Optimization Of Omnidirectional Antenna Radiation Performance For IoT Applications

The thesis focuses on addressing the new requirements for antenna radiation performance in the Internet of Things(Io T)era.Omnidirectional antennas are commonly used in Io T systems,and their performance is critical to the communication quality of the system.The thesis proposes a solution for bandwidth expansion and miniaturization design of omnidirectional circularly polarized antennas,as well as beamwidth expansion of omnidirectional linearly polarized antennas.For omnidirectional circularly polarized antennas,the thesis proposes a new accurate analytical solution for a tilted dipole array,correcting errors in traditional models.A multisegment tilted dipole array with more degrees of freedom is also proposed,which demonstrates the principle of axial ratio bandwidth expansion and miniaturization effect brought about by meander design.The thesis also proposes two broadband omnidirectional circularly polarized antennas based on continuous curvilinear dipoles,which significantly expand the axial ratio bandwidth while maintaining a compact antenna structure.Finally,an omnidirectional circularly polarized antenna with a usable bandwidth of 65% was designed.For omnidirectional linearly polarized antennas,the thesis conducts theoretical and simulation studies on the possibility of beamwidth expansion for normal biconical antennas.Based on parameter analysis and structural optimization,two wide-beam linearly polarized antennas with a beamwidth exceeding 160° are obtained,laying the foundation for subsequent design of omnidirectional wide-beam antennas that meet practical requirements in terms of dimensions and bandwidth.Overall,the thesis aims to address the challenges posed by Io T communication by improving the radiation performance of omnidirectional antennas.