sdd ads

does anybody have some information about the SDD control in ADS, the help in ADS is so general , i can't catch it ,please give some more detail about the SDD,how to define the port voltage or current ,and how to add equations in it ,so i can model some complicated device electrical characteristic.
many thanks!

purian

Have you looked at Files > Example Projects... then in Tutorials for SDD_Examples_prj. There are many working examples there:-

after studying the examples of the SDD_Examples_prj,i still have some difficulty in understanding the SDD control,can anyone give some more infromation about the SDD,i mean the further step.
thanks!