HFSS radiation boundary radius (50 points for best answer)

hfss directivity

Hello all,

I am learning how to use HFSS to simulate the radiation pattern of antennas. As a first step, I created a model of a half-wavelength dipole. I tried to verify the simulation agrees with the theoretical value to check if the simulation is correct or not. I plotted the radiation pattern and it has a donut-like 3-d pattern as expected. However, the peak gain does not agree with the expected value (2.15dB)

I thought that the problem is due to incorrect setting on the radius of the radiaton boundary sphere. So, I did a parametric sweep with the radius of the radiation boundary as a sweeping variable. I expected the result converges to the theoretical one as the radius increases. But the simulated gain flucuates with the radius of the sphere between 1.7 and 2.2dB and it did not converge as opposed to what I expected. I am wondering why the result changes so much with the radius. I know that the recommended setting is lambda/4 away from the object. But I think the result should not change with the radius if it is larger than lambda/4.

Does anyone have any idea on what's wrong with my model?

Thanks in advance.

-Hiro

richtigkeit hfss

Hello all,

I am still looking for someone's help on this issue. I'll give 50 points for the best answer.

Thanks.

-Hiro

radiation boundary hfss

Hi, try seeding the radaition boundary to at least lambda/10. That should fix the problem.

radiation boundary in hfss

kawakubo shalom,

It could be one of the following:

1) Use HFSS v10.1 (which has improved)
2) Try using better convergence criteria in the solution setup (such as 0.01)
3) Try doing manual mesh seeding on the FACE of the radiation boundary
4) Choose the face of the sphere and create a new facelist from it. In the farfield radiation sphere setup select that facelist (click the radiation surface tab). I do not know what is your model, but by default HFSS integrates on all of the Radiation boundary in the model and not just the sphere.
5) If you like my answer, instead of giving me 50 points, just tell 50 of your friends, how much you like HFSS
6) You may drop me an email (itai@anafa-em.com) and I'll make sure that an Ansoft AE in your region will contact you promptly.

Regards,
Itai Frenkel
Anafa - EM solutions Ltd.
(Anafa-EM is Ansoft's rep in Israel)

hfss radiation boundaries

Hi itai and savedadog,

Thanks for your suggestions.

I had tried to fix the problem using the hints you gave to me. But none of them fixed the problem of the directivity different from the theoretical one (2.2dB). I spent hours to figure out the problem and finally I found out that this is due to a bug in calculating directivity by HFSS. I doubted the accuracy in HFSS directivity calculation, so I calculated directivity by myself using a beam pattern exported from HFSS. When I calculated by myself, the directivity was very close to the theoretical value and was stable to changes in the radiation boundary shape and mesh operation.

Even though his suggestion didn't solve the issue, I'll give savedadog 50pts for his suggestion.

Thanks for your help.

-Hiro

radiation patterns using hfss version 10

kawakubo,

I am sorry that you decided to leave it like that.

Please specify which version of HFSS you are using.
Have you contacted official Ansoft support?

Regards,
Itai

hfss directivity

Hi Ita,

Thanks for your post.
I first tried to get help from their technical support web site, but I could not get my account because I am just one of the students using the HFSS installed on a PC in a computer lab at my university. Only one person (software administrator) has the account for Ansoft tech support, but he did not let me use his account to login.

Please let me know if you know other ways to get technical support from Ansoft.

I'm using HFSS v9.2.
Version 10 will be available at my university by this fall. FYI, I attend a school in Michigan, USA.

Thank you.

-Hiro

hfss radiation

Hi all,

What is exatly "seeding the radaition boundary to at least lambda/10" ?

If I lick on the rad-boundary / right click/ Assign Mesh Operation / On Selection.
Then:
Length Based or Skin-Depth Based ?

If Length Based, then:
Maximum Length of Element:
600 mm ? (or something = lambda/10) ?

Thank you for your help?

hfss radiation pattern backpropagation direction

If you post your project I can simulate it in HFSSv10 to see if the directivity problem is fixed in the new version.

radiation boundary of hfss

Hi, Kawakubo,
How can you calculate the directivity of a half dipole by yourself. Please describe you simulation. Thank you!

kawakubo said:

Hi itai and savedadog,

Thanks for your suggestions.

I had tried to fix the problem using the hints you gave to me. But none of them fixed the problem of the directivity different from the theoretical one (2.2dB). I spent hours to figure out the problem and finally I found out that this is due to a bug in calculating directivity by HFSS. I doubted the accuracy in HFSS directivity calculation, so I calculated directivity by myself using a beam pattern exported from HFSS. When I calculated by myself, the directivity was very close to the theoretical value and was stable to changes in the radiation boundary shape and mesh operation.

Even though his suggestion didn't solve the issue, I'll give savedadog 50pts for his suggestion.

Thanks for your help.

-Hiro

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