## Electronics

#### Definition of S,Y,Z matrix in HFSS

• rolsen
Subscriber

I'm using HFSS to calculate S, Y, and Z matrices.  Then I'm trying to extract from these parameters the inductance and capacitance for a microwave circuit with multiple components.  The results I am finding do not make sense.  For instance, I have a circuit which is mainly capacitive, but the components of my Z matrix are all linear, which would mean that the circuit is mostly inductive since Z=i*2 pi f*L.

After consulting a textbook on the topic, I find that I have a basic fundamental question about how HFSS does these calculations. Whenever textbooks discuss S,Y, Z matrices, they are discussed in terms of ports that are defined as a pair of conductors -one the input conductor and another the output conductor.  The outputs for all the ports may be a common ground, but the outputs must still be defined.  Depending on if you're calculating S,Y, or Z, each input/output pair is open, short, or connected by a matched impedance.

In contrast, when I define ports in HFSS, each port is only one conductor.  I assume that these are the inputs, and the outputs are all some common ground?  But what is this common ground?  A perfect conductor at infinity?  Or if there is no common ground, then what are the outputs for all of the ports?  Or are the definitions for these matrices somehow different in ANSYS than in textbooks?