Ray, 1x1, 2x2, 4x4, 8x8 and 16x16 are only suggestions ... you can enter anything you want (just type it in, don't pick a selection from the pull-down menu). - Heiko -----Original Message----- From: Ray Anderson [mailto:Raymond.Anderson@xxxxxxx] Sent: Dienstag, 28. Mai 2002 18:55 To: si-list@xxxxxxxxxxxxx Cc: arpad.muranyi@xxxxxxxxx Subject: [SI-LIST] Re: Decoupling capacitors Arpad- I think you are probably correct. I really hadn't looked at the meshing selections in the sqpi preferences menu for quite a while. I believe in a very early pre-release version sqpi had the ability=20 to select meshing up to 32x32 (or something like that), but the execution time was so long that apparently they opted to limit the available size to 16x16 in the released version. Currently the selections are 1x1, 2x2, 4x4, 8x8, and 16x16. I kind of wonder what practical use the 1x1 and 2x2 (and even 4x4) meshing serves. Meshing that coarse will limit the accuracy of the simulation to very low frequencies (but it sure will simulate fast...). I have written some simple C code that can generate plane models equivalent to the ones in sqpi for use with hspice with any arbritrary meshing. Models with very dense meshing can be very expensive in terms of compute time. So to re-answer the the original question, 16x16 meshing is more than adequate for most real world problems if one realizes that the selection = of a mesh size is a tradeoff of accuracy vs time. Most of our simulations = are done with 8x8 meshing which provides good accuracy at "SI" frequencies (i.e. < say ~600 MHz or so depending on the board size), but introduces=20 some error at higher frequencies. At one point in time I built a simple=20 test board consisting of just a couple planes and measured the impedance = profile in the lab with a VNA. Then I simulated the same board (about 4" = x 6")=20 using the plane model with 8x8 meshing. I found real good measurement to = simulation correlation up to about 1.3 GHz from which point on there was increasing divergence between the measured and simulated data. Referencing back to my fouled-up numerical example of yesterday, with 16x16 meshing, accuracy should be fine up to 1 GHz on a board of about 240mm x 240 mm size. (1/10 lambda @ 1GHz ~ 15mm on FR-4, so 16 x 15 mm =3D 240 mm). (thanks to Scott for pointing out=20 my metric unit errors yesterday:) -Ray > >Ray, > >I think he was asking you whether SQPI's maximum mesh >density (16x16) is good enough... > >Arpad >=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D > > > > >>sogo_hsu wrote: >>. >> ..... text deleted.... >> >> Besides, don't you think the mesh density in 16 by 16 is too rough to >> analyze a real PDS plane in SQPI? >>=20 >> Sogo ------------------------------------------------------------------ To unsubscribe from si-list: si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field or to administer your membership from a web page, go to: //www.freelists.org/webpage/si-list For help: si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field List archives are viewable at: =20 //www.freelists.org/archives/si-list or at our remote archives: http://groups.yahoo.com/group/si-list/messages=20 Old (prior to June 6, 2001) list archives are viewable at: http://www.qsl.net/wb6tpu =20 ------------------------------------------------------------------ To unsubscribe from si-list: si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field or to administer your membership from a web page, go to: //www.freelists.org/webpage/si-list For help: si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field List archives are viewable at: //www.freelists.org/archives/si-list or at our remote archives: http://groups.yahoo.com/group/si-list/messages Old (prior to June 6, 2001) list archives are viewable at: http://www.qsl.net/wb6tpu