Ulllted States Patent [19]
`Fisher et al.
`
`US006140911A
`[11] Patent Number:
`[45] Date of Patent:
`
`6,140,911
`Oct. 31, 2000
`
`[54] POWER TRANSFER APPARATUS FOR
`CONCURRENTLY TRANSMITTING DATA
`AND POWER OVER DATA WIRES
`
`1/1995 Shambroom .......................... .. 128/731
`5,381,804
`5,457,629 10/1995 Miller et al.
`340/82552
`5,477,091 12/1995 Fio?na et a1. ..
`340/310.01
`5,684,826 11/1997 Ratner .......... ..
`340/310.01
`
`
`
`Inventors: David AI Fisher, Menlo Park; Lawrence M. Burns, Mountain View;
`
`
`
`FlShef 618.1. ..................... .. OTHER PUBLICATIONS
`
`Stephen E. Muther, Palo Alto, all of
`Calif
`
`[73] Assignee: 3Com Corporation, Santa Clara, Calif.
`
`[21] Appl. No.: 09/416,067
`[22] Filed:
`Oct 12’ 1999
`
`Related US. Application Data
`
`[63] Continuation of application No. 08/865,016, May 29, 1997,
`Pat‘ NO‘ 5994998‘
`Int. Cl.7 ............................ .. H04B 1/00; G08C 19/00
`[51]
`[52] US. Cl. .............................. .. 340/310.01; 340/310.02;
`340/31008; 340/8572; 375/257; 375/259;
`455/31; 455/33
`[58] Field of Search ....................... .. 340/31001 310.02
`34061008 82572. 455/31 33. 370/487’
`490 41,9 442. 375/257 559? 307/126’
`’
`’
`’
`’
`’ 128 127’
`’
`
`[56]
`
`References Cited
`
`us PATENT DOCUMENTS
`7/1991 Bowling et al. ................. .. 340/31001
`
`5 033 112
`
`.. 340/310.01
`9/1992 Sutterlin et al. .
`5,148,144
`5,368,041 11/1994 Shambroom .......................... .. 128/731
`
`JVC Information Products Company of America, sales bro
`chure and price list for “VIPSLAN—10 Infrared Wireless
`LAN System”, May 1996.
`Clegg, P., “VIPSLAND—10 Streaks Off the Wire”, Lan
`T1me$> 56P- 1995
`Primary Examiner—Donnie L. Crosland
`Attorney, Agent, or Firm—Wilson Sonsini Goodrich &
`Rosati
`
`ABSTRACT
`[57]
`Electrical supply current, sufficient to power a wireless
`access point, is transmitted concurrently with a network data
`signal across a transmission line Apewer and data coupler
`couples the network data signal and the power signal,
`received through a data input and a power input respectively,
`and transmits the Coupled SignaL to a distance of three
`meters or more, over the transmission line to a power and
`data decoupler. The power and data decoupler separates the
`power signal from the network data signal and supplies
`those signals to a power output port and a data output port,
`respectively, for use by a wireless access node. The power
`signal may be modulated at a low frequency relative to the
`frequency of the data signal, and the network data signal has
`‘1 data transmission rate of one megabit/Second or higher
`
`10 Claims, 5 Drawing Sheets
`
`Communications
`Network
`140
`
`Extegtijallrsgwer
`150
`
`CD
`
`L
`
`J
`
`Ta
`‘<7: 3
`Data Cable
`E
`130
`‘3
`Power Cable r
`120 D
`*-—1._'- A
`Power Signal
`105 /
`
`Network Cable
`160
`)
`
`L
`
`——-1--—-_
`Data & Power Signal
`107
`
`Data Signal
`104
`'-'1-
`
`J
`
`Network Device
`‘ ,1?- 100
`Power Signal
`105
`
`Power and Data Coupler
`110
`
`Power and Data Decoupler
`170
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`U.S. Patent
`
`0a. 31, 2000
`
`Sheet 2 of5
`
`6,140,911
`
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`28
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`U.S. Patent
`
`0a. 31, 2000
`
`Sheet 3 of5
`
`6,140,911
`
`Coupler Power
`Input Port
`320
`
`Power Cable
`
`120
`
`Data Signal
`Data Rate >= lMb/s
`
`Data Cable
`130
`Coupler Data
`Port
`a 380
`\V/
`
`I
`
`Power and Data Coupler
`110
`
`A
`\Qoupler Port
`360
`
`Network Cable
`
`160\
`
`Decoupler Port
`/ 365
`
`Decoupler
`Power Outpm
`Port 325
`~>>Power and Data Decoupler
`
`Wireless
`Access Point
`200
`
`Decoupler
`Data Port
`335
`
`Network Access Point
`307
`
`Figure 3
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`1
`POWER TRANSFER APPARATUS FOR
`CONCURRENTLY TRANSMITTING DATA
`AND POWER OVER DATA WIRES
`
`RELATIONSHIP TO COPENDING
`APPLICATIONS
`
`This application is a Continuation of application Ser. No.
`08/865,016, ?led May 29, 1997, now US. Pat. No. 5,994,
`998 Which is incorporated herein by reference in its entirety.
`
`BACKGROUND OF THE INVENTION
`
`1. Field of the Invention
`The invention relates in general to the ?eld of data
`networking and communications, and in particular to inter
`connecting computers to a local area netWork (“LAN”) or a
`Wide area netWork (“WAN”) through data lines that also
`carry poWer.
`2. Description of the Related Art
`Network devices typically communicate via Wired data
`lines and receive poWer from a separate line. For example,
`personal computers (“PCs”) may communicate ethernet
`signals via category three (CAT-3) or category ?ve (CAT-5)
`tWisted pair Wire and receive poWer from a second cable
`connected to a poWer source, such as a Wall socket or a
`battery. HoWever, it is desirable to be able to eliminate the
`need for the second cable. The folloWing describes examples
`of netWork devices that bene?t from the elimination of the
`separate poWer line, and then describes some of the inad
`equacies of previous solutions.
`Plain old telephone service (“POTS”) combines a voice
`signal With a poWer signal. The combined signal is trans
`mitted over tWisted pair cable betWeen the telephone and the
`line card at the public telephone exchange of?ce. The line
`card also supplies poWer over the tWo Wires carrying the
`voice signal. HoWever, the voice signal supported by POTS
`is not suf?cient for bandWidth intensive communications
`needs, such as, ethernet communications. Similarly, ISDN
`communications transmit poWer and digital data over
`betWeen an ISDN modem and a telephone sWitch. HoWever,
`ISDN data rates are more than an order of magnitude loWer
`than ethernet data rates.
`Wireless netWork adapters can interconnect PCs, or other
`netWorked device. The Wireless netWork adaptors use, for
`example, infrared (IR) or radio frequency (RF) modulation
`to transmit data betWeen Wireless access points and the
`Wireless adaptors connected to PCs. Although the Wireless
`adaptors and Wireless access points may be more expensive
`than comparable Wired equipment, they provide savings in
`Wiring costs and permit greater ?exibility by alloWing the
`PCs to be moved to any location Within the range of the
`system Without the necessity of reWiring the building.
`Typically, a transceiver (meaning transmitter and
`receiver) called a Wireless access point, mounted at an
`elevated location, such as on a ceiling or high on a Wall,
`provides netWork data communications betWeen a netWork
`hub, sWitch, router or server, to all the PCs located in that
`room Which are equipped With a compatible Wireless net
`Working adaptor. The Wireless access point is an active
`electronic device that requires a communications link to a
`hub or server as Well as electrical poWer to operate. Both the
`data signal and poWer signal must be provided to the
`Wireless access point. The data signal is typically at a loWer
`voltage than the poWer signal, but at a signi?cantly higher
`frequency, suf?cient to sustain a high data transfer rate (e.g.,
`100 kilobits per second or higher). The available poWer is
`
`6,140,911
`
`2
`usually 110V or 220V AC at frequencies beloW one hundred
`HZ. Often tWo separate sets of Wires are used to carry the
`data signal and poWer signal. One set of Wires is used to
`couple the Wireless access point and the hub and the other set
`of Wires is used to couple the Wireless access point to the
`poWer outlet.
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`Eliminating the need for separate poWer and data Wiring
`simpli?es the installation of a Wireless access point and can
`reduce the cost of the installation. Therefore, it is desirable
`to transmit suf?cient electrical poWer to operate the Wireless
`access point through the netWork cable that is used to
`connect the Wireless access point to the hub or server.
`
`One possible solution is to transmit poWer on the unused
`Wires of the data cable. An example of this approach can be
`found in the VIPSLAN-10TM product manufactured by the
`JVC Information Products Company of Irvine, Calif. Of
`course this requires that additional, unused Wire pairs be
`available in the data cable, Which may not alWays be
`available. Also, if a change in the netWorking standard in the
`future dictates the use of the currently unused Wire pairs in
`the netWorking cable, this solution becomes dif?cult to
`implement.
`Therefore, What is needed is a solution that reduces the
`Wiring requirements to transmit data and poWer to a Wireless
`access point Without having to use additional Wire pairs.
`
`SUMMARY OF THE INVENTION
`
`One embodiment of the invention includes an apparatus
`for providing electric poWer supply current to a netWork
`device across a transmission line. ApoWer and data coupler
`(“the coupler”) is coupled to one end of the transmission
`line. The transmission line is also adapted for transmission
`of a data signal. The coupler has a data input and a poWer
`input. PoWer supply current from the poWer input is coupled
`to data signal from the data input and the combined poWer
`supply current and data signal is coupled to one end of the
`transmission line. The opposite end of the transmission line
`is coupled to a poWer and data decoupler (“the decoupler”).
`The decoupler has a poWer output and a data output. Both
`the data output and poWer output of the decoupler are
`coupled to the netWork device. The combined poWer supply
`current and data signal is decoupled by the decoupler, and
`the data signal is supplied to the data output and the poWer
`supply current is supplied to the poWer output. Thus, the data
`signal and the poWer supply current are coupled and trans
`mitted via the transmission line from the coupler to the
`decoupler and then decoupled and provided separately to the
`netWork device.
`
`In another embodiment, the transmission line includes
`tWo transmission lines. One of the transmission lines carries
`both data and poWer signals.
`
`55
`
`In other embodiments, the poWer signal includes alter
`nating current and/or direct current.
`
`In another embodiment, the transmission lines include
`tWisted pair cables.
`
`In other embodiments, the netWork devices include Wire
`less access points, netWork interface cards, peripheral
`devices and/or netWork computers.
`
`65
`
`These features of the invention Will be apparent from the
`folloWing description Which should be read in light of the
`accompanying draWings.
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`3
`BRIEF DESCRIPTION OF THE DRAWINGS
`FIG. 1 is an overview of an installation of a power transfer
`apparatus.
`FIG. 2 is an overview of a power transfer apparatus for
`use with wireless access points.
`FIG. 3 is a schematic diagram of a power transfer appa
`ratus.
`FIG. 4 is a more detailed schematic drawing showing a
`DC power transfer apparatus and corresponding circuitry
`located in the wireless access point.
`FIG. 5 is a more detailed schematic drawing showing an
`AC power transfer apparatus and corresponding circuitry
`located in the wireless access. This apparatus provides
`electrical isolation to the wireless access point.
`
`DESCRIPTION OF THE PREFERRED
`EMBODIMENT
`The following describes multiple embodiments of the
`invention. In one embodiment, power and data are combined
`and transmitted to a network device such as a wireless access
`point. The wireless access point uses the power signal to
`power communication circuits for communicating with
`wireless network nodes. Because the power and data are
`combined, the installation of the wireless access point is
`simpli?ed and may reduce the cost of installing the wireless
`access points.
`Power Transfer Apparatus Overview
`FIG. 1 shows the overall con?guration of one embodi
`ment of the invention including a power transfer apparatus.
`The following lists the elements in FIG. 1 and then describes
`those elements.
`FIG. 1 includes the following elements: an external power
`source 150; a power cable 120; a data cable 130; a power and
`data coupler 110; a network cable 160; a power and data
`decoupler 170; and, a network device 100.
`The following describes the coupling of the elements of
`FIG. 1. The external power source 150 couples to the power
`and data coupler 110 via the power cable 120. The power
`cable 120 couples to the power and data coupler 110. The
`communications network 140 couples to the data cable 130.
`The data cable 130 couples to the power and data coupler
`110. The power and data coupler 110 also couples to the
`network cable 160. The network cable 160 couples to the
`power and data decoupler 170. The power and data decou
`pler 170 couples to the network device 100.
`The following describes the elements in greater detail and
`then describes how the elements act together.
`The external power source 150 provides a power signal
`105 to the power and data coupler 110. Various embodi
`ments of the invention use different external power sources
`150: such as, a computer’s power supply, a battery, or a wall
`outlet and adaptor. What is important, however, is that there
`is some source of power that can eventually be supplied to
`the network device 100.
`In one embodiment, the power cable 120 is a standard two
`wire power cable. Other embodiments use other power
`transfer apparatuses to provide power to the power and data
`coupler 110.
`The communications network 140 is representative of
`many different types of communications networks supported
`by various embodiments of the invention. Example commu
`nications networks 140 include FDDI, ethernet (including
`ten Mbits/s, one hundred Mbits/s, and one gigibits/s
`standards), ATM, token ring, and AppleTalk. However, what
`is important is that a data signal 104 is communicated
`between the communication network 140 and the network
`device 100.
`
`4
`The power and data coupler 110 couples the power signal
`105 with the data signal 104 to produce a combined power
`and data signal 107. The power and data coupler 110 is
`described in greater detail below. What is important is that
`there is some combined power and data signal 107 that can
`eventually be supplied to the network device 100.
`The network cable 160 includes one or more wires for
`transmitting the combined power and data signal 107. In one
`embodiment, the network cable 160 includes an CAT-3,
`CAT-5 twisted pair cable, or coaxial cable.
`The network device 100 represents a class of devices
`supported by various embodiments of the invention. For
`example, in one embodiment, the network device 100
`includes a wireless access point. In another embodiment, the
`network device 100 includes a personal computer having a
`network interface card. In another embodiment, the network
`device 100 includes a network computer.
`The following describes the general operation of the
`elements of FIG. 1. A data signal is communicated to the
`power and data coupler 110 via the data cable 130 from a
`communications network 140. The combined power and
`data signal 107 is transmitted over the network cable 160 to
`the network device 100. In this embodiment, the network
`cable 160 is longer than three meters and the combined
`power and data signal 107 communicates data at greater than
`one megabit/second. (In another embodiment, the network
`cable length conforms to the IEEE 802.3 speci?cation.)
`Thus, the power and data coupler 110 supplies both power
`and data to the network device 100. The network device 100
`uses the power to operate which includes receiving,
`processing, and generating the data signal.
`Wireless Access Point Having a Power Transfer Apparatus
`FIG. 2 is an overview of a power transfer apparatus for
`use with wireless access points. The following lists the
`elements in FIG. 2 and then describes those elements. FIG.
`2 includes: an external power source 150, a power adaptor
`256, a power cable 120, a hub 240, a data cable 130, a power
`and data coupler 110, a network cable 160, a wireless access
`point 200, and a number of remote nodes. The remote nodes
`include laptop computers 280 and a desktop computer 270.
`Each computer includes a wireless adaptor card 295.
`The power adaptor 256 steps down available electrical
`power from 117 or 220 volts AC to an AC or DC voltage that
`is high enough to provide adequate voltage for the wireless
`access point 200. In one embodiment, the power adaptor 256
`supplies an output voltage of approximately twenty-four
`volts. Other embodiments of the invention have other output
`voltages, such as thirty-six and forty-eight volts. The power
`adaptor 256 is described in greater detail in the description
`of FIG. 5.
`The hub 240 is not needed in one embodiment of the
`invention to supply the data signal. Therefore, in other
`embodiments of the invention, the data signal is supplied by
`a network computer, a router, and a bridge. In one
`embodiment, the hub 240 provides an ethernet based data
`signal supporting a data transfer rate of at least one megabit/
`second.
`Regarding the power and data coupler 110, what is
`important is that there is some combined power and data
`signal 107 that can eventually be supplied to the wireless
`access point 200. Therefore, for example, in one
`embodiment, the power and data coupler 110 is included in
`a network card in the hub 240. The power signal 105, taken
`from the hub’s power supply, can then be combined with the
`data signal provided by the hub 240.
`The wireless access point 200 is an example of a network
`device 100. The wireless access point 200 includes a trans
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`ceiver for providing Wireless communications With the Wire
`less adaptor cards 295. In this example, the Wireless access
`point 200 is mounted on the ceiling. The Wireless access
`point 200 is described in greater detail beloW.
`The Wireless adaptor cards 295 also include a transceiver
`for communicating With the Wireless access point 200.
`The desktop computer 270 and the laptop computer 280
`are examples of some devices that may be included in one
`embodiment of the invention. For example, the desktop
`computer 270 can include an IBM compatible personal
`computer, or a MacOSTM compatible computer. HoWever,
`other embodiments of the invention include other remote
`netWork nodes such as a NeWtonTM personal digital assistant
`and a pager.
`The folloWing describes the general operating of the
`system shoWn in FIG. 2. The poWer adapter 256 supplies
`poWer to the poWer and data coupler 110 While the hub 240
`provides a data signal to the poWer and data coupler 110. The
`poWer and data coupler 110 communicates a combined
`poWer and data signal 107 to the Wireless access point 200.
`The Wireless access point 200 is poWered from the poWer
`part of the poWer and data signal 107. The Wireless access
`point 200 communicates a Wireless data signal With the
`Wireless adapter cards 295. The Wireless data signal corre
`sponds to the data signal from the hub 240. The Wireless
`adapter cards 295 provide the desktop computer 270 and the
`laptop computers 280 With the Wireless data signal.
`Schematic Diagram of a PoWer Transfer Apparatus
`FIG. 3 is a schematic diagram of a poWer transfer appa
`ratus. The folloWing ?rst lists the elements in FIG. 3, then
`describes the elements’ couplings, and then describes the
`elements’ interactions.
`FIG. 3 includes: the poWer cable 120, the data cable 130,
`poWer and data coupler 110, the netWork cable 160, and the
`Wireless access point 200. The poWer and data coupler 110
`includes a coupler poWer input port 320, a coupler data port
`380 and a coupler port 360. The Wireless access point 200
`includes a poWer and data decoupler 170 and a netWork
`access point 307. The poWer and data decoupler 170
`includes a decoupler port 365, a decoupler poWer output port
`325 and a decoupler data port 335.
`The elements of FIG. 3 are coupled as folloWs. The poWer
`cable 120 is coupled to the coupler poWer input port 320.
`The data cable 130 is coupled to the coupler data port 380.
`The netWork cable 160 is coupled to the coupler port 360
`and to the decoupler port 365. The Wireless access point 200
`is coupled to the decoupler poWer output port 325 and to the
`decoupler data port 335.
`The poWer and data decoupler 170 performs a function
`similar to that performed by the poWer and data coupler 110.
`HoWever, the poWer and data decoupler 170 decouples the
`poWer signal from the data signal. The poWer and data
`decoupler 170 can then supply the poWer signal to the
`netWork access point 307 separately from the data signal.
`The netWork access point 307 includes the transceiver for
`communicating With the remote nodes.
`The elements of FIG. 3 interact as folloWs. The poWer
`cable 120 provides poWer supply current to the coupler
`poWer input port 320. The data cable 130 transmits the
`netWork data signal to the coupler data port 380. The poWer
`and data coupler 110 combines the poWer signal and the data
`signal and outputs this signal at the coupler port 360. The
`combined poWer and data signal is transmitted on the
`netWork cable 160. The Wireless access point 200 receives
`the combined poWer and data signal through the decoupler
`port 365. The poWer and data decoupler 170 separates the
`netWork data signal from the poWer supply current. The
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`poWer and data decoupler 170 then supplies the poWer signal
`at the decoupler poWer output port 325 and communicates
`the data signal to the netWork access point 307 at the
`decoupler data port 335. The netWork access point 307 uses
`the poWer signal to poWer Wireless data signals to the remote
`nodes. The Wireless data signals correspond to the data
`signal communicated With the decoupler data port 335.
`In another embodiment of the invention, separate transmit
`and receive paths are supported betWeen the poWer and data
`coupler 110 and the poWer and data decoupler 170. In this
`embodiment, the data cable 130 includes at least tWo Wires
`supporting a transmit path and tWo Wires supporting a
`receive path. Note that poWer is only coupled to the transmit
`path Wires in one embodiment. While in another
`embodiment, all four Wires are used in the poWer transmis
`sion.
`FIG. 4 shoWs a more detailed schematic of one con?gu
`ration of this invention. The example shoWn in FIG. 4 is
`speci?cally adapted for the 10Base-T tWisted pair netWork
`ing protocol. Other embodiments of the invention support
`other netWork protocols. These embodiments include modi
`?cations for the number of Wires used by the particular
`netWork protocol. The folloWing lists the elements of FIG.
`4, describes their interconnections, and then describes the
`operation of the elements.
`FIG. 4 includes: the poWer adapter 256, the poWer cable
`120, the data cable 130, the netWork cable 160 and the
`Wireless access point 200. The poWer adapter 256 includes
`a step-doWn transformer 451, a diode bridge 453, and a
`capacitor 455. The poWer and data coupler 110 includes: the
`coupler data port 380, a pair of isolation transformers
`(isolation transformer 412 and isolation transformer 413), a
`pair of center tapped inductors (inductor 416 and inductor
`417), a pair of capacitors (capacitor 414 and capacitor 415),
`a pair of inductors (inductor 418 and inductor 419), a light
`emitting diode (LED 402), a resistor 403, and the coupler
`poWer and data port 360. The Wireless access point 200
`includes the netWork access point 307 and the poWer and
`data decoupler 170. The poWer and data decoupler 170
`includes: the decoupler poWer and data port 365, a pair of
`inductors (inductor 422 and inductor 423), a pair or center
`tapped inductors (inductor 524 and inductor 425), a pair of
`common mode chokes (choke 426 and choke 427), a pair of
`capacitors (capacitor 428 and capacitor 429), a pair of
`isolation transformers (transformer 432 and transformer
`433), a receive ?lter 434, a transmit ?lter 435, a DC-DC
`converter 410, a decoupler poWer output port 325, and the
`decoupler data port 335. In one embodiment, the loWpass
`?lters, the common mode choke, and the transformers are all
`part of the Wireless access point.
`The elements in the poWer adapter 256 are coupled as
`folloWs. The primary Winding of the transformer 451 is
`coupled to receive the poWer signal from the poWer adapter
`256. The diode bridge 453 is connected to the secondary
`Winding of the transformer 451. The capacitor 455 is con
`nected across the output of the diode bridge 453. The output
`of the diode bridge 453 is connected to poWer cable 120.
`The elements in the poWer and data coupler 110 are
`coupled as folloWs. In this example, the data signal is carried
`on four Wires. Thus, the coupler data port 380 includes a four
`Wire connection to the data cable 130. The primary Windings
`of the transformer 412 are connected to the tWo data input
`Wires of the coupler data port 380. Similarly, the primary
`Windings of the transformer 413 are connected to the tWo
`data output Wires of the coupler data port 380. The capacitor
`414 and the capacitor 415 are connected in series With the
`secondary Windings of the transformer 412 and the trans
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`Juniper v Chrimar
`IPR2016-01397
`
`

`

`6,140,911
`
`7
`former 413, respectively. The center tapped inductor 416
`and tWo output data Wires of the coupler output port 360 are
`coupled across the secondary Winding of the isolation trans
`former 412. Similarly, the center tapped inductor 417 and
`tWo input data Wires of the coupler input port 360 are
`coupled across the secondary Winding of the isolation trans
`former 413. The inductor 418 is connected betWeen the
`center tap of the inductor 416 and to the positive Wires of the
`poWer cable 120. The inductor 419 is connected betWeen the
`center tap of the inductor 417 and the negative Wires of the
`poWer cable 120. The resistor 403 and LED 402 are con
`nected across the positive and negative Wires of the poWer
`cable 120.
`The elements in the Wireless access point 200 are coupled
`as folloWs. The center tapped inductor 422 and the center
`tapped inductor 423 connect across the tWo input Wires and
`tWo output Wires, respectively, of the decoupler port 365.
`The inductor 422 connects to the center tap of the center
`tapped inductor 424 and to the positive terminal of the
`DC-DC converter 410. Similarly, the inductor 423 connects
`to the center tap of the center tapped inductor 425 and to the
`negative terminal of the DC-DC converter 410. The choke
`426 connects to the ends of the center tapped inductor 424
`and across the primary Winding of the transformer 432. The
`choke 427 connects to the ends of the center tapped inductor
`425 and across the primary Winding of the transformer 433.
`The receive ?lter 434 connects betWeen the secondary
`Winding of the transformer 432 and the tWo output Wires of
`the decoupler port 335. The transmit ?lter 435 connects
`betWeen the secondary Winding of the transformer 433 and
`the tWo input Wires of the decoupler port 335. The DC-DC
`converter 410 connects to the decoupler poWer output 325.
`The poWer adapter 256 operates as folloWs. PoWer is
`received from the external poWer supply at the primary
`Winding of the transformer 451. The transformer 451 elec
`trically isolates the poWer adapter 256. The diode bridge 453
`performs ?ll Wave recti?cation of the alternating current
`from the secondary Winding of the transformer 451. The
`capacitor 455 helps in the full Wave recti?cation to create a
`DC output. The Winding ratio of the transformer 451 and the
`value of the capacitor 455 is selected to provide the proper
`voltage output given the input voltage connected to the
`primary of the transformer 451. The poWer adapter 256 is
`representative of a variety of commercially available poWer
`adapters.
`The poWer and data coupler 110 operates as folloWs.
`There is one isolation transformer (e.g., transformer 412)
`and one center-tapped inductor (e.g., 416) for each pair of
`networking data Wires used in the particular networking
`standard. The data signal passes through these transformers
`With minimal loss. The transformers eliminate ground loops
`betWeen the poWer and data coupler 110 and any netWork
`devices attached to coupler data port 330. The isolation
`transformers also isolate the poWer and data coupler 110 in
`case of accidental contact betWeen the data cable 130 and a
`high voltage source. In one embodiment, the isolation trans
`former 412 and the isolation transformer 413 have a Winding
`ratio of approximately 1:1 and an isolation of one thousand
`?ve hundred volts. The capacitor 414 and the capacitor 415
`remove DC current from the data signal.
`Each center-tapped inductor (e.g., inductor 416) presents
`an impedance close to Zero Ohms for DC or loW frequency
`AC current, hoWever, the impedance across each Wire pair to
`the data signal is signi?cantly higher. (The loW frequency
`AC current is loW relative to the data signal frequency. In
`one embodiment, the loW frequency AC current is less than
`one hundred HertZ While the data signal is greater than one
`
`10
`
`15
`
`25
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`35
`
`45
`
`55
`
`65
`
`8
`MegahertZ.) The use of center-tapped inductors permits the
`current to How relatively unimpeded and balanced doWn
`each Wire of the Wire pairs connected across the Winding of
`each center-tapped inductor. The equal current ?oW reduces
`the line resistance to DC and permits the current to How
`equally to/from each end of the center-tapped inductor. The
`equal ?oW creates an equal and opposite DC ?uX Within the
`core of the center-tapped inductor, preventing the saturation
`of the core of the center-tapped inductor. In one embodiment
`of the invention, the series inductor 418 and the series
`inductor 419 provide additional isolation betWeen the poWer
`signal and the high-frequency data signal. The series induc
`tors 418 and 419 are optional in some embodiments.
`The data signal connection to the data cable 130 is
`provided through coupler data port 330 Which is selected for
`compatibility With the particular netWork protocol used.
`Certain data cables have Wires that are not used for data
`communication With certain protocols. For eXample, the
`CAT-3 or CAT-5 cable has four Wires that are not used With
`the 10BASE-T standard (i.e. tWo sets of pairs). The poWer
`transmission apparatus of the invention transmits the poWer
`signal using only the Wires normally used for data commu
`nication. The unused Wires are not used.
`One embodiment of the invention includes the resister
`403 and the LED 402. The LED 402 indicates Whether the
`poWer signal is being received by the poWer and data coupler
`110. Although this indication is desirable from an opera
`tional point of vieW, the LED 402 and resistor 403 are not
`required for the operation of one embodiment of the inven
`tion.
`The Wireless access point 200 operates as folloWs. The
`Wireless access point 200 receives the combined poWer and
`data signal at the decoupler port 365. The DC, or AC poWer,
`?oWs through the center-tap of the center-tapped inductor
`424 and the center-tapped inductor 425. The DC-DC con
`verter 410 is preferred because of its high efficiency and loW
`self-poWer dissipation (the DC-DC converter 410 alloWs for
`loWer input voltages). HoWever other devices, such as linear
`regulators, may be used to regulated the speci?c voltage and
`varying current loads required by the netWork access point
`307. The series inductor 422 and the series inductor 423
`enhance the isolation betWeen the data and poWer lines. The
`common mode choke 426 and the common mode choke 427
`help suppress high frequency signal components that cause
`electromagnetic interference With the netWork access point
`307. The data signal is provided across the secondary
`Windings of the isolation transformer 432 and the isolation
`transformer 433. The data signal being sent to the netWork
`access point 307 is then ?ltered using the receive ?lter 434.
`The data signal being sent from the netWork access point 307
`is ?ltered before being sent out on the netWork cable 160.
`The netWork access point 307 can then use the poWer signal
`from the DC-DC converter 410 and communicate informa
`tion to and from the remote nodes and the netWork using the
`data signal.
`FIG. 5 shoWs an alternate embodiment of the invention. In
`this embodiment, the poWer adapter 256 has been modi?ed
`so that the secondary Winding of transformer 451 is directly
`coupled to the poWer ca