United States Patent (19)
`Fisher et al.
`
`54
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`(75)
`
`73)
`
`POWER TRANSFER APPARATUS FOR
`CONCURRENTLY TRANSMITTING DATA
`AND POWER OVER DATA WIRES
`
`Inventors: David A. Fisher, Menlo Park;
`Lawrence M. Burns, Mountain View;
`Stephen E. Muther, Palo Alto, all of
`Calif.
`
`Assignee: 3Com Corporation, Santa Clara, Calif.
`Notice:
`This patent issued on a continued pros
`ecution application filed under 37 CFR
`1.53(d), and is subject to the twenty year
`patent term provisions of 35 U.S.C.
`154(a)(2).
`
`Appl. No.: 08/865,016
`Filed:
`May 29, 1997
`Int. Cl." ........................... H04B 1700; G08C 19/00
`U.S. Cl. ................................ 340/310.01; 340/310.02;
`340/310.08; 340/825.72; 375/257; 375/259;
`455/3.1; 455/3.3
`Field of Search ......................... 340/310.01, 310.02,
`340/310.08, 825.72; 370/490, 487,419,
`442; 375/257, 259; 307/126, 128, 127;
`455/3.1, 3.3
`
`56)
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`7/1991 Bowling et al. ................... 340/310.01
`5,033,112
`5,148,144 9/1992 Sutterlin et al. ................... 340/310.01
`
`USOO5994.998A
`Patent Number:
`11
`(45) Date of Patent:
`
`5,994,998
`*Nov.30, 1999
`
`5,368,041 11/1994 Shambroom ............................ 128/731
`5,381.804
`1/1995 Shambroom ............................ 128/731
`5,457,629 10/1995 Miller et al. ...
`... 340/825.52
`5,477,091 12/1995 Fiorina et al. ..
`... 340/310.01
`5,684.826 11/1997 Ratner ................................ 340/310.01
`OTHER PUBLICATIONS
`JVC Information Products Company of America, sales bro
`chure and price list for “VIPSLAN-10 Infrared Wireless
`LAN System”, May 1996.
`Clegg, P., “VIPSLAN-10 Streaks Off the Wire”, LAN
`Times, Sep-1995.
`Primary Examiner Donnie L. Crosland
`Attorney, Agent, or Firm-Kent R. Richardson; Wilson,
`Sonsini, Goodrich & Rosati
`57
`ABSTRACT
`Electrical Supply current, Sufficient to power a wireleSS
`access point, is transmitted concurrently with a network data
`Signal acroSS a transmission line. A power 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
`a data transmission rate of one megabit/second or higher.
`
`32 Claims, 5 Drawing Sheets
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`Communications
`Network
`140
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`Data Cable
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`Network Cable
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`Data Signal
`104
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`External Power
`Source
`150
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`Power Cable
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`Power Signal
`105
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`Data & Power Signal
`107
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`Power Signal
`105
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`Network Device
`1OO
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`Power and Data Coupler
`11O
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`Power and Data Decoupler
`170
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`HPE 1028-0001
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`HPE Co. v. ChriMar Sys., Inc.
`IPR Pet. - U.S. Patent No. 8,902,760
`
`

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`U.S. Patent
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`5,994,998
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`| eun61-I
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`HPE 1028-0002
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`5,994,998
`5,994,998
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`U.S. Patent
`U.S. Patent
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`Nov.30, 1999
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`Sheet 2 of 5
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`HPE 1028-0003
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`U.S. Patent
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`Nov.30, 1999
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`Sheet 3 of 5
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`5,994,998
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`Data Signal
`Data Rate = 1 Mb/s
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`Data Cable
`130
`Coupler Data
`Port
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`Power and Data Coupler
`110
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`Coupler Power
`Input Port
`32O
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`Power Cable
`120
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`Coupler Port
`360
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`NetWork Cable
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`"N.
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`Decoupler Port
`365
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`Decouple?
`Power Output
`Port 325
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`C Power and Data Decoupler
`170
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`Wireless
`Access Point
`2OO
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`Decoupler
`Data Port
`335
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`NetWOrk ACCeSS Point
`307
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`Figure 3
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`HPE 1028-0004
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`U.S. Patent
`U.S. Patent
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`Nov.30, 1999
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`U.S. Patent
`U.S. Patent
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`Nov.30, 1999
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`Sheet 5 of 5
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`5,994,998
`5,994,998
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`90-90
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`HPE 1028-0006
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`

`1
`POWER TRANSFER APPARATUS FOR
`CONCURRENTLY TRANSMITTING DATA
`AND POWER OVER DATA WIRES
`BACKGROUND OF THE INVENTION
`1. Field of the Invention
`The invention relates in general to the field 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 five (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 benefit 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 office. The line
`card also Supplies power over the two wires carrying the
`voice signal. However, the voice signal supported by POTS
`is not Sufficient for bandwidth intensive communications
`needs, Such as, ethernet communications. Similarly, ISDN
`communications transmit power and digital data 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 devices. 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 flexibility 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 significantly higher
`frequency, Sufficient to Sustain a high data transfer rate (e.g.,
`100 kilobits per second or higher). The available power is
`usually 110V or 220VAC 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.
`Eliminating the need for Separate power and data wiring
`Simplifies the installation of a wireless access point and can
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`reduce the cost of the installation. Therefore, it is desirable
`to transmit Sufficient 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 difficult 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. A power 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.
`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.
`These features of the invention will be apparent from the
`following description which should be read in light of the
`accompanying drawings.
`
`BRIEF DESCRIPTION OF THE DRAWING
`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
`
`HPE 1028-0007
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`

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`5,994,998
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`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
`Simplified and may reduce the cost of installing the wireleSS
`acceSS points.
`Power Transfer Apparatus Overview
`FIG. 1 shows the overall configuration 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
`50
`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.
`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.
`
`4
`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 specification.)
`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 point200. 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
`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
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`computer, or a MacOSTM compatible computer. However,
`other embodiments of the invention include other remote
`network nodes Such as a Newton' 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 first 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 point200
`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
`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
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`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
`SO.
`FIG. 4 shows a more detailed Schematic of one configu
`ration of this invention. The example shown in FIG. 4 is
`specifically adapted for the 10Base-T twisted pair network
`ing protocol. Other embodiments of the invention Support
`other network protocols. These embodiments include modi
`fications 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 stepdown 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 filter 434, a transmit filter 435, a DC-DC
`converter 410, a decoupler power output port 325, and the
`decoupler data port 335. In one embodiment, the lowpass
`filters, 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
`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
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`HPE 1028-0009
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`7
`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 filter 434 connects between the secondary
`winding of the transformer 432 and the two output wires of
`the decoupler port 335. The transmit filter 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 full wave rectification of the alternating current
`from the secondary winding of the transformer 451. The
`capacitor 455 helps in the full wave rectification 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
`five 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 significantly 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
`Megahertz.) The use of center-tapped inductors permits the
`current to flow relatively unimpeded and balanced down
`each wire of the wire pairs connected acroSS the winding of
`each center-tapped inductor. The equal current flow reduces
`the line resistance to DC and permits the current to flow
`equally to/from each end of the center-tapped inductor. The
`equal flow creates an equal and opposite DC flux 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
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`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,
`flows 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 Specific 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 b