In my humble opinion: The dither works really well since the time that the clock is on any one frequency is small with respect to the receiver 120 kHz resolution bandwidth, and you get a lot of averaging. However at around 200 MHz you might not be in band to a radio broadcast, but rather a television broadcast (4 MHz bandwidth or greater) and there your dither might be completely within the victim receiver band and dithering wouldn't reduce that interference and there are some within this forum who have said it can hurt.
In conclusion, dithering will help you meet a test requirement, but it might not actually reduce potential interferences. Ken Javor 6/15/01 9:07 AM, Binnom, Cyril A at [email protected] wrote: > > Group, > > I am experiencing a EMI failure during testing and it has been isolated to > the processor board in which the fundamental frequency is 66.6 MHz the 3rd > harmonic that is our failure frequency is 199.8 MHz. We consulted the > manufacturer of the board and they have come up with a "spectrum spreading" > application for me to try. As I understand it, these type of applications > work by essentially jittering the clock frequency in order to spread the > energy over a wider band of frequencies. Thus the level at any particular > frequency is reduced even though the overall amount of energy radiated is > the same. The file they are sending me is a test application. If it works > well enough to get the unit to pass test, they have the ability to enable > the same application in the BIOS so it is always running. > > Does anyone have any experience using this type of application? Any opinions > on its validity? To those that can attest to its validity, any pros or cons > to the use of this application? > > Regards, > > Cyril A. Binnom Jr. > EMI/EMC Approvals Engineer > LXE, Inc. > (770) 447-4224 Ext. 3240 > (770) 447-6928 Fax > [email protected] > > > > ------------------------------------------- > 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: > Michael Garretson: [email protected] > Dave Heald [email protected] > > For policy questions, send mail to: > Richard Nute: [email protected] > Jim Bacher: [email protected] > > All emc-pstc postings are archived and searchable on the web at: > http://www.rcic.com/ click on "Virtual Conference Hall," > ------------------------------------------- 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: Michael Garretson: [email protected] Dave Heald [email protected] For policy questions, send mail to: Richard Nute: [email protected] Jim Bacher: [email protected] All emc-pstc postings are archived and searchable on the web at: http://www.rcic.com/ click on "Virtual Conference Hall,"
