On Missile-borne Miniaturized Widebeam Dual-polarization Antennas And Enhanced Bandwidth Of A Horizontally Polarized Omni-directional Antenna

The research works are made on the basis of scientific research projects.And the major research can be divided into two parts:The first part is the design of a miniature wide-beam dual-polarized missile-borne antenna.And the second part mainly focuses on the design process of a broadband horizontally polarized omni-directional printed antenna array.The main contexts of the dissertation are outlined as follows:1.Design of the wide-beam dual-polarized missile-borne antenna.The dissertation combines scientific research projects to conduct research on topic selection and designs a miniaturized wide-beam dual-polarized antenna for use in a missile-borne environment,including S/C band and X-band antennas.According to the requirements of dual polarization,miniaturization,wide beam,wide frequency band,and complex installation environment(metal cavity with multi-layer dielectric material covering the top),difficulties are analyzed and corresponding solutions are given.In this study,the cross slot fed by U-shaped microstrip coupled feed is used as the basic form,and the antenna carrier structure is designed to weaken the impact of the metal cavity.At the same time,the antenna layout is optimized.On this basis,the simulation analysis is performed using HFSS 13.0.The simulation results show that the overall installation size of the antenna is 90.5 mm×75.5 mm×30.7 mm,which meets the size requirements.The working mode in the bandwidth is dual-polarized radiation,VSWR?2.5,which satisfies the design requirements and lays the foundation for subsequent work.2.Design of a broadband horizontally polarized omni-directional printed antenna array.A horizontally polarized(HP)omni-directional antenna array with a broadband characteristic is presented.The proposed antenna consists of a circular array based on four planar arc dual-dipole structures,a wideband 1-to-4 feeding network with baluns,four reflectors and twelve directors.The arc dual-dipoles with four etched slots are introduced to obtain the broadband characteristic.And by using twelve directors in the front of the dipoles,the gain variation in the horizontal plane is improved.In addition,the reflector elements are able to improve the gain for the middle frequency band.With the concept,the prototype antenna with an overall size of 0.66?_L×0.66?_L×0.01?_L(?_L is the free-space wavelength at the lowest frequency)is fabricated and measured.The designed antenna exhibits a relative impedance bandwidth of 98.3%(1.245-3.652 GHz)for|S11|<-10 dB.The HP omni-directional patterns provide a gain variation less than 3.0 dB over the frequency band 1.245-3.519 GHz(95.5%).Within the impedance bandwidth,the cross-polarization level is lower than-20 dB in the horizontal plane.