I had to design my own transmission lines in layout and I have used HFSS to EM simulate the structure and then I use the result by employing NPORT in my schematic.
The problem is that I cannot run LVS since it does not produce netlist for a schematic that contains NPORT.
Any idea how I can run LVS while keeping my transmission line?
It depends on whether you want to be able to recognize the structure as part of the LVS, or whether it is just going to be seen as routing by LVS.
Either way, I would probably create a symbol for the structure, and then have two schematics. One schematic would connect all the ports of the symbol to corresponding ports of the nport - so it's a simple wrapper around the nport.
The second schematic would be for LVS - and this would either use cds_thru (from basic) to create effective shorts between the pins representing the opposite ends of each line, or it would use metal resistor components from your PDK. If use use the latter, you could mark the nets on the layout with whatever marker is used to identify a metal resistor (or place an instance of the metal resistor). This allows you (at least) to verify that there is something specific on the layout to distinguish it from a simple metal track - but whether it is worth doing this or not is debatable, since what you'd be verifying is nothing more than the presence of some marker layers...
There's probably other ways, but hopefully this is a start.
In reply to Andrew Beckett:
Thank you so much Andrew.
Finally I replaced the TL with PINs to do the LVS.