RE: [SI-LIST] : Conducted EMC Testing of PLL jitter

Farrokh Mottahedin ([email protected])
Tue, 29 Sep 1998 13:33:21 -0700


I don't consider myself an expert on this subject but would like to
bring to your attention a piece of equipment available from HP which can be
used for this application without direct or transformer coupling. The
equipment I have in mind is called the 11945A Close-field Probe Set that can
supply 0.5 watts of power over 9KHz to 1 GHz.


Farrokh Mottahedin
Quantum Corporation
(408) 324-7934
[email protected]

> -----Original Message-----
> From: Ray Anderson [SMTP:[email protected]]
> Sent: Tuesday, September 29, 1998 9:51 AM
> To: [email protected]
> Subject: [SI-LIST] : Conducted EMC Testing of PLL jitter
> Perhaps some of the EMI/EMC savvy people on the list have
> some comments and/or opinions on how best to couple an interfering
> RF signal into the power planes of a digital board to accomplish
> some EMC testing.
> Basically I have a system (CPU's, memory, PLL's etc.) that
> runs at a clock rate of several hundred MHz. I need to do
> some tests to evaluate what effect noise on the power planes
> over the range of ~DC to 1GHz has on the PLL jitter.
> I would like to inject a signal (in the range of ~DC to 1 GHz)
> into the power planes (up to maybe 200 mv p-p amplitude) to
> see how the PLL handles the noise on it's power feed.
> I have a broadband (10KHz to 1GHz) amplifier that can provide
> an excitation level of up to 20 watts into 50 ohms.
> We believe the system power distribution system (planes, bypass
> caps etc.) looks like a broadband 50 milliohm (or less) impedance.
> The question is: would impedance matching the 50 ohm amplifier
> impedance to the sub-ohm plane impedance by means of a broadband
> ferrite transmission line transformer be a prudent thing to do,
> or is there another accepted way of doing this?
> Any comments or suggestions on alternate ways of evaluating the
> jitter performance of a system PLL in response to power supply
> noise over a wide bandwidth would be of interest.
> Ray Anderson
> Sun Microsystems Inc.
> [email protected]
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