METHOD AND APPARATUS WITH NEGATIVE RESISTANCE IN WIRELESS POWER TRANSFERS

PROBLEM TO BE SOLVED: To provide systems and methods for adjusting operating characteristics of antennas to adapt to different circumstances and optimize power transfer characteristics.SOLUTION: Antenna circuits use negative resistance to offset resistance from other elements in the circuit. The antenna circuits include an antenna for coupling with a near field radiation at a resonant frequency, and a capacitance element connected in series with the receive antenna. The antenna circuits also include a negative resistance generator connected in series with the capacitance element. In the case of a receive antenna, and possibly a repeater antenna, a load is connected in series with the negative resistance generator. The load may draw power from the near field radiation when the antenna circuit oscillates near the resonant frequency. In the case of a transmission antenna, a signal generator is coupled in series with the antenna for applying signal power to the antenna circuit to generate an electromagnetic field at the resonant frequency creating a coupling-mode region within a near field.