Electricity: electrical systems and devices – Housing or mounting assemblies with diverse electrical... – For electronic systems and devices
Reexamination Certificate
2001-05-24
2004-01-06
Martin, David (Department: 2841)
Electricity: electrical systems and devices
Housing or mounting assemblies with diverse electrical...
For electronic systems and devices
C361S760000, C361S819000, C361S736000, C174S050000
Reexamination Certificate
active
06674645
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a high frequency signal switching unit for switching a plurality of output terminals to selectively output therefrom a high frequency signal inputted from an input terminal or for switching between at least one input terminal and at least one output terminal.
2. Description of the Related Art
FIG. 17
depicts a conventional high frequency signal switching unit (known as the coaxial switch or high frequency unit) that includes three high frequency relays
10
fixed within a generally box-shaped metallic casing
1
by means of a conductive adhesive. The high frequency relays
10
are connected at their relay contact terminals
11
to five coaxial connectors
3
mounted on a side wall of the metallic casing
1
by coaxial cables
30
, and also connected at their coil terminals
12
to a relay connector
40
mounted on another side wall of the metallic casing
1
by lead wires
41
. The central coaxial connector
3
is an input terminal into which a high frequency signal is inputted, while other four coaxial connectors
3
are output terminals from which the high frequency signal is selectively outputted.
Each high frequency relay
10
is provided with a shielding plate
4
disposed around the relay contact terminals
11
. Each coaxial cable
30
includes an internal conductor (core)
31
connected to one of the relay contact terminals
11
by soldering, and also includes an external conductor (in the case of the illustrated coaxial cable
30
, the whole sheath is the external conductor)
32
joined to the shielding plate
4
, which is in turn grounded. The shielding plate
4
is provided with chip capacitors C mounted thereon for absorbing high frequency signals that leak from the coaxial cables
30
to the lead wires
41
.
By the above-described construction, the high frequency relays
10
are supplied with electricity via the relay connector
40
so that the high frequency signal inputted from one of the coaxial connectors
3
forming the input terminal may be selectively outputted from any one of the remaining four coaxial connectors
3
.
In the conventional high frequency signal switching unit of the above-described construction, because the high frequency relays
10
are fixed to the metallic casing
1
by means of the conductive material, the positions of the high frequency relays
10
are not always fixed. Furthermore, because the coaxial cables
30
are supported by only the opposite connecting portions, a difficulty is encountered in positioning and temporarily fixing the coaxial cables
30
during assembling, thus lowering the working efficiency and increasing variation in the product characteristics. Also, shielding is not performed between the relay contact terminals
11
of the neighboring high frequency relays
10
, thus deteriorating the insulation properties (high frequency characteristics).
SUMMARY OF THE INVENTION
The present invention has been developed to overcome the above-described disadvantages.
It is accordingly an objective of the present invention to provide a high frequency signal switching unit having improved high frequency characteristics, wherein the positions of the high frequency relays are fixed, and the coaxial cables can be readily positioned and temporarily fixed.
In accomplishing the above and other objectives, the high frequency signal switching unit according to the present invention includes a casing and a printed circuit board accommodated in the casing and having a first surface and a second surface opposite to each other. The printed circuit board also has a ground layer formed on substantially the entire first surface. The high frequency signal switching unit also includes at least one input terminal and at least one output terminal both mounted on the casing, and at least one high frequency relay mounted on the printed circuit board for switching between the input terminal and the output terminal so that a high frequency signal inputted into the input terminal is selectively outputted from the output terminal. The high frequency relay has a plurality of relay contact terminals and a grounding terminal. A plurality of coaxial cables having respective internal and external conductors are accommodated in the casing to connect the input and output terminals to the relay contact terminals of the high frequency relay. The grounding terminal of the high frequency relay and the external conductors of the coaxial cables are connected to the ground layer of the printed circuit board, while each of the internal conductors of the coaxial cables is connected to one of the relay contact terminals of the high frequency relay.
With this arrangement, because the high frequency relay is secured to the printed circuit board, the position thereof is fixed. Accordingly, the positioning and temporary fixing of the coaxial cables within the casing can be readily carried out. Furthermore, the grounding terminal of the high frequency relay and the external conductors of the coaxial cables are all connected to the ground layer of the printed circuit board, making it possible to improve the high frequency characteristics.
The printed circuit board has a plurality of recesses defined therein in which end portions of the coaxial cables are respectively received. This arrangement further facilitates the positioning of the coaxial cables relative to the printed circuit board.
Preferably, the external conductors have a diameter substantially equal to a width of the recesses. With this configuration, when the coaxial cables are inserted into respective recesses, the former are temporarily fixed. Accordingly, the distance between the relay contact terminals of the high frequency relay and the internal conductors of the associated coaxial cables is made substantially constant, thus stabilizing the high frequency characteristics.
The recesses are elongated in the axial directions of the coaxial cables. By so doing, the temporary fixing of the coaxial cables relative to the printed circuit board can be readily carried out, making it possible to enhance the working efficiency during assemblage of the coaxial cables.
The depth of the recesses is determined such that the internal conductors are aligned with the second surface of the printed circuit board. By so doing, the distance between the relay contact terminals of the high frequency relay and the internal conductors of the associated coaxial cables can be reduced, enhancing the high frequency characteristics.
The printed circuit board has a plurality of grooves defined therein so as to extend across a thickness thereof, in which end portions of the coaxial cables are respectively received. Because the formation of the grooves in the printed circuit board is relatively easy, the manufacturing cost of the high frequency signal switching unit can be reduced.
Advantageously, each of the grooves has an electrically conductive layer formed on an inner wall thereof, which is connected to the ground layer of the printed circuit board. The formation of the electrically conductive layer increases the contact area and connecting strength of the coaxial cables. Furthermore, the external conductors of the coaxial cables and the ground layer of the printed circuit board are connected at a reduced distance, resulting in an increase in ground strength and ensuring more reliable grounding.
Again advantageously, the printed circuit board has a plurality of through-holes defined therein, each of which communicates with a neighboring one of the grooves to accommodate one of the relay contact terminals of the high frequency relay. Each of the through-holes has an electrically conductive layer formed on an inner wall thereof, which is connected to the ground layer of the printed circuit board. The electrically conductive layer acts to shield the relay contact terminals, making it possible to enhance the insulation properties.
Conveniently, each of the internal conductors has a planar free end and a through-hole defined therein, into which one of the rela
Anzai Tsunehiro
Fujii Kazuhisa
Inoue Kazuhiko
Nishikawa Masakazu
Greenblum & Bernstein P.L.C.
Levi Dameon E.
Martin David
Matsushita Electric & Works Ltd.
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