COAXIAL WITH INSULATORS
Kinda new to this. am working on a coaxial model in hfss. manage to get it run and up with results, but problem is my coaxial are model in ssuch that in between the innner and outer cable there would not be totally an air gap but instead bout s smaller portion is filled up by insulative material (gap = air + insulative material). comparing to the model with totally air gap, insertion loss and return loss are bad and i can't control the impedance at 50 ohm (but i'm able to do that with air gap model at that specified dimension). Question is, theoritically would this work? as there are insulative material presents and high F i found that there are still current movements through the insulators from the inner cable to the outer cable. anyone?
regards
L
I can hardly get your point, I think you are trying to make the coaxial cable half filled with a dielectric material. I think this wouldn't work, since the inhomogeneous cross section won't allow for TE and TM modes decomposition, so you will get hybrid modes. for the fundamental TEM mode you would get smaller impedance than that of the air filled. so you may need to adjust the radius of the inner and outer conductor to get a 50 ohms impedance
Caoxial cabes like this does exist in practice. Air is the best dielectric to a coaxial cabes , so in some applications insulattors are used just to keep the inner and outter conductors apart.
These are restricted used because the mechanicals caracteristis, in other words, they are easily damaged.
The most common comercial coaxials cables with high performance has foam as dieletric, foam provide a better mechanical resistance than insulators rings, the foam is noting less than a dieletric with bulbles of air inside, we are back to your issue in a diferent way, but in the same sense , the dieletric is air plus foam.
I dont know how to simulate this in hfss.
To see this cables from manufactures go to www.andrew.com or www.rfsworld.com and welcome to practice.
hi !
If the structure of the foam is far less than the wavelength then it could be treated just as a media with apropriate parameters (eps, tangent..)
If you don't know the parameterts of the foam you have to measure it (feeling it in well known resonator for example)