Design And Research Of High Gain Ground-penetrating Radar Lens Antenna

As one of the main components of ground penetrating radar(GPR),the radiation performance of antenna directly affects the depth and resolution of detection.Therefore,ultra-wideband antennas with low profile and high gain have attracted wide attention of researchers.Compared with high gain antennas such as reflectarray antennas and array antennas,transmitarray antennas have the advantages of simple structure,high gain and low profile.This paper focuses on the research of transmitarray antenna working in low frequency band.Through theoretical analysis,simulation verification,experimental test and other steps,the following aspects are studied:(1)Design and research of graded index lens antenna.In the lens antenna,an antipodal tapered slot antenna with ultra-wideband characteristics is used as the feed source,and two kinds of units are innovatively formed into the lens according to the annular gradient of refractive index.Simulation and measurement results show that the impedance bandwidth and-3 d B gain bandwidth of the lens antenna reach 175.5% and 65.8%,respectively,and the maximum gain reaches 20.55 d Bi.Compared with the feed antenna,the gain of the lens antenna is increased averagely by 4.81 d B in the whole working band,and the radiation performance is significantly improved.(2)Design and analysis of coplanar lens antenna.Aiming at the defect of large profile of lens antenna with three-dimensional structure,a coplanar lens antenna with antipodal tapered slot antenna as feed is designed,and the feed antenna and the coplanar lens are placed on the same plane.Simulation and measurement results show that the impedance bandwidth and-3 d B gain bandwidth of the coplanar lens antenna reach 107.4% and 54.5%,respectively.The maximum gain reaches 15.4 d Bi.Compared with the original feed antenna,the gain is increased averagely by 6 d B in the whole working band,and the design of low profile,high gain and coplanar lens antenna is realized.(3)According to impedance matching theory,a phase gradient metasurface lens antenna based on phase compensation principle is designed.Multi-layer unit structure is adopted to achieve a larger phase shift range,and impedance matching units are adopted in the outer layer to improve transmit magnitude and reduce reflected waves.Finally,the units with impedance matching layers are combined into a 14?14 transmission array,and a planar log-periodic dipole antenna is used as the feed antenna.Simulation and measurement results show that the impedance bandwidth and-3 d B gain bandwidth of the lens antenna reach 45% and 40%respectively.The maximum gain reaches 16.1 d Bi,which is 9.56 d B higher than the feed antenna.Because the impedance matching layer is loaded on both sides of the lens,the back lobe of the lens antenna is improved significantly.Through the research and analysis of lower band transmitarray antennas,three types of high-gain and ultra-wideband transmitarray antennas are designed by using graded index and impedance matching theory,which provide technical basis for related practical applications and have certain potential application value.