http://www.ieee-pses.org/symposium http://www.emc2004.org/ -------------------------------------------------- Marko, here is an example, although it might be unlikely. A PC and a port cable happen to form a resonant dipole at 50 MHz. There is a 100 MHz clock running and it puts 1 mV at the cable/PC junction. The radiated power is 166 pW at 100 MHz. The clock is now dropped to 10 MHz. The 5th harmonic of the clock puts 1/5 mV at the cable/PC junction. The radiated power is 279 pW at 50 MHz. Although the energy in each clock harmonic has been reduced the new (and improved) spectral content is causing radiation at a frequency where there was none before. Dave Cuthbert Micron Technology
From: [email protected] mailto:[email protected]] On Behalf Of [email protected] Sent: Tuesday, June 01, 2004 12:37 PM To: [email protected]; [email protected] Subject: RE: Q on testing different power modes for PCs http://www.ieee-pses.org/symposium http://www.emc2004.org/ -------------------------------------------------- Charles, Interesting question. Here is my view. In my product lines, there are dozens upon dozens of operational modes that could be exercised. I don't believe that it adds any value nor meets the intent of any EMC legislation to test them all. We apply engineer judgment to identify the worst-case and test it. In some situations, the analysis cannot be conclusive and we test more than one mode. So with that background and without knowing the details of your product, I suspect that your low-power mode is also a low-EMI mode (almost by definition) especially if the clock frequencies are less. (The Fourier transform peaks will all be reduced even if the rise time and pulse duration are the same.) Less overall energy + less high-frequency energy = Less EMI Any other opinions? Cheers, Marko From: [email protected] mailto:[email protected]]On Behalf Of ext Grasso, Charles Sent: Tuesday, June 01, 2004 11:03 AM To: '[email protected]' Subject: Q on testing different power modes for PCs http://www.ieee-pses.org/symposium http://www.emc2004.org/ -------------------------------------------------- Greetings: Power saving modes becoming ubiquitous is consumer electronics and one of the techniques is to lower the clock frequency (while in low power mode). Heres the testing question: Given that different clock frequencies are used for power saving should we also be testing in standby modes? Best Regards Charles Grasso Senior Compliance Engineer Echostar Communications Corp. Tel: 303-706-5467 Fax: 303-799-6222 Cell: 303-204-2974 Email: [email protected]; <mailto:[email protected]; > Email Alternate: [email protected] From: Zhang Guoqing [mailto:[email protected]] Sent: Monday, May 31, 2004 10:29 PM To: [email protected] Cc: chendunli; Kelvin Shi Subject: a question http://www.ieee-pses.org/symposium http://www.emc2004.org/ -------------------------------------------------- Hi, I have a question on UL60950-1, in clause 2.6.4.2: "Equipment required to have protective earthing shall have a main protective earthing terminal.For equipment with a DETACHABLE POWER SUPPLY CORD, the earthing terminal in the appliance inlet is regarded as the main protective earthing terminal." in clause 2.3.2 "- for PLUGGABLE EQUIPMENT TYPE A, a separate protective earthing terminal shall be provided in addition to the main protective earthing terminal, if any (see 2.6.4.1)." My questions is how to mark the separate protective earthing terminal, do you think the symbol 60417-1-IEC-5019 is correct? For some equipment(for example, telecommunication centre equipment), seperate earthing terminal in the equipment may be a better way for connecting earth than earthing terminal in the appliance inlet. So my question is, if seperate earthing terminal is not required only from the standards UL60950-1, do you think the equipment which provide one seperate earthing terminal and indicated by symbol 60417-1-IEC-5019 do not comply with UL60950-1? Zhang Guoqing Huawei Technologies CO.,LTD. P.R. CHINA [email protected] Tel: +86-755-89653394 Fax: +86-755-89653384 Mobile: 13686493636 This e-mail and its attachments contain confidential information from HUAWEI, which is intended only for the person or entity whose address is listed above. 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