[SI-LIST] Re: SMA for launching 5-10Gbs signals
- From: ray_waugh@xxxxxxxxxxx
- To: si-list@xxxxxxxxxxxxx
- Date: Wed, 17 Jul 2002 11:28:12 -0600
Drew...
You would have to be pretty muscular to pull these end-launchers from a board.
With two ground fingers soldered to the top ground pads and two soldered to the
bottom ground plane, they are very solidly attached to the board. I would
guess that a hundred pounds or more of force would be required to break one off.
Ray Waugh
Agilent Technologies
-----Original Message-----
From: Drew [mailto:drew@xxxxxxxxxx]
Sent: Wednesday, July 17, 2002 10:14 AM
To: ray_waugh@xxxxxxxxxxx
Subject: Re: [SI-LIST] Re: SMA for launching 5-10Gbs signals
Ray,
I would like to receive a copy of the photo. A few of my customers use these
end launch connectors frequently, but have never informed me of SMAs being
pulled off the PCB. However, our SI guru frequently specs the same geometries
you mention in his layout guidelines of the SMA.
Thank you for your time and bandwidth.
Cheers!
Drew
----- Original Message -----
From: <ray_waugh@xxxxxxxxxxx>
To: <si-list@xxxxxxxxxxxxx>
Sent: Wednesday, July 17, 2002 9:58 AM
Subject: [SI-LIST] Re: SMA for launching 5-10Gbs signals
>
>
> This is an age-old issue with we RF and microwave designers.
>
> First, you need to avoid a shunt capacitance at the launch from SMA to
> microstrip (or, in my case, coplanar waveguide with ground plane). This
> means having a 50 ohm microstrip line with a linewidth of 0.040" or more
> (wider than the connector pin). If that line is too wide for your system,
> you can transition to the final linewidth a short distance from the SMA
> connector.
>
> Second, you need to cut back that pin to something like two diameters (about
> 0.050"). This also eliminates shunt capacitance at the connector/board
> interface.
>
> Third, you need to cover the exposed crescent of Teflon on the ground plane
> side by using a generous fillet of solder. I can send a PDF file with a
> photo to anyone who is interested.
>
> Ray Waugh
> Agilent Technologies
>
> -----Original Message-----
> From: D_Enos@xxxxxxxxxxxxxxxxxxxxxx
> [mailto:D_Enos@xxxxxxxxxxxxxxxxxxxxxx]
> Sent: Wednesday, July 17, 2002 9:42 AM
> To: ray_waugh@xxxxxxxxxxx
> Cc: si-list@xxxxxxxxxxxxx
> Subject: Re: [SI-LIST] Re: SMA for launching 5-10Gbs signals
>
>
>
> I would be interested in what you mean by properly mounted. We have
> experienced some of the same problems with the edge launch SMAs.
>
>
>
>
> ray_waugh@xxxxxxxxxxx@freelists.org on 07/17/2002 11:15:45 AM
>
> Please respond to ray_waugh@xxxxxxxxxxx
>
> Sent by: si-list-bounce@xxxxxxxxxxxxx
>
>
> To: si-list@xxxxxxxxxxxxx
> cc:
>
> Subject: [SI-LIST] Re: SMA for launching 5-10Gbs signals
>
>
>
>
> My colleagues and I have had great success with the end launch SMA
> connectors, such as the 142-0701-881. Properly mounted, they work very
> nicely to 18 GHz.
>
> Ray Waugh
> Agilent Technologies
>
> -----Original Message-----
> From: zanella, fabrizio [mailto:zanella_fabrizio@xxxxxxx]
> Sent: Wednesday, July 17, 2002 8:49 AM
> To: SI List (E-mail)
> Subject: [SI-LIST] SMA for launching 5-10Gbs signals
>
>
>
> We have test boards which are used for testing the quality of 2-4Gbs
> signals across backplanes. The serial signals can be generated from
> evaluation boards provided by the serdes vendors or signal generators.
> We've been using the Johnson Components surface mount SMA, part number
> 142-0711 on these test boards. One problem is that at times the cable
> pulls
> these SMAs off the boards, including the pads. Another concern is whether
> these SMAs can be used for launching signals at 5-10Gbs.
> Does anyone have suggestions for other SMA types which make a stronger
> connection to test boards and provide a good launch which can be used at
> 5-10Gbs?
> thanks,
>
> Fabrizio Zanella
> Signal Integrity
> EMC Corporation
> fzanella@xxxxxxx
>
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