Reconfigurable Gap-Coupled Back-to-Back Truncated Rhombus-like Slotted Patch Antenna with Steerable Beams S. Muhamud-Kayat 1 , M. T. Ali 1 , M. K. M. Salleh 1 , M. H. M. Rusli 2 1 Antenna Research Group (ARG), Microwave Technology Centre (MTC), Faculty of Electrical Engineering, Universiti Teknologi MARA (UiTM), Shah Alam, Selangor, Malaysia Email: suzilawati.mkayat@yahoo.com, mizi732002@yahoo.com 2 Faculty of Mechanical Engineering, Universiti Teknologi MARA (UiTM), Shah Alam, Selangor, Malaysia Abstract— The paper presents an innovative antenna structure by incorporating a reconfigurable planar array antenna with parasitic elements, in which it comprises of two truncated rhombus-like slotted patch antennas in back-to-back configuration. The antenna emphasizes on these two design elements: slotted patch and parasitic elements to reconfigure its frequency and radiation pattern, respectively. On top of that, the deployment of an aperture coupling technique which separates feed network from the antenna radiating elements help to reduce spurious effects from the feed work. The main focus of this work is to design a reconfigurable antenna structure that is capable of operating at two different frequencies with steerable beams. In other words, both frequency and radiation pattern can be reconfigured by using the same antenna. A ‘state-of-the-art’ design of rhombus-like slotted patch with truncated edges is also introduced in this paper. The integration of PIN diodes as RF switches with the feed network and parasitic elements enables the antenna to activate at two different frequencies with six different steerable beam directions at each frequency mode, F1=5.3GHz (0°, 10°, 170°, 180°, 190° and 350°) and F2=5.9GHz (0°, 20°, 160°, 180°, 200° and 340°). Both simulation and measurement results are presented and they agree well to each other. The antenna is compatible to be embedded with other mobile devices owing to its small and compact size. Furthermore, it has the potential to be applied in multiple applications based on 5.3GHz and 5.9GHz bands. Index Terms—antenna, aperture coupling, beam steering, reconfigurable, slotted patch I. INTRODUCTION Over the years, reconfigurable microstrip antennas have been of a great interest owing to its attractive features that could meet the demand for compact and multifunctional devices. They have the ability to provide diversity functions to wireless communications based on their operating frequency, radiation pattern and polarization [1]-[3]. In addition, microstrip antennas are well-known for their lightweight and compatibility to embed with other devices. Basically, reconfigurable antennas are activated with the integration of RF switching components such PIN diodes, MEMs and varactor diodes [4]-[6]. Among them, PIN diodes are considerably cheap and reliable. Besides, the activation of reconfigurable antennas also depend on the various antenna shapes and additional elements such parasitic elements. Size reduction and compactness of the antennas can be achieved by controlling the shape of the slots. The resonant frequencies can also be affected by having different orientations of the patch slot in x- or y-axis [7]. The approach of parasitic elements has been widely used to reconfigure radiation patterns without affecting the antenna operating frequencies [8] significantly. Therefore, this paper focuses on the design of a reconfigurable microstrip antenna for multiple applications based on IEEE 802.16e Standard Compliant (WiMAX) and IEEE 802.11p Dedicated Short Range Communications/Wireless Access in Vehicular Environments (DSRC/WAVE) family of standards. The interoperation between WiMAX and DSRC system in vehicles can improve traffic management, mobility environment and public safety applications such as collision avoidance. The proposed antenna is compatible to be embedded with other mobile devices owing to its small and compact size. Furthermore, it has the potential to be applied as a tool for inventory control which enhances JIT production, streamlining inter-department communication and strengthens visual control which enables the implementation of Lean Manufacturing in Malaysian Industry i.e automotive component industry [9]. On top of that, by integrating the product with an appropriate system, it can provide better control of inventory which in turn enabling stock reduction and unfreezes capital tie-up, in overall reducing cost of manufacturing. The initial stage of the work has been presented in [10] by using copper strips that function as ideal switches. In this paper, further enhancement on the overall structure and its main beam directions including the integration of real PIN diodes is presented. II. ANTENNA STRUCTURE This paper presents a novel antenna structure which comprises of two reconfigurable truncated rhombus-like slotted patch antennas (RTRSAs), namely RTRSA-1 and RTRSA-2 in back-to-back configuration. The structure of 2014 21st International Conference on Telecommunications (ICT) 978-1-4799-5141-3/14/$31.00 ©2014 IEEE 338