Impedance-tuned termination assembly and connectors...

Electrical connectors – Electromagnetic or electrostatic shield – Multi-part shield body

Reexamination Certificate

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Details

C439S502000

Reexamination Certificate

active

06454605

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates generally to terminations for connectors and more particularly to connectors used in connection with signal cables.
Many electronic devices rely upon transmission lines to transmit signals between related devices or between peripheral devices and circuit boards of a computer. These transmission lines incorporate signal cables that are capable of high-speed data transmissions.
These signal cables may use what are known as one or more twisted pairs of wires that are twisted together along the length of the cable, with each such twisted pair being encircled by an associated grounding shield. These twisted pairs typically receive complimentary signal voltages, i.e., one wire of the pair may see a +1.0 volt signal, while the other wire of the pair may see a −1.0 volt signal. Thus, these wires may be called “differential” pairs, a term that refers to the different signals they carry. As signal cables are routed on a path to an electronic device, they may pass by or near other electronic devices that emit their own electric field. These devices have the potential to create electromagnetic interference to transmission lines such as the aforementioned signal cables. However, this twisted pair construction minimizes or diminishes any induced electrical fields and thereby eliminates electromagnetic interference.
In order to maintain electrical performance integrity from such a transmission line, or cable, to the circuitry of an associated electronic device, it is desirable to obtain a substantially constant impedance throughout the transmission line, from circuit to circuit or to avoid large discontinuities in the impedance of the transmission line. The difficulty of controlling the impedance of a connector at a connector mating face is well known because the impedance of a conventional connector typically drops through the connector and across the interface of the two mating connector components. Although it is relatively easy to maintain a desired impedance through an electrical transmission line, such as a cable by maintaining a specific geometry or physical arrangement of the signal conductors and the grounding shield, an impedance drop is usually encountered in the area where a cable is mated to a connector. It is therefore desirable to maintain a desired impedance throughout the connector and its connection to the cable.
Typical signal cable terminations involve the untwisting of the wire pairs and the unbraiding of the braided shield wire surrounding the wire pairs. These wires are unbraided manually and this manual operation tends to introduce variability into the electrical performance. This is caused by unbraiding the grounding shield wires, then typically twisting them into a single lead and subsequently welding or soldering the twisted tail of a connector terminal. This unbraiding and twisting often results in moving the signal conductors and grounding shield out of their original state in which they exist in the cable. This rearrangement may lead to a decoupling of the ground and signal wires from their original state that may result in an increase of impedance through the cable-connector junction. Moreover, this twisting introduces mechanical variability into the termination area in that although a cable may contain multiple differential pairs, the length of the unbraided shield wire may vary from pair to pair. This variability and rearrangement changes the physical characteristics of the system in the termination area which may result in an unwanted change (typically an increase) in the impedance of the system in the area.
Additionally, it is common for the signal and ground termination tails of a connector to be arranged into whatever convenient space is present at the connector mounting face without any control of the geometry or spatial aspects of the signal and ground terminals being considered. When signal wires and ground shields are pulled apart from the end of a cable, an interruption of the cable geometry is introduced. It is therefore desirable to maintain this geometry in the termination area between the cable and the cable connector to reduce any substantial impedance increase from occurring due to the cable termination.
The present invention is therefore directed to a termination structure for providing improved connections between cables and connectors that provides a high level of performance and which maintains the electrical characteristics of the cable in the termination area.
SUMMARY OF THE INVENTION
Accordingly, it is a general object of the present invention to provide an improved termination structure for use in high-speed data transmission connections in which the impedance discontinuity through the cable termination is minimized so as to attempt to better match the impedance of the transmission line.
Another object of the present invention is to provide a termination assembly for use in conjunction with signal cables that provides a connection between the twisted wire pairs and grounding shield of the cable and the connector, the termination assembly having an improved electrical performance due to its structure, which eliminates large impedance discontinuities attributable to operator assembly.
A further object of the present invention is to provide an improved termination assembly for effecting a high-performance termination between a transmission line having at least one pair of differential signal wires and an associated ground and a connector having at least two signal and one ground terminal disposed adjacent to the signal terminals for contacting opposing corresponding signal ground terminals.
It is a further object of the present invention to provide such a connector wherein, by varying the size of the ground terminal and its location relative to its two associated signal wires, the impedance of the connector may be “tuned” to obtain a preselected impedance through the connector.
Yet another object of the present invention is to provide a connector for connecting cables, such as those of the IEEE 1394 type, to a circuit board of an electronic device, wherein the connector has a number of discrete, differential signal wires and associated grounds equal in number to those contained in the cables, the ground terminals of the connector being configured in size and location with respect to the signal terminals of the connector in order to minimize the drop in impedance through the connector.
It is a further object of the present invention to provide a termination assembly that provides a simple manner of termination for a signal cable in which the ground termination portion is both sized to control the impedance through the termination and to provide a nest for the grounding shield of the cable, the ground terminal portion of the connector being located rearwardly of the signal terminal portions to thereby permit the facilitation of the cable termination with selective stripping of the cable and minimal wire end preparation.
Yet still another object of the present invention is to provide a termination structure for a cable connector, the connector having a plurality of terminals, at least two of the terminals being signal terminals and one of the terminals being a ground terminal, each of the terminals having opposing contact and termination portions, the termination portions having the form of hollow, curved cups the signal terminal termination portion cups being circumscribed by the ground terminal termination portion cup so that the ground terminal termination portion cup serves to orient the shield of the cable in a preferred orientation and to direct the placement of the signal conductors of the cable in the signal termination cups.
Yet it is still another object of the present invention to provide a connector with a unique termination structure that is particularly suitable for termination to cables, the termination structure maintaining the mechanical arrangement of the cable conductors and grounding shield as they enter the cable connector so that the signal and ground

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