Terada, Yuji (Tokyo, JP)
Ishii, Koichi (Tokyo, JP)
Yanata, Takeshi (Tokyo, JP)

Plaque It!

11/525935

11/04/2008

09/25/2006

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TDK Corporation (Tokyo, JP)

361/119

361/117

H01C7/12

361/120, 361/118, 361/119, 361/117

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JP2001060838A	March, 2001			COMPOSITE PARTS
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KR10-2005-0014094	February, 2005
WO/2003/103091	December, 2003			CIRCUIT FOR DIVERTING SURGES AND TRANSIENT IMPULSES

Sherry, Michael J.

Nguyen, Danny

Oliff & Berridge, PLC

What is claimed is:

1. A connector comprising: a first terminal; a second terminal connected to the first terminal; a third terminal; a fourth terminal connected to the third terminal; and a surge absorbing circuit provided between the first and second terminals and between the third and fourth terminals; the surge absorbing circuit comprising: a first inductor having one end connected to the first terminal; a second inductor having one end connected to the other end of the first inductor and the other end connected to the second terminal, the first and second inductors being electromagnetically coupled together so as to increase each other's inductance; a third inductor having one end connected to the third terminal; a fourth inductor having one end connected to the other end of the third inductor and the other end connected to the fourth terminal, the third and fourth inductors being electromagnetically coupled together so as to increase each other's inductance; a first surge absorbing element having one end connected to the other end of the first inductor and the one end of the second inductor and the other end connected to a ground terminal; and a second surge absorbing element having one end connected to the other end of the third inductor and the one end of the fourth inductor and the other end connected to the ground terminal.

2. A connector according to claim 1, wherein the surge absorbing circuit further comprises: a first capacitance element provided between the one end of the first inductor and the other end of the second inductor; and a second capacitance element provided between the one end of the third inductor and the other end of the fourth inductor.

3. A connector comprising: a first terminal; a second terminal connected to the first terminal; a third terminal; a fourth terminal connected to the third terminal; and a surge absorbing circuit provided between the first and second terminals and between the third and fourth terminals; the surge absorbing circuit comprising: a first inductor having one end connected to the first terminal; a second inductor having one end connected to the other end of the first inductor and the other end connected to the second terminal; a third inductor having one end connected to the third terminal; a fourth inductor having one end connected to the other end of the third inductor and the other end connected to the fourth terminal; a first surge absorbing element having one end connected to the other end of the first inductor and the one end of the second inductor and the other end connected to a ground terminal; and a second surge absorbing element having one end connected to the other end of the third inductor and the one end of the fourth inductor and the other end connected to the ground terminal; the first, second, third, and fourth inductors being electromagnetically coupled together so as to increase each other's inductance when a differential signal is applied thereto.

4. A connector according to claim 3, wherein the surge absorbing circuit further comprises: a first capacitance element provided between the one end of the first inductor and the other end of the second inductor; and a second capacitance element provided between the one end of the third inductor and the other end of the fourth inductor.

5. A connector comprising: a first terminal; a second terminal connected to the first terminal; a third terminal; a fourth terminal connected to the third terminal; and a surge absorbing circuit provided between the first and second terminals and between the third and fourth terminals; the surge absorbing circuit comprising: a first inductor having one end connected to the first terminal; a second inductor having one end connected to the other end of the first inductor and the other end connected to the second terminal; a third inductor having one end connected to the third terminal, the first and third inductors being electromagnetically coupled together so as to increase each other's inductance when a differential signal is applied thereto; a fourth inductor having one end connected to the other end of the third terminal and the other end connected to the fourth terminal, the second and fourth inductors being electromagnetically coupled together so as to increase each other's inductance when a differential signal is applied thereto; a first surge absorbing element having one end connected to the other end of the first inductor and the one end of the second inductor and the other end connected to a ground terminal; a second surge absorbing element having one end connected to the other end of the third inductor and the one end of the fourth inductor and the other end connected to the ground terminal; a first capacitance element provided between the one end of the first inductor and the other end of the second inductor; and a second capacitance element provided between the one end of the third inductor and the other end of the fourth inductor.

6. A connector comprising: a first terminal; a second terminal connected to the first terminal; a third terminal; a fourth terminal connected to the third terminal; and a surge absorbing circuit provided between the first and second terminals and between the third and fourth terminals; the surge absorbing circuit comprising: a first inductor having one end connected to the first terminal; a second inductor having one end connected to the other end of the first inductor and the other end connected to the second terminal; a third inductor having one end connected to the third terminal; a fourth inductor having one end connected to the other end of the third inductor and the other end connected to the fourth terminal; a first surge absorbing element having one end connected to the other end of the first inductor and the one end of the second inductor and the other end connected to a ground terminal; a second surge absorbing element having one end connected to the other end of the third inductor and the one end of the fourth inductor and the other end connected to the ground terminal; a first capacitance element provided between the one end of the first inductor and the other end of the second inductor; and a second capacitance element provided between the one end of the third inductor and the other end of the fourth inductor.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a connector.

2. Related Background Art

Connectors have been known as a device for connecting signal transmission lines between instruments. The connectors are exposed to the outside in general. Therefore, there is a possibility of electrostatic surges being inputted through a connector from the outside and breaking circuit elements in the instruments.

As measures against such electrostatic surges, surge absorbing elements such as varistors may be used. However, the surge absorbing elements such as varistors have stray capacitance components and stray inductance components. Therefore, employing a surge absorbing element in a circuit handling a high-speed signal may deteriorate the high-speed signal. For employing a surge absorbing element in a circuit handling a high-speed signal, rise and delay characteristics of the high-speed signal cannot be kept from deteriorating unless the stray capacitance component in the surge absorbing element is made small. However, lowering the stray capacitance component of a surge absorbing element increases the control voltage of the surge absorbing element and decreases the energy tolerance in the surge absorbing element.

Known as a surge absorbing element which alleviates the influence of the stray capacitance component is one comprising an inductor and two varistors (see, for example, Patent Document 1: Japanese Patent Application Laid-Open No. 2001-60838). The surge absorbing device disclosed in Patent Document 1 comprises a parallel circuit composed of a first varistor and an inductor, a second varistor electrically connected in series to the parallel circuit, and an I/O electrode and a ground electrode which are connected to both ends of a series circuit constructed by the second varistor and parallel circuit.

SUMMARY OF THE INVENTION

However, it is difficult for the surge absorbing element disclosed in Patent Document I to effect impedance matching over a wide band for a transmission line connected to the surge absorbing device, since the stray capacitance of the first varistor and the inductor construct a bandpass filter. Therefore, employing the surge absorbing element disclosed in Patent Document 1 in a circuit handling a high-speed signal may fail to realize a sufficient characteristic for the high-speed signal. Surge absorbing elements employed in circuits handing high-speed signals are desired to not only achieve favorable impedance matching for the high-speed signals, but also reduce the size of the elements themselves.

Therefore, it is an object of the present invention to provide a connector which can lower electrostatic surges without deteriorating high-speed signals.

A first connector of the present invention comprises a first terminal, a second terminal connected to the first terminal, and a surge absorbing circuit provided between the first and second terminals. The surge absorbing circuit comprises (a) a first inductor having one end connected to the first terminal; (b) a second inductor having one end connected to the other end of the first inductor and the other end connected to the second terminal, the first and second inductors being electromagnetically coupled together so as to increase each other's inductance; and (c) a surge absorbing element having one end connected to the other end of the first inductor and the one end of the second inductor and the other end connected to a ground terminal.

The surge absorbing circuit of the first connector has a surge absorbing circuit which is excellent in reducing electrostatic surges, and thus can lower the electrostatic surges. Also, this surge absorbing circuit has first and second inductors electromagnetically coupled to each other, and thus can set such a coupling factor as to keep a constant input impedance over a wide band. Further, this surge absorbing circuit can set the inductance of the first inductor and the inductance of the second inductor with respect to the stray capacitance component of the surge absorbing element such that the input impedance of the surge absorbing circuit and a characteristic impedance of a transmission line match each other. Therefore, this surge absorbing circuit is excellent in reducing electrostatic surges, and enables impedance matching over a wide band. Hence, the first connector equipped with this surge absorbing circuit can reduce electrostatic surges without deteriorating transmitted/received signals.

A second connector of the present invention comprises a first terminal, a second terminal connected to the first terminal, and a surge absorbing circuit provided between the first and second terminals. The surge absorbing circuit further comprises a capacitance element provided between the one end of the first inductor and the other end of the second inductor in addition to the surge absorbing circuit in the fist connector.

The surge absorbing circuit in the second connector can set the coupling factor between the first and second inductors and the capacitance value of the capacitance element such as to keep a constant input impedance over a wide band. Further, this surge absorbing circuit can set the respective inductances of the first and second inductors and their coupling factor with respect to the stray capacitance component of the surge absorbing element such that the input impedance of the surge absorbing circuit and a characteristic impedance of a transmission line match each other.

Even when the stray inductance component of the first surge absorbing element must be taken into consideration, the electromagnetic coupling between the first and second inductors can yield a negative inductance component which cancels out the stray inductance component of the surge absorbing element. Further, the respective inductances of the first and second inductors, their coupling factor, and the capacitance value of the capacitance element can be set such that the input impedance matches the characteristic impedance of the transmission line while being kept constant over a wide band. Therefore, the second connector equipped with this surge absorbing circuit can reduce electrostatic surges without deteriorating transmitted/received signals.

A third connector of the present invention comprises a first terminal, a second terminal connected to the first terminal, and a surge absorbing circuit provided between the first and second terminals. The surge absorbing circuit comprises (a) a first inductor having one end connected to the first terminal; (b) a second inductor having one end connected to the other end of the first inductor and the other end connected to the second terminal; (c) a surge absorbing element having one end connected to the other end of the first inductor and the one end of the second inductor and the other end connected to a ground terminal; and (d) a capacitance element provided between the one end of the first inductor and the other end of the second inductor.

The surge absorbing circuit of the third connector has a surge absorbing circuit which is excellent in reducing electrostatic surges, and thus can lower the electrostatic surges. Also, this surge absorbing circuit can set the capacitance value of the capacitance element such as to keep a constant input impedance over a wide band. Further, this surge absorbing circuit can set the inductance of the first inductor and the inductance of the second inductor with respect to the stray capacitance component of the surge absorbing element such that the input impedance of the surge absorbing circuit and a characteristic impedance of a transmission line match each other. Therefore, this surge absorbing circuit is excellent in reducing electrostatic surges, and enables impedance matching over a wide band. Hence, the third connector equipped with this surge absorbing circuit can reduce electrostatic surges without deteriorating transmitted/received signals.

A fourth connector of the present invention comprises a first terminal, a second terminal connected to the first terminal, a third terminal, a fourth terminal connected to the third terminal, and a surge absorbing circuit provided between the first and second terminals and between the third and fourth terminals. The surge absorbing circuit comprises (a) a first inductor having one end connected to the first terminal; (b) a second inductor having one end connected to the other end of the first inductor and the other end connected to the second terminal, the first and second inductors being electromagnetically coupled together so as to increase each other's inductance; (c) a third inductor having one end connected to the third terminal; (d) a fourth inductor having one end connected to the other end of the third inductor and the other end connected to the fourth terminal, the third and fourth inductors being electromagnetically coupled together so as to increase each other's inductance; (e) a first surge absorbing element having one end connected to the other end of the first inductor and the one end of the second inductor and the other end connected to a ground terminal; and (f) a second surge absorbing element having one end connected to the other end of the third inductor and the one end of the fourth inductor and the other end connected to the ground terminal.

The surge absorbing circuit of the fourth connector has first and second surge absorbing elements which are excellent in reducing electrostatic surges, and thus can lower the electrostatic surges. Also, this surge absorbing circuit has first and second inductors which are electromagnetically coupled together and third and fourth inductors which are electromagnetically coupled together, and thus can set the coupling factor between the first and second inductors and the coupling factor between the third and fourth inductors such as to keep a constant input impedance over a wide band. Further, this surge absorbing circuit can set the inductance of the first inductor and the inductance of the second inductor with respect to the stray capacitance component of the first surge absorbing element and the inductance of the third inductor and the inductance of the fourth inductor with respect to the stray capacitance component of the second surge absorbing element such that the input impedance of the surge absorbing circuit and a characteristic impedance of a transmission line match each other. Therefore, this surge absorbing circuit is excellent in reducing electrostatic surges, and enables impedance matching over a wide band. Hence, the fourth connector equipped with this surge absorbing circuit can reduce electrostatic surges without deteriorating differential transmitted/received signals.

A fifth connector of the present invention comprises a first terminal, a second terminal connected to the first terminal, a third terminal, a fourth terminal connected to the third terminal, and a surge absorbing circuit provided between the first and second terminals and between the third and fourth terminals. The surge absorbing circuit further comprises a first capacitance element provided between the one end of the first inductor and the other end of the second inductor and a second capacitance element provided between the one end of the third inductor and the other end of the fourth inductor in addition to the surge absorbing circuit in the fourth connector.

The surge absorbing circuit of the fifth connector can set the coupling factor between the first and second inductors, the coupling factor between the third and fourth inductors, the capacitance value of the first capacitance element, and the capacitance value of the second capacitance element so as to keep a constant input impedance over a wide band. Further, this surge absorbing circuit can set the respective inductances of the first, second, third, and fourth inductors, the coupling factor between the first and second inductors, and the coupling factor between the third and fourth inductors with respect to the stray capacitance component of the first surge absorbing element and the stray capacitance component of the second surge absorbing element such that the input impedance of the surge absorbing circuit and a characteristic impedance of a transmission line match each other.

Even when the stray inductance components of the first and second surge absorbing elements must be taken into consideration, the electromagnetic coupling between the first and second inductors can yield a negative inductance component which cancels out the stray inductance component of the first surge absorbing element, whereas the electromagnetic coupling between the third and fourth inductors can yield a negative inductance component which cancels out the stray inductance component of the second surge absorbing element. Further, the respective inductances of the first and second inductors, their coupling factor, the respective inductances of the third and fourth inductors, their coupling factor, and the capacitance value of the capacitance element can be set such that the input impedance matches the characteristic impedance of the transmission line while being kept constant over a wide band. Therefore, the fifth connector equipped with this surge absorbing circuit can reduce electrostatic surges without deteriorating differential transmitted/received signals.

A sixth connector of the present invention comprises a first terminal, a second terminal connected to the first terminal, a third terminal, a fourth terminal connected to the third terminal, and a surge absorbing circuit provided between the first and second terminals and between the third and fourth terminals. The surge absorbing circuit comprises (a) a first inductor having one end connected to the first terminal; (b) a second inductor having one end connected to the other end of the first inductor and the other end connected to the second terminal; (c) a third inductor having one end connected to the third terminal; (d) a fourth inductor having one end connected to the other end of the third inductor and the other end connected to the fourth terminal; (e) a first surge absorbing element having one end connected to the other end of the first inductor and the one end of the second inductor and the other end connected to a ground terminal; and (f) a second surge absorbing element having one end connected to the other end of the third inductor and the one end of the fourth inductor and the other end connected to the ground terminal. The first, second, third, and fourth inductors are electromagnetically coupled together so as to increase each other's inductance when a differential signal is applied thereto.

The surge absorbing circuit of the sixth connector has first and second surge absorbing elements which are excellent in reducing electrostatic surges, and thus can lower the electrostatic surges. Also, this surge absorbing circuit has first to fourth inductors which are electromagnetically coupled together, and thus can set the coupling factor among the first to fourth inductors such as to keep a constant input impedance over a wide band. Further, this surge absorbing circuit can set the respective inductances of the first to fourth inductors and their coupling factor with respect to the stray capacitance components and stray inductance components of the first and second surge absorbing elements such that the input impedance of the first surge absorbing element and a characteristic impedance of the transmission line match each other. Therefore, this surge absorbing circuit is excellent in reducing electrostatic surges, and enables impedance matching over a wide band. Hence, the sixth connector equipped with this surge absorbing circuit can reduce electrostatic surges without deteriorating differential transmitted/received signals.

A seventh connector of the present invention comprises a first terminal, a second terminal connected to the first terminal, a third terminal, a fourth terminal connected to the third terminal, and a surge absorbing circuit provided between the first and second terminals and between the third and fourth terminals. The surge absorbing circuit further comprises a first capacitance element provided between the one end of the first inductor and the other end of the second inductor and a second capacitance element provided between the one end of the third inductor and the other end of the fourth inductor in addition to the surge absorbing circuit in the sixth connector.

The surge absorbing circuit of the seventh connector can set the coupling factor among the first, second, third, and fourth inductors and the respective capacitance values of the first and second capacitance elements so as to keep a constant input impedance over a wide band. Further, this surge absorbing circuit can set the respective inductances of the fist, second, third, and fourth inductors and their coupling factor with respect to the stray capacitance components of the first and second surge absorbing elements such that the input impedance of the surge absorbing circuit and a characteristic impedance of a transmission line match each other.

Even when the stray inductance components of the first and second surge absorbing elements must be taken into consideration, the electromagnetic coupling among the first, second, third, and fourth inductors can yield a negative inductance component which cancels out the stray inductance components of the first and second surge absorbing elements. Further, the respective inductances of the first, second, third, and fourth inductors, their coupling factor, and the respective capacitance values of the first and second capacitance elements can be set such that the input impedance matches the characteristic impedance of the transmission line while being kept constant over a wide band. Therefore, the seventh connector equipped with this surge absorbing circuit can reduce electrostatic surges without deteriorating differential transmitted/received signals.

An eighth connector of the present invention comprises a first terminal, a second terminal connected to the first terminal, a third terminal, a fourth terminal connected to the third terminal, and a surge absorbing circuit provided between the first and second terminals and between the third and fourth terminals. The surge absorbing circuit comprises (a) a first inductor having one end connected to the first terminal; (b) a second inductor having one end connected to the other end of the first inductor and the other end connected to the second terminal; (c) a third inductor having one end connected to the third terminal, the first and third inductors being electromagnetically coupled together so as to increase each other's inductance when a differential signal is applied thereto; (d) a fourth inductor having one end connected to the other end of the third terminal and the other end connected to the fourth terminal, the second and fourth inductors being electromagnetically coupled together so as to increase each other's inductance when a differential signal is applied thereto; (e) a first surge absorbing element having one end connected to the other end of the first inductor and the one end of the second inductor and the other end connected to a ground terminal; (f) a second surge absorbing element having one end connected to the other end of the third inductor and the one end of the fourth inductor and the other end connected to the ground terminal; (g) a first capacitance element provided between the one end of the first inductor and the other end of the second inductor, and (h) a second capacitance element provided between the one end of the third inductor and the other end of the fourth inductor.

The surge absorbing circuit of the eighth connector has first and second surge absorbing elements which are excellent in reducing electrostatic surges, and thus can lower the electrostatic surges. Also, this surge absorbing circuit can set the respective capacitance values of the first and second capacitance elements so as to keep a constant input impedance over a wide band. Further, this surge absorbing circuit has first and third inductors which are electromagnetically coupled together and second and fourth inductors which are electromagnetically coupled together, and thus can set the respective inductances of the first, second, third, and fourth inductors, the coupling factor between the first and third inductors, and the coupling factor between the second and fourth inductors with respect to the stray capacitance components and stray inductance components of the first and second surge absorbing elements such that the input impedance of the first surge absorbing element and a characteristic impedance of the transmission line match each other. Therefore, this surge absorbing circuit is excellent in reducing electrostatic surges, and enables impedance matching over a wide band. Hence, the eighth connector equipped with this surge absorbing circuit can reduce electrostatic surges without deteriorating differential transmitted/received signals.

A ninth connector of the present invention comprises a first terminal, a second terminal connected to the first terminal, a third terminal, a fourth terminal connected to the third terminal, and a surge absorbing circuit provided between the first and second terminals and between the third and fourth terminals. The surge absorbing circuit comprises (a) a first inductor having one end connected to the first terminal; (b) a second inductor having one end connected to the other end of the first inductor and the other end connected to the second terminal; (c) a third inductor having one end connected to the third terminal; (d) a fourth inductor having one end connected to the other end of the third inductor and the other end connected to the fourth terminal; (e) a first surge absorbing element having one end connected to the other end of the first inductor and the one end of the second inductor and the other end connected to a ground terminal; (f) a second surge absorbing element having one end connected to the other end of the third inductor and the one end of the fourth inductor and the other end connected to the ground terminal; (g) a first capacitance element provided between the one end of the first inductor and the other end of the second inductor; and (h) a second capacitance element provided between the one end of the third inductor and the other end of the fourth inductor.

The surge absorbing circuit of the ninth connector has first and second surge absorbing elements which are excellent in reducing electrostatic surges, and thus can lower the electrostatic surges. Also, this surge absorbing circuit can set the respective capacitance values of the first and second capacitance elements so as to keep a constant input impedance over a wide band. Further, this surge absorbing circuit can set the respective inductances of the first and second inductors with respect to the stray capacitance component of the first surge absorbing element and the respective inductances of the third and fourth inductors with respect to the stray capacitance component of the second surge absorbing element such that the input impedance of the surge absorbing circuit and a characteristic impedance of a transmission line match each other. Therefore, this surge absorbing circuit is excellent in reducing electrostatic surges, and enables impedance matching over a wide band. Hence, the ninth connector equipped with this surge absorbing circuit can reduce electrostatic surges without deteriorating differential transmitted/received signals.

Preferably, each of surge absorbing circuits in the above-mentioned first to ninth conductors is constructed by a multilayer body having a conductor pattern therewithin and on a surface thereof. This structure can make the surge absorbing circuit smaller and reduce the stray capacitance component.

The present invention provides connectors which can reduce electrostatic charges without deteriorating high-speed signals.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partly broken perspective view showing the connector in accordance with a first embodiment of the present invention;

FIG. 2 is a circuit diagram showing a surge absorbing circuit employable in the connector in accordance with the first embodiment;

FIG. 3 is a circuit diagram equivalently illustrating the surge absorbing circuit shown in FIG. 2;

FIG. 4 is a circuit diagram showing the surge absorbing circuit in accordance with Modified Example 1 employable in the connector of the first embodiment;

FIG. 5 is a circuit diagram equivalently illustrating the surge absorbing circuit shown in FIG. 4;

FIG. 6 is an equivalent circuit diagram of the first surge absorbing element;

FIG. 7 is a circuit diagram showing the surge absorbing circuit in accordance with Modified Example 2 employable in the connector of the first embodiment;

FIG. 8 is a partly broken perspective view showing the connector in accordance with a second embodiment of the present invention;

FIG. 9 is a circuit diagram showing a surge absorbing circuit employable in the connector in accordance with the second embodiment;

FIG. 10 is a circuit diagram equivalently illustrating the surge absorbing circuit shown in FIG. 9;

FIG. 11 is a circuit diagram showing the surge absorbing circuit in accordance with Modified Example 1 employable in the connector of the second embodiment;

FIG. 12 is a circuit diagram equivalently illustrating the surge absorbing circuit shown in FIG. 11;

FIG. 13 is a circuit diagram showing the surge absorbing circuit in accordance with Modified Example 2 employable in the connector of the second embodiment;

FIG. 14 is a circuit diagram equivalently illustrating the surge absorbing circuit shown in FIG. 13;

FIG. 15 is a circuit diagram showing the surge absorbing circuit in accordance with Modified Example 3 employable in the connector of the second embodiment;

FIG. 16 is a circuit diagram equivalently illustrating the surge absorbing circuit shown in FIG. 15;

FIG. 17 is a circuit diagram showing the surge absorbing circuit in accordance with Modified Example 4 employable in the connector of the second embodiment;

FIG. 18 is a circuit diagram showing the surge absorbing circuit in accordance with Modified Example 5 employable in the connector of the second embodiment;

FIG. 19 is a perspective view showing in a partly broken fashion a multilayer surge absorbing component for the surge absorbing circuit in accordance with Modified Example 1 in the connector of the first embodiment;

FIG. 20 is an exploded perspective view illustrating layer by layer the multilayer body shown in FIG. 19;

FIG. 21 is an exploded perspective view illustrating layer by layer the multilayer body of the multilayer surge absorbing component for the surge absorbing circuit in accordance with Modified Example 2 in the connector of the first embodiment;

FIG. 22 is a perspective view showing the multilayer surge absorbing component for the surge absorbing circuit in accordance with Modified Example 1 in the connector of the second embodiment;

FIG. 23 is an exploded perspective view illustrating layer by layer the multilayer body shown in FIG. 22;

FIG. 24 is an exploded perspective view illustrating layer by layer the multilayer body of the multilayer surge absorbing component for the surge absorbing circuit in accordance with Modified Example 3 in the connector of the second embodiment;

FIG. 25 is an exploded perspective view illustrating layer by layer the multilayer body of the multilayer surge absorbing component for the surge absorbing circuit in accordance with Modified Example 4 in the connector of the second embodiment; and

FIG. 26 is an exploded perspective view illustrating layer by layer the multilayer body of the multilayer surge absorbing component for the surge absorbing circuit in accordance with Modified Example 5 in the connector of the second embodiment.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the following, preferred embodiments of the present invention will be explained in detail with reference to the drawings. In the drawings, the same or equivalent parts will be referred to with the same numerals.

First Embodiment

FIG. 1 is a partly broken perspective view showing the connector in accordance with a first embodiment of the present invention. This connector 10 comprises a frame 12 , a substrate 14 , and a multilayer surge absorbing component 26 .

The frame 12 has a rectangular cylindrical form extending along an axis X. Specifically, the frame has inner faces 12 a , 12 b , 12 c , 12 d defining an inner hole. The inner faces 12 a and 12 b are substantially parallel to each other, whereas the inner faces 12 c and 12 d are substantially parallel to each other. The inner faces 12 c and 12 d are substantially orthogonal to the inner faces 12 a and 12 b . The substrate 14 is provided on the inner face 12 a of the fame 12 .

The substrate 14 is fixed to the inner face 12 a of the frame 12 . One main face 14 a of the substrate 14 is separated from the inner face 12 b . External connectors to connect with the connector 10 are inserted between the substrate 14 and inner face 12 b.

Provided on the main face 14 a of the substrate 14 are a first power wiring pattern 15 , a second power wiring pattern (e.g., grounding pattern) 16 , a first signal wiring pattern 17 , a second signal wiring pattern I 8 , and a ground pattern 19 which are used for connecting with the external connectors.

The first power wiring pattern 15 and second power wiring pattern 16 are conductor patterns extending along the axis X. The first power wiring pattern 15 and second power wiring pattern 16 are leads for feeding a power between an instrument connected to the connector 10 and an instrument connected to an external connector. The first signal wiring pattern 17 and second signal wiring pattern 18 are provided between the first power wiring pattern 15 and second power wiring pattern 16 .

The first signal wiring pattern 17 and second signal wiring pattern 18 are conductor patterns extending along the axis X, and are successively provided along the axis X. One end part of the first signal wiring pattern 17 in the direction of the axis X is used as a first terminal 20 . The other end part of the second signal wiring pattern 18 in the direction of the axis X is used as a second terminal 22 . The ground pattern 19 is provided between the first signal wiring pattern 17 and second wiring pattern 18 . The ground pattern 19 is a conductor pattern extending in a direction orthogonal to the axis X. The ground pattern 19 is used as a ground terminal 24 . The ground pattern 19 is connected to the second power wiring pattern 16 acting as a grounding pattern, for example, through a via and a conductor pattern provided on a main face opposing the main face 14 a of the substrate 14 . The ground pattern 19 may be connected to the second power wiring pattern 16 acting as a grounding pattern through a conductor pattern provided on the main face 14 a of the substrate 14 as well. The ground pattern 19 may also be connected to other grounding patterns through a via and a conductor pattern provided on the main face opposing the main face 14 a of the substrate 14 . The multilayer surge absorbing component 26 is mounted between the first signal wiring pattern 17 and second signal wiring pattern 18 .

The multilayer surge absorbing component 26 has a first electrode 30 , a second electrode 32 , and third electrodes 34 , 36 on surfaces of a substantially rectangular parallelepiped multilayer body 28 . The first electrode 30 is connected to the first signal wiring pattern 17 , whereas the second electrode 32 is connected to the second signal wiring pattern 18 . The third electrodes 34 , 36 are connected to the ground pattern 19 . The multilayer surge absorbing component 26 constructs a surge absorbing circuit by a conductor pattern formed within the multilayer body 28 .

Thus, the connector 10 comprises the first terminal 20 , second terminal 22 , ground terminal 24 , and surge absorbing circuit, whereby an instrument or external connector connected to the first terminal 20 and an instrument or external connector connected to the second terminal 22 can be connected to each other.

A surge absorbing circuit employable in the connector 10 in accordance with the first embodiment will now be explained. FIG. 2 is a circuit diagram showing a surge absorbing circuit employable in the connector in accordance with the first embodiment. The surge absorbing circuit 40 shown in FIG. 2 has a first I/O terminal 40 a , a second I/O terminal 40 b , a third I/O terminal 40 c , a first inductor 42 , a second inductor 44 , and a surge absorbing element 46 .

The first I/O terminal 40 a corresponds to the first electrode 30 of the multilayer surge absorbing component 26 , whereas the second I/O terminal 40 b corresponds to the second electrode 32 of the multilayer surge absorbing component 26 . The third I/O terminal 40 c corresponds to the third electrodes 34 , 36 of the multilayer surge absorbing component 26 .

The first inductor 42 has one end connected to the first I/O terminal 40 a and the other end connected to a node N 1 . The second inductor 44 has one end connected to the node N 1 and the other end connected to the second I/O terminal 40 b . The first inductor 42 and second inductor 44 are electromagnetically coupled together. Specifically, the first inductor 42 and second inductor 44 are magnetically coupled so as to increase each other's inductance. Namely, they are coupled such that, when a current is directed from the first I/O terminal 40 a to the second I/O terminal 40 b or vice versa, the respective magnetic fields generated in the first inductor 42 and second inductor 44 by this current are oriented in the same direction, whereby their inductances increase. Preferably, the coupling factor between the first inductor 42 and second inductor 44 is greater than 0.01 but not exceeding 1.

The first surge absorbing element 46 has one end connected to the node N 1 . The other end of the first surge absorbing element 46 is connected to the third I/O terminal 40 c . The first surge absorbing element 46 is a varistor made of a metal oxide such as ZnO in this embodiment. The first surge absorbing element 46 exhibits a large resistance value between terminals when the voltage between the terminals is lower than a predetermined voltage. When the voltage between the terminals is higher than the predetermined voltage, on the other hand, the first surge absorbing element 46 lowers the resistance value between the terminals, so as to allow a current to flow between the terminals, thereby clamping the voltage between the terminals at a predetermined voltage. The predetermined voltage is a value determined by a characteristic of the first surge absorbing element 46 . 100691 Therefore, when a signal with a lower voltage level is fed to the first I/O terminal 40 a , the surge absorbing circuit 40 outputs the signal to the second I/O terminal 40 b , since the resistance value between the terminals of the first surge absorbing element 46 is greater. Similarly, when a signal with a lower voltage level is fed to the second I/O terminal 40 b , the surge absorbing circuit 40 outputs the signal to the first I/O terminal 40 a , since the resistance value between the terminals of the first surge absorbing element 46 is greater.

When an electrostatic surge is fed to the first I/O terminal 40 a , on the other hand, the first surge absorbing element 46 lowers the resistance value between the first I/O terminal 40 a and third I/O terminal 40 c , whereby the surge absorbing circuit 40 allows a current to flow between the first I/O terminal 40 a and third I/O terminal 40 c and clamps the voltage of the node N 1 . Thus, even when an electrostatic surge is fed to the first I/O terminal 40 a , the surge absorbing circuit 40 lowers the voltage outputted to the second I/O terminal 40 b.

Similarly, when an electrostatic surge is fed to the second I/O terminal 40 b , the first surge absorbing element 46 lowers the resistance value between the second I/O terminal 40 b and third I/O terminal 40 c , whereby the surge absorbing circuit 40 allows a current to flow between the second I/O terminal 40 b and third I/O terminal 40 c and clamps the voltage of the node N 1 . Thus, even when an electrostatic surge is fed to the second I/O terminal 40 b , the surge absorbing circuit 40 lowers the voltage outputted to the first I/O terminal 40 a.

FIG. 3 is a circuit diagram equivalently illustrating the surge absorbing circuit shown in FIG. 2. The first inductor 42 and second inductor 44 are electromagnetically coupled together, and thus can be equivalently represented by two inductors 48 , 50 and a negative inductor (negative inductance element) 52 . The first surge absorbing element 46 can be equivalently represented by a variable resistance element and a stray capacitance element (stray capacitance component) 54 connected in parallel, and can be approximated by the stray capacitance element 54 alone for small high-speed signals.

In the equivalent circuit shown in FIG. 3, the inductor 48 has one end connected to the first I/O terminal 40 a and the other end connected to a node N 2 . The inductor 50 has one end connected to the node N 2 and the other end connected to the second I/O terminal 40 b . The negative inductor 52 has one end connected to the node N 2 and the other end connected to one end of the stray capacitance element 54 . The stray capacitance element 54 is connected to the third I/O terminal 40 c.

Letting Lz be each of the inductance of the first inductor 42 and the inductance of the second inductor 44 , and Kz be the coupling factor between the first inductor 42 and second inductor 44 , each of the inductance of the inductor 48 and the inductance of the inductor 50 becomes “(1+Kz)·Lz”, whereas the inductance of the negative inductor 52 becomes “−Kz·Lz”. Let Cz be the capacitance value of the stray capacitance element 54 . Therefore, the input impedance of the surge absorbing circuit 40 shown in FIG. 3 is represented by the following expression (1):

$\begin{array}{cc}\left[\mathrm{Expression}1\right]\mathrm{Zin}=\sqrt{\frac{2\left(1+\mathrm{Kz}\right)\mathrm{Lz}}{\mathrm{Cz}}+{\omega }^2{\mathrm{Lz}}^2\left({\mathrm{Kz}}^2-1\right)}& \left(1\right)\end{array}$

The above-mentioned expression (1) shows that, when Kz=±1, the second term including ω in the right side becomes 0, whereby the input impedance Zin is constant independently of frequency. However, the case where Kz=−1 is inappropriate, since Zin=0.

When Lz is set so as to satisfy the following expression (2) while letting Kz=1, the input impedance Zin of the surge absorbing circuit 40 can match a characteristic impedance Zo of a transmission line connected to the surge absorbing circuit 40 .

$\begin{array}{cc}\left[\mathrm{Expression}2\right]\mathrm{Lz}=\frac{Z_0^2\mathrm{Cz}}{4}& \left(2\right)\end{array}$

Thus, the surge absorbing circuit 40 in accordance with this embodiment has the first surge absorbing element 46 excellent in reducing electrostatic surges, and consequently can lower the electrostatic surges. The surge absorbing circuit 40 in accordance with this embodiment has the first inductor 42 and second inductor 44 electromagnetically coupled together, and thus can set the coupling factor between the first inductor 42 and second inductor 44 such as to keep a constant input impedance over a wide band. Further, the surge absorbing circuit 40 of this embodiment can set the inductance of the first inductor 42 and the inductance of the second inductor 44 with respect to the stray capacitance component of the first surge absorbing element 46 such that the input impedance of the surge absorbing circuit 40 and a characteristic impedance of a transmission line match each other. Therefore, this surge absorbing circuit 40 is excellent in reducing electrostatic surges, and enables impedance matching over a wide band. Hence, the connector 10 equipped with the surge absorbing circuit 40 in accordance with this embodiment can reduce electrostatic surges without deteriorating transmitted/received signals.

[Modified Example 1 of surge absorbing circuit employable in the connector of the first embodiment] FIG. 4 is a circuit diagram showing the surge absorbing circuit in accordance with Modified Example 1 employable in the connector of the first embodiment. The surge absorbing circuit 40 A shown in FIG. 4 further comprises a first capacitance element 56 in addition to elements similar to those of the surge absorbing circuit 40 .

The first capacitance element 56 has one end connected to a node N 3 for connecting the first I/O terminal 40 a and one end of the first inductor 42 to each other. The other end of the first capacitance element 56 is connected to a node N 4 for connecting the second I/O terminal 40 b and the other end of the second inductor 44 to each other.

FIG. 5 is a circuit diagram equivalently illustrating the surge absorbing circuit shown in FIG. 4. As in the surge absorbing circuit 40 , the first inductor 42 and second inductor 44 that are electromagnetically coupled together can be represented by two inductors 48 , 50 and a negative inductor (negative inductance element) 52 . The first surge absorbing element 46 can be approximated by a stray capacitance element (stray capacitance component) 54 alone for small high-speed signals.

Letting Lz be each of the inductance of the first inductor 42 and the inductance of the second inductor 44 , and Kz be the coupling factor between the first inductor 42 and second inductor 44 , each of the inductance of the inductor 48 and the inductance of the inductor 50 becomes “(1+Kz)·Lz”, whereas the inductance of the negative inductor 52 becomes “−Kz·Lz”. Let Cs and Cz be the respective capacitance values of the first capacitance element 56 and stray capacitance element 54 . Therefore, the input impedance of the surge absorbing circuit 40 A shown in FIG. 5 is represented by the following expression (3):

$\begin{array}{cc}\left[\mathrm{Expression}3\right]\mathrm{Zin}=\sqrt{\frac{2\left(1+\mathrm{Kz}\right)\mathrm{Lz}}{\mathrm{Cz}}\frac{1-{\omega }^2\mathrm{Lz}\left(\left(1-\mathrm{Kz}\right)\mathrm{Cz}\text{/}2\right)}{1-{\omega }^2\mathrm{Lz}\left(2\left(1+\mathrm{Kz}\right)\mathrm{Cs}\right)}}& \left(3\right)\end{array}$

The above-mentioned expression (3) shows that, when Cs is set so as to satisfy the following expression (4), the input impedance Zin is constant independently of frequency.

Further, when Cs is set so as to satisfy the following expression (4), while Lz is set so as to satisfy the following expression (5), the input impedance Zin of the surge absorbing circuit 40 A can match the characteristic impedance Zo of a transmission line connected to the surge absorbing circuit 40 A.

$\begin{array}{cc}\left[\mathrm{Expression}4\right]\mathrm{Cs}=\frac{1-\mathrm{Kz}}{4\left(1+\mathrm{Kz}\right)}\mathrm{Cz}& \left(4\right)\end{array}$

$\begin{array}{cc}\left[\mathrm{Expression}5\right]\mathrm{Lz}=\frac{Z_0^2\mathrm{Cz}}{2\left(1+\mathrm{Kz}\right)}& \left(5\right)\end{array}$

As the above-mentioned expressions (4) and (5) illustrate, the surge absorbing circuit 40 A of Modified Example 1 can arbitrarily choose Kz. Namely, the surge absorbing circuit 40 A of Modified Example 1 can change Cs and Lz by altering Kz, and thus makes it possible to design circuits with a higher flexibility than in the surge absorbing circuit 40 .

Thus, the surge absorbing circuit 40 A of Modified Example 1 can set the coupling factor between the first inductor 42 and second inductor 44 and the capacitance value of the first capacitance element 56 such as to keep a constant input impedance over a wide band. Further, the surge absorbing circuit 40 A of Modified Example 1 can set the respective inductances of the first inductor 42 and second inductor 44 and the coupling actor between the first inductor 42 and second inductor 44 with respect to the stray capacitance component of the first surge absorbing element 46 such that the input impedance of the surge absorbing circuit 40 A and a characteristic impedance of a transmission line match each other. Hence, the connector 10 in accordance with this embodiment equipped with the surge absorbing circuit 40 A of Modified Example 1 in place of the surge absorbing circuit 40 can reduce electrostatic surges without deteriorating transmitted/received signals.

The first surge absorbing element 46 is approximated by the stray capacitance element 54 alone in the foregoing explanation, but actually includes a stray inductance element (stray inductance component). FIG. 6 is an equivalent circuit diagram of a first surge absorbing element. The fist surge absorbing element 46 shown in FIG. 6 is represented by a variable resistance element 58 and a stray capacitance element 54 which are connected in parallel, and a stray inductance element 59 connected in series thereto. The stray inductance element 59 also causes the impedance of the surge absorbing circuit 40 to fluctuate with respect to frequency. Namely, the stray inductance element 59 also causes transmitted/received high-speed signals to deteriorate.

In the surge absorbing circuit 40 A of Modified Example 1, however, the first inductor 42 and second inductor 44 that are electromagnetically coupled together have the negative inductor 52 , which can cancel out the stray inductance element 59 . Since the resulting state appears as if the coupling is made smaller, Kz and Lz are left as they are, whereas Cs is set as defined by the following expression (6):

$\begin{array}{cc}\left[\mathrm{Expression}6\right]\mathrm{Cs}=\frac{1-\mathrm{Kz}+2\mathrm{Le}\text{/}\mathrm{Lz}}{4\left(1+\mathrm{Kz}\right)}\mathrm{Cz}& \left(6\right)\end{array}$

Here, Le is the inductance of the stray inductance element 59 , and KzLz≧Le. Setting Cs so as to satisfy the above-mentioned expression (6) allows the input impedance Zin of the surge absorbing circuit 40 A to match the characteristic impedance Zo of a transmission line connected to the surge absorbing circuit 40 A even when the first surge absorbing element 46 includes the stray capacitance element 54 and stray inductance element 59 .

Thus, the surge absorbing circuit 40 A of Modified Example 1 can attain a negative inductance component which cancels out the stray inductance component of the first surge absorbing element 46 by the electromagnetic coupling between the first inductor 42 and second inductor 44 . Further, the respective inductances of the first inductor 42 and second inductor 44 , their coupling factor, and the capacitance value of the first capacitance element 56 can be set such that the input impedance matches a characteristic impedance of the transmission line and is kept constant over a wide band. Therefore, the connector 10 in accordance with this embodiment equipped with the surge absorbing circuit 40 A of Modified Example 1 in place of the surge absorbing circuit 40 can reduce electrostatic surges without deteriorating transmitted/received signals.

[Modified Example 2 of surge absorbing circuit employable in the connector of the first embodiment] FIG. 7 is a circuit diagram showing the surge absorbing circuit in accordance with Modified Example 2 employable in the connector of the first embodiment. The surge absorbing circuit 40 B shown in FIG. 7 differs from the surge absorbing circuit 40 A of Modified Example 1 in that the first and second inductors are not electromagnetically coupled together. The other structure of the surge absorbing circuit 40 B is the same as the surge absorbing circuit 40 A of Modified Example 1.

The surge absorbing circuit 40 B comprises a first inductor 60 and a second inductor 62 which are not electromagnetically coupled together in place of the first inductor 42 and second inductor 44 that are electromagnetically coupled together in the surge absorbing circuit 40 A, respectively. Preferably, the coupling factor between the first inductor 60 and second inductor 62 is 0.01 or less.

Let Lx be each of the inductance of the first inductor 60 and the inductance of the second inductor 62 , and Cx be the capacitance value of the first capacitance element 56 . The first surge absorbing element 46 is approximated by the stray capacitance element (stray capacitance component) 54 alone for small high-speed signals, and Cz is assumed to be the capacitance value of the stray capacitance element 54 . As a consequence, the input impedance of the surge absorbing circuit 40 B shown in FIG. 7 is represented by the following expression (7):

$\begin{array}{cc}\left[\mathrm{Expression}7\right]\mathrm{Zin}=\sqrt{\frac{2\mathrm{Lx}}{\mathrm{Cz}}\frac{1-{\omega }^2\mathrm{Lx}\left(\mathrm{Cz}\text{/}2\right)}{1-{\omega }^2\mathrm{Lx}\left(2\mathrm{Cx}\right)}}& \left(7\right)\end{array}$

The above-mentioned expression (7) shows that, when Cx is set so as to satisfy the following expression (8), the input impedance Zin becomes constant independently of frequency.

Further, when Cx is set so as to satisfy the following expression (8), while Lx is set so as to satisfy the following expression (9), the input impedance Zin of the surge absorbing circuit 40 B can match the characteristic impedance Zo of a transmission line connected to the surge absorbing circuit 40 B.

$\begin{array}{cc}\left[\mathrm{Expression}8\right]\mathrm{Cx}=\frac{\mathrm{Cz}}{4}& \left(8\right)\end{array}$

$\begin{array}{cc}\left[\mathrm{Expression}9\right]\mathrm{Lx}=\frac{Z_0^2\mathrm{Cz}}{2}& \left(9\right)\end{array}$

Thus, the surge absorbing circuit 40 B of Modified Example 2 has the first surge absorbing element 46 excellent in reducing electrostatic surges and thus can lower the electrostatic surges. Also, the surge absorbing circuit 40 B of Modified Example 2 can set the capacitance value of the first capacitance element 56 such as to keep a constant input impedance over a wide band. Further, the surge absorbing circuit 40 B of Modified Example 2 can set the inductance of the first inductor 60 and the inductance of the second inductor 62 with respect to the stray capacitance component of the first surge absorbing element 46 such that the input impedance of the surge absorbing circuit 40 B matches a characteristic impedance of a transmission line. Therefore, the surge absorbing circuit 40 B of Modified Example 2 is excellent in reducing electrostatic surges and enables impedance matching over a wide band. Hence, the connector 10 in accordance with this embodiment equipped with the surge absorbing circuit 40 B of Modified Example 2 in place of the surge absorbing circuit 40 can reduce electrostatic surges without deteriorating transmitted/received signals.

Second Embodiment

FIG. 8 is a partly broken perspective view showing the connector in accordance with a second embodiment of the present invention. This connector 10 A differs from the connector 10 of the first embodiment in that it comprises a multilayer surge absorbing component 26 A in place of the multilayer surge absorbing component 26 . The other structure is the same as that of the connector 10 . The connector 10 A is a USB connector, for example.

The substrate 14 A is fixed to an inner face 12 a of a frame 12 . One main face 14 a of the substrate 14 A is separated from an inner face 12 b of the frame 12 opposing the inner face 12 a . External connectors to connect with the connector 10 A are inserted between the substrate 14 A and the inner face 12 b of the frame 12 . Provided on the main face 14 a of the substrate 14 A are a first power wiring pattern 15 , a second power wiring pattern (e.g., grounding pattern) 16 , a first signal wiring pattern 17 , a second signal wiring pattern 18 , a third signal wiring pattern 66 , a fourth signal wiring pattern 67 , and a ground pattern 68 which are used for connecting with the external connectors.

The first power wiring pattern 15 , second power wiring pattern (e.g., grounding pattern) 16 , first signal wiring pattern 17 , and second signal wiring pattern 18 are conductor patterns similar to their corresponding wiring patterns in the connector 10 . Therefore, one end part of the first signal wiring pattern 17 in the direction of an axis X is used as a first terminal 20 , whereas the other end part of the second signal wiring pattern 18 in the direction of the axis X is used as a second terminal 22 .

The third signal wiring pattern 66 is provided between the first signal wiring pattern 17 and second power wiring pattern 16 , whereas the fourth signal wiring pattern 67 is provided between the second signal wiring pattern 18 and second power wiring pattern 16 . The third signal wiring pattern 66 and fourth signal wiring pattern 67 are conductor patterns extending along the axis X, and are successively provided along the axis X. One end part of the third signal wiring pattern 66 in the direction of the axis X is used as a third terminal 70 . The other end part of the fourth signal wiring pattern 67 in the direction of the axis X is used as a fourth terminal 72 .

The ground pattern 68 is provided between the other end part of the third signal wring pattern 66 and the other end part of the first signal wiring pattern 17 and between the fourth signal wiring pattern 67 and second signal wiring pattern 18 . The ground pattern 68 is a conductor pattern extending along the axis X. The ground pattern 68 is used as a ground terminal 24 . The, ground pattern 68 is connected to the second power wiring pattern 16 acting as a grounding pattern, for example, through a conductor pattern provided on the main face 14 a of the substrate 14 A. The ground pattern 68 may be connected to the second power wiring pattern 16 acting as a grounding pattern through a via and a conductor pattern provided on a main face opposing the main face 14 a of the substrate 14 A as well. The ground pattern 68 may also be connected to other grounding patterns through a via and a conductor pattern provided on the main face opposing the main face 14 a of the substrate 14 A.

A multilayer surge absorbing component 26 A is mounted between the first signal wiring pattern 17 and second signal wiring pattern 18 and between the third signal wiring pattern 66 and fourth signal wiring pattern 67 .

On surfaces of a rectangular parallelepiped multilayer body 74 , the multilayer surge absorbing component 26 A has a first electrode 76 , a second electrode 77 , a third electrode 78 , a fourth electrode 79 , fifth electrodes 80 , 81 , a sixth electrode 82 , and a seventh electrode 83 . The first electrode 76 is connected to the first signal wiring pattern 17 , whereas the second electrode 77 is connected to the second signal wiring pattern 18 . The third electrode 78 is connected to the third signal wiring pattern 66 , whereas the fourth electrode 79 is connected to the fourth signal wiring pattern 67 . The fifth electrodes 80 , 81 are connected to the ground pattern 68 . The sixth electrode 82 and seventh electrode 83 are provided for connecting with conductor patterns formed within the multilayer body 74 . The multilayer surge absorbing component 26 A constructs a surge absorbing circuit by conductor patterns formed within the multilayer body 74 .

Thus, the connector 10 A comprises the first terminal 20 , second terminal 22 , third terminal 70 , fourth terminal 72 , ground terminal 24 , and surge absorbing circuit, whereby instruments or external connectors connected to the first terminal 20 and third terminal 70 can be connected to instruments or external connectors connected to the second terminal 22 and fourth terminal 72 .

The surge absorbing circuit of the second embodiment will now be explained. FIG. 9 is a circuit diagram showing a surge absorbing circuit employable in the connector of the second embodiment. This surge absorbing circuit 86 has a first I/O terminal 86 a , a second I/O terminal 86 b , a third I/O terminal 86 c , a fourth I/O terminal 86 d , a fifth I/O terminal 86 e , a first inductor 88 , a second inductor 90 , a first surge absorbing element 92 , a third inductor 94 , a fourth inductor 96 , and a second surge absorbing element 98 .

The first I/O terminal 86 a corresponds to the first electrode 76 of the multilayer surge absorbing component 26 A, whereas the second I/O terminal 86 b corresponds to the second electrode 77 of the multilayer surge absorbing component 26 A. The third I/O terminal 86 c corresponds to the third electrode 78 of the multilayer surge absorbing component 26 A, whereas the fourth I/O terminal 86 d corresponds to the fourth electrode 79 of the multilayer surge absorbing component 26 A. The fifth I/O terminal 86 e corresponds to the fifth electrodes 80 , 81 of the multilayer surge absorbing component 26 A.

The first inductor 88 has one end connected to the first I/O terminal 86 a and the other end connected to a node N 5 . The second inductor 90 has one end connected to the node N 5 and the other end connected to the second I/O terminal 86 b . The first inductor 88 and second inductor 90 are electromagnetically coupled together. Specifically, the first inductor 88 and second inductor 90 are magnetically coupled so as to increase each other's inductance. Namely, they are coupled such that, when a current is directed from the first I/O terminal 86 a to the second I/O terminal 86 b or vice versa, the respective magnetic fields generated in the first inductor 88 and second inductor 90 by this current are oriented in the same direction, whereby their inductances increase. Preferably, the coupling factor between the first inductor 88 and second inductor 90 is greater than 0.01 but not exceeding 1.

The first surge absorbing element 92 has one end connected to the node N 5 . The other end of the first surge absorbing element 92 is connected to a node N 6 , to which the fifth I/O terminal 86 e is connected. As with the first surge absorbing element 46 of the first embodiment, the first surge absorbing element 92 is a varistor made of a metal oxide such as ZnO.

On the other hand, the third inductor 94 has one end connected to the third I/O terminal 86 c and the other end connected to a node N 7 . The fourth inductor 96 has one end connected to the node N 7 and the other end connected to the fourth I/O terminal 86 d . The third inductor 94 and fourth inductor 96 are electromagnetically coupled together. Specifically, the third inductor 94 and fourth inductor 96 are magnetically coupled so as to increase each other's inductance. Namely, they are coupled such that, when a current is directed from the third I/O terminal 86 c to the fourth I/O terminal 86 d or vice versa, the respective magnetic fields generated in the third inductor 94 and fourth inductor 96 by this current are oriented in the same direction, whereby their inductances increase. Preferably, the coupling factor between the third inductor 94 and fourth inductor 96 is greater than 0.01 but not exceeding 1.

The second surge absorbing element 98 has one end connected to the node N 7 . The other end of the second surge absorbing element 98 is connected to the node N 6 . As with the first surge absorbing element 46 of the first embodiment, the second surge absorbing element 98 is a varistor made of a metal oxide such as ZnO.

Therefore, when a differential signal with a lower voltage level is fed to the first I/O terminal 86 a and third I/O terminal 86 c , the surge absorbing circuit 86 outputs the differential signal to the second I/O terminal 86 b and fourth I/O terminal 86 d , since the resistance value between the terminals of the first surge absorbing element 92 and the resistance value between the terminals of the second surge absorbing element 98 are greater. Similarly, when a differential signal with a lower voltage level is fed to the second I/O terminal 86 b and fourth I/O terminal 86 d , the surge absorbing circuit 86 outputs the differential signal to the first I/O terminal 86 a and third I/O terminal 86 c , since the resistance value between the terminals of the first surge absorbing element 92 and the resistance value between the terminals of the second surge absorbing element 98 are greater.

When an electrostatic surge is fed to the first I/O terminal 86 a , on the other hand, the first surge absorbing element 92 lowers the resistance value between the first I/O terminal 86 a and fifth I/O terminal 86 e , whereby the surge absorbing circuit 86 allows a current to flow between the first I/O terminal 86 a and fifth I/O terminal 86 e and clamps the voltage of the node N 5 . When an electrostatic surge is fed to the third I/O terminal 86 c , the second surge absorbing element 98 lowers the resistance value between the third I/O terminal 86 c and fifth I/O terminal 86 e , whereby the surge absorbing circuit 86 allows a current to flow between the third I/O terminal 86 c and fifth I/O terminal 86 e and clamps the voltage of the node N 7 . Thus, even when an electrostatic surge is fed to the fist 10 terminal 86 a or third I/O terminal 86 c , the surge absorbing circuit 86 lowers the voltage outputted to the second I/O terminal 86 b or fourth I/O terminal 86 d.

Similarly, when an electrostatic surge is fed to the second I/O terminal 86 b , on the other hand, the first surge absorbing element 92 lowers the resistance value between the second I/O terminal 86 b and fifth I/O terminal 86 e , whereby the surge absorbing circuit 86 allows a current to flow between the second I/O terminal 86 b and fifth I/O terminal 86 e and clamps the voltage of the node N 5 . When an electrostatic surge is fed to the fourth I/O terminal 86 d , the second surge absorbing element 98 lowers the resistance value between the fourth I/O terminal 86 d and fifth I/O terminal 86 e , whereby the surge absorbing circuit 86 allows a current to flow between the fourth I/O terminal 86 d and fifth I/O terminal 86 e and clamps the voltage of the node N 7 . Thus, even when an electrostatic surge is fed to the second I/O terminal 86 b or fourth I/O terminal 86 d , the surge absorbing circuit 86 lowers the voltage outputted to the first I/O terminal 86 a or third I/O terminal 86 c.

FIG. 10 is a circuit diagram equivalently illustrating the surge absorbing circuit shown in FIG. 9. The first inductor 88 and second inductor 90 are electromagnetically coupled together, and thus can be equivalently represented by two inductors 100 , 102 and a negative inductor (negative inductance element) 104 . Similarly, the third inductor 94 and fourth inductor 96 are electromagnetically coupled together, and thus can be equivalently represented by two inductors 106 , 108 and a negative inductor (negative inductance element) 110 . As mentioned above, the first surge absorbing element 92 can be approximated by a stray capacitance element (stray capacitance component) 112 alone for small high-speed signals. Similarly, the second surge absorbing element 98 can be approximated by a stray capacitance element (stray capacitance component) 114 alone for small high-speed signals.

In the equivalent circuit shown in FIG. 10, the inductor 100 has one end connected to the first I/O terminal 86 a and the other end connected to a node N 8 . The inductor 102 has one end connected to the node N 8 and the other end connected to the second I/O terminal 86 b . The negative inductor 104 has one end connected to the node N 8 and the other end connected to one end of the stray capacitance element 112 . The other end of the stray capacitance element 112 is connected to the node N 6 , to which the fifth I/O terminal 86 e is connected.

On the other hand, the inductor 106 has one end connected to the third I/O terminal 86 c and the other end connected to a node N 9 . The inductor 108 has one end connected to the node N 9 and the other end connected to the fourth I/O terminal 86 d . The negative inductor 110 has one end connected to the node N 9 and the other end connected to one end of the stray capacitance element 114 . The other end of the stray capacitance element 114 is connected to the node N 6 .

Letting Lz be each of the inductances of the first inductor 88 , second inductor 90 , third inductor 94 , and fourth inductor 96 , and Kz be each of the coupling factor between the first inductor 88 and second inductor 90 and the coupling factor between the third inductor 94 and fourth inductor 96 , each of the inductances of the inductors 100 , 102 , 106 , and 108 becomes “(1+Kz)·Lz”, whereas each of the inductances of the negative inductors 104 and 110 becomes “−Kz·Lz”. Let Cz be each of the capacitance values of the stray capacitance elements 112 and 114 . Therefore, the input impedance between the first I/O terminal 86 a and third I/O terminal 86 c of the surge absorbing circuit 86 shown in FIG. 10 is represented by the following expression (10). The input impedance between the second I/O terminal 86 b and fourth I/O terminal 86 d of the surge absorbing circuit 86 is also represented by the following expression (10):

$\begin{array}{cc}\left[\mathrm{Expression}10\right]\mathrm{Zin}=2\times \sqrt{\frac{2\left(1+\mathrm{Kz}\right)\mathrm{Lz}}{\mathrm{Cz}}+{\omega }^2{\mathrm{Lz}}^2\left({\mathrm{Kz}}^2-1\right)}& \left(10\right)\end{array}$

The above-mentioned expression (10) shows that, when Kz=±1, the second term including ω in the right side becomes 0, whereby the input impedance Zin is constant independently of frequency. However, the case where Kz=−1 is inappropriate, since Zin=0.

When Lz is set so as to satisfy the following expression (11) while letting Kz=1, the input impedance Zin of the surge absorbing circuit 86 can match an impedance which is twice the characteristic impedance Zo of a transmission line connected to the surge absorbing circuit 86 .

$\begin{array}{cc}\left[\mathrm{Expression}11\right]\mathrm{Lz}=\frac{Z_0^2\mathrm{Cz}}{4}& \left(11\right)\end{array}$

Thus, the surge absorbing circuit 86 in accordance with this embodiment has the first surge absorbing element 92 and second surge absorbing element 98 that are excellent in reducing electrostatic surges, and consequently can lower the electrostatic surges. The surge absorbing circuit 86 in accordance with this embodiment has the first inductor 88 and second inductor 90 electromagnetically coupled together and the third inductor 94 and fourth inductor 96 electromagnetically coupled together, and thus can set the coupling factor between the first inductor 88 and second inductor 90 and the coupling factor between the third inductor 94 and fourth inductor 96 such as to keep a constant input impedance over a wide band. Further, the surge absorbing circuit 86 of this embodiment can set the inductance of the first inductor 88 and the inductance of the second inductor 90 with respect to the stray capacitance component of the first surge absorbing element 92 and the inductance of the third inductor 94 and the inductance of the fourth inductor 96 with respect to the stray capacitance component of the second surge absorbing element 98 such that the input impedance of the surge absorbing circuit 86 and a characteristic impedance of a transmission line match each other. Therefore, the surge absorbing circuit 86 in accordance with this embodiment is excellent in reducing electrostatic surges, and enables impedance matching over a wide band. Hence, the connector 10 A equipped with this surge absorbing circuit 86 in accordance with this embodiment can reduce electrostatic surges without deteriorating transmitted/received signals.

[Modified Example 1 of surge absorbing circuit employable in the connector of the second embodiment] FIG. 11 is a circuit diagram showing the surge absorbing circuit in accordance with Modified Example 1 employable in the connector of the second embodiment. The surge absorbing circuit 86 A shown in FIG. 11 further comprises a first capacitance element 116 and a second capacitance element 118 in addition to elements similar to those of the surge absorbing circuit 86 .

The first capacitance element 116 has one end connected to a node N 10 for connecting the first I/O terminal 86 a and one end of the first inductor 88 to each other. The other end of the first capacitance element 116 is connected to a node N 11 for connecting the second I/O terminal 86 b and the other end of the second inductor 90 to each other.

The second capacitance element 118 has one end connected to a node N 12 for connecting the third I/O terminal 86 c and one end of the third inductor 94 to each other. The other end of the second capacitance element 118 is connected to a node N 13 for connecting the fourth I/O terminal 86 d and the other end of the fourth inductor 96 to each other.

FIG. 12 is a circuit diagram equivalently illustrating the surge absorbing circuit shown in FIG. 11. As in the surge absorbing circuit 86 , the first inductor 88 and second inductor 90 that are electromagnetically coupled together can be represented by two inductors 100 , 102 and a negative inductor (negative inductance element) 104 . The third inductor 94 and fourth inductor 96 that are electromagnetically coupled together can be represented by two inductors 106 , 108 and a negative inductor (negative inductance element) 110 . The first surge absorbing element 92 can be approximated by a stray capacitance element (stray capacitance component) 112 alone for small high-speed signals, whereas the second surge absorbing element 98 can be approximated by a stray capacitance element (stray capacitance component) 114 alone for small high-speed signals.

Letting Lz be each of the inductances of the first inductor 88 , second inductor 90 , third inductor 94 , and fourth inductor 96 , and Kz be each of the coupling factors between the first inductor 88 and second inductor 90 and between the third inductor 94 and fourth inductor 96 , each of the inductances of the inductors 100 , 102 , 106 , 108 becomes “(1+Kz)·Lz”, whereas each of the inductances of the negative inductors 104 and 110 becomes “−Kz·Lz”. Let Cs be each of the capacitance values of the first capacitance element 116 and second capacitance element 118 , and Cz be each of the capacitance values of the stray capacitance elements 112 and 114 . Consequently, the input impedance between the first I/O terminal 86 a and third I/O terminal 86 c of the surge absorbing circuit 86 A shown in FIG. 12 is represented by the following expression (12). The input impedance between the second I/O terminal 86 b and fourth I/O terminal 86 d of the surge absorbing circuit 86 A is also represented by the following expression (12):

$\begin{array}{cc}\left[\mathrm{Expression}12\right]\mathrm{Zin}=2\times \sqrt{\frac{2\left(1+\mathrm{Kz}\right)\mathrm{Lz}}{\mathrm{Cz}}\frac{1-{\omega }^2\mathrm{Lz}\left(\left(1-\mathrm{Kz}\right)\mathrm{Cz}\text{/}2\right)}{1-{\omega }^2\mathrm{Lz}\left(2\left(1+\mathrm{Kz}\right)\mathrm{Cs}\right)}}& \left(12\right)\end{array}$

The above-mentioned expression (12) shows that, when Cs is set so as to satisfy the following expression (13), the input impedance Zin is constant independently of frequency.

Further, when Cs is set so as to satisfy the following expression (13), while Lz is set so as to satisfy the following expression (14), the input impedance Zin of the surge absorbing circuit 86 A can match an impedance which is twice the characteristic impedance Zo of a transmission line connected to each I/O terminal in the surge absorbing circuit 86 A.

$\begin{array}{cc}\left[\mathrm{Expression}13\right]\mathrm{Cs}=\frac{1-\mathrm{Kz}}{4\left(1+\mathrm{Kz}\right)}\mathrm{Cz}& \left(13\right)\end{array}$

$\begin{array}{cc}\left[\mathrm{Expression}14\right]\mathrm{Lz}=\frac{Z_0^2\mathrm{Cz}}{2\left(1+\mathrm{Kz}\right)}& \left(14\right)\end{array}$

As the above-mentioned expressions (13) and (14) illustrate, the surge absorbing circuit 86 A of Modified Example 1 can arbitrarily choose Kz. Namely, the surge absorbing circuit 86 A of Modified Example 1 can change Cs and Lz by altering Kz, and thus makes it possible to design circuits with a higher flexibility than in the surge absorbing circuit 86 .

Thus, the surge absorbing circuit 86 A of Modified Example 1 can set the coupling factor between the first inductor 88 and second inductor 90 , the coupling factor between the third inductor 94 and fourth inductor 96 , the capacitance value of the first capacitance element 116 , and the capacitance value of the first capacitance element 118 such as to keep a constant input impedance over a wide band. Further, the surge absorbing circuit 86 A of Modified Example 1 can set the respective inductances of the first inductor 88 , second inductor 90 , third inductor 94 , and fourth inductor 96 , the coupling factor between the first inductor 88 and second inductor 90 , and the coupling factor between the third inductor 94 and fourth inductor 96 with respect to the stray capacitance component of the first surge absorbing element 92 and the stray capacitance component of the second surge absorbing element 98 such that the input impedance of the surge absorbing circuit 86 A and a characteristic impedance of a transmission line match each other. Hence, the connector 10 A in accordance with this embodiment equipped with the surge absorbing circuit 86 A of Modified Example 1 in place of the surge absorbing circuit 86 can reduce electrostatic surges without deteriorating differential transmitted/received signals.

The first surge absorbing element 92 and second surge absorbing element 98 are approximated by the stray capacitance elements 112 and 114 alone, respectively, in the foregoing explanation, but actually include a stray inductance element (stray inductance component) as shown in FIG. 6. This stray inductance element also causes the impedance of the surge absorbing circuit 86 to fluctuate with respect to frequency. Namely, the stray inductance element also causes transmitted/received high-speed signals to deteriorate.

In the surge absorbing circuit 86 A of Modified Example 1, however, the first inductor 88 and second inductor 90 that are electromagnetically coupled together have the negative inductor 104 , which can cancel out the stray inductance element included in the first surge absorbing element 92 . Also, in the surge absorbing circuit 86 A of Modified Example 1, the third inductor 94 and fourth inductor 96 that are electromagnetically coupled together have the negative inductor 110 , which can cancel out the stray inductance element included in the second surge absorbing element 98 . Since the resulting state appears as if the coupling is made smaller, Kz and Lz are left as they are, whereas Cs is set as defined by the following expression (15):

$\begin{array}{cc}\left[\mathrm{Expression}15\right]\mathrm{Cs}=\frac{1-\mathrm{Kz}+2\mathrm{Le}\text{/}\mathrm{Lz}}{4\left(1+\mathrm{Kz}\right)}\mathrm{Cz}& \left(15\right)\end{array}$
where Le is the inductance of the stray inductance element, and KzLz≧Le. Setting Cs so as to satisfy the above-mentioned expression (15) allows the input impedance Zin of the surge absorbing circuit 86 A to match an impedance which is twice the characteristic impedance Zo of a transmission line connected to each I/O terminal in the surge absorbing circuit 86 A even when the first surge absorbing element 92 and second surge absorbing element 98 include the stray capacitance element and stray inductance element.

Thus, the surge absorbing circuit 86 A of Modified Example 1 can attain a negative inductance component which cancels out the stray inductance component of the first surge absorbing element 92 by the electromagnetic coupling between the first inductor 88 and second inductor 90 , and a negative inductance component which cancels out the stray inductance component of the second surge absorbing element 98 by the electromagnetic coupling between the third inductor 94 and fourth inductor 96 . Further, the respective inductances of the first inductor 88 and second inductor 90 , their coupling factor, the respective inductances of the third inductor 94 and fourth inductor 96 , their coupling factor, and the respective capacitance values of the first capacitance element 116 and second capacitance element 118 can be set such that the input impedance matches a characteristic impedance of the transmission line and is kept constant over a wide band. Therefore, the connector in accordance with this embodiment equipped with the surge absorbing circuit 86 A of Modified Example 1 in place of the surge absorbing circuit 86 can reduce electrostatic surges without deteriorating differential transmitted/received signals.

[Modified Example 2 of surge absorbing circuit employable in the connector of the second embodiment] FIG. 13 is a circuit diagram showing the surge absorbing circuit in accordance with Modified Example 2 employable in the connector of the second embodiment. The surge absorbing circuit 86 B shown in FIG. 13 differs from the surge absorbing circuit 86 in that it has a first inductor 120 , a second inductor 122 , a third inductor 124 , and a fourth inductor 126 in place of the first inductor 88 , second inductor 90 , third inductor 94 , and fourth inductor 96 , respectively. The first inductor 120 , second inductor 122 , third inductor 124 , and fourth inductor 126 are electromagnetically coupled together.

The first inductor 120 has one end connected to the first I/O terminal 86 a and the other end connected to a node N 5 . The second inductor 122 has one end connected to the node N 5 and the other end connected to the second I/O terminal 86 b.

The third inductor 124 has one end connected to the third I/O terminal 86 c and the other end connected to a node N 7 . The fourth inductor 126 has one end connected to the node N 7 and the other end connected to the fourth I/O terminal 86 d.

The first inductor 120 , second inductor 122 , third inductor 124 , and fourth inductor 126 are electromagnetically coupled together. Specifically, the first inductor 120 and second inductor 122 are magnetically coupled together so as to increase each other's inductance, while the third inductor 124 and fourth inductor 126 are magnetically coupled together so as to increase each other's inductance. Also, the first inductor 120 and third inductor 124 are magnetically coupled together so as to increase each other's inductance when a differential signal is applied thereto, while the second inductor 122 and fourth inductor 126 are magnetically coupled together so as to increase each other's inductance when a differential signal is applied thereto. Preferably, the coupling factor among the first inductor 120 , second inductor 122 , third inductor 124 , and fourth inductor 126 is greater than 0.01 but not exceeding 1.

FIG. 14 is a circuit diagram equivalently illustrating the surge absorbing circuit shown in FIG. 13. As in the surge absorbing circuit 86 , the first inductor 120 , second inductor 122 , third inductor 124 , and fourth inductor 126 electromagnetically coupled together can be represented by inductors 128 , 130 , 132 , 134 and negative inductors (negative inductance elements) 136 , 138 . The first surge absorbing element 92 can be approximated by the stray capacitance element (stray capacitance component) 112 alone for small high-speed signals, whereas the second surge absorbing element 98 can be approximated by the stray capacitance element (stray capacitance component) 114 alone for small high-speed signals.

In the equivalent circuit shown in FIG. 14, the inductor 128 has one end connected to the first I/O terminal 86 a and the other end connected to a node N 8 . The inductor 130 has one end connected to the node N 8 and the other end connected to the second I/O terminal 86 b . The negative inductor 136 has one end connected to the node N 8 and the other end connected to one end of the stray capacitance element 112 .

The inductor 132 has one end connected to the third I/O terminal 86 c and the other end connected to a node N 9 . The inductor 134 has one end connected to the node N 9 and the other end connected to the fourth I/O terminal 86 d . The negative inductor 138 has one end connected to the node N 9 and the other end connected to one end of the stray capacitance element 114 .

Letting Lz be each of the inductances of the first inductor 120 , second inductor 122 , third inductor 124 , and fourth inductor 126 , Kz be each of the coupling factors between the first inductor 120 and second inductor 122 and between the third inductor 124 and fourth inductor 126 , and Kc be each of the coupling factors between the first inductor 120 and third inductor 124 and between the second inductor 122 and fourth inductor 126 , each of the inductances of the inductors 128 , 130 , 132 , 134 becomes “(1+Kz+Kc)·Lz”, whereas each of the inductances of the negative inductors 136 and 138 becomes “−Kz·Lz”. Let Cz be each of the capacitance values of the stray capacitance elements 112 and 114 . Consequently, the input impedance between the fist I/O terminal 86 a and third I/O terminal 86 c of the surge absorbing circuit 86 B shown in FIG. 14 is represented by the following expression (16). The input impedance between the second I/O terminal 86 b and fourth I/O terminal 86 d of the surge absorbing circuit 86 B is also represented by the following expression (16):

$\begin{array}{cc}\left[\mathrm{Expression}16\right]& \\ \mathrm{Zin}=2\times \sqrt{\frac{2\left(1+\mathrm{Kz}+\mathrm{Kc}\right)\mathrm{Lz}}{\mathrm{Cz}}\left(1-{\omega }^2\mathrm{Lz}\left(\left(1-\mathrm{Kz}+\mathrm{Kc}\right)\mathrm{Cz}/2\right)\right)}& \left(16\right)\end{array}$

The above-mentioned expression (16) shows that, when Kz and Kc are set so as to satisfy the following expression (17), the input impedance Zin is constant independently of frequency.

Further, when Kz and Kc are set so as to satisfy the following expression (17), while Lz is set so as to satisfy the following expression (18), the input impedance Zin of the surge absorbing circuit 86 B can match an impedance which is twice the characteristic impedance Zo of a transmission line connected to each I/O terminal in the surge absorbing circuit 86 B.

[Expression 17]
Kz−Kc= 1 (17)

$\begin{array}{cc}\left[\mathrm{Expression}18\right]\mathrm{Lz}=\frac{Z_0^2\mathrm{Cz}}{2\left(1+\mathrm{Kz}+\mathrm{Kc}\right)}& \left(18\right)\end{array}$

As the above-mentioned expressions (17) and (18) illustrate, the surge absorbing circuit 86 B of Modified Example 2 can arbitrarily choose Kz and Kc. Namely, the surge absorbing circuit 86 B of Modified Example 2 can change Lz by altering Kz and Kc, and thus makes it possible to design circuits with a higher flexibility than in the surge absorbing circuit 86 .

Thus, the surge absorbing circuit 86 B of Modified Example 2 has the first surge absorbing element 92