> -----Original Message-----
> From: Muriel Bittencourt de Liz [SMTP:[email protected]]
> Sent: Thursday, October 07, 1999 5:43 AM
> 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]
>
> ---------
Muriel:
Narrowband and Broadband are the two extremes of the spectral
distribution of a signal's power.
The classic NB emission has all of its power contained within a
narrow range of the spectrum. Think of a perfect sine wave generator, with
no sidebands or frequency instability. But how narrow is narrow? All of the
power is within 100 Hz? Or 10 Hz? Or 1 Hz? Or......
Classifying a signal as NB depends a lot on your prejudices and
experiences. At 10 GHz, a radar signal might occupy 10 MHz of spectrum.
That's a lot of spectrum to an audio guy, even though it's only 0.1% wide!
My particular experience says that a signal is NB if its occupied
bandwidth is around 1% or less.
The classic BB emission has its power distributed over a wide range
of the spectrum. Think of the spectra from an infinitely fast transition.
The power will exist no matter where you choose to sample it.
Practically, there are no perfect NB or BB emissions. The problem
lies in where (and how) we try to define the dividing line. Should we use
percentage of occupied bandwidth? Or tuneability (with what detector
bandwidth)? Or maybe modulation repetition rate? Is a NB signal which hops
around quickly still NB? What about two NB signals real close together?
Have you ever heard the story about the 4 blind men and an elephant?
Regards,
Ed
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Ed Price
[email protected]
Electromagnetic Compatibility Lab
Cubic Defense Systems
San Diego, CA. USA
619-505-2780 (Voice)
619-505-1502 (Fax)
Military & Avionics EMC Services Is Our Specialty
Shake-Bake-Shock - Metrology - Reliability Analysis
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