Joe, Let me try this one, The near field is composed of a sum of terms 1/r, 1/r^2, etc. and the far field is only composed of the 1/r term. If your 10dB reduction was solely due to a reduction in the higher order terms, 1/r^2 etc, then in the far field no reduction will have taken place.
I hope this helps, William D'Orazio CAE Electronics Ltd. Electrical System Designer Phone: (514) 341-2000 (X4555) Fax: (514)340-5552 Email: [email protected] -----Original Message----- From: [email protected] [mailto:[email protected]] Sent: Thursday, September 14, 2000 1:08 PM To: [email protected] Subject: Near Field Versus Far Field I am having a difficult time answering the following question for a non-technical person. Hopefully, someone can put the answer into a language that a non-technical person can understand. We have a 400 MHz clock and are failing radiated emissions at 10 meters by 10 dB at 400 MHz. We bring the product back to our lab and start making modifications on the clock circuit and taking measurements with a near field probe. With these modifications and measuring with a near field probe, we realize a 10 dB reduction in emissions at 400 MHz. Why would we not see the same reduction when taking the product back to a 10 meter site? Your help is appreciated. Regards Joe Martin [email protected] ------------------------------------------- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. To cancel your subscription, send mail to: [email protected] with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Jim Bacher: [email protected] Michael Garretson: [email protected] For policy questions, send mail to: Richard Nute: [email protected] ------------------------------------------- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. To cancel your subscription, send mail to: [email protected] with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Jim Bacher: [email protected] Michael Garretson: [email protected] For policy questions, send mail to: Richard Nute: [email protected]
