Antennas and their coupling characteristics for wireless power transfer via magnetic coupling

A method for wirelessly receiving power from a transmitter, the, the method comprising:

• optimizing transfer efficiency of power received wirelessly from the transmitter, provided that an amount of the power received wirelessly and provided to a load is greater than or equal to a received power threshold;
• or
• optimizing the amount of the power received wirelessly from the transmitter, provided that the power transfer efficiency is greater or equal to an efficiency threshold.

An apparatus configured to receive wireless power from a transmitter, the apparatus comprising:

• means for optimizing transfer efficiency of power received wirelessly from a transmitter, provided that an amount of the power received wirelessly and provided to a load is greater than or equal to a received power threshold;
• or
• means for optimizing the amount of the power received wirelessly, provided that the power transfer efficiency is greater or equal to an efficiency threshold.

An apparatus for receiving power via a wireless field and for delivering power to a load, the apparatus comprising:

• a first antenna circuit coupled to the load and comprising an antenna, the first antenna circuit being configured to receive power via the wireless field for powering the load, the received power corresponding to a time-varying voltage signal from a second antenna circuit, the load being characterized by a reactance X and the first antenna circuit being characterized by an inductance L and a capacitance C, at least one of the inductance L and capacitance C configured to maintain the reactance X to be substantially equal to a first value that is inversely proportional to the capacitance C minus a second value that is directly proportional to the inductance L;
• and
• a controller coupled to the first antenna circuit and configured to adjust at least one parameter of the first antenna circuit.

A method of receiving power via a wireless field and for delivering power to a load, the apparatus comprising:

• wirelessly receiving power at a first antenna circuit for powering the load, the received power corresponding to a time-varying voltage signal from a second antenna circuit, the load being characterized by a reactance X and the first antenna circuit being characterized by an inductance L and a capacitance C, at least one of the inductance L and capacitance C configured to maintain the reactance X to be substantially equal to a first value that is inversely proportional to the capacitance C minus a second value that is directly proportional to the inductance L;
• and
• adjusting at least one parameter of the first antenna circuit.

An apparatus for receiving power via a wireless field and for delivering power to a load, the apparatus comprising:

• means for wirelessly receiving power for powering the load, the received power corresponding to a time-varying voltage signal from a second antenna circuit, the load being characterized by a reactance X and the means for wirelessly receiving power being characterized by an inductance L and a capacitance C, at least one of the inductance L and capacitance C configured to maintain the reactance X to be substantially equal to a first value that is inversely proportional to the capacitance C minus a second value that is directly proportional to the inductance L;
• and
• means for adjusting at least one parameter of the means for wirelessly receiving power.

An apparatus for delivering power to a load via a wireless field, the apparatus comprising:

• a power source configured to output a time-varying voltage signal at a voltage level and characterized by a reactance X;
• and
• a first antenna circuit configured to receive the voltage signal from the power source and to output power to a second antenna circuit to power the load via the wireless field, the first antenna circuit characterized by an inductance L and a capacitance C, at least one of the inductance L and capacitance C configured to maintain the reactance X to be substantially equal to a first value that is inversely proportional to the capacitance C minus a second value that is directly proportional to the inductance L.