RE: [SI-LIST] : SMA launch

About this list Date view Thread view Subject view Author view

From: Patel, Bhavesh (bpatel@ciena.com)
Date: Mon Jun 04 2001 - 11:18:43 PDT


Hi! I had a question, is this impdeance drop seen using a TDR? If yes then
it is the impdeance mismatch caused by the SMA cable & the SMA connector on
the board. I don't have a solution for the SMA but if you are ineterseted in
looking at some signals using SMA then you could use a TDR probe head to
launch your signal and this will give much better impedance matching then
SMA.
Hope I did not confuse the matter.
Bhavesh

-----Original Message-----
From: Michael Allen [mailto:mallen@teraconnect.com]
Sent: Monday, June 04, 2001 10:45 AM
To: si-list@silab.eng.sun.com
Subject: [SI-LIST] : SMA launch

Group,
        I have a problem here we are trying to launch an SMA connection
inside a multilayer PC board. I have found that the 50 ohm impedance of
the board drops to around 28 ohms. I have discovered that the power and
ground layers around the through hole via are minimum distance from the
via barrel. This can account for some of the impedance reduction due to
the capacitive coupling of the barrel to the power and ground planes.
Does anyone have other suggestions as to how to increase this impedance
to near 50 ohms. These lines are all striplines by the way so even in
the launch area I need a plane above and below the signal. Now, should
these planes also be pulled back from the barrel but that would cause a
discontinuity in the signal. I realize that this is a complex problem
and that there may be many different solutions. Thank you in advance.

Mike Allen
mallen@teraconnect.com

**** To unsubscribe from si-list or si-list-digest: send e-mail to
majordomo@silab.eng.sun.com. In the BODY of message put: UNSUBSCRIBE
si-list or UNSUBSCRIBE si-list-digest, for more help, put HELP.
si-list archives are accessible at http://www.qsl.net/wb6tpu
****

**** To unsubscribe from si-list or si-list-digest: send e-mail to
majordomo@silab.eng.sun.com. In the BODY of message put: UNSUBSCRIBE
si-list or UNSUBSCRIBE si-list-digest, for more help, put HELP.
si-list archives are accessible at http://www.qsl.net/wb6tpu
****


About this list Date view Thread view Subject view Author view

This archive was generated by hypermail 2b29 : Thu Jun 21 2001 - 10:12:14 PDT