Questions tagged [signal-processing]

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16 views

Estimating 3D movement from Apple Watch [closed]

I am trying to understand if there is a way to estimate 3D movement using the below variables along all three axis and relative to the orientation of the device: Attitude Acceleration Gravity ...
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1answer
42 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
49 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
27 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
26 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
34 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
22 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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15 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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22 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
49 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
39 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
40 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
59 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
33 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
66 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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91 views

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
108 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
48 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
62 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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1answer
33 views

How to solve this problem involving the “longest interval”?

The problem is shown as follows: If one wants to make a digital record of sound such that no audible information is lost, what is the longest interval, $\Delta t$, between samples that could be ...
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0answers
63 views

The validity of some “applications” of the uncertainty principle

Given a $L^2$ function $f$ with $\int_\mathbb{R}xf(x)dx=0$, define its variance to be $\sigma_f^2=\int_{\mathbb R}x^2f(x)dx$. The uncertainty principle states that $\sigma_f\sigma_\hat f\geq 1/4\pi$,...
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49 views

Why is the optimum window length for a discrete fourier transform of a signal less than 100%?

I'm trying to determine the best settings for a discrete Fourier transform on a signal with noise. Now I've stumbled on something that I can't seem to explain, I'm hoping someone can give me some ...
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0answers
25 views

Measuring signal shorter than instrument response function

If one has a well-defined instrument response function (IRF) of some known full-width half maximum (FWHM), and they are measuring a signal that is shorter (but the shape is known), is it possible to ...
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43 views

“Synchronization” Probability of Multiple Waves with Varying Frequencies

Update 1: I've done some digging and I think this is related to signal coherence, namely, that I'm seeing a coherence time of ~3 σ, which is consistent with the definition where Ct=1/Δv where Δv is ...
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0answers
10 views

How certain we are that two signals (μ1, σ1) and (μ2, σ2) are distinct?

Suppose we have N1 measurements of first signal and N2 of second. Both are normally distributed with (μ1, σ1) and (μ2, σ2) respectively. How certain we are that these signals are distinct?
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10 views

Shifting identical but offset pulses in frequency domain

Supposes I have 2 identical pulses, but one is offset by some phase. I want to take fourier transform of the signal in time domain to frequency domain. In freq domain, their spectrums are identical, ...
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1answer
81 views

Fractional Fourier Transform and Fresnel Propagation

I am currently trying to wrap my head around Fresnel propagation, and I understand it is mathematically linked to the Fractional Fourier Transform, but I'm having a hard time with the units and the ...
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0answers
18 views

Exponential decay and growth oscillations at beginning and end of Fourier transform of data

I have some data from an photo-detector, which I think should correspond to white noise, but when I plot the Fourier transform of the data, I get a plot with exponential decay at the beginning and ...
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0answers
25 views

Low acoustic frequencies creating ripples in video

When watching this video about a sound synthesier I noticed that low frequencies (bass) create a visual ripple effect. I'd like to know why a how this is possible. I guess this can't be due to ...
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8 views

Is it possible to enhance Lombard speech effect, whisper, other types of “non-audible” (having non-linear spectrum?) but present sounds?

I would certainly like to ask Floris (New England) user directly, since Floris brilliantly answered one of the questions, related to whisper (and its enhancement) posted by another user, please. My ...
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31 views

Signal parameter estimation in PyCBC

I have a gravitational wave signal (strain vs. time). And I want to find out the corresponding parameters of the compact binary. But I do not know how to create injection for this signal in PyCBC. ...
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1answer
43 views

Can faster sampling frequency solve the x-ray diffraction phase problem?

In the x-ray diffraction, only the intensity the light that hits the detector is captured while the phase of the light is not determined. The energy flux of the light is the Poynting vector. For a ...
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0answers
21 views

Fourier transform of some discrete, finite, non-uniform signal

Suppose I have some finite signal $x(t)$ of $N$ data points. This signal is produced by some program or some experiment and so is discrete and the difference in time between each data point $\delta t$ ...
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99 views

Photo Multiplier Tube (PMT) and charge sensitive pre-amplifier

I have an H7195 assembly type Photo Multiplier Tube (PMT) used to be tested for single photon measurement. I would like to use the dynode output to check the spectrum by connecting to a charge ...
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2answers
52 views

Why we use Nyquist frequency limits

Can someone in simple terms why you would use Nyquist frequency limits when processing a signal? What benefit does it provide, and how does it affect the results? And how does it relate to the Nyquist ...
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1answer
141 views

Why do people study plane wave in wave physics?

I have recently been studying a structure for high sound absorption. There are a lot of literature on similar design, where all of them are using the plane wave as an input to the structure. I have ...
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1answer
75 views

Integer multiples of fundamental time period? [closed]

If we define harmonics to be positive integer multiple of fundamental frequency What will we say to positive integer multiples of fundamental period?
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2answers
76 views

Multiple frequencies [closed]

could someone please inform me how it is possible to send multiple frequencies down one wire? I’m referring specifically to a communication protocol known as HART. It seems they send a 4-20mA signal ...
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3answers
139 views

Can a sound wave begin with rarefaction?

Some digital recording samples (audio files) of recorded acoustic sounds present sound waves which begin with rarefaction. Is this an actual phenomena that can occur or is it a result of sound ...
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1answer
247 views

Applying Kramers-Kronig relation to a simple damped oscillator

I just discovered the Kramers-Kronig relation and am trying to apply it to a simple damped oscillator of the form subjected to an impulse at $t=0$, which is a causal system: $$m\ddot x + c\dot x + k ...
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0answers
39 views

Mathematical Resolution of Overlapping Signals

I would like to take the opinion of physicists (my area is chemistry). During instrumental analysis, the output is a instrument response vs. time. Each peak corresponds to a molecule which is ...
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1answer
68 views

Proving a theorem about the average value of a function over a specific region

Let's say transient phenomenon in a function. A transient phenomenon is defined as: "A transient event is a short-lived burst of energy in a system caused by a sudden change of state." So, for ...
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1answer
21 views

What does the phase discriminator portion of the Costas Receiver do mathematically?

What does the phase discriminator portion of the Costas Receiver do mathematically? The output of the $I$-channel is $ \frac{1}{2}A_C \cos \phi \, m(t) $. Which means for small deviation of phase $ \...
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1answer
57 views

What exactly is the output impedance in this circuit, and why must it be low?

I'm currently considering this circuit: Which is really just two RL filters added together. A single RL-filter looks like this: I want to be able to multiply the transfer functions of the left and ...
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0answers
48 views

Fourier Coefficients

Suppose i've a two voice samples v1 and v2. Comparatively voice v1 is louder than the v2. If both the voice is spoken by the same person.(Spoken normally as he speaks) Is it good to state the ...
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1answer
361 views

Calculation of speed from accelerometer data

I am trying to use my accelerometer on my mobile device fitness band to find the speed of walking and running. I conducted my experiment of walking and running on treadmill where I asked a person to ...
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0answers
53 views

Dispersion of light

I've been taking digital signal processing course. It's pretty interesting for me. One thought came to my mind while I've been practicing numerical problem on Fourier transform. So my question is ...
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0answers
530 views

Fraunhofer diffraction problem in Python: How to interpret discrete Fourier transform (DFT) spectrum?

I have a periodic phase grating consisting of lenslets along the x-direction, invariant in y. I want to use python to calculate the far-field (Fraunhofer) diffraction pattern that one gets when ...
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2answers
712 views

What is a “Fourier transform limited pulse”?

I have some doubts about the definiton of a Fourier transform limited pulse. For example if I consider a generic pulse: $$E(z,t)=\frac{1}{\sqrt{2\pi}}\int_{-\infty}^{+\infty}A(\omega)e^{i(-\beta(\...

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