900MHz Yagi simulation

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mzk
Posts: 4
Joined: Fri 26 Apr 2019, 15:20

900MHz Yagi simulation

Post by mzk » Sun 05 Jul 2020, 15:16

Hello,

I would like to re-simulate antenna that I've simulated in 4nec2. There I have good SWR.
However in openEMS I do get different impedance.

I changed the mesh several times, played with the boundary conditions (MUR, PML) and also with the elements shape (cylinder vs square). I did notice that the cylinder (wire primitive) didn't work or is much different despite it should be almost the same. Do I have to use cylindrical mesh instead of rectangular?

Attached are the nec file and the octave script.

Any ideas would be helpful.
Thanks!

PS: the zip file contains both the nec and the openems' .m files.
Attachments
yagi900-nec+openems.zip
(2.67 KiB) Downloaded 38 times
openems-impedance.png
openems-impedance.png (20.97 KiB) Viewed 825 times
4nec-impedance.png
4nec-impedance.png (28.3 KiB) Viewed 827 times

mzk
Posts: 4
Joined: Fri 26 Apr 2019, 15:20

Re: 900MHz Yagi simulation

Post by mzk » Thu 09 Jul 2020, 12:56

I have some progress! I used cylinder primitive instead of wire and square. Probably the square (not hollow) element is very different.

The simulation with the cylinder achieves almost the same result as the real measurement.

Hale_812
Posts: 171
Joined: Fri 13 May 2016, 02:54

Re: 900MHz Yagi simulation

Post by Hale_812 » Mon 13 Jul 2020, 05:41

there is no difference between primitives. Every object is converted into a set of rectangular boxes. so define the mesh carefully.

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