Design Of A Monopulse Array Antenna With Low Side Lobe Level At Ku-Band

The monopulse antenna is a simultaneous multi-beam antenna.It only needs one echo pulse to obtain target all location information.The performance of a monopulse antenna largely determines the accuracy of the monopulse radar angle measurement and the positioning accuracy.Waveguide slot antenna has the advantages of compact structure,low profile,convenient processing,low cost,high gain,and easy beamforming,So is often used as a basic unit of a single pulse antenna.Based on the actual project,this paper designs a Monopulse Array Antenna at Ku-Band with supported by the Joint Research Fund in Astronomy(U1631115)under cooperative agreement between the Natural Science Foundation of China(NSFC)and Chinese Academy of Sciences(CAS).The key components of the monopulse antenna were designed and manufactured,namely a high-efficiency,low-sidelobe waveguide slit line array.Meanwhile,the sum-difference network was designed and simulated.The specific research content is as follows:1)The overall structure of a monopulse plane array antenna was designed.The planar array antenna is composed of 4 identical waveguide slot linear arrays and a sum-difference network.Each linear array is composed of 46 longitudinal slots alternately distributed on both sides of the broad edge axis of the waveguide and the sum-difference network is composed of the waveguide magic tee and the waveguide power divider group.2)In order to obtain the high efficiency and low sidelobe array antenna characteristics,the normalized current of each array unit in the 46 unit linear array is obtained by using the Taylor distribution synthesis method in the antenna synthesis theory.And the admittance values of each array unit were calculated,and the product theorem and the finite element method were used to calculate the radiation pattern of a linear array.3)In the case of mutual coupling between the array units,in order to design the slot accurately,the resonant length of the slot was calculated by short circuit method.On the basis of the calculation results of short circuit method,the admittance value of the slot with different offset distance and resonance length was calculated more accurately by the load method.4)The sum-difference network composed of the waveguide magic tee and the waveguide power divider was designed.First,the geometric structure and initial value of the magic tee and power divider were set up.Then,the optimum geometric parameters were optimized with the scattering parameters as the optimization target.5)The performance parameters of the azimuth pattern of a monopulse plane array antenna were obtained by using the test results of a single linear array.At the same time,the performance parameters such as the pattern of the elevation plane of the planar array antenna were calculated by the simulation results of the difference network,and the design of the whole planar array antenna was completed.