Questions tagged [signal-processing]

The subfield of electrical engineering that focusses on analysing, modifying, and synthesizing signals such as sound, images, and scientific measurements.

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What is the difference between radar cross section and intensity/amplitude?

I've been tasked with simulating a radar system, and I think I understand the problem, except I'm supposed to be providing the outputs in both radar cross section and amplitude. What's the difference? ...
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Applications of Signal and System theory

I recently heard a lecture about Signals and Systems and find the subject extremely exciting. I would like to do more in this direction, so I would be interested to know in which modern research area ...
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Calculating Fourier Coefficients for this 50% bipolar square wave [closed]

I'm getting stuck trying to derive an equation for the Fourier coefficients of this waveform. Following along from this example: https://lpsa.swarthmore.edu/Fourier/Series/ExFS.html It is clear that ...
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Understanding the Fourier transform of a signal already with amplitude and phase information

I'm from an image processing background and am working my way into optics. I'm working on phase retrieval problems, trying to understand the Gerchberg-Saxton algorithm. I found this video which is ...
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How can we show that a lens is a low pass filter?

I understand from the derivation in Goodman Chapter 6 that a lens Fourier transforms light from the front focal plane onto the back focal plane, ignoring aperture effects. I've also read that a lens ...
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Physical interpretation of FFT frequencies

I need to calculate the PSD of a discrete signal and want to compare it to other processes. By Nyquist theorem, I only can account half of the frequencies. Assume I have a signal of length $N=100$, ...
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Data transmission through optical fiber and copper wire

I read the following in one reference: A copper wire (twisted pair), the link traditionally associated with low bit rate transmission, is still in use in the modern data centers transmitting data at ...
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How do I solve for the normalization constant of a discrete time-frequency Gabor atom?

Given the mathematical expression for the discrete Gabor time-frequency atom $$g_{s,u,\omega,\theta}(n) = \frac{K_{s,u,\omega,\theta}}{\sqrt{s}} e^{-\pi(n-u)^2/s^2} \cos[2\pi\omega(n-u)+\theta]$$ ...
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Velocity from acceleration equation

I've been working with an accelerometer, and was assigned the job of trying to find the velocity from the accelerometer, I take acceleration data every 10 ms (sampling rate 100KHz) and I used the ...
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Converting PSD against spatial frequency to RMS against temporal frequency

I am putting together some simple ride comfort models that use road surface PSDs from ISO 8606 (road surface profiles) as inputs to a quarter car suspension model to produce body acceleration spectra. ...
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What happens during under-modulation?

I need clarification regarding what exactly happens to the information in amplitude modulation if it is under-modulated. I know that if it is over-modulated, some information will not reach the ...
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How to find peak power at 1550nm using an optical meter?

I have a setup of tunable laser source at 1550nm connected to a spectrometer(Can't publish the name of spectrometer). The spectrometer has a range of 1510-1595 nm. The graph shows wavelength vs ...
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Is there any known result about the "average period" of a complicated oscillating function?

Say we have some frequency spectrum, $f(\omega)$, where $$ f(t) = \frac{1}{2\pi} \int_{-\infty}^\infty d\omega \; f(\omega)e^{-i\omega t}, $$ and we know that $f(t)$ is some sort of ...
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Difference Between a Time-Domain and a Simulation Domain Acoustic Pressure Simulation

I would appreciate it if someone would be able to clarify my doubts. I'm currently working on acoustic simulations in COMSOL and is currently confused on the information provided by the simulations ...
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About multiple reflection along a transmission line

I was trying to examine the multiple reflections happening at both ends of a cable after some customized modifications done in the machine shop. I started from a transmission line model and ...
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"All continuous time signals are analog but all analog signals are not continuous time"

I heard the above and pondered. The Wikipedia's definition for "analog signal" goes as follows "An analog signal is any continuous signal for which the time-varying feature of the ...
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Phase difference of two time series

Consider we have two time series and for each of them , we know the phase (Phase1 and Phase2). We want to compute phase difference between these two time series. We define the phase difference as (...
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What is meant by 2D fourier transform of an image?

I have some questions about this interesting concept I came across about 2D Fourier transform, please... Firstly, the Fourier transform of a 1D signal (such as a sound recording) is as follows: The ...
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During a wheelie, is there a braking effect on the back wheel of the scooter that is triggered physically when the bike is close to vertical?

When someone does a wheelie using a motorcycle (scooter), it looks to me like something is stopping the the motorcycle from tipping over backwards so far that it crashes. Is there some sort of (built ...
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Is the human singing voice different from a linear, time-invariant (LTI) system?

Typically the human voice is modelled by a linear, time-invariant (LTI) system. An LTI system cannot add any frequency components to an input signal. This is obvious from the input-output relation in ...
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Removing $1/f$ noise with lock-in-amplifiers

On the Wikipedia page for 1/f noise (at the bottom of the page) it suggests the noise can be reduced if the signal of interest is at DC. DC signals suffer from significant 1/f noise, so one method of ...
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How fast, based on the laws of physics can the Internet be? [closed]

Assuming the actual physics, optics, signal processing and similar, how fast can we increase the 'speed' of the Internet? I know the limit would be $$v \le c,$$ but are there some other limits: ...
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Drawing digital signal from analog signal

I was doing a question related to analogue to digital conversion. Here's the question, Draw the digital signal corresponding to the analogue signal given below. Assume that the system has a bit rate ...
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Physical validity of taking limits inside an integrand

Consider an integral expression for the spectrum, $$I(\omega)=\int_{-\infty}^{\infty}G(\omega,t)dt\tag{1}$$ with $$G(\omega,t)=g(\omega,t)e^{t/\tau}.$$ Here $t$ is time, $\omega$ is frequency and $\...
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Signal Generated from Transmitter [closed]

Suppose that we have a transmitter of $150.100\ \mathrm{ MHz}$. We also have a receiver at a fixed point. The transmitter constantly generates signals toward the direction of the receiver. Based only ...
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Is this system linear? [migrated]

$$y(t)=\begin{cases}0 \hspace{4.86cm}x(t)<0\\ x(t)+x(t-2)\hspace{2cm} x(t)\geq0\end{cases}$$ Assuming $C>0$. If $x(t) = C$ is an input, the output will be $2C$, and the output of $-x(t)=-C$ must ...
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Which one is more precise: Phase locked loop or log the waveform then do sliding FFT?

I have an experimental confusion. I am using an interferometer to monitor the movement of a translation stage by monitoring the intensity of the coaxis interference pattern of the He-Ne laser. ...
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Infer 3D location (Height, Latitude, Longitude) based on Signal Strength

Sorry if my question is irrelevant. Let's consider two cases: $1)$ Suppose that we have an Antenna and a tagged individual that can be pinged from the Antenna. Suppose that the individual is pinged ...
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Capacitor microphones for recording studios

This question is formulated exclusively for high school students precisely to interest them in a more concrete way. Condenser microphones are characterized by a capsule that functions exactly like an ...
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Is it possible to use a distributed camera array to fake an interferometric sensor without phase data?

Astronomical interferometry is a technique which uses multiple small telescopes to mimic one giant telescope. It requires the phase of the light to be captured for it to work. It is widely used in ...
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Once LIGO confirms a gravitational wave signal, can data from less sensitive detectors give more insight?

Only detectors above a certain sensitivity can measure with a high enough signal to noise ratio (SNR) to successfully pick out gravitational waves using matched filtering. However, once we have ...
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Physicality of the square root of the modulation frequency bandwidth in NEP

The NEP or noise - equivalent - power describes the ratio of electron counts that are displaced for a given unit number of photon incident at an area in which these electrons "resides". ...
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What is the relation between the frequency vector and the Nyquist frequency?

When trying to comprehend the concept of Nyquist frequency in FFT, I came across the following definition for half of the frequency range: $$f = -f_{n}/2:df:f_{n}/2-1;$$ where $f$ represents the ...
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2 votes
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Why can't you filter out the sound of running water using noise-cancelling software?

The book "Clint Emerson - 100 deadly skills", a fun illustrated book of spy techniques claims the following: Deadly skill No 054, Civilian BLUF: While noise-canceling software can override ...
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Would increase the size of an antenna theoretically improve the ability to capture signals, if we allow changing the shape?

I have an argument with my friend about drone radio systems. My assumption is this: the bigger the receiver the better reception is possible to achieve. The logic behind this is geometry: transmitter ...
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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 ...
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2 votes
1 answer
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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 ...
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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 ...
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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, ...
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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 ...
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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 ...
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Does less than half a wavelength antenna spacing help?

In Metamaterial based Holographic Beamforming (Holographic Beam Forming and MIMO), the spacing of the elements is much lesser than half wavelength. The inventors claim that it works better than the ...
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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{...
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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