Partial Focus Parabolic Reflector Antenna Radiation Characteristics

The radiation characteristic of offset paraboloidal antenna's distant area is analyzed in the paper, and it is numerically computed with varying of △y , which is transverse offset variable of feedback source.Firstly, the development of paraboloidal antenna and the conception of reflective antenna are introduced. Then some high-frequency approximate methods are studied, these methods include geometrical optics method, physical optics method, geometrical theory of diffraction method, physical theory of diffraction method, FFT method and Gauss numerical integral method.After that, calibre field method is used to analyse the far field characteristic of offset feed paraboloidal antenna's front axis with varying of △y . Base on coordinate transform and phase computing, the approximate expression of far area's electric field is deduced by mean of calibre field. The different antenna pattern according to △y is computed, analysed and compared, and also the selection, which concerns about the direction and location of the best focus-deflected feedback source, is discussed. The result shows: with increasing of △y, the angle between paraboloidal focus axis and antenna's major lobe increases, but the gain of antenna decreases; And if the major lobe becomes wider, the side lobe turns more asymmetric, and the relative intensity of the first side lobe becomes stronger. Both main and side lobe become narrow when frequency increases, and also the asymmetry become poignant. This part is the key of the paper, the consecution of deducing antenna's electrical field is clarity and simple, and the numerical integral method can compute very fast with high precision.Then geometrical theory of diffraction method is used to analyze and compute diffractive field of the area except for offset paraboloidal antenna's front axis, and it is the difficulty of the paper. In the end, modifying shape technique of paraboloidal antenna is introduced, and it lays the foundation for designing satisfied offset feed paraboloidal antenna.The researches in this paper can definitude the radiation characteristic of the offset feed paraboloidal reflector antenna, and brings theoretic basis to engineering.