The Research And Optimization Design Of The Ultra-wideband Antennas With High Gain

The ultra-wideband(UWB)antenna with high gain is researched and optimization designed in this paper.Two types of antenna elements are proposed based on the essential theory and the analytic procedure of the UWB antenna by Simulator CST software based on finite-element method.Moreover,the techniques of broadband feeding network and antenna array are intensively studied.The multi-sectional impedance convertor and the gradual changing line impedance convertor are introduced to group the antenna elements into arrays.Finally,the 2-element and 4-element linear arrays are measured,then,the measured results are compared with the simulated ones.The bowtie dipole is introduced to extend the bandwidth of the Quasi-Yagi antenna element,and the elements are grouped into array by the multi-sectional impedance convertor.The final antenna array's bandwidth of the return loss on a-10dB level is up to 59%,the half-power beam-width in E-plane is just 18 degrees,and the half-power beam-width in the H-plane is up to 128 degrees,and the gain is 10dB at the low frequency and 11.8dB at the high frequency,respectively.This antenna array could radiate energy in the horizontal direction with a great range,while a quite concentrated radiation is obtained in the vertical direction,and has been used in the cosco-distance and broad angle terrestrial broadband communications with the distance of 300m.The circular patch and the gradual changing line impedance convertor are introduced to broaden the operation frequency range of the 4-element circular patch antenna array.The radiation patterns of the antenna are improved by the truncated ground.The operation frequency of the antenna array is from 2 to 10.3 GHz,and the gain is from 8 to 12.1dB between the frequency range of the design index.Because of the transverse current component in the circular patch,the cross-polarized level of the H-plane patterns is not very well,while the main lobe of radiation energy and the gain are still very steady.And could obtain the directional cosco-distance terrestrial broadband communications effectively;hence can be considered as a good candidate for UWB systems.