Study On Novel Antenna Technology In Wireless Communication System

With the development of wireless communications, mobile devices have evolved into intelligent terminals. The high-speed data services, multimedia function and the connection to multi-standards according to the necessary of mobile requirements, request the antenna and RF front end requirements have a higher degree of miniaturization and high performance. Diversity antenna technology and dual-band technology is of particular concern in recent years.Based on the requests of small volume, multi-band, high performance and high bandwidth in current wireless communication, diversity technology and dual-band technology are investigated in this paper. Meanwhile, the simulation and experimental results are given. The main thesis is divided into the following sections:Firstly, the statuses of the antenna in wireless communications are presented. Then several important parameters, which describe the performance of antennas, methods and software for antenna analyze are introduced.Secondly, a novel dual-polarized microstrip patch antenna fed by aperture coupled feed and probe feed is presented. The T-shaped microstrip feedline and the hybrid feed are adopted to improve the isolation between two ports. In order to improve the input impedance of the proposed antenna, the "hour-glass" shaped slot is used. The measured center frequency of the antenna is 2.37 GHz, the return loss for port 1 is -16.08 dB and -21.92 dB for port 2, and the isolation between the two ports is -24.24 dB. Then, four slots are embedded along the centerline of the ground plane so that the bandwidth of antenna is highly improved. Good agreement between the measured and simulated results has been achieved.At last, a novel broadband differential dual-frequency antenna is designed, simulated and measured. The antenna is designed on an LTCC (Low Temperature Co-Fired Ceramics) substrate. The rectangular ring patch is etched on the top of the substrate, and the fork-shaped 50Ωmicrostrip feedline is on its back. It is a wide slot antenna with a balanced structure, and is fed by the differential signal. This substructure makes the antenna has a wide bandwidth. The proposed antenna can work at both 2.63 GHz and 5.13 GHz, with the odd mode reflection coefficients -14.43 dB and -15.67 dB respectively. A good broadband characteristic is obtained. At the lower working band, the impedance bandwidth is about 220 MHz (for the relative bandwidth 8.37%), while those for the higher working band are 1.49 GHz (for the relative bandwidth 29.04%). The proposed antenna has a good gain and the radiation patterns are nearly omni-directional at both two working bands. Good agreement between the measured and simulated results has been achieved.