ysenthilece said:I just want to know what is happening there physically in an antenna . How is it radiating ?? I tried all the basic books like Kraus, Balanis,etc .But no book even considers it .They just explain the properties , construction ,etc .But without even knowing how it works, what's the use ??
The explanation is simple. The power comes in on a cable. If little of the power is reflecting back on that cable, and if the antenna is not melting from the heat, then the power must be radiating into free space.
Hi!
I'm usually using the attached picture.
Imagine 2 E-field lines a-b, c-d (2 other arrows is the H field, but it's not important now).
lines are travelling within the waveguide (for example 2 wire line), with distance λ/2.
d) first line reaches the end of the transm.line and keeps boundary conditions there (E perpendicular to conductor). Next we have to accept that field line has momentum (inertia). Thus the "ends" of the first field line are "glued" to end of the guide and it's centre is travelling into free space e)
f) the second field line reached the "glued" first one and they get connected
g) the connected lines are forming a loop-spherical wave (thus rot E≠0 for HF problems!), separating from the guide and flying to the free space. Of course the separation process is some kind of "violence" to the guided wave and thus some part of energy is going back to the source (reflected wave represented by reactance X). Radiated energy is represented by R as resistor which charges the transmitter
The area where the process f) is realized, is said to be the "near field region", region where the waves are still connected to the antenna and where the field lines are going out and back, the "reactive region"
I'm sorry for antenna specialist and people who like theory, I know it was not very rigorous
Anyway, if one looks into FDTD simulation of say radiating waveguide, this simplified process could be seen there...
I just want to know what is happening there physically in an antenna . How is it radiating ?? I tried all the basic books like Kraus, Balanis,etc .But no book even considers it .They just explain the properties , construction ,etc .But without even knowing how it works, what's the use ??
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