Research On Cognitive Waveform Optimization Design For GPR Imaging

The construction of modern industry is inseparable from the planning and utilization of underground space.The shallow geology underground is complex and diverse,and it needs to be detected in advance in the process of development.Ground Penetrating Radar(GPR)is a non-destructive exploration technology for underground areas that uses electromagnetic waves to explore underground areas,and detects targets through refraction and reflection generated at the interface in the medium.It can be widely applied in underground space detection of urban traffic construction.Traditional GPR transmits fixed signals which cannot adaptively adjust the transmission waveform and observation mode when facing complex structure of the underground medium and the presence of specific clutter,it is impossible to adaptively adjust the transmission waveform and observation method,resulting in poor imaging and detection effects of targets during detection.Therefore,this paper combines cognitive theory to carry out research on cognitive imaging technology of GPR and introduce waveform optimization design.The main research contents are as follows:1.The basic theory of GPR is introduced,the detection model of subsurface targets is constructed,and the GPR imaging algorithm is deduced and researched.The system architecture of cognitive radar is introduced,and the optimized waveform criterion is clarified,which lays the foundation for the subsequent research.The clutter amplitude distribution and power spectrum model are introduced.2.To address the problem of poor imaging resolution adaptation of LFM-GPR,the optimal transmitting waveform for imaging is obtained by modeling two point targets in the subsurface scene,deriving the variance of the echo signals of the two point targets according to the difference of wave velocities in the medium,and simplifying the time delay resolution constants in this way.To address the problem of low target detection performance of LFMGPR,the optimal waveform design method for GPR detection with the criterion of maximizing the SCNR is proposed.By constructing the objective function of maximizing the SCNR criterion and optimizing the solution using Lagrange multiplier method and water injection method to obtain the detection optimal transmit waveform,the clutter and noise suppression based on the optimal design of cognitive waveform is realized.Finally,the feasibility of the above waveform optimization design method is verified by experimental simulation.3.For the demand of high imaging resolution adaptation and high detection performance of GPR,the joint optimal waveform design method of integrated imaging and detection capability is studied.Firstly,a joint optimal objective function with constant energy constraint is constructed,and the relevant parameters of imaging and detection performance are adjusted by solving and searching for the eligible weight vector factors to finally obtain the joint optimal transmit waveform.The joint optimal waveform is then simulated in different clutter models and verified by calculating the SCNR,and the results show that the joint optimal waveform can adjust the transmitting power adaptively according to the spectral distribution of clutter.Finally,the joint optimal waveform is simulated for imaging,and the performance evaluation analysis of the imaging results verifies the effectiveness of the designed waveform.