[SI-LIST] Fw: Transmission line impedance is related to signal switching frequency ?
- From: "Pang Ning" <pangning2000@xxxxxxxxx>
- To: <itasup@xxxxxx>
- Date: Tue, 25 Jan 2005 17:35:04 +0800
Dear Giancarlo,
Appreciate your reply. I agreed with you that the dielectric constant is a
important parameter to calculate impedance. Do you mean the frequency will
impact the value of dielectric constant or dielectic constant will change with
variable frequency? I really don't know it before.
Thanks,
Best Regards,
Peter Pang
MacroSynergy Technology Co., Ltd.
+86-21-54258855 Ext. 8219
-----Original Message-----
From: Giancarlo Guida [mailto:itasup@xxxxxx]
Sent: Tuesday, January 25, 2005 5:15 PM
To: pangning2000@xxxxxxxxx; si-list@xxxxxxxxxxxxx
Cc: Pang Ning(Peter)
Subject: Re: [SI-LIST] Transmission line impedance is related to signal
switching frequency ?
Hi Pang,
the charateristic impedance depends on the permittivity of the substrate.
This quantity depends on the frequency and this a way for the Z0 to depends
on the frequency.
I would say that at 1.25 Ghz this effect could be not so big
so I am surprised that the PCB manufact cannot control the impedance
Giancarlo
________________________
----- Original Message -----
From: "Pang Ning" <pangning2000@xxxxxxxxx>
To: <si-list@xxxxxxxxxxxxx>
Cc: <peter_pang@xxxxxxxxxxxxxxxx>
Sent: Tuesday, January 25, 2005 10:11 AM
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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