Amund, If you do manage to get through, please ask about signals that never leave the silicon of an ASIC (described by Andy & others). A strict interpretation of the FCC wording clearly includes all such signals, but it causes us a lot of pain, especially as frequencies continue to climb.
As an example, a micro-processor we have used here has as an input, a 66 MHz clock. It then multiplies that up, to say 866 MHz (memory is fuzzy here). That output is immediately divided by 2 (presumably for a good square wave). It's that 433 MHz that's actually used for internal clocking and is published as the operating speed of that particular processor. I have no problem considering the 433 MHz as the highest fundamental even though it never gets onto an IC pin. Harmonics of that will still possibly/likely be on all the bus lines which do go out to pins and PWB etch. However, the 866 MHz is technically the highest frequency signal used even though it presumably is used only to toggle the one internal divider. Regards, Jack Xerox EMC -----Original Message----- From: am...@westin.org [mailto:am...@westin.org] Sent: Friday, August 03, 2001 8:23 AM To: emc-p...@majordomo.ieee.org Subject: RE: FCC - radiated emission up to 10th harmonic Hi all! Thanks for responding. I have tried to get in touch with some folks at FCC today, if I manage to get through, I will return with their information / interpretations. Have a nice weekend! Best regards Amund Westin, Oslo/Norway On Fri, 3 Aug 2001 00:29:23 -0700 Don Rhodes <don.rho...@infocus.com> wrote: > >I second Jack's thoughts on the wording from part 15, the wording "generated >or used" is very clear. Furthermore, it seems obvious that a PLL generates a >"new" fundamental frequency when multiplying its input frequency. This in >turn, of course, creates a new set of harmonics and subharmonics related to >the PLL's output frequency. Unfortunately, the FCC's rules do not make >exceptions for generated signals which are only used internal to an IC. I >know, anyone who's ever struggled with the emissions from a noisy PLL, like >myself, has wished for such a break in the rules. > >Regards, >Don >EMC Engineering >InFocus Corp. > >> ---------- >> From: Cook, Jack[SMTP:jack.c...@cax.usa.xerox.com] >> Reply To: Cook, Jack >> Sent: Thursday, August 02, 2001 10:27 PM >> To: 'John Harrington'; Gary McInturff >> Cc: emc-p...@majordomo.ieee.org >> Subject: RE: FCC - radiated emission up to 10th harmonic >> >> >> >> So far, I haven't seen anyone quote the actual wording in FCC Part 15. >> Here >> it is, from the table in para. 15.33 (4). >> >> "Highest frequency generated or used in the device or >> on which the device operates or tunes (MHz)" >> >> It doesn't appear to concern itself with *how* the signal is generated >> (ocillator, PLL, etc.) or whether it's a fundamental or not. So, it seems >> clear enough to me. Or maybe I'm missing something. >> >> Regards, >> Jack >> Xerox EMC >> ------------------------------------------- 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: http://www.rcic.com/ click on "Virtual Conference Hall,"
