Electrical transmission or interconnection systems – Switching systems – Condition responsive
Reexamination Certificate
2001-10-25
2003-12-02
Scott, J. R. (Department: 2832)
Electrical transmission or interconnection systems
Switching systems
Condition responsive
C029S846000, C333S101000, C333S105000, C333S124000, C333S262000, C438S689000
Reexamination Certificate
active
06657324
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a micromachine switch for use in millimeter wave circuits and microwave circuits.
BACKGROUND ART
Switch devices for use in millimeter wave circuits and microwave circuits include PIN diode switches, HEMT switches, and micromachine switches. Micromachine switches in particular suffer a smaller loss, are less costly, and have a lower power requirement than the other switch devices.
One conventional micromachine switch is disclosed in Japanese laid-open patent publication No. 9-17300, for example. FIG.
1
(A) of the accompanying drawings is a plan view of the conventional micromachine switch. FIG.
1
(B) is a cross-sectional view taken along line I(B)—I(B) of FIG.
1
(A). FIG.
1
(C) is a cross-sectional view taken along line I(C)—I(C) of FIG.
1
(A). FIG.
1
(D) is a cross-sectional view taken along line I(D)—I(D) of FIG.
1
(A).
As shown in FIG.
1
(A), high-frequency signal lines
101
a
,
101
b
spaced from each other by a small gap are disposed on substrate
110
. Lower electrode
111
is disposed on substrate
110
at a position spaced from high-frequency signal lines
101
a
,
101
b
. Post
112
is disposed on substrate
110
at a position on a line extending from the gap between high-frequency signal lines
101
a
,
101
b
through lower electrode
111
.
Arm
113
has a proximal end fixedly mounted on an upper surface of post
112
. Arm
113
extends from the upper surface of post
112
over lower electrode
111
to a position above the gap between high-frequency signal lines
101
a
,
101
b
. Arm
113
is made of an insulating material.
Upper electrode
114
is disposed on an upper surface of arm
113
. Upper electrode
114
extends from a position above post
112
to a position above lower electrode
111
.
Contact
115
is disposed on a lower surface of the distal end of arm
113
. Contact
115
extends from a position above the end of high-frequency signal line
101
a
over the gap to a position above the end of high-frequency signal line
101
b.
Control signal line
102
is connected to lower electrode
111
for applying a control signal to change connected states of high-frequency signal lines
101
a
,
101
b
to lower electrode
111
.
When a positive voltage, for example, is applied as the control signal to lower electrode
111
, positive charges are generated on the upper surface of lower electrode
111
, and negative charges are developed on the lower surface of upper electrode
114
which confronts lower electrode
111
due to electrostatic induction. Upper electrode
114
is now attracted to lower electrode
111
under attractive forces developed therebetween. Arm
113
is curved to displace contact
115
downwardly. When contact
115
is brought into contact with both high-frequency signal lines
101
a
,
101
b
, high-frequency signal lines
101
a
,
101
b
are connected to each other by contact
115
in a high-frequency fashion.
When the positive voltage is no longer applied to lower electrode
111
, since no attractive forces are developed between upper and lower electrodes
114
,
111
, contact
115
returns to its position spaced from high-frequency signal lines
101
a
,
101
b
under recovering forces of arm
113
. High-frequency signal lines
101
a
,
101
b
are now disconnected from each other.
The conventional micromachine switch shown in
FIG. 1
has a complex three-dimensional structure because post
112
and arm
113
are required to support contact
115
, other than contact
115
for connecting and disconnecting high-frequency signal lines
101
a
,
101
b
and also because lower electrode
111
and upper electrode
114
are required control displacement of contact
115
. A complex fabrication process composed of many steps is needed to manufacture the micromachine switch of the complex structure.
The present invention has been made in an attempt to solve the above problems. It is an object of the present invention to provide a micromachine switch of a simple structure.
DISCLOSURE OF THE INVENTION
In order to achieve the above object, a micromachine switch according to the present invention has first and second high-frequency signal lines having their respective ends spaced from each other, a cantilever fixed to the end of either the first or the second high-frequency signal line and extending to a position above the end of the other high-frequency signal line, the cantilever including an electrically conductive member, first insulating means disposed on the first high-frequency signal line, second insulating means disposed in an area where the cantilever and the other high-frequency signal line confront each other, and a first control signal line connected between the end of the first high-frequency signal line and the first insulating means, for applying the control signal which is represented by DC voltage level variations.
An arrangement of the first insulating means comprises a capacitor.
An arrangement of the second insulating means comprises an insulating film disposed on at least one of a lower surface of the cantilever and an upper surface of the other high-frequency signal line.
The cantilever has both a function as a movable contact and a function as a support means for supporting the movable contact. The cantilever
11
functionally corresponds to contact
115
, arm
113
, and post
112
of the conventional micromachine switch, and the former is of a simpler structure than the latter.
Since the control signal is applied to the first or second high-frequency signal line to control operation of cantilever, lower electrode
111
and upper electrode
114
which have heretofore been required are no longer necessary. For this reason, the micromachine switch is thus further simple in structure.
While the first insulating means disposed on the first high-frequency signal line and the second insulating means for providing a capacitive coupling are indispensable according to the present invention, the micromachine switch is of a simple structure as a whole according to the present invention.
The micromachine switch may further comprise first high-frequency signal blocking means connected to the first control signal line, for blocking the passage of a high-frequency signal flowing through the first and second high-frequency signal lines.
A first arrangement of the first high-frequency signal blocking means comprises a high-impedance line having an end connected between the end of the first high-frequency signal line on which the first insulating means is disposed and the first insulating means, and having a line length which is about ¼ of the wavelength of the high-frequency signal and a characteristic impedance larger than the characteristic impedance of the first or second high-frequency signal line, and a low-impedance line having an end connected to the other end of the high-impedance line and an opposite end which is open, and having a line length which is about ¼ of the wavelength of the high-frequency signal and a characteristic impedance smaller than the characteristic impedance of the high-impedance line, the first control signal line being connected to the other end of the high-impedance line.
A second arrangement of the first high-frequency signal blocking means comprises a high-impedance line having an end connected between the end of the first high-frequency signal line on which the first insulating means is disposed and the first insulating means, and having a line length which is about ¼ of the wavelength of the high-frequency signal and a characteristic impedance larger than the characteristic impedance of the first or second high-frequency signal line, and a capacitor having an electrode connected to the other end of the high-impedance line and another electrode to ground, the first control signal line being connected to the other end of the high-impedance line.
A third arrangement of the first high-frequency signal blocking means comprises an inductive element.
A fourth arrangement of the first high-frequency signal blocking means comprises a resistive element h
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