| Cylindrical Luneberg lens antennas in millimeter-wave frequency band possess many advantages such as high gain,broad band,wide scanning angle,low cost,small size,light weight,and convenience of integration,etc.They are promising antenna candidates for the future 5G communication,interstellar communications,and car radars,etc.With the focus on some key techniques of cylindrical Luneberg lens antennas such as the beam widening and lens arrays,this thesis presents a series of relatively thorough studies: on their analytical solution,fast analysis,a design and optimization methodology,and extremely flat beams.The content of the thesis is organized as following:Firstly,the research background and significance of this topic are elaborated.The development of cylindrical Luneberg lens antennas is summarized,and the state of the art research of this field is revealed.Secondly,based on the dyadic Green's functions of stratified media,the analytical solution of cylindrically layered media within a parallel-plate waveguide is derived.By combing this theoretical solution with certain electromagnetic principles,a fast analysis approach of cylindrical Luneberg lens antennas is proposed,which has high efficiency and quite good accuracy.Thirdly,by integrating the fast analysis method with a heuristic algorithm,a systematical design and optimization methodology is presented.Regarding requirements of two dimensional(2-D)and wide-angle scanning lens antennas,a cylindrical Luneberg lens antenna with extremely flat beams is designed in millimeter-wave frequency band.The permittivity distribution related to extremely flat beams is analyzed.With simulations of a linear array configuration,the wide-angle scanning capacity of this lens antenna is validated.Finally,the proposed lens antenna is fabricated by using drilling holes and layered substrates.The lens antenna is then measured.When operating during 58-62 GHz,the measured results show a wide beam in the vertical plane whose beamwidth is up to 120 deg thus verifying the simulated results and confirming the extremely flat beam. |
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