| An antenna has been extensively used in modern wireless communication systemsas a very important component to radiate and receive electromagnetic waves. At thesame time, the severe demand on portable mobile terminals stimulates antenna todevelop towards multi-band, compact size. This paper first review the developmenthistory of microstrip multi-band antennas, then basic theory concerns microstripantennas is introduced. Various techniques to make microstrip multi-band antennasmore compact are discussed and summarized, especially, the method to reducemulti-band antennas sizes are discussed in detail, which are used in WLAN andWIMAX. At last, according to the current hot research topics and practical applications,two multi-band antennas of different types are designed, which are used in specificcases, besides the miniaturization is realized. Moreover, a high gain quadrifilar helixantenna is investigated as well.Two multi-band antennas applied to the wireless local area network andmicrowave access network are proposed: A compact quad-band circular slot antennawith two T-patch is present. The prototype of the proposed antenna is designed tosatisfy specific bandwidth specifications of current communication systems, includingthe global positioning system for communication (GPS;1.575-1.625GHz) the wirelesslocal area network (WLAN;2.4-2.485GHz,5.15–5.35GHz and5.725-5.825GHz),and the Microwave Access Network (WIMAX;3.3-3.6GHz). The proposed antennahas compact size of57mm×46mm×1.6mm. The antenna has been successfullysimulated, designed and measured, and the results shown that the antenna has goodimpedance match, stable gain and near omni-directional radiation patterns. A novelcompact CPW-fed slot antenna for quad-band operation is proposed. The antenna isprinted on a25×20mm2FR4substrate with thickness of1.6mm and relativepermittivity of4.6. Three L-shaped slots and a rectangular slot are fabricated on thesubstrate to achieve quad-band operation of WLAN (2.4GHz-2.485GHz,5.15GHz-5.35GHz,5.75GHz-5.95GHz) and WIMAX (3.3GHz-3.7GHz)). As the fourresonant frequencies of antenna are excited by certain parts of the patch respectively, one resonant frequency can be flexibly tuned with little effect on the other.Experimental results demonstrate the good broadside radiation patterns for the fourbands and suggest that the proposed antenna is suitable for the M-WIMAX and WLANapplications.The antennas used for the system3G technology of Mobile SatelliteCommunication usually are requested to provide high gain, wide beam and circularpolarization. To fulfill that need, we have designed of a dual-band quadrifilar helixantenna. The antenna is fed by sleeve balun and used90°self-phased structure. Wesimulated the antenna with the software of CST. The results show that the antenna canwork in about uplink1.98-2.01GHz and downlink2.17-2.2GHz two frequencies atsame time and get the emitting and receiving. The3dB of respective beam are180°and95°. |
PDF Full Text Request