Abstract:
The present invention comprises a device which may be attached to a cable ground block ( 62 ) such that the level and type for signal emitted through the upstream flow of the signal, from a residence or business ( 59 ), may be determined along with the location of the source of ingress of any such signals. The invention, further includes a device ( 10 ) to transmit a signal of predetermined frequency towards a residence, such the source of errant signal ingress may be determined. Further, a method of causing the transmission of the signal at a predetermined time, measurement of the signal and determination of the source of the ingress of the signal is provided.

Description:
[0001]    This application claims the benefit of the early filing date of provisional application No. 60/204,584, filed May 16, 2000. 
     
    
     
       FIELD OF THE INVENTION  
         [0002]    The present invention concerns a device and method for determining the location and source of errant signals in a cable television system such that signals which cause interference upstream may be identified and eliminated at their source. More particularly, the present invention concerns a device which may be attached at the cable junction of a building, and the method of using the device and an electronic signal radiated at the building, to determine the location of ingress (to the system) of errant signals.  
         BACKGROUND OF THE INVENTION  
         [0003]    Cable television systems, or Community Access Television (CATV) systems, generally comprise a source of cable information (program), a headend, with such systems typically including a satellite receiving device, such as a satellite dish, and a network of cables connected between a cable facility and customers of the cable provider. These systems typically operate in the 50 MHz to 1 GHz spectrum for transmitting signals downstream from the cable source to the end consumer.  
           [0004]    The network of cables typically is provided adjacent to other utilities, such as telephone lines and electrical power cables. The network of cables reach homes and businesses from an overhead connection or through underground connections, depending on the means that the electrical and telephone service is provided in the area. In both situations, the cable access to a particular residence or business is provided via a local tap through a cable directed to the destination location, which cable is attached to a ground block and is then routed into the destination location.  
           [0005]    It is now a practice to also provide high-speed data communications via cable systems. The telecommunications industry has rapidly upgraded coaxial cable systems to facilitate bi-directional communications services. Bi-directional communications services include Plain Old Telephone Service (“POTS”), Internet access, high speed data exchange, interactive video, and other services. Upstream signals from the residence to the cable facility are typically transmitted in the 5 to 50 MHz spectrum. This facilitates two way communications. The upstream path is used with devices such as cable modems and special services devices, such as burglar alarms, fire alarms, and personal health monitors.  
           [0006]    While downstream CATV signals are typically of very high quality, upstream signals are more susceptible to noise and interference. Typically, downstream CATV signals are superior to upstream signals because each subscriber receives CATV signals from an individual tap connected directly from the cable system. On the upstream side, however, signal interference accumulates from each subscriber as the signals return towards the cable source.  
           [0007]    Because the upstream signals are all typically in the same frequency range, they are particularly susceptible to radio frequency (RF) energy ingress signals from everyday electrical devices. RF signals or ingress enter coaxial cables through weak points or leaks in the system and generally travel upstream. Such signals enter the coaxial network and combine with RF ingress from other points in the network on a power basis as the signals make their way through the network to the headend. The accumulation of errant ingress signals in the 5 to 50 MHz region can render a bi-directional system useless. It is, therefore, necessary to have an ingress integrity system that can detect the RF ingress and the location of RF ingress into the system.  
           [0008]    In a typical cable system, the upstream path uses digital signals which are susceptible to unreliable operation if interference signals are present. Examples of devices capable of causing interference are: CB radios, hair dryers, washing machines, food mixers, toasters, vacuum cleaners, and almost any home appliance that has a motor or a power switch. The interference may last for an instant or may be continuous while the device is on, but in either event can catastrophically effect the communication desired.  
           [0009]    Ingress problems in the upstream path are typically compounded by the multitude of residences connected to the CATV distribution system. Any one residence is capable of adding an interference signal to the upstream path and degrading and/or inhibiting communications. A multitude of residences, each only adding only a small amount of interference, can also render the upstream path useless because interference signals add on a power basis.  
           [0010]    Further, the CATV cabling inside a residence is typically hidden in areas such as crawl spaces, behind walls, attics, and basements. The effects of aging on the cable (especially metal connectors), damage caused by rodents, and possibly improper installation may reduce the shielding integrity of the system within the residence. Poor shielding integrity permits the inside cabling to essentially become a “receiving antenna” for interfering signals. A signal or noise entering (ingress) the internal cabling may travel upstream and cause problems.  
           [0011]    Currently, RF detection is accomplished by maintenance personnel in a vehicle driving around the cable plant (network of cables) with transmitters. The transmitters radiate a specific RF signal which can be identified when it leaks into the cable system. This approach is clumsy and unable to provide correlation between the ingress and the location of the mobile transmitter that is providing the test.  
           [0012]    U.S. Pat. No. 5,777,662, (the &#39;662 patent), assigned to the owner of the subject invention, Comsonics Corporation of Harrisburg, Va., discloses a system for radiating a signal for capture by cable systems having ingress and egress problems. The system of the &#39;662 patent utilizes a signature RF signal with a GPS (Global Positioning Satellite) signal encoded therein, thus allowing the upstream cable distribution system to determine if an ingress is occurring and, by analysis of the GPS data, the location of the ingress. It is believed that more precise GPS signals would provide more accurate determination of the house or business that is the source of the ingress. However, without a more precise GPS signal, it is still necessary to determine the source of the signal by surveying all of the houses or businesses in the area of the signal. Further, past systems do not allow for the easy determination of the precise location of the ingress source within a house or business.  
           [0013]    Because all residences and business locations have the potential to cause problems in the upstream path, a test is needed to qualify each individual residence.  
         SUMMARY OF THE INVENTION  
         [0014]    In accordance with the present invention, a method of determining the location of an ingress of errant signals into a cable system is provided. The method comprises the steps of providing a transmitter and an antenna for radiating an RF signal of a desired frequency, and providing a shielded receiver at the cable entry location of a test site. The receiver includes a tuner, a signal detector, and a display responsive to signals of a particular frequency that pass solely through the cable system of the test site. The method further comprises the step of radiating a signal of the particular frequency and observing a display device, for an indication that errant signals are entering the cable system in a house, business or other cable subscriber location.  
           [0015]    In a preferred embodiment, the method is adapted for use in a test site having a plurality of cable connections, such as a plurality of televisions, or cable modem locations in different rooms having a plurality of cables leading from a single hub to each device. The method includes the steps of individually and temporarily disconnecting any one of the plurality of cable connections in the test site and radiating an RF signal of the desired frequency so as to observe the display for reaction showing an ingress of errant signals into the system.  
           [0016]    In a preferred embodiment, the method includes the steps of providing an activation encoder and an activation transmitter in the receiver, and further providing an activation receiver and an activation decoder in the transmitter, such that the receiver may signal the transmitter to transmit a signal of a desired frequency, which may be received by the receiver.  
           [0017]    Further, in accordance with the present invention, the receiving device for use in measuring the ingress of errant signals of a predetermined frequency range includes an input tuner section for filtering upstream signals and a signal detector in communication with the input tuner. The receiving device further includes an errant signal display in communication with the signal detector, a connector for connecting the receiving device to the cable system cable ground block.  
           [0018]    In a preferred embodiment of the receiving device, an antenna, an activate transmitter and an activate encoder are provided, such that the receiving device may specifically activate the transmitter such that ingress of a coded signal is detected.  
           [0019]    Further, in accordance with the present invention, a transmitting device for radiating a test location with signals of a predetermined frequency is provided. The transmitting device radiates an errant test signal which is captured by the receiving device In a preferred embodiment, the transmitting device includes an antenna, a signal filter in electrical communication with the antenna, and a test signal transmitter for radiating a signal of a desired frequency. The transmitting device further includes a transmitter enable switch for permitting the powering-up of the transmitter, an activation receiver for receiving an activation signal from a distant test device (e.g. the receiver) and an activation decoder connected to the activation receiver. The antenna of the transmitting device may receive an activation signal through the filter. In this manner, upon receipt of the activation signal from the test device, the activation decoder causes the transmitter enable switch to permit the powering-up of the test signal transmitter for test signal production. The test signal transmitter creates a signal of the desired frequency, and the signal filter feeds the signal to the antenna for radiation to the coaxial cable system.  
           [0020]    A more detailed explanation of the invention is provided in the following description and claims and is illustrated in the accompanying drawings.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0021]    [0021]FIG. 1 is a pictorial of a test setup of the present invention.  
         [0022]    [0022]FIG. 2 is a block diagram of a transmitter device of the present invention.  
         [0023]    [0023]FIG. 3 is a block diagram of a receiver device of the present invention.  
         [0024]    [0024]FIG. 4 is a pictorial representation of an overhead routing of a CATV distribution system, to a private residence.  
         [0025]    [0025]FIG. 5 is a pictorial representation of an underground routing of a CATV distribution system to a private residence.  
         [0026]    [0026]FIG. 6 is a pictorial representation of an embodiment of a display device of the receiver of the device of FIG. 3.  
         [0027]    [0027]FIG. 7 is a pictorial representation of another embodiment of a display device of the receiver of the device of the FIG. 3.  
         [0028]    [0028]FIG. 8 is a pictorial representation of an alternate test setup of the present invention.  
         [0029]    [0029]FIG. 9 is a pictorial representation of coded test setup of the present invention. 
     
    
     DETAILED DESCRIPTION  
       [0030]    While the present invention is susceptible of embodiment in various forms, there is shown in the drawings a number of presently preferred embodiments that are discussed in greater detail hereafter. It should be understood that the present disclosure is to be considered as an exemplification of the present invention, and is not intended to limit the invention to the specific embodiments illustrated. It should be further understood that the title of this section of this application (“Detailed Description”) relates to a requirement of the United States Patent Office, and should not be found to limit the subject matter disclosed herein.  
         [0031]    Referring to FIGS. 1, 4 and  5 , a cable system  9  and an ingress detection system  10  are shown. The ingress detection system  10  includes a transmitter  11  for radiating a specific radio frequency (RF) signal. The transmitter  11  is mounted in and powered from a service vehicle  12 . A radiating antenna  14  is connected to the transmitter  11  and may be mounted on the vehicle&#39;s roof  12   a . Preferably, the antenna  14  is placed in a location free of other metallic objects so as to produce a clear unimpeded signal. It is to be understood that any type of suitable antenna that can assist in the transmission of signals, known to those having skill in the art, may be used without departing from the novel scope of the present invention.  
         [0032]    A receiver  30 , which may be connected to the building&#39;s cable outlet includes means for tuning receiver  30  to a specific frequency, and a signal detector for detecting ingress of errant signals into the cable system of the building being tested.  
         [0033]    Referring now to FIGS. 4 and 5, the cable system  9  is shown and described. Cable television system  9  distributes signals via cables  54  suspended on utility poles  56  (FIG. 4) or by a cables  54   a  buried in the ground  55  (FIG. 5). A combination of both methods is common. From the main distribution cable  54  ( 54   a ), a local tap  58  is used to interface the distribution system cable  54  ( 54   a ) to the residence, business or subscriber  59 . Typically, from one to eight, and possibly more, subscribers may be served from a single local tap  58 . A multitude of local taps  58  are used through out the typical distribution system to provide cable services to subscribers.  
         [0034]    In overhead systems (FIG. 4), a drop cable  60  is suspended from the local tap  58  and secured to the residence  59  at a safe distance from ground  55 . The drop cable  60  is typically routed along a side  59   a  of residence  59  to a ground block  62 . The ground block  62  is a “pass-through” device connected to an earth ground. The ground block  62  prevents static build up between cable system  9  and the electrical power wiring of residence  59 . This reduces the risk of electrical damage to devices within the residence that are connected to cable system  9 .  
         [0035]    From the ground block  60  cable signals enter the residence  59  and are routed via an inside cable  60   i  (FIG. 1) to devices within residence. The cable signals within the residence  59  may be split (branched) into multiple paths to supply cable services to many locations within the residence. Examples of devices connected to the internal cabling  60   i  are television sets, VCRs, cable modems, digital carrier receivers, and special service transceivers (not shown).  
         [0036]    The underground distribution system  9 , shown in FIG. 5, has cable  54   a  buried in the ground  55 . The cable  54   a  only surfaces into above ground enclosures at selected locations throughout cable system  9 , called distribution pedestals  64 . Opening a pedestal  64  allows access to cable system  9  for maintenance. Distribution pedestals  64  contain local taps  58 . An underground cable  60   a  from the pedestal  64  provides cable services to residence  59 , in a similar manner that the drop cable  60  is used in above ground systems. The underground cable  60   a  typically surfaces just below ground block  62  for connection thereto.  
         [0037]    As illustrated in FIGS. 4 and 5, a downstream signals  66  travel from the cable source (not shown) to the subscriber (residence or business)  59 , and are typically in the 50 MHz to 1 GHz frequency range. Upstream signals  68  travel from the subscriber (residence or business)  59  to the cable source, and are typically in the 5 to 50 MHz frequency range. In order to enable two way communications on a cable system  9 , the upstream signals  68  originate within the residence travel to a central location in the cable system  9 . The upstream signals  68  are used for devices such as cable modems (not shown) and special services devices. Special service devices include burglar alarms, fire alarms, and personal health monitors (not shown).  
         [0038]    Because upstream signals  68  use the 5 to 50 MHz range, they are vulnerable to interference from the operation of devices that radiate electrical energy in the 5 to 50 MHz frequency range. In a typical cable system  9 , the upstream signals  68  are digital signals and, as such, are subject to very unreliable operation if interference signals find their way into system  9 . Examples of devices capable of causing interference are: CB radios, hair dryers, washing machines, food mixers, toasters, vacuum cleaners, and almost any appliance having a motor or a power switch. The interference may last for an instant or may be continuous while the device is on, but in either event can catastrophically effect the communication desired.  
         [0039]    Ingress problems are typically compounded by the multitude of residences  59  connected to CATV distribution system  9 . Any one residence  59  is capable of adding an interference signal on the upstream path thereby disrupting communications. A multitude of residences  59 , each only adding only a small amount of interference, can also render upstream path  68  useless. Interference signals add on a power basis.  
         [0040]    The CATV cabling inside a residence  59  is usually hidden in areas such as crawl spaces, behind walls, attics, and basements. The effects of aging on the internal cable  60   i  (especially metal connectors), damage caused by rodents, and possibly improper installation may reduce the shielding integrity of the system within residence  59 . Poor shielding integrity permits inside cabling  60   i  to essentially become a “receiving antenna” for interfering signals. A signal or noise entering (ingress) internal cabling  60   i  may travel upstream and disrupt communications.  
         [0041]    Referring now to FIG. 2, a block diagram of the transmitter  11  is shown. A diplex filter  16  routes an activation signal to an activation receiver  18 . An activation decoder  20  determines a code match between the received signal and setting of the transmitter  11 . If a code match occurs, the activation decoder  20  activates a transmitter enable switch  22 . If a code match does not occur, transmitter  11  remains off. The transmitter enable switch  22  activates the test signal transmitter  23 . The test signal transmitter  23  generates a test signal, which is fed to the dual band antenna  14  by the diplex filter  16 . The diplex filter  16  prevents the test signal from being improperly routed to the activation receiver  18 , and facilitates both transmission and reception of signals.  
         [0042]    Referring to FIG. 3, a receiver  30  is powered by a battery  32 , and is portable in design. The receiver  30  further includes a test signal connection port  34 , which is preferably a coaxial-type connector. It will be understood by persons having skill in the art that any type of connector and any manner of connection may be used without departing from the novel scope of the present invention. In a preferred embodiment, the connection port  34  is connected to an input tuner section  36 , which is in turn connected to a signal detector  38 . The signal detector  38  is connected to a display converter  40 , which provides output to a visual display device  42 . In a preferred embodiment, a data memory  44  can also be connected to the test signal detector  38  to save data. Data memory  44  may be, for example, a hard disk, a floppy disk, a zip disk drive, a CD-ROM or other type of device capable of receiving and storing data known to those having skill in the art. The receiver  30  further includes an activation encoder  74 , an activation code transmitter  72  as well as an antenna  70  transmitting activation codes, the use of which will be described in greater detail below.  
         [0043]    Referring now to FIGS. 1, 2, and  3 , in the present invention, the transmitter  11  (FIG. 2) is used to provide a known signal source to allow the integrity of residence  59  to be checked. In the operation of the device, as illustrated in FIG. 1, the transmitter  11  transmits on a frequency in the 5 to 50 MHz range. The transmitter  11  is typically mounted in and powered by the service vehicle  12 . In a preferred embodiment, the transmitter  11  also has a feature of variable power output, which will be described in detail below. The antenna  14 , which may be omni-directional, is connected to the transmitter  11  and is mounted on the vehicle  12 . Preferably, the antenna  14  is mounted on a vehicle roof  12   a  in an area clear of other metallic objects such as other antennas, ladders, and lifting apparatus. The vehicle  12  is then parked adjacent to the test site dwelling or residence  59  (preferably within 100 feet) and the transmitter  11  is activated. The residence  59  is radiated with the test signal. Preferably, the test signal frequency should be chosen so as not to cause interference with known upstream communications.  
         [0044]    To qualify the shielding integrity, ie, the ability of the cables  60   i  (FIGS. 4 and 5) to withstand ingress of errant signals, the drop cable  60  is disconnected from the ground block  62  (FIG. 4). The receiver  30  is then connected to the ground block  62  with a length of high-quality coaxial cable. The receiver  30  is tuned to the frequency of the transmitter  11  and measures the level of test signal being received by internal cabling  60   i . It is important to note that the receiver  30  and all connections thereto are completely shielded. This means that none of the radiated signals transmitted by the transmitter  11  can enter the receiver through the receiver box itself or through the test signal connector  34 . The only way that the transmitted test signal can be received by the receiver  30  is if the transmitted test signal enters the internal cabling  60   i  via ingress. In this way the fault path is detected. The level of the received ingress test signal is compared to a reference standard to determine if the shielding integrity of the cabling  60   i  within the residence  59  is acceptable. Test signal level measurements indicated by the visual display  42  of the receiver  30  (FIG. 3) can be shown in common units of measurement, such as μV or dBmV (FIG. 6). The receiver  30  may automatically compare the levels of signal ingress to accepted standards and produce a pass/fail message (FIG. 7).  
         [0045]    If the measured level of the test signal is greater than acceptable limits, each routing of the internal cables  60   i  may be tested individually to determine the fault. Usually a CATV signal splitter (not shown) is located in close proximity to the ground block  62  to facilitate disconnecting individual cables  60   i  from the splitter and retesting.  
         [0046]    A further test, illustrated in FIG. 8, involves testing the drop cable  60  section of the residential system. The drop cable  60  is disconnected from the ground block  62  and is connected to the receiver  30 . With the transmitter  11  activated and the receiver  30  tuned to the frequency of the transmitter  11 , the level of the test signal is measured. The level of the received test signal is compared to a reference standard to determine if the shielding integrity of the drop cable  60  is acceptable. Because the receiver  30  is completely shielded, as described above, any portion of the transmitted test signal that is measured by the receiver  30  must have entered the system via drop cable ingress. A greater than acceptable level measurement would most likely indicate a faulty connection at the local tap  58 .  
         [0047]    Referring to FIG. 9, a further embodiment, includes the function of the receiver  30  activating the transmitter  11  only when measurements need to be made. In this manner, vehicle power drain, transmitter heating, and general RF pollution is reduced and user or technician working efficiently is increased. Additionally, in this embodiment, an activation signal  76  from the receiver  30  can be encoded to permit the transmitter  11  to recognize the encoded activation signal such that errant signals do not cause a premature radiation of the test signal. The activation signal  76  is transmitted by the activate transmitter  72  and the internal activate antenna  70  of the receiver  30  (FIG. 3), and is received by an activate antenna  76   a  mounted on the vehicle  12 . In this manner, false transmitter activation is eliminated. As will be understood by persons having skill in the art, a multitude of activation codes are available to permit multiple test systems to operate in the same vicinity. In this manner, only the transmitter  11  associated with a given receiver  30  is activated.  
         [0048]    Alternatively, as will be understood by persons having skill in the art, a separate transmit antenna  14  and activate antenna  76   a  need not be used, rather, a single antenna  14  on service vehicle  12  can act as both the transmitter antenna and the activate antenna  76   a . Such an antenna  14  can then be used with the diplex filter  16  in the transmitter so as to distinguish and properly utilize the different signals.  
         [0049]    A test sequence, of the present embodiment, may, for example, consist of the following steps. The receiver  30  is connected to ground block  62  of a residence  59  under test. A user interface  45  (such as a push button or a switch) activates the activate encoder  74  (FIG. 3), which has been previously configured so as to be matched to the particular transmitter  11 . The activate transmitter  72  is powered on and the activate signal  76  (FIG. 9) is radiated by the internal antenna  70  (FIG. 3).  
         [0050]    The transmitter  11  (in the vehicle  12 ) receives the activate signal  76  and verifies the coding. If the coding matches, the vehicle transmitter  11  powers on and radiates the residence  59  with the test signal. The input tuner  36  section of the receiver  30  receives the test signal resulting from ingress into the residence  59 . If the test signal detector  38  qualifies the test signal as originating from the test transmitter  11 , the display converter  40  (FIG. 3) sends the level measurements to the visual display  42 , which may display a pass/fail message (FIG. 7).  
         [0051]    In another embodiment, coding of the transmitter  11  signal is provided: In this manner, the receiver  30  can reject measurements not recognized as those from the test transmitter  11 .  
         [0052]    In another embodiment, measurement data is stored within the receiver  30  for later retrieval and analysis. Further, integration of the transmitter  11  with a GPS system (not shown) is contemplated to allow for location and time data to be encoded in the test signal allowing for more precise location of signal ingress. In a further embodiment, integration of the receiver  30  with a cable modem or wireless device (not shown) is provided to allow data gathered in a test to be transferred directly to a central CATV location or internet access for immediate evaluation. It is contemplated that persons having ordinary skill in the art may make these modifications to the various embodiments described without departing from the novel scope of the present invention.  
         [0053]    Although an illustrative embodiment of the invention has been shown and described, it is to be understood that various modifications and substitutions may be made by those skilled in the art without departing from the novel spirit and scope of the invention.