(12) United States Patent
`Boys
`
`(10) Patent No.:
`(45) Date of Patent:
`
`US 8,639,191 B2
`Jan. 28, 2014
`
`USOO8639191 B2
`
`(54) COMMUNICATION APPARATUS AND
`METHOD
`
`(75) Inventor: John Talbot Boys, Auckland (NZ)
`(73) Assignee: Auckland Uniservices Limited,
`Auckland (NZ)
`Subj
`y disclai
`h
`f thi
`ubject to any d1Sclaimer, the term of this
`patent is extended or adjusted under 35
`U.S.C. 154(b) by 832 days.
`10/595561
`
`(21) Appl. No.:
`
`*) Not
`Ot1Ce:
`
`Oct. 29, 2004
`PCT/NZ2004/OOO274
`
`(22) PCT Filed:
`(86). PCT No.:
`S371 (c)(1),
`Feb. 6, 2007
`(2), (4) Date:
`(87) PCT Pub. No.: WO2005/043775
`PCT Pub. Date: May 12, 2005
`
`(65)
`
`(30)
`
`Prior Publication Data
`US 2007/O281625A1
`Dec. 6, 2007
`
`Foreign Application Priority Data
`
`Oct. 31, 2003 (NZ) ........................................ 529291
`(51) Int. Cl.
`H04B I/38
`(52) U.S. Cl.
`USPC ............................................................ 455/73
`(58) Field of Classification Search
`USPC ....................................... 455/4.1.1, 41.2, 41.3
`See application file for complete search history.
`
`(2006.01)
`
`(56)
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`
`1, 1987 Ochs
`4,636,771 A
`1/1992 Turnbullet al.
`5,084,864 A
`3/1994 Boys et al.
`5,293,308 A
`5,583,525 A 12/1996 Nekomoto et al.
`5,983,076 A 11/1999 Takasan et al.
`6,005,475 A 12/1999 Takasan et al.
`... 375,238
`6.459,363 B1 * 10/2002 Walker et al. ......
`7,023,301 B2 * 4/2006 Kawahara et al. ............ 333.204
`2002/0183003 Al 12/2002 Chang et al.
`2003/0232181 A1* 12/2003 Simpson et al. .............. 428.212
`
`
`
`FOREIGN PATENT DOCUMENTS
`
`JP
`JP
`JP
`JP
`
`3, 1955
`55133652
`1, 1975
`50-2810
`10, 1986
`61224735
`3, 1994
`6-69839
`(Continued)
`
`OTHER PUBLICATIONS
`
`International Search Report for International Application No. PCT/
`NZ2004/000274, dated Feb. 14, 2005.
`(Continued)
`
`Primary Examiner — Ping Hsieh
`Assistant Examiner — Ankur Jain
`(74) Attorney, Agent, or Firm — Law Office of Richard F.
`Jaworski, PC
`
`(57)
`ABSTRACT
`A communication apparatus comprises a communication
`path capable of conveying communication signals, a commu
`nication device adapted to receive or generate VHF or UHF
`communication signals, and a near field antenna associated
`with the communication device. The near field antenna is
`provided sufficiently near to the communication path to
`couple VHF or UHF communication signals to or from the
`communication device to the communication path. A HID/
`IPT system and a communication method are also provided.
`
`3,829,836 A
`4,428,078 A
`
`8, 1974 Clarke
`1, 1984 Kuo ............................. 455,306
`
`33 Claims, 4 Drawing Sheets
`
`50?.
`
`|300
`50
`
`14
`
`16
`
`10
`
`11
`
`\
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`18
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`son
`
`12
`
`Momentum Dynamics Corporation
`Exhibit 1014
`Page 001
`
`

`

`US 8,639,191 B2
`Page 2
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`(56)
`
`References Cited
`
`FOREIGN PATENT DOCUMENTS
`
`JP
`JP
`WO
`
`1122.5097
`2003 15O247
`WOO141315 A2
`
`8, 1999
`5, 2003
`6, 2001
`
`WO
`WO
`
`O1-50545
`WO-03/005380
`
`T 2001
`1, 2003
`
`OTHER PUBLICATIONS
`European Search Report No. 04793738.8, dated Apr. 29, 2010.
`English translation of corresponding Taiwanese Office Action.
`
`* cited by examiner
`
`Momentum Dynamics Corporation
`Exhibit 1014
`Page 002
`
`

`

`U.S. Patent
`
`Jan. 28, 2014
`
`Sheet 1 of 4
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`US 8,639,191 B2
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`PRIOR ART
`
`14
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`
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`Momentum Dynamics Corporation
`Exhibit 1014
`Page 003
`
`

`

`U.S. Patent
`
`Jan. 28, 2014
`
`Sheet 2 of 4
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`US 8,639,191 B2
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`
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`Momentum Dynamics Corporation
`Exhibit 1014
`Page 004
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`

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`U.S. Patent
`
`Jan. 28, 2014
`
`Sheet 3 of 4
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`US 8,639,191 B2
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`62
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`54
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`56
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`-11
`\-30 1.5mm
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`1.6mm
`1.5mm
`1.5mm
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`52
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`Fig. 12
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`Momentum Dynamics Corporation
`Exhibit 1014
`Page 005
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`U.S. Patent
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`Jan. 28, 2014
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`Sheet 4 of 4
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`US 8,639,191 B2
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`Distance (mm)
`1
`2
`3
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`4.
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`O
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`25
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`29
`-33 "re-
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`-37
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`N a-----
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`Fig. 13
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`24
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`Fig. 14
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`32
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`-34 -72
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`Fig.15
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`Momentum Dynamics Corporation
`Exhibit 1014
`Page 006
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`

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`US 8,639,191 B2
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`1.
`COMMUNICATION APPARATUS AND
`METHOD
`
`CROSS REFERENCE TO PRIORAPPLICATION
`
`This is a U.S. National Phase application under 35 U.S.C.
`S371 of International Patent Application No. PCT/NZ2004/
`000274, filed Oct. 29, 2004, which claims priority to New
`Zealand Patent Application Serial No. 529291, filed on Oct.
`31, 2003. The International Application was published on
`May 12, 2005 as WO 2005/043775 A1 under PCT Article
`21(2).
`
`FIELD OF INVENTION
`
`10
`
`15
`
`This invention relates to communication apparatus and
`methods, and has particular but not exclusive relevance to
`communication with or between one or more moveable
`devices.
`
`BACKGROUND
`
`2
`In U.S. Pat. No. 6,005,475 a communications system
`where the HID/IPT track is tuned to two frequencies at the
`same time has been disclosed. This system has the advantages
`of low cost (as no additional conductors are required) and
`applicability, as wherever there is power there are communi
`cation signals as well. But the range of applicability of this
`technique is limited as the bandwidth that is available using
`pick-ups tuned to both a power frequency and a communica
`tions frequency at the same time is limited. In practice band
`widths of less than 50 kHz are to be expected. The method has
`the advantage that it is operable with all HID/IPT media, for
`example wood, concrete, water, and air. However, in many
`circumstances its bandwidth is simply too small.
`Wider bandwidth communication systems use micro
`waves, for example adhering to standards such as IEEE
`802.11a orb, but these bands are becoming congested and
`microwave is not acceptable by many potential users of HID/
`IPT systems. In factory conditions microwaves can also Suf
`fer from shadowing. This means that extra diversity must be
`introduced which adds to spectral clutter. Wideband systems
`can also use leaky feeders. These are essentially distributed
`antennas and radiate widely making compliance with emis
`sion standards difficult when wide bandwidths are needed.
`Leaky feeders are also very expensive. Other communica
`tions systems economise by using the HID/IPT cables to
`propagate radio signals as well and having antennas distrib
`uted around the track to receive the signals. These systems are
`effective but leak radiation as power wires are not good RF
`conductors, and consequently they have a restricted band
`width and range.
`In another system, which is disclosed in International
`Application WO03.005380, a data cable runs alongside the
`primary power cable of an HID/IPT system. The conductors
`of the data cable are arranged in Such a way as to keep
`coupling between the data cable and the power cable to a
`minimum, and therefore reduce “crosstalk”. The frequency of
`the information signal in the data cable is typically less than 1
`Megahertz and the transmission rate is about 10 to 150 kbit/s.
`This system requires a very specific geometric relationship
`between the data cable and the power cable.
`
`25
`
`30
`
`35
`
`There are many applications in which high bandwidth
`communication is required over a transmission line with a
`device that may be moveable relative to the transmission line.
`One example is a communications network in an environ
`ment such as a hospital where imaging equipment needs to
`transmit or receive high Volumes of data at various locations
`in the hospital. It can be difficult providing appropriate physi
`cal connections between the equipment and the transmission
`line. This problem is compounded if the equipment needs to
`be moved for use around a variety of physical locations.
`Another example is communication with pick-up devices
`Supplied with power from an energised track, Such as an
`HID/IPT (High Efficiency Inductive Power Distribution/
`Inductive PowerTransfer). HID/IPT systems are very popular
`for many practical applications. They can work in very harsh
`environments, as they transfer power without physical con
`tact and are therefore tolerant of environmental hazards such
`40
`as water, acids, dirt and grime. Yet they themselves produce
`no harmful residues.
`In consequence HID/IPT systems can operate in factories
`where they provide high reliability and immunity to paint and
`fumes. They can also operate in Clean Rooms where the level
`45
`of cleanliness is very high and the HID/IPT system is com
`patible.
`The ability for communication with a device powered by
`an HID/IPT system is becoming increasingly important.
`HID/IPT systems usually transfer power to devices that have
`a task to perform, for example the devices may be carriages
`which perform automated processes or which are required to
`travel to a selected location. The tasks that the devices are to
`perform can be automated to a greater degree and made far
`more efficient by providing a means of communication
`between devices and/or between each device and a system
`control module.
`A communications system for an HID/IPT system must
`share the same advantages as the HID/IPT system i.e. it must
`transfer information without physical contact and must be
`tolerant of a harsh environment yet produce no residues, or
`electromagnetic interference, itself.
`HID/IPT systems operate in a wide range of environments
`where the power cables of the primary conductive path or
`track may be in air, or water, or even concrete. In these special
`65
`circumstances it is unlikely that one particular type of com
`munications system will be universally applicable.
`
`50
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`60
`
`SUMMARY OF INVENTION
`
`It is an object of the present invention to provide commu
`nication apparatus or methods which overcome orameliorate
`one or more disadvantages of known communication sys
`tems. Alternatively it is an object of the invention to at least
`provide the public with a useful altemative.
`Accordingly in one aspect the invention consists in com
`munication apparatus comprising:
`a communication path capable of conveying communication
`signals,
`a communication device adapted to receive or generate VHF
`or UHF communication signals, and
`a near field antenna associated with the communication
`device, the near field antenna being provided sufficiently
`near to the communication path to couple VHF or UHF
`communication signals to or from the communication
`device to the communication path.
`The near field antenna is preferably adapted to limit elec
`tromagnetic radiation therefrom.
`In a preferred embodiment the near field antenna com
`prises an inductance, although a capacitive element could
`also be used.
`
`Momentum Dynamics Corporation
`Exhibit 1014
`Page 007
`
`

`

`3
`The near field antenna may comprise a partial, single or
`multiple turn of a conductive material. The conductive mate
`rial may be a thin metal track provided on a non-conductive
`planar Substrate.
`In a preferred embodiment the conductive material com
`prises one or more turns being approximately 5 mm to 15 mm
`in a lateral dimension and approximately 20 mm to 60 mm in
`a longitudinal dimension.
`A shielding means may be provided to limit electromag
`netic radiation. The shielding means preferably comprises a
`screen, and the screen is provided on one side of the coupling
`means and the communication path is provided on an oppo
`site side of the coupling means.
`The screen may be constructed of an electrically conduc
`tive material having a low magnetic permeability, and be
`provided on a side of the planar Substrate opposite to a side of
`the substrate on which the metal track is provided.
`The communication path most preferably comprises a
`transmission line in the form of a cable having two parallel
`conductors. The conductors may be separated by an insulat
`ing web.
`The communication device is preferably moveable along
`the communication path and the near field antenna moves
`with the communication device and relative to the communi
`cation path to allow the communication device to receive or
`generate VHF or UHF communication signals to or from the
`communication path.
`In a second aspect the invention consists in an HID/IPT
`system including:
`a power Supply path adapted to be energised by a power
`Supply to provide an electromagnetic field associated with
`the power supply path;
`one or more moveable pick-up devices associated with the
`power Supply path and adapted to receive electrical energy
`from the electromagnetic field to Supply a load;
`a communication path capable of conveying communication
`signals,
`a communication device provided on each of the one or more
`pick-ups, the communication device being adapted to
`receive or generate VHF or UHF communication signals:
`and
`a coupling means associated with the communication device,
`the coupling means being provided Sufficiently near to the
`communication path to couple VHF or UHF communica
`tion signals to or from the communication device to the
`communication path whereby the one or more pick-ups
`may communicate with each other or with a further device.
`The further device may interface with a control system and
`may be directly connected to the communication path.
`The coupling means preferably comprises a near field
`antenna.
`In a third aspect the invention consists in a communication
`method, the method including the steps of
`providing a communication path capable of conveying com
`munication signals;
`55
`providing a communication device, the communication
`device including a near field antenna provided near to the
`communication path, and either,
`a) imposing a VHF or UHF communication signal on the
`communication path and using the near field antenna to
`provide the signal to the communication device, or
`b) using the communication device to generate a VHF or
`UHF communication signal and using the near field
`antenna to provide the signal to the communication path.
`In a fourth aspect the invention consists in a near field
`antenna comprising a thin planar Substrate of a non-conduc
`tive material, a conductive track on one side of the Substrate
`
`4
`adapted to inductively or capacitively couple with a transmis
`sion line, and a screen provided on the other side of the
`substrate.
`Further aspects of the invention, which should be consid
`ered in all its novel aspects, will become apparent to those
`skilled in the art upon reading the following description
`which provides at least one example of a practical application
`of the invention.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`One or more examples of applications of the invention will
`be described below with reference to the accompanying
`drawings in which:
`FIG. 1 is a diagrammatic illustration of a known HID/IPT
`system,
`FIG. 2 is a diagrammatic illustration of a communication
`system according to the invention,
`FIG. 3 is a diagrammatic illustration of another embodi
`ment of a communication system according to the invention,
`FIG. 4 is a sketch of a near field antenna,
`FIG. 5 is a partial elevation of a cable used in accordance
`with the invention,
`FIG. 6 is an end elevation of the cable of FIG. 5,
`FIG. 7 is a diagrammatic elevation of the inductor of FIG.
`4 in use relative to the cable of FIGS. 5 and 6,
`FIG. 8 is an end elevation of the arrangement shown in FIG.
`7, and
`FIG. 9 is an end elevation in cross section showing the
`orientation of the communication path and antenna relative to
`the power conductors in an example of an HID/IPT applica
`tion,
`FIG.10 is an end elevation is cross section of an alternative
`arrangement of a communication path and a near field
`antenna in an HID/IPT application,
`FIG. 11 is a plan view from below of the near field antenna
`of FIG. 10,
`FIG. 12 is a partial view of the near field antenna and
`communication path of FIG. 10, showing the arrangement in
`greater detail,
`FIG. 13 is a graph of insertion loss against distance
`between a near field antenna as shown and described with
`reference to FIGS. 10 to 12 and a communication path com
`prising a 300-Ohm ribbon,
`FIG. 14 is a diagrammatic end elevation in cross section of
`a capacitive near field antenna near aparallel conductor trans
`mission line,
`FIG. 15 is a partial plan view of the near field antenna
`shown in FIG. 14.
`
`DETAILED DESCRIPTION OF THE PREFERRED
`EMBODIMENTS
`
`An example of the invention will be discussed below with
`reference to use in an HID/IPT system. However, the inven
`tion is applicable to communications systems for many other
`applications.
`Referring to FIG. 1 a known HID/IPT system is shown.
`Such a system is described in U.S. Pat. No. 5.293,308, the
`contents of which are included by reference herein in their
`entirety. The system includes a conductive path 1 that is
`electrically energised by a power Supply 2. The path 1 may
`include compensation capacitors 3. A device 4 is Supplied
`with power from the path 1 by being selectively coupled to the
`path. Thus the device 4 has a tuned power pick-up circuit 5.
`rectifier bridge 6 and control components as described in U.S.
`Pat. No. 5,293,308 to provide power as required by a load.
`
`US 8,639,191 B2
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`Exhibit 1014
`Page 008
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`US 8,639,191 B2
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`The load supplied will vary upon the application of the sys
`tem, and may for example be a light, or an electric motor. In
`many applications the path 1 will be provided along a rail or
`track on which bodies such as carriages are provided, and the
`load will include an electric motor which moves the carriage
`along the track.
`As discussed above, communication with or between
`devices 4 is important to the operation and efficiency of Such
`systems. For example, if the carriages are used to move
`articles through a manufacturing process area, it is important
`to know where each carriage is to avoid collisions or to
`correctly synchronise the manufacturing process. Communi
`cation can be used to allow each carriage to report its position,
`or to perform certain tasks.
`The present invention provides a communication system
`where IPT concepts may be applied to allow communication
`between devices. Referring to FIG. 2, an example of the
`communication system is shown having a communication
`path 10. Characteristically a Suitable communication path is a
`transmission line that in principle does not radiate energy. It is
`preferably terminated with its characteristic impedance to
`avoid standing waves. A communication device 12 may trans
`mit or receive (or both) VHF and/or UHF signals in the form
`of electrical energy to or from the path 10. For the purposes of
`this document the VHF band is 30 MHZ to 300 MHZ and the
`UHF band is 300 MHZ to 3000 MHz. The device 12 includes,
`or is associated with, a near field antenna 11. Communication
`signals propagating in the communication path are in prin
`ciple not disturbed by extraneous electromagnetic radiation,
`as parallel wire transmission lines neither radiate nor receive
`radiation. Thus the pathway is resistant to unwanted noise.
`However, near field disturbances can be coupled into or out of
`the path using near field antennas 11. These are essentially
`mutual inductances or capacitances that affect the two wires
`of the communication path differently. In FIG. 2 the near field
`antennas 11 are essentially inductors having inductance L
`which is coupled to path 10 by mutual inductance M. In this
`document reference to “near field antenna’ refers to an
`antenna designed to operate in the very near field, preferably
`within approximately /6" of a wavelength or 1 radian phase
`displacement.
`In FIG. 2 a communication signal transmitter and/or
`receiver 14 (a 50-Ohm device in this example) is directly
`coupled to the path 10 which comprises a transmission line
`having a 300-Ohm characteristic impedance (such as 300
`45
`Ohm television ribbon) via a matching transformer 16. The
`path is terminated with its characteristic impedance, which in
`this example comprises a 300-Ohm resistor 18. The commu
`nication unit 14 may interface with a controller to communi
`cate instructions to a device associated with communication
`unit 12.
`An alternative arrangement (using like reference numerals
`to designate like features) is shown in FIG. 3. The path 10 in
`this example is terminated at both ends with resistors 18
`corresponding to the characteristic impedance of the cable
`that provides path 10, and two communication units are
`coupled to the path so that the path allows communication
`signals to be transmitted and/or received between the units 12.
`Conventional 2-wire transmission lines, such as the 300
`Ohm ribbon cable described above are effective at propagat
`ing VHF and UHF signals with very little loss of signal over
`large distances, for example 100 meters or so. Such ribbon
`looks like a HID/IPT track and we have found that near-field
`antennas 11 can be used to insert or extract signals from the
`300-Ohm ribbon. The near field antennas 11 are in the pre
`ferred form Small mutual inductances that couple inductance
`L to the path 10. However, a near field antenna that is in effect
`
`55
`
`6
`primarily capacitive (that is to say is operative by primarily
`producing an electric field rather than a magnetic field) could
`alternatively be used (as shown in FIGS. 14 and 15). The
`mutually coupled near-field antennas are designed to be
`physically Small, so that they themselves do not radiate. In
`practice this condition is easily met, and practical implemen
`tation of the near field antennais discussed further below. The
`mutual inductance so formed is small, being of the order of 10
`nH. However, at these frequencies (for example 320 MHz in
`a preferred embodiment) the radian frequency (2 Juf) is high
`(in the order of 2x10) so that the product coM is a quite
`reasonable value (in this example 20 Ohms).
`We have found that a 300-Ohm ribbon HID/IPT system
`with near field antennas behaves in a very similar manner to a
`10-20 kHz, HID/IPT system. However there are also signifi
`cant differences. In both systems power is introduced at one
`end of the cable and may be extracted by pick-ups placed or
`moving along the track. The conventional track is terminated
`by a short circuit and at regular intervals along a (long) track
`compensation capacitors must be placed to prevent the driv
`ing voltage from becoming too high. The 300-Ohm ribbon
`cable is terminated in its characteristic impedance so no com
`pensation capacitors are required. It is not practical to termi
`nate the conventional HID/IPT system in its characteristic
`impedance as the power losses would be too high. For
`example, for a track with a track current of 80 A and a
`characteristic impedance of 180 Ohms the losses in a termi
`nating resistor would be 1.15 MW and the operating voltage
`would be 14.4 kV. These differences apart, we have found that
`the two systems behave almost identically. The communica
`tion units 12 and their antennas 11 used with the 300-Ohm
`ribbon cable are very simple AC (RF) devices and are fully
`reversible. The near field antennas are designed to repel flux
`rather than attract it and do not require decoupling from the
`communication path as they do not have to be tuned and they
`place very little load on the track. Their reversibility is an
`advantage.
`One embodiment of a communications system is described
`below with reference to FIGS. 4 to 9. Referring to those
`Figures, an antenna for use with a 300-Ohm ribbon cable is a
`Small single turn inductor (although those skilled in the art
`will realise that other physical arrangements may be used
`Such as a partial turn or more than one turn) with a shape that
`is preferably rectangular as shown in FIG. 4. In that Figure,
`the longitudinal side 20 of the rectangular shape may be 20
`mm to 60 mm (preferably 40 mm) for example, and the lateral
`(shorter) side 22 may be 5 mm to 15 mm (preferably 8 mm to
`match the width of the 300-Ohm ribbon) for example. The
`inductor may be formed using a printed circuit board (PCB)
`so that the majority of the conductive surface of the original
`board is etched away to leave the generally rectangular con
`ductive strip. The inductor so formed is connected to the
`communication device 12, for example by a coaxial cable 24.
`Turning to FIGS. 5 and 6, a portion of ribbon cable is
`shown, generally referenced 30, having two conductors 32
`that are spaced approximately 10 mm apart being separated
`by an insulating web 34.
`In FIGS. 7 and 8 the typical disposition of the antenna 11
`relative to the ribbon cable is shown. A side 20 of the inductor
`L is placed parallel to, and in close proximity with (for
`example within 5 mm to 10 mm of) one of the conductors 32
`of the ribbon. The antenna 11 and the ribbon are preferably in
`the same plane in this example. This antenna has a self
`inductance of around 40 nPI and a mutual inductance to the
`track of approximately 10 nh. If the antenna path 10 is truly
`in the near-field of the antenna then simple circuit theory may
`be used to calculate its performance. With the dimensions
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`Momentum Dynamics Corporation
`Exhibit 1014
`Page 009
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`7
`given as above and with a path comprising a 300-Ohm ribbon
`terminated in 300 Ohms at both ends, the calculated loss from
`one antenna driven by a 50 Ohm generator to anotherantenna
`is 49.5 dB; the measured loss in the same circumstances is 51
`dB. Similarly if the ribbon is driven with a matching trans
`former to match 300 Ohms to a 50 Ohm generator the calcu
`lated loss from the generator to the antenna is 28 dB against a
`measured loss of 31 dB. For propagation in the opposite
`direction from the pick-up to the generator the figures are
`again 28 dB and 31 dB.
`In FIG. 9a diagrammatic cross section is shown through a
`rail assembly 40 of an IPT system installation. The rail sup
`ports the track or primary power conductors 42 which are
`arranged to allow passage of a power pick-up core 44. The
`communication conductor 10 (comprising ribbon 30) is
`shown provided on the rail assembly, and the antenna 11 is
`shown in close proximity to the ribbon, being Supported by an
`arm 46 from the core so as to move with the core if necessary.
`In an HID/IPT system the effect of a loaded antenna is to
`reflect an impedance back into the track. Thus a 3 kW load
`reflects a resistance of 0.469 Ohms back into a track with 80
`A in it to produce the 3 kW (assuming no loss). Similarly the
`300-Ohm ribbon also has a reflected impedance of approxi
`mately 0.7 Ohms induced in it. This is small compared with
`the characteristic impedance and has very little effect on the
`propagation of signals in the ribbon. With the ribbon an
`antenna sending power to the ribbon also sees a back-re
`flected impedance (again of 0.7 Ohms). This is small and even
`though it is a mismatch it has very little effect on the perfor
`mance of the antenna or the ribbon.
`Referring now to FIGS. 10 to 12, another embodiment will
`be described. In FIGS. 10 to 12, features that are the same as,
`or similar to, those of preceding Figures have the same refer
`ence numerals.
`In FIG. 10, the ribbon 30 is shown provided on an alterna
`tive rail assembly 50 of an IPT system installation. For pur
`poses of clarity, the primary power conductors are not shown,
`but are supported from structure 52 (which may comprise an
`“I beam for example). The antenna 11 is provided in a plane
`substantially parallel to but above that of the ribbon 30.
`Referring to FIG. 11, one side of the near field antenna 11
`is shown in greater detail. As described above, the near field
`antenna may be constructed in a number of different ways, but
`is preferably formed from etching a PCB to provide track 54
`which in this example forms a two-turn inductor. We have
`found that the near field antenna may beformed from a double
`sided printed circuit board to create two turns of narrow
`(preferably 1 mm) wide copper track about 1 mm apart on one
`side, and a copper screen 56 (not shown in FIG. 11, but
`illustrated in FIG. 12) on the other side. The screen 56 has a
`low magnetic permeability and therefore repels magnetic
`flux, so it acts as a “flux frightener” rather than HID/IPT
`system power transfer units which try to attract flux using
`ferrite or similar high permeability materials. We have made
`these on a double sided PCB laminate 1.6 mm thick (to give
`1.6 mm between the loop and the screen behind it) and on two
`separate single sided laminates that were then glued together
`to get a thickness of 3.2 mm. Thicker antennas allow greater
`spacing between the 300 Ohm ribbon and the antenna. The
`distance from the ribbon to the physical structure (typically
`aluminium) it is attached to is preferably 1.6 mm for the 1.6
`mm thick antennas but for larger separations 3-5 mm is pre
`ferred with the thicker antennas. The longitudinal dimension
`20 is 40 mm in this example, and the lateral dimension 22 is
`8mm. We use a direct connection to a 50 Ohm coax cable with
`the central conductor going to one terminal 58 and the earth
`screen to the other terminal 60. We have found that we do not
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`US 8,639,191 B2
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`8
`require any matching networks. We have also made antennas
`30 mm long (i.e. 30 mm in the longitudinal dimension 20).
`These are slightly less sensitive (-2 to -3dB). The length and
`width (i.e. the longitudinal and lateral dimensions respec
`tively) may be changed as required. Increased width may be
`desirable for a wider ribbon to accommodate the greater
`spacing between the parallel conductors, or to allow greater
`spacing between the antenna and the ribbon (since a greater
`width may allow flux to extend further toward the ribbon).
`Increased length allows higher gain, although this needs to be
`kept
`relatively
`Small
`(longitudinal
`dimension
`I<wavelength) to prevent radiation and to communication in
`locations where the ribbon is bent around corners.
`The PCBlaminate is preferably cropped to extendabout 20
`mm from the loop in all directions to prevent radiation. Thus
`the screen 56 extends beyond the dimensions of the track 54.
`In cases where this is not possible we have found that the
`laminate may be cropped more closely where needed. The
`extra screening helps to suppress unwanted radiation. The
`result is a near field antenna that has very little radiation at the
`operating frequency of typically 320 MHz. Furthermore, the
`balanced and properly terminated ribbon 30 also radiates
`essentially no power.
`Turning to FIG. 12, the arrangement of FIG. 10 is shown in
`greater detail. The ribbon 30 is spaced from the structure 52
`by a spacer 62 (which is preferably constructed from a plastic
`material Such as a plastics tape or web) which is approxi
`mately 1.5 mm high in this example. The ribbon may typi
`cally extend approximately 1.5 mm above the spacer, and the
`near field antenna may be provided about 1.5 mm to 5 mm
`above the ribbon, as discussed above. Therefore, the overall
`profile may be as low as about 3 mm without the near field
`antenna, and 6 mm-7 mm with the near field antenna.
`The structure 52 will often be aluminium, and we have
`found that this causes significant signal attenuation, for
`example up to 0.4 dB per meter. This together with the near
`field antenna design which is physically Small, and may
`include screen 56 to limitany radiation, substantially prevents
`any power being radiated, and thus avoids EMI (Electromag
`netic Interference) problems. Also, the extreme difference in
`the HID/IPT operating frequency (around 20 kHz) compared
`with the communications path operating frequency (around
`320 MHz) prevents crosstalk from being an issue. In FIG. 13
`a graph showing insertion loss (in dB) against distance (in
`mm) between the near field antenna described above with
`reference to FIG. 10 to 12 and the 300-Ohm ribbon 30 is
`shown. As can be seen, the loss increases linearly at 4 dB per
`mm after 1 mm separation (i.e. from approximately 0.1% of a
`wavelength).
`FIGS. 14 and 15 show an alternative embodiment (using
`like reference numerals to designate like features) of the near
`field antenna in which the near field antenna is a capacitive
`near field antenna 70. The coaxial cable 24 which is con
`nected to a communication device is coupled to the near field
`antenna 70 by a transformer 72. Each terminal of the other
`side of the transformer is connected to one of elongate con
`ductors 74 and 76 which are each near to one of the parallel
`conductors 32 of the ribbon 30. The plan view in FIG. 15
`omits the transformer detail and the coaxial cable for clarity.
`In use an electric field is formed between the near field
`antenna conductors 74 and 76 and the cable conductors 32,
`allowing near field disturbances to be coupled into and out of
`the ribbon 30.
`