Miniaturized dipole antennas for ground-penetrating radar using metamaterial techniques

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The goal of this project is to examine the feasibility of miniaturized, metamaterial-based dipole antennas in replacing the large dipole antennas in existing ground-penetrating radar (GPR) systems, while examining the effect of `metamaterialization' on pulse dispersion, antenna-current distributions, radiation pattern, bandwidth, radiation efficiency, and polarization purity. The negative-refractive-index transmission-line (NRI-TL) metamaterial has proven itself effective in miniaturizing devices whose performance relies on their size with respect to the wavelength of operation. The NRI-TL approach is ideally suited to high-frequency planar PCB TL technologies, such as microstrip, and has enabled the development of miniaturized microstrip couplers, dividers, baluns, and even miniaturized printed dipole antennas. However, these planar metamaterial technologies may be unsuitable for the high-voltage or low-frequency conditions associated with GPR systems. GPR can operate at frequencies as low as the tens of megahertz, requiring antennas that can be several metres long. Typically, these antennas are simple wire dipole antennas, and their miniaturization will necessitate the development and characterization of a suitable metamaterial topology capable of handling high-voltage signals at scaled-down frequencies. Furthermore, GPR is based on the delivery of pulses, which consist of a spectrum of frequency components. The designed metamaterial technology must also, therefore, provide broadband performance. However, the same property which enables metamaterials to provide miniaturization also introduces strong frequency dispersion, and this must be adequately characterized and compensated for by either pre- or post-processing both the transmitted and received signals according to the known frequency dispersion of the designed metamaterial. In summary, this project will investigate robust NRI-TL metamaterial topologies aimed at GPR-antenna miniaturization and will devote significant time to the theoretical investigation of pulse dispersion, recovery, and dispersion compensation.