| The back lobe level is an important technical parameter of a radar antenna. As one of key techniques of modern high-performance radars, low back lobe is of equal importance to low side lobe. Taking an array antenna with 8 radiation elements as the object,the changing of the electromagnetic wave diffraction in the back of the antenna and the reduction of antenna back lobe as the core, the author conducts a series of studies on such key problems as the transmission characteristics of electromagnetic wave through a discontinuous metal surface,the effect of varied discontinuous reflecting surfaces of the antenna upon the back lobe and the other radiation characteristics and the optimization of antenna performance due to the integrated design of the array antenna in this dissertation.Firstly, the permeability coefficient of electromagnetic wave through discontinuous metal surface especially through slot-shaped perforated holes and the variation of the permeability coefficient with the perforated holes are analyzed. By perforating holes on the metal surface to change the permeability coefficient, the energy of the electromagnetic wave diffraction in the back of the antenna will be altered.Secondly, the author introduces the integrated antenna design, by wich the radiation network consisting of radiation elements of the array antenna and its feed network are integrated , and takes the coupling between two networks into unified account. By using the scattering matrix elements of two networks, the output voltage distortion of the feed network resulting from intercoupling will be obtained, and then the voltage distribution requirement of the feed network will the intercoupling taken into account will be worked out.Finally, it is proved that slots with appropriate size cut in the upper and lower shield plates can effectively improve the antenna back lobe in a wide band by simulation operation and antenna test, and the antenna performance is optimized by means of the theory of integrated design. |
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