Questions tagged [frequency]
Frequency in signal processing is the number of cycles (of the signal) per second.
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Why is the digital frequency highest at $\pi$ and what does it mean in terms of analog frequency? [duplicate]
I can't seem to comprehend why the digital frequency is highest at $\pi$. I know the relationship between the digital and analog frequency is given by:
$$\omega = 2\pi\frac{F}{F_s}=2\pi f$$
Where $F$ ...
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2answers
24 views
Extracting different frequency bands (alpha, beta, gamma) from brain activity data
I am new to signal processing and despite googling about my question, I still couldn't find the solution.
I have an Electrocorticography (ECoG) dataset. This consists of recording brain activity from ...
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2answers
25 views
Discrete-time system: getting the true frequency from normalized frequency
Lеt's say that i have a plot where i can see the spectrum of some discrete signal and let's say that it's x axis is normalized (by normalized i mean $\omega/\pi$ on the $x$ axis). Now, i know that in ...
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How to extract information about each constituent 'wave' of a signal?
I have a vector containing wind speeds sampled at 1Hz over ten minutes.
I have applied a lowpass filter of 0.25Hz to get only the wind speeds I am interested in.
I now want to use MATLAB to ...
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1answer
25 views
Time response of complex frequency response function
In the frequency domain I have the following function:
$$
H(f)=A(f)\cdot e^{i\beta(f)}
$$
Where both $A(f)$ and $\beta(f)$ are known functions. The thing I would like to do is to model the response ...
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5answers
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A question about sampling rate of cosine signal
Given $$c(t) = \cos(2\pi\cdot 30 \cdot t) $$
If we sample this signal at the Nyquist rate 60 Hz and at a higher rate of 80 Hz, we get the following:
There is no aliasing as $f$ = 30 Hz is less than ...
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43 views
frequency amplitude asymmetry
I want to calculate the frequency amplitude asymmetry between two signals, EEG signals in particular. As a result, I expect a value ranging from 0 to 1. I have some references regarding that, but it's ...
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1answer
190 views
The selection of the amplitude of the signal, consisting of rectangular pulses, at different frequencies
I already asked a similar question, but did not receive an answer and did not find a solution, I want to make another attempt to get to the bottom of the truth.
There is a signal consisting of ...
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2answers
49 views
Sampling $x(t)=\cos(4\pi t)+\cos(2\pi t)$
Imagine that we sample the signal $x(t)=\cos(4\pi t)+\cos(2\pi t)$ with a certain sample frequency $f_s$ and we obtain $x[n]$. Now, by ideal interpolation, we get $y(t)$ from $x[n]$.
How can we know ...
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1answer
75 views
Positive slope of BER with a greater frequency deviation?
I am trying to implement a frequency-modulated communication channel on MatLab. However, there is something I don't understand about the sensitivity of the frequency modulator (or the frequency ...
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3answers
90 views
Does a .wav file created from a .mp3 file have better quality than the .mp3 file itself?
A .wav file created from a .mp3 file has the same frequency domain plot as the mp3 file itself https://stackoverflow.com/questions/58706674/difference-between-frequency-domain-in-mp3-and-wav.
However,...
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1answer
30 views
How to get RMS to Frequency chart for discrete samples of acceleration?
I’m reading a book on Motorcycle dynamics and want to compare the vibration profile of my motorbike against this chart:
I am not sure how to get the RMS of acceleration at different frequencies.
I ...
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2answers
55 views
Estimate “speed” of repeating signal pattern
I have a digitized signal containing a repeating pattern. One could call it periodic, but the time for one period is not constant. The "speed" with which the period is advanced can change over time. ...
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4answers
117 views
instantaneous frequency for a sum
In the literature, the instantaneous frequency for a signal $s(t)=e^{-j \phi(t)}$ is given by: $$f(t)=\tfrac{1}{2\pi}\frac{d\phi(t)}{dt}$$
This my problem: I have a signal $$u(t)=e^{-j \alpha_1 \phi(...
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2answers
54 views
DFT frequency resolution exercise [closed]
I have a discrete signal that goes as follows:
$$x[n]=[-1,4,-1,0]$$
I have already done the DFT for the signal, with the following result:
$$X[0] = 2, X[1]=-4i,X[2]=-6,X[3]=4i$$
But for some reason, I ...
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1answer
49 views
Modal analysis and frequency response function - interpretation needed
For couple of weeks now, I have been trying to measure cutting forces during machining processes. The system which I am currently examining is highly distorted at high frequencies due to its ...
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0answers
32 views
FFT first frequency
I have some problems understanding FFT. If I know Fourier analysis frame (1024 samples) and sample rate (48 000 Hz), how can I find the first frequency of harmonic sines and cosines?
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0answers
21 views
Measuring respiratory rate from a 3d accelerometer signal? How do I preprocess this data and move forward with it?
I have read a decent amount of papers that used wrist smartwatches to measure respiratory rate, or papers that used sensors attached to a persons chest. I can link them if it is necessary.
I am ...
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0answers
9 views
Physical meaning of a signal with 4 IMF?
If a signal is composed of four implicit mode functions, where the last one is a constant residue, does the instantaneous frequecy of the signal have physical meaning?
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1answer
145 views
Scaling Function in Wavelet Analysis
I was watching a YouTube tutorial on wavelets https://www.youtube.com/watch?v=wgRgodvU_Ms, where the presenter showed that if we multiply a Gaussian with a sine wave (and follow some other conditions),...
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1answer
74 views
with given Sampling rate, what max frequency human voice can be captured?
I'm new to signal processing and sampling rate, I was asked interview question related to this.
This is the exact question asked:
With 8Khz of sampling rate, whats the max frequency that human ...
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1answer
50 views
Sampling of frequency response
Let's consider any physical quantity depending on the frequency. For example, the impedance of a certain electrical component: $Z(f)$.
Now, imagine to measure it in a continuous interval of ...
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2answers
105 views
What Is the Bilateral Filter Category: LPF, HPF, BPF or BSF?
I`m reading about Bilateral filter with images, I knew that it uses Gaussian filter (which is a LPF) as a domain filter plus a range filter and it is used to preserve edges(high freq component).
Can ...
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1answer
43 views
How does one interpret an element of the “transfer matrix” used to calculate frequency domain granger causality (via VAR models)?
I am attempting to gain a better mathematical understanding for how autoregressive models can be used to infer frequency-domain granger causality. All freq. domain measures of causality that utilize ...
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1answer
81 views
Tracking a sine wave with noise
This will probably be an extremely simple question for some one with any background in signal processing(not my background)
Let say I have signal $$x(t)=A\sin(\omega t)$$ where A is known and $\omega$...
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1answer
76 views
White noise in range of frequencies [duplicate]
If I have this function:
while (true)
{
frequency = 8000;
wave = sin(sampleNumber*2*PI*frequency/sampleRate)
sampleNumber++;
}
it will produce an ...
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1answer
65 views
Difference between OFDM and FDM
In Frequency Division Multiplexing we provide one channel to one user.
Example like BandWidth of user1's voice is 200Khz. I provide one channel of 200KHz in FDM for uplink as shown in the figure.
...
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1answer
52 views
How to calculate bitrate of PAL?
I have to calculate the bitrate of PAL format $\ (576*720) $. I have the following data:
$\ 25 $ frames per second
Interlaced
Interior representation is: $\ 4:2:0 $
$\ 8 $ bpp
I have tried the ...
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1answer
161 views
DC Components and Frequency
I have started learning digital communication and was on line coding. I read there are certain characteristics that we need to keep in mind while choosing the right line coding method. One of these is ...
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1answer
28 views
relationship of frequency with range in Underwater acoustic channel
I am interested to know what range of frequencies can be used/ or are effective for wireless communication, within the underwater acoustic channel. I do know a table exists from \cite{...
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1answer
840 views
How do I find the peak frequency of a wav file in python?
I am fairly new to python and signal processing and I was given a task to record audio for 'x' seconds and then find the peak frequency in the audio file.
So far I have successfully implemented the ...
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1answer
64 views
DFT and integer valued basis functions'sf requencies
In Matlab the function
W=dftmtx(N)
gives the DFT matrix of size N.
Each row is computed for an integer frequency k. $W_{k,n} = e^{-i2\pi kn/N}$, k-th frequency, ...
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1answer
75 views
Correlation between frequency and initial phase estimates using FFT
Why is there a high negative correlation between frequency estimation errors and initial phase estimation errors when measured using FFT?
I have a simple code showing this negative correlation.
is ...
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1answer
267 views
Power and Energy of an Audio file
I have a question about calculating the power and Energy of an audio recording.
I have imported a waveform of an audio recording in WAV format into Matlab and then calculated the energy and power in ...
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0answers
47 views
Aliased Signal's Frequency
So I have an incoming signal of 137.9 MHz and a sampling frequency of 1.4 MHz. Once sampled how do I calculate the aliased ...
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1answer
33 views
Digital carrier recovery
I was reading Chapter 2 from "Telecommunication Breakdown" by Johnson and Sethares and came across this paragraph:
However, sometimes it is more cost effective to perform certain tasks
in analog ...
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0answers
248 views
Butterworth cutoff frequency normalization
The issue: I am trying to reproduce the step detection technique as described in this paper. You can see the proposed step detection in the image below. The first part of this technique is to use a ...
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1answer
69 views
Is there a good method to extract a reference sin/cos from a group of signals?
For the removal of a pure interference from a group of sampled signals, if I know the exact frequency of the interference I can simply use an I/Q demodulation technique (i.e., a phasor projection) to ...
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1answer
67 views
STFT output frequency does not match sin wave frequency
I have the following function and pre definition for producing a sin and its' stft:
...
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0answers
136 views
How to find frequency and corresponding time for an audio signal?
I want to read in a sound file and get the frequency at each time interval of the signal.
I thought that the best way to approach this is by applying FFT to small chunks of the signal. Because FFT ...
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1answer
68 views
Calculate aliasing of $x_a(t) = \cos{(2\pi300t)} + \cos(2\pi600t)$ when sampled with $F_s = 1000$
I'm asked to sample the signal
$$x_a(t) = \cos{(2\pi300t)} + \cos(2\pi600t)$$
with sampling frequency $F_s = 1000$ and plot the magnitude spectrum for the resulting sampled signal.
My thinking is ...
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1answer
159 views
What does a fractional frequency (for discrete-time signals) mean/how to interpret it? [closed]
This question has bugged me for a while as it's not addressed in any books I've read. I was wondering how folks from this community interpreted it. Below are my personal notes on the matter (please ...
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0answers
26 views
Is it possible to create a causal filter with a positively-sloped phase response?
I am currently prototyping a set of noise-cancelling headphones that utilize active EQ to modify the noise-cancelling signal, allowing the user to modify the frequencies that they hear or don't hear. ...
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0answers
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Practical Signal Processing by Mark Owen Exercise 2.1. and 2.2
The following exercises don't have answers in Practical Signal Processing by Mark Owen. What is the author looking for here? A mathematical proof?
2.1 A cosine wave of frequency f is sampled at $t = ...
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Complex Spectral Phase Evolution (CSPE) Performance depending on signal windowing?
I am look into CSPE. "Signal Analysis Using the Complex Spectral Phase Evolution (CSPE) Method"
The method is simple. It compares the original signal's FFT and shifted signal FFT in phase domain so ...
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2answers
238 views
Do Fourier frequencies actually exist in real life in form of “fundamental frequency”?
For me, this is a very awkward question to be asked, as at this point in my studies I'm supposed to be quite expert with elementary mathematical tools like Fourier transforms, but this has always ...
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0answers
21 views
Interpreting results of multiplying signal and wavelets in the frequency domain
I have followed a lot of stuff on mike cohens website and have managed to make a filterbank of Morlet wavelets and convolve with an incoming block of samples. This of course is a computationally heave ...
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1answer
107 views
Term for integral multiples of fundamental period?
As we know that a signal has fundamental frequency and integral multiples of fundamental frequency are known as harmonics
I am curious about the term that will be used for integral multiples of ...
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1answer
127 views
Formant Analysis Frequency - What makes a peak value?
from spectrograms, how can you tell which peak is really a formant. Like why is the pink arrow the first formant. And in the spectrogram below, which has fewer samples, what makes a value the peak ...
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1answer
506 views
Chebyshev I or Chebyshev II?
I am new to DSP, and I am trying to recreate some analysis of a signal,
They use a chebyshev I filter to go from a 100Hz signal to a 50Hz signal. Whereas I am currently using a chebyshev II filter, ...
