VIVALDI ANTENNA DESIGN FOR GPR APPLICATION

Abstract

Ground Penetrating Radar (GPR) is a radar which detects objects and interfaces buried beneath the earth’s surface. It is considered as a very effective tool for nondestructively sensing of the subsurface environment, since the radar can detect any object that has different electrical properties than the surrounding soil. Thus it senses both metallic and nonmetallic targets as opposed to metal detectors. The GPR system usually contains a receiver and transmitter antennas. Transmitter connected with a source, and receiver connected with signal processing. Civil and military sections are the most popular areas for the GPR applications. In military area, it is commonly used for finding unexploded bombs, underground warehouses, bomb shelters, discovering enemy communication channels, secret rooms. In civil life GPR is commonly applied for finding, buried pipes and undetected voids. Together with these, GPR is used to find people behind the rubble also. The antennas type is very important, so the antenna plays an important role in GPR systems. The antenna efficiency is also an important part of the system. The high efficiency provides reliable and more information. Having better antenna efficiency depends on the optimization works in antenna's physical features. Therefore, Vivaldi antenna is one of UWB Antenna that used to build GPR , because it has some properties like great bandwidth , end-fire radiation, moderate gain , small dimension and easy to fabricate. So, in this thesis we have a plan to build two types of Vivaldi antenna one is Antipodal Vivaldi Antenna (AVA) and another Double Slot Vivaldi Antenna (DSAVA), for AVA the substrate material that used is Taconic with dielectric constant 3.55 we aim in this design to get a good antenna pattern at low frequencies and a high radiation pattern at high frequency , whereas it has a small dimension (70×50×0.76)mm3 . In DSAVA we have to get radiation pattern greater than that in AVA , because DSAVA is improved to enhance the Directivity and radiation pattern , the substrate material that used is FR4 with dielectric constant 4.3 and dimension 50×70×1 mm3 , in two designs we used the dielectric lens to improve the radiation pattern at low and high frequency , and for AVA we used a technique elliptical curved edge to enhance the return loss or S11 at low frequencies.