# 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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1 vote
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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 ...
• 83
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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 ...
55 views

### 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 ...
• 101
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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 ...
• 1,256
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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 $N=100$, ...
29 views

### 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 ...
• 101
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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 $$g_{s,u,\omega,\theta}(n) = \frac{K_{s,u,\omega,\theta}}{\sqrt{s}} e^{-\pi(n-u)^2/s^2} \cos[2\pi\omega(n-u)+\theta]$$ ...
184 views

### 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 ...
• 33
22 views

### 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. ...
22 views

### 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 ...
38 views

### 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 ...
45 views

### 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 ...
• 170
1 vote
20 views

### 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 ...
66 views

### 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 ...
35 views

### "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 ...
37 views

### 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 (...
• 1
214 views

### 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 ...
• 709
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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 ...
1 vote
85 views

### 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 ...
64 views

### 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 ...
• 1,626
109 views

### 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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42 views

### 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 ...
47 views

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1 vote
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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 ...
31 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 ...
• 611
1 vote
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 ...
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 ...
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1 vote
32 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 ...
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1 vote