Tagged Questions

The tag has no wiki summary.

learn more… | top users | synonyms

0
votes
0answers
20 views

How to perform Wiener deconvolution in Matlab

I have an output signal y which is an input signal x convolved * with an impulse response ...
1
vote
2answers
45 views

How does taking the absolute value of a complex signal reflect in the frequency domain?

I have a frequency-domain representation $F[n]$ of the complex discrete one-dimensional signal $x[n]$: $F=\mathcal{F}(x)$. Is there a frequency-domain transformation of $F$ into $F'=\mathcal{F}(|x|)$? ...
0
votes
0answers
48 views

Simplest approach to classify signal based on its 'smoothness'?

First of all, I have no experience with signal processing whatsoever and I may not even use proper terms so please bare with me. I am just humble software developer trying to find the simplest and the ...
1
vote
0answers
37 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 ...
0
votes
1answer
49 views

What is doppler tolerance

Can anybody explain the meaning of Doppler tolerance for the waveforms(Linear frequency modulated, Barker code, Polyphase codes) used for Pulse compression. The Doppler frequency shift $f_{d}$ due to ...
2
votes
1answer
85 views

How does the number of frequency-domain sampling points influence the outcome of an inverse FFT?

Given some frequency-domain representation of an impulse response. How does the number of frequency-domain sampling points influence the outcome of an inverse FFT, if I keep the sampling frequency ...
0
votes
1answer
71 views

how to get the phasor(frequency domain) representation of a digitalized signal?

I know that we can get the phasor representation(frequency domain) of a signal through Fourier transform, but the picture above gives a method that can get the phasor representation of a signal in a ...
0
votes
2answers
57 views

Convolution theorem

As stated by the convolution theorem, a convolution in spatial domain is equivalent to a multiplication in the frequency domain.Nevertheless, when should the first be preferred over the latter?
0
votes
0answers
26 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 ...
2
votes
1answer
104 views

Magnitude of gradient in frequency domain

I'm learning some basics of image processing. Recently I've read about image filtering and two-dimensional Fourier transform, because I'm preparing for exam. And I have one question I don't know ...
0
votes
1answer
17 views

2 by 2 bit orthogonal encoding mult-kronecker expansion matrices?

What is the name of the following bit encoding generator matrices?
1
vote
1answer
59 views

Why multiplying frequency kernel with sinusoid results shifting frequency domain

I am having great time while reading "The Scientist and Engineer's Guide to Digital Signal Processing" book. In "Chapter-14 Introduction to Filters" author indicates we can create high pass filter ...
1
vote
1answer
47 views

Similarity theorem in Fourier analysis

I have a homework problem that I'm not quite sure how to complete. The problem is as follows: PROBLEM Write the definition of the Fourier coefficients, and show that $$f(t + \frac{1}{2}T) = f(t) ...
0
votes
1answer
333 views

Convert normalized frequency to real frequency in AR model

Let us suppose that we have modeled signal using AR model, and suppose we have following model: I used spectral estimation function from MATLAB pyulear Now ...
1
vote
0answers
36 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 ...
0
votes
0answers
65 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) ...
1
vote
2answers
470 views

Convolution in the frequency domain

We often hear that "convolution in time is the same as multiplication in frequency", and vice versa, that "convolution in frequency is the same as multiplication in time". So in a typical windowing ...
1
vote
1answer
73 views

What's the frequency transform of a random matrix?

Assume the following: img = 255*rand(512); %Generating a 2D matrix with random numbers between 0 to 255. fftimg = abs(fft2(img)); %FFT of the image. The frequency transform of this image is a ...
1
vote
1answer
65 views

Standard deviation of Gaussian corresponding to perfect low pass filter [1,1]

For a time discrete signal, the rect-filter (for 1D signal [1,1]) is a perfect low pass filter. I was wondering, what is the best gaussian approximation of this filter? For a current problem, I ...
1
vote
3answers
184 views

What does the negative sign mean in the image frequency domain?

When I transform an image from the spatial domain to the frequency domain, some frequencies are negative. What is the meaning of the negative sign? For example:
1
vote
3answers
287 views

How to get Instantaneous Magnitude for a Instantaneous Frequency From FFT?

My understanding if a frequency in my signal doesn't line up exactly with a bin, it is smeared over a few bins to the right and left. How can the instantaneous magnitude be determined? (do I have to ...
-2
votes
1answer
124 views

WIDELY UNKNOWN?? Wireless Channel Transfer Function or freq response - frequency vs attenuation

We know that the signal attenuates out with distance and according to the channel transfer function or frequency response, the signal frequency components attenuate to different values based on ...
0
votes
1answer
219 views

Frequency domain to time domain conversion-(varying sample count)

I need to convert 150 Frequency domain samples to the time domain. The problem is, I have been provided with 250 time domain samples for comparing my results. How am I supposed to relate the 150 ...
1
vote
2answers
202 views

What is relationship between entropy and frequency in image

When I was studying spatial frequency and entropy, it occured to me that "is there a relationship between entropy and frequency?". As you can see, if we consider only horizontal line, the frequency ...
1
vote
0answers
162 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
votes
1answer
99 views

what I'll get if I take FFT of a frequency domain data

What I'll get if I take FFT of a frequency domain data. I have two questions related to this. For ex, x is a time domain data where X = fft(x), now fft(X)= what i'll get ? While reading SCFDMA, ...
2
votes
1answer
40 views

Stability varying with order

I have been doing some research into modelling acoustic spaces, and (with help from this site) I've managed to take the frequency response of fibrous layer model, convert it to a reflection response ...
0
votes
0answers
136 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
votes
0answers
65 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 ...
8
votes
1answer
356 views

How to circularly shift a signal by a fraction of a sample?

The shift theorem says: Multiplying $x_n$ by a linear phase $e^{\frac{2\pi i}{N}n m}$ for some integer m corresponds to a circular shift of the output $X_k$: $X_k$ is replaced by $X_{k-m}$, where ...
1
vote
2answers
207 views

Examples of Causal and Complex Wavelets?

I'm looking for wavelets that are both: causal (a wavelet coefficient $W(j,k)$, where $j$ is scale and $k$ is translation, does not use data from $t > k$ to be estimated). complex (such as the ...
3
votes
1answer
168 views

Spectral Leakage, Phase and other questions about FFT

I'm currently implementing a voice recognition algorithm using FFT and now some questions came up to me: Spectral Leakage: I know what it is, why it appears and how to solve it using a Windowing ...
7
votes
2answers
878 views

When should I calculate PSD instead of plain FFT magnitude spectrum?

I have a thirty-second speech signal that was sampled at 44.1 kHz. Now, I would like to show what frequencies the speech has. However, I'm not sure what would be the best way to do that. It seems ...
2
votes
2answers
179 views

Does the number of samples matter for FFT, and how to get a specific frequency visible?

If I have a signal that has 740 samples, the sampling frequency is 1000 Hz, and I take an FFT of length 1024, are the frequencies I get now 0, fs/1024, 2*fs/1000, ..., 511*fs/1024? I mean, do I get ...
0
votes
1answer
84 views

Image with specific frequencies

I have created a frequency domain image filter and would like to test it against some images where it is known that the frequencies only occur within a given band. Trouble is, I don't know how to go ...
0
votes
0answers
141 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
vote
0answers
374 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
vote
1answer
731 views

frequency domain phase shift

While going through FFT I came to know that, shifting of phase in frequency domain results on shifting of time in time domain. According to this, in wireless communications, from the transmitter side ...
0
votes
1answer
51 views

Square of Frequency characteristic of the system

What does $|H(j\omega)|^2$ in $20 \log_{10}|H(j\omega)|$ mean? Is it some ratio of energy or power? And why? How to derive it? I'm sorry for curtness of my questin.
3
votes
3answers
414 views

How to compute fundamental frequency from a list of overtones?

Given a list of overtones (F1, F2, F3, etc), how do I compute the fundamental frequency? Can I do something like F2/F1=F1/F0? Is it the correct method to use?
0
votes
2answers
576 views

What is the basic concept of Fourier transform

I use discrete Fourier transform for digital image processing purposes , but I don't understand basic concept behind it. For example : What information exists in frequency domain? What is ...
0
votes
2answers
270 views

Fourier series - time and frequency domain confusion

I am computing the fourier series of the following function between $[-0.5, 0.5]$ $$\displaystyle f(t) = \frac{1}{2} - |t|$$ According to the definition of Fourier Series the coefficients are given by ...
1
vote
1answer
209 views

How to do image reconstruction from array data?

i have 15 set of data which is the s-parameter, consist of 2 column (1001x2) each set. The first column is frequency and the second column is magnitude in dB. I have transform the magnitude from (dB) ...
1
vote
1answer
298 views

Performing classification based on FFT results

It is perhaps important to start with the fact that I am a complete beginner in DSP. I have got a number of audio recordings (of sampling rate 22 kHz) - of bird songs - which I have been trying to ...
1
vote
0answers
74 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 ...
1
vote
1answer
76 views

What features to use for multilayer perceptron model of an EEG signal?

I have an EEG signal that I want to extract features to apply multilayer perceptron (MLP). What I should use, Fourier or wavelet coefficients?
2
votes
2answers
547 views

Extract frequencies from PCM signal

I have an PCM (pulse-code modulation) signal. If I want to work out the frequency of a sample $ x $ long, I count the number of peaks/troughs of the sample, and divide by $ x $. The equivent dB of ...
7
votes
2answers
2k views

Determining the noise floor of a signal in the frequency domain

Is there an accepted way of determining the noise floor of a signal by looking at it in the frequency domain? Is it a matter of averaging all the bins, or median, or some more complex calculation ...
1
vote
3answers
249 views

Chop out frequencies outside human hearing range

I have a bunch of audio files all sampled at 44100 Hz sample frequency. I am trying to remove all the frequencies which are outside the human hearing range (I use the following as reference: Frequency ...
0
votes
1answer
280 views

Time -Domain to Frequency Domain

I am constructing a MFCC and come to a section which is kind of confusing me. It is: Step 4: Fast Fourier Transform and has this equation: Now I understand that FFT needs to be carried out, I ...