Antenna design for frequency modulated continuous wave ground penetrating radar for density evaluations

Shafiei, Mohammad Mahdi (2010) Antenna design for frequency modulated continuous wave ground penetrating radar for density evaluations. Masters thesis, Multimedia University.

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The Ground Penetrating Radar (GPR) system is an impressive solution for non-destructive sensing of subsurface environment. It can be defined as radar which is provided for the goal of detection and recognition structures inside the ground. GPR uses high frequency electromagnetic waves to obtain subsurface characteristics and collect underground information. When electromagnetic power propagates toward the ground and underground layers, it will be reflected back to the surface from each boundary between the materials with different permittivity (dielectric constants). A GPR system includes three parts: a transmitter, a receiver and a micro-processor control unit. Transmitter and receiver have their own antenna to propagate the electromagnetic wave into layers and receive the reflected wave. Four different architectures have been used by different researchers to build a GPR system: pulse wave radar, synthetic pulse radar, continuous wave radar and modulated continuous wave radar that this modulation can be amplitude modulation (AM), frequency modulation (FM) or something else. The Frequency-Modulated Continuous-Wave (FMCW) radar is chosen to achieve the goal of GPR for density evaluation. A signal will be sent to the media through transmitter antenna. The return signal achieves the radar by using the other antenna. Transmitter and receiver antenna are identical. The received signal should be mixed with a portion of transmitted signal which is directed to the receiver part by directional coupler. This mixture of these two signals creates the beat frequency signal that is needed for subsurface analysis. A block diagram for this type of FMCW GPR is explained and then the effect of changing chirp signal is shown briefly. One of the most important parts of GPRs is antenna that is highly effective on achieved results. This project is concentrated on antenna design for this purpose. The frequency range of the radar would be 1.7GHz to 2.6GHz. It is a demand in civil engineering. The center frequency is 2.15GHz and at least 900MHz bandwidth is needed. Firstly, a slotted probe-feed Microstrip antenna is designed and presented. Results were relatively satisfying and the designed antenna achieved good results in comparison with other works but it was not enough for the needed target. The second design was a slotted probe-feed Microstrip antenna which has slots on both patch area and ground layer. It also obtained good results but it was not satisfying for our purpose. The center frequency was 2.1GHz and bandwidth around 70MHz. Although 70MHz means 50% improvement in comparison with similar attempts by other researchers, but still is too small for the requirement of 900MHz. In the third antenna design, a Coplanar Waveguide (CPW) antenna has been designed and it provides 50% bandwidth around center frequency of 2.1 GHz. By changing the structure and using CPW feed instead of probe feed, more than 1GHz bandwidth around fc=2.1GHz is achieved. This design is a single layer CPW antenna. It has a simple structure as well as its acceptable characteristics.

Item Type: Thesis (Masters)
Additional Information: Call No.: TK6592.G7 M64 2010
Uncontrolled Keywords: Ground penetrating radar
Subjects: T Technology > TK Electrical engineering. Electronics Nuclear engineering
T Technology > TK Electrical engineering. Electronics Nuclear engineering > TK5101-6720 Telecommunication
Divisions: Faculty of Engineering (FOE)
Depositing User: Ms Nurul Iqtiani Ahmad
Date Deposited: 12 Jan 2016 03:51
Last Modified: 12 Jan 2016 03:51

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