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

Abstract

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-I relations (admittance or impedance) are computationally more efficient than methods employing numerical procedure to iteratively process the device at each time step. For circuits providing complex functionality, two-port or possibly multi-port 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 multi-port devices would be useful for hybrid microwave circuit designs. In this dissertation, an efficient scheme for processing arbitrary multi-port devices in the finite-difference time-domain (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.Multi-port 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.iii

Hybrid field-circuit simulation based on the extended time-domain finite element method

“…The computed results of the magnitude of S 11 are shown in Fig. 2, which agree well with those computed by a FDTD scheme [8] and the deviation from those of HP ADS is due to the lack of the full-wave capability of ADS.…”

“…1 with good agreement with the results computed by other methods [4]- [7]. We then simulate a microwave FET amplifier circuit which consists of a generic FET mounted over a microstrip gap whose configuration and dimensions and a small-signal extrinsic equivalent circuit model of the FET are given in [8]. The VECTFIT technique is invoked to obtain the poles and residues numerically based on the frequency samples of [Y LN (s)], which is then cast into a two-port four-pole lumpednetwork subsystem and hybridized with the FEM and circuit subsystems.…”

“…Finally, a global system of equations for only the FEM and circuit unknowns can be formed by coupling the FEM and modified circuit subsystems following the scheme described earlier. All the lumpednetwork port variables can be eliminated by utilizing (7) and (8) and by enforcing the voltage continuity across the lumpednetwork ports and the associated FEM edges or circuit nodes.…”

Embedding the Behavior Macromodel Into TDIE for Transient Field-Circuit Simulations

“…The admittance matrices in the Laplace domain can be transformed into the time domain. Thus the time-domain I-V relationship of the lumped network is obtained, which can be coupled with the field equations to complete the hybrid field-circuit simulation [18]- [20]. Whereas for lumped circuits with nonlinear components, the admittance matrices based method cannot work.…”

Co-simulation of distributive and lumped systems using the discontinuous Galerkin time domain finite element method

“…One is using network parameters such as scattering or admittance matrices [1]- [2] to represent the complex circuit networks. Another one is using SPICE-like models [3]- [5] to replace the networks. Compared with SPICE-like models, network parameters based methods have genuine advantages since lumped circuit systems could have been predesigned and characterized in terms of the measured or simulated S-parameters.…”