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

Ray Anderson (
Tue, 29 Sep 1998 13:23:27 -0700 (PDT)

> Greetings,
> The application of enough rf power to cause your power to groundplane
> voltage to be modulated up to 200mV p-p would certainly cause things
> to jitter though I don't know how you would know cause from effect.
> Over a 1GHz bandwidth the impedance presented by the module will vary
> significantly as probably will the coupling transformer.

The 200mv p-p number is a guess at the maximum amplitude
someone thought we should use. In reality we intend on ramping
up the level slowly and developing a pertubation vs. jitter

We have methods to control the broadband impedance of the
power distribution system (planes, bypass caps etc.) to
maintain a relatively constant and controlled impedance,
so the Z we have to drive may not be as wildly varying as
one might imagine.

> A less drastic method would be to isolate the power to specific
> devices and apply the rf to them one at a time. This could be done
> though a small current transformer, with a ferrite, or with a very
> small resistor. In this way you would be able to apply a known level
> of noise and be able to check that it is realistic. (If the device is
> extremely well decoupled you might need an unrealistic ammount of
> power to induce 200mV p-p)

We've already looked at and characterized individual sections
of the circuitry without too much problem. Now we've been asked
to evaluate the response of the entire system to noise pertubation.

> Good luck,
> Colin..

Thanks for the comments and suggestions!


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