While the analog and digital grounds are isolated on the Zynq\ UltraScale+\ RFSoC, eventually they must connect to each other on the PCB. The recommended method to ensure that the analog ground planes on the Zynq\ UltraScale+\ RFSoC connect to the digital ground plane with as little noise transfer as possible is to use one common ground plane.
When connecting analog ground and digital ground as one common plane, adhere to the following guidelines:
•Do not add any slots in the ground plane.
•Place digital voltage regulator modules (VRMs) and capacitors near the digital power rails.
•Place RF VRMs and capacitors near RF power rails.
•Add ground stitching around groups of RF signals to 158 mil (4.0 mm) pitch. See This Figure, This Figure and This Figure.