Powered by Invision Power Board


Forum Rules Forum Rules (please read before posting)
  Reply to this topicStart new topicStart Poll

> What's The Dual Of A Transmission Line?
StevensElectronicAccount
Posted: November 22, 2010 03:15 am
Reply to this postQuote Post


Jr. Member
***

Group: Trusted Members
Posts: 73
Member No.: 31,855
Joined: September 28, 2010




The theoretical model of a transmission line is has parrelel and series resistors, parelel caps and series coils.
Capacitors and coils are sort of dual to each other. Is there any thing in real life that corresponds to the dual of a transmission line which would have series caps and parrelel coils? In other words, is there a use for two dielectric wires seperated by a conductive shield?
P.S. Thanks to the guys which helped with my last question in Theoretical Analog Electronics.
PMEmail Poster
Top
tekwiz
Posted: November 22, 2010 08:01 pm
Reply to this postQuote Post


Forum Addict ++
Group Icon

Group: Moderators
Posts: 28,711
Member No.: 5,746
Joined: July 24, 2006




Balanced audio comes to mind, although balanced lines, audio or RF, are usually not shielded. One reason balanced lines are used is to avoid the need of shielding.
This is possible because the signals in balanced lines are equal & opposite, so effects tend to cancel out.
Every telephone line in the world employs this principle.

BTW: AFAIK, the lumped constant way of looking at balanced transmission lines is only an approximation...in reality the resistance, inductance, & capacitance are continuous throughout.


--------------------
Trouble rather the tiger in his lair, than the sage among his books.
For to you, kings & armies are things mighty & enduring.
To him, mere toys of the moment, to be overturned at the flick of a finger.

Fortuna favet fortibus.
PMEmail Poster
Top
ChipUser
Posted: November 22, 2010 08:39 pm
Reply to this postQuote Post


Forum Addict ++
*******

Group: Trusted Members
Posts: 2,406
Member No.: 15,445
Joined: May 30, 2008




May be he is thinking of more of a waveguide?
PMEmail Poster
Top
CWB
Posted: November 23, 2010 02:27 am
Reply to this postQuote Post


Forum Addict ++
*******

Group: Spamminator Taskforce
Posts: 21,453
Member No.: 15,154
Joined: May 15, 2008




google : "twinax"

balanced lines come in two flavors : shielded and non-shielded .
the shielded types are generally used where :
the impedance is high
the environment is electrically noisy
the signals being shipped are very low in level
immunity to noise injection and crosstalk is a primary concern .

in the case of rf transfer ...
the shielding prevents an unbalanced condition from happening if the line has to run along metal , changes in impedance and loss increases in wet/icing conditions .


--------------------
"Know how to solve every problem that has been solved"
R. Feynman '88
PM
Top
Sch3mat1c
Posted: November 23, 2010 07:31 am
Reply to this postQuote Post


Forum Addict ++
Group Icon

Group: Moderators
Posts: 19,588
Member No.: 73
Joined: July 24, 2002




None of those are appropriate -- a transmission line is low-pass (indeed, it passes DC), whereas the "inverse transmission line" is high-pass.

Article here:
http://mysite.du.edu/~jcalvert/tech/back.htm

Tim


--------------------
Answering questions is a tricky subject to practice. Not due to the difficulty of formulating or locating answers, but due to the human inability of asking the right questions; a skill that, were one to possess, would put them in the "answering" category.
PMEmail PosterUsers Website
Top
StevensElectronicAccount
Posted: November 25, 2010 06:41 am
Reply to this postQuote Post


Jr. Member
***

Group: Trusted Members
Posts: 73
Member No.: 31,855
Joined: September 28, 2010




The picture in the article matches exactly what I was thinking of but the text is really opaque.
I can figure out that what I wanted was a backwards-wave line but I still can't figure out what a backwards-wave line is.
Thanks anyways though.
PMEmail Poster
Top
Sch3mat1c
Posted: November 25, 2010 12:46 pm
Reply to this postQuote Post


Forum Addict ++
Group Icon

Group: Moderators
Posts: 19,588
Member No.: 73
Joined: July 24, 2002




I don't blame you, it's a strange object after all.

It's not really all that strange, because there is another common phenomenon which is highly dispersive: ripples on water. Have you ever noticed how, try as you might, you can't get a square wave on water? It always forms ripples. And if you look closely.... the waves move inward toward the disturbance (phase velocity), while the average position moves outward (group velocity). Crazy stuff!

The text is intimidating, but read it carefully. He tends to explain things cleanly without taking too much liberty between steps. It's the kind of thing that, unless you already know the material, you will simply get confused by scanning it, but if you follow along with a pad of scratch paper, you'll see how it works.

Tim


--------------------
Answering questions is a tricky subject to practice. Not due to the difficulty of formulating or locating answers, but due to the human inability of asking the right questions; a skill that, were one to possess, would put them in the "answering" category.
PMEmail PosterUsers Website
Top
0 User(s) are reading this topic (0 Guests and 0 Anonymous Users)
0 Members:

Topic Options Reply to this topicStart new topicStart Poll

 


:: support us ::




ElectronicsSkin by DutchDork & The-Force