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A inductor is behaved open-circuit in high frequency, it is used to isolate the "high frequency grounding" AGND and GND. But I think it is not a good practice for grounding, I prefer all signal go back to ground.
I prefer using same GND Plane for both analog and digital components.
You can look at this paper by Henry Ott:
"Partitioning and Layout of Mixed Signal PCBs"
If in a circuit you have both analog and digital signals it is always good practice to separate AGND from DGND. PCB layout should also separate A from D.
In some data sheets you can read: "For best results connect the grounds together at a single point with a 0.050 inch trace..."
This trace acts infact as an inductor, so if you prefer to use copper trucks, breads or RF-chokes it is your choice, but I think that separation is good engineering practice..
You can only separate Agnd and Dgnd if and only if you analog and digital signal are completely isolated using either transformer or optocoupler. Otherwise, it is not recommended to separate the ground. So if these grounds are separated, then you can use a ferrite beads (which you called an inductor) to connect the power and ground plane between the Agnd and Dgnd.
But if the digital and analog signals are not isolated, then the Agnd and Dgnd have to be joined together at one place. There are techniques to minimize cross talk such as having a mote to separate digital and analog region and provide a bridge where these two domain can talk to each other.
This techniques are found in this book:
The author of this book also wrote another very good book that talks more in details about Agnd and Dgnd which I can't find here at this website. But you can purchase at Amazon:
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