Help regarding oscillations in LDMOS die

[BMR]

Hello ,

I am supposed to compare the measured S parameter data and the simulated S parameter for a discrete LDMOS power transistor package which has 2 die in it.
Based on the previous experience I know there will be some deviations between both the results as it's always obvious. But in this case I see oscillation only at a particular frequency in the measured data. I ran all stability analysis in the simulation and it did not even show tiny variation. So I am confused as to how to go about this. Thanks

 

[BigBoss]

Unstability may come from the implementation of the board.connectors.vias etc.The measured s-parameters are generally measured on basic 50 Ohm input/output PCB and any practical implementation with biaising,matching,filtering,decoupling etc. may induce some unstability problems.

 

[BMR]

Oh yes. But how to verify it's the board which caused the oscillations? Or Is there some factors affecting the whole circuit due to which I cannot see it in the simulation ?