Design Of UWB Antenna For Ground Penetrating Radar Systems

Ground Penetrating Radars GPR have been shown to be a good candidate in the field of nondestructive detection benefit from its larger penetrating range than optical or infrared sensors and better spatial resolution than acoustic,which make it widely used in varies detection applications.Recent years,it has been widely used for many critical applications such as archeology,desert soil inspection,lossy dielectrics measurement,boundary layer detection,airborne GPR,diffraction tomography,excavation,landmine detection,forensic surveys,directional borehole,layered vegetation and so on.The antenna that function as device for emitting and receiving EM waves is one of the most critical parts of the GPR system.It is desired to have ultra-wide band,high gain,small late-time ringing and so on.At the same time,it should be small,light,and robust to ensure it work in different application scenarios.Based on this background and requirements,the chief contributions of this thesis are as follows:1.The research background of the GPR system is introduced and its requirements of antenna.Based on the ultra-wideband requirement,different types of antennas are investigated and introduced,especially the bow-tie antenna,horn antenna,and Vivaldi.2.The design steps of the bow-tie antenna are introduced,followed by two examples for different methods of miniaturization.One is distributed resistance loaded bow-tie antenna,and the other bow-tie antenna with curved shape.Both antennas can meet the requirements of the ultra-wideband frequency band of 0.8GHz-3.2GHz.At the same time,the principle of HFSS simulation time-domain waveform is explored,and related code are developed to obtain the time-domain waveform for a given the input signal in time domain.The simulation results are in good agreement with the waveforms from measurements.Back ground cancellation are also discussed in detail.3.Tightly coupled antenna explored in Chapter four.The principle of ultra-wideband and a multi-layer combination of tightly-coupled dipole arrays is presented.The inspection of antenna performance in time-domain and frequency domain is also shown.What's more,according to the actual application background,tightly-coupled dipole arrays with integrated balun was presented,which improved the shortcomings of the first version,such as heavy weight and complicated installation process.4.Introduced the working principle of the Vivaldi antenna.Aiming at the shortcomings of its high profile,two kinds of Vivaldi antennas are designed.One is miniaturized by opening a number of slits on both sides and placing the metal plate in the vertical direction of the antenna,and another method is to achieve miniaturization by loading resistors and add metal pieces on the same side,and the size can be 0.13 ? * 0.23?.The method proposed in this thesis have certain engineering application value and can also be used to design the same type of ultra-wideband antenna.