Experimental research on transient electromagnetic wave transmission characteristics in single-hole

Borehole radar has a large detection range and relative high resolution, which makes up for the deficiency of the conventional logging tools and has been widely accepted as a highly efficient logging tool. The experimental research on the transmission characteristics of transient electromagnetic (EM) wave in a single borehole is of great significance to analyze the working characteristics of borehole radar system. After completing the time delay calibration, the transmission characteristics experiment in a single borehole filled with air at a limestone mine is carried out. The experimental results and theoretical analyses show that the direct wave travels along the sidewall, whose amplitude is very intense. The impedance mismatch can result in strong periodic reflection signals. These strong signals will bring about a serious disturbance to extract weak target echoes. Therefore, the impedance matching among the system modules when developing a borehole radar system should be regulated. Appropriate actions should be taken to highlight the weak echo signals during the data gathering and processing.