Abstract:
The exemplary embodiments of the present invention provide a high-speed contactless data coupling that is adaptable to use with mechanical rail car couplers. The exemplary embodiments utilize a primarily magnetic field coupling to communicate either baseband data or RF signals through a pair of signal coupling units that do not need to contact either other, which can be easily housed in two heads attached to each of two mechanical rail car couplers.

Description:
RELATED APPLICATION 
       [0001]    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 Jul. 7, 2005, and assigned Ser. 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 
       [0002]    1. Field of the Invention 
         [0003]    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. 
         [0004]    2. Description of the Related Art 
         [0005]    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 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. 
         [0006]    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. 
         [0007]    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. 
       SUMMARY OF THE INVENTION 
       [0008]    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 DESCRIPTION OF THE DRAWINGS 
         [0009]    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. 
           [0010]      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; 
           [0011]      FIG. 2  is an inter-car network architecture using baseband inter-car coupling units according to a first exemplary embodiment of the present invention; 
           [0012]      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; 
           [0013]      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; 
           [0014]      FIG. 5  is a schematic diagram of the segment interface unit of  FIG. 4 ; 
           [0015]      FIG. 6  is a schematic diagram of the non-contact sending unit of  FIG. 4 ; and 
           [0016]      FIG. 7  is a schematic diagram of the non-contact receiving unit of  FIG. 4 ; and 
           [0017]      FIG. 8  is a graph of frequency response for the non-contact Ethernet baseband coupling system of  FIG. 4 . 
       
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
       [0018]    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 802.11a 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. 
         [0019]      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 embodiment, 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 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. 
         [0020]    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. 
         [0021]      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 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. 
         [0022]      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). 
         [0023]    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. 
         [0024]      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 diameter 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 transformer. 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 . 
         [0025]    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 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 . The segment interface unit  204  uses Data Terminal Equipment (DTE) transmit and receive connections. 
         [0026]      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  through 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 . 
         [0027]      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 coil  401 , 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. 
         [0028]      FIG. 7  illustrates a schematic  700  of the non-contact receiving unit  106 . The non-contact receiving unit  106  includes a connection to an “Xfmr”, as illustrated on the left side of schematic  700 . The “Xfmr” is a transformer secondary, i.e., coil  402 , 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 . 
         [0029]      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 diameter 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. 
         [0030]    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. 
         [0031]    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. 
         [0032]    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.