(12) United States Patent
`US 7,627,289 B2
`(0) Patent No.:
`Dec. 1, 2009
`(45) Date of Patent:
`Huddart
`
`US007627289B2
`
`(54)
`
`(75)
`
`WIRELESS STEREO HEADSET
`
`Inventor: David Huddart, Westbury-on-Trym
`(GB)
`
`(73)
`
`Assignee: Plantronics, Inc., Santa Cruz, CA (US)
`
`(*)
`
`Notice:
`
`Subject to any disclaimer, the term ofthis
`patent is extended or adjusted under 35
`U.S.C. 154(b) by 517 days.
`
`(21)
`
`Appl. No.: 11/317,984
`
`(22)
`
`Filed:
`
`Dec. 23, 2005
`
`(65)
`
`(51)
`
`(52)
`
`Prior Publication Data
`
`US 2007/0149261 Al
`
`Jun. 28, 2007
`
`Int. Cl.
`
`(2006.01)
`HO4B 7/00
`US. Ch. oe 455/41.2; 455/575.2; 455/343.1;
`455/413
`
`(58)
`
`7,089,434
`7,103,344
`7,215,924
`7,333,838
`2002/0132585
`2003/0073460
`2004/02 14614
`2005/0037823
`2005/0164636
`2006/00 13432
`2006/0251277
`2007/0004464
`2007/0037615
`
`B2*
`B2*
`B2*
`B2*
`Al*
`Al
`Al*
`Al*
`Al*
`Al*
`Al
`Al*
`Al*
`
`8/2006 Kuo weceeccccccccceececeeeenee 713/300
`9/2006 Menard .........
`. 455/343.2
`
`............ 455/41.1
`5/2007 Palermo etal.
`2/2008 Pattabiraman etal.
`...... 455/574
`9/2002 Palermo et al. oo... 455/41
`4/2003 Van Pelt etal.
`10/2004 Aman.
`......... eee 455/569.1
`........... 455/575.6
`2/2005 Seshadri etal.
`
`............ 455/41.2
`7/2005 Palermoet al.
`1/2006 Husung ou... eee 381/396
`11/2006 Cho
`1/2007 Lairetal. oe 455/569.1
`2/2007 Glezerman ............... 455/575.2
`
`FOREIGN PATENT DOCUMENTS
`
`EP
`EP
`WO
`WO
`
`1185138 A
`1715718 A
`WO09852295 A
`WO2005099301 A
`
`3/2002
`10/2006
`11/1998
`10/2005
`
`* cited by examiner
`
`Primary Examiner—Lana N Le
`(74) Attorney, Agent, or Firm—Intellectual Property Law
`Office of Thomas Chuang
`
`(57)
`
`ABSTRACT
`
`Field of Classification Search.............. 455/575.2,
`455/343.1-343.6, 41.1-41.3; 381/380, 376,
`381/367; 379/428.02
`See application file for complete search history.
`Systems and methods for a wireless stereo headset are dis-
`References Cited
`(56)
`closed. The system generally includesafirst headset compo-
`U.S. PATENT DOCUMENTS
`nent and a second headset component. Both the first headset
`componentand the second headset component may be wire-
`less devices.
`
`2/1992 Groppe ..... eee 381/380
`5,086,464 A *
`
`........ 455/41.1
`6,134,420 A * 10/2000 Flowerdew etal.
`6,320,959 B1* 11/2001 Crouch etal. oe. 379/430
`6,381,308 BL*
`4/2002 Cargo etal. 0.0.0... 379/428.02
`
`200
`
`Wireless Earbud 6
`
`Headset 4
`
`16
`
`ees)
`MI
`Receiver
`
`Mi
`Transmitter
`
`BT
`
`Transceiver
`
`20 Claims, 8 Drawing Sheets
`
`BT Cell Phone 100
`
`BT
`Transceiver
`
`\108
`
`Digital Music Player 106
`
`BT
`Transceiver
`
`104
`
`110
`
`116
`
`Landline Telephone Base
`
`
`112
`Landline
`
`
`Telephone
` BT
`
`
`118
`Transceiver
`
`
`114
`
`APPLE 1024
`
`APPLE 1024
`
`1
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`

`

`U.S. Patent
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`Dec. 1, 2009
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`Sheet 1 of 8
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`U.S. Patent
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`Dec. 1, 2009
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`U.S. Patent
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`Dec. 1, 2009
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`Sheet 3 of 8
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`US 7,627,289 B2
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`

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`U.S. Patent
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`Dec. 1, 2009
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`Sheet 4 of 8
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`US 7,627,289 B2
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`50
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`Receive Aerial
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`Dec. 1, 2009
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`Sheet 5 of 8
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`U.S. Patent
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`US 7,627,289 B2
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`Wake-up Signal
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`FIG. 5
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`U.S. Patent
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`Dec. 1, 2009
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`US 7,627,289 B2
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`Sheet 6 of 8
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`FIG. 6
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`U.S. Patent
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`Dec. 1, 2009
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`U.S. Patent
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`Dec. 1, 2009
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`Sheet 8 of 8
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`US 7,627,289 B2
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`FIG. 8
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`9
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`

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`US 7,627,289 B2
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`1
`WIRELESS STEREO HEADSET
`
`BACKGROUND OF THE INVENTION
`
`Conventional wireless communication headsets are mon-
`
`aural. As a result, many headsets utilize an “over the ear”
`configuration not requiring the use of a headband. However,
`there are certain usage scenarios in which the user of a wire-
`less communication headset may wish to listen to a stereo
`signal using both ears. Such usage scenarios are expected to
`increase withthe availability of a variety ofelectronic devices
`and multi-function devices. Such devices include cellular
`
`10
`
`2
`Descriptions of specific embodiments and applications are
`provided only as examples and various modifications will be
`readily apparentto those skilled in the art. The general prin-
`ciples defined herein may be applied to other embodiments
`and applications without departing from the spirit and scope
`ofthe invention. Thus, the present invention is to be accorded
`the widest scope encompassing numerousalternatives, modi-
`fications and equivalents consistent with the principles and
`features disclosed herein. For purposeofclarity, details relat-
`ing to technical material that is known in the technicalfields
`related to the invention have not been described in detail so as
`not to unnecessarily obscure the present invention.
`Generally, this description describes a method and appara-
`tus for a wireless stereo headset system having a headset
`component and a wireless earbud component.
`In one
`example, the wireless headset system has a stereo modeuti-
`lizing a wireless earbud to output one channel of a stereo
`signal. The invention may be utilized in conjunction with a
`variety of electronic devices, including cell phones, PDAs,
`and MP3 or other digital format players. While the present
`invention is not necessarily limited to such devices, various
`aspects ofthe invention may be appreciated through a discus-
`sion of various examples using this context.
`According to an example ofthe present invention, a wire-
`less headset includes a magnetic induction (MI) transmitter
`such that a wireless link may be formed with a wireless
`earbud containing a magnetic induction receiver. One chan-
`nel of a stereo signal is transmitted from the headset to the
`earbud over the wireless link to enable a userto listen to the
`stereo signal. In one example modeofoperation, the wireless
`headset is Bluetooth enabled and communicates with a Blue-
`
`munication transceiver 10. In a further example, headset 4
`and electronic device 2 may communicate via a wired link.
`Althoughonly one electronic device 2 is illustrated, headset 4
`may communicate with and switch between multiple elec-
`tronic devices. Electronic device 2, for example, may be any
`electronic device capable oftransmitting data such as voice or
`text data to headset 4. Examples of electronic device 2
`include, but are not limited to cellular telephones, digital
`
`telephones, digital music players, personaldigital assistants,
`and devices combining one or more of these devices into a
`single integrated device.
`Conventional prior art stereo headsets use a headband to
`support the two speakers outputting the stereo channels. A
`headband solution implements stereo operation by using the
`headbandto carry theelectrical signals from one side of the
`head to the other with an electrical wire. Another prior art
`solution utilizes wires to conduct the electrical signals with-
`out the headband. For example, a wired earbud may extend
`from a wireless monaural headset.
`However, the use of a headbandorwiresis not desired in a
`variety of situations. For example, users may have a personal
`preference against wearing a headband. The user may not
`wish to have any wires attached to any part of the headset or
`worn about the body. In certain situations, the user will wish
`to have a headset capable of stereo operation. However, the
`user also wishes to have the option of wearing only a mon-
`aural earpiece during monaural operation such as during a
`tooth enabled cellular telephone. The headset can be used in
`telephonecall. The user is then required to use two different
`a monaural mode and switched seamlessly between monaural
`headsets—a monauralheadsetfor telephone operation and a
`and stereo operational modes. For example, Bluetooth Mul-
`wireless stereo headset for stereo listening applications.
`tipoint mode maybe used.
`As a result, there is a need for improved methods and
`According to an example of the invention, a stereo headset
`apparatuses for stereo headsets.
`system includes a first wireless component havingafirst
`BRIEF DESCRIPTION OF THE DRAWINGS
`speaker, a microphone,a first wireless communication mod-
`ule, and a second wireless communication module. Theste-
`reo headset system includes a second wireless component
`having a second speakerand a third wireless communication
`module for receiving an audio signal from the second wireless
`communication module during stereo mode operation.
`According an example of the invention, a headset system
`includesan electronic device capable of outputting a monau-
`ral or a stereo audio signal, a first headset component for
`receiving the monaural or the stereo signal from the electronic
`device, and a second headset componentcapable of wireless
`communications with the first headset component. The sec-
`ond headset componentreceives the stereo signal or a com-
`ponentofthe stereo signal from thefirst headset component.
`FIG.1 illustrates a system view of a wireless stereo headset
`system in use in one exampleof the invention. A headset4 is
`in proximity to an electronic device 2. In one example of the
`invention, both headset 4 and electronic device 2 have wire-
`less communication functionality to implement wireless
`communications there between over a wireless communica-
`tion link 12. Electronic device 2 includes a wireless commu-
`nication transceiver 8 and headset 4 includes a wireless com-
`
`15
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`20
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`25
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`30
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`40
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`55
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`60
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`The present invention will be readily understood by the
`following detailed description in conjunction with the accom-
`panying drawings, wherein like reference numerals designate
`like structural elements.
`FIG.1 illustrates a system view ofa wireless stereo headset
`system in one example of the invention.
`FIG.2 illustrates a simplified block diagram of a headset
`and wireless earbud in one example of the invention.
`FIG.3 illustrates a magnetic induction transmitter in a
`headset and a magnetic induction receiver in a wireless ear-
`bud.
`FIG.4 illustrates simplified block diagram of a receive
`circuit in an earbud in one exampleof the invention.
`FIG.5 illustrates a simplified receiver circuit filter in one
`example of the invention.
`FIG.6 illustrates a wireless stereo headset system worn by
`a user in one example of the invention.
`FIG.7 illustrates a system view ofa further example of a
`wireless stereo headset system in one example of the inven-
`tion.
`
`FIG. 8 illustrates coupling between a magnetic induction
`transmitter and a magnetic induction receiver.
`
`DESCRIPTION OF SPECIFIC EMBODIMENTS
`
`Methods and apparatuses for wireless stereo headsets are
`disclosed. The following description is presented to enable
`any person skilled in the art to make and use the invention.
`
`65
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`US 7,627,289 B2
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`3
`music players, personal digital assistants, or combinations
`thereof. A particular electronic device 2 may output only a
`monauralsignal or only a stereo signal. In a further example,
`a particular electronic device 2 may output both a monaural
`signal anda stereo signal, dependent uponthe device mode of
`operation.
`Whenstereo listening operation is desired by a user, a
`wireless earbud6 is used in conjunction with headset 4. Both
`headset4 and wireless earbud 6 have wireless communication
`
`functionality to form a wireless communication link 18. In
`one example of the invention, wireless communication link
`18 is implemented using magnetic induction. Headset 4
`includes a magnetic induction transmitter 14 and wireless
`earbud 6 includes a magnetic induction receiver 16. Although
`reference is made to a wireless earbud herein, any wireless
`device capable of receiving and outputting an audio signal
`into a user’s ear may be utilized including, for example,
`over-the-ear or in-the-ear devices.
`In one example of the invention, a magnetic induction
`wireless communication link is established between headset
`4 and wireless earbud 6. Magnetic induction provides short
`range wireless communication at low power and cost while
`providing good audio signal quality. Magnetic induction
`allows the use of very simple analogue RF technologies to
`generate and receive signals. In one example, analogue FM
`modulation with carrier frequenciesin the range 1-15 MHzis
`used. In further examples of the invention, AM modulation
`maybe used, as well as various formsof digital modulation.
`The use of magnetic induction is particularly advanta-
`geous. The magnetic field strength drops as a 4” power of
`distance, resulting in a limited range. Interference between
`two or more users will be limited by the 4” power field
`strength characteristic hence a single operating carrier chan-
`nel will suffice. Use of FM modulation also helps due to the
`capture effect. Magnetic induction communication systems
`are discussed, for example, in U.S. Pat. No. 6,134,420 entitled
`“Vector Measuring Aerial Arrays for Magnetic Induction
`Communication Systems” and U.S. Pat. No. 6,061,030
`entitled “Aerial Arrays for Magnetic Induction Communica-
`tion Systems Having Limited Power Supplies”, which are
`assignedto the present applicant Plantronics, Inc. and hereby
`incorporated by referencefor all purposes.
`The range of transmission required between the magnetic
`induction transmitter and magnetic induction receiver is
`small and is approximately between 200 and 300 mm depend-
`ing on the size of the user. Due to the short range required in
`this application, low power operation is possible. In opera-
`tion, wireless earbud 6 may automatically activate when
`broughtin range of headset 4.
`Magnetic induction generally requires the transmit and
`receive coils to be aligned, preferably axially. In this applica-
`tion alignmentis automatic since the user’s ears are normally
`axially aligned either side of the head. As a result, when the
`headset 4 and wireless earbud 6 are worn, the transmit and
`receive coils are automatically axially aligned. In further
`examples of the invention, other methods of wireless com-
`munication maybe used to establish wireless communication
`link 18 between headset 4 and wireless earbud 6. For
`example, wireless earbud 6 may be Bluetooth enabled to
`communicate with either headset 4 or electronic device 2.
`FIG.2 illustrates a more detailed view ofthe headset 4 and
`
`wireless earbud 6 shown in FIG. 1. Headset 4 may include a
`headset controller 35 that comprises a processor, memory and
`software to implementfunctionality as described herein. The
`headset controller 35 receives input from the headset user
`interface and manages an audio signal detected by micro-
`phone 34, and manages an audio signal sent to an audio
`
`4
`transducer such as speaker 36. The headset controller 35
`further interacts with wireless communication transceiver 10
`
`(also referredto herein as a wireless communication module)
`to transmit and receive signals between the headset 4 and
`electronic device 2 employing wireless communication trans-
`ceiver 8. Controller 35 further interacts with magnetic induc-
`tion transmitter 14 and stereo decoder 20 to transmit audio
`
`from headset 4 to wireless earbud 6. In a further example, the
`wireless communication transceiver 10 may include a con-
`troller which controls one or more operations ofthe headset 4.
`Although one example is discussed in reference to a head-
`set 4, other mobile communication devices may beutilized
`instead of a headset. In one example of the invention, headset
`4 is an over-the-ear headset. Headset 4 may be boomless, as
`the particular category of headset used may vary. Headset 4
`includes a wireless communication transceiver 10 for com-
`munication with a wireless communication transceiver 8
`located in the electronic device 2.
`Referring again to FIG. 1, the wireless communication
`transceivers 8 and 10 can bein the form ofa digital wireless
`transceiver for bi-directional communication. For example,
`the wireless communication transceivers 8 and 10 can be a
`transceiver used in known wireless networking devices that
`operate underthe standard of Bluetooth.
`Bluetooth is a radio-frequency protocol which allowselec-
`tronic devices to connect to one another over short-range
`radio links. Bluetooth devices operate in the ISM (industrial,
`scientific, medical) band at about 2.4 to 2.5 GHz, and have a
`range limited to about 10 meters. Spread spectrum frequency
`hoppinglimits interference from other devices using the ISM
`bandwidth. The Bluetooth specification, version 2.0,
`is
`hereby incorporated by reference.
`A prescribed interface such as Host Control Interface
`(HCI) is defined between each Bluetooth module. Message
`packets associated with the HCI are communicated between
`the Bluetooth modules. Control commands, result informa-
`tion of the control commands, user data information, and
`other information are also communicated between Bluetooth
`
`modules. In operation, electronic device 2 is activated and
`polls for possible headset devices. Activation and polling may
`be performed in a mannersimilar to the Bluetooth Device
`Discovery Procedure as described in the Bluetooth Specifi-
`cation. A link establishmentprotocolis then initiated between
`headset 4 and electronic device 2. The BT Advanced Audio
`Distribution Profile (A2DP) is used to transmit stereo audio
`from electronic device 2 to headset 4. A2DP utilizes Audio/
`Video Control Transport Protocol (AVCTP) for command
`response messaging, including for example volumecontrol
`and track selection. A2DP utilizes Audio/Video Distribution
`
`Transport Protocol (AVDTP) for transport of audio/video
`streams.
`
`The wireless communication transceivers 8 and 10 may
`also, for example, operate under other wireless communica-
`tion protocols such as DECT or the 802.11a, 802.11b, or
`related standards. Wireless communication transceivers 8 and
`10 may transmit voice, data, or voice and data communica-
`tions. Wireless communication transceivers 8 and 10 may be
`configured with a variety of protocols, including a Bluetooth
`hands-free protocol. Other protocols include, for example,
`service discovery application,file transfer protocol, and gen-
`eral access profile.
`Headset 4 also includes typical components found in a
`communication headset. For example, headset 4 includes a
`speaker 36, a microphone 34, a user interface, and status
`indicator. The user interface may include a multifunction
`power, volume, stereo/monaural, mute, and select button or
`buttons. Otheruser interfaces may be includedon the headset,
`
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`US 7,627,289 B2
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`5
`such as a link active/endinterface. It will be appreciated that
`numerous other configurations exist for the user interface.
`The particular button or buttons andtheir locations are not
`critical to the present invention.
`The headset 4 includes a boom with the microphone 34
`installed at the lower end of the boom. The headset 4 may
`include a loop attachment to be worn over the user’s ear.
`Alternatively, the main housing of the headset may be in the
`shape of a loop to be worn behinda user’s ear. The headset 4
`further includes a power source such as a rechargeable battery
`installed within the housing to provide powerto the various
`components of the receiver. User speech detected by micro-
`phone 34 is transmitted from the headset 4 to electronic
`device 2 with wireless communication transceiver 10.
`
`6
`A practical implementation within a headset and wireless
`earbud are also influenced by the headset and earbud geom-
`etry.
`Transmit and receive aerials utilize air-cored coils in one
`example of the invention. These air-cored coils may be pan-
`cake shaped. Transmit and receive aerials will operate at
`13.56 MHz, although frequency ranges between 1 MHz and
`20 MHz may be employed. 13.56 MHzis an internationally
`approved ISM bandfor use with plasma cutting equipment
`and wireless MIlinked identification tags. The air-cored coils
`may be formed of conductive wire, self-adhesive foil, or
`tracks on a printed circuit board. The shape of the aerial may
`be altered to conform to the physical shape of the package.
`The loop may be formedat the timeofinstallation.
`Referring to FIG. 3, there is shown a front view of one
`embodimentof a horizontal field configuration of aerials in
`accordance with the present invention. The configuration
`includesan air core loop aerial 40 in a headset 44 and an air
`core loop aerial 38 in an earbud 42. The loop aerial 40 and
`loop aerial 38 are axially aligned along an axis 45 to provide
`maximum coupling betweenthe aerials. Due to the alignment
`ofa user’s ears, axial alignmentof the loop aerial 40 and loop
`aerial 38 is easily achieved to provide maximum coupling
`when the headset and earbud are worn. Theaxially aligned
`loop aerial 40 and loop aerial 38 maybe rotated about axis 45
`without affecting coupling, allowing for flexible wearing of
`the earbud and headset. In a further example, loop aerial 40
`and loop aerial 38 may be rotated by ninety degrees (i.e.,
`radially aligned) ortilted to direct the magnetic fields, and
`sufficient coupling will exist. Referring to FIG. 8, the loop
`In the magnetic induction transmitter 14, the audio pream-
`aerial 40 generates magnetic flux lines defined by a magnetic
`plifier 19 outputs an amplified audio signal to the AGC/
`flux vector 130 (“H”) that extends through the center of the
`Limiting pre-emphasis function 21, which performs fre-
`loop aerial 40. As shown in FIG.8, the magnetic flux lines
`quency and amplitude shaping of the audio signal. In one
`generated by the loop aerial 40 close on themselves and link
`example, oscillator 22 is a voltage controlled oscillator. The
`with loop aerial 38 to induce a signal in loop aerial 38.
`transmit aerial 26 is typically a small MIaerial having a ferrite
`Referring to FIG.4, there is shown a block diagram illus-
`core to achieve transmission efficiency. Alternatively, an air
`trating a receive circuit 50 for a magnetic induction receiver in
`core may be used depending upon the operating frequency
`accordance with one example. The receivecircuit 50 includes
`and desired form factor. The magnetic field generated by
`a receive aerial 52, filter 54, pre-amplifier 56, filter 58, limit-
`transmit aerial 26 provides a carrier that can be modulated by
`ing amplifier 60, FM demodulator 62, amplifier 64, and con-
`an information signal from, for example, a stereo decoder 20.
`troller 66. Filter 54 removes unwanted interfering signals
`Stereo decoder 20 decodes a stereo signal received on
`detected by the receive aerial 52, including WiFi signals or
`wireless communication transceiver 10 into a left audio chan-
`radio signals. For example,filter 54 may be a capacitor across
`nel andaright audio channel. Either the left audio channel or
`the output of the receive aerial 52. The pre-amplifier 56 is a
`45
`right audio channelis sent to the magnetic induction receiver
`conventional preamplifier.
`16 using magnetic induction transmitter 14. The received
`One advantage of the inventionis that the wireless earbud
`signal is then output by speaker 32 at earbud 6. Theleft or
`6 does not require an on or off user interface to activate or
`right audio channel not transmitted is output at the headset 4
`deactivate the wireless earbud.Ifwireless earbud 6 is brought
`by speaker 36. In one configuration, the user may select
`within close range to the magnetic induction transmitter, a
`whether the earbud receives the left or right channel and
`voltage inducedin the receive aerial 52 generates an activate/
`whether the headset receives the left or right channel,
`wake up signal whichis passed to controller 66. To powerthe
`enabling the user to decide which ear has the monosignal and
`earbud up, it would only be necessary to touch the earbud to
`microphone boom.In a further example of the invention, a
`the headset or bring the earbud within range of less than
`stereo decoder may be located at the wireless earbud 6 for
`approximately 3 inches. As the magnetic field strength is so
`decoding a stereo signal received at wireless earbud 6.
`dependent on separation distance, very small separation dis-
`An information signal modulated on a MIcarrierandtrans-
`tances result in very high coupling. The receive signal at very
`small distances would be sufficient to turn onasilicon diode
`mitted by a distant unit is receivedvia a receive aerial forming
`part of the magnetic induction receiver 16. A voltage is
`inducedin the receive aerial when it experiences a changing
`flux. The change maybe producedby varying the magnitude
`or the direction of the incidentfield. Alternating the magni-
`tude of a flux in a sinusoidal manner induces a sinusoidal
`voltage in the receive aerial. The receive aerial may also have
`a ferrite core to achieve efficient reception of the information
`signal. After the signal is received by the receive aerial it is
`further processed by the magnetic induction receiver prior to
`output by speaker 32.
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`Headset 4 and wireless earbud 6 include internal compo-
`nents which are described below in reference to FIGS. 2-5.
`
`Referring again to FIG.2, there is shown a block diagram of
`a MI communication system that uses magnetic induction
`fields as a communication link. The MI communication sys-
`tem includes magnetic induction transmitter 14 in a headset 4
`and a magnetic induction receiver 16 in a wireless earbud 6.
`The magnetic induction transmitter 14 includes an audio
`preamplifier 19, AGC/Limiting pre-emphasis function 21,
`oscillator 22, amplifier 24, and transmit aerial 26. Wireless
`earbud 6 includes a magnetic induction receiver 16 and
`speaker 32. Wireless earbud 6 also includes a power source
`such as a rechargeable battery and a controller comprising a
`processor, memory and software to implementfunctionality
`as described herein.
`
`rectifier or a bipolar junctiontransistor (>0.7V) and so power
`up the earbud from a zero powerstate. The voltage generated
`may be in the magnitudeof volts. Controller 66 then activates
`the wireless earbud 6. In one example, the activate current is
`passed througha diodein filter 54. Once powered,the carrier
`strength is monitored and onceit falls below a predetermined
`threshold for a pre determinedperiod, the earbud powers off
`again.
`Another advantage of the invention is that the wireless
`earbud 6 may powerdownorgo into “sleep mode” automati-
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`US 7,627,289 B2
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`7
`cally to conserve battery power uponloss of its MI carrier for
`a period of time. The controller 66 receives and monitors a
`receiver signal strength indicator (RSSI) associated with the
`transmission of an audio signal from the headsetto the wire-
`less earbud. Ifthe RSSI drops below a predetermined thresh-
`old level, the controller 66 places the wireless earbud 6 in
`sleep modesorinitiate a timer after which a predetermined
`time expires activate sleep mode. In one example, the RSSI
`signal is output from limiting amplifier 60 to controller 66.
`Referring to FIG.5, there is shown a moredetailed view of
`filter 54 from FIG. 4. A capacitor C1 76 is located across the
`output of a receive aerial 52 creating a tuned circuit and hence
`filtering interference in the receive signal. A diode 78 and
`capacitor C2 80 are in parallel to capacitor C1 76 to rectify
`large receive signals and hence provide a DC signal 82 thatis
`output to controller 66. This signal is used to wake-up the
`controller from a sleep, or low powerstate.
`FIG.6 illustrates a wireless stereo headset worn by a user
`201 in an example of the invention. An over-the-ear headset
`202 is capable of monaural telephone communications or
`stereo listening. As shownin FIG.6, headset 202 is shown in
`a stereo listening mode with a wireless earbud 204 outputting
`one channel of the stereo signal.
`FIG.7 illustrates a system 200 of a further example of the
`present invention. Although FIG.7 illustrates a headset 4 used
`with three possible host electronic devices, fewer or greater
`electronic devices may be used.
`A headset4 is in proximity to a Bluetooth enabled cellular
`telephone 100, digital music player 106, and landline tele-
`phone base 112. Headset 4 includes a Bluetooth transceiver
`10 capable ofcommunication with Bluetooth enabled cellular
`telephone 100, digital music player 106, and landline tele-
`phonebase 112. Landline telephone base 112 is coupled to a
`landline telephone 118. Although system 200 is illustrated
`using Bluetooth between headset 4 and cellular telephone
`100, digital music player 106, and landline telephone base
`112, other wireless communication standards may be used in
`further examples, including IEEE 802.11.
`Bluetooth enabled cellular telephone 100 includes a Blue-
`tooth transceiver 102 for communication with headset 4 over
`
`a wireless communication link 104. Digital music player 106
`includes a Bluetooth transceiver 108 for communication with
`headset 4 over a wireless communication link 110. Landline
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`telephone base 112 includes a Bluetooth transceiver 114 for
`communication with headset 4 over a wireless communica-
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`tion link 116. A headset 4 user may switch between cellular
`telephone 100, digital music player 106, and landline tele-
`phone base 112.
`Whenstereo listening operation is desired by a user, a
`wireless earbud6 is used in conjunction with headset 4. Both
`headset4 and wireless earbud 6 have wireless communication
`functionality to form a wireless communication link 18. In
`one example of the invention, wireless communication link
`18 is implemented using magnetic induction. Headset 4
`includes a magnetic induction transmitter 14 and wireless
`earbud 6 includes a magnetic induction receiver 16.
`The present invention allows for a variety of usage modes.
`The headset may be used as a conventional telecommunica-
`tions headset without the earbud when the user merely wishes
`to receive and make calls on an electronic device such as acell
`phone 100 or landline telephone 118.
`The headset 4 may be used in conjunction with the earbud
`6 for stereo listening from a cellular telephone 100, digital
`music player 106, or other electronic device. In operation, the
`headset may be switched from stereo to monaural mode when
`an incoming call is received on Bluetooth cellular telephone
`100 or landline telephone 118. When switching between
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`modes of operation, the user either removes or inserts the
`wireless earbud. For example, a user listening to music from
`a digital music player 106 will have the music interrupted
`when an incomingcall is received on cellular telephone 100.
`The user may then removethe wireless earbud 6. Switching
`may be implemented automatically by the headset controller
`at headset4 upon signaling by the cellular telephoneor digital
`music player.
`In a further example of the invention, wireless earbud 6
`mayreceive a stereo audio signal or a componentof a stereo
`audio signal from an electronic device 2 rather than from
`headset 4. In such an example, both wireless earbud 6 and
`headset 4 have a wireless communication link (e.g., Blue-
`tooth or IEEE 802.11) with the electronic device. Both the
`headset 4 and wireless earbud 6 output one channel of the
`stereo signal. In one example, the BT A2DPprofile is used to
`implementa proprietary system for time stamping, buffering,
`and synchronizing the audio stream.
`The headset system described herein may have additional
`features. For example, wireless earbud 6 may employ a sleep
`function. If the headset 4 is not within range for a predeter-
`mined time, wireless earbud 6 is powered down. A push
`button user interface powers the wireless earbud6 upor, after
`a prolonged depression, powers down.
`The headset system may further include a charger/carrier,
`such as a pocket charger, including a small plastic storage
`case for storing the headset 4 and wireless earbud 6 for pro-
`tection and charging. The pocket charger includes a battery
`and chargercircuit for charging both the headset battery and
`wireless earbud battery wheninserted into the pocket charger/
`carrier. The use of a pocket charger/carrier provides a conve-
`nient mechanism by which the earbud 6, having a relatively
`smaller capacity battery due to its limited size, may be
`recharged in the absence of a primary charger.
`Ina further example, the charger/carrier utilizes a charging
`coil to provide charging currentto the wireless earbud battery
`84 via receive aerial 52 shown in FIG.4. The earbud advan-
`tageously does not require charging contacts on its small
`exterior surface when charging is performed with inductive
`charging. In this example, the single receive aerial 52 func-
`tions multiply to receive charging powerfor battery 8