CST : How to simulate a coaxial cable properly

Dear all,

I'm trying to do some measurement of coaxial cable on CST.
I found out that if i change the backgrounds conditions or simply the background material, results will be completely different.

I want to simulate a coaxial cable with these dimensions :
-inner conductor outer diameter : 1.52 mm
-outer conductor inner diameter : 3.5 mm

The inner conductor is PEC , the outer conductor is PEC , the dielectric is AIR.
The frequency range is 1 - 32 GHZ.


I'm using these settings:
- waveguide ports on the faces of the dielectric
- Time domain solver ( using the default settings )
- Background material : Normal ( without changing any properties )
- Boundary conditions : Open add space on every plane.


The problem is that if i change one of the setting above, i'll achieve different resaults.
So, could you explain me how to simulate this coaxial in the right way?

Thank you in advice :shock::shock::shock:

- - - Updated - - -

...
Using the time domain solver I also see differences if i simulate in the frequency range 0 - 32 GHz or 1 - 32 GHz, (so, including or not the 0 ) and it was totally unexpected from me.
I really need your help.
...

Hi

CST takes center frequency for meshing. so if you are using 0-32 GHz it takes 16 GHz for meshing, if you use 1-32 Ghz it takes 16.5 GHz as meshing frequency.You shouldn't change background material if you are gonna use it in vacuum space or in air(not submerged in water,sand or closed in a metal box,dielectric.) You should use big waveguide ports(like 4-5x of the diameter of coaxial cable) Reducing the range of frequency is also better for simulation(CST takes linearly 1001 samples between frequencies as default). Also use air as a material between inner and outer conductor.