An autonomous wireless sensor network device powered by a RF energy harvesting system

In this paper, we present an energetically autonomous wireless sensor network (WSN) device designed to enhance safety in vehicles capable to connect extra gear/equipment to the main chassis. The proposed system allows the vehicle stability control system to automatically recognize the connected trailer or implement through a purposely designed WSN device, which is integrated into trailer /implement and wirelessly sends its identification number. The WSN device we developed integrates also a novel RF energy harvesting circuit which gathers the energy from an 868MHz RF signal source, which is purposely transmitted from the vehicle towards the trailer or implement for remote powering. Measurements performed on fabricated WSN system prototypes show that the RF harvester can gather up to ≈50uW@3m from the RF power source with efficiency higher than 30% over a range of 10dBm. The combination of the RF energy harvesting circuit with the ultra-low power architecture and a custom task manager designed for the WSN system allows to further increase primary battery lifetime, making the wireless system capable to operate autonomously for several years.