Research On Reconfigurable Filtering Antenna Technology For 5g Mobile System

With the 5G mobile communication technology gradually entering the commercial process,people put forward higher performance requirements and more functional requirements for the corresponding communication equipment.For a terminal device,it often needs to be compatible with multiple functions including 5G,which brings a problem: how to fit a large number of communication components suitable for different communication bands and standards in a small space.As an important part of the wireless communication system,the filtering antenna also faces the compatibility problems of different communication frequency bands and standards.In the existing studies,the filtering antenna is mainly reconstructed in the following dimensions: pattern reconfigurable,frequency reconfigurable,polarization reconfigurable,bandwidth reconfigurable,etc.At present,more than 70% of the existing researches mainly focuses on the frequency reconfigurable aspect.There are relatively few reconfigurable filtering antennas with radiation pattern and polarization characteristics,and even fewer researches on the reconfigurable filtering antennas with both characteristics and more dimensions.Therefore,this thesis carries out a research on the reconfigurable filtering antenna.The contents include three parts:(1)A low-profile directional pattern reconfigurable filtering antenna is proposed,which consists of a one-quarter microstrip power divider,a pair of short-circuit filtering branches with one-quarter wavelength,and four half-mode slot antennas.The filtering ability is realized by the electrically coupled filtering branches,and the pattern reconfigurability of the filtering antenna is realized by controlling the PIN diode on and off of the four arms of the power divider.The whole antenna has the characteristics of low-profile and compact size.The measured results show that the antenna's working frequency is from 1.90 GHz to 2.28 GHz,covering n34 and n84 for 5G.The max gain of the antenna is 3.52 d Bi.The proposed antenna can realize the reconstruction of four directions in horizontal scanning.It can be applied to a communication occasion of point to multipoint,which shows a good practical value.(2)A frequency reconfigurable filtering antenna is proposed.Based on the basic rectangular patch antenna,the proposed antenna is fed by insert coupling microstrip line to increase the bandwidth.Two radiation nulls are introduced by adding two pairs of halfopening slots along the direction of mode current,so that the antenna has the filtering effect.The antenna achieves the effect of frequency reconstruction by loading the varactor diode,and the metal-pin loaded at the end of the varactor diode widens the bandwidth to some degree.The designed antenna has been simulated and tested.The frequency tuning range obtained by simulation is 2.12GHz-2.67 GHz,and the tuning range obtained by test is 2.11GHz-2.61 GHz.When the varactors are set to 0.5p F,the simulated Peak-Realizedgain is 3.89 d Bi and the measured Peak-Realized-gain is 4.32 d Bi.When the offset voltages of the varactors are changed,the Peak-Gain of the filtering antenna is slightly changed.The maximum realized gain is 5.26 d Bi.The frequency tuning range covers the N30,N34 and N40 bands in 5G applications,with a strong practicality.(3)A filtering monopole with reconfigurable frequency and direction pattern is proposed.The radiation null of the low frequency is obtained by introducing the filtering defect ground structure under the feed branch,and the radiation null of the high frequency is obtained by loading a U-shaped slot on the monopole radiation part,so that the antenna can obtain the filtering performance.At the same time,the radiating part of the rectangular monopole is cut apart and reconnected by two varactor diodes.The frequency reconfigurability of the filtering antenna is realized by adjusting the offset voltage at both ends of the varactor diodes and adjusting the electrically equivalent length of the radiating part of the monopole antenna.The measured frequency tuning range of the filter antenna is 2.2GHz-2.75 GHz,and the test result is in good agreement with the simulation results,which proves the correctness of the design method.Based on the above-mentioned antenna,a pair of inverted L-shaped metal reflection branches are added.The connection between the branches and the ground is controlled by PIN diode to realize the ability of pattern reconstruction.The effect of loading the controllable reflector on the working frequency of the antenna is weak.Then we accomplishing the goal of filtering the antenna pattern and the mixed frequency reconfigurability.