## fft problem

Started by in Matlab DSP16 years ago 4 replies

Hi, i generate 2 signals in matlab and when i see there spectrum ,the closely space signals mixed up here what i have done Fs...

Hi, i generate 2 signals in matlab and when i see there spectrum ,the closely space signals mixed up here what i have done Fs = 400 ; % sampling rate Nres = 0.1 ; %spectral resolution of fft Nfft = fs/Nres ; % number of points in fft i.e 4000 t = (1:64)/fs ; %lengt

## fft and pitch

Started by in Matlab DSP15 years ago

hi, I am using the fft to get pitch. i have a speech sample which i have divided into frames. i ckeck if the frame is voiced or...

hi, I am using the fft to get pitch. i have a speech sample which i have divided into frames. i ckeck if the frame is voiced or unvoiced by geting the energy and if is voiced i get its fft. i then get the magnitude of it. the magnitude shows peaks at multip

## calculating Instantaneous frequency (IF) using fft

Started by in Matlab DSP11 years ago 2 replies

Hi, i have a big problem, i need to calculate Instantaneous frequency (IF) using fft (Fast Fourier Transform) and STFT (Short Time Fourier...

Hi, i have a big problem, i need to calculate Instantaneous frequency (IF) using fft (Fast Fourier Transform) and STFT (Short Time Fourier Transform). I have a discrete sinusoidal signal: n=1:1024; omega=0.2; X=exp(j*omega*n); To calculate clear signal IF using fft i should find max(fft(X)) and that would be the IF. the quetsion is, would be the IF=0.2? Becouse this is a discrete sig...

## Re: FFT amplitude and frequencies

Started by in Matlab DSP12 years ago 1 reply

Denilson- > In the time domain i want to see 4 different sinewave plots for the 4 > different frequencies. But one plot with the FFT of the...

Denilson- > In the time domain i want to see 4 different sinewave plots for the 4 > different frequencies. But one plot with the FFT of the 4 frequencies. > The problem is that it's having different FFT amplitudes. Thanx It's still not clear to me what's your objective. There's lots of reasons why freq domain magnitude amplitudes may not be identical, some valid some not. So you have e

## to remove periodical component from time series

Started by in Matlab DSP11 years ago 1 reply

hi all, my question is about time series and fft. I want to remove periodical component from my time series by using fft analysis. I know that...

hi all, my question is about time series and fft. I want to remove periodical component from my time series by using fft analysis. I know that I find magnitude and phase values respectively finds magn=abs(fft(b)) and phase=angle(fft(b)) commands in matlab.these values belong to frequency domain. ? don't know following processes. Can anybody help me, please? Thanks...

## Signal amplitude and FFT's

Started by in Matlab DSP18 years ago 2 replies

I have a very simple problem. The answer might be complicated... :) I define a signal as: dx = 1000; x = -pi:dx:pi; y =...

I have a very simple problem. The answer might be complicated... :) I define a signal as: dx = 1000; x = -pi:dx:pi; y = A * sin(freq * x); now, I would like to look at the FFT of the signal: padding = 1000; ffty = fft(y,padding);

## handling fft

Started by in Matlab DSP14 years ago

I am producing a signal modulated by a gaussian. What I do not control are the small peaks that appear in the signal. Are they a consequence...

I am producing a signal modulated by a gaussian. What I do not control are the small peaks that appear in the signal. Are they a consequence of the discretenes of fft's? N=1024; k=1:1:N; for i=1:N, phireal0(i)=10.*exp(-i^2/(N/10)^2/2); end phir0=fft(phireal0); for i=1:1:N, phir(i)=phir0(i)*exp(2*pi*j*ran

## Higher resolution FFT

Started by in Matlab DSP16 years ago

Hi, Thank u all for being so nice and supporting . Now there is another technique of getting higher resolution fft i have learned...

Hi, Thank u all for being so nice and supporting . Now there is another technique of getting higher resolution fft i have learned from mathematical journal without taking long sample here is steps involved in it (1)On input Data perform FFT using Nres NFFT = Length of data

## need to regenerate the original signal.

Started by in Matlab DSP10 years ago

Hi, all I am motin. I am new in matlab. I fft a signal. and when i fft i take just half part of the fft value because replica is ignored and take...

Hi, all I am motin. I am new in matlab. I fft a signal. and when i fft i take just half part of the fft value because replica is ignored and take the absolute value. now i simple change this value. now i want to regerate the original signal. that means i need a mirror of the half value to get the whole signal. but how i give my code below. [x, fs]=wavread('attack.wav'); block=256; n=floor(leng...

## ploting frequncy information of a sin wave

Started by in Matlab DSP13 years ago 1 reply

hai friends, i was just trying to use inbuilt function fft(x,n) to find out the frequency information of a sin wave and tried to plot it ...

hai friends, i was just trying to use inbuilt function fft(x,n) to find out the frequency information of a sin wave and tried to plot it i took n=0:.003:2 x=a*sin(2*pi*50*n) y=fft(x,1024) stem(y); -- i could't get any correct wave form , ic peak at 50 hz how can this be done i intension is to demonstrate the windowing and taking FFT of long sequencs signal regards, ...

## Help on IFFT

Started by in Matlab DSP12 years ago

Hi, All I have original mass spectrom which is time domain signal. Then I use fft in Matlab to fourier transform into powerspectrum. Code as...

Hi, All I have original mass spectrom which is time domain signal. Then I use fft in Matlab to fourier transform into powerspectrum. Code as below: a=textread(C:\notebook\070111.txt') %load data into a single column matrix called "a" A=fft(a,65536); %built in m file, fft of matrix a for 2^16 element. Pa=A.*conj(A)/65536; %calculate the intensity of A f = (0:32768)/65536; % create the freq...

## looking for a best fit fft algorithm

Started by in Matlab DSP8 years ago

Hi to all the Gurus here, Im looking for a fft algorithm which does operations in chunks of memory. I have a 4k internal memory and im going...

Hi to all the Gurus here, Im looking for a fft algorithm which does operations in chunks of memory. I have a 4k internal memory and im going for a 32k point fft. i assume one point sits in 32 bits in my processor. Can anyone give some pointers where to look at or which algo can be best suited when memory is a concern,my current challenge is once i bring in the 4k data into the internal memo...

## ofdm simulation (ifft/fft) & NoiseVar

Started by in Matlab DSP14 years ago

Hi all, I have some problems in simulating the OFDM using matlab. I will list them one by one. 1). Normailsation of the signal after ifft...

Hi all, I have some problems in simulating the OFDM using matlab. I will list them one by one. 1). Normailsation of the signal after ifft & fft. Do we have to multiply by any factor after taking the ifft and fft in the matlab?. Please explain me about this for the OFDM symbol with Useful Subcarriers. 2). Finding the NoiseVariance in to create the

## Zoom FFT - RESAMPLING HELP

Started by in Matlab DSP11 years ago

dear everyone, i need some help about Zoom FFT. i've read some literature about this from B&K but there is one question that make me stuck when perform this. from the literature ,the final step for accomplish this method is RESAMPLING. i've try to simulate the ZOOM FFT based on sinusoidal signal, but i dont understand in the last step, RESAMPLING. if you try this code its work, ...

## probable PCM problem with FFT noise added after wavwrite

Started by in Matlab DSP12 years ago

Hi all, I am fairly new to MatLab. I am trying to do a project to separate audio. I have generated to tones, C0 and G0, and added them, checked...

Hi all, I am fairly new to MatLab. I am trying to do a project to separate audio. I have generated to tones, C0 and G0, and added them, checked the fft (two clean mirrored spikes, as expected) and written them to a wav file. when I read the file back and check the FFT it shows a load of noise between the two spikes and between their mirrors, took this to be some kind of aliasing so increased ...

Started by in Matlab DSP14 years ago

Hi, I'm in desperate need to understand how to inverse FFT my data. I believe I've successfully performed a forward transform, now I need to ...

Hi, I'm in desperate need to understand how to inverse FFT my data. I believe I've successfully performed a forward transform, now I need to inverse it back to the time domain to make sure I can play the original data. Yes, I'm a DSP newbie and from what I've read, I think I can run the forward transformed data back through the FFT function to get it back

## Matlab fft different result! where is the error?

Started by in Matlab DSP10 years ago

Dear all Hi There is different results in the imaginary parts of Matlab FFT function and my own function. where is the error come from? her is...

Dear all Hi There is different results in the imaginary parts of Matlab FFT function and my own function. where is the error come from? her is the code: clear all close all clc x=[3 2 1 1 2]'; N=length(x); n=0:N-1; y=fft(x); % matlab function %----------------------------------------- %this part contains my own function k=n; X=[]; for a=1:length(k) Xk=x'*exp(-j*2*pi*n'*k...

## OFDM simulation (without using FFT)

Started by in Matlab DSP11 years ago

Good day everyone. I am currently doing my thesis on OFDM and my supervisor wants me to simulate continuous-time OFDM (i.e without using FFT)....

Good day everyone. I am currently doing my thesis on OFDM and my supervisor wants me to simulate continuous-time OFDM (i.e without using FFT). I've been able to simulate it using FFT but I have been unsuccessful in simulating the continuous-time OFDM. I would really appreciate it if anyone could help me out with the code. Thanks

## Finding peaks

Started by in Matlab DSP15 years ago

Hi all, ? I am analyzing some data using FFT. ? Once one perform FFT on signal and get the magnitude,I want to find...

Hi all, ? I am analyzing some data using FFT. ? Once one perform FFT on signal and get the magnitude,I want to find peaks in the FFT of signal. ? Is there any function in MATLAB to do that. ? Can anyone help me on this.

## Problem with IFFT and FFT in Matlab

Started by in Matlab DSP9 years ago 2 replies

Hi, I am working on an OFDM system using Matlab. The bits received at the receiver have a constant error ( i.e., avg 200 bits out of 1000 are...

Hi, I am working on an OFDM system using Matlab. The bits received at the receiver have a constant error ( i.e., avg 200 bits out of 1000 are always wrong).. when I decreased no. of bits in a symbol to let say 49 and FFT length to 64, there was no error. It looks like that there is some error in the computation of IFFT/FFT bolcks by Matlab (maybe some rounding of the data by Matlab). I am unsu...