Questions tagged [frequency-domain]
The frequency-domain tag has no usage guidance.
265
questions
2
votes
2answers
57 views
2D Spatial Fourier Tranform on a pressure field
I'm doing some research on Fourier Near-field Acoustic Holography (NAH). The basic theory behind Fouerir NAH is that you take a sound pressure field measurement in a 2d plane p(x,y), 2d spatial ...
1
vote
2answers
111 views
Frequency response of an ideal low pass filter
I have an ideal low pass filter having unity gain and cutoff frequency 100Hz. If I provide an input having single frequency component at 100Hz(E.g.- cos(200pi t), will the low pass filter block the ...
0
votes
2answers
60 views
Relation of zero-padding and frequency resolution
Consider simple rectangular pulse and FFT of it in Python:
...
0
votes
1answer
60 views
Frequencies calculation of discrete signal in frequency domain
I have some misunderstanding in definition of frequency resolution of the signal. Here it is assumed that the resolution is: $$\hat{f_k}=f_{signal}\cdot T_{sampling}$$ (which is just relation of ...
5
votes
1answer
35 views
The Proper Way to Do Sinc Upsampling (DFT Upsampling) for Uniformly Sampled Discrete Signals with Finite Number of Samples
Given a signal $ \left\{ x [ 0 ], x [ 1 ], ..., x [ N - 1 ] \right\} $ what would be the correct way to upsample it in the frequency domain (Sinc interpolation)?
Note: Added as a request by the answer ...
0
votes
1answer
57 views
Removing Attenuator and Real Mixer influence on the received Baseband signal in Radar IQ Transmitter - De-embedding
Radar IQ Transmitter Measurement Setup:
Waveform Generator + IQ Transmitter + Attenuator + Real Downconversion mixer + Oscilloscope + Post-processing (Hilbert Transform)
With the above arrangement ...
1
vote
1answer
94 views
When if an FFT more efficient than Goertzel?
Given a block, $x[n]$, of M samples.
Calculating abs(fft(x)).^2 returns the power spectrum of that block through the use of a $M$-point FFT.
I can calculate the same using Goertzel's algorithm.
At ...
0
votes
0answers
27 views
PSD of DWT details signal
I am working on a project involves sensor data analysis. I have a data for entire year that is sampled every 15 minutes. I used DWT (db4 up to three levels) to analyze the high-frequency content of ...
0
votes
1answer
31 views
How to convert passband and stopband frequencies to poles and zeros
I have a NI 9229 digitizer with the following datasheet.
The datasheet mentions:
a passband frequency of $0.453f_s$ with a flatness of $\le0.1\,\text{dB}$
a stopband frequency of $0.547f_s$ with ...
0
votes
0answers
52 views
Frequency offset estimation accuracy
To improve frequency offset estimation, we could:
Use the second order interpolation / equation in the frequency domain based on the coarse estimation fc, e.g. BPSK frequency offset estimation;
Zero ...
5
votes
2answers
131 views
Explain the Process of Spectral Pooling and Spectral Activation in the Context of CNN in Frequency Domain
I am reading the paper Design of an energy efficient accelerator for training of convolutional neural networks using frequency Domain Computation:
which uses Frequency Pooling, from Spectral ...
0
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0answers
95 views
Why is the mel filter bank used to create a mel spectrogram?
The formula for converting frequencies from Hz to mel scale is as follows:
$$2595\log(1+f/700).$$
So why is the mel filter bank used? What is the origin of the mel filter bank?
0
votes
1answer
29 views
Going from an MFCC coefficient to Hz range?
I have not worked with MFCCs before, but I am faced with the observation that the 5th MFCC of a signal is actually of interest for me in my speech research. In order to understand why that one is ...
0
votes
2answers
49 views
unsymmetric fft in matlab
This is the FFT of a 4khz sin signal. I wonder why the negative part and positive part of X axis is not symmetrical?
...
4
votes
2answers
122 views
Constructing frequency domain filter from a 2d spatial kernel
Given a 2d spatial kernel $h$, I want to construct the corresponding frequency filter $H$. In theory, $H$ is simply obtained by calculating the DFT of $h$ using a FFT algorithm. But in practice, there ...
0
votes
1answer
44 views
Spectrum in real life with Spectrum in theory
as you know it is possible to measure the power spectral density ($|X(f)|^2$) of a certain voltage signal $x(t)$ through a Spectrum Analyzer.
As far as I'm concerned, the simplest spectrum analyzer ...
1
vote
1answer
264 views
Why is modern control theory in the time domain instead of the S-domain?
I am not sure if I am missing something, but from what I read I understand that modern control systems work in the time domain rather than the frequency frequency or S-domain.
Wikipedia article ...
0
votes
2answers
53 views
Power Spectral Density as a single number confusion
I'm trying to recreate the results of a machine learning applied to the DSP classification in the article: link.
I have a signal (activity measurements from a smartwatch) per patient, so about 30 ...
0
votes
1answer
77 views
Frequency domain filtering: must filter coefficients always be conjugate symetric?
While trying to do frequency domain filtering of audio signals using windowed overlap-add methodology, I came across some pre-calculated frequency domain coefficients. I noticed that the coefficients, ...
0
votes
1answer
108 views
What does frequency weighting an acceleration signal mean? And How do I frequency weight the raw acceleration data collected?
Disclaimer: I have very little knowledge in signal processing.
I'm trying to calculate a Whole Body Vibration(WBV) measure called Vibration Dose value(VDV).
$$VDV = \left(\int_{0}^{T}a(t)^4\,dt\right)^...
1
vote
1answer
70 views
Train of impulses in frequency domain
Why compressing a train of impulses in time domain produce a wide-spaced train of impulses in frequency domain and vice versa? i want to know the intuition behind that.
4
votes
1answer
136 views
Frequency-domain deconvolution: "Direct" filtering vs "Wiener" filtering
Can someone help with clarifying the difference between two approaches
to frequency domain "deconvolution:
For the frequency domain problem:
We want to find a filter $F(\omega)$ which will ...
1
vote
1answer
87 views
Measuring frequency response with white noise signal
I need to measure a frequency response of an eleсtric circuit (simple like an RC-filter). I suppose that I can generate an input signal that has spectrum like white noise (for example, m-sequence ...
0
votes
1answer
64 views
How to do sliding window multiplication in frequency domain
I want to perform the following computations with the impulse response of length L of a LTI system:
Multiply the impulse response with a window w(n) of length M << L.
Take the FFT of the result ...
5
votes
4answers
307 views
Estimation of Amplitude, Frequency and Phase of Linear Combination of Harmonic Signal Beyond the Leakage Resolution of DFT
How can I find a rough ( as accurate as possible) Amplitude of each frequency when there is spectral leakage.
Currently, I am dealing with a system that contains special leakage which seems ...
0
votes
7answers
234 views
Where do harmonics come from?
At first, I thought harmonics come from the signal being periodic. However, we know a sine wave is also periodic but contains a single frequency and no harmonics.
A harmonic for me is a component (...
1
vote
1answer
129 views
Estimating the SNR of 2-FSK
I have some iq data recordings of a 2-FSK waveform that I've created periodograms from. How do you estimate the SNR of this waveform in the frequency domain? I've heard two opinions:
One:
Integrate ...
0
votes
1answer
37 views
Amplitude in frequency domain of the same signal measured at different bandwidth (f_max - f_min) and different FFT lines
Fourier series in complex form
Fourier series in trigonometry form
Here, I'm measuring the same signal (an impulse force - or at least as close as possible to an impulse, represented by a knocking ...
0
votes
0answers
25 views
What is the requirement to reconstruct a spatial domain signal if we sample in the frequency domain?
I've come across an interesting question with regarding to signal reconstruction.
The sampling theorem states that a signal in the time or spatial domain must be sampled at twice a rate twice the ...
0
votes
1answer
40 views
Meaning of the frequencies vector using fft
I'm so confused, and it would be nice if someone could clear my head, or at least direct me to suitable references.
Assume that I have two gaussian pulses with the same bandwidth in time, but for 2 ...
1
vote
0answers
19 views
The best method to convert piano sound to music notes in real time [duplicate]
I was looking for a way to convert piano sounds to piano notes for my research. I discovered the conversion of piano sound to piano notes using FFT and piano note recognition using CQT. I am also a ...
0
votes
1answer
37 views
I need help interpreting FFT diagram
I need help with analyzing the computed FFT of my signal. I don't wanna bother by going into the details of how my signal is formed so I will just state which frequencies I know my signal has. I know ...
6
votes
1answer
480 views
The Proper Way to Do Sinc Downsampling (DFT Downsampling) for Uniformly Sampled Discrete Signals with Finite Number of Samples
Given a discrete signal $ \left\{ x [ 0 ], x [ 1 ], \ldots, x [ N - 1 ] \right\} $ what would be the correct way to downsample it in the frequency domain (Sinc interpolation)?
5
votes
1answer
90 views
Finding the Transfer Function of a Multiplicative Distortion in MATLAB
I have the frequency response of two signals shown above. One is uncontaminated, and the other is the same signal contaminated by a multiplicative distortion with two poles and two zeros. I need to ...
2
votes
1answer
118 views
Dealing with bias in an FFT for frequency correction
I'm working on using an FFT for frequency correction of a generic modulation signal. My algorithm basically attempts to balance the energy in the positive and negative frequencies of the FFT to be ...
2
votes
1answer
141 views
Designing a Chirp in the Frequency Domain
I am trying to create a chirp signal in the frequency domain, by simply setting the magnitudes of each frequency bin to one, and then setting the phase delay function such that the resulting time ...
1
vote
1answer
55 views
The cost function of LS algorithm
I'm trying to understand the derivation of LS algorithm for channel estimation in OFDM.
Could anyone explain why do we need complex conj transpose in the below equation?
1
vote
0answers
108 views
Sweep synthesis in frequency domain: How to correctly adjust magnitude?
I'm attempting to synthesize a logarithmic sweep signal to measure the IR of a system. For the most part, I'm following Section 5.2 of the paper Transfer Function Measurement with Sweeps.
To generate ...
0
votes
1answer
50 views
Continuously changing pitch of stable-pitch audio sample
I have an 44100-rate 4 second sample of a legato violin playing at 440 Hz. I would like to modulate this sample so that it starts at 440 Hz, then transforms its frequency continuously and ...
1
vote
3answers
623 views
If a square wave is a sum of odd harmonic impulses, why is it continuous in the frequency domain?
A square wave is a sum of sinusoids so surely it should be represented as individual discrete impulses in the frequency domain, where all other frequencies are 0. Why instead are those intermediate ...
1
vote
0answers
39 views
How to downsample a fourier transformed signal?
I have a signal of length 100000 timestamps sampled at a frequency of 25kHz. First I apply a high pass filtering at (300Hz) and then do the Fast Fourier Transformation. Then the absolute values are ...
0
votes
1answer
34 views
Names of system functions in frequency domain
I was just trying to refresh my systems theory known from long ago, and I realized that I had forgetten the name of the basic functions. Specifically, what are the names of these functions ...
-1
votes
1answer
71 views
Is pitch detection for bass instruments a solved theme?
I would like to know if pitch detection is a solved theme for an instrument like a bass (bass tones).
Is it, or there is always a percentage of error rate on the detection?
0
votes
1answer
104 views
Why use PSD to analyze a signal instead of its Fourier Transform?
Let's imagine I have a perfectly known signal $s(t)$ and I want to analyze its frequency components.
I noticed that mostly everyone would use the PSD of $s(t)$ to do that, instead of simply use the ...
1
vote
1answer
81 views
Steady state variance of a stochastic differential equation - relation between the frequency and time domains
Consider a stochastic differential equation:
$$
dx(t) = a x(t)dt + b y(t)dt \quad (1)
$$
where $y(t)$ is a stochastic process satisfying $\langle y(t)y(t')\rangle = \delta(t-t')$. We will assume that ...
-2
votes
1answer
27 views
Is it possible to prove that dither VS PWM can result the same output?
Assume that we have a SISO transfer function model $G(s)$ and we want to look how the output looks like when we have a input signal $u(t)$ that looks like this:
$$u_1(t) = \left\{\begin{matrix}
50 + ...
3
votes
2answers
661 views
Proof of fourier transformation of multiplication of two signals
I've been trying to find a proof of the following, but still I m unable to proof it, can someone help me?
$$
ℱ[x(t)g(t)] = \frac{1}{2\pi}
[X(\omega)*G(\omega)]
$$
-1
votes
1answer
71 views
Time domain analysis vs frequency domain analysis? Applications wise? [closed]
When do we use time domain analysis and when do we use frequency domain analysis?
As far i studied i know that when we need to study individual sinusoidal components of a signal, we choose frequency ...
0
votes
3answers
583 views
What is the Effect of Multiplying a Function by the Unit Impulse Function in the Frequency Domain?
I know about the the shifting property of the impulse function in the time domain as can be seen in equation $(1)$.
$$
\int_{-\infty}^{\infty} f(x)\delta(x - a)dx = f(a)\tag{1}
$$
But what is the ...
0
votes
1answer
181 views
phase offset extraction using matched filter
I'm looking for an application of detecting the drift of a received signal carrier frequency from ADC clock of the receiver (in case of no drift, ADC clock should be optimally an integer multiple of ...
