A Study Of Multiband Miniaturization Omnidirectional Antennas

With the rapid development of the wide-band wireless communication technology,the design of the wide-band antenna has been paid much more antentions.This thesis mainly studies the development of wide-band omni-direction antennas and their realization.Three types of wide-band omni-directional antennas are simulated and verified.Broadband antennas are required for the high-speed transmission of a large amount of information.Reduce the number of antennas on the carrier,it can achieve the miniaturization of equipment.In this thesis,we develop several boradband omnidirectional antennas with different polarizations,including horizontal polarization and vertical polarization.Base on the wide-band omnidirectional vertical polarization of the single-cone antenna,a compact vertical polarized omnidirectional antenna element and its array are proposed.The bandwidth of the antenna is improved by loading the cylinder,the shorting column and the short circle,while reducing the height of the antenna profile.The influence of different loading conditions on the antenna performance is analyzed in detail.The simulated results show that the bandwidth of the antenna is 86% respectively,and the gain variation is less than 3d B.On the basis of the antenna element,a four-element vertical polarized omnidirectional antenna array is designed,and a wide broadband feed network is designed.Two kinds of broadband horizontal polarized omnidirectional antennas are proposed.Antenna includes arc-shaped dipoles,coupling dipoles and a broadband feed network,and the parasitic branches form a horizontal current loop to achieve a horizontally polarized omnidirectional radiation.The 10-d B return loss bandwidth of the antenna is 47% and 53%,respectively,and the roundness is less than 1.5 and 1.7,respectively.On the basis of the antenna unit composed of four antenna array to achieve high gain antenna.In order to feed the array,Designed a broadband power splitter.A miniaturized balanced balun applied in a broadband communication system,which has the characteristics of a power splitter and a phase shifter that couples the energy through a floor slot through a short-circuited branch line of an unbalanced port To the two balanced output ports,to achieve the energy of the equal power and phase of the phase.The simulation results show that the difference between the amplitude of the balanced output of the two-balanced ports is that the balun medium is in the range of 1GHz ~ 3.3GHz(relative bandwidth of 105%).Board size of 0.1 * 0.1 wavelength to achieve the purpose of Balon miniaturization.Through the simulation analysis of different forms of omnidirectional antenna,the design method and radiation mechanism of different polarized omnidirectional antenna are mastered,and the technical basis is provided for the wide application of omnidirectional antenna.