Near-Field Wireless Power Transfer Using Free-Running and Injection-Locked Oscillators

Near-field wireless power transfer with a high-power oscillator avoids the need of both an independent source and an amplifier, which reduces the number of system elements and thus, the total energy consumption. However, the coupling to the external resonator modifies the oscillator output load, which will lead to changes in the oscillation frequency with the distance between the coils and their orientation. It may also give rise to undesired phenomena, such as the oscillation extinction or the generation of undesired oscillation modes, especially when a relay resonator is used. A reliable prediction of the circuit behavior will be essential for an optimized design. Here an efficient and insightful method will be illustrated through its applications to a coupled system based on Class-E oscillator that has been analyzed and experimentally characterized.