I have to add to all of the previous replies:: Broadband in the sense of EMC :
1 a repeating square wave signal (no sinus) has harmonics in multiple of it's frequency its harmonics descend in amplitude with modulo sin(f)/f function this means that the harmonics in the peak of the sinus ( in the formula) descend linearly with frequency 2 a repeating small width pulse (no sinus) has harmonics in multiples of it's frequency f but the harmonics tend to descend in amplitude much slower. 3 a repeating infinite small pulse has a infinite bandwidth of harmonics on f distance from each other 4 a single pulse with infinite short time (dirac pulse) has infinite harmonics on 0 Hz spaced at even amplitude A ignition engine produces much of the third category pulses, it's repeating period is long (low frequency) and the pulse width is very small. It's frequency range goes well into several 100 of MHz. The spacing of the harmonics however is very close, equal to the ignition frequency (4-100 Hz) If one uses a spectrum analyzer with 10 kHz bandwidth the signal seems to have a continuous spectrum as many harmonics fall into this bandwidth : broadband interference (with 10 Hz bandwidth : many narrow band harmonics) Most frequency measurements are taken with a bandwidth of 120 kHz. so all pulse sources slower then approx. 60 kHz tend to appear as broadband interference . Attention : square waves don't have that much harmonics; it's pulses that do have Another way of generating broadband frequencies is modulation. Not just plain AM or FM modulation but also the kind of modulation that happens in databuses or address buses of microprocessors. Regards, Gert Gremmen Ing. == Ce-test, Qualified testing == Consultants in EMC, Electrical safety and Telecommunication Compliance tests for European standards and ce-marking Member of NEC/IEC voting committee for EMC. Our Web presence: http://www.cetest.nl List of current harmonized standards http://www.cetest.nl/emc-harm.htm 15 great tips for the EMC-designer http://www.cetest.nl/features01.htm -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Muriel Bittencourt de Liz Sent: donderdag 7 oktober 1999 14:43 To: Lista de EMC da IEEE Subject: broadband & narrowband emissions Group, I'd like to have a clear definition of what are narrowband and broadband emissions. This question may seem very plain for many members of EMC-PSTC, but I always heard/saw this definition for emission and I still couldn't make them clear to me.. Thanks in advance for your attention Regards Muriel -- ====================================================================== Muriel Bittencourt de Liz GRUCAD - Group for Conception & Analysis of Electromagnetic Devices Santa Catarina Federal University - UFSC PO Box: 476 ZIP: 88040-900 - Florianópolis - SC - BRAZIL Phone: +55.48.331.9649 - Fax: +55.48.234.3790 e-mail: [email protected] ICQ#: 9089332 Alternativa Adreso: [email protected] --------- 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).
