SPICE-based mixed-mode S-parameter calculations for four-port and three-port circuits

Mixed-mode s-parameters assist in the design and characterization of four-port and three-port differential RF/microwave circuits. A new method for extracting mixed-mode s-parameters for four-port and three-port circuits modeled with SPICE is presented in which the s-parameters are extracted from node voltages. This method is efficient for circuits that are designed in SPICE and is free from any assumptions or approximations. Furthermore, this method provides valuable information on the relationships between the extracted mixed-mode s-parameters and the circuit's operation. This method is verified for a differential transformer circuit.