Slot Antennas For Dual And Wideband Operation In Wireless Communication Systems Abdelnasser A. Eldek, Cuthbert M. Allen, Atef Z. Elsherbeni, Charles E. Smith and Kai-Fong Lee Department of Electrical Engineering, The University of Mississippi, University, MS 38677 ABSTRACT Two antenna designs were achieved for dual and wide band operation in wireless systems. One design was realized using a tapered meander slot with a microstrip feed to give dual band operation at 1.8 and 2.4 GHz. In this design both operating frequencies are controlled mainly by the horizontal slot width of the meander and the distance of the microstrip line termination from the slot. The other design was accomplished by the use of a coplanar patch-slot antenna (CPA) fed by a coplanar waveguide (CPW). This later design is easily tuned to operate at 2.45 and 5.75GHz, with wide bandwidth (BW). The operating frequency is controlled by modifying the patch dimensions. Return loss, input impedance, radiation pattern, directivity, gain and efficiency of the proposed designs are computed and presented. Keywords: Wideband, dual band, coplanar patch antennas, meander slot antennas. 1. INTRODUCTION In present-day personal communication devices the need for antennas of small size and high efficiency has generated much attention to the study of compact microstrip antennas. These antennas exhibit low profile and lightweight properties as well as low cross polarization radiation in some designs. However, microstrip antennas inherently have narrow bandwidths and in general are half-wavelength structures operating at the fundamental resonant mode TM 01 or TM 10 [1]. In this study coplanar patch antennas (CPAs) as well as meander slot antennas have been designed for communication systems with improved bandwidth and size reduction. Researchers have made efforts to overcome the problem of narrow bandwidth in coplanar patch antennas (CPAs) and various configurations have been presented to extend the bandwidth. Adding a short on the upper slot of the CPA and varying its length achieved 30 to 40% BW [2] at higher frequencies for radar applications. In this paper a simple design of a CPA is introduced that achieves high efficiency and reasonable BW, and can easily be tuned to work at different frequency bands. A compact meander-type slot antenna with 56% size reduction has been reported in [3] in which non-uniform slot line widths give rise to lower operating frequency of the antenna. In this paper we show that a dual-frequency operation is achieved by using a tapered meander slot antenna with a short-ended microstrip line feed. The tapered meander slot antenna was derived from [4] in which a meander line was tapered to achieve operation at lower frequencies. The bands of interest for this research project are those of wireless local area networks (WLANs), US industrial, medical, and scientific bands (ISM), and personal communication systems (PCS). 2. ANTENNA ANALASIS AND RESULTS 2.1 Coplanar Patch Antenna The CPA geometry and its parameters are shown in Fig. 1. The antenna consists of a rectangular patch surrounded by a non-uniform width slot. As shown in Fig. 1, W represents the patch width, L is the patch length, and S1, S2 and S3 are the widths of the upper slot, left-right slot, and lower slot, respectively. S4 and S5 are the gap width and feed line width of the CPW, and Lcpw represents the length of the CPW. In addition to these parameters, h is the height of the substrate, and ε r is the dielectric constant. The dielectric material is RT/duriod 5880 of ε r =2.2. Two antennas are designed for each band of the WLANS 2.4-2.48GHz and 5.7-5.85Ghz. Designs 1 and 2 are operating at a center frequency (f c ) of 5.75GHz, while designs 3 and 4 are operating at f c = 2.4GHz. Dielectric superstrate of the same thickness and as the substrate is included in the antennas labeled designs 2 and 4. The dimensions of these antennas are listed in Table 1. This analysis is performed using the commercial computer software package of Agilent Technologies, Advanced design System (ADS), which is based on the method of moment (MoM) technique for layered media. The ADS simulator, Momentum, solves mixed potential integral equations (MPIE) using full wave Green’s functions. A verification of our simulation procedure is confirmed by comparing the numerical results of a CPA return loss from a FDTD computation, which uses Liao’s second order absorbing boundary conditions, with that of ADS Momentum. This comparison reveals good agreement as shown in Fig. 2 for a simulated antenna with (W, L, Lcpw, S1, S2, S3 S4, S5, h) = (23, 4, 3.5, 1, 1, 1, 0.5, 3.5, 1.6002mm) and ε r = 2.2. The first parameter under study was Lcpw. For all the designs in Table 1, Lcpw was set at 3.5mm. By increasing Lcpw, it is seen that the resonance frequency decreases, but returns back at certain lengths for all antennas. It is known that the input impedance for a CPW structure is given by