Analysis of Wave Characteristics between Cylindrical and Cartesian Coordinate System-based Structure Using FDTD Method

Numerical computation is needed to solving the problem of electromagnetic waves. There are many methods that can be used to analyze electromagnetic waves like Method of Moment (MOM), Finite Element Method (FEM), Finite Volume Method, and also Finite Difference Time Domain (FDTD). FDTD is chosen because it has several advantages that are easy to understand has short development time and naturally explicit. In this work, FDTD will be used to modeling and comparing wave characteristic and propagation in 3D Cartesian and cylindrical coordinate. The size that used in 3D Cartesian structure is x = 60cm, y = 30cm, and z = 120cm whereas the dimension in cylindrical structure is r = 60cm, phi = 30, and z = 120cm. The grid size of both structure is made equal so either Cartesian or cylindrical structure has identical Delta t. TE mode is applied in this simulation with propagation along z-axis. The source for this simulation is sinusoidal wave modulated with Gaussian pulse with frequency 1GHz. The simulations are undertaken in some variations of condition. The first condition is for modeling free space in both Cartesian and cylindrical structure. The result is in the form of frequency cut-off for both structures. The second and the third are for modeling dielectric and conductive medium which objective is for observing the effect of adding these medium in wave propagation characteristic. The result from cylindrical structure will be analyzed and compared to the result of Cartesian structure.