Coupled Mircostrip Line Coupler design in HFSS

I've been trying to design a coupled mircostrip line coupler with only 2 ports. I know all about the Even and Odd modes and the rules that i need to satisfy to achieve the best coupling but i couldn't find any sources on how to actually design and construct the line. I have build the line in HFSS but the coupling isn't there to a satisfactory level, i want to get the S21 parameter above -5db. I have designed the microstrip to have an impedance of 50ohms and i want the coupling to occur at 10Ghz.

I have attached my design (with .doc at end) and hope that someone here maybe able to help me out in any way possible or steer me onto the right path.

Thanks in advance!