Micromachine switch

Details Micromachine switch Micromachine switch

2002-01-28

2004-10-19

Lee, Benny T. (Department: 2817)

Wave transmission lines and networks

Plural channel systems

Having branched circuits

C333S259000, C333S262000, C200S181000

Reexamination Certificate

active

06806788

ABSTRACT:

TECHNICAL FIELD
The present invention relates to a micromachine switch used in a milliwave circuit and microwave circuit.
BACKGROUND ART
Switch devices such as a PIN diode switch, HEMT switch, micromachine switch, and the like are used in a milliwave circuit and microwave circuit. Of these switches, the micromachine switch is characterized in that the loss is smaller than that of the other devices, and the cost and power consumption are low.
FIG. 16
is a block diagram showing the overall arrangement of a conventional micromachine switch.
FIG. 17
is a perspective view showing the arrangement of a switch main body in FIG.
16
.
As shown in
FIG. 17
, RF signal lines
101
a
and
101
b
are formed on a substrate
110
at a small gap.
A contact
111
is supported by a support means
113
above the gap between the RF signal lines
101
a
and
101
b
so as to freely contact the RF signal lines
101
a
and
101
b.
The support means
113
is constituted by a post
113
a
and two arms
113
b
. The post
113
a
is formed on the substrate
110
to be spaced apart from the RF signal lines
101
a
and
101
b
. The two arms
113
b
extend from the upper portion of the side surface of the post
113
a
, and the contact
111
is attached to the distal ends of the arms
113
b.
A control electrode
112
is formed at the gap between the RF signal lines
101
a
and
101
b
on the substrate
110
, i.e., at a position immediately under the contact
111
. The thickness of the control electrode
112
is smaller than that of each of the RF signal lines
101
a
and
101
b.
A control signal line
104
which is connected to a controller
105
is connected to the control electrode
112
. The controller
105
outputs a control signal for switching the connection states of the RF signal lines
101
a
and
101
b
. Therefore, a control signal output from the controller
105
is applied to the control electrode
112
through the control signal line
104
.
The operation of this micromachine switch will be described next.
When a voltage is applied to the control electrode
112
as a control signal, e.g., when a positive voltage is applied, positive charges appear on the surface of the control electrode
112
, and negative charges appear on the lower surface of the contact
111
opposing the control electrode
112
by electrostatic induction. The contact
111
is attracted toward the RF signal lines
101
a
and
101
b
by an attraction force between the control electrode
112
and contact
111
.
At this time, since the length of the contact
111
is larger than the gap between the RF signal lines
101
a
and
101
b
, the contact
111
is brought into contact with both the RF signal lines
101
a
and
101
b
, and the RF signal lines
101
a
and
101
b
are connected to each other through the contact
111
in a high-frequency manner.
When stopping applying the positive voltage to the control electrode
112
, since the attraction force disappears, the contact
111
returns to the home position by a restoring force of the arms
113
b
. Thus, the RF signal lines
101
a
and
101
b
are released.
In the conventional micromachine switch shown in
FIG. 16
, however, an RF signal RF flowing when the RF signal lines
101
a
and
101
b
are kept connected may leak out into the control signal line
104
through the control electrode
112
.
If an RF signal RF leaks out, an insertion loss increases by the leakage signal. In addition, the leakage power may be coupled to another RF signal line depending on the shape of the control signal line
104
. This adversely affects the characteristics of the entire circuit and causes resonance.
The present invention has been made to solve the above problem, and has as its object to reduce the insertion loss of a micromachine switch.
It is another object to improve the RF characteristic of a circuit using a micromachine switch.
DISCLOSURE OF INVENTION
In order to achieve the above objects, according to the present invention, a micromachine switch is characterized by comprising driving means for displacing a contact on the basis of a control signal, a first control signal line for apply ng the control signal to the driving means, and a first RF signal inhibiting means connected to the first control signal line to inhibit, from passing therethrough, an RF signal flowing into RF signal lines.
In this case, in the first arrangement, the first RF signal inhibiting means is constituted by a high-impedance line having one end connected to the driving means, a line length of about ¼ a wavelength of the RF signal, and a characteristic impedance higher than a characteristic impedance of each of the RF signal lines, and a low-impedance line having one end connected to the other end of the high-impedance line, the other end which is open, a line length of about ¼ the wavelength of the RF signal, and a characteristic impedance lower than the characteristic impedance of the high-impedance line, and the first control signal line is connected to the other end of the high-impedance line.
In the second arrangement, the first RF signal inhibiting means is constituted by a high-impedance line having one end connected to the driving means, a line length of about ¼ a wavelength of the RF signal, and a characteristic impedance higher than a characteristic impedance of each of the RF signal lines, and a capacitor having one electrode connected to the other end of the high-impedance line and the other electrode connected to ground, and the first control signal line is connected to the other end of the high-impedance line.
In the third arrangement, the first RF signal inhibiting means comprises an inductance element. The inductance element may be a spiral inductor or meander line inductor.
In the fourth arrangement, the first RF signal inhibiting means comprises a resistive element having an impedance much higher than a characteristic impedance of each of the RF signal lines.
At this time, the resistive element may be serially inserted into the first control signal line. Alternatively, one terminal of the resistive element may be connected to the first control signal line, and the other terminal may be open.
As described above, the first RF signal inhibiting means for inhibiting, from passing therethrough, the RF signal flowing into the RF signal lines is connected to the first control signal line, thus preventing the RF signal from leaking out from the RF signal lines into the first control signal line. Accordingly, an insertion loss of the micromachine switch can be reduced. Also, since electromagnetic coupling from the first control signal line to another control signal line can be prevented, the RF characteristic of a circuit using a micromachine switch can be improved.
According to the present invention, a micromachine switch is characterized by comprising support means for supporting a contact, driving means for displacing the contact on the basis of a control signal, a first control signal line for applying the control signal to the driving means, and a first RF signal inhibiting means connected to the first control signal line to inhibit, from passing therethrough, an RF signal flowing into the RF signal lines.
In this case, in an arrangement, the driving means comprises a control electrode arranged immediately under the contact between the RF signal lines.
At this time, the support means has conductivity, and the switch may further comprise a second control signal line for storing, through the support means, charges which appear on the contact by electrostatic induction upon starting applying the control signal to the control electrode, and removing the charges from the contact through the support means upon stopping applying the control signal to the control electrode, and second RF signal inhibiting means connected to the second control signal line to inhibit, from passing therethrough, an RF signal flowing into the RF signal lines.
In another arrangement, the driving means comprises a lower electrode arranged at a position spaced apart from each of the RF signal lines and a ga

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