Near-Field Beam Pattern for 6G Extremely Large-Scale Arrays
Due to the sharp increase in the number of antennas in extremely large-scale arrays(XL-array),the communication between users and base station(BS)will be within the Rayleigh distance of the XL-array,resulting in the traditional far-field beam pattern based on the plane wavefront no longer applicable.In order to solve this problem,an approximate near-field field strength expression is firstly obtained by considering the near-field spherical wavefront and using Taylor expansion.According to the obtained near-field beam pattern,a novel phe-nomenon i.e.,the beam angle deflection,is revealed,and a new metric,i.e.,the regression distance,is introduced to characterize the de-gree of the beam angular deflection.Next,the regression distance fitting function is proposed,which describes the relationship between the regression distance and the target beam angle,the array aperture,and the carrier frequency.The simulation results demonstrate that the pro-posed regression distance fitting function can well characterize the near-field beam pattern characteristics.
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