Exploitation of capacitive coupling at UHF for remote sensing in a kW WPT system

In this work we discuss the design of a near-field link, based on capacitive plates, operating in the 868 MHz band, usually adopted for far-field applications. This system, capacitively coupled, serves as a wireless information transfer unit in a temperature-controlled system. Capacitive and inductive coupling are simultaneously exploited to integrate in a unique, robust, and reliable platform the contactless transmission of temperature data and electric power, respectively. A UHF rectifier is exploited to supply and sense the resistive variations of a Pt100-based temperature probe located in an inaccessible part of an industrial rotary tool. An extensive comparison with solutions in the HF band is presented. Results show reduced link losses and improved system performances in terms of accuracy and component tolerances.