Abstract:
The present invention relates to the use of RFID technology to identify specific cables in a bundle, and in particular to a cable identification device in which RFID devices are connected to the far end of a plurality of cables and splitters, and an RF measurement device is used to identify each cable from the central location. The RF measurement device provides the AC RF electrical signal power required to pass through the at least one AC couple splitter to operate the plurality of RFID devices, and includes means to identify the unique identification numbers associated with the plurality of coaxial cables from the plurality of identification signals received simultaneously.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    The present invention claims priority from U.S. Patent Application No. 60/950,442 filed Jul. 18, 2007, which is incorporated herein by reference. 
     
    
     TECHNICAL FIELD 
       [0002]    The present invention relates to the use of radio frequency identification (RFID) technology to identify specific cables in a bundle, and in particular to a cable identification system in which RFID devices are connected to the far end of a plurality of cables and splitters, and an RF measurement device is used to identify each cable from a central location. 
       BACKGROUND OF THE INVENTION 
       [0003]    When wiring a house or a building the coax cable network is installed prior to the mounting of the dry wall being, and the network installation is completed after the dry wall has been finished. Accordingly, a technician is faced with a bundle of unlabeled cables hanging in a wiring closet, and their task is to identify each cable, label them, and connect them to the appropriate service. Install technicians from service providers are faced with a similar problem when installing a new service in a home. Typically, there is a group of cables that enter at a side of a house which terminate somewhere within the house, and it is important for a technician to be able to quickly and positively identify where each cable goes, so that new devices and services can be installed quickly and correctly. 
         [0004]    Currently resistive based devices are used to perform the task of cable identification; however, in coax based systems, splitters prevent this technique from working effectively. Moreover, resistive devices are limited to less than thirty unique identifiers. Conventional systems that are able to work through splitters are based on active devices that are large, expensive and require batteries. 
         [0005]    Conventional RFID systems include RFID tags positioned on everything from employees badges to carcasses of meat, and RFID readers positioned at specific stations or points of entry for reading the RFID tags, as they pass by in close proximity thereto. The RFID tags provide specific information about the item they are attached to the RFID reader to store, tabulate or act upon, e.g. allow access. 
         [0006]    RFID tags are tiny microchips with memory and an antenna coil, which can be thinner than paper, e.g. only 0.3 mm across. RFID tags listen for a radio signal sent by the RFID reader. When an RFID tag receives the radio signal query, it responds by transmitting a unique identification code and other data back to the RFID reader. 
         [0007]    There are two types of RFID tags: passive RFID tags, and active RFID tags. Passive RFID tags can be as small as 0.3 mm and don&#39;t require batteries, as they are powered by the radio signal of the RFID reader, which “wakes them up” to request a reply. Passive RFID tags can be read from a distance of about 20 feet. Semi-passive RFID tags contain a small battery that boosts the range. Passive tags are generally read-only, meaning the data they contain cannot be altered or written over. Active RFID tags, also called transponders, because they contain a transmitter that is always “on”, are powered by a battery, about the size of a coin, and are designed for communications up to 100 feet from the RFID reader. Active RFID tags are larger and more expensive than passive RFID tags, but can hold more data about the product, and are commonly used for high-value asset tracking. Active RFID tags may be read-write, i.e. data contained therein can be written over. 
         [0008]    RFID readers are used to query RFID tags in order to obtain identification, location, and other information about the device or product to which the tag is attached. RF energy from an antenna on the RFID reader is collected by the antenna on the RFID tag and used to power up the microchip on the RFID tag. 
         [0009]    There are two types of RFID readers: RFID read-only readers and RFID read-write readers. RFID read-only readers can only query or read information from a nearby RFID tag, and are found in fixed, stationery applications, as well as portable, handheld varieties. RFID read-write readers, also known as encoders, read and also write, i.e. change, information in an RFID tag. Such RFID encoders can be used to program information into a “blank” RFID tag. A common application is to combine an RFID reader with a barcode printer to print “smart labels”, which contain a UPC bar code on the front and an RFID tag embedded on the back. 
         [0010]    The antennas on the RFID reader and the RFID tag each have a coil, which together form a magnetic field. The RFID tag draws electrical energy from this field, which powers the microchip therein. The microchip then changes the electrical characteristics of the tag antenna, which are sensed up by the reader antenna and converted into a serial number for the RFID tag 
         [0011]    There are 4 major frequency ranges that RFID systems operate at. Normally, low-frequency systems are distinguished by short reading ranges, slow read speeds, and lower cost. Higher-frequency RFID systems are used in which longer read ranges and fast reading speeds are required, e.g. vehicle tracking and automated toll collection. Microwave frequencies requires the use of active RFID tags. 
         [0000]    
       
         
               
               
               
               
             
           
               
                   
               
             
             
               
                 Low-frequency 
                 3 feet 
                  $1+ 
                 Pet and ranch animal identification; 
               
               
                 125-148 KHz 
                   
                   
                 car keylocks 
               
               
                 High-frequency 
                 3 feet 
                  $0.50 
                 library book identification; 
               
               
                 13.56 MHz 
                   
                   
                 clothing identification; smart cards 
               
               
                 Ultra-high freq 
                 25 feet  
                  $0.50 
                 Supply chain tracking: 
               
               
                 915 MHz 
                   
                   
                 Box, pallet, container, trailer 
               
               
                   
                   
                   
                 tracking 
               
               
                 Microwave: 
                 100 feet  
                 $25+ 
                 Highway toll collection; 
               
               
                 2.45 GHz 
                   
                   
                 vehicle fleet identification 
               
               
                   
               
             
          
         
       
     
         [0012]    The 13.56 MHz solution was developed in an effort to lower the cost of RFID tags, and address applications of high quantity tags usage. At 13.56 MHz, a tag&#39;s antenna coil need not be made of hard copper wrappings, and can actually be a printed ink on a paper-like substrate, to which an EEPROM is added. Typical applications include: library books, laundry identification, access control, OEM applications. 
         [0013]    Both power and bi-directional communications form the air interface between the RFID tags and the reader device. It is the flexibility of the interface to select one or two sub-carriers when communicating from RFID tags to reader device, whilst also using slow or fast data rates from the reader device to the RFID tags, that allows systems to be tuned to suit different operational requirements ranging from use with high RF noise at short range to low RF noise at long range. ISO/IEC 15693 forms part of a series of International Standards that specify a vicinity or contactless tag. ISO/IEC 15693-2:2006 defines the power and communications interface between the tag and the reading device. Other parts of ISO/IEC 15693 define the physical dimensions of the tag and the commands interpreted by the tag and reading device. 
         [0014]    Published WIPO Application WO90/16119, entitled Cable Identification System and Method, filed by Brent James, teaches probing each individual coaxial cable at the junction box using a one-to-one communication protocol powered by DC electricity. Unfortunately, the reading device is unable to supply DC power to a plurality of identification devices across a splitter, which is AC coupled. Consequently, the James reference teaches probing one RFID at a time with DC power and with no splitters in the line, whereby sufficient power is available from the test meter to operate the RFID. 
         [0015]    An object of the present invention is to overcome the shortcomings of the prior art by providing a passive RFID device to identify installed cables even if the cable has splitters or actives inline using a communication protocol enabling many devices to be read simultaneously. Accordingly, all the identification devices on all the coaxial cable ends can be probed in a single operation. 
       SUMMARY OF THE INVENTION 
       [0016]    Accordingly, the present invention relates to a system for simultaneously determining locations of a plurality of coaxial cable outlets connected to a coaxial cable inlet with at least one AC coupled splitter therebetween, comprising: 
         [0017]    a cable identification device connected to each of the plurality of coaxial cables outlets, wherein each cable identification device comprises: 
         [0018]    an integrated circuit having a unique identification number stored in electronic memory for association with a respective one of the coaxial cable outlets; 
         [0019]    a power converter for converting an AC RF electrical test signal into power to operate the integrated circuit; and 
         [0020]    a responsive circuit for sending a response signal including an RF identification signal containing the unique identification number upon receiving the test signal; and 
         [0021]    a reader device for positioning at the coaxial cable inlet for sending the AC RF electrical test signal to each of the cable identification devices, and for receiving the response signals from the cable identification devices; 
         [0022]    wherein the reader device provides the AC RF electrical test signal with enough AC RF electrical signal power required to pass through each AC coupled splitter to operate the plurality of cable identification devices; and 
         [0023]    wherein the reader device stores or displays the unique identification numbers associated with each of the cable identification devices from the plurality of RF identification signals received. 
         [0024]    Another aspect of the present invention relates to a method of mapping a cable network, which includes: a plurality of coaxial cable branches extending from a network input; at least one AC coupled splitter; a plurality of sub-branches extending from each AC coupled splitter; and an outlet at the end of each sub-branch, comprising the steps of: 
         [0025]    a) connecting a plurality of RF cable identification devices to each of the outlets; 
         [0026]    b) sending an AC RF electrical test signal from a reader device positioned at the network input onto one of the cable branches through any AC coupled splitters to the plurality of RF cable identification devices at the outlets thereof, each of which in response thereto sends a response signal with an RF identification signal containing a unique identification number back to the reader device; 
         [0027]    c) identifying the unique identification numbers associated with the outlets from the plurality of identification signals received; 
         [0028]    d) repeating steps b) and c) for each of the other cable branches; and 
         [0029]    e) mapping the cable network for storage in memory or display. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0030]    The invention will be described in greater detail with reference to the accompanying drawings which represent preferred embodiments thereof, wherein: 
           [0031]      FIG. 1  is a schematic diagram of a CATV network in a building; 
           [0032]      FIG. 2   a  is a schematic of an RFID device in accordance with  FIG. 1 ; 
           [0033]      FIG. 2   b  is a side view of the RFID device of  FIG. 2   a ; and 
           [0034]      FIG. 3  is a schematic diagram of a CATV network from a network interface device to a building; 
       
    
    
     DETAILED DESCRIPTION 
       [0035]    With reference to  FIG. 1 , a unique radio frequency identification (RFID) device  11   a  to  11   e  is connected to the far end of each coax cable  12   a  to  12   e  in each room of a building  13  temporarily or permanently by a technician, who records the location and unique identifier of each RFID device  11   a  and  11   e . A radio frequency (RF) measurement device  14  is located by the technician in a position in which all the coax cables  12   a  to  12   e  from the building  13  converge, e.g. a wiring closet  16  or a side of the building  13 . Sometime during the process, the technician enters which RFID device  11   a  to  11   e  correspond to which location and room in the building  13  into the RF measurement device  14 . Subsequently, the RF measurement device  14  is connected to each coax cable  12   a  to  12   e  consecutively in turn, and the RF measurement device  14  sends a radio frequency (RF) test signal down each coax cable  12   a  to  12   e  to the respective RFID device  11   a  to  11   e . Each RFID device  11   a  to  11   e  receives the test signal and generates a response signal, which is transmitted back down the coax cable  12   a  to  12   e  under test, and received by the RF measurement device  14 . The RF measurement device  14  detects the presence of each uniquely numbered RFID device  11   a  to  11   e  connected to each cable  12   a  to  12   e , thereby enabling the technician to quickly identify marked and unmarked cables, even if those cables have splitters or actives inline. With the knowledge of where the far end of each cable is, the technician can quickly connect the proximate ends of the cables to the correct locations in the wiring closet  15 , label each cable, and test individual cables, as required. 
         [0036]    Passive RFID devices  11   a  to  11   e  have no internal power supply. A small amount of electrical current is induced in an antenna on the RFID device  11   a  to  11   e  by the incoming RF test signal from the RF measurement device  14 , which provides just enough power for a CMOS integrated circuit in the RFID devices  11   a  to  11   e  to power up and transmit the response signal. Preferably, the RFID devices  11   a  to  11   e  transmit the response signal by backscattering the carrier signal from the incoming RF test signal, which is modulated to transmit data. Accordingly, the antenna on the RFID devices  11   a  to  11   e  has to be designed to both collect power from the incoming RF test signal, and to transmit the backscatter response signal. The response of the passive RFID devices  11   a  to  11   e  is not necessarily just an ID number; the tag chip can contain non-volatile EEPROM for storing data. Each RFID device  11   a  to  11   e  has a label with a simple identification number (1-8) printed thereon. The user of the system expect these simple identification numbers on the reader. The RFID device&#39;s simple identification number is stored in the EEPROM, and read out when an RFID device is found. Non-silicon ID devices made from polymer semiconductors are currently being developed by several companies globally. 
         [0037]    The RF measurement device  14  emits an AC power test signal at a suitable frequency, e.g. between 5 MHz and 25 MHz, but 13.56 MHz according to ISO/IEC 15693-3 protocol, which is incorporated herein by reference, is preferable. With reference to  FIGS. 2   a  and  2   b , in accordance with a preferred embodiment of the present invention, the RFID devices  11   a  to  11   e  include an RFID tag  16  placed over a small antenna  17  etched on a PC board  18 . The PC board  18  is coupled to an F-Type connector  19 , which is pluggable into the coax network to be tested. The RF measurement device  14  sends the 13.56 MHz test signal to the antenna  17  on each of the RFID devices  11   a  to  11   e , simultaneously if connected to the same cable, e.g.  12   a  and  12   b , and in succession for the different cables, via the coax cables  12   c  to  12   e . The RF power test signal must have a frequency that enables the propagation of electromagnetic waves through the co-axial cable  12   a  to  12   e  and the AC coupled splitters with low loss. The RFID devices  11   a  to  11   e  are comprised of a small integrated circuit (IC), which is powered via the power test signal. In most applications of RFID devices, the radio frequency signals propagates through air; however, the 13.56 MHz signal frequency is selected for the test signal in the present invention because this frequency propagates through the co-axial cable  12   a  to  12   e , and the RFID devices  11   a  to  11   e  operate at a very low power. Furthermore, the RFID devices  11   a  to  11   e  are mass produced for other applications and are available commercially at a very low cost. 
         [0038]    Power is coupled to the RFID device  11   a  to  11   e  by an AC field produced in the RF measurement device  14 , the powering field has a frequency of 13.56 MHz, which is one of the industrial, scientific and medical (ISM) frequencies available for worldwide use. When sufficient power is received by the RFID devices  11   a  to  11   e , they are able to respond to commands sent from the RF measurement device  14 . The RF measurement device  14  sends commands to the RFID devices  11   a  to  11   e  by modulating the powering field and by using a modulation system known as pulse position modulation, whereby the position of a single pulse relative to a known reference point codes the value of a nibble or byte of data, which enables the RFID device  11   a  to  11   e  to draw the maximum energy from the field almost continuously. 
         [0039]    An RFID device  11   a  to  11   e  only respond after receiving a valid command that selects a single RFID device from a possible collection of RFID devices connected to the RF measurement device  14 , i.e. connected to the end of the selected cable  12   a  to  12   e  directly or through a splitter. The process of collision detection and selection, also known as anti-collision, is made possible by detecting the unique identification number encoded into every RFID device  11   a  to  11   e . Anti-collision and the commands used are defined in ISO/IEC 15693-3. The ISO 15693 standard defines a algorithm for the response, such that the devices generally don&#39;t response simultaneously, they respond in an address slot. The ISO 15693 standard algorithm also defines a method for handling the collision caused by RFIDs that respond simultaneously, which can occur if the RFID devices  11   a  to  11   e  have similar unique identification numbers. 
         [0040]    The RFID device  11   a  to  11   e  responds to the RF measurement device  14  by drawing more or less power from the field and generates one or two sub-carriers of around 450 kHz, which are switched on and off to provide Manchester-encoded data that are then detected by the RF measurement device  14 . 
         [0041]    Each RFID device  11   a  to  11   e  has a laser tuned tank circuit with a rectifier circuit, which will efficiently convert the test power signal to a DC supply voltage to power the IC. Each RFID device  11   a  to  11   e  is manufactured with a unique ID embedded in its memory. However, in the invention the RF measurement device  14  can provide sufficient power to operate all the RFID devices, e.g.  11   a  and  11   b , that are connected to the RF measurement device  14  via the connected coaxial cables, e.g.  12   a  and  12   b , having splitters in the line. Thus all the cable ends are identified in one operation. 
         [0042]    When the IC in each of the RFID devices  11   a  to  11   e  is powered up they will listen for commands from the RF measurement device  14 , i.e. the source of the 13.56 MHz test signal. The RF measurement device  14  sends commands to the RFID devices  11   a  to  11   e  through modulation of the test signal. Each RFID device  11   a  to  11   e  can respond to a number of commands, but the command of interest in accordance with the present invention is an inventory command. When any one of the RFID devices  11   a  to  11   e  receives an inventory command, the RFID device  11   a  to  11   e  will respond with a unique identification (ID) signal including the respective unique ID. The ID response signal is sent via a serial data stream by modulating a transistor connected to the tank circuit. The transistor is configured to short out the tank circuit and cause a standing wave pattern that an integrated circuit IC in the RF measurement device  14  can detect and decode, i.e. the RFID devices  11   a  to  11   e  never transmits a signal of their own. 
         [0043]    A relative signal strength index (RSSI) value can also be read by the measurement device  14  from the response signal. The RSSI is used as an indicator of the loss between the measurement  14  and the RFID devices  11   a  to  11   e.    
         [0044]    In a simple embodiment, the technician only sees the unique identification numbers on a cable under test, e.g. 1 thru 8, on the display screen of the measurement device  14 , and then references a previously filled memory location in the measurement device  14  to get the corresponding position of the RFID device  11   a  to  11   e , whose identification number is displayed on the measurement device  14 . Alternatively, the corresponding position to identification number mapping can also be done by control software/hardware inside the measurement device  14 . 
         [0045]    The information is then saved in memory on the RF measurement device  14  and/or displayed on a display screen provided on the RF measurement device  14  to inform the user which of the RFID devices  11   a  to  11   e  are connected to the particular cable  12   a  to  12   e , and therefore where the end of the particular cable is located in the building  13 . If two or more RFID devices  11   a  to  11   e  respond, then the user knows that the coax network must contain RF splitters. During installation, it is important that the user find a cable run that contains no splitters for residential gateways and/or very high speed digital subscriber lines (VDSL) to maximize throughput and minimize losses caused by splitters. 
         [0046]    With reference to  FIG. 3 , a home network  20  is illustrated extending from the network&#39;s inlet, i.e. a network interface device (NID)  21 , to four main branches  22  to  25 , three of which divide into eight sub-branches  23   a ,  23   b ,  24   a ,  24   b ,  24   c ,  25   a  and  25   b  via a first, e.g. high quality, splitter  26  and second and third, e.g. low quality, splitters  27   a  and  27   b . The network&#39;s inlet can be anywhere in the network from which one or more cables originate and terminate elsewhere, but typically is the location at which the coaxial cable enters the building from the exterior at some form of junction box. In use, an installation technician places an RFID device  28   a  to  28   h  (same as  11   a  to  11   e  above) at an outlet at the end of each branch or sub-branch, e.g. on each wall jack in the house, and records where, e.g. which location and/or room, each outlet and RFI device  28   a  to  28   h  are located. Then the technician relocates to the NID  21 , located inside or outside the house, and performs a cable ID test by initiating the AC RF test signal from an RF measurement device  14  on each one of the branches  22  to  25  sequentially. The results of the test identifies, which sub-branches  23   a ,  23   b ,  24   a ,  24   b ,  24   c ,  25   a  and  25   b  are connected to each branch  22  to  25 , and to which locations in the house the sub-branches  23   a ,  23   b ,  24   a ,  24   b ,  24   c ,  25   a  and  25   b  extend. In  FIG. 2 , the cable branch  22  would respond with a single ID signal, the cable branches  23  and  25  would respond with two ID signals, i.e. indicating the presence of the second and third splitters  27   a  and  27   b , and the cable branch  24  would respond with three ID signals, i.e. indicating the presence of the first splitter  26 . The RF measurement device  14  is able to differentiate between the different ID signals simultaneously being transmitted thereto. 
         [0047]    The NID  21  includes a VDSL balun  31 , which is a passive electronic device that converts between balanced and unbalanced electrical signals; a diplexer  32 , which directs incoming signals to a main splitter  33  and which directs incoming and outgoing signals to and from a residential gateway (RG)  34  or host computer for internet access. Ideally the cable branch  22  that extends from the Diplexer  32  to the RG  34  must be a home run (minimal loss) due to the affect loss has on the data rates of VDSL.