Slotted ultra wideband antenna for bandwidth enhancement

Abstract

In choosing an antenna topology for ultra wideband (UWB) design, several factors must be taken into account including physical profile, compatibility, impedance bandwidth, radiation efficiency, and radiation pattern. The main challenge in UWB antenna design is achieving the very broad bandwidth with high radiation efficiency and small in size. Accordingly, many techniques to broaden the impedance bandwidth of small antennas and to optimize the characteristics of broadband antennas have been widely investigated in many published papers as listed in references. Some examples of the techniques used to improve the impedance bandwidth of the planar monopole antenna include the use of beveling technique (Z.N. Chen(a) et al., 2006), (Giuseppe R. & Max J. Ammann, 2006), (M.C. Fabres(a) et al.,2005), semi-circular base (X.N. Qiu et al., 2005), cutting notches at bottom (Seok H. Choi, et al., 2004), (H. Ghannoum et al., 2006), an offset feeding (Z.N. Chen(a) et al., 2006), (Giuseppe R. & Max J. Ammann, 2006), (M. J. Ammann & Z. N. Chen, 2004), a shorting pin (Z.N. Chen(a) et al., 2006), (E. Lee et al., 1999), and a dual/triple feed (Z.N. Chen(a) et al., 2006), (S. Boris et al., 2005), (K.L. Wong et al., 2005), (H. Ghannoum et al., 2006), (E. Antonio-Daviu et al., 2003), magnetic coupling (N. Behdad & K. Sarabandi, 2005), folded-plate (D. Valderas et al.,2006),(Z.N. Chen et al., 2003), hidden stripline feed (E.Gueguen et al., 2005). The radiators may be slotted to improve the impedance matching, especially at higher frequency(Z.N. Chen(a) et al., 2006),(Z.N. Chen(b)et al., 2006). Planar monopole antennas are good candidates owing to their wide impedance bandwidth, omnidirectional radiation pattern, compact and simple structure, low cost and ease of construction. Further detail on various bandwidth enhancement techniques will be discussed in section 2.