Designing a Directional Coupler in HFSS. Need Help!

Hi guys, Been working on designing a simple single section directional coupler and simulating it in HFSS. However once I get the simulation working the results aren't exactly what i expect. I'm not very experienced in this field of engineering but i'd really appreciate it if you could help me to figure out what I maybe doing work.

I've attached the HFSS simulation file for you to look at (Just take off the .doc).

The coupler is designed to be -20dB at 5gHz ..