Study On The Multi-beamantenna Of Conformal Spherical Array

With the development of the civilian and military information technology，theintegrated space-ground network technology is the way of the future and the spatialomnidirectional communication plays a very important role. In satellite communications,airborne communication and COTM system, aerial platform is becoming more and moreimportant for defence, military and civilian purposes. The establishment of emergencysystem for aerial platform is a powerful means to improve the disposal ability and maintaincommunication especially in some natural calamities (earthquake, fire, floods etc.) andTerrorist attacks. USA has established integrated space-ground network used formicrowave relay communication in specific regions by aerial platform, and it realize theregional broadcast communication which has been applied in remote mountain areas ofcommunications and broadcasting, the army’s regional operations, and emergency etc..In order to meet the air platform communication system and realize the half space afull range of electromagnetic radiation, conformal spherical array antenna hasincomparable advantages in antenna system designing. It can not only be used for otherground communication system, especially mobile communication, but also positioning,radar and navigation.The research works are made with projects of national natural science foundation. Thedesign methods of spherical conformal array are discussed in this thesis.The main contentand achievements of this works are as follows:1. The circular polarization microstrip patch antenna is adopted as unit in theconformal spherical array design. The dielectric substrate loading and apertureelectromagnetic coupling method are used to improve gain and bandwidth. Experimentalresults show that the designed circular polarization microstrip patch antenna works well inwide bandwidth. Besides, high gain and excellent axis ratio is also obtained.2. In the layout design of conformal spherical array, two objective needs to beconsidered:1) multi-beams cover targets within the azimuth angle from0o to360o and theelevation angle from0o to90o, and2) high gain. In order to meet the above goals, theconformal spherical array and antenna subarray partition technologies are adopted. Toachieve the specific subarray beamforming, genetic algorithm is used to synthesis thepattern of the antenna subarray. The simulation and analysis results show that the wholeconformal spherical array is divided into25subarrays, and generating25beams, and fulfillthe beam coverage demand for the azimuth angle of360o, the elevation angle of90o by multiplexing the array elements.3. The conformal spherical array antenna units which have different polarizationdirections are studied in this thesis, and cross polarization of circularly polarized antennahas been studied. Besides, we deduced the computation formula for far field pattern ofconformal spherical array which adopts circularly polarized antenna as a unit. Furthermore,a method on decreasing cross polarization level of circularly polarized conformal sphericalarray antenna is presented; the theoretical analysis and the actual test proved the validityand practicability about this method.4. The beamforming of conformal spherical array is studied, and a pattern synthesisalgorithm for three dimensional conformal spherical array antennas is proposed. Thisalgorithm combines the existing mainstream intelligent optimization algorithms, such asgenetic algorithm, particle swarm optimization algorithm. A control operator and adaptiveoperator are added in it to improve the algorithm. Simulation results show that thealgorithm has the advantages of fast convergence and good global search.5. The design method of microstrip T-type unequal power divider with a high dividingratio is discussed. the design limitations of conventional T-type unequal power divider isillustrated and on this basis, the design method of two kinds of T-type unequal powerdivider is proposed: One is to replace the high impedance line by using single sectionequivalent network to realize high power dividing ratio, and it solves the practicalprocessing problems of the high impedance line. The other is to avoid the high impedanceline processing problem by using the stub line to obtain arbitrary power dividing ratio.On the basis of theory research, the conformal spherical array antenna is fabricatedand tested. Test results show that the conformal spherical array antenna can meet thedesign requirements and the measured pattern is in good agreement with the simulationresults.