Thread Links Date Links
Thread Prev Thread Next Thread Index Date Prev Date Next Date Index

RE: XAUI electrical issues

I normally observe the discussion on this reflector. But I cannot help
reacting to this "measurement" issue. Mr. Greiss is using terms like "DC
Impedance" which cause chills to run over my backbone. I strongly recommend
to use (source/load and/or cable) return loss as a qualifying parameter.
Return loss parameters can be measured directly. The measurement of
characteristic impedance is a major issue, and I do not think you want
specify parameters which you cannot verify. Mr. Kesling is correct.

Henriecus ("Henri" or "Riekus") Koeman
Fluke Networks
P.O. Box 9090
Everett, WA 98206

		-----Original Message-----
		From:	Israel Greiss [mailto:israelg@xxxxxxxxxxxx]
		Sent:	Sunday, September 24, 2000 7:29 AM
		To:	'Kesling, Dawson W'; 'stds-802-3-hssg@xxxxxxxx'
		Subject:	RE: XAUI electrical issues

		DC "impedance" is not defined well. You probably want to say
that DC
		resistance can not be measured. The impedance at the
required frequency
		range of the traces is needed in order to define the return
		requirement. For trace impedance of 100 ohm +/- 10 ohm as
defined in the
		draft, receiver impedance of 80-120 ohm can be used in order
to meet the 10
		dB return loss requirement. There is no contradiction
between the two and
		the impedance can be measured even if the capacitors are
integrated in the
		chip, however I agree that the receiver impedance
requirement is not
		necessary as long as the trace impedance tolerance is
		Israel Greiss,   Chief Technology Officer, MystiCom Ltd.
		P.O. Box 8364,      Netanya 42504,          Israel
		Tel: 972-9-8636450	            FAX: 972-9-8636466

		-----Original Message-----
		From: Kesling, Dawson W [mailto:dawson.w.kesling@xxxxxxxxx]
		Sent: Friday, September 22, 2000 12:57 AM
		To: 'stds-802-3-hssg@xxxxxxxx'
		Subject: XAUI electrical issues

		2. Both transmitter and receive impedances are defined by
the 10 dB return
		loss requirement. There does not appear to be a need to
define DC
		"impedance" as 100 ohms since a) it contradicts the return
loss requirement
		due to normal parasitic capacitances and b) it is not
directly measurable if
		AC coupling capacitors and resistive terminations are both
integrated into
		an IC.
		Dawson Kesling
		Intel Corporation
		916 855-5000 ext. 1273