Questions tagged [signal-processing]

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6
votes
5answers
1k views

Existence of monochromatic pulses?

Why there can not be a monochromatic pulse? My physics professor told us that we can't generate a monochromatic light pulse and I was wondering what are the physical limitations causing this.
14
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4answers
1k views

Reconstruction of “wavefunction” phases from $|\psi(x)|$ and $|\tilde \psi(p)|$

Consider a "wavefunction" $\psi(x)$, which has a Fourier transform $\tilde \psi(p)$ Suppose that we know, for each $x$, $|\psi(x)|^2$, and that we know, for each $p$, $|\tilde \psi(p)|^2$. Have we ...
10
votes
3answers
1k views

Can the Kramers–Kronig relation be used to correct transfer function measurements?

In experimental physics, we often make measurements of linear transfer functions; these are complex-valued functions of frequency. If the underlying system is causal, then the transfer function must ...
8
votes
2answers
6k views

Why is bandwidth, range of frequencies, important when sending wave signals, such as in radio?

So in wired/wireless networking and radio, signals are sent in form of wave. Then the concept of bandwidth comes in, which is the difference between highest frequency and lowest frequency in a signal. ...
8
votes
2answers
3k views

How to distinguish female and male voices via Fourier analysis?

What makes one, without looking, be able to identify the gender of the talker as male or female? I mean if we Fourier analysed the voice of males and females, how the 2 spectrums are different which ...
2
votes
3answers
151 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 ...
10
votes
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 ...
1
vote
1answer
1k views

Parseval's Theorem on a Random Signal

NB - I'm re-posting this question in physics because I haven't had any luck getting a response from the maths StackExchange site - it's a rather applied problem so is probably better suited here ...
1
vote
0answers
39 views

Is there a Bayesian theory of deterministic signal? Prequel and motivation for my previous question

This is a prequel to my question: What's the probability distribution of a deterministic signal or how to marginalize dynamical systems? Clearly my question looks at the same time fairly ...
7
votes
1answer
856 views

Frequency shift without affecting signal length

Non-physicist here. From what I've learned in university and what common sense says, a shift in frequency of a signal results in a change in its length in time. For example, if a sinusoid signal of ...
1
vote
0answers
164 views

What's the probability distribution of a deterministic signal or how to marginalize dynamical systems?

In many signal processing calculations, the (prior) probability distribution of the theoretical signal (not the signal + noise) is required. In random signal theory, this distribution is typically a ...
1
vote
2answers
142 views

Energy of a signal

"The energy" of a signal $x(t)$ is defined as : $$E_s = \int_{-\infty}^{\infty}|x(t)|^2$$ Why is it called energy if it's not homogeneous to energy ? What does it actually represent ? Parseval's ...
5
votes
1answer
288 views

Products of Gaussian stochastic process variables

In the classic experimental physics text "Statistical Theory of Signal Detection" by Carl. W. Helstrom, Chapter II, section 4 concerns Gaussian Stochastic Processes. Such a process is observed at ...
3
votes
1answer
303 views

What is a Nyquist edge?

I've come to this sentence and I don't understand the term Nyquist edge. Because observing in the FM band is not feasible, a sampling frequency of 200 MHz has been chosen for most of the receiver ...
2
votes
4answers
104 views

An apparent contradiction in various explanations of frequency bands and data bandwidth

From wikipedia: "A key characteristic of bandwidth is that any band of a given width can carry the same amount of information, regardless of where that band is located in the frequency spectrum. For ...
1
vote
1answer
2k views

How is energy conserved for discrete Fourier transforms of different bin size?

I have gotten myself into a muddle regarding the discrete Fourier transform (DST) and would appreciate if someone could help me become unstuck. I noticed that the fft of the following are the same: ...
0
votes
2answers
2k views

Negative SNR and Shannon–Hartley theorem

It is intuitive to think that if the noise amplitude is more than signal amplitude, it will obscure the signal. But using Shannon–Hartley theorem, one can see that a receiver can read the signal even ...
-1
votes
3answers
2k views

Can human ear distinguish between sounds of different phase?

A noise cancelling headphone produces a sound that's out of phase with ambient noise, mixes them and hence cancels them. But I wonder if we were to here the 2 sounds which are out of phase to each ...