[SI-LIST] EMC Issue at 266 MHz
- From: Jean_Pierre.Bouthemy@xxxxxxxxxx
- To: si-list@xxxxxxxxxxxxx
- Date: Mon, 1 Mar 2004 19:24:01 +0100
Hi SI experts,
I have a question regarding an EMC issue.
Our system has failed the EMC radiated emissions with a 266.6 MHz emission
+3dB above Class A gabarit !
We have many 66.66 MHz clocks in our system, made with 50MHz oscillator
feeding a PLL, whose 400 MHz VCO frequency divided by 6 gives 66.66 MHz.
My question is the following:
I could understand an emission at the odd harmonics:
- 66.66MHz x 3 = 200 MHz or,
- 66.66MHz x 5 = 333.33 MHz or,
- 66.66 MHz x 7 = 466.66 MHz or,
- so on ...
But I don't understand why we have problem with the fourth harmonic : 66.66
MHz x 4 = 266.6 MHz !!
=> Does anyone have an idea ?
=> Is it possible the 266MHs emission doesn't come from our 66.66MHz
clocks?
=> In this case wher could it be from?
Thank you for your help.
Regards.
Jean-Pierre Bouthemy
--------------------------------------------------------------------
Jean-Pierre BOUTHEMY
Hardware Design Engineer
ALCATEL - Mobile Networking Division (MCG)
Mobile Core R&D
+33 (0)2 99 26 08 18
mailto:jean_pierre.bouthemy@xxxxxxxxxx
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