody explain to me why is it necessary to do the fftshift(fft(fftshift(x))) where x is a 'temporal' signal? I know that...

Hi everyone, could somebody explain to me why is it necessary to do the fftshift(fft(fftshift(x))) where x is a 'temporal' signal? I know that the fftshift function makes a shift to fix the 0,2Pi to -Pi,Pi problem, but why do I have to do the first ffshift? Is there any problem with the phase of the signal or something? Thanks!

## Fast Fourier Transform

Started by in Matlab DSP13 years ago

Hi, I am very new to Matlab, and I'm supposed to use the built-in FFT function to do discrete Fourier Transform for f(x) = sin x + 4 cos(5x) +...

Hi, I am very new to Matlab, and I'm supposed to use the built-in FFT function to do discrete Fourier Transform for f(x) = sin x + 4 cos(5x) + (sin(6x))^2 on the interval [-pi, pi] with a uniform partition for the interval with n = 9. Then I have to (a) Plot the magnitudes of the Fourier coefficients and (b) Compute the first-order derivates at the grid points via FFT and compare them with f'(...

## test fourier fft

Started by in Matlab DSP18 years ago

hi, I have found differents periods in a time serie with the fft function. I wonder how to test and validate these periods. ...

hi, I have found differents periods in a time serie with the fft function. I wonder how to test and validate these periods. thanks pierre Pierre Fouillaron DEA Oc?anologie biologique Laboratoire LEMAR IUEM place Nicolas Copernic, 29280 Plou

## FFT phase curios problem

Started by in Matlab DSP12 years ago

Hi Guys, I hope someone can help, I am trying to perform an FFT on 2 seperate signals the first signal is a Sin(w_o*t) (with a...

Hi Guys, I hope someone can help, I am trying to perform an FFT on 2 seperate signals the first signal is a Sin(w_o*t) (with a dt=9.7656e-005) the second is cos(wt) when I perform the trasnform the phase of these come out a little strange. say if i use a block size of 512. then the cos term phase in the frequency domain gives a perfect 180 degree phase change over the the n...

## Prime factor fft algorithm

Started by in Matlab DSP16 years ago

Hi, What is prime factor fft algorithm ? Does anyone have algo or implementation in C? PLease send it to me (my add ) or post...

Hi, What is prime factor fft algorithm ? Does anyone have algo or implementation in C? PLease send it to me (my add ) or post it. How do I convert matlab codes to stand alone(it should work outside matlab) C code ? (using matlab or otherwise) Thanx in advance, RK

## FFT PLOT

Started by in Matlab DSP16 years ago 1 reply

hi, i want to get fft and plot it when i know the sampling frequency fs, frame duration, no. of samples per frame.I also want to...

hi, i want to get fft and plot it when i know the sampling frequency fs, frame duration, no. of samples per frame.I also want to know the code to plot normal audio signal in time domain and frequency domain w/o using dsp blockset smruts

## FFT has a size not equal to 2^N

Started by in Matlab DSP11 years ago

Hi all- I want to apply the FFT to a data has a size not equal to 2^N in a simulink model and I want to generate code from this model. I used...

Hi all- I want to apply the FFT to a data has a size not equal to 2^N in a simulink model and I want to generate code from this model. I used the Matlab Fcn block and although it succeded in the simulation , the code generation doesn't accept it. I knew that the best method to do this operation is to use the S-function Builder but I don't know C language and I need to Know the code and ...

## pink noise

Started by in Matlab DSP14 years ago 1 reply

Hi everybody I m generating pink noise (1/f noise) using following procedure. 1. Generate uniformly distributed white noise. ...

Hi everybody I m generating pink noise (1/f noise) using following procedure. 1. Generate uniformly distributed white noise. 2. Calculate the fastFourier transform (FFT), 3. Impose 1=f distribution on the power spectrum 4. Calculate inverse FFT. I have used following code for generating

## Help with FFT and IFFT

Started by in Matlab DSP11 years ago 5 replies

Hi!! I am new to matlab so please bear with me. I don't understand the IFFT and FFT matlab functions. Here is the code i am...

Hi!! I am new to matlab so please bear with me. I don't understand the IFFT and FFT matlab functions. Here is the code i am using: [sig,fs]=wavread('aemixed.wav'); time=(1:length(sig))'/fs; figure(1) plot(time,sig) fsig1 = fft(sig,fs); Y=real((ifft(fsig1,length(sig)))); figure(3) plot(time,Y) What I don't understand is that Y and sig are not the same. Can someone please explain...

## Area Under the Curve -- INTEGRATION

Started by in Matlab DSP11 years ago 1 reply

*URGENT Hi, I am using the NI DAQ USB 6008 as my data acquisition tool. My task is to get the signal from a source and make the AVERAGED...

*URGENT Hi, I am using the NI DAQ USB 6008 as my data acquisition tool. My task is to get the signal from a source and make the AVERAGED FFT of the signal and INTEGRATE the FFT throughout specific limits. I have been trying to use the TRAPZ function for the integration and here is the code: area = trapz(f,100*abs(fft_average(1:nfft/2))) However, i think trapz integrates the si...