Development of GPR system using high gain wideband antenna and microwave imaging technique for buried object detection

Abstract

Ground Penetrating Radar (GPR) is one of the non-destructive methods which employ electromagnetic waves of frequency that ranges from few MHz to tens of GHz to map the buried features inside the ground or man-made structures. In transmitter and receiver parts of GPR, the demand for high gain, wideband and small antenna is increasing, owing to its benefits such as deeper signal penetration, ability to carry higher data rate and easy to handle particularly when space is a constraint. Instead of antenna, geological aspects such as soil types, humidity and soil temperature need to be considered as well since it has a significant effect to the GPR measurement performance. The GPR measurement results are much dependent on the geological aspects, for example, soil condition of different areas has different properties. The other important parameter of GPR system is the microwave imaging technique. This technique is required to map the buried object into 2-dimensinal graphical form and finally shows the overall performances of the GPR system. In order to fulfil these requirements, the methodology in this thesis is divided into three phases. In Phase I, the design of the Slotted Bowtie Antenna (SBA) and Notch Circular Patch (NCP) which have low ringing field, light weight and wideband characteristic frequency that ranges from 1.25 GHz to 3.0 GHz and 0.5 GHz to 3.0GHz respectively, is proposed. In order to obtain higher gain, a metallic reflector has been located at the back of the antennas and the performances of the proposed antenna in term of S-parameter, radiation pattern and gain is observed. The antennas are fabricated using Taconic TLY-5 and the measured performances are compared and analysed. Both antennas have a good agreement for simulated and measured results such as wide bandwidth which are higher than 60% for SBA and 150% for NCP antennas, higher gain more than 8 dB and have a directional radiation pattern. In Phase II the geological aspect, Eight (8) types of soil samples in local region (Perlis) have been collected to measure the dielectric properties in three (3) different condition which are normal (ambience), wet (10% water content) and dry (50oC).