Re[3]: impedance across ground plane

Todd Hubing (
Thu, 22 Feb 1996 14:09:13 GMT+0600

You are correct, Barry. A low impedance connection to earth
ground is not a prerequisite for low radiation at RF frequencies.
Returning signal currents to their source through a low impedance
path, on the other hand, is very important.

Todd Hubing
---------------------- referenced message -----------------------
>Hi Gentlemen,
>Please allow me to present an alternative viewpoint and correct me.
>What does "good ground" mean? The definition of "good GND" should be
>"a low-impedance return path back to the source." If some unwanted
>current at low frequency (say, 50 Hz) can get back to it's source easily
>through earth GND, let's secure the connection from the unit to the
>earth. If EMI at RF comes from a chip inside the unit, why do we have to
>reduce the impedance at 3 GHz to earth ground through GND plane of PCB and
Dr. Todd Hubing email:
Electromagnetic Compatibility Laboratory Phone: (314) 341-6069
University of Missouri-Rolla FAX: (314) 341-4532
Rolla, MO 65401 web: