NFC system optimization for simultaneous powering and communication with wireless sensors

The need for using wireless sensor that can work autonomously (no battery maintenance), scavenging energy from the surrounding environment is a real need that will become more demanding in the future. This document demonstrates a method for using Near Field Communications (NFC), not only for communicating with short range NFC devices, but also to power coupled devices, such as wireless power sensors. It is first demonstrated analytically how the concept works, showing the possibility of combining communications, via NFC, and Wireless Power Transfer (WPT), using the same device. The circuit that optimizes both NFC and WPT, is implemented into a regular NFC radio transceiver. So an NFC radio front-end is provided with the possibility of communicating optimally, based on data rate constraints, with NFC devices such as mobile phones or NFC-tags, and also for powering wireless sensors, both at HF and UHF frequency bands. In this case we expose the context on which such optimal matching circuit can be implemented, and how to dimension the components based on design constraints, and some experimental results are shown.