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# Questions tagged [frequency]

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

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1answer
19 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?
1answer
72 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 ...
1answer
18 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 ...
1answer
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 ...
0answers
18 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 ...
0answers
61 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: ...
0answers
57 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 ...
1answer
38 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 ...
1answer
34 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 ...
2answers
53 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. ...
1answer
23 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. ...
0answers
15 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 ...
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 ...
0answers
25 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 ...
0answers
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 ...
1answer
82 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 ...
1answer
74 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 ...
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 ...
1answer
31 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 ...
1answer
42 views

2answers
122 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 ...
0answers
22 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-...
1answer
55 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 ...
1answer
60 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 ...
2answers
154 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,...
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 ...
0answers
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 ...
3answers
225 views

### 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 ...
1answer
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?
1answer
121 views

### Aliasing below $f_s/2$

phi = exp(linspace(0, log(511), 1024)) - 1 x = cos(2 * pi * phi) Above will alias, despite peak instantaneous frequency evaluating to ...
1answer
41 views

### A basic question regarding frequency analysis of an EEG signal

Assume that an EEG signal is sampled at $f_s = 300$ Hz then a 10000-point segment of it is selected, called $x[n]$. The corresponding 10000-point DFT is then computed and called $X[k]$. Assume further ...
1answer
91 views

### SMA, SVM and PSD python

I'm looking for python functions (package) to calculate SMA (signal magnitude area), SVM (signal vector magnitude) and PSD (Power Spectral Density). The goal is to extract features from an ...