Wave transmission lines and networks – Long lines – Shielded type
Reexamination Certificate
2002-03-20
2004-04-06
Pascal, Robert (Department: 2817)
Wave transmission lines and networks
Long lines
Shielded type
C333S246000, C333S185000
Reexamination Certificate
active
06717494
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a printed-circuit board, a coaxial cable, and an electronic device, and more specifically to those capable of reducing electromagnetic interference (EMI) which occurs when a current flows in the same direction in a ground pattern and a power supply pattern, both of which are respectively made up of a wide electric conductor pattern and disposed, opposed to each other.
The present application claims priority of Japanese Patent Application No. 2001-188912 filed on Jun. 21, 2001, which is hereby incorporated by reference.
2. Description of the Related Art
An electronic device including various electronic components such as active elements and passive elements is assembled by packaging desirable electronic components on a printed-circuit board. On the printed-circuit board there are formed a ground pattern for providing reference electric potential to the electronic components and a power supply pattern for supplying electric power by making use of electric conductor patterns. Use is sometimes made of a wide electric conductor pattern as such the ground pattern and the power supply pattern. For example, in a printed-circuit board on which an ordinary integrated circuit is packaged there is known wide electric conductor patterns having longitudinal and lateral width sizes of several centimeters.
In such the printed-circuit board, electromagnetic energy is supplied to the wide electric conductor pattern through terminal resistance during operation of the electronic device. A current is hereby conducted to the wide electric conductor pattern to cause resonance, whereby unnecessary electromagnetic waves (so-called “radiated emission”) are radiated from the wide electric conductor pattern to the surroundings.
Radiation of unnecessary electromagnetic waves causes occurrence of EMI, whereby the electronic device is subject to electromagnetic interference.
Occurrence of such EMI is more increased particularly when the wide electric conductor pattern acts as an antenna.
When the ground pattern and the power supply pattern are formed in opposition to each other to permit a current to conduct in the same direction through both patterns, that is to say, a current flows in a same phase through both patterns, both patterns act as if they are a single wide electric conductor pattern, whereby the wide electric conductor pattern acts as an antenna to radiate strong unnecessary electromagnetic waves. Such a current conducted through the wide electric conductor pattern is called a common mode current, and resonance at that time is called a common mode resonance.
Referring here to
FIG. 20A
the common mode resonance is intensified provided a size of a wide electric conductor pattern
110
in a lateral direction X is set into an elongated configuration. Referring further to
FIG. 20B
, the common mode resonance is intensified provided the wide electric conductor pattern
110
is formed into a T-shaped pattern by uniting a first electric conductor section
111
and a second electric conductor section
112
both having different longitudinal sizes in a vertical direction Y. Referring furthermore to
FIG. 20C
, the common mode resonance is intensified when the wide electric conductor pattern
110
is formed into an L-shaped pattern by uniting a first electric conductor section
113
and a second electric conductor section
114
both having different longitudinal sizes in the vertical direction Y.
More specifically, when the wide electric conductor pattern
110
is formed into a pattern configuration having partly a recessed section
115
such as the aforementioned T-shaped pattern or L-shaped pattern for example, the common mode resonance is intensified in particular. Any pattern configuration partly having the recessed section
115
as such is inevitably formed because of limitation to an area of a printed-circuit board on which many electronic components are packaged when the printed-circuit board is manufactured which is then actually assembled into varieties of electronic devices.
Japanese Laid-open Patent Application No. Hei 10-190237 for example discloses a printed-circuit board (first prior art technique) in which EMI occurring owing to the aforementioned common mode current is reduced.
FIG. 21A
is a plan view illustrating the printed-circuit board, and
FIG. 21B
is a cross sectional view illustrating the same but viewed in the direction of arrows E—E.
Referring to
FIGS. 21A and 21B
, a ground pattern
101
and a power supply pattern
102
are formed, opposed to each other, in an insulating layer
103
, and a signal wiring layer
104
is formed on the face and back of the insulating layer
103
, and further a resistor
105
is provided at an end of the insulating layer
103
such that it is prevented from making any contact with the ground pattern
101
and the power supply pattern
102
. The common mode current is suppressed owing to the resistor
105
to reduce the occurrence of EMI.
There are known, as the prior art printed-circuit board, ones where the common mode current is suppressed (a second prior art technique), ones where a high frequency loss material such as rubber ferrite is provided on the ground pattern and the power supply pattern such that it is in close contact with the latters. With the high frequency loss material the common mode current is suppressed to reduce the occurrence of EMI.
However the prior art printed-circuit board described above suffers from the following problems: In the first prior art technique the resistor
105
must be provided at the end of the insulating layer
103
with high accuracy such that it is prevented from making contact with the ground pattern
101
and the power supply pattern
102
thus causing a high manufacturing cost.
In the second prior art technique the material such as rubber ferrite that is the high frequency loss material is likely to be changed in its physical property (magnetic permeability) with the passage of time, so that the operation to suppress the common mode current becomes unstable.
SUMMARY OF THE INVENTION
In view of the above, it is an object of the present invention to provide a printed-circuit board, a coaxial cable, and an electronic device, which are capable of reducing the occurrence of EMI without a severe increase of the manufacturing cost by stably suppressing the common mode current.
According to a first aspect of the present invention, there is provided a printed-circuit board including:
a printed-circuit board including:
an insulating layer;
a wide electric conductor pattern formed into a plane configuration having a recessed section in part so as to make up a ground pattern or a power supply pattern on the insulating layer; and
an an additional electric conductor electrically connected with the wide electric conductor pattern so as to close the recessed section.
In the foregoing first aspect, a preferable mode is one wherein the wide electric conductor pattern comprises a T-shaped pattern, an L-shaped pattern, or an H-shaped pattern.
Another preferable mode is one wherein the wide electric conductor pattern and the additional electric conductor are formed on different surfaces of the insulating layer respectively.
Still another preferable mode is one wherein the wide electric conductor pattern and the additional electric conductor are electrically connected with each other through a via plug formed on the insulating layer.
Additional preferable mode is one wherein the additional electric conductor is electrically connected with a side surface of the electronic components of the wide electric conductor pattern at a position of packaging of the electronic components.
Further preferable mode is one wherein the additional electric conductor is electrically connected with a side surface of the wide electric conductor pattern on at least one side of the wide electric conductor pattern in a longitudinal direction of the wide electric conductor pattern.
Still further preferable mode is one wherein, the additional electric conduct
Akimoto Yutaka
Kaiya Kiyohiko
Kaneko Toshiyuki
Kikuchi Hideki
Kikuchi Hideo
NEC Toppan Circuit Solutions, Inc.
Pascal Robert
Takaoka Dean
LandOfFree
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