Questions tagged [frequency]

Frequency in signal processing is the number of cycles (of the signal) per second.

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43 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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38 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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48 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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30 views

Belt tension measurement (36 Hz): What should my FFT size be?

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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76 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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19 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 ...
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23 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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21 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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64 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: ...
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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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39 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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36 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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76 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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26 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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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
71 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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26 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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40 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
84 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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75 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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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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33 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
45 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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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
37 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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47 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 ...
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92 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 ...
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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 ...
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71 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
59 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 ...
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25 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 ...
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1answer
23 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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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 ...
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107 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 ...
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202 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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2answers
37 views

How to Quantify a Difference in Spectral Information of two Signals?

As the title states, I am looking for established methods to quantify the difference in two FFTs. I have come across methods such as using cross correlation in the time domain or the coherence ...
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7answers
155 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 (...
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1answer
394 views

Meaning of a null coefficient at 0 Hz

I am analysing a wave with a timespan $\tau$ and after applying the fft I obtain the following plot of the coefficients I assume that the peak at $t=1$ followed by smaller coefficients means that the ...
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2answers
52 views

Estimating sampling frequency offset

I am searching a paper or article on this subject. I have heard of a function that estimates the sampling frequency offset between nominal and actual (sample rate of samples) sampling frequency and ...
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0answers
41 views

Instantaneous amplitude of a constant frequency sine wave?

I am playing around with the Hilbert transform using Python's scipy.signal.hilbert package to better understand what the various instantaneous properties are given different input signals. One input ...
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29 views

estimating peak frequency close to bin zero

Given a half complex spectrum (positive frequency bins from DC to Nyquist) as the result of a real FFT, to estimate the true (non integer) peak frequency I usually rely on Eric Jacobsen's estimator: $$...
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2answers
132 views

How to implement an RF Mixer for chirp signal in python?

According to this link, all I need to do to mix two signals is to multiply them. I have two chirp signals with same properties, one leading the other. If I multiply them to get the IF output, I don't ...
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23 views

SPL dB to voltage conversion misunderstanding

base on these links: https://electronics.stackexchange.com/questions/96205/how-to-convert-volts-to-db-spl https://electronics.stackexchange.com/questions/302833/convert-digital-and-analog-values-to-...
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56 views

how to find frequency response of microphone

hello I want to find the frequency response of a microphone. I give the input signal to my speaker and it produces a specific SPL with specific frequency. on the other side, I read the microphone ...
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1answer
64 views

What is the effect of a larger window size on “temporal resolution”?

I guess my question boils down to what "temporal resolution" means? I'm taking a signal processing class right now and we're learning about DFT and windowing at the moment. We've learned ...
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2answers
157 views

Most efficient way to find single dominant frequency (without amplitude) in analog signal

I want to construct a reference locked sine oscillator. The multibit sine wave is calculated using DDS. The multibit reference signal is typically not sinusoidal, can have offset and substantial noise,...
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1answer
84 views

What is the Uncertainty or error due to sampling frequency?

If I want to detect the distance between two peaks in a signal sampled at 100 Hz. Then is it right to say that the first and second peaks occurred within 0.01 seconds of uncertainty? Therefore, the ...
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22 views

How to handle cross products in feedback loop?

I'm trying to simplify the following block diagram from to the following block diagram However, h(t), H(s) in time domain, has a cross product in it (gyroscopic torque). How can I represent the ...
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Discrete-time signals increase in frequency and period

I am studying Discrete-Time Signal Processing by Alan V. Oppenheim and Ronald W. Schafer. I am confused when it says periodic discrete signal oscillates more rapidly when its frequency is increased ...
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59 views

what does frequencies in non periodic signals mean?

What do the frequencies in the a Fourier transform of a non-periodic signal mean physically? Are there another definition of frequency that doesn't include the FT?

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