matlab FFT and time shift

Started by Anonymous in Matlab DSP18 years ago

Hi everybody! if anybody can answer to that (would be really helpful..): how to time shift (ts) a real signal (N samples, T...

Hi everybody! if anybody can answer to that (would be really helpful..): how to time shift (ts) a real signal (N samples, T time period, dt sample rate) using matlab: timeshift signal = ifft (fft(signal)*exp(2i.pi.f.ts)) ??? and then what is 'f' in t


digital filtering problem

Started by xijingzh in Matlab DSP14 years ago

Please help me, I have been struck here for a long time. Here is my problem I have a real signal in the time domain.I need to remove...

Please help me, I have been struck here for a long time. Here is my problem I have a real signal in the time domain.I need to remove a band of frequency from it to get a new real signal. So first I FFT this input real signal and multiply the FFT ouput by a filter function I chose from matlab. I hope I can get a new power spectrum with that


Re: Digest Number 88 - Frequency and FFT

Started by Anonymous in Matlab DSP18 years ago

Aloha Aloha! The Digital Spectrum, calculated by the FFT, is a sampling of the true analog spectrum. If you want to have the...

Aloha Aloha! The Digital Spectrum, calculated by the FFT, is a sampling of the true analog spectrum. If you want to have the frequency samples to coincide with "Fs" sub-multiples, then you can either do what you have done first, that is, use a number of points withou


Multithreaded FFT & Filter Support

Started by arun...@gmail.com in Matlab DSP11 years ago

I have Matlab 2008a installed on a Server housing 2 Intel Xeon Quad core processor (i.e. a total of 8 cores) and 64 GB RAM. When I perform...

I have Matlab 2008a installed on a Server housing 2 Intel Xeon Quad core processor (i.e. a total of 8 cores) and 64 GB RAM. When I perform operations like matrix multiplication, matrix inverse, Schur product of two matrices I can see all the 8 cores being utilized in the system monitor tool. However the fft(A) routine (where A is an N by N real matrix and N=8192, a power of 2) runs only on a singl...


Real-time plotting of FFT in MATLAB with C++

Started by ujal...@gmail.com in Matlab DSP10 years ago

Hi, I am capturing some digital data samples in a C++ program. I now want to give these directly to Matlab so that it can plot its FFT. The data...

Hi, I am capturing some digital data samples in a C++ program. I now want to give these directly to Matlab so that it can plot its FFT. The data coming is real-time, and I now want to see its real-time spectrum. Is there a way I can do this?


Taking FFT of Oscilloscope Based Data

Started by matlab_fft in Matlab DSP9 years ago

Hi guys, I am new to DSP related stuff, I have been trying to take the FFT of data taken from oscilloscope. It consisted of 2 Million points,...

Hi guys, I am new to DSP related stuff, I have been trying to take the FFT of data taken from oscilloscope. It consisted of 2 Million points, it has two vector one for Magnitude and one for Time. I don't now how to start as I don't know the Sampling Frequency of the signal. As long as I remember that data has frequency of 83K to 94K Hz but not sure. How can I see the frequency response of this ...


EEG analysis in Matlab

Started by srin...@gmail.com in Matlab DSP12 years ago

hello Friends, I am doing a project on EEG signal analysis in Matlab, I would like to know, what all frequency dependent features we can...

hello Friends, I am doing a project on EEG signal analysis in Matlab, I would like to know, what all frequency dependent features we can identify using FFT. All that I was able to identify are the heartbeat, the input power frequency, the eye blink. What is the advantage of using FFT in analysing the EEG signals. with regards, Srinivas.


Using fft to obtain power spectral density of a gaussian distribution

Started by Anonymous in Matlab DSP18 years ago

Hi, I am currently writing this programme to simulate the AWGN using the rand function in C and the polar box muller algorithm. I...

Hi, I am currently writing this programme to simulate the AWGN using the rand function in C and the polar box muller algorithm. I managed to simulate a series of random numbers of gaussian distribution with variance 1 and mean 0. I would like to now test using fft the power spe


Unknown phase delay after fft of rect

Started by lore...@gmail.com in Matlab DSP11 years ago

Hi, My goal is to normalize out a linear phase shift from the Fourier transform of a rectangle with settable delay and width. I have a...

Hi, My goal is to normalize out a linear phase shift from the Fourier transform of a rectangle with settable delay and width. I have a strange phenomena that I have not been able to track down. I want to take the fft of a rectangular pulse (with settable delay (tah) and width (pw)) and then look at the magnitude and phase response versus time. Mathematically taking my representation of the r...


Simulink buffer

Started by c r in Matlab DSP16 years ago 1 reply

How would I set up "ping-pong" buffers inside of simulink. I am having problem creating a 1.5 second buffer inside simulink for a...

How would I set up "ping-pong" buffers inside of simulink. I am having problem creating a 1.5 second buffer inside simulink for a pre-calculation analysis. Basically, I need to fill 1.5 seconds of a wav file and then take that data and run it through an fft, log10(fft) and


Power Spectral Density

Started by berra tosun in Matlab DSP17 years ago 3 replies

Hi there, I need to find the power spectral densities of the following signals: t = [0:1/1800:1]; ...

Hi there, I need to find the power spectral densities of the following signals: t = [0:1/1800:1]; x=sin(2*pi*300*t)+sin(2*pi*330*t); y=sin(2*pi*700*t)+sin(2*pi*900*t); X = fft(x,8192); Y = fft(y,8192); f=[0:8191]/8192; Pyy=Y.*conj(Y


Fwd: Need help on FFT error msg

Started by Sameer Herlekar in Matlab DSP11 years ago

Hello all, Just thought I'll post to the group a one-on-one correspondence email from a few weeks ago, for the group...

Hello all, Just thought I'll post to the group a one-on-one correspondence email from a few weeks ago, for the group members' interest/thoughts/discussions Thanks Sameer ---------- Forwarded message ---------- From: Sameer Herlekar Date: Tue, Mar 18, 2008 at 11:41 PM Subject: Re: [matlab] Need help on FFT error msg To: Haizad Mohamad Haizad,


phase spectrum

Started by rosita hamidi in Matlab DSP11 years ago 2 replies

Hi every body, ? I want too plot phase spectrum of a signal. I've used this code: ? X=fftshift(fft(signal)); phi=unwrap(angle(X)); ? But...

Hi every body, ? I want too plot phase spectrum of a signal. I've used this code: ? X=fftshift(fft(signal)); phi=unwrap(angle(X)); ? But it doesn't work. Although the similar code for amplitude is correct: ? X=fftshift(fft(in)); amp=(abs(X)/2)/max(abs(X)/2); ? ? Can anybody help me? Regards; Rosita


truncating the function and taking fft

Started by rahul ramchandran in Matlab DSP14 years ago

% Rectangular pulse,FFT shifted N=400; t=linspace(-10,10,2000); n=0:N-1;%index x = [zeros(1,220) ones(1,60)...

% Rectangular pulse,FFT shifted N=400; t=linspace(-10,10,2000); n=0:N-1;%index x = [zeros(1,220) ones(1,60) zeros(1,120)];%rectangular pulse % plot(n,x);axis([0 400 -0.5 1.5]);grid on xlabel('n');ylabel('x[n]');%pause; X = ifft(x,2000);%fourier transfo


Applying FFT on the data obtained from oscilloscope

Started by yeok...@ntu.edu.sg in Matlab DSP13 years ago 2 replies

Hi all, Firstly I would like to apologise if this message appears to be a repost. Anyway I saved data of a sine wave from the Agilent...

Hi all, Firstly I would like to apologise if this message appears to be a repost. Anyway I saved data of a sine wave from the Agilent oscilloscope and imported it into MATLAB. I have 2 sets of data, one is the timing data and one is the amplitude data. My task is to obtain the fourier transform for the sine wave and analyse the harmonic content of the wave. I can apply the fft function in...


Raised (numerical) noisefloor FFT between sine/square

Started by pete...@essensium.com in Matlab DSP12 years ago

Dear all, I have taken the FFT of a sine wave and the spectrum shows a nice, single tone at the expected frequency (32MHz) with the numerical...

Dear all, I have taken the FFT of a sine wave and the spectrum shows a nice, single tone at the expected frequency (32MHz) with the numerical noise floor going down as low as -250dB. It has to be noted that this sine wave was output from a Simulink model/simulation (structure with value/time points). Next, I wanted to model the clipping of this sine wave (or actually the conversion to d...


Low - pass filter explanation

Started by szuc...@gmail.com in Matlab DSP10 years ago

Hi all, I have some basic questions regarding a low-pass filter. I have never studied audio signal processing that's why my questions might...

Hi all, I have some basic questions regarding a low-pass filter. I have never studied audio signal processing that's why my questions might seem trivial for most of you. So I have to design a low-pass filter. Here is the way I do it. I have my matrix with the signals signalMatrix. I create a FFT so I do : newVector = fftsfift(fft(signalMatrix)); Here is my first question : what do I get n...


urgent ...fft of steady state part of response

Started by abhijit potadar in Matlab DSP17 years ago

Dear matlab experts , i am a mechanical student& relatively new user of matlab. I am finding out the response of a vibrating...

Dear matlab experts , i am a mechanical student& relatively new user of matlab. I am finding out the response of a vibrating system ...,& now I want to find out the fft of steady state part of the response .., How can I remove the Transient part from the signal &a


Frequency response function (FRF) from input and output with different sampling frequency

Started by apad...@yahoo.co.uk in Matlab DSP12 years ago

Dear scholars, My present work centres on extraction of modal parameters from the plots of magnitude of frequency response response functions,...

Dear scholars, My present work centres on extraction of modal parameters from the plots of magnitude of frequency response response functions, FRFs, versus frequency. FRF is simply the ratio of the FFT of the response (output) to the FFT of the excitation (input). My questions can be summarised as follows: 1. The time histories of the response and excitation are 250Hz and 500Hz respectively....


freqresp with fft command

Started by ilke...@yahoo.com in Matlab DSP13 years ago

Hi, I want to identify a system's parameters from time domain response. To do this, i want to find frequency response function of the system...

Hi, I want to identify a system's parameters from time domain response. To do this, i want to find frequency response function of the system by using time domain response(impulse response). I compare the result of fft with real freq. resp. function value(by "freqresp" command), but these are not same. My code is here : %constructing system A=[-0.8 -16;1 0]; B=[0.2;0]; C=[-0.8 -16];...