Incorporating non-linear lumped elements in FDTD: the equivalent source method

✍ Scribed by Jason Mix; Jonathan Dixon; Zoya Popovic; Melinda Piket-May

• Publisher: John Wiley and Sons
• Year: 1999
• Tongue: English
• Weight: 230 KB
• Volume: 12
• Category: Article
• ISSN: 0894-3370
• DOI: 10.1002/(sici)1099-1204(199901/04)12:1/2<157::aid-jnm323>3.0.co;2-v

✦ Synopsis

A new approach is presented for modelling three-dimensional lumped elements in the "nite-di!erence time-domain (FDTD) solution of Maxwell's equations. The "nite-di!erence equations for the lumped element's circuit behaviour are derived to produce discrete relationships between the device's terminal currents and voltages. These di!erence equations are then implemented in the FDTD grid with equivalent voltage and current sources based on static "eld approximations. The method can be used for a wide range of applications which include lumped elements that may be passive, active, linear, non-linear, single, and multiple port devices. The underlying advantages of modelling a lumped element in this manner as compared to the more traditional extended FDTD technique is that the lumped element is easily extended across multiple FDTD cells and the need for a separate transcendental equation solver is eliminated. The method is demonstrated by a speci"c example based on the Curtice}Cubic non-linear model for a MESFET. The s-parameters from an FDTD simulation are compared to the manufacturer's measured data and to results from simulations using Hewlett-Packard's Microwave Design System (MDS). Finally, the method is used to model the MESFET in a three port oscillator.