All Questions
28
questions
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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
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0
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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
2
answers
166
views
Coaxial Confusion, what really are unbalanced transmission lines? [closed]
Thanks for clicking on my question.
I do not understand how an unbalanced transmission line works.
Take for instance coaxial cable which is the subject of my confusion.
This confusion arises from the ...
- 35
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
0
answers
54
views
Does antenna Q cause distortion?
Everyone knows that a 1/2 λ dipole has on the elements a standing wave the voltage and current of which are a bit less than 90° out of phase with each other, and the departure of this phase difference ...
- 145
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 ...
2
votes
3
answers
794
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Why is the half-wave dipole the most used antenna design?
When producing em waves using a dipole antenna (of length L), you could theoretically use any L and adjust the frequency of the oscillating voltage to get the desired wavelength. Then why are most ...
- 47
4
votes
5
answers
3k
views
Why are the electric and magnetic fields in phase in EM waves?
Consider a radio wave emanating from a dipole antenna. Close to the antenna, I would think the electric and magnetic fields would be 90 degrees out of phase (i.e. if the strength of the magnetic ...
- 123
0
votes
0
answers
56
views
What is the gain of an isotropic antenna?
My question is simple:
What is the gain of an isotropic antenna in dBi?
I cannot find a consistent answer on the internet. Some sources define it to be 0dBi and others define it to be 1dBi.
Thanks.
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
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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