=== Defining S-Parameters ===
Each multiport network device has a property dialog where you can specify its S-[[parameters]] as a function of frequency. Each row of the S-parameter table in the property dialog represents a frequency sample. The complex-valued elements of the scattering matrix are listed column by column in each row of the table after the frequency value. For example, for a two-port, the format is as follows:
Freq Real(s11) Imag(s11) Real(s21) Imag(s21) Real(s12) Imag(s12) Real(s22) Imag(s22)
Among [[RF.Spice]]'s multiport network device, the one-port, two-port, three-port and four-port are all defined based on their S-[[parameters]]. All multiport network devices have a "Port Reference Impedance" parameter. The default value of the reference impedance is 50 Ohms for the one-port, two-port, three-port and four-port. For most RF circuits, you do not have to touch the 50Ω default value.
Besides entering the S-parameter values manually using in the parameter table, you can directly import these values from a text file with a ".TXT" file extension. For this purpose, click the button labeled "Load from File..." in the property dialog. This opens up the standard [[Windows]] Open dialog, with the file type set to text files. Browse your folders and select the text file to load the data from. The S-[[parameters]] you import to [[RF.Spice]] can come from manufacturer data sheets or they can be generated by electromagnetic simulation suites such as [[EM.Cube]]. For example, among [[EM.Cube]]'s computational modules, the FDTD, Planar MoM, Wire MoM and Surface MoM simulation engines all generate S-parameter text files for structures with port definitions. These files can directly be loaded into [[RF.Spice]].
===The Complex Impedance Device ===