Questions tagged [signal-processing]

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4
votes
2answers
704 views

Rope as Communication Media [closed]

I'm a computer student that used to play microcontroller and sensor. I'm not sure whether this topic fits on this site. I'm thinking about using rope as media communication instead of fiber optic. I ...
2
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1answer
66 views

Analog Is Digital (Discrete)?

As I started reading a bit about analog vs digital signals, I keep returning to this thought. This could be something pretty obvious to the pros out there, but is it safe to assume that underneath it ...
4
votes
1answer
195 views

What, mathematically, is the power spectrum of a signal?

Given a signal $f(t)$ defined on $t\in(-\infty,\infty),$ what is the precise definition of the power spectrum of $f$, i.e., what is the mathematical operation that takes $f$ to the output of an ideal ...
4
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0answers
47 views

Pink noise and averaging

Disclaimer: I am aware this is somehow at the boundary between physics and statistics, but I have the impression that it is more likely that somebody doing/studying physics, rather than statistics, ...
0
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0answers
93 views

How can the Fourier delta function produce different matrices in single-pixel imaging?

The pattern in the masks used for single-pixel imaging are created applying equation $(1)$, $$P_\phi (x,y) = \frac{1}{2} \left[ 1 +| F^{-1} \{\delta_H (u,v) e^{i\phi}\}|\right], \tag{1}$$ in which the ...
1
vote
1answer
30 views

What is the meaning of the absolute of the Fourier transform in this context?

In a course talking about Fourrier transform and Nyquist frequency, there is this sentence that I can't understand: "If a signal has $|F(w)| \geq 0$ only for frequencies till f, than such ...
0
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0answers
11 views

Does less than half a wavelength antenna spacing help?

In Metamaterial based Holographic Beamforming (https://pivotalcommware.com/wp-content/uploads/2017/12/Holographic-Beamforming-WP-v.6C-FINAL.pdf), the spacing of the elements is much lesser than half ...
0
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0answers
16 views

Two forms of spectral density, how to explain their equivalence?

This question was posted on 1 but got not reply. The mathematical definition of the spectrum of a stationary process $\mathbf{x}(t)$is to take the Fourier transform of a finite segment $$\hat{\mathbf{...
1
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1answer
41 views

Can we decompose sound like white light is decomposed (dispersed) in different colors?

When we send white light through a prism, the light is decomposed in the colors that constitute it due to the different velocities which different frequencies. Is there a way to decompose "white ...
0
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1answer
28 views

Why does CW imaging not provide the same data as Pulsed imaging?

"Unlike pulsed THz imaging, the CW imaging (...) only yields intensity data and does not provide any depth, frequency-domain or time-domain information (...)." [1] Why does a pulsed signal ...
1
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0answers
34 views

Can a signal calculate its time period?

I wanted to know if a radio wave has some kind of data for example a kind of packet information (if its a thing) and it gets transmitted and gets received by a receiver, then can it calculate the time ...
0
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1answer
32 views

Apparent superluminal signals, is it as simple a variation on the following?

I know that astronomers observe jets that apparently move faster than light but really don't. I think I can simulate something that looks superluminal using just a bunch of x-mas lights and i am ...
1
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1answer
27 views

Computing correlation between two time series: confusion regarding nonlinear relationship and nonlinear data

I am trying to understand if correlation can be computed between two time series generated from two different initial conditions for chaotic dynamical systems. In general, correlation is applicable ...
1
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0answers
35 views

Fourier transform of sound wave

I am a high school student doing a project in Fourier transform. I was planning to learn Fourier transform and manually apply the calculations to a section of a song and see what I get. However, I ...
0
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0answers
9 views

Expression for covariance matrix as a function of distance

I am studying a tracking problem in which the measurement noise, assumed to be Gaussian, increases as a function of the distance to the target. I am seeking an expression for the covariance of this ...
0
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0answers
13 views

Interference fringes movement analysis

I am registering interference fringes on CCD linear sensor from Michelson inteferometer runned by He-Ne laser. I am sampling every 15-20 ms. I made a program to follow fringe movement and to track ...
1
vote
1answer
29 views

Is it possible to reveal a slight chronological change in frequency of Voyager 1 and 2 signals due to Hubble flow effect?

Is it possible to reveal a slight change in frequency of Voyager 1 and 2 signals due to Hubble flow effect? As both are about 1 light-day from Earth and as it is unbelievebly small distance compared ...
0
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2answers
39 views

Can unjammable radio communication be achieved by transmitting an error-correcting code of high-energy pulses in a secret, unpredictable pattern?

Signal jamming seems like an annoyingly simple way to sabotage a lot of interesting ideas. It has historically been used to block reception of propaganda broadcasts, and also to ruin military ...
-2
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1answer
71 views

Breaking apart a sin wave but phase doesn't seem to match up sometimes

I am trying to create a known signal with a known wavelength, amplitude, and phase. I then want to break this signal apart into all of its frequencies, find amplitudes, phases, and wavelengths for ...
0
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0answers
37 views

Unexpected frequencies on the Fourier spectrum. Are them due to aliasing from Shannon-Nyquist Theorem?

I have recently performed an experiment in which the light produced by a pulsed Ti-Sa Laser is detected. The detection can be consider in this simply way: the laser is turned on and when the first ...
1
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0answers
29 views

Interpreting a normalized Power Spectral Density (PSD)

I am using software to produce power spectral density (PSD) plots of time-series (voltage versus time). Unfortunately, the units of the produced plots are alien to me. I'm used to reading and ...
0
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0answers
15 views

Phase retrieval [duplicate]

Can Gerchberg saxton algorithm reconstruct a wave function if we know the squared modulus of its wave function $|\psi(x)|^2$ and the squared modulus of its momentum wave function $|\phi(p)|^2$?
0
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1answer
27 views

Terminology: “3σ detection over the continuum”

I am reading a research paper and they use the expression: "This is a weak signal, i.e. 3-4σ detection over the continuum". I saw this sentence in a lot of papers, but I can not find what ...
0
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0answers
29 views

Fringe movement analysis to extract displacement

I am using a Michelson interferometer with the interferogram recorded on a CMOS sensor. I have taken a video of the fringes moving when a displacement of 50 $\mu m$ is imposed to one of the mirrors. ...
0
votes
2answers
34 views

If radio signals attenuate when travelling through space, then what kinds of emissions are we looking for when searching for extraterrestreal life?

My understanding is that radio waves travel forever, like ripples in a pond, but attenuate with distance. They get mixed with other signals and become cosmic noise. I'm looking at these answers, which ...
0
votes
1answer
31 views

Implement EPR Imaging deconvolution

I have bruker's EPRI data and I want to deconvolute it. I read some article, that says $$ f(r) = x(r) \circledast g(r) \\ F(ω) = X(ω) \times G(ω) \\ X(ω) = \frac{F(ω)}{G(ω)} $$ $f(r)$: imaging spectre,...
0
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1answer
41 views

Does phase of a signal (very low frequency, 0-100Hz) change due to pink noise?

One might experience pink noise when dealing with low frequency signals (0-100Hz). Curious to know whether pink noise has an effect on phase of the signal specially in lowest frequencies 0-10Hz.
0
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0answers
15 views

How can I track the resonance of a tuning fork through a PLL if my phase lag graph is discontinuous?

I am programming a phase-locked loop to track the resonance of a tuning fork so that the tuning fork is always on resonance. This will be used in condensed matter physics through atomic force ...
0
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0answers
11 views

Required Optical Fiber Bandwidth from (Radar) Signal Bandwidth

I have a radar background and am currently struggling to understand even basic photonics because I feel the terms used are quite similar, but not identical and additionally very confusing. Let's say I ...
0
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2answers
64 views

Maximum distance between two towers for space wave propogations

Context: Space waves are a form of radio wave propagations, a space wave travels in a straight line from the transmitting tower. The problem here is related to line of sight communication. In the ...
0
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0answers
5 views

Transmission spectrum of non-negative principal components

I am going through this research paper which talks about extracting Raman spectra out of low SNR spectra. It does that using Wiener estimation which is given by an equation(see page 4 for details). ...
1
vote
0answers
19 views

Computing a second harmonic resistance out of a wave-like resistance signal

I want to reproduce the results of a paper, in which they measure the Anharmonic Hall Effect (AHE) resistance $R_{AHE}^{2\omega}$. There are several protocols for measuring it experimentally, but I'm ...
0
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0answers
14 views

Dicke switching for radars

A question about Dicke switching for e.g. radio antennas. Some background so that we're all on the same page: fluctuations in the gain of the detector can dominate the low power signal. Dicke ...
1
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0answers
40 views

Are there any application in the exp of log of DFT matrix? [closed]

Just a fun thought. Since the N point DFT matrix $W$ is a complex rotation matrix: $$W^*W = I$$ $$det(W)=1$$ It may make sense to work on a rotated domain with a projection matrix $W_\phi$: $$W_\phi=...
1
vote
0answers
31 views

Why square wave-form output is higher than a sin or a triangle wave-form output?

I'm working on a digital audio synthesiser and I'm facing out an issue about the amplitude level. I'have a sinusoid signal which have a max amplitude of $-1 / +1$ and a square signal which have a max ...
0
votes
1answer
32 views

Does Fourier Series “decodes” the sources of the signal?

I understand the mathematical concept behind Fourier Series that every periodic function can be represented as the sum of sines and cosines. But I can't understand its applications. Lets assume that ...
1
vote
2answers
193 views

Amplitude based “filtering”

Standard filters in electronic circuits are devices that allow a certain range of frequencies to pass through while attenuate other frequencies. I was wondering if something similar could be built ...
0
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0answers
22 views

Positive vs. Negative pulse on an electrode

For a particle detector (e.g. ionization chamber, proportional counter,...), what factor determines the polarity of the pulse of the "raw" signals (signals straight from the electrodes ...
0
votes
0answers
31 views

FFT on a signal with a length that is not a multiple of the period of its harmonics

I was very surprised to find an apparent limitation to a FFT on a simple signal. Let's consider a timeseries made of L=100 points, and simply composed of the sum of two sinus waves: one with a ...
0
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0answers
32 views

Octave analysis Versus FFT analysis?

Why is the one-octave method more significant or of great value compared to FFT analysis? Is it because of the sensitivity of the human ears to perceive sound in octaves? is there any other reason?
-2
votes
1answer
90 views

How to hide radio communications between airplanes? [closed]

I have 2 airplanes and I would like completely hide the communications between them. There is a possible way that this communications would not be detected by our radio receivers around the world? ...
0
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0answers
14 views

Analogue to digital signal graph

I star‌ted the digital electronic course on youyube recently and i am new to the signals concept In the pictures below i tried to convert an analogue signal graph to a digital signal graph So first i ...
14
votes
10answers
4k views

Why does a capacitor act as a frequency filter?

What is it about a capacitor which allows it to filter frequencies? I understand the construction of a high-pass RC filter, and the mathematics behind it, but I'm struggling to find an explanation of ...
0
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0answers
10 views

How to extract wavelet from signal?

I got signal with different wavelets, the first wavelet is strongest one and I need to extract it from signal. It could start at t >= 0, it is not intersects ...
0
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0answers
17 views

What distribution shape does this broadband signal have if the bandwidth changes?

In the Lumerical tool, I'm simulating a setup using a broadband dipole signal. It is (or should be) centered at $\lambda=$ 922.5 nm and has various bandwidths $\Delta \lambda$ for different ...
1
vote
1answer
152 views

What causes the non-arrival of the signal of my remote (infrared) control device for our TV?

Recently I made this video. It can be seen and heard that the remote control (MTLogic) of our TV doesn't work when I place an object between it and the TV. This is the remote control: It's obvious ...
0
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0answers
11 views

Autocorrelation Matrix of sub-band

So, I'm dealing with the smart antenna and different DoA algorithms. In order to define narrowband signal directions I have to calculate autocorrelation matrix of this antenna in the frequency domain. ...
0
votes
1answer
34 views

How to determine waveform of thermal (white) noise?

Here, the mean power of thermal noise is given by: $P = 4kT$ ($T$ = temperature, $k$ = Boltzmann’s constant) And the voltage in the instrument is, of course, thus given by: $V^2/R = 4kT$ The thermal ...
1
vote
0answers
42 views

Intuitive explanation of Nyquist rate?

Is there an intuitive way to understand Nyquist rate (i.e., that, in order to prevent loss, an analog signal must be digitized at a rate twice as high as the highest frequency component of the signal)....
0
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0answers
14 views

How to calculate resolution given sampling rate/size?

In a research paper documenting the analog to digital conversion process of an experiment’s radio receiver, the following is written: The station consists of 10 channels. Each channel writes 1 ...

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