===Scattering Parameters and Port Characteristics===
<font color="red"><u>'''If your physical structure is excited by a Lumped Source or a Waveguide Source or a Distributed Source, and one or more ports have been defined, the FDTD engine calculates the scattering (S) parameters, impedance (Z) parameters and admittance (Y) parameters of the selected ports.'''</u></font> The S parameters are calculated based on the port impedances specified in the project's "Port Definition". If more than one port has been defined in the project, the FDTD engine runs an internal port sweep. Each port is excited separately with all the other ports turned off. When the ''j''th port is excited, all the S<sub>ij</sub> parameters are calculated together based on the following definition:
[[Image:FDTD82(1).png]]