Non-foster impedance matching for electrically small capacitive antennas
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Device scaling and component-miniaturization are the main drivers of the development of electronic technology. In time, electronic devices have become smaller in size and hence, the scaling down of antenna dimensions has come to be not only an interesting but also substantial areas of research. The gain - bandwidth product of an antenna is limited by its electrical size, therefore reducing the size of an antenna narrows the bandwidth or lowers the gain. The work presented in this thesis contributes to the existing body of research on the structure of electrically small antennas and complications of its design with regard to the fundamental limitations. The large input reactance of electrically small antennas (ESA) are conventionally matched with passive circuits, however, the matching works at a single frequency which shrinks the bandwidth. In previous studies, non-Foster impedance matching which employs active networks of negative inductors and capacitors to overcome the restrictions of gain-bandwidth theory has been examined. In this study, the origins and development of Non-Foster impedance matching is reviewed and its stability issues are discussed. The design and simulation of a negative impedance converter circuit and together with an electrically small disk loaded dipole are presented. In this research, the designed matching circuit is fabricated, measured and its results are analyzed. Additionally, promising future studies and their possible effects in the antenna field are reviewed.
Disk Loaded Dipole