Low-profile Dual-polarized Omnidirectional Ceiling Antenna Design

After more than 40 years of development of mobile communication,nowadays,people’s entertainment,official business and daily communication have been inseparable from mobile communication technology.As most of the mobile communication applications are carried out indoors,it is difficult to completely cover the indoor area with the radio signal emitted from outdoor base stations.In urban areas,the propagation of the electromagnetic wave will produce serious multipath effects.In order to reduce this kind of signal fading,the polarization diversity technique was applied and then the application demand of dual-polarization ceiling antennas came into being.Also,in order to ensure the antenna has a wide range of absorption,transmission and good symmetry characteristics,dual-polarized ceiling antenna should also have omnidirectional performance.In this thesis,several omnidirectional antennas are researched and designed.After that,they are combined into dual-polarized omnidirectional ceiling antenna.Finally,the concept of blind-free indoor distribution antenna has been proposed.The main contents are as follows:1.Several omnidirectional vertically polarized ceiling antennas have been researched and designed.The first antenna was designed on the basis of the traditional single cone antenna,and the step structure is added to increase the current path and reduce antenna height.It can cover 0.80GHz-3.68 GHz.The second antenna is composed of the single cone antenna made by the compound of truncated cone and disk,a hollow disk and short-circuit pins set on the outside of it,and the hollow disk will excite the coupling between itself and the single cone antenna to increase the impedance of the antenna.An additional low resonance frequency is introduced by those shored pins.It can cover 0.80GHz-0.98 GHz and 1.40GHz-2.20 GHz with |S11|<-10 d B.In order to simplify the manufacture,the third antenna removes the hollow disk in the second antenna,and connects the bent short circuit pins directly to the disk which links to the single cone antenna.The antenna still has a good radiation performance,and its impedance bandwidth covers 0.80GHz-0.97 GHz and1.64GHz-2.27 GHz.The fourth antenna is a trapezoidal monopole antenna covering3.3-3.6GHz,which will be combined with a horizontal polarization antenna later to achieve dual polarization coverage of 3.3-3.6GHz.2.The design and manufacture of the dual-polarized omni-directional ceiling antenna was completed.First,a dual-polarization combination antenna design was completed.The dual-polarization combination antenna has six printed dipoles arranged along the circumference to achieve horizontal omnidirectional radiation,and the vertically polarized monopole is realized by a trapezoidal metal with rectangular slits.The floor of the six printed dipoles can be used as the floor of the vertically polarized monopole at the same time.The omnidirectional horizontally polarized antenna covers 3.20GHz-4.73 GHz,and the vertically polarized trapezoidal monopole covers 3.09GHz-3.98 GHz.Then,several combination arrangements of the second low-frequency vertically polarized antenna and the omnidirectional horizontally polarized antenna realized by six printed dipoles are tried,the simulation results of several different arrangements are analyzed to clarify the subsequent design scheme.At last,with the determined arrangement,a low-profile dual-polarized omnidirectional ceiling antenna has been realized,it can cover0.80GHz-0.96 GHz,1.62GHz-2.20 GHz,3.27GHz-3.97 GHz with vertical polarization and3.30-3.60 GHz with horizontal polarization.3.The idea of indoor distribution antenna without blind area is proposed and verified.The design of an omnidirectional horizontally polarized antenna and a small circularly polarized antenna have been completed respectively,as part of blind-free indoor distribution antenna.The omnidirectional horizontally polarized antenna is composed of 8segments of curved metals with certain type slits printed on FR4 dielectric plate with a circular arrangement.The slits not only improve the impedance matching,but also equalize the amplitude and phase distributions from the originally unevenly distributed current,and the bandwidth of the antenna is 3.30GHz-3.64 GHz.The small circularly polarized antenna is realized by using two orthogonal dipoles,and the overall size of the antenna is small enough to be placed just above the blank part of the center of the omnidirectional horizontally polarized antenna.It has a bandwidth of 3.29GHz-3.70 GHz.Finally,the first designed omnidirectional vertically polarized antenna,the omnidirectional horizontally polarized antenna and the small circularly polarized antenna are combined to get an indoor distribution antenna without blind area.It can supplement the blind area of horizontally polarized radiation.