A TDR SYSTEM FOR SUBSURFACE POLLUTANTS DETECTION (I): DESIGN & MODELING

This work presents the development of a TDR system for in-situ detection of subsurface pollutants. The developed system is simple to implement using a typical pulse generator, with a repetition rate of 125 MHz and rinse/fall times of 2ns, and a conducting probe connected via a transmission line (coaxial cable). The system probe is designed using antenna theory to match its input impedance to that of the used transmission line connecting the pulse generator and the probe. This improved the system performance since reflected pulses in this case are due to detected materials and not from mismatches at the probing end. On operation, the pollutant concentration in the soil is detected by measuring and analyzing the variation of soil-pollutant dielectric properties as a function of concentration of the pollutant in the soil. The developed TDR detection system is modeled by electrical parameters using transmission line theory. The modeled system is simulated by an electrical circuit simulator and the electrical parameters were optimized via the determined experimental data and the developed model. Based on the optimized parameters (resistance and capacitance), a criterion is developed in order to quantify pollutant concentration in subsurface soil.

R.A. Said and N.K. AlShawawreh
Electrical Engineering Department
United Arab Emirates University
A-Alin, United Arab Emirates

A.M.O. Mohamed
Civil Engineering Department
United Arab Emirates University
A-Alin, United Arab Emirates