Questions tagged [signal-processing]

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1answer
73 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 ...
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3 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. ...
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27 views

What is the standard deviation of thermal noise?

What is the standard deviation of thermal (“Johnson” or “Nyquist”) noise? I know the RMS is given by: $$\sqrt{4RkTB}, \tag{1}$$ where $R = $ resistance (Ohms), $k = $ Boltzmann’s constant, $T =$ ...
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1answer
31 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 ...
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0answers
30 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)....
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13 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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21 views

Why is the worst case input/output impedance of an $RC$ filter $R$?

I'm going through the Art of Electronics in my spare time, and I ran across a problem I've been scratching my head about for a few days. The book states that in the worst case for any $RC$ filter, the ...
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1answer
41 views

What is the maximum electromagnetic bandwidth achievable between planets? [closed]

As an example, if communication was done using visible light, communication would be limited by the respective atmospheres, dust and obstacles along the line of sight. At the same time, multiple ...
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1answer
40 views

How does an optical chopper work?

How is an optical chopper eliminating drift? Or in more concrete words: Why is a chopped signal eliminating drift (DC -> AC)?
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1answer
35 views

Does the “direction” of a signal physically matter?

I am thinking of the typical (sound, electromagnetic or whatever) signal which can be represented in time or frequency domain as a collection of infinite amplitudes for, respectively, each time-point ...
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1answer
16 views

Frequency of signal means changing or moving?

I saw some where frequncy means how fast a signal is changing and i am confused. Since frequncy means how much cycle a signal completes in unit of time and we may say how fast a signal is moving but ...
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3answers
115 views

How does a spectrum analyzer works. Example with particular case: eyes [closed]

[edit]: I reformulated my question to first talk about general spectrum analyzer and then ask about how vision works (which is a particular case of spectrum analyzer as I explain below). Let's assume ...
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1answer
77 views

Noise spectral density for waveguide: I don't understand this calculation

In Introduction to Quantum Noise, Measurement and Amplification, on page 64 is computed the power spectral density of noise on a classical waveguide. I am really struggling to understand a step of the ...
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46 views

Noise power spectral density and $|X(\omega)|^2$. Why are those quantities associated usually ? Their definitions are different

I consider a generic signal $X(t)$. We could imagine to fix ideas $X(t)=\sqrt{R}I(t)$ ($R$ being a resistor and $I$ current flowing through it) The energy of this signal is defined as $E=\int_{-\infty}...
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1answer
56 views

Why don't we have heat circuits?

Common circuits use electricity to transmit power and signals. I know we transfer heat power using things like HVAC (heating, ventilation, and air conditioning). I don't know anything that encodes/...
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27 views

Difference in mathematical formula between signal to noise ratio (SNR) and signal to noise and distortion ratio (SINAD)

I am trying to get a grip on mathematical meaning of signal to noise ratio (SNR) and signal to noise and distortion ratio (SINAD). What I found out is that in terms of power: $$SNR=\frac{P_{signal}}{...
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4answers
70 views

Why exponential terms like $\exp (i\omega t)$ make no contribution when averaged over a long time?

In the physics of waves, I often see expressions like $$A\exp(i\omega t) + f(t)$$ where $A$ is a constant, $w$ is the angular frequency and $f(t)$ is an arbitrary function that depends on time. It ...
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21 views

How to normalize a deconvolution of a signal?

What I have: A recorded signal, in dimensions voltage (or any kind of intensity) over time A response function of the system, responding to a nearly gaussian input signal What I try to achieve: I ...
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34 views

In square wave modulation: should the low frequency part of the graph not take place in the low amplitude part of the pulse?

I try to get my sound program right, and hoped to find some help here with the understanding of frequency modulation by a square wave. My modulation looks like this: (please excuse if my formula ...
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35 views

Substitution of frequation in Fourier transform of the signal $\hat x(f)$ to $\hat x(\omega)$

In wikipedia of ESD and PSD, there is a pair of equations, one is $$\hat x(f) = \int_{-\infty}^\infty e^{-2\pi ift}x(t){\rm d}t$$ We know $\omega= 2\pi f$. How can we obtain then the other $$\hat x(\...
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19 views

A problem with high pass filter circuit

What physically happens when the input frequency is "too high"? At "normal" frequencies the circuit should act as expected and block lower frequencies while getting only higher ones. I found that if ...
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2answers
1k views

Convolutions in Physics

At a high-level Wikipedia states: "A convolution between two functions produces a third expressing how the shape of one is modified by the other." But there are clearly many ways of combining ...
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1answer
39 views

Doppler effect on non-periodic signals

I would like to understand what's happening to a signal emitted from a moving source and arriving to a moving receptor. But, when I am looking on internet about Doppler effect, I can only find ...
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0answers
30 views

How to calculate Doppler Shift for multipaths from moving objects?

Let's say we have a radar where the transmitter and receiver are placed together, and form an angle theta with a target object moving with velocity ...
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1answer
27 views

Does the light pulse broadens in time when passing bandpass filter?

What I don't understand about relationship between laser pulse width in time and frequency, is where these rules apply, namely rules of Bandwidth-limited pulses. Say, I have a femtosecond laser ...
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0answers
29 views

A question on $s$-parameters

I have been playing around on CST to create a rectangular 2-port waveguide with a block of material at the centre and plot s-parameters. I have done this successfully, however I cannot get my head ...
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2answers
46 views

Wireless data transmission more than a bit at a time

I'm not that educated in wireless data transmission, but, the basics of frequency modulation and or amplitude modulation are quite basic. Is there any examples of transferring more than a bit at a ...
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0answers
15 views

Copper or Glass for Low Latency?

I'd like to preface the main content of this post with the following: I understand this question may be equally suited to the Network Engineering Stack Exchange, but I believe the answer relies on a ...
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0answers
40 views

Any method to detect extremely weak electromagnetic wave signal? (10^12Hz, level ~10^(-28) Watt per meter^2 per Hz)

Could you please let me know whether there is any method on the Earth to detect some EXTREMELY weak electromagnetic wave signal, if it is a planar wave, if its exact waveform is completely known (...
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0answers
16 views

Is there a graphical summary of which modulation technique to use in communication systems using Visible Light Communication techniques?

I am currently looking at various papers written (some listed at the bottom) that discuss how laser pulses can be modulated to send encoded messages to a receiver for communication systems. The more I ...
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20 views

Scattering matrix for a reversed mirror

Suppose I have a mirror which is asymmetric, for example, it is a dielectric coating put onto a glass substrate. Call the air side of the coating the primary side and the glass side of the coating the ...
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1answer
49 views

How are sampled signals reconstructed to original?

Recently I've read an article and watched a video by Monty Montgomery, where he's dealing with the so-called "staircases" in sampled signals. He clearly demonstrated that a signal within Nyquist ...
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3answers
64 views

Can a resonance plot be upside down, i.e., inverted?

Given the following RLC circuit with an AC driving source, $\hskip3in$ I have found an expression for the amplitude to be $$ I(t) = \left(\frac{V_{0}}{R}\right)\frac{(\omega \tau)}{\sqrt{(\omega\...
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1answer
38 views

Power Spectrum Density of real valued time series data

There are real valued time-series data X(t) and corresponding auto-correlation function ACF(t)=$\left<X(0)X(t)\right>$. As written in wikipedia, Power Spectrum Density (PSD) can be calculated ...
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1answer
27 views

RLC Bandpass Filter network

Can anybody tell me what the "s" in this equation is? I am looking for the transfer function of this circuit
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1answer
35 views

Why are an audio signal and its cochlear response modelled as two-dimensional variables?

According to Eguíluz et al, amplification of an incoming audio signal by the human ear can be described by a supercritical Hopf-bifurcation $$\dot x(t) =(\lambda-i\omega_0-|x(t)|^2)x(t)+S(t),$$ ...
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1answer
25 views

Signal demodulation in a frequency mixer

Let's assume we have a signal $f(t)=A\sin(\omega t)+B\cos{\omega t}$. In order to isolate the '$A$-part', the signal is mixed with an oscillator signal $g(t)=\sin(\omega t)$ generating a constant ...
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0answers
21 views

How to determine at what point regeneration of a signal is necessary?

I have a "homework" question that has raised some doubts in my mind about when regeneration of a signal is necessary and whether it can be determined from a given SNR (signal to noise ratio) alone or ...
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0answers
23 views

Broadband Wireless Access Technology

I am looking for a textbook or online resource that covers the physics of 4G and 5G, perhaps even 3G. having read about the new energy levels of each generation, I am curious and interested in ...
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1answer
59 views

How LHC sensors work? [closed]

newbie here. I am here because after working with Raspberry Pi sensors and Analog to Digital converters, and computer processors, I wondered how exactly do sensors in large scale physics experiments ...
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1answer
61 views

Fourier Transform of finite time series

I have some signal $s(t)$ which is real data i.e. finite. The time runs from $-T$ to $+T$. The signal amplitude is large at $t=0$ and small ($\rightarrow 0$) at the $\pm T$ limits. I can do a finite ...
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14 views

What (in silico information) defines the transfer function of a Quantum Amplifier, in the form of a molecule?

Let’s say a team of scientists have published the structure of a molecule they claim acts as a quantum amplifier. Photons travel along a quantum channel carrying qubits in their polarization. The ...
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1answer
46 views

Why does a photomultiplier tube (PMT) traditionally present better signal-to-noise ratio (SNR) than an avalanche photodiode (APD)?

Empirically, a photomultiplier tube (PMT) is said to present better signal-to-noise ratio (SNR) than an avalanche photodiode (APD). Some materials say that it is attributed to the higher gain and ...
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0answers
63 views

How to interpret doppler curve images of Chandrayaan-2 lander?

The frequency transmission data for Vikram, lander of Chandrayaan-2, received by 25 meter Dwingeloo radio telescope is plotted and tweeted by Cees Bassa. Kinks in the Doppler curve are interpreted as ...
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1answer
36 views

Why doesn't stochastic resonance allow us to ignore noise?

I don't know how to formulate the question better. This question is inspired from here where the author states that satellite communication is sometimes lost when radio noise from the sun makes the ...
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2answers
88 views

Superimposed Waves

This question has been bothering me for a very long time. Imagine a wire carrying electric current. It carries two alternating current (AC) signals of different frequencies (say $50$ Hz and $60$ Hz). ...
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The frame of truncated momentum basis on a 1D lattice

$\def\ket#1{\left|#1\right\rangle } \def\bra#1{\left\langle #1\right|}$ (This is part of a research problem) The Setup: Consider a single particle on a finite 1D lattice with the Hilbert space ...
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1answer
156 views

How much is the phase difference between current and voltage in RC circuit?

In a purely capacitive circuit it is $\pi/2$. But in a RC circuit $$V=v \sin \omega t(1-e^{-t/RC})$$ while $$I=i \sin\omega t (e^{-t/RC}).$$ For such a function how to calculate phase difference?
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1answer
52 views

Catching the beat! [closed]

I'm lately fascinated with the whole "beat" concept, and have been doing some experiments. I'm trying to capture the beat waveform on an oscilloscope in run mode, but am having no luck. I'm putting a ...
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1answer
84 views

Detection of an optical noise with a photodetector, noise-equivalent power (NEP)

I am trying to find the minimum power that can be detected by a photodetector for which I know its noise-equivalent power (NEP). The standard formulas are: $$\mathrm{SNR} = \frac{\langle i_s^2(t)\...

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