Questions tagged [signal-processing]

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Computing a second harmonic resistance out of a wave-like resistance signal

I want to reproduce the results of a paper, in which they measure the Anharmonic Hall Effect (AHE) resistance $R_{AHE}^{2\omega}$. There are several protocols for measuring it experimentally, but I'm ...
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13 views

Dicke switching for radars

A question about Dicke switching for e.g. radio antennas. Some background so that we're all on the same page: fluctuations in the gain of the detector can dominate the low power signal. Dicke ...
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Are there any application in the exp of log of DFT matrix? [closed]

Just a fun thought. Since the N point DFT matrix $W$ is a complex rotation matrix: $$W^*W = I$$ $$det(W)=1$$ It may make sense to work on a rotated domain with a projection matrix $W_\phi$: $$W_\phi=...
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29 views

Why square wave-form output is higher than a sin or a triangle wave-form output?

I'm working on a digital audio synthesiser and I'm facing out an issue about the amplitude level. I'have a sinusoid signal which have a max amplitude of $-1 / +1$ and a square signal which have a max ...
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1answer
27 views

Does Fourier Series “decodes” the sources of the signal?

I understand the mathematical concept behind Fourier Series that every periodic function can be represented as the sum of sines and cosines. But I can't understand its applications. Lets assume that ...
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2answers
37 views

Amplitude based “filtering”

Standard filters in electronic circuits are devices that allow a certain range of frequencies to pass through while attenuate other frequencies. I was wondering if something similar could be built ...
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0answers
18 views

Positive vs. Negative pulse on an electrode

For a particle detector (e.g. ionization chamber, proportional counter,...), what factor determines the polarity of the pulse of the "raw" signals (signals straight from the electrodes ...
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28 views

FFT on a signal with a length that is not a multiple of the period of its harmonics

I was very surprised to find an apparent limitation to a FFT on a simple signal. Let's consider a timeseries made of L=100 points, and simply composed of the sum of two sinus waves: one with a ...
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29 views

Octave analysis Versus FFT analysis?

Why is the one-octave method more significant or of great value compared to FFT analysis? Is it because of the sensitivity of the human ears to perceive sound in octaves? is there any other reason?
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1answer
83 views

How to hide radio communications between airplanes? [closed]

I have 2 airplanes and I would like completely hide the communications between them. There is a possible way that this communications would not be detected by our radio receivers around the world? ...
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13 views

Analogue to digital signal graph

I star‌ted the digital electronic course on youyube recently and i am new to the signals concept In the pictures below i tried to convert an analogue signal graph to a digital signal graph So first i ...
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10answers
4k views

Why does a capacitor act as a frequency filter?

What is it about a capacitor which allows it to filter frequencies? I understand the construction of a high-pass RC filter, and the mathematics behind it, but I'm struggling to find an explanation of ...
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0answers
10 views

How to extract wavelet from signal?

I got signal with different wavelets, the first wavelet is strongest one and I need to extract it from signal. It could start at t >= 0, it is not intersects ...
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0answers
14 views

What distribution shape does this broadband signal have if the bandwidth changes?

In the Lumerical tool, I'm simulating a setup using a broadband dipole signal. It is (or should be) centered at $\lambda=$ 922.5 nm and has various bandwidths $\Delta \lambda$ for different ...
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1answer
80 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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7 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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1answer
34 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
37 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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0answers
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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28 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
74 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
36 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
117 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
78 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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0answers
47 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
61 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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0answers
28 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
72 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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0answers
27 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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0answers
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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40 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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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
43 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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31 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
30 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
31 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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16 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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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
18 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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26 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
57 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
75 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
46 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
28 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
36 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
26 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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