System and method for transmission-line termination by signal cancellation, and applications thereof
View Patent ↗An active terminating device ( 30 ) for an electrical transmission line with optional line-receiving and line-driving capabilities. The basic device is a two-terminal unit, denoted as a Signal Canceling Unit (SCU), which sensesthe signal available at its terminals ( 34 a, 34 b ), and applies negative feedback in order to cancel and absorb the signal. When applied to the end of a transmission line ( 15 a, 15 b ) as part of wired communication network, the SCU functions as a terminator. When connected in the middle of such wired transmission line, the SCU splits the transmission line into two separate and isolated segments. In such a configuration, the SCU can be used to isolate a portion of a network from signal degradation due to noise or bridge-tap. Furthermore, the two isolated segments may each employ independent communications, such that no interference exists between the segments. In another embodiment, line receiver functionality is integrated into the SCU, designated as a Signal Canceling and Receiving Unit (SCRU) ( 90 ). The SCRU can perform all the SCU functions, and also serves as a line receiver in the communication network. In yet another embodiment, line driver functionality is integrated into the SCRU, designated as a Signal Canceling, Receiving and Transmitting Unit (SCRTU) ( 120 ). The SCRTU can perform all the SCRU functions, and also serves as a line driver in the communication network. Upon connecting multiple SCRTU's to a continuous transmission line, terminated independent point-to-point communication segments are formed.
1. A communication system for concurrently carrying multiple distinct signals over a shared transmission line composed of at least two conductors, the system comprising:
first and second transmission line segments connected to each other at a single connection point and each connected to a communication device in order to carry a different one of the distinct signals; and
a termination device coupled to said connection point and operative to at least attenuate signal propagation between said segments when said segments are concurrently carrying different ones of the distinct signals.
2. The communication system according to claim 1 wherein said termination device comprises:
two device ports each coupled to a respective conductor of said transmission line at said connection point;
a sensor having sensor inputs coupled to said two device ports, and a sensor output, said sensor being operative for sensing a signal at said connection point and for supplying to said sensor output a signal that is a function of the signal that is sensed;
a driver having a driver input and driver outputs, said driver outputs being coupled to said device ports for placing a signal on said transmission line; and
a processing unit coupled to said sensor output and to said driver input, and operative to supply said driver input with a signal that is effective to at least attenuate the signal at said connection point.
3. The communication system according to claim 2 wherein said termination device further comprise a data unit port coupled to said device ports and operative to couple a data unit to said transmission line.
4. The communication system according to claim 1 wherein said transmission line has at least a third transmission line segment connected to said connection point.
5. The communication system according to claim 4 wherein at least one of said transmission line segments is open-ended at an end remote from said connection point.
6. The communication system according to claim 1 , further comprising a receiver coupled to said connection point and operative couple to a data unit.
7. The communication system according to claim 1 wherein the transmission line comprises existing wiring in walls of a building.
8. The communication system according to claim 7 wherein the wiring is one: telephone wiring; power wiring; and CATV cabling.
9. A termination device for actively terminating a data signal carried over a two-conductor transmission line connected to said device, said device comprising:
a sensor having sensor inputs couplable to the two conductors of the transmission line at a connection point of the transmission line, and a sensor output, said sensor being operative for sensing the data signal at the connection point and for supplying to said sensor output a signal that is a function of the signal that is sensed;
a driver having a driver input and driver outputs, the driver outputs being couplable to the connection point for placing a signal on the transmission line; and
a processing unit coupled to said sensor output and to said driver input, and operative to supply said driver input with a signal that is effective to at least attenuate the signal at the connection point.
10. The device according to claim 9 further comprising a receiver port coupled to said processing unit, and wherein said processing unit is operative to generate a signal that is a function of the cancelled data signal and to supply the generated signal to said receiver port.
11. The device according to claim 9 further operative for transmitting signals to the transmission line, wherein said device further comprises a transmitter port coupled to said driver input, and said device further has a transmit state in which said processing unit is disconnected from said driver input.
12. A method for actively terminating a data signal carried over a two-conductor transmission line, said method comprising the steps of:
sensing the data signal and generating a first signal which is a function thereof; and
processing the first signal to generate a second signal and placing the second signal on the transmission line in order to at least attenuate the sensed data signal.
13. The method according to claim 12 , further comprising generating signal that is a function of the sensed data signal.
14. A method for concurrently carrying multiple distinct signals over a shared transmission line comprising at least two conductors composed of first and second transmission line segments connected to each other at a single connection point and each connected to a communication device in order to carry a respective one of the distinct signals, said method comprising:
coupling a termination device to said connection point; and
operating said termination device to at least attenuate signals propagating from one segment to the other when said segments are concurrently carrying different ones of the distinct signals.
15. The method according to claim 14 wherein the termination device comprises:
two coupling ports coupled to the conductors at the connection point;
a sensor having sensor input and sensor output ports, said sensor input port being coupled to the coupling ports and operative for sensing signals at the connection point and for generating on the output port a signal which is a function of the sensed signals;
a driver having driver input and driver output ports, the driver output port being coupled to the coupling ports and operative for placing a signal on the transmission line; and
a processing unit coupled to said sensor output port and said driver input port, and operative for at least attenuating the sensed signals.
16. The method according to claim 15 wherein the termination device further comprise a data unit port coupled to the coupling ports and operative for coupling a data unit coupled to the data unit port to the transmission line.
17. The method according to claim 14 wherein at least three transmission line segments are connected to the connection point.
18. The method according to claim 17 wherein at least one of the transmission line segments is open-ended.
19. The method according to claim 14 further comprising coupling a receiver to the connection point, said receiver being operative to couple to a data unit.
20. The method according to claim 14 wherein the transmission line comprises existing wiring in walls of a building.
21. The method according to claim 20 wherein the wiring is one of: telephone wiring; power wiring and CATV cabling.