JP2007166111A - Brancher for transmission system and transmission system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a brancher for a transmission system capable of much more suppressing attenuation of a low frequency signal in comparison with prior arts and compensating reduction of impedance with respect to a high frequency signal and to provide the transmission system. <P>SOLUTION: The brancher 3 includes a filter section 12 that is inserted between a first connection terminal 10 and a second connection terminal 11, relatively reduces the attenuation in a frequency band of the low frequency signal than the attenuation in a frequency band of the high frequency signal and relatively increases the impedance in the frequency band of the high frequency signal than the impedance in the frequency band of the low frequency signal. Further, since the attenuation (impedance) of the low frequency signal (e.g. several hundreds of kHz) is relatively small and the impedance of the high frequency signal (e.g. several MHz to several tens of MHz) is relatively higher in the filter section 12, the attenuation of the low frequency signal is suppressed more than that of prior arts and the reduction of the impedance with respect to the high frequency signal can be compensated. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  In the present invention, a plurality of terminals are connected via a transmission line by a bus type wiring form, and a low frequency signal using a relatively low frequency band and a relatively high frequency band are connected between the plurality of terminals. The present invention relates to a branching device for branching another transmission line from a main transmission line, and a transmission system having such a branching part.

  As a conventional transmission system, there are intercom systems for apartment houses as described in Patent Documents 1 to 4. In such an intercom system, a lobby intercom installed at the common entrance (lobby) of the apartment house, a plurality of dwelling units installed in each dwelling unit of the apartment house, a main line connected to the lobby intercom, and the main line are branched. Residents who use a dwelling unit by transmitting audio signals and video signals via a trunk line (transmission path) between the lobby intercom and each dwelling unit, with multiple branching units that connect each dwelling unit Can make a call with the visitor while viewing the video of the visitor using the lobby intercom. However, the video signal transmitted from the lobby intercom to the dwelling unit and the audio signal transmitted bidirectionally between the lobby intercom and the dwelling unit are frequency-division multiplexed and transmitted through the same transmission path.

Here, in the interphone system (transmission system) as described above, the impedance is matched between the transmission path (branch line branched by the trunk line and the branching unit) and the terminal unit (lobby intercom and dwelling unit), and the signal is transmitted. It is necessary to suppress the attenuation. For this reason, the branching device is provided with a resistor that makes the branch line have a high impedance with respect to the main line. In other words, the impedance of the transmission line is lowered by the impedance of the terminal connected to the transmission line via the branching unit, the impedance between the terminal and the transmission line is not matched, and the signal is attenuated. In the branching device, the transmission line is branched through a resistor in order to compensate for a decrease in impedance due to the connection.
JP 2004-186834 A JP 2004-186835 A JP 2004-186836 A JP 2004-186837 A

  By the way, the degree of impedance reduction due to branching varies depending on the frequency band of the signal. Compared with a low frequency signal using a relatively low frequency band, a high frequency signal using a relatively high frequency band has a lower impedance. The degree of signal attenuation is increased. Further, when the frequency is high, the influence of resonance due to reflection caused by impedance mismatch becomes remarkable, and the power loss (attenuation) at the resonance frequency becomes remarkably large. On the other hand, since the above-described resonance does not occur at a low frequency, the power loss (attenuation) is small.

  However, since the branching unit of the conventional system branches the transmission line through a fixed resistor, the drop in impedance for the low frequency signal and the drop in impedance for the high frequency signal are compensated to the same extent, and the low frequency signal is more than necessary. There was a problem of attenuation.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a branching device and a transmission system of a transmission system capable of suppressing attenuation of a low-frequency signal and compensating for a decrease in impedance with respect to a high-frequency signal as compared with the conventional example. There is to do.

  In order to achieve the above object, the invention of claim 1 uses a bus type wiring form to connect a plurality of terminals via a transmission line, and uses a relatively low frequency band between the plurality of terminals. A branching device for branching another transmission path from a main transmission path, used in a transmission system that transmits a low-frequency signal and a high-frequency signal using a relatively high frequency band by frequency division multiplexing. A first connection terminal connected to the transmission line, a second connection terminal to which another branch transmission line is connected, and the first connection terminal and the second connection terminal, The attenuation of the low frequency signal in the frequency band is relatively less than the attenuation in the frequency band of the high frequency signal, and the impedance in the frequency band of the high frequency signal is relatively higher than the impedance in the frequency band of the low frequency signal. Characterized by comprising a data unit.

  The invention of claim 2 is characterized in that, in the invention of claim 1, the filter means makes the impedance variable in the frequency band of the high-frequency signal.

  The invention of claim 3 is a transmission system comprising a plurality of terminals, a plurality of branching units according to claim 2, and a master unit connected to each branching unit via a transmission path, Each branching unit is provided with a recognition signal sending means for sending a recognition signal to the transmission line when the transmission line is connected to the second connection terminal, and the recognition signal sent from each branching unit via the transmission line The base unit is provided with counting means for counting the number of branching units connected to the transmission path based on the base unit, and notification means for notifying all branching units of the count value of the counting unit via the transmission path. Each branching device is provided with a control means for adjusting the impedance by controlling the filter means in accordance with the count value notified from.

  According to the first aspect of the present invention, the amount of attenuation in the frequency band of the low frequency signal is made relatively smaller than the amount of attenuation in the frequency band of the high frequency signal, and the impedance in the frequency band of the high frequency signal is set in the frequency band of the low frequency signal. Since the filter means for making the impedance relatively higher than the impedance is provided, it is possible to suppress the attenuation of the low frequency signal and to compensate for the impedance decrease with respect to the high frequency signal as compared with the conventional example.

  According to the invention of claim 2, since the impedance of the filter means in the frequency band of the high-frequency signal is variable, an optimum impedance value can be selected according to the number of branches of the entire system. Compared to the above, it is possible to easily increase or decrease the number of branches by expanding the range in which the drop in impedance can be compensated.

  According to the invention of claim 3, a count value obtained by counting the number of branches in the entire system (the number of distribution devices) by the master unit is notified to each branch device, and the control means controls the filter means in each branch device and Since the impedance of the (branch line) can be set to an optimum value, the impedance of each branching device can be optimized automatically and quickly.

(Embodiment 1)
In the transmission system of this embodiment, a plurality of terminals 1 are connected via a transmission path (two-wire signal line) 2 in a bus-type wiring form as shown in FIG. A transmission system for transmitting a low-frequency signal using a relatively low frequency band and a high-frequency signal using a relatively high frequency band by frequency-division multiplexing and transmitting a main signal line (hereinafter referred to as a trunk line) .) A plurality of branching devices 3 are inserted at appropriate positions 2 and a terminal device 1 is connected to a signal line (hereinafter referred to as a branching line) 2 ′ branched by the branching device 3. Each terminal device 1 has a function of modulating / demodulating a digital signal by a method such as ASK (amplitude shift keying), FSK (frequency shift keying), or PSK (phase shift keying), and the transmission speed. When transmitting data that does not hinder even if it is relatively slow, use a relatively low frequency band (for example, several hundred kHz) and transmit data that needs to be transmitted at a relatively high speed. Uses a relatively high frequency band (for example, several MHz to several tens of MHz), and transmits such low frequency signals and high frequency signals by frequency division multiplexing. However, since the terminal device 1 having such a function can be realized using a conventionally known technique, a detailed description of the configuration, operation, and illustration are omitted. The signal lines (the main line 2 and the branch line 2 ′) are balanced lines.

  On the other hand, the branching device 3 includes a pair of first connection terminals 10 connected to the main line 2, a pair of second connection terminals 11 to which the branch line 2 ′ is connected, a first connection terminal 10, and a first connection terminal 10. Between the two connection terminals 11, the attenuation in the frequency band of the low frequency signal is relatively less than the attenuation in the frequency band of the high frequency signal, and the impedance in the frequency band of the high frequency signal is reduced. And a filter unit 12 that is relatively higher than the impedance in the frequency band.

  As shown in FIG. 2, the filter unit 12 includes a fourth-order simultaneous Chebyshev type low-pass filter, and specifically connects the first connection terminals 10 and 10 and the second connection terminals 11 and 11, respectively. A parallel circuit of an inductor L1 and a capacitor C1, and a parallel circuit of an inductor L2 and a capacitor C3 are connected to each other in series on the line (main line 2), and the connection points of these two parallel circuits are connected to each other via the capacitor C2. In addition, the connection point of the parallel circuit of the inductor L2 and the capacitor C3 and the second connection terminal 11 is connected via the capacitor C4. FIG. 3 shows the frequency characteristics of the filter unit 12 composed of a fourth-order simultaneous Chebyshev type low-pass filter. In the frequency band lower than about 1 MHz, the attenuation is relatively small (impedance is small). The amount of attenuation suddenly increases (impedance increases) in the range of 1 MHz to 2 MHz, and the amount of attenuation decreases again (impedance decreases) in a frequency band higher than 2 MHz.

  Thus, in the filter unit 12, the attenuation amount (impedance) with respect to the low-frequency signal (for example, several hundred kHz) is relatively small, and the impedance with respect to the high-frequency signal (for example, several MHz to several tens of MHz) is relatively Therefore, as compared with the conventional example, the attenuation of the low frequency signal can be suppressed and the impedance reduction with respect to the high frequency signal can be compensated. In the present embodiment, the case of having a bus-type wiring configuration is illustrated, but a plurality of terminals 1 are connected to a branch line 2 ′ of the branching device 3 via a hub (concentrator), thereby providing a bus type and a star type. The same effect can be expected even in a wiring form combining the above.

(Embodiment 2)
This embodiment is characterized in the configuration of the filter unit 12 in the branching device 3, and the other configurations are the same as those in the first embodiment. Therefore, the same code | symbol is attached | subjected to the same component as Embodiment 1, and description is abbreviate | omitted.

The branching device 3 in this embodiment connects a plurality of (four in the illustrated example) filter circuits 13 ₁ , 13 ₂ , 13 ₃ , and 13 ₄ and the first connection terminals 10 and 10 as shown in FIG. The selector switch SW for selectively switching and connecting the line (main line 2) and one end of the filter circuits 13 _{1 to} 13 ₄ , the second connection terminal 11 and the other end of the filter circuits 13 _{1 to} 13 ₄ are selected. It is composed of a change-over switch SW that is switched and connected. However, the change-over switches SW and SW of the filter unit 12 are switched in conjunction with each other when an operation unit (not shown) is operated. The filter circuits 13 _{1 to} 13 ₄ include the fourth-order simultaneous Chebyshev type low-pass filters described in the first embodiment, and are set to different frequency characteristics by changing the capacitances of the capacitors C2 and C4 ( (See FIG. 5). That is, attenuation in the high frequency band the capacitance of the capacitor C2, C4 in the filter circuit 13 ₁ is the smallest is minimized (see the solid line b in FIG. 5), the electrostatic capacitors C2, C4 in the filter circuit 13 ₄ The capacitance is maximum and the attenuation in the high frequency band is also maximum (see the solid line in FIG. 5), and the capacitances of the capacitors C2 and C4 in the filter circuits 13 ₂ and 13 ₃ are the second and third, respectively. The amount of attenuation in the high frequency band is also the second and third (see the solid lines b and c in FIG. 5).

Thus, by selecting the filter circuits 13 _{1 to} 13 ₄ by switching the changeover switches SW and SW, the impedance value for the high-frequency signal of the filter unit 12 is optimal according to the number of branching devices 3 inserted into the main line 2. Can be set to any value. Therefore, compared with the first embodiment in which the impedance value for the high-frequency signal is fixed, there is an advantage that the range in which the drop in impedance due to the insertion of the branching device 3 can be compensated is expanded and the number of branches can be easily increased or decreased. . Instead of selectively switching and connecting the plurality of filter circuits 13 _{1 to} 13 ₄ , variable capacitors having variable capacitance values may be used as the capacitors C 2 and C 4.

(Embodiment 3)
The transmission system of this embodiment includes a master unit 4 connected to the main line 2 as shown in FIG. However, since the basic configuration of the present embodiment is the same as that of the second embodiment, the same components are denoted by the same reference numerals and description thereof is omitted.

  The base unit 4 includes a signal transmission unit 20 for performing signal transmission with the branching unit 3 via the trunk line 2, a control unit 21 having a microcomputer as a main component, and a memory unit including a nonvolatile memory 22.

  On the other hand, in addition to the first and second connection terminals 10 and 11 and the filter unit 12, the branching unit 3 includes a signal transmission unit 14 for performing signal transmission between the main unit 4 via the trunk line 2, And a control unit 15 having a microcomputer as a main component. In the control unit 15, a signal (identification signal) including an identification code assigned to itself when the trunk line 2 is first activated with the first connection terminal 10 being connected is transmitted from the signal transmission unit 14 to the trunk line 2. To the base unit 4 via the network.

  In the master unit 4, the identification signal transmitted from the branching unit 3 is received by the signal transmission unit 20 and sent to the control unit 21, and the control unit 21 is inserted into the main line 2 based on the identification code included in the identification signal. The number of branching devices 3 is counted, and the count value is stored in the memory unit 22. Further, the control unit 21 transmits a signal (notification signal) including the latest count value stored in the memory unit 22 from the signal transmission unit 20 to all the branching devices 3 via the trunk line 2.

In each branching device 3, the signal transmission unit 14 receives the notification signal transmitted from the parent device 4 and sends it to the control unit 15. The control unit 15 determines an impedance value for a high-frequency signal suitable for the number of branching devices 3 based on the count value included in the notification signal, and controls the changeover switches SW and SW to have a value closest to the impedance value. Switch to the filter circuits 13 _{1 to} 13 ₄ .

  Thus, in the second embodiment, it is necessary to manually operate the changeover switches SW and SW to set the impedance value of the filter unit 12 to an optimum value, but in this embodiment, the filter unit 12 in each branching device 3 is set. There is an advantage that the impedance value can be automatically set to an optimum value without human intervention. As a method for the control unit 15 of the branching device 3 to determine the impedance value suitable for the number of the branching devices 3 based on the count value, the relationship between the number of the branching devices 3 and the optimum impedance value for the high-frequency signal in advance is used. A method may be employed in which the determined data table is stored in a nonvolatile memory or the like, and the control unit 15 determines the optimum impedance value by referring to the data table.

  Here, as shown in FIG. 7, by simply connecting the connector of the functional module 108 to the connection port of the gate device 103, the power path and the information path of the functional module 108 can be secured at the same time. There is a wiring system that can be connected also to the gate device 103 and is excellent in workability. In this wiring system, one or a plurality of switch boxes 102 embedded and disposed at appropriate positions in a building are provided, and a power line 110 and an information line 111 that are wired in advance in a wall surface between the switch boxes 102 are sent and wired. At the same time, with respect to the switch box 102 at the starting end, the power line 110 drawn indoors through the main breaker MB and the branch breaker BB drawn into the wiring board 101, and the gateway 120 (router) to the external Internet network NT. And the information line 111 connected via the hub). And it is also possible to branch and wire the information line 111 (that is, the trunk line 2) using the branching device 3 according to the present invention in such a wiring system.

  In this case, it is conceivable that not only the commercial power supply from the power line 110 but also the signal superposition type power from the information line 111 is supplied to the branching device 3 according to the present invention. In order to avoid such confusion between multiple types of power sources, a separation partition member is prepared on the outer surface of the branching device 3 so as to prepare for a short circuit due to contact with different wirings during construction, and then commercial power is supplied from the power line 110. In the specification, it is only necessary to perform signal transmission with respect to the information line 111 while avoiding power supply, and in the specification in which signal superposition type power supply from the information line 111 is performed, it is necessary to avoid commercial power supply from the power line 110. In the specification in which the power line 110 is not passed through the branching device 3 or the power line 110 must be connected to the branching device 3, the power line 110 and the information line 111 in the branching device 3 should be insulated. What is necessary is just to set it as high impedance about a commercial AC frequency band.

1 is a system configuration diagram illustrating a first embodiment of the present invention. It is a block diagram of the filter part in the same as the above. It is a figure which shows the frequency characteristic of the filter part in the same as the above. It is a system configuration figure showing Embodiment 2 of the present invention. It is a figure which shows the frequency characteristic of the filter circuit in the same as the above. It is a system configuration | structure figure which shows Embodiment 3 of this invention. It is a system configuration diagram of a wiring system using the same.

Explanation of symbols

1 Terminal 2 Main line (transmission path)
2 'branch line (transmission path)
DESCRIPTION OF SYMBOLS 3 Branch device 10 1st connection terminal 11 2nd connection terminal 12 Filter part

Claims (3)

A plurality of terminals are connected via a transmission line in a bus-type wiring form, and a low frequency signal using a relatively low frequency band and a high frequency signal using a relatively high frequency band between the plurality of terminals. Is a branching device for branching another transmission path from the main transmission path, which is used in a transmission system for frequency division multiplexing transmission.
Inserted between the first connection terminal connected to the main transmission line, the second connection terminal to which another branch transmission line is connected, and the first connection terminal and the second connection terminal The attenuation in the frequency band of the low frequency signal is relatively less than the attenuation in the frequency band of the high frequency signal, and the impedance in the frequency band of the high frequency signal is relatively higher than the impedance in the frequency band of the low frequency signal. A branching unit for a transmission system, comprising a filtering means for performing   2. A branching device for a transmission system according to claim 1, wherein the filter means makes the impedance variable in the frequency band of the high frequency signal. A transmission system comprising a plurality of terminals, a plurality of branching units according to claim 2, and a master unit connected to each branching unit via a transmission line,
Each branching unit is provided with a recognition signal sending means for sending a recognition signal to the transmission line when the transmission line is connected to the first and second connection terminals, and sent from each branching unit via the transmission line. Counting means for counting the number of branching units connected to the transmission path based on the recognition signal, and notification means for notifying all branching units via the transmission path of the count value of the counting means are provided in the master unit. The transmission system is characterized in that each branching unit is provided with a control means for adjusting the impedance by controlling the filter means according to the count value notified from the master unit.

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