Research On Mobile Terminal Diversity Antennas And Their Receiving Characteristics In Confined Space

Electromagnetic wave will refract,reflect,scatter or diffract when propagating in confined space due to the existence of obstacles and interfaces,which will lead to multipath fading effect,seriously affecting the stability of mobile communication radio coverage,and then affecting the quality of communication.As a recognized mainstream technology that can effectively suppress multipath fading,diversity technology is widely applied in the field of mobile communication.However,the research of terminal diversity antennas based on confined space is few,and most of them are to optimize the coverage of radio wave from the perspective of transmitting antennas.Few scholars study the receiving diversity antennas considering the transmitting antenna and the environment factors simultaneously.With the development of mobile communication,antennas tend to be integrated and miniaturized.Therefore,it is of great theoretical significance and practical value to study the integrated and miniaturized mobile terminal diversity antenna and analyze its radio receiving characteristics in confined space.In this paper,three kinds of typical diversity antennas are studied,including linear polarization diversity antenna,circular polarization diversity antenna and ultra-wideband pattern diversity antenna.The radiation characteristics of these three types of di'versity antennas and their receiving characteristics in confined space like tunnels are studied through simulation and measurement,and the good diversity performance of the antennas are verified.The main work and innovation include the following three aspects:(1)Based on microstrip patch antenna^a simple linear polarized diversity antenna is designed by orthogonal arrangement of antenna elements.The antenna operates at 5.8GHz and has isolation of higher than 23.2 dB taking the advantage of polarization orthogonality.The cross-polarization is better than-43.0 dB in the main direction of radiation,and the envelope correlation coefficient over the working frequency band is less than 0.00059,which means that the polarization diversity antenna realizes good diversity effect.The feed structure is then optimized and the characteristic of dual-frequency polarization diversity of 3.5GHz and 5.8GHz is realized by slotting on the patch,making the antenna more practical.In addition,the receiving characteristics of polarization diversity antenna in confined space are measured,which verifies the feasibility of polarization diversity antenna for improving the stability of signal reception in confined space.(2)In this paper,a miniaturized UWB monopole antenna is designed using the method of "Cutting-Half Symmetricallyalong E-plane".The pattern diversity antenna which consists of two unipolar monopole units placing in the same direction has miniaturized size and ideal patterns to realize good pattern diversity.At the same time,the existing decoupling technology is deeply studied and analyzed in this paper.The hybrid decoupling structure which combines floor branches and Y-shaped floor slots achieves the optimal isolation effect,meeting the requirements of diversity antenna.Experiments are carried out to verify the receiving characteristics of pattern diversity antenna in confined space.The diversity effect is remarkable,which can effectively improve the stability of signal reception.(3)Based on the rectangular wide slot structure,a wide-band circularly polarized antenna element is designed using linear polarization excitation and perturbation.The antenna element radiates different circularly polarized wa'ves in different directions perpendicular to the plane of the antenna.Two circularly polarized diversity antennas are designed by means of orthogonal combination and spatial three-dimensional combination of four elements.Two diversity antennas show good and adaptable diversity performance,which can meet the needs of different environments and equipments.