Research On Miniaturized MIMO Antennas In Mobile Communication

With the rapid development of wireless communication system,the information transmission of wireless communication devices has greatly increased from the 2G,3G,4G to the 5G which will be commercialized.The 5G communication systems demands the higher transmission rate,lower communication error rate,shorter delay,and the larger channel capacity.All these high performance indicators depend on the research and design of antenna,especially,the MIMO(multiple-input multiple-output)antenna.Since the mobile devices and base station equipments used in the fifth generation communication technology are smaller,considering the data transmission stability and channel capacity of the MIMO antenna technology,it is widely used in communication and other related fields.The smaller devices,however,lead to many problems for the MIMO antenna such as the coupling between antenna units,activaing the surface current of the gound,etc.These problems greatly affect the performance of the MIMIO antenna.Therefore,how to improve the isolation of the miniaturized MIMO antenna becomes the key issue of modern communication technology.The thesis designed the following antennas to solve the problem.1.A dual-band MIMO antenna with ground branch has been designed.The whole dimensions of antenna are 50?26 mm2,which is fabricated by FR4 substrate material with 0.8mm thick and 4.4 relative dielectric constant.The antenna achieves the high isolation by adding the ground branch structure.Besides,the introducing of the ground branch resonance structure reduce the whole dimension of antenna.This antenna is used in 2.4GHz and 5.8GHz WLAN bands,with higher than 15 d B isolation.2.A UWB(Ultra Wideband)MIMO antenna with E-plane cutting method has been designed and measured.Its dimensions are 29?33 mm2,using FR4 substrate material and 1mm thick dielectric substrate.By the E-plane cutting method,the semicircle radiating patch antenna is divided into two antennas of a quarter circle patch,achieving the result of miniaturization.Besides,a T shaped loaded branch and a defected ground structure on the ground are loaded between the two antennas,which improve the isolation of the antenna.The designed antenna operates in 3.1-12 GHz frequency band,with higher than 15d B isolation,even higher than 30 d B in partial frequency bands.3.A miniaturized UWB MIMO antenna,which utilizes the ground branch loaded technology to improve the isolation,has been designed.Its dimensions are 50?35 mm2,which is fabricated by FR4 substrate material with 1.6mm thick and 4.4 relative dielectric constant.The antenna uses the T shaped branch to improve the isolation and the surface slotting technology of antenna is employed to adjust the impedance matching.The antenna has higher than 15 d B isolation operating in 3.1-12 GHz frequency band.4.Summary of the paper and prospects for future antennas.