Sorry if this question has been asked before, I just can't find any answer in the archive. And sorry for not completely knowing what I am...

Sorry if this question has been asked before, I just can't find any answer in the archive. And sorry for not completely knowing what I am asking. I have a set of data in spherical coordinates (phi, theta, r) and I need to subject these to a fft operation. When I search the literature, I am being warned of regular FFT since the spherical data are not defined on a regular grid having we...

hi i want to ask whether there is any difference between taking n-point ifft and then fft for OFDM Vs taking ifft and then n-point fft in...

hi i want to ask whether there is any difference between taking n-point ifft and then fft for OFDM Vs taking ifft and then n-point fft in matlab. the difference i get is the signal with n-point ifft and then fft has a spectrum which do not have good resolution can anyone help me in this regard. Regards

Hello, I have constructed a 256 pt complex fft. My scaling is causing problems as the outputs from each stage are divided by 4 to...

Hello, I have constructed a 256 pt complex fft. My scaling is causing problems as the outputs from each stage are divided by 4 to avoid overflow. The input data and the twiddle factor coeffs are 16 bits wide (Q15). My problem is that when the data arrives at the last two butterfly stages of the FFT, it is non-existant, due to all the scaling beforehand. All inputs to these stages are zero....

I follow the instruction from manual to implement a FFT .But i'm wondering how can i convert my signal to FRAC16 type? the example code show the...

I follow the instruction from manual to implement a FFT .But i'm wondering how can i convert my signal to FRAC16 type? the example code show the program structure. But Who can help to complement the code which define the input data? eg: the data is [1 2 3 1 2 3 1 2] the Result comes from matlab with the commands fft([1 2 3 1 2 3 1 2],8) is ========== 15.0000 -1.0000 + 0.5858i...

Hi All, I've been surprised by my last plots. I've design a CW detection algorithm on matlab. I use a Welch periodogram (FFT:8192...

Hi All, I've been surprised by my last plots. I've design a CW detection algorithm on matlab. I use a Welch periodogram (FFT:8192 Signal:4096 Overlap 0.5) I normalize my fft by the square root of the signal length. On the dsp, the CW power lost 3dB when I multiply the number of points by 2. For me all the power of a CW is in 1Hz. Where is my mistake please ? Bruno ...

Hi, I am trying to process audio came from microphone using FFT. But audio driver gives only 512 bytes in a buffer. Sampling rate...

Hi, I am trying to process audio came from microphone using FFT. But audio driver gives only 512 bytes in a buffer. Sampling rate is 44Khz. Whether to do FFT complete sample for 1 sec is required ? Or I can process these 512 Bytes buffer one by one ? If yes any examples on net ? I already have a Function which takes buffer and sampling rate and does FFT. (i.e from Numerical Recipies usin...

Hi I want to do a 1024 point FFT of input data using the TI C28X FFT library. I am new to this library. I am sure someone on this group must...

Hi I want to do a 1024 point FFT of input data using the TI C28X FFT library. I am new to this library. I am sure someone on this group must have used it on input data in real time using eZdsp f2812. I believe ipcb buffer stores the results. I wanted to know what part of the code i need to modify to make the library (fft1024r/c) compute the FFT of my input data?

hi I have written a program that performs correlation via FFT. The concept is to search a base image for occurrences of a particular shape. To...

hi I have written a program that performs correlation via FFT. The concept is to search a base image for occurrences of a particular shape. To do this first I took the FFT of the base image, then FFT of the shape (padded with zeros) which I want to search in the base Image. After this I got 4 arrays of real and imaginary data. Next I multiplied the array (real & imaginary) of the shape with the...

I need to do an FFT of time-varying 2D position data. ie, I have got x=f(t), and y=f(t) at equal discrete time intervals and the objective is...

I need to do an FFT of time-varying 2D position data. ie, I have got x=f(t), and y=f(t) at equal discrete time intervals and the objective is to filter desired frequency ranges and do an inverse fft. Please guide me! Thanks, Binesh

Hello again, As always, Im curious about something. Is it possible to implement frequency inversion in the frequency domain? Frequency...

Hello again, As always, Im curious about something. Is it possible to implement frequency inversion in the frequency domain? Frequency inversion is defined here: http://www.cescomm.co.nz/about/scrambling.html Given that, can I take a signal and process it in real time, say in 64 sample chunks: Take the FFT, and simply "mirror" the values in the FFT domain, and bring it back to the tim...

Hello everybody I have made a little program in Matlab that calculates the PSD of a signal in two ways. One is based on FFT of the...

Hello everybody I have made a little program in Matlab that calculates the PSD of a signal in two ways. One is based on FFT of the autocorrelation function and the other PSD is based on an FFT of the signal. For some reason the resulting graphs do not look alike. One has a much higher peak than the other. I have had no luck in finding out how to calculate the scaling factor so I hope th...

Dear all, I have a question about the FFT and IFFT on real signals. For example, I want to perform 512-point FFT/IFFT pair on real...

Dear all, I have a question about the FFT and IFFT on real signals. For example, I want to perform 512-point FFT/IFFT pair on real signals, x[0], x[1], ... , x[511]. There is a well-known method that 512-point FFT on real signals can be simplified to 256-point FFT. However, how about the IFFT? The spectrum of real signals is conjugate symmetric about N/2. I need to perform 512-point IFFT or ...

Hello, I am processing an audio signal with CS4244 codec at 24 bits and 48kHz. Every 2048 samples the FFT is calculated and its...

Hello, I am processing an audio signal with CS4244 codec at 24 bits and 48kHz. Every 2048 samples the FFT is calculated and its amplitude. Without input signal I get FFT values ​​close to 30dB. With maximum input values ​​(overflow) I get values ​​of 90dB, with a scale of 0 to 120dB. Why not get a dynamic range of 100-110dB as is logical

Hi, I have been using a relatively small (256 point) FFT and some interpolation to estimate the actual input frequency when I do not have a bin...

Hi, I have been using a relatively small (256 point) FFT and some interpolation to estimate the actual input frequency when I do not have a bin at exactly that frequency. However I was wondering if any such method exists for estimating the phase at that frequency? Is it possible to interpolate the real and complex numbers of adjacent bins? If I zero pad and use a large FFT (say 2048 points...

Hello, I am working with FFT v.3.2 from Xilinx. Some questions relate directly to that core, some do not. 1. Why is block floating point...

Hello, I am working with FFT v.3.2 from Xilinx. Some questions relate directly to that core, some do not. 1. Why is block floating point unavailable for Pipelined/streaming FFT? Is it because the dynamic range is too hard to predict? 2. a) Is the output of A/D converter fixed point (generally)? b) Then only division can introduce floating point, right? 3. For the output ordering, the ou...

Hi, I am trying to use FFT lib provided by TI sprc081. I am not able to compile / link the code. I have downloaded the software tet bench, but...

Hi, I am trying to use FFT lib provided by TI sprc081. I am not able to compile / link the code. I have downloaded the software tet bench, but no use. Any help would be appreciated. regards, Nams

I am the actuary for a reinsurance company in Bermuda. I have come across a problem that would be solved faster using the FFT. all i need to use...

I am the actuary for a reinsurance company in Bermuda. I have come across a problem that would be solved faster using the FFT. all i need to use it for is convolution. For instance does anyone have a code that would convolute (.26274,.21074,.15547,.11472)*(.26274,.21074,.15547,.11472) using the FFT? I would actually be convoluting 2^13 or 8192 numbers in each vector instead of 4. I just want to ge...

Matlab's "fft" function is of course highly optimized over the years... Will I be able to speed it up by a factor of at least 10, by using...

Matlab's "fft" function is of course highly optimized over the years... Will I be able to speed it up by a factor of at least 10, by using a third-party C/C++ or Fortran FFT/IFFT program that is callable from within Matlab? That's to say, I try to find a third-party program, and modify it into a MEX format, and compile it, and then call this function from within Matlab. Will I be able to ...

Hi! Ive been recently using FFT for Pitch Detection and I notice that, although the notes are correct (e.g. C, D#, etc.), there are a lot of...

Hi! Ive been recently using FFT for Pitch Detection and I notice that, although the notes are correct (e.g. C, D#, etc.), there are a lot of notes that are in the wrong octave (e.g. E2 is categorized as E3, C3 is categorized as C4, always an octave up). Why is this the case? My algorithm is after calculating the FFT bins, I get the bin with the greatest intensity and calculate which frequenc...

Hi all I am complete beginner in DSP and FFT in matlab. Thanks for helping guys ! I have a vector of signal x(t) with its time vector. I...

Hi all I am complete beginner in DSP and FFT in matlab. Thanks for helping guys ! I have a vector of signal x(t) with its time vector. I want to obtain a frequency representation of the signal, in particular the energy spectrum of x(t) in the following definition: _____________________________________________________________________________ I stumbled on this explanation to obtain the e...