[SI-LIST] Re: impedance and Characteristic impedance

If I read Raj's question correctly, he is asking a question many of us
have asked :

How can the impedance for a transmission line be so independent of
frequency when normal circuit impedance is so extremely dependent on
frequency?

If you look into the telegrapher's equations you will see the derivation
of t-line impedances...this shows a logical, yet hard to understand,
trail to our familiar equation for the Z of a t-line.

Jim Peterson
Honeywell

-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
On Behalf Of Tom Dagostino
Sent: Wednesday, March 21, 2007 12:34 AM
To: nagaup1@xxxxxxxxx; 'si-list'
Subject: [SI-LIST] Re: impedance and Characteristic impedance

Zo =3D3D SQRT(2PiFL/2PiFC).  Yes there are terms for resistance and =3D
conductance
too but for this we can ignore them.  The frequency dependence drops out
=3D
so
Z0 =3D3D SQRT(L/C).  L and C can be functions of frequency but that is =
=3D
minor
compared to their magnitudes for most frequencies in most applications.

Tom Dagostino
Teraspeed(R) Labs
13610 SW Harness Lane
Beaverton, OR 97008
503-430-1065
tom@xxxxxxxxxxxxx=3D20
www.teraspeed.com=3D20

Teraspeed Consulting Group LLC
121 North River Drive
Narragansett, RI 02882
401-284-1827

-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
=3D
On
Behalf Of nagaraj
Sent: Tuesday, March 20, 2007 9:04 PM
To: si-list
Subject: [SI-LIST] impedance and Characteristic impedance



When I say impedance, it depends on the
capacitance and inductance. So, these two components depend on frequency
=3D
(wL
and 1/wC, where w=3D3D 2xpixF).




When I say characteristic impedance, it too
has capacitance and inductance involved. So when I say I maintain 50 ohm
characteristic impedance on my board... there may be lot of frequencies
involved in the design resulting in different characteristic impedance.
=3D
then
how the board is said as a 50 ohm impedance controlled..? =3D20


=3D20


=3D20


Thanks and regards,


Raj.






=3D20
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_=3D
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________
The fish are biting.=3D20
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