[SI-LIST] Re: extraction of RLGC when there is no reference plane
- From: "Jon Powell" <jonpowell@xxxxxxxxxxxx>
- To: <zhang_kun@xxxxxxxxxx>, <si-list@xxxxxxxxxxxxx>
- Date: Sun, 9 May 2004 08:22:53 -0700
In order to have a transmission line, you must have a well defined return
path (you may have an electric circuit, but it isn't the modeling construct
called a transmission line). Your return path in reality is the lowest
impedance path back to the driver. This is usually a nearby plane (GND or
Power). If no plane is present, the nearby parallel wires may serve as the
return mechanism. In the absence of planes you will probably have more and
more of the return path being in the form of EMI.
Most algorithms for estimating Transmission Line Properties require a
defined return path (or GND). Without that, they cannot calculate a C or L
and so cannot make Z and S. One trick that will give an answer (though with
greatly varying accuracy depending on the situation) is to define a GND
plane at a relatively great distance from the signal. This will probably
make some answer appear, but if the parallel wires in the area are not
captured, the answer will not be very good.
This is one reason it is extremely difficulty to automatically simulate
PCB's with no planes or define return (ground) wires for all signals.
In short, your problem isn't necessarily that HSPICE can't give you an
answer. But rather that you haven't designed your return path and modern
tools are not capable of finding one.
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx
[mailto:si-list-bounce@xxxxxxxxxxxxx]On Behalf Of Zhangkun
Sent: Sunday, May 09, 2004 1:28 AM
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] extraction of RLGC when there is no reference plane
Dear all:
In Hspice, there must be one reference plane. We are analyze some
transmission line which have no reference plane. Which tools is suitful for
this kind situation?
Best Regards
Zhangkun
2004.5.9
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