Note: Descriptions are shown in the official language in which they were submitted.
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CONTACTLESS DATA COMMUNICATIONS COUPLING
RELATED APPLICATION
[oool] The present application is related to and claims priority of a
provisional application
entitled CONTACTLESS DATA COMMUNICATIONS COUPLER IN A TRAIN
COUPLING ENVIRONMENT METHOD AND SYSTEM, filed July 7, 2005, and assigned
Serial No. 60/697,317, which application is assigned to the present assignee,
and which
application is hereby fully incorporated by reference herein.
BACKGROUND OF THE INVENTION
Field of the Invention
[0002] This invention generally relates to the field of contactless high-speed
data signal
coupling and more specifically to the field of contactless high-speed data
signal coupling
systems and devices optimized for a train coupler environment.
Description of the Related Art
[0003] Railroad cars, including trams, streetcars and light rail cars
(hereinafter "cars"), are
generally connected together by mechanical couplers. An electrical coupler
head (hereinafter
"head"), which comprises a box-like electrical insulator, is mounted to each
mechanical
coupler. The electrical insulator of the head has a plurality of approximately
0.375-inch
diameter cylindrical openings for acceptance of metallic pins. Known
electrical couplings for
electrical power or low bandwidth data signals are generally accomplished
through the use of
ohmic contact between corresponding pins of two heads, each head mounted to a
pair of
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coupled mechanical couplers. Without intensive signal conditioning, such
electrical couplings
are limited to conveying electrical power or low bandwidth data signals of
less than one
megabit per second because of a large difference between the impedance of high-
speed data
cable and the impedance of the pins and of the junction between the pins. Such
coarse pin
connections are also subject to electrical radiation and interference due to
the large spacings
between adjacent pins of a head. An electrical coupling through the use of
pins is considered a
quick-disconnect coupling, in that the electrical coupling is quickly broken
when the
mechanical couplers are uncoupled.
[0004] There is a need to provide higher bandwidth data communications between
cars that are
connected together to form a train, i.e., a "consist". Providing, for example,
real time video
observation of the interior of one or more cars, real time observation of a
multitude of system
monitoring data values and other data communications among cars requires a
data rate for data
transmissions between cars greater than 50-Mbit/sec and sometimes greater than
90-Mbit/sec.
The physical size, structure and environment of railroad couplers generally
limit the ability to
achieve such high data rate transfers through quick-disconnect pin couplings.
[0005] Other known methods of achieving high bandwidth data transfer between
cars include
using conventional RF communication. Conventional RF communication, however,
is subject
to interference and cross-talk between different consists because of the use
of a common carrier
frequency (e.g., 2.4-GHz in the case of 802.11g), especially when conventional
antenna
systems are used.
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SUMMARY OF THE INVENTION
[0006] The exemplary embodiments of the present invention provide a non-
contact data
connection that is adaptable to use in a mechanical rail car coupler
environment using
conventional electrical coupler heads. These embodiments utilize a primarily
magnetic field
coupling to communicate either baseband data or RF signals through a quick-
disconnect
electrical coupling device that can be easily mounted in an electrical coupler
head.
BRIEF DESCRII'TION OF THE DRAWINGS
[0007] The subject matter that is regarded as the invention is particularly
pointed out and
distinctly claimed in the claims at the conclusion of the specification. The
foregoing and other
objects, features, and advantages of the invention will be apparent from the
following detailed
description taken in conjunction with the accompanying drawings.
[0008] FIG. 1 is a cross-sectional view of a portion of two electrical coupler
heads
incorporating signal coupling units according to exemplary embodiments of the
present
invention;
[ooo9] FIG. 2 is an inter-car network architecture using baseband inter-car
coupling units
according to a first exemplary embodiment of the present invention;
[o01o] FIG 3 is an inter-car network architecture using RF based inter-car
coupling units
according to a second exemplary embodiment of the present invention;
[0011] FIG. 4 is a block diagram of a non-contact Ethernet baseband coupling
system
according to the first exemplary embodiment of the present invention,
including a segment
interface unit, a non-contact sending unit, and a non-contact receiving unit;
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[0012] FIG. 5 is a schematic diagram of the segment interface unit of FIG. 4;
[0013] FIG. 6 is a schematic diagram of the non-contact sending unit of FIG.4;
and
[0014] FIG. 7 is a schematic diagram of the non-contact receiving unit of FIG.
4; and
[0015] FIG. 8 is a graph of frequency response for the non-contact Ethernet
baseband coupling
system of FIG. 4.
DETAILED DESCRIPTION OF EMBODIMENTS
[0016] Exemplary embodiments of the present invention utilize one of two
different
approaches for transferring high-speed data across two coupled cars using a
signal coupling
system that neither requires nor uses ohmic contact between the cars. Each
approach is able to
carry, for example, 100-Mbit/sec Ethernet signals from one car to another
across signal
coupling units that are easily incorporated into a head of a mechanical train
coupler. The first
of these approaches directly couples the Ethernet baseband signal through
custom-designed
magnetics within each signal coupling unit that are used in combination with
specialized active
signal conditioning circuitry of the system. This approach is capable of full-
duplex Ethernet
communication at 100-Mbits/sec. The second of these approaches incorporates an
intermediate
conversion to a radio frequency (RF) signal, such as an IEEE 802.1 la wireless
format, that
operates in the vicinity of 5-GHz. The RF signal is transmitted across the
signal coupling units
through a specially designed short-range, near-field antenna-like coupling
arrangement within
each signal coupling unit. The RF approach is limited to half-duplex operation
at 54-Mbits/sec
(with standard equipment) or 108-Mbits/sec (with special non-standard
equipment) in one
direction at a time.
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[0017] FIG. 1 is a cross-sectional view of a portion of two heads 101 and 102.
Each head, 101
and 102, which includes an electrical insulator 103 and 104, respectively, is
mounted to a
mechanical coupler (not shown) of a car. At least one signal coupling unit
according to
exemplary embodiments of the present invention is mounted in each head 101 and
102. There
are two types of signal coupling units, non-contact sending units 105 and 108
and non-contact
receiving units 106 and 107. Each signal coupling unit includes electrical
coupling
components contained within a pin-shaped housing 109. The housing 109 is
easily mountable
within a cylindrical mounting opening in the head 101 and 102. In one
exemplary
einbodiment, the outer diameter of the housing is 0.7-inch, and because the
outer diameter of
the housing 109 is slightly larger than the outer diameter of a prior art pin,
the diameter of the
cylindrical mounting opening assigned to the housing is enlarged
appropriately. Each signal
coupling unit replaces a prior art pin. One non-contact sending unit 105 on a
car is paired, or
mated to, one non-contact receiving unit 106 on an adjacent, coupled car. In
FIG. 1, head 101
has one non-contact sending unit 105 and one non-contact receiving unit 107,
and head 102 has
one non-contact receiving unit 106 and one non-contact sending unit 108.
Sending unit 108
mates with receiving unit 107 and they constitute a pair. Sending unit 105
mates with
receiving unit 106 and they constitute another pair. A gap 120 appears between
the non-
contact sending unit 108 that is mounted in head 102 and the non-contact
receiving unit 107
that is mounted in head 101. The gap 120 also appears between the non-contact
receiving unit
106 that is mounted in head 102 and the non-contact sending unit 105 that is
mounted in head
101. The gap 120 is approximately 50-thousandths of an inch, or less. The
signal coupling
units of the invention, unlike prior art pins, do not come into physical
contact with its mate on
an adjoining car. Only an electromagnetic field bridges the gap 120 between
paired signal
coupling units. The above statements apply to the baseband coupling approach.
With the RF
coupling approach, the distinction between sender and receiver vanishes, and
only one pair of
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special pins (e.g., 105 and 106) is required to carry the signal. This
distinction comes about
because of the half-duplex nature of any single radio channel.
[0018] Referring now to FIGS. 1 and 2, the top pair of facing signal coupling
units, non-
contact sending unit 108 and non-contact receiving unit 107, carries data from
a car 202 on the
right to a car 201 on the left, while the bottom pair of signal coupling units
carries data in the
opposite direction. Two pairs of signal coupling units are used in the
Ethernet baseband
approach, which provides full-duplex communications. Only one pair of signal
coupling units
is used in the second approach, which converts to RF signal, resulting in half-
duplex
operations.
[0019] FIG. 2 illustrates a network architecture 200 coupling car 201 with car
202 of a consist,
which network architecture incorporates non-contact Ethernet baseband signal
coupling,
according to a first exemplary embodiment of the invention. A segment
interface unit 204 is
contained in a small box located within each car 201 and 202, and includes
active circuitry that
provides the correct signal amplitude and termination impedance for an intra-
car Local Area
Network (LAN) 206 wired in each car using conventional category-5 (CAT-5) or
CAT-5E
Ethernet cable. The segment unit interface 204 acts as an interface to the
Ethernet LAN cable,
provides further amplification of transmitted and received signals, and
contains the initial stage
of the equalization network for transmitted signals. Power is furnished to the
segment interface
unit 204 by means of surplus twisted wire pairs contained inside a CAT-5 cable
208. The
segment interface unit 204 furnishes power to the non-contact receiving unit
106 and the non-
contact sending unit 108 at a first end 250 of the car 202. A cable 210 and
212 connects the
segment interface unit 204 to the non-contact receiving unit 106 and to the
non-contact sending
unit 108, respectively. Preferably, cable 210 and 212 is twinax. There are no
other connectors
on the segment interface unit 204 in this embodiment other than those required
for the cables
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shown in the diagram. The segment interface unit 204 is coupled to a vehicle
information
controller 220. The vehicle information controller 220 acts as a controlling
intelligence behind
the subsystems that share data over the LAN 206. The vehicle information
controller 220 is
coupled to a switching hub 230 and to a second segment interface unit 234. The
second
segment interface unit 234 is coupled to a second set of non-contact coupling
units (not shown)
at a second end 252 of the car 202. The switching hub provides a place to
couple the various
devices that communicate over the LAN 206, and intelligently routing Ethernet
frames
according to their source and destination addresses. The segment interface
unit 204 is part of
the LAN 206, although it is not, strictly speaking, an Ethernet device. The
segment interface
unit 204 carries the Ethernet signal but does not have a media access control
address of its own.
[0020] FIG. 3 illustrates a network architecture 300 coupling car 301 with car
302 of a consist,
which network architecture incorporates RF signal coupling according to a
wireless network
standard such as IEEE 802.11. The RF-based network architecture 300 includes a
LAN 306.
The RF-based network architecture 300 has several similarities to the Ethernet
baseband
network architecture 200 illustrated in FIG. 2, but the segment interface unit
204 is replaced by
a wireless network bridge 304 and the twinax 210 is replaced by a high-
frequency coax 310.
The wireless network bridge 304 includes an RF transceiver and a network
adaptor. Another
difference is that the RF-based network architecture 300 includes power-over-
Ethernet adapters
362 and 364 that are coupled to the vehicle information controller 320, to the
switching hub
330, and to the wireless network bridge and second wireless network bridge
334. The power-
over-Ethernet adapters 362 and 364 place 48V DC on one of the unused twisted
pairs in the
CAT-5 cable, to deliver power to devices (such as the 802.11 bridge) that
communicate over
the LAN 306 while drawing their power from the LAN, according to IEEE standard
802.3af.
Inside each signal coupling unit 311 and 312 is a high-frequency, near-field
antenna (not
shown).
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[0021] In both the Ethernet baseband network architecture 200 and RF-based
network
architecture 300, a control signal 222 and 322 enables a vehicle information
controller 220 and
320, respectively, to disable the wireless coupling of the system at one or
both ends of the car
202 and 302. This feature prevents unintentional radiation of signals from an
uncoupled end of
the car 202 and 302, and also aids in consist enumeration.
[0022] FIG. 4 illustrates block diagrams of components that form a non-contact
Ethernet
baseband coupling system of the first exemplary embodiment. The segment
interface unit 204
is typically located inside a car 202. The non-contact sending unit 108 and
non-contact
receiving unit 106 are located outside the car 202. The non-contact sending
unit 108 and non-
contact receiving unit 106 include a coil 401 and 402, respectively. In one
exemplary
embodiment, the coil 401 and 402 has a diaineter of 0.6-inch. Coil 401 of the
non-contact
sending unit 108 (located at car 202) and a coil similar to coil 402 but in
the non-contact
receiving unit 107 (located at the adjacent, coupled car 201) form a
transfonner. Likewise, coil
402 of the non-contact receiving unit 106 (located at car 202) and a coil
similar to coil 401 but
in the non-contact sending unit 105 (located at the adjacent, coupled car 201)
form a second
transformer. The non-contact receiving unit 106 and the non-contact sending
unit 108 are
connected to the segment interface unit 402 through shielded differential
signal cables 210 and
212, respectively. The segment interface unit 204 provides connections to
power and to the
LAN 206 routed throughout the car 202.
[0023] Equalization circuits 411, 412 and 413 (the first located in the
segment interface unit
402 and the second two in the non-contact sending unit 108) together perform
frequency
equalization for the transmit path, compensating for the high-pass response of
the transformer.
The line matching and power injection circuits 421 and 422 provide line
termination
(impedance matching) and power injection for the non-contact sending unit 108
and for the
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non-contact receiving unit 106. The line matching and power extraction
circuits 431 and 432
provide line termination (impedance matching) and power extraction for the non-
contact
sending unit 108 and for the non-contact receiving unit 106. A send amplifier
442, located in
the non-contact sending unit 108, boosts the power of the transmitted Ethernet
signal for the
purpose of driving the primary winding, coil 401, of the transformer. A
receive amplifier 451,
located in the non-contact receiving unit 106, amplifies the attenuated
Ethernet signal picked
up by the secondary, coil 402, of the transformer, boosting the Ethernet
signal for transmission
back to the segment interface unit 402. A transformer load 404 is connected
between the
receive amplifier 451 and the coil 402. Voltage regulator circuits 461 and 462
(one in the non-
contact sending unit 108 and one in the non-contact receiving unit 106) take
unregulated power
from the line matching and power extraction circuits 431 and 432, and present
a constant
voltage to the power terminals of the send amplifier 442 and of the receive
amplifier 451,
respectively. The send amplifier 471, located in the segment interface unit
402, provides the
proper source impedance and signal voltage levels for driving the differential
shielded cable
212 that connects the non-contact sending unit 108 to the segment interface
unit. Receive
amplifiers 472 and 473, located in the segment interface unit 402, boost the
receive signal to a
2V peak-to-peak level required for driving the Ethernet LAN (CAT-5) cable
connection.
Isolation transformers 474 and 476, located in the segment interface unit 402,
are standard
printed-circuit-mounting Ethernet transformers similar to those used on
network interface cards
in personal computers. The isolation transformers 474 and 476 provide
protection from stray
voltages picked up on the CAT-5 cable through misconnection, static discharge,
or
electromagnetic interference. A voltage regulator circuit 477 provides
regulated voltages to the
other circuits in the segment interface unit 402, and provides an intermediate
power bus for
delivering power to the non-contact sending unit 108 and the non-contact
receiving unit 106.
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The segment interface unit 204 uses Data Terminal Equipment (DTE) transmit and
receive
connections.
[0024] FIG. 5 illustrates a schematic 500 of the segment interface unit 402.
The segment
interface unit 402 connects to 100-baseT Ethernet routed through the car 202
and connects to
power. These connections are illustrated on the right side of schematic 500.
The segment
interface unit 402 connects to the non-contact receiving unit 106 and to the
non-contact
sending unit 108 througli the twinax connectors 210 and 212, respectively, as
illustrated on the
left side of schematic 500. The segment interface unit 402 acts as an
interface to the Ethernet
LAN cable 208; provides further amplification of transmitted and received
signals; performs
the initial stage of equalization for transmitted signals; and furnishes power
to the non-contact
sending unit 108 and the non-contact receiving unit 106.
[0025] FIG. 6 illustrates a schematic 600 of the non-contact sending unit 108.
The non-contact
sending unit 108 connects to the segment interface unit 402 through a twinax
connector 212
shown on the left side of schematic 600, and includes a transformer primary,
the coi1401,
shown on the right side of the schematic. This loosely coupled transformer is
formed across
the two heads 101 and 102, each head attached to a different mechanical
coupler.
[0026] FIG. 7 illustrates a schematic 700 of the non-contact receiving unit
106. The non-
contact receiving unit 106 includes a connection to an "Xfinr", as illustrated
on the left side of
scheinatic 700. The "Xfinr" is a transformer secondary, i.e., coi1402, that
forms the loosely
coupled transformer with the transformer primary, as discussed above. The non-
contact
receiving unit 106 provides an output, as shown on the right side of schematic
700, through the
shielded twinax 212 to the segment interface unit 402.
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[0027] FIG. 8 is a graph 800 of a frequency domain transfer function for a
signal coupled
through the Ethernet baseband coupling of the first exemplary embodiment of
the present
invention. The x-axis signifies frequency. The left y-axis signifies
magnitude. The right y-
axis signifies phase. In FIG. 8, four curves are shown. They are: a "V(out),
magnitude" 801,
which is a simulated magnitude of the output of the receive amplifier 473 in
the segment
interface unit 204; a "V(out), phase" 802, which is a simulated phase of the
output of the
receive amplifier 473 in the segment interface unit 204; a "V(x4s+), phase",
which is a
simulated phase of the output of a cascaded pair of packaged commercial
Ethernet
transformers; and a "V(x4s+), magnitude", which is a simulated magnitude of
output of a
cascaded pair of packaged commercial Ethernet transformers. The simulated
outputs of the
packaged commercial Ethernet transformer are shown for comparison purposes.
The
contactless data communications coupling system of the invention has
successfully coupled an
Ethernet baseband signal through an air gap of up to 50-thousandths of an
inch, and it may be
possible to couple an Ethernet baseband signal through an air gap of up to 150-
thousandths of
an inch. FIG. 8 illustrates that the frequency response 801 and 802 for the
contactless data
communications coupling system of the invention advantageously closely
approximates the
coupling characteristics of a prior art Ethernet transformer pair. It should
be noted that the size
of the gap 120 across which the contactless data communications coupling
system of the
invention can successfully couple an Ethernet signal is dependent, in part, to
the diaineter of
the coil 401 and 402, and increases as the diameter increases. The
transmission distance can
also be increased by adding gain to the receive amplifier chain in the segment
interface unit
402 and by adding an automatic gain control.
[0028] Advantageously, once the cars of a consist, such as cars 201 and 202,
are joined
together and the network devices in various cars have found one another and
established
communications, a train-wide network is formed and effectively functions as a
single LAN.
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[0029] It is important to note, that these embodiments are only examples of
the many
advantageous uses of the innovative teachings herein. In general, statements
made in the
specification of the present application do not necessarily limit any of the
various claimed
inventions. Moreover, some statements may apply to some inventive features but
not to others.
In general, unless otherwise indicated, singular elements may be in the plural
and vice versa
with no loss of generality.
[003o] Although a specific embodiment of the invention has been disclosed, it
will be
understood by those having skill in the art that changes can be made to this
specific
embodiment without departing from the spirit and scope of the invention. The
scope of the
invention is not to be restricted, therefore, to the specific embodiment, and
it is intended that
the appended claims cover any and all such applications, modifications, and
embodiments
within the scope of the present invention.
