A branchline hybrid is comprised of four quarterwave transformers. By it's very nature, it will be a narrowband structure. Depending on how much ripple you can afford in your thru and coupled paths, and return loss at the edges of your band, a single box hybrid may be sufficient. You can get more broadband by using a double box branchline, too. Read up on Microwaves101 for more info.
**broken link removed**
Depending on your implementation, a Lange coupler could also be used (Microwaves101, Coupler pages). They are more compact, but can take more time to initially design and refine. It's all a trade-off. Hope that helps.