Wave transmission lines and networks – Plural channel systems – Having branched circuits
Reexamination Certificate
1998-07-20
2001-07-17
Lee, Benny (Department: 2817)
Wave transmission lines and networks
Plural channel systems
Having branched circuits
C333S100000, C333S112000
Reexamination Certificate
active
06262636
ABSTRACT:
TECHNICAL FIELD
The present invention relates generally to an apparatus for network transmission, and in particular to a broadband signal tap with a reversible directional coupler and a make-before-break continuity bridge for use as part of a cable television, cable telephone, or data distribution system.
BACKGROUND OF THE INVENTION
Typical cable television system networks, such as for cable TV or CATV, include four main elements, a headend, a trunk system, a distribution system consisting of feeder cables bridged from the trunk system, and subscriber drops fed from broadband signal taps in the distribution system.
The headend, which is the central originating point of all signals carried on the network, receives signals from satellite, broadcasted, or transmitted by cable and transmits these signals as a broadband signal to numerous distribution nodes via trunk cables. Each distribution node, in turn, distributes the signals along with power, via feeder cables, with each feeder cable terminating at a termination block. Each feeder cable has numerous broadband signal taps inserted between the distribution node and the termination block. Each of these broadband signal taps draws a portion of the broadband signal and power for use by a subscriber, typically a home or business, and transmits the remaining broadband signal to the next tap along the feeder cable. Typically, there are hundreds, and sometimes thousands, of subscribers connected to each feeder cable. At a subscriber's site, the subscriber's equipment is connected to the tap via a drop cable, which may terminate directly into the television receiver on 12-channel systems, or into a converter where more than 12 channels are provided.
The individual broadband signal taps are connected in series along the feeder cable, the feeder cable being connected to an input terminal of the broadband signal tap. Within the broadband signal tap the broadband signal is split, and a small portion of the broadband signal is delivered to the subscriber through a subscriber drop cable. The remainder of the signal is returned to the feeder cable. By their very nature, these broadband signal taps are directional, so they must be installed so they can extract signal in the direction of the signal flow.
A disadvantage of prior broadband signal taps is that if one of the taps in a series of taps is out of service, the subscribers downstream of the out-of-service tap will be deprived of service. Service interruptions, even if for just a few milliseconds, can have serious and even catastrophic consequences for the transmission of digital data. Unlike analog signals, loss of even a small portion of a digital data transmission can render the transmission unintelligible, or cause a failure of the signals to reach the intended destination. With the advent of pay-per view and interactive television, and the increased use of cable systems for telephone voice and data transmission, it has become extremely important to provide means to maintain continuity of service to the subscribers.
Furthermore, the growth in the broadband industry has created a need for an infrastructure that can be readily modified and that can grow with the customer needs. Such modifications must be able to be provided with only minimal adverse impact to the existing customers. Thus, it is often necessary to add extra trunks, branches along the feeder cables or trunk lines, or to make other modifications to the system infrastructure. When this is done, it is often necessary to reverse the direction of signal flow along the feeder cables. This is typically accomplished by disconnecting the tap from the feeder cable and installing the tap in the opposite direction. Such a reversing of the tap, however, is a costly and time-consuming process that deprives hundreds or thousands of downstream subscribers of service during the time required to disconnect and reconnect the tap in the opposite direction.
Accordingly, there is a need for a broadband signal tap having a reversible directional coupler. Thus, if a change in the direction of the signal flow is required, such a reversal in signal direction is easily accomplished by merely changing the direction of the coupler, rather than removing the entire tap. Preferably, during the time required to reverse the directional coupler, there should not be any disturbance or interruption of service. Thus, there is a need for a broadband signal tap with a reversible directional coupler, which has a make-before-break connection such that the continuity of the broadband signal is maintained through the tap while the directional coupler is being reversed.
SUMMARY OF THE INVENTION
The present invention includes a broadband signal tap for use in connection with a network communication system that has one or more distribution nodes, with at least one feeder cable connected to a distribution node and broadband signal taps serially connected along the feeder cable. The broadband signal tap of the present invention includes a reversible directional coupler and a make-before-break signal continuity bridge. The reversible directional coupler allows for the reversal of the directional coupler's connections in the tap, and the continuity bridge maintains broadband signal continuity to downstream subscribers during the reversal of the direction coupler.
The directional coupler includes an input for receiving the broadband signal from the system through a first coupling means on a motherboard in the tap, a subscriber output for providing the extracted portion of the broadband signal to a subscriber through subscriber coupling means on the motherboard, and a return output for providing the remainder of the broadband signal to the system through second coupling means on the motherboard.
The electronic circuitry of the directional coupler is provided on a daughterboard that is removably connected to the motherboard within the tap. The removable daughterboard has a plurality of symmetrically arranged output connection means that constitute the input, subscriber output, and return output. The daughterboard may also contain symmetrically arranged outputs that constitute ground connectors.
The motherboard includes a plurality of symmetrically arranged connection points for accepting connections with the plurality of symmetrically arranged connection means on the daughterboard. The motherboard preferably includes connection points that constitute the first coupling means, subscriber coupling means, and second coupling means. The motherboard many also include connection points for the grounding means. Preferably, the connection means on the daughterboard are connection pins and the connection points on the motherboard are small apertures of a suitable dimension to accept the pins on the daughterboard.
The connections on the motherboard and on the daughterboard are physically and functionally symmetrical, thereby permitting the daughterboard to be reversed. The connection of the daughterboard to the motherboard can be reversed such that the daughterboard can be connected to the motherboard in either a first or second position. When the daughterboard is connected to the motherboard in a first position, the input of the directional coupler on the daughterboard is connected to the first coupling means on the motherboard, the subscriber output on the daughterboard is connected to the subscriber coupling means on the motherboard, and the return output on the daughterboard is connected to the second coupling means on the motherboard.
Conversely, when the daughterboard is reversed and connected to the motherboard in the second position, the input on the daughterboard is connected to the second coupling means on the motherboard, the subscriber output on the daughterboard is connected to the subscriber coupling means on the motherboard, and the return output on the daughterboard is connected to the first coupling means on the motherboard.
In this manner, when the daughterboard is connected to the motherboard in the first position, the broadband signal is transmitted
Adams Mark E.
Brown James T.
Harton, IV Thomas B.
McLain Dennis J.
Tunnell Timothy
Antec Corporation
Boss Gerald R.
Jones Stephen E.
Lee Benny
Troutman Sanders LLP
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