Abstract:
A CATV/MoCA signal distribution system includes a first 2-way hybrid splitter for receiving a CATV input signal and splitting it into first and second CATV output signals, a second 2-way hybrid splitter for receiving the second CATV output signal and splitting it into third and fourth CATV output signals, with the latter being connected to a CATV output port. A first diplex filter is receptive of the first CATV output signal, and MoCA signals for providing electrical isolation therebetween and connecting them to a modem port. A second diplex filter is receptive of the third CATV output signal and MoCA signals for providing electrical isolation therebetween and connecting them to a Gateway port. A resistive splitter is connected between the first and second diplex filters and a plurality of individual MoCA signal ports for providing bidirectional MoCA signal flow therebetween.

Description:
FIELD OF THE INVENTION 
     The present invention applies broadly to cable television devices, and more specifically to cable television devices associated with receiving a cable television (CATV) signal, and distributing the same to a plurality of devices such as television sets, modems, and Multimedia over Coax Alliance (MoCA) devices, and so forth. 
     BACKGROUND OF THE INVENTION 
     Typical cable television (CATV) systems provide for sharing a common coaxial medium relative to CATV signals for permitting various users in the system to communicate with the headend of the system, where the CATV signals originate, but not with each other due to the directionality of signal flow imposed by the requirement that the various users be signal isolated from one another. 
     In recent years Multimedia over Coax Alliance (MoCA) systems have been developed that operate in a different frequency spectrum or band than CAT systems. MoCA systems are designed to communicate bilaterally with each other, meaning that any port of a MoCA system device serves both an input and output port. MoCA devices are typically located within a home or building for permitting users therein to communicate with a single or dedicated MoCA networking device for permitting each user to selectively record a television program for later viewing. It is important in such MoCA systems to keep the CATV input signals wholly isolated from the MoCA signals within the system. More specifically, one portion of such systems permit typical CATV signals to be connected to individual devices such as television sets, cable boxes, and so forth, in a standard manner, whereby all standard CATV signal ports are isolated from all MoCA ports in the system, as previously mentioned. 
     The development of what is now typically known as “Cable Gateway Devices” has progressed to providing such devices with the capability to communicate in both the CATV signal band of typically 5 to 1002 MHz, in conjunction with permitting communication by users in the MoCA frequency band that typically is from 1125 MHz to 1675 MHz (megahertz). Accordingly, such Cable Gateway devices permit information that is transmitted through a public CATV system to be shared amongst MoCA device users joined in a private network within a commercial or residential building. Such Cable Gateway devices permit CATV signals to be rebroadcast within a different frequency band via connections controlled through typically digital logic means, completely avoiding the use of physical switching or movement of cables between certain ports. 
     The present inventors recognize that there is a need in the art for a simplified and cost effective Cable Gateway device that isolates the CATV and MoCA bands, insuring that MoCA band signals cannot become involved with the CATV signals. 
     SUMMARY OF THE INVENTION 
     The present invention is a Passive Gateway device that avoids a direct signal path and electrical isolation between a CATV signal input port, and MoCA client or user input/output ports, a function not known to be provided in extended bandwidth conventional splitters. The present inventive device permits users in a building to connect a CATV signal to various TV sets, modems, and so forth, while at the same time permitting bidirectional communication between a plurality of users of individual in-home media devices within a building, each connected through a coaxial cable network terminated at the output ports of the invention and utilizing the RF spectrum allocated to Multimedia over Coax Alliance (MoCA), for example. The dedicated devices for users can be Media Center client devices enabling Multi-room Digital Video Recording (MR-DVR), multi-player gaming, or high-speed data communications. The recording device can be a Gateway recording device, for example. 
     In one embodiment of the invention providing a Passive Gateway device, two-way splitter means receptive of CATV input signals connects these signals to first and second diplex filters, and to an RF output port for connection of CATV signals to legacy devices such as known cable boxes, television sets, and so forth. The first diplex filter means is for providing a lowpass filter section that cuts off near the high end of the CATV signal band, that is at about 1002 MHz, and a highpass filter section for passing MoCA band signals. The first diplex filter means provides a modem output port for feeding both CATV signals or MoCA band signals from both the lowpass and highpass filter sections thereof. The highpass filter section of the first diplex filter means provides a MoCA signal connection to a resistive splitter means connected to a plurality of MoCA ports. The second diplex filter means also includes a lowpass filter section for passing CATV signals, and a highpass filter section for passing MoCA signals, whereby the highpass and lowpass filter sections provide for connection to a Gateway output port for connecting CATV signals and/or MoCA signals to a Gateway recorder and controller, for example. The highpass filter section of the second diplex filter means provides for the connection of MoCA signals to a plurality of independent MoCA ports via the resistive splitter. 
     In a second embodiment of the invention, the present invention provides a portion of the first embodiment of the invention for providing users with a CATV connection port, a Gateway port, and a plurality of MoCA ports. More specifically, the second embodiment of the invention includes a 2-way hybrid splitter for receiving a CATV input signal, and splitting off to a CATV port for connection thereto by users, and to a hybrid filter. The hybrid filter provides for an output to a Gateway port, and another output from a highpass section thereof to a resistive splitter. The resistive splitter provides connection to a plurality of MoCA port. 
     In a third embodiment of the invention, the 2-way hybrid splitter of the second embodiment is eliminated, and a CATV input signal is connected directly to the lowpass filter section of a hybrid filter. An output from the hybrid filter is connected to a Gateway port, and the highpass filter section is again connected to a resistive splitter for permitting bidirectional communication devices connected to a plurality of ports of the resistive splitter. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Various embodiments of the present invention are described with reference to the drawings, in which like items are identified by the same reference designation, wherein: 
         FIG. 1  is a block circuit schematic diagram for one embodiment of the invention; 
         FIG. 2  is a circuit schematic diagram of a 2-way hybrid splitter for an embodiment of the invention; 
         FIG. 3  is a circuit schematic diagram of a resistive splitter used in an embodiment of the invention; 
         FIG. 4  is a circuit schematic diagram of a diplex filter used in various embodiments of the invention; 
         FIG. 5  is a circuit schematic diagram showing circuitry details for a prototype device providing the various necessary functions for an embodiment of the invention; and 
         FIG. 6  is a top view of a “MoCA Gateway splitter” prototype housing developed by the inventors for an embodiment of the invention. 
         FIGS. 7 and 8  are block circuit schematic diagrams for second and third embodiments of the invention, respectively. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     With reference to  FIG. 1 , a simplified block diagram of the present CATV MoCA splitter includes an input terminal  2  for receiving a CATV signal typically having a frequency range of 5 MHz to 1002 MHz, and is connected via an electrically conductive line path or lead  30  to the input of a 2-way hybrid splitter  4 . The 2-way hybrid splitter  4  has a first output connected via an electrically conducted path  34  to the input of a first diplex filter  14 , and a second output connected via an electrically conductive path  38  to an input  32  of a second 2-way hybrid splitter  6 . The 2-way hybrid splitter  6  has a first output connected via an electrically conductive path  36  to a second diplex filter  18 , and a second output connected via an electrically conductive path  40  to a CATV (RF output) terminal  7 . The first diplex filter  14  includes a lowpass filter section  15  for passing CATV signals in the frequency range from 5 MHZ to 1002 MHz for outputting on an electrically conductive path  35  for connection to a modem terminal  8 . When a modem (not shown) is connected to the modem terminal  8 , typically the modem will provide a voltage feed of 12 volts DC that is connected via electrically conductive path  35  through a resistor  10  (typically 1 k Ω), to a light emitting diode  12 , for indicating by its light output connection of a modem to terminal  8 . Diplex filter  14  also includes a highpass filter section  16  for passing MoCA signals having a frequency range 1125 MHz to 1675 MHz, for connection via an electrically conductive path  39  to a 6-way resistive splitter  24 . The second diplex filter  18  includes a lowpass filter section  19  passing CATV signals having a frequency range of 5 MHZ to 1002 MHz via an electrical conductive path  37  to a Gateway terminal  22 . The Gateway terminal  22 , in one example, may be connected to a Gateway recording and programmable apparatus (not shown). In this example, indicated CATV signals are passed from the Gateway terminal  22  to the programmable recording apparatus (not shown), MoCA signals having a frequency range of 1125 MHz to 1675 MHz are bidirectionally passed between Gateway terminal  22  and the Gateway recording device (not shown). 
     MoCA signals, in this example, as previously mentioned, having a frequency range of 1125 MHz to 1675 MHz, are bidirectionally passed between a highpass filter section  16  diplex filter  14  via an electrically conductive pass  39  to a 6-way resistive splitter  24 . Similarly, the highpass filter section  20  of diplex filter  18  is connected via an electrically conductive path  41  to bidirectionally pass MoCA signals to the 6-way resistive splitter  24 . However, splitter  24  is not meant to be limited to a 6-way resistive splitter, and can be configured to provide any desired number of MoCA ports within practical limits. The 6-way resistive splitter  24  bidirectionally passes MoCA signals via individual electrically conductive paths  3 ,  5 ,  7 , and  9 , to MoCA terminals or ports  25 ,  26 ,  27 , and  28 , respectively. In this example, individual MoCA clients (not shown) can be individually connected to the ports or terminals  25  through  28 , respectively, for permitting each of them to program the Gateway device (not shown) to record desired cable television programs for later viewing. The diplex filters  14  and  18  insure that the CATV signals are electrically isolated from the MoCA signals. 
     A typical 2-way hybrid splitter circuit schematic is shown in  FIG. 2 . In this example, the typical hybrid 2-way splitter  4 ( 6 ) includes a matching transformer having a primary winding  42  with one end individually connected to an electrically conductive path  30 ( 32 ), with the other end of the winding  42  being connected to ground. The splitter  4 ( 6 ) also includes a secondary winding  44  having one end individually connected to electrically conductive paths  34 ( 36 ), respectively, and another end connected to electrically conductive paths  38 ( 40 ). In this example, the primary winding  42  has a turns ratio of 2:5 relative to a center tap  43  connected between the primary winding  42  and the secondary winding  44 . The secondary winding  44  has a turns ratio of 2:2 relative to the center tap  43 . A capacitor  46  is connected between the center tap and ground to match the leakage inductance inherent in the interconnection of the transformer windings  42  and  44 . A series circuit of a resistor  47  and two inductors  49  and  50  are connected across the secondary winding  44 , as shown. Note that the inductors  49  and  50  are chokes that modify the phase cancellation at the very high end of the frequency band of signals outputted from either of the splitters  14  and  18 . The resistor  47 , in combination with the chokes  49  and  50  sets the phase cancellation between the two output lines from the secondary winding  44  in order to maximize the electrical isolation therebetween. Note that the value of the capacitor  46  is typically 1 pF (picofarads), the chokes  49  and 50 typically have values of 5 nH (nanohenries), and resistor  47  a value of 200 ohms. 
     The circuit schematic diagram for a 6-way resistive splitter  24  for an embodiment of the invention is shown in  FIG. 3 . Six resistors  52  through  57  each have one end connected in common as shown. The other end of resistor  55  is connected to electrically conductive circuit path  39  to the highpass filter section  16  of diplex filter  14 . The other end of resistor  52  is connected via electrically conductive path  41  to the highpass filter section  20  of diplex filter  18 . The other end of resistor  53  is connected via electrically conductive path  3  to MoCA terminal  25 . The other end of resistor  54  is connected via electrically circuit path  5  to MoCA terminal  26 . The other end of resistor  56  is connected via electrically conductive path  7  to MoCA terminal  27 . The other end of resistor  57  is connected via electrically conductive path  9  to MoCA terminal  28 . 
     A diplex filter circuit schematic diagram, shown in  FIG. 4 , can be used to provide diplex filters  14 ,  18 , respectively. As shown, each diplex filter  14  ( 18 ) includes a plurality of inductors  60  through  72 , and a plurality of capacitors  73  through  88 , connected in series and parallel circuit combinations, as shown. Values of the aforesaid inductors and capacitors are selected for obtaining the required lowpass filter frequency range, and highpass filter frequency range, as previously indicated. 
     A circuit schematic diagram for a prototype Gateway splitter developed by the inventors is shown in  FIG. 5 . As will be explained, the circuitry for the prototype design differs in this embodiment from the previously described embodiments of the invention, whereby additional components have been added. More specifically, spark gaps  100  have been connected individually between input port  2 , CATV port  7 , modem port  8 , Gateway port  22 , MoCA port  25 , MoCA port  26 , MoCA port  27 , MoCA port  28 , and ground, respectively. Note that use of the terminology port is meant to be also analogous to a terminal, whereby typically each of the aforesaid ports are coaxial connector ports. Also, as shown, DC blocking capacitors  89  have been added to 2-way hybrid splitters  4 ,  6 , diplex filters  14 ,  18 , and the 6-way resistive splitter  24 , each of the blocking capacitors  89  being connected as shown. Each of the 2-way hybrid splitters  4  and  6  include two matching capacitors in parallel between the tap offs from primary winding  42  and secondary winding  44  and ground, as shown. The lowpass filter sections  15  and  19  of diplex filters  14 ,  18 , respectively, now each further include additional capacitors  96  and  99 , and a choke for inductance  98 , as shown. The highpass filter sections  16  and  20  of the diplex filters  14 ,  18 , respectively, remain identical to the circuitry previously shown in  FIG. 4 . Also note that in the 6-way resistive splitter  24 , a connection pad  60  has been included in order to provide a common connection node for all of the resistors of the resistive splitter  24 . Pad  60  is large enough to provide a low impedance node via the copper material of the pad providing body capacitance on a dielectric PC Board substrate. If MoCA ports  25  through  28  are all terminated to MoCA device ports each having a 75 ohm input impedance, the characteristic impedance at pad or node  60  will be 21.5 ohms. In this example, as is typical with CATV systems, the impedance at the various ports is 70 ohms. 
     In the 2-way hybrid splitters  4  and  6 , the reason that two capacitors  46  are used in parallel between the ferrite transformer windings  42  and  44  is to obtain a more distributed ground connection. The capacitors  46  provide for canceling small amounts of stray inductance in the interconnection between the ferrite core transformers  42  and  44 , for improving high frequency return loss and isolation therebetween. Note further that in the prototype the resistor  94  of the 2-way hybrid splitters  4  and  6  have a value 180 ohms, but can have a resistance range of 150 ohms to 220 ohms depending on the characteristics of the particular ferrite core transformers  42 ,  44 , at low frequencies between 5 MHz and 50 MHz. Note further that resistors  94  are connected in series with an inductor (not shown) that is printed on an associated printed circuit board rather than being a discrete component, with the series circuit thereof being connected therebetween capacitors  90  and  92 . Capacitors  90  and  92  improve isolation and return loss at low frequencies. 
     With further reference to the diplex filters  14  and  18 , as shown in  FIG. 5 , note that the lowpass filter sections  15  and  19  thereof, respectively, differ from the circuitry of  FIG. 4 . More specifically, in the prototype circuitry four parallel tank circuits are included in the associated lowpass filter sections  15  and  19 , rather than three as shown in  FIG. 4 . The additional parallel tank circuit in each section includes capacitors  96  and  99 , and inductor  98 , for further insuring a frequency roll off above 1.0 GHz, thereby avoiding adding additional inductors to every shunt element. 
     With further reference to the prototype circuit schematic diagram of  FIG. 5 , values of various of the components utilized will now be given, but are not meant to be limiting. The DC blocking capacitors  89  each have a value of 2200 (picofarads), and a voltage rating of 50 volts in this example. 
     In the 2-way hybrid splitter circuits  4  and  6 , the tapoff  43  for the ferrite core transformer  42  is between the second turn and the fifth turn of the seven turns thereof, whereas in the ferrite core transformer  44  the tapoff  43  is between the second turn from each end of the four turns included. The capacitors  90  each have a value of 1000 pf. Capacitors  92  each have a value of 1000 pf. Capacitors  46  each have a value of 1 pf. 
     For diplex filters  14  and  18 , the inductances  60  each have a 0.3 mm (millimeter) wire diameter, a 1.5 mm coil diameter, and 2.5 turns. Capacitors  73  each have a value of 2.0 pf. Capacitors  74 ,  78 , and  96  each have a value of 0.75 pf. The inductances  65 ,  66 ,  67 , and  98  each have a 0.3 mm wire diameter, 1.7 mm coil diameter, and 2.5 turns, respectively. Capacitors  75  each have a value of 1.8 pf. The capacitors  77  and  79  each have a value of 1.8 pf. Capacitor  99  has a value of 2.2 pf. Inductor  68  has a 0.3 mm wire diameter, a 2.0 mm coil diameter, and 2.5 turns. Capacitor  99  has a value of 2.2 pf. In the highpass filter sections  16  and  20  of diplex filters  14 ,  18 , respectively, capacitor  80  has a value of 1.2 pf. Capacitors  82 ,  86 , and  87  each has a value of 1.8 pf, respectively. Capacitor  81  has a value of 2.2 pf. Capacitor  83  has a value of 2.0 pf. Capacitor  84  has a value of 1.5 pf. Capacitor  85  has a value of 6.8 pf. Capacitor  88  has a value of 2.5 pf. Inductor  69  has a 0.3 mm wire diameter, a 1.5 mm coil diameter, and 2.5 turns. Inductors  70 ,  71  and  72  each have a 0.3 mm wire diameter, a 1.7 mm coil diameter, and 2.5 turns, in this example. In the 6-way resistive splitter  24 , each of the resistors  52  through  57 , respectively, has a value of 54 ohms, in this example. Note that none of the component values used in the prototype as given above are meant to be limiting. 
     In  FIG. 6 , a housing  102  for a Gateway prototype splitter  1  is shown. The MoCA ports  25  through  28  are located at one end of the associated housing  102 , whereas the input port  2 , modem port  8 , RF output port  7 , and Gateway port  22  are located at an opposite end of the housing  102 . Also shown is a terminal  104  for receiving a ground connection. Screw receptive brackets  105  are provided for securing the Gateway splitter to a desired seating surface, such as a mounting base within a cavity or enclosure (not shown). 
     In the second embodiment of the invention, as shown in  FIG. 7 , an input port  2  for receiving a CATV signal is connected via electrically conductive line path  31  to an input  32  of the 2-way hybrid splitter  6 . The 2-way hybrid splitter  6  outputs are connected as in the embodiment of  FIG. 1  to the lowpass section  19  of a diplex filter  18 , and the CATV port  7 . Further, as with the embodiment of  FIG. 1 , the diplex filter  18  has a connection to a Gateway port  22 , and to a resistive splitter  24 , as shown. Relative to the first embodiment of the invention of  FIG. 1 , in the second embodiment the 2-way hybrid splitter  4 , diplex filter  14 , modem port  8 , resistor  10 , and LED  12  have been removed. 
     A third embodiment of the invention is shown in  FIG. 8 . In the third embodiment an input port  2  for receiving a CATV signal provides for connection thereof via an electrical lead line or conductive path  33  directly to the lowpass section  19  diplex filter  18 . In comparison to the second embodiment of the invention of  FIG. 7 , in the third embodiment the 2-way hybrid splitter  6  has been eliminated, which in turn eliminates the provision of a CATV port  7 , as in the other embodiments. Accordingly, relative to embodiment of  FIG. 1 , the embodiment of  FIG. 7  eliminates the provision of allowing a user to connect a modem, but otherwise retains all of the other connections of the first embodiment. The third embodiment of the invention relative to the second embodiment eliminates the provision of a CATV port  7 , and only provides for a user to have use of MoCA ports, and a Gateway port. Note further that as shown the resistive splitter  24  of  FIG. 1  is a 6-way splitter, whereas the resistive splitter  24  of the second and third embodiments of  FIGS. 7 and 8  is a 5-way resistive splitter. However, it should be understood that the resistive splitter  24  can be configured to provide any number of MoCA ports within practical limits. 
     Although various embodiments of the invention have been shown and described, they are not meant to be limiting. Those of skill in the art may recognize certain modifications to these embodiments, which modifications are meant to be covered by the spirit and scope of the appended claims.