Patent Publication Number: US-2002010940-A1

Title: Two-conductor medium communication systems and methods for transmission and reception of multiple-channel data signals

Description:
CROSS REFERENCES TO RELATED APPLICATIONS  
     [0001] This application claims the benefit of U.S. Provisional Application Ser. No. 60/205,005 filed May 17, 2000. 
    
    
     
       BACKGROUND OF THE INVENTION  
       [0002] 1. Field of the Invention  
       [0003] The present invention relates generally to communication systems.  
       [0004] 2. Description of the Related Art  
       [0005] Conventional communication systems have typically utilized signal carriers to separate different information channels and compact multiple channels into a specific frequency range. The channel bandwidths are preferably narrowed in order to fit more channels into the specific frequency range and this narrowing is generally realized with various modulation schemes (e.g., m-ary bi-orthogonal keying). These modulation schemes, however, add significant cost to a communication system because they are parts-intensive and generally require complex digital signal processing techniques to modulate and demodulate data.  
       BRIEF SUMMARY OF THE INVENTION  
       [0006] The present invention is directed to simple, inexpensive communication systems for communicating data signals over a plurality of different respective communication channels.  
       [0007] These systems are realized with sets of signal filters wherein each filter set defines a respective communication channel. The filters of each set are distributed among transceivers which are coupled together with a two-conductor medium. Accordingly, a significant number of communication end-users and a system headend can share data signals over a substantial number of communication channels without the need for complex modulation and demodulation hardware.  
       [0008] The novel features of the invention are set forth with particularity in the appended claims. The invention will be best understood from the following description when read in conjunction with the accompanying drawings. 
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0009]FIG. 1 is a block diagram of a communication system embodiment of the present invention;  
     [0010]FIG. 2 is a block diagram of a transmitter embodiment in the communication system of FIG. 1;  
     [0011]FIG. 3 is a diagram of exemplary frequency allocations in the communication system of FIG. 1  
     [0012]FIG. 4 is a block diagram of a receiver embodiment in the communication system of FIG. 1; and  
     [0013]FIG. 5 is a flow chart which shows communication processes that can be practiced with the communication system of FIG. 1. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
     [0014]FIG. 1 illustrates a data communication system  20  of the invention that facilitates communication of data signals over a two-conductor medium  22  between a headend  24  of the system and transceivers  26  of end-users of the system. In particular, FIG. 1 shows that the medium (e.g., a coaxial cable or a twisted pair) is generally formed by a network of medium branches  28  that are joined with signal-steering devices such as a signal splitter  30  and hubs  32 .  
     [0015] The headend has a headend transceiver  34  that is coupled to one of the medium branches and the end-user transceivers  26  are coupled to respective ones of the other medium branches. Medium branches  28  are preferably coupled to hubs  32  so that N end-user transceivers  26  are coupled to the medium  22  via each respective one of M hubs  32 .  
     [0016] Each of the end-user transceivers  26  facilitates data communication over the medium  22  for a variety of end-user data devices such as telephones  36 , personal computers  37  and televisions  38 . Although this communication can be between end-users of the communication system  20 , it is generally through the headend  24  to external data sources  39  (e.g., satellites and the internet).  
     [0017]FIG. 2 illustrates a transmitter embodiment  40  for the headend and end-user transceivers ( 34  and  26  in FIG. 1). The embodiment  40  includes a plurality of bandpass filters  42 , an amplifier  44  that is preferably coupled to the medium ( 22  in FIG. 1) by a coupling capacitor  46 , and a signal combiner  48  that couples the filters to the amplifier. An exemplary combiner is a high-bandwidth operational amplifier in a non-inverting configuration that is coupled to the filters  42  by additional coupling capacitors  49 .  
     [0018] The filters  42  have different passbands that each define a respective communication channel of the data communication system ( 20  in FIG. 1). For example, filter  42 A has a passband (e.g., 100 Hz to 4 KHz) suitable for passing an audio transmit signal from an audio source  50  (e.g., a telephone), filters  42 B-N have passbands (e.g., with widths on the order of 10 MHz) suitable for passing digital and analog transmit signals from digital and analog sources  52  (e.g., computers), and filter  42 N+ 1  has a video passband (e.g., with a width on the order of 6 MHz) suitable for passing video transmit signals from video sources  54  (e.g., a television set). Accordingly, the filters  42  insure that each source instrument communicates over the medium ( 22  in FIG. 1) via a respective communication channel.  
     [0019] Operation of the transmitter embodiment  40  is best described with reference to the frequency-allocation diagram  60  of FIG. 3. This diagram plots exemplary filter passbands for the transmitter filters ( 42  in FIG. 2) as a function of a logarithmic frequency coordinate. An exemplary passband  62 A of the audio filter ( 42 A in FIG. 2) is shown to extend substantially from 100 Hz to 4 KHz. Exemplary adjacent passbands  62 B-N of the digital and analog filters ( 42 B-N in FIG. 2) are shown with widths of substantially 10 MHz that are located, as indicated by the insert  66 , in a frequency region  68  which extends from substantially 2 MHz up to the roll-off frequency of typical two-conductor mediums (e.g., 1000 MHz).  
     [0020] The transmit signals that are generated by the audio, digital and analog sources  50  and  52  of FIG. 2 and passed through the filters  42 A-N are generally conducted directly by the medium ( 22  in FIG. 1), i.e., without the aid of a carrier signal. The medium, however, can also conduct carrier signals onto which the communication signals have been modulated.  
     [0021] For example, the video source(s)  54  of FIG. 2 may generate modulated carrier signals and their respective filters  42 N+ 1  may have a plurality of adjacent video passbands  62 N+ 1  in FIG. 3 with exemplary widths on the order of 6 MHz. The passbands  62 N+ 1  are distributed over a video frequency portion (e.g., 65-860 MHz) of the frequency region  68  as indicated by the insert  70 .  
     [0022] Another exemplary modulated carrier source that may be communicated by the invention is one associated with a home phone network application (HPNA). This source can also be provided with a respective video filter that has a suitable passband  72  (e.g., with a width of 4 MHz that is centered at substantially 7.5 MHz). Yet another exemplary modulated carrier source is one associated with Ethernet systems that generally operate in the range of 10 megabits/second and this source could also be provided with a respective transmit filter.  
     [0023] Each of the transmit filters of the transmitter embodiment  40  of FIG. 2 preferably has a corresponding receive filter in the receiver portion of the transceivers of FIG. 1. FIG. 4 illustrates a receiver embodiment  80  for the headend and end-user transceivers ( 34  and  26  in FIG. 1) that includes receive bandpass filters  82  which provide this operational parameter.  
     [0024] In particular, the receiver  80  has an audio filter  82 A whose passband substantially matches the passband of the audio filter  42 A of FIG. 2, digital and analog filters  82 B-N whose passbands substantially match the passbands of the digital and audio filters  42 B-N of FIG. 2, and a video filter  82 N+ 1  whose passband substantially matches the passband of the video filter  42 N+ 1  of FIG. 2.  
     [0025] Transmit signals from any of the transceivers ( 26  and  34  of FIG. 1) can therefore be passed through a respective one of the receive filters  82  of the receiver  80  of FIG. 4 to a corresponding one of receivers  90 ,  92  and  94 . For example, transmit signals that pass through the audio filter  42 A of FIG. 2 can be received from the medium ( 22  in FIG. 1) via the audio filter  82 A of FIG. 4 and provided to an audio receiver  90  (e.g., a telephone).  
     [0026] Similarly, transmit signals that pass through the digital and analog filters  42 B-N of FIG. 2 can be received via the digital and analog filters  82 B-N of FIG. 4 and provided to digital and analog receivers  92 . Finally, transmit signals that pass through the video filter  42 N+ 1  of FIG. 2 can be received via the video filter  82 N+ 1  of FIG. 4 and provided to video receivers  94 . Although not shown in FIG. 4, the coupling between the receive filters  80  and the medium may be augmented with an appropriate signal splitting device (e.g., the signal splitter  30  of FIG. 1).  
     [0027] It is apparent that corresponding filters of the transmitter  40  of FIG. 2 and the receiver  80  of FIG. 4 form sets of filters and each filter set defines a respective communication channel in the communication system  20  of FIG. 1. The audio filter  42 A of FIG. 2 and the audio filter  82 A of FIG. 4, for example, are part of a set of filters that define an audio channel of the system. Similarly, the digital filter  42 B of FIG. 2 and the digital filter  82 B of FIG. 4 are part of a set of filters that define a digital channel of the system and the video filter  42 N+ 1  of FIG. 2 and the video filter  82 N+ 1  of FIG. 4 are part of a set of filters that define a video channel of the system.  
     [0028] The flow chart  100  of FIG. 5 illustrates process steps in a method of communicating data that can be practiced with the communication system  20  of FIG. 1. In process step  102 , data signals are transmitted to a two-conductor medium through transmit filters whose passbands define respective and different communication channels in the frequency region below 1000 megahertz. Subsequently, data signals are received in process step  104  from the medium through a plurality of receive filters whose passbands substantially match respective ones of the transmit filters.  
     [0029] Although energizing power may be provided locally to transceivers of the communication system of FIG. 1, the two-conductor medium  22  provides a conduit for sharing power supplies. A DC power supply  110 , for example, is coupled in FIG. 4 to the medium  22  on the system side of a blocking capacitor  112 . Accordingly, various elements of the communication system can draw energizing power from the medium  22 .  
     [0030] Communication systems have been described which provide secure communication channels for sharing data signals between a system headend and a plurality of system end-users. Because these systems isolate the data signals with respective filter sets that are coupled to a two-conductor medium, they provide substantial cost reduction because they relieve the need for complex signal modulation and demodulation hardware.  
     [0031] Systems of the invention offer data communication to end-users over a significant number of communication channels and the number of end-users can be substantially increased (as shown in FIG. 1) by the use of communication hubs  32  which extend the medium  22  by providing two-way signal amplification.  
     [0032] The embodiments of the invention described herein are exemplary and numerous modifications, variations and rearrangements can be readily envisioned to achieve substantially equivalent results, all of which are intended to be embraced within the spirit and scope of the invention as defined in the appended claims.