A few issues. You haven't said if the quiet zone is the same 1.5 meter square. Assuming it is, I can't imagine using a horn, which is a constant aperture antenna with gain increasing with increasing frequency. You need a constant gain antenna, a log periodic.
The antenna separation needs to be such that the quiet zone is in the far field. With a log periodic having significant depth, the three meter separation used by 1000-4-3 seems reasonable. If you are testing above 1 GHz, you need the hybrid absorber made up of microwave cones backed by ferrite tiles. My experience is you do need absorber on the floor between antenna and quiet zone. ---------- >From: scott....@jci.com >To: emc-p...@majordomo.ieee.org >Cc: craig.har...@jci.com, james.e.te...@jci.com >Subject: RF Field Uniformity and Antenna location >Date: Fri, Jan 18, 2002, 10:13 AM > > > To All, > > We are working toward adding capability to perform Radiated Immunity Free > Field Testing (Substitution Method), which is very similar to the IEC > 61000-4-3 method. The main differences are the following: > > 1. We have a 15 position target area for uniformity instead of 16 > 2. Uniformity for 14 of the points is defined as being within +6/-0 dB > with respect to the center position on the bottom row. (position 3 in the > diagram below) > > > ******************************************* > 11 12 13 14 15 > > 6 7 8 9 10 > > 1 2 3 4 5 > ******************************************* > - position 3 must be higher in field strength than all 14 remaining points. > > > > My Questions: > > 1. Does anyone have experience with the physical placement of the > transmitting antenna and its relative positioning to the target area? I'm > looking for things like height between antenna/floor, distance between > antenna/target, and antenna angle with respect to horizontal, etc. > 2. Is there a need for absorbing material to be placed on the floor > between the target and the antenna? If so, what areas, and how much is > typically needed? > 3. From experience, in general, how achievable is uniformity at low > frequency (200MHz - 1GHz) vs. high frequency (1GHz - 4GHz). What hurdles, > or obstacles are typical/need to be overcome? > 4. Our experience has been that position 3, is generally lower in field > strength when compared to other points in the grid. Is this normal? We > have tried adjusting the antenna in several different > positions/orientations etc. with not much success. > > Givens: > > 1. We are using a Double Ridged Wave Guide for 200MHz - 1GHz, and a high > gain Horn antenna for 1GHz - 4GHz. > 2. We are performing testing in a semi-anechoic chamber. > > > > Any help would be greatly appreciated. > > > > Regards, > > Scott Mee > EMC Engineer > > Johnson Controls Inc. > PH: 616.394.2565 > EMAIL: scott....@jci.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: > majord...@ieee.org > with the single line: > unsubscribe emc-pstc > > For help, send mail to the list administrators: > Michael Garretson: pstc_ad...@garretson.org > Dave Heald davehe...@mediaone.net > > For policy questions, send mail to: > Richard Nute: ri...@ieee.org > Jim Bacher: j.bac...@ieee.org > > All emc-pstc postings are archived and searchable on the web at: > No longer online until our new server is brought online and the old > messages are imported into the new server. > ------------------------------------------- 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: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson: pstc_ad...@garretson.org Dave Heald davehe...@mediaone.net For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: No longer online until our new server is brought online and the old messages are imported into the new server.
