## xilinx FFT core simulation

Started by in comp.dsp9 years ago

Hi, I am trying to simulate fft of a sinewave of certain frequency with Modelsim. To simulate the fft code, first we have to find the Bin...

Hi, I am trying to simulate fft of a sinewave of certain frequency with Modelsim. To simulate the fft code, first we have to find the Bin size. I have found that. Bin size = ( i/p freq*point fft)/sampling rate. (point fft = 1024) For a sine wave of i/p freq 10Hz, and Fs = 50Hz, bin size is 204.8. FFT of a sine wave is a delta at a frequency same as that of the input frequency. No...

## Is FFT Overlap-add needed here?

Started by in comp.dsp15 years ago 8 replies

Hello DSP community, Im attempting a band-splitter voice scrambler based on the FFT. I collect 64 samples of voice, take the FFT, shuffle...

Hello DSP community, Im attempting a band-splitter voice scrambler based on the FFT. I collect 64 samples of voice, take the FFT, shuffle the magnitudes of the frequency bins (i keep the phase intact), then take an inverse FFT and send it out to the speaker. And the cycle repeats. On the other side I do the inverse process. However Im getting a lot of "digital" noise and I am unable to...

## fft

Started by in comp.dsp11 years ago 24 replies

Hi, I am an italian student (excuse me for my bad english). I have to evaluate the numerical accuracy of an fft algorithm. How can I do? Is...

Hi, I am an italian student (excuse me for my bad english). I have to evaluate the numerical accuracy of an fft algorithm. How can I do? Is there any standard method to follow? What paper describe this standard method? I had the idea to follow this process: 1) I start from a random signal, 2) I calculate the fft 3) I calculat the IfFT (inverse fft), 4) at the end, I compare the rms of t...

## real time FFT on c6713 DSK

Started by in comp.dsp13 years ago 3 replies

I'm trying to do a 2048 pt real FFT using fft6713.c as my reference code. When I tested this code with a CD music, (fs changed to 44.1KHz) I...

I'm trying to do a 2048 pt real FFT using fft6713.c as my reference code. When I tested this code with a CD music, (fs changed to 44.1KHz) I realize some of the samples from the ADC were overwritten while the FFT is being done (Obviously I can't do the FFT process in one sample time) Is there a way to store samples from the ADC and do the FFT prcoessing simultaneouly on the C6713 DSK. The mai...

## I need a FFT algorithm that doesn't use SIN, COS, EXP function.

Started by in comp.dsp14 years ago 9 replies

Hi, I've a FFT problem. This is the situation: 1.I'm working with a DSP56824 (Motorola). 2.I need to do a FFT (maybe 512 or 1024 points). ...

Hi, I've a FFT problem. This is the situation: 1.I'm working with a DSP56824 (Motorola). 2.I need to do a FFT (maybe 512 or 1024 points). 3.I'm working with a C compiler (Codewarrior, but I DON'T HAVE SDK). 4.I was trying to do a FFT with standart FFT C library. Here I have problems, because, the algorithm calls to sin or cos function, but the compiler doesn't support it, I think thta...

## Re: Newbie questions inspired by Re: Complexity of not 2^n FFT

Started by in comp.dsp15 years ago

> > 2. Can someone point me to description of how one would combine "small > > FFT's" to make a "large FFT"? Here i also suspect the...

> > 2. Can someone point me to description of how one would combine "small > > FFT's" to make a "large FFT"? Here i also suspect the explanation > > would be illuminating of how/why FFT/FT works. > > Ya know, I'm startin' to think that there > may well be a way to do this > (if there's no time gap between the time-domain > samples used to compute the "small size" FFTs). Combining small FFTs to m

## FFT Size calculation.

Started by in comp.dsp12 years ago 8 replies

Hi, I have the following problem that I am trying to address. Lets say we take 64 numbers and apply FFT of size 64. Then we concatenate 100...

Hi, I have the following problem that I am trying to address. Lets say we take 64 numbers and apply FFT of size 64. Then we concatenate 100 of these 64 numbers, and perform D/A conversion. This signal is digitized at a rate other than the original sampling rate, say we have oversampling of 3/2. Then per FFT we have 96 samples. And further assume that I know I have 96 samples per FFT (but I...

## Compose FFT

Started by in comp.dsp15 years ago 5 replies

Hello FFT can convert a given number of samples from time domain to frequency domain. Ok... what about the inverse? Basically I'd like to...

Hello FFT can convert a given number of samples from time domain to frequency domain. Ok... what about the inverse? Basically I'd like to have something like that: input -> FFT -> "something" -> output with input = output I think I could do that generating sinusoides on the frequency/amplitude given by FFT and summing them, but it probably will be very slow Any ideas? thanks

## LTE, FFT, OFDM

Started by in comp.dsp3 years ago 55 replies

Hello, In LTE specification, OFDM is implemented using FFT of sizes 128/256/512/1024/1536/2048. These correspond to Downlink bandwidth...

Hello, In LTE specification, OFDM is implemented using FFT of sizes 128/256/512/1024/1536/2048. These correspond to Downlink bandwidth of 1.4/3/5/10/15/20 MHz. I don't know how these N point FFT are selected for OFDM implementation. Let us take 1.4 MHz and 128 point FFT for example. 128 point FFT has N value of (2^N = 128) of 7. With a sub-carrier spacing of 15 KHz, this covers = 7*15 KH...

## Fixed point toolbox and fft

Started by in comp.dsp12 years ago 2 replies

hi, I have written program for fft in M file and using fixed point toolbox i simulated FFT . The final results` WordLength was 35...

hi, I have written program for fft in M file and using fixed point toolbox i simulated FFT . The final results` WordLength was 35 and FractionLength 27. I then took normal fft and compared results ,error was in the range of 10^-3. Just for curiosity i converted output of normal(Double Precision ) fft into fixed point using fi. The resulting fi object was having WordLength of 16 ...

## FFT dynamic range question

Started by in comp.dsp16 years ago 3 replies

I have a FFT implementation in single precision floating point. The requirement now is to Implement a short version of the FFT using the FFT...

I have a FFT implementation in single precision floating point. The requirement now is to Implement a short version of the FFT using the FFT already available the algorithm would be: 1. Convert the short(16-bit int) valued samples to single precision float 2. Call the available float FFT function 3. Convert back the float results to short What scaling algorithm should be used in the ...

## any smart methods - FFT related

Started by in comp.dsp10 years ago 3 replies

Hi, I am trying to optimize a piece of code where am stopped at the following point: I have Y(F) = FFT[ x(n) * w(n)] where * is...

Hi, I am trying to optimize a piece of code where am stopped at the following point: I have Y(F) = FFT[ x(n) * w(n)] where * is multiplication. 0

## name of fft(log(fft())) algorithm?

Started by in comp.dsp16 years ago 19 replies

What is the name of the algorithm where one takes the fft of the log amplitude of the fft of a waveform? Where might one find more information...

What is the name of the algorithm where one takes the fft of the log amplitude of the fft of a waveform? Where might one find more information (books, publications, web ...) about this procedure? It seems to be useful for detecting signals which have lots of harmonic content (some musical instrument notes). Thanks. -- Ron Nicholson rhn AT nicholson DOT com http://www.nicholson.com...

## fft help

Started by in comp.dsp16 years ago 5 replies

I am a high school student, senior, and I am intrested in fft. The only problem is that the mathmatics are over my head. I am a ham radio...

I am a high school student, senior, and I am intrested in fft. The only problem is that the mathmatics are over my head. I am a ham radio operator and fluent in Java, could someone help me with the mathmatics of fft andrewjj20

## Large FFT --- NOT radix-2

Started by in comp.dsp15 years ago 25 replies

Any pointers to doing non-radix 2 FFT's. Specifically I wish to do 44100 pt FFT's on 16 bit data. Simplicity of coding OUTWEIGHS speed! [...

Any pointers to doing non-radix 2 FFT's. Specifically I wish to do 44100 pt FFT's on 16 bit data. Simplicity of coding OUTWEIGHS speed! [ Scilab is slow but adequate ]

## A problem on FFT

Started by in comp.dsp14 years ago 7 replies

Hi, Could anyone give solution to this problem ? Write a program to compute the 128 point FFT for the signal, x(n) = cos(n *pi)/2.Also plot...

Hi, Could anyone give solution to this problem ? Write a program to compute the 128 point FFT for the signal, x(n) = cos(n *pi)/2.Also plot the FFT spectra. any pointer would be helpful Thanks Pramod

## FFT Narrowband Reconstruction

Started by in comp.dsp13 years ago 4 replies

Is it possible to reconstruct a narrowband, time domain signal from a subset of wideband FFT output coefficients ? Maybe a simple example will...

Is it possible to reconstruct a narrowband, time domain signal from a subset of wideband FFT output coefficients ? Maybe a simple example will help explain: Let's suppose I sampled a wideband set of signals (at different carrier frequencies) and applied a 128K-pt FFT. I know that I can get the original wideband signal back out by taking the inverse FFT, howevever, is it possible to recons...

## Problem with FFT

Started by in comp.dsp12 years ago 4 replies

Hi, I use a FFT and when I send a pure 1 MHz sinus in my 1024 pts FFT sampled at 10 MHz, I have a lot of amplitude variation in the...

Hi, I use a FFT and when I send a pure 1 MHz sinus in my 1024 pts FFT sampled at 10 MHz, I have a lot of amplitude variation in the output visualization.. 20% variation I send to the complex FFT, the 1MHz sinus sampled at 10 MHZ at the input real part and '0' at the input imaginary part... > From the FFT ouput, I compute Re[X(n)]^2 + Im[X(n)]^2 so I have the squared magnitude with a li

## FFT problem

Started by in comp.dsp12 years ago 3 replies

Hi, I have implemented a 256 pts FFT at 10.24 MHz sampling frequency so I have a frequency resolution of 40 kHz... I compute the FFT output...

Hi, I have implemented a 256 pts FFT at 10.24 MHz sampling frequency so I have a frequency resolution of 40 kHz... I compute the FFT output to have the squared magnitude : Re(X(m))^2 + Im(X(m))^2 When I send a pure 500kHz sine to the ADC input (12 bits) I see on the FFT output one peak at bin frequency 500 kHz and 9.74 MHz Then when I send 510kHz sine to the ADC I read on the FFT ou...

## Multiple Reverse FFTs don't work?

Started by in comp.dsp13 years ago 9 replies

Hello, I am trying to impliment a simple FFT algorithm I found on the web. Algorithm is here. When I set up a single 1 dimensional...

Hello, I am trying to impliment a simple FFT algorithm I found on the web. Algorithm is here. When I set up a single 1 dimensional 'row' of (any) data, I can perform the FFT on it, and then perform the reverse FFT on it and the final output is identical to the input. What I want to do is perform a 2d fft on a grayscale