Optimizing using ADS

Hello,
When using ADS to extract equivalent circuit parameter. How to know that I got the right values for the parameters, since I can get an infinite combinations of oarameters values.


thanks

depends on the type of component. For linear circuit, you can use S2p. for non-linear circuit, you can use SDD or FDD. You can simulate the equivalent circuit before you embark a design. But SDD/FDD is quite complicated, you need to perform some testing before writting the non-linear equations...

While extracting equivalent circuit parameters, you have to match the s-parameters of the equivalent circuit to that of the measured data. You are right that there may be different sets of values for the equivalent circuit for which the S-parameters may be same. Depending on the circuit (active or passive) you must have an idea about the functionality of the equivalent circuit elements (R, L, C, current source etc.) so that you can have some idea about the order of the component values you are expecting. Otherwise if you try to do an open ended optimisation then you may land up in values which have no physical meaning and though you may get the model for the device you may have difficulties in simulating the same in a circuit under different conditions. So it's always a good idea to know what sort of values you are expecting before you embark on doing a parameter extraction optimisation. Also it's better to run a Random optimisation before performing a gradient optimisation so that you do not run into a local minima.

8)

can you some thing in the detail?

Try to get good starting values for you parameters to begin the optimization with. This is only possible if you understand the model and model parameters very well.