| From the appearance of the first generation(1 Generation,1G)wireless communication system to extensive commercial application of the fourth generation(4 Generation,4G)wireless communication system,the function of wireless communication system has been expanded from supporting voice service only to supporting voice and high-speed data service.With the gradual deployment of the fifth generation(5G,5 Generation)wireless communication system,wireless communication technology will be filtered into all aspects of the human production and life,making profound changes in the whole society.In the age of 4G Communication,the number of mobile communication devices has been increased dramatically,and the data usage of individual devices has also been increased rapidly.However,5G communication aims to support Enhanced Mobile Broadband(EMBB),Massive Machine Type Communication(MMTC),and UltraReliable Low Latency Communication(URLLC),which will further introduce massive device connections and thousandfold increase in data traffic growth.Therefore,both the commonly used 4G communication and the future 5G communication require the communication system to have the characteristics of high data transmission rate and large channel capacity.Antenna is the last step of signal emission and the first step of signal reception in communication system,the performance of antenna will directly affect the overall system performance.Multi-band and broadband antennas can satisfy the requirements of high data rate and large channel capacity of communication systems,and they are conducive to realize miniaturization of the system.What's more,the combination of circular polarization with multi-band/broadband antenna can realize the multi-function of antenna and meet the diverse application scenarios of wireless communication systems.Multiple Input Multiple Output(MIMO)antenna technology adopts multiple antennas at the receiver and transmitter.By combining spatial multiplexing,the channel capacity of the system can be doubled improved without increasing the bandwidth.Based on the application background of 4G and 5G communication,this thesis has made a thorough research on multi-band/broadband antenna and MIMO antenna in order to improve the antenna performance.The specific contents are as follows:1.Research on multi-band planar antenna.Firstly,a triple band planar monopole antenna is proposed,which can cover various communication standards of GPS/LTE/WLAN/Wi-Fi/WiMAX.By loading different resonant elements,three working bands of 1.55-1.67 GHz,2.2-3GHz and 5.13-6GHz are achieved.Meanwhile,a dual-band circularly polarized planar printed antenna covering WLAN/Wi-Fi/Bluetooth/WiMAX wireless communication system is proposed.By loading a parasitic inverted L-shape strip on the top plane of the substrate,and etching a slot in the ground and loading an L-shape strip on the ground,the circular polarization is achieved in two bands of 2.39-2.75 GHz and 5.15-6GHz.2.Research on broadband circularly polarized antenna.The folded frame slow wave structure used in traveling wave tube has wideband characteristic.Here,by transforming a three-dimensional folded frame structure into a two-dimensional plane structure,and utilizing the structural characteristics of providing transverse and longitudinal electric field components,a single-period circularly polarized planar foldedframe antenna is proposed.In order to further improve the performance,the final tapered multi-period planar folded frame antenna is obtained by increasing the number of period and gradually changing the length of microstrip strips in each period.The test results show that the-10 dB impedance bandwidth of the tapered multi-period planar folded frame antenna is 1600MHz(4.5-6.10GHz)and the corresponding 3dB axial ratio bandwidth is 1100MHz(4.7-5.8GHz).3.Research on high isolation dual-element MIMO Antenna.The isolation between antenna elements is one focus of MIMO antenna design.Based on the simplest rectangular patch antenna,the effect of loading meander line to improve the isolation between antenna elements is studied.The results show that the isolation between two rectangular patch antenna elements is increased by 18 dB compared with the one with a slot in the ground by inserting a slot in the ground and loading one mender line in the slotted ground.The isolation between antenna elements can be increased by 31 dB by loading two meander lines in the slotted ground.Thus,the high isolation between MIMO antenna elements is realized.4.Research on self-isolated broadband MIMO antenna.The improvement of isolation between MIMO antenna elements often comes at the cost of increasing the complexity or spacing between the antenna elements,which is not conducive to the simple processing and miniaturization design of MIMO antenna.A broadband circularly polarized dual-element MIMO antenna with self-isolation characteristics is proposed.Two antenna elements with circular polarization characteristics are printed on different sides of substrate.By using polarization diversity technology and loading inverted Lshape metal branches on the ground of antenna elements,high isolation between elements is achieved with a spacing of 0mm.In addition,extensible broadband MIMO antenna with self-isolation characteristic is presented.Two inverted L-shape metal branches on the ground of the antenna elements can help achieve high isolation between adjacent elements when the spacing is 0mm.At the same time,the number of elements can be expanded according to the actual engineering requirements... |
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