I made some measurements once in a 3 meter anechoic chamber built for EN61000-4-3. I was interested in the disturbance a wire causes in a field due to picking up the field, the resultant currents flowing in such a way as to cancel the field that caused them, etc. In order to assess the effect, I needed to monitor the undisturbed field. While EN61000-4-3 allows a x-y-z field sensor total output to represent the field intensity, I needed to measure the relative vector components. I found that in this tile-lined chamber, that the only vector of any magnitude was that parallel to the radiating antenna. I would say that given this kind of performance, a plane wave has been established.
But I was working at 300 MHz. I am suggesting that this simple test could be performed at all frequencies of interest to assess the anechoic properties of the room. > From: [email protected] > Reply-To: [email protected] > Date: Tue, 22 Jul 2003 02:35:08 +0000 > To: [email protected] > Cc: [email protected] > Subject: 3m vs. 10m chamber for radiated immunity > > > Has anyone investigated the difference in performance of different chamber > sizes when performing the radiated immunity (-3) test at low frequencies > (e.g., > between 80 MHz and 100-150 MHz)? The field uniformity is calibrated in > E-field, > but I would expect the total EM field (E and H components) to have different > distribution as a function of different chamber sizes. Specifically, keeping > the distance between the antenna and the DUT constant at 3 m, I still expect > different performances due to size (chamber loading the antenna and > reflections/near field). Consequently, it seems that the interfering signal > can > be quite different in a small chamber vs. large chamber, with possibly large > variations in the H-field components, even though they are both calibrated for > the E-field uniformity, and both tests performed at the antenna distance of > 3m. > > I know of a case in which testing in a smaller (3m) chamber makes product > consistently fail at significantly lower level than in a larger, 10 m chamber > (6 V/m vs. nearly 10 v/m). Fixing a product to pass the 10 V/m level (required > by the customer) in the large chamber seems to be relatively easy and > inexpensive, while fixing it to pass the same level in a small chamber may be > very costly and time consuming. > > Is there any precedence like in case of the radiated emission, where 10m > results prevail in case of a dispute? Any papers to support or dismiss my > expectation from above? > > Thanks, Neven > > ------------------------------------------- > 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] > > Archive is being moved, we will announce when it is back on-line. > All emc-pstc postings are archived and searchable on the web at: > http://www.ieeecommunities.org/emc-pstc > 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] Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
