[SI-LIST] Re: HFSS solution issue
- From: "Xin Wu" <lifehappiest@xxxxxxxxxxx>
- To: si-list@xxxxxxxxxxxxx
- Date: Fri, 24 Jan 2003 09:36:10 -0500
Hi, Chandra
One thing you need to pay a little bit attention is the convergence.
Sometimes the Delta-S curve might not be converged even the accuracy
satisfies the condition you name. So the HFSS soling process is like
searching an optimum of accuracy, convergence and time consumption.
Cheers,
Xin Wu
Ph.D student,
University of Maryland, College Park
Http://www.wam.umd.edu/~xwu
>From: "Chandrasekhar Arun" <achandra@xxxxxxx>
>Reply-To: achandra@xxxxxxx
>To: <Dan_Swanson@xxxxxxxxxxxx>,
><mike_bihan@xxxxxxxxxxxx>,<si-list@xxxxxxxxxxxxx>
>Subject: [SI-LIST] Re: HFSS solution issue
>Date: Fri, 24 Jan 2003 11:45:57 +0100
>
>
>Hello Dan and all HFSS users,
> Excellent comments from Dan and it really summarises what every HFSS =
>new user needs to know reg. solving his/her model. A few points from my =
>experience
>1. My primary application with HFSS is solving chip-package =
>interconnects and I use a delta-S of 0.005. This number is not =
>sacrosanct, but when coverted to dB is -0.043 dB for insertion loss and =
>-46 dB for return loss
>IL=3D20log10(1-0.005) and RL=3D20log10(0.005)
>The key is finding an optimum between solution accuracy and time. I =
>expect my structures to have an insertion loss of about 1 dB at 5 GHz =
>and it is Ok for me if my HFSS results are 1.043 or 0.957 dB. However if =
>you are trying to extract the S-parameters of a low-loss short line, =
>maybe this error is too high. However, already to achieve 0.005 eroor I =
>have to live with about 25000 tetrahedra and this takes a few hours to =
>simulate for 20 points and there is no way I can think of delta-S lower =
>than 0.005!
>2. If you are usinh HFSS at low frequencies, remembet to Solve Inside =
>Metals !
>3. To compare your results with VNA measurements always de-embed and =
>re-normalise with 50 ohms
>
>one question
>does anyone know how you can manipulate the amount of memory used by =
>HFSS while solving in the RAM and the disk? I have 1GB of RAM, still =
>HFSS always swaps some data with the disk. I remember that the deafult =
>is 70% RAm and 30% dis, but I do not see this always!
>Regards
> =20
>Arun Chandrasekhar
>PhD Student: RF Packaging =09
>IMEC | MCP/MaRS Group =09
>Phone: +32 16 28 82 28 =09
>Fax: +32 16 28 10 97 =09
>Email: achandra@xxxxxxx <mailto:achandra@xxxxxxx> =09
>Seeds for Tomorrow's World <http://www.imec.be/> =09
> =20
>IMEC, Kapeldreef 75, 3001 Leuven, Belgium | Phone:+32 16 28 12 11 =
>Fax:+32 16 22 94 00 | Website: www.imec.be <http://www.imec.be/>=20
>
>
>
>This e-mail and/or its attachments may contain confidential information. =
> It is intended solely for the intended addressee(s).
>Any use of the information contained herein by other persons is =
>prohibited. IMEC vzw does not accept any liability for the contents of =
>this e-mail and/or its attachments.=20
>
>
>-----Original Message-----
>From: Swanson, Dan [mailto:Dan_Swanson@xxxxxxxxxxxx]
>Sent: Thursday, January 23, 2003 17:23
>To: 'mike_bihan@xxxxxxxxxxxx'; si-list@xxxxxxxxxxxxx
>Subject: [SI-LIST] Re: HFSS solution issue
>
>
>
>
>Bi, Han
>
>I think you are a little confused on how the solution setup goes.
>
>Adaptive Single Frequency can be run by itself or it
>is the starting point for a Frequency Sweep.
>
>So you adapt the mesh at some frequency, typically the highest
>freq you are interested in. Then you start the frequency sweep
>using that adapted mesh. So the mesh is "overkill" for the low
>freqs and just right for the high freqs. Knowing this, if you
>are trying to cover many octaves in frequency, then maybe
>several runs using different adapt freqs is more efficient.
>
>So in the setup menu you select both the Single Freq Adapt
>and the Freq Sweep you want at the same time. The software then
>does both.
>
>If you run a Discreet Sweep, results should be fine. A Fast Sweep
>tries to derive the result from the minimum number of discreet=3D20
>freq solutions. Watch out for the both ends of the sweep range
>and always check the results at least once with a discreet sweep.
>If you ask for a very wide Fast Sweep range, the software often
>suggests that you break it up into smaller segments.
>
>As to number of adapts, that is very tricky. Basically you need
>to identify the key parameter in your analysis and figure out
>what it takes to get there. For example, I do a lot of resonators.
>So I look at convergence of resonant frequency as function of meshing
>parameters. Remember this is very general purpose software, you always
>know more about you particular problem than the developer or the =3D
>software.
>You have to use that knowledge to guide the software to the right
>solution.
>
>Using the default settings, the starting mesh in HFSS is very coarse.
>I typically set LAMBDA_REFINE_TARGET (system variable) to .02 or .033
>Refinement percentage to 40% (default is 20%). And maybe run 5 to 10
>adapts. I set Delta-S limit to 1e-6, Delta-S achieved is very problem
>dependent and does not always imply absolute convergence. Of course
>you are looking for a convergence curve that is a nice smooth =3D
>parabolla.
>
>The geometrical resolution in your model will also affect convergence.
>I tend to draw cylinders, etc kind of coarse, 8 or 12 sides to a =3D
>cylinder.
>I do this to speed things up. But sometimes if you make things too =3D
>coarse
>the convergence curve will oscillate, or you may converge to the wrong
>final value. For example, look at impedance of a coax line as a =3D
>function
>of how many segments you use to define the cylinders.
>
>All this is in my new book, coming out in May 2003:
>
>http://www.artechhouse.com/default.asp?Frame=3D3DBook.asp&Book=3D3D1-5805=
>3-3=3D
>08-6&Cou
>ntry=3D3DUS&Continent=3D3DNO&State=3D3DMA
>
>
>Best regards,
>
>
>Dan
>
>Dan Swanson EMAIL: d.swanson@xxxxxxxx
>Forem USA PHONE: 978-834-4085
>37 South Hunt Road FAX: 978-388-7077
>Amesbury, MA 01913
>
>
> > -----Original Message-----
> > From: Bi Han [mailto:mike_bihan@xxxxxxxxxxxx]
> > Sent: Thursday, January 23, 2003 10:52 AM
> > To: List` Si
> > Subject: [SI-LIST] HFSS solution issue
> >=3D20
> >=3D20
> >=3D20
> > hi, ansoft guies:
> >=3D20
> > There is one simple question about HFSS.
> >=3D20
> > Since Adaptive 'Single frequency' analysis will allow users=3D20
> > to setup 'Requested Passes', what number will be suitable? I used 7.
> >=3D20
> > However, issues come up!
> > The results,obtained by 'Single Frequency', differs greatly=3D20
> > from 'Sweep' analysis=3D20
> >=3D20
> > results? Because of the higher accuracy of 'Single frequency'=3D20
> > analysis, I prefer it than sweep one. (Actually,sweep results=3D20
> > is the Pass 1 results on Single Frequency analysis.)
> >=3D20
> > Then, what value does 'sweep' analysis have, with so poor=3D20
> > accuracy, whose mesh will not be refined. In another way, in=3D20
> > which way should we treat the data from 'sweep analysis'?
> >=3D20
> > Sincerely,
> > Bi, Han
> > Sjtu, EMLAB
> >=3D20
> >=3D20
> >=3D20
> > ---------------------------------
> > Do You Yahoo!?
> > =3D
>"=3DBF=3DEE=3DBF=3DEE=3DB8=3DDF=3DB9=3DF3=3DB5=3DE4=3DD1=3DC5=3DA3=3DAC=3D=
>B5=3DE3=3DBB=3DF7=3DB2=3DCE=3DBC=3DD3=3DC6=3DFB=3D
>=3DB3=3DB5=3DB5=3DF7=3DB2=3DE9!"
> >=3D20
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