Application of multigrid FDTD to the simulation and design of microwave processing system

The multigrid finite-difference time-domain (FDTD) method is more efficient and accurate in characterizing electrically large and complex electromagnetic devices and structures. Detailed results of electromagnetic fields distribution in critical areas of interest can be obtained, thus accurately identifying hot spots and potential design faults. We present results illustrating the use of multigrid FDTD for the simulation and design of microwave processing systems. A realistic microwave dryer is simulated. New designs to improve the uniformity of the power distribution pattern in the ware samples are presented. It is shown that by using a slotted waveguide with slots varying in size along the waveguide, the absorption and the power uniformity can be significantly improved. The dependence of the power distribution pattern on the number of samples and a comparison between the slotted waveguide feed and the mode stirrer design is presented.