Investigations On Cylindrical Phased Array With Omnidirectional Covering

At present,phased array antenna technology has been widely used in communication,radar and other fields.Especially in the field of military radar,in order to monitor all possible targets in space,phased array antenna is required to achieve the omnidirectional coverage of beam,which has become a hot research direction of phased array at present.Generally used planar array antennas can only support the maximum beam scanning range of 120 degrees.If you want to achieve full coverage,it is necessary to use at least three planar arrays in different directions at the same time,which will greatly increase the manufacturing cost.Therefore,this paper studies and designs a cylindrical phased array based on the basic principle of beam control of phased array antenna.It realizes the change of azimuth within 360 degrees and has the ability to change the pitch Angle by ±60 degrees.The design mainly includes three parts:antenna array,direction pattern synthesis method and beam control system software.Specific research contents and results are as follows:Firstly,the antenna element of cylindrical phased array is designed.The antenna element design is considered from two aspects of structure fabrication and radiation characteristics.Considering that the antenna element applied to the cylindrical phased array needs to have the conditions of wide beam width and low gain,the antenna structure based on microstrip patch is chosen in this design.On this basis,two antenna elements of linear polarization and circular polarization are designed respectively.In the design,the bandwidth of the microstrip antenna is expanded by the U-shaped slot structure,and the circular polarization of the antenna is realized by the way of Angle cutting.The index performance of the final design of the circularly polarized antenna is as follows: in the operating frequency,the band internal standing wave is less than-10 d B,and the axial ratio is less than 3d B,basically meeting the array requirements.Secondly,the design simulation and direction diagram synthesis of cylindrical phase controlled cell surface are presented.The design of cylindrical phased array plane mainly considers the influence of the arrangement mode on the axial ratio and direction pattern.On this basis,the arrangement mode of four adjacent elements rotating 90° in turn is chosen.The simulation results show that the axial ratio of the cylindrical array is less than 3d B,and the standing wave of the working frequency point is less than-10 d B.In addition,in order to suppress the sidelobe level of antenna radiation,a synthetic method of first projection and then amplitude weighting is proposed.The simulation results show that the radiation sidelobe level decreases obviously after using this comprehensive method,and the highest is less than-12 d B.Then,the beam control system of cylindrical phased array is researched and designed,mainly the design of software part.The design of the software of the cylindrical phased array beam control system mainly considers the control logic and mechanism.This paper establishes a control mechanism with lookup table method as the core algorithm and FPGA as the core processor.The two key technologies of this mechanism are introduced in detail,including the making of lookup table and the determination of communication protocol.On this basis,the software programming of the system is completed,and the beam control is finally realized.Finally,the measurement method of cylindrical phased array is presented.This paper briefly introduces the automatic calibration method of phased array based on near field test and the main indexes and parameters of far field measurement.The actual parameters of the cylindrical phased array measured by these methods accord with the simulation results basically.