Microwave And Millimeter Wave Wide Angle Scanning Circularly Polarized Antenna Arrays

Compared with linearly polarized scanning antenna arrays,circularly polarized scanning antenna arrays have lower polarization loss and excellent anti multipath interference ability,so they are widely used in satellite communication.Scholars from home and abroad have done a lot of research and designed many achievements based on single frequency circularly polarized scanning antenna arrays and dual frequency circularly polarized scanning antenna arrays.However,these circularly polarized scanning antenna arrays often have defects such as scanning angles less than 60°,axial ratios more than 3d B,high profile and operating bandwidths less than 10%.In addition,the frequency ratios(high band center frequency/low band center frequency)of the existing dual band circularly polarized scanning antenna arrays are less than 2.Based on the above situation,this thesis takes the microwave and millimeter wave circularly polarized scanning antenna array as the research topic.Starting from the theory and structure of circularly polarized antenna array,taking the final index and function as the foothold,and aiming at the above problems,the research on the wide angle scanning circularly polarized antenna array,wide angle wide band circularly polarized scanning antenna array,and dual frequency shared aperture circularly polarized scanning antenna array have been carried out.The main research contents and innovative achievements of this thesis are as follows:1.Research on low profile wide angle scanning circularly polarized antenna array based on polarizer: Starting from the circular polarizer in the existing literature,the reason why it is difficult to achieve high integration and wide angle scanning at the same time is explored.Firstly,A hybrid circular polarizer is proposed,which can be integrated into the antenna array and the scanning angle can reach 60°,is proposed by combining the metasurface polarizer and the dipole polarizer.Notably,the metasurface polarizer can transform the polarization type of the beams with small scanning angle into circular polarization,while the dipole polarizer can transform the polarization type of the beams with large scanning angle into circular polarization.Then,the wide-angle scanning circularly polarized antenna array made up of the hybrid integrated circular polarizer and SIW slot antenna array is designed.2.Research on millimeter wave end-fire wide-angle scanning circularly polarized antenna array: Starting from the end-fire circularly polarized antenna arrays in the previous literatures,the reason why their scanning angles are generally less than 45° is explored,and the research is focused on the small size end fire antenna element.Then,the wide-angle scanning circularly polarized antenna array is designed based on the end-fire antenna element with a small size.A circularly polarized Yagi antenna element is proposed,which achieves a miniaturized size and a wide axis ratio(AR)beam-width at the same.Then,an end-fire circularly polarized antenna array is designed with the unit,and the maximum scanning angle of the array is 60°.3.Research on low profile wide-angle wide-band circularly polarized scanning antenna array: Focusing on the previous circularly polarized antenna array,the feasibility of wide-angle wide-band circularly polarized scanning antenna array is analyzed.Specifically,based on the sequential rotation method(SR),two existing derivative schemes named subarray rotation method and subarray periodic continuation method are analyzed and studied in depth.Then,two wide-angle circularly polarized scanning array based on the above two schemes are designed.The circularly polarized antenna array based on the subarray rotation method is composed of four uniform planar subarrays arranged in a sequential rotation manner,where each subarray is composed of4 ×4 circularly polarized antenna elements.The measured results show that the antenna array can achieve the scanning angle up to 45°and an axial ratio bandwidth close to17%.The circularly polarized antenna array based on subarray periodic continuation method consists of 4 × 4 periodically arranged sequential rotation sub arrays,each of which consists of 2 × 2 linearly polarized antenna elements.The simulated results show that the antenna array can achieve a scanning angle up to 60° and an axial ratio bandwidth close to 20%.Moreover,the circularly polarized antenna array based on the subarray periodic continuation method uses linear polarized antennas as the array elements,which enables it to realize the dual circular polarization function,which is different from the circularly polarized antenna array based on the subarray rotation method.4.Research on dual frequency shared-aperture circularly polarized scanning antenna array: Based on dual frequency common aperture linear polarized antenna array,a dual frequency common aperture circularly polarized scanning array with large frequency ratio is designed from the perspective of antenna structure and array layout.First of all,for the large frequency ratio linearly polarized common aperture antenna array,a scheme that both the high-frequency antenna array and the low-frequency antenna array use miniaturized antenna elements,and the high-frequency elements and low-frequency elements are interlaced with each other is proposed.The proposed dual frequency shared-aperture linearly polarized antenna array has realized beam scanning function in two frequency bands,and achieved a frequency ratio of 3.Then,in view of the fact that there is less research on the large frequency ratio circularly polarized shared aperture scanning antenna array,a dual frequency common aperture circularly polarized antenna array is proposed according to the above dual frequency linear polarized common aperture array.Specifically,the high-frequency antennas of the dual frequency shared-aperture circularly polarized array are SIW slot fed chamfered patch,and the antennas of low-frequency array are cross dipole antenna fed by microstrip power dividers with phase shifters.The proposed dual frequency shared aperture circularly polarized antenna array can realize circularly polarized beam scanning in both frequency bands,and its frequency ratio reaches 4.6,and the scanning angles of the two frequency bands reach 41° and 45°,respectively.Finally,in order to solve the problem that the operation bands of existing circularly polarized shared aperture scanning antenna arrays are norrow,a scheme that using miniaturized microstrip dipole antennas as array elements in two frequency bands,and the arrays are rotated in order is proposed.The dual frequency shared aperture circularly polarized antenna array based on the proposed scheme not only achieves a frequency ratio of 2,but also makes the axial ratio bandwidth of C band and X band reach 18% and 20%,respectively.