N-ports are generic components for which characteristics may be defined in the form of user-supplied network-parameter data. They are called black box elements because no information regarding their function is provided except for their network parameters. The network parameters may be supplied as complex scattering parameters (S parameters), complex admittances (Y parameters), complex impedances (Z parameters), complex propagation constants (gamma parameters), or complex terminal characteristic impedances (Z0 parameters). The data may be given in either polar form or in rectangular form.
Generally, the characterizing network parameters are frequency-dependent and is supplied for several frequency points. A common application of this capability is to introduce measured data into the simulation for comparison or modeling, or to represent a part of a circuit for which modeling is difficult or inappropriate. User-supplied network-parameter data may be entered in spreadsheet form or called from external files. This data then may be extracted on the data files and used in the simulation. Three data file formats are supported:
- Touchstone/EESof Data — This format uses the .sNp, .yNp, .zNp, .tou, or .ts file name extension. Only one dataset may be present in each Touchstone data file.
- Circuit (Compact FLP) – This format uses the .flp file name extension, and may contain several data groups, each of which is preceded by a header. The data group header identifies the group by means of a label, which is used as a reference name.
- CITIfile – This format uses the .cit file name extension, and contains S-parameter data in a proprietary format.