| As the energy transmitting and receiving window of the wireless communication system,the antenna is a key device of military early warning and control systems.While different military early warning and control systems have requirements for the antenna gain,antennas needed to meet the other needs such as reliability,beam-scanning,stealth.In this thesis,the wideband dipole array antennas and Fabry-Perot antennas based on Absorptive Frequency Selective Structure(AFSS)are mainly studied for the application of different military early warning and control systems.The main contents of this thesis are as follows:1.A compact low-cost wideband dipole array antenna for military vehicle test and control systems is designed.The 2×2 dipole array is designed based on the array antenna theory to enhance the antenna gain.Then,in order to achieve the power distribution from the coaxial line to the antenna elements,a feeding network which is comprised of baluns and microstrip lines is designed.The baluns combine with antenna elements produce a new resonance mode,which effectively widen the antenna bandwidth.Finally,the feeding network and the dipole array are printed on a dielectric substrate,and no additional power divider is needed.The antenna can be directly fed by coaxial line.Therefore,the proposed array antenna has the advantages of compact structure,high reliability and low-cost while achieves 10 ～ 12 d Bi of gain.2.A dual-polarization wideband tightly coupled phased array antenna for military radar detection systems is proposed.The strong coupling is achieved by the staggered overlap at the end of adjacent dipole elements,which effectively widens the bandwidth and realizes wideband and wide beam scanning.A new structure of the metal plane is designed to eliminate the radiation singularities in high frequency.The slits etching cut off the current of the corresponding mode on the plane at the frequency of the singularity appearance,resulting in a broadband and stable radiation pattern.3.A low RCS and gain enhanced Fabry-Perot antenna based on AFSS for stealth requirements of military test and control systems is designed.AFSS as part of the partially reflecting surface of the Fabry-Perot antenna,achieve the antenna gain enhancement and radar cross section reduction simultaneously.The proposed Fabry-Perot antenna has higher aperture efficiency compared to the reported Fabry-Perot antenna when they have similar gain.Moreover,the gain and aperture efficiency of the Fabry-Perot antenna are studied with the variation of aperture size,and a design reference for the aperture size of Fabry-Perot antenna is given.4.The H-plane beam broadening of the Fabry-Perot antenna is studied.Based on the conventional Fabry-Perot antenna,metal planes are loaded on both sides of the Fabry-Perot resonance cavity to reduce the electric field on the surface of the edge AFSS element,resulting in a wide Hplane beamwidth of the Fabry-Perot antenna.The results show that the new structural Fabry-Perot antenna not only obtains gain enhancement but also achieves a H-plane wide beam performance,which has more practical application value. |
PDF Full Text Request