RF Wireless Power Transfer to Chip-Scale Apparatuses



An inductive wireless power system is particularly appealing for secured short-range operation, considering its non-contacting and non-radiative nature. However, one of the major challenges of inductively and wirelessly powering chip-scale apparatuses stems from the miniature size of chip-scale apparatus. The effective range of power transfer or communication is limited by the size of the coil that resides on the implanted chip or the hardware root of trust. For a distance exceeding five diameters of the coils, the power transfer efficacy diminishes to practically nothing even with high Q coils and magnetic resonance enhanced designs. 

The lab employs a novel approach of treating multi-coil WPT systems as RF filters formed by spatially and weakly coupled resonators, for which the final power transfer efficacy (PTEF) can be determined similarly to the insertion loss of a filter. The effectiveness and accuracy in predicting the performance of the designed WPT systems are tested by micro fabricating the coils on a Si wafer and measuring the power transfer efficacy. The measurement and modeling results reach excellent agreement. As a result, inductive wireless power transfer over a long distance (~5 times the coil diameter) has been achieved with an unprecedented high efficacy (-27 dB).