, Islamic Azad University
Despatch Group, Khaje Nasir Toosi University of Technology
Electerical Engineering, Khaje Nasir Toosi University of Technology
Top-hat monopole antennas loaded with radially layered dielectric are analyzed using the finite-difference time-domain (FDTD) method. Unlike the mode-matching method (MMM) (which was previously used for analyzing these antennas) the FDTD method enables us to study such structures accurately and easily. Using this method, results can be obtained in a wide frequency band by performing only one time-domain simulation. For the FDTD modeling, the type of medium at each grid point is specified by a code. Also an efficient non-uniform meshing scheme and a novel perfectly matched layer (PML) are presented and used. The excitation signal can be chosen in the form of Gaussian pulse (GP) or sine carrier modulated by Gaussian pulse (SCMGP). These enable us to increase the accuracy of simulation and decrease the required memory and CPU time. Simulation results are presented in the form of graphical figures, which display the spatial variations in amplitude and phase of radiated field. Also, the FDTD computed input impedances of several top-hat monopole antennas are compared with those obtained by measurement. The agreement between computed and measured results is quite well.