thank you izaz ali sha 

but as far i want to fabricate my design so wanna to use pin diode instead of lumped element 

Mr. Ahmad

You can attach in the 3D model a discrete port (50 Ohms). Later, on the Design Studio canvas, you connect between this port and a ground the model you might have of this PIN diode.

So you'll need two PIN diode models - ON and OFF, for two different simulations.

Dear Mr. Ahmad, 

You can use RLC circuit (parallel or serial) to modeled the diode depend on its state.

If diode turn on, it's equivalent to resistor and, for OFF state, it's equivalent to parallel RC circuit.

The values of R and C is chosen from a data sheet  

Firstly you complete the whole Design in CST and leave the place where you have to attach the diode. when design is completed, simulate it and see the result. Now Export this file in dxf form and import in software ADS. where you can add whatever you want. and then simulate in ADS and get the results.

Thank you Abhishek nd mohamed for your king response

u cannot simulate PIN diode in CST software u just used it in practical and u can used patch connection Instead of PIN diode than don't forget this case is ideal