Development of packaging and products
for use in microwave ovens
Chapter 18: Modelling of cavities and loads with FDTD and FEM Methods
Abstract: This chapter aims at providing an insight into simulations of microwave heating scenarios with both the FDTD and FEM algorithms in order to make advanced modelling easier and better understood. Several examples are provided to better illustrate the basic concepts of the modelling methods. Properties important in the analysis of microwave power phenomena are stressed and shown to affect the computational accuracy when handled improperly. The specific topics presented in subsequent sections include background of the modelling methods, with emphasis on mechanisms useful in coupled multi-physics analysis, error bounds due to numerical dispersion inherent to numerical algorithms, modelling of lossy materials crucial in the analysis of the microwave heating effect, modelling of dispersive media, and coupled analysis of microwave heating involving thermal variations of material parameters, heat conduction and load rotation effects besides the EM phenomena.
Examples illustrated and referred in the Chapter:

Simulation projects and results of a simple microwave cavity with potato (shown in Fig. 18.9) for different FDTD discretization applied to the model. The analysis aims at extracting reflection characteristic of the oven (results presented in Fig. 18.12 and in Table 18.1).
The model with optimum discretization is delivered also for calculation with QProny module of QuickWave software, employing Generalized Pencil of Function Method for enhancing calculation efficiency of FDTD method in modelling of structures with high quality factor.
A set of examples is complemented with a high-Q scenario, in which an empty cavity is uniformly filled with low-loss material (results shown in Fig. 18.16). The simulation model is delivered as a standard scenario and the one enabling QProny analysis.

Simulation scenarios showing the application of Generalized Pencil of Function Method in QProny module of QuickWave software for enhancing calculation efficiency of FDTD method in modelling of high Q structures.
The models include:
- Comb-line filter consisting of two cavity resonators coupled via rectangular aperture (