Study Of Variable Frequency GPR Antenna Pairing And Frequency Band Adjustment Match Filtering For Shallow Investigations

Ground penetrating Radar(GPR)is an efficient tool for subsurface geophysical investigations,particularly at shallow depths.The non-destructiveness,cost efficiency,and data reliability are the important factors that make it an ideal tool for the shallow subsurface investigations.The selection of the central frequency GPR antenna and of the bandwidth is an important issue,and primarily depends on the type of subsurface application.The resolution,maximal investigation depth,size of the burial object and the soil properties are major parameters which are influencing the frequency range.Hence,for each and every survey a set of GPR antenna frequency constraints can be developed.However,for the requirement of higher resolution subsurface image with greater depth further improvement in technologies is still need.In order to give new insights,the variable frequency transmitting and receiving(Tx-Rx)GPR antenna scheme for data and frequency band enhancement match filtering for data processing are discussed in this thesis.Normally,the frequency of the both Tx-Rx antennas remains similar to each other whereas in this study we have experimentally changed the frequencies of Tx-Rx and deduce the response.Instead of normally adopted three pairs,a total of nine Tx-Rx pairs were made from 50MHz,100MHz,and 200MHz antennas.The experimental data was acquired from Mojiao Shan,Liangzhu,Hangzhou,China.After the impulse response analysis of acquired data through conventional as well as varied Tx-Rx pairs,different swap effects were observed.Actually,the frequency band and exploration depth are influenced by transmitting frequencies rather than the receiving frequencies.The impact of receiving frequencies was noticed on the resolution;the more noises were observed using the combination of high frequency transmitting with respect to low frequency receiving.Therefore,this study reveals that a Tx-Rx combination of low frequency transmitting with high frequency receiving is a better choice.Application of filters in geophysical data processing provides better subsurface image for the visualization and interpretation about beneath earth and match filters provides information more efficiently of certain environments or conditions.Here in this dissertation work three frequency band adjustment match filters for GPR data was constructed and estimated.The all three match filters are principally same but difference is transmitting and receiving frequency.One is constant frequency transmitting(CFT)band adjustment match,second is based on similar transmitting and receiving frequency(SFT)and the other is variable frequency transmitting(VFT)band adjustment filter.In the CFT match filter,receiving frequencies are variable and in the VFT match filter receiving frequencies are constant and in the SFT match filter the frequencies of transmitting and receiving antennas are same.The GPR data were acquired from a geophysical test site of Zhejiang University,Hangzhou,Zhejiang,China.The major theme behind the fabrication of filters is to incorporate lower and higher frequency components with intermediate one by constructing a match filter for a particular environment.The all filters provide better radargrams in respect of high resolution and deep penetration.