RE: [SI-LIST] : Oscillation in lumped circuits and transmission l

Peterson, James F (jfpeterson@space.honeywell.com)
Fri, 5 Feb 1999 13:04:17 -0500

Dima,
There is a link between equations (good point), but the Pd also has to be
multiplied by overall length in the reflection equation (then divide by 4)
to establish reflection period.
thanks,
Jim

-----Original Message-----
From: Dima Smolyansky [mailto:dima@easystreet.com]
Sent: Friday, February 05, 1999 12:08 PM
To: Peterson, James F (FL51); si-list@silab.Eng.Sun.COM
Subject: Re: [SI-LIST] : Oscillation in lumped circuits and transmission
l ines

Although, it could be noted that the propagation delay of a transmission
line Pd is related to L and C as
Pd = (LC)^1/2. In addition, the factor of 2*pi is just a conversion between
linear and angular frequency, and therefore for even-handed comparison must
be dropped. Then, the factor of 4 is apparently due to assumption of quarter
wavelength oscillation. But then, there will be a similar high-order
oscillation for an LC circuit. I think this implies good correlation between
the two models. The choice between the two comes down to a standard
lumped-distributed type analysis.

Hope this helps.

--
Thanks,

-Dima

========================= Dima Smolyansky TDA Systems, Inc. 7465 SW Elmwood St. Portland OR 97223 503-977-3629 503-245-5684 (FAX) dima@tdasystems.com http://www.tdasystems.com

Peterson, James F (FL51) wrote:

> Good question Arani, > I have often wondered the same thing (every time someone uses the term > ringing and reflection to describe the same phenomenon). The more I study > the SI area of engineering the more I notice that people can be describing > things differently based on different perspectives but still be correct. > That said, I believe that a lumped LRC circuit's behavior is not related to > a transmission line reflection. One good reason is that the period of the > lumped circuit's oscillation will be 2*pi*(LC)^1/2, whereas the period of a > reflection will always be 4*Pd (where Pd is the 1 way prop. time of the > signal). In fact this is a great way to tell the difference. If the period > of a measured signal is much larger than 4 * Pd, then it's a lumped LRC > problem (add some series r to get rid of it). > Hope this helps, > Jim > > > -----Original Message----- > From: Arani Sinha [mailto:sinha@poisson.usc.edu] > Sent: Friday, February 05, 1999 3:02 AM > To: si-list@silab.Eng.Sun.COM > Cc: sinha@poisson.usc.edu > Subject: [SI-LIST] : Oscillation in lumped circuits and transmission > lines > > Hi, > > I have the following question. > > We can model an interconnect as either a lumped circuit or a > transmission line. By means of lumped modeling, we can say that > it has an oscillatory response if its damping factor is less > than 1. By means of transmission line modeling, we can say that > it has an oscillatory response if the signal reflection > co-efficients at source and load satisfy certain conditions. > > My question is whether oscillation in a lumped circuit and > signal reflection in a transmission line are actually the same > phenomenon. If so, there should be a correlation between > conditions for oscillation in a lumped circuit and those for > oscillation in a transmission line. > > After many discussions and much thought, I have not been able > to determine a correlation. I am also ambivalent about whether > they are the same phenomenon. > > I understand that the damping factor in a lumped circuit is > equivalent to the attenuation constant in a transmission line > and that condition of no reflection is equivalent to the > maximum power transfer theorem. > > I will really appreciate help in this regard. > > Thanks, > > Arani > > **** To unsubscribe from si-list: send e-mail to > majordomo@silab.eng.sun.com. In the BODY of message put: UNSUBSCRIBE > si-list, for more help, put HELP. si-list archives are accessible at > http://www.qsl.net/wb6tpu/si-list **** > > **** To unsubscribe from si-list: send e-mail to majordomo@silab.eng.sun.com. In the BODY of message put: UNSUBSCRIBE si-list, for more help, put HELP. si-list archives are accessible at http://www.qsl.net/wb6tpu/si-list ****

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