| As two research hotspots of 5G communication system,Multi-Input Multiple-Output(MIMO)technology and beamforming technology have received more and more attention in the industry and academia.As an important part of modern wireless communication system,handheld mobile terminal equipment is developing toward miniaturization and intelligence,and the space reserved for terminal antenna is getting smaller and smaller.How to achieve the communication requirements of miniaturization and multi-function in a limited space is a great challenge for antenna design engineers.In order to solve the problems faced by the current handheld terminal antenna,this paper takes the handheld intelligent terminal as the research object and designs two kinds of intelligent multi-antenna arrays by combining MIMO and beamforming technologies.The main research contents of this paper include:1.An eight-element MIMO smart antenna array operating in 3.3-3.5GHz band for mobile handset applications is proposed.The antenna array is composed of two symmetrical four-element subarrays,which are arranged on the upper half along the two long sides of the mobile handset.Good isolations and envelope correlation coefficients are obtained by introducing isolation slots between the elements to achieve the MIMO functions when the array is used for receiving.Based on the method of maximum power transmission efficiency(MMPTE),the optimal distribution of excitations for the antenna array is obtained to beam the radiation energy to a desired direction with a maximum possible gain when antenna is used for transmitting.An in-house made beamforming controller is used to realize the optimal distribution of excitation to insure the antenna beam to be directed to the desired direction.By simulating the working environment of the antenna,the influence of the cellphone body and the human body on the antenna radiation performance is simulated and analyzed.2.An eight-element MIMO smart antenna system consisting of two different array modules for handheld device is proposed.The system is composed of two antenna array modules.The first module is a six-element array operating in N78(3.3-3.8GHz)band for 5G,which achieves MIMO functions for receiving and beam scanning for transmitting.The second module is a two-element antenna array,which operates in LTE/WWAN/N78(0.7-0.91 GHz,1.63-2.61 GHz,3.3-3.8 GHz)bands.To take full advantage of the existing antenna resources in the mobile device,the six elements in the first module are combined with the two elements in the second module to form an 8-element array in the overlapping N78 band.Good isolations and envelope correlation coefficients are achieved in the receiving mode by loading L-shaped slots for the combined module.The distribution of excitations for the combined array in the transmitting mode is optimized by the method of maximum power transmission to direct the beam to the desired direction with maximum possible gain,and is realized by an in-house designed beamforming controller.The impacts of the environments on the antenna array performance are investigated. |
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