Portable Ground Penetrating Radar (GPR) Prototype

Abstract

Proficiency in subsurface imaging has always been a dream of mankind; knowing something buried underground without even seeing or touching it, that is, seeing the unseen. Ground Penetrating Radar (GPR) is a Nondestructive Measurement Technique (NDT), which uses electromagnetic waves to locate targets or interfaces buried within a visually opaque substance or Earth material. This project was intended to circumvent the lack of portability in the previous GPR design made in MCS Session 2011-2012. It used a Vector Network Analyzer (VNA) as its Transceiver. The goal was to replace VNA, a very expensive commodity, by a custom transceiver serving the purpose of GPR. The radar, being CW, has its transmitter continuously on thus requiring far less average power per cycle than an Impulse Radar. The transmitter consists of a Voltage Controlled Oscillator (VCO) driven by a Triangular Wave Generator, a Coupled-Line Bandpass Filter, Wilkinson’s Power Divider (WPD) and a High Power Amplifier (HPA). The receiver consists of a Low Noise Amplifier (LNA), a Bandpass filter same as of in the transmitter and a high signal level down-converting mixer. Both transmitter and receiver have separate broadband antennas as the system operates from 2.1 to 2.6 GHz thus making the mode of operation bistatic. The transceiver is powered and controlled by a control circuitry. The whole system is mounted over a platform. A simple frequency vs. time plot after scanning the target area can indicate the presence of an object underneath ground. GPR has a variety of applications ranging from locating minerals to disaster recovery. From the engineering and learning point of view, this project involves mastering applications of four major overlapping fields: RF Electronics, RF Filter Design, Antenna Design and SAR. GPR can be a powerful tool in favorable conditions (uniform sandy soils are ideal). Like other geophysical methods used in archaeology (and unlike excavation) it can locate artifacts and map features without any risk of damaging them. A few more applications of GPR are: water pipes and cable detection, investigation of buried bodies, railway tracks inspection, road survey, water/oil beds detection, land mine detection, road survey and building and machinery cracks inspection.