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(一)引言现在有三种计算镜面天线方向图的方法,即:孔径法、电流法以及几何绕射理论法。几何绕射理论法在研究旁辫辐射方面较好,而电流法和孔径法则在研究主瓣和头几个旁瓣方面较好,因而相互补充。而孔径法与电流法之间在主瓣和头几个旁瓣方面的关系过去却从来没有研究过。孔径法的优点在于无论在正算问题上或在逆算问题上都曾作过大量的计算。这是因为通过傅里叶变换使孔径中的电场分布近似于方向图,而对此特性利用傅里叶变换正在进一步研究。另一方面,电流法比较准确,因为它不采用按几何光学规律再近似计算从镜面至孔径的电场,并且确切地考虑到镜面深度。可是,电流分布与方向图之间的关系比孔径法中电场分布与方向图的关系更复杂。
(A) Introduction Now there are three methods to calculate the pattern of the mirror antenna, namely: aperture method, current method and the theory of geometric diffraction method. The theory of geometrical diffraction is better in studying the side-braid radiation, while the current method and the aperture method are better in studying the main lobe and the first few sidelobes and complement each other. The relationship between the aperture method and the current method between the main lobe and the first few side lobes has never been studied before. The advantage of the aperture method is that it has done a lot of calculations in both the positive and the negative calculations. This is because the distribution of the electric field in the aperture is approximated by the direction of the Fourier transform, and the Fourier transform is used for this property for further research. On the other hand, the current method is more accurate because it does not use the principle of geometrical optics to approximate the electric field from the mirror to the aperture, and takes the mirror depth into account. However, the relationship between the current distribution and the pattern is more complicated than the relationship between the field distribution and the pattern in the aperture method.