  A technique for efficient mid-range wireless energy transfer between two
coils via a mediator coil is proposed. By varying the coil frequencies three
resonances are created: emitter-mediator (EM), mediator-receiver (MR) and
emitter-receiver (ER). If the frequency sweeps are adiabatic and such that the
ER resonance precedes the MR resonance, the energy flows sequentially along the
chain emitter-mediator-receiver. If the MR resonance precedes the ER resonance,
then the energy flows directly from the emitter to the receiver via the ER
resonance; then the losses from the mediator are suppressed. This technique is
robust to noise, resonant constraints and external interferences.
