Study On Wideband And Multiband Monopole Antennas With Multi-branch And Meandered Radiators

With the rapid development of wireless communication and electronic technologies, applications in present-day mobile communication systems usually require the antenna with small size, multiband and wideband. Research on the compact multiband and wideband antennas has important value both in theory and practical engineering application. In consideration of related research projects and the need of wireless mobile communication, an in-depth study of multiband and ultra-wideband antenna for WLAN/Wi MAX/UWB applications is carried out. And a series of multiband and ultra-wideband antennas with compact size have been designed.The major contributions of the dissertation can be outlined as follows:1. The multiband antennas with several branches are studied. The design methods of miniaturizing the antenna and the radiator of antenna are presented based on the research of miniaturizing. A compact tri-band planar monopole antenna is designed by slotting the radiator of antenna and the lateral size of the radiator is just 3.5mm. Then the mutual coupling between the different stubs is used to realize the distributed capacitive loading in order to miniaturize the antenna. The size of the proposed tri-band planar monopole antenna is 21mm×29mm, while the lateral size of the radiator is also 3.5mm. At last, the meandering technology is used to reduce the vertical size of the antenna. By combine the meandering and loading technologies,a compact tri-band monopole antenna with size of 17.2mm×28mm is designed and the height of the radiator of antenna is 16 mm. All the designed antennas can cover the 2.4/5.2/5.8 WLAN and 3.5 /5.5 Wi MAX bands. They can be applied for the electronic system which needs the tri-band monopole antenna with small radiator.2. The multiband antennas with the meandering radiator are studied. The design methods of using the high mode of the resonant branche s to cover high band is presented to design the tri-band antenna with high performance based on the research of the multiband monopole antenna with wider bandwidth in the lower band. By loading one and two rectangles to the radiator, respectively, the resonant frequency of the high mode shifts toward lower frequencies to cover the high band of the tri-band monopole antenna. The sizes of the designed antennas are both 25mm×36mm。The meandering technology not only can lower the resonant frequency of the high mode, but also can reduce the size of the antenna. By combining the loading technology and the mutual coupling between the different reso nant branches, the size of the tri-band monopole antenna can be reduced further. The sizes of the proposed Ψ-shaped and meandering ring monopole antenna, respectively, are 24mm×31.5mm and 21mm×33mm. With the strategy of mode, all the designed tri-band monopole antennas can cover the 2.4/5.2/5.8 WLAN and 3.5 /5.5 Wi MAX bands. They can be applied for the electronic system which needs the tri-band monopole antenna with small size and high performance.3. The ultra-wideband monopole antennas are studied. The design method of reducing the effect of the ground plane of the planar UWB monopole antenna is presented. According to Hertz’s edge effect of radio current distribution, the asymmetrical structure of the radiator can decrease the surface current distribution on the other portion of the ground plane. This suggests the ground plane have weak effect on the antenna performance. We designed a UWB monopole antenna covering the 3.1-10.6GHz, for the purpose of validation the design strategy.4. The multiband UWB planar monopole antennas are studied. Based on the wireless communication standards WLAN/Wi MAX/UWB, the related research of the multiband UWB antennas is carried out. We designed an integrated WLAN 2.4 GH and UWB monopole antenna with two resonant branches structure. It can be applied for the electronic system which integrated more wireless services. By notched the radiator, we design a dual-band UWB monopole antenna, which can produce suppression in the WLAN 5.2/5.8GHz and Wi MAX 5.5GHz bands.