Abstract:
A power line communication apparatus includes a mains power connector assembly with three or more first connectors connectable to a mains distribution network. A mains filter provides a filter path between each of its first ports and a corresponding one of second ports, wherein each first port is connected to one of the first connectors. Each second port is connected to one of three or more second connectors of an AC power socket. A power line communication unit is connected with each of the first ports and transmits and/or receives data according to a transmission method using more than one transmission channel between two devices connected via the mains distribution network. The mains filter improves PLC transmission quality by suppressing disturbances generated by the appliances and reduces PLC stray radiation.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation application of U.S. application Ser. No. 13/352,788, filed Jan. 18, 2012, which is in turn based upon and claims the benefit of priority from European Patent Application No. 11000956.0, filed on Feb. 7, 2011, the entire contents of each of which are incorporated herein by reference. 
     
    
     DESCRIPTION 
       [0002]    Embodiments of the invention refer to a power line communication apparatus comprising an AC (alternating current) power socket and a method of operating a power line communication apparatus. 
         [0003]    Some communications systems like PLC (power line communications) use power distribution systems for data communication, wherein a modulated carrier is superimposed to the 50 or 60 Hz alternating current of the power lines. For example, a power cable containing two or more electrical conductors is used for transmission of AC (alternating current) electric power, wherein the power cable may be installed as permanent wiring within buildings or may be buried in the ground. Power line communication modems may be plugged into any outlet of the power distribution system. 
     
    
     
         [0004]    The object of the invention is to increase ease of use of a power line communication system. The object is achieved with the subject-matter of the independent claims. Further embodiments are defined in the dependent claims, respectively. Details and advantages of the invention will become more apparent from the following description of embodiments in connection with the accompanying drawings. Features of the various embodiments may be combined unless they exclude each other. 
           [0005]      FIG. 1  is schematic block diagram of a power line communications system comprising a power line communication apparatus in accordance with an embodiment of the invention. 
           [0006]      FIG. 2  is a schematic block diagram showing details of a power line communication apparatus with a mains filter in accordance with another embodiment of the invention. 
           [0007]      FIG. 3A  is a simplified perspective view of a power line communication apparatus in accordance with an embodiment related to a wall-mounted outlet. 
           [0008]      FIG. 3B  is a simplified side view of a power line communication apparatus including a mains power plug in accordance with an embodiment. 
           [0009]      FIG. 4  is a simplified flowchart of a method of operating a power line communication apparatus according to a further embodiment. 
       
    
    
       [0010]      FIG. 1  refers to a communications system  100  using a power distribution system  190  for data communication. By way of example, the communications system  100  may be a power line communications (PLC), mains communications, power line telecommunications (PLT), broadband power line (BPL) or power band or power line networking (PLN) system using a modulated carrier superimposed to the 50 or 60 Hz alternating current of the power lines respectively. 
         [0011]    The communications system  100  is operable as a MIMO (multiple input multiple output) or MISO (multiple input single output) system with at least a first and a second modem device  110   a,    110   b.  The first modem device  110   a  outputs data signals at two or more first interface ports  101   a.  The second modem device  110   b  recovers the data signals from signals received at three or more second interface ports  101   b.  The power distribution system  190  forms the transmission channel connecting the first and second modem devices  110   a,    110   b.  The power distribution system  190  represents a multi-wire connection. For example, the power distribution system  190  may include power cables comprising two or more electrical conductors used for transmission of AC electric power (mains) and for providing earth connection, wherein the power cables may be installed as permanent wiring within buildings or may be buried in the ground. 
         [0012]    For example, the first modem device  110   a  may output two differential transmit signals using the live or phase wire (L, P), the neutral wire (N), and protective earth (PE), wherein the differential transmit signals are modulated on a carrier superposing the AC frequency on the mains voltage. The second modem device  110   b  may receive three differential receive signals between live wire and neutral wire, between neutral wire and protective earth, and between live wire and protective earth. According to another embodiment, the second modem device  110   b  may receive the three differential receive signals and a common mode signal resulting from a leakage current from the wiring as a fourth receive signal. The transmit signals in the transmission channel  190  interfere with each other through capacitive coupling between the wires such that the first and second modems may use multi-channel techniques like beamforming for enhancing transmission throughout. 
         [0013]    One of the first and second modem devices  110   a,    110   b  is a power line communication apparatus  200  as illustrated in  FIG. 2 . The other modem device  110   a,    110   b  may also be of the type of the power line communication apparatus  200 , another stand-alone type PLC modem or may be integrated in an electronic device for consumer applications, for example in a storage unit, a television set, an audio receiver, a video recorder, or in sensor devices. 
         [0014]    As shown in  FIG. 2 , the power line communication apparatus  200  comprises a mains power connector assembly  210  with at least three first connectors  211 . Each of the first connectors  211  is adapted to connect the power line communication apparatus  200  to one of the wirings L 1 , L 2 , L 3 , N, PE of a power distribution system. According to an embodiment the first connectors  211  are terminals, for example clamps or connector blocks into which the wirings L 1 , L 2 , L 3 , N, PE may be clamped. According to another embodiment, the mains power connector assembly  210  is a mains power plug where at least two of the first connectors  211  assigned to live and neutral connections are pins or prongs. The mains power plug may be a standardized one, for example a mains power plug in accordance with the CEE 7/4, 7/5, 7/7, NEMA5-nn or SEV1011 standard. 
         [0015]    The power line communication apparatus  200  further includes a mains filter  220  with at least three first ports  221  and a corresponding number of second ports  222 . Each first port  221  is electrically connected to one of the first connectors  211 . According to an embodiment each first port  221  is directly connected with the corresponding first connector  211  in a low resistive manner through wires, conductors, and/or clamps. The mains filter  220  comprises a low-pass filter path between each first port  221  and a corresponding one of the second ports  222 . 
         [0016]    An AC power socket (receptacle)  280  comprises at least three second connectors  282 , wherein each second connector  282  is electrically connected to one of the second ports  222  of the mains filter  220 . At least two of the second connectors  282  assigned to live and neutral connections are female connectors. The AC power socket  280  may by standardized and may comply with any of the CEE 7/4, 7/5, 7/7, NEMA5-nn or SEV1011 standards, by way of example. In case the mains power connector assembly  210  is a standardized mains power plug, the AC power socket  280  may comply with the same standard. A power strip or an electric/electronic appliance may be plugged into the AC power socket to connect an electric/electronic appliance to the mains power distribution system. 
         [0017]    A power line communication unit  250  is electrically connected with each of the first connectors  211  and first ports  221 , wherein the power line communication unit  250  is configured to transmit and/or receive data according to a transmission method using more than one wired connection or transmission path between two devices connected via the power distribution wiring. The power line communication unit  250  includes a power lines communication modem that may be configured as a receiving device, as a transmitting device or as bidirectional communication device incorporating the functionalities of both a receiving and a transmitting device. The power lines communication modem may be a PLC modem, a mains communications modem, a PLT modem, a BPL modem or a power band or PLN modem. 
         [0018]    The power line communication apparatus  200  with integrated AC power socket  280  and mains filter  220  allows the user to easily install or plug a power line modem into any outlet which is convenient to access for him and without that the outlet is lost for connecting further electric/electronic appliances. The data signals go directly from the integrated power line communication unit  250  to the wall outlet and the power distribution wiring. Neither do they radiate nor are they attenuated by the cable resistance of a multiple-outlet power strip, which often has to be installed for providing a sufficient number of outlets for appliances and modems. 
         [0019]    In addition, the mains filter  220  suppresses disturbances and noise from appliances connected to the AC power socket  280 . Since Appliances connected to the filtered AC power socket  280  cannot cause asymmetry to the mains at the respective outlet, differential mode MIMO signals of the power line communication unit  250  are not converted into common mode signals that may radiate from the mains. Hence the system emits less stray radiation. 
         [0020]    According to an embodiment, at least one of the first connectors  211  of the mains power connector assembly  210  is an earth (grounding) connection and at least one of the second connectors  282  of the AC power socket  280  is an earth connection. The filter paths may differ in their effect on the assigned wired connection. According to an embodiment each filter path provides interference suppression. For example, each filter path provides interference suppression to approximately the same degree. 
         [0021]    In accordance with an embodiment, the mains filter  220  includes a low-pass filter  224  which is effective on each of the at least three filter paths. Where one of the filter paths provides an earth connection, the low-pass filter  224  is also effective on this filter path approximately to the same degree. For example, the low-pass filter  224  includes filter elements in each of the filter paths, including a filter path assigned to an earth connection, wherein corresponding filter elements of different filter paths have the same nominal values such that all at least three filter paths are configured in the same way. According to an embodiment, the low-pass filter  224  attenuates signal frequencies above 1 MHz, for example in the range between 2 and 30 MHz by at least 3 dB, for example 6 dB, 10 dB or 20 dB. According to an embodiment the attenuation is at least 50 dB. According to other embodiments, the mains filter  220  attenuates another frequency-range above a frequency greater 2 MHz to comply with the specific frequency range of the powerline communication unit  250 . 
         [0022]    The low-pass filter  224  may contain serial filter elements  224   a  in each filter path. The serial filter elements  224   a  may differ from each other. In accordance with an embodiment, the serial filter elements  224   a  in each filter path may be elements that are approximately equivalent to each other with regard to the effect they have. For example, each serial filter element  224   a  may be effective as a low-pass filter that lets pass the 50 Hz or 60 Hz AC frequency and that blocks HF (high frequency) and VHF (very high frequency). The low-pass filter  224  may provide the same filter degree and the same cutoff frequencies in each filter path. Each serial filter element  224   a  may include one or more inductors, wherein corresponding inductors in different filter paths may have the same nominal values for inductivity and resistance. The low-pass filter  224  may also comprise a number of capacitive units  224   b,  wherein each capacitive unit  224   b  is electrically arranged between each pair of filter paths. Each capacitive unit  224   b  may provide a parallel filter path with a cutoff frequency defining a pass-band effective up to at least 50 Hz or 60 Hz and blocking HF and VHF. Each capacitive unit  224   b  may include one ore more capacitors. According to an embodiment, at 1 MHz each filter path may provide an attenuation of at least 40 dB. Each capacitive unit  224   b  may be connected to a node between two identical inductors of the same filter path, respectively. 
         [0023]    According to an embodiment the mains filter  220  may also include a common-mode filter unit  228  to attenuate common mode signals. The common filter unit  228  may include a common mode choke, a ferrite bead or ring. The common filter unit  228  is effective on each of the at least three filter paths in the same way and to the same degree. For example, elements with the same nominal values for inductivity, resistance and coupling values may be provided in each filter path such that all at least three filter paths are configured in the same way. Where one of the filter paths provides an earth connection, the elements are provided in this filter path, too. 
         [0024]    The power line communication apparatus  200  may have four first connectors  211  for two live connections L 1 , L 2 , a neutral connection N and an earth connection, or five connectors for three live connections L 1 , L 2 , L 3 , a neutral connection N and an earth connection PE. According to an embodiment, the power plug comprises three first connectors  211  for one live connection L, a neutral connection N and the earth connection PE. 
         [0025]    The power line communication apparatus  200  may further comprise a data outlet  292  connected to the power line communication unit  250 , wherein the power line communication unit  250  outputs data received via the mains power connector assembly  210  at the data outlet  292  and/or outputs data received via the data outlet  292  at the mains power connector assembly  210 . The data outlet  292  may be a standardized one, for example according to the USB, Ethernet, Firewire or any other wired communication standard. 
         [0026]    Alternatively or in addition, the power line communication apparatus  200  may comprise a wireless modem  294  connected to the power line communication unit  250 , wherein the power line communication unit  250  outputs data received via the mains power connector assembly  210  via the wireless modem  294  and/or outputs data received via the wireless modem  294  via the mains power connector assembly  210 . The wireless modem may be a standardized one and may comply with the IEEE 802.11 standard by way of example. 
         [0027]      FIG. 3A  shows an on-wall or in-wall mounted power line communication apparatus  200  with an AC power socket  280 , which may be a CEE 7/7 socket, and a data outlet  292 , which may be a female modular connector, like a 8P8C jack (socket). Terminals at the backside oriented to the wall side provide interfaces to the power distribution wiring. 
         [0028]      FIG. 3B  shows a plug-in power line communication apparatus  200  with an AC power socket  280 , a data outlet  292 , and a mains power plug  210   a,  which may be CEE 7/7 plug, by way of example. 
         [0029]      FIG. 4  refers to a method of operating a power line communication apparatus. AC electric current is supplied to an electric appliance connected to an AC power socket using at least three mains connections ( 402 ). The at least three mains connections may provide two live connections and a neutral connection. According to an embodiment one of the at least three mains connections provides an earth connection. Noise and disturbances output by the electric appliance at the mains connections are low-pass filtered using a mains filter effective on each of the at least three mains connections ( 404 ) in the same way. According to an embodiment, each low-pass filter path of the mains filter provides interference suppression. The mains filter has a mains side oriented to the mains and an appliance side oriented to the AC power socket. A power line communication unit that is connected to the mains side of the mains filter is operated in a MIMO or MISO mode ( 406 ). The mains filter attenuates signal frequencies in the range used by the powerline communication unit and may attenuate common mode signals.