Questions tagged [frequency-domain]

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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, $I$ ...
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0answers
103 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 ...
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0answers
816 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 ...
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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 ...
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3answers
251 views

How to effectively teach topic of frequency domain?

This is a soft question. The frequency domain has made revolution in the field of Mathematics, Digital Signal and Image Processing etc. Some of concepts which are very difficult to analyse in spatial ...
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2answers
4k 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 ...
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2answers
272 views

Why do frequencies of analog signals range from $-\infty$ to $\infty$ while frequencies of digital signals are restricted to $[0,2\pi]$?

In Fourier analysis while dealing with discrete-time signals, frequencies range from $0$ to $2\pi$ why? Intuitively how can i understand it?
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2answers
143 views

Fourier transform

Fourier transform of a DC signal is an impulse at the origin. Now if the spectrum of a signal is the plot of the amplitudes of the respective frequencies of each harmonic, then the Fourier transform ...
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2answers
285 views

Smallest FFT buffer size given zero-padding

I am currently working on a project that involves processing an audio signal by dividing it into chunks of size B. The buffer is then zero padded to have a size of 44100 points, after which FFT is ...
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1answer
225 views

Determining the Nyquist rate of signals added and multiplied together

Suppose I have a signal in the frequency domain $x(\omega)$. Suppose I know that its Nyquist rate is $\omega_0$ (and let $\omega_m$ be the its maximum frequency). I need to get the Nyquist rate of $...
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3answers
2k 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 ...
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2answers
385 views

Sampling with an alternating impulse train

The have the following question: A signal $m(t)$ with bandwidth 500Hz is first multiplied by a signal $g(t)$ where $\displaystyle g(t)=\sum_{k=-\infty}^{\infty}(-1)^k \delta(t-0.5*10^{-4}k)$. The ...
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2answers
660 views

sketching frequency domain representation

I've been given this signal and asked to sketch a frequency domain representation how do i do that? how do you know which frequency components are present in the signal?
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2answers
1k views

Finding maxima and minima of a continuous time signal by using frequency method?

I have a PPG signal and I wanted to write a code that gives the maxima and minima value of signal by using frequency domain method. Any suggestions?
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1answer
318 views

How to convert filter into frequency domain to do filtering?

I have this filter: filter_2 = firceqrip(2,0.6,[0.05 0.03]); I want to convert it to the frequency domain to multiply it by a signal (i.e filter in the frequency ...
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1answer
2k 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 ...
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1answer
58 views

Why is the size of results from FFT half the size of the input, while that is not the case in image processing?

When dealing with real data, Fourier Transform produces symmetric results and FFT algorithms discards half of it. An input with 1024 points will yield only 513 points in the output. However, in image ...
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1answer
50 views

Counting blinks of a LED

I'm working on an algorithm that counts blinks of a LED. I have series of non-neagtive integers. They represent brightness of a LED in time. I give you two examples of these integer series below. ...
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2answers
2k views

Understanding the frequency domain [duplicate]

I'm trying to understand what frequency domain is. I found general explanations on the Internet, for example: frequency-domain graph shows how much of the signal lies within each given frequency band ...
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2answers
861 views

Implementing a Band-Pass Filter from Scratch

I am trying to implement a band-pass filter from scratch. Here is an article which I thought explained the nuts and bolts of how to build one; the author combines a low-pass with a high-pass filter (...
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2answers
454 views

What proportion of a padded FFT should be actual values

For a given signal, I've been told that you can pad the vector with $0$s at the end to get a larger DFT, and as a result get more precision in frequency bins. What are the limits to this approach? ...
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1answer
1k views

Comparing PSD two signals of different length

I have two time signals A and B which are of different length, length(A) < length(B). Now I calculated the cumulative PSD of both signals. What is the best way to compare this result? If I am ...
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2answers
606 views

filtering in frequency domain

I am performing decorrelation of two channels of audio using all pass filtering. The two all pass filters for two channels are of very high order (>1000 but with not all coefficients non zero). I have ...
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1answer
43 views

What is the result of fourier transform of an image

I am new to computer vision and Fourier transform concept. I have examined some codes. In those codes, an image is performed Fast Fourier transform by using the function ...
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1answer
58 views

why transmitting a long pulse its spectrum gets spread?

I'm transmitting an RF signal with a CC1101 at 440 MHz. This signal is a constant of 1, so the spectrum should be a delta. Using a SDR dongle, I've checked the spectrum and it's wider than a delta ...
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1answer
63 views

Bilateral Laplace transform and existence of Fourier transform

I was reading from Athanosios Papoulis' "The Fourier integral and its applications." and they referenced the bilateral Laplace transform and Fourier Transform as: $$F(p)=\int_{-\infty}^{\infty}e^{-pt}...
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1answer
45 views

Complex FFT reversing

I've succeeded to compute complex FFT of a data array of interleaved values using the arm_cfft_f32() API of the CMSIS DSP library for Cortex-M4, and got in the same array the FFT results as frequency ...
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1answer
260 views

characterization of DC component

Consider the following two statements: In time axis: A signal without a DC component is a signal which doesn't have the zero frequency (the DC frequency) A signal without a DC component is averaged ...
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1answer
200 views

Convolution of BPSK signal in frequency domain implementation

Here is the simplified version of code which implement convolution of BPSK-signal in frequency domain: ...
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1answer
36 views

Does each pixel of the original image has a corresponding coefficient for every scale and every direction calculated by the DWT?

I want to take a pixel and find its coefficients calculated by the discrete wavelet transform for every scale and every direction. But as the DWT subsamples images, I don't see how to do that. Do I ...
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1answer
419 views

Derivation of downsampling in the frequency domain

I'm having some trouble with this derivation $$s_d = \begin{cases}1&\text{for}\quad m\quad\text{multiples of}\quad D\\ 0 &\text{otherwise} \end{cases}$$ then $s_d$ is somehow rewritten to: $...
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1answer
529 views

Corresponding frequency domain filter of spatial domain filter in image processing?

My question is: Suppose that we have low pass spatial domain filter that averages 4-connected neighbors of that pixel and it doesn't consider its pixel in averaging. Find its corresponding filter in ...
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4answers
105 views

Why does changing the frequency of a single component change total sum of amplitudes in my FFT?

I have the following code which generates a single simple sine wave with amplitude $1$ and then calculates the Fourier transform, normalises it, and finally takes the sum of all the components. ...
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1answer
32 views

Relationship between $y(t)$ and $Y(f)$ in LTI system

If I'm given an LTI system. And I'm supposed to find the input $x(t)$, given $y(t)$ and $h(t)$. Am I able to use this relationship: $$X(F) = \frac{Y(f)}{H(f)}$$ Another question I have is if I'm ...
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1answer
763 views

Phase wrapping in Bode plot

I'm trying to model the transfer function of a linear system (a MOEMS mirror) based on a datasheet plot of its response. I'm developing the model in the python-control model and I think that I've got ...
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1answer
111 views

iZotope RX's FFT processing?

How does iZotope RX handle the FFT (i.e. how does it manage to perform those processes in the frequency domain without creating glitches) since its able to e.g. Apply another DSP process (even time-...
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1answer
90 views

Proof of a CTFT property

How do I prove that the absolute value of CTFT of a positive continuous time signal is less than or equal to its value at central frequency(0)?
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1answer
425 views

Calculate amplitude of noise added Sine Gaussian signal from frequency domain

How to calculate the time domain amplitude of noise added Sine Gaussian signal from corresponding frequency domain. Here time domain amplitude is 2. How to get this from frequency domain. ...
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1answer
1k views

Applying Gaussian Blur in Frequency Domain

Please see second update I'm trying to implement gaussian blur in frequency domain using c#. Those are steps that I'm doing: Load bitmap. Split bitmap into separate color channels. Convert every ...
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1answer
2k views

Oversampling and Aliasing

I am really confused about oversampling and upsampling. I know that upsampling means stretching our signal in time domain by a factor of K, then interpolating some values or using just zeros. As I ...
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1answer
5k views

DFT and Inverse DFT in Image Processing

I have implemented DFT from this link. 1) Tried taking dft for the three Channels(R, G and B) and reconstructed the original image by taking inverse dft for all three channels and merged them ...
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1answer
230 views

Discrete Time Fourier Transform to Frequency Domain

I failed to do this question on the exam and finding it very difficult, I would be glad if you can help me solve it. How shall I start?
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1answer
1k 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 ...
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1answer
50 views

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

What is the name of the following bit encoding generator matrices?
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1answer
5k 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 ...
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1answer
645 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 ...
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1answer
61 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.
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1answer
417 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 ...
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8 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.
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15 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 ...