Uncovering the Mystery of the Electric Field of a Dipole Antenna

[Maike]

Hello,

Is it possible to derive the electric field of a dipole antenna mathematically?
Does it look like a pure dipole far away?
I am experimenting with these things and they are a bit mysterious to me.

Thanks for your answers!

 

[Paul Colby]

By "drive mathematically" do you mean a computer simulation or are you referring to some arbitrary function voltage function generator?

 

[marcusl]

I assume you mean electromagnetic field, since "far away" means you are looking at radiation? The answer is yes, more or less. Antennas can be surprisingly complex to compute due to interactions between the drive, the currents/voltages induced in the conductors, and the reaction that the resulting fields produce back onto those currents/voltages. As a result, both analytic and numerical calculations are often iterative. The method of moments is one that is very widely used. You can also a perform multipole expansion. A half-wave dipole turns out to be mostly dipolar, with a small quadrupolar component (I forget how big--just a few percent, I think), and fairly negligible higher-order contributions.