We have an old design using MC19192 then after MC13203 Zigbee controler which work very fine.
It use also a 2.4 GHz Low Noise Amplifier based on transistor Freescale MBC13900.
This transistor is obsolete and we want to move to another one before redesigning the whole project.
Our design is moreorless similar to the Freescale Eval Kit.
It's decribed in details in document Document
I've tried other transistors without changing the matching but range decreases and sometimes, I can see oscillations.
If I want to change the Rf transistor, I have also to change the Rf adaptation at input and output of this transistor.
In the document, at the end of page 3.3 and beginning of page 3.4, it's indicated that the Z parameters for MBC13900 are
36+j21 Ohm at the input
and 64-j70 Ohm at the output.
With these values, it's not difficult to calculate the adaptation.
My question is : how are calculated these values ?
I can not find from where these values are comming.
I've tried to transform the MBC13900 S parameters to Z parameters with without any success.
For Vce = 2 V, Ic = 3 mA, f = 2.4 Ghz
f S11 S21 S12 S22
2.4 0.472 -166 3.778 66 0.077 25 0.554 -48
I've tried with RfSim99 but again, not the same values.
Are those values comming directly from in situ measurement on the board or from another calculation?
Any help would be welcome