Log-periodic antenna in HFSS. need help!

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yzriver

Joined: 15 Sep 2002
Posts: 47
Helped: 1

12 Mar 2007 17:15 log-periodic antenna hfss

Hello all:

Could any one take a look at the HFSS file in attachment. It is a log-periodic antenna for THz application. I can't have the similiar S11 as the papar presents.
Do you see any problem is excitation? The frequency ranges from 100GHz-1.5THz. The mesh number may be huge if you try to run this model.

Thanks a lot.

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yzriver

Joined: 15 Sep 2002
Posts: 47
Helped: 1

12 Mar 2007 17:18 Re: Log-periodic antenna in HFSS. need help!

Log-periodic Antenna in HFSS file

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abdoeng

Joined: 22 Feb 2004
Posts: 685
Helped: 14
Location: EGYPT

16 Mar 2007 16:45 Log-periodic antenna in HFSS. need help!

yzriver,i will try to simulate it in cst,give some time
regards

yzriver

Joined: 15 Sep 2002
Posts: 47
Helped: 1

16 Mar 2007 16:56 Re: Log-periodic antenna in HFSS. need help!

Thank you.
I have done it on CST. The result matches that from ADS momentum at (100GHz~200GHz). However at high frequency, for example, 300GHz, because the large number of mesh, the momentum cannot run. Could you please check my HFSS file?

I would like to compare the result from CST and HFSS, time, accuracy. If you have interest, I can upload the CST file tomorrow.

I alos upload the antenna dxf file for any of you has interest to run this simulation.

Thank you.

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rfmw

Joined: 10 May 2001
Posts: 520
Helped: 38

16 Mar 2007 19:08 Re: Log-periodic antenna in HFSS. need help!

@yzriver

i'll give it a shot in hfss during the weekend...

abdoeng

Joined: 22 Feb 2004
Posts: 685
Helped: 14
Location: EGYPT

16 Mar 2007 21:31 Log-periodic antenna in HFSS. need help!

hi yzriver pls tell me ur substrate u used and its thickness,ur band,what ur request,s par. or radiation pattern?,for what frequency?

yzriver

Joined: 15 Sep 2002
Posts: 47
Helped: 1

16 Mar 2007 21:45 Log-periodic antenna in HFSS. need help!

substrate: Si, thickness:1mm. Could you give S paramenter from 100GHz~200GHz?

If your computer is powerful, could you try higher band to 500GHz? HFSS will generate a huge amount of mesh at higher band. So be careful. Thank you very much.

abdoeng

Joined: 22 Feb 2004
Posts: 685
Helped: 14
Location: EGYPT

16 Mar 2007 21:53 Log-periodic antenna in HFSS. need help!

i know ,what is silicin epsr=?

yzriver

Joined: 15 Sep 2002
Posts: 47
Helped: 1

16 Mar 2007 21:55 Re: Log-periodic antenna in HFSS. need help!

I post the result from ADS and CST here. It is interesting to compare them with HFSS.

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yzriver

Joined: 15 Sep 2002
Posts: 47
Helped: 1

16 Mar 2007 21:56 Log-periodic antenna in HFSS. need help!

eps=11.3

jallem

Joined: 23 Jul 2005
Posts: 477
Helped: 67

16 Mar 2007 22:01 Log-periodic antenna in HFSS. need help!

It appears that the impedance is close to 200 ohms.
If you normalize to 200 the S11 will improve.

yzriver

Joined: 15 Sep 2002
Posts: 47
Helped: 1

16 Mar 2007 22:17 Log-periodic antenna in HFSS. need help!

Now the impedance is 50Ohm, PEC boundary condiction.

rfmw

Joined: 10 May 2001
Posts: 520
Helped: 38

16 Mar 2007 23:15 Re: Log-periodic antenna in HFSS. need help!

I had a look at your hfss file.

First of all, a request. Do you have any other paper/article like the one you posted here. It is very interesting to me due to the fact that i'm designing the same thing!!!

1. Your lumped port is not well defined or should i say its very wrong. Look at my port for the log-periodic.

2. Why is your radiation boundary unequally distanced from the antenna (in the z-axis it is +-50um, but in the xy-axis it's more). I assume 50um is lambda/4 for your lowest frequency (i haven't checked this).

In the following pictures i post my hfss results of the planar log-periodic antenna without substrate or anything additional beside the antenna.

Hope this helps,
rfmw

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yzriver

Joined: 15 Sep 2002
Posts: 47
Helped: 1

17 Mar 2007 23:16 Re: Log-periodic antenna in HFSS. need help!

Thank you rfmw.
I have solve my problem. The result from HFSS has the similiar result with CST, but HFSS run faster than CST at 100GHz~200GHz.

I have another paper for this log-periodic antenna. Good luck.

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yzriver

Joined: 15 Sep 2002
Posts: 47
Helped: 1

19 Mar 2007 16:15 Log-periodic antenna in HFSS. need help!

hi, rfmw:

why you chose CST? It looks the HFSS can work well.

rfmw

Joined: 10 May 2001
Posts: 520
Helped: 38

19 Mar 2007 21:51 Re: Log-periodic antenna in HFSS. need help!

I think HFSS is a really superb simulation software. But unfortunatelly its magnificent properties have its price - memory requirements.

Currently, I'm simulating my 3D structure in CST at two to three-times the frequency, which I had barely achieve in HFSS on my Win32 PC. If only one can run HFSS on a cluster computer with let say 8GB or more ram, that would be awesome...

Although, comparing CST to HFSS, CST has worse user interface and also some features i don't like...

What computer are you running cst and HFSS on?

yzriver

Joined: 15 Sep 2002
Posts: 47
Helped: 1

19 Mar 2007 22:48 Log-periodic antenna in HFSS. need help!

I am using the the regular PC. 1G memeory, 2.4GHz CPU. I can request a powerful PC or use cluster. Before that, I need to find out which one is the better.

I read the paper i attached. It talks about the Si lens. Will you make it? how do you simulate it?

rfmw

Joined: 10 May 2001
Posts: 520
Helped: 38

20 Mar 2007 13:50 Re: Log-periodic antenna in HFSS. need help!

I'm already in the log-periodic+Si Lens. Problem is my PC doesn't have enough memory for high frequencies in both, HFSS and CST. However I could manage to get higher in the CST, since its a little less memory hungry.

The problem with log-periodic is that it is non-symetrical, so none symmetry planes can be used...