Analysis Of Antenna By Using FDTD

The main work of this paper is analysis of antenna by using FDTD. Some practical antennas examples were simulated. Near-to far-zone transformation for the FDTD method is introduced primarily and an improved near-to far-zone method is developed..According to the equivalent principle, the far-zone of an antenna can be calculated by the integral of the equivalent electric and magnetic current on a surface enclosing the antenna. However, the electric and magnetic fields in the Yee grids are spatially shifted which causes difficulty to the near- to far-zone transformation.In this paper, precise formulas are derived based on Maxwell equations in integral form to calculate the equivalent electric and magnetic currents on the same surface from the FDTD simulation, and an improved near-to far-zone transformation is developed. This method demonstrates its accuracy by calculating the radiation fields of a current element. It is shown that this method is more accurate than both conventional average method and the mixed surface method at high frequencies or in coarse grids.In this thesis, the finite-difference time-domain Yee's method is reviewed briefly; the important parameters of antennas is introduced; and the way to calculate scattering parameters and the input impedance of antennas is explained. Examples are calculated by above method, a microstrip inset-fed patch antenna, monopole antenna mounted near the edge of a conducting plane and notch antennas.