Huang Chunlin

A new GPR calibration method for high accuracy thickness and permittivity measurement of multi-layered pavement

To improve the measurement accuracy for the layer thickness and the permittivity of multi-layered pavement, this paper proposes a new calibration method. Based on the layerstripping EM inversion, single or two calibrating coefficients are introduced into the calculation equations of thickness and permittivity. After the processing of calibration the nonlinear meaisurement errors. can be diminished effectively, and the accuracy of overlaid delamination can be improved. Moreover, the affection of calibration factors is discussed, and a lot of pavement data have been used to test and prove the performance of the calibration methods.To improve the measurement accuracy for the layer thickness and the permittivity of multi-layered pavement, this paper proposes a new calibration method. Based on the layer-stripping EM inversion, single or two calibrating coefficients are introduced into the calculation equations of thickness and permittivity. After the processing of calibration the nonlinear measurement errors can be diminished effectively, and the accuracy of overlaid delamination can be improved. Moreover, the affection of calibration factors is discussed, and a lot of pavement data have been used to test and prove the performance of the calibration methods. Keywords-calibration; thickness; permittivity; measurement; GPR; multi-layered pavement; high accuracy

A study of the interference stripe phenomenon caused by electromagnetic wave propagating in multi-layered medium

The interference stripe appears in the penetrating scan experiments of multi-layered medium detection, the experiments are implemented by the single-frequency plane array or the moved single transmitting/receiving (T/R) antenna. Based on the medium boundary conditions of Maxwell equations from the classic electromagnetic theory, the interference stripe phenomenon is studied in the paper. And the commercial simulation software CST Microwave Studio is used to construct the simulation models. Under the near-field condition, the propagation and reflection of electromagnetic wave in the monolayer medium and the multi-layered media are simulated. Two situations, the electromagnetic wave being perpendicular and oblique to the dielectric plate, are specially carried out to compare. The echo waves received by the antenna changed position are analyzed. It can be found that there is no interference stripe when the incident wave is perpendicular to the dielectric plate. However, the interference stripe phenomenon will arise when there is a certain angle between the incident wave and the normal of the dielectric plate. This can be proved by the scan experiments results. The existence of the interference stripe will cause serious disturbance to the target echo, because the former is greater than the latter. So it will affect the performance of target detection and identification. From the point of view of the electromagnetic wave incidence and reflection theorem, the existence reason of this phenomenon is discussed. The relationship between the incident angle and interference stripe is illuminated. The study of this phenomenon will be helpful for the signal processing of the plane array and the moved single T/R antenna scanning system, such as the interference stripe phenomenon reducing and the target imaging quality improving. It can also be helpful for solving some problems encountered in the highways detecting, archeology, geology survey, etc.

Design of receiver with wide dynamic range for deep ground penetrating radar

Because of the depth limitation when using the impulse ground penetrating radar(GPR) for deep detecting, a ultra-wideband(UWB) deep GPR receiver system using ADC for sampling is designed. Several simulations to the traditional balanced door sampling circuit are carried out, the results demonstrate that the main factors which limit the systems dynamic range is the jitter of sampling trigger pulse. The overall structure of new receiver system is designed, as well as the timing control circuit. The highly integrated, low-cost receiver system has improved systems dynamic range from 50dB to 80dB, and has been applied in the deep GPR system of our laboratory.

Optimization based underground cylindrical objects position and electromagnetic parameters joint reversion

In the applications of surface penetrating radar(SPR), the localization and recognition of cylindrical objects such as conduits and cavities is a typical problem. To obtain high accuracy subsurface profile, wide band signals are adopted in SPR system. Thus the problem of subsurface point objects’ location can be implemented by maximum likelihood parametric algorithm in the frequency domain. Subsurface objects recognition is a challenging task. Based on feature extraction and judgment, it needs adequate typical subsurface objects’ feature. In this paper, a novel method of optimization based joint reversion is presented. Based on the first order Born approximation, the relationship between receiving signals at each aperture and the objects’ position, electromagnetic parameters is established and maximum likelihood parametric algorithm is introduced to estimate unknown parameters. Through processing experimental data obtained by a SPR system-RadarEye, the maximum likelihood parametric algorithm validates its capability at the aspect of subsurface cylindrical objects’ position and electromagnetic parameters joint reversion. Keywordssurface penetrating radar; object localization; object recognition; maximum-likelihood estimation