JP2006325004A - Catv system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a CATV system capable of using electric signals with frequency bands, different from frequency bands where a bidirectional amplifier can amplify signals, for two-way communications. <P>SOLUTION: A CATV system 1 includes first to fourth cable modems 33A to 33D for generating modem signals, a bidirectional amplifier 15, and branching/mixer 37. The amplifier 15 amplifies CATV signals. The modem 33B converts a first downlink modem signal generated by the modem 33A and received through a CATV transmission path 13A and the branching/mixer into a downlink data signal. The modem 33D converts a second uplink modem signal generated by the modem 33C and received through the CATV transmission path 13B into an uplink data signal. The modems 33B and 33D generate a first uplink modem signal and a second downlink modem signal from the uplink data signal and downlink data signal received through a communication path C1. The modem 33A receives the first uplink modem signal, and the modem 33C receives the second downlink modem signal. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a CATV system capable of bidirectional communication.

  Originally, the CATV system was a one-way transmission in which a video signal or the like was distributed from a head end to a subscriber's home via a CATV transmission path composed of a coaxial cable or the like. However, in recent years, in order to realize a cable Internet, a cable videophone, etc. by utilizing the broadband nature of the CATV transmission line, a so-called two-way communication CATV capable of transmitting information from the subscriber's home side to the headend side is possible. A system has been developed. In the CATV system capable of such two-way communication, the frequency band to be used is changed in order to distinguish the downlink signal and the uplink signal transmitted through the same CATV transmission line. For example, the downstream signal uses 70 MHz to 770 MHz as the frequency band, and the upstream signal uses 10 MHz to 55 MHz as the frequency band.

When a cable Internet is realized using a CATV system capable of bidirectional communication, a terminal such as a personal computer (PC) is connected to a CATV transmission path via a cable modem. As this cable modem, there is known a cable modem that enables high-speed data transmission by using an arbitrary 50 MHz band in a frequency band of 800 MHz to 1.5 GHz that is not used in conventional upstream signals and downstream signals. .
JP-A-10-229551 Japanese Patent Laid-Open No. 2001-358742

  However, when a conventional cable modem that uses an electric signal having a frequency component in a frequency band that is not used for an upstream signal or a downstream signal is applied to a CATV system including an apartment house such as a condominium, the following problem occurs. Has occurred.

  That is, when the housing complex is subscribed to the CATV system, the electric signal from the head end is distributed in the housing complex. In order to prevent the deterioration of the electric signal due to the distribution, an amplifier for amplifying the electric signal is installed in the apartment house. In the bidirectional CATV system as described above, the bidirectional signal for amplifying the downstream signal and the upstream signal is installed. An amplifier will be used. This bi-directional amplifier is designed so as to compensate for amplification of an electric signal having a frequency component within a frequency band used by conventional downstream and upstream electrical signals, and thus has not been conventionally used as described above. When the frequency band is used, there has been a problem that data cannot be transmitted via the bidirectional amplifier.

  Accordingly, an object of the present invention is to provide a CATV system in which an electric signal having a frequency band different from a frequency band that can be amplified by a bidirectional amplifier can be used for bidirectional communication.

In order to solve the above problems, a CATV system according to the present invention is a CATV system capable of two-way communication between a head end and a subscriber's house in an apartment house, and is (1) connected to the head end. The first CATV transmission line and the second CATV transmission line connected to the subscriber's house, and the downstream CATV having a frequency component in the first frequency band inputted from the first CATV transmission line The signal is amplified and output to the second CATV transmission line, and the upstream CATV signal having a frequency component in the second frequency band input from the second CATV transmission line is amplified to obtain the first CATV transmission line. And (2) a first cable model that is connected to the first CATV transmission line and generates a first downlink modem signal having a frequency component in the third frequency band. And (3) a branching / mixing device provided on the first CATV transmission line downstream from the connection between the first cable modem and the first CATV transmission line and to the bidirectional amplifier. (4) The first CATV transmission line is connected to the first CATV transmission line via a branch / mixer, and generates a first uplink modem signal having a frequency component within the third frequency band, and the first CATV transmission. A second cable modem that converts a first downlink modem signal input via a path and a branch / mixer into a downlink data signal; and (5) a frequency component in a third frequency band installed in a subscriber's house. A fourth cable modem connected via a second CATV transmission line to a third cable modem that generates a second upstream modem signal having a frequency component within the third frequency band Second downstream modem signal Provided in the fourth cable modem a second upstream modem signal into a upstream data signal generated by through the second CATV transmission path input, a,
(A) The second cable modem and the fourth cable modem are connected by a communication path for transmitting the downlink data signal and the uplink data signal, and (B) the second cable modem transmits the downlink data signal to the first data modem. The fourth cable modem generates a second downlink modem signal by converting the received downlink data signal, and (C) the fourth cable modem transmits the uplink data signal to the first cable modem. The second cable modem generates the first upstream modem signal by converting the received upstream data signal, and (D) the branch / mixer is input from the upstream side. The downstream CATV signal is output to the first downstream CATV transmission line, the upstream CATV signal input from the downstream side is output to the upstream first CATV transmission path, and is input from the upstream side. The first downlink modem signal is outputted to the second cable modems, and outputs the first upstream modem signal input from the second cable modem to the first CATV transmission path on the upstream side.

  In the above configuration, the branch / mixer passes the downstream CATV signal from the first CATV transmission path upstream of the branch / mixer to the first CATV transmission path downstream of the branch / mixer. The CATV signal is input to the bidirectional amplifier through the first CATV transmission path and amplified. Since the bidirectional amplifier outputs the amplified downlink CATV signal to the second CATV transmission line, the downlink CATV signal reaches the subscriber's house in the apartment house.

  Further, the upstream CATV signal is input to the bidirectional amplifier via the second CATV transmission line. The bidirectional amplifier amplifies the upstream CATV signal and then outputs it to the first CATV transmission line. As a result, the upstream CATV signal is input to the branch / mixer provided on the first CATV transmission line. This branch / mixer passes the upstream CAV signal from the downstream first CATV transmission line to the upstream first CATV transmission line, so that the upstream CATV signal can reach the head end.

  Further, the first downlink modem signal generated by the first cable modem is input to the first CATV transmission line via the connection unit. As a result, the downlink CATV signal and the first downlink modem signal are transmitted on the first CATV transmission path downstream of the connection unit. The branch / mixer provided between the connection unit and the bidirectional amplifier outputs the first downlink modem signal input from the first CATV transmission path to the second cable modem. The first downstream modem signal is input to the second cable modem.

  The second cable modem converts the first downlink modem signal into the aforementioned downlink data signal and transmits it to the fourth cable modem. The fourth cable modem converts the received downlink data signal to generate a second downlink modem signal. Then, the second downstream modem signal reaches the third cable modem installed in the subscriber's house via the second CATV transmission line.

  The second upstream modem signal generated by the third cable modem is input to the fourth cable modem via the second CATV transmission line. The fourth cable modem converts the inputted second upstream modem signal into an upstream data signal and transmits it to the second cable modem, and the second cable modem transmits the received upstream data signal to the first upstream data signal. Convert to modem signal and output to branch / mixer.

  Since the branching / mixing device outputs the first upstream modem signal from the second cable modem to the first CATV transmission line on the upstream side, the first upstream modem signal is transmitted through the connection unit to the first upstream modem signal. It will be input to the cable modem.

  As described above, in the CATV system configured as described above, the first downlink modem signal generated by the first cable modem reaches the third cable modem as the second downlink modem signal without passing through the bidirectional amplifier. Will do. Conversely, the second upstream modem signal reaches the first cable modem as the first upstream modem signal without going through the bidirectional amplifier. As a result, even if the first and second CATV transmission lines are connected by a bidirectional amplifier, bidirectional communication can be performed between the first cable modem and the third cable modem.

  In the CATV system according to the present invention, the first downlink modem signal and the first uplink modem signal have a frequency component in the fourth frequency band of the third frequency band, and the second The downstream modem signal and the second upstream modem signal preferably have a frequency component in a fifth frequency band different from the fourth frequency band in the third frequency band.

  In this case, since the fourth frequency band and the fifth frequency band are different, the first downlink modem signal (first uplink modem signal) and the second uplink modem signal (second downlink modem signal) Will not interfere. As a result, more accurate communication is possible between the first cable modem and the third cable modem.

  Furthermore, in the CATV system according to the present invention, it is preferable that the first frequency band is 70 MHz to 770 MHz, the second frequency band is 10 MHz to 55 MHz, and the third frequency band is 800 MHz to 1.5 GHz. is there.

  Further, in the CATV system according to the present invention, the connection portion between the third cable modem and the second CATV transmission line that is upstream of the receiving terminal provided at the subscriber's home and connected to the second CATV transmission line. It is preferable to further include a filter that is provided on the second CATV transmission line up to and selectively attenuates the second downstream modem signal and the second upstream modem signal.

  In the above configuration, since the filter is provided between the connection portion between the third cable modem and the second CATV transmission line and the receiving terminal, the third CATV transmission line and the second CATV transmission line are provided. Input of the second downlink modem signal and the second uplink modem signal transmitted through the path to the receiving terminal is suppressed.

  According to the CATV system of the present invention, bidirectional communication can be realized by using an electrical signal having a frequency component in a frequency band different from the frequency band that can be amplified by the bidirectional amplifier.

  A preferred embodiment of a CATV system according to the present invention will be described below with reference to the drawings.

  As shown in FIG. 1, the CATV system 1 has an apartment house 5 such as an apartment having a plurality of subscriber homes 3 and 3 in its service area. The CATV system 1 is a two-way CATV system that has a head end 7 that delivers a broadcast program or the like to a subscriber's home 3 and that allows two-way communication between the head end 7 and the subscriber's home 3. The head end 7 is also connected to a telephone network (not shown), so that a cable videophone or the like can be realized.

  In this specification, a signal flow from the head end 7 side toward the subscriber home 3 side is referred to as “downward”, and a signal flow from the subscriber home 3 side toward the head end 7 side is referred to as “upstream”.

  In the CATV system 1, an optical fiber cable 11 is laid from the head end 7 to the optical node 9 installed in the service area, and a CATV transmission line (having a plurality of coaxial cables from the optical node 9 to the housing complex 5 ( A first CATV transmission line) 13A is laid. That is, the CATV transmission line 13A is connected to the head end 7 via the optical node 9 and the optical fiber cable 11. In the apartment house 5, a network is formed by a CATV transmission line (second CATV transmission line) 13B having a plurality of coaxial cables.

  The optical node 9 converts an optical signal and an electrical signal to each other, and converts the optical signal transmitted from the head end 7 into an electrical signal having a frequency component within a frequency band of 70 MHz to 770 MHz (first frequency band). To the CATV transmission line 13A. In addition, the head converts the electrical signal having a frequency component within the frequency band of 10 MHz to 55 MHz (second frequency band) transmitted from the subscriber home 3 and transmitted via the CATV transmission lines 13A and 13B into an optical signal. Send to end 7.

  In this specification, an electrical signal having a frequency component within the frequency band of 70 MHz to 770 MHz and an optical signal corresponding to the downstream signal are referred to as a downstream CATV signal, and is an upstream signal having a frequency within the frequency band of 10 MHz to 55 MHz. An electrical signal having components and an optical signal corresponding to the electrical signal are referred to as upstream CATV signals. The downlink CATV signal includes, for example, a broadcast signal and a video signal, and the uplink CATV signal includes an audio signal, a request signal such as a broadcast distribution request, a response signal of a transmission device, and the like.

  In the building of the apartment house 5, a bidirectional amplifier 15 connected to the CATV transmission line 13A is installed. In addition, the housing 5 is provided with a receiver 17 (for example, an antenna) for receiving BS broadcasting. The receiver 17 converts the received broadcast signal into an electrical signal having a frequency band of 1032 MHz to 1350 MHz, and inputs the electrical signal to the bidirectional amplifier 15 via the CATV transmission line 13C formed of a coaxial cable. An electric signal of 1032 MHz to 1350 MHz in the frequency band is also referred to as a BS signal.

  Terminals 15a and 15b are provided at the end of the bidirectional amplifier 15 on the head end 7 side, and a terminal 15c is provided at the end of the subscriber house 3 side. The CATV transmission lines 13A and 13C are connected to the terminals 15a and 15b, and the CATV transmission line 13B is connected to the terminal 15c. The bidirectional amplifier 15 electrically connects the CATV transmission lines 13A and 13C and the CATV transmission line 13B.

  The bidirectional amplifier 15 is a pair of high-pass filters 19A and 19B that selectively pass an electric signal having a frequency component of 1000 MHz or more, and a pair of medium paths that selectively pass an electric signal having a frequency component within a frequency band of 70 MHz to 770 MHz. The filters 21A and 21B and a pair of low-pass filters 23A and 23B that selectively pass electric signals having frequency components in the frequency band of 5 MHz to 55 MHz.

  The high pass filter 19A is connected to the terminal 15b, the medium pass filter 21A and the low pass filter 23A are connected to the terminal 15a, and the high pass filter 19B, the medium pass filter 21B and the low pass filter 23B are connected to the terminal 15c. .

  The high pass filters 19A and 19B are connected to each other via an amplifier 25A that amplifies an electric signal in the frequency band of the BS signal. Similarly, the medium pass filters 21A and 21B are connected to each other via an amplifier 25B that amplifies an electric signal in the frequency band of the downstream CATV signal. The low pass filters 23A and 23B are connected to each other via an amplifier 25C that amplifies an electric signal in the frequency band of the upstream CATV signal.

  Therefore, when an electrical signal is input to the bidirectional amplifier 15 from the CATV transmission lines 13A and 13C via the terminals 15a and 15b, the downstream CATV signal among the electrical signals is electrically transmitted by the amplifier 25B through the medium pass filter 21A. After being amplified, the signal passes through the medium pass filter 21B and is output to the CATV transmission line 13B. Of the electrical signals input from the upstream side, the BS signal passes through the high-pass filter 19A, is electrically amplified by the amplifier 25A, passes through the high-pass filter 19B, and is output to the CATV transmission line 13B.

  Further, the upstream CATV signal among the electrical signals input from the downstream side via the terminal 15c passes through the low-pass filter 23B and is electrically amplified by the amplifier 25C, and then passes through the low-pass filter 23A and passes through the CATV transmission line. It is output to 13A.

  Thus, in the bidirectional amplifier 15 having the above-described configuration, amplification of the downlink CATV signal and BS signal included in the downlink signal is reliably compensated. In addition, amplification of the upstream CATV signal included in the upstream signal is also reliably compensated.

  A CATV transmission line 13B is laid from the bidirectional amplifier 15 to the subscriber homes 3 and 3. The CATV transmission line 13B forms a network between the bidirectional amplifier 15 and the subscriber homes 3 and 3 by connecting a plurality of coaxial cables via the branch / mixer 27A. The CATV transmission line 13B drawn into the subscriber's home 3 is provided with a set top box (hereinafter referred to as “STB”) 29 as a CATV signal receiving terminal.

  A television receiver 31 is connected to the STB 29, and the STB 29 converts the received downlink CATV signal into audio / image data and inputs it to the television receiver 31. Further, the STB 29 has a function of outputting a request signal such as a broadcast distribution request to the head end 7 to the head end 7 as an electric signal having a frequency component within the frequency band 10 MHz to 55 MHz (that is, an upstream CATV signal). It is also suitable to have.

  In addition, a BS tuner 32 as a BS signal receiving terminal is connected to the television receiver 31. The BS tuner 32 is connected to the CATV transmission line 13B via a branch / mixer 27E provided at the front stage of the STB 29, and converts the BS signal input via the branch / mixer 27E into audio / image data. And input to the television receiver 31.

  The CATV transmission line 13B is also connected to a telephone or the like installed in the subscriber's house 3 via a modem, and the voice of the telephone or the like has an electrical signal having a frequency component in the frequency band of 10 MHz to 55 MHz (ie, , An upstream CATV signal) and transmitted as an audio signal upstream.

  In addition, the CATV system 1 includes a first cable modem 33A, a second cable modem 33B, a third cable modem 33C, and a fourth cable modem 33D in order to realize the cable Internet. In the following description, the first to fourth cable modems 33A, 33B, 33C, and 33D are simply referred to as modems 33A, 33B, 33C, and 33D. The modems 33A to 33D are, for example, c. Using Link technology c. Link modem.

  The modems 33A to 33D mutually convert an Ethernet (registered trademark) standard data signal and a modem signal (for example, a c.Link signal) that can be transmitted by the CATV system 1. Hereinafter, the data signal is also referred to as an Internet signal.

  The modem signals generated by the modems 33A to 33D use an arbitrary 50 MHz bandwidth out of the frequency band 800 MHz to 1.5 GHz (third frequency band) that is not used for the downlink CATV signal, the BS signal, the uplink CATV signal, and the like. is doing. Also, the modems 33A to 33D employ an OFDM (Orthogonal Frequency Division Multiplexing) modulation scheme as a modulation scheme.

  The modem 33A and the modem 33B use the same frequency band of 50 MHz out of the frequency band 800 MHz to 1.5 GHz, and high-speed data transmission is possible between the modem 33A and the modem 33B. A frequency band (fourth frequency band) having a 50 MHz bandwidth used for communication between the modem 33A and the modem 33B is referred to as a frequency band α.

  Further, the modem 33C and the modem 33D use a frequency band of 50 MHz bandwidth different from the frequency band α in the frequency band of 800 MHz to 1.5 GHz, and high-speed data transmission between the modem 33C and the modem 33D. Is possible. A frequency band (fifth frequency band) having a bandwidth of 50 MHz used by the modem 33C and the modem 33D for communication is referred to as a frequency band β.

  Further, the modem 33B and the modem 33D are connected by, for example, an Ethernet (registered trademark) cable C1 (hereinafter simply referred to as “cable C1”). As a result, the modem 33A and the modem 33C can communicate via the modem 33B and the modem 33D. Here, the modem 33B and the modem 33D are connected by the cable C1, but may be connected by a communication path capable of transmitting an Ethernet (registered trademark) standard data signal.

  The network between the modems 33A to 33D will be described in detail.

  As shown in FIG. 1, the modem 33 </ b> A is provided outside the apartment house 5 and is connected to the Internet network 35 via, for example, an Ethernet (registered trademark) cable C <b> 2. The modem 33A is connected to the CATV transmission line 13A via a CATV transmission line 13D made of a coaxial cable. More specifically, the CATV transmission line 13D is connected to the CATV transmission line 13A via a branch / mixer (connection unit) 27B provided on the CATV transmission line 13A.

  The modem 33A converts the Internet signal input from the Internet network 35 to generate a modem signal having a frequency component within the frequency band α and outputs it to the CATV transmission line 13D. The modem signal generated by the modem 33A is also referred to as a first downstream modem signal. Also, the modem 33A converts a modem signal (a first uplink modem signal described later) having a frequency component within the frequency band α input from the CATV transmission path 13D into an Internet signal and outputs it to the Internet network 35.

  The branching / mixing device 27B connecting the CATV transmission lines 13A and 13D receives the first downlink modem signal transmitted from the modem 33A to the CATV transmission line 13D and outputs it to the CATV transmission line 13A. Further, the branching / mixing device 27B outputs a first uplink modem signal (described later) transmitted upstream by the CATV transmission path 13A to the CATV transmission path 13D. As a result, the first upstream modem signal is input to the modem 33A.

  A modem 33B that communicates with the modem 33A via the CATV transmission line 13A is installed outside the subscriber's home 3 in the building. The modem 33B is connected to a branch / mixer 37 provided on the CATV transmission path 13A between the bidirectional amplifier 15 and the branch / mixer 27B via a CATV transmission path 13E made of a coaxial cable.

  The branch / mixer 37 has three terminals 37a, 37b, and 37c. The terminal 37a is connected to the CATV transmission line 13A upstream of the branch / mixer 37 (that is, the CATV transmission line 13Aa in the figure). The terminal 37b is connected to the CATV transmission line 13E, and the terminal 37c is connected to the CATV transmission line 13A on the downstream side of the branch / mixer 37 (that is, the CATV transmission line 13Ab in the figure).

  In addition, the branching / mixing unit 37 includes a high-pass filter 39 that selectively passes an electric signal having a frequency component of 770 MHz or higher, and a low-pass filter 41 that selectively passes an electric signal having a frequency component within a frequency band of 5 MHz to 770 MHz. Have

  The CATV transmission line 13A upstream of the branch / mixer 37 is connected to the high-pass filter 39 and the low-pass filter 41 via the terminal 37a, and the CATV transmission line 13E is connected to the high-pass filter 39 via the terminal 37b. The CATV transmission line 13A on the downstream side of the branch / mixer 37 is connected to the low-pass filter 41 via a terminal 37c.

  As a result, an electrical signal having a frequency component of 770 MHz or more among electrical signals input from the upstream CATV transmission path 13A is output to the CATV transmission path 13E through the high-pass filter 39, and the frequency within the frequency band of 5 MHz to 770 MHz. The electrical signal having a component passes through the low-pass filter 41 and is output to the downstream CATV transmission line 13A.

  An electric signal having a frequency component in the frequency band of 5 MHz to 770 MHz among the electric signals input from the downstream CATV transmission path 13A is output to the upstream CATV transmission path 13A through the low-pass filter 41. Further, an electric signal having a frequency component of a frequency band of 770 MHz or more input from the CATV transmission line 13E is output to the upstream CATV transmission line 13A through the high-pass filter 39.

  Therefore, the first downstream modem signal output from the modem 33A is not input to the bidirectional amplifier 15, but is input to the modem 33B via the branch / mixer 37 and the CATV transmission path 13E.

  The modem 33B converts the first downlink modem signal into an Internet signal, and transmits it to the modem 33D, for example, via the cable C1. The internet signal generated by the modem 33B is also referred to as a downlink internet signal (downlink data signal). Also, the modem 33B converts an Internet signal (uplink Internet signal) input from the modem 33D via the cable C1, for example, into a modem signal and outputs the modem signal to the CATV transmission line 13E. The modem signal generated by the modem 33B is also referred to as a first upstream modem signal. Note that the first downlink modem signal and the first uplink modem signal are signals having the same frequency component.

  A modem 33D that transmits and receives Internet signals to and from the modem 33B is installed outside the subscriber's house 3 in the building 5 and connected to the CATV transmission line 13B via the CATV transmission line 13F made of a coaxial cable. Has been. More specifically, the CATV transmission line 13F is connected to a branching / mixing device 27C provided on the CATV transmission line 13B.

  The modem 33D converts a downstream Internet signal input from the modem 33B through, for example, the cable C1, and generates a modem signal having a frequency component in the frequency band β. The modem signal generated by the modem 33D is also referred to as a second downstream modem signal. Also, the modem 33D converts a modem signal having a frequency component within the frequency band β input from the CATV transmission line 13F into an Internet signal, and transmits it to the modem 33B via the cable C1, for example. The internet signal generated by the modem 33D is also referred to as an upstream internet signal (upstream data signal).

  A modem 33C that communicates with the modem 33D via the CATV transmission line 13B is installed in the subscriber's home 3, and an Ethernet (registered trademark) cable is connected to a personal computer (PC) 43 as an Internet terminal in the subscriber's home 3. It is connected via C3 (hereinafter simply referred to as “cable C3”). The modem 33C is connected to the CATV transmission line 13B via a CATV transmission line 13G made of a coaxial cable. More specifically, the CATV transmission line 13G is connected to a branch / mixer (connection unit) 27D provided on the CATV transmission line 13B.

  The modem 33C converts the Internet signal input from the PC 43 to generate a modem signal having a frequency component within the frequency band β. The modem signal generated by the modem 33C is also referred to as a second upstream modem signal. The second downlink modem signal and the second uplink modem signal are signals having the same frequency component. Also, the modem 33C converts the second downstream modem signal input via the CATV transmission path 13G into an Internet signal and inputs it to the PC 43 via the cable C3.

  The branching / mixing device 27D as a connecting portion for connecting the CATV transmission line 13B and the CATV transmission line 13G receives the second uplink modem signal transmitted from the modem 33C to the CATV transmission line 13G and transmits the CATV transmission line 13B. Output to. Further, the branching / mixing device 27D outputs the second downlink modem signal transmitted through the CATV transmission line 13B to the CATV transmission line 13G. It is preferable that the branching / mixing device 27D selectively extracts the second downlink modem signal from the downlink signal and outputs it to the CATV transmission line 13G.

  By the way, the second downlink modem signal and the second uplink modem signal transmitted / received between the modem 33C and the modem 33D are temporarily input to the STB 29 and the BS tuner 32 together with the downlink CATV signal and the BS signal. Then, the audio / image data converted from the downstream CATV signal and the BS signal may be affected in the STB 29 and the BS tuner 32, respectively.

  Therefore, in the CATV system 1, an electrical signal having a frequency component in the frequency band β is selectively cut off on the CATV transmission path 13B between the branch / mixer 27D and the branch / mixer 27E, and the downstream CATV signal And a notch filter (NF) 45 for passing the BS signal. As a result, the downstream CATV signal and the BS signal are surely input to the STB 29 and the BS Chu 32 without inputting the electric signal having the frequency component within the frequency band β.

  The operation of the CATV system 1 will be described.

  When a CATV signal as an optical signal is output from the head end 7 to the optical fiber cable 11, the optical node 9 converts the optical signal into an electric signal having a frequency component within the frequency band of 70 MHz to 770 MHz to convert the optical signal into a CATV transmission line. Output to 13A. As a result, the downlink CATV signal is transmitted to the CATV transmission line 13A downstream from the optical node 9.

  When an internet signal is input from the internet network 35 to the modem 33A, the modem 33A converts the internet signal into a first downstream modem signal and outputs it to the CATV transmission line 13D. The first downstream modem signal transmitted through the CATV transmission line 13D is output to the CATV transmission line 13A via the branch / mixer 27B. Thus, the downlink signal propagating through the CATV transmission line 13A downstream of the branching / mixing device 27B includes the downlink CATV signal and the first downlink modem signal.

  A branch / mixer 37 is provided on the CATV transmission line 13A, and the branch / mixer 37 outputs the first downlink modem signal among the input downlink signals to the CATV transmission line 13E, and outputs the downlink signal. The CATV signal is output to the downstream CATV transmission line 13A (CATV transmission line 13Ab). As a result, the first downlink modem signal is input to the modem 33B via the CATV transmission line 13E, and the downlink CATV signal is input to the bidirectional amplifier 15 via the CATV transmission line 13A.

  The modem 33B converts the input first downlink modem signal into a downlink Internet signal and then transmits it to the modem 33D. Then, the modem 33D converts the received downlink internet signal into a second downlink modem signal, and then outputs it to the CATV transmission line 13F. As a result, the second downstream modem signal is input to the CATV transmission line 13B via the branch / mixer 27C.

  Further, the bidirectional amplifier 15 amplifies the input downlink CATV signal and then outputs it to the CATV transmission line 13B. At this time, the bidirectional amplifier 15 also amplifies the BS signal input to the bidirectional amplifier 15 via the CATV transmission line 13C and outputs the amplified signal to the CATV transmission line 13B. Therefore, the amplified downlink CATV signal and BS signal are transmitted on the CATV transmission line 13B.

  The downlink CATV signal and BS signal output from the bidirectional amplifier 15 are transmitted to the subscriber's home 3 after being superimposed on the first downlink modem signal transmitted through the CATV transmission path 13F by the branching / mixing device 27C. The

  The second downstream modem signal transmitted through the CATV transmission line 13B is input to the modem 33C via the branch / mixer 27D and the CATV transmission line 13G in the subscriber's home 3. The modem 33C converts the input second downstream modem signal into an Internet signal, and then outputs it to the cable C3. As a result, an Internet signal corresponding to the second downlink modem signal is input to the PC 43.

  The downstream CATV signal and BS signal that have passed through the branching / mixing device 27D are input to the STB 29 and the BS tuner 32 after passing through the NF 45, respectively. Accordingly, the STB 29 and the BS tuner 32 are inputted with the downlink CATV signal and the BS signal, respectively, while not receiving the second downlink modem signal. Then, the STB 29 converts the received downlink CATV signal into audio data and image data and inputs the audio data and image data to the television receiver 31. The BS tuner 32 converts the received BS signal into audio data and image data and inputs the audio data and image data to the television receiver 31.

  Next, the uplink signal will be described. Since the operation is the same except that the flow is reverse to that of the downlink signal, a brief description will be given. The Internet signal output from the PC 43 is converted into a second upstream modem signal by the modem 33C.

  The second uplink modem signal output from the modem 33C is input to the CATV transmission line 13B via the CATV transmission line 13G and the branching / mixing device 27D. At this time, since the upstream CATV signal output from the STB 29 or the telephone is transmitted to the CATV transmission line 13B, the second upstream modem signal is superimposed on the upstream CATV signal. As a result, the second upstream modem signal and the upstream CATV signal are transmitted to the bidirectional amplifier 15 side in the CATV transmission line 13B upstream from the branching / mixing device 27D.

  The bidirectional amplifier 15 selectively passes an electrical signal having a frequency component in the frequency band 5 MHz to 55 MHz to the upstream side, and blocks an electrical signal having a frequency component in another frequency band. In particular, since the frequency band through which the low-pass filter 23B passes is separated from the frequency band β, the second upstream modem signal is prevented from passing through the bidirectional amplifier 15. Therefore, the second upstream modem signal is input to the modem 33D via the branch / mixer 27C provided downstream of the bidirectional amplifier 15 and the CATV transmission line 13F.

  The modem 33D converts the second upstream modem signal into an upstream Internet signal and transmits it to the modem 33B. The modem 33B converts the received upstream internet signal into a first upstream modem signal and outputs it to the CATV transmission line 13E. The first upstream modem signal output to the CATV transmission line is input to the branching / mixing unit 37.

  On the other hand, the bi-directional amplifier 15 amplifies the upstream CATV signal having a frequency component within the frequency band of 10 MHz to 55 MHz and then outputs it to the CATV transmission line 13A. Therefore, the upstream CATV signal is branched / mixed via the CATV transmission line 13A. Is input to the device 37.

  The branch / mixer 37 outputs the first uplink modem signal input from the CATV transmission line 13E via the terminal 37b to the CATV transmission line 13A (CATV transmission line 13Aa) on the head end 7 side, and via the terminal 37c. The upstream CATV signal input from the downstream CATV transmission line 13A (CATV transmission line 13Ab) is output to the CATV transmission line 13A (CATV transmission line 13Aa) on the head end 7 side. Therefore, the first upstream modem signal and the upstream CATV signal are transmitted on the CATV transmission line 13A upstream of the branching / mixing unit 37.

  The first upstream modem signal is input to the modem 33A via the branch / mixer 27B and the CATV transmission path 13D. The modem 33A converts the input first upstream modem signal into an Internet signal and converts it to the Internet. Output to the network 35.

  The upstream CATV signal is transmitted through the CATV transmission path 13A, converted into an optical signal by the optical node 9, and then input to the head end 7.

  As described above, in the CATV system 1, the modem 33A and the modem 33B can communicate with each other using the modem signal (first downlink modem signal, first uplink modem signal) having a frequency component within the frequency band α. 33C and the modem 33D can communicate with each other by a modem signal (second downlink modem signal, second uplink modem signal) having a frequency component in a frequency band β different from the frequency band α. Furthermore, since the modem 33B and the modem 33D are connected by the cable C1, bidirectional communication based on the Ethernet (registered trademark) standard is possible.

  As a result, high-speed data communication is possible between the modem 33A and the modem 33C.

  Thus, since the modem 33A and the modem 33C can communicate without going through the bidirectional amplifier 15, frequency components in a frequency band different from the frequency band in which the bidirectional amplifier 15 compensates for amplification are obtained. Even if an electrical signal (modem signal) is used, bidirectional communication can be reliably performed between the modem 33A and the modem 33C.

  Further, since the bidirectional amplifier 15 is not provided, the bidirectional amplifier 15 does not amplify noise in the frequency band of the modem signal. Furthermore, since the frequency band α used between the modem 33A and the modem 33B is different from the frequency band β used between the modem 33C and the modem 33D, the modem signal temporarily passes through the bidirectional amplifier 15. Even so, the second modem signal and the first modem signal do not interfere with each other. As a result, accurate data communication can be reliably performed between the modem 33A and the modem 33C.

  Further, since the branch / mixer 37 including the high-pass filter 39 and the low-pass filter 41 is provided on the upstream side of the bidirectional amplifier 15 on the CATV transmission path 13A, the first modem signal is transmitted to the bidirectional amplifier 15. Is suppressed from being input.

  The preferred embodiment of the present invention has been described above, but the present invention is not limited to the above embodiment. For example, the frequency band used by the modems 33A to 33D is not limited to a frequency band having a bandwidth of 50 MHz out of the frequency band 800 MHz to 1.5 GHz.

  The frequency bands used by the modems 33A to 33D are the frequency bands of the downstream CATV signal and the upstream CATV signal input to the bidirectional amplifier 15 (more specifically, the frequency band 10 MHz to 55 MHz and the frequency band 70 MHz to 770 MHz), and Any frequency band other than the frequency band of the BS signal may be used.

  When the BS signal is not input to the bidirectional amplifier 15, a frequency band other than the frequency band of the downstream CATV signal and the upstream CATV signal input to the bidirectional amplifier 15 may be used.

  Moreover, although the apartment house 5 is set as an apartment, it may be anything that includes a plurality of subscribers such as buildings and hotels. In the above embodiment, the modem 33A and the branch / mixer (connector) 27B are installed outside the building, but they may be installed inside the building.

  Further, the modem 33B and the modem 33D are connected by the cable C1 as a communication path. However, if the communication path is established by the Ethernet (registered trademark) standard (in other words, connected by the communication path). Good if) Therefore, for example, a data signal based on the Ethernet (registered trademark) standard can be transmitted and received by a wireless LAN.

  The modem 33D and the CATV transmission line 13B are connected by the branch / mixer 27C. The branch / mixer 27C, like the branch / mixer 37, is the second upstream modem signal among the upstream signals. It is preferable to have a frequency selection characteristic of selectively outputting to the CATV transmission line 13F. As a result, the input of the second upstream modem signal or the second downstream modem signal to the bidirectional amplifier 15 is suppressed.

  Furthermore, although the frequency band used for the communication between the modem 33A and the modem 33B is different from the frequency band used for the communication between the modem 33C and the modem 33D, the modem signal is passed through the amplifier. May be the same if they are sufficiently attenuated and do not affect each other.

It is a block diagram which shows the structure of one Embodiment of the CATV system which concerns on this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... CATV system, 3 ... Subscriber house, 5 ... Apartment house, 7 ... Head end, 13A ... CATV transmission line (first CATV transmission line), 13B ... CATV transmission line (second CATV transmission line), 15 ... Bidirectional amplifier, 27B ... Branch / mixer (connection between first cable modem and first CATV transmission line), 27D ... Branch / mixer (third cable modem and second CATV modem) Connection unit), 32 ... BS tuner, 33A ... first cable modem, 33B ... second cable modem, 33C ... third cable modem, 33D ... fourth cable modem, 37 ... branch / mixer.

Claims (4)

A CATV system capable of two-way communication between a headend and a subscriber's house in an apartment house,
A first frequency band input from the first CATV transmission line, connected to the first CATV transmission line connected to the head end and the second CATV transmission line connected to the subscriber premises. An upstream CATV signal having a frequency component in the second frequency band input from the second CATV transmission line and amplifying a downstream CATV signal having a frequency component within the second CATV transmission line A bi-directional amplifier for amplifying and outputting to the first CATV transmission line;
A first cable modem connected to the first CATV transmission line and generating a first downlink modem signal having a frequency component in a third frequency band;
A branch / mixer provided on the first CATV transmission line downstream from the connection between the first cable modem and the first CATV transmission line and to the bidirectional amplifier;
The first CATV transmission line is connected to the first CATV transmission line via the branch / mixer, generates a first uplink modem signal having a frequency component within the third frequency band, and the first CATV transmission. A second cable modem for converting the first downlink modem signal input via a path and the branch / mixer into a downlink data signal;
A fourth cable modem installed at the subscriber's home and generating a second upstream modem signal having a frequency component within the third frequency band and connected via a second CATV transmission line; A cable modem, which generates a second downstream modem signal having a frequency component within the third frequency band and inputs the second upstream modem signal input via the second CATV transmission line as upstream data A fourth cable modem for converting to a signal;
With
The second cable modem and the fourth cable modem are connected by a communication path that transmits the downlink data signal and the uplink data signal,
The second cable modem transmits the downlink data signal to the fourth cable modem, and the fourth cable modem converts the received downlink data signal into the second downlink modem signal. Generate
The fourth cable modem transmits the upstream data signal to the second cable modem, and the second cable modem converts the received upstream data signal into the first upstream modem signal. Generate
The branch / mixer outputs the downstream CATV signal input from the upstream side to the first CATV transmission line on the downstream side, and outputs the upstream CATV signal input from the downstream side to the first CATV signal on the upstream side. The first downstream modem signal output from the upstream side to the CATV transmission line is output to the second cable modem, and the first upstream modem signal input from the second cable modem is upstream. Output to the first CATV transmission line on the side. The first downlink modem signal and the first uplink modem signal have a frequency component within a fourth frequency band of the third frequency band,
The second downlink modem signal and the second uplink modem signal have a frequency component in a fifth frequency band different from the fourth frequency band in the third frequency band. The CATV system according to claim 1, characterized in that: The first frequency band is 70 MHz to 770 MHz,
The second frequency band is 10 MHz to 55 MHz;
The CATV system according to claim 1 or 2, wherein the third frequency band is 800 MHz to 1.5 GHz.   The first cable between the third cable modem and the second CATV transmission line and upstream of the receiving terminal provided at the subscriber's home and connected to the second CATV transmission line. 4. The apparatus according to claim 1, further comprising a filter that is provided on two CATV transmission lines and selectively attenuates the second downlink modem signal and the second uplink modem signal. The CATV system according to item.

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