A Design of Switched-Beam Yagi-Uda Antenna for Wireless Sensor Networks

In this paper, we present a design of the Yagi-Uda antenna, which can be switched to achieve radiation patterns toward different angles with a step of 45 degree. The antenna covers the ISM band for SRDs with a center frequency of 2.45 GHz. There are eight Yagi-Uda antennas combined in a circle form. Each Yagi-Uda antenna consists of a bended reflector, a bended driven and a bended director. The bended reflector is shared for different Yagi-Uda antenna by PIN diodes. Simulated results show that eight switching beams covered all directions in E plane with particular direction beam-width around of 60 degree. The gain of the main lobe is greater than 5.5dBi, whereas the side lobe is kept 11dB smaller than the main lobe. Thanks to the pattern switchable ability and its simple design, the antenna can be used for the master sensors in wireless sensor networks, or for communicating devices in cognitive radios.