All Questions
15
questions
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votes
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60
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Effective aperture as a function of Azimuth and Elevation Angle
Wikipedia says
The effective aperture of an antenna is given by $$A_{\mathrm{e}}(\theta, \phi)=\eta A \cos \theta \cos \phi ,$$
where, $(\theta, \phi)$ are the azimuth and elevation angles relative to ...
- 101
0
votes
2
answers
70
views
Why do parabolic antennas need to be the same width as their wavelength?
I am reading the wikipedia page for parabolic antennas, and have a question about the below quote:
In order to achieve narrow beamwidths, the parabolic reflector must be much larger than the ...
- 137
0
votes
0
answers
30
views
Overview work on radio solitons?
I've heard about solitons in dense mediums (water), sparse mediums (acoustic) and optical fiber.
But I can't find a good overview work on solitons in radio spectrum. Something like generating EM ...
- 111
0
votes
1
answer
49
views
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 ...
- 115
0
votes
3
answers
138
views
Why is it that we never see visible spectrum waves being generated by oscillating currents in an Antenna?
Studying Maxwell's equations brings surprising clarity and odd questions to my mind. In this case, I was going through the Point form and Time Harmonic form of the four equations and a line in my ...
0
votes
1
answer
357
views
How do you polar-plot the complex-valued array factor (AF) of a phased antenna array? [closed]
If a normalized array factor for an $N$-element linear antenna array (without per-element phase shifts) is calculated as
$$
AF = \frac{1}{N}\sum_{m=0}^{N-1} e^{jmkd\cos\theta}
$$
where:
$\theta$ is ...
- 113
3
votes
1
answer
519
views
Why does an ideal antenna not absorb all incident power?
http://farside.ph.utexas.edu/teaching/em/lectures/node94.html states:
So, in the optimum case half of the power absorbed by the antenna is immediately re-radiated. Clearly, an antenna which is ...
- 151
0
votes
1
answer
372
views
Characteristics of a traveling wave on a half wave dipole antenna
For a center fed dipole antenna when operated at resonance, the AC electric potential applied at the feed point results in traveling waves of AC current which emanate from the feed point out towards ...
- 145
2
votes
1
answer
875
views
Source of cylindrical electromagnetic waves
I have a question about waves with cylindrical wavefront. Precisely, I have read that they may be generated by a linear source, while for instance plane and spherical waves are respectively generated ...
- 1,319
0
votes
1
answer
220
views
Derivation of the total received field in ground reflection model
I am reading this book by J.D. Parsons.
The problem concerned, is how to find the propagation model for propagation over a curved reflecting surfac, i.e.:
I would like to know where is the ...
- 177
0
votes
1
answer
539
views
Poynting vector flux on a closed surface
What does the flux of the Poynting vector through a closed surface represent?
I know that the flux of the Poynting vector on a certain surface represents the power flowing through it. But if the ...
- 1,319
1
vote
1
answer
7k
views
A Formula for the Phase Difference Between the Electric and Magnetic Wave Oscillations?
A) Is there a formula for the phase difference between the electric and magnetic field oscillations, in vacuum, in an electromagnetic wave emitted from an antenna, as a function of the frequency the ...
- 3,369
1
vote
2
answers
2k
views
Will radio waves bend to reach receiver?
I was wondering if receivers just catch the radio waves that pass through, or if they actually attract the waves like a magnet. In other words, will a radio wave moving in a straight line bend in ...
- 19
4
votes
5
answers
3k
views
Radio antenna producing waves in the visible spectrum [closed]
If a radio could produce waves in the visible light spectrum, what would the result be?
This is a thought experiment that I've pondered for a few years now. I realize there are a few/many real-world ...
- 171
1
vote
2
answers
160
views
What is difference between the miltary radar in 1940's from commercial antenna that is for the use of TV
What is difference between the miltary radar in 1940's from commercial antenna that is for the use of TV?
I have read article from some of the WW2 history website that call the German radar the ...
- 780