[SI-LIST] Re: characteristic impedance at DC
- From: mohammad haaeri <haaeri@xxxxxxxxx>
- To: twesterh@xxxxxxxxxx
- Date: Mon, 9 Apr 2012 16:11:19 -0700
Hi Todd,
Is TEM mode a propagating wavefront? Does it have a cutoff frequency? How
much is the characteristic impedance for a TEM mode propagating wavefront
at 1Hz?
On Mon, Apr 9, 2012 at 3:53 PM, Todd Westerhoff <twesterh@xxxxxxxxxx> wrote:
> Mohammad,
>
> Characteristic Impedance (sometimes called surge impedance) is the
> impedance seen by a propagating wavefront. It's been covered at length
> multiple times, including this overview in Wikipedia:
>
> http://en.wikipedia.org/wiki/Characteristic_impedance
>
> DC impedance from a typical transmission line ranges from nil to a few
> ohms, depending on the line geometry and length. It's amenable to direct
> physical measurement in many cases. Here's a device that can be used to
> affordably make such measurements with 4 digits of precision:
>
> http://www.radioshack.com/product/index.jsp?productId!03176
>
> Hope that helps,
>
> Todd.
>
> Todd Westerhoff
> VP, Software Products
>
> Signal Integrity Software Inc. ? www.sisoft.com
> 6 Clock Tower Place ? Suite 250 ? Maynard, MA 01754
> (978) 461-0449 x24 ? twesterh@xxxxxxxxxx
>
>
> ?I want to live like that ?
> -Sidewalk Prophets
>
>
> -----Original Message-----
> From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
> On Behalf Of mohammad haaeri
> Sent: Monday, April 09, 2012 6:31 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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