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`as) United States
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`a2) Patent Application Publication 10) Pub. No.: US 2010/0190436 Al
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`(43) Pub. Date: Jul. 29, 2010
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`Cooket al.
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`US 20100190436A1
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`CONCURRENT WIRELESS POWER
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`TRANSMISSION AND NEAR-FIELD
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`COMMUNICATION
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`Inventors:
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`Publication Classification
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`(51)
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`Int. Cl.
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`HO4B 5/00
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`(2006.01)
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`(52) US. CMe cocccecsescssssssssssssssnseeseeseesesssssssnsssneeses 455/41.1
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`Nigel P. Cook, El Cajon, CA (US);
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`LukasSieber, Olten (CH);
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`Hanspeter Widmer, Wohlenschwil
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`(CH)
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`Correspondence Address:
`QUALCOMM INCORPORATED
`5775 MOREHOUSEDR.
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`SAN DIEGO, CA 92121 (US)
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`QUALCOMM
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`INCORPORATED,San Diego,
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`CA (US)
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`Assignee:
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`Appl. No.:
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`Filed:
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`12/547,200
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`Aug.25, 2009
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`Related U.S. Application Data
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`Provisional application No. 61/092,022, filed on Aug.
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`26, 2008.
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`(57)
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`ABSTRACT
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`Exemplary embodiments are directed to wireless power
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`transfer and Near-Field Communication (NFC)operation. An
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`electronic device includes an antenna configured to resonate
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`at an NFC frequency and generate an induced current. The
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`electronic device further includingrectifier circuitry and NFC
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`circuitry each concurrently coupled to the induced current.
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`Therectifier circuitry configured to rectify the induced cur-
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`rent into DC power for the electronic device and the NFC
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`circuitry configured to demodulate any data on the induced
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`current. A method for concurrent reception of wireless power
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`and NFC includes receiving an induced current from an
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`antenna,rectifying the induced current into DC powerfor use
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`by an electronic device, and demodulating the induced cur-
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`rent concurrent with rectifying to determine any data for the
`NFC.,
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`(54)
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`(75)
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`(73)
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`(21)
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`(22)
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`(60)
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`™
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`RX
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`Antenna
`120
`108
`[Tt jaife --
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`Rectifier,
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`Switching
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`108
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`110
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`FIG. 1
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`104 \
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`108 L 120
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`[ "TNA ATLASTST SLSIT
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`Rectifier,
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`Switching
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`match’
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`bed Losses|
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`Jul. 29, 2010 Sheet 3 of 6
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`US 2010/0190436 Al
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`DEO]0bawweeennnnnennnepeeeeeeeeeencepooTeO¢z(ZH09/0)
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`310
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`314
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`Wireless
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`Power
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`Receiver
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`Near-Field
`Communication
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`Tranceiver
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`Transmitter 312
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`Wireless
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`Power
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`Near-Field
`Communication
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`Reader
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`Reader
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`combined
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`Power
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`Near-Field
`Communication
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`372
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`314
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`Wireless
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`Power
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`.
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`Receiver
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`Near-Field
`Communication
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`Tranceiver
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`FIG. 6
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`Jul. 29, 2010 Sheet 5 of 6
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`404 \
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`Rectifier=|———________ ee
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`Circuitry
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`Device
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`408
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`418
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`420
`Le
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`Device
`Electronics
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`402 \
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`FIG. 7
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`Receiving An Induced Current From
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`An Antenna
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`Rectifying The Induced Current Into
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`DC PowerFor Use By An Electronic
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`Device
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`Determine Any Data For The RFID
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`Demodulating The Induced Current
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`Concurrent With Rectifying To
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`FIG. 8
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`US 2010/0190436 Al
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`Jul. 29, 2010
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`CONCURRENT WIRELESS POWER
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`TRANSMISSION AND NEAR-FIELD
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`COMMUNICATION
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`FIG. 8 illustrates a flowchart of a methodfor receiv-
`[0015]
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`ing wireless power and NFC, in accordance with an exem-
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`plary embodiment.
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`CLAIM OF PRIORITY UNDER 35 U.S.C. §119
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`[0001] This application claims priority under 35 U.S.C.
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`§119(e) to:
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`[0002] U.S. Provisional Patent Application 61/092,022
`entitled “JOINT INTEGRATION OF WIRELESS
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`POWER ANDRFID INTO ELECTRONIC DEVICES
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`USING DUAL FUNCTION ANTENNA”filed on Aug.
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`26, 2008, the disclosure of which is hereby incorporated
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`by reference in its entirety.
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`DETAILED DESCRIPTION
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`[0016] The word “exemplary”is used herein to mean “serv-
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`ing as an example, instance, or illustration.” Any embodiment
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`described herein as “exemplary”is not necessarily to be con-
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`strued as preferred or advantageous over other embodiments.
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`[0017] The detailed description set forth below in connec-
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`tion with the appended drawingsis intended as a description
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`of exemplary embodiments ofthe present invention andis not
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`intended to represent the only embodiments in which the
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`present invention can be practiced. The term “exemplary”
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`used throughout
`this description means “serving as an
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`example, instance, or illustration,” and should not necessarily
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`be construed as preferred or advantageous over other exem-
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`plary embodiments. The detailed description includes spe-
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`cific details for the purpose of providing a thorough under-
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`standing of the exemplary embodiments of the invention.It
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`will be apparentto those skilled in theart that the exemplary
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`embodimentsofthe invention may be practiced without these
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`specific details. In someinstances, well-knownstructures and
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`devices are shown in block diagram form in order to avoid
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`obscuring the novelty of the exemplary embodiments pre-
`sented herein.
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`[0018] The term “wireless power”is used herein to mean
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`any form of energy associated with electric fields, magnetic
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`fields, electromagnetic fields, or otherwise that is transmitted
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`from a transmitter to a receiver without the use of physical
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`electromagnetic conductors. Power conversion in a system is
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`described herein to wirelessly charge devices including, for
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`example, mobile phones, cordless phones, iPod, MP3 play-
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`ers, headsets, etc. Generally, one underlying principle of
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`wireless energy transfer includes magnetic coupled reso-
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`nance (1.e.,
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`induction) using frequencies,
`for
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`example, below 30 MHz. However, various frequencies may
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`be employed including frequencies where license-exempt
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`operation at relatively high radiation levels is permitted, for
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`example,at either below 135 kHz (LF) or at 13.56 MHz (HF).
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`At these frequencies normally used by Radio Frequency
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`Identification (RFID) systems, systems must comply with
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`interference and safety standards such as EN 300330 in
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`Europe or FCC Part 15 norm in the United States. By way of
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`illustration and not limitation, the abbreviations LF and HF
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`are used herein where “LF”refers to f,=135 kHz and “HF”to
`FIG. 1 illustrates a simplified block diagram of a
`[0008]
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`refers to f,=13.56 MHz.
`wireless powertransmission system.
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`[0019] The term “NFC”mayalso include the functionality
`FIG.2 illustrates a simplified schematic diagram of
`[0009]
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`of RFID and the terms “NFC” and “RFID” may be inter-
`a wireless powertransmission system.
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`changed where compatible functionality allows for such sub-
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`[0010]
`FIG. 3 illustrates a schematic diagram of a loop
`stitution. The use of one term or the otheris not to be consid-
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`antenna, in accordance with exemplary embodiments.
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`ered limiting.
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`FIG. 4 illustrates a functional block diagram of a
`[0011]
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`[0020] The term “transceiver” may also include the func-
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`wireless power transmission system, in accordance with an
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`tionality of a transponder and the terms “transceiver” and
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`exemplary embodiment.
`“transponder” may be interchanged where compatible func-
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`FIG. 5 illustrates a transmitter arrangement for
`[0012]
`tionality allows for such substitution. The use of one term
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`coexistence of wireless power transmission and NFC,
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`over or the other is not to be considered limiting.
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`accordance with an exemplary embodiment.
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`[0021] FIG.1illustrates wireless power transmission sys-
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`FIG.6 illustrates another transmitter arrangement
`[0013]
`tem 100, in accordance with various exemplary embodi-
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`for coexistence of wireless power transmission and NFC, in
`ments. Input power 102 is provided to a transmitter 104 for
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`accordance with another exemplary embodiment.
`generating a magneticfield 106 for providing energy transfer.
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`FIG. 7 illustrates an electronic device including
`[0014]
`A receiver 108 couples to the magnetic field 106 and gener-
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`coexistent wireless power charging and NFC, in accordance
`ates an output power 110 for storing or consumption by a
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`with an exemplary embodiment.
`device (not shown) coupledto the output power 110. Both the
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`BACKGROUND
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`1. Field
`[0003]
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`[0004] The present invention relates generally to wireless
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`charging, and more specifically to devices, systems, and
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`methodsrelated to wireless charging systems.
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`2. Background
`[0005]
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`[0006] Typically, each powered device such as a wireless
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`electronic device requires its own wired charger and power
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`source, which is usually an alternating current (AC) power
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`outlet. Such a wired configuration becomes unwieldy when
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`many devices need charging. Approaches are being devel-
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`oped that use over-the-air or wireless power transmission
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`between a transmitter and a receiver coupled to the electronic
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`device to be charged. The receive antenna collects the radi-
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`ated powerandrectifies it into usable power for powering the
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`device or charging the battery of the device. Wireless power-
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`ing of devices mayutilize transmission frequencies that may
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`be occupied by other communication systems. One such
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`example,
`is a Near-Field Communication (NFC) system
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`(commonly knownas a type of “RFID”) which mayutilize,
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`for example, the 13.56 MHz band.
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`[0007]
`Furthermore, there may be separate applications
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`resident in as single electronic device that utilize a common
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`frequency band. Accordingly, there is a need to allow com-
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`patible interoperation ofvarious applications over a common
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`frequency band.
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`BRIEF DESCRIPTION OF THE DRAWINGS
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`transmitter 104 and the receiver 108 are separated by a dis-
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`tance 112. In one exemplary embodiment, transmitter 104
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`and receiver 108 are configured according to a mutual reso-
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`nant relationship and when the resonant frequency ofreceiver
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`108 and the resonant frequency of transmitter 104 are
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`matched, transmission losses betweenthe transmitter 104 and
`the receiver 108 are minimal whenthe receiver 108is located
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`in the “near-field” of the magneticfield 106.
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`[0022] Transmitter 104 further includes a transmit antenna
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`114 for providing a means for energy transmission and
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`receiver 108 further includes a receive antenna 118 for pro-
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`viding a meansfor energy reception or coupling. The transmit
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`and receive antennas are sized according to applications and
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`devices to be associated therewith. As stated, an efficient
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`energy transfer occurs by coupling a large portion of the
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`energyin the near-field ofthe transmitting antenna to a receiv-
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`ing antennarather than propagating most of the energy in an
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`electromagnetic wave to the far-field. In this near-field, a
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`coupling may be established between the transmit antenna
`114 andthe receive antenna 118. The area aroundthe anten-
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`nas 114 and 118 wherethis near-field coupling may occuris
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`referred to herein as a coupling-moderegion.
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`FIG. 2 showsa simplified schematic diagram of a
`[0023]
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`wireless power transmission system. The transmitter 104,
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`driven by input power 102, includes an oscillator 122, a power
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`amplifier or powerstage 124 and a filter and matching circuit
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`126. The oscillator is configured to generate a desired fre-
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`quency, which may be adjusted in response to adjustment
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`signal 123. The oscillator signal may be amplified by the
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`power amplifier 124 with a power output responsive to con-
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`trol signal 125. Thefilter and matching circuit 126 may be
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`includedto filter out harmonics or other unwanted frequen-
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`cies and match the impedanceofthe transmitter 104 to the
`transmit antenna 114.
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`[0024] An electronic device 120 includes the receiver 108
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`mayinclude a matchingcircuit 132 anda rectifier and switch-
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`ing circuit 134 to generate a DC poweroutput to charge a
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`battery 136 as shownin FIG. 2 or power a device coupled to
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`the receiver (not shown). The matching circuit 132 may be
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`included to match the impedance ofthe receiver 108 to the
`receive antenna 118.
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`[0025] A communication channel 119 may also exist
`between the transmitter 104 and the receiver 108. As
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`described herein, the communication channel 119 may be of
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`the form of Near-Field Communication (NFC). In one exem-
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`plary embodiment described herein, communication channel
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`119 is implementedas a separate channel from magneticfield
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`106 and in another exemplary embodiment, communication
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`channel 119 is combined with magneticfield 106.
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`[0026] As illustrated in FIG. 3, antennas used in exemplary
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`embodiments may be configured as a “loop” antenna 150,
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`which mayalso be referred to herein as a “magnetic,” “reso-
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`nant” or a “magnetic resonant” antenna. Loop antennas may
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`be configured to include an air core or a physical core such as
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`a ferrite core. Furthermore, an air core loop antenna allows
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`the placement of other components within the core area. In
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`addition, an air core loop may morereadily enable placement
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`of the receive antenna 118 (FIG. 2) within a plane of the
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`transmit antenna 114 (FIG. 2) where the coupled-mode
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`region of the transmit antenna 114 (FIG. 2) may be more
`effective.
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`[0027]
`Asstated, efficient transfer of energy between the
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`transmitter 104 and receiver 108 occurs during matched or
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`nearly matched resonance between the transmitter 104 and
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`the receiver 108. However, even when resonance between the
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`transmitter 104 and receiver 108 are not matched, energy may
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`be transferredat a lowerefficiency. Transfer of energy occurs
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`by coupling energy from the near-field of the transmitting
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`antennato the receiving antennaresiding in the neighborhood
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`where this near-field is established rather than propagating
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`the energy from the transmitting antennainto free space.
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`[0028] The resonant frequency of the loop antennas is
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`based on the inductance and capacitance. Inductancein a loop
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`antenna is generally the inductance created by the loop,
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`whereas, capacitance is generally addedto the loop antenna’s
`inductanceto create a resonant structure at a desired resonant
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`frequency. As a non-limiting example, capacitor 152 and
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`capacitor 154 maybe addedto the antenna to create a resonant
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`circuit that generates a sinusoidal or quasi-sinusoidal signal
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`156. Accordingly, for larger diameter loop antennas, the size
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`of capacitance needed to induce resonance decreases as the
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`diameter or inductance of the loop increases. Furthermore, as
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`the diameter of the loop antenna increases,
`the efficient
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`energy transfer area of the near-field increases for “vicinity”
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`coupled devices. Of course, other resonant circuits are pos-
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`sible. As another non-limiting example, a capacitor may be
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`placed in parallel between the two terminals of the loop
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`antenna. In addition, those of ordinary skill in the art will
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`recognize that for transmit antennas the resonant signal 156
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`may be an input to the loop antenna 150.
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`[0029] Exemplary embodiments of the invention include
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`coupling power between two antennasthat are in the near-
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`fields of each other. As stated, the near-field is an area around
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`the antenna in which electromagnetic fields exist but may not
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`propagate or radiate away from the antenna. They are typi-
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`cally confined to a volumethatis near the physical volume of
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`the antenna. In the exemplary embodimentsof the invention,
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`antennas such as single and multi-turn loop antennasare used
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`for both transmit (Tx) and receive (Rx) antenna systemssince
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`most ofthe environmentpossibly surrounding the antennasis
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`dielectric and thus has less influence on a magnetic field
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`comparedto an electric field. Furthermore, antennas domi-
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`nantly configured as “electric” antennas (e.g., dipoles and
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`monopoles) or a combination of magnetic andelectric anten-
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`nas is also contemplated.
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`[0030] The Tx antenna can be operatedat a frequency that
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`is low enough and with an antennasizethat is large enough to
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`achieve good coupling efficiency (e.g., >10%) to a small Rx
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`antennaat significantly larger distances than allowed byfar-
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`field and inductive approaches mentionedearlier. If the Tx
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`antenna is sized correctly, high coupling efficiencies (e.g.,
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`30%) can be achieved when the Rx antenna on a host device
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`is placed within a coupling-moderegion(i.e., in the near-field
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`or a strongly coupled regime) of the driven Tx loop antenna
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`[0031] The various exemplary embodiments disclosed
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`herein identify different coupling variants which are based on
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`different power conversion approaches, and the transmission
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`range including device positioning flexibility (e.g., close
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`“proximity” coupling for charging pad solutions at virtually
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`zero distance or “vicinity” coupling for short range wireless
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`powersolutions). Close proximity coupling applications(1.e.,
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`strongly coupled regime, coupling factor typically «>0.1)
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`provide energy transfer over short or very short distances
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`typically in the order ofmillimeters or centimeters depending
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`on the size of the antennas. Vicinity coupling applications
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`(i.e., loosely coupled regime, coupling factor typically «<0.1)
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`Page 9 of 13
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`Page 9 of 13
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`

`

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`US 2010/0190436 Al
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`Jul. 29, 2010
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`provide energy transfer at relatively low efficiency over dis-
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`tances typically in the range from 10 cm to 2 m depending on
`the size of the antennas.
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`[0032] As described herein, “proximity” coupling and
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`“vicinity”
`coupling may require
`different matching
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`approaches to adapt the power source/sink to the antenna/
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`coupling network. Moreover, the various exemplary embodi-
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`ments provide system parameters, design targets, implemen-
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`tation variants, and specifications for both LF and HF
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`applications and for the transmitter and receiver. Some of
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`these parameters and specifications may vary, as required for
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`example, to better match with a specific power conversion
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`approach. System design parameters may include various
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`priorities and tradeoffs. Specifically, transmitter and receiver
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`subsystem considerations may include high transmission
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`efficiency, low complexity of circuitry resulting in a low-cost
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`implementation.
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`FIG. 4 illustrates a functional block diagram of a
`[0033]
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`wireless power transmission system configured for direct
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`field coupling between a transmitter and a receiver, in accor-
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`dance with an exemplary embodiment. Wireless powertrans-
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`mission system 200 includesa transmitter 204 and a receiver
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`208. Input power P,,,,, 1s provided to transmitter 204 for
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`generating a predominantly non-radiative field with direct
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`field coupling « 206 for providing energy transfer. Receiver
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`208 directly couples to the non-radiative field 206 and gen-
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`erates an output power Ppy,,,, for storing or consumption by a
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`battery or load 236 coupled to the output port 210. Both the
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`transmitter 204 and the receiver 208 are separated by a dis-
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`tance. In one exemplary embodiment, transmitter 204 and
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`receiver 208 are configured according to a mutual resonant
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`relationship and when the resonant frequency, f,, of receiver
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`208 and the resonant frequency of transmitter 204 are
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`matched, transmission losses betweenthe transmitter 204 and
`the receiver 208 are minimal while the receiver 208 is located
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`in the “near-field” of the radiatedfield generated by transmit-
`ter 204.
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`[0034] Transmitter 204 further includes a transmit antenna
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`214 for providing a means for energy transmission and
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`receiver 208 further includes a receive antenna 218 for pro-
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`viding a means for energy reception. Transmitter 204 further
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`includes a transmit power conversion unit 220 at least par-
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`tially function as an AC-to-AC converter. Receiver 208 fur-
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`ther includes a receive power conversion unit 222 at least
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`partially functioning as an AC-to-DC converter.
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`[0035] Various
`receive
`antenna
`configurations
`are
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`described herein which use capacitively loaded wire loops or
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`multi-turn coils forming a resonant structure that is capable to
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`efficiently couple energy from transmit antenna 214 to the
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`receive antenna 218 via the magnetic field ifboth the transmit
`antenna 214 and receive antenna 218 are tuned to a common
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`resonance frequency. Accordingly, highly efficient wireless
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`charging of electronic devices (e.g. mobile phones) in a
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`strongly coupled regime is described where transmit antenna
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`214 andreceive antenna 218 are in close proximity resulting
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`in coupling factors typically above 30%. Accordingly, vari-
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`ous receiver concepts comprised of a wire loop/coil antenna
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`and a well matched passive diode rectifier circuit are
`described herein.
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`[0036] Many Li-Ion battery-powered electronic devices
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`(e.g. mobile phones) operate from 3.7 V and are charged at
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`currents up to 1 A (e.g. mobile phones). At maximum charg-
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`ing current, the battery may therefore present a load resis-
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`tance to the receiver on the order of 4 Ohms. This generally
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`Page 10 of 13
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`renders matching to a strongly coupled resonant induction
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`system quite difficult since higher load resistances are typi-
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`cally required to achieve maximum efficiency in these con-
`ditions.
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`[0037] An optimum load resistance is a function of the
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`secondary’s L-C ratio (ratio of antenna inductance to capaci-
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`tance). It can be shown however that there generally exist
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`limits in the choice of the L-C ratio depending on frequency,
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`desired antenna form-factor and Q-factor. Thus, it may not
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`alwaysbe possible to design a resonantreceive antennathatis
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`well matched to the load resistance as presented by the
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`device’s battery.
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`[0038] Active or passive transformation networks, such as
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`receive power conversion unit 222, may be used for load
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`impedance conditioning, however, active transformation net-
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`works mayeither consume poweror add losses and complex-
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`ity to the wireless powerreceiver andtherefore are considered
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`inadequate solutions. In various exemplary embodiments
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`described herein, receive power conversion unit 222 includes
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`dioderectifier circuits that exhibit input impedanceat a fun-
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`damental frequencythat is larger than the load impedance R,
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`of load 236. Suchrectifier circuits, in combination with a low
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`L-C resonant receive antenna 218, may provide a desirable
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`(i.e., near optimum)solution.
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`for
`[0039] Generally, at higher operating frequencies,
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`example above 1 MHzandparticularly at 13.56 MHz, loss
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`effects resulting from diode recovery time(1.e., diode capaci-
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`tance) become noticeable. Therefore, circuits,
`including
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`diodes exhibiting diode voltage waveforms with low dv/dt,
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`are desirable. By way of example, these circuits typically
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`require a shunt capacitor at the input which may function as
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`an anti-reactor needed to compensate antenna inductance
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`thus maximizing transfer efficiency.
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`[0040] The fact that required shunt capacitance maximiz-
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`ing transfer efficiency is a function of both coupling factor
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`and battery load resistance and would required automatic
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`adaptation (retuning)if one ofthese parameters was changed.
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`Assuming a strongly coupled regime with changes of cou-
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`pling factor within a limited range and maximumefficiency
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`only at highest power, a reasonable compromise may how-
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`ever be found not requiring automatic tuning.
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`[0041] Another design factor for wireless power transmis-
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`sion based on magnetic induction principles is that harmonics
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`are generated by a rectifier circuit. Harmonic content in the
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`receive antenna current and thus in the magnetic field sur-
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`rounding the receive antenna may exceedtolerable levels.
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`Therefore, receiver/rectifier circuits desirable produce mini-
`mum distortion on the induced receive antenna currents.
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`[0042]
`FIGS. 5-8 illustrate various configurations of sup-
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`porting RFID (e.g., NFC) in the presence of wireless power
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`transmission, in accordance with various exemplary embodi-
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`ments. Various transmitter arrangements are described for
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`interacting with a receiver including both wireless power
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`charging capabilities and NFC functionality.
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`[0043] Generally, RFID systems, including NFC, operated
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`in Europe have to comply to ECC standard andto the corre-
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`sponding standard in the United States. These standards
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`define dedicated frequency bands and emission (field
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`strength) levels. These frequencies bands that mostly coin-
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`cide with ISM-bandsare also interesting for wireless power-
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`ing and charging of portable electronic devices as they gen-
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`erally permit license exemptuse at increased emissionlevels.
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`[0044] NFC readers (e.g., RFID readers) supporting pas-
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`sive transceivers (e.g., transponders) must transmit a signal
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`Page 10 of 13
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`US 2010/0190436 Al
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`Jul. 29, 2010
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`sufficiently strong to energize the transceiver(e.g., transpon-
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`der) sometimes in unfavorable conditions. By way of
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`example, a 13.56 MHz RFID/NFCtransmitter typically emits
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`an Amplitude Shift Keying (ASK) modulated carrier using
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`power, for example, in the range from 1 W to 10 W. The
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`degree of modulation is typically very low. In the frequency
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`domain, the ASK-modulated NFC signal appears as a strong
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`discrete carrier wave component and a much weaker lower
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`and upper side-band containing the transmitted information.
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`The carrier wave component ofa 13.56 MHz transmitter must
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`be within a narrow frequency band defined by 13.5600 MHz
`+/- 7 kHz.
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`Principally, the high power carrier componentof a
`[0045]
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`NFC-radiated field is not distinguishable from that of a wire-
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`less power transmission system operating at the same fre-
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`quency. Therefore, wireless power transmission systems may
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`coexist with NFC without producing harmfulinterference. In
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`contrast, if not coherent(i.e., absolutely frequency synchro-
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`nous), the combination of an NFC system with a wireless
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`power transmission system merely increases the received
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