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In this paper, injection-locked MESFET oscillators are analyzed using several numerical models. The injectionlocking behavior of the van der Pol equation and of a more complex representation using the Curtice-Cubic MESFET model are investigated. Analysis and experimental results are compared for an NE71083 transistor oscillator operating at 0.5 GHz. The deficiencies of using a van der Pol oscillator model are pointed out. Time-domain results from the complex model exhibiting multicycle and apparently chaotic behaviors are also examined, and point to problems with common nonlinear simulation techniques for these circuits.

A new approach is presented for modelling three‐dimensional lumped elements in the finite‐difference time‐domain (FDTD) solution of Maxwell's equations. The finite‐difference equations for the lumped element's circuit behaviour are derived to produce discrete relationships between the device's terminal currents and voltages. These difference equations are then implemented in the FDTD grid with equivalent voltage and current sources based on static field 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 specific 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. Copyright © 1999 John Wiley & Sons, Ltd.

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