[SI-LIST] Re: time domain simulation w/ PDN planes

  • From: Cristian Gozzi <cristian.gozzi@xxxxxxxxx>
  • To: shlepnev@xxxxxxxxxxxxx
  • Date: Wed, 22 Oct 2014 19:19:41 -0700

Hi Yuri
Both Ansys SIwave and Cadence PowerSI have great modeling of interaction
between PDN and trace...  They do not simulate transmission line and plane
separately as you described.

For instance in SIwave a 2D MoM is used to capture trace-trace, trace-plane
and plane-plane coupling all along the signal path...  The MoM matrix is
then assembled together with transmission line model with the hybrid EM
circuit (spice like)  sim...

Of course it's always a matter of the frequency vs simulation time
trade-off you are looking for...

For instance if you have an area of high Swiss cheese / perforation and you
want to well capture noise between trace and plane in these conditions, in
that case the 3D solvers are better, but you may need to reduce the problem
size only around the plane you want to simulate, otherwise the sim could be
too huge...

Fortunately the great job you and other EDA companies are doing on HPC can
drastically reduce the sim time of 3D for a PI analysis and makes things
possible today ;-)

Regards
Cristian
Il 22/ott/2014 13:14 "Yuriy Shlepnev" <shlepnev@xxxxxxxxxxxxx> ha scritto:

> Hi Sherman,
>
> Now you explained the problem :-)
> All hybrid solvers (both frequency or time domain) that use separate
> transmission line and transmission plane (parallel plane) models will not
> take this type of coupling into account.
>
> The reason is simple. Transmission plane model of the parallel planes
> includes electric field with only one component perpendicular to the planes
> and magnetic field components parallel to the planes (may be formalized as
> TM waves). These fields couple or excited by only to the currents flowing
> in
> the direction orthogonal to the planes - currents on vias for instance. On
> the other hand, T-line strips have currents predominantly parallel to the
> planes and are simulated in these hybrid solvers separately with the
> coupling only at the vertical transitions.
> In a simplified case with parallel planes with strips between them and TM
> waves propagating along the strips will be exactly orthogonal (do not
> interact) to the TEM waves propagating along the strips (even in presence
> of
> dielectric and conductor losses). Such modes do not interact!
>
> In reality, TM waves are not exactly TM and do not propagate along the
> strips. Small coupling takes place mostly due to discontinuities,
> inhomogeneities and losses. To construct a model with the coupling, you
> will
> need 3D analysis that accounts for all major factors contributing to the
> coupling. You should see that the coupling at the transition to the strip
> will be dominant. Though, I have not seen such investigation - may be
> someone on this list can provide further references.
>
> Best regards,
> Yuriy
>
> Yuriy Shlepnev, Ph.D.
> President, Simberian Inc.
> 3030 S Torrey Pines Dr. Las Vegas, NV 89146, USA
> Office +1-702-876-2882; Fax +1-702-482-7903
> Cell +1-206-409-2368; Virtual +1-408-627-7706
> Skype: shlepnev
>
> www.simberian.com
> Simbeor - Accurate, Fast, Easy and Affordable Electromagnetic Signal
> Integrity Software
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>
> -----Original Message-----
> From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
> On
> Behalf Of Chen, Sherman
> Sent: Wednesday, October 22, 2014 11:47 AM
> To: nilesh_kamdar2@xxxxxxxxxxxx; si-list@xxxxxxxxxxxxx
> Subject: [SI-LIST] Re: time domain simulation w/ PDN planes
>
> Nilesh,
>
> Thanks for the paper. My question is regarding how to model the coupling
> from PDN to the transmission line, not the transmitter or the receiver
> chip.
> The coupling effect across the whole span of the tline need to be
> calculated. To do that in circuit simulator what I can think of is to use a
> multi-port sparam which's ports are extracted btw the locations along the
> tline and the VRM, at the interval of say lambda/20. At each location the
> port need to be set at four points: DP+, DP-, Vcc on power plane, and GND
> on
> the ground plane.
> Any comments on this thought?
>
>
> -----Original Message-----
> From: nilesh_kamdar2@xxxxxxxxxxxx [mailto:nilesh_kamdar2@xxxxxxxxxxxx]
> Sent: Wednesday, October 22, 2014 11:38 PM
> To: si-list@xxxxxxxxxxxxx; Chen, Sherman
> Subject: RE: [SI-LIST] time domain simulation w/ PDN planes
>
> Sherman
>
> If I understood your question correctly, I believe that this simulation can
> be handled in ADS. To do this you need to create an SI/PI model of the
> physical interconnects that includes all the power/ground planes and also
> signal lines. Then you can apply specific time domain stimulus in a
> Transient simulation.
>
> Here is a DesignCon 2014 paper that explains how we can do this:
>
> Paper:
> http://cp.literature.agilent.com/litweb/pdf/5991-4083EN.pdf
>
> Slides:
>
> http://www.xilinx.com/events/designcon2014/11_WE5Slides_Touchstonev2SIPISPar
> ameterModels.pdf
>
> If you have more questions about this technique, you can contact me
> offline.
>
> Thanks
> Nilesh Kamdar
> Applications Engineer, Keysight Technologies
>
>
>
> -----Original Message-----
> ----------------------------------------------------------------------
>
> Msg: #1 in digest
> From: "Chen, Sherman" <sherman.chen@xxxxxxx>
> Subject: [SI-LIST] time domain simulation w/ PDN planes
> Date: Tue, 21 Oct 2014 14:07:19 +0000
>
> Hello experts,
> I'm trying to evaluate the impact of power plane noise on the HS signals.
> The sim setup would require to apply a noise source on the PDN (somewhere
> btw power plane and ground plane), also a PRBS source at the initial end of
> the t-line. To my knowledge it looks only Cadence Sigrity Speed2000 can run
> such SI/PI combined sim since the feedback I got from Keysight and ANSYS
> both said that neither ADS nor SIWave can handle such sim case where time
> domain sim needs to be run w/ the noise coupled from power/ground plane.
> Note the coupling needs to be from the whole plane rather than injected at
> one point for the latter we can simply use a sparam model of the PDN as the
> means of noise injection but this would not be the equivalent of the plane
> coupling, right?
> Any suggestion will be appreciated.
>
> Best Regards,
>
> Sherman Chen
> Signal Integrity
> EMC Global Hardware Engineering
> Tel: +86 21 60951100-3329
>
>
>
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