Millimeter-Wave Feeding Network Miniaturized Wide-Angle Scanning Array Antenna

With the rapid development of communication technology,the future 5G technology is developing in the direction of diversification,broadband,synthesis and intelligence.As one of the important carriers of the Massive Multiple-Input Multiple-Output（MIMO）technology,millimeter-wave multibeam array antenna（MBA）has the characteristics of simple structure and low design difficulty,which has received wide attention from academic and industrial circles in recent years.However,due to the excessive size of its feeding network,it can no longer meet the demand of ultra-large-scale circuits to achieve high integration.Therefore,in this dissertation,the research of miniaturized feeding network is carried out to address the drawbacks of the millimeter-wave multibeam array antennas such as complex structure and large size.In addition,the research of wide-angle multibeam array antenna is carried out to address the problem of limited scanning beam range of the millimeter-wave multibeam array antenna.The research conducted in this dissertation is as follows:1.Research on transverse miniaturized multibeam array antenna:Firstly,the physical structure,field distribution,and transmission characteristics of the folded C-type substrate integrate waveguide（FCSIW）transmission line are comprehensively analyzed,and the geometric dimensions of the FCSIW transmission line are determined.Compared to the substrate integrated waveguides（SIW）with similar transmission characteristics,the size of the FCSIW transmission lines can be reduced to 60%.Next,a millimeter-wave four polarization array antenna is designed based on the FCSIW transmission lines,which includes four mutually perpendicular single branch slot array antennas and a combined differential feed network.Four single branch slot array antennas are placed perpendicular to each other to form a windmill shaped antenna,achieving four polarization modes with a pair of orthogonal linear polarization,left circular polarization,and right circular polarization.Secondly,a millimeter-wave multibeam array antenna with sidelobe suppression is designed based on the FCSIW transmission lines,which can achieve the sidelobe levels of-25d B and-17d B for the H-plane and the E-plane radiation patterns,respectively.Finally,a transverse miniaturized 4×4 butler matrix and the multibeam array antennas are designed with size of 1.24λ×5.54λ×0.1016λand 2.84λ×11.01λ×0.1016λ.Compared with their conventional counterparts,their occupied areas can be reduced by40%and 33.2%,respectively.2.Research on longitudinal miniaturization of the multibeam array antenna:Firstly,a coexistence mode composite left-/right-handed transmission line technology is proposed to solve the miniaturization problem of beamforming networks in the longitudinal dimension.Its core is to introduce a longitudinally extending interdigital gap at the center line of the SIW transmission line,forcing the SIW transmission line to incorporate the interdigital capacitance,and achieving reverse changes in phase constantsβ₁₀ andβ₂₀.By increasing the phase constantβ₁₀ and decreasing the phase constantβ₂₀,the length of the coupling region of the coupler is reduced,and the longitudinal miniaturized directional couplers and the cross coupler are obtained,respectively.Subsequently,different types of longitudinal miniaturized beamforming networks and multibeam array antennas are designed.That is,the coexistence mode composite left-/right-handed H-plane 4×4 SIW butler matrix,the coexistence mode composite left-/right-handed 4×4 FCSIW butler matrix,the coexistence mode composite left-/right-handed E-plane 4×4 SIW butler matrix and the coexistence mode composite left-/right-handed H-plane multibeam array antenna.Compared with their conventional counterparts,their longitudinal sizes can be reduced by 32%,30.7%,22.1%,and 29%,respectively.Secondly,in order to break through the size constraints brought about by the traditional butler matrix topology,a multimode composite left-/right-handed transmission line technology is proposed.Finally,the 3×3 beam forming network,the 4×4 beam forming network and the three-port multibeam array antenna have been designed.Compared to the traditional SIW butler matrix,their longitudinal dimensions have been reduced by58%,43%,and 60%,respectively.3.Research on the wide-angle multibeam array antenna based on the point-to-point phase compensation metasurface:A passive metasurfaces for gain enhancement and gain fluctuation weakening of the wide-angle millimeter-wave multibeam array antennas has been proposed.Its core technology includes the wide-angle Huygens’unit cell and the point-to-point phase compensation method.The Huygens’unit cell is composed of an umbrella type electric dipole pair with position offset,which can achieve high transmission performance of the TM electromagnetic waves from-70°to+70°.The point to point phase compensation method is to map all beams of the multibeam array antenna onto the phase modulation plane,and then block the phase modulation plane.That is,each beam corresponds to an independent block area,and each block area can achieve independent adjustment and control of the phase of the associated beam.Based on the proposed passive metasurfaces,two applications for improving the beam performance of the array antennas have been proposed,namely,enhancing beam gain and weakening beam gain fluctuations.The former can achieve beam coverage with a pointing angle ranging from-55°to+57°.At 30GHz,the gain difference between the edge beam and the center beam is 2.69d Bi,and the beam gain enhancement range is 7.53d Bi to 8.04d Bi.The latter can reduce the fluctuation of beam gain within the range of-70°to+70°.In theory,the gain difference between the edge beam and the center beam can be controlled within the range of 0.32d B.4.Research on the wide-angle multibeam array antenna based on the controllable beamwidth antenna:The antenna with controllable beamwidth is proposed.It consists of a traditional slot array antenna loaded with the dumbbell-type metamaterial arrays,and can be applied to the millimeter-wave multibeam array antennas to achieve wide-angle scanning.The slot array acts as the primary excitation source,and the parasitic currents can be induced on the dumbbell-type metamaterial array,which are vertical currents located on the dumb handle and horizontal currents located on the dumbbell sheet,respectively.By changing the size of the dumbbell sheet,the horizontal current distributed on both sides of the antenna element can be adjusted,and their phase difference and amplitude can be changed.As the size of the dumbbell sheet increases,the beam pointing angle of the pattern generated by the horizontal current gradually shifts from the broadside direction to the endfire direction.Finally,under the combined action of the various excitation sources,the antenna with controllable beamwidth is proposed,and its half power beamwidth can be changed from 108°to 218°.In addition,the 8×2 array antenna is composed by using the proposed antenna element.An optimal dumbbell sheet can be sought to maximize the beam coverage of the array antenna.Finally,the wide-angle multibeam array antenna is designed with a half power beamwidth that can achieve a coverage range of-70°to+69°.