Unite two object in HFSS

you can't unite a surface with solid, your patch should be with certain thickness.

Thank you for your response
I'm designing a simple micro-strip antenna with coaxial feed.As you see in this project it shows me 3D error.I did the way that this topic mentioned https://www.edaboard.com/thread48031.html
what are my problems?
Project2.zip

you should know that intersection between solids is prohibited. you should modify the dimensions or subtract the substrate from the coaxial.

Thanks
In real we punch the inner core of coaxial cable to patch and it is common that we have intersection between inner core and substrate. but it shows me "[error] Objects "Substarte" and "CoaxIn" intersect.".
and for simulate the coaxial cable we should draw three cylindrical shape?(inner core material is PEC , second cylindrical shape is vaccum and the last one should be PEC?)

yes your whole coaxial should not intersect the substrate even the vacuum and the inner.