A Software Deﬁned MEMS-Reconﬁgurable PIXEL-Antenna for Narrowband MIMO Systems Alfred Grau † , Jordi Romeu ∗ , Lluis Jofre ∗ , and Franco De Flaviis † ∗ Technical University of Catalonia, Spain † University of California at Irvine, USA Abstract— In this paper we propose a software deﬁned highly multifunctional pixeled antenna for narrowband Multiple-Input Multiple-Output (MIMO) wireless communication systems, that uses Micro Electromechanical Switches (MEMS) to reconﬁgure its radiation modes and operating frequency. These capabilities can be used to improve the performance of current narrowband communication systems and also to ﬁt some of the requirements needed by software deﬁned radio architectures. The radiation characteristics and return loss response of the present structure are presented. I. I NTRODUCTION New technologies in communications such as Software- Deﬁned Radio (SDR) [1] and Radio-Frequency (RF) switches implemented using micro-electromechanical systems (MEMS), present new challenges and opportunities for an- tenna design. For example, there is a fundamental limitation to realize electrically small antennas that are both efﬁcient and broadband. As a result, for example, covering several frequency bands concurrently with a single antenna having enough efﬁciency and bandwidth is a major challenge. One possible solution to this problem is to use an antenna that can tune to different frequency bands. Such an antenna would not cover all bands simultaneously, but would provide narrower instantaneous bandwidths that are dynamically selectable at higher efﬁciency than conventional antennas. Such antenna is referred in the literature as a frequency reconﬁgurable antenna. In the literature one can ﬁnd several reconﬁgurable antenna designs which have as objective to change the operating frequency, such as in [2][3][4]. Similarly, having to excite several radiation patterns and polarization states concurrently with a single antenna may be also impractical. Therefore, several designs exist in the literature of pattern [5][6][7][8][3] and polarization [9][10][11][12][13] reconﬁgurable antennas. Thus, with the introduction of reconﬁgurable antennas, it is now possible to dynamically change properties such as the radiation pattern, the polarization and the operating frequency, which have traditionally been assumed to be ﬁx. Reconﬁg- urable antennas work based on the principle that by altering the antenna physical conﬁguration, the current density on the antenna may be controlled in a desirable manner and therefore its radiation pattern/polarization/frequency can be changed. To change the antenna physical conﬁguration, one can use Microelectromechanical (MEM) switches or active devices such as diodes or ﬁeld-effect transistors (FETs), which are strategically located over the geometry of the antenna. SOFTWARE DEFINED ANTENNA (SDA) - External Bank of DC Voltage Drivers - Integrated Circuit (on Chip) - Integrated Circuit (on Chip), - Laptop, - Portable Control Unit SDA Control Unit (D/A Converter) Communications Unit Radio Frequency Front End ... Fig. 1. Conceptual schematic of a software deﬁned antenna using the MMRPA. Having an antenna that could integrate all the aforemen- tioned reconﬁgurable capabilities would be desirable because such antenna would result in a compact design that could perform multiple tasks. Having this in mind, in this paper, we present an envisioned design of a highly multifunctional antenna which through the use of MEM switches can re- conﬁgure any of the aforementioned properties (radiation patter, polarization, frequency). By having these capabilities the antenna could operate into a wide variety of communi- cations standards and perform multiple functionalities such as sensing, communications, telemetry, etc. Within the same time-line, in [14], a similar antenna structure was proposed and fabricated which uses active switching devices to reconﬁgure the antenna in distinct conﬁgurations. As it will be shown, in this paper, MEM switches have been used to reconﬁgure the radiation characteristics of the proposed antenna. This has to do with the fact that MEM switches offer superior performance than active switching devices such as diodes or ﬁeld-effect transistors (FETs), in terms of smaller insertion NASA/ESA Conference on Adaptive Hardware and Systems 978-0-7695-3166-3/08 $25.00 © 2008 IEEE DOI 10.1109/AHS.2008.74 141 NASA/ESA Conference on Adaptive Hardware and Systems 978-0-7695-3166-3/08 $25.00 © 2008 IEEE DOI 10.1109/AHS.2008.74 141 NASA/ESA Conference on Adaptive Hardware and Systems 978-0-7695-3166-3/08 $25.00 © 2008 IEEE DOI 10.1109/AHS.2008.74 141