JPH10163665A - Electronic unit suppressing unnecessary radiation - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the unnecessary radiation of an electronic unit. SOLUTION: A circuit board 1, a casing 2 storing the circuit board 1 and a conductor connecting a ground provided for the circuit board 1 with the casing 2 are provided. Then, unnecessary radiation is suppressed by constituting the conductor by a member having a magnetic body. Since high frequency current can be suppressed by the magnetic body when the conductor connecting the ground provided for the circuit board 1 with the casing 2 is constituted by the member having the magnetic body, unnecessary radiation can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for suppressing unnecessary radiation from an electronic circuit device.

[0002]

2. Description of the Related Art EMC aims at achieving both an electromagnetic environment of EMI (side emitting noise) and immunity (side receiving noise). In recent years, the higher operating frequency associated with higher performance of products has increased the radiation intensity of the unnecessary radiation, leading to a severe situation of EMI. Also, with the spread of these electronic products, EMI countermeasures for electronic products and the like are becoming more serious.

The amount of unwanted radiation expected to increase in the future is 4
Although it is said to be dB / year, the increase in unwanted radiation in this way worsens the electromagnetic environment and causes social problems such as disruption of the TV screen and loss of control of aircraft control systems. There is no doubt that it will cause it.

For this reason, noise regulations are becoming more and more strict in terms of radiant intensity, range of products to be applied, and the like. At present it is trying to improve.

[0005] As a prior art relating to this, for example, IE
EE Transactions on Electro Magnetic Compatibility October 1992, G. Seri, "Theoretical and Experimental Evaluation of the Electro Magnetic Radiation From Aperture and Shielded Enclosures": (G. Cerri) "h
eoretical and Experimental Evaliation of the Elect
romagnetic Radiation From Apertures in Shielded En
closures '' IEEE Transaction on Electro Magnetic Com
There is patibillity, vol.34, No.4, November 1992.

In this case, unnecessary radiation is suppressed by connecting the ground (signal ground) of the circuit board and the housing (frame ground) with a conductor such as a spacer.

[0007]

However, at present, the mechanism of the unnecessary radiation has not been elucidated. Even with the above-mentioned conventional technology, the operating frequency will be increased with the increase in the performance of products in the future. A sufficient effect cannot be obtained.

Accordingly, it is an object of the present invention to suppress unnecessary radiation of electronic equipment.

[0009]

[Means for Solving the Problems] We have been studying the mechanism of unwanted radiation. As a result, in the related art, a noise voltage is generated in the signal ground by the operation of the circuit board mounted inside the housing, and the resonance system constituted by the entire housing is driven through a connection point between the housing and the frame ground. It became clear.

That is, it has been clarified that the noise of the circuit board is transmitted to the entire housing and causes unnecessary radiation (electromagnetic radiation) to increase.

Based on the research results, the present invention achieves the above object by suppressing unnecessary radiation by preventing a noise current flowing from a circuit board that generates noise into a housing.

That is, a circuit board, a housing for accommodating the circuit board, and a conductor for connecting the ground provided on the circuit board to the housing, and the conductor is made of a member having a magnetic material. This suppresses unnecessary radiation.

If the conductor for connecting the ground provided on the circuit board to the housing is made of a member having a magnetic material, the magnetic material can suppress high-frequency current, thereby reducing unnecessary radiation.

As an example in which the conductor is constituted by a member having a magnetic material, a metal spacer and a magnetic core mounted on the spacer are preferable.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings.

FIG. 1 shows an example in which the structure of the present invention is applied to an electronic device.

The electronic apparatus shown in FIG. 1 has a circuit board 1, a housing 2 for housing the circuit board 1, and a housing 2 for housing the circuit board 1.
Spacer 3 to be housed in
And a core 4 on which a magnetic material is mounted.
The spacer 3 connects the ground of the circuit board and the ground of the housing.

In the electronic device of the present invention, the magnetic core 4 is mounted around the spacer 3, so that the core 4 is
Acts to increase the loss with respect to the high-frequency current flowing through. In other words, unnecessary radiation is caused by the generation of a noise voltage in the signal ground. Therefore, the use of the core 4 increases the loss with respect to the high-frequency current flowing through the spacer 3 and suppresses the unnecessary radiation.

FIG. 3 shows a magnetic core 4 around the spacer 3.
4 shows an effect of suppressing unnecessary radiation of the electronic device of the present invention equipped with a.

The measured sample is as shown in FIG.
The board is housed in a housing (size 240 mm x 300 mm x 200 mm), and the signal ground of the board and the frame ground of the housing are connected by a metal spacer (diameter 20 mm). Further, a ferrite core using ferrite as a magnetic material is mounted on the metal spacer.

FIG. 3 shows a comparison between a sample with a core of the present invention and a sample without a conventional core, and shows the maximum radiated electric field strength with respect to the operating frequency of an IC mounted on a substrate.

As can be seen from FIG. 3, in a conventional electronic device connected only by a metal spacer, an increase in radiation due to resonance of the housing is observed at around 150 MHz. On the other hand, in the present invention in which the magnetic material is attached to the spacer, radiation near 150 MHz is suppressed by about 25 dB as compared with the related art.

According to the present invention, similar effects can be obtained by the configuration shown in FIG.

In FIG. 4, by mounting a resistance sheet 5 between the metal spacer 3 and the housing 2, noise current flowing through the spacer 3 is prevented. Thus, unnecessary radiation can be suppressed as in the structure shown in FIG.

The above concept can be applied to large electronic devices and notebook electronic devices.

FIG. 5 shows a large electronic device to which the present invention is applied.

The large-sized electronic device comprises a conductor frame 6 and a circuit board (not shown) incorporated in a frame formed by the conductor frame 6. The signal ground of the circuit board is connected to the ground of the conductor frame 6.

As shown in FIG. 5, since the high-frequency current flowing through the conductor frame 6 can be reduced by disposing the magnetic material 7 on the conductor frame 6, unnecessary radiation can be reduced.

FIG. 6 shows a notebook electronic device to which the present invention is applied.

In a flat panel display 9 used in a notebook electronic device, for example, a notebook computer 11,
It has a conductor frame 10 for the purpose of ensuring mechanical strength. When a noise current is applied from the display control board, the conductive frame 10 operates as an antenna, causing an increase in unnecessary radiation.

Therefore, by sandwiching the conductor frame 10 between the magnetic sheets 8, unnecessary radiation is suppressed by converting high-frequency current flowing through the conductor frame 8 into heat loss.

[0032]

As described above, according to the present invention, unnecessary radiation can be reduced by suppressing high-frequency current by using a magnetic material.

[Brief description of the drawings]

FIG. 1 is a block diagram of the present invention.

FIG. 2 is a diagram showing a sample of the present invention.

FIG. 3 illustrates the effect of the present invention.

FIG. 4 is a block diagram of the present invention.

FIG. 5 is a block diagram of the present invention.

FIG. 6 is a block diagram of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Circuit board 2 Housing 3 Metal spacer 4 Magnetic core 5 Resistance sheet 6, 10 Conductor frame 7, 8 Magnetic sheet 11 Notebook personal computer

Claims (1)

[Claims] 1. A circuit board, a housing for accommodating the circuit board, and a conductor for connecting a ground provided on the circuit board to the housing, wherein the conductor is made of a member having a magnetic material. Electronic equipment characterized by the following.