| As radio communication technology becomes more and more mature,broadband antenna technology and array antenna technology have always been the key research directions of scholars at home and abroad.Wideband antenna technology is favored in the fields of UAV detection,target recognition,and radar direction finding due to its advantages of large system capacity,high transmission rate,and strong penetration ability.On the other hand,the development of array antenna technology has also made great progress.It is no longer restricted to the traditional array form.In some special use requirements,new requirements are put forward for the performance and structure of the array antenna.First,In this paper,for the UAV direction finding system,a broadband array antenna for UAV direction finding is designed.First of all,the form of adding ridges inside the antenna unit is used to realize the ultra-wide frequency band operating characteristics.Secondly,the45-degree polarized feed and the 9-element circular array are used to achieve omnidirectional coverage of the horizontal plane obliquely polarized beam in the working frequency range of 2～18GHz.The final experimental results show that the in-band standing wave ratio of the unit satisfies VSWR<3,and has good full-band beam overlap performance.In addition,this paper also conducts research on the amplitude comparison direction finding algorithm,clarifies the working principle of the algorithm,and introduces the direction finding accuracy analysis of the amplitude comparison direction finding algorithm in the system.The wideband antenna array of direction finding is simulated and analyzed and the accuracy of direction finding is simulated.Then,this paper studies the beamforming antenna and designs a new waveguide slot traveling wave array antenna working in the C-band.First of all,the radiation form of the non-standard rectangular waveguide with narrow sides and slanted slits is adopted,which not only ensures the electrical performance,but also greatly reduces the size and weight of the unit in engineering.Secondly,in order to meet the shaping requirements,the cosecant square radiation pattern beamforming is performed on the elevation plane using a hybrid algorithm of GA and PSO,and the amplitude and phase distribution characteristics of the corresponding slots are obtained.By establishing a waveguide slot sub-array model,the normalized conductance value of the slot is extracted,and on the premise of ensuring resonance,the conductance vs.inclination angle curve and the resonance relationship curve are fitted by adjusting the inclination angle and chamfering depth of the slot.The waveguidecoaxial converter and the absorbing load for the traveling-wave waveguide slot array are developed.The final experimental results show that the designed new waveguide slot array antenna satisfies VSWR<1.2,and the elevation plane pattern satisfies the requirement of cosecant square forming.The gain fluctuation of the flat section is less than 3d B,the sidelobe level is less than-14 d B,and the gain drop curve of the cosecant section meets the requirements.In order to realize the radiation characteristics of narrow beam and low sidelobe in the azimuth plane,an 8-element linear array is formed for the new waveguide slot antenna,combined with a one-to-eight low-sidelobe Taylor power division network.The final results show that the antenna array achieves the radiation characteristics of low sidelobe and narrow beam in the azimuth plane,the gain is greater than 21 d Bi,the sub-discrimination level in the azimuth plane reaches-20 d B,and the 3d B beam width is less than 14°. |
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