MEMS-Reconfigurable Antenna based on a Multi-Size Pixelled Geometry D. Rodrigo 1 , Y. Damgaci 2 , N. Biyikli 2 , B.A. Cetiner 2 , J. Romeu 1 , L. Jofre 1 1 Signal Theory and Communications Department, Universitat Politècnica de Catalunya Barcelona 08034 Spain rodrigo@tsc.upc.edu 2 Electrical and Computer Engineering, Utah State University Logan UT 84322 Utah Abstract— A MEMS reconfigurable antenna with beam steering capability and resonance frequency reconfigurability is presented. The design is based in an interconnected patch grid structure and employs a hybrid geometry with different sized patches in a biclustered distribution on order to reduce the structure complexity and the number of necessary switches. A small antenna of λ/2 by λ/2 using only 12 RF-MEMS switches is optimized using genetic algorithms, demonstrating beam tilting over a range of 120º and resonant frequency reconfigurability over 4, 5 and 6GHz. The described design constitutes a step forward in the accomplishment of multiple parameter reconfiguration. I. INTRODUCTION Present antennas, as part of a multimode multi-band communication system, are required to maintain performances under changing environment conditions or over different ranges of parameters. Instead of using a multiple of single- function legacy antennas, where each antenna is optimized for one of the different requirements, a single multifunctional reconfigurable antenna (MRA) can be employed. The behaviour of a reconfigurable antenna can be dynamically changed, thus a single antenna can accommodate multiple systems requirements. This is accomplished by modifying the current distribution, as a result of dynamic architectural changes. Reconfigurable antenna parameters can be classified in two categories: impedance and radiation parameters. The first group refers to bandwidth and resonant frequency tuning, which are achieved by the electrical or physical modification of some critical dimension of the antenna, usually using capacitive loading or small structural modifications [1]-[2]. The second group controls polarization and radiation pattern and common techniques include parasitic elements modification and structural modifications preserving the main geometry [3]-[4]. To increase the reconfiguration capability achieving impedance and radiation reconfigurability simultaneously, poses a greater challenge which requires more general structures. Promising architectures are pixelled geometries, that consist of an electrically small patch grid interconnected by switches [5]-[6]. These structures, and thereby the antenna property, are modified by the activation/deactivation of the interconnecting switches. The main disadvantage of pixelled geometries is the large number of necessary switches, reducing the antenna efficiency and requiring a higher reconfiguration time. The purpose of this article is to present a novel reconfigurable antenna at 5.5 GHz based on a multisize pixelled geometry, focusing in the steering capability and resonant frequency modification while maintaining a low number of switches and a small size. II. RECONFIGURABLE ANTENNA A. Antenna Geometry The antenna main geometry is depicted in Fig. 1 and consists on a grid of electrically small metallic patches. Some pairs of adjacent patches are interconnected by a switch. The activation or deactivation of these switches modifies the current distribution over the antenna surface providing reconfigurability to the antenna structure. The patch grid is located over a 30x40mm substrate vertically placed on a metallic ground plane and is fed through it using a coaxial probe. For this reason the antenna will be referred as reconfigurable pixelled monopole. Fig. 1 Reconfigurable monopole antenna design (units in mm)