JP2006166015A - Power line carrier communication system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a power line carrier communication system capable of realizing both a reduction in common-mode current and restraint on the generation of a standing wave and besides a common-mode current reducing filter suitable for the construction of the system. <P>SOLUTION: There is provided a power line carrier communication system (a PLC modem 10) equipped with a power line carrier communication (PLC modem 10) apparatus, a power line 11 connected to the PLC modem 10 to transmit communication signals, and filters 1, 2 arranged on the power line 11 to reduce the common-mode current. In the power line communication system, an impedance for the common-mode current of the filter 1 arranged in the PLC modem 10 side is made larger than that of the filter 2. The filters 1, 2 each comprise magnetic members 1a, 2a and windings 1b, 2b wound around the magnetic members 1a, 2a, while the number of turns of the winding 1b in the filter 1 is made larger than that of the winding 2b in the filter 2 to thereby increase a common mode impedance. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a power line carrier communication system that performs communication using a power line, and a common mode current reduction filter suitable for the power line carrier communication system. In particular, the present invention relates to a power line carrier communication system and a common mode current reduction filter that can suppress the occurrence of standing waves while suppressing the common mode current.

  In recent years, power line communication (PLC) that performs high-speed communication by superimposing a high-frequency signal on a power line has been studied (for example, see Non-Patent Document 1).

  FIG. 6 is an explanatory diagram schematically showing an overview of a PLC communication system, and shows a case where the PLC user house is a detached house. In this method, as shown in FIG. 6, a power line for supplying power to the PLC user house 200 is used as a signal transmission path. In the example shown in FIG. 6, the optical fiber cable 103 is used for communication from the host network 300 to the transformer 102 side arranged on the utility pole 101, and the low-voltage distribution line 100 and the lead-in line are used for communication from the transformer 102 side to the house 200. Power lines such as 201 and indoor wiring 202 are used. On the utility pole 101 on which the low-voltage distribution line 100 and the optical fiber cable 103 are installed, a PLC modem (parent modem) 104 is connected to the host network 300 and transmits and receives communication signals. The house 200 includes PLC modems (child modems) 203A and 203B that transmit and receive communication signals to and from the parent modem 104. The terminal devices 204A and 204B such as personal computers are connected to the child modems 203A and 203B, and the PLC user transmits a communication signal from the parent modem 104 via the terminal device 204A (or 204B) and the child modem 203A (or 203B). The communication signal is transmitted to the parent modem 104.

  The signal frequency band used in the communication system is approximately 1 to 50 MHz, which is higher than the frequency of the power supply current normally transmitted to the power line (commercial frequency, for example, 50 Hz or 60 Hz). When the high-frequency communication signal is superimposed on the power line from the parent modem or the child modem, a common mode current is generated. This common mode current becomes a drive source, and the power line becomes an antenna to generate a leakage magnetic field. May adversely affect the radio equipment. Therefore, a ferrite core or a common mode choke coil is used as a common mode filter in order to prevent the common mode current from being transmitted downstream from the signal source (parent modem, child modem, etc.) (for example, Patent Document 1). (See paragraph 0003). These common mode filters are used by directly wrapping a power line such as a wiring cord to which the PLC modem is connected around a ferrite core, or by connecting a choke coil in the vicinity of the PLC modem in the power line to which the PLC modem is connected. The power line and coil wound around the ferrite core function as an inductor that generates a large impedance with respect to the common mode current. This impedance attenuates the common mode current and suppresses the transmission of the common mode current downstream of the filter as viewed from the PLC modem.

JP 2000-114048 Kiyoshi Eto, “Current Status of Power Line Communication (PLC)”, Interface, CQ Publisher, September 2000, p.70-81

In order to more effectively reduce the common mode current, it is effective to increase the impedance. Increasing the impedance includes increasing the number of windings of power lines and coils with respect to the ferrite core. However, increasing the number of turns increases the common mode impedance, which may cause a mismatch between the impedance of the filter portion and the impedance of the power line to which the PLC modem is connected. At this time, a reflected wave is generated with the filter portion as a reflection end, and a standing wave due to the reflected wave is generated on the power line that is the signal transmission path. This standing wave valley, peak of the mountain, especially peak of the peak May affect other radio equipment. FIG. 5 is an explanatory diagram for explaining the mechanism by which a standing wave is generated. As shown in FIG. 5, a common mode filter F _{0 in} which a winding is wound around a ferrite core is disposed in the vicinity of a PLC modem 110 (for example, a parent modem). This filter F ₀ is assumed to increase the number of turns of the winding in order to effectively attenuate the common mode current from the PLC modem 110. That is, the common mode impedance Z ₀ of the filter F ₀ is much larger than the common mode impedance Z of the power line 120 to which the PLC modem 110 is connected, and Z ₀ >> Z. At this time, a part of the signal (incident wave in ₀ ) emitted from the end 130 (for example, the child modem) side of the power line 120 is reflected by the filter F ₀ and the remaining (transmitted wave thr ₀ ) is transmitted to the PLC modem 110. Is done. The reflected wave ref ₀ and the incident wave in ₀ are combined to generate a standing wave. In particular, when the distance between the terminal 130 and the filter F ₀ (standing wave generation possibility section 0) becomes longer, a plurality of standing wave peaks appear continuously.

  Accordingly, a main object of the present invention is to provide a power line carrier communication system capable of suppressing the generation of a standing wave even when the number of windings wound around a magnetic member is increased in order to reduce the common mode current. There is. Another object of the present invention is to provide a common mode current reduction filter suitable for the power line carrier communication system.

  The present invention achieves the above-mentioned object by providing a plurality of filter parts made of a magnetic member around which windings are wound, and by providing a set of filter parts having different winding numbers.

  That is, the present invention comprises a power line carrier communication device, a power line connected to the power line carrier communication device and transmitting a communication signal, and a plurality of filter units arranged on the power line to reduce a common mode current. The power line carrier communication system. The plurality of filter units include a combination of at least two or more filter units that have a larger impedance to the common mode current as the filter unit is arranged on the power line carrier communication device side.

  The common mode current reducing filter of the present invention includes a plurality of magnetic members and a common winding wound around each magnetic member, and the windings in the respective magnetic members are different so that the impedance to the common mode current by power line carrier communication is different. The number of windings of the wire is different.

  In a common mode filter using a ferrite core or common mode choke coil, in order to reduce the common mode current more effectively, increase the number of windings (power line or coil) wound around the core and Increasing the common mode impedance is the simplest technique. However, an increase in the common mode impedance in the filter section causes a mismatch with the common mode impedance of the power line to which the PLC modem is connected, and the standing wave generated on the power line due to this mismatch is found in existing wireless equipment. May have adverse effects. In order to improve such a problem, it is desired to reduce the degree of impedance mismatch. Therefore, in the present invention, at least two filter units are provided, and one of the two filter units is mainly functioned as a common mode impedance increasing unit, and the other filter unit is mainly configured as a common mode impedance of the filter unit. In order to function as a matching part with the impedance of the power line, it is proposed to change the impedance (common mode impedance) of the filter part with respect to the common mode current. Therefore, in the system of the present invention, the filter unit arranged on the power line carrier communication device side in the two adjacent filter units is compared with the filter unit arranged on the side farther from the power line carrier communication device than this filter unit. With a large common mode impedance. Further, in the filter of the present invention, at least two magnetic members, that is, a magnetic member having a large number of winding turns so as to increase the common mode impedance and a magnetic member having a small number of winding turns so as to reduce the common mode impedance. The system of the present invention can be constructed by arranging a magnetic member having a large number of windings on the power line carrier communication device side. Hereinafter, the present invention will be described in more detail.

  Examples of the power line carrier communication device (hereinafter referred to as PLC modem) provided in the system of the present invention include those used as so-called child modems and parent modems. The child modem is placed in the indoor wiring of the PLC user's house, and connected to a terminal device such as a personal computer. The communication signal from the terminal device can be injected into the power line and transmitted to the parent modem, and the communication signal from the parent modem can be transmitted. The thing which comprises the structure which can be extracted from a power line and transmitted to a terminal device is mentioned. The parent modem is placed on a pole such as a power pole, in a power equipment room, a transformer room, etc. provided in an apartment house, connected to a higher-level network, and communication signals from this network are injected into the power line / communication from the power line One having a configuration capable of extracting a signal is mentioned. The parent modem is configured to transmit communication signals to a plurality of child modems. Specifically, the parent modem controls the time sharing of each child modem and transmits the communication signal to each child modem. You may utilize what comprises a structure. In addition, a relay device (repeater) that relays communication signals between the child modem and the parent modem may be used as the PLC modem. These PLC modems are connected to a power line which is a signal transmission path for communication signals. These PLC modems keep impedance matching with the power line as much as possible.

  A plurality of filter units for reducing the common mode current are arranged on the power line to which the PLC modem is connected. In particular, the present invention includes at least a set of filter units that satisfy the relationship that the common mode impedance of the filter unit arranged on the PLC modem side is larger. The group that satisfies such a relationship may be a group that includes at least two filter units, and may include a group that includes three filter units, a group that includes four filter units, and so on. For example, when the first filter unit and the second filter unit are arranged in this order from the PLC modem side, the common mode impedance of the first filter unit is made larger than the common mode impedance of the second filter unit. When arranging the first filter part, the second filter part, and the third filter part in order from the PLC modem side, the common mode impedance of the first filter part> the common mode impedance of the second filter part> the common mode impedance of the third filter part The common mode impedance is changed so that An arbitrary filter unit other than the filter unit that constitutes a set that satisfies such specific conditions may be included, but in order to more effectively reduce the common mode current and suppress the occurrence of standing waves, all It is preferable to satisfy the relationship that the common mode impedance is larger as the filter section is arranged on the PLC modem side. In order to change the common mode impedance of each filter portion in this way, for example, the filter portion is composed of a magnetic member and a winding wound around the magnetic member, and the number of turns of the winding is changed. Is mentioned.

  In particular, the magnetic member is preferably made of a ferromagnetic material having a high magnetic permeability and having a low loss characteristic even in a frequency range (for example, about 1 to 50 MHz) used for a communication signal. Specifically, a ferrite core is mentioned, for example. The winding may be a power line such as a wiring cord to which the PLC modem is connected, or may be a linear body having a conductor portion that can flow a current as used in a coil of a choke coil. The former is a configuration in which a power line to which a PLC modem is connected is directly wound around a magnetic member. In this configuration, it can be formed by wrapping a power line such as a wiring cord used as a power source for a PLC modem around a magnetic member, so even an existing PLC modem can be easily formed at the place where the modem is used. can do. Alternatively, a power line in which a filter unit is formed in advance may be prepared, and the power line with the filter unit may be connected to the PLC modem. On the other hand, the latter is a configuration in which a magnetic member wound with a winding is connected to a power line to which a PLC modem is connected. In this configuration, since a commercially available choke coil can be used, the size can be reduced as compared with a configuration in which a power line is directly wound around the magnetic member. Therefore, it is preferable to employ this configuration when it is desired to further reduce the size, particularly when it is desired to increase the number of windings. The magnetic members around which the windings are wound may be cut between the power lines connected to the PLC modem and arranged between the power lines, and the power lines and the linear bodies forming the windings may be connected. As an integrated structure, this integrated object may be disposed between the power lines. Alternatively, a power line in which a filter unit is formed in advance may be prepared, and the power line with the filter unit may be connected to the PLC modem.

  Further, the magnetic member is preferably annular so that the power line and the linear body can be easily wound. You may utilize what is comprised in cyclic | annular form combining several division pieces. For example, a pair of semicircular arc-shaped pieces may be combined to form a circular cross section. It is preferable that the divided pieces are connected to each other by a connecting member such as a hinge because the arrangement on the power line can be performed more easily. The annular shape is not limited to a circular shape as long as it has a shape having a hole through which a power line can be inserted in the center.

  As described above, the number of turns of the windings of each filter unit is made different, and the filter unit set having a relation that the number of windings of the windings is increased as the filter unit arranged on the PLC modem side is provided. For example, when the first filter unit and the second filter unit are arranged in this order from the PLC modem side, the number of windings of the first filter unit is larger than the number of windings of the second filter unit. When the first filter unit, the second filter unit, and the third filter unit are arranged in this order from the PLC modem side, the number of windings of the first filter unit> the number of windings of the second filter unit> It comprises a set of three filter parts that have the relationship of the number of windings of the three filter parts. In particular, the number of windings of the first filter section is set to a number that can have a large common mode impedance that can attenuate a common mode current generated by a communication signal from the PLC modem. At this time, the first filter unit is considered to have a large common mode impedance that causes a mismatch with the common mode impedance of the power line to which the PLC modem is connected. Therefore, the number of windings of the filter unit (for example, the second filter unit and the third filter unit) arranged on the side farther from the PLC modem than the first filter unit is the common mode impedance of the first filter unit. Is adjusted so as to have a common mode impedance that can suppress the occurrence of a standing wave due to a mismatch between the power line and the common mode impedance of the power line to which the PLC modem is connected. By adjusting the number of windings of each filter section in this way, the common mode current can be effectively attenuated and the occurrence of standing waves can be suppressed to reduce the influence on existing radio equipment and the like. be able to. The windings of each filter part may be all power lines connected to the PLC modem, or may be a linear body having a conductor part. The windings of some filter parts may be power lines and the remaining filters. Different types of windings may be present in one system, with the windings of the part being linear.

It is sufficient that at least two sets of the filter units are provided as described above, and the number of windings of the winding is changed in a stepwise manner by three or more, so that the standing wave due to impedance mismatching can be changed. Generation | occurrence | production can be suppressed more effectively. FIG. 4 is an explanatory diagram for explaining a mechanism for suppressing the occurrence of a standing wave. As shown in FIG. 4, a magnetic member and a winding wound around the magnetic member in the vicinity of the PLC modem 110 in a power line 120 (for example, a distribution line such as an indoor wiring) 120 to which the PLC modem 110 (for example, a parent modem) is connected. Filter sections F ₁ and F ₂ consisting of In this example, the filter unit F ₁ is arranged on the PLC modem side, and the filter unit F ₂ is arranged on the end (for example, child modem) 130 side of the power line 120. The filter unit F _{1 has} a common mode impedance Z ₁ , a filter unit F _{2 has} a common mode impedance Z ₂ , and the power line 120 has a common mode impedance Z, and Z <Z ₂ <Z _{1 1,} to adjust the number of turns of F ₂ windings. There is a possibility that a standing wave is generated, the section 1 from the filter unit F ₁ to the end, which is a period 2 from the filter unit F ₂ to the end portion. In section 2, when a part of the signal (incident wave in ₂ ) emitted from the end 130 side is reflected by the filter unit F ₂ , the reflected wave ref ₂ and the incident wave in ₂ are combined to generate a standing wave. . Reflection in this case is due to the difference between the impedance Z ₂ of the impedance Z and the filter section F ₂ of the power line 120. Therefore, by adjusting the number of turns of winding of the filter unit F _2, the impedance Z ₂ of the filter unit F ₂ so as to match the impedance Z of the power line 120, or by leaving to mitigate the degree of mismatch, Standing waves generated in section 2 can be suppressed.

On the other hand, when a part of the signal (incident wave in ₁ ) emitted from the end 130 side is reflected by the filter unit F ₁ in the section ₁ , the reflected wave ref ₁ and the incident wave in ₁ are combined to form a standing wave. Occurs. Reflection at this time, the impedance Z ₂ of the impedance Z and the filter unit F ₂ of the end 130, will be due to the difference between the impedance Z ₁ of the filter unit F _1. Therefore, since the impedance Z ₁ of the filter section F ₁ is even greater than the impedance Z of the power line 120, by interposing a filter section F _2, the difference in impedance between the filter section F ₁ and the power line 120 is reduced, Generation of standing waves in the section 1 can be suppressed. This standing wave suppression effect is more likely to be obtained as the number of filter units increases in a set of filter units that satisfy the above-described specific condition (the common mode impedance is greater as the unit is arranged on the PLC modem side).

In addition, the standing wave actually generated between the terminal and the filter unit F ₂ includes a standing wave generated by combining the reflected wave ref ₁ generated in the section ₁ and the incident wave in _1, and a reflected wave ref ₂ generated in the section _2. And a standing wave by combining the incident wave in ₂ with each other. At this time, since the distance between the sections 1 and 2 is different, even if reflection occurs in the filter unit F ₁ and the filter unit F ₂ , respectively, the reflected wave ref ₁ and the incident wave in ₁ generated in the section 1 The frequency of the standing wave by combining the reflected wave ref ₂ generated in section 2 and the incident wave in ₂ is different. Therefore, actually occurs standing wave between the termination and the filter section F ₂ (composite wave) is suppressed. In this way, by preparing a plurality of filter units and increasing the number of windings of each filter unit to the side of the PLC modem that generates the common mode current, the generation of the common mode current is suppressed. The generation of standing waves can be suppressed.

As described above, the common mode impedance can be changed by the number of windings wound around the magnetic member. In particular, the filter unit disposed farthest from the PLC modem 110 (the filter unit closest to the termination 130, the filter unit F _{2 in} FIG. 4) has a ratio of the reflected wave to the incident wave, that is, the reflection coefficient Γ is 3/4 or less. It is preferable to adjust the number of turns so that Since the reflection coefficient Γ is Γ = (Z ₂ −Z) / (Z ₂ + Z) (Z ₂ : common mode impedance of the filter unit F ₂ , Z: common mode impedance of the power line 120), Γ ≦ 3 / If 4, Z ₂ ≦ 7Z. The number of turns may be adjusted so as to satisfy this relational expression.

In the set of filter units that satisfy the above specific condition (the one that is arranged on the PLC modem side has a larger common mode impedance), if the interval between the filter units is extremely short, even if a plurality of filter units are arranged, It seems that they are arranged in a concentrated constant, and eventually, a plurality of filter parts connected in series becomes one filter part having a large impedance, and the effect of suppressing the generation of the standing wave can be sufficiently obtained. It is possible that there is not. Therefore, it is preferable to appropriately adjust the interval between the filter units according to the frequency band used by the PLC modem. When the circuit length of the magnetic member is 1/1000 or more of the wavelength, it is considered to be a distributed constant circuit. Therefore, the interval between the filter units is preferably set to 1/1000 or more of the maximum wavelength of the frequency band to be used. For example, when the use frequency band of the PLC modem is 2 to 30 MHz, the maximum wavelength is taken at 2 MHz. At this time, if the speed of the communication signal is 3 × 10 ⁸ m / s, the maximum wavelength is 150 m, and therefore the interval between the filter sections is preferably 0.15 m or more.

On the other hand, if the interval between the filter units is extremely long in the set of filter units that satisfy the above specific condition (the common mode impedance that is arranged closer to the PLC modem is larger), it is due to impedance mismatch between the filter units. A standing wave may be generated. Accordingly, it is preferable to adjust the interval between the filter units as appropriate according to the frequency band used by the PLC modem, as described above. Specifically, it is preferable to set it to 1/2 or less of the minimum wavelength of the frequency band to be used. For example, when the use frequency band of the PLC modem is 2 to 30 MHz, the minimum wavelength is taken at 30 MHz. At this time, if the speed of the communication signal is 3 × 10 ⁸ m / s, the minimum wavelength is 10 m, and therefore the interval between the filter sections is preferably 5 m or less. For these reasons, in the set of filter units that satisfy the above specific condition, the interval between the filter units is preferably 1/1000 or more of the maximum wavelength and 1/2 or less of the minimum wavelength in the use frequency band of the communication signal.

  In the system of the present invention, the PLC modem can be applied to any of a parent modem, a child modem, and a relay device. At this time, it is assumed that the common mode current to be attenuated by the filter unit is generated by a PLC modem arranged in the vicinity of the filter unit. For example, when a filter group consisting of a plurality of filter units is provided on both the transmission side and the reception side of the communication signal with the parent modem as the transmission side and the child modem as the reception side, it is arranged on the transmission side (upstream side) of the communication signal. The filter group mainly performs attenuation of common mode current and suppression of standing wave generation, and the filter group arranged on the receiving side (downstream side) suppresses attenuation of common mode current and generation of standing wave at this time. Hardly contribute. More specifically, for example, the filter group A including the first filter unit a and the second filter unit aa is disposed on the parent modem side, and the filter including the third filter unit b and the fourth filter unit bb on the child modem side. Consider the case where part B is arranged. At this time, the common mode current generated when the parent modem transmits a communication signal toward the child modem is mainly attenuated by the filter group A arranged in the vicinity of the parent modem, and the child modem is directed toward the parent modem. The common mode current generated by transmitting the communication signal is attenuated mainly by the filter group B disposed in the vicinity of the child modem.

  The filter of the present invention comprises a plurality of magnetic members and a common winding wound around these magnetic members. That is, the filter of the present invention is a filter group including a plurality of filter portions each including a magnetic member and a winding. The magnetic member is preferably made of a ferromagnetic material as described above, particularly a ferrite core. As the winding, it is preferable to use a linear body having a conductor portion through which a current can flow as described above. The common winding is not limited as long as it is electrically continuous, may be composed of one continuous linear body such as a power line connected to the PLC modem, or is wound around a certain magnetic member. The wire and the winding wound around another magnetic member are separate members, and these windings may be connected and made continuous. When the filter of the present invention has a larger common mode impedance, that is, a winding having a larger number of windings, it is arranged on the PLC modem side to reduce the common mode current and suppress the generation of standing waves as described above. This is preferable because it can be carried out effectively.

  The power line carrier communication system of the present invention having the above-described configuration includes a plurality of filter units having different common mode impedances. In particular, the power line carrier communication system includes a combination of filter units having higher common mode impedances as they are arranged on the power line carrier communication side. Thus, both effects of reducing the common mode current and suppressing the occurrence of standing waves can be achieved. Specifically, the common mode current can be sufficiently reduced by disposing a filter unit having a large common mode impedance on the power line carrier communication device side. In addition, by arranging a filter unit with a small common mode impedance downstream of the communication signal transmitted from the device, the common mode impedance of the filter unit and the common mode impedance of the power line to which the device is connected are not matched. By reducing the degree, the occurrence of standing waves is effectively suppressed, and other wireless facilities are prevented from being damaged. Such adjustment of the common mode impedance can be easily performed by configuring the filter portion from a magnetic member and a winding wound around the magnetic member, and changing the number of turns of the winding. Moreover, the said system of this invention can be easily constructed | assembled by arrange | positioning this invention filter to the power line to which a power line carrier communication apparatus is connected.

  Embodiments of the present invention will be described below.

  FIG. 1 is a schematic configuration diagram of a power line carrier communication system of the present invention, (A) shows a state in which a filter of the present invention is arranged in the vicinity of a parent modem, and (B) is a filter unit constituting the filter of the present invention. A specific arrangement example is shown. In the drawings, the same reference numerals denote the same items. In this system, the power line 11 connected to the parent modem 10 includes a filter group F (the present invention filter) including filter units 1 and 2 that suppress common mode currents from the parent modem 10. As shown in FIG. 1 (B), the filter unit 1 includes a magnetic member 1a and a winding 1b wound around the magnetic member 1a, and the filter unit 2 is similarly wound around the magnetic member 2a and the magnetic member 2a. Consists of line 2b. The most characteristic feature of the present invention is that the filter unit 1 is configured such that the impedance (common mode impedance) with respect to the common mode current from the parent modem 10 is larger than that of the filter unit 2. In this example, the number of turns of the winding 1a of the filter unit 1 and the number of turns of the winding 2a of the filter unit 2 are made different. Specifically, the number of turns of the filter unit 1 arranged on the parent modem 10 side is changed. The common mode impedance of the filter unit 1 is increased by increasing the number of the filter units 2 that are arranged on the side away from the parent modem 10.

  In this example, the magnetic members 1a and 2a used for the filter portions 1 and 2 are ferrite cores that are ferromagnetic materials, and are configured to have a circular cross-section by combining a pair of semicircular arc-shaped pieces. Both semicircular arc-shaped pieces are connected at one end by a hinge and have a fastener at the other end. By opening this fastener, it is possible to open the two semicircular arc pieces, and after winding the power line 11 in a state where the two pieces are open, the two pieces can be closed to form an annular shape. In addition, the power line 11 in which the filter group F is arranged in this example is a wiring cord including a tap 12 that can be plugged into an outlet 51 connected to a power line 50 such as indoor wiring, and a winding 1b wound around a ferrite core, 2b was this wiring cord. Then, as shown in FIG. 1 (B), the filter unit 1 disposed on the side closer to the parent modem 10 increases the number of turns of the power line 11 (winding 1b) wound around the magnetic member 1a, and is on the side farther from the parent modem 10. In the filter unit 2 arranged in the above, the number of turns of the power line 11 (winding 2b) wound around the magnetic member 2a is smaller than the number of turns of the winding 1b.

  As described above, the filter group F including the plurality of filter units 1 and 2 is arranged in the vicinity of the parent modem 10, and the child modem 20 is connected to the outlet 52 provided in the power line 50 as shown in FIG. Consider a case where a terminal device 60 such as a personal computer is connected to the child modem 20. At this time, when a communication signal is transmitted from the parent modem 10 toward the child modem 20, the common mode current tends to flow through the power lines 50 and 21. However, in this example, in particular, the common mode current from the parent modem 10 can be attenuated by the filter unit 1, and the common mode current is downstream of the filter unit 1 (in this example, the power line 50 and the child modem 20 side). Can be reduced. On the other hand, if transmission is performed from the child modem 20 toward the parent modem 10 with only the filter unit 1 arranged, the filter is caused by a mismatch between the common mode impedance of the filter unit 1 and the common mode impedance of the power line 11 (50). Since the part 1 becomes a reflection end, a standing wave is generated in the power line 50 between the filter part 1 and the child modem 20, and there is a possibility of affecting other wireless facilities. However, in this example, since the impedance mismatch can be relaxed by the filter unit 2, the occurrence of standing waves can be suppressed. Therefore, it is possible to reduce the risk of adversely affecting existing wireless equipment due to the occurrence of standing waves. The filter unit 2 functions mainly to mitigate impedance mismatch as described above, but also contributes to attenuation of the common mode current.

  In this example, the distance L between the filter part 1 and the filter part 2 was 80 cm. This distance L may be appropriately adjusted according to the frequency band of the communication signal used by the parent modem 10, and in this example, the use frequency band is set to 2 to 30 MHz. In particular, if the distance L is 1/1000 or more of the maximum wavelength of the used frequency band (15 cm or more in this example) and 1/2 or less of the minimum wavelength (5 m or less), the distance between the filter unit 2 and the child modem 20 or the filter Generation of a standing wave between the part 1 and the filter part 2 can be effectively suppressed.

  The parent modem 10 and the child modem 20 used in this example are those having a known configuration. Further, the parent modem 10 and the child modem 20 are matched with the impedance of the power line 50. Further, the parent modem 10 and the child modem 20 are grounded via a capacitor C as shown in FIG.

  In the first embodiment, the wire cord connected to the PLC modem is directly wound around the ferrite core to configure the filter unit. However, a choke coil may be used. FIG. 2 is a schematic view showing a specific arrangement example of the filter unit constituting the filter of the present invention, and shows an example using a common mode choke coil as the filter unit. The filter units 1 and 2 shown in FIG. 2 include magnetic members 1a and 2a and windings 1c and 2c wound around the magnetic members 1a and 2a, as in the first embodiment. , 2c is not a wiring cord (power line 11) but a metal wire having a connection end 13 connectable to the wiring cord. The metal wire only needs to have a conductor that can pass current. For example, a commonly used coated wire, enameled wire, bare wire, copper wire, or the like can be used. . In this example, enameled wire was used. As in Example 1, the number of turns of the winding 1c is larger than the number of turns of the winding 2c, and the connection end of the winding 1c of the filter unit 1 having a large number of turns is connected to the parent modem 10 side in the wiring cord. The connection end of the winding 2c of the filter unit 2 having a small number of turns is connected to the side away from the parent modem 10 in the wiring cord. In this example, since the wiring cord is a single-phase two-wire system, two continuous enamel wires are prepared, and each enamel wire is connected to one magnetic member 1a (or 2a) as shown in FIG. The same number was wound in the same direction (direction in which the magnetic flux generated in the magnetic member 1a (or 2a) is in the same direction). The wiring cord was previously configured so that the connection end 13 was connectable.

  By connecting the filter unit having the above-described configuration to the power line, it is possible to reduce the possibility that the existing radio equipment is affected by the occurrence of the standing wave, as in the first embodiment. In this example, the connection end is provided, but the wiring cord is cut and the filter of the present invention is arranged between the wiring cords, and the enameled wire may be connected to each wiring constituting the wiring cord, A wiring cord including the filter of the present invention may be prepared, and the wiring cord with filter may be connected to the PLC modem. Further, a commercially available choke coil may be used.

  In Example 1, the filter unit is configured to wind the wiring cord directly around the ferrite core. In Example 2, the filter unit is a choke coil. However, any filter unit having any configuration may be included in one filter group. It may be. For example, in the first embodiment, the filter unit 1 disposed on the parent modem 10 side is configured to directly wind a wiring cord as illustrated in FIG. 1B, and the filter unit 2 disposed on the outlet 51 side is illustrated in FIG. Such a choke coil may be used.

In the first and second embodiments, only the parent modem is provided with the filter of the present invention, but a common mode current is also generated from the child modem. Therefore, it is preferable to provide the filter of the present invention on the side of the child modem. In this example, a configuration in which the filter (filter group) of the present invention is provided also on the child modem side will be described. FIG. 3 is a schematic configuration diagram of the power line carrier communication system of the present invention, showing a state in which the filter of the present invention is arranged in the vicinity of the parent modem and the child modem. In the system shown in this example, the power line 11 connected to the parent modem ₁₀ is provided with a filter group F10 that suppresses the common mode current caused by the parent modem 10, and the power line 21 connected to the child modem 20 is connected to the common mode by the child modem 20. A filter group F ₂₀ for suppressing current is provided.

  The parent modem 10 is connected with a wiring cord having a tap 12 that can be plugged into an outlet 51 connected to a power line 50 such as indoor wiring, and the child modem 20 can be plugged into an outlet 52 connected to the power line 50 A wiring cord with a simple tap is connected. Further, a terminal device 60 such as a personal computer is connected to the child modem 20. By connecting the wiring cords of the parent modem 10 and the child modem 20 to the outlets 51 and 52, both the modems 10 and 20 can be connected via the power line 50 and can perform communication using communication signals.

Filter group F ₁₀ in this embodiment is made of a three filter unit 3, 4, 5, filter group F ₂₀ is consisted of three filter sections 6, 7 and 8. Each of the filter units 3 to 8 used a choke coil (see FIG. 2) including a magnetic member and a winding wound around the magnetic member. Then, the filter unit F _10, most often the turns of the filter unit 3 of the windings arranged in the parent modem 10 side, the winding of the filter unit 5 disposed on the side (outlet 51 side) away from the parent modem 10 The number of wire turns was minimized. The number of windings of the filter unit 4 disposed between the filter unit 3 and the filter unit 5 was set between the number of windings of the filter unit 3 and the number of windings of the filter unit 5. Similarly, the filter unit F _20, most often the turns of the winding of the filter unit 6 arranged on the child modem 20 side, of the filter section 8 disposed on the side (outlet 52 side) away from the child modem 20 The number of windings was minimized. The number of windings of the filter unit 7 disposed between the filter unit 6 and the filter unit 8 was set between the number of windings of the filter unit 6 and the number of windings of the filter unit 8.

By providing the filter group F ₁₀ in the vicinity of the parent modem 10 as described above, the common mode current from the parent modem 10 generated when the communication signal is transmitted from the parent modem 10 to the child modem 20 is filtered. As a result, the mismatch between the common mode impedance of the filter unit 3 and the common mode impedance of the power line 11 (50) can be gradually reduced by the filter units 4 and 5. Therefore, as reflected by the transmission signal filter group F ₁₀ from the slave modem 20, effectively prevent the standing wave is generated in the power line 50 between the filter group F ₁₀ and the child modem 20, the standing wave Reduces adverse effects on existing radio equipment, etc. The filter units 4 and 5 also contribute to the reduction of the common mode current.

In addition to the above effect, in this example, a filter group F ₂₀ is provided in the vicinity of the child modem 20. Therefore, the common mode current from the child modem 20 generated when the communication signal is transmitted from the child modem 20 to the parent modem 10 can be attenuated by the filter unit 6. At the same time, the filter units 7 and 8 can alleviate the mismatch between the common mode impedance of the filter unit 6 and the common mode impedance of the power line 21 (50) in a stepwise manner. Therefore, the transmission signal from the main modem 10 is reflected by the filter group F _20, and effectively suppress the standing wave is generated in the power line 50 between the filter group F ₂₀ and parent modem 10, the standing wave Reduces adverse effects on existing radio equipment, etc. The filter units 7 and 8 also contribute to the reduction of the common mode current.

In this example, the distance L ₁ between the filter unit 3 and the filter unit 4 and the distance L ₂ between the filter unit 4 and the filter unit 5 were 100 cm, respectively. The distance L ₃ between the filter unit 6 and the filter unit 7 and the distance L ₄ between the filter unit 7 and the filter unit 8 were 50 cm, respectively. These distances L _{1 to} L ₄ may be appropriately adjusted according to the frequency band of the communication signal used by the parent modem 10 and the child modem 20, and in this example, the use frequency band is set to 2 to 30 MHz. In this example, the distances L ₁ and L ₂ are equal, but may be different. The distances L ₃ and L ₄ may be similarly varied. At any distance, in order to effectively suppress the occurrence of standing waves between filter groups and between filter parts, the minimum wavelength is 1/1000 or more of the maximum wavelength of the used frequency band (15 cm or more in this example). It is preferable to set it to 1/2 or less (5 m or less).

  In this example, the number of filter units included in the filter group is three, but may be four or more. As the number of filter units included in the filter group increases, impedance mismatching can be easily reduced, and generation of standing waves can be more effectively suppressed.

  The power line carrier communication system of the present invention is suitable for use when performing power line carrier communication. In addition, the common mode current reduction filter of the present invention can be suitably used when constructing the system of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic configuration diagram of a power line carrier communication system of the present invention, where (A) shows a state in which a filter of the present invention comprising a plurality of filter units is arranged in the vicinity of a parent modem, and (B) constitutes the filter of the present invention The specific example of arrangement | positioning of a filter part is shown. In the power line carrier communication system of the present invention, it is a schematic diagram showing a specific arrangement example of the filter unit constituting the filter of the present invention, and shows an example using a common mode choke coil as the filter unit. It is a schematic block diagram of this invention power line carrier communication system, and shows the state which has arrange | positioned this invention filter which consists of a some filter part in the vicinity of a parent modem and a child modem, respectively. It is explanatory drawing explaining the mechanism which suppresses generation | occurrence | production of a standing wave by arrange | positioning a some filter part to a power line. It is explanatory drawing explaining the mechanism in which a standing wave generate | occur | produces. It is explanatory drawing which showed the outline | summary of the communication system of a PLC system typically, and shows the case where a PLC user house is a detached house.

Explanation of symbols

1,2,3,4,5,6,7,8 Filter 1a, 2a Magnetic member 1b, 1c, 2b, 2c Winding
10 Parent modem 11,21,50 Power line 12 Tap 13 Connection end 20 Child modem
51,52 Outlet 60 Terminal equipment
100 Low voltage distribution line 101 Telephone pole 102 Transformer 103 Optical fiber cable
104 Parent modem 105 Junction box 110 PLC modem 120 Power line 130 Termination
200 PLC user house 201 Service line 202 Indoor wiring 203A, 203B Child modem
204A, 204B Terminal equipment 300 Upper network

Claims (5)

A power line carrier communication device;
A power line connected to the power line carrier communication device and transmitting a communication signal;
A plurality of filter units disposed on the power line to reduce common mode current;
The plurality of filter units include a combination of at least two or more filter units having a larger impedance to the common mode current as the filter unit arranged on the power line carrier communication device side. Each filter part consists of a magnetic member and a winding wound around this magnetic member,
2. The power line carrier communication system according to claim 1, wherein the number of windings of the filter unit disposed on the power line carrier communication device side is larger.   3. The power line carrier communication system according to claim 1, further comprising three or more filter units.   4. The power line carrier communication system according to claim 1, wherein an interval between the filter units is 1/1000 or more of the maximum wavelength and 1/2 or less of the minimum wavelength in the use frequency band of the communication signal. . A plurality of magnetic members;
It consists of a common winding wound around each magnetic member,
A common mode current reduction filter, wherein the number of windings of each magnetic member is made different so that the impedance to the common mode current by power line carrier communication is different.

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