how to find Rn and S-optimum(gamma-opt)

[rakesh228]

hi....i am designing a LNA all i have is my transistor. I dnt knw my s-parameter files. i created a biasing circuit and i calculated s-parameters(s11,s12,s21,s22) from circuit. i need to design input and output matching networks, so i need gamma-optimum and Rn value to draw noise circles . i am using awr microwave office for simulation. Please help me.

---------- Post added at 02:54 PM ---------- Previous post was at 02:44 PM ----------

actually i need source reflection coefficient (GammaOpt), the minimum noise figure (FMin), and the normalized effective noise resistance (Rn).. i know only my s-parameters.

 

[tony_lth]

The gamma-opt and Rn should be provoded by the transistor vendor

 

[rakesh228]

if we have a ckt , we cant find them in microwave office?

 

[BigBoss]

if we have a ckt , we cant find them in microwave office?

If you don't know s-parameters, you can't find Rn Gamma_Opt.You should have s-parameters of the acive device.
Otherwise you can also measure but I don't think that you have measurment equipments because they are very expensive

 

[rakesh228]

i know my s-parameters(s11,s12,s21,s22)......then how to calculate Rn Gamma_Opt?

 

[BigBoss]

i know my s-parameters(s11,s12,s21,s22)......then how to calculate Rn Gamma_Opt?

Put these s-parameters in a "Data Items Black Box" in ADS and terminate the ports with proper impedance e.g. 50Ohm and make a s-parameter simulation with noise option and then find Rn and SOpt for the frequencies which you're interested in.
In MWOffice, there should be similar components as in ADS but I'm not familiar with that..

 

[rakesh228]

i am doing this project in microwave office....so nay one an help me?

 

[vfone]

Noise Resistance Rn is a measured parameter (by the manufacturer), deducted from measured minimum Noise Figure and Gamma_optimum (Reflection coefficient for that particular NF point). You cannot get Rn only from S parameters.

**broken link removed**

 

[ltrlspree]

Put these s-parameters in a "Data Items Black Box" in ADS and terminate the ports with proper impedance e.g. 50Ohm and make a s-parameter simulation with noise option and then find Rn and SOpt for the frequencies which you're interested in.
In MWOffice, there should be similar components as in ADS but I'm not familiar with that..

This does not sound right to me, my take is that through simulation, the only way is to fetch this from the non linear model of the device, if available.

 

[flyhigh]

Hi

I guess BigBoss didn't assume that noise parameters are not available for the particular device. If they were, they should be listed in the same .s2p file.

Rakesh, as vfone pointed out, you got to have frequency dependent noise data known before start your work in MWO, otherwise you cannot calculate noise figure, circles etc. They must be supplied form the manufacturer otherwise the transistor is usually not good for LNA design.

The MWO program comes with a set of S parameter libraries, some of them contain noise parameters as well.

flyhigh