How to design 10dB Directional Coupler at 15.7GHz in Microstrip Line

Can someone guide me to design a 10 db Directional Coupler at 15.7 GHz in microstrip line.
I have already designed it in Alumina Substrate but when i tried to match its i/p and o/p port
with 50 ohm,result totally deteriorate.

Can you give more details like the software being used for simulation? It would be helpful if u can attach an image of your results or your design. Sometimes, u need to play a little with the dimensions of the lines, to get the desired result.

Thanks for showing interest.
I am using ADS 2011 for simulation