FreeLists / si-list / [SI-LIST] .NET Statements in HSPICE for S-Parameters

["Chien-Min Lin" <cmlin@xxxxxxxxxxx>]

Hi, Dear All,

In reference to
  David M. Pozar, Mircowave Engineering, 1990 on Page 223:
  Find S-parameters of the 3dB attenuator circuit --

             o---(8.56ohms)--o--(8.56ohms)-----o
                             |
     Port 1 ==>          (141.8ohms)         <== Port 2
                             |
             o--------------GND----------------o

the S parameters are given by: S11 = 0  and  S21 = 0.707.
In use of HSPICE 2001.4, here is its equivanent .sp script:

*********************************************************************
*  David M. Pozar, Microwave Engineering, 1990: Page 223
*  Also, Reference: HSPICE 2001.4 User Guide: Page 12-17
*********************************************************************
.OPTION Post
       + DCSTEP=1
*--[ 3dB Attenuator]------------------------------------------------*
*
*        IN---[R1]---A---[R2]---OUT---[Rx]
*         |          |                  |
*       [Vin]       [Rc]                0
*         |          |
*         0          0
*-------------------------------------------------------------------*
  Vin   IN     0     AC  1

  R1    IN     A     8.560
  R2     A   OUT     8.560
  Rc     A     0   141.800

  Rx   OUT     0    50.000
*-------------------------------------------------------------------*
.AC  lin  30000  0  3000Meg

.NET  V(OUT)  Vin  Rout=50  Rin=50

.plot AC S11 S11(dB) (-50,10)  S11(P) (-180,180)
.plot AC S21 S21(dB) (-50,10)  S21(P) (-180,180)
*-------------------------------------------------------------------*
.END
*********************************************************************

The simulation results are | S11 | = 166.9m and
                           | S21 | = 471.8m

Nonetheless, the analytical solution would be

  S11 = V1-/V1+ = (Zin - Zo) / (Zin + Zo) = 0  (matched)

                      ZB          Rx
  S21 = V2-/V1+ = --------- x --------- = 0.707
                   ZB + R1     R1 + Rx

     where ZB = Rc // (R2 + Rx) = 41.444

Would you all please comment on the simulation results?
Meanwhile, how to probe the AC analyses for V1-, V1+, and
V2-?  Is there something wrong with the .NET statement in
the .sp script?  Is it needed to put a source resistor in
series with Vin s.t.

  Vin   IN     0     AC  1

  Rs    IN     S    50.000

  R1     S     A     8.560
  R2     A   OUT     8.560
  Rc     A     0   141.800

  Rx   OUT     0    50.000

(It turns out: | S11 | = 263.07m  and  | S21 | = 297.95m)

Appreciate so much for all your comment and assistance.

- Jamie




.AC  lin  30000   0       3000Meg

.NET  V(0)  Vin  Rout=50  Rin=50

.plot AC S11 S11(dB) (-50,10)  S11(P) (-180,180)
.plot AC S21 S21(dB) (-50,10)  S21(P) (-180,180)

.plot AC Zin(M) (5,130)  Zin(P) (-90,90)





_________________________________________________________________
Send and receive Hotmail on your mobile device: http://mobile.msn.com

------------------------------------------------------------------
To unsubscribe from si-list:
si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field

or to administer your membership from a web page, go to:
http://www.freelists.org/webpage/si-list

For help:
si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field

List archives are viewable at:     
                http://www.freelists.org/archives/si-list
or at our remote archives:
                http://groups.yahoo.com/group/si-list/messages 
Old (prior to June 6, 2001) list archives are viewable at:
                http://www.qsl.net/wb6tpu