From pgilliland@methode.com Thu Dec 2 01:20:18 1999 Received: from ruebert.ieee.org (ruebert.ieee.org [199.172.136.3]) by gatekeeper.pdd.3com.com (8.9.1/8.9.1) with ESMTP id BAA00845; Thu, 2 Dec 1999 01:20:16 GMT Received: by ruebert.ieee.org (8.9.3/8.9.3) id QAA23030; Wed, 1 Dec 1999 16:56:09 -0500 (EST) Message-Id: <3.0.5.32.19991201155134.008e65d0@mail0.methode.com> X-Sender: pgilliland@mail0.methode.com X-Mailer: QUALCOMM Windows Eudora Light Version 3.0.5 (32) Date: Wed, 01 Dec 1999 15:51:34 -0600 To: stds-802-3-hssg@majordomo.ieee.org From: Patrick Gilliland Subject: Traces of.....PCBs Mime-Version: 1.0 Sender: owner-stds-802-3-hssg@ieee.org Precedence: bulk X-Resent-To: Multiple Recipients X-Listname: stds-802-3-hssg X-Info: [Un]Subscribe requests to majordomo@majordomo.ieee.org X-Moderator-Address: stds-802-3-hssg-approval@majordomo.ieee.org X-Lines: 40 Status: RO Content-Type: text/plain; charset="us-ascii" Content-Length: 1242 Larry, Forget the impedance matching, there are radiative losses associated with the microstrip gemoetry (copper trace over ground plane) most PCB designers are using which do limit the usable distances to a few inches at these frequencies. One improvement is to use buried stripline. In this transmission line geometry, the radiative losses are greatly reduced. The ground plane-copper trace-ground plane construction confines the fields in a much smaller cross section. However, 4-5 inches in FR-4 is still a very long distance even at 3.125 X 0.7 = 2.2Ghz. Best Regards, Pat Gilliland patgil@methode.com ---------------------------------------------------------- How long of traces are you getting on FR-4? Have you actually fabricated these? Our network analyzer tests indicate that FR-4 dies horribly (lossy) above about 1.5 Gb/s. By the time we get to 3 GHz all the analyzer is displaying is the analyzer receiver input noise, looking in vain for signals...... (HP8752C) Your Tricks & Tips look like they would help, but I would be very interested in hearing from anyone who claims to have successfully used FR-4 in 5+ GHz circuits over more than 3-4 inches and, if so, what kind of signals. Thanks, Larry Miller