[SI-LIST] Re: Amplitude loss ?
- From: "Yuriy Shlepnev" <shlepnev@xxxxxxxxxxxxx>
- To: "'rajneesh shukla'" <rajneeshs123@xxxxxxxxx>, "'steve weir'" <weirsi@xxxxxxxxxx>
- Date: Fri, 6 Jan 2012 08:56:30 -0800
Rajneesh,
Steve and Wolfgang explained the high-frequency behavior of the transmission
line very well.
Though, I would like to add that the outcome you expect is actually correct
at DC or at very low frequencies in case if dielectric does not have
conductive losses (only polarization).
Transmission line can be considered as a lumped structure at DC and all
voltages and currents can be simply computed with Ohm's low. Both TDR
response and S-parameters should converge to the values defined by Ohm's low
at low frequencies when t-line is electrically small. Electrically long
transmission line behavior (line segment length is a fraction of wavelength)
is governed by Telegrapher's equations in addition to Ohm's low at the
boundaries (or Maxwell's equations if t-line cross-section is not
electrically small). In that case, a pulse response may reach the voltage
defined by the DC solution or may not. It depends on pulse length, spectral
content, line length and so on - only simulation can provide the answer.
Best regards,
Yuriy
Yuriy Shlepnev, Ph.D.
President, Simberian Inc.
3030 S Torrey Pines Dr. Las Vegas, NV 89146, USA
Office +1-702-876-2882
Cell +1-206-409-2368
Skype: shlepnev
www.simberian.com
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On
Behalf Of rajneesh shukla
Sent: Friday, January 06, 2012 3:14 AM
To: steve weir
Cc: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: Amplitude loss ?
Thanks Steve but question remains unanswered !!
I agree there will be a loss in energy due to dielectric loss but I was
talking about loss in amplitude of signal (voltage) not loss in total
energy, Energy loss does not always translates into voltage loss, right ?
Receiver senses voltage( Potential Energy per unit charge) not total energy.
As per basic circuit theory, If I have a driver that has zero o/p impedance
is driving a 50 Ohm load and now if I connect 100 Ohm resistance across this
load, Though there is energy loss due to 100 ohm resistance but still my
load will see the same voltage, agree ?
In transmission line, If series loss i.e. conductor loss is zero then I
don't find the reason of any voltage drop in transmission line coz
dielectric loss which is shunt loss can only dissipate total energy but
can't change amplitude(voltage) of signal.
Do you find any discrepancy in this analogy ?
On Fri, Jan 6, 2012 at 2:40 PM, steve weir <weirsi@xxxxxxxxxx> wrote:
> Follow the energy. Achieve enlightenment. Of the energy that a shunt
> draws, how much of that energy remains available to the signal?
>
> Steve.
> On 1/6/2012 12:54 AM, rajneesh shukla wrote:
> > Experts,
> > As we know for perfectly matched line insertion loss is due to
> > ohmic& dielctric losses and due to these losses we see loss in
> > rise/fall time as well as loss in amplitude of signal.
> >
> > My question is what actually affects amplitude loss, is it ohmic
> > loss or dielectric loss ? My understanding says, it should be ohmic
> > loss as it comes in series coz dielectric one is shunt loss. If this
> > analogy is correct then a channel having very low ohmic loss but
> > significant dielectric loss will have only changes in rise time but
> > minimal amplitude loss, right ??
> >
> > Rajneesh
> >
> >
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