I have a customer who has a part data sheet that specifies 75ohm
impedance on Diff.Pair lines. The data sheet states that *trace
separation*
should be considered when calculating impedance!? The particulars
are as
follows: Embedded Microstrip <- this is my assumption
	 data rate - 1 gigabit/s
	 Mtl. - FR4
	 8 layer board

-----------  trace outer(no copper will be allowed over special
sig.s)
-----------  impedance routing layer 6 mil trace/? space <- this is
my assumption
   10mils
-----------  ref. plane
-----------  trace inner
-----------  trace inner
-----------  ref. plane
   10mils
-----------  impedance routing layer 6 mil trace/? space <- this is
my assumption
-----------  trace outer(no copper will be allowed under special
sig.s)

Can anyone help? Is this achievable? Please let me know if there is
any more
info. needed.

	Regards,

	Charles Emory, Sr. Designer/Web-master
	Interconnect Design Services
	6855 Jimmy Carter Blvd.
	Suite 2890
	Norcross, Ga. 30071

	Email: [log in to unmask]
	Ftp  : idspwbs.com (call for login and password)
	WWW  : www.idspwbs.com

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