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Generate a Time Series from Power Spectral Density Python

I am trying to generate a time series from a defined PSD function, however i tried to do this in python , with the following steps: Define the Power Spectral Density Define the time parameters Define ...
zouatine mohamed's user avatar
2 votes
1 answer
64 views

Confusion over deconvolution cost function gradient

A basic deconvolution problem is defined by the cost function $C(f) = ||f \star h - g||^2_2$, where $f$ and $g$ are unknown latent and measured images, $h$ is known kernel. I want to derive the ...
baronett's user avatar
1 vote
2 answers
149 views

Why is reconstruction of window function from its DFT difficult/noisy when the sidelobes of DFT are higher?

I am able to use the DFT and IDFT formulae to get the DFT of a window and reconstruct it but only if the sidelobes is very low (or the main lobe is narrow) as shown in the image below: Why does this ...
RajaKrishnappa's user avatar
1 vote
1 answer
95 views

computing convolution via zero, Periodic padding and FFT - confused about pad length and infinite signals

I’m trying to understand the answer to a test question. The question defines a new transformation for a discrete signal $x[n]$ which is defined for $0 \le n \le N-1$: $$X^c[k] = \sum_{n=0}^{N-1} x[n] ...
Piratemetaldrinkingcrew's user avatar
0 votes
1 answer
48 views

How to correctly perform inverse Fourier transform when input length is greater than output length?

Suppose I have $N$ length input sequence and need to inverse transform the input to length $K$ where $K<N$? Is possible at all?
jomegaA's user avatar
  • 659
1 vote
2 answers
63 views

FFT2 to RFFT2 Fourier plane and similarities

I'm trying to understand how Python's fft2 is different from irfft2. Basically, I have some continuous Fourier 2D samples that I need to put in a (n,n) grid (this can be done by a simply count-in-cell ...
Miguel Cárcamo's user avatar
0 votes
0 answers
18 views

How can i add overlap-add into this

Im new to DSP and i wanna know how i can add overlap-add into this to remove artifacts. ...
SignalWhisperer's user avatar
0 votes
1 answer
22 views

How to reorder the OFDM index before computing IFFT for CFR?

I used Intel 5300 NIC and the CSI tool to get CFR. I also want to apply for a IFFT to get CIR. Do I need to rearrange CFR before I apply ifft? The OFDM subcarrier indexes (for 20MHz) are: ...
evelyn's user avatar
  • 1
0 votes
1 answer
99 views

inverse FFT for creating pattern

I have created a code which created the plot below. The heart of the code is the AF expression.(array factor) I want to do the inverse process , to take the plot do the inverse of it and somehow to ...
user70731's user avatar
0 votes
0 answers
75 views

Noise at Corners of MATLAB's ifft2

I'm trying to implement the code in this tutorial in MATLAB using MATLAB's ifft2() function instead of the algorithm used in the shader (looks to be some type of Radix-2 algorithm). It is used to ...
eball's user avatar
  • 131
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0 answers
26 views

Issue with cudafft library and fftshift on odd image dimensions

I'm facing with a code I'm implementing for an exam using the GPU. Specifically, the code I'm writing is in C++, and I'm using the CUFFT library to perform the Fast Fourier Transform (FFT). The ...
overflow''s user avatar
1 vote
1 answer
60 views

What are the theoretical maximum values of the complex bins in an unscaled FFT of size N?

I am using FFTs to perform real-time convolution of audio signals on small embedded microcontrollers. I am thinking about testing different/smaller data types to represent the complex bins. I am ...
Tobias Hienzsch's user avatar
0 votes
1 answer
51 views

Radix-4 DIT Inverse Transform Reordering Issue

I am trying to implement a radix-4 DIT FFT. It looks like the forward transform is working correctly, but the backward transform output is not in the correct order. I'm pretty sure that the ...
Tobias Hienzsch's user avatar
0 votes
1 answer
55 views

Do you have to receive a whole OFDM signal to be able to demodulate?

An OFDM signal is made of subcarriers that are orthogonal to each other. This terminology makes me think that if one is only interested in information on a specific subcarrier, only that subcarrier ...
Eind997's user avatar
  • 101
4 votes
0 answers
85 views

Recover the first half of the time-domain signal of the N-point frequency domain signal using an N/2-point FFT

Let X be an N-point sequence in the frequency domain (where N is a power of two): $$ X = (X[0], ..., X[N-1]) $$ where $X$ is the complex and conjugate symmetric forward DFT of the real sequence $x = (...
keith's user avatar
  • 906
1 vote
0 answers
40 views

How to evaluate inverser fourier transform?

A function $f(\tilde{\phi}_i,\tilde{\theta}_j)$ defined on the sphere. The interpolation or filtering of the function is depending on $K$. I am confused on how to perform inverse-transformation using $...
jomegaA's user avatar
  • 659
0 votes
0 answers
66 views

OFDM Problem with Simulink IFFT

I'm studying OFDM modulation and trying to implement the Tx system on Simulink. I did what is shown in the picture. I was expecting to see subcarriers but I got "nothing". What am I doing ...
Fabio Andrei Cardos's user avatar
0 votes
0 answers
23 views

Impulse response aquired by ifft seems to require circshift

On the system below: I have found W by inputing 20-1000 frequency and found amplitude and phase for each frequency. I've tested for minimum phase and none min S. But the answer is not logical for me. ...
mohammadsdtmnd's user avatar
0 votes
1 answer
92 views

Understanding FFT size in OFDM

The number of subcarriers = the size of the FFT? The size may be the same or different depending on the document.
Ryo Onishi's user avatar
2 votes
1 answer
243 views

Generating time-domain noise from PSD

I have a question regarding generating a time-domain noise from the power spectral density (PSD), this was addressed in this question (How to generate time-series from a given one-sided PSD?) but I ...
Mohamed Osama's user avatar
0 votes
0 answers
105 views

Need to write a simple code in matlab of training sequence or zadoff Chu sequence for my OFDM signal-synchronization

I have written a complete code, in matlab, for my ofdm signal for the transmitter and receiver. Now I want to transmit my ofdm signal via wireless channel using SDR. Now, I need to combine a simple ...
Walkürie's user avatar
0 votes
0 answers
92 views

How to Eliminate Clicking Sounds in WAV File Generated from NFM Demodulation using FFTW?

I am working on a Digital Signal Processing (DSP) project where I am processing signals received from an SDR (Software Defined Radio) device. I am using the SoapySDR library to interface with the SDR ...
SignalWhisperer's user avatar
0 votes
0 answers
46 views

Why does FFTPack 5.1 not give the same complex numbers as Matlab's FFT2 command does?

I'm doing FFT2 with FFTPack 5.1 and it's working great. But it does not give the same result as Matlab's FFT2 command. Turning Time domain -> Frequency domain -> Time Domain give the same result ...
euraad's user avatar
  • 405
1 vote
2 answers
348 views

How to do FFT with complex numbers - Ansi C code

I have a small issue. I'm going to do FFT2 onto a matrix $X$, and the only library I have is FFTPack. FFTPack is the oldest FFT library, but it's one of the fastest and 100% portable too. The problem ...
euraad's user avatar
  • 405
2 votes
2 answers
334 views

Xilinx ISE IP Core 7.1 - FFT (settings) give incorrect results, whats missing

I am quite new to the VHDL domain and totally new to using its ip core. I'm trying to implement an 8 point FFT using the ip core FFT 7.1 but my results are a bit off and I cannot figure out why that ...
Mart's user avatar
  • 195
1 vote
1 answer
443 views

how to convert s-parameters in frequency domain to time domain?

How to convert s-parameters in Matlab's frequency domain to the time domain with code example?
mohammad abedi's user avatar
0 votes
1 answer
56 views

GNSS Acquisition in time domain: Why is conjugate of FFT replica used for the mixer?

Pretty new on all this GNSS stuff, I'm just studying from scratch an acquisition unit based in time domain using a parallel FFT structure. Just like the image got from "Acquisition Strategies of ...
ferdepe's user avatar
  • 103
0 votes
0 answers
64 views

pffft equivalent of fftwf_plan_dft_r2c_1d function from fftw

I am trying to convert my project from using FFTW to pffft. I only need to call the following two functions: ...
Thinium's user avatar
  • 25
1 vote
1 answer
229 views

3D convolution product with Fourier transforms, FFTW and MPI in C

My question is not really from the field of signal processing but I think you are the most suited for answering my question. I am willing to compute the gravitational potential which can be written as ...
YouShallNotPass's user avatar
-1 votes
1 answer
53 views

How to compute the ifft of a constant value?

I am clearly missing something obvious here because I am trying to do something that ought to be very simple: compute the ifft of a continuous signal. My understanding is that the ifft of a continuous ...
Darcy's user avatar
  • 296
1 vote
2 answers
114 views

Perfect channel estimation for OFDM (via H=Y/X) in MATLAB

Despite using the same channel for convolution, each time I get a different estimated channel. Could you please tell me what I'm doing wrong? I want to demonstrate that I can estimate the same channel ...
Zeynep's user avatar
  • 13
0 votes
1 answer
635 views

How can I generate a OFDM baseband signal with the output of the ifft?

I have some understanding problems with OFDM. I think I have understood most of the theoretical concept. At the moment, I am trying to write some Python code to simulate the transmitter part. This is ...
Not A Hobbit's user avatar
1 vote
0 answers
135 views

The correct way to perform signal processing on S-parameter data

I have a question to ask you which has been bugging me as of late. I have s-parameter data with 5001 samples acquired from a vector network analyzer. I am trying to 'gate' this s parameter data, i.e. ...
Vatatia's user avatar
  • 41
0 votes
1 answer
73 views

Power spectral density of melodic contours

DESCRIPTION OF SIGNALS I have several sung melodies under each of nine experimental contexts ("conditions"). The melodies are all of slightly different lengths (ranging more or less from 3s ...
z8080's user avatar
  • 51
0 votes
1 answer
120 views

How to process a signal in frequency domain then convert it bakc to time domain?

Maybe a example of coupling effect in frequency modulated continuous (FMCW) radar will be helpful to better demonstrate my problem. Let us consider a FMCW radar system. We have a complex transmitted ...
tyrela's user avatar
  • 155
1 vote
0 answers
185 views

IFFT confusion, sampling frequency

I made a previous post about what I am trying to do Previous Post I have band-limited data in the frequency domain from a VNA and I am trying to convert it into the time domain. VNA data saved in .s2p ...
Frank's user avatar
  • 33
0 votes
1 answer
85 views

Do the direct multiplication of a matrix with vector and divided matrix with part of vector have the same complexity?

According to my understanding the FFT operation for a vector whose length is $N$ has a complexity of $ \frac{N}{2}\log_{2}{N}$ complex multiplication and $ N\log_{2}{N}$ complex addition. I was ...
Sajjad's user avatar
  • 167
2 votes
2 answers
740 views

IFFT gives complex values in Matlab

I have frequency data from a VNA. I am trying to convert to time domain, and I can't figure out why I am getting complex valued time domain data. This is for ISAR measurements, and I can't get passed ...
Frank's user avatar
  • 33
0 votes
0 answers
130 views

Artefactual results in the Welch PSD (FFT) of melodic contours (pitch profiles)

DESCRIPTION OF SIGNALS I have several sung melodies under each of nine conditions. The melodies are all of slightly different lengths (ranging more or less from 3s to 12s), and each is encoded as a ...
z8080's user avatar
  • 51
0 votes
1 answer
1k views

Inverse Fourier transform in Python not yielding the original signal

I am trying to do a Fourier Transform and Inverse Fourier Transform. The problem is that I am not getting the original signal after inverse transform. ...
Reza Afra's user avatar
0 votes
1 answer
75 views

Bandpass function in Matlab inverting the Frequency spectrum when using a hermitic transformed signal

I have a VNA response (S11 parameters) from 3.5 to 40 GHz. Then I apply a hermitic transformation (complex conjugate) to it since we only have the spectrum for the positive frequencies. Then I use ...
Gabriel Llorens's user avatar
2 votes
1 answer
166 views

FFT, why my program works but doesn't?

I'm working on a simple 1D FFT and iFFT for two days now but no matter what I do, the code fails. I'm using FFTW library and libsndfile on linux and my goal is to use FFT for filtering audio. The code ...
user174174's user avatar
2 votes
1 answer
125 views

Unstable deconvolution in frequency domain (spurious high frequency component?)

I have a black box-like deterministic model $h(t)$, which provided with a real-valued input $x(t)$ returns a real-valued response $y(t)$. The model should produce little to no noise. My goal is to ...
Isaia Ismaele's user avatar
1 vote
0 answers
88 views

Azimuth image extent in frequency domain SAR algorithms (RDA, omega-k)

When looking at the practical implementation of frequency domain SAR imaging algorithms like the range Doppler algorithm (RDA) and the omega-k algorithm (also called range migration algorithm, RMA) as ...
contiguousCentipede18's user avatar
1 vote
2 answers
1k views

Order of using FFT, IFFT, FFT shift and IFFT shift

I considered a time sequence of sine wave t = [0,0.707,1,0.707,0,-0.707,-1,-0.707] I took spectrum = fft(t) and got the ...
Yatish Pachigolla's user avatar
0 votes
1 answer
492 views

What is inverse Fourier transform of real spectrum?

I am trying to retrieve the origin signal in time domain (or path-length domain) from a spectrum obtained by CCD-matrix of interferometer. I understand how to transform a real signal in the time ...
Виктор Легкоступ's user avatar
0 votes
1 answer
112 views

What steps are necessary to get the same impulse as before a FFT + IFFT

What steps are necessary to get the same impulse as before a FFT + IFFT. At the moment I am trying out my code a bit and would like to do an FFT from an impulse response followed by an IFFT to ...
Hannes Broschk's user avatar
0 votes
1 answer
122 views

Reason for "buzzing" artifact over processed audio after IFFT

I made a program that can change pitch of a recorded audio clip while maintaining its duration. Basically, it takes the FFT of windowed segments of a recorded signal, processes them using phases to ...
BigChungus443's user avatar
0 votes
0 answers
219 views

Trying to get an FFT to work on an fpga to get sound data

I am trying to get an FFT to work with Verilog to bin frequency data to be able to tell what note is being played. I am using an FPGA BASYS3 with a pmodmic3 which samples at $20\,KHz$ and outputs 12-...
Prince Pereira's user avatar
0 votes
1 answer
500 views

How to reconstruct original signal using IFFT after cutting past Nyquist limit

I'm working on a pitch shifting program. Everything works up to the point where I try to do the IDFT. Because I cut the DFT array past the Nyquist limit, when I run the IDFT, I don't get the same ...
BigChungus443's user avatar

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