An ideal bias t is a combination of a DC block and a DC feed (fig. 9.1). During DC simulation the MNA matrix of an ideal bias t writes as follows:
The MNA entries of the bias t during AC analysis write as follows.
The scattering parameters writes as follows.
A bias t is noise free. A model for transient simulation does not exist. It is common practice to model it as an inductor and a capacitance with finite values which are entered by the user.