Regarding segmented ground planes if you want to read an interesting article:
Common mode currents induced on wires attached to multilayer PCBs with segmented ground planes by: R. Lee_Hill and others, IEEE Transactions on Electromagnetic Compatibility, 4/94 (0-7803-1398) What they say is basically the same that one of the forum participants already wrote: sometimes it helps, sometimes it does not. Sometimes it helps for immunity and adversely effects radiation. It may be beneficial for low frequency applications, for power supplies, analog circuits, but it could be bad for high frequency circuits. Regards: Janos Vajda
