Abstract:
There is provided an arrangement of inductive couplers. The arrangement includes a first inductive coupler on a conductor, and a second inductive coupler on the conductor. The first inductive coupler has a first winding for a data signal, and the second inductive coupler has a second winding for the data signal. The arrangement also includes a connection module that connects the first winding to the second winding.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention relates to data communications. It is particularly suitable for power line communications (PLC) between locations having a common electrical distribution system.  
         [0003]     2. Description of the Related Art  
         [0004]     PLC, also known as Broadband over Power Line (BoPL), is a technology that encompasses transmission of data at high frequencies through existing electric power lines, i.e., conductors used for carrying a power current. Power current is typically transmitted through power lines at a frequency in the range of 50-60 hertz (Hz). In low voltage lines, power current is transmitted with a voltage between about 90 to 600 volts, and in medium voltage lines, power current is transmitted with a voltage between about 2,400 volts to 35,000 volts. The frequency of the data signals is greater than or equal to about 1 megahertz (MHz), and the voltage of the data signal ranges from a fraction of a volt to a few tens of volts. Data communication can employ various modulation schemes such as amplitude modulation, frequency modulation, pulse modulation or spread spectrum modulation.  
         [0005]     An inductive coupler couples PLC signals to and from a power line. The inductive coupler has a high pass frequency characteristic. Therefore, a signal attenuation or path loss through the inductive coupler may be excessive below a lower cutoff frequency of the inductive coupler.  
         [0006]     It is desirable to provide for PLC communications over a range of frequencies that extends below a lower cutoff frequency of an inductive coupler.  
       SUMMARY OF THE INVENTION  
       [0007]     There is provided an arrangement of inductive couplers. The arrangement includes a first inductive coupler on a conductor, and a second inductive coupler on the conductor. The first inductive coupler has a first winding for a data signal, and the second inductive coupler has a second winding for the data signal. The arrangement also includes a connection module that connects the first winding to the second winding. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]      FIG. 1  is a drawing of a circuit having two inductive couplers connected in series.  
         [0009]      FIG. 2  is a schematic diagram of the circuit of  FIG. 1 .  
         [0010]      FIG. 3  is a drawing of a circuit having three inductive couplers connected in series.  
         [0011]      FIG. 4  is a schematic diagram of the circuit of  FIG. 3 . 
     
    
     DESCRIPTION OF THE INVENTION  
       [0012]     Described herein is a technique for communication over a power line. The technique employs two or more proximal couplers connected electrically in series or parallel with one another.  
         [0013]     Generally, an inductive coupler includes a split magnetic core and a winding situated around the core. The core may be configured, for example, with two C-shaped portions. When the two C-shaped portions are placed together, they form a cylinder with an aperture extending through the center of the cylinder. The two C-shaped portions may be separated and placed on an energized or de-energized wire so that the wire is routed through the aperture. The wire may be a power line or other conductor. The wire, the core, and the winding situated around the core, together, form a transformer, where the wire serves as a primary of the transformer and the winding around the core serves as a secondary of the transformer. The secondary may be connected to a modem or other communications equipment directly or via a surge protection circuit.  
         [0014]     PLC employs data signal frequencies greater than or equal to about 1 MHz. However, a bandpass of an inductive coupler may have a lower cutoff frequency of greater than 1 MHz, and so, the inductive coupler may not provide adequate performance at signal frequencies down to 1 MHz. Increasing the inductance of a wire passing through the inductive coupler extends the lower cutoff frequency, thus allowing lower signal frequencies to be used for communications. One technique of increasing inductance is increasing a number of magnetic cores in the coupler. The increase in the number of magnetic cores can be accomplished by a coupling together of individual inductive couplers.  
         [0015]      FIG. 1  is a drawing of a circuit  10  that includes an inductive coupler  100  and an inductive coupler  200  situated on a conductor  105 . Conductor  105  may be, for example, a phase conductor of an outside power line, i.e., a power line external to a building.  
         [0016]     Inductive coupler  100  includes a core  107  and a winding  110 . Inductive coupler  100  is situated on conductor  105  such that conductor  105  is routed through an aperture  106  in core  107 . Together, conductor  105 , core  107  and winding  110  form a transformer where a portion  108  of conductor  105  serves as a primary of the transformer, and winding  110  serves as a secondary of the transformer. Inductive coupler  100  couples a data signal between conductor  105  and winding  110 . Winding  110  is connected via connectors  134  and  135  to a surge protection module  120 , which is, in turn, connected via a cable  125  to a modem  130 . In a preferred implementation, connector  135  and cable  125  are integral parts of surge protection module  120 .  
         [0017]     Inductive coupler  200  includes a core  207 , and a winding  210 . Inductive coupler  200  is situated on conductor  105  such that conductor  105  is routed through an aperture  206  in core  207 . Together, conductor  105 , core  207  and winding  210  form a transformer, where a portion  208  of conductor  105  serves as a primary of the transformer, and winding  210  serves as a secondary of the transformer. Inductive coupler  200  couples a data signal between conductor  105  and winding  210 . Winding  210  is connected via connectors  234  and  235 , to a connection module  260 . Connection module  260  connects winding  210 , via a jumper connection  262  and a jumper  265 , to a cable  250 , which connects to surge protection module  120 .  
         [0018]      FIG. 2  is a schematic diagram of circuit  10 .  FIG. 2  shows that surge protection module  120  includes a connection section  121  and a surge suppression circuit  122 . Connection section  121  connects winding  110  in series with winding  210 . Thus, the secondary of inductive coupler  100  is connected in series with the secondary of inductive coupler  200 . This connection is arranged such that induced voltages from these secondaries add in the same phase, consistent with the direction of the primary wires, as indicated in  FIG. 2B  by phasing dots.  
         [0019]     Couplers  100  and  200  need not be any particular distance from one another to perform as described herein. However, for best performance, couplers  100  and  200  should be adjacent to each other, and longitudinal separation should not exceed one tenth of a wavelength, at the highest signal frequency in use.  
         [0020]     Surge suppression circuit  122  protects modem  130  from voltage that can result from an excessive surge current on conductor  105 , such as in a case of a lightening strike on conductor  105 . Surge suppression circuit  122  can be implemented, for example, with a gas tube surge arrestor or an avalanche diode surge arrestor.  
         [0021]      FIG. 3  is a drawing of a circuit  20 , which is an enhancement of circuit  10 . Circuit  20  includes an inductive coupler  300 . Inductive coupler  300 , similarly to couplers  100  and  200 , includes a winding  310  that serves as a secondary of a transformer.  FIG. 4  is a schematic diagram of circuit  20 .  
         [0022]     In circuit  20 , in contrast to circuit  10 , jumper connection  262  is not jumped, but is instead, connected to winding  310  via a connection module  360 . Connection module  360  is terminated by a jumper  350 .  
         [0023]     A daisy chain is a collection of standardized modules connected to each other in a chain. Typically, an output cable of one module is plugged into an input connector of the next module in the chain. Thus, inductive couplers  100 ,  200  and  300  are daisy-chained.  
         [0024]     The chain of inductive couplers  100 ,  200  and  300  shares surge suppression circuit  122  (see  FIG. 2 ). Thus, only one surge suppression circuit  122  is required. This arrangement is less expensive than equipping each inductive coupler  100 ,  200  and  300  with its own surge suppression circuit  122 , and may reduce RF signal loss for the aggregate of inductive couplers  100 ,  200  and  300 .  
         [0025]     Note that in  FIGS. 1 and 2  cable  250  is represented as being hard wired to surge protection module  120  and connection module  260 . In contrast, in  FIGS. 3 and 4 , connections between connection module  260  and surge protection module  120  are made via connectors  340  and  345 .  
         [0026]     Any number of inductive couplers may be daisy chained. When the inductive couplers are chained via connection modules (e.g., connection modules  260  and  360 ) the last connection module in the chain (e.g., connection module  360 ) has its jumper terminals shorted together.  
         [0027]     While a series connection of inductive couplers  100 ,  200  and  300  is illustrated in  FIGS. 1-4 , a parallel connection may be implemented along the same lines.