Normalized gain patterns, HPBW

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teepegg
Posts: 5
Joined: Tue 11 Dec 2012, 06:27

Normalized gain patterns, HPBW

Post by teepegg » Sat 15 Dec 2012, 22:50

I think I found two mistakes in the calculation of gain patterns and HPBW in
http://www.openems.de/gitweb/?p=openEMS ... ads/master

The first is:
theta_HPBW = thetaRange(find(nf2ff.E_norm{1}(:,1)<max(nf2ff.E_norm{1}(:,1))/2,1))*2;

Should be:
theta_HPBW = thetaRange(find(nf2ff.P_rad{1}(:,1)<max(nf2ff.P_rad{1}(:,1))/2,1))*2;

The second is:
E_far_normalized = nf2ff.E_norm{1} / max(nf2ff.E_norm{1}(:)) * nf2ff.Dmax;

Doesn't give correct patterns. If the output should be power gain then it should read something like:
P_far_normalized = (nf2ff.E_norm{1} / max(nf2ff.E_norm{1}(:))) .** 2 * nf2ff.Dmax;

If the output should be voltage gain then it should read something like:
E_far_normalized = nf2ff.E_norm{1} / max(nf2ff.E_norm{1}(:)) * sqrt(nf2ff.Dmax);

thorsten
Posts: 1393
Joined: Mon 27 Jun 2011, 12:26

Re: Normalized gain patterns, HPBW

Post by thorsten » Sat 15 Dec 2012, 23:04

Hi,

thanks for looking into this and I think you are right.
Sebastian what do you think?

Maybe we also need to create an example with a known result to test these figures. Maybe an inf. dipole? Or what kind of antennas would have an analytic result to validate against?

regards
Thorsten

thorsten
Posts: 1393
Joined: Mon 27 Jun 2011, 12:26

Re: Normalized gain patterns, HPBW

Post by thorsten » Mon 17 Dec 2012, 23:03

Hi,

I had a look at the Hertzian dipole example (found in examples/antennas/infDipole.m).
I modified it but it is obvious, that you only get the correct 90° HPBW if you use 1/sqrt(2).
See attachment.

Regarding the normalized E-field or "power" pattern you are right as well: http://en.wikipedia.org/wiki/Directivity

I will fix both in the Helix example.

regards
Attachments
infDipol.m
(4.4 KiB) Downloaded 599 times

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