Z0 in HFSS

I simulate a microstrip for calculating the characteristic impedance.

I try to do so by 2 diffrent methods.

1. Is simply by looking at the data matrix at the Z0, (Should be ok, the microsteip is define actually by 2D)

2. With the equation sqrt(B/C) (with 50 ohm ports).

The case is that in the 1st option I gate 53 ohm and in the 2nd way I get 62 ohm .

I sany one can explain why there is diffrent...

Do you have the same structures in 2D and HFSS? fully gnd referenced, and at the same frequency, how did you define your ports?

Make sure you use the proper impedance definition for microstrip i.e. Zp. Please check it in the manual. when you use ABCD matrix, make sure you used the proper length.

what I mean 2D is the port Z0 that the Hfss calculate by the 2D surface of the port,
the ports are wave port with integration line from ground to the strip.

I can eather take ground plan or narrower ground (strip width + 2*higth +2*strip thiickness)

and the resual are almost the same