Study Of Hemispherical Coverage Circularly Polarized Conformal Array Antennas

As the launch cost of artificial satellites continues to decrease,the number of satellites will increase,and correspondingly,the number of satellite ground stations will also increase.In order to communicate with one or multiple satellites constantly moving in space,satellite ground station antennas often need to have hemispherical coverage capability,which means that the antenna beam can point to any direction in the sky.Among antennas that can achieve hemispherical coverage,conformal array antennas are being used more and more because of their ability to quickly scan beams and generate multiple beams simultaneously.However,due to the complexity of the structure of conformal array antennas and the resulting imperfect theory,their design and processing difficulties are relatively high.Therefore,research on hemispherical coverage conformal array antennas is of great practical significance and theoretical value.The main research content of thesis can be divided into the following points:1.Design of dual-circularly-polarized antenna element for hemispherical coverage conformal array.Firstly,a dual-linearly-polarized microstrip antenna with a circular metal back cavity was designed.Then,based on this design,dual circular polarization was achieved by utilizing the amplitude and phase characteristics of the 3d B quadrature hybrid coupler.The antenna element operates in the frequency range of 2.2～2.4 GHz.During the research process,the working mechanism of each structure was analyzed,and parameter analysis was carried out on important structures.Finally,the designed antenna element has an axial ratio of less than 1.5 d B,a gain greater than 8.1 d B,and a gain variation of less than 0.5d B within the operating frequency band.2.Implementation of element uniform distribution algorithm based on minimum potential energy principle.Due to the limited number of existing element uniform distribution methods and their significant limitations in application,thesis presents an element uniform distribution algorithm based on the minimum potential energy principle that can be used for any number of elements and is suitable for most conformal array shapes.The implementation principle of the algorithm is to treat the array elements as charged particles,and these charged particles will be uniformly distributed in the array to achieve the minimum potential energy state of the system.3.Investigation of excitation amplitude and phase of conformal array antenna and measurement verification.Based on the research results of the first two points,a conformal array antenna with hemispherical coverage capability was designed,and the array antenna was excited using both the maximum array gain theorem and the theoretical phase compensation method.In the excitation using the maximum array gain theorem,the gain variation was less than1.3 d B during elevation beam scanning and less than 0.4 d B during azimuth beam scanning.Finally,the antenna is manufactured.And using the relationship between the rotation angle and phase of the circularly polarized element,the phase control of the element is realized by rotating the element,so as to directly measure the radiation pattern of different beam directions.The measured results are almost consistent with the simulated results,except for a slight decrease in gain.