you can choose from different types of power dividers / couplers. Some of them are narrow bandwidth, some of them have better isolation. In fact is a compromise between a lot of parameters. It depends on your application
You can find some good articles on the Ansoft site :
hxxp://www.ansoft.com/about/academics/training_materials.cfm
(x=t)
I made some wilkinson type power dividers(1/2) for the 2.2 - 2.7 GHz band, I got insertion loss of 3.5-3.6 dB and isolation27dB@2.2GHz, 43dB@2.4GHz and 21dB@2.7GHz. For my application is was enough.
Cheers, Al