Cylindrical coordinates FD-TD analysis of cylindrical microstrip GPS antennas for ships

A cylindrical coordinates FD-TD algorithm is developed for analysing antennas whose structure mainly consists of circular and/or cylindrical shapes. The absorbing boundary condition scheme employed is that of Berenger's (see J. Compt. Phys., vol.114, p.185-200, 1994) PML (perfectly matched layers) algorithm adapted to the cylindrical coordinates. The model for excitation is that of a coaxial line inside which the voltage and current are are calculated by a one dimensional FD-TD method. The algorithm is applied to the analysis of circular polarization cylindrical microstrip antennas (MSA) with a wide hemispherical beam radiation pattern, the GPS antenna for ships. The results agree very accurately with those of the experiment.