| The 5th Generation(5G)uses both sub-6 GHz and millimeter-wave frequency bands for mobile communication,which puts forward higher requirements for antenna design of both base stations and terminal equipment.The radio frequency(RF)system of 5G equipment should be compatible with old models such as 2G and 4G as well,so a large number of antennas need to coexist,making antenna miniaturization one of the research hotspots.Filtering antenna is a potential miniaturization solution,combining the two major parts of the RF front end,the antenna and the filter,to reduce the size and loss significantly.Wideband planar filter antennas are widely used in terminal equipment.Millimeter-wave frequency band has been applied to commercial communication system for the first time.Its broadband characteristic guarantees the advantages of large capacity and high bit rate of 5G communication,but its loss,fabricate and cost are quite tricky issues.In this thesis,some new technologies on antenna design are introduced,including the formation methods of filter antennas,magneto-electric(ME)dipole antennas theory,array de-coupling operations and principle of Defected Ground Structure(DGS).Then,a planar filter monopole antennan for terminal equipment is proposed,which has the characteristics of broadband and omnidirectional radiation.In addition,one 4×4 millimeter-wave array with high isolation for 5G base stations is proposed,in a low-cost PCB structure.The main research work and conclusions are as follows:1.Investigate and analyze the development status of planar monopole antenna,and propose a broadband planar monopole antenna.According to the symmetry of the disc monopole,the half-cutting operation is adopted to reduce the antenna size.When a parasitic ring is loaded around the disk radiator,the current on its surface is in the opposite direction to the current on the disk,so the far field can cancel each other out.For the first and second order resonance,two gain nulls of different frequencies exist respectively to realize the filtering characteristics.Then,a second order semi-dumbbell type DGS is etched under the feedline of the monopole antenna,whose low pass characteristic is used to reduce the high frequency out of band gain.In addition,a new null outside the band at high frequency is constructed by etching an L-shaped slit in the metal disk to disturb the surface current.As a result,the antenna can work in the broadband range from 1.98 GHz to 3.68 GHz,and the relative bandwidth reaches 57.1%.Its out-of-band suppression is more than 7 dB,and the two radiation zeros have suppression of 17.1 dB and 14.4 dB,respectively.2.To meet the requirements of 5G millimeter wave base station array,a 4×4 broadband high isolated antenna array is proposed,which has the ability of large angle scanning.Its size is only 20 mm×35 mm.Firstly,this chapter improve a planar ME dipole antenna.In order to ensure sufficient mechanical strength,a single-layer dielectric plate is changed into a double-layer dielectric plate.Then a strip-line structure of one-to-four power divider is simulated,and the transition from strip-line to microstrip line is analyzed.Symmetric plated through holes are used to improve the transitional fluency.Following,1×4 and 4×4 arrays were formed by the improved ME dipole elements,and the simulation results of the arrays were analyzed.To improve the isolation,the coupling between channels is reduced by using beam downdip and split resonant ring with ground connection.Finally,the simulation results prove that the impedance bandwidth of the array completely covers the 24.25 GHz ?29.5 GHz frequency band needed,with the isolation between adjacent ports better than 20 dB,and the array can scan to ±55° on the whole.The measured results of prototype are in overall agreement with the simulation. |
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