| In this paper,a circular-to-linear polarization conversion module based on the frequency selection surface is designed and used as a periodic unit to design a radome with polarization conversion function.The radome can be applied to a satellite link system to compensate for and solve the problem of energy loss of a circularly polarized signal received by a conventional antenna.It can also protect the antenna against a complex natural environment,and increase the caliber area of the antenna,the performance is also improved.The radome is also used in radar systems and can effectively reduce the radar cross section.The polarizer is designed based on the antenna-filter-antenna(AFA)structure principle and has a circular-to-linear polarization conversion function.Based on the principle of frequency-selective surfaces,it features frequency selection,bandpass,and insensitivity to incident angles.The polarization converter consists of a pair of symmetrical circularly polarized antenna pairs and a pair of anti-symmetric circularly polarized antenna pairs consisting of 2x2 sub-arrays.The sub-arrays are then arranged into periodic planes of 24x24 units.The periodic unit is designed as a rectangular cut-corner loading cross slot with a working frequency of 5.8 GHz,a conversion efficiency of 94.5%,and a wide-angle incident performance within 60°.This polar modulation module can not only achieve circular-to-line conversion.The inverse process(line-circle)it is also possible to achieve the same highly efficient conversion characteristics.The radome designed in this thesis is used to improve the antenna receiving efficiency.Therefore,a specific size of microstrip antenna is designed to verify the performance of the radome.The same caliber area of linear and circular polarization microstrip antenna that work in the same frequency band are designed respectively.The verification of the radome is divided into three steps:receiving by a linearly polarized antenna alone,measuring the receiving effect,and then loading the radome on a linearly polarized antenna for measurement.Finally,receiving and measuring with a circularly polarized microstrip antenna alone,three experimental results are obtained.For comparison,experiments show that the radome can effectively improve the receiving efficiency of the antenna,and has good frequency selection characteristics,transmission efficiency and line/circular polarization conversion performance. |
PDF Full Text Request