using s-parameters in pspice student

I want to design one small signal preamplifier.
The S parameter is given for VCE = 10V & 7 ma.
I am designing the premap with VCE 6V & 7 ma.
The S parameter of the device for my design VCE 6V & 7ma must be different.
Now tell me what to do?

u have three options

1) contact the transistor manufacturer to get ur desired S parameter

2) if u have a VNA u can build ur own caliration board , and measure the S paramter file by urself

3) use the nonlinear model of the transistor , , to design the amp in a small sinal way

and after that optimize the circuit

Khouly

Another option is to buy a model from a company specialized in device modelling, for example Modelithics, Inc.

I can get excess to VNA. Guide me how to make calibration board & measure S parameter.

How to use nonlinear model of transistor & design the amp small signal way?

Start from reading all related docs in:
http://www.home.agilent.com/agilent/...IT&lc=ita&sm=g
in particular the 8510-8A.

Let me suggest also to ask for a support of experienced RF Lab guys, if you have one near to you!

With bias-tee you'll be able to bias your device in the same conditions you'll use in your circuit, and measure S par in these conditions.

I hope it can help.
Mazz

Which transistor are you using? Frequency of your application? Do you need noise parameters as well?

Here is the file of transistor to be used.
Can i make the real world PCB & put the input/output RF connectors & check S parameters.
Initially i will take S parameter measurement at 100 mhz to start with.
I want to use it with 75 ohm input output impedance.

To get accurate results you need to do in-fixture measurements. You can read about it in application notes from Agilent.

The NE85639 non-linear SPICE model file can be found here:

http://www.cel.com/pdf/models/ne85639.cir

Using this model file, it's easy to create a circuit for determining the s-parameters at any arbitrarily bias condition, as long as the bias stays within the model limits of Vce=2.5 V to 10V, Ic=0.3 mA to 7 mA, freq range 0.1 GHz to 3.0 GHz. In your case VCE = 6 V, Ic = 7 mA which are within these limits.

In the test circuit below, IS1 has been selected for Ic = 7 mA at VCE = 6 V.

The file 6_7.s2p (RAR'ed) contains the resulting s-parameters at VCE = 6 V, Ic = 7 mA.

If your microwave circuit analysis program can import and use non-linear SPICE models, you can use the ne85639.cir file directly.

Very much appreciating ur help VSWR.
I hv appcad, serenade student version & RFsim99. Is any of this useful for non-linear SPICE model?

VSWR
which software u hv used for modelling & getting s parameter as required.

VSWR
waiting for ur reply about using the which software? Ur method is nice. As i am in designing process we change bias many times. hence looking for new S parameter for new biasing conditions till the design is finalised.

Judging from the schematic VSWR posted, he's using Genesys from Agilent.

You can use any microwave EDA software which can handle nonlinear models and has a harmonic balance simulator, for example:

Advanced Design System from Agilent Technologies.
Genesys from Agilent Technologies.
Ansoft Designer from Ansoft.
Microwave Office from Applied Wave Research.

Appcad and serenade student version doesn't have these features. I'm not familiar with RFsim99.

Thanks alexx!
This r all professional softwares. It is not possible for newbie like to me even think about this. They r very expensive & cannnnot buy just to learn RF design.
Is there any other way to do so? I think it must not be there.
Thanks to all for the help & guidance shared by fellow members.

VSWR
I now hv got excess to genesys 7.5 programme.
if possible, pl. post the genesys file u hv created.
can u send me s parameter for 10 Mhz, 100 mhz, 200mhz 300Mhz & 500 Mhz.
noise parameter for just 100 mhz & 200 mhz. for bias 6V 7 ma.
I will try to learn from ur finding & try to get/check the same the results.