276 Progress In Electromagnetics Research Symposium 2005, Hangzhou, China, August 22-26 Development of an Adaptive and a Switched Beam Smart Antenna System for Wireless Communications F. E. Fakoukakis, S. G. Diamantis, A. P. Orfanides, and G. A. Kyriacou Democritus University of Thrace, Greece Abstract This study concentrates on the development of two separate Smart Antenna Systems for the 2.45GHz ISM band. Both systems incorporate the RF-beamforming method. Each system has the ability to point the beam in a three dimensional space, both in azimuth and in elevation direction. The Switched Beam System adopts a passive network-based beamforming approach, using 2-D Butler matrix topologies. The Adaptive System utilizes the vector modulator method, but only in the azimuth direction, increasing beam-steering accuracy, whereas introducing complexity and cost. The system design is presented for both cases, along with some module design and testing examples. A comparison of the two systems will be also discussed. Introduction SDMA (Space Division Multiple Access) is a new technique that aims to improve the capacity and quality of wireless systems. It is based on the use of steerable antennas, incorporating electronically controllable Beamforming Networks (BFNs). New standards for Switched Beam and Point-to-Multipoint Smart Antenna Systems are under development by ETSI (European Telecommunications Standards Institute), [1]. Beamforming networks can be developed either at RF or IF level. The use of IF-BFNs results in a Smart Antenna System fully exploiting the advantages of an Adaptive Antenna. Also, their implementation and control are easier. However, IF-BFNs suffer from increased complexity, since they are incorporated into a multichannel topology requiring the development of the system from scratch. On the other hand, RF-BFNs offer decreased complexity, but harder control requirements. Similarly, RF-Beamforming Networks exploit only some of the Smart Antenna Systems capabilities. Their critical advantage is the easy integration with the existing architectures in Base Stations (retro-fit), since only the replacement of the RF front-end is needed. Since the RF-Beamforming method has been adopted, the critical point is the use of either passive or active beamformers. Once again, active beamformers offer more capabilities and particularly higher beam pointing accuracy than the passive BFNs. But, the active BFNs introduce non-linearities, difficulties in achieving the desired dynamic range and their most serious drawback is their non-reciprocal nature. Namely, separate active RF-BFNs are required for the transmitter and receiver RF-stages. In contrary, passive RF-BFNs can be reciprocal and linear, retaining the system dynamic range. The Switched Beam System The proposed Switched Beam System uses the Butler matrix network for the beamforming procedure, [2,3,4,5]. The system’s basic demand is the pointing of the beam both in azimuth and in the elevation direction. For this reason, two alternative system topologies are considered. The first proposed system consists of an 8x8 Figure 1: Block diagrams of the proposed Switched Beam Smart Antenna Systems.