Research Of Fractal Antenna Of Im-GPR

Ground penetrating radar(GPR) is a non-destructive testing equipment for the distribution of underground medium with the help of electromagnetic wave. Compared with the damage detection, GPR is gifted with faster detection speed, and wider coverage, and thus, it has been applied in the field of municipal construction, military security, archaeological and hydrological detection and so on. Within all GPR form, impulse ground penetrating radar(Im-GPR) has a relatively more mature technology and a higher degree of commercialization. Fractal is a kind of structure which is generated by the iterative function system(IFS). Fractal structure has the characteristics of space-filling property and self-similarity property, and these two characteristics attribute fractal antenna of small scale, multi band and mechanical robustness behavior, and this makes the fractal antenna has a broad application prospect in the field of communication.The antenna in GPR has very important influence on the resolution of the GPR. The parameters and characteristics of the fractal structure of the dipole antenna and the planar antenna are studied in this work based on simulations and experimental. During the research, the function between the bending angle of the antenna with the same length and the resonant frequency of the antenna is build; and then the Sierpinski loaded Bowtie antenna is simulated. And on the basis of previous research, a new ultra wideband fractal antenna structure is proposed.In the process of research of fractal antenna of Im-GPR, the work below is done:1) The relationship between bending angles of dipole antenna and its resonant frequencies.During the analyzing of parameters of different fractal structures with the same hight and fractal antennas with different iterations to the resonant frequencies of dipole antenna, it’s found that the total lenth of antenna has the most important effect on the resonant frequency, next to which is the shape. In order to measure the shape, we use the sum of the vector angles.And then the effect of sum of bending angles to the resonant frequencies with the same length is studied, it’s found that the bending angle of antenna and the resonant frequency of the antenna show a logarithmic relationship, then a module is proposed, and this module has a certain significance for the miniaturization of the antenna.2) Research on fractal Botie antenna.During the research of fratal Bowtie antenna with different iterations and modified fractal Botie antenna with different iterations, it’s found that the fractal structure, can’t achieve the advantages achieved in communication field while meet the performance of GPR antenna。When the input resistanse is low, the time domain characteristic of the antenna is not good; when the input resistanse is high, the matching characteristic of the antenna is not good.3) Research on Double-triangle structure of UWB GPR antenna.Double-triangle structure is adapted while the triangle of radiation end use the Sierpinski structure. This structure can meet the design requirements both in time domain and in frequency domain, and the loading structure has a higher radiation efficiency than the concentrated loading structure in theory. The method of loading at the radiation end reduced the sensitivity of antenna input to the change of shape. It is found thatfour load times and eight load times have no effect on the low frequency band, and the effect of the change of the minimum load on the matching performance is greatly reduced.