Questions tagged [frequency-domain]
The frequency-domain tag has no usage guidance.
39
questions with no upvoted or accepted answers
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0answers
126 views
$\tt ifft()$ function - absolute vs real form
I have multiple files from an experiment in frequency-domain that I would like to use ifft() function to convert to the time domain in R to apply signal processing ...
1
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1answer
290 views
Normalized cross-correlation in frequency domain
I never worked with signal processing and never really used Fourier transforms before, still I am working on a project consisting on taking the output of an accelerometer to detect some movement ...
1
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1answer
141 views
Is it right to talk about dynamic range on frequency domain?
I'm comparing three frequency response's plots from simulations and experiments and I observed that two of them look like clamped to a DC component, where the max dB value is i.e. 100 and the min is ...
1
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1answer
69 views
Break a signal into segments, add them together and then perform an FFT on the result
If you break a 4 second signal into 0.5 second segments, add them together and then perform an FFT on the resultant 0.5 second data.
Will the FFT / frequency spectrum be the simlar to an FFT on the ...
1
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0answers
434 views
How to convert a spatial frequency in a 2D-DFT into the units radians per pixel?
Let's say I have a 2D image, and I take the discrete Fourier Transform (via FFT) of that image. In the frequency domain, I get the following image:
In this image, let's just assume all the spatial ...
1
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0answers
215 views
How do I find amplitude modulation effects in natural signals
It is relatively easy to discover overlaid (additive) signals in natural phenomena using wavelet decomposition, Fourier Transforms, CEEMD, etc, because addition in the time domain is the same as ...
1
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0answers
897 views
Envelope detection in frequency domain with MATLAB
I need to compute the envelope of a spectrum in MATLAB. Is there a specific function that can do it? I saw the function
[yupper,ylower] = envelope(x,np,'peak')
...
1
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0answers
67 views
Comparing the spatial frequency between groups of images
I have 2 groups of images, and I want to compare these groups based on the spatial frequencies of the images.
In the end, I'd like to be able to say "group A is/is not significantly different from ...
1
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0answers
103 views
Creating synthetic frequency domain box filter vs 4 pixels in corners
Creating two 10x10 black images.
1st image, adding a 2x2 white box in the middle (Low pass filter).
2nd image, adding 1 pixel in each of the corners.
Then performing the following steps in that order:...
1
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0answers
296 views
Why does my overlap-add integrator in frequency domain result in distorted signals?
With help from the dsp guide and DSP-Related, I tried to implement a leaky integrator in octave/matlab. It seems to work in general, but there are a few problems.
So that's what I do:
Calculate the ...
1
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0answers
92 views
question about the frequency of Gabor filters
The Fourier transform of 2D Gabor filters is shown below:
F is the radial frequency of the Gabor functions.
Another parameter Fm is denoted as highest central frequency.
Fr is the constant frequency ...
1
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0answers
726 views
Adding shot noise in frequency domain
I have a current signal represented by an array in python, which I would like to add shot noise to. Shot noise is defined as
$$
σ_i = \sqrt{2qI \Delta f}
$$
where $q$ is the elementary charge, $I$ ...
1
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0answers
105 views
How to optimize a wavelet transform?
I am using complex morlet wavelet to estimate frequencies and damping ratios in a 1-D signal. I have done it so far, and the results are accurate enough. Now my question is how can I modify or ...
1
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0answers
824 views
adaptive filter does not converge for all inputs
I am trying to make a frequency domain adaptive filter in matlab. It uses matlab adaptfilt.fdaf to create the filter parameters like step size and initializing initial filter weight values. Then I ...
1
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0answers
88 views
Keep the exact frequency content - Multidimensional fft
In Matlab I've got to generate a Gaussian process embodying a certain frequency content. Not to go multidimensional, I have used reshape function. I explain better ...
0
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0answers
14 views
Do negative frequencies count towards null-to-null bandwidth?
I am aware that negative frequencies do not normally count towards the bandwidth when transmitting in the baseband. However when specifically asked to look at the null-to-null or zero-crossing ...
0
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0answers
24 views
Find repeating sequences in audio file
I have a long audio file (12+ hours). I know that there are some unknown small (2 minutes each or thereabout, it varies) repeating (not bit by bit: it is recorded with a mic) chunks in it, repeating ...
0
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0answers
15 views
How to search for irregular signals: Fourier, DWT or k-means?
See my notebook here
I want to search for irregular time signals in a data set of ~3 500 000 time signals. By eyeballing I have found hundreds of flat and oscillating signals, but just a few that are ...
0
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1answer
41 views
0
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0answers
10 views
Is the Channel Equalization corrects Carrier Frequency Offset (CFO) in signal?
As we know channel equalization is used for restoring the distortion ocured in signal. Hence, can we say the Carrier Frequency Offset (CFO) is being corrected and restored the actual signal.
0
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0answers
20 views
Generating a phase modulation frequency spectrum with jitter
I would like to produce a frequency spectrum plot like this:
(from All About Circuits)
I know that one can take the modulation frequency and multiply it by a given order and scale by the modulation ...
0
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0answers
14 views
How to match resolution of two or more signals
I have received the following 4 time-series signals and wanted to do some data analytics using these. Although the sampling is the same for all of these signals, 2 samples per second, problem is that ...
0
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0answers
16 views
Analysis of linear acceleration and angular velocity, how to?
Excuse me If you don't feel that this question is good enough, but at the moment this is my level of entry knowledge.
Imagine that you have 200 recordings from the sensors, and information that you ...
0
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0answers
67 views
Encoder: Quantization in Frequency Domain
The article, "Let’s build an MP3-decoder!" describes quantization noise in the time domain:
[masking] This property is very useful: not only can the nearby
masked signals be removed; the audible ...
0
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1answer
55 views
LP to BP transformation steps
Considering the following problem, What i know to convert from LP signal to BP signal is to:
Draw the FD of the LP equation
From it I can draw the FD for BP
From this graph I can deduce the equation ...
0
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0answers
15 views
Is there a criterion that says at what point you can distinguish 2 partially overlapping Lorentzian peaks?
If you have 2 Lorentzian peaks that partially overlap and you have some frequency resolution df (your points in frequency space are separated by df) and both Lorentzian peaks have FWHM $\Gamma$ is ...
0
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0answers
67 views
Plot Background Noise
I am a total newbie in signal processing.
I have been trying to plot on simulink a time/frequency domain noise in PLC (Powerline Communication) that matches a real-world research "...
0
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0answers
16 views
What is the best spline to interpolate freq analiser graph
the question is as it is in the topic: What is the best spline to interpolate freq analiser graph?
I am looking something simply and fast to implement. I read about catmull-rom it looks it could be ...
0
votes
1answer
460 views
When listening in to an AM signals of various frequencies, how do we exactly tune in?
Alright, so I read on AM and Double Sideband AM, but I don't the more fundamental idea - the frequencies.
Frequency is just: $ \frac{1}{T} $, where T is period
So difference between 5 Hz and 30 Hz ...
0
votes
1answer
585 views
frequency domain zero padding in OFDM
I have a matlab code for OFDM system, in this code the auther added a zero padded subcarriers before the IFFT stage, in the middle of the raws, and added zero padded guard interval after IFFT, my ...
0
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0answers
2k views
Operations applied to functions in time domain and frequency domain
I am trying to make a succinct summary of how algebraic operations in the time domain translate in the frequency domain (via the use of Fourrier/Laplace transforms). Here is what I have derived so far:...
0
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0answers
61 views
Frequency Domain Equalization [Sources request]
When I read papers, I often see the term "Frequency Domain Equalizer".
I do not understand what a "frequency domain equalizer" is.
Do they mean equalizers like MMSE, LMMSE?
Or is there an equalizer ...
0
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0answers
154 views
Poles and zeros from FRF
How can I determine the poles and zeros of a system given its frequency Response?
I can understand how one can find the Frequency response from poles and zeros of a system. Is it possible to do it ...
0
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0answers
218 views
Determining Valid DTFT's
Are the following frequency domain signals valid DTFT's (Discrete Time Fourier Transforms)? Answer yes or no, and justify your answer.
a) $X(\omega) = \omega + \pi$
b) $X(\omega) = i + \pi$
c) $X(\...
0
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0answers
369 views
FFT frequency domain averaging and zero padding
I'm trying to get the average frequency response of an entire piece of audio by splitting it into segments, doing an FFT on each one, and averaging the magnitudes together. Its working great until I ...
0
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0answers
393 views
FFT of irregular shaped data
I have an irregular shaped 3D image that I want to do frequency domain filtering on. Currently I simply zero-pad the data to make it a cube, then do an fft.
I was wondering if this was a valid ...
-1
votes
1answer
279 views
Alignment of signals for ensemble averaging? Something else?
I have been applying ensemble averaging (adding signals of different trials to obtain one signal) to improve Signal to noise ratio in my data. I have achieved good results in terms of classification ...
-1
votes
1answer
368 views
fft2 of interferometric image - how to interpret the result in term of dominant frequency
I have an interferometric image which shows fringes at a certain frequency, basically a dominantly periodic signal overlaying the information that I want to extracthere are the fringes that I want to ...
-2
votes
1answer
1k views
