| The conformal microstrip antenna with some unique character has been applied in many fields,especialy on speedy objects.In this paper,an efficient FDTD algorithm is introduced to analyse the microstrip antenna.Firstly,the FDTD formula in Descartes coordinate system and in cylindrical coordinate system are obtained from the time_dependent Maxwell equations using the Yee algorithm in a calculating region where the dielectric parameters are independent of time and space.The choice of the space discretization units and the time discretization interval are discussed which are decided by the accuracy and stability respectively.The shape and setup of the excitation source are discussed too.The excitation source is chosen to be Gaussian pulse in shape.Secondly,the Mur's first-order and second-order boundary condition are deduced in cylindrical coordinate system.The methods of transforming radiation fields from near zone to far zone in the frequency domain and in the time domain are presented when FDTD is applied to analyse the characteristics of far zone.Finally,three kinds of microstrip antennas are analysed. They are a slot antenna that lies on a plane ground of a microstrip, a slot antenna that lies on a cylindrical ground of a microstrip and a microstrip line_fed aperture coupled stacked rectangular patch antenna in cylindrical coordinate system. The influence of the structural parameters on the performance of these antennas are analysed. Some useful conclusions are deduced.
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