A modern day antenna designer knows the complete current distribution over his radiating structure and thus, with enough computational horsepower, can predict electromagnetic fields emanating from his device.
When the radiating device is an unintentional radiator where the current distribution is completely unknown, and we use a pickup device to sample one particular aspect of the field at one particular separation from the EUT, then we have no information on which to base any extrapolation. > From: Cortland Richmond <[email protected]> > Date: Fri, 24 Jun 2005 03:20:06 -0400 > To: ieee pstc list <[email protected]> > Subject: Re: ??? RE: ??? RE: Near field H-field measurement. > > Ken Javor wrote > >>> The only practical solution is to use a > probe that looks like the one the victim of rfi is going to be using, > connected to a receiver of equal to or greater sensitivity than the victim, > and similar bandwidth, and verify that the level of rfi at a particular > separation is sufficiently low as to not interfere with a predetermined > level of broadcast reception. And the measurement is made in such a way as > to maximize emissions, in the traditional manner. > > And you cannot of course extrapolate the near field from the far field; not > that anyone is trying. << > > Yes, my rant does fall into the realm of "significant oversimplification" > (grin). In _practice_, as you say, using a transducer similar to the > expected victims', we end up with a useful number. It's not what the label > says it is, but it'll do. (I eat no-fat cheese food, too.) > > Near field/far field extrapolation is useful when there's too little room > to get into the far field of high-gain antennas; I've seen papers in the > APS journal on this. Antenna designers do start knowing a lot about their > radiating structures. Should we know more about our EUT's considered as > antennas? > > > Cortland Richmond > KA5S > > ---------------------------------------------------------------- > This message is from the IEEE Product Safety Engineering Society > emc-pstc discussion list. Website: http://www.ieee-pses.org/ > > To post a message to the list, send your e-mail to [email protected] > > Instructions: http://listserv.ieee.org/listserv/request/user-guide.html > > List rules: http://www.ieee-pses.org/listrules.html > > For help, send mail to the list administrators: > > Scott Douglas [email protected] > Mike Cantwell [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://www.ieeecommunities.org/emc-pstc > This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to [email protected] Instructions: http://listserv.ieee.org/listserv/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas [email protected] Mike Cantwell [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://www.ieeecommunities.org/emc-pstc
