Questions tagged [antennas]
The interfaces between radio waves propagating through space and electric currents moving in metal conductors, used with a transmitter or receiver. Antennas are essential components of all radio equipment.
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Why does the length of an antenna matter when electromagnetic waves propagate perpendicular to the antenna?
The optimum length for a dipole antenna is a multiple of half the wavelength that it is designed to receive or emit. Why is this? If an electromagnetic wave has E in the x-axis, B in the y-axis, and ...
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Polarization Derivation
Can how I can find the phi and theta unit vectors as described (Eq. 4a and 4b) in the following paper on antenna cross polarization? I thought the thetha and phi unit vectors were the same as those of ...
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How many photons are received per bit transmitted from Voyager 1?
As of 2024, according to https://voyager.jpl.nasa.gov/ , Voyager 1 is around one light·day away from Earth and still in radio contact. When Voyager 1 sends messages to Earth, roughly how many photons ...
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Magnetic object affected by electromagnetic wave
If a dipole antenna is strong enough, can it make a compass needle oscillate?
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Electromagnetic field of dipole antenna
Why do dipole antennas generate EM waves by alternating electric fields instead of alternating magnetic fields?
Why don't alternating magnetic poles detach the magnetic field like how it can do so ...
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Minimum frequency for a dipole antenna to work
Does a dipole antenna need a minimum frequency of AC to make the electric field detach and propagate?
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Measure electrical fields in space with oscilloscope and wire [closed]
I have an oscilloscope with its standard probe. Combined they have 1MOhm resistance and 71pF capacitance.
I attach a 50cm wire floating in space to the probe and connect the ground clip of the probe ...
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Do small electrical field generators generate "different" electrical fields than long antennas - how to measure?
Modern electronic devices often generate electrical fields in the frequency range of 10-50kHz.
I want to distingush 2 categories:
Loaded onto mains (e.g. solar inverters) and then mains wiring emits ...
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Is the current direction in transmitting and receiving dipole antenna opposite?
I googled for quite a while, but couldn't get a confirmation to this basic question. So I wonder if someone would help me out here.
Suppose we have 2 dipole antennas, each of length 1 meter. One ...
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Phasors and propagating modes in a waveguide
I'm currently studying antennas. The notes I'm following, while discussing the EM fields at the antenna feed port, make the following statement:
It can be shown that a propagating mode in a ...
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How does the presence of a static electric field affect the normal operation of an antenna (if at all)?
For arguments sake lets say I have a receiving antenna that has been positioned between two large conductive plates. Are there any differences in how that antenna operates (gain, efficiency etc.) when ...
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Can cell phones send message in the elevator?
From Gauss's theorem, a closed, hollow conductor shields its interior from fields due to charges outside, but does not shield its exterior from the fields due to charges placed inside it. So my ...
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Understanding radiation mechanism of inset fed microstrip antenna
I have designed a simple inset-fed microstrip antenna, resonating at 2.45 GHz.
The transmission line model of the antenna reduces it to two radiating slots separated by a microstrip line, and it's ...
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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 ...
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Prime operator for sinusoidal testing function in self-term approximation for Thin Wire using Method of Moments (MoM) $s_m^{'}(x_p)$?
I am implementing thin wire method of moments using W.Gibson's "Method of Moments in Electromagnetics". The approximation for self-term using piecewise sinusoidal basis function is given as
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