| The antenna for ground penetrating radar (GPR) should have broadband working range, a clean radiated pulse in the time domain, and good impedance matching. In addition, it must be convenient to carry, and can test targets automatically. In this dissertation, we present a double-sided exponentially tapered broadband antenna, which operates from 500 MHz up to 10.5 GHz, and satisfy all requirements for GPR. Meanwhile, its transmission line feed structures are demonstrated as well. According to this broad range, the spatial resolution would be 3 cm.; First, double-sided transmission lines are investigated to be employed as the feed line for the antenna. Traditionally coplanar transmission lines, like slot line, are often used as feed lines. However, for our case the gap of the slot line is small if 50-ohm impedance is required. Therefore, the double-sided line (parallel-plate line) are employed herein. The design and analysis are carried out theoretically and experimentally.; Next, a double-sided exponentially tapered broadband antenna is designed, analyzed and measured. The whole design process is demonstrated herein. A dipole array model is applied to simulate this type of antenna, and radiation pattern is also calculated. The measured results match the simulations very well. In addition, the performance of this antenna is compared with a V antenna and a Vivaldi antenna with the same dimensions. The results demonstrate that our design is the best for use in GPR applications. HFSS (High Frequency Structure Simulator) simulation is also carried out, and the radiation pattern is also measured. Through the measurement and simulation, it is verified that this type of antenna works quite well for GPR requirements. In addition, some modified antennas are presented.; Then, to connect a coaxial line to a double-sided feed line, baluns ( balance to unbalance) are studied to make the impedances match and no radiation on the cable. The boards of gradually tapered back-to-back baluns are fabricated and tested. Together with the double-sided line, the back-to-back baluns are numerically simulated by HFSS. The designed balun has a good effect and matches the simulated result quite well. The comparison of antennas with and without a balun is presented as well.; Finally, this antenna is used to measure the buried targets. Also, it is employed to detect the target in a scattering environment. The setup of the experiments and the measurement results are presented. These applications prove that this type of antenna is very good to be used as a GPR antenna.; In summary, in this dissertation a whole GPR antenna system is presented. From the feed line, balun to antenna, every component is designed, simulated and tested. In addition, the applications of this antenna are also demonstrated. To the best of our knowledge, it is a novel design as a GPR antenna. |
