JP2011244388A - Wired communication system and terminator used for the same - Google Patents

Abstract

In a communication method using different frequency bands, relatively high communication quality can be ensured without hindering transmission of communication power as much as possible.
A termination circuit is provided at the ends of branch lines. The termination circuit 70 is shunt connected to the outlet 41. The termination circuit 70 includes a filter 73 and a circuit element 74. The filter 73 blocks the signal in the first frequency band, but passes the signal in the second frequency band. The impedance of the circuit element 74 is adjusted so as to suppress the generation of a reflected wave at the end of the branch line 21 or 22.
[Selection] Figure 2

Description

  The present invention relates to a wired communication system, and more particularly to a wired communication system related to wired communication performed via a branch line branched toward a terminal and a termination device used therefor.

  In wired communication, for example, communication is performed by placing a signal on a carrier wave in a certain frequency band. Power line carrier communication (so-called PLC), which is an example of such wired communication, performs communication using a power line that supplies power as a transmission path. In indoor power line communication, a communication device is connected to a power supply outlet to which power wiring is connected, and transmission / reception is performed between the communication devices connected to the outlet. Such a PLC includes a so-called high-speed PLC that uses a frequency band of 2 MHz to 30 MHz and a so-called low-speed PLC that uses a frequency band of 10 kHz to 450 kHz. The high-speed PLC is assumed to have a physical transmission speed of about 200 Mbps (bit per second), and is suitable for transmission of video signals and the like. The low-speed PLC is assumed to have a physical transmission rate of about 7.5 kbps and is suitable for transmission of control signals and the like of electrical equipment.

  By the way, in a PLC to which an electrical device is not connected, the branch portion of the power wiring including the outlet may be in an open stub state, which may adversely affect communication quality. As a technique for solving this problem, Patent Document 1 discloses a technique for matching impedance by inserting a termination circuit into a power line outlet. The termination circuit is adjusted to have a termination impedance equivalent to the characteristic impedance of the power line cable at the usage frequency of the PLC.

JP 2003-264486 A

  In the high-speed PLC, for example, a quarter wavelength in a signal carrier wave when a VVF (600 V vinyl insulated vinyl sheath cable flat type) line is used is 1.5 m to 22 m. This length is equal to or shorter than the length of the cable normally used in the power wiring corresponding to the branch line branched from the main line in the PLC indoor wiring. Therefore, in order to prevent the branch line power line cable from being in an open stub state, it is appropriate to provide a termination circuit having a termination impedance equivalent to the characteristic impedance of the power line cable.

  However, in the low-speed PLC, the ¼ wavelength in the signal carrier when the VVF line is used is 100 m to 4400 m. This length is sufficiently longer than the length of cables normally used in branch lines for indoor wiring. For this reason, the cable normally used with the branch line of an indoor wiring is difficult to be in an open stub state at a low speed PLC. That is, in the low-speed PLC communication, it is less necessary to provide a termination circuit to prevent the open stub state from occurring in comparison with the high-speed PLC. On the other hand, when a termination circuit is applied to a branch line to which no electrical device is connected, power is transmitted to the termination circuit even though transmission of communication power is not required. Communication power will be reduced. Therefore, in a low-speed PLC, transmission of the original communication power may be hindered because of a termination circuit that is less necessary than a high-speed PLC.

  An object of the present invention is to provide a wired communication system capable of ensuring a relatively high communication quality without interfering with transmission of communication power as much as possible in a communication system using different frequency bands, and a termination device used therefor.

  In the wired communication system according to the present invention, both the first frequency band that does not overlap with the frequency band used for power supply and the frequency band used for power supply are connected to each other through the power wiring that supplies power to the electrical device. A wired communication system in which communication is performed in each of the second frequency bands that do not overlap with the first frequency band, the branch line branching toward a terminal to which an electrical device is connected in the power wiring, A filter circuit that blocks a signal in the first frequency band and passes the signal in the second frequency band; and a circuit element having an impedance that suppresses generation of a reflected wave at an end of the branch line; The circuit and the circuit element are connected in series with each other and are shunt-connected to the end of the branch line.

  In addition, the termination device of the present invention includes both a first frequency band that does not overlap with a frequency band used for power supply and a frequency band used for power supply via a power wiring that supplies power to an electrical device. In the wired communication system in which communication is performed in each of the second frequency bands that do not overlap with the first frequency band, the termination device is shunt-connected to the end of the branch line in the power wiring, and the first frequency A filter circuit that blocks a signal in a band and passes a signal in the second frequency band and a circuit element having an impedance that suppresses generation of a reflected wave at the end of the branch line are connected in series.

  According to the wired communication system and the termination device of the present invention, in the filter circuit, a signal passes through one circuit band and passes through a circuit element, but a signal is blocked in the other frequency band. Therefore, in one frequency band that requires a termination circuit to ensure communication quality, the circuit element plays the role of a termination circuit, and in the other frequency band where it is not necessary to provide a termination circuit, the signal passes through the circuit element. Thus, a configuration in which communication power is not easily transmitted unnecessarily is realized.

  Further, in the present invention, a quarter wavelength in the second frequency band of the signal carrier wave propagating through the branch cable is compared with a quarter wavelength of the signal carrier in the first frequency band, It is preferable that the length of the branch cable is closer. According to this, the branch cable is likely to be in an open stub state in the second frequency band, and the branch cable is not likely to be in an open stub state in the first frequency band. For this reason, in the second frequency band that requires a termination circuit, the circuit element plays the role of a termination circuit, and in the first frequency band where the necessity of providing a termination circuit is low, no signal passes through the circuit element, and communication The power is not easily transmitted unnecessarily.

  In the present invention, the first frequency band may be a band from 10 kHz to 450 kHz, and the second frequency band may be a band from 2 MHz to 30 MHz. According to this, the present invention is applied when both a low speed PLC (frequency band of 10 kHz to 450 kHz) and a high speed PLC (frequency band of 2 MHz to 30 MHz) are used.

  In the present invention, the quotient obtained by dividing the impedance of the circuit element by the characteristic impedance when the branch cable side is viewed from the circuit element side is 0.7 or more and 3 or less in the second frequency band. Is preferred. According to this, VSWR (voltage standing wave ratio) becomes relatively good, and communication quality is improved.

  In the present invention, the filter circuit may include a capacitor, and the circuit element may include a resistance element. According to this, the filter circuit and the circuit elements are realized with a simple configuration.

In the present invention, the quotient obtained by dividing the impedance of the circuit element by the characteristic impedance when the branch cable side is viewed from the circuit element side is 1 or more and 2 in both the first and second frequency bands. The product of the capacitance of the capacitor and the characteristic impedance when the branch cable side is viewed from the circuit element side is 7 * 10 ⁻⁸ or more and 9 * in both the first and second frequency bands. It is preferably 10 ⁻⁸ or less. According to this, VSWR becomes relatively good, and communication quality is improved.

  In the present invention, the filter circuit and the circuit element may be provided in any of a tap, an outlet, and an electric device connected to the end of the branch cable.

It is a block diagram which shows the wiring structure of the power line communication system which concerns on one Embodiment of this invention. FIG. 2 is a circuit diagram of a termination circuit provided in the system of FIG. 1. It is a graph which shows the characteristic of VSWR in the branch line which concerns on a 1st Example. It is a graph which shows the relationship between VSWR and a return loss in a 1st Example. FIG. 6 is a circuit diagram of a termination circuit according to a second embodiment. It is a graph which shows the characteristic of VSWR in the branch line which concerns on a 2nd Example. It is a graph which shows the range where VSWR satisfies a predetermined condition. FIG. 6 is a circuit diagram of a termination circuit according to a third example. FIG. 9 is a circuit diagram of a termination circuit according to a fourth example.

  A communication system 1 according to an embodiment of the present invention will be described. The communication system 1 has a communication wiring laying structure as shown in FIG. The communication wiring uses power wiring for supplying power to a plurality of outlets 41 provided indoors, and branches into a plurality of wirings toward the outlet 41 provided at the end. Specifically, a single-phase three-wire main line 10 that is a main line, and branch lines 21 and 22 that are branch lines branched from the main line 10 are provided. Both branch lines 21 and 22 are connected in phase with the main wiring 10. Electrical devices such as communication devices 51 and 52 connected to the outlet 41 communicate with each other via the main wiring 10 and the branch lines 21 and 22 and receive power supply from the outlet 41.

  In a wired communication system such as the communication system 1, a plurality of frequency bands may be used depending on a communication method. Power line carrier communication (so-called PLC) that uses power wiring as communication wiring includes so-called low-speed PLC that uses a frequency band of 10 kHz to 450 kHz and so-called high-speed PLC that uses a frequency band of 2 MHz to 30 MHz. As the communication system 1, a system that can support both high-speed PLC and low-speed PLC is assumed. For power supply, a frequency band that does not overlap with either the high-speed PLC or the low-speed PLC is used. For example, in the case of a general commercial frequency in which a frequency such as 50 Hz or 60 Hz is used, the power supply frequency band is a frequency band lower than that of the low-speed PLC.

  By the way, when an electrical device such as the communication devices 51 and 52 is not connected to the outlet 41, the branch lines 21 and 22 are in an open stub state. The signal wave propagated from the main wiring 10 to the branch lines 21 and 22 is reflected at the outlet 41 at the end. The reflected wave reflected at the outlet 41 overlaps with the signal wave propagating through the main line 10 when returning to the main line 10. This may adversely affect the quality of communication via the main line 10. In order to prevent such an adverse effect, it is conceivable to provide a terminal resistance at the ends of the branch lines 21 and 22.

  On the other hand, whether or not the reflected wave adversely affects the quality of communication via the main wiring 10 is determined between the reflected wave and the signal wave propagating through the main wiring 10 at the branch point between the main wiring 10 and the branch lines 21 and 22. Depends on phase difference. The closer these phase differences are to 180 degrees, the easier the original signal wave in the main wiring 10 is weakened by the reflected wave, and the communication quality deteriorates. How much phase difference occurs depends on the length L1 of the branch line 21 and the length L2 of the branch line 22, the characteristics of the cables used for these branch lines, and the frequency of the signal wave.

  For example, when a VVF (600V vinyl insulated vinyl sheath cable flat type) cable is used for the branch lines 21 and 22, the length of the quarter wavelength of the cable is 1.5 m to 22 m in the frequency band of the high-speed PLC. That is, in 2 MHz to 30 MHz, which is the frequency band of the high-speed PLC, the quarter wavelength of the signal wave propagating through the VVF cable is 1.5 m to 22 m. This length is equal to or shorter than the lengths L1 and L2 of cables normally used as branch lines in indoor wiring. In this case, since the phase difference between the reflected wave and the original signal wave at the branch point of the wiring is close to 180 degrees, the adverse effect of the reflected wave on the signal wave of the main wiring 10 tends to be a problem. Therefore, since the generation of the reflected wave can be suppressed by providing a terminal resistor at the end of the branch line 21 or 22, the adverse effect of the reflected wave on the signal wave of the main wiring 10 can be appropriately suppressed.

  On the other hand, in the frequency band of the low-speed PLC, the length of the quarter wavelength of the VVF cable is 100 m to 4400 m. This length is sufficiently larger than the lengths L1 and L2 of cables normally used as branch lines in indoor wiring. In this case, since the phase difference between the reflected wave and the original signal wave at the branch point of the wiring is sufficiently smaller than 180 degrees, the adverse effect on the original signal wave due to the reflected wave becomes a problem compared to the case of the high-speed PLC. Hateful. Therefore, in the low-speed PLC, there is a possibility that the communication power is wasted because the signal passes through the termination resistor although the necessity of providing the termination resistor at the end of the branch lines 21 and 22 is low.

  Therefore, in the communication system 1 according to the embodiment of the present application, the following configuration that can appropriately ensure relatively high communication quality is adopted while considering the difference between the above circumstances between the high-speed PLC and the low-speed PLC.

  That is, a termination circuit 70 is provided at each end of the branch lines 21 and 22. The termination circuit 70 is inserted into the outlet 41 or built into the outlet 41. Or you may incorporate in the tap connected to the electrical outlet 41, or an electric equipment. Specifically, the termination circuit 70 is connected to terminals 75 and 76 via wirings 71 and 72 as shown in FIG. The terminal 75 is connected to the end of the branch line 21 or 22, and the terminal 76 is connected to the outlet 41. Wires 71 and 72 are connected to the terminals 75 and 76 to connect them. The termination circuit 70 includes a filter 73 and a circuit element 74 that are connected in series with each other. The filter 73 and the circuit element 74 are shunt-connected to the outlet 41 so as to straddle between the wirings 71 and 72. The filter 73 blocks the signal in the frequency band (first frequency band) corresponding to the low-speed PLC, and passes the signal in the frequency band (second frequency band) corresponding to the high-speed PLC. The impedance of the circuit element 74 is adjusted to match the characteristic impedance of the power wiring. Specific adjustment methods will be described in first to fourth embodiments described later.

  When an electrical device such as the communication devices 51 and 52 is not connected to the outlet 41, the signal is blocked by the filter 73 in the low-speed PLC frequency band. For this reason, the impedance when the terminal circuit 70 side is viewed from the terminal 75 in FIG. 2 is a characteristic of the terminal 76 to which no electrical device is connected, that is, open. On the other hand, in the frequency band of the high-speed PLC, the filter 73 passes the signal. Therefore, the impedance when the terminal circuit 70 side is viewed from the terminal 75 in FIG.

  When an electrical device such as the communication device 51 or 52 is connected to the outlet 41, the signal is blocked by the filter 73 in the low-speed PLC frequency band. For this reason, the impedance when the termination circuit 70 side is viewed from the terminal 75 side in FIG. 2 is the characteristic of the terminal 76 to which the electrical device is connected, that is, the input impedance of the electrical device. On the other hand, in the frequency band of the high-speed PLC, the impedance when the terminal circuit 70 side is viewed from the terminal 75 side in FIG. 2 is the impedance of the parallel connection of the input impedance of the electrical equipment connected to the terminal 76 and the impedance of the circuit element 74. Become.

  With the above configuration, in the frequency band corresponding to the low-speed PLC, the filter 73 blocks the signal, so the circuit element 74 does not function as a termination resistor. And in the outlet 41 to which an electric equipment is not connected, the outlet 41 is terminated with high impedance. Thereby, in the frequency band corresponding to the low-speed PLC, when the branch line 21 or 22 is viewed from the branch point from the main line 10 to the branch line 21 or 22, the impedance is high, and there is no branch line 21 or 22 Close to. For this reason, unnecessary communication power consumption is prevented. On the other hand, in the frequency band corresponding to the high-speed PLC, the filter 73 passes the signal, so that the circuit element 74 functions as a termination resistor. Thereby, since it is suppressed that each terminal of branch lines 21 and 22 becomes inconsistent with the characteristic impedance of electric power wiring, the reflected wave in the terminal of branch lines 21 and 22 is controlled, and via basic wiring 10 Communication quality is ensured.

(First embodiment)
Hereinafter, first to fourth examples according to the present embodiment will be described. In the first embodiment, the filter 73 and the circuit element 74 are configured as follows. 2, the impedance of the circuit element 74 is Z, the input impedance of the electrical equipment connected to the terminal 76 is R, and the characteristic impedance of the power wiring is Zo. At this time, the filter 73 blocks the signal in the frequency band of the low-speed PLC and passes the signal in the frequency band of the high-speed PLC, so the ratio of the impedance Zin viewed from the terminal 75 to the termination circuit 70 side to Zo is become that way.

  (1) When no electrical device is connected to the terminal 76 (open) and in the low-speed PLC frequency band: Zin (open, low-speed PLC) / Zo = high impedance (Equation 1)

  (2) When no electrical device is connected to the terminal 76 (open) and in the frequency band of the high-speed PLC: Zin (open, high-speed PLC) / Zo = Z / Zo (Equation 2)

  (3) When electrical equipment is connected to the terminal 76 and the frequency band is low-speed PLC: Zin (connection, low-speed PLC) / Zo = R / Zo (Equation 3)

  (4) When electrical equipment is connected to the terminal 76 and in the frequency band of high-speed PLC: Zin (connection, high-speed PLC) / Zo = 1 / {1 / (R / Zo) + 1 / (Z / Zo) } (Formula 4)

  The voltage standing wave ratio (VSWR) in the branch line 21 or 22 is expressed as VSWR = (1+ | S |) / (1- | S |), where S is the reflection coefficient. Here, S = (Zin / Zo-1) / (Zin / Zo + 1). Therefore, VSWR is VSWR = Zin / Zo when Zin> Zo, and VSWR = Zo / Zin when Zin <Zo. In the case of (2) or (3), k = R / Zo or k = Z / Zo, and in the case of (4), when k = Z / Zo = R / Zo, The dependence of VSWR on k in each case of 4) is as shown in FIG. 3A and FIG. In FIG. 5, “(open, high speed PLC)”, “(connection, high speed PLC)” and “(connection, low speed PLC)” indicate the cases (2) to (4), respectively.

  In the above case, in the case of (4), k = Z / Zo = R / Zo is that the two parameters of Z / Zo and R / Zo are considered independently, and the VSWR described later is within an appropriate range. Since it becomes complicated to set the following conditions, the conditions are simplified. Further, the simplification of k = Z / Zo = R / Zo is that the input impedance R of the electric device to be connected is usually adjusted to match the characteristic impedance Zo of the power wiring. Also, the termination impedance Z in the high-speed PLC when no electrical device is connected is usually adjusted to match the characteristic impedance Zo of the power wiring. Because Z and R are close to each other from these, it is appropriate to simplify Z = R.

  In general, the matching circuit is relatively matched when the condition of VSWR ≦ 3 is satisfied, and very well matched when the condition of VSWR ≦ 2 is satisfied. In all cases (2) to (4), the conditions satisfying VSWR ≦ 3 are 0.7 ≦ Z / Zo ≦ 3 and 0.7 ≦ R / from FIGS. 3 (a) and 3 (b). This is the case when Zo ≦ 3. Therefore, when this condition is satisfied, the circuit can be relatively matched in all cases (2) to (4). Also, in all cases (2) to (4), VSWR ≦ 2 is satisfied from FIGS. 3A and 3B, from 1 ≦ Z / Zo ≦ 2 and 1 ≦ R / Zo ≦. 2 Therefore, when this condition is satisfied, the circuit can be very well matched in all cases (2) to (4). In the case of (1), the branch lines 21 and 22 are terminated with high impedance. Therefore, when an electrical device is not connected to the outlet 41, the influence of the branch line to the outlet 41 on the main wiring 10 in the frequency band of the low-speed PLC can be ignored.

  FIG. 3C shows the dependence of VSWR on k1 at k2 when k1 = Z / Zo and k2 = R / Zo in the case of (4) without k = Z / Zo = R / Zo. Showing sex. From FIG. 3C, even in the case of k1 ≠ k2, VSWR ≦ 3 is obtained when the conditions of 0.7 ≦ k1 ≦ 3 and 0.7 ≦ k2 ≦ 3 are satisfied, and 1 ≦ k1 ≦ 2 and 1 ≦ It is confirmed that VSWR ≦ 2 is satisfied when the condition of k2 ≦ 2 is satisfied. As described above, according to the first embodiment, when Z and R satisfy the above conditions, it is possible to prevent deterioration in communication quality in both the high-speed PLC and the low-speed PLC frequency bands.

The significance of adopting the condition of VSWR ≦ 3 is as follows in more detail. Assuming that the reflection coefficient is S, the return loss at the terminal 75 is return loss [dB] = − 20 * log ₁₀ (| S |). On the other hand, since VSWR is expressed as VSWR = (1+ | S |) / (1- | S |), the relationship between VSWR and return loss is as shown in FIG. As shown in FIG. 4, VSWR = 3 is a point where the loss due to reflection increases rapidly. Therefore, by setting VSWR ≦ 3, loss due to reflection can be suppressed.

(Second embodiment)
In the second embodiment, as shown in FIG. 5, a termination circuit 170 in which a capacitor element 173 and a resistance element 174 are connected in series is used. When the capacitance of the capacitor element 173 is C1 and the resistance value of the resistance element 174 is R1, the ratio of the impedance Zin viewed from the terminal 75 to the termination circuit 170 side to the characteristic impedance Zo of the power wiring is as shown in the following equation. . In the following equation, ω is the angular frequency (2 * π * frequency) of the signal wave, and j is an imaginary unit.

  (5) When an electrical device is not connected to the outlet 41 (open): Zin (open) / Zo = R1 / Zo-j / (ω * C1 * Zo) (Formula 5)

  (6) When an electrical device is connected to the outlet 41: Zin (connection) / Zo = 1 / [1 / {(R1 / Zo) -j / (ω * C1 * Zo)} + 1 / (R / Zo ]] ... (Formula 6)

  When the reflection coefficient is S, VSWR is VSWR = (1+ | S |) / (1- | S |), and S = (Zin / Zo-1) / (Zin / Zo + 1). Therefore, when the above formulas 5 and 6 are substituted into this, the VSWR in each case of (5) and (6) is obtained as follows.

  Here, k = R1 / Zo = R / Zo. The reason for this condition is the same as in the first embodiment. FIGS. 6A to 6D show the dependency of VSWR on (Zo * C1) when k = 1 or k = 2 in the cases of (5) and (6). . In each figure, graphs are drawn when the frequency of the signal wave is a lower limit of 10 kHz and an upper limit of 450 kHz in the low-speed PLC frequency band, and when the frequency of the signal wave is a lower limit of 2 MHz and an upper limit of 30 MHz in the frequency band of the high-speed PLC. It is. 6A shows a graph when k = 1 in the case of (5), and FIG. 6B shows a graph when k = 2 in the case of (5). ) Represents a graph when k = 1 in the case of (6), and FIG. 6D represents a graph when k = 2 in the case of (6).

From FIG. 6A and FIG. 6B, in a state where no electrical device is connected to the outlet 41, 7 * 10 ⁻⁸ [ΩF] ≦ ( It is shown that VSWR ≦ 3 in the frequency band of the high-speed PLC when Zo * C1) is satisfied. It is also shown that VSWR> 10 in the low-speed PLC frequency band when (Zo * C1) ≦ 9 * 10 ⁻⁸ [ΩF] is satisfied. From FIG.6 (c) and FIG.6 (d), when the electric equipment was connected to the outlet 41, it was shown by the graph in the range which becomes the range of 1 <= k <= 2. In any value of C1), it can be seen that VSWR is less than 3 regardless of whether the frequency band is a low speed PLC or a high speed PLC.

  Note that VSWR> 10 is set so that the termination is close to the open state. More specifically, in FIG. 4, VSWR = 10 corresponds to a point that when the VSWR becomes larger than this, the return loss becomes sufficiently small and the state becomes close to an open state.

From the above, within the range of 1 ≦ k ≦ 2, when the condition of 7 * 10 ⁻⁸ [ΩF] ≦ (Zo * C1) ≦ 9 * 10 ⁻⁸ [ΩF] is satisfied, (a) the electric device is connected (B) Matching can be performed in the frequency band of the high-speed PLC in a state where no electrical equipment is connected. c) The branch line to the outlet 41 can be terminated with high impedance in the frequency band of the low-speed PLC in a state where no electrical device is connected.

  Similarly, with respect to k having various sizes other than the range of 1 ≦ k ≦ 2, the condition of (Zo * C1) that satisfies all the following conditions (A) to (C) is obtained. FIG. The thick line in FIG. 7 satisfies all of (A) to (C) in each case of k = 0.6, 0.7, 0.8, 1, 1.5, 2, 2.5 (Zo The range of * C1) is shown. (B) VSWR> 10 in the low-speed PLC frequency band when no electrical equipment is connected to the outlet 41, and (b) VSWR in the high-speed PLC frequency band when no electrical equipment is connected to the outlet 41. ≦ 3, and (c) In a state where the electrical device is connected to the outlet 41, VSWR ≦ 3 is satisfied regardless of whether the frequency band is the low speed PLC or the high speed PLC. As shown in FIG. 7, in order to take a relatively wide range of (Zo * C1) and take a somewhat wide range that satisfies the conditions (a) to (c) with respect to k, 1 ≦ k ≦ It is preferable to assume 2.

(Third embodiment)
In the third embodiment, it is assumed that the outlet 41 is not used for supplying power to the electric device in the first embodiment. In this case, unlike the termination circuit 270 shown in FIG. 8, there is no terminal to which an electrical device is connected, and only proper termination is performed. Accordingly, since only the case (2) in the first embodiment is assumed, the impedance Z of the circuit element 74 is adjusted so as to satisfy VSWR ≦ 3 in FIG. 3A corresponding to the case (2). It only has to be done. The condition for satisfying VSWR ≦ 3 is 0.3 ≦ Z / Zo ≦ 3 from FIG. Further, the condition for satisfying VSWR ≦ 2 is 0.5 ≦ Z / Zo ≦ 2. As a result, the branch line of the present embodiment is terminated with high impedance in the frequency band of the low-speed PLC, and the influence of the branch line on the communication quality in the main wiring 10 can be suppressed in the frequency band of the high-speed PLC. In addition, since it is only necessary to cope with the case where the electrical device is not connected, the range of Z where VSWR ≦ 3 becomes wider than that in the first embodiment.

(Fourth embodiment)
In the fourth embodiment, in the second embodiment, it is assumed that the outlet 41 is not used for supplying power to the electrical equipment. In this case, unlike the termination circuit 370 shown in FIG. 9, there is no terminal to which the electrical device is connected, and only proper termination is performed. Therefore, since only the case of (5) in the second embodiment is assumed, the conditions of (a) and (b) in FIGS. 6 (a) and 6 (b) corresponding to the case of (5) are assumed. Should be satisfied. Assuming that 1 ≦ k ≦ 2, the condition is 7 * 10 ⁻⁸ [ΩF] ≦ (Zo * C1) ≦ 9 * 10 ⁻⁸ [ΩF] as described in the second embodiment. .

<Modification>
The above is a description of a preferred embodiment of the present invention, but the present invention is not limited to the above-described embodiment, and various modifications can be made within the scope described in the means for solving the problem. It is possible.

  For example, in the above-described embodiment, a frequency band of a high-speed PLC and a frequency band of a low-speed PLC are assumed as two frequency bands used for communication. However, the present invention may be applied to a communication system using two different frequency bands other than the case of using a high-speed PLC and a low-speed PLC.

  In the above-described embodiment, it is assumed that power line communication is performed using a single-phase three-wire power line, and communication in the same phase is performed. However, the case where the communication in a different phase is included may be assumed and systems other than a single phase 3 wire type may be used as a power line.

  Further, in the above-described embodiment, it is assumed that the power wiring branches by one stage. That is, it is assumed that the branch line 21 and the branch line 22 are branched only once from the main line 10 serving as the main line. However, the present invention may be applied to power wiring in which branch lines branch from the power transmission source in multiple stages. For example, the present invention may be applied to a power wiring having a tree structure in which a branch line branched from a power transmission source into a plurality of branches is further branched into a plurality of branch lines.

  Further, in the above-described embodiment, a capacitor is used as a specific example of the filter 73. However, as long as it is configured to pass the high-speed PLC frequency band and suppress the signal in the low-speed PLC frequency band, Any circuit configuration may be used. The filter 73 and the circuit element 74 may be provided as a single element, or may be provided as a circuit element including a plurality of elements.

DESCRIPTION OF SYMBOLS 1 Communication system 10 Main line 21,22 Branch line 41 Outlet 51,52 Communication equipment 73 Filter 74 Circuit element 173 Capacitor element 174 Resistance element 70,170,270,370 Termination circuit

Claims (8)

The first frequency band that does not overlap with the frequency band used for power supply via the power wiring that supplies power to the electrical equipment, and the frequency band used for power supply does not overlap with the first frequency band A wired communication system in which communication is performed in each of the second frequency bands,
In the power wiring, a branch line branched toward the end to which the electrical equipment is connected,
A filter circuit that blocks the signal of the first frequency band and passes the signal of the second frequency band;
A circuit element having an impedance for suppressing generation of a reflected wave at an end of the branch line,
The wired communication system, wherein the filter circuit and the circuit element are connected in series to each other and are shunt-connected to the end of the branch line.   The quarter wavelength in the second frequency band of the signal carrier propagating through the branch line is longer than the quarter wavelength of the signal carrier in the first frequency band, depending on the length of the branch line. The wired communication system according to claim 1, wherein the wired communication system is close.   The wired communication system according to claim 1 or 2, wherein the first frequency band is a band from 10 kHz to 450 kHz, and the second frequency band is a band from 2 MHz to 30 MHz.   The quotient obtained by dividing the impedance of the circuit element by the characteristic impedance when the branch line side is viewed from the circuit element side is 0.7 or more and 3 or less in the second frequency band. The wired communication system according to any one of?   The wired communication system according to any one of claims 1 to 4, wherein the filter circuit includes a capacitor, and the circuit element includes a resistance element. The quotient obtained by dividing the impedance of the circuit element by the characteristic impedance when the branch line side is viewed from the circuit element side is 1 or more and 2 or less in any of the first and second frequency bands,
The product of the capacitance of the capacitor and the characteristic impedance when the branch line side is viewed from the circuit element side is 7 * 10 ⁻⁸ or more and 9 * 10 ⁻⁸ or less in any of the first and second frequency bands. The wired communication system according to claim 5, wherein:   The wired communication according to any one of claims 1 to 6, wherein the filter circuit and the circuit element are provided in any of a tap, an outlet, and an electrical device connected to an end of the branch line. system. The first frequency band that does not overlap with the frequency band used for power supply via the power wiring that supplies power to the electrical equipment, and the frequency band used for power supply does not overlap with the first frequency band In a wired communication system in which communication is performed in each of the second frequency bands, a termination device that is shunt connected to an end of a branch line in the power wiring,
A filter circuit that blocks the signal of the first frequency band and passes the signal of the second frequency band, and a circuit element having an impedance that suppresses generation of a reflected wave at the end of the branch line are in series with each other A terminal device characterized by being connected.