In this paper, an ultra wideband antenna employing a defected ground structure is presented. The radiating element is a circular patch on which a fractal based geometry is inscribed in the form of slots and excited by a tapered feed-line for impedance matching. The antenna has an impedance bandwidth of 8.2 GHz (117% at centre frequency of 7 GHz) and a peak gain around 6 dB. To improve the impedance bandwidth and gain, a Swastika shape Electromagnetic band gap (EBG) structure is proposed. The unit cell of the proposed EBG has a compact size of 3 mm × 3 mm and is obtained by introducing discontinuities in the outer ring of the Cross-Hair type EBG. The stop band (-20 dB) achieved with this EBG is 3.6 GHz (7.5 GHz-11.1 GHz) which is 1.6 GHz more than that achieved by a standard mushroom-type EBG of the same size and same number of elements. After application of the proposed EBG, there is an improvement of 12% in the impedance bandwidth while the peak gain increases by about 2-3 dB. The radiation of the antenna shows a dumb-bell shaped pattern in the E-plane and Omni-directional pattern in the H-plane. All the measured results are in good agreement with simulated results.
"An UWB Fractal Antenna with Defected Ground Structure and Swastika Shape Electromagnetic Band Gap," Progress In Electromagnetics Research B,
Vol. 52, 383-403, 2013. doi:10.2528/PIERB13051509
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