Design Of Multiband Antenna For Miniaturized Communication Systems

With the flourishing development of wireless communication,smart portable devices such as smart phones,tablet PCs,smart wear equipments have become an indispensable part of our lives.Compared with the traditional mobile phones,smarts phones could not only make a call,but also browse the Web,watch the video,send the files or use the GPS system for navigation.Although portable devices with multi-functional modules will bring us more conveniences,these features should be supported by more protocol standards like Wireless Local Area Network(WLAN),Worldwide Interoperability for Microwave Access(WiMAX)and Ultra Wideband(UWB).Therefore,an antenna supporting multiple standards with multiband,simple structure,and compact size is highly desired for wireless portable devices.This thesis makes a research on the design of miniaturized and multi-band antennas.In the first design,two novel printed anchor-shaped slot antennas for multiband wireless applications are proposed.The first proposed anchor-shaped slot antenna(ASA1)can generate two wide bands centered at about 2.5 GHz and 5.5 GHz.The second proposed design is established on the basis of ASA1.By introducing a pair of F-shaped slits,an extra resonant mode will be excited at 3.5 GHz.Without changing the original design parameters of the ASA1,it can be converted to a triple-band anchor-shaped slot antenna(ASA2).From the aspect of system design,a platform using the proposed antennas would exhibit more flexibility and expansibility.Monopole-like radiation patterns almost remain unchanged in the E-planes and H-planes over the operating bands and sufficient gains are also obtained.Good agreement can be observed between the simulated and measured results.Having overall dimensions of 35 x 30 mm2,the proposed antennas can be easily integrated into portable devices.In the second design,an umbrella-shaped monopole antenna with band-notched characteristic for UWB systems is designed.The proposed antenna is mainly composed of an umbrella-shaped patch,a tapered microstrip,and a half-ellipse-shaped ground plane in the back.The first notched band for WiMAX application(3.3-3.7 GHz)is realized by adding an inverted U-slot in the umbrella-type patch.And the second notched band is generated by employing a U-shaped defected ground structure(DGS).The size of the umbrella-shaped monopole UWB antenna is 33 x 40 mm2 and the simulation results of the UWB monopole antenna using HFSS and CST have a good agreement.It can meet the band requirements of the UWB system with omni-directional radiation patterns.