Investigation On Broadband Miniaturized Omnidirectional Reconnaissance Antenna

In recent years,omnidirectional antennas have been widely used in electronic reconnaissance,passive direction finding,broadcasting,mobile communication,base station communication,identification friend-or-foe system;guided weapons,modern medical and other fields.With the rapid development of radio communication systems,the demand of miniaturized broadband antenna is becoming more and more urgent.Based on the sleeve antenna,this paper discusses the methods for realizing the characteristics of antenna broadband,miniaturization,omnidirectional and high gain,and provides theoretical analysis,antenna design,processing and testing.The main work of this paper can be summarized as follows:1.The research background and significance of omnidirectional antenna and DF antenna array are discussed.The main advantages and disadvantages of various types of omnidirectional antennas and the research status at home and abroad are summarized.The research status and performance characteristics of DF antenna arrays at home and abroad are introduced.The development trend of omnidirectional antennas and DF antenna arrays is summarized.2.The basic theory of the traditional sleeve antenna is introduced,and the design theory and empirical formula of the antenna are verified by simulation.In order to improve the performance of the antenna,the structure of the antenna is deformed,a new type of broadband sleeve antenna is designed.The S₁₁ of the antenna is less than-10 dB in the frequency range of 0.71 GHz to 2.06 GHz,and the relative impedance bandwidth is 97.5%.The maximum gain on azimuth plane is greater than 0 dBi in the frequency range of 0.71GHz-1.83GHz and unroundness is less than±1.5dB.The measured results are in good agreement with the simulation ones.3.The theory of the antenna array is introduced.The monopole antenna is used as a element to form the antenna array,and the design theory is verified by simulation.Then,a new type of high-gain broadband omnidirectional antenna array is designed with the broadband sleeve antenna as the element.The feed lines are placed spirally to reduce the influence on gain and unroundness on the azimuth plane.Finally,the S₁₁ of antenna is less than-10dB in the frequency range of 0.58GHz-2.17GHz,and the relative impedance bandwidth is 115%.On the azimuth plane,the measured gain is basically greater than 6dBi,and the unroundness is less than±1.5dB in the frequency range of 0.63GHz-1.68GHz.The measured results and the simulation ones are in good agreement.4.The basic theory of printed antennas is introduced.Based on rectangular printed monopole and triangular printed monopole antenna,a new stepped printed sleeve antenna and a new triangular printed sleeve antenna are designed to realize the miniaturization and low profile of the sleeve antenna.After testing,the S₁₁ of the antennas are less than-10dB in the frequency range of 0.6GHz-4.6GHz and1.3GHz-8.5GHz,and the relative bandwidths are 154%and 147%respectively.The measured results are in good agreement with the simulation ones.5.The basic theory of interferometer direction finding system and uniform circular array is introduced,and it is verified by simulation.Finally,the new printed sleeve antenna is used as the element to form a five-element uniform circular array and a nine-element uniform circular array respectively.The simulation results are analyzed and provide the theoretical basis for the design of circular direction-finding array.