[SI-LIST] Re: High-Speed (coax) PCB Connector Transitions -- selection, PCB footprint, and performance

Hello Heidi,
thanks for sharing those tricks! Actually if anything I observed a (very 
small) inductive parasitic at the launch point, so your tweak may even 
improve performance since the added capacitance will compensate for the 
inductance.

Wolfgang






"Barnes, Heidi" <heidi.barnes@xxxxxxxxxx> 
03/09/2009 07:42 PM

To
<wolfgang.maichen@xxxxxxxxxxxx>
cc
"Michael Rodrigues" <michael.rodrigues@xxxxxxxxxx>, 
<si-list@xxxxxxxxxxxxx>, <si-list-bounce@xxxxxxxxxxxxx>
Subject
RE: [SI-LIST] Re: High-Speed (coax) PCB Connector Transitions -- 
selection, PCB footprint, and performance






Hi Wolfgang,
I use the 5mil pin that steps to 8 mils and then pull it forward until the 
stepped edge lines up with the overhang on the connector (Southwest 
confirmed that there is plenty of pin length internal to the connector to 
do this), the larger diameter hitting the board edge adds a bit more 
pressure for the pin contacting the board, makes it easier to visually 
align since the pin sticks out further, and a bit of a capacitive stub 
right at the board edge doesn't seem to hurt.  Also, I shouldn't admit 
it... but I use the backing piece from the Rosenberger connectors since it 
uses a slightly more robust screw that can handle the 250 mil + ATE 
Loadboards and I can use the Torx head with them so they don't strip quite 
so fast. 
 
Connectors are always a bit of an art at high speeds...
-Heidi

From: wolfgang.maichen@xxxxxxxxxxxx [mailto:wolfgang.maichen@xxxxxxxxxxxx] 

Sent: Monday, March 09, 2009 5:08 PM
To: Barnes, Heidi
Cc: Michael Rodrigues; si-list@xxxxxxxxxxxxx; si-list-bounce@xxxxxxxxxxxxx
Subject: Re: [SI-LIST] Re: High-Speed (coax) PCB Connector Transitions -- 
selection, PCB footprint, and performance


I would second the recommendation for the Southwest Microwave edge launch 
connectors. A bit on the pricey side, but that gets compensated by the 
fact that you can re-use them easily since they are press-fit (only 
screwed down, not soldered). The only issue I had with them was out of 
some reason with thicker boards (over 100 mils) sometimes the center 
conductor would not make contact and I had to manually bend it downwards 
slightly (VERY carefully because it is thin and fragile). Otherwise, 
performance is great - of course you need take great care with the board 
(trace) layout & landing pattern / vias in order to get the most out of 
the connector. Southwest has a few standard landing patterns available on 
demand. 

Rosenberger works well, too, and with a bit of luck and carefulness you 
can desolder an re-use them, too (that usually takes two peope, one 
unscrewing and holding the connector, and one operating the heat gun, 
otherwise you'll break off the fragile center connector). 

Wolfgang 




"Barnes, Heidi" <heidi.barnes@xxxxxxxxxx> 
Sent by: si-list-bounce@xxxxxxxxxxxxx 
03/09/2009 02:00 PM 


To
"Michael Rodrigues" <michael.rodrigues@xxxxxxxxxx> 
cc
<si-list@xxxxxxxxxxxxx> 
Subject
[SI-LIST] Re: High-Speed (coax) PCB Connector Transitions -- selection, 
PCB footprint, and performance








I prefer the Southwest 2.4mm since it just clamps to the PCB, can easilby 
be re-adjusted if mis-aligned and is re-usable.  Also the pins are 
replaceable and SMA versions are available.  The footprint is 
interchangeable with the Rosenberger 09K243-40ME3 if one needs a permenant 
soldered connection.  Let me know if you need the footprint I am using 
which is different from the Southwest data sheet and closer to what 
Rosenberger has for their connector.

Molex has a lower performance clamped on verticle SMA connector that may 
provide more mounting flexibility if you need it...Molex used it for a 
DesignCon paper in 2006 "Practical Design and Implementation of Stripline 
TRL Calibration Fixtures for 10-Gigabit Interconnect Analysis" 
http://www.designcon.com/infovault/paper.asp?PAPER_ID=219  They may have 
made improvements in the footprint since then.


Regards,
Heidi Barnes





-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] 
On Behalf Of Michael Rodrigues
Sent: Monday, March 09, 2009 10:51 AM
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] High-Speed (coax) PCB Connector Transitions -- 
selection, PCB footprint, and performance

Hello all at SI-List,


I am trying to implement a PCB connector transition board for the purpose 
of measuring a structure at up to 20 GHz. I would be interested in using 
the best performing coax-to-PCB launch I can find so that it will not 
contribute losses to the actual structure losses I am interested in 
measuring (i.e., it will be invisible to the measurement, or as much so as 
possible).



Two questions I have would be:

1)       What would be the best connector type for this purpose (i.e.,
interfacing to VNA and high-speed o-scopes for s-parameter, TDR, and TDT 
measurements)?

2)       How important is the PCB footprint for the connector; what
would be the best way to make sure you are using the best footprint 
possible (assuming the case where PCB footprint for a PCB connector are 
not a no-brainer)?



Some connectors I have been looking at would include:



2.4 mm (DC to 50 GHz):

*                 Rosenberger 09K243-40ME3
*                 Southwest 1493-03A-5





Mini-SMP (DC to 65 GHz):

*                 Rosenberger 18 S 203- 40M L5 
*                 Rosenberger 18 S 102- 40M L5



Thank you in advance for any replies.



Best regards,

Michael



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