>5 to 1000 MHz range and need to keep the noise pick to less than -90 dBm
>have achieved -75 dBm micro noise

	Isn't mixed signal FUN?  This is an area peppered with challenges.

	I'll assume you're already doing the normal physical isolation
	techniques, perhaps with a "picket fence", to achieve the 75 dBm.

	Unlikely but possible you've got radiation above board, this can
	be checked by making "covers" to try containing circuits in the
	z-axis.  This can often be done in the lab, even if it's kludgy
	it will help rule out this coupling mechanism.

	More subtle but in the same vein could be coupling across a gap
	in the gnd plane (I assume you've got a split), the field effects
	around the edge of planes can be such a coupling mechanism if you
	have signals too close to the edge of the void, and/or the void is
	too narrow.  Possible fix for this is a "barrier" gnd, or small
	web of gnd connected back to the pwr source "in between" the two
	gnds you suspect of coupling.  Farraday was right.

	Often you get noise coupling through a power supply or return
	path with inadequate isolation, particularly over such a sweep of
	frequency.

	I'd need alot more info to guess any further.  Contact me off-line
	and perhaps I could look at your database, depending on your plat-
	form.  Sorry, but I'm gone 'till Monday afternoon.

	Good luck,

        Jeff Seeger                             Applied CAD Knowledge Inc
        Chief Technical Officer                      Tyngsboro, MA  01879
        [log in to unmask]                               508 649 9800

***************************************************************************
* TechNet mail list is provided as a service by IPC using SmartList v3.05 *
***************************************************************************
* To unsubscribe from this list at any time, send a message to:           *
* [log in to unmask] with <subject: unsubscribe> and no text.        *
***************************************************************************