| With the rapid growth of communication speed and throughput demand in modern information society,the fifth generation wireless systems(5G)has become the mainstream topic of research in the field of communication.Since there are abundant spectrum resources available in the millimeter wave(mm Wave)band,5G mm Wave applications have attracted a lot of research interest.Massive multiple-input multipleoutput(MIMO)which adopts a vast amount of antenna elements focusing energy to target region through beamforming to improve link gain,signal-to-noise ratio(SNR)and anti-interference ability,is one of the key-enabling technologies to realize 5G communication.Multibeam antenna array provides the most crucial candidate for massive MIMO systems.In this dissertation,the mm Wave planar integrated onedimensional multibeam antenna arrays and two-dimensional multibeam antenna arrays are studied in the field of analog beamforming.The main contents are as follows:Firstly,a one-dimensional(1-D)multibeam antenna array based on substrate integrated waveguide(SIW)Butler matrix and a 1-D multibeam antenna array based on substrate integrated coaxial line(SICL)Butler matrix these two forms were proposed and implemented.According to the principle of Butler matrix,some key circuit devices such as 90° hybrid coupler,crossovers and phase shifter were designed utilizing SIW and SICL technology respectively and then two kinds of 4×4 broad band Butler matrix were realized.For the SIW Butler matrix,its operating band of is 24-28 GHz and its impedance bandwidth is more than 15.4%.For the SICL Butler matrix,its operating band of is 23-31 GHz and its impedance bandwidth is more than 29.6% with higher integration.Feeding the 4-element tapered slot antenna(TSA)linear array and Vivaldi linear array with these two Butler matrices respectively,two types of 4-beam planar integrated 1-D multibeam antenna arrays were implemented.They both have excellent impedance broadband and gain broadband characteristics。According to the principle of two-dimensional(2-D)orthogonal beamforming that the 2-D coverage can be achieved by two types of 1-D beamformers in two orthogonal planes with a transformation of coordinates,the proposed 1-D multibeam antenna array based on SIW Butler matrix were expanded to 2-D passive multibeam antenna array and 2-D hybrid multibeam antenna array.For the 2-D passive multibeam antenna array,the TSA array is fed by two stages of 16-way Butler matrices placed orthogonally to generate 16 beams simultaneously,where the 4 first-stage Butler matrices control the vertical angle and the 4 second-stage ones control the horizontal angle.A novel 2-D interconnection method with twisted SIW is applied to connect these two stages of Butler matrices.The measured results exhibit that the 2-D passive system is capable of steering the 2-D coverage from-45° to 45° in the horizontal and vertical directions with a gain fluctuation less than 5 d B and its maximal beam gain is 9.4 d Bi at 26 GHz.For the 2-D hybrid multibeam antenna array,the horizontal phase is controlled by 4mm Wave active beamformer chips,while the vertical phase is controlled by 4 SIW Butler matrices.The Butler matrices and the active beamformers are interconnected by connectors and cables.The hybrid system consists of 16 antenna elements,which can generate 4 beams scanning flexibly in the horizontal direction simultaneously.The measured results exhibit that the 2-D hybrid system is capable of steering the 2-D coverage from-45° to 45° in the horizontal and vertical directions and the gain fluctuation is less than 4 d B in the horizontal direction.At 26 GHz,the maximum measured beam gain of the array is 10.9 d Bi and the chip channel gain is 27 d B.These two 2-D multibeam antenna arrays demonstrate the 2-D orthogonal beamforming principle at analog beamforming level successfully.Part of the work in this dissertation will be published in IEEE Transactions on Microwave Theory and Techniques(Accepted). |
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