Study On Novel Antenna Design In Modern Wireless Communication System

At present, along with the wireless communication development, the mobile terminal already evolves the personally intelligent equipment, which could listen to the FM program, watch the television program. Simultaneously the wireless terminal becomes the small computer on the palm, which could realize high-speed access to the net as necessary. Moreover, the behind 3G system (B3G) will integrate the different standards of the wireless communication. People can connect between the multi-standards according to the demands, switch among different systems seamlessly.The multimedia function, the high-speed data service and the connection to multi-standards according to the necessary of mobile terminal, request the antennas have a wider bandwidth and a higher performance. At the same time, the cost pressure that is increasing unceasingly requests the size of the antenna more and more compact. Moreover, the tendency may request integrating mult-antenna in a wireless terminal (at least in high-frequency unit), and introduce the diversity technology as well as the MIMO technology, which proposed a higher request and a bigger challenge to the antenna.In this thesis, based on the requests of small volume, high bandwidth, high performance and polarization diversity to the antenna, several novel antennas applied to the modern wireless communication system are presented. In addition, the characteristics of antennas are studied and the experimental verifications are given. The dissertation will include the following contents.Firstly, the numerical methods such as Finite-Difference Time-Domain method, Method of Moments and Finite Element Method are introduced, which are used to analysis the novel antennas. Further more, the above three methods are compared.Secondly, the miniaturized technology of microstrip antennas is introduced. Several compact microstrip antennas operating in the 2.4GHz band, which are suitable for the wireless local area network (WLAN), have been proposed. All of the antennas obtain satisfactory radiation performance around the 2.4GHz frequency band and even the gain of individual antenna could achieve 1.2dBi.Thirdly, based on the study of short-range wireless communication, a novel CPW-fed ultra-wideband wide slot antenna is proposed. Because of the round corner of rectangular slot and partial circular patch, the bandwidth of antenna is enhanced largely. The test results show that the impedance bandwidth ratio of the antenna is more than 7.2:1 (2.5-18GHz) for the return loss S₁₁<-10dB. Meanwhile, good omnidirectional radiation performance has also been achieved.Fourthly, a coplanar wide slot diversity antenna with CPW-fed is proposed. Two orthogonal CPW-fed wide slot conformations are etched in the ground plane. The improved antenna can obtain polarization diversity signal and a higher gain (7.7dBi).Finally, based on the novel ultra-wide band antenna, a wide band layered polarization diversity antenna design suitable for the MIMO wireless communication system is proposed. Two orthogonal wide slot antennas are etched in two different ground planes individually. Two ground planes are separated by air to increase the isolation. The simulated results show that the return loss curves of two antennas almost coincide and a high isolation is also achieved.