[SI-LIST] EMI Question Related to Spread Spectrum Clock Generator
- From: "Steven M. Waldstein" <swldstn@xxxxxxxxxxxx>
- To: <si-list@xxxxxxxxxxxxx>
- Date: Tue, 4 May 2004 19:41:58 -0400
To all,
Here's another spread spectrum PLL question.
Assume you are taking a 33 MHz clock in generating
800 MHz from it with a spread spectrum PLL. ( 24x multiplier ).
From the 800 MHz you divide by 4 and 6 to get 200 MHz and 133 MHz.
Since the 800 MHz is the signal that has been modulated to spread
the energy, the 200 MHz and 133 MHz or even lower ( say 66 MHz ),
have different power densities. The 200 MHz would have a low power
density than the 133 or 66 MHz because it is divided by a smaller
amount.
So the question is....
Do FCC emission limit change as a function of frequency band to
allow a single high frequency clock to be divided down to several
different bands?
Does anybody know where I can find info on allowed emissions energy
and is it a function of frequency or a hard and fast maximum limit,
independent of frequency?
Thanks in advance for any help
Steve
swldstn@xxxxxxxxxxxx
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