Classifications

• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04B—TRANSMISSION
  • H04B5/00—Near-field transmission systems, e.g. inductive or capacitive transmission systems
  • H04B5/70—Near-field transmission systems, e.g. inductive or capacitive transmission systems specially adapted for specific purposes
  • H04B5/79—Near-field transmission systems, e.g. inductive or capacitive transmission systems specially adapted for specific purposes for data transfer in combination with power transfer
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01Q—ANTENNAS, i.e. RADIO AERIALS
  • H01Q1/00—Details of, or arrangements associated with, antennas
  • H01Q1/12—Supports; Mounting means
  • H01Q1/22—Supports; Mounting means by structural association with other equipment or articles
  • H01Q1/2208—Supports; Mounting means by structural association with other equipment or articles associated with components used in interrogation type services, i.e. in systems for information exchange between an interrogator/reader and a tag/transponder, e.g. in Radio Frequency Identification [RFID] systems
  • H01Q1/2225—Supports; Mounting means by structural association with other equipment or articles associated with components used in interrogation type services, i.e. in systems for information exchange between an interrogator/reader and a tag/transponder, e.g. in Radio Frequency Identification [RFID] systems used in active tags, i.e. provided with its own power source or in passive tags, i.e. deriving power from RF signal
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01Q—ANTENNAS, i.e. RADIO AERIALS
  • H01Q7/00—Loop antennas with a substantially uniform current distribution around the loop and having a directional radiation pattern in a plane perpendicular to the plane of the loop
• • H—ELECTRICITY
  • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
  • H02J—ELECTRIC POWER NETWORKS; CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
  • H02J50/00—Circuit arrangements or systems for wireless supply or distribution of electric power
  • H02J50/10—Circuit arrangements or systems for wireless supply or distribution of electric power using inductive coupling
  • H02J50/12—Circuit arrangements or systems for wireless supply or distribution of electric power using inductive coupling of the resonant type
• • H—ELECTRICITY
  • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
  • H02J—ELECTRIC POWER NETWORKS; CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
  • H02J50/00—Circuit arrangements or systems for wireless supply or distribution of electric power
  • H02J50/50—Circuit arrangements or systems for wireless supply or distribution of electric power using additional energy repeaters between transmitting devices and receiving devices

Definitions

• the system can use transmit and receiving antennas that are preferably resonant antennas, which are substantially resonant, e.g., within 10% of resonance, 15% of resonance, or 20% of resonance.
• the antenna (s) are preferably of a small size to allow it to fit into a mobile, handheld device where the available space for the antenna may be limited.
• An efficient power transfer may be carried out between two antennas by storing energy m the near field of the transmitting antenna, rather than sending the energy into free space in the form of a travelling electromagnetic wave.
• Antennas with high guality factors can be used.
• Two high-Q antennas are placed such that they react similarly to a loosely coupled transformer, with one antenna inducing power into the other.
• the antennas preferably have Qs that are greater than 1000.
• the present application describes transfer of energy from a power source to a power destination via electromagnetic field coupling.
• Embodiments describe techniques for new coupling structures, e.g., transmitting and receiving antennas .
• Figure 1 shows a block diagram of a magnetic wave based wireless power transmission system
• Figure 2 illustrates circuit diagrams of the circuits in the figure 1 diagram
• Figure 3 illustrates an exemplary near field condition plot
• a power transmitter assembly 100 receives power from a source, for example, an AC plug 102.
• a frequency generator 104 is used to couple the energy to an antenna 110, here a resonant antenna.
• the antenna 110 includes an inductive loop 111, which is inductively coupled to a high Q resonant antenna part 112.
• the resonant antenna includes a number N of coil loops 113 each loop having a radius R A .
• a capacitor 114 here shown as a variable capacitor, is in series with the coil 113, forming a resonant loop. In the embodiment, the capacitor is a totally separate structure from the coil, but in certain embodiments, the self capacitance of the wire forming the coil can form the capacitance 114.
• the frequency generator 104 can be preferably tuned to the antenna 110, and also selected for FCC compliance.
• This embodiment uses a multidirectional antenna. 115 shows the energy as output m all directions.
• the antenna 100 is non-radiative, m the sense that much of the output of the antenna is not electromagnetic radiating energy, but is rather a magnetic field which is more stationary. Of course, part of the output from the antenna will in fact radiate.
• Another embodiment may use a radiative antenna.
• a receiver 150 includes a receiving antenna 155 placed a distance D away from the transmitting antenna 110.
• the receiving antenna is similarly a high Q resonant coil antenna 151 having a coil part and capacitor, coupled to an inductive coupling loop 152.
• the output of the coupling loop 152 is rectified in a rectifier 160, and applied to a load.
• That load can be any type of load, for example a resistive load such as a light bulb, or an electronic device load such as an electrical appliance, a computer, a rechargeable battery, a music player or an automobile.
• the energy can be transferred through either electrical field coupling or magnetic field coupling, although magnetic field coupling is predominantly described herein as an embodiment .
• Electrical field coupling provides an inductively loaded electrical dipole that is an open capacitor or dielectric disk. Extraneous objects may provide a relatively strong influence on electric field coupling. Magnetic field coupling may be preferred, since extraneous objects in a magnetic field have the same magnetic properties as "empty" space .
• the embodiment describes a magnetic field coupling using a capacitively loaded magnetic dipole.
• a capacitively loaded magnetic dipole is formed of a wire loop forming at least one loop or turn of a coil, in series with a capacitor that electrically loads the antenna into a resonant state.
• FIG. 2 shows an equivalent circuit for the energy transfer.
• the transmit circuit 100 is a series resonant circuit with RLC portions that resonate at the frequency of the high frequency generator 205.
• the transmitter includes a series resistance 210, and inductive coil 215, and the variable capacitance 220. This produces the magnetic field M which is shown as magnetic lines of force 225.
• the signal generator 205 has an internal resistance that is preferably matched to the transmit resonator's resistance at resonance by the inductive loop. This allows transferring maximum power from the transmitter to the receiver antenna.
• the receive portion 150 correspondingly includes a capacitor 250, transformer coil 255, rectifier 260, and regulator 261, to provide a regulated output voltage.
• the output is connected to a load resistance 265.
• Figure 2 shows a half wave rectifier, but it should be understood that more complex rectifier circuits can be used.
• the impedance of the rectifier 260 and regulator 261 is matched to the resistance of the receive resonator at resonance. This enables transferring a maximum amount of power to the load.
• the resistances take into account skin effect / proximity effect, radiation resistance, as well as both internal and external dielectric loss.
• a perfect resonant transmitter will ignore, or minimally react with, all other nearby resonant objects having a different resonant frequency. However, when a receiver that has the proper resonant frequency encounters the field of the transmitting antenna 225, the two couple in order to establish a strong energy link. In effect, the transmitter and receiver operate to become a loosely coupled transformer. [0023] The inventors have discovered a number of factors that improve the transfer of power from transmitter to receiver. [0024] Q factor of the circuits, described above, can assist with certain efficiencies. A high Q factor allows increased values of current at the resonant frequency. This enables maintaining the transmission over a relatively low wattage.
• the transmitter Q may be 1400, while the receiver Q is around 300.
• the receiver Q may be much lower than the transmitter Q, for example 1/4 to 1/5 the transmitter Q.
• other Q factors may be used.
• the Q of a resonant device is the ratio of the resonant frequency to the so-called "3 dB" or "half power" bandwidth of the resonant device. While there are several “definitions, " all are substantially equivalent to each other, to describe Q in terms of measurements or the values of resonant circuit elements. [0025]
• High Q has a corresponding disadvantage of narrow bandwidth effects. Such narrow bandwidths have typically been considered as undesirable for data communications. However, the narrow bandwidth can be used in power transfer.
• an embodiment may use a resonant frequency with a substantially un-modulated fundamental frequency. Some modulation on the fundamental frequency may be tolerated or tolerable, however, especially if other factors are used to increase the efficiency. Other embodiments use lower Q components, and may allow correspondinqly more modulation on the fundamental.
• An important feature may include use of a frequency which is permitted by requlation, such as FCC regulations.
• the preferred frequency in this exemplary embodiment is 13.56 MHz but other frequencies may be used as well.
• the capacitors should be able to withstand high voltages, for example as high as 1000 V, since the resistance may be small in relation to the capacitive reactance.
• a final important feature is the packaging: the system should be in a small form factor.
• One aspect of improving the coupling between the transmit and receive antenna is to increase the Q of the antenna.
• the efficiency of power transfer ⁇ may be expressed as
• the frequency of the wave used for transmitting the power is in the "ISM band” e.g., at 135kHz.
• Other "low” frequencies can be used, for example, 160 KHz, 457 Khz, or any frequency less than 1 Mhz is considered herein to be “low” frequency.
• This frequency band is referred to herein as low frequency, or "LF".
• LF Low Frequency
• This LF system uses frequencies with a longer wavelength. In essence, this system effectively sends power to a shorter range in regards to the slope of the field strength. Because of the properties of the LF system, the quality factor of the circuits and antennas may be somewhat lowered. The inventors prefer a Q of 1000 or higher.
• Higher frequency systems of this type have used lower numbers of coil turns to increase Q.
• the LF system has a lower skin effect than other (HF) systems.
• the LF system has a higher number of turns.
• a first embodiment of the LF system may use Ferrites, e.g., non-conductive ferromagnetic ceramic compounds as cores within the coils.
• Ferrites e.g., non-conductive ferromagnetic ceramic compounds
• any material XY 2 O 4 where X and Y are each a different metal cation, can be used as the ferrites m an embodiment.
• One preferred material may be ZnFe 2 O 4 .
• the ferrites can be used as "cores" for the antennas e.g., any or all of 111, 112, 151, 152.
• antenna 152 is shown with a ferrite core 153 therein.
• Another embodiment may use Litze wire as the coils, e.g., any or all of 111, 112, 151, 152 may be formed of Litze wire. This is a bundle of thin wires that are interwoven, but mutually isolated to force current to be distributed over the full cross section of the wire.
• the receiver is the highest priority in order to get good performance.
• the receiver will have high relative power values, will need a few hundred nanofarads of capacitance, and a Q value that is "high", e.g, greater than 100, more preferably greater than 300, or greater than 1000.
• the receiver is of PDA size, e.g. (60mm x 100mm) .
• the transmitter preferably uses vacuum capacitors to keep a high Q.
• Another embodiment of the receiver uses air coils, optimized with capacitors as described herein.
• An embodiment may use multiple transmitters and / or passive parasitic loops (pure resonators) placed behind picture frames or under tables to act as repeaters that are activated by the transmitter.
• One such repeater is shown as 155 in figure 1.
• the transmitter then acts as a mother antenna for the long range hop.
• the parasitic loops act as a short range hop. This configuration is in fact multiple transmitters, but requiring neither separate feeding nor mutual frequency synchronization parasitic antennas (energy relays) .
• One aspect of the embodiment is the use of a high efficiency that comes from increasing the Q factor of the coupling structures (primarily the antennas) at the self- resonant frequency used for the sinusoidal waveform of the electromagnetic field, voltage or current used.
• the efficiency and amount of power is superior for a system which uses a single, substantially un-modulated sine wave.
• the performance is superior to a wide-band system which attempts to capture the power contained in a wideband waveform or in a plurality of distinct sinusoidal waveforms of different frequencies.
• Other embodiments may use less pure waveforms, in recognition of the real-world characteristics of the materials that are used.

Landscapes

• Engineering & Computer Science (AREA)
• Computer Networks & Wireless Communication (AREA)
• Power Engineering (AREA)
• Signal Processing (AREA)
• Near-Field Transmission Systems (AREA)
• Cable Transmission Systems, Equalization Of Radio And Reduction Of Echo (AREA)
• Coils Of Transformers For General Uses (AREA)
• Soft Magnetic Materials (AREA)
• Details Of Aerials (AREA)

Priority Applications (4)

Applications Claiming Priority (2)

Publications (2)

Family

ID=40351435

Family Applications (1)

Country Status (6)

Cited By (88)

Families Citing this family (137)

Family Cites Families (33)

• 2008
  • 2008-08-11 US US12/189,720 patent/US20090058189A1/en not_active Abandoned
  • 2008-08-11 EP EP08797642.9A patent/EP2186211A4/en not_active Withdrawn
  • 2008-08-11 WO PCT/US2008/072827 patent/WO2009023646A2/en not_active Ceased
  • 2008-08-11 KR KR1020107005559A patent/KR101159565B1/ko not_active Expired - Fee Related
  • 2008-08-11 CN CN200880102575A patent/CN101803224A/zh active Pending
  • 2008-08-11 JP JP2010521112A patent/JP2010537496A/ja not_active Withdrawn
  • 2008-08-11 CN CN201310466904.9A patent/CN103560811A/zh active Pending
• 2013
  • 2013-12-20 JP JP2013264354A patent/JP2014113040A/ja active Pending

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