Questions tagged [frequency]
Frequency in signal processing is the number of cycles (of the signal) per second.
646
questions
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41 views
What kind of noise features should I know before removing them programmatically?
This is my first question here in DSP StackExchange and honestly speaking I don't have any experience in this field, but one of the school project I'm currently working in is building an application ...
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1answer
32 views
Sampling of sine wave :which one to choose? start with zeroth sample or 1st sample
sampling rate=200KHz
signal freq =1KHz
When I sample 1KHz signal I'll get 200 samples.
Should I consider 0 to 199 samples?
Or 1 to 200?
I want only 1 cycle.
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0answers
55 views
Super resolution for narrowband signal
How effective it is to apply super resolution techniques (like MUSIC, ESPRIT) on low bandwidth signals for indoor (BW=30Mhz) and outdoor (BW = 1MHz) location estimation?
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1answer
70 views
Shifting frequency in Fourier domain
Assume I have a continuous function $f(x)$. Its spectral representation is $F(X)=\mathbb{F}(f)$. I need to calculate another function $f'(x)$ which has a spectral representation of $F'(X)=g(F(x))$, so ...
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1answer
27 views
Minimum discernible frequency in power spectral analysis
Say I have a signal of length 20s that contains signal from various (unknown) biological sources, e.g. heartbeat (~0.2Hz), respiration (~1Hz), and possibly som very-...
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3answers
68 views
Convolve with a box filter in time domain
To low pass filter a signal, we have to convolve it with a sinc function because it's the same as multiplying the Fourier transform of the signal with a rect function, resulting in the high frequency ...
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1answer
22 views
Convert A frequency weight to Z frequency weight
I want to get the SPL of a monotonic sound like a 1khz tone but the problem is that I have a SPL meter which gives data in terms of A frequency weight. Is it possible to get the SPL of a 1khz signal, ...
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0answers
12 views
How to find the number of vectors to sample in Compressed Sensing?
When comparing my MATLAB code to a previously written one, I come across the following formula for the number of vectors to sample:
...
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2answers
78 views
Specify minimum trigger frequency for recording audio in Python
I'm writing a script for sound-activated recording in Python using pyaudio. I want to trigger a 5s recording after a sound that is above a prespecified volume and frequency. I've managed to get the ...
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2answers
132 views
ELI5: How do biquad filters like bandpass "know" the frequency of a signal?
I understand the code behind biquads, but I fail to understand how 5 coefficients in a biquadratic formula can isolate frequencies so precisely, especially considering it only takes the last two ...
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1answer
34 views
Extracting different frequency bands (alpha, beta, gamma) from MEG source estimated data
I have a dataset that consists of source estimated data of MEG brain signals.
I need to extract the different frequency band features (i.e., alpha, beta, gamma, etc) from them.
What steps/procedure ...
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1answer
50 views
DSP: newbie not understanding z transform/complex sinusoidal frequency and phase
Im reading Will Pirkles Designing audio effect plugins book and I'm not sure if I'm understanding the z transform correctly. I got up to differential equations in college, but haven't done math in ...
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2answers
37 views
What should be my sampling frequency for a peak detector output where it is extremely important for me to capture the first time the peak occured?
Following is the output of the peak detector:
The amplitude is not important to me, however the time when the peak occurs is extremely important. So my microcontroller will have an algorithm like ...
3
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1answer
48 views
Perform Transposed Convolution in Spectral / Frequency Domain?
I'm doing some experimentation on performing end to end generative modeling in the frequency domain. I've got a working convolutional layer, but do not yet have a Conv2DTranspose equivalent. Please ...
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1answer
51 views
How do I determine the carrier frequency of a given AM signal?
I am trying to figure out what the carrier frequency of a signal is given only its discrete-time domain information and the fact that it is a signal on the AM radio frequency band(550 - 1700kHz). Is ...
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1answer
58 views
How to calculate the instantaneous frequency for one specfic signal?
I have a signal which like this:
I want to calculate this signal's instantaneous frequency.I have tried hht and so on which method I can find but can not get the result.
So does somebody can give me ...
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1answer
51 views
Karplus-Strong with Jaffe-Smith sample rate-independent
I tried to implement the Karplus-Strong algorithm with some of the Jaffe-Smith extensions (improve pitch, dynamics, etc). Here is the code.
When I run it with a sampleRate of 48000Hz, I get very ...
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1answer
61 views
Bandpass filter equivalent for amplitude
I have a signal where I am using a bandpass filter to limit the frequency range. I am also interested in filtering the remaining frequencies (after bandpass filtering) within the signal by their ...
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1answer
31 views
Belt tension measurement (36 Hz): What should my FFT size be? [closed]
These are my setting that I can adjust and I need to measure 36 Hz. +- 1 Hz.
What settings do you recommend?
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1answer
86 views
Finding Frequencies from Log Indexed FFT
I have FFT data that has logarithmically scaled at x-axis as shown on the image. But the problem is I do have only array of float numbers that has 1024 element in it, but I know that is already not a ...
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1answer
44 views
Fine frequency correction : grouping and finding max amplitude inside a group
I work on phase and frequency estimation algorithm. Currently I am working on a derivation and determination of the Doppler shift( dF – frequency step).
For each dF, The following algorithm was ...
0
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1answer
24 views
Transmitting an approximate CW with an FM modulator
Imagine we had an FM modulator with carrier frecuency $f_c$. My doubt is about the optimal approach to use it for transmitting a tone (CW) of a frequency $f_c+\Delta f$.
Let $x(t)$ a and $y(t)$ be the ...
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0answers
24 views
Breaking EEG signal into epochs: why should we multipy windows-time length by frequency?
I am new to EEG data, Could you please explain why we need to multiply Fs by window_time_length ? I thought by defining window_time_length, we define the length of epoch!
I am working on P300 BCI ...
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0answers
70 views
Transfer of the signal spectrum to zero frequency
There is a signal at a frequency of 6 kHz-6.5 kHz. Sample rate 40kHz. It is required to transfer it to zero frequency.
I counted two arrays cos and sin:
...
2
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0answers
66 views
DTFT and Eigenvalues in frequency domain
Consider an LTI system with impulse response $h[k]$. Does the frequency response $H(e^{j\Omega})$ equal the eigenvalue corresponding to an eigensignal of frequency $\Omega$?
So if I convolve an ...
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1answer
45 views
Optimal sampling frequency
I am working with microcontroller's ADC to sample the data. I know that Nyquist criteria tells us that the sampling frequency should be at least twice the highest frequency, but it might involve ...
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1answer
41 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 ...
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3answers
138 views
What is really the Mel-filterbank?
After applying STFT to a signal, you typically need to convert the frequencies to the Mel scale. Typically the frequency values range from $0$ to $N/2$, where $N$ is the width of each sliding window.
...
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1answer
51 views
Extraction of the phase lag form cross-correlation function
I would like to find out the phase offset that my signal contains at the receiver side. For this, I use the cross-correlation function, where I cross-correlate signal before and after matched filter. ...
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0answers
21 views
Estimating Average HR from PPG sensor
I am reading Smartphone based Blood Pressure Monitoring via the Oscillometric Finger Pressing Method, which is trying to estimate blood pressure from a PPG sensor and a small applied force finger ...
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1answer
80 views
Why is GPS 1575 MHz?
I’ve read that that frequency is a ‘window’ in weather, impacted less by raindrops for example. I otherwise would’ve thought that simply increasing the wavelength would decrease impact. I don’t ...
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0answers
29 views
RRC filter in receiver side well applied?
I would like to ask question bout the rrc filter that I applied as an matched filter for receiver side in communication. My aim after RRC filter is to draw the eye diagram, and so far the eye opening ...
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0answers
45 views
The timing offset remains after Gardner loop
I would like to use Gardner loop to remove the timing offset in order to demodulate the signal. My signal contains the frequency offset, however I know that the Gardner loop can handle substantial ...
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1answer
143 views
Symbol timing recovery in Python
My objective is to demodulate QPSK signal. At the receiver I apply RRC filter and interpolate the signal to get the values of the signal (approximately) at the sampling instances. Then I am concerned ...
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1answer
83 views
How to take into account phase differences when doing Fourier Transform?
I apologize if the title seems very vague, I don't really know how to put it a different way.
From what I understand, the Fourier transform is essentially just doing a dot product between multiple ...
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0answers
8 views
Matlab function rpmfreqmap doesn't show diagonal lines though there is variation in speed
Matlab function rpmfreqmap doesn't show diagonal lines though there is variation in speed. I'm using vibration and tachometer data from dataset. I'm trying to perform order analysis as shown in Matlab ...
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1answer
88 views
How to obtain the exact value of wavelength from a 2D FFT amplitude vs wavenumber plot like it is obtainable from 1D FFT amplitude vs wavenumber plot?
I have a two dimensional multi modal spatial signal generated from a MATLAB code using sinusoidal functions of different wave numbers, amplitudes and phases. What I want to know is that if I have the ...
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1answer
66 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)^...
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0answers
17 views
What is the use of quasi logarithmic frequency distribution in multisine frequency signal in finding FFT
I'm using multisine but recommended to use quasi log frequency distribution to find out FFT.
What is the advantage of using this?
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1answer
38 views
Amplitude decrease in FFT at higher frequency for multisine
I am adding sine signals with different frequencies but same amplitude=100.
Sampling frequency is 50MHz.
I am not getting 100 in frequency domain for frequency 787KHz.
At 1K, 3K I am getting 100 ...
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2answers
54 views
Nyquist Frequency and Window Length
The Nyquist theorem states that the sampling rate must be twice the highest frequency to be observed. How does the length of the interval play into this relationship?
The main resource that I found ...
1
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1answer
96 views
QPSK demodulation
My objective is to demodulate QPSK signal. At this moment, my constellation in the best case looks like in the picture below:
and the corresponding eye-pattern:
Eyes are completely closed, which ...
1
vote
0answers
41 views
Why we only can transmit a real signal? [duplicate]
i just wondering, why we always transmit a real signal but when we deal with a baseband signal we use a complex signal ? are this is related to up and down conversion of the signal (Because complex ...
0
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3answers
101 views
Unexpected imaginary part in the fft of a zero-padded cosine
I simulated a cosine waveform $ y = \cos(\omega t) $ and I applied the FFT algorithm to it. As expected, I have a frequency peak at $\pm \omega$ only in the real part, and nothing in the imaginary ...
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2answers
62 views
Understanding FFT for a vibrational analysis experiment
I am trying to understand how FFT works in order to measure the vibrations of a 3D printer. I will be doing this with an Arduino Nano and a MPU6050 accelerometer.
In order to program the Arduino ...
2
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0answers
30 views
Adaptive Delta Modulation: Logic for step size control at receiver
I read that in adaptive delta modulation, we have a block for step size control (diagram below) which takes into account the one bit quantizer output in a feedback loop and modulates it, the intent ...
1
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1answer
28 views
How to get velocity from PSD graph
Hello everyone!
I have a graph, which is Spectra inside cavity. PSD vs. frequency.
I need to get velocity [m/s] from PSD [dB/Hz].
Does anyone know how to do that?
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2answers
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Does the Nyquist frequency of the Cochlear nerve impose the fundamental limit on human hearing?
The bandwidth of human hearing by empirical data is $20 \; Hz$ to $20 \; kHz$. A cochlear implant stimulates the auditory or acoustic or Cochlear nerve directly so that the hearing can be improved in ...
2
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1answer
304 views
Scalograms in python
I am reading this paper to learning basic concepts of dsp and I want to reproduce the following scalogram of a test signal (fig 4.2 of the paper):
It has been produced from the discretization of the ...
4
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4answers
246 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 ...
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