Questions tagged [frequency]
Frequency in signal processing is the number of cycles (of the signal) per second.
610
questions
0
votes
1answer
842 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 ...
1
vote
1answer
167 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 ...
0
votes
3answers
51 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 ...
1
vote
2answers
53 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 ...
1
vote
1answer
19 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?
0
votes
2answers
745 views
frequency divider
How would one implement a frequency divider? I know I can resample up and then treat it as if I'm at the same frequency, however I want to divide the frequency of my signal by 2 and keep the same ...
2
votes
0answers
23 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
vote
4answers
311 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 ...
10
votes
2answers
2k views
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 ...
4
votes
4answers
170 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 ...
2
votes
1answer
63 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 ...
2
votes
2answers
34 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 ...
-1
votes
1answer
364 views
Finding frequency of data given in time domain
Think there is an analog signal source and we are recording it with a data logger. Sampling rate isn't important in here. We know the analog signal is 0 mV when time 0 and goes to 1000mV in 1000 ...
0
votes
7answers
146 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 (...
3
votes
1answer
376 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 ...
0
votes
3answers
5k views
What is the real meaning of “frequency” for a non periodic signal?
For a non periodic signal, in the first one second the frequency of a particular amplitude (value) may be of 4 Hz, and then in the next one second it may or may not be 4 Hz. Then which value of ...
3
votes
3answers
775 views
Carrier Frequency Offset, Rotating Constellation and Correlator
I have been further reading up on carrier recovery methods and something is not clear to me:
It's written that a carrier frequency offset results in a rotating constellation diagram but if you are ...
0
votes
2answers
196 views
Coding an LFO in C
I want to know how I could implement a Low Frequency Oscilator on a simple synth I've coded in C. First in order to understand how to make this happen I would like just to modulate a sine wave by a ...
0
votes
2answers
48 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 ...
1
vote
1answer
117 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 ...
0
votes
0answers
30 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 ...
0
votes
1answer
54 views
How to calculate PSD if i have power vs freq spectrum?
i have a signal something like this
how to calculate PSD?
i have freq from 191000200 to 196500000
time gap or delta t = 1 or 2 sec, (what i mean is [tn] - [tn-1])
i will be computing in python any ...
1
vote
0answers
28 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:
$$...
0
votes
4answers
6k views
What are real-valued and complex signals and why is the Fourier transform of a real-valued signal Hermitian?
I have confusions in these concepts:
What are real-valued signals?
What is the difference between it and complex signals?
Why is it so that for real-valued signals, the spectrum of negative ...
0
votes
2answers
51 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 ...
0
votes
0answers
17 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-...
5
votes
1answer
49 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 ...
0
votes
1answer
63 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
votes
1answer
50 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 ...
0
votes
2answers
145 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,...
0
votes
2answers
609 views
What does it mean for a function to have frequencies?
In a lecture, my professor mentioned that $\cos$ has two frequencies. I see that using the inverse Euler's formula we can express $\cos$ as a some linear combination of complex exponentials, each with ...
1
vote
1answer
39 views
What is role of BW and frequency in internet speeds?
First the bandwidth (BW):
It is the amount of data that can be transferred simultaneously.just like more no. of highway lanes so that many cars can travel side by side simultaneously.
Frequency
It ...
0
votes
1answer
65 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 ...
2
votes
3answers
13k views
FFT Zero Padding - Amplitude Change
I'm just learning about Fourier Transforms and as an input I'm using a WAV file (Matlab) and taking one channel of it and performing a quick Fourier transform. I've zero padded the input, as I've been ...
1
vote
1answer
11k 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
vote
1answer
83 views
Frequency of a DFT Bin
I've been wrestling with this question for way too long. I appreciate any insight you can offer. Thanks.
If the $9$-point sample sequence $x(n)$ represents a time domain signal sampled at $48\...
0
votes
1answer
69 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 ...
3
votes
3answers
2k views
Understanding FFT of an Image
I am having trouble identifying the frequency components of an image,
Here I simply generated, 256x256 binary-image.
a = [zeros(256,128) ones(256,128)];
imshow(a);
...
0
votes
1answer
48 views
Generating a time domain signal using the fundamental frequencies
I currently have the power spectrum (in dB) of a signal through which I obtained the fundamental frequencies and amplitudes. My question is: how to generate a time domain signal using these amplitudes ...
0
votes
2answers
47 views
Are there standards/references for determining spatial scale in photographic images?
EDIT, 12/12/20:
Images below are of the radial sinusoid pattern. Left side is the "unrotated" version. Right side is what the a photograph of the pattern would look like if the disc was ...
0
votes
0answers
21 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 ...
0
votes
3answers
229 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.
...
1
vote
1answer
93 views
Why does this transfer function estimation not work? System identification
Goal:
I have an unknow dynmical system $G(s)$ and I want to find it from measurement data, output $y(t)$ and input $u(t)$. The data is frequency responses.
Method:
I begun first with creating the ...
6
votes
3answers
207 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 ...
1
vote
2answers
50 views
Frequency slows faster when it's decreasing
I'm sure there's a simple explanation but I can't discover it. Consider two frequencies, a and b. a is higher than b. I can create a wave with both frequencies. But when I create a wave with frequency ...
1
vote
1answer
46 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?
0
votes
3answers
1k 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 ...
2
votes
1answer
40 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 ...
0
votes
1answer
87 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, ...
1
vote
1answer
43 views
What is the importance of signal bandwidth in radar systems for velocity and localization estimation
So I know about the basics of doppler shift which relates the velocity of a moving object with the frequency carrier shift seen at the reciever.
But, I don't understand the importance of the ...