Electrical connectors – With insulation other than conductor sheath – Plural-contact coupling part
Reexamination Certificate
2000-07-07
2001-08-07
Nguyen, Khiem (Department: 2839)
Electrical connectors
With insulation other than conductor sheath
Plural-contact coupling part
C439S941000, C333S001000
Reexamination Certificate
active
06270381
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to electrical connectors, and, more particularly, to such connectors designed to reduce crosstalk between adjacent pairs comprising different communication paths.
BACKGROUND OF THE INVENTION
The advent and subsequent development of optical communication systems which employ high transmission speeds and frequencies have been responsible for increased development of electrical systems capable of operating at much higher frequencies than heretofore. Inasmuch as, at least for the present, there is still a predominance of electrical systems, for such systems to be competitive, they must operate at the higher frequencies of which optical systems are capable.
In an electrical communication system, it is sometimes advantageous to transmit information (video, audio, data) in the form of balanced signals over a pair of wires (hereinafter “wire-pair”) rather than a single wire, wherein the transmitted signal comprises the voltage difference between the wires without regard to the absolute voltages present. Each wire in a wire-pair is capable of picking up electrical noise from sources such as lightning, automobile spark plugs and radio stations to name but a few. Balance is affected by impedance symmetry in a wire-pair as between its individual conductors and ground. When the impedance to ground for one conductor is different than the impedance to ground for the other conductor, then common mode (longitudinal) signals are undesirably converted to differential mode (transverse) signals and vice versa. Additionally, return loss is a reflection of the incoming signal, and it occurs when the terminating impedance does not match the source impedance. Of greater concern, however, is the electrical noise that is picked up from nearby wires that may extend in the same general direction for long distances. This is referred to as crosstalk, and so long as the same noise signal is added to each wire in the wire-pair, then the voltage difference between the wires will remain the same. In all of the above situations, undesirable signals are present on the electrical conductors that can interfere with the information signal. Existing crosstalk compensation schemes in connectors for adjacent pairs of conductors are designed to compensate for differential crosstalk on an idle pair induced, i.e., coupled, from a nearby driven pair. However, most such schemes do not provide for compensation for the differential-to-common mode crosstalk between the driven pair and the idle pair. In the absence of compensation for this latter form of crosstalk, an unbalanced signal is induced in the adjacent pair. Thus, to achieve balance, it is desirable to compensate not only for differential crosstalk caused by a differential input signal, but, also, to compensate for common mode crosstalk caused by a differential input signal and differential mode crosstalk caused by a common mode signal. In U.S. Pat. No. 5,967,853 of Hashim, the disclosure of which is incorporated herein by reference, there is shown a compensation arrangement using capacitors between different pairs of conductors which offset both differential-to-differential crosstalk coupling as well as differential-to-common-mode coupling. The capacitors generally are designed within a printed wiring board (PWB) connected to the connector, and are carefully chosen as to value to produce the desired amount of compensation (or coupling) between discrete pairs. In any such compensation arrangement, design techniques require good judgement and are applicable only to achieve a certain level of balance performance for the specific parameters of the signal transmission.
In U.S. Pat. No. 5,186,647 to Denkmann et al. and U.S. Pat. No. 5,997,358 of Adriaenssens et al., the disclosures of which are incorporated herein by reference, there are shown connectors wherein compensating crosstalk is introduced by establishing stages wherein predetermined magnitudes and phases of compensating crosstalk are generated. The stages are created by cross-overs of certain conductors within the connector or by appropriately placed capacitors. Both patents disclose differential crosstalk compensation but do not address the differential-to-common mode crosstalk, as is done in the Hashim patent.
SUMMARY OF THE INVENTION
The present invention is an arrangement for the conductors within a connector, preferably, but not necessarily, using the crossover techniques disclosed in the Denkmann et al. and Adriaenssens et al. patents, wherein there are n stages of compensation, where n≧3, and is based upon the algorithm
(
a−b
)
n
(1)
When the algorithm is solved for any value of n of three (3) or more, the coefficients of the individual terms give the amplitudes of the crosstalk components, the first of which is the original crosstalk and the rest being compensation in each of the several stages of compensation. Thus, for
(
a−b
)
3
=a
3
−3
a
2
b+
3
ab
2
−b
3
(2)
the coefficients are +1, −3, +3, −1. As is pointed out in the analysis given in the Adrienssens et al. patent, more than one stage is necessary to compensate for the phase differences of the generated crosstalk and the compensating crosstalk. The algorithm is applicable to values of n of three (3) or more and, hence, three or more stages, and the coefficients of the terms dictate the magnitudes and polarities of the compensation while the exponent n is determinative of the number of stages. The greater the value of n, the more stages and better compensation result. However, there are practical limits to the value of n≧3, as will be apparent hereinafter.
In an illustrative embodiment of the invention a connector having eight leads forming four pairs, I, II, III, and IV, has the conductors configured for optimum crosstalk compensation involving the first and third pairs, I and III, which, as will be apparent hereinafter, are the most important because, during normal connector usage, they exhibit the most crosstalk. Crosstalk between pairs II-III and III-IV are also important. In accordance with the algorithm (1) and for n=3, the pair II (leads
1
and
2
) has two crossovers of the type shown for example in the Denkmann et al. patent, as do pairs I (leads
4
and
5
) and IV (Leads
7
and
8
). The pair III (leads
3
and
6
) has one crossover, which, in interaction with pairs I, II, and IV produces a sum of three stages as dictated by algorithm (1) for n=3 and the amplitudes of compensating crosstalk in the several stages conform to the coefficient values of algorithm (1) and to the polarities. As will be more apparent from the detailed discussion hereinafter, there are, within the connector, three stages of differential mode coupling between pairs I and III, II and III, and III and IV, all of which couplings produce, as an end result, vector sums for optimum phase, as discussed in the Adriaenssens et al. patent and magnitudes of compensation for minimizing crosstalk.
The principles of the invention which involve the algorithm (1) are applicable to other connector arrangements, as will be discussed hereinafter, and to other possible configurations wherein crosstalk among pairs of leads presents problems.
The principles and features of the present invention will be more readily understood from the following detailed description, read in conjunction with the accompanying drawings.
REFERENCES:
patent: 5096442 (1992-03-01), Arnett et al.
patent: 5186647 (1993-02-01), Denkmann et al.
patent: 5362257 (1994-11-01), Neal et al.
patent: 5432484 (1995-07-01), Klas et al.
patent: 5997358 (1999-12-01), Adriaenssens et al.
Adriaenssens Luc Walter
Hashim Amid Ihsan
Larsen Wayne David
Moffitt Bryan Scott
Avaya Technology Corp.
Nguyen Khiem
Nguyen Son V.
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