Electricity: conductors and insulators – Anti-inductive structures – Conductor transposition
Reexamination Certificate
1998-01-27
2001-10-30
Reichard, Dean A. (Department: 2831)
Electricity: conductors and insulators
Anti-inductive structures
Conductor transposition
C174S034000, C174S1020SP, C174S1130AS
Reexamination Certificate
active
06310286
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to the field of network cabling. More particularly, the present invention relates to the field of network cabling for use with an IEEE 1394 serial bus network.
BACKGROUND OF THE INVENTION
The IEEE 1394 standard, “P1394 Standard For A High Performance Serial Bus,” Draft 8.01v1, Jun. 16, 1995, is an international standard for implementing an inexpensive high-speed serial bus architecture which supports both asynchronous and isochronous format data transfers. The IEEE 1394 standard provides a high-speed serial bus for interconnecting digital devices thereby providing a universal I/O connection. The IEEE 1394 standard defines a digital interface for the applications thereby eliminating the need for an application to convert digital data to analog data before it is transmitted across the bus. Correspondingly, a receiving application will receive digital data from the bus, not analog data, and will therefore not be required to convert analog data to digital data. An ‘application’ as used herein will refer to either an application or a device driver.
The cable specified by the IEEE 1394 standard is very thin in size compared to many other cables, such as conventional co-axial cables, used to connect such devices. Devices can be added and removed from an IEEE 1394 bus while the bus is active. If a device is so added or removed the bus will then automatically reconfigure itself for transmitting data between the then existing nodes. A node is considered a logical entity with a unique address on the bus structure. Each node provides an identification ROM, a standardized set of control registers and its own address space.
A standard IEEE 1394 cable is illustrated in FIG.
1
. An IEEE 1394 network using the standard IEEE 1394 cable
10
is a differential, copper wire network, which includes two differential pairs of wires
12
and
14
, carrying the differential signals TPA and TPB, respectively. As shown in
FIG. 1
, the pairs of wires
12
and
14
are twisted together within the cable
10
. The signals TPA and TPB are both low voltage, low current, bidirectional differential signals used to carry data bits or arbitration signals. The signals TPA and TPB have a maximum specified amplitude of 265 mVolts. The twisted pairs of wires
12
and
14
have a relatively high impedance, specified at 110 ohms, such that minimal power is needed to drive an adequate signal across the wires
12
and
14
. The standard IEEE 1394 cable
10
also includes a pair of power signals VG and VP, carried on the wires
16
and
18
, respectively. The wires
16
and
18
are also twisted together within the cable
10
. The pair of power signals VP and VG provide the current needed by the physical layer of the serial bus to repeat signals. The wires
16
and
18
have a relatively low impedance and are specified to have a maximum power level of 60 watts.
The IEEE 1394 cable environment is a network of nodes connected by point-to-point links, including a port on each node's physical connection and the cable between them. The physical topology for the cable environment of an IEEE 1394 serial bus is a non-cyclic network of multiple ports, with finite branches. The primary restriction on the cable enviromnment is that nodes must be connected together without forming any closed loops.
The IEEE 1394 cable connects ports together on different nodes. Each port includes terminators, transceivers and simple logic. A node can have multiple ports at its physical connection. The cable and ports act as bus repeaters between the nodes to simulate a single logical bus. Because each node must continuously repeat bus signals, the separate power VP wire
18
and ground VG wire
16
, within the cable
10
, enable the physical layer of each node to remain operational even when the local power at the node is turned off. The pair of power wires
16
and
18
can even be used to power an entire node if it has modest power requirements. The signal VG carried on the wire
16
is a grounded signal. The signal VP carried on the wire
18
is powered from local power of the active devices on the IEEE 1394 serial bus. Accordingly, at least one of the active devices must be powered by local power. Together, the signals VG and VP form a power signal which is used by the nodes.
A maximum cable length of 4.5 meters is specified for an IEEE 1394 cable. The cabling limitations of an IEEE 1394 serial bus are set by the timing requirements and signal waveform characteristics for transmitted signals. The default timing is set after at most two bus resets, and it is adequate for
32
cable hops, each of 4.5 meters, for a total of 144 meters. This maximum cable length is not practical in some environments in which the distance between active devices is greater than 4.5 meters. One such environment is within an aircraft which can require cable lengths well over 4.5 meters.
U.S. patent application Ser. No. 08/714,659, entitled “IEEE 1394 ACTIVE WALL DISCONNECT AND AIRCRAFT QUALIFIED CABLE” and filed on Sep. 16, 1996, which is hereby incorporated by reference, teaches an IEEE 1394 cable having a length greater than 4.5 meters. The longer cable lengths taught in this application incorporate heavier gauge wire for the two twisted data pairs
12
and
14
in order to match the performance characteristics of a standard IEEE 1394 cable and comply with the signal levels and timing requirements of the IEEE 1394 specification over the increased distance. U.S. patent application Ser. No. 08/714,659 teaches an IEEE 1394 cable having a length of 20 meters including twisted pairs of wire of 18 gauge wire and an IEEE 1394 cable having a length of 30 meters including twisted pairs of wire of 16 gauge wire. While the cables taught in U.S. patent application Ser. No. 08/714,659 achieve longer cable lengths than 4.5 meters and still perform according to the appropriate parameters set by the IEEE 1394 specification, the cables are large in diameter, due to the heavier gauge wire used to achieve the longer length and the thick dielectric material required to maintain signal characteristics. When wiring within a closed environment such as an aircraft where space taken up by the cable is a consideration, large diameter cables are disadvantageous and present problems in assembling and routing the cables. The large diameter cables also add extra weight to the aircraft.
What is needed is a cable for use between IEEE 1394 devices which has a length greater than 4.5 meters and a relatively small diameter and minimum weight.
SUMMARY OF THE INVENTION
A quad cable includes four conductors arranged as two differential pairs for carrying the differential signals TPA and TPB. Preferably, the quad cable is used to transmit data signals between devices within an IEEE 1394 network. The two differential conductor pairs are included, with filler material, within a braided inner shield. A shield separator is formed outside of the braided inner shield. A braided outer shield is formed outside of the shield separator. The shield separator provides electrical isolation between the inner and outer shields. A cable jacket is formed outside of the braided outer shield to encase the cable. Each end of the cable includes a cable connector having a plurality of pins for coupling to a receiving connector. The four conductors and the inner shield are each coupled to a respective pin within each cable connector. When coupled to a receiving connector, the outer shield is coupled to a housing of the connector. Within unit electronics at the port housing the receiving connector, a capacitor is preferably coupled between the inner shield and the outer shield. Preferably, the quad cable has a length of 4.5 meters and includes 24 gauge wire for the conductors. Longer, alternate embodiments of the cable incorporate heavier gauge wire for the conductors. Preferably, DC power conductors are not included within the quad cable, but are provided within a separate cable or by each active local device. Alternatively, the DC power conductors are included beside th
Cardon Jay Edward
Ninh Loi Quang
Troxel Robert Vincent
Haverstock & Owens LLP
Mayo III William H.
Reichard Dean A.
Sony Corporation
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