#### arthury

##### Junior Member level 1

**simulation of microstrip transmission line hfss**

Hi everyone:

I am working on a minor study of microstrip simulation in HFSS.

I created a model of a microstrip line and add 2 waveports as the excitations .

In the results it shows the port Z0=59ohm@40GHz. the length of the microstrip is set to 2.5mm

The strange thing is about the S matrix data:

S11=-0.58+j0.34 and S21=0.092+j0.26

If i did not consider in a wrong way, S11 should be 0 and S21 should be 1, since the waveport is supposed to simulate the same microstrip line when it is connected tomy microstrip line. And the structure should have no reflections at the input and the output.

I saw some similar discussions on this site but still can not figure out where is the problem. Am I thinking wrongly? Why the S11 is a non-zero value

Btw: from the result I could also find the complex propagation constant Gamma. And according to my previous reading, the real part is the attenuation constant Alapha and the imaginary part is the propagation constant from which I could extract the effective dielectric constant of the transmission line. These two data match the results I get from another simple microstrip transmission line calculator: TXline.exe.

Thanks in advance