Sam,
The key phrase is "free-space wave impedance". At the source, the wave
impedance matches the impedance of the driving circuit. The electric
fields and magnetic fields interact (near-field conditions), working
toward the free-space wave impedance of about 377 ohms. The impedance
actually overshoots 377 ohms a little bit (see Figure H-1 in my book,
Electronic System Design: Interference and Noise Control Techniques),
but past about lambda/(2*pi) has stabilized at a nominal 377 ohms
(far-field conditions).
Since the wave impedance also affects the antenna factor, and thus the
V/m or A/m that the antenna "thinks" it sees, you have to measure both
ways.
John Barnes
dBi Corporation
http://www.dbicorporation.com/
-------------------------------------------
This message is from the IEEE EMC Society Product Safety
Technical Committee emc-pstc discussion list.
Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/
To cancel your subscription, send mail to:
[email protected]
with the single line:
unsubscribe emc-pstc
For help, send mail to the list administrators:
Ron Pickard: [email protected]
Dave Heald: [email protected]
For policy questions, send mail to:
Richard Nute: [email protected]
Jim Bacher: [email protected]
All emc-pstc postings are archived and searchable on the web at:
http://ieeepstc.mindcruiser.com/
Click on "browse" and then "emc-pstc mailing list"
