Planar Cone-shaped Monopole Antenna with Tapered Ground for UWB Application # Hashimu Uledi Iddi 1,2 , M.R. Kamarudin 1 , T.A. Rahman 1 and Raimi Dewan 1 1 Wireless Communication Center(WCC), Universiti Teknologi Malaysia 81310 UTM Skudai, Malaysia, hashimuledi@yahoo.com 2 College of Information and Communication Technologies, University of Dar es Salaam P.O. Box 35131 Dar es Salaam, Tanzania 1. Introduction Compared to the narrow band antenna design, ultra wideband (UWB) antenna design has a lot of challenges. One of such challenge is the requirement that the return loss must be below 10dB bandwidth from 3.1-10.6GHz throughout the UWB frequency range. Other challenges include low cost, small size, light weight and good radiation patterns [1]. One of the characteristic of conventional planar monopole antenna have narrow impedance bandwidth due to their high quality factor [2]. For on-body communications, the UWB antenna design become even more challenging as the design have to include other important on-body antenna requirements. The antenna should be insensitive to the close proximity effects and must have radiation pattern in the intended direction that could minimizes the link loss [3]. Additionally, the Planar Inverted Cone Antenna (PICA) designs have been investigated to further enhance the UWB wireless communication applications. The PICA original design approach was proposed by Suh [4]. Later, several researchers have developed different variations of the PICA [5, 6]. One of the PICA antenna designed is printed slot planar inverted cone antenna proposed in [7] which has good return loss results for the UWB frequency band and the antenna size was 2 60 60 mm x . However, some of the notable disadvantages of such variations include large physical size and protruding part which makes it unsuitable for applications in portable communications and on-body communication [7]. Thus, in this paper a planar cone-shaped monopole antenna with tapered ground plane for UWB application has been investigated. The proposed antenna is low profile, compact and small in size with improved performance. The antenna can be used in wireless communication and on-body communications. The results of return loss and radiation pattern are presented in the paper. 2. Antenna Design The planar cone-shaped monopole antenna is printed on FR4 substrate of thickness 1.6mm, permittivity 4.4 and loss tangent 0.019. The overall dimension is 2 38 30 mm x . The geometry and the parameters of the proposed antenna are shown in Fig. 1.The antenna comprises of a semi-circular shape patch radiating element of radius R and is connected to a trapezoidal shape patch. The patch has base width, W and upper width equal to the radius of the semi circular patch. The two shapes are connected through the micro strip, fed with width, f W and is fixed to 2.5mm. Partial ground plane of width sub W and length, gnd L is placed at the back of the substrate, and is separated by radiating elements of gap, g . The ground plane is tapered in order to enhance the impedance bandwidth. The impendence bandwidth was improved by chamfering the ground plane 4mm at an angle of o 45 . The antenna is fed by microstrip line and simulated using CST Microwave studio. The parameters of the final design are shown in Table 1. The fabricated antenna is shown in Fig. 2. 3B3-2 Proceedings of ISAP2012, Nagoya, Japan 834