Research On Multi-band/Broadband And Compact Antennas For Wireless Communication Systems

With the rapid developments of modern mobile communication and wirelesscommunications, much higher requirements are proposed for modern communicationdevices. As one of the important parts, antenna will affect the quality ofcommunication directly. In recent years, technologies of antenna’s multi-band,miniaturization and broadband have aroused more attention.The author’s major contributions are summarized as following:1. A tri-band printed WLAN/WiMAX monopole antenna is proposed in this paper.The main radiators of the antenna are a rectangular ring with vertical strip on theupper side and an L-shaped strip etching on the other side, the L-shaped strip isconnected to the rectangular ring by a via hole. Adjusting each parameters of theantenna, the rectangular ring can operate at the lower band and upper band, theL-shaped strip can operate at the middle band. So the antenna can cover theWLAN/WiMAX bands. Experimental results demonstrate that the antenna can notonly meet the requirement of impedance bandwidth, but also have good radiationperformance.2. A compact circularly polarized printed antenna for GPS is proposed. The antennaadopts the two-layered structure, in which a diagonally rectangular patch in thelower layer is used as the driven part and capacitively-loaded patch-based crosseddipoles are used as the main radiators. A via hole symmetrical with the feedingprobe is inserted into the lower layer, and the driven rectangular patch and theradiant crossed dipoles form an impedance transformer. Adjusting each parametersof the antenna, the antenna can operate at1.5754GHz of GPS.3. A100-400MHz center-fed antenna using a composite structure is proposed. Theantenna has wider impedance bandwidth and radiation pattern bandwidth. Twosides of the antenna are cage-cylinder, and an asymmetrical bicone is in the middle.Ahelical shorting wire is used to connect the two cones of the asymmetrical bicone.Using the asymmetrical structure, the impedance bandwidth and radiation pattern bandwidth are enhanced, and the tilting and ripping of radiation patterns areeliminated; a helical shorting wire is used to reduce the antenna height effectively.With this antenna as the element, a two-element array antenna with high gain issimulated.