Dear berraco,
if you are involved in wideband digital beamforming, you will find useful to have a look to what have been done by decades on SONAR processing , where for its nature, the involved bandwidth covers several octaves.
The starting point to understand the principles of wideband beamforming is the sum and delay architecture.
When the signal band is small the time delay can be replaced by a phase delay, and this is the principle of many RF DBF architectures.
When this assumption is no more valid, true time delay must be implemented in a digital fashion (e.g interpolation).
Let me know if you need any specific clarification.
Bye, Satellite