Exemplary embodiments are directed to wireless power transfer. 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 transmit 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.