| With the acceleration of urbanization,people's utilization of land resources is getting higher and higher.Land development often requires underground survey operations in advance.Although traditional engineering drilling can directly obtain information such as underground structures,it inevitably destroys the soil structure and is costly.The ground penetrating radar is more and more widely used due to its advantages of non-destructive,ground imaging,and acquisition of overall underground information.The antenna is a key component of the ground penetrating radar system and plays a decisive role in the detection results.The ground penetrating radar system emits nanosecond-level narrow pulses,so the antenna needs to have the characteristics of ultra-wideband,low ringing,good radiation directivity and high signal retention.Butterfly antennas and TEM horn antennas are the two most commonly used ultra-wideband ground penetrating radar antennas.Therefore,this article mainly studies these two antennas.The design of the butterfly antenna consists of three parts.One part is to simulate and model the traditional butterfly antenna and analyze its shortcomings;the second part is to optimize the butterfly structure by arcing the butterfly arm and end loading extension Improve the impedance characteristics of the antenna;the third part is to design a metal shielded cavity to achieve unidirectional radiation to the ground,increase antenna gain and reduce external interference.The final designed antenna impedance bandwidth is 0.175?1GHz,and the relative bandwidth is140.43%.The gain in the bandwidth range is above 3.86 d B.It has good unidirectional uniform radiation characteristics to the ground.TEM horn antenna design includes flat TEM horn antenna and exponential progressive TEM horn antenna.The flat plate type is the structural optimization of the traditional TEM horn antenna.Through the arced horn arm,the semi-elliptical plane at the end,resistance loading and the addition of metal reflectors,etc.,the antenna impedance bandwidth is expanded,the impedance characteristics are improved,and the antenna gain is increased..Because there is no curved structure,the designed antenna structure is relatively simple,but the performance is good.The antenna impedance bandwidth of the final design is 0.175?4GHz,and the relative bandwidth is 183.23%.In the frequency range of 1.5?4GHz,the antenna gain is greater than 10 d B,and it has good uniform radiation characteristics to the ground.Considering further expanding the antenna's low-frequency performance and optimizing the radiation directivity,an exponentially graded TEM horn was then designed to expand the antenna impedance by optimizing the progressive impedance line of the horn antenna,compound loading,and extending the metal reflector on both sides of the feed port.The bandwidth is 0.125?3.1GHz,the lowest operating frequency is reduced to 125 MHz,and the relative bandwidth is 184.50%.In the frequency range of 1?3.1GHz,the antenna gain is greater than 11.2d B,and the gain is relatively high.And the radiation characteristics are better.The FEKO electromagnetic simulation software is used for modeling,simulation and optimization.The designed antenna is theoretically analyzed through simulation data,and the design method and working principle of the antenna are described.The results show that the antenna designed in this paper is suitable for use in ground penetrating radar systems. |
PDF Full Text Request