Had to pitch in here, The GTEM is a very valuable tool when used properly, but it is not, in any way, shape, or form, correlatable to an open field site across a broad range of products.
That said, for the FCC, specific correlation by product is allowed. Yes, this means there is no economic advantage for _initial_ certification/verification. It does provide some advantage for later upgrades, modifications and audit testing. For the EU, the GTEM would be an "alternate test facility" and would need to meet the volumetric uniformity requirements of EN55022 for ITE. This is seriously difficult for moderately sized (meaning affordable) GTEMs. For immunity to 1000-4-3, again, only the planar uniformity is specified. It should be noted that a rather large GTEM is needed to make the uniformity over a 1.5 by 1.5 meter plane. In the emissions area, the problem is not with the GTEM, but with the OATS. A "specific harness" is not part of the OATS procedure. Cables are to be "maximized" for emissions. Depending on frequency, phase front, and physical dimensions, it is a terribly random procedure for complex devices. I know, I've tried to make sense if it for better than twenty years. Still haven't! Best regards..... Brent DeWitt > -----Original Message----- > From: [email protected] > [mailto:[email protected]]On Behalf Of Leslie Bai > Sent: Wednesday, July 07, 1999 6:15 PM > To: Mike Hopkins; Qu Pingyu; 'emc' > Subject: RE: GTEM cell > > > > > Mike, > > Your comments can't be over stressed any more. > We did find the deviation between correlations > from products to products, however, as long as > a suitable harness is used properly, the correlation > is pretty consistent. Also we use modeling tools > to assist correlation prediction. It helps as well. > > I am wondering if it is a mandatory to correlation > GTEM cell result with OATS result for each of > EUT, why we have to duplicate the test, why > not just get the result from OATS to comply. > > For immunity test against CE using GTEM, > it is stated in EN61000-4-3, Annex , as an > alternative test facility. > > For emission test, as mentioned above, > ANSIC63.4 accept GTEM result. EN has > no specific standard such as EN55022 to > accept GTEM result. However, compliance > can be declared through TCF route against > generic standards as allowed by EMC Directive. > > I personally have no doubt GTEM and also things > like Reverberation Chambers (another alternative > facility) will be fully recognized eventually, > it's just the matter of time. > > Rgds, > Leslie > > --- Mike Hopkins <[email protected]> wrote: > > > > Careful -- for FCC emissions it's allowed only if > > correlation with an OATS > > is achieved for a given product. For the next > > product, correlation may have > > to be re-done. > > > > For immunity to EN's, it isn't so clear. IEC > > 61000-4-3 is written as if any > > type of TEM cell is NON compliant, but a draft annex > > is now being circulated > > that would allow TEM cells, but ONLY if a TEM wave > > can be demonstrated > > throughout the frequency range being used (3-axis > > measurement, undesired > > vectors > 6 db down). > > > > For emissions to EN's, TEM cells are not allowed for > > compliance testing. > > > > Mike Hopkins > > [email protected] > > > > > -----Original Message----- > > > From: Leslie Bai [SMTP:[email protected]] > > > Sent: Wednesday, July 07, 1999 11:25 AM > > > To: Qu Pingyu; 'emc' > > > Subject: Re: GTEM cell > > > > > > > > > Pingyu, > > > > > > I guess GTEM cell is a good choice for your case. > > > Pls refer to IEC61000-4-3 (for immunity) and > > > ANSI C63.4 (for emission), GTEM cell is not only > > > recognized for pre-compliance test but also > > > can be used for compliance test as long as > > > some correlation can be achieved. > > > We did correlation through both modeling, > > simulation > > > using FDTD and actual testing to verify the > > results. > > > We are using GTEM cell for many different kinds of > > products > > > compliance test and PCB trouble-shooting. > > > It is pretty good. But you have to pay attention > > > to the uniformity volume of GTEM cell, it's > > > a bit tricky, especially the cabling of EUT may > > affect > > > the result, thus, during the correction, a harness > > > is supposed to be used to simulate the EUT > > cabling. > > > > > > Hope it helps. > > > Leslie > > > > > > --- Qu Pingyu <[email protected]> wrote: > > > > > > > > Hello, Everyone: > > > > > > > > I have some questions regarding the GTEM cell. > > Here > > > > in our Institute we are > > > > considering setting up some EMC measurement > > > > capability for precompliance > > > > testing. The EUTs we are dealing with are not > > very > > > > large, probably not > > > > larger than a desktop PC. Do you think that GTEM > > > > cell is a good choice ? Do > > > > many of you use GTEM as a precompliance testing > > > > facility ? Your comments are > > > > highly appreciated. > > > > > > > > Regards > > > > > > > > Qu Pingyu > > > > > > > > > > > > --------- > > > > This message is coming from the emc-pstc > > discussion > > > > list. > > > > To cancel your subscription, send mail to > > > > [email protected] > > > > with the single line: "unsubscribe emc-pstc" > > > > (without the > > > > quotes). For help, send mail to > > [email protected], > > > > [email protected], [email protected], or > > > > [email protected] (the list > > > > administrators). > > > > > > > > > > > > > > > > > > > > _________________________________________________________ > > > Do You Yahoo!? > > > Get your free @yahoo.com address at > > http://mail.yahoo.com > > > > > > > > > --------- > > > This message is coming from the emc-pstc > > discussion list. > > > To cancel your subscription, send mail to > > [email protected] > > > with the single line: "unsubscribe emc-pstc" > > (without the > > > quotes). For help, send mail to > > [email protected], > > > [email protected], [email protected], or > > > [email protected] (the list > > administrators). > > > > > > > --------- > > This message is coming from the emc-pstc discussion > > list. > > To cancel your subscription, send mail to > > [email protected] > > with the single line: "unsubscribe emc-pstc" > > (without the > > quotes). For help, send mail to [email protected], > > [email protected], [email protected], or > > [email protected] (the list > > administrators). > > > > > > > > _________________________________________________________ > Do You Yahoo!? > Get your free @yahoo.com address at http://mail.yahoo.com > > > --------- > This message is coming from the emc-pstc discussion list. > To cancel your subscription, send mail to [email protected] > with the single line: "unsubscribe emc-pstc" (without the > quotes). For help, send mail to [email protected], > [email protected], [email protected], or > [email protected] (the list administrators). > > > --------- This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to [email protected] with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to [email protected], [email protected], [email protected], or [email protected] (the list administrators).
