Learning Forum

[jure.soklic]

Hello everyone,

Using HFSS, I would like to simulate the radiation of a coaxial cable which typically occurs when the cable is attached to an unbalanced antenna. I would like to do this independent of the antenna itself by only simulating the cable and varying different through different signal levels. Coaxial cable radiation occurs when the current on the outer shield of the cable is not equal in magnitude and opposite in sign to the current on the inner conductor, so a classical wave/lumped port approach cannot be used to observe this phenomena. I have discussed the matter with some Ansys experts but did not find a solution to the problem, so it was suggested to me that I ask in this forum.

I would greatly appreciate any ideas/suggestions regarding this topic.

[Praneeth]

Hi Jure,

I think your problem can be more simplified - do you want to see the fields in a coaxial cable which is terminated by load impedance other than its characteristic impedance? Please correct me if my understanding is not appropriate.

If it is correct then you can simulate a cross section of coaxail cable geometry for a length. Assign lumped ports at both the ends. Chage the port impedance of one port and see the response.

All the very best,
Praneeth.

[jure.soklic]

Hi Praneeth,

Thanks for your reply. Unfortunately, that is not the problem I am trying to solve. An impedance mismatch will cause reflections on the coaxial cable that will result in standing waves, but the current on the shield will still be equal to the current on the inner conductor, just moving in the opposite direction. I need to somehow obtain currents of different magnitude on the two conductors in order to simulate cable radiation.

Cheers,

Jure

[Praneeth]

Hi Jure,

Thank you for providing more information. We would like to know if you are trying to see the shielding effect on the cable or analyzing the cable radiation for an unbalanced antenna. This will help us to serve you better.

Best regards,
Praneeth.

[jure.soklic]

Hi,

I would like to analyze the cable radiation for an unbalanced antenna. However, I would like to do this without actually including the antenna in the simulation in order to be able to tell apart the radiation contributions of the cable and the antenna and obtain their corresponding spherical wave coefficients.

Best regards,

Jure

[Nathan D]

I would also love to know how to do this.