| The precision guidance system has been widely used in modern military strikes.The multi-mode composite guidance system has improved its adaptability and antiinterference ability to complex battlefield environments by using two sets of tracking systems,high and low frequency,and has become the main development direction of precision guidance systems.The monopulse antenna is a key component of the precision guidance system.The guidance system on the missile-borne platform requires the antenna to have the characteristics of high gain and compactness.The existing dual-frequency monopulse antenna technology has certain shortcomings in terms of compactness,high efficiency,and structural complexity.It is of positive significance to seek a more flexible and efficient dual-frequency implementation method to promote the development of related technologies.The periodic structure is an array structure formed by periodic arrangement of elements,which can realize special electromagnetic transmission characteristics by controlling the structural parameters of the elements,and has the structural advantages of easy processing,low profile and light weight,and has huge advantages in the field of antenna design.Application potential and research value.In this thesis,focusing on the shortcomings of the existing dual-frequency monopulse antenna in the application of the missile-borne platform,starting from the characteristics of the periodic structure,an indepth study of the dual-frequency common aperture compact monopulse antenna technology is carried out,and a compact structure and aperture multiplexing is proposed.Ku/Ka dual-band Cassegrain antenna design.The specific research contents and related results are as follows:1.Theoretical research on a new type of planar reflectarray antenna was carried out,and a corresponding solution was proposed for the problem of low aperture efficiency of the card-type planar reflectarray antenna in the existing research.The scheme innovatively proposes a new type of concave front structure,which can effectively reduce the maximum incident angle of electromagnetic waves received by the front,improve the phase compensation performance of the front,and improve the aperture efficiency of the antenna.Based on this scheme,a Cassegrain monopulse antenna working in the Ku frequency band is designed in this thesis,and the aperture efficiency is about 47.5%,which verifies the feasibility of the scheme.2.On the basis of the above design scheme,the Ku/Ka dual-frequency Cassegrain monopulse antenna is studied.The main research contents include:(1)A dual-frequency reflection array unit is designed by using the polarization isolation method,and the isolation of high and low frequency units is good;(2)A combination of waveguide feeding and microstrip feeding is proposed.The design scheme of the dual-frequency monopulse feed system can realize the compact structure of the dual-band monopulse feed and the sum-difference network;(3)The overall structure of the antenna is built using the new front structure proposed in this paper.The simulation results show that the designed antenna gain is 32.31 d B and 24.67 d B at 35 GHz and 16 GHz frequency,respectively.3.The physical processing and testing of the Ku-band Cassegrain monopulse antenna designed in this thesis are carried out.The test results show that the designed antenna has good radiation performance of the sum-difference beam,the peak gain of the sum-difference beam at the 16 GHz frequency point is 27.1 d B,the sidelobe level is less than-12 d B,and the sum-difference contradiction of the elevation plane and azimuth plane is 3.7 d B and 2.8 d B.The test and simulation results are basically consistent,and the feasibility of the new front structure proposed in this thesis in practical application is successfully verified. |
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