FFT

Started by josif josifovski 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 simha j 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 sundar janaa 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 hspk...@yahoo.com 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 arkkimede 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 eddylamhk 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 mmg1928 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 pavan sarma 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 nasti20002001 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 umer_farooque78 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 roge...@gmail.com 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 Rayne 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 Pierre Fouillaron 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 mcese1 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 rravikiran 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 smruts14 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 gihan_gomah 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 wajid lone 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 marc...@gmail.com 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 Aimee Guerrero 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...