Hello,

Is there any solution to play with S2p file of transistor, i.e, in case when the simulated and measured results are not agree especially in S11. For that, i tried to many way to see what is th problem but still no thing good. I have checked on the net, i saw that if we play on s2P parameters (little variation) we can see approximately the variation...

Is any idea for that ??

Means that :
1. both shunt capacitors in the transistor input and output ?
2. series inductor in the transistor input and both shunt capacitors in the transistor input and output ?
3. series resistor in the input of transistor ?
4. ....?

in ADS sof

Thank you in advance,

Nass

Nass,

You think that your s-parameters are wrong?
Here are some ideas
1. S-parameters contain no bias condition other a snapshot of the transistor working at a bias condition and they are only accurate in that state as a small signal (AC) model.  
2.  If you think they where measured incorrectly the try the following.  
a. if you suspect that extra shunt capacitance is at the input or output then place a shunt cap in your test bench with a negative value of what you think the shunt cap is.
b. if the port extention is suspect then use a t-line of negative length in your schematic etc
Basically you can try to debug the s-parameter measurement errors by using negative components to give you some "insight" as to what might be an issue.

To get the real result you need to verify that the measurements are taken correctly.  That your circuit matches the exact test structure. That your simulation include the parasitics of the board. And in general most errors are just DC biasing issues.

RF_Designer wrote on Jun 10^th, 2010, 9:43am:
RF_Designer wrote on Jun 10^th, 2010, 9:43am:

What do you mean by "model" ?

Don't you have S-parameter model file ?

Do you mean nonlinear model ?
If so, I showed you a location where you can get nonlinear model of "NE3514S02" in another your post.
Again surely see the followings.
http://www.designers-guide.org/Forum/YaBB.pl?num=1273409182
http://www2.renesas.com/microwave/ads/NE3514S02_v127.ads

But I don't think your problem require nonlinear model of transistor.

RF_Designer wrote on Jun 10^th, 2010, 9:43am:
What do you want to mean ?
Do you mean that you use standard distributed component of ADS as layout blocks ?
Or do you mean that you invoke EM-Cosimulation of Momentum and SP-analysis in Agilent ADS ?

RF_Designer wrote on Jun 10^th, 2010, 9:43am:
Your problem is very easy problem.
I think your problem is simply you can't reflect actual measurement conditions in simulation.
Show me reference plane location for actual measurement and simulation.
If you use SMA connector in actual measurement, how to treat it in simulation ?
Or do you use "Port Extension" in actual measurement ?

Again surely read http://www.designers-guide.org/Forum/YaBB.pl?num=1273408947/1#1

Or your problem might be due to discrepancy of bias conditions as "rfcooltools.com" says.
The followings are bias conditions for provided S-parameter model.
Coompare your bias conditions with bias conditions of S-parameter you use.

! NEC Compound Semiconductor Devices Ltd.
! NE3514S02
! N-channel HJ-FET

! 1. Dec. 2005
! VDS = 0 V   VGS = 0 V

! 24. May 2006
! VDS = 2 V  ID = 5 mA

! 29. July 2005
! VDS = 2 V  ID = 10 mA

! 24. May 2006
! VDS = 2 V  ID = 20 mA

! 24. May 2006
! VDS = 3 V  ID = 15 mA

! 1. Dec. 2005
! VDS = 0 V   VGS = -2.5 V

! 24. May 2006
! VDS = 2 V  ID = 7 mA

! 24. May 2006
! VDS = 2 V  ID = 15 mA

! 24. May 2006
! VDS = 3 V  ID = 10 mA

There is no meaningful reply also in your same post in another following forum.
http://www.edaboard.com/viewtopic.php?t=392582
Do you understand the reason ?