| Frequency selective surface(FSS)is an array structure composed of several units arranged in cycles or quasi-periods.It has the function of selecting and adjusting spatial electromagnetic waves with different operating frequencies,polarization and incident angles.With flexible electromagnetic wave control capabilities and unique physical characteristics,FSS has been widely used in the design of microwave and terahertz devices and antennas.Among them,the transmission array antenna constructed by FSS has an excellent performance in realizing directional radiation and beam control,scanning and shaping,and plays a vital role in reducing the complexity of the antenna system and increasing the degree of design freedom.However,the traditional two-dimensional FSS usually works in a single-mode state,which results in a focused array antenna constructed based on it with a narrower bandwidth and a higher profile.Moreover,the current focusing array antenna lacks a precise design method,and its design efficiency is relatively low.To solve these problems,this paper systematically studied a new type of 3D Frequency Selective Structure(3D-FSS),established an accurate equivalent circuit model and formed a comprehensive design method.Subsequently,3D-FSS was applied to the design of transmission array antennas,and two new types of transmission array antennas were efficiently designed.The specific research contents are as follows:(1)The performance indicators of the transmission array are analyzed from the perspective of the unit and the array,and the design process of the single-beam transmission array antenna is given.For the design of multi-beam transmission array antennas,the parallel particle swarm optimization algorithm(PSO)is used to optimize the distribution of the transmission array elements,which improves the radiation performance of the transmission array antenna obtained by the traditional direct synthesis method(such as high side lobe,low main lobe radiation gain,etc.),to obtain a more ideal radiation performance,and achieve-30 dB sidelobe suppression in the theoretical calculation of the pattern.Due to the introduction of the parallel PSO algorithm model,the optimization time is reduced by 87.8% compared with the traditional PSO algorithm model.(2)Aiming at the shortcoming of high profile in the transmission array based on the traditional FSS,the 3D-FSS unit is used to design the transmission array.First,the equivalent circuit model is used to analyze the order of the filter response required to meet the 360° phase shift value in the passband and based on this as an index,a 3D-FSS unit based on the series slot line is proposed.While achieving a 67.5% fourth-order band-pass filter response with a relative bandwidth of 67.5%,it can provide a 466.5° transmission phase value change,and the profile is only 0.213?0.Subsequently,a transmission array antenna based on the series slot line 3D-FSS was designed,which achieved a high-gain radiation performance of 23.7 dB at 8.4 GHz,an aperture efficiency of49%,a 3 dB gain bandwidth of 18%,and an in-band radiation pattern.Stable with frequency changes.(3)Aiming at the shortcoming of narrow bandwidth in the transmission array based on the traditional FSS,a 3D-FSS based on the coupled cascade slot line is proposed and the transmission array is constructed.The 3D-FSS can not only provide a fifth-order bandpass filter response with a relative bandwidth of 90% but also the transmission amplitude of each periodic unit at the operating frequency is close to 0 dB.Subsequently,a transmission array antenna based on the cascaded slot line 3D-FSS was designed,and the physical processing test was carried out.The test results show that the antenna achieves a 3 dB gain bandwidth of 73%,a peak gain of 22.93 dB at 4.8 GHz,an aperture efficiency of 46.8%,and the in-band radiation pattern is stable with frequency changes. |
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