Fractal-Based Composite Right/Left-Handed Transmission Line and its Applications in Miniaturized Negative-Order Resonant Antennas

In this article, a fractal-based composite right/left-handed transmission line (TL) is proposed, and its applications in miniaturized negative-order resonant (NOR) antennas are investigated. The TL unit-cell is constructed by etching a Hilbert-fractal slot on the surface of a substrate integrated waveguide structure. The dispersion analysis shows that the proposed TL can be used to design miniaturized NOR antennas. Then, two fractal-based NOR antennas are designed and fabricated. According to the measured results, the electrical sizes of the fabricated open-ended and short-ended antennas are 75.8% and 74.6% smaller than those of the reported counterparts, respectively. In addition, compared with the microstrip patch antennas, the fabricated antennas exhibit similar gain level and radiation patterns, but have a much smaller electrical size.