Is it a Microstrip? Help.

Hello people.
I found recently for the first time a different kind of transmission line.
It is composed of a flat conductor passing over a ground plane. Just line a microstrip line but without the substrate.

My question: Can I use the normal standard formulas for microstrip design (setting epsylon to 1) to find the impedance of this type of transmission line?

The parammeters of my transmission line are W=2mm and h=4mm.

I tryed design formulas for microstrip and for suspended substrate microstrip and found an impedance of about 160 ohms. Is that right?

Greetings to all.

S.

Ps: Normally the microstrip formulas are made in such a way that they work without substrate. This allows comparison of standard microstrips with the special case (my case) where epsylon is equal to 1 (the only case where there is a closed formula according to one of the famous articles of Hammerstad). Am I right?

Yes, this is ordinary microstrip. It has the special feature that all of the parameters are independent of frequency until the radiation and modes start in.

Thank you Flatulent.
That is good. The results are then valid.
The bad part is that I expected to have 50 ohms in the place where I found this transmission line and in fact I have 160. Bad news.
But this missmatch will be "absorbed" by the component itself. I fond all this inside of a circulator, and since the circulator is a resonating component (only works for a very limited bandwidth) I believe this inductance was already tuned out when the circulator was adjusted/tuned.
Thanks again Flatulent.

S.

Hello Sinatra;
I advise you to check your results by use of a microwave analysis software.

yes the Z0 is correct if you need 50 ohm you must use W=19.6mm for the same H=4mm

Is this the air microstrip line? Like the air microstrip antenna

Yes, this configurarton is used to eliminate the dielectric loss. I am not sure that it will also get rid of the surface wave or not.