A Reduced Finite-Difference Time-Domain Method And Its Application To The Analyses Of Microstript-Fed Slot Antennas

The finite-difference time-domain (FDTD) scheme for the time-dependent Maxwell's equations is reviewed firstly. Then a reduced finite-difference time-domain (R-FDTD) method is introduced. The principle of the R-FDTD and the related questions in computation are discussed in detail. It is then applied to the analyses of microstrip-fed slot antennas. The choice of the space increment and the time increment is discussed for the sake of its accuracy and stability. The simulation of an imposed source is also considered. The finite-difference equations of the Mur absorbing boundary condition are derived. Methods for transforming near field to far field are also presented for the analyses of the radiation characteristics of the antennas. To validate the theoretical model and computer program, a microstrip-fed rectangular-slot antenna is analyzed with the R-FDTD. After that, microstrip-fed dumbbell-slot antenna, microstrip-fed swallow- tailed-slot antenna and microstrip-fed fractal-slot antenna are analyzed with R-FDTD. The influence of the shape and the size of the slot on the input impedance, frequency band and radiation patterns of the antenna are discussed based on the numerical results. Some useful conclusions are deduced for engineering design.