The Design And Realization Of A Circular Microstrip Array Antenna For The Long-range UVA-relay System

UAV refers to the unmanned aerial vehicles,which has been widely used in both civil and military applications.The autonomy of UAV is currently limited by the communications links used for sending telecommands and the data captured by the sensors of the airborne platform.Using and S,C or K band line-of-links is the most common strategy.However,these links imply reduced autonomies,which are highly dependent on the terrain orography.The second strategy is the usage of a satellite connection link,in which case,either a very expensive space segment or an Iridium-like system is used.To overcome these problems,in this paper,a second UAV is used as a communications relay,and a circular microstrip antenna is designed to guarantee a multichannel long-range communication link with high quality of service,moderate bandwidth and affordable cost.The main contents are as follows:The basic theory of microstrip antenna is introduced firstly,including the principle of radiation and the main characteristics of antenna array.Take rectangle patch antenna as an example,the design procedure for the substrate and the patch's size is given.Besides that,different feeding methods are compared,which provides the theoretical support for the following chapters.A circular microstrip antenna working in C band is designed,where the coaxial feeding approach is adopted.On one hand,a good linear polarization radiation pattern is obtained by optimizing the size of patch and the parameters of substrate.On the other hand,T-shape feed network is used to generate circular polarization as a comparison.The simulation results from CST shows that₁₁parameters less than-20 dB and an isolation better than 35 dB between transmitting and receiving antennas are achieved in the considered bandwidth(5.03GHz-5.091GHz).The highest gain is about 8.51dB.A cylinder microstrip antenna array is designed based on the proposed patch antenna.By optimizing the parameters of antenna array,we obtain the optimal number of array element and its spacing.The simulation results show that the antenna array composed by a pair of 8 linearly polarization patches can obtain the best performance.It is achieved with gain of 10.7 dB,half power beamwidth of 45.6^°in horizontal plane and 55.4^°in vertical plane respectively by exciting two adjacent radiating elements simultaneously.In addition,the aluminum plate is added to get the isolation of 35dB between the transmitting and receiving antenna.The proposed patch and antenna array are fabricated and measured.The tested results show good agreement with the simulated results.