[SI-LIST] Re: Transmission line simulation at 1.25GHZ

Ashok,

In the work we have done here at SiQual on OC48 and OC192 systems we follow 
this general procedure.

First we use a field solver to develop good, coupled line SPICE models for 
the transmission system. Generally, we will use a combination of AnSoft 2D 
and 3D field solvers and the HSPICE field solver for this purpose. We 
believe using a field solver is required because it is the only way to 
accurately model the properties of the transmission system, in particular 
the impedance, coupling, and the loss due to skin effect and the 
dielectric, both of which become significant at these frequencies. The 2D 
solver is used primarily to produce the lossy, coupled line models and the 
3D solver for things like vias that can be modeled reasonably well as 
lumped elements, at these frequencies. We use the information the fields 
solvers provide to produce a SPICE model for the transmission system. We 
use HSPICE preferentially. So for us, this will usually include several 
segments of coupled W-elements with lumped elements at various locations to 
model vias and terminations.

Regarding the actual analysis, you may be able to infer what you need from 
rise time and AC sweep but we find that it is usually a better and more 
direct approach to simulate the interconnect scheme as part of the overall 
system. That is, we will simulate the driver to the receiver using multiple 
aggressors against a victim. We set up HSPICE so that we can see and 
measure the data eye pattern. We use a bit pattern that will push the 
system into all the data dependency corners as well as making certain we 
have hit the process corners for both the silicon and the substrate. To 
accomplish this you will need good device models from your silicon vendors 
as well as a clear understanding of the process tolerances your substrate 
suppliers can hold.

As you develop your methodologies, it is always helpful, when possible, to 
compare your simulation results to actual measurements. This will allow you 
to tune your process and gain confidence in your approach.


Rob Hinz
Senior Consulting Engineer
SiQual, Signal Quality Engineering
18735 SW Boones Ferry Road
Tualatin, OR 97062-3090
(503) 885-1231
http://www.siqual.com





At 12:43 PM 7/24/2001 +0530, you wrote:

>Hi all,
>
>I am supposed to do the simulation of transmission lines of OC48 section.
>Since I am a newby to this, I dont know where to start,, what are the things
>needed for this, etc. The rough idea I have is to simulate it in SPICE
>(WinSPICE or SPICE OPUS). I would like to know,
>
>1. Which SPICE transmission line model is to be used? How to get deduce its
>parameters from the PCB line parameters for the same? How differential lines
>are modelled in SPICE?
>
>2. What are the analysis to be done? Will transient analysis (for rise time
>degradition etc) and ac Sweep analysis would suffice?
>
>The very idea I am having may be incorrect. Please guide me in this work.
>
>Thanks and Regards,
>Ashok.

Rob Hinz
SiQual Corporation
rob@xxxxxxxxxx
phone (503)885-1231 x30
fax   (503)885-0550


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