Study Of Miniaturized And Multiband Antenna Technologies

In recent years, Radio Frequency Identification (RFID), mobile communication and other various wireless communication technologies have enjoyed rapid development. As one of the most important components in wireless communication system,however, the dimension of antennas has become one of the bottlenecks restricting the further miniaturization of systems. Therefore, antenna miniaturization plays a decisive role in the research for the miniaturization, high integration, and high performance of wireless communication system. On the other hand, with the swift development of VLSI (very large scale integrated circuit) and high-performance battery technologies, mobile communication terminals have integrated more and more functions, which requires mobile communication terminal antennas to be able to work at multi-frequency bands so as to meet the requirements of mobile communication, satellite communication, short-range communication and broadband access communication of different criteria and in different regions.The dissertation is devoted to the study of miniaturized and multiband antenna technologies, especially for RFID systems and mobile communication systems, consisting mainly of the study of the miniaturized, wideband and multiband RFID tag antennas design, the passive and electrical reconfigurable multiband antennas design for mobile communication terminals, and the study of measurement of RFID tag antennas and RFID system propagation model analysis. The concrete contents are as follows:1. First, a simple estimating formula for meander dipole antennas which are commonly used in miniaturized RFID tag has been deduced when such antennas are designed to match the high Q RFID tag chips, by which the parameter estimation for initial modeling of such kind of antenna is facilitated and simplified. Then various RFID tag antennas are studied: a broadband RFID tag antenna with its bandwidth from 840MHz to 960 MHz is proposed, which is not only capable of meeting the communication requirements of the whole frequency band of ISO 18000 6c, but also capable of covering the new Chinese RFID frequency band (840-845MHz); a novel dual band RFID antenna along with its equivalent circuit is proposed, and the advantages of this antenna is that it can match different impedance of the same chip at two frequency band without additional matching circuit; a novel asymmetrical dipole antenna with Omni-directional radiation by the utilization of the field component offset principle is proposed to reduces the effect on its radiation performance caused by other metal components in circuit.2. In accordance with multi-functional tendency of mobile communication terminals, a single feed passive penta-resonant antenna which covers eight wireless communication bands is proposed, while the detail of its design guidelines and principles is discussed. The proposed antenna can satisfy not only the requirement for 2G and 3G mobile communication systems, but also the requirement for IMT-Advanced (4G) mobile communication, satellite positioning and wireless broadband access communicational systems.3. In order to deal with the conflict between the dimension and the coverable bandwidth of the antenna, the reconfigurable technology is applied to cover more communication bands without changing the dimension of the antenna. Only one RF switch is used to realize antennas with nine, ten, and eleven communication bands respectively through repeated optimization of antenna structure. Thereinto, the hendeca-band antenna which has the best performance is fabricated and measured. The measured results show that the proposed antenna can satisfy not only the requirements for 2G,3G IMT-Advanced (4G)mobile communication,satellite positioning and wireless LAN, but also the requirements for TD-LTE,Bluetooth and WiMAX communication system..4. To obtain accurate performance parameters of the RFID tag antenna, a testing jig used for its measurement is designed and fabricated. To get a determinacy propagation model of the RFID system, a method combining time-domain finite integration method and moment method is used to calculate forward link of RFID system in half-open space. The results calculated through this method agree well with the experiment results in half anechoic chamber. This method can also be applied to backward link analysis of the RFID system.