Switched-beam antenna for WSN nodes enabling hardware-driven power saving

Energy saving is one of the most important issues in Wireless Sensor Network (WSN) context. Since the communication task is the most power-consuming operation, it is quite important to achieve an energy efficient communication in order to increase the lifetime of the devices through an intelligent use of the power transmission. In this context, the integration of WSN nodes with switched-beam antennas is becoming more and more appealing due to the possibility to extend sensor node lifetime by optimizing the transmitted power. In this work a switched-beam antenna for WSNs nodes in the ISM band (2.4-2.4835 GHz) is proposed. The radiating structure consists of four identical antennas, composed of an array of two L-shaped quarter-wavelength slot antenna elements arranged in a compact and symmetrical planar structure. Thanks to a properly designed switching circuit which controls the feeding of the antenna elements, one among eight possible different radiation patterns in the azimuth plane can be selected on the basis of specific needs. Simulations and experimental results, referred to a prototype realized on a FR-4 substrate, demonstrate the appropriateness of the proposed switched-beam antenna system as hardware element enabling new power saving strategies in WSN contexts.