Electric dipole antenna voltage

1 reply · 3K views · last reply
loki4000
Messages
15
Reaction score
0

Homework Statement


Greetings.
Can someone give me hint how to solve following problem:
Hand-drawn sketch of a half-wave dipole antenna of length λ/2 with a sinusoidal current distribution I(x) drawn along one arm, a gap labelled V at the feed point, and an arrow marking the current I at the centre.

Homework Equations


From my understanding, you need following formula to solve problem:
Diagram of a half-wave dipole antenna fed by a sinusoidal source, with a spacing marked lambda/2, a red half-sine current distribution I0(z) = Im cos(2 pi z / lambda), and the vector potential integral A written below.

and then potential can be obtained by integrating over the current distribution.
But right now these foormuas really confuse me (have probem understanding what is going on in picture). So I don't understand how to find current distribution.

The Attempt at a Solution


My guess is:
potential = (int) current distribution
V = I0(z)e^iwt
 
I don't think your suggested method is of any avail. That's for determining the strength of an e-m signal at a distance r away from the antenna.

Also: antennas have radiation resistance R. You need to come up with that resistance. You can look that up most anywhere for your half-wave dipole. You need to assume that your receiving antenna is also terminated in this resistance.

Then: you're given the B field so you can determine the E field and hence the Poynting vector which is power per unit area. So you also need to look up the effective area for your antenna.

Once you have the power input to your antenna you just go P = V^2/R to get your V.
 
Last edited: