Designing of Directional coupler

Can someone help me in Designing the two hole directional coupler at X band waveguide operating at 10 GHz. The required coupling is 25 dB.We also have to design the bend at the coupling end to have the practical measurements for the device.

I want some help on "designing the bend at the coupling end"

have u checked out book by T C Edwards on microstrip structures

I have not been given the value of directivity...............so can anyone helpme out in calculating the radius of holes.......its urgent please..