| Lens antenna is widely used because of its advantages of low sidelobe,high gain and no feed shielding.But,modern wireless systems such as radar,communication,electronic countermeasures and measurement often require antennas with wide operating frequency band,high gain,high aperture efficiency and excellent radiation pattern,which makes the traditional lens antenna difficult to meet the requirements.However,the high design degree of freedom of the lens antenna means that it is possible to achieve the desired lens antenna through structural design,especially the development of 3D printing technology enables us to achieve the complex structure of the lens antenna.However,the high design freedom and complex structure bring great trouble to lens design.The traditional method of parametric scanning needs a lot of time and manpower and is often difficult to get the desired results.To solve these problems,this paper optimized the all-dielectric lens antenna based on genetic algorithm to solve the time-consuming problem,and set the appropriate objective function to make the antenna achieve ultra-wideband,high gain and high aperture efficiency.The lenses studied in this paper are all all-dielectric structures and can be made by 3D printing technology.The work of this paper is as follows:1.Design and research of ultra-wideband lens based on genetic algorithm(GA)and Finite difference Time domain(FDTD).The traditional lens antenna is designed for single frequency,so it is difficult to achieve the ultra-wideband characteristics.In this study,according to the characteristics of the phase center of the feed antenna,Photoshop was used to customize the graphic rectangular focusing area electric field to adapt to the frequency changing phase center of the feed antenna,so as to realize the ultra-wideband characteristics.For the rectangular focusing region,the objective function of the specific electric field is established,and GA optimization is adopted.Meanwhile,FDTD is used instead of CST to calculate the electric field distribution of the lens,so as to reduce the calculation time and accelerate the optimization.A high gain all-dielectric lens antenna operating at 6-18 GHz is designed in this paper.The antenna consists of a broad ridged horn antenna and a "targetlike" all-dielectric lens.The measured results show that the antenna gain can be increased up to 7.4 d B after loading the lens,and the gain is 14.7-20.6 d Bi in 6-18 GHz.The maximum Aperture efficiency was increased by 33% and 92.4%.The 1-d B gain bandwidth can reach32.3%(13-18 GHz).The all-dielectric lens designed in this chapter is made by 3D printing technology,which has the advantages of simple processing,low cost and light weight.2.Design and research of ultra-wideband high-gain all-dielectric lens antenna based on integrated optimization of Genetic algorithm.The traditional lens antenna separates the lens design from the feed,which leads to the problems of uncontrollable antenna characteristics and low degree of automation.In this paper,the integrated design technology of lens and feed antenna is established based on genetic algorithm.The feed-source of this paper is the double-ridged horn antenna,and the initial structure of the lens borrows from the characteristics of the convex lens.The multi-objective genetic algorithm is used to design the lens antenna,which can control the antenna characteristics better and improve the design automation.The gain of each frequency point and the 1-d B gain bandwidth of the lens antenna are taken as the optimization objective,and the 1-d B gain bandwidth is broadened on the premise of ensuring the high gain of the lens antenna.The measured results show that the antenna gain is 16.4-23.8 d Bi in 6-18 GHz after loading the lens(the maximum gain reaches 23.8 d Bi at 17 GHz),which is 6.4-10.0 d B higher than that of the feed antenna.The maximum aperture efficiency of the lens antenna is 51.9% and the 1-d B gain bandwidth is40%.The all-dielectric lens is also made using 3D printing technology.3.Design and research of ultra-wideband and equal beam width dielectric loaded Vivaldi antenna based on integrated optimization of Genetic algorithm.The gain of traditional Vivaldi antenna cannot meet the requirements of radar detection,satellite communication and other fields.Usually,researchers use the method of dielectric loading to improve the gain of Vivaldi antenna,but the lens designed by the traditional method cannot improve the gain of the antenna in the wide band because of the narrow working band of the lens.In order to solve this problem,this paper first designs a Vivaldi antenna working at 2-24 GHz.It is found that the antenna has some disadvantages,such as lower gain and large difference of beam width between plane E and plane H.To solve these problems,a "mushroom" type dielectric lens is designed.The lens consists of three parts,and different parts act on different frequency bands.Since the antenna has many optimization targets and the lens structure is complex,the traditional optimization methods are not qualified.Therefore,the multi-objective genetic algorithm is used to optimize the lens antenna.The gain of each single frequency and the beam width of plane E and plane H are taken as the optimization targets.The gain and beam width of plane E and plane H of Vivaldi antenna are improved after optimization.The simulation results show that the antenna gain is 8-19.1 d Bi in 2-24 GHz after loading "mushroom" dielectric,which is 2.7-9.3 d B higher than that of Vivaldi,and the 3-d B beam width of plane E and plane H can be approximately equal at multiple frequency points.The characteristics of high gain and equal width beam makes it very competitive in the feed-selection of reflector antenna. |
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