| Ground penetrating radar is mainly used to detect the shape and position of various invisible objects buried under the ground,such as hidden tunnels,cables,pipelines and mines.Therefore,it is also widely used in various detection fields,such as road pavement inspection,bridge inspection,ice detection and through-wall imaging.Ultra-wideband ground penetrating radar based on impulse system has the advantages of high transmission rate,low power consumption,strong penetrating power and good time domain resolution.It helps to solve bottlenecks problem such as small detection depth and lower imaging accuracy with increasing depth of detection.The antenna plays a vital role in the entire ground penetrating radar system.After extensive preliminary research,this paper is based on the full understanding of the existing commercial ground penetrating radar product types and the main advantages and disadvantages of various common types of ground penetrating radar antennas.Two antennas are designed later qualified for ultra-wideband ground penetrating radar.The main research work of this paper is as follows:First,a small omnidirectional ultra-wideband monopole antenna for ground penetrating radar is proposed.By introducing a grounding point at a suitable position and adjusting the coupling to ground,the bandwidth of the antenna is expanded to the low frequency direction.By slotting on the reference ground,the overall reflection coefficient is improved.The overall size of the antenna is 140mm*165mm*1.5mm,completely covering the frequency range of 0.54GHz~10GHz.This antenna has a relatively stable omnidirectional radiation pattern in the working frequency band.Compared with other antennas of the same type,the antenna has a smaller volume,a wider working bandwidth,and can operate at a lower frequency,and can meet the requirements as a ground penetrating radar transmitting antenna.Secondly,a novel ultra-wideband omnidirectional printed wide-slot antenna for ground penetrating radar is proposed.Combined with the relevant theory,the relationship between antenna size and standing wave ratio is qualitatively and quantitatively analyzed,and the approximate calculation relationship between the two is derived.At the same time,by analyzing the surface current,the advantages of using a deformed toroidal ground are illustrated.The total antenna size is 160 mm x 120.5 mm x 1.6 mm.According to experiments for the fabricated antenna,its results show that the antenna operates at a frequency of 0.8-5 GHz and has a stable omnidirectional radiation pattern over the entire operating frequency band,achieving a gain of 1.2-7.1dB.In addition,the differences between the simulation results and the experimental results are compared,and the reasons for the errors are discussed.The in-depth reasons need to be resolved in the future work. |
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