| With the continuous development of wireless communication technology,equipments are updated rapidly.And the needs of the market for antennas,especially for the miniaturization,easy to conformal,high gain and multifunction,are increasing.The dual-frequency dual-polarization microstrip array antenna can not only improve the overall performance of equipments,but also satisfy the requirements of communication system's upgrade,solve the problem of multipath fading,reduce the number and the cost of antennas.In this thesis,two kinds of dual-band dual-polarization microstrip antenna arrays will be researched and designed.Firstly,the theories of the microstrip antenna are introduced,including the radiation mechanism,the classification,the feeding methods,the theory of linear array and planar array,the feeding network and Taylor distribution.Then,the methods to realize dual-band and dual-polarization are analyzed in detail.Secondly,this paper expounds the design process of C band dual-frequency dual-polarization microstrip antenna array.Two bands share a rectangular element.The antenna works in two bands,and generates two linear polarization characteristics in the horizontal and vertical directions by feeding at the center of two adjacent edges of the rectangular patch.Using the software HFSS to simulate the antenna,and the size of the unit,element spacing and feed network can be determined.The antenna is designed as a 4?4 array and both transmitting and receiving antenna's feeding network are designed as parallel feed.The excitation amplitude of each output port is in line with the Taylor distribution.The simulation results show that the gain of the transmitting antenna is 20.64 d Bi,and the gain of the receiving antenna is 17.03 d Bi.The first side lobe of both antennas is less than-14 d B.Then test the antenna and compare with the simulation data.Further,another S/X band dual-frequency dual-circular-polarization co-plane microstrip antenna array is designed.The array contains two kinds of circular polarized antenna.One of them is a cross printed dipole antenna at S band and another is a square microstrip antenna at X band.The cross printed dipole array is designed as a 2?2 array and radiating with circular polarization by four 90°hybrid couplers.The X band array is designed as a 8?8 array and its feeding network is designed as parallel feed with the T-type splitter,whose excitation amplitude of each output port is in line with the Taylor distribution.Then the results show that the gain of S band array is 11.55 d Bi and the 3d B circular polarization axis ratio has a beam width of 84°.The gain of X band array is 21.77 d Bi and the 3d B circular polarization axis ratio has a beam width of 27°.And the isolation is better than 30 d B.At last,the antenna is tested and compared with the simulation results. |
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