[SI-LIST] Re: RLGC matrix



-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]On
Behalf Of Bob Patel
Sent: Wednesday, January 23, 2002 2:04 AM
To: si_list
Subject: [SI-LIST] RLGC matrix



Hi! I know this could be a dumb question but let me
put it out because somehow I am at loss in figuring it
out.
I have simulated a transmission line i.e. using the
stack up & trace dimensions to come up with the RLGC
matrix in HSPICE. Now, should I use Z =
sqrt(R+jwl/G+jwC) to calculate Z. And the R, L,C,G
values can be calculated by solving the individual
matrix in determinant form.

-> In case of low frequency or below 1GHz, the R and G is ignored to make it
simple.

The next question is can I calculate impedance in this
way for individual sections because I have three
sections: Driver( bond wire length) + trace 1(width =
9mil to achieve 34 ohm)+ Trace 2( width = 5mil to
achieve 50ohms).The overall impedance seen by the
driver has to be around 34 ohms but I know with the
values given above that it won't be so. Hence I am on
this path to calculate the impedance of each section
and then take the average to calculate Zeffective and
also the propagation delay.

-> You mean,
---------^^^-----()()()------------
              |            |
              >           |
              <          =
              >           |
              |            |
------------------------------------

   is equal with
 ---------^^^-----()()()---------------------^^^-----()()()-----------------
----^^^-----()()()------------
              |            |                     |            |
|            |
              >           |                     >           |
>            |
              <          =                     <          =
<            =
              >           |                     >           |
>            |
              |            |                     |            |
|            |
----------------------------------------------------------------------------
--------------------------------
How about using the summation for example, Req=R1+R2+R3, Leq=L1+L2+L3,
Ceq=C1+C2+C3, Geq=G1+G2+G3?
Then I think the Zeffective = sqrt(Req + jwLeq/Geq + jwCeq).


Thanks in advance
Bob

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