FreeLists / si-list / [SI-LIST] Re: Measuring high speed signals

["Brent DeWitt" <bdewitt@xxxxxxxxxxxxx>]

One suggestion would be to use the 50 ohm coax/SMA, but to build it with a
10 to 20dB pad very close to the connection point.  One of the MiniCircuits
devices or hand built might work.  You still have to account for 50 ohms to
ground at the attachment point, but the rest of the scope system should have
limited effect.

Best of luck....

Brent DeWitt


-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx
[mailto:si-list-bounce@xxxxxxxxxxxxx]On Behalf Of Alex Horvath
Sent: Monday, June 11, 2001 11:00 AM
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Measuring high speed signals



I'm looking for some techniques for probing differential signals 1 Gig and
above. I could use a differential probe but the one I have has no easy way
to connect to the board other than physically holding it which is not
acceptable. On the other hand I could use 50 Ohm coax with a SMA connection
except then the scope circuit becomes part of the PCB circuit. In some of
the papers at teradyne.com, they say they use an SMA connection in
conjunction with resistors to provide some isolation. Anyone have any
suggestions or know what circuit they are using to provide isolation?


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