JP2011070950A - Mems rf switch - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a MEMS RF switch which can reduce driving force for changing over the MEMS RF switch and can attain miniaturization and reduced cost and can attain long lifetime and can improve durability. <P>SOLUTION: The MEMS RF switch has structural members 12, 13, 14 manufactured by using micro-machining technology and internally forming a cavity 16, and two signal contacts 22a, 23a are formed separated from each other on the surface facing the cavity 16 of the structural member 12. A movable member 20 which is not in contact with any parts of the structural members in the cavity 16 is arranged in the cavity 16. The movable member 20 is movably driven in the cavity 16, and a conductor 20a of the movable member 20 can be changed over between a first switch changing over state wherein the conductor 20a comes in contact with two signal contacts 22a, 23a and a second switch changing over state wherein the conductor 20a is separated from the two signal contacts 22a, 23a. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a MEMS (Micro Electro Mechanical Systems) RF switch manufactured using micromachining technology.

  Conventionally, many types of switches have been proposed as means for interrupting a high-frequency current.

  For example, an electronic switch includes a switch using a semiconductor element such as a PIN diode or a transistor. These electronic switches utilize a phenomenon in which the interelectrode impedance of the semiconductor element is greatly changed by an externally applied voltage.

  Although these electronic switches have the feature of being small and capable of high-speed operation, there is a limit in reducing the resistance value and peripheral impedance of the semiconductor substrate that becomes the current flow path in the diode and transistor elements. There is. For this reason, there is a limit to the reduction of the high frequency insertion loss in the switch ON state. In addition, the impedance becomes a value that cannot be ignored even in the switch OFF state, which is ideally infinite impedance, and there is a limit to isolation. For this reason, it is difficult to realize low loss and high isolation, and it is extremely difficult to realize practical performance particularly in a high frequency region (for example, a millimeter wave band) with a high frequency.

  On the other hand, as a mechanical switch, an electromagnetic force is generated by passing an electric current through a winding, a lever is mechanically driven by this electromagnetic force, and a spatial movement of a moving contact provided near the tip of the lever is performed. There is a switch that switches between a contact state and a non-contact state with a fixed contact provided in the vicinity of the contact, and interrupts high-frequency current. A typical example of this is a component well known as a coaxial relay.

  Although it can be said that this mechanical switch uses an impedance change in a contact / non-contact state between metals, the change width is dramatically larger than that of an electronic switch. Particularly when the contacts are in contact, the resistance value of the current flow path is much smaller than that of an electronic switch, so that a switch with extremely small insertion loss can be obtained. However, since the parts are manufactured by using conventional machining, there is a problem that an increase in size and an increase in mass are inevitable, and an operation speed is slow. In addition, as a result of the increase in size, a relatively large distributed capacitance is formed between the current flow path and the surrounding conductor, and reflection characteristics and isolation deteriorate in high-frequency regions such as the millimeter wave band. This causes a problem that it is difficult to obtain practical performance.

  In recent years, parts having a micro mechanical structure manufactured using photolithography technology, that is, MEMS (Micro Electro Mechanical Systems) have become practical, and several RF switches using this technology have been proposed. (Patent Documents 1 to 4).

  A typical MEMS type RF switch configuration proposed is shown in FIG. In the figure, a fixed contact 54 is formed on the structural member 52, and a movable contact 58 is formed in the vicinity of the tip of a movable lever 56 such as a cantilever that can come in contact with and separate from the fixed contact 54.

  Although not shown, driving force generating means (for example, an electrode for generating electrostatic force) that deforms the movable lever 56 is provided, and when the driving force is not generated, the movable lever 56 is shown in FIG. As shown to (a), it does not deform | transform, it becomes a non-contact state between contacts, and it is in an OFF state as a switch. When a driving force is generated by means such as applying a voltage, the movable lever 56 is attracted downward in the figure as shown in FIG. 5B, and as a result, the contacts come into contact and turn on.

  In this MEMS type RF switch, the impedance change can use the contact / non-contact state of the metal as well as the mechanical type, so that the insertion loss can be reduced and the size can be miniaturized and the size can be reduced. Is possible. As a result of the miniaturization, the practical upper limit frequency can be increased, and performance that can be used even in the millimeter wave band is obtained.

US Pat. No. 6,768,403 Japanese Patent No. 3935477 JP 2007-42644 A JP 2006-210265 A

  However, in the conventional MEMS type RF switch, in order to maintain the OFF state, it is necessary to avoid that a movable lever such as a cantilever is deformed by an external force that is normally assumed and contacts are brought into contact. Therefore, the movable lever is given a certain level of hardness. On the other hand, in order to be in the ON state, the movable lever must be elastically deformed, and in addition, contact pressure must be applied to ensure electrical connection between the contacts.

  As a result, the driving force required for the switch in this structure is relatively large. This means that a high voltage or a large current is required to generate the driving force, and the circuit scale for driving becomes large, which is a big obstacle for downsizing and cost reduction of the entire switch. .

  Furthermore, since a large deformation is repeatedly applied to a part of a movable lever such as a cantilever, there is a problem in life and durability.

  The present invention has been made in view of the above-described conventional problems, and can reduce the driving force for switching the switch to achieve downsizing and cost reduction. In addition, the life can be extended and the durability can be improved. An object of the present invention is to provide a MEMS type RF switch capable of improving the characteristics.

In order to achieve the above object, the present invention according to claim 1 is a MEMS type RF switch manufactured using micromachining technology,
A structural member having a cavity formed therein;
Two signal contacts formed on and spaced apart from each other on at least one of the two opposing surfaces of the structural member facing through the cavity;
The structural member has a dimension slightly smaller than the cavity, and is disposed in the cavity without being connected to any part of the structural member in the cavity and is movable in the cavity. A movable member whose part is a conductor;
Drive means for moving the movable member within the cavity;
A first switch switching state in which the conductor of the movable member is in contact with the two signal contacts, and a second switch switching state in which the conductors of the movable member are separated from the two signal contacts. The movable member is movable so as to switch between the two.

  According to a second aspect of the present invention, in the switch according to the first aspect, the driving means includes a driving electrode pair provided on each of the two opposed surfaces, and a driving electrode of either of the two driving electrode pairs. And switching means for selectively applying a voltage to the pair.

  According to a third aspect of the present invention, in the switch according to the first or second aspect, two signal contacts are formed on both of the two opposing surfaces, and the conductor of the movable member is formed on one surface. It is possible to switch between a first switch switching state in contact with one signal contact and a second switch switching state in contact with two signal contacts formed on the other surface. And

  According to a fourth aspect of the present invention, in the switch according to the third aspect, the conductor of the movable member is connected to one signal contact formed on one surface and one signal contact formed on the other surface. The third switch switching state in contact with each other, and the fourth switch in which the conductor of the movable member is in contact with the other signal contact formed on one surface and the other signal contact formed on the other surface, respectively. It is possible to switch to a switching state.

  According to the present invention, when the movable member disposed in the cavity contacts the two signal contacts, the two signal contacts can be brought into conduction, and a certain switch switching state can be obtained. Alternatively, when the movable member is separated from the two signal contacts, the two signal contacts can be made non-conductive, and another switch switching state can be obtained.

  Since the two signal contacts are conducted by the conductor, the insertion loss can be extremely reduced. Further, when the conductor is not conducting, the conductor is separated from the signal contact, so that the isolation can be ensured.

  Since it is manufactured by micromachining technology, the switch itself can be miniaturized. Furthermore, since the movable member is not connected to any part of the structural member in the cavity and there is no portion that is greatly elastically deformed, the driving force for moving the movable member can be reduced. Therefore, the driving means can be reduced in size, and the entire switch can be reduced in size and cost. In addition, since there is no portion that is greatly elastically deformed, the life can be extended and the durability can be improved.

It is explanatory sectional drawing of the MEM type | mold RF switch by 1st Embodiment of this invention, and represents an OFF state. It is explanatory sectional drawing of the MEM type | mold RF switch by 1st Embodiment of this invention, and represents an ON state. It is explanatory drawing sectional drawing of the MEM type | mold RF switch by 2nd Embodiment of this invention. It is explanatory sectional drawing of the MEM type | mold RF switch by 2nd Embodiment of this invention, and shows a certain switch switching state. It is explanatory sectional drawing of the MEM type | mold RF switch by 2nd Embodiment of this invention, and shows another switch switching state. It is explanatory sectional drawing of the MEM type | mold RF switch by 3rd Embodiment of this invention, and shows a certain switch switching state. It is explanatory sectional drawing of the MEM type | mold RF switch by 3rd Embodiment of this invention, and shows another switch switching state. It is explanatory sectional drawing of the MEM type | mold RF switch by 3rd Embodiment of this invention, and shows another switch switching state. It is explanatory sectional drawing of the MEM type | mold RF switch by 3rd Embodiment of this invention, and shows another switch switching state. It is explanatory drawing sectional drawing of the MEM type | mold RF switch using the conventional cantilever.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
(First embodiment)
FIG. 1 shows a MEMS type RF switch according to a first embodiment of the present invention. As shown in the figure, in the MEMS RF switch 10, a cavity 16 is formed by structural members 12, 13, and 14 mainly made of an insulating material, and a movable member 20 is disposed in the cavity 16.

  A ground electrode 21 for RF signals is provided on the lower surface of the structural member 12, and signal electrodes 22 and 23 for RF signals are provided on the upper surface so as to be separated from each other. One signal electrode 22 is for input and is connected to an RF signal source, and the other signal electrode 23 is for output and is connected to an RF load. End portions of the signal electrode 22 and the signal electrode 23 that are close to each other extend into the cavity 16, and contact points 22 a and 23 a project into the cavity 16, respectively. The structural member 12, the signal electrodes 22 and 23, and the ground electrode 21 constitute a microstrip line. However, the signal electrodes 22 and 23 can be arbitrary high-frequency transmission lines.

  The movable member 20 has a slightly small size with respect to the cavity 16 and is disposed in the cavity 16 without being connected or supported anywhere in the cavity 16. Although it is exaggerated in the figure, it is actually manufactured with a dimension that leaves a slight gap from the cavity 16. A metal layer 20 a that is a good conductor is provided on the surface of the movable member 20 that faces the structural member 12.

  Therefore, when the metal layer 20a of the movable member 20 contacts the contact points 22a and 23a of the signal electrodes 22 and 23 at the same time, the contact point 22a and the contact point 23a are turned on, and the metal layer 20a is connected to the contact points 22a and 23a. By separating, the contact 22a and the contact 23a are in an OFF state in which the contact is not established.

  The structural member 12 and the structural member 14 facing the structural member 12 are each provided with driving means for driving the movable member 20. The driving means may be any means that uses an arbitrary force, but in this example, an electrostatic force is used. That is, the drive electrode pair 30 is provided on the upper surface of the structural member 12 in the cavity 16, and the drive electrode pair 32 is embedded in the portion of the structural member 14 facing the upper surface. The one drive electrode 30a and the drive electrode 32a of each drive electrode pair are connected to the drive power supply 42 via the switch 40, respectively. The other drive electrodes 30b and 32b of each drive electrode pair are grounded.

  The MEMS type RF switch 10 described above can be manufactured by a micromachining technique. The structural members 12, 13, 14 and the movable member 20 having necessary electrodes and the like are respectively manufactured by a micromachining technique, and then bonded to each other to form the cavity 16 by inserting the movable member 20, or The structural members 12, 13, and 14, the movable member 20, and the cavity 16 may be formed using a sacrificial layer. Preferably, the cavity 16 is a completely closed space that has been evacuated by evacuation, but a part thereof may be open to the outside. Further, the switch 40 and the driving power source 42 can be integrated together. In the present embodiment, an example in which a part of the movable member 20 is conductive is shown, but the entire movable member 20 may be made of a conductive material (for example, metal).

  The operation of the MEMS RF switch 10 configured as described above will be described.

  In a state where no voltage from the drive power supply 42 is applied to any of the drive electrode pairs 30 and 32, the movable member 20 follows an external force that always acts, for example, gravity. Therefore, if the direction of gravity is upward in the figure, the movable member 20 is closer to the structural member 14, and the contact 22a and the contact 23a are non-conductive, so the switch is in the OFF state.

  On the other hand, when the switch 40 is switched and a voltage from the driving power supply 42 is applied to the drive electrode pair 30, an electric field is formed, and a downward attractive force in the figure acts on the movable member 20. The initial suction force at this time needs to have a magnitude that overcomes the external force that the movable member 20 always acts on. When this condition is satisfied, the movable member 20 starts to approach the drive electrode pair 30, but the electrostatic attractive force is inversely proportional to the square of the distance between the two. Will receive. When the movable member 20 approaches the structural member 12 in this way, the movable member 20 comes into contact with the contacts 22a and 23a and is turned on (FIG. 2). The movable member 20 receives the maximum suction force in contact with the contact, and the metal layer 20a of the movable member 20 is pressed against the contacts 22a and 23a to ensure contact.

  Further, in order to transition from the ON state to the OFF state, when the switch 40 is switched and a voltage from the driving power source 42 is applied to the drive electrode pair 32, an electric field is formed, and the movable member 20 is shown in FIG. The upward suction force works. As a result, the movable member 20 starts to move upward in the figure, so that the contacts 22a and 23a become non-conductive and are turned off (FIG. 1). The movable member 20 finally reaches the structural member 14. However, the movable member 20 receives a large suction force compared with the suction force at the initial stage of movement and is pressed and restrained against the structural member 14. It is possible to configure so that the impedance between the terminals is not changed by an external force.

  After switching to the OFF state, voltage application to the drive electrode pair 32 may be continued according to the required switch specifications, or it is sufficient that the movable member 20 depends on an external force such as gravity. In such a case, no voltage may be applied to either of the drive electrode pairs 30 and 32.

  As described above, according to the MEMS RF switch 10 of the present invention, since the contacts 22a and 23a are conducted by the metal layer 20a made of a good conductor, the resistance value of the current flow path can be reduced, and the insertion loss is extremely reduced. Can be small.

  Since the movable member 20 is not connected to any structural member in the cavity 16, the driving force for driving the movable member 20 for the switch operation can be small. When it is assumed that the movable member and the lever are the same size and move the same moving distance compared to the conventional example where the lever is connected to a structural member etc. at some point, such as a cantilever or a both-end support lever The present invention can reduce the maximum driving power required for the switch operation. Further, in the conventional example, the thickness of the cantilever is a design factor that is closely related to the operation. However, in the present invention, the thickness of the movable member 20 can be set almost freely, and further, the portion unnecessary for the movable member 20 It is possible to make full use of the means for weight reduction by, for example, removing or drilling. As a result, the required driving power can be further reduced.

  Even in the OFF state, as described above, since the movable member is restrained while being stably pressed against the structural member 14 and there is little fluctuation in the inter-electrode impedance, the isolation characteristic hardly changes. On the other hand, in the conventional example, when the cantilever changes the interval due to the external force, the capacitance between the electrodes changes, so that the high frequency impedance changes and the phenomenon that the isolation fluctuates occurs. In order to prevent such a fluctuation of isolation, in the conventional example, it is necessary to increase the hardness of the lever. However, this causes a dilemma that the required maximum driving power increases as described above. In the present invention, by using the movable member 20 that is not connected to the structural member in the cavity 16, this trade-off can be completely eliminated, and low voltage driving can be realized.

  Further, unlike the conventional example shown in FIG. 5, the movable member 20 does not have electrodes constituting a signal line connected to an RF signal source or an RF load. For this reason, in the conventional example, the movable contact 58 forms a small antenna at the time of OFF, and there is a defect that it is easy to receive external radiation and external interference, but the present invention does not have such a defect.

(Second Embodiment)
FIG. 3 shows a second embodiment of the present invention. In this embodiment, in addition to the first signal line constituted by the signal electrodes 22 and 23, signal electrodes 24 and 25 constituting the second signal line are formed on the structural member 14. The signal electrodes 24 and 25 constitute a high-frequency transmission line on the structural member 14, and end portions of the signal electrodes 24 and 25 that are close to each other extend through the structural member 14 toward the cavity 16. , Contact points 24a and 25a project into the cavity 16, respectively. A ground electrode 26 is formed between the signal electrodes 24 and 25.

  The movable member 20 is provided not only with the metal layer 20 a on the surface facing the structural member 12 but also with the metal layer 20 b on the surface facing the structural member 14. Alternatively, the entire movable member 20 may be formed using a conductive material.

  In this embodiment, when no voltage from the drive power supply 42 is applied to any of the drive electrode pairs 30 and 32, the movable member 20 follows an external force that always acts, for example, gravity.

  When the switch 40 is switched and a voltage from the drive power supply 42 is applied to the drive electrode pair 30, as shown in FIG. 3B, a downward attractive force acts on the movable member 20 in the figure, so the contact 22 a and the contact 23a is conducted, the signal electrodes 22 and 23 are conducted, and the first signal line is turned on. On the other hand, the second signal line is turned off.

  On the other hand, when the switch 40 is switched and the voltage from the drive power supply 42 is applied to the drive electrode pair 32, as shown in FIG. 3C, an upward suction force in the figure acts on the movable member 20, The contact 24a and the contact 25a are conducted, the signal electrodes 24 and 25 are conducted, the second signal line is turned on, and the first signal line is turned off.

  Thus, the two signal lines can be selectively turned on or off.

  In this embodiment, normally, it is sufficient that a voltage is applied to one of the drive electrode pairs so that one of the signal lines is always ON, or the movable member 20 depends on an external force such as gravity. In such a case, no voltage may be applied to either of the drive electrode pairs 30 and 32.

(Third embodiment)
FIG. 4 shows a third embodiment of the present invention. In this embodiment, instead of the drive electrode pair 30, 32 of the second embodiment, the structural member 12 is formed with two drive electrode pairs 50, 52 facing the cavity 16, The two drive electrode pairs 54, 56 are formed facing the cavity 16. The conductors 20a and 20b of the movable member 20 are connected by a through hole 20c. As described above, the entire movable member 20 may be formed using a conductive material.

  In a state where no voltage from the driving power supply 42 is applied to any of the drive electrode pairs 50, 52, 54, 56, the movable member 20 follows an external force that always acts, for example, gravity.

  Then, when the switch 40 is switched and the voltage from the drive power supply 42 is applied to the drive electrode pairs 50 and 52, as shown in FIG. 4A, the movable member 20 approaches the drive electrode pairs 50 and 52. Thus, the contact 22a and the contact 23a are conducted, the signal electrodes 22 and 23 are conducted, and the first signal line composed of the signal electrode 22 and the signal electrode 23 is turned on. Become.

  On the other hand, when the switch 40 is switched and the voltage from the drive power supply 42 is applied to the drive electrode pairs 54 and 56, the movable electrode 20 approaches the drive electrode pairs 54 and 56 as shown in FIG. 4B. Thus, the contact force 24a and the contact point 25a are conducted, the signal electrodes 24 and 25 are conducted, and the second signal line including the signal electrode 24 and the signal electrode 25 is turned on. Become.

  Alternatively, when the switch 40 is switched and the voltage from the drive power supply 42 is applied to the drive electrode pairs 52 and 54, the drive electrode pair 52 and 54 approaches the movable member 20 as shown in FIG. 4C. Therefore, the contact 23a and the contact 24a are conducted, the signal electrodes 23 and 24 are conducted, and the third signal line composed of the signal electrode 23 and the signal electrode 24 is turned on. Become.

  Alternatively, when the switch 40 is switched and the voltage from the drive power supply 42 is applied to the drive electrode pairs 50 and 56, the drive electrode pair 50 and 56 approaches the movable member 20 as shown in FIG. 4D. Thus, the contact 22a and the contact 25a are conducted, the signal electrodes 22 and 25 are conducted, and the fourth signal line including the signal electrode 22 and the signal electrode 25 is turned on. Become.

  As described above, the movable member 20 is not formed with the electrodes constituting the signal lines, but only with the conductors for conducting the electrodes constituting the signal lines. It is also possible to take a switch switching state for switching a large number of signal lines.

  The MEMS type RF switch described above can be used in various communication devices such as mobile phones and radio wave application equipment such as radar.

10 MEMS RF switch 12, 13, 14 Structural member 20 Movable member 20a, 20b Metal layer (conductor)
22a, 23a, 24a, 25a Signal contact 30, 32, 50, 52, 54, 56 Drive electrode pair 40 Switch

Claims (4)

A MEMS type RF switch manufactured using micromachining technology,
A structural member having a cavity formed therein;
Two signal contacts formed on and spaced apart from each other on at least one of the two opposing surfaces of the structural member facing through the cavity;
The structural member has a dimension slightly smaller than the cavity, and is disposed in the cavity without being connected to any part of the structural member in the cavity and is movable in the cavity. A movable member whose part is a conductor;
Drive means for moving the movable member within the cavity;
A first switch switching state in which the conductor of the movable member is in contact with the two signal contacts, and a second switch switching state in which the conductors of the movable member are separated from the two signal contacts. MEMS type RF switch in which the movable member can move in the cavity so as to switch between the two.   The drive means includes a drive electrode pair provided on each of the two opposed surfaces, and a switching means for selectively applying a voltage to one of the two drive electrode pairs. The MEMS type RF switch according to claim 1, characterized in that:   Two signal contacts are formed on each of the two opposing surfaces, and the first switch switching state in which the conductor of the movable member is in contact with the two signal contacts formed on one surface, and the other 3. The MEMS RF switch according to claim 1, wherein the MEMS type RF switch can be switched to a second switch switching state in which the signal contacts formed on the surface are in contact with each other.   A third switch switching state in which the conductor of the movable member is in contact with one signal contact formed on one surface and the one signal contact formed on the other surface; and the conductor of the movable member is It is possible to switch between the other signal contact formed on one surface and the fourth switch switching state in contact with the other signal contact formed on the other surface. Item 4. The MEMS RF switch according to Item 3.

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