Research And Design Of Compact UWB Printed Antennas

Since the Federal Communication Commission(FCC)regulated the 3.1-10.6 GHz band for unlicensed UWB applications in 2002,UWB technologies have gradually become a hot research area in short distance communications.As the key component of UWB systems,the UWB anternnas play an important role in the whole system.Due to planar structure,compact size,low-cost and easy integration with printed circuit board,UWB printed antennas have attract more and more attention in the academia.This dissertation is mainly concerned with key technologies in the design of UWB printed antennas.Considering the practical application demands of UWB communication systems,some challenging issues existing in the design of the UWB antenna are discussed and studied for automotive communications,portable terminals and WLAN/LTE/UWB applications,respectively.The main works and contributions are as follows:1.For automotive communications,a compact integrated Bluetooth UWB dual-band notch antenna is proposed.The proposed antenna consists of a quasi U-shape patch,four stubs and the ground plane with a stepped slot,which is fed by a microstrip feed line and has a compact size of 30× 30 mm2."Stub 1" and "Stub2" are added to the quasi U-shape patch to realize the integration of Bluetooth and UWB,which helps to provide more wireless applications."Stub3" and "Stub4" are employed to achieve dual band-notches for lower WLAN band and upper WLAN band,which are benefit for automotive communication systems to eliminate the potential interference.In addition,the simulation for housing effects of the proposed antenna is investigated to approximate the antenna performance in presence of in-vehicular environment under two different scenarios.Results of the housing effects show stable impedance match and radiation characteristics in Bluetooth and UWB bands except rejected bands,which can ensure the suitability of the proposed antenna for automotive communications.Finally,a two-element MIMO antenna is designed for automotive communications.2.A quasi-self-complementary half-slot structure is proposed to design UWB MIMO printed antennas.Such structure is inspired by the design concepts of quasi-self-complementary structure and half-slot structure and combines the advantages of both.A two-element quasi-self-complementary half-slot antenna is designed,which has compact size of 22.8×18 mm2 and operates from 2.88 to 11.87 GHz.A semi-ellipse radiator and a quasi-ellipse shaped protuberant ground plane are adopted to build the basic structure and further to design the proposed antenna element,which is called quasi-self-complementary half-slot structure.Owing to the advantage of the special structure,the proposed antenna can achieve good isolation without using decoupling structures,obtain an ultrawideband operation and also keep a compact size like the MIMO antenna with half-slot structure.Simulated and measured results show that the proposed two-element quasi-self-complementary half-slot antenna has good directional radiation properties,wide impedance bandwidth and both the radiator and ground plane are the parts of the antenna.In addition,to investigate the performance of the two-element quasi-self-complementary half-slot UWB MIMO antenna when installed in the portable terminals,the simulations of the proposed anternna attached to the PCB of the motherboard and the PCB of the motherboard with an USB connector are carried on,respectively.Results shows the proposed two-element quasi-self-complementary half-slot UWB MIMO antenna exhibits effective performance for portable devices.At last,in order to further study the potential application of the proposed quasi-self-complementary half-slot structure,a four-element UWB MIMO antenna is designed and discussed.3.A four-element WLAN/LTE/UWB MIMO antenna is proposed.The half-slot structure and modified half-cut monopole antenna technique are adopted to realize WLAN/LTE/UWB bands with 2-10.6 GHz while maintaining good isolation and compact size with 31×31 mm2.Compared to the two-element MIMO antenna,the four-element MIMO antenna can improve the quality of communication channels prominently.From the view of the circuit design for practical,providing MIMO antenna configurations with multiple separate not-connected grounds should be avoided,since the signals should have a common reference plane,i.e.,a common ground to help the system interprets all signal levels properly.Thus,to be practical in a real application scenario,four antenna elements with interconnected/common ground are placed orthogonal to each other for good isolation.Analysis results illustrate that the four-element WLAN/LTE/UWB MIMO antenna exhibits satisfactory performance,which proves it is a good candidate for modern wireless communication systems.Finally,the performance of the antenna with portable device housing are studied using simulation.