From: Dan Swanson ([email protected])
Date: Mon Nov 13 2000 - 04:33:01 PST
From an RF point of view, you have a microstrip
to slotline transition. Putting a cap or shorting bar
right next to the trace shorts out the slotline mode
at the source. A frequency domain analysis of the
transition might tell you something about its bandwidth.
Dan Swanson EMAIL: [email protected]
Bartley RF Systems, Inc. TEL: 978-834-4085
37 South Hunt Road FAX: 978-388-7077
Amesbury, MA 01913
> -----Original Message-----
> From: abe riazi [SMTP:[email protected]]
> Sent: Thursday, November 09, 2000 3:02 PM
> To: '[email protected]'
> Subject: RE: [SI-LIST] : Plane Splits Inspection
> Pat Zabinski Wrote:
> You also mention the stitching capacitors. We have found them to
> be useful. However, what I did not predict is the frequency
> (spacing) in which you must place them. Using one test board,
> we placed an ideal stitching capacitor (shorting bar) across the split,
> and slid the capacitor along the split. We then injected signals
> of various edge rates ranging from 35 psec to 1 nsec. Prior
> to making the measurements, I predicted that there would be
> a relationship between the edge rate and how far the cap could be
> away from the trace. What I found was that the regardless of
> edge rate, the stitching cap needed to be within 2 mm of the
> trace! This was quite unexpected.
> Thank you for the reply.
> The separation of 250 mils between neighboring stiching capacitors (that I
> referred to in my post) has been recommended for use on high speed PCBs.
> One draw back of this rule is that at times the high density of the board
> prevents utilization of that many capacitors.
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