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Questions tagged [signal-processing]

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69 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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1answer
40 views

How to calculate average power? [closed]

With a baseband signal with a total period, $T$, of 4, and an amplitude $x(t)$ of 3, I have to find the peak to average power ratio. I know how to find this using the average power but I don't know ...
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2answers
72 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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30 views

Are Wavelets Just a geometric method for understanding how a wave moves forward or are they an actual thing?

Wavelets are emitted from every point on a wave towards all directions is what I read on a book but on another book I read Wavelets are emitted towards the same direction of the wave. And They create ...
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0answers
13 views

Sawtooth synthesis using random harmonic phase

I was experimenting with Octave and NumPy/SciPy by synthesizing (reverse) sawtooth waves and decided to find out what a sawtooth comprised of harmonics with arbitrary phases would sound like. Note ...
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0answers
2k views

How is it that two electric currents can travel in opposite directions on the same wire, at the same time, without interfering with each other? [migrated]

I asked this same question on electronics.stackexchange, but the answers either don't clearly and directly address my question, or are seemingly conflicting or greatly varying to the point that it is ...
1
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1answer
66 views

Fourier transform of power

In the notes I am reading they use the following. Let $U$ be the voltage (depends on time) and $I$ the current in a circuit with some resistor with resistance $R$. Then the power is given by: $$P(t)=...
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1answer
59 views

Bandwidth of a control system

Why is it said that larger bandwidth leads to better command following , better disturbance rejection and speedy response , but the practical bandwidth being limited by external noise?
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2answers
29 views

Why doesn't central obscuration put a big dot in the middle of a PSF for a centrally obscured optic?

I'm confused as to how central obscuration effects the PSF. Low pass filters make sense since they are inherently oriented with dealing with spatial frequency, resulting in blur in the spatial domain....
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1answer
11 views

What influences the variance of signal transmission speed?

I'm currently thinking about the various sources that influence time when it is synchronized with the NTP protocol. One of them is the physical layer (OSI-model). When sending a bit over a cable, ...
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1answer
23 views

How do scintillation detectors work, for gamma ray spectroscopy

So I understand what happens in the crystal with respect to the interactions and how the electrons in PMT are multiplied by hitting dynodes etc. But what I can't really seem to find any information on ...
2
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1answer
67 views

Why non-linear fiber capacity limit decrease for higher signal-noise ratios?

In fiber optics communication, there is the concept of nonlinear Shannon limit (see e.g. this article), implying that the communication capacity of an optical fiber decreases for high SNR. I don’t ...
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14 views

Bleding in convolution reverb

Since I use crystallography a lot in my studies I know that, when light or X-rays are considered many error and abberations add up to a total by the means of mathematical convolutions. So in order to ...
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0answers
45 views

Can the periodicity in k-space of the electronic band structure be understood as a result of aliasing?

Discrete sampling in the case of phonons In the case of phonons in periodic solids, the picture is quite intuitive. The motion of the atoms in the lattice is described as a continuous wave (amplitude ...
3
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1answer
54 views

Mathematical term for the on/off gradient functions in MRI imaging

The slice selection gradients, as well as the phase and frequency, in MRI imaging are traditionally represented by on/off box or rectangular symbols: or My question is what is the mathematical name ...
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0answers
65 views

Using lock-in to measure $ f $ instead of $ f' $

What I know about lock-in measurement is the following: you have a device you want to test and instead of giving it a DC input, you would modulate your DC input with some sinusoidal modulation and ...
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0answers
13 views

Noise reduction approaches in optical spectral measurement

I am using an optical spectrometer to measure some surfaces in the visible, and since the signal is quite noisy I wondering what would be the best way to reduce the noise. In particular, are there ...
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0answers
69 views

Mean velocity in unsteady flow

I'm starting hydraulic experiments, where I'd have to measure velocity in an unsteady flow with a device called Acoustic Doppler Velocimeter (acquisition rate: 100 Hz) . In DSP terms, I'd have a ...
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3answers
78 views

Does a 1 kHz signal have harmonics above or below 1 kHz, and where is its fundamental frequency?

I'm having an argument with a friend ─ he believes a 1 kHz audio signal has its fundamental frequency at 1 kHz with harmonics above that value, while I believe the fundamental frequency will be far ...
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2answers
58 views

How does ultrasound work? How is the signal processed?

Why is ultrasound 2D? Is there a way of making ultrasound 3D without piecing together 2D? How close is ultrasound to sonar?
1
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1answer
39 views

Multilateration of Sound in 3D Space

TL:DR - How can you find the 3D coordinates of a emitter than transmits an impulse signal? STORY: I'm working on something to improve my bird-watching. I've got a camera that can take pictures of ...
0
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1answer
63 views

Superposition of waves whose wavelengths are continuous

I know how to find the resultant waves when finitely or countably many waves are superimposed but how do I find the wave equation when there are infinitely many waves whose wavelength is continuous? ...
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0answers
204 views

Blocking Infrared Signals [closed]

I am currently working on a project that involves infrared signals. This project has an infrared receiver, but I would like for it to receive signals from front side only. For example, if the signal ...
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1answer
29 views

Can a gaussian pulse be a pure tone?

I was given a signal dataset, and I was told it is a gaussian pulse and a pure tone. I am unsure how this is related as when I read about this two terms, there are differences in them. so can a ...
2
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2answers
55 views

Why we can assert, in general, that physical processes have the behaviour of low-pass filter?

Consequently, why is it not allowed to produce physically some controllers for processes that are described by a transfer function that is an improper function? A simple example is the driven ...
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2answers
139 views

Is it fair to say that signal processing is a quantum phenomenon?

I recently saw a video by 3Blue1Brown, in which he explained that the uncertainty principle isn't a quantum phenomenon, but a result of basic signal properties. The basic premise was: the more precise ...
3
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1answer
46 views

Sound an amplifier makes when you plug / unplug a cable [closed]

When you plug, unplug or even touch a jack cable of an aplifying system with speakers, one can hear a low-pitch sound that is of roughly always the same frequency, which does not seem to depend on the ...
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2answers
69 views

Low frequency wave ability to penetrate object

as shown in this em wave spectrum image, the lower the frequency the better a wave ability to penetrate object. https://c479107.ssl.cf2.rackcdn.com/files/20642/area14mp/pvgrynkw-1361853572.jpg my ...
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1answer
28 views

what does the “T” really represent in the signal power equation

In the signal power equation $$ P(g(t)) = \lim _{T\to \infty }{\frac{\left(\int_{-\frac{T}{2}}^{\frac{T}{2}}g\left(t \right)^2dt\ \right)}{T}} $$ What does the $T$ really represent ? From my ...
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0answers
98 views

High speed data transfer over a fiber optic cable

Can someone please explain how can we transmit very high speed data (e.g. $10~\rm Gbps$) over fiber optics, knowing the fact that the wave that travels through the fiber is an optical wave (in the ...
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0answers
32 views

Low frequency waves influence of high frequency waves

If I have a 20 MHz surface wave travelling along a material, and then introduce a 50 or 100 Hz wave source, will there be a noticeable difference to the output? (Surface acoustic wave type device, ...
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2answers
27 views

How can I send a wave towards something and have it respond with a specific value?

Imagine a bat, for example. It uses its echo-location to send waves which get reflected back and thus return information about the surroundings. I want to do the same thing, but instead of just ...
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2answers
48 views

Recognizing speech at 1bit quantise depth?

i found on german wikipedia an audio example of 1 bit depth quantising, where the speech still can be recognized. how is it possible if at 1 bit depth we have just two values: "signal" and "no-signal"?...
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1answer
122 views

What is the difference between collimating, waveguiding, attenuating, and polarizing? [closed]

What's the difference between collimating, waveguiding, attenuating, and polarizing? Are they related on any level at all?
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0answers
52 views

How do I analyze this frequency spectrum obtained from pouring water into a bottle?

I measured the frequency of sound in the bottle neck while pouring water into a bottle and obtained a frequency spectrum which is in the comment section of the link in Quora. Please tell me how to ...
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1answer
25 views

When can raw data can be used to look for phase synchronization between time series?

I'm studying a system formed by multiple rotors non-linearly coupled to each other. If I want to look for phase synchronization, I could just look at the angle for predefined points around the ...
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0answers
132 views

Autocorrelation function of derivative

I have a question, I am stuck on for quite some time now. Imagine you can choose a two dimensional autocorrelation function $C_V(x,y)$. From this I can create the two dimensional random process $V(x,y)...
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1answer
63 views

Acoustic power spectral density change due to diffraction

Say we have an acoustical point source emitting white noise - i.e., a power spectral density of $$S_x(f) = \frac{N_0}{2}$$ The source is embedded in the plane such that it radiates in half-space - i.e....
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3answers
99 views

Use of negative frequency for the sake of simplifying mathematics?

How can we use the idea of negative frequency for the sake of simplifying mathematics if negative frequency does not exist (to my knowledge) in nature ? For example, when plotting the spectra of a ...
0
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1answer
28 views

reading radar / waves changing after hitting each other

Can you read a radar or any wave when it hits another wave...it changes? So say a radar wave hits another wave changing it miles away, can you get info of that hit happening miles away from the radar ...
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1answer
42 views

Understanding feedback =1 and comparing with a system with no feedback

I was studying this system In this V its a Voltage in a circuit and V_c its the voltage in a capacitor, the circuit was not provided, then calculated the step response (well I was told the step ...
0
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1answer
31 views

Can the telephone signals be tapped by an intruder? [closed]

I have a doubt. There are lots of telecommunication signals moving across the world, at the same time. For example, take the case of mobile phone calls. Millions of speech signals are propagating ...
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0answers
154 views

How can I calculate the sensitivity of a seismometer?

I would like to know how to find the minimum ground motion a seismometer can measure, specifically if a certain seismometer can measure 1 micron/sec velocity. I have a few specs from the datasheet but ...
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6answers
8k views

Why are cosine and sine functions used when representing a signal or a wave? [closed]

Actually, in the mathematics sine and cosine functions are defined based on right angled triangles. But how will the representation of a wave or signal say based on these trigonometric functions (we ...
0
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2answers
137 views

Example of transfer function and driving signal equation

In a text I am using it states that for linear dynamical systems, there is a very simple relationship between the power spectrum of the driving signal and that of any one of the system variables. If ...
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1answer
46 views

How to quantify elevated tails of a Gaussian like signal?

From some simulations I have obtained as an output a signal which roughly looks like a Gaussian with some elevated tails. Note that the input was a Gaussian. Now I would like to quantify the ...
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1answer
79 views

The importance of -20dB in signal analysis

I built a resonator designed to resonate at 30MHz. To verify the resonant frequency I use a network analyzer with a 4.3 pF capacitor in series with cavity. The physicists at my work claim that the ...
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1answer
327 views

How to estimate the frequency of the sample rate?

I'm studying for my class of physics laboratory and I need help with something: Let's say I need to deduce the constant of elasticity of a spring and I will do it using a dual-range force sensor, ...
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2answers
85 views

Meaning of $v_\mathrm{source}$ in the Doppler effect

The Doppler equation is given by $$f_{observed} = \frac{c+v_r}{c+v_s} \cdot{ f_{emitted}}$$ Does $v_s$ refer to the velocity of the source, relative to the receiver at the time the wave (now at the ...
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0answers
81 views

Find the tranfer function for this signal flow graph? [closed]

I already sovle this by 2 different ways and had 2 different results. I don't know which one is right. Can someone use the matlab or something like that to solve this quickly to find the right answer. ...