Groundplanes for Wideband synthesizer
At 2 GHz I strongly recommend a single ground plane. 

Separating planes with a star topology certainly has its place in low noise audio designs, keeping digital noise out of analog circuitry.

But at 2GHz, the dangers of accidentally building resonant circuitry and antennae when you divide up the ground plane completely outweighs any possible benefits. 

Use a single ground plane. Keep all loop areas as small as possible. Minimise inductances; if necessary, use multiple vias in parallel around decoupling capacitors. Decouple as close as you can to PSU and ground pins.

Or invest in serious signal integrity simulation tools (Hyperlynx?) and get/create Ibis models for everything, spend a few months learning the tools and simulating the exact PCB layout until it's right.