JPH06215647A - Balanced-to-unbalanced transducer - Google Patents

Abstract

PURPOSE:To realize a stable and high-performance balanced-to-unbalanced transducer by raising ground impedance on the unbalanced side and reduce inexpensively undesired electromagnetic wave radiation. CONSTITUTION:In a balanced-to-unbalanced transducer wherein a balanced signal transmitted along a balanced cable 1 and an unbalanced signal transmitted along an unbalanced cable 2 are mutually transduced, a magnetic material 3 is added to the cable 2 on the unbalanced side. Or otherwise, a magnetic material may be added to a connector on the unbalanced side. Accordingly, ground impedance on the unbalanced side is raised, so that though the construction is simple and inexpensive, the undesired radiation is reduced by suppressing in-phase current.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a balanced-unbalanced converter used for converting a balanced signal and an unbalanced signal in an information wiring system.

[0002]

2. Description of the Related Art Conventionally, wiring such as a coaxial cable has been used for communication between computers and terminals. In some cases, this may be replaced with unshielded twisted pair wire (UTP). In such a case, a balanced-unbalanced converter (balun) is used to mutually convert the unbalanced signal on the coaxial cable and the balanced signal on the twisted pair wire. The balanced-unbalanced converter has the effect of suppressing the common-mode (in-phase) signal voltage that causes unnecessary electromagnetic radiation, but with the recent increase in the speed of digital signal transmission due to the development of computer communication, the transmission band becomes wider. Because it spread
Since the degree of balance must be ensured over a wide band, making a balanced-unbalanced converter difficult, and further noise countermeasures are required. However, the conventional method has a problem in that the radiation amount of unnecessary electromagnetic waves increases due to the laying state of electric wires and the change in ground impedance after the construction of transmission equipment.

[0003]

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and an object of the present invention is to increase the ground impedance on the unbalanced side to achieve stable high performance. A balanced-unbalanced converter is realized, and the radiation amount of unnecessary electromagnetic waves can be reduced at low cost.

[0004]

In the balanced-unbalanced converter of the present invention, in order to solve the above-mentioned problems, as shown in FIG. 1, a balanced signal transmitted on a balanced cable 1 is used. In the balanced-unbalanced converter that converts an unbalanced signal transmitted on the unbalanced cable 2, the cable 2 on the unbalanced side
The magnetic material 3 is added to the above.
Further, as shown in FIG. 2, the magnetic material 3 may be added to the connector 4 on the unbalanced side. Here, when the cable 2 on the unbalanced side is a coaxial cable, it is preferable to arrange the annular magnetic material 3 such as ferrite beads so as to surround the outer circumference of the cable 2 on the unbalanced side. Further, as shown in FIG. 3, the magnetic material 3 may be added to the wiring that connects the ground of the cable 2 on the unbalanced side and the circuit board ground or the wiring that connects the circuit board ground and the housing ground. Particularly, in the balanced-unbalanced converter using the transformer 5, it is preferable to add the magnetic material 3 to the wiring that connects the midpoint of the balanced-side winding N1 to the ground of the unbalanced-side circuit.

[0005]

In the present invention, by adding the magnetic material 3 to the cable 2 or the connector 4 on the unbalanced side in the balanced-unbalanced converter, the impedance between the unbalanced side ground and the ground can be increased. , It is possible to suppress the common mode current and reduce unnecessary radiation. In addition, a ferrite bead is arranged so as to surround the outer circumference of the cable 2 on the unbalanced side, or wiring for connecting the ground of the cable 2 on the unbalanced side to the circuit board ground or wiring for connecting the circuit board ground to the chassis ground. When the magnetic material 3 is added, in the balanced-unbalanced converter using the transformer 5,
Even when the magnetic material 3 is added to the wiring that connects the middle point of the balanced side winding N1 to the ground of the unbalanced side circuit, the impedance between the unbalanced side ground and the ground can be increased and the common mode current can be suppressed. It has an effect.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a schematic structure of an embodiment of the present invention. A balanced-unbalanced converter using a transformer 5 is built in the information wiring member 6 to which the balanced cable 1 made of a twisted pair wire is connected. The transformer 5 includes a toroidal core made of ferrite as shown in FIG.
1 and an unbalanced side winding N2, and a balanced cable 1 made of a twisted pair wire is connected to both ends of the balanced side winding N1. The middle point of the balanced side winding N1 is connected to the ground side terminal of the unbalanced side winding N2.
The ground side terminal of the unbalanced side winding N2 is connected to the peripheral conductor of the unbalanced cable 2 made of a coaxial cable,
This peripheral conductor is grounded. The ungrounded side terminal of the unbalanced side winding N2 is an unbalanced cable 2 made of a coaxial cable.
Is connected to the core wire. An annular magnetic material 3 such as ferrite beads is added to the peripheral conductor of the unbalanced cable 2. A balanced-unbalanced converter using the midpoint grounding type transformer 5 as in this embodiment has a characteristic that the degree of balance is high in a high frequency band, but the condition of the midpoint and the circuit ground are Its characteristics tend to change due to the influence from the outside. Therefore, the radiation amount of unnecessary electromagnetic waves may not be stable due to changes in ground impedance, ground conditions, and the like caused by being connected to an actual device. In order to improve this, in the embodiment shown in FIG. 1 and FIG. 2, a ring-shaped magnetic material 3 such as ferrite beads is added to the unbalanced side of the balance-unbalance converter to stabilize the balance regardless of external conditions. In order to obtain good characteristics.

FIG. 3 shows another embodiment. The ground 7 of the unbalanced side circuit and the circuit board ground or the housing ground 8 are shown.
If there is a potential difference Vc between the two, the removable magnetic material 3
Is added to increase the ground impedance, suppress the common-mode current Ic, and reduce the radiation amount of unnecessary electromagnetic waves. The insertion position of the magnetic material 3 on the unbalanced side is not limited, and either the wiring or the component for connecting the middle point of the balanced side winding N1 of the transformer 5 to the circuit board ground or the housing ground 8 is used. A magnetic material may be added to the.

[0008]

According to the balanced-unbalanced converter of the present invention,
By adding a magnetic material to the cable or connector on the unbalanced side, the impedance between the ground on the unbalanced side and the ground can be increased, and this reduces the common mode current while maintaining a simple and inexpensive structure. Is effective.

[Brief description of drawings]

FIG. 1 is a diagram showing a schematic configuration of an embodiment of the present invention.

FIG. 2 is a perspective view showing a schematic configuration of another embodiment of the present invention.

FIG. 3 is a diagram showing a schematic configuration of another embodiment of the present invention.

[Explanation of symbols]

 1 balanced cable 2 unbalanced cable 3 magnetic material 4 connector 5 transformer

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Eiji Kishimoto 1048 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Works, Ltd.

Claims (5)

[Claims] 1. In a balanced-unbalanced converter for converting a balanced signal transmitted on a balanced cable and an unbalanced signal transmitted on an unbalanced cable, a magnetic material is added to the cable or connector on the unbalanced side. A balanced-unbalanced converter characterized by the above. 2. The balanced-unbalanced converter according to claim 1, wherein an annular magnetic material is arranged so as to surround the outer circumference of the cable on the unbalanced side. 3. A balanced-unbalanced converter for converting a balanced signal transmitted on a balanced cable and an unbalanced signal transmitted on an unbalanced cable, wherein the ground of the cable on the unbalanced side and the circuit board ground are connected. A balanced-unbalanced converter in which a magnetic material is added to a wiring to be connected or a wiring to connect a circuit board ground and a chassis ground. 4. The balanced-unbalanced converter according to claim 3, wherein the magnetic material is detachably added. 5. A balanced-unbalanced converter using a transformer, wherein a magnetic material is added to a wire connecting the middle point of the balanced-side winding to the ground of the unbalanced-side circuit. converter.