Journal of Electromagnetic Analysis and Applications, 2013, 5, 182-188 http://dx.doi.org/10.4236/jemaa.2013.54029 Published Online April 2013 (http://www.scirp.org/journal/jemaa) Double-Sided Microstrip Circular Antenna Array for WLAN/WiMAX Applications Ruwaybih Alsulami, Heather Song * Department of Electrical and Computer Engineering, University of Colorado, Colorado Springs, USA. Email: * hsong@uccs.edu Received February 8 th , 2013; revised March 10 th , 2013; accepted March 25 th , 2013 Copyright © 2013 Ruwaybih Alsulami, Heather Song. This is an open access article distributed under the Creative Commons Attri- bution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. ABSTRACT The design, fabrication, and characterization of the microstrip circular antenna arrays were presented. The proposed an- tennas were designed for single band at 2.45 GHz and dual bands at 3.3 - 3.6 and 5.0 - 6.0 GHz to support WLAN/WiMAX applications. The proposed single and dual band antennas showed omnidirectional radiation pattern with the gain values of 3.5 dBi at 2.45 GHz, 4.0 dBi at 3.45 GHz, and 3.3 dBi at 5.5 GHz. The dual band antenna array was placed on both top and bottom layers to obtain the desired antenna characteristics. The proposed double-sided dual band antenna provides omnidirectional radiation pattern with high gain. Keywords: Antenna Arrays; Circular Patch; Dual Band; Single Band; Omnidirectional; WLAN/WiMAX Applications; UWB 1. Introduction Ultra-wideband (UWB: 3.1 to 10.6 GHz) frequency spec- trum has been approved by the US Federal Communi- cations Commission (FCC) for unlicensed short range wireless communications since 2002. In this frequency range, wireless local-area network (WLAN) IEEE802.11a and HIPERLAN/2 WLAN operates in 5.0 - 6.0 GHz band. In some European and Asian countries, world interop- erability for microwave access (WiMAX) service is pro- vided in the frequency range of 3.3 - 3.6 GHz [1-4]. To support the WLAN/WiMAX application, antenna arrays that provide omnidirectional radiation pattern are required. To respond to this need, recent antenna design efforts were focused on omnidirectional antennas with high gain and no sidelobes [5-8]. Rectangular arrays are common type used for antenna arrays. Studies on dual band an- tennas employing rectangular arrays were reported [9-12]. Compared to rectangular patch antenna arrays, there are limited numbers of studies performed on circular patch antenna arrays due to difficulties in fabrication [13]. Ad- vantages of circular antenna array include high gain and narrow beam width [13]. In this paper, a new microstrip circular antenna arrays were designed, fabricated, and characterized to provide omnidirectional radiation pattern for WLAN/WiMAX applications. Two antenna arrays were designed—one for single band at 2.45 GHz and the other for dual bands at 3.3 - 3.6 GHz and 5.0 - 6.0 GHz. For single band opera- tion, circular patch array was placed on the top layer of the microtrip and a small rectangular patch was placed on the bottom layer for ground connection. For dual band operation, similar circular patch array was placed on both top and bottom layers of the microstrip with larger rec- tangular patch placed on the bottom layer. Both single band (single sided) and dual band (double-sided) micro- strip antenna arrays provided desirable antenna charac- teristics for the intended application. 2. Design and Simulation 2.1. Single-Band Antenna at 2.45 GHz The configuration of the proposed single band antenna at 2.45 GHz is shown in Figure 1. It consists of six circular patches which are placed only on the top layer. The small rectangular patch is placed on the bottom layer for ground connection. The directivity for the circular patch antenna is   2 0 0 rad 120 e ka D G  (1) * Corresponding author. Copyright © 2013 SciRes. JEMAA