Hi Hakim,
If you want the Transition from SMA to PCB as clean as possible, then you need
to run a 3D simulation and optimization of the Transition. You need to optimize
either the Stack-up, or the Footprint and void for a given Stack-up. For
tracewidth smaller than the Contact pad you need to add Cutouts/voids in the
Copper plane underneath the pad to compensate the capacitive impact of the pad.
Or you select a stack-up and a connector, and then ask the connector vendor to
provide a footprint for your Stack-up. A lot of Vendor do that for you free of
charge (Rosenberger, Southwest...) if the Projekt is interesting enough
(Volume).
Or you check the web for Design Studies about SMA to PCB Transition (there are
a lot of papers out there on this topic), and then Copy their Stack-up and
footprint (check if it is IP-free before designing it into a real Product).
Since it is only 5GHz, you might be able to just use the Vendors recommended
Footprint, but very often these aren't optimized at all. That’s the more
dangerous way.
Hope this helps
Gert
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-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On ;
Behalf Of Hakim Sellaoui
Sent: Tuesday, October 11, 2016 1:25 PM
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Input Matching for SMA Connectors
Hi all,
I'm designing a test board that will have differential trace widths of 4 mil
and I want to connect SMA connectors to them, but I'm not sure what connector
would be suitable as the ones I've found have connector widths that are neither
equal to or smaller than the trace widths, as well as the recommended pad sizes
are much larger. For an RF design I did at Uni, I just added a quarter wave
transformer to provide the matching at the operating frequency; is it still
possible to do this with a high-speed design with a 200 ps rise time (5 GHz)
signal?
Or can anyone recommended a way to connect VNA coaxial cables to a PCB with
trace widths around 4 mils, such that the Zo is maintained.
Thanks,
--
Hakim Sellaoui
Associate Hardware Engineer
DisplayLink (UK) Limited
Tel: +44 (0)1223 443920
Fax: +44 (0)1223 443921
E: hakim.sellaoui@xxxxxxxxxxxxxxx<mailto:hakim.sellaoui@xxxxxxxxxxxxxxx>
W: http://www.displaylink.com/
140 Science Park, Milton Road,
Cambridge, CB4 0GF,
United Kingdom.
Registered in England No. 04811048
DisplayLink Corp.
A US incorporated company.
480 S. California Avenue Ste 305, Palo Alto, CA 94306, USA.
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