基于均匀圆环阵列，研究其产生的携轨道角动量(OAM，orbital angular momentum)双模复用的涡旋电磁波。首先从理论上论述均匀圆环阵列可以产生携OAM涡旋电磁波，并提出3种不同结构的均匀圆环阵列，阵元的激励设置及传输增益的计算方法；其次从均匀圆环阵列中阵元的数量、阵列的半径及阵元的排列方式3个角度分别讨论其对所产生的携OAM双模复用的涡旋电磁波在主轴方向上远场增益的影响；最后从阵元的排列方式研究OAM双模复用时的模间干扰程度。仿真结果表明，圆环阵列中阵元的数量越多，主轴上的远场增益越大；阵列的半径对主轴上的远场增益影响较小；相对于采用单一的排列方式，采用两种不同排列方式相结合的均匀圆环阵所产生的涡旋波在主轴上的远场增益更大，模间干扰程度更小。
Generating vortex electromagnetic waves carrying OAM (orbital angular momentum) dual-mode multiplexing based on a uniform circular array is studied. Firstly, it theoretically discusses that a uniform circular array can generate OAM vortex electromagnetic waves,three uniform arrays of different structures, excitation settings of array elements and calculation of transmission gain are proposed. Secondly, the influence of the generated OAM dual-mode multiplexed vortex electromagnetic wave on the far-field gain in the main axis direction is discussed from the angles of the array elements in the array, the radius of the array, and the arrangement of the array elements. Finally, the degree of inter-mode interference in OAM dual-mode multiplexing is studied from the arrangement of array elements. The simulation results show that the greater the number of array elements in the circular array,the greater the far-field gain on the main axis; the difference radius in the circular array has a less influence on the far-field gain on the main axis; compared with the single arrangement, the vortex wave generated by the uniform circular array combined by two different arrangement modes has larger far-field gain on the main axis and less inter-mode interference.
[1] Poynting J. The wave motion of a revolving shaft,and a suggestion as to the angular momentum in a beam of circularly polarised light[J]. ProcR Soc Lond A,1909,82(557):560-567.
[2] Nguyen T, Hirabe M, Miyamoto H, et al. An ex-perimental study of high capacity link using orbital angular momentum mode multiplexing in E-band[J]. International Symposium on Antennas and Propagation,2018,12:1-2.
[3] Yan Y, Li L, Zhao Z, et al. 32-Gbit/s 60-GHz millimeter-wave wireless communication using orbital angular momentum and polarization multiplexing[J]. Proc IEEE ICC, 2016,104:1-6.
[4] Tamburini F, Mari E, Sponselli A, et al. Encoding many channels on the same frequency through radio vorticity:first experimental test[J]. New J Phys,2012, 14(3):78001-78004.
[5] Shu G, Wang W, Liang D, et al. Chirp signal transmission and reception with orbital angular momentum multiplexi[J]. IEEE Antennas and Wireless Propagation Letters, 2019, 18(5):986-990.
[6] Allen L, Beijersbergen G, Spreeuw H, et al. Orbital angular momentum of light and the transformation of Laguerre-Gaussian laser modes[J]. Phys Rev A,1992, 45(11):8185-8189.
[7] Lavery M, Robertson P. Efficient measurement of an optical orbital angular momentum spectrum comprising more than 50 states[J]. New J Phys, 2013, 15:1354-1357.
[8] Thidé B, Istomin Y N, Khamitova R, et al. Utilization of photon orbital angular momentum in the low-frequency radio domain[J]. Phys Rev Lett, 2007, 99(8):087701.
[9] Hui X, Zheng S, Hu Y, et al. Ultralow reflectivity spiral phase plate for generationof millimeter-wave OAM beam[J]. IEEE Antennas and Wireless Propagation Letters, 2015,14(1):966-969.
[10] Tennant A, Allen B. Generation of OAM radio waves using circular time-switched array antenna[J]. Electron Letters, 2012,48(21):1365-1366.
[11] Liu Q, Chen Z N, Liu Y A, et al. Circular polarization and mode reconfig-urable wideband orbital angular momentum patch arrayantenna[J]. IEEE Transactions on Antennas and Propagation, 2018,66(12):7010-7020.
[12] Gong Y, Wang R, Deng Y, et al. Generation and transmission of OAM carrying vortex beams using circular antenna array[J].IEEE Transactions on Antennas and Propagation, 2017,65(6):2940-2949.
[13] Edfors O, Johansson A J. Is orbital angular momentum (OAM) based radio communication an unexploited area?[J]. IEEE Transaction on Antennas and Propagation, 2012, 60(2):1126-1131.
[14] Bai Q, Tennant A, Allen B. Experimental circular phased array for ge-nerating OAM radio beams[J].Electron Lett,2014,50(20):1414-1415.
[15] Tan S, Dong J, Wang M, et al. New circular array configurations for generating orbital angular momentum(OAM) beams[J]. International Applied Computational Electromagnetics Society Symposium,2018,67:1-2.
[16] Lin M, Gao Y, Liu P, et al. Theoretical analyses and design of cir-cular array to generate orbital angular momentum[J].IEEE Transactions on Antennas and Propagation, 2017,65(7):10-19.
[17] Yuan T, Wang H, Cheng Y. Electromagnetic vortexbased radar imaging using a single receiving antenna:theory and experimental results[J]. Sensor,2017, 17(3):630-635.
[18] Mohammadi S M, Daldorff L K S, Bergman E S, et al. Orbital angular momentum in radio:a system study[J]. IEEE Transactions on Antennas and Propagation, 2010,58:565-572.
[19] Deng C, Chen W, Feng Z. Generation of OAM radio waves using circular vivaldi antenna array[J]. Int J Antennas Propagation, 2013,17:90-97.
[20] Zhang Y, Li J. radial uniform circular antenna array for dual-mode OAM communication[J]. IEEE Antennas and Wireless Propagation Letters, 2018,17(4):719-721.
[21] Guo Z, Yang G. Radial uniform circular antenna array for dual-mode OAM communication[J]. IEEE Antennas and Wireless Propagation Letters, 2017,16:404-407.
[22] Wu H,Yuan Y, Zhang Z, et al. UCA-based orbital angular moment-um radio beam generation and reception under differe-nt array configurations[C]//6th International Conference on Wireless Communications and Signal Processing (WCSP),2014:1-6.
[23] Zheng S, Hui X, Jin X, et al. Transmission characteristics of a twisted radio wave based on circular traveling wave antenna[J]. IEEE Transactions on Antennas and Propagation, 2015,63(4):1530-1536.
[24] Guo C, Zhao X, Zhu C, et al. An OAM patch antenna design and its array for higher order OAM mode generation[J]. IEEE Antennas and Wireless Propagation Letters, 2019, 18(5):816-820.
[25] Spinello F, Someda C G, Ravanelli R A, et al. Radio channel multiplexing with superpositions of opposite sign OAM modes[J]. AEU-International Journal of Electronics and Communications, 2016, 70(8):990-997.
[26] Hui X, Zheng S, Chen Y, et al. Multiplexed millimeter wave communication with dual orbital angular momentum (OAM) mode antennas[J]. Scientific Reports, 2015, 5:10148.
