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Log-periodic antenna in HFSS. need help!

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yzriver

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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.
 

yzriver

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Log-periodic Antenna in HFSS file
 

abdoeng

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

yzriver

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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.
 

rfmw

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@yzriver

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

abdoeng

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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

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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

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i know ,what is silicin epsr=?
 

yzriver

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

jallem

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

yzriver

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Now the impedance is 50Ohm, PEC boundary condiction.
 

rfmw

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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
 

yzriver

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hi, rfmw:

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

rfmw

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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

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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

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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...
 

yzriver

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Can CST understand the Si lens? If you cover the antenna with Si lens, the CST will simulate the lens reshape the beam?
 

long88

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Hi all, i am design log periodic loop antenna by using CST. I already simulate the antenna and frabricate but the main problem is that the simulation result was totally different with my simulation result. Anyone can tell me whether my simulation result is correct or wrong?i attache the photo of how i design and measurement results!
Pls help me take a look!urgent!!


thank you
 

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