[SI-LIST] Re: characteristic impedance at DC

Characteristic impedance applies to propagating EM waves, so it does not apply 
to DC. 

Or, if you look at the general equation that you cited, you can see that when 
jw = 0, the impedance approaches the line resistance. Somewhere in college I 
remember seeing a graph of the general impedance equation compared to actual 
measurement at low frequency. They are the same above some kHz, but diverge as 
frequency decreases.

Weston


-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On 
Behalf Of mohammad haaeri
Sent: Monday, April 09, 2012 3:31 PM
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] characteristic impedance at DC

Hi,
What is the characteristic impedance of a transmission line at DC? If you are 
saying Z0=sqrt(Rdc/Gdc) at DC, since Gdc=0, and Rdc is not zero, therefore Z0 
is infinite. Is it correct?

How does behavior of L, R, G, and C (line parameters) change vs. frequency (at 
low and DC, and at very high frequency)?

Can Z0=sqrt(R+jwl/G+jwc) be used for all frequencies?

Thanks,
mohammad


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