2013 7th European Conference on Antennas and Propagation (EuCAP) RECONFIGURABLE ANTENNA USING SMART MATERIAL Khalid Aljonubi\ Ahmed O. AlAmoudj2, Richard J Langle/, Ian Reane/ I ECP, KACST, P. O. Box 6086, 11442, Riyadh, Saudi Arabia, k.a.aljonubi@sheffield.ac.uk 2 ASED, KACST, P. O. Box 6086, 11442, Riyadh, Saudi Arabia, alamoudi@kacst.edu.sa 3 EEE Dept., University of Sheffield, Sheffield, S1 3JD, UK, r.janglesheffield.ac.uk 4 Materials Science & Engineering dept., university of Sheffield, Sheffield SI 3JD, UK, i.m.reaney@sheffield.ac.uk Abstract- Results for a reconfigurable PIFA using smart materials are presented. A novel approach is investigated by using PZT materials that switch into contact using a dc control voltage to reconfigure the PIFA structure and hence produce a tunable antenna. Index Terms- Sma Antenna, Reconfigurable Antenna, PZT, Sma Material, PIFA I. INTRODUCTION Historically antenna structure materials are typically stationary conductive elements that emitlreceive radio equency waves. This paper demonstrates the potential benefits of using smart materials in antenna design. In ture wireless communication, whether voice, data or video, it will be necessary to tune the  ont end over a very wide range of equencies to make better use of the specum, so called Cognitive Radio systems will be required. In many cases electronic tuning using devices such as varactors are used to improve equency scanning. Reconfiguring the antenna structure using MEMs switches is also feasible. However, the materials om which antennas are fabricated have remained largely unchanged [1, 2]. In this paper a PIFA is described which can be reconfigured by connecting and disconnecting conducting sips conolled by piezo elecic displacement [3, 4]. The antenna has been simulated using CST Microwave Studio and experimentally verified. This is a preliminary investigation as the mechanics of incoorating active materials must be overcome. However the basic principle is demonstrated together with experimental results. II. PZT MATERlAL Piezo actuators convert elecical energy into mechanical energy and by using a bimorph type PZT strip, a 2 -layer element can be made to elongate, bend, or twist depending on the polarization and wiring configuration of the layers. The two layer design offers the opportunity to reduce drive voltage by half when configured for parallel operation. A bimoh "2- layer" refers to the number of piezo layers, but a standard bimoh element actually has nine layers, consisting of: four electrode layers, two piezoceramic layers, two adhesive layers, and a center metallic shim, this center shim being laminated between the two piezo layers adding mechanical strength and stifess, but reducing motion. A bimorph "2-layer" element 978-88-907018-3-2/13 ©2013 IEEE 917 produces curvature when one layer expands while the other layer contracts. These ansducers are oſten referred to as benders, bimohs, or flexural elements. Total bender motion is usually on the order of l-lOmm, while the bender force ranges om tens to hundreds of grams. Typical DC voltages to deflect the sip are 10V to 15V. Many other types of piezo actuators exist and are suitable for use as smart materials in reconfigurable structures. In this experiment the piezo sip makes contact with a PIFA to give reconfigurability. III. EXPERIMENTAL SETUP The focus of this experimental effort is to demonstrate the potential of using a smart material in specific antenna design. The basic antenna consists of a Cu ground plate, 100 mm by 100 mm, an inverted F radiating element 20 mm above the ground plate 50 mm in length as shown in Fig.la. Copper sips all 4mm in width, 20mm in length were attached in t to the main PIFA arm as shown in Fig.lb. (a) (b) Fig.l PlFA Antenna (a) simple PTFA (b) PTFA with Cu strip added Three conductive elements in different positions and combinations were attached to the  (Fig.2) and simulations showed that this sucture will allow the PIFA to be tuned over a 10% equency range but the puose of the study is to establish principles and solve the problems of integrating the piezo materials into the antenna. These scenarios simulate the effect of PZT elements which initially are not in contact with the PIFA arm but when actuated creates a contact. There are a total of eight combinations for possible switching of the PZT positions, six of which are shown in Fig.3. The first combination represents a 'switch of state for all three strips,