Discussion Closed This discussion was created more than 6 months ago and has been closed. To start a new discussion with a link back to this one, click here.

How to model a coaxial cable in AC/DC electrical circuit interface?

Please login with a confirmed email address before reporting spam

Hi everyone,

I' am modeling a configuration of two devices which are connected by a coaxial cable. My model includes both Electrical Currents and Electrical Circuits interfaces: The only problem is the connection between them, I cannot find a "coaxial cable" tool in Electrical circuit interface.

Has anyone been faced with such a task? Many thanks in advance!

-------------------
Sh.Arakelyan

5 Replies Last Post 26 Dec 2018, 21:04 GMT-5
Edgar J. Kaiser Certified Consultant

Please login with a confirmed email address before reporting spam

Posted: 11 months ago 19 Dec 2018, 05:14 GMT-5

Hi,

in the context of AC/DC the coaxial cable can be replaced by the equivalent circuit. This is a series inductor, series resistor and parallel capacitors. The coaxial cable must be much shorter than any wavelength in the model.

Cheers Edgar

-------------------
Edgar J. Kaiser
emPhys Physical Technology
www.emphys.com
Hi, in the context of AC/DC the coaxial cable can be replaced by the equivalent circuit. This is a series inductor, series resistor and parallel capacitors. The coaxial cable must be much shorter than any wavelength in the model. Cheers Edgar

Please login with a confirmed email address before reporting spam

Posted: 11 months ago 20 Dec 2018, 20:00 GMT-5

Hi,

in the context of AC/DC the coaxial cable can be replaced by the equivalent circuit. This is a series inductor, series resistor and parallel capacitors. The coaxial cable must be much shorter than any wavelength in the model.

Cheers Edgar

Thanks for your comment Mr. J. Kaiser,

the approach proposed by you is very rough approximation for my task, since I investigate the effect of coaxial cable length. Regards Shant

-------------------
Sh.Arakelyan
>Hi, > >in the context of AC/DC the coaxial cable can be replaced by the equivalent circuit. This is a series inductor, series resistor and parallel capacitors. The coaxial cable must be much shorter than any wavelength in the model. > >Cheers >Edgar Thanks for your comment Mr. J. Kaiser, the approach proposed by you is very rough approximation for my task, since I investigate the effect of coaxial cable length. Regards Shant

Edgar J. Kaiser Certified Consultant

Please login with a confirmed email address before reporting spam

Posted: 11 months ago 21 Dec 2018, 04:45 GMT-5

I would say, it depends. The equivalent parameters depend on the length, e.g. the capacitance for a typical 50 Ohm cable is 90 pF/m. The equivalent circuit can be good enough as long as the wavelength of the signal is much larger than the cable length. If the cable length gets longer than lambda/10 (this limit depends on the accuracy requirements) and you have to take transmission line effects into account you need a different approach.

-------------------
Edgar J. Kaiser
emPhys Physical Technology
www.emphys.com
I would say, it depends. The equivalent parameters depend on the length, e.g. the capacitance for a typical 50 Ohm cable is 90 pF/m. The equivalent circuit can be good enough as long as the wavelength of the signal is much larger than the cable length. If the cable length gets longer than lambda/10 (this limit depends on the accuracy requirements) and you have to take transmission line effects into account you need a different approach.

Dave Greve Certified Consultant

Please login with a confirmed email address before reporting spam

Posted: 11 months ago 21 Dec 2018, 14:10 GMT-5

Modeling the coaxial cable with several lumps per wavelength will provide a good approximation. For "several"- four is enough, eight better, more probably not necessary. Most accurate will be to use T or pi sections.

D.W. Greve DWGreve Consulting

Modeling the coaxial cable with several lumps per wavelength will provide a good approximation. For "several"- four is enough, eight better, more probably not necessary. Most accurate will be to use T or pi sections. D.W. Greve DWGreve Consulting

Please login with a confirmed email address before reporting spam

Posted: 11 months ago 26 Dec 2018, 21:04 GMT-5
Updated: 11 months ago 27 Dec 2018, 02:00 GMT-5

Thanks a lot, for your valuable comments.

-------------------
Sh.Arakelyan
Thanks a lot, for your valuable comments.

Note that while COMSOL employees may participate in the discussion forum, COMSOL® software users who are on-subscription should submit their questions via the Support Center for a more comprehensive response from the Technical Support team.