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Which one is better, HFSS or CST ?

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Re: comparison between simulators

For simulation (since we already have results), I suggest the structures described in
**broken link removed**
Click to expand...

But there aren't measured results...

kato01: Yes, I know about low reliableness of such papers as in MWEE. I hope we will find some good structures with measured results.
Maybe I can give up measured data of some patch antennas we've built.
 

HFSS vs. CST

Guys,

I find that topic about comparing the 2 tools a bit obsolete. Reasoning being that much of the quality of any simulation goes to the setup, size of the structure (in terms of wavelengths), solver used and many other factors (PC, cache, CPU, Memory etc) and to me it seems nearly wasted efforts to do in a concerted manner. I'd rather suggest discussing what the 2 tools must improve, share some knowledge and generate good suggestions. In return we may hope that some CST or HFSS folks read that:) (joking over here) and they get serious about making it better. To me the bottom line of our very good discussion was that the 2 tools were good and efficient. It should be a matter of personal preference which one individual may choose - last but not least is the price and support - we haven't touched that sensitive issue and I don't think we can do it inhere. Besides, I've seen some suggestions concerning stripline, or rather - Stratified media simulations being done with HFSS - it is ultimately irrational approach for such kind of structures and no one can beat the 2.5D tools (or planar 3D if you will) for many reasons not subject of thaty post. Last but not least comes the personal skills and knowledge of the particular designer to utilize such tools to accomplish maximum. After all, we are not working for those companies and have no direct interest.
I am sorry to say but the MWEE test (Vivaldi one) and the respective results is very much prejudiced (did anyone witnessed the results or took the effort to chek'em - i doubt it) - if one looks the data, one must choose EMPIRE and not CST - right? But like I said, to me it is just scratching the issue and is emotions laden discussion.

truly,
 

HxJi : very fast comment, can you explain it more?

BTW I have very good experience with MWS.

We've simulated an 50Ohm load for SMA connector - coaxial ended with 50Ohm resistor. Resistor was modeled as ceramic cylinder with resistive layer thin only 7 microns!! I've computed required conductivity to reach 50Ohms (considering the resistor's dimensions) and simulated.
With about <2 mins of running I've get results (0-5GHz) which excellently agree with vector measurement (error is smaller than error of measurement!). Note that mesh has about 80k of nodes which (considering max and min dimensions) isn't reachable without PBA!! Results from another FDTD routines were (after some hours of running) totally wrong.
 

for further discussion i invite you to EM simulators forum

With Regards,
 

Cheng,

I agree with most of your comments. Its nice to see this subject being debated in such a polite and thoughtfull manner.

However, I do think it would be usefull to compare results between the two packages, if only for peace of mind.

eirp,

Please be patient, I'm a busy man. Your post made me realise that the the structures I was going to model all related to the type of work which I do and may not give usefull information to people working in other fields. If any of you have drawings of structures with measured results you could let me have, I would be greatfull.

sviodo,

Thank you for creating the new forum for us. Following posts will go there.
 

Dear all,

I feel very impressed by all the discussions. I agree that the best is to try out some benchmark samples to see which one runs better. Would like to thank all members involving in this discussion.

mwpro
 

In my opinion CST is the best choise especially if you have to solve radiation problems. In fact HFSS is very memory consuming and without good accuracy. Further, since is a FEM based, sometime is possible to have spurios frequencies from the method itself and other spurios frequencies using the fast frequency solver.
 

I've moved this discussion to EM simulators.
Eirp
 

I'm use both programs and I can note the following:

1. HFSS (@gilent) allocates a huge memory, but the calculation accuracy not fine (for example: calculated VSWR=1.05, measured VSWR=1.4). Device (coaxial connector) geometry was not very complex !
2. HFSS (@nsoft) works more accurate, but very slow. We used this program for dielectric resonator calculation and obtain satisfactory results, but this results only satisfactory (not good).
3. CST-MWS (on my opinion) now the best choise. I'm test this program on some structures, which have an accurate (analytical) solution (such as magic-tee etc.) and obtain very good comparision between numerical and analytical solutions without incredible memory and calculation time cost. In general, CST-MWS is a best choise.

With responce,
Kit-the-great
 

I agree with Kit-the Great.
 

Did anyone use MWStudio to model many curved geometry? I am wondering how good the PBA is.

Now if you look at the literature, Finite Integration Time Domain (on which MWStudio is based, so I heard) is somewhat different from the FDTD. In general, if a method is good, then many people would study it. It seems to me, there has not been a lot of interest in the finite integration method.

According to textbook, another thing one needs to look at is the numerical dispersion of the time domain method. Can somebody suggest a good problem for testing this?
 

CST Microwave Studio is based on Finite Integration Technique (FIT). This method is similar to FDTD; the only difference is related to the fact that the Maxwell equations are solved in integral form instead of differential form. This feature allows to have a local conformal model of curved surfaces like PBA technique. If you are interested is possible to see several papers from Mittra on IEEE MTT or the book "Computational Electrodynamics - The FDTD method" Taflove-Hagness, Artech House, 2000, second edition, chapter 10.
 

Well, there are also locally conformal schemes using the FD(TD) technique. The performance, as far as I know, is mixed. My guess is that PBA also has its limits.

If it is so good, there should be a lot people applying it, and hence a lot of papers. Otherwise the name would appear as a commercial tool. I searched the word "perfect boundary approximation" in IEEE, and I was surprised to see no match! Is there any other name for it?
 

Hi Loucy,

When I refer to IEEE papers or Artech House book about locally confarmal schemes, FDTD locally conformal schemes are understood. In this case, in practice, an integral formulation of the classical FDTD method is applied and then we have an FIT method (locally).
PBA is a proprietary algoritm of CST (now with release 4 with TST) and there is a paper (if you want I send to you) without any detail for obvious reasons. Anyway, this is the most important thing, PBA works very well. Probably is similar to Day-Mittra methods.
 

Do you need antenna semulator?

you can test your antenna by using NEC software.. have a 3d pattern semulation and all over what you need of calculations (impedance, losses, power, current dist., etc)... I post this software in this form:

Antenna Test Measurement + Cross polarisation

this is the directory where you can find it in:

elektroda.pl Forum Index -> RF & Microwave

or if the link is warkable:

**broken link removed**

:idea: if you want me to design your antenna on NEC send me it's discreptions: length, diameter, freq. and direction
 

I happen to have read the Day-Mittra papers, something bothering me is that in their guideline for conformal mesh, a rule refers to the ratio of length to area. If PBA is something similar, I can certainly understand why they want to keep it secret.

Can you post the paper here, we all want to read it.
 

Can anyone post the link to the paper for PBA used in MWStudio?
 

The link of boundary element method:
**broken link removed**

With responce,
Kit-the-great
 

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