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The fast Fourier transform is an efficient algorithm to compute the discrete Fourier transform (DFT) and its inverse.

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34 views

How do MATLAB and/or Python treat $2^n$ samples rule in FFT

As far as I have read, an FFT requires that the number of original data points must be a power of 2. I'm wondering whether the tools like MATLAB or Python which have FFT functions take care of this ...
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0answers
11 views

Algorithm for “Signal => STFT with reassignment => masking => ISTFT => Output signal”

It is well known in DSP that this is a successful method to modify audio signals: Signal => STFT => masking => ISTFT => Output signal For example, ...
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0answers
99 views

Approximate Numerical Convolution with a Singularity in the kernel

I am trying to perform a numerical convolution where one of the operands is singular at t = 0. Concretely: $\int_{0}^{t}G(t-\tau)\dot{\epsilon}(\tau)d\tau$, where $\dot{\epsilon}(\tau)$ can be ...
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1answer
56 views

What is about the circular convolution in OFDM

In an OFDM system, serial-to-parallel conversion for data is done, then the DFT is performed and then adding the cyclic prefix (CP). My question is related to that step of adding a CP. As I know, ...
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1answer
66 views

Separate two sinusoids with very close frequencies (5 Hz difference) in a 44.1 Khz audio signal, with good time-domain resolution

Here is an audio signal which is a mix of (WAV file available here): a 2000 Hz sinusoid, beginning at 1.00 sec, without fade-in/fade-out a 2005 Hz sinusoid, beginning at 1.031 sec, with a slow fade-...
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0answers
11 views

I keep getting error messages on FFT Signal with two sinusoids (100 Hz and 200 Hz) with -10 dB

I am new in matlab. This code supposed to show 2 graphs - magnitude spectrum, and phase spectrum. The problem is it wont show anything and keeps getting error messages. In this code, I want to make ...
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1answer
40 views

discrete fourier transform and continuous fourier transform [on hold]

I have a signal $s(t)$. With a Fourier transform, I have $S=[S_1,...,S_N]$. I add $2$ zeros between each component of $S$, I have $D=[S_1,0,0,S_2,...,S_N,0,0]$. How to find the expression $d(t)$n in ...
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1answer
31 views

Time signal FFT different for whole signal than half signal on high frequencies

I have a time signal of u from 0 to 1000 time units. If I chop the signal in two halves and compare the frequency spectrum of both it looks similar, as it should (...
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0answers
11 views

artifact identification in irregular-samped data

There is a dataset combined by different datasets a,b,c,d,e. The time intervals are irregular(i1, i2, i3:intervals between a and b, b and c...), but the sampling rate SR in every single dataset is the ...
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0answers
19 views

accurate amplitude detection using Goertzel

I am using DSP from TI and trying to implement Goertzel. I am unable to get exact magnitude of input signal.The value are not changing. Random values are displayed and fluctuating. Sampling frequency ...
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1answer
52 views

Phase shift problem in Fast Fourier Transform

I try to make graph/print for magnitudes and phase shifts for impulse response calculated by FFT. For magnitude everything works perfect, but for phase shift I get some strange curve for higher ...
0
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1answer
37 views

Why am I seeing a negative frequency on FFT graph in Gnu Radio Companion? [on hold]

I have a pretty simple flow here in GRC, but for some reason I'm seeing a negative frequency mirroring the 10khz signal that I'm generating. What's causing this negative frequency to show up in the ...
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0answers
79 views

Frequency translation with FFT

I'm new to DSP and I would like to make an SDR receiver. For this I want to shift bins in the frequency domain in order to bring to 0Hz any portion of the base band spectrum (I know that there are ...
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0answers
23 views

FFT phase spectrum not correlate with DSA

I am trying to use an USB DAQ to replace DSA 35670A (Keysight) as the instrument is going to be discontinued the end of this year. I am measuring target vibration response by driving chirp signals ...
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0answers
15 views

How could I calculate Interbeat Intervals (IBI)?

I would like to understand how I could calculate interbeat intervals to determine human respiration rate. Using frame image from camera I have applyed FastICA (Indipendent component analisys) on ...
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0answers
8 views

Bit-reversal algorithm by Rutkowska [migrated]

I found a very interesting paper about bit-reversal algorithm suitable for in-place FFT: "A simple algorithm for the bit-reversal permutation" by Urszula Rutkowska from 1990 (doi.org/10.1016/0165-...
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0answers
24 views

I have performed an FFT and would like to filter the results to produce a 'points per octave' result

Where I am at the moment I can perform realtime FFTs, however the size is too great for me to plot in realtime, I need to try and filter extraneous data when I plot it. I have come to the conclusion ...
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0answers
31 views

Remove a line in image with FFT

I would like to remove vertical line from an image (an example). I took a 2D FFT and try to apply a mask to suppress the line. Nonethelesse the approch is not very efficient, because i lose an ...
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0answers
24 views

Help understanding how to convert the fft to bins and decide the number of filters - Cepstral features

I am doing recognition of bird chirps and the signals are obtained from recording of different bird sounds as a course project. My main focus is to apply some machine learning tool and report the best ...
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1answer
36 views

Reconstruction of a signal from non-uniform samples [duplicate]

So I'm having some troubles with a signal that's been sampled but where the samples don't have consistent intervals. I've been looking into the NFFT (in python) as a starting point but I'm a complete ...
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0answers
30 views

FFT filtering a gradient

I am trying to remove noise from an image and one of the patterns that I found is a gradient over the entire image. I was wondering if there is an easy way to remove this in the fft of the image. I ...
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1answer
35 views

Spectrogram with square or non-square magnitude of STFT: power vs. magnitude

As seen in this question and answer, to do a spectrogram, it's common to plot either: the square magnitude $|\text{STFT}(\text{frame}, \text{bin})|^2$ ("power spectrum") the magnitude $|\text{STFT}(\...
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3answers
28 views

harmonic algorithm for extending compressed bandwidth of audio file

I just found this site and feel at home :) I've been playin around with python and some compression ideas and was wondering if there's anything like what I am trying to figure out... I've noticed ...
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2answers
56 views

Relating phase difference in a signal with its frequency

I have a 134 point complex signal. Using MATLAB, I have observed that the phase difference between any two adjacent samples of this signal is 2 radians i.e. the phase increases linearly from 0 to 268 ...
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2answers
39 views

wrong output using numpy fft on a tone

I am getting the wrong output with the following simple implementation of Python fft. Can someone please explain what I need to fix? ...
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1answer
33 views

Image zooming with Fourier transform

I want to go from this image into this one: So basically I need to scale the white square. The authors of the paper claim that this can be done in four steps: zero-padding in real space (image is ...
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0answers
27 views

Acceleration time series to velocity conversion using DFTs

I have 1000 Hz time series data for acceleration (512 data points), which I want to convert to velocity. I am trying to use the omega arithmetic method to achieve this. Following are the steps I am ...
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1answer
55 views

Pitch detection algorithms “give up” after very little

I'm sorry if pitch detection has become a stale topic here, but I'm really interested if anyone has any advice on this topic. I'm looking for the best pitch detection algorithm for stringed ...
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1answer
24 views

Application of Parsevals theorem with Welch method

For my project I had to manually code the welch method using the code below. Pretty much it involves finding the spectral density through fft and incorporating windowing and segmenting with overlap. ...
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2answers
47 views

I'm confused about the notion of frequency when it comes to arbitrary data

In signal processing class we keep learning about how it's so useful to bring things into the frequency domain instead of the time or space domain but I'm very confused about what the motivation is or ...
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0answers
30 views

Error of Fourier Transform Estimation

Let $x(t)$ be a signal. The Fourier Transform of $x$: $$F_x(f)=\int_{-\infty}^\infty x(t)e^{-2\pi t fi}dt$$ is estimated by: $$G_x(f)=\frac 1N \sum_{r=-\infty}^\infty x(\frac rN)e^{-2\pi \frac rN ...
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2answers
20 views

Window length in matplotlib's specgram

In the paper about speaker verification I can read that Two quantities have to be set: the length of the window and the shift between two consecutive windows. For the length of the window, two ...
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2answers
78 views

FFT vs DFT Run Time Comparison (Complexity Analysis) in MATLAB

So we were given an assignment to plot the time taken by the FFT algorithm by MATLAB and a DFT algorithm written by me in MATLAB.G The expected output should have been the DFT algorithm following the ...
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0answers
36 views

How to get Inverse FFT (exact procedure or algorithm) , when input sequence length isn't $2^N$?

Commonly the FFT has input length of $2^N$ while when its not $2^N$ we use composite FFT where length does not matter. But in case of IFFT only $2^N$ length sequence is used. I want to get the IFFT ...
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1answer
55 views

How to get the MLSEEqualizer work with IFFT and FFT blocks in the communication system?

Matlab MLSEE equalizer works fine with the QPSK modulated signal when the signal is propagated over the multipath channel. However, if there are IFFT and FFT blocks used at TX and RX sides, ...
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2answers
75 views

How to get around the circular shift property of Discrete Fourier Transform?

I understand that when we introduce a linear time shift using DFT on a finite sequence, the algorithm assumes that the signal repeats itself outside of the given range. Here is an example explaining ...
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2answers
63 views

Square Wave with Random Edge Shifting

I took a square wave signal and individually shifted all the rising and falling edges by a random amount of time, within certain +/- bounds (a random time for each edge, not shifting all edges by the ...
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1answer
29 views

Maximum of cross-correlation not moving

I already asked this question here yesterday, but it was very poorly worded I think. I made a much more detailled post explaining my problem of stackoverflow, as it might also be a code problem. Here ...
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1answer
59 views

DFT (FFT) of Non Uniformly Sampled Signal

I am trying to perform an FFT of a non-uniformly sample signal. My input comes from Simulink and PLECS which uses variable-time solver. So far, I have used ...
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0answers
46 views

Hilbert transform “pass band”

I sample a human speech at 24kHz, to make the Hilbert transform using FFT and iFFT. What are the minimum and maximum frequencies (or range of frequencies), which will be 90 degrees shifted? Maximum ...
0
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1answer
42 views

Computation of the Inverse DCT (IDCT) Using DCT Or IFFT

Is there a way to compute the inverse discrete cosine transform (type-2) by leveraging either a DCT, FFT, or IFFT algorithm? I have seen ways to compute the DCT using FFTs, and I've seen ways to ...
0
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1answer
40 views

Emulating a Variable Delay

I am trying to emulate a satellite link where the delay time between the satellite and ground station changes over time due to the satellite's motion. I plan do this by converting to the frequency ...
0
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1answer
43 views

Extracting positive frequencies of discrete-time signal

Convolution in the time domain is the same as multiplication in the frequency domain. My data is sampled at 200 Hz, which means that the Nyquist frequency is 100 Hz, and all frequency content is <=...
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3answers
146 views

Calculate ifft using only REAL forward FFT

There are already questions on this topic here and here. I am trying to calculate the ifft using a DSP that only has a library function for a forward REAL (assumes conjugate symmetry) fft. For a given ...
0
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1answer
19 views

How to calibrate a signal with respect to frequency

I have recordings from accelerometers (non-flat response with respect to frequency) and I'd like to convert my voltage time series into acceleration values. Is there a standard method for doing this? ...
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2answers
67 views

Orthogonal signals in frequency and time domains [closed]

I have 3 orthogonal signals obtained by Fourier transformation. But when I do the inverse Fourier transform in Matlab, my signals are no longer orthogonal in the time domain. Here is my question: ...
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1answer
52 views

Seven term Blackman Harris window

I am currently trying to evaluate a high resolution ADC for which I need to window my output data for the FFT. Up until now I have been using the default 4 term Blackman harris window in MATLAB. ...
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0answers
59 views

Music Spectral Analysis

Let's say I have any arbitrary mp3 song that's been decoded to a 16-bit signed pcm (little endian) at 44,100Hz, and I'm analyzing it at 60fps for realtime visualization, giving 735 samples per frame, ...
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2answers
54 views

A question about Gibbs phenomenon example in Richard Lyons book

If anyone has a copy of this book could you please shed some light here: I was trying to reproduce the example shown in Chapter 5, section 5.3.1 Window Design Method's Figure 5-19 which illustrates ...
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1answer
47 views

Perform overlap add with available FFT size smaller than filter coefficients

I would like to process 12 to 20 seconds of incoming audio at a sample rate of 44100. I must process this audio in real time in an STM embedded kit (perhaps also an Android Smartphone). I'm trying to ...