Design of a battery-free wireless sensor node

In this paper, a battery-free wireless sensor designed to harvest energy from electromagnetic waves at 866.6MHz and its detachable antenna system are described, with an emphasis on high frequency front-end design. In addition to having no local power source, the proposed sensor node is programmable, since it integrates a general-purpose microcontroller. Other features of the device are a standard 50Ω port and an interface for debugging and expansion, with of a total of 26 pins. In practice, the proposed system is capable of carrying out communication and processing tasks at up to a distance of 4.1 meters away from a transmitter antenna operating within the limits imposed by local regulatory entities, with respect to radiated power. Uplink communication is achieved using modulated backscattering. The proposed antenna system consists of a printed dipole-based antenna, with an overall efficiency in the order of 96%.