Hi Guys, I want to use FFT for an audio programming project I'm working on and had some (what are probably quite simple questions). I...

Hi Guys, I want to use FFT for an audio programming project I'm working on and had some (what are probably quite simple questions). I understand the concept that FFT converts a time based array of data into a frequency based array of data, and I found a nice library called FFTW which looks like it will fit the bill. My questions are... (These questions are based on an input array of 16...

Hi I had made a fft c program and it is working perfectly for discrete values. I have also checked it on MATLAB and quite sure that...

Hi I had made a fft c program and it is working perfectly for discrete values. I have also checked it on MATLAB and quite sure that the program is correct. However I have two doubts. I inputted the samples of a sine wave of 1000 Hz with a sampling frequency 4000Hz. For a simple 16 point FFT I got two peaks one at x[4] and other at x[12]. Now shouldn't a simple sine wave show just one...

Hi all, FFT converts a time domain signal to frequency domain value. The output of FFT is the amplitudes corresponding to each frequency...

Hi all, FFT converts a time domain signal to frequency domain value. The output of FFT is the amplitudes corresponding to each frequency content at the input. Well my doubt is how can we select the frequency for which we want to know the amplitude.I read that frequencies for which we get the amplitudes corresponds to Twiddle factor frequencies.. But my doubt is that we are not selectin...

I have the knowledge of fourier transform of the circular convoluion of two vectors say h and s, ie i know FFT (s ** h) [saying ** stands for...

I have the knowledge of fourier transform of the circular convoluion of two vectors say h and s, ie i know FFT (s ** h) [saying ** stands for circular convolution]. I want to know FFT of linear convolution of s and h ie my target is to calculate FFT(s*h) [where * is the linear convolution]. I neither know s nor h. Is it possible and if yes then how?

I am working on a tutorial about IQ modulation and demodulation. I have been thinking about this topic for a long time and have begun putting...

I am working on a tutorial about IQ modulation and demodulation. I have been thinking about this topic for a long time and have begun putting together some stuff. Here is an interactive page (exclusively for comp.dsp to look at :-) This shows the difference between an FFT that is stuffed with real data and an FFT that is stuffed with complex data. This has been real eye opening for me t...

Hi, I would appreciate if someone could help me by advising me on the implementation of a polyphase FFT filter bank on a FPGA. I understand...

Hi, I would appreciate if someone could help me by advising me on the implementation of a polyphase FFT filter bank on a FPGA. I understand the basic fundamentals & computationally-efficient/improved side-lobe rejection advantages of polyphase fft filter banks. My implementation is based on a polyphase decimation by D FIR filter and the end application is to split the input ADC samples into '...

I was asked to see if I could find a back-of-envelope time estimate for the fastest time in microseconds that could be expected for execution of...

I was asked to see if I could find a back-of-envelope time estimate for the fastest time in microseconds that could be expected for execution of a 65536 point real FFT on whatever high end DSP was available. all the processor literature has smaller fft's, like 256 or 1024. Can I scale those numbers by log2 or log4 to get an estimate for 65536? all the data we have internally is for older...

Hi guys, I am building a synchroniser for OFDM. I read in a paper that the FFT window can start anywhere in the Cyclic prefix, & that this only...

Hi guys, I am building a synchroniser for OFDM. I read in a paper that the FFT window can start anywhere in the Cyclic prefix, & that this only results in Phase rotation at the output of FFT. 1st, is this right? 2nd, how do we fix these phase rotation? In some papers I read, I think I am supposed to calculate the angle of the 1st symbol, & rotate all the other symbols by same degree. But thi...

Hello, How long will it take to finish one 128 Pt FFT with 16bits data using the low-end DSP? Thanks in advance, Mike

Hello, How long will it take to finish one 128 Pt FFT with 16bits data using the low-end DSP? Thanks in advance, Mike

Hi all, I'm a bit confused on computing correlation integral with FFT. I'm able to use FFT to replicate the result from xcorr in matlab,...

Hi all, I'm a bit confused on computing correlation integral with FFT. I'm able to use FFT to replicate the result from xcorr in matlab, but what's next? Say I want to compute: I(x) = int{ sin(x + y) * 1{y> =0 & y

Any random length FFT algorithm can work? Here I am emphasizing a FAST algo and implementation other than ordinary DFT. Where can I download...

Any random length FFT algorithm can work? Here I am emphasizing a FAST algo and implementation other than ordinary DFT. Where can I download such a FAST FFT algo and implementation (c or matlab)? HyeeWang

Hello, Does anyone implement 256pt fixed point FFT on TI's DSP chip? If so, would you please let me know the model, response time and...

Hello, Does anyone implement 256pt fixed point FFT on TI's DSP chip? If so, would you please let me know the model, response time and etc? Thanks in advance, Mike

Hi I have a small problem. I'm looking for algorithm "zoom fft". Does anybody know where I could find it (preferably C...

Hi I have a small problem. I'm looking for algorithm "zoom fft". Does anybody know where I could find it (preferably C language). Greeting Rendgen.

I have implemented simple modification of Dmitry Terez frequency estimation method and get awesome results: - CWT-like time resolution for one...

I have implemented simple modification of Dmitry Terez frequency estimation method and get awesome results: - CWT-like time resolution for one instantly found frequency - much faster than FFT - final algorithm uses only INTEGERS floating point can be needed for finding center of mass, but this code is very small. Main loop have no any rounding errors related to usual FFT "butterfly". I did...

Hello All, Suppose I have a non linear system with four inputs x1,x2,x3,x4 and one output y? x1(n) --> --> y1?(n)-------\ x2(n)...

Hello All, Suppose I have a non linear system with four inputs x1,x2,x3,x4 and one output y? x1(n) --> --> y1?(n)-------\ x2(n) --> (H) --> y2?(n)------ +-----> y?(n) = y1?(n)+y2?(n)+y3?(n)+y?4(n) x3(n) --> --> y3?(n)------/ x4(n) --> --> y4?(n)-----/ I'm only interested in the energy of signals. sum(y?(n)) = sum(Y?(k)) where Y?(k) = |FFT(y(n))|? (I

Hello every one I am new to FFTW library and currently i am using version FFTW3.1.2. My problem is i have a real no matrix of size 32 x 2048...

Hello every one I am new to FFTW library and currently i am using version FFTW3.1.2. My problem is i have a real no matrix of size 32 x 2048 and i want to calculate one-dimensional real to complex FFT of all 32 rows(each with 2048 points) using FFTW library. One simple approach in my mind is to use for loop for 32 times and compute one-dimensional FFT of each row saperately using "fftw_pl...

Assume a given number of FFT operations per second, e.g. 1000 - Based on this how can one calculate the corresponding utilization of a DSP when...

Assume a given number of FFT operations per second, e.g. 1000 - Based on this how can one calculate the corresponding utilization of a DSP when 1000 64-point FFTs are to be calculated each second. thanks celes

Hi All, Can any one tell what is the differance between complex fft and the real fft and also can any one provide me a link to good...

Hi All, Can any one tell what is the differance between complex fft and the real fft and also can any one provide me a link to good material also. Thanks a lot in advance, with warm regards, -Prasad

Hi, I'm trying to convert an image to frequency domain and back using kiss FFT. The problem is that when I ONLY apply the forward transform than...

Hi, I'm trying to convert an image to frequency domain and back using kiss FFT. The problem is that when I ONLY apply the forward transform than (just after that) the inverse transform I obtain a brightened image. I'm using complex numbers this way: const int dims[2] = {h,w}; // dimensions of fft ( height, width) const int ndims = 2; // number of dimensions. here 2 (2D) kiss_fftnd_cfg ...

Hi, I have an FFT question related to spectral leakage between bins... Setup: I am investigating the use of an FFT as a channelizer. I...

Hi, I have an FFT question related to spectral leakage between bins... Setup: I am investigating the use of an FFT as a channelizer. I apply no window (i.e. rectangular) and take each bin to be one of my channelizer output channels. The tone is not located at the center of a bin. Result: As I expect, I see spectral leakage between bins. What I don't understand is why the signal in t...