Research On Indoor Broadband Omnidirectional MIMO Base Station Antenna

Due to the increasing number of users,a communication system will require its antenna to have omnidirectional radiation patterns and wide frequency bandwith.With the development of indoor communication systems,miniaturization is required to save space and costs.At the same time,to increase data throughputs,dual polarized MIMO(multiple-input multiple-output)antenna technology is introduced to indoor communication systems.High isolation among antennas elements is required for the MIMO antennas that are often mousted on room ceilings.Base on these requirements,an indoor broadband omnidirectional dual polarized MIMO antenna is presented in this thesis.This thesis is organized in the following manner:First,the development of ceiling antenna in recent years is briefly described.Second,ceiling antenna's parameters as well as some basic technical means to achieve miniaturization,broadband and omnidirectional radiation are presented.Third,the design of a horizontally polarized antenna is following where a microstrip antenna is made of four arc dipoles and three slots to increase resonance points.By introduction of a series of parasitical strips,a wide bandwidth is realized with a bandwidth from 1.69 to 2.92 GHz and a return loss of less than-10 dB.Forth,a vertically polarized antenna is developed.The vertically polarized antenna is a monopole antenna by adding a top loading ring and three shorted patches to expand bandwidth and achieve miniaturization.The monopole antenna's terminal is designed as a trapezoidal sheet.An operating bandwidth of 0.74 to 4.31 GHz and a return loss of less than-10 dB are achieved.Fifth,once the horizontally and vertically polarized atennas antenna are developed,a dual-polarized MIMO antenna is constrcued by combing the two antennas.The volume of the dual polarized antenna is 3168?168?103.5mm.After the combination,the horizontally polarized antenna element operates from 1.67 to 2.94 GHz with out-of-roundness of the radiation pattern less than 1.5 dB.The vertically polarized antenna element operates from 0.75 to 4.35 GHz with out-of-roundness of the radiation patter less than 1.5 d B.The isolation between the two elements is more than 25 dB.Sixth,the antenna is fabricated and measured.The measured results are found to be similar to the simulated results.