FreeLists / si-list / [SI-LIST] Re: uStrip question - repost

["Grasso, Charles" <Charles.Grasso@xxxxxxxxxxxx>]

 As I have learned the hard way - make sure you model
what you measure and measure what you model.  Make accurate
crossections of your test boards, check the board material
- the charactersitics FR4 can vary wildly - did you sim with 
the solder mask - do the the freebies use closed form eqns or
EM simulation? Do the freebies account for resistive losses
at high freq? Some qs that spring to mind...

-----Original Message-----
From: Bill Dempsey
To: bdempsey85@xxxxxxxxxxx; si-list@xxxxxxxxxxxxx
Sent: 3/8/2004 8:57 PM
Subject: [SI-LIST] uStrip question - repost

--sorry for the repost but the server is adding junk to the message that
made it unclear to read --

I recently built 3 different uStrip construction testboards and was
surprised by the results: it didn't work!

I built two boards as trace over copper with soldermask and one board
as a co-planar waveguide. I constructed the geometries of the boards by
following the results of some "freebie" tools out there.

After the boards were built I connected them to an HP network analyzer
(I calibrated out the cables/cons) to look at S21 response. What I
found was surprising. The S21 was extremely poor: approx 6.5dB loss
over 4". This just does not compare to the results of the tools I have
access to. I expected about 1.2 - 1.5 dB of loss at this frequency.

Has anyone else out there had some bad experiences with uStrip @
2.5GHz? What tools are you using? How are you correlating your
tool's results to real-world?

The construction of the three boards was as follows:

Board 1: 12 mil trace, 1/2 oz foil with 1 oz plating, 8 mil to gnd
(three
sheets of 1080 prepreg), 1oz copper gnd

Board 2: (CPW): 8 mil trace, 8 mils to gnd (again, 3 sheets of 1080
prepreg), 6 mil to gnd return on signal layer, same plating/thicknesses

Board 3: 4.75 mil trace, ~2.83 mils to gnd (one sheet of 1080 prepreg),
1/2 oz foil, 1oz plating, 1oz copper gnd

Regards,

Bill

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