[SI-LIST] Re: Transmission line impedance is related to signal switching frequency ?
- From: "Doug Hopperstad" <doug.hopperstad@xxxxxxxxxx>
- To: <pangning2000@xxxxxxxxx>, <si-list@xxxxxxxxxxxxx>
- Date: Tue, 15 Mar 2005 15:05:15 -0600
Hi Peter,
The quick answer is that the dielectric constant will change slightly
with higher frequencies. What type of board material are you using in
the design? You can contact (or look on the web) for the board material
vendor specifications for the Dielectric constant versus frequency.=20
Hope this helps.
Douglas Hopperstad
QLogic Corporation - Switch Products Group
Staff/Signal Integrity Engineer
(voice) 952-932-4007
(cell) 612-203-3822
(fax) 952-932-4037
doug.hoppperstad@xxxxxxxxxx
=20
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
On Behalf Of Pang Ning
Sent: Tuesday, January 25, 2005 3:12 AM
To: si-list@xxxxxxxxxxxxx
Cc: peter_pang@xxxxxxxxxxxxxxxx
Subject: [SI-LIST] Transmission line impedance is related to signal
switching frequency ?
Dear all,
I have a confusion about the PCB transmission line impedance. As I knew
before, the transmission line impedance depends on the square root of
L/C. That is to say, signal switching frequency will not impact
transimission line impedance.
But just now one famous PCB manufacturer informed me that they can't
control differential pair impedance to 100ohm at the 1.25GHz frequency.
I felt confused about the frequency will impact transmission line
impedance. Does anybody can give me some idea about this question?
Thanks a lot!
Best Regards,
Peter Pang
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