Hi Group, Here are some of my questions and thoughts about EN61000-4-6. Any corrections and comments are greatly appreciated. In discussion of "Wisdom behind all these standards", Richard Nute summarized three points raised by Martin Rowe. One of them is "reasonableness or appropriateness of the standard". Please allow me to have better understanding of "reasonableness or appropriateness of the EN61000-4-6".
Both EN61000-4-3 (4-3 in short below) and EN61000-4-6 (4-6) verify the immunity of EUT against induced disturbances caused by incident electromagnetic fields from 150 KHz to 1 GHz. The chamber test approach used in 4-3 is not suitable at lower frequencies (150 KHz to 80 MHz), - not in principle only technically. That's why we need to perform 4-6 differently from 4-3. The methodology of 4-6 is to inject conducted disturbance to cables connected to the EUT by using direct injection or clamp coupling. The injected cable currents are supposed to be the same as induced by incident electromagnetic fields in real world. The methodology of 4-6 also implies that at low frequencies the possible disturbance directly coupled into the EUT from incident electromagnetic fields can be ignored in comparison with the disturbance indirectly coupled to the EUT via attached cables. For many well-shielded EUT that assumption works because it is difficult for low frequency electromagnetic fields to directly get into the EUT through apertures (such as slots, seams, and holes), whose dimensions are small compared to wavelength. But what if the EUT has larger openings or only plastic enclosure? Let's see an extreme example. A component cannot work properly under the illumination of 2.5 V/m incident field at 50 MHz The component would feel 2.5 V/m field when installed if the EUT is illuminated by 3 V/m incident field. But the component could work OK if injecting cable current of 3V into the EUT. The boundary 80 MHz between 4-3 (80 to 1000 MHz) and 4-6 (0.15 to 80 MHz) is not always fixed. It may be adjusted depending on different scenario. That principle is mentioned only in principle. I would like to see a real example to adjust the boundary between 4-3 and 4-6. Does it make more sense to setup a transition region, say 50 to 100 MHz, for both 4-3 and 4-6 to overlap? For the same EUT the test level of 4-3 is 3V/m, and the test level of 4-6 is 3V (80% AM @ 1KHz). Is there any explanation or verification available to show the equivalence (even roughly) between these two levels in interferences with the EUT at boundary frequency? In real world all attached cables would have induced currents at the same time if an incident field illuminates upon the EUT. In 4-6 test procedure, however, all cables are injected one by one in turn. On the other hand, in Radiated Emission test we have to manipulate the placement of all attached cable to maximize the resultant emission from all cables. Is it fair? I mean there seems to be a "double standard" for Radiated Emission and Conducted Immunity. Best Regards, Barry Ma b...@anritsu.com ____________________________________________________________________ For the largest MP3 index on the Web, go to http://mp3.altavista.com ____________________________________________________________________ ------------------------------------------- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. 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: Jim Bacher: jim_bac...@mail.monarch.com Michael Garretson: pstc_ad...@garretson.org For policy questions, send mail to: Richard Nute: ri...@ieee.org
