An Efficient Scheme for Processing Arbitrary Lumped Multiport Devices in the Finite-Difference Time-Domain Method

Developing full-wave simulators for high-frequency circuit simulation is a topic many researchers have investigated. Generally speaking, methods invoking analytic pre-processing of the device's $V{\hbox{–}}I$ relations (admittance or impedance) are computationally more efficient than methods employing a numerical procedure to iteratively process the device at each time step. For circuits providing complex functionality, two-port or possibly multiport devices whether passive or active, are sure to appear in the circuits. Therefore, extensions to currently available full-wave methods for handling one-port devices to process multiport devices would be useful for hybrid microwave circuit designs. In this paper, an efficient scheme for processing arbitrary multiport devices in the FDTD method is proposed. The device's admittance is analytically pre-processed and fitted into one grid cell. With an improved time-stepping expression, the computation efficiency is further increased. Multiport devices in the circuit can be systematically incorporated and analyzed in a full-wave manner. The accuracy of the proposed method is verified by comparison with results from the equivalent current–source method and is numerically stable.