Questions tagged [frequency]
Frequency in signal processing is the number of cycles (of the signal) per second.
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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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1answer
4k views
No of samples 4mega samples per second,using 8 bit ADC,V p_p is6V. calculate frequency and peak power
This place has been great in helping me to understand my online image and signals class!
I've moved on to another question and wanted to see if I'm correctly grasping the subject. The next question ...
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0answers
38 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
179 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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3answers
708 views
Distribution of energy in frequency bands
On my wav-file (music), I do a short-time Fourier transform (STFT). I have spectrum, which spans from $0\textrm{ Hz}$ to $f_s/2$. I took out the range between $1$ and $1000\textrm{ Hz}$, which I ...
0
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1answer
62 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, ...
0
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1answer
545 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 ...
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1answer
86 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 ...
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2answers
47 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 ...
3
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1answer
70 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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4answers
230 views
How to see the amplitude of each frequency?
do you know software that exports spectrograms to images of 500x22000 pixels?
all the spectrograms that I know show diffused frequencies and it does not look very good
I just want to see the amplitude ...
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3answers
77 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
21 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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1answer
43 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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4answers
113 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 $$u(t)=e^{-j \alpha_1 \phi(...
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2answers
53 views
Estimate “speed” of repeating signal pattern
I have a digitized signal containing a repeating pattern. One could call it periodic, but the time for one period is not constant. The "speed" with which the period is advanced can change over time. ...
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2answers
6k views
Frequency Shifting in MATLAB
I am currently attempting to demodulate an audio file using MATLAB. After taking the fft of the signal, I receive this:
After some more coding, I found the following values:
Fs = 44100;
Window ...
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2answers
54 views
DFT frequency resolution exercise [closed]
I have a discrete signal that goes as follows:
$$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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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
18 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 ...
0
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1answer
73 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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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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3answers
17k views
Why are sidebands generated in AM and FM?
When the signal is modulated onto the carrier in the electromagnetic spectrum,
that signal occupies the small portion of the spectrum surrounding the carrier frequency. It also cause sidebands to be ...
0
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1answer
38 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 ...
2
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1answer
105 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),...
0
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1answer
70 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
62 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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2answers
1k views
Frequency Analysis of a Signal Without a Constant Sampling Frequency (Non Uniform Sampling in Time Domain)
I'm a stack exchange user for some time and now I'm registering to ask a simple question (I think!).
I have a vibration signal with an amplitude and time (sampling frequency not constant) in a $...
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1answer
49 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
89 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
66 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
39 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 ...
0
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0answers
48 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.
...
0
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1answer
123 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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4answers
9k views
Calculate and interpret the instantaneous frequency
I'm new to the principle of calculating the instantaneous frequency, and came up with a lot of questions on it. You find them all in a bullet-point list at the end of this text. The text might be a ...
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1answer
25 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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3answers
23k views
Calculating values of frequency bins in Python
I have to use FFT to determine the period of waves inside a signal. After applying FFT on a window of 10000 point from a signal, I get something like this:
What I don't understand is that FFT is ...
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0answers
538 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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2answers
8k views
How to calculate the frequency of a signal without knowing the sampling frequency using Matlab
I have a signal and I am using Matlab command pwelch to calculate the frequency of the signal, but the frequency I obtained is changed as I change the sampling frequency.
For example, when using ...
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1answer
63 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
46 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
212 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 ...
0
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1answer
6k views
How to change a continuous signal to form a discrete signal? [closed]
I have a continuous signal $$ x(t)= 2\cos(200\pi t)+8\cos(250\pi t)$$ and it is sampled at 400Hz.
How is this changed into the discrete time domain in order to determine the two discrete frequency ...
1
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1answer
31 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 ...
2
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1answer
68 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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0answers
205 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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2answers
879 views
Impact of modulation index in FM
If I have the spectrum of a FM modulation, does the frequency of the carrier disappear when the modulation index is too big?
Does the amplitude of any side band depend from the modulation index?
And ...
0
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0answers
110 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 ...
0
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1answer
163 views
Mel separated filter banks
I am currently a bit confused.
I am currently trying to understand the MFCC extraction process, and don't understand how the Mel filter banks only provide a scalar output from each filter bank. What ...
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1answer
60 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 ...
