The term crosstalk was originally coined to indicate the presence in a telephone receiver of unwanted speech sounds from another telephone conversation. Of particular interest is crosstalk that is caused by signal coupling between adjacent circuits. The most common coupling is due to near-field effects and can usually be characterized by mutual inductance and direct capacitance. This is best illustrated by considering two parallel balanced transmission paths. One circuit (the disturbing circuit) is a source of signal energy that is undesirably coupled into an adjacent circuit via stray capacitance and mutual inductance. Near-end crosstalk NEXT) is crosstalk energy that travels in the opposite direction to that of the signal in the disturbing circuit, whereas far-end crosstalk is crosstalk energy that travels in the same direction as the signal in the disturbing circuit. Circuit analysis indicates that NEXT is frequency dependent and, for communication connectors, its magnitude typically increases with frequency at a 6.0 dB per octave rate NEXT is introduced within an electrical cable as a result of signal energy being coupled between nearby wires; and within an electrical connector, particularly modular plugs and jacks, as a result of signal energy being coupled between nearby conductors. NEXT is undesirable and is frequently referred to as offending crosstalk.
U.S. Pat. No. 5,096,442 discloses a modular jack whose NEXT is about 25 dB below the level of the incoming signal at 100 MHz. Such NEXT is attributable to crosstalk that is introduced by the combination of a standard modular plug with a standard modular jack such as are generally used for voice-grade communications. However, this level of crosstalk is generally too high for modern high-speed data applications.
U.S. Pat. No. 5,186,647 discloses a substantial improvement to the design of a standard modular jack by crossing the path of one of the conductors within the jack, over the path of another of the conductors within the jack to produce crosstalk of an opposite polarity. Such compensating crosstalk attempts to cancel NEXT rather than merely minimizing it by, for example, increasing the separation between conductors. This simple technique improves NEXT at 100 MHz by a startling 17 dB, thereby enabling popular modular jacks to meet Category 5 requirements specified in ANSI/EIA/TIA-568A. An example of such a modular jack is the M100 Communication Outlet, which is manufactured by Lucent Technologies Inc.
Techniques have been developed that further improve the crosstalk performance of an electrical connector so that NEXT is now more than 60 dB below the level of the incoming signal at 100 MHz. U.S. Pat. No. 5,997,358 shows such techniques. However, this level of crosstalk performance represents the very best that can be attained since crosstalk will vary according to how the plug is seated within the jack. At least one manufacturer has disposed the jack springs within the modular jack at a relatively large contact angle (about 36.degree.) with respect to the longitudinal axis of the modular jack in order to push the modular plug into a fixed location within the jack. However, since there are many jack springs that need to make electrical contact with the blades of an inserted modular plug, large contact angles make this task difficult. Whereas large contact angles create increased pressure against the plug blades, increased pressure by some of the jack springs can preclude other spring contacts from making contact with the plug blades unless the plug blades and the jack springs are all precisely aligned. Indeed, current FCC standards recommend a relatively small contact angle (i.e., between 13 and 24 degrees) to assure that all plug blades make contact with the jack springs.
Accordingly, what the prior art appears to lack and what is now desired is a technique for assuring the consistent positioning of a modular plug within a modular jack, where the modular jack includes jack springs that are disposed at relatively small angles with respect to the longitudinal axis of the jack.