I 1111111111111111 11111 1111111111 111111111111111 IIIII IIIII lll111111111111111
`US008934836B2
`
`c12) United States Patent
`Lefley
`
`(IO) Patent No.:
`(45) Date of Patent:
`
`US 8,934,836 B2
`Jan.13,2015
`
`(54) NFC DEVICE WITH PLL CONTROLLED
`ACTIVE LOAD MODULATION
`
`(75)
`
`Inventor: Alastair Lefley, Kemble (GB)
`
`(73) Assignee: Broadcom Corporation, Irvine, CA
`(US)
`
`( *) Notice:
`
`Subject to any disclaimer, the term ofthis
`patent is extended or adjusted under 35
`U.S.C. 154(b) by 238 days.
`
`FOREIGN PATENT DOCUMENTS
`
`WO WO 2009/063214 Al
`
`5/2009
`
`OTHER PUBLICATIONS
`
`European Search Report directed to related European Patent Appli(cid:173)
`cation No. EP2013/0003064, mailed on Oct. 10, 2014; 3 pages.
`European Search Report directed to related European Patent Appli(cid:173)
`cation No. EP2013/0003064, mailed on Oct. 30, 2014; 15 pages.
`
`* cited by examiner
`
`Primary Examiner - Sonny Trinh
`(74) Attorney, Agent, or Firm - Sterne, Kessler, Goldstein
`& Fox P.L.L.C.
`
`(57)
`
`ABSTRACT
`
`A wireless communication device for communicating in the
`near-field via active load modulation. The device including an
`antenna configured to receive a magnetic field, a recovery
`device configured to recover a clock from the magnetic field,
`and a multiplexer configured to receive the recovered clock
`and a reference clock, and to output one of the recovered
`clock and the reference clock based on a current operational
`state of the wireless communication device, The wireless
`communication device further including a shunt regulator
`configured to produce the active load modulation by modu(cid:173)
`lating an impedance of the wireless communication device, a
`phase-locked loop (PLL) configured to receive one of the
`recovered clock and the reference clock and to utilize the
`received clock to control the active load modulation, and a
`driver configured to contribute to the active load modulation
`by adjusting an amplitude of a voltage across the antenna.
`
`20 Claims, 6 Drawing Sheets
`
`(21) Appl. No.: 13/535,874
`
`(22) Filed:
`
`Jun.28,2012
`
`(65)
`
`Prior Publication Data
`
`US 2014/0003548 Al
`
`Jan. 2, 2014
`
`(51)
`
`(2006.01)
`
`Int. Cl.
`H04B 7100
`(52) U.S. Cl.
`USPC ...... 455/41.1; 455/180.3; 455/41.2; 340/10.1
`( 58) Field of Classification Search
`CPC .... H04B 5/00; H04B 5/0056; H04M 2250/04
`USPC ........ 455/41.1, 41.2, 180.3; 375/256; 178/43;
`340/10.1
`See application file for complete search history.
`
`(56)
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`
`6,321,067 Bl*
`8,395,485 B2 *
`8,432,070 B2 *
`8,450,877 B2 *
`2009/0040022 Al
`2012/0071089 Al
`
`11/2001 Sugaetal. ................... 455/41.2
`3/2013 Wuidart ....................... 340/10.4
`4/2013 Cook et al. .................... 307/150
`5/2013 Baarman et al. .............. 307/104
`2/2009 Finkenzeller
`3/2012 Charrat et al.
`
`110
`
`NFC
`DEVICE
`
`Petitioner Samsung and Google
`Ex-1009, 0001
`
`

`

`U.S. Patent
`
`Jan. 13,2015
`
`Sheet 1 of 6
`
`US 8,934,836 B2
`
`110
`
`NFC
`DEVICE
`
`I ____ ( __ ) ______________________ _
`
`120
`
`NFC
`DEVICE
`
`1\/'v······1
`(
`.
`/
`!
`121
`I
`
`FIG. 1
`
`Petitioner Samsung and Google
`Ex-1009, 0002
`
`

`

`U.S. Patent
`
`Jan. 13,2015
`
`Sheet 2 of 6
`
`US 8,934,836 B2
`
`,:~
`
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`co
`CV)
`N
`
`Petitioner Samsung and Google
`Ex-1009, 0003
`
`

`

`U.S. Patent
`
`Jan. 13,2015
`
`Sheet 3 of 6
`
`US 8,934,836 B2
`
`00
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`N
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`
`-Q)
`
`e>
`<ti
`N
`
`Petitioner Samsung and Google
`Ex-1009, 0004
`
`

`

`U.S. Patent
`
`Jan.13,2015
`
`Sheet 4 of 6
`
`US 8,934,836 B2
`
`0
`0
`C")
`
`Petitioner Samsung and Google
`Ex-1009, 0005
`
`

`

`U.S. Patent
`
`Jan.13,2015
`
`Sheet 5 of 6
`
`US 8,934,836 B2
`
`.
`~
`-
`el
`LL
`
`'.
`
`I....
`
`..g 0
`·- <D
`.~ ~
`0
`
`Petitioner Samsung and Google
`Ex-1009, 0006
`
`

`

`U.S. Patent
`
`Jan.13,2015
`
`Sheet 6 of 6
`
`US 8,934,836 B2
`
`502
`
`communication device
`
`!°
`
`l···R;~eive a magnetic fi~-,d--;t·;-~ireless L,. __ }
`---------~---------
`l
`-------~
`so4
`l
`t
`k-..,,
`i
`!
`i
`--------·J
`
`C
`
`I
`
`Recover a clock from the
`magnetic field
`.J...
`
`506
`\
`
`Yes
`
`-----<< communication
`
`...
`·'-....
`'-...,
`/_
`/
`/.. Is the
`·-....,_(
`No
`/....- wireless
`"-....
`:,...------------- ·.,
`·'4evice acting a~,,...
`!
`·-.'-...~targe3./,.•·
`
`508
`_)
`
`,...........ln_p....,.ih-tl·:=~~~~fii·~~·-~-P-cl-~P-ct-~-~-a-,
`
`V
`
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`
`'":h~s~;~=~~~~ot~: ]
`
`l -----------·····----·--------..------------------------·--------------'
`..l
`51,2
`..
`\
`/
`"··
`"· (
`/
`/"
`/'
`"-\,
`, /
`./· Is the wireless ·-...._
`No
`communication
`·-......,_
`'"""1 ----<-......,....._, device transmitting /,:>-. --·--------7
`,........... _____ (/_\_ ~ _ ~ /
`I _2 1
`! ...... Adjust at least on~ charact;ristic of t .. ,---)
`
`Place the PLL into a memory I
`Place the PLL into a locked
`~----m_, ....,..ode ______ ___J
`state
`(.___----·----.----~---------·····--------~--
`f
`518
`I
`
`._...
`
`V1arge1(0) using an output of the PLL
`
`j
`........ -... - - -...............
`---------____ [
`j Create a modulated magnetic field
`~--·-/
`i__ _______ based on the adjusted V1arge._1(_0)_..........,
`
`520
`
`lr--c~ntribute to a driv;·-~f·t·h;··;odulated ~~~J2
`
`l
`
`524
`
`magnetic field
`~--------,·
`I Transmit the .. modulated magnetic field
`from the wireless communication
`device to a second wireless
`i
`communication device
`t
`} -----------------------~
`FIG. 5
`
`!,
`
`.. /
`
`Yes
`
`516
`
`1·
`
`
`
`·"'1.oad modulation? . ./
`
`11
`
`
`
`514
`
`Petitioner Samsung and Google
`Ex-1009, 0007
`
`

`

`US 8,934,836 B2
`
`1
`NFC DEVICE WITH PLL CONTROLLED
`ACTIVE LOAD MODULATION
`
`FIELD OF THE INVENTION
`
`The disclosure generally relates to near field communica(cid:173)
`tions (NFC), and more specifically to an NFC device for
`performing active load modulation controlled using a phase(cid:173)
`locked loop (PLL).
`
`BACKGROUND
`
`Related Art
`
`2
`inhibit the NFC devices' ability to perform load modulation
`because the second NFC device may only be able to effect a
`small portion of the total energy that was actually transmitted
`by the first NFC device. Thus, the net effective energy recog-
`5 nized back the first NFC device may be relatively small.
`Thus, a need exists for NFC devices that are capable of
`communicating with one another even in the presence of poor
`magnetic coupling.
`
`10
`
`BRIEF DESCRIPTION OF THE
`DRAWINGS/FIGURES
`
`Near field communication (NFC) devices are being inte(cid:173)
`grated into communication devices, such as mo bile devices to
`provide an example, to facilitate the use of these communi(cid:173)
`cation devices in conducting daily transactions. For example,
`instead of carrying numerous credit cards, the credit informa(cid:173)
`tion provided by these credit cards could be stored onto an 20
`NFC device. The NFC device is simply tapped to a credit card
`terminal to relay the credit information to the terminal to
`complete a transaction. As another example, a ticket writing
`system, such as those used in a bus or train terminal, may
`simply write ticket fare information onto the NFC device 25
`instead of providing a ticket to a passenger. The passenger
`simply taps the NFC device to a reader to ride the bus or the
`train without the use of a paper ticket.
`Generally, NFC requires that NFC devices be present
`within a relatively small distance from one another so that
`their corresponding magnetic fields can exchange informa(cid:173)
`tion. Typically, a first NFC device transmits or generates a
`magnetic field modulated with the information, such as the
`credit information or the ticket fare information. This mag(cid:173)
`netic field inductively couples the information onto a second 35
`NFC device that is proximate to the first NFC device, which
`is received by an antenna of the second NFC device. The
`second NFC device may respond to the first NFC device by
`inductively coupling its corresponding information onto an
`antenna of the first NFC device.
`However, in the field of NFC there is an increasing diver(cid:173)
`sity of products, specifically in terms of the effective area of
`antennas. In particular, there is strong demand for solutions
`using ever smaller antennas. Therefore, NFC devices are
`being implemented having increasingly small antennas, 45
`despite a common desire to interoperate with legacy devices,
`which generally have larger antennas, and to pass test speci(cid:173)
`fications defined with these larger antennas.
`The disparity in antenna size generally results in poor
`magnetic coupling between the small and large antennas, 50
`which inhibits the ability to pass energy from one antenna to
`the other. This problem of energy transfer is compounded at
`low magnetic fields when the device with the small antenna is
`attempting to transmit using load modulation.
`Additionally, a voltage associated with a response signal 55
`may vary depending on the distance between the first and
`second NFC devices, which in turns varies the magnetic
`coupling between these NFC devices. A large distance
`between the devices generally causes the received response
`signal to have a small voltage, and thus a poor magnetic 60
`coupling may result between the devices.
`Several problems generally arise when NFC devices expe(cid:173)
`rience poor magnetic coupling. For example, when only a
`small portion of energy transmitted from the first NFC device
`is actually received by the second NFC device, it becomes 65
`difficult for the second NFC device to be able to power itself
`from the magnetic field. Further, poor magnetic coupling may
`
`15
`
`Embodiments of the disclosure are described with refer-
`ence to the accompanying drawings. In the drawings, like
`reference numbers indicate identical or functionally similar
`elements. Additionally, the left most digit(s) of a reference
`number identifies the drawing in which the reference number
`first appears.
`FIG. 1 illustrates a block diagram of an NFC environment
`according to an exemplary embodiment of the disclosure.
`FIG. 2A illustrates a block diagram of an initiator NFC
`device that is implemented as part of the NFC environment
`according to an exemplary embodiment of the disclosure.
`FIG. 2B illustrates a block diagram of a target NFC device
`that is implemented as part of the NFC environment accord(cid:173)
`ing to an exemplary embodiment of the disclosure.
`FIG. 3 illustrates a graphical representation of a modula(cid:173)
`tion vector that is subject to active load modulation according
`30 to an exemplary embodiment of the present disclosure.
`FIG. 4 illustrates a block diagram of a phase-locked loop
`(PLL) that may be implemented as part of the NFC devices
`according to an exemplary embodiment of the present disclo(cid:173)
`sure.
`FIG. 5 is a flowchart of exemplary operational steps of
`performing active load modulation according to an exem(cid:173)
`plary embodiment of the present disclosure.
`Embodiments of the disclosure will now be described with
`reference to the accompanying drawings. In the drawings,
`40 like reference numbers generally indicate identical, function(cid:173)
`ally similar, and/or structurally similar elements. The draw(cid:173)
`ing in which an element first appears is indicated by the
`leftmost digit(s) in the reference number
`
`DETAILED DESCRIPTION
`
`The following Detailed Description refers to accompany(cid:173)
`ing drawings to illustrate exemplary embodiments consistent
`with the disclosure. References in the Detailed Description to
`"one exemplary embodiment," "an exemplary embodiment,"
`"an example exemplary embodiment," etc., indicate that the
`exemplary embodiment described may include a particular
`feature, structure, or characteristic, but every exemplary
`embodiment may not necessarily include the particular fea(cid:173)
`ture, structure, or characteristic. Moreover, such phrases are
`not necessarily referring to the same exemplary embodiment.
`Further, when a particular feature, structure, or characteristic
`is described in connection with an exemplary embodiment, it
`is within the knowledge of those skilled in the relevant art(s)
`to affect such feature, structure, or characteristic in connec(cid:173)
`tion with other exemplary embodiments whether or not
`explicitly described.
`The exemplary embodiments described herein are pro(cid:173)
`vided for illustrative purposes, and are not limiting. Other
`exemplary embodiments are possible, and modifications may
`be made to the exemplary embodiments within the spirit and
`scope of the disclosure. Therefore, the Detailed Description is
`
`Petitioner Samsung and Google
`Ex-1009, 0008
`
`

`

`US 8,934,836 B2
`
`5
`
`3
`not meant to limit the disclosure. Rather, the scope of the
`disclosure is defined only in accordance with the following
`claims and their equivalents.
`Embodiments of the disclosure may be implemented in
`hardware, firmware, software, or any combination thereof.
`Embodiments of the disclosure may also be implemented as
`instructions stored on a machine-readable medium, which
`may be read and executed by one or more processors. A
`machine-readable medium may include any mechanism for
`storing or transmitting information in a form readable by a 10
`machine ( e.g., a computing device). For example, a machine(cid:173)
`readable medium may include read only memory (ROM);
`random access memory (RAM); magnetic disk storage
`media; optical storage media; flash memory devices; electri(cid:173)
`cal, optical, acoustical or other forms of propagated signals 15
`( e.g., carrier waves, infrared signals, digital signals, etc.), and
`others. Further, firmware, software, routines, instructions
`may be described herein as performing certain actions. How(cid:173)
`ever, it should be appreciated that such descriptions are
`merely for convenience and that such actions in fact result 20
`from computing devices, processors, controllers, or other
`devices executing the firmware, software, routines, instruc(cid:173)
`tions, etc.
`The following Detailed Description of the exemplary
`embodiments will so fully reveal the general nature of the 25
`disclosure that others can, by applying knowledge of those
`skilled in relevant art(s), readily modify and/or adapt for
`various applications such exemplary embodiments, without
`undue experimentation, without departing from the spirit and
`scope of the disclosure. Therefore, such adaptations and 30
`modifications are intended to be within the meaning and
`plurality of equivalents of the exemplary embodiments based
`upon the teaching and guidance presented herein. It is to be
`understood that the phraseology or terminology herein is for
`the purpose of description and not oflimitation, such that the 35
`terminology or phraseology of the present specification is to
`be interpreted by those skilled in relevant art(s) in light of the
`teachings herein.
`Although the description of the present disclosure is to be
`described in terms of near field communication (NFC), those 40
`skilled in the relevant art(s) will recognize that the present
`disclosure may be applicable to other communications that
`use the near field and/or the far field without departing from
`the spirit and scope of the present disclosure. For example,
`although the present disclosure is to be described using NFC 45
`capable communication devices, those skilled in the relevant
`art(s) will recognize that functions of these NFC capable
`communication devices may be applicable to other commu(cid:173)
`nications devices that use the near field and/or the far field
`without departing from the spirit and scope of the present
`disclosure.
`An Exemplary Near Field Communications (NFC) Environ(cid:173)
`ment
`FIG. 1 illustrates a block diagram of an NFC environment
`according to an exemplary embodiment of the disclosure. An
`NFC environment 100 provides wireless communication of
`information, such as one or more commands and/or data,
`among a first NFC device 110 and a second NFC device 120
`that are sufficiently proximate to each other. The first NFC
`device 110 and/or the second NFC device 120 may be imple(cid:173)
`mented as a standalone or a discrete device or may be incor(cid:173)
`porated within or coupled to another electrical device or host
`device, such as a mobile telephone, a portable computing
`device, another computing device such as a personal digital
`assistant, a laptop, or a desktop computer, a computer periph(cid:173)
`eral such as a printer, a portable audio and/or video player, a
`payment system, a ticketing writing system such as a parking
`
`4
`ticketing system, a bus ticketing system, a train ticketing
`system or an entrance ticketing system to provide some
`examples, or in a ticket reading system, a toy, a game, a poster,
`packaging, advertising material, a product inventory check-
`ing system and/or any other suitable electronic device that
`will be apparent to those skilled in the relevant art(s) without
`departing from the spirit and scope of the disclosure.
`The first NFC device 110 and the second NFC device 120
`interact with each other to exchange the information, in a
`peer-to-peer (P2P) communication mode or a reader/writer
`(R/W) communication mode. In the P2P communication
`mode, the first NFC device 110 and the second NFC device
`120 may be configured to operate according to an active
`communication mode and/or a passive communication mode.
`The first NFC device 110 modulates its corresponding infor(cid:173)
`mation onto a first carrier wave, referred to as a modulated
`information communication, and generates a first magnetic
`field by applying the modulated information communication
`to the first antenna to provide a first information communi(cid:173)
`cation 111. The first NFC device 110 ceases to generate the
`first magnetic field after transferring its corresponding infor-
`mation to the second NFC device 120 in the active commu(cid:173)
`nication mode. Alternatively, in the passive communication
`mode, the first NFC device 110 continues to apply the first
`carrier wave without its corresponding information, referred
`to as an unmodulated information communication, to con-
`tinue to provide the first information communication 111
`once the information has been transferred to the second NFC
`device 120.
`The first NFC device 110 is sufficiently proximate to the
`second NFC device 120 such that the first information com(cid:173)
`munication 111 is inductively coupled onto a second antenna
`of the second NFC device 120. The second NFC device 120
`demodulates the first information communication 111 to
`recover the information. The second NFC device 120 may
`respond to the information by modulating its corresponding
`information onto a second carrier wave and generating a
`second magnetic field by applying this modulated informa(cid:173)
`tion communication to the second antenna to provide a sec-
`ond information communication 121 in the active communi(cid:173)
`cation mode. Alternatively, the second NFC device 120 may
`respond to the information by modulating the second antenna
`with its corresponding information to modulate the first car(cid:173)
`rier wave to provide the second information communication
`121 in the passive communication mode.
`In the R/W communication mode, the first NFC device 110
`is configured to operate in an initiator, or reader, mode of
`operation and the second NFC device 120 is configured to
`operate in a target, or tag, mode of operation. However, this
`50 example is not limiting. Those skilled in the relevant art(s)
`will recognize that the first NFC device 110 may be config(cid:173)
`ured to operate in the tag mode and the second NFC device
`120 may be configured to operate in the reader mode in
`accordance with the teachings herein without departing from
`55 the spirit and scope of the present disclosure. The first NFC
`device 110 modulates its corresponding information onto the
`first carrier wave and generates the first magnetic field by
`applying the modulated information communication to the
`first antenna to provide the first information communication
`60 111. The first NFC device 110 continues to apply the first
`carrier wave without its corresponding information to con(cid:173)
`tinue to provide the first information communication 111
`once the information has been transferred to the second NFC
`device 120. The first NFC device 110 is sufficiently proximate
`65 to the second NFC device 120 such that the first information
`communication 111 is inductively coupled onto a second
`antenna of the second NFC device 120.
`
`Petitioner Samsung and Google
`Ex-1009, 0009
`
`

`

`US 8,934,836 B2
`
`5
`The second NFC device 120 derives or harvests power
`from the first information communication 111 to recover
`and/or process the received information, and/or to provide a
`response to the information. The second NFC device 120
`demodulates the first information communication 111 to 5
`recover and/or to process the information. The second NFC
`device 120 may respond to the information by modulating the
`second antenna with its corresponding information to modu(cid:173)
`late the first carrier wave to provide the second information
`communication 121.
`Further operations of the first NFC device 110 and/or the
`second NFC device 120 may be described in International
`Standard ISO/IE 18092:2004(E), "Information Technol(cid:173)
`ogy-Telecommunications and
`Information Exchange
`Between Systems-Near Field Communication-Interface
`and Protocol (NFCIP-1 )," published on Apr. 1, 2004 and
`International Standard ISO/IE 21481:2005(E), "Information
`Technology-Telecommunications
`and
`Information
`Exchange Between Systems-Near Field Communication(cid:173)
`Interface and Protocol-2 (NFCIP-2)," published on Jan. 15,
`2005, each of which is incorporated by reference herein in its
`entirety.
`An Exemplary Initiator NFC Device and Target NFC Device
`FIG. 2A illustrates a block diagram of an Initiator NFC
`device 200 that is implemented as part of the NFC environ(cid:173)
`ment 100 according to an exemplary embodiment of the
`disclosure. FIG. 2B illustrates a block diagram of a Target
`NFC device 220 that is implemented as part of the NFC
`environment 100 according to an exemplary embodiment of
`the disclosure. Initiator NFC device 200 and Target NFC
`device 220 may represent exemplary embodiments of first
`NFC device 110 and second NFC device 120, respectively.
`Initiator NFC device 200, shown in FIG. 2A, and Target
`NFC device 220, shown in FIG. 2B, may be NFC peers. NFC
`is an asymmetric interface, which means that one of the NFC
`devices will always be tasked with creating a magnetic field
`234, and the other NFC device will always be configured to
`receive magnetic field 234. However, when the NFC devices
`are manufactured, it is undefined as to which NFC device will
`perform which function. Therefore, Initiator NFC device 200 40
`and Target NFC device 220 may each have dual functionality
`(e.g. the ability to function both as an initiator NFC and a
`target NFC). In FIG. 2A, Initiator NFC device 200 is func(cid:173)
`tioning as an initiator, and thus Initiator NFC device 200's
`target circuitry (load modulator resistor 210, shunt regulator
`212 and recovery device 214) is inactive and is thus shown
`having dashed lines. Similarly, in FIG. 2B, Target NFC device
`220 is functioning as a target, and thus Target NFC device
`220's initiator circuitry (demodulator 228) is assumed to be
`high impedance and is thus shown having dashed lines as
`well.
`As discussed above, several factors can potentially lead to
`a poor magnetic coupling between Initiator NFC device 200
`and Target NFC device 220 ( e.g. a disparity in a size of each
`NFC devices' antenna and/or a relatively large distance
`between the antennas), which may inhibit the ability to pass
`energy between Initiator NFC device 200 and Target NFC
`device 220. This problem of energy transfer may be most
`severe at low magnetic fields when one of the NFC devices is
`attempting to transmit using load modulation ( e.g. Target 60
`NFC device 220 is attempting to vary the energy being trans(cid:173)
`mitted), as discussed below.
`To produce a coupling between Initiator NFC device 200
`and Target NFC device 220, Initiator NFC device 200 (or
`Target NFC device 220) passes an alternating current through 65
`an antenna 216 (or an antenna 240). This results in an alter(cid:173)
`nating magnetic field 234 (or magnetic field 234'). When
`
`6
`Target NFC device 220 (or Initiator NFC 200) is placed
`within the alternating magnetic field 234 ( or magnetic field
`234'), an alternating voltage will appear across antenna 240
`(or antenna 216). This voltage may then be rectified and
`coupled to shunt regulator 242 ( or shunt regulator 212) such
`that a reservoir of charge accumulates, which Target NFC
`device 220 (or Initiator NFC device 200) can then use to
`perform load modulation. In particular, load modulation is
`achieved by modulating the impedance of Target NFC device
`10 220 ( or Initiator NFC device 200) as seen by the Initiator NFC
`device 200 (or Target NFC device 220). In some embodi(cid:173)
`ments, load modulation may be performed by allowing shunt
`regulator 242 (or shunt regulator 212) to actively modulate
`15 the impedance of Target NFC device 220 ( or Initiator NFC
`device 200).
`In an embodiment, successful communication between the
`NFC devices is achieved via load modulation, as Target. NFC
`device 220 ( or Initiator NFC device 200) may send data back
`20 to the Initiator NFC device 200 ( or the Target NFC device
`220) using a desired load modulation technique. Communi(cid:173)
`cation between the NFC devices via load modulation may be
`achieved because current that may be drawn from antenna
`240 ( or antenna 216) will give rise to its own relatively small
`25 magnetic field, which will oppose the Initiator NFC device
`200's (or Target NFC device 220's) field. Antenna 216 (or an
`antenna 240) may detect this small change in the magnetic
`field as a relatively small increase or decrease in the current
`flowing through antenna 216 (or an antenna 240), which is
`30 detected by the demodulator circuits 206 ( or demodulator
`circuit 228). This current will then be proportional to the load
`applied to the antenna 240 ( or antenna 216). In embodiments,
`initiator NFC device 200 and Target NFC device 220 are each
`configured to communicate using load modulation, even in
`35 the presence of a poor magnetic field.
`Initiator NFC device 200's initiator circuitry includes a
`phase-locked loop (PLL) 202, a digital-to-analog converter
`(DAC) 204, a demodulator 206, a driver 208 and an antenna
`216 (e.g. an inductor).
`PLL 202 is configured to receive a reference clock 218, and
`to output a signal to DAC 204. In some embodiments, PLL
`202 may be implemented as an electronic circuit, consisting
`of a variable frequency oscillator and a phase detector, among
`other functionality. PLL 202 will be discussed in greater
`45 detail below, with reference to FIG. 4.
`DAC 204 is configured to perform digital-to-analog con(cid:173)
`versions of initiator transmission signal 236 and the signal
`received from PLL 202, such that the resulting analog signal
`may be filtered and driven using driver 208. In some embodi-
`50 ments, initiator transmission signal 236 may represent a sinu(cid:173)
`soidal or square wave in the form digital bits, and the analog
`signal output from DAC 204 may be a modulated sinusoidal
`wave represented in the analog domain. Thus, driver 208 may
`be a modulated sinusoidal driver, and/or variable gain ampli-
`55 fier.
`During the reception of load modulation at Initiator NFC
`device 200, Initiator NFC device 200 is configured to drive
`antenna 216 to create magnetic field 234. In particular, Ini(cid:173)
`tiator NFC device 200 may synthesize the sine wave using
`PLL 202 and DAC 204, prior to the sine wave being fed into
`driver 208. Driver 208 may then filter and drive the sine wave
`on antenna 216.
`After the sine wave is output from driver 208, the sine wave
`may then represent an initiator voltage (V,nitiatorC cp )). The sine
`wave then travels through a matching interface before reach(cid:173)
`ing antenna 216, where the sine wave appears as a voltage
`(V,n,tiatorC<P)) across antenna 216's pins. Therefore, the sine
`
`Petitioner Samsung and Google
`Ex-1009, 0010
`
`

`

`US 8,934,836 B2
`
`7
`wave is configured to create a current flow through antenna
`216, which will then translate into magnetic field 234.
`As discussed above, load modulation may be achieved by
`modulating an impedance of Target NFC device 220 (Zrarge,))
`as seen by Initiator NFC device 200, and that load modulation 5
`may be performed by allowing shunt regulator 242 to actively
`modulate Zrarger Thus, when the NFC devices communicate
`using load modulation, demodulator 206 may be configured
`to demodulate changes in the current through antenna 216,
`which may be caused by shunt regulator 242's active modu- 10
`lationofZrarger Demodulator206 is also configured to output
`an initiator receipt signal 238 form Initiator NFC device 200,
`which represents the impedance changes caused by Target
`NFC device 220.
`Following the transmission of magnetic field 234 from
`antenna 216, magnetic field 234 may be received at an
`antenna 240 located on Target NFC device 220. This received
`magnetic field 234 may then induce a corresponding voltage
`across antenna 240. This voltage then travels through another
`matching interface before being processed by Target NFC
`device 220's target circuitry. The transmission of magnetic
`field 234 from Initiator NFC device 200 and the reception of
`magnetic field 234 by Target NFC device 220 may form a
`transformer. For example, depending on the amount of cou(cid:173)
`pling, Initiator NFC device 200 and Target NFC device 220
`may form a transformer having varying degrees of coupling
`there between.
`Similar to Initiator NFC device 200, Target NFC device
`220's target circuitry includes a phase-locked loop (PLL)
`222, a digital-to-analog converter (DAC) 226, a driver 232 30
`and an antenna 240. Target NFC device 220's target circuitry
`also includes a recovery device 224, a shunt regulator 242 and
`a multiplexer (MUX) 230. PLL 222, DAC 226 and driver 232
`may be configured to function substantially similar to PLL
`202, DAC 204 and driver 208, respectively. For example,
`DAC 226 is configured to perform digital-to-analog conver(cid:173)
`sions of initiator/target transmission signal 244 as well as a
`signal output from PLL 222, such that the resulting analog
`signal may be filtered and driven using driver 232. In some
`embodiments, initiator/target transmission signal 244 may
`represent a sinusoidal or square wave in the form digital bits,
`and the analog signal output from DAC 226 may be a modu(cid:173)
`lated sinusoidal wave represented in the analog domain.
`Thus, driver 232 may be a modulated sinusoidal driver, and/or
`variable gain amplifier. The functionality of PLL 222 will also
`be discussed in greater detail below, with reference to FIG. 4.
`In some embodiments, implementing driver 232 within
`Target NFC device 220 may allow some conventional func(cid:173)
`tionality to be omitted from Target NFC device 220. For
`example, by reusing driver 232 to aid in the modulation and
`demodulation of magnetic field 234, Target NFC device 220
`may be implemented without a variable resistor, load modu(cid:173)
`lation resistor, or other load-modulator device. Additionally,
`driver 232 may also function as an amplifier, and may be
`configured to actively drive energy towards magnetic field
`234.
`As discussed above, shunt regulator 242 may be configured
`to actively modulate Zrarget such that load modulation may be
`performed. Additionally, shunt regulator 242 may be config(cid:173)
`ured to maintain a safe voltage level within Target NFC
`device 220. For example, shunt regulator 242 may be config(cid:173)
`ured to vary its resistance in accordance with a load associ(cid:173)
`ated with Target NFC device 220, which may allow Target
`NFC device 220 to derive a voltage (V,arge,(8)). In some
`embodiments, when performing passive load modulation
`using shunt regulator 242, V targe,( 8) may be transformed from
`V,n,tiator(<P), and thus V,arge,(8) will be derived. This result
`
`8
`may be different when using active load modulation, as V,arget
`(8) is being output (not derived) when using active load
`modulat