| With the improvement of antenna technology requirements in the communications industry,phased array technology is increasingly used in radar and communications.In recent years,5G communication has been further improved and popularized.The military and civilian demand for phased array technology has gradually increased,and phased array technology will have more room for development in the future.Based on the existing phased array technology,the technology developed with the times will bring phased array circularly polarized antennas with wider bandwidth,better axial ratio performance and wider angular scanning.In this thesis,two power division networks are designed and optimized in HFSS.It is intended to realize four-feed feed through the power division network so that the array antenna can obtain better axial ratio characteristics in the working frequency band.The antenna operates from 400 MHz to 600 MHz and has a wide frequency band.When the antenna scans the normal direction,a better circular polarization performance with an axial ratio of less than 2 d B can be obtained.The short-circuit branches of the vertical structure are respectively loaded around the antenna,so that a better gain effect and working bandwidth can be obtained under the premise of miniaturization of the microstrip antenna.The array element gain is up to 5d B,and the radiation efficiency is greater than 90% in most operating bands.The height of the selected antenna is only 70 mm,which takes into account the axial ratio performance of the antenna and the radiation efficiency of the antenna.Based on the above research,this study analyzes the active standing wave ratio,the axial ratio of the antenna elements in the infinite array and the active standing wave ratio and axial ratio characteristics of the antenna in the wide-angle scanning.In the case of impedance mismatch in wide-angle scanning,the array antenna can have better impedance matching performance in wide-angle scanning by increasing the wide-angle matching layer.For the subsequent processing and measurement,based on the original array element antenna,the array element antenna with the working frequency band between 2GHz and 3GHz is optimized.Then the design simulates a 25-element 5×5 square array antenna,and studies the changes of the active standing wave ratio,the axial ratio change and the gain when the antenna is wide-angle scanning in the case of a finite array,and the antenna is in an infinite array.Compare in the case of scanning.It is found that the gain of the center frequency can reach 17 d B when the array is scanned to the zenith direction,the gain is greater than 18 d B at the high frequency point of 3GHz,the circular polarization axis is less than 2d B in the working frequency band,and the radiation efficiency is more than 85%.As the scanning angle of the antenna increases,the electrical performance indicators of the antenna are weakened to varying degrees.The array elements on the edge of the array have the most significant fluctuations in the active standing wave ratio due to the edge effect.When scanning to 60°,the main lobe gain of the antenna is reduced by 5 d B compared to the zenith direction,and the grating lobe level is increased.In general,the antenna of the design has the characteristics of ultra-wideband,wide scanning angle,good circular polarization and low profile,and the overall quality is light,stable and robust,and cost-saving.In addition,this paper also designed a turntable vector control system,which greatly improved the working efficiency when the antenna was repeatedly measured. |
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