BROADBAND BEAM-STEERING RECONFIGURABLE ANTENNA Zhouyuan Li, Israfil Bahceci, and Bedri A. Cetiner Department of Electrical and Computer Engineering, Utah State University, Logan, UT 84341; Corresponding author: bedri.cetiner@usu.edu Received 13 June 2016 ABSTRACT: A broadband reconfigurable antenna (RA) capable of steering its main beam into three different directions is presented. The 15% bandwidth of the antenna covers the frequency range of 5.1 – 5.9 GHz compatible with IEEE 802.11ac standard. This RA consists of an aperture-coupled stacked patch with a parasitic layer placed above it. The surface of the parasitic layer has a grid of 3 3 2 electrically small rectangular-shaped metallic pixels. The pixels are connected/dis- connected by means of switching resulting in reconfigurability in beam- direction. Only two PIN diode switches are utilized to provide three beam-steering directions yielding a simple RA. The simulations and measurements from fabricated prototypes show that the antenna main- tains its beam-steering capability with a flat maximum realized gain (6.5 dB) over the whole operational bandwidth. An RA Array (RAA) formed by the linear combination of four (4 3 1) identical RA elements is also designed, fabricated and measured. Despite being linear this RAA is capable of performing beam-steering in the plane, which is per- pendicular to the plane containing the central line of the array. The measured and simulated results agree well indicating a flat maximum realized array gain of 12.2 dB from 5.2 to 5.8 GHz. V C 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 59:63–65, 2017; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.30223 Figure 1 Structure of the broadband RA and RAA: (a) A photograph of the RA with an enlarged portion of switching, (b) Cross section view of the RA, and (c) A photograph of the RAA. [Color figure can be viewed at wileyonlinelibrary.com] Key words: multifunctional reconfigurable antenna; full-wave electro- magnetic analysis; beam-steering; antenna radiation pattern measure- ments; broadband antenna 1. INTRODUCTION Wireless communication technology has been growing rapidly in recent years. With the introduction of fifth generation (5G) and beyond wireless technologies, new products such as routers, laptops, and handsets are developed quickly in the market. The recently released wireless local area network (WLAN) 802.11ac standard [1] supports a frequency band from 5.17 to 5.83 GHz corresponding to a 12% bandwidth. To develop products under this standard using simple and low-cost microstrip antenna tech- nology is difficult since a legacy microstrip patch antenna typi- cally only has a bandwidth of 3%. Thus, a broadband technique must be employed to cover the whole frequency band while at the same time taking advantage of compact design of microstrip antenna. In addition, the rapid trend towards smaller cell size with the goal of achieving high rate mobile data traffic of 5G systems calls for antennas with dynamically changeable radiation patterns. This feature is mainly needed to deal with the interference thereby increasing signal-to-noise-ratio. In this work, a single antenna element that can provide beam-steering capability over a large frequency band is pre- sented. To accomplish this performance, a reconfigurable anten- na (RA) based on parasitic layer approach [2] is developed. This RA consists of an aperture-coupled fed stacked patch antenna [3], which is used as the driven antenna to realize the required broadband characteristic, with a parasitic layer placed above it (see Fig. 1). It is capable of producing three steerable DOI 10.1002/mop MICROWAVE AND OPTICAL TECHNOLOGY LETTERS / Vol. 59, No. 1, January 2017 63