## Help on IFFT

Started by in Matlab DSP13 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...

## matlab FFT and time shift

Started by in Matlab DSP19 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

## PAPR

Started by in Matlab DSP12 years ago 1 reply

Hi, I?m trying to calculate the PAPR in OFDM system, but I don?t know why there is no result? I know there is something wrong! Can any one help...

Hi, I?m trying to calculate the PAPR in OFDM system, but I don?t know why there is no result? I know there is something wrong! Can any one help me to get it? this is my program code close all clear all clc; M = 64; % QAM Modulation Level N = 256; % IFFT Size % QAM 16 MODULATION data = qammod(randint(1,N,M),M); % CALCULATE PAPR OF BASELINE OFDM ofdm_out =sqrt(length(data))*iff...

Started by in Matlab DSP15 years ago

I have some questions regarding implementing OFDM in Simulink... I'm using BPSK, thus my output after BPSK would be a complex number. ...

I have some questions regarding implementing OFDM in Simulink... I'm using BPSK, thus my output after BPSK would be a complex number. I've splited up the real (16 samples) and imag (16 samples) numbers into 2 matrices. I plan to use IFFT with 64 samples. Except for the DC (sample 1), Nyquist center frequency (sample 32) and the real (13~31) and i

## mc-cdma matlab simulation

Started by in Matlab DSP13 years ago

Hi, i m trying to simulate mc-cdma BER performance using MATLAB and since mc-cdma is composed of the integration of DS-CDMA and OFDM so my first...

Hi, i m trying to simulate mc-cdma BER performance using MATLAB and since mc-cdma is composed of the integration of DS-CDMA and OFDM so my first step was building an OFDM model which passes bits on to a "pskmod" mapper and then to "ifft", and the reverse at the receiver side. When integrating with DS-CDMA for multiusers i m facing the problem that "pskmod" function only accepts positive val...

## scaling question for PAPR in OFDM

Started by in Matlab DSP14 years ago

I have a simple question about calculating the PAPR in matlab. I am doing an OFDM simulation where I have say N data points and then I do the IFFT...

I have a simple question about calculating the PAPR in matlab. I am doing an OFDM simulation where I have say N data points and then I do the IFFT on these N data points with 4 times oversampling. Now when I calculate the Peak to Average Power Ratio I get a very small number so what I'm trying to figure out is what number I should multiply it by to get it scaled correctly. Is it 4*N? or am I missi...

## filterbanks problem?

Started by in Matlab DSP13 years ago

This MATLAB program is for making a suitable wavelet kernel It derives the Low pass filter by sampling from analog raised cosine function in...

This MATLAB program is for making a suitable wavelet kernel It derives the Low pass filter by sampling from analog raised cosine function in frequency domain and taking ifft from this function to yield the impulse response. (other filters are derived using orthogonal relations). first i wnat know if the filter design method has any problems? The filter has 2 parameters in frequency domain ...

Started by in Matlab DSP17 years ago 2 replies

I am doing some analysis on an fft function inside simulink, that requires me to take the log10 of the incoming signal.  My input...

I am doing some analysis on an fft function inside simulink, that requires me to take the log10 of the incoming signal.  My input signal is a wav file and so the first frame is always zero, so when I want to take the ifft of the log10 function, I get an error and invalid data for the first frame.

## Generating correlated data with a given power spectrum.

Started by in Matlab DSP12 years ago

Hi there. I'm working with realizations of random correlated data using a given power spectra (no correlation matrix is given). What I do to...

Hi there. I'm working with realizations of random correlated data using a given power spectra (no correlation matrix is given). What I do to perform such realizations is that I generate a vector of normally distributed data, calculate the fft of this vector and multiply that by the square root of the given power spectra. Then I make the ifft of this product, which I expect to represent...

## FFT and IFFT

Started by in Matlab DSP19 years ago 5 replies

Hi Everyone,       I have a matlab problem which has been bothering me.       I have a vector&

Hi Everyone,       I have a matlab problem which has been bothering me.       I have a vector&

## IFFT in OFDM Simulation

Started by in Matlab DSP15 years ago

I have met the same problem in simulating an OFDM system in baseband. When I finished a single-user BPSK modulated simulation in flat...

I have met the same problem in simulating an OFDM system in baseband. When I finished a single-user BPSK modulated simulation in flat Rayleigh fading channel. The BER performance is very strange and cannot match the ideal performance for BPSK signals in flat Rayleigh fading channel. When I check the Matlab program, I can find that if I use y=fft(x), x=fadi

## Signal processing help required

Started by in Matlab DSP12 years ago 3 replies

I am de-convolving A and B by the standard method of taking FFTs of both time signals and dividing FFT of B by FFT of A, then taking the iFFT of...

I am de-convolving A and B by the standard method of taking FFTs of both time signals and dividing FFT of B by FFT of A, then taking the iFFT of the result to get the de-convolved time signal. A is a time domain signal of 650 discrete data points and B is a time domain signal of 3500 discrete data points. My question/problem is about the differing signal lengths, also getting my head around the...