Ultra Wideband Antenna with WLAN Band-Notch Characteristic Zeeshan Ahmed 1 , Gul Perwasha 1 , Saleem Shahid 2 , H. Zahra 3 , Ilyas Saleem 1 , S. Muzahir Abbas 1 1 Department of Electrical Engineering, COMSATS Institute of Information Technology, Islamabad, Pakistan 2 Department of Electrical Engineering, School of Electrical Engineering and Computer Science (SEECS), National University of Sciences and Technology (NUST), Islamabad, Pakistan 3 Department of Electrical and Computer Engineering, Center for Advanced Studies in Engineering, Islamabad, Pakistan zeeshan.ahmed5490@gmail.com, gul.perwasha@gmail.com, 11mseesshahid@seecs.edu.pk, hijab.zahra@ymail.com, ilyas-saleem@hotmail.com, muzahir_abbas@comsats.edu.pk Abstract —The presented paper exhibits a coplanar waveguide (CPW)-fed symmetrical staircase shaped, planar monopole Ultra Wideband (UWB) antenna having dimensions 40x30x1.6mm 3 with 5GHz WLAN notch band characteristic. The staircase pattern in the radiating patch and the U-shaped slot resonator in the feed line are used to achieve the UWB and notch the 5GHz WLAN band, respectively. The proposed antenna has impedance bandwidth ranging from 2.84GHz- 13.9GHz to cover UWB. Interference caused by WLAN band from 5.15GHz-5.35GHz and 5.725GHz-5.825GHz is notched effectively. The proposed antenna has been printed on FR4 substrate with dielectric constant of 4.4 and thickness of 1.6mm. Moreover, the fabricated prototype antenna shows a good agreement between the simulated and measured results. Keywords— CPW, monopole, staircase rectangular patch, notched band, ultra wide band (UWB) I. INTRODUCTION Federal Communication Commission’s (FCC) allotment of the UWB ranging from 3.1GHz to 10.6GHz in 2002 [1], has made a great impact on commercial uses of this technology. Several antenna types have been used to implement this technology among which the microstrip patch antennas are of great importance because of their eye- catching attributes as they are light weight, low profile, inexpensive and top of all, quick and simple to fabricate [2]. Despite the progressions in designing microstrip antennas for UWB technology, the major issues are bandwidth, gain and radiation losses which limit their performance. To shorten the limitations, different design techniques have been implemented to achieve the UWB using microstrip patch antennas. Some of the noteworthy techniques include aperture coupling [3], stacking [4], slot compact planar design [5], parasitic patch [6] and thickening the substrate. With the advancements in antenna technology for UWB applications, the interference challenges in the frequency bands were the major ones to consider. The Wireless Local Area Network (WLAN) technology has significant contribution to electromagnetic interferences with the UWB applications. Numerous techniques have been devised to eliminate the interference in the UWB due to WLAN bands which include a rectangular tuning stub entrenched on a circular annular ring [7], a printed UWB antenna with couple slotted elements (H-shaped) for WLAN notching [4]. A few of the other approaches towards band-notching include Co- Planar Waveguide (CPW) fed C-shaped slot antenna [8], an antenna with a wide slot [9], a CPW-fed rectangular patch antenna with L-shaped slot in ground plane[10], an inverted U-slot antenna [11], a circular radiating patch with two L- shaped slots in the ground [12], a rectangular patch antenna with an E-shaped slot [13] and a CPW resonant cell as narrow stop-band filter in CPW feed-line [14]. In this paper, a CPW-fed planar monopole staircase antenna with a WLAN notch band characteristic is presented. The WLAN band notch is achieved by subtracting a U- shaped slot in the feed-line of the antenna. The stair-case structure covers the UWB range while the U-shaped slot in the feed-line prevents the interference with WLAN systems. The detailed parametric analysis in term of Voltage Standing Wave Ratio (VSWR) has been presented for the proposed antenna. Furthermore, gain, current distribution and radiation pattern plots of the proposed antenna are also presented. The proposed paper is formulated to describe the antenna geometry in section-II, modeling, analysis and comparison between results are presented in section-III while section IV concludes the paper. II. BAND NOTCH ANTENNA GEOMETRY The geometry of the proposed CPW fed antenna with WLAN band-notch is given in Fig. 1. The antenna is designed on a cost effective FR4 substrate with thickness 1.6mm, dielectric constant of 4.4 and with a compact size of 40x30mm 2 . There are 8 ‘Area’ steps added in increasing order from bottom to top. With the addition of each area step, increase in bandwidth is noticed which subsequently helps in achieving the ultra wideband. The U-shaped slot is added at 3.5mm from the bottom end of the transmission line with nearly square shaped CPW ground plane with dimensions 12.8x13.0mm 2 on either side. The gap width ‘g’ and the distance between the radiating patch and CPW 978-1-4673-5885-9/13/$31.00 © 2013 IEEE