Research On The Dense Focal Plane Array Feed For Giant Reflector Antenna With Multiple Beams

Multi-beam reflector antenna is widely used in radio astronomy,radar and satellite communication and so on.The feed is the "heart" of the reflector antenna.The multi-beam reflector antenna with different feeds has different performance.Compared with the classical multi-beam feed with multiple independent radiators,the dense focal plane array feed can achieve more beams in the same space,which can make the adjacent beams intersect at the half-power beam width point,so as to expand the field of view and ensure the continuity of the field of view and the observation efficiency are improved;it can flexibly control its beam shape,thus increasing the gain of each beam and reducing the gain difference between the edge beam and the center beam and the side lobe level are reduced.Therefore,the dense focal plane array feed has attracted widespread attention,and scholars at home and abroad have been actively researching it.With the support of the joint research fund in astronomy under cooperative agreement between the National Natural Science Foundation of china and Chinese Academy of Science(U1631115),and the fund of Five-hundred-meter Aperture Spherical Telescope(FAST),according to the technical requirements of FAST upgrading in the future,the research on the dense focal plane array feed is carried out and compared with the multi-beam feed with multiple independent radiators currently in use.The main work and innovations of this dissertation can be summarized as follows:1.With the Vivaldi antenna as the array element,the nested array structure is adopted to solve the problem that the array spacing of the conventional broadband and dual polarized array is too large.The influence of active impedance on the performance of the antenna efficiency and so on is analyzed by using the measured data of the fabricated array feed.2.Based on the inherent characteristics of reflector antenna,combined with the theory of array antenna,fused focal plane electric field matching technology and Lorentz reciprocity theorem,a new method is proposed to determine the array element of sub-array corresponding to each beam and to solve the excitation voltage of array element rapidly and stably.The derivation process and simulation results are provided,and the dense focal plane array feed of different structures are compared and analyzed.At the same time,the dense focal plane array feed is compared with the classic multi-beam feed with multiple independent radiators.3.In order to estimate the direction of arrival(DOA)of the signal when the reflector antenna is working,based on the contributing factor that the correlation between the signals received by the array elements has been reduced after the source signal is reflected by the reflector,taking advantage of the fact that the array feed of instantaneous multi-beam paraboloid such as FAST can move accurately along the axis of reflector,an improved DOA estimation algorithm matching the dense focal plane array feed with unfixed and irregular structure,complex array manifold and high angle resolution is proposed.