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This paper presents a novel design of fractal antenna on a flexible substrate that operates in UMTS band (universal mobile telecommunication system, 1.92–2.17 GHz). The antenna consists of a Sierpinski carpet fractal radiator, which reduces the overall size of the antenna, and it is realized on top of a Hilbert slot in the ground layer, to achieve required impedance matching. The antenna is compact with the overall dimensions equal to 70 mm × 31 mm × 0.075 mm. Influence that folding has on the initial planar topology is investigated in detail. The obtained results show that the proposed antenna is more tolerant to folding than the conventional patch and that it exhibits relatively stable radiation patterns even when folded in complex manners.

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mlbirch@ sun.ac.za palmer@sun.ac.zaThe bowtie antenna provides a solution to the requirements of a broadband non-dispersive antenna for low frequency pulsed ground penetration radar (GPR) applications. This paper reports on a bowtie antenna numerically optimized with respect to bandwidth and radiation performance into the ground over the 10-100 MHz band.Rounding the edges of the bowtie was found to stabilize the antenna performance by reducing the internal angle dependence of the 1St resonant frequency.Half hemisphere radiation was achieved using a nonabsorptive cylindrical cavity placed over the rounded geometry bowtie.Late time ringing due to reflections was minimized by the use of edge termination resistors connected between the cavity wall and the bowtie.The antenna match to the ground was improved using an optimized low permittivity polypropylene slab. This restored the radiation pattern distortion due to the presence of the ground and stabilized the input impedance for fluctuations in ground parameters. This also permitted the antenna to be wheel mounted at various heights above the ground with minimal influence on the antenna performance.