| As a numerical calculating method of electromagnetic field, the Finite-Difference Time-Domain (FDTD) method is generally favored in the professional field because of its simplicity. Arranged in an order from simple to complex, this paper introduces respectively the basic operating technique of FDTD used in one dimensional, two dimensional and three dimensional electromagnetic field problems. It is aimed to explain the basic structure of this method and use it to analyze and calculate a slot antenna.Proceeding from the principle of duality, the paper analyzes and compares the field features of half-wavelength band dipole and half-wavelength aperture antenna, which is the theoretical basis of slotted antenna array, Based on this then, the author will analyze the mechanism of a aperture in on a waveguide and the features of slotted-waveguide antenna array formed by a number of aperture. Finally, the author presents the relevant formulas.Excited from a single end of a waveguide, the length of a slotted-waveguide antenna is restricted by the width of radar transmitted pulse, so it is difficult to implement a large-scale radar slot antenna with narrow beams. However, we should not ignore the fact that slot antenna has many advantages. To overcome this contradiction, the paper provides a design of slotted-waveguide antenna which is excited from both end of the waveguide, and simulates it with the help of HFSS. According to the requirement of directivity, this researcher designs the amplitude distribution of the apertures based on modified Chebyshev array, and calculates it by writing program using MATLAB. The complex arrangement of the slots in the narrow face of a waveguide brings much trouble to model it in HFSS, so the present paper offers a method to create the model by producing model scripts in MATLAB. This method can establish a complex model quickly and exactly. The simulating result shows that this antenna can basically satisfy the practical requirement. |
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