| In the field of information and communication in recent years,mobile communication technology has been the fastest growing and most widely used.The base station antenna,as a signal relay station in mobile communications determines the quality of signal transmission.MIMO technology is widely used in modern mobile communication systems due to its communication capacity and spectrum utilization several times that of traditionalantennas.Based on the above practical application requirements,this paper focuses on the research of the radiation characteristics of the elements in the array environment,the specific work is as follows:A low-profile high-gain dual-polarized MIMO base stationantenna loaded with a meta-surface is proposed in this paper.The operating frequency of theantenna is 1.8?2.9 GHz,and theantenna is composed of meta-surface,dipoles,short-circuit construct and plastic pillars.In this paper,high gain is obtained by reducing theantenna profile,and the meta-surface is loaded to achieve the impedance mismatch caused by the low profile.Reducing the profile brings high gain but leads to impedance mismatch too.It has been mentioned in the literature to reduce the profile height by loading a meta-surface,but the dimension of the loaded meta-surface in those papers are often too large to be applied for massive array for practical applications.Therefore,a multi-layer and compact size meta-surface is adopted in this paper.According to the transmission line theory,theantenna can be equivalent to a two-port network,and the meta-surface introduces capacitive reactance to offset inductive reactance introduced by low profileantenna.The multi-layer meta-surface is equivalent to loading multiple equivalent capacitors in parallel,and the overall capacitive reactance can also be increased to obtain the same effect as loading a large-size meta-surface.In a tri-sector base station application,it is necessary to ensure that the 10 dB beamwidth of each element in the massive MIMO array are about 125°.Based on this requirement,a 48-port MIMOantenna array composed of two types of elements is proposed.The overall size of the array is 600 mm×530 mm,the array scale is 6×4 the horizontal spacing of the array elements is 80 mm,and the vertical spacing is 110 mm.Due to the small horizontal spacing and the large number of elements in the horizontal direction,the middle of the array The beam width of the array element pattern of the position is very wide,so it is necessary to use a highly directionalantenna to offset the beam width expansion caused by coupling.Due to the small row spacing,the array element is much more affected by the electromagnetic coupling of adjacent elements in the same row than adjacent elements in the same column.Therefore,the array elements with different structures are designed for different rows to ensure that the beam width of all elements in the array meet the requirements.This method also increases the freedom ofantenna array design.The final processing test results show that the operating frequency band of the array element can basically cover 1.8?2.9 GHz,the 10 dB beamwidth of each port pattern is about 125°,and the front-to-back ratio in the range of 180±20° are above 25dB. |
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