[SI-LIST] Re: Common-mode return loss in Hspice
- From: "Tracy Barclay" <Tracy.Barclay@xxxxxxxxxxxx>
- To: <Tae-Kwang.Jeon@xxxxxxxx>
- Date: Tue, 30 May 2006 10:56:41 -0700
Hi TK,
There is a much easier and more effective way to do this. HSPICE
supports extracting both common (beginning in 2003.09) and mixed mode
S-parameters (beginning in 2004.03) using the linear analysis command
(.LIN). Unlike the .NET command, the .LIN command extracts noise and
linear transfer parameters for a general multi-port network, not just 1
or 2 ports. The .LIN command is used in conjunction with the .AC
analysis command and automatically calculates a series of noise and
small-signal transfer parameters between the terminals identified using
port (P) elements. The results can be output to a .sc* file, a
Touchstone file, or a CITIfile.
.OPTIONS post
Xline1 vcm_in1 vcm_in2 vcm_out1 vcm_out2 0 trace1
* Define differential port elements. Reference node is 3rd node.
P1 vcm_in1 vcm_in2 0 port=3D1 ac=3D1 $ input port
element, default z0=3D50, AC magnitude=3D1
P2 vcm_out1 vcm_out2 0 port=3D2 $ input port
element, default z0=3D50
* Define linear analysis. Output common mode S-parameters
(mixedmode2port keyword) in Touchstone format.
.LIN format=3Dtouchstone mixedmode2port=3Dcc
.AC lin 1k 10meg 10000meg
.PROBE scc11(db)
.SUBCKT trace1 in1 in2 out1 out2 Vss
Wline1 in1 in2 Vss out1 out2 Vss
+ RLGCFILE=3D 'my_trace.rlc' N=3D2 L=3D.049
.ENDS
.END
Please email me directly if you have any further questions about this.
Tracy Barclay
CAE
Synopsys
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
On Behalf Of Jeon, Tae-Kwang
Sent: Friday, May 26, 2006 19:45
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Common-mode return loss in Hspice
Hello all,
=20
I'm trying to simulate common-mode return loss in hspice, and want to
double check my simulation with you because the result showed me was
somewhat different than what I expected over 100MHz ~ 10GHz.
First of all, below is my simple diagram implemented in the spice deck.
=20
Port1 Port2
+ -------[[[[[[[[[[[[[[[[[[[[[[[[[[[[[-------+
+----+ dif'l traces +-------+
| +--------[[[[[[[[[[[[[[[[[[[[[[[[[[[[[-------+ |
((V)) common-mode /////
| input voltage source
/////
=20
Since I assume that both source impedance and the load impedance are
50ohms, I put 25ohms of Zcm to Rin and Rout variable as shown in the
input file below. So, here are my questions to ask.
=20
1. Is my diagram is reasonable for scc11 measurement?
2. What impedance value should both Rin and Rout have in the .NET
statement. Is it Zo, Zeven or Zcm? If I set it to Zo(=3D50ohms), I have
6dB less loss than I expected. My W-elements model was based on dif'l
traces having roughly 70ohms of even mode impedance, which is Zcm =3D
Zeven/2 =3D 35ohms, although the odd mode impedance is ~53ohms.
Interestingly, If I set both Rin and Rout in .NET statement to
35ohms(=3DZcm of trace), then it resulted in exactly what I expected. So =
I
want to clarify what is the right setting.
3. Is it right to use Sij(db) rather than either Sij(m) or Sij(r) for
the simple math like scc11=3D(s11+s21+s12+s22)/2?
=20
*My spice deck
Vin vcm_in 0 AC=3D1
=20
Xline1 vcm_in vcm_in vcm_out vcm_out 0 trace1
=20
Rdummy vcm_out 0 1meg
=20
.OPTIONS accurate post=3D2 probe
.NET v(vcm_out) Vin Rin=3D25 Rout=3D25
.AC lin 1k 10meg 10000meg
.PROBE scc11=3Dpar('(s11(db)+s21(db)+s12(db)+s22(db))/2')
=20
.SUBCKT trace1 in1 in2 out1 out2 Vss
Wline1 in1 in2 Vss out1 out2 Vss
+RLGCFILE=3D 'my_trace.rlc' N=3D2 L=3D.049
.ENDS
.END
=20
Thanks,
TK
=20
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=20
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