RF PCB layout questions

[that_guy]

Hi, for a hobby project I've decided to step outside my digital comfort zone and implement an FM (88-108MHz) broadcast receiver around one of Silabs' devices, probably the Si4770. I've never 'done RF' before so I've been researching best practices and have so far decided to use a 4 layer board arranged as [component,GND,split power,routing].

The questions I'd like to ask are around grounding. I will have an uninterrupted ground plane at layer 2 so do I need to split it into RF and digital regions? Where online opinion can be found that comes down onto one side of the fence the consensus seems to be for uninterrupted instead of split. But the SiLabs EV board seems to have a split in the copper (see attached and fig. 37-40 in PDF) that runs through all 4 layers with no obvious footprints that connect the two planes. Are they relying on the metal can to join the two halves do you think?

I assume that the top layer should have a ground fill with a grid of vias. Correct? I know about the clearance rules between the fill and the antenna microstrip lines but should the top fill extend out to below the antenna connectors? Silabs do it; but I've seen other designs where the top fill does not extend out to below the connectors.

Guard traces and via fences. Most designs seem to feature the RF IC and its dependencies fenced in with an exposed guard trace and then boxed under an aluminium can. Should the LDO that supplies the analog (and/or digital) circuits be within this protected region?

Any words of experience would be helpful.