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

Norman Wong (
Wed, 30 Sep 1998 18:21:10 -0400

> >
> > Ray,
> >
> > 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.
> >
> > Regards,
> >
> > Farrokh Mottahedin
> > Quantum Corporation
> > (408) 324-7934
> >
> From what I read in the HP catalog this looks like a receive probe
> for sniffing the B field near a board. Is it a passive device that
> functions bidirectionally?
> -Ray


I am no expert in this area too but I do use this probe. I believe
it can be used as either a sniffer or a transmitter. However, in your
situation, I am not sure by inducing noise this way could help as the power
rail would have a much lower impedance to pick up any noise generated by
this probe.

On another note, we have encounter similar problem that we have to
measurement PLL's PSRR .vs. frequency. Our engineer here designed a small
circuit that can modulate an input from a sig-gen and produce a DC with a
riding sine-wave. However, the bandwidth of the op-amp in this circuit is
limited to ~ 1MHz. We have not spent much time to make this circuit to work
at higher frequency but I assume that can be done. You may consider the
same approach.

Norman Wong
Baseband Hardware Development
Nortel, Wireless Networks