The Simulates And Designs Of Transmit-receive Antennas In Borehole Radar System

In more and more engineering applications,ground penetrating radar(GPR)can meet the needs of geological environment,but the medium with high dielectric constant will restrain the transmission distance of signal,which leads to the limited detection range.Therefore,more and more attention has been paid to the use of borehole radar in wells for borehole detection.According to the design requirements of borehole radar antenna,this paper simulates and designs the borehole radar system transceiver antenna,which are omni-loaded dipole transmitting antenna,omni-directional circularly polarized transmitting antenna and elliptical conformal monopole antenna.This paper firstly introduces the developments and research status of borehole radar and borehole radar transceiver antenna at home and abroad,then briefly describes the theoretical basis of borehole radar and antenna theory,and emphatically discusses the factors that affect the propagation of electromagnetic waves(especially the influence of dielectric constant,frequency and conductivity on the detection range of radar wave).Secondly,the working frequency of borehole radar system is discussed and the frequency spectrum of transient narrow pulse is analyzed.Then,the characteristic parameters of antenna in frequency domain and time domain,the characteristics of borehole radar antenna and antenna miniaturization technology are systematically introduced.Finally,three types of transceiver antennas are designed in this paper,which are as follows:A resistively loaded dipole omni-directional transmitting antenna is design with resistive load so as to let the spaced multiple lumped resistor be loaded on the column type dipole arm which reflects current dipole at the top,combines the electromagnetic simulation software CST simulation optimization,analyzes of the influence of key parameters on the performance of the antenna and expands the bandwidth of the antenna when reducing the antenna radiation pulse trailing shock.Compared with the linear polarized wave,the circular polarized wave has the advantages of strong anti-interference ability,based on which a four inclined broadband dipole antenna radiation which is omni-directional circularly polarized is designed.The dipole tilt angle is 45 degrees.The feeding network consists of four broadband Balun circuit and an impedance.Feeding on the four broadband dipoles,optimized antenna ischaracterized by broadband,low out-of-roundness and compact structure,which realizes the azimuth plane omni-directional radiation with excellent performance;again,in order to meet the requirements of miniaturization of the radar system and increase the resolution,a new set of elliptic total loading parameters of the conformal monopole antenna directional antenna is designed,whose diameter is 67 mm,height is 182 mm and which feed on bipolar pulse antenna to achieve a better low frequency time domain and orientation.The designed monopole antenna is processed and debugged,after which the test results are in good agreement with the simulation results.Finally,the paper summarizes the full text,describes the characteristics and shortcomings of this paper,and looks forward to the future of the borehole radar system transceiver antenna.