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.
Questions tagged [antennas]
375 questions
6
votes
1 answer
How is an inflatable parabolic antenna created?
I'm intrigued by this, and how it would work:- 3 sub-questions if I may:
Construction:
As I understand it's a flexible sphere constrained by a rigid edge.
a. Do we simply glue 2 flat circular pieces of flexible material together at the edges and…
velniukas
- 319
1
vote
1 answer
Why is the beamwidth of this antenna shown like this ?
I am not yet super familiar with the way beamwidth are calculated, but from what I've read, it's based on the point where the strength of the signal reaches -3dB.
Here is an excerpt from CCNA Wireless 200-355 Official Cert Guide.
I don't know if…
Arthur Attout
- 113
1
vote
2 answers
Directive gain and radiated power of an antenna
while attending a lecture on antennas, we were explained an example where it was stated that a lossless antenna with a directive gain of +6 db is going to radiate 4 mW of power if it is fed 1mW of power. However, working on this example myself, I am…
Amit Sonik
- 21
1
vote
0 answers
Impact of antenna spacing larger than a half of wavelngth
I am building a uniform linear antenna array (ULA) of Wi-Fi to extract channel state information, or channel matrix $H$.
With some literature search, as not familiar with antennas and electromagnetic wave, I found that antennas spacing $\Delta$…
Jeon
- 111
1
vote
2 answers
What happens when length of antenna >> lambda
Length of a dipole antenna according to antenna theory should be lambda/2 for best reception. I am just curious about the outcome when length of dipole antenna >> lambda. Impedance will be zero in such a case and there will be no signal received. Is…
user43794
- 570
0
votes
1 answer
Shortening a Dipole Antenna: What happens?
Say we have an AC voltage load that is connected to a transmitter dipole, radio antenna. The antenna has a length of $L =\frac{\lambda}{2}$ where $\lambda$ is the wavelength of the electromagnetic wave. Does this mean if we shorten the length of the…
0
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0 answers
Is the electric flux from the antenna able to exist without connecting electric charge?
https://en.wikipedia.org/wiki/Radio_wave#/media/File:Dipole_xmting_antenna_animation_4_408x318x150ms.gif
According to above figure, the electric flux is in the close loop state like a balloon and is pushed out by the other electric flux. So it looks…
superkappy
- 21
0
votes
1 answer
QFH antennas and their construction
I just wanted to ask the reason for having two loops in a QFH antenna. and what is the advantage of having them oriented the way they are?
0
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1 answer
Beamwidth of reflector antenna problem
The beamwidth of a reflector antenna of diameter $=70 $ cm at $30$ GHz is:
a) $3.7$ degree
b) $0.5$ degree
c) $1.1$ degree
d) $1$ degree
My Approach:
We Know Directivity : $D= \frac{4 \pi}{\lambda^2}A_e$
Here, $A_e \approx \pi…
Suresh
- 123
- 7
0
votes
1 answer
How does one adapt an antennae to an electrically conductive medium?
Most antennae are deployed in earth's atmosphere which can be approximated as a vacuum. But what about an antennae for a submarine underneath the ocean? Or how about an antennae deployed in a copper mine? What about the most extreme case where one…
0
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2 answers
Difference between directional and omnidirectional transmission or reception?
It is suggested that the next generation wireless technology will be highly directional since this increases the signal gain (MIMO) and decreases interference.
How will the receiver still be able to decode or observe many signals from many…
George Smith
- 11