Modular jack for low crosstalk electrical connector

Details Modular jack for low crosstalk electrical connector Modular jack for low crosstalk electrical connector

2001-12-21

2003-06-03

Ta, Tho D. (Department: 2833)

Electrical connectors

With insulation other than conductor sheath

Plural-contact coupling part

C439S941000

Reexamination Certificate

active

06572414

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to an electrical connector; and, more particularly, to a modular jack of an electrical connector implementing a low crosstalk.
BACKGROUND OF THE INVENTION
A communications terminal used in an office or home is electrically connected to an outdoor transmission cable via an electrical connector, which usually includes a modular jack and a plug. Though a four-pin connector has been widely used for the communications terminal, an eight-pin connector is now being developed to satisfy the need for a high transmission speed. Telecommunication Industry Association (TIA) and Electronic Industry Association (EIA) of U.S. are specifying Category 6, a new industrial specification, to keep up with a rapid development of communication parts including the eight-pin connector.
In a transmission cable, each pair of lines forms a signal pair to transmit a specific electrical signal. If a signal pair transmitting a first signal is adjacent to another pair transmitting a second signal, a capacitive coupling and an inductive coupling are induced between the first and the second signal, thereby causing an error in the signals. Such an electromagnetic interference between two adjacent signals is referred to as a crosstalk.
As shown in
FIG. 1
, an insert
2
of a conventional eight pin modular jack (not shown) includes an insert housing
4
and eight insert conductors “R
1
” to “R
4
” and “T
1
” to “T
4
”. The insert conductors “R
1
” to “R
4
” and “T
1
” to “T
4
” are arranged to run parallel to each other on one plane while maintaining a constant pitch therebetween. Portions of the insert conductors are embedded in the insert housing
4
serving to maintain relative positions thereof.
Such a single level arrangement of the insert conductors causes significant crosstalks both inside and outside the insert housing
4
. Therefore, an electrical connector adopting the conventional modular jack can hardly satisfy specifications of Category
6
.
In
FIG. 2
, there is illustrated a schematic arrangement of the conventional insert conductors “R
1
” to “R
4
” and “T
1
” to “T
4
” in order to explain the crosstalks therebetween, herein only a few capacitive coupling components are depicted for the sake of simplicity.
In the drawing, a first conductor “R
1
” and a second conductor “T
1
” form a first signal pair to transmit a first signal; a fourth conductor “T
2
” and a fifth conductor “R
2
” form a second signal pair for a second signal; a third conductor “R
3
” and a sixth conductor “T
3
” form a third signal pair for a third signal; and a seventh conductor “R
4
” and an eighth conductor “T
4
” form a fourth signal pair for a fourth signal. The second conductor “T
1
” and the third conductor “R
3
” are adjacent to each other and transmit different signals, i.e., the first signal and the third signal, respectively. Therefore, a strong electromagnetic coupling is induced between the first signal of the second conductor “T
1
” and the third signal of the third conductor In other words, a first capacitance “C
13
” is induced between the first conductor “R
1
” and the third conductor “R
3
” while a second capacitance “C
23
” is induced between the second conductor “T
1
” and the third conductor “R
3
”. The second capacitance “C
23
” is larger than the first capacitance “C
13
” (C
23
>C
13
), because the capacitance is inversely proportional to a distance between two conductors and the third conductor “R
3
” is closer to the second conductor “T
1
” than the first conductor “R
1
” is. The above-explained capacitance difference causes an electrical potential difference between the second conductor “T
1
” and the third conductor “R
3
”, thereby increasing the capacitive coupling of the first signal of the second conductor “T
1
” and the third signal of the third conductor “R
3
”.
Further, a third capacitance C
16
is induced between the first and sixth conductor “R
1
” and “T
3
”. However, because the sixth conductor “T
3
” is located relatively very far away from the first conductor “R
1
”, the third capacitance C
16
is very small and an effect thereof can be disregarded.
Like the second and the third conductor “T
1
” and “R
3
”, if two conductors are respectively involved with different signal pairs but electromagnetically coupled, they are referred to as a crosstalk pair. The crosstalk mainly occurs between the conductors of the crosstalk pairs, such as “T
1
-R
3
”, “R
3
-T
2
”, “R
2
-T
3
”, and “T
3
-R
4
”.
Though the previous explanation is focused on the first to the third capacitances “C
13
”, “C
23
” and “C
16
”, other capacitances including a fourth to a sixth capacitances “C
12
”, “C
36
” and “C
26
” are also induced among the insert conductors. A detailed explanation about the fourth to the sixth capacitances, however, is omitted for the sake of simplicity.
The U.S. Pat. No. 5,299,956 teaches a method for preventing the crosstalk. In the method in accordance with the above-mentioned U.S. patent, an opposite electromagnetic coupling is induced to cancel the inductive or capacitive coupling. With reference to
FIG. 3
, the purport of the U.S. Pat. No. 5,299,956 will be explained.
As shown, a first signal pair “S
1
” includes a first tip conductor “T
1
” and a first ring conductor “R
1
” while a second signal pair “S
2
” includes a second tip conductor “T
2
” and a second ring conductor “R
2
”. In a first portion “Z
1
”, the second tip conductor “T
2
” and the second ring conductor “R
2
” are disposed adjacent to the first ring conductor “R
1
” and the first tip conductor “T
1
”, respectively. In a second portion “Z
2
”, however, positions of the second tip and the second ring conductor “T
2
” and “R
2
” are interchanged with each other, such that the second ring conductor “R
2
” and the second tip conductor “T
2
” are disposed adjacent to the first ring conductor “R
1
” and the first tip conductor “T
1
”, respectively.
In the above-described configuration, a first crosstalk occurs between the first and the second signal pair “S
1
” and “S
2
” in the first portion “Z
1
” while a second crosstalk occurs therebetween in the second portion “Z
2
”. Because of the above-mentioned interchange of positions in the second portion “Z
2
”, the first crosstalk and the second crosstalk have opposite phases, thereby canceling each other.
That is to say, first inductive and the first capacitive coupling induced in the first portion “Z
1
”, and second inductive and second capacitive couplings induced in the second portion “Z
2
” have phases opposite to each other. Accordingly, the first inductive and the first capacitive coupling are canceled by the second inductive and the second capacitive coupling, such that a total crosstalk is reduced.
The method in accordance with the prior art can provide a simple configuration for a low crosstalk electrical connector by way of simultaneously canceling each of the capacitive coupling and the inductive coupling in the same portion. For the same reason, however, at least one of the capacitive coupling and the inductive coupling cannot be wholly canceled and a considerable amount of the crosstalk still remains.
The crosstalk cannot be actually reduced below a level of −46 dB even if the above-explained method is employed, if the transmission frequency of signal is around 250 MHz. That is to say, though a higher transmission frequency is required as the data transmission speed increases, the method in accordance with the prior art can rarely satisfy newly required specifications.
SUMMARY OF THE INVENTION
It is, therefore, an object of the present invention to provide a modular jack for an electrical connector that implements a low crosstalk for transmitting high frequency signals.
In accordance with one aspect of the invention, a preferred embodiment of the present invention provides a modular jack for a low crosstalk electrical connector, the jack including: a housing; a first signal pair passing through the housing and including a first conductor and a second conductor, a first imaginary plane containing the first and th

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