Electricity: conductors and insulators – Anti-inductive structures – Conductor transposition
Reexamination Certificate
1999-07-21
2002-05-28
Reichard, Dean A. (Department: 2831)
Electricity: conductors and insulators
Anti-inductive structures
Conductor transposition
C174S07500C, C174S078000
Reexamination Certificate
active
06395977
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a method for connecting electronic devices and a connecting cable.
BACKGROUND OF THE INVENTION
As shown in FIGS.
12
(
a
) and (
b
), to transmit a signal from a first electronic device l
a
to a second electronic device
1
b
, a connection is provided as shown in FIG.
12
(
a
) or FIG.
12
(
b
), using a connecting cable
4
in which a signal line
2
is shielded by a first external conductor
3
a.
In the connection of FIG.
12
(
a
), one end of the signal line
2
is connected to the signal output
5
of the first electronic device
1
a
, the other end of the signal line
2
is connected to the signal input
6
of the second electronic device
1
b
, one end of the first external conductor
3
a
is connected to a frame
7
, which is the reference potential of the first electronic device
1
a
, and the other end of the first external conductor
3
a
is connected to a frame
8
, which is the reference potential of the second electronic device
1
b.
In such connection, if there is no potential difference between the frames
7
and
8
, good signal transmission can be realized, but, if the signal level is low and there is a potential difference between the frames
7
and
8
, then noise mixes into the signal input
6
of the second electronic device
1
b.
In this case, one-point grounding connects the first external conductor
3
a
only to the frame
7
of the first electronic device
1
a
, without connecting the other end of the first external conductor
3
a
to the frame
8
of the second electronic device
1
b.
However, assuming the case in which the first electronic device
1
a
and the second electronic device
1
b
are spaced a long distance apart from each other and low-frequency signals (the frequency band is several tens KHz to several tens MHZ) and high frequency signals (the frequency band is several tens MHZ or higher) are transmitted by the signal line
2
, or the case in which a digital signal of a high-frequency is transmitted, the one-point grounding as shown in FIG.
12
(
b
) problematically increases the level of undesired radiation of high-frequency signals from the first external conductor
3
a
into the air.
In this conventional example, the description has been made to one connecting cable
4
by way of example, but, in the connection by a plurality of connecting cables which are placed in parallel between the first electronic device
1
a
and the second electronic device
1
b
, there is a problem that noise radiated from the respective juxtaposed connecting cables
4
interferes with each other to further increase the undesired radiation level.
It is the object of the present invention to provide a connection method and a connecting cable, which enable good transmission of low-frequency signals as well as lowering the radiation level of high-frequency signals in such case as described above.
BRIEF SUMMARY OF THE INVENTION
The method for connecting electronic devices of the present invention is characterized by connecting a first electronic device
1
a
and a second electronic device
1
b
with a first external conductor being one-point grounded, and connecting an end of a second external conductor on the second electronic device
1
b
side to reference potential of the second electronic device
1
b
for high-frequency signals, thereby providing a connection between the electronic devices, and enabling good transmission of low-frequency signals as well as lowering the radiation level of high-frequency signals.
The method for connecting electronic devices as set forth in a first embodiment is characterized in that, to connect electronic devices by a connecting cable, the part between the ends of the signal line of the connecting cable is shielded by a first external conductor, one end of the first external conductor is connected to the reference potential of one electronic device of the electronic devices, the first external conductor is shielded by a second external conductor, the second external conductor is connected to the reference potential of the other electronic device, whereby the reference potential of one electronic device and the reference potential of the other electronic device are coupled through the stray capacity between the first external conductor and the second external conductor.
With this arrangement, the first external conductor is one-point grounded to the first electronic device preventing the difference in the reference potential levels of the first and second electronic devices from being brought into the second electronic device, whereby good transmission of low-frequency signals can be accomplished, and the impedance of the first external conductor to high-frequency signals decreases, reducing undesired radiation.
The method for connecting electronic device as set forth in a second embodiment is characterized in that, to connect electronic devices by a connecting cable, the signal lines of a plurality of connecting cables are respectively shielded by a first external conductor between the ends thereof, one of the respective first external conductors is connected to the reference potential of one electronic device of the electronic devices, the respective first external conductors are shielded by a common second external conductor, and the second external conductor is connected to the reference potential of the other electronic device, whereby the reference potential of one electronic device and the reference potential of the other electronic device are coupled through the stray capacity between the first and second external conductors.
With this arrangement, the respective first external conductors are one-point grounded to the first electronic device preventing the difference in the reference potential level between the first device and second electronic devices from being brought into the second electronic device, whereby good transmission of low-frequency signals can be accomplished, and the impedance of the respective first external conductors decreases, reducing undesired radiation.
The method for connecting electronic devices as set forth in a third embodiment is characterized in that, to connect electronic devices by a connecting cable, the signal lines of a plurality of connecting cables are respectively shielded by a first external conductor in the part between the ends thereof, one end of the respective first external conductor is connected to the reference potential of one electronic device of the electronic devices, the respective first external conductors are electrically connected to each other in the other end thereof, the respective first external conductors are shielded by a common second external conductor, and the second external conductor is connected to the reference potential of the other electronic device, whereby the reference potential of one electronic device and the reference potential of the other electronic device are coupled through the stray capacity between the first external conductor and the second external conductor.
With this arrangement, because the first external conductors are electrically connected to each other, in addition to the construction of the second embodiment, the system of each first external conductor for high-frequency signals is stable as compared with the case in which the first external conductors are not positively made equipotential in the other end thereof, and no independent standing wave occurs in the respective first external conductors.
The method for connecting electronic devices as set forth in a fourth embodiment is characterized in that the length of opposition between the first and second external conductors is adjusted according to a frequency for which undesired radiation is to be suppressed.
The method for connecting electronic devices as set forth in a fifth embodiment is characterized in that the adjustment is performed by connecting, between the first and second external conductors, a element having a capacitance according to the frequency for which undesired radiation is to be suppressed.
With thi
Mayo III William H.
Reichard Dean A.
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