JP4288353B2 - Variable inductor - Google Patents

Description

  The present invention relates to a variable inductor capable of changing an inductance.

  Conventionally, in order to make the characteristics of an electronic circuit variable, the characteristics of an active element or the characteristics of a passive element (resistance value, capacitance value, etc.) included in the circuit are changed.

For the active element, the characteristics of the active element can be changed by changing the bias voltage applied to the active element.
As for the passive element, for example, a variable resistance element can be easily realized by using an on-resistance of a MOSFET, and a variable capacitance element can be easily realized by using a PN junction.

  However, it is difficult for an inductor as a passive element to have a variable inductance while maintaining good characteristics.

  On the other hand, there is a method of configuring an inductor using an active element and making the inductor variable. However, in this configuration, since the active element is used, there is a problem that noise and distortion characteristics are poor.

  Further, in order to change the mutual coupling coefficient, there is a method of physically changing the shape of the inductor (see, for example, Patent Document 1), but it is difficult to reduce the size and cost of the circuit to be configured. There's a problem.

  Therefore, a configuration has been proposed in which a plurality of coils are provided as variable inductors that can be easily reduced in size, reduced in cost, and integrated, and the distribution ratio of the current flowing through each of the coils can be changed by a distributor ( For example, see Patent Document 2.)

JP 7-320942 A JP 2004-165612 A

However, in the configuration described in Patent Document 2, a distributor is required in addition to the inductor, and a plurality of inductors must be switched.
For this reason, the circuit configuration is restricted by providing the variable inductor.

  Further, since it is difficult to change the inductance significantly, it is necessary to select an inductor configuration corresponding to an application to which the variable inductor is applied.

  In order to solve the above-described problems, the present invention provides a variable inductor capable of changing an inductance value with a simple structure without changing the shape of the inductor.

The variable inductor of the present invention includes a plurality of thin film coils, and an actuator is provided for at least one of the plurality of thin film coils, and the actuator is bent by thermal expansion, whereby the film surface of the thin film coil is provided. The thin film coil is moved in a direction substantially perpendicular to the first and second thin film coils, and the interval between the plurality of thin film coils in the direction substantially perpendicular to the film surface of the thin film coil is changed .

In the variable inductor of the present invention, the actuator may have a structure in which a first wiring layer, an insulating layer, and a second wiring layer are stacked .

The variable inductor according to the present invention includes a plurality of thin film coils in which spiral coils are formed in a rectangular shape as a whole, and actuators are provided near the four corners of at least one thin film coil among the plurality of thin film coils. The actuator is formed by alternately arranging fixed first comb electrodes and movable second comb electrodes, and a potential difference between the first comb electrodes and the second comb electrodes. Is applied to move the second comb electrode and the thin film coil in a direction substantially parallel to the film surface of the thin film coil. The first comb electrode and the second comb tooth The longitudinal direction of the electrode is formed obliquely with respect to the vertical direction and the horizontal direction of the rectangular thin film coil .

According to the present invention described above, by moving the thin film coil by the actuator, the mutual inductance between the coils can be changed, and the inductance of the entire variable inductor can be changed.
Therefore, the inductance value can be changed without changing the shape of the inductor.
Further, the inductance value of the variable inductor can be controlled by controlling the actuator.

Then, by manufacturing the actuator using MEMS (Micro Electro Mechanical Systems) technology, the variable inductor can be manufactured on a semiconductor substrate, for example, a silicon substrate.
As a result, it is possible to realize a variable inductor that has a simple configuration and can be integrated, reduced in size, reduced in power consumption, and reduced in cost.

In addition, by manufacturing the actuator using the MEMS technology, the distance between the coils can be reduced, so that the electromagnetic coupling force can be increased.
In addition, since the mutual inductance of the plurality of coils is changed using the actuator, the inductance can be changed arbitrarily and continuously, and it is not necessary to make the specification based on switching of the coil.

  In addition, the amount of change in inductance can be adjusted by changing the amount of current and voltage applied to the coil, and the inductance can be continuously changed over a wide range with the change in mutual inductance by the actuator. Is possible.

  In addition, the number of mounted variable inductors is expected to increase due to the demand for higher performance of mobile communication devices, and a large market can be expected in the future. Therefore, the variable inductor of the present invention reduces the size of high performance mobile communication devices. Can be realized at a low price.

First, an outline of the present invention will be described prior to description of specific embodiments of the present invention.
In the variable inductor according to the present invention, the inductance is changed by changing the distance between the plurality of coils to change the mutual inductance.

This principle will be described with reference to FIGS. 16A and 16B.
In FIG. 16A and FIG. 16B, the coil 1 having the inductance L1 and the coil 2 having the inductance L2 are arranged vertically with the central axis being substantially the same.
As shown in FIG. 16A, when the distance between the coil 1 and the coil 2 is short, among the magnetic fluxes generated when the current i is passed through the coil 1, the interlaced magnetic flux passing through the coil 2 increases, so that the mutual inductance increases. .
As shown in FIG. 16B, when the distance between the coil 1 and the coil 2 is long, among the magnetic fluxes generated when the current i flows through the coil 1, the interlaced magnetic flux passing through the coil 2 decreases, and the leakage that does not pass through the coil 2 Since the magnetic flux increases, the mutual inductance decreases.

A case where the two coils of FIG. 16 are constituted by thin film coils will be described with reference to the cross-sectional views of FIGS. 17A and 17B.
As shown in FIG. 17A, when the horizontal relative positions of the lower layer thin film coil 71 and the upper layer thin film coil 72 coincide with each other and the distance between the two coils 71 and 72 is small, the two coils 71 and 72 Mutual inductance is maximized.
As shown in FIG. 17B, the horizontal relative positions of the lower layer thin film coil 71 and the upper layer thin film coil 72 are shifted, and the conductors of the coils 71 and 72 are located between the conductors of the other coil and are in a staggered position. When the distance between the two coils 71 and 72 is large, the mutual inductance of the two coils 71 and 72 is minimized.

In the configuration described in Patent Document 1 described above, the mutual inductance is changed according to the principle described above.
However, in the configuration described in Patent Document 1, since the coil is attached to the slider and the distance between the coils is manually changed by the operation of the slider, it is difficult to reduce the size or incorporate the electronic circuit. .

Therefore, in the variable inductor according to the present invention, an actuator using thermal expansion or electrostatic action of a fine material is configured, and the coil is moved using this actuator. As a result, the inductance of the variable inductor can be controlled by controlling the actuator.
And the coil which consists of a thin film coil is provided with two or more layers, and it is set as the structure which moves at least 1 layer coil by an actuator among the coils of several layers.

An actuator using thermal expansion is formed by laminating two materials having different thermal expansion coefficients, such as bimetal.
And the actuator of this structure can be bent to the material side with a small thermal expansion coefficient by applying heat.
An actuator having a configuration utilizing this thermal expansion has characteristics such that a large force can be extracted, the actuator can be configured with a simple structure, and it is suitable for integration.

As an actuator using an electrostatic action, for example, the configuration shown in FIG.
As shown in FIG. 13A, a first comb electrode 101 made of a metal plate electrode is attached to the left substrate in the drawing, and a second comb electrode 102 is interposed between the first comb electrodes 101. Has been placed.

Here, for example, when the first comb electrode 101 is connected to the ground potential and the second comb electrode 102 is connected to the positive potential, as shown in FIG. The potential becomes -potential, and the second comb electrode 102 has a relatively positive potential. As a result, an electrostatic force directed from the second comb electrode 102 to the first comb electrode 101 as indicated by a thin arrow in the figure is generated.
Of the electrostatic force, the force directly upward in the figure and the force downward in the figure are balanced and offset, so only the component in the left direction in the figure remains. As a result, a leftward force F is generated as indicated by a thick arrow in the figure.
Then, due to the action of the force F, the second comb electrode 102 moves leftward as shown in FIG. 13B. At this time, if the second comb electrode 102 is attached to the object to be moved, the object can be moved using the electrostatic action.

  An actuator using such an electrostatic action has features such as high operating speed, low power consumption, and suitability for integration.

Further, FIG. 14A shows a configuration of an actuator using the principle shown in FIGS. 13A and 13B.
In the actuator shown in FIG. 14A, the first comb-tooth electrodes 111 and the second comb-tooth electrodes 112 are alternately arranged, and the first comb-tooth electrodes 111 are attached to the left support member 111A. The comb electrode 112 is attached to the right support 112A.
The support material 112 </ b> A of the second comb electrode 112 is connected to the conductive spring 113. The left side of the spring 113 is attached to the support material of the second comb electrode 112, and the right side is fixed to the fixing material 114.
Further, the support material 111A of the first comb electrode 111 and the fixing material 114 are connected by wiring, and a power source 115 and a switch 116 are provided in the middle of the wiring. In the state shown in FIG. 14A, the switch 116 is disconnected, and the support material 111A and the fixing material 114 of the first comb electrode 111 are not electrically connected.

As shown in FIG. 14B, when the switch 116 is connected, the support material 111A of the first comb-tooth electrode 111 and the fixing material 114 are electrically connected, and the power supply 115 supports the support material 111A and the fixing material of the first comb-tooth electrode 111. 114 is applied with a voltage + V.
As a result, the first comb-tooth electrode 111 has a relatively positive potential, and the second comb-tooth electrode 112 electrically connected to the fixing material 114 has a relatively negative potential. In the same manner as shown in FIG. 5, the electrostatic force acts to cause the second comb electrode 112 to receive a force to the left.
Accordingly, the second comb-tooth electrode 112 is moved to the left side by overcoming the elastic force of the spring 113 by receiving a leftward force as indicated by an arrow in the figure.

After that, as shown in FIG. 14C, when the switch 116 is cut, the support material 111A and the fixing material 114 of the first comb-tooth electrode 111 are not electrically connected, so the leftward force due to the electrostatic force shown in FIG. 14B disappears. .
Accordingly, the second comb-tooth electrode 112 moves to the right side by receiving a rightward force as indicated by an arrow by the elastic force of the spring 113.

  In the configuration shown in FIGS. 13 and 14, the operation is the same even if the polarity of the potential applied to the two comb electrodes is reversed, and when the electrostatic force is generated, the second comb electrode is on the left side. Move to the left under the force of.

  Subsequently, specific embodiments of the variable inductor of the present invention will be described.

FIG. 1 shows a schematic configuration diagram (perspective view) of an embodiment of the variable inductor of the present invention.
The variable inductor 1 includes two coils 2 and 3 made of a thin film coil and an actuator 5.

In the two coils 2 and 3, a thin-film coil is formed in a spiral shape (spiral shape), one terminal T1 is provided outside the spiral, and the portion extending from the center of the spiral to the outside through the spiral The other terminal T2 is provided.
The lower coil 2 is formed on the substrate 6.
The upper layer side coil 3 is formed on a frame-like frame 4.
The frame 4 is placed on an actuator 5 provided near the four corners of the coils 2 and 3.

The coils 2 and 3 of each layer are constituted by a thin film coil 51 whose sectional view is shown in FIG.
In the thin film coil 51 shown in FIG. 2, a first conductive layer 54 is formed on a base 52 via an insulating layer 53, and a second conductive layer 57 is formed thereon via an insulating layer 55. Made up.
The second conductive layer 57 is formed in a spiral shape (spiral shape), and its surface is covered with an insulating layer 58. Although not shown, one terminal T1 described above is provided outside.
The first conductive layer 54 is connected to a central portion of a second conductive layer 57 formed in a spiral shape through a conductive layer 56 formed so as to penetrate the insulating layer 55. The first conductive layer 54 is provided with the other terminal T2 described above at the end, although not shown.

  In the lower coil 2, the substrate 6 is the base 52 in FIG. 2. In the coil 3 on the upper layer side, the frame 4 is the base 52 in FIG.

  Each actuator 5 is provided on a support base 7 disposed on a substrate 6. Although not shown, the end of each actuator 5 opposite to the coils 2 and 3 (that is, the outer side) is fixed to the support base 7.

The actuator 5 is configured to use thermal expansion. A detailed configuration of the actuator 5 of FIG. 1 is shown in FIGS. 3A to 3C.
FIG. 3A shows a top view of the actuator 5, and FIG. 3B shows a perspective view of the actuator 5. As shown in FIGS. 3A and 3B, the actuator 5 is formed in a rectangular bar shape that is bent into an elongated U-shape.
The U-shaped tip portion is disposed outside and fixed to the support base 7, and the U-shaped bent portion is disposed on the coils 2 and 3 side.

FIG. 3C shows a cross-sectional view of the rectangular bar-like actuator 5.
As shown in FIG. 3C, the first wiring layer 11, the metal layer 12, the insulating layer 13, the insulating layer 14, the insulating layer 15, the metal layer 16, and the second wiring layer 17 are laminated from the lower layer.

For example, gold (Au) can be used for the first wiring layer 11 and the second wiring layer 17. Further, the first wiring layer 11 and the second wiring layer 17 are configured such that a current can flow in the wiring layers 11 and 17 by connecting both ends to the outside.
For the metal layers 12 and 16, for example, titanium Ti can be used.
For the insulating layers 13 and 15, for example, plasma SiO ₂ can be used.
For example, SiO ₂ can be used for the insulating layer 14.

Then, for example, a 0.1 μm thick Au film as the first wiring layer 11, a 0.05 μm thick Ti film as the metal layer 12, a 1 μm thick plasma SiO ₂ film as the insulating layer 13, and a film as the insulating layer 14 A 1 μm thick SiO ₂ film, a 1 μm thick plasma SiO ₂ film as the insulating layer 15, a 0.05 μm thick Ti film as the metal layer 16, and a 0.1 μm thick Au film as the second wiring layer 17 are laminated. Thus, the actuator 5 that is symmetrical in the vertical direction can be configured.

Next, the operation of the actuator 5 will be described with reference to FIG.
As shown in FIG. 4A, when a current i is passed through the upper second wiring layer 17, the second wiring layer 17 side layer (for example, the second wiring layer 17 and the metal layer) is thermally expanded due to heat generated by the current i. 16) stretches. On the other hand, the lower first wiring layer 11 side remains as it is.
For this reason, the actuator 5 bends so that the upper side is convex, and since the tip portion is fixed to the support base 7, the bent portion bends downward as indicated by a thick arrow in the figure.

As shown in FIG. 4B, when a current i is passed through the lower first wiring layer 11, the first wiring layer 11 side layer (for example, the first wiring layer 11 and the first wiring layer 11) is expanded by heat generated by the current i. The metal layer 12) extends. On the other hand, the upper wiring layer 17 side remains the same.
For this reason, the actuator 5 bends so that the lower side is convex, and since the tip end portion is fixed to the support base 7, the bent portion bends upward as indicated by a thick arrow in the figure.

In this way, the bent portion of the actuator 5 can be bent downward or upward by passing a current through either the first wiring layer 11 or the second wiring layer 17.
The coil 3 placed on the bent portion of the actuator 5 can be moved up and down depending on the state in which a current is passed through the first wiring layer 11 and the state in which a current is passed through the second wiring layer 17. it can.
Furthermore, the actuator 5 can be straightened by setting a state in which no current flows through either the first wiring layer 11 or the second wiring layer 17.
Further, by changing the amount of current flowing through either the first wiring layer 11 or the second wiring layer 17, the amount by which the bent portion of the actuator 5 bends up and down can be changed. Can be arbitrarily adjusted within the movable range of the actuator.

For example, as shown in FIG. 5A and FIG. 5B, the coil is formed by a state in which no current flows through either the first wiring layer 11 or the second wiring layer 17 and a state in which current flows through only the first wiring layer 11. Can be moved.
In the state shown in FIG. 5A, the actuator 5 is straightened by passing no current through either the first wiring layer 11 or the second wiring layer 17.
In the state shown in FIG. 5B, when a current is passed through the first wiring layer 11, the bent portion of the actuator 5 is bent upward, and the frame 4 on which the upper coil 3 is placed moves upward. Thereby, compared with the state shown in FIG. 4A, the distance between the lower coil 2 and the upper coil 3 is widened, so the mutual inductance of the two coils 2 and 3 is reduced.

Conversely, when the distance between the lower coil 2 and the upper coil 3 is reduced, the mutual inductance of the two coils 2 and 3 increases.
And the inductance of the variable inductor 1 whole can be changed by the magnitude | size of the mutual inductance of the two coils 2 and 3 changing.

  In addition, for example, by forming a recess in the support base 7 below the bent portion of the actuator 5 or by making the support base 7 not below the bent portion of the actuator 5, Can be bent into

According to the configuration of the variable inductor 1 of the above-described embodiment, the two-layer coils 2 and 3 formed of thin film coils are provided, and the upper-layer coil 3 is placed on the actuator 5 that bends in the vertical direction. Therefore, the distance between the two layers of the coils 2 and 3 can be changed by moving the coil 3 in the vertical direction by the operation of the actuator 5.
Thereby, the mutual inductance of the two-layer coils 2 and 3 can be changed, and the inductance of the entire variable inductor 1 can be changed.

In addition, if the actuator 5 has a configuration in which the bent portion is bent by passing a current through the first wiring layer 11 or the second wiring layer 17, the amount of current flowing through the wiring layers 11 and 17 can be changed. The amount by which the bent portion bends can be changed.
Thus, by adjusting the amount of current flowing through the wiring layers 11 and 17 of the actuator 5, the moving amount of the coil 3 is adjusted, and the inductance of the variable inductor 1 can be arbitrarily and continuously within the movable range of the actuator 5. It becomes possible to change.

Furthermore, the actuator 5 of the variable inductor 1 according to the present embodiment can be manufactured using MEMS (Micro Electro Mechanical Systems) technology.
Thus, by manufacturing the actuator 5 using the MEMS technology, the variable inductor 1 can be manufactured on a semiconductor substrate, for example, a silicon substrate.
As a result, it is possible to realize the variable inductor 1 that has a simple configuration and can be integrated, downsized, reduced in power consumption, and reduced in cost. For example, an integrated circuit including the variable inductor 1 can be formed on one chip.

Next, a variable inductor obtained by modifying the configuration of the variable inductor 1 shown in FIG.
FIG. 6 shows a schematic configuration diagram (perspective view) of another embodiment of the variable inductor of the present invention.
The variable inductor 20 according to the present embodiment has a configuration in which a coil 8 is further provided above the coil 3 placed on the bent portion of the actuator 5 to provide a total of three layers of coils 2, 3, and 8. is there.

In the present embodiment, by providing the three layers of coils 2, 3, and 8, mutual inductance can be generated between the coils.
Then, the second-layer coil 3 is moved in the vertical direction (direction perpendicular to the film surface of the thin-film coil) by using the actuator 5, whereby the second-layer coil 3 and the other coils 2, 8 are mutually connected. The inductance of the entire variable inductor 8 can be changed by changing the inductance.

The strength of the mutual inductance is determined according to the number of windings, the outer shape, the inner diameter, and the distance between the inductors.
Therefore, by changing these dimensions, distances, etc., and combining them with different mutual inductances, it is possible to widen the range in which the inductance changes in the variable inductor 20 having three layers of coils 2, 3, and 8. .

Here, the variable inductor 20 having the configuration shown in FIG. 6 was actually manufactured and the characteristics thereof were examined.
The three layers of coils 2, 3 and 8 are formed in the same material and in the same shape, and the actuator 5 moves the second layer of the coil 3 in a direction perpendicular to the film surface of the coil 3 so that the distance between the coils is increased. A variable inductor 20 was produced as a configuration to be changed.

Then, when the second-layer coil 3 is moved closer to or away from the upper-layer third-layer coil 8, the change characteristics of the respective self-inductance and mutual inductance are obtained by simulation. The results are shown in FIG.
In FIG. 7, L11 is the self-inductance of the coil 2 in the lower layer (first layer), L22 is the self-inductance of the coil 3 in the second layer, and L33 is the self-inductance of the coil 8 in the upper layer (third layer). is there. L12 is the mutual inductance between the first layer coil 2 and the second layer coil 3, L23 is the mutual inductance between the second layer coil 3 and the third layer coil 8, and L13 is the first layer coil. This is the mutual inductance between the coil 2 and the third layer coil 8. Further, the horizontal axis of FIG. 7 indicates the movement distance [μm] in the direction perpendicular to the film surface of the coil 3 of the second layer, and the case where it moves upward (on the side of the coil 8 of the third layer) is set as +. The case of moving downward (on the coil 2 side of the first layer) is indicated as-.

From FIG. 7, since the materials and shapes of the three-layer coils 2, 3, and 8 are the same, the self-inductances L11, L22, and L33 are equal.
The mutual inductances L12 and L23 between the second layer coil 3 and the other coils 2 and 8 change corresponding to the movement of the second layer coil 3. When the moving distance is +, since the second layer coil 3 is moved to the third layer coil 8 side, the mutual inductance L23 between them is increased, and the second layer coil 3 and the first layer coil 3 are moved. Conversely, the mutual inductance L12 with the coil 2 becomes smaller. When the movement distance is-, the second layer coil 3 is moved to the first layer coil 2 side, so that the mutual inductance L12 between them is increased and the second layer coil 3 and the third layer coil 3 are moved. The mutual inductance L23 with the coil 8 becomes smaller.
Thus, it was confirmed that the mutual inductances L12 and L23 change depending on the distance between the coils.

  The variable inductors 1 and 20 according to the above-described embodiments have the configuration including the actuator 5 using thermal expansion. The configuration including the actuator using the electrostatic action described above is shown below.

FIG. 8 shows a schematic configuration diagram (plan view) of still another embodiment of the variable inductor of the present invention.
The variable inductor 30 includes a first layer coil (not shown) formed on a substrate and a second layer coil 31 provided above the same as in the previous embodiment.
The second layer coil 31 has a thin film coil formed in a spiral shape, a first terminal T1 provided on the outer side, and a second terminal at the tip of the wiring extending from the inner side to the outer side under the coil 31. A terminal T2 is provided.

The second-layer coil 31 is attached to the actuator 32 in the vicinity of its four corners.
The actuator 32 includes a first comb-teeth electrode 33 and a second comb-teeth electrode 34, and the first comb-teeth electrode 33 is fixed to the substrate, and two layers are formed on the second comb-teeth electrode 34. An eye coil 31 is attached.
The second comb-tooth electrode 34 is disposed near the four corners of the coil 31 of FIG. 8, and the first comb-tooth electrode 33 is disposed to face the second comb-tooth electrode 34 of FIG.

The second comb-teeth electrode 34 is also attached to a conductive elastic material such as the spring 113 shown in FIG. 14A, and is attached in a direction away from the first comb-teeth electrode 33 by the elastic material when there is no electrostatic force. It is energized.
Since the actuator 32 is configured in this manner, the actuator 32 operates in the same manner as the actuator shown in FIGS. 14A to 14C. That is, when a voltage is applied, the second comb electrode 34 enters between the first comb electrodes 33 due to electrostatic force, and when no voltage is applied, the first comb electrode is caused by the elastic force of the elastic material. The second comb electrode 34 is separated from the comb electrode 33.

  In addition, since the second comb electrode 34 is stationary at the location where the elastic force and the electrostatic force of the elastic material are balanced by connecting the elastic material as described above, it is applied to the two comb electrodes 33 and 34. If the magnitude of the electrostatic force is adjusted according to the potential difference, the position where the second comb electrode 34 is stationary can be adjusted. Thereby, the movement amount of the coil 31 of the second layer attached to the second comb electrode 34 can be adjusted.

Moreover, in this Embodiment, with respect to the 1st comb-tooth electrode 33 and the 2nd comb-tooth electrode 34 which are arrange | positioned alternately, a voltage is applied only to every other comb-tooth electrode 33,34, respectively. Configure to be able to.
For this purpose, the first comb electrode 33 and the second comb electrode 34 are configured as a comb electrode 60 as shown in FIG.
A comb-tooth electrode 60 shown in FIG. 9 includes a first wiring 62 and a second wiring 63 to which independent potentials φ1 and φ2 are applied to a support material 61, respectively, and is attached to the support material 61. A large number of comb teeth 64 and 65 are electrically connected to the wirings 62 and 63 every other line. That is, the comb teeth 64 are electrically connected to the first wiring 62 and the first potential φ1 is applied. Further, the comb teeth 65 are electrically connected to the second wiring 63, and the second potential φ2 is applied.

  By configuring the first comb electrode 33 and the second comb electrode 34 using the comb electrode 60 having such a configuration, the actuator 32 can be operated as shown in FIGS. 10A to 10C. it can.

First, as shown in FIG. 10A, for example, by applying a relatively negative potential to all the first comb-teeth electrodes 33 and applying a relatively positive potential to all the second comb-teeth electrodes 34. 13 and 14, the second comb electrode 34 moves so as to approach the support material of the first comb electrode 33.
In this case, the same potential is applied to the first wiring 61 and the second wiring 62 in the support material in each of the comb electrodes 33 and 34.

Next, as shown in FIG. 10B, in the first comb-teeth electrode 33 and the second comb-teeth electrode 34, a potential is applied to every other comb-teeth electrode so that the first comb-teeth electrode 33 is applied. If the comb electrode to which the positive potential of the second comb electrode 34 is applied is positioned to the left of the comb electrode to which the negative potential is applied, the comb electrodes to which the potential is applied are electrostatic forces. Thus, the second comb electrode 34 moves to the right.
In this case, in each of the comb electrodes 33 and 34, a potential is applied to only one of the first wiring 61 and the second wiring 62 in the support material.

Next, as shown in FIG. 10C, in the first comb-teeth electrode 33 and the second comb-teeth electrode 34, a potential is applied to every other comb-teeth electrode so that the first comb-teeth electrode 33 is applied. When the comb electrode to which the positive potential of the second comb electrode 34 is applied is positioned to the right of the comb electrode to which the negative potential is applied, the comb electrodes to which the potential is applied are electrostatic forces. Thus, the second comb electrode 34 moves to the left.
In this case, in each of the comb electrodes 33 and 34, a potential is applied to only one of the first wiring 61 and the second wiring 62 in the support material.

When the actuator 32 operates in this way, the second layer coil 31 shown in FIG. 8 moves in the vertical direction of FIG. 8 in the case of FIG. 10A, and in the case of FIG. 10B and FIG. Move in the direction.
That is, the coil 31 moves in a direction parallel to the film surface.

In the present embodiment, since the actuator 32 has the configuration shown in FIGS. 8 and 10, the movement amount of the second comb electrode 34 is larger in the longitudinal direction of the comb electrodes 33 and 34 (FIG. 10A). It is larger than the direction perpendicular to the longitudinal direction (FIGS. 10B and 10C).
Accordingly, the amount of movement of the second layer coil 31 also increases in the direction (front-rear direction) Y along the longitudinal direction of the comb electrodes 33 and 34 and decreases in the left-right direction X perpendicular to the longitudinal direction.

According to the configuration of the variable inductor 30 of the present embodiment described above, the first layer of the actuator 32 is provided with two layers of thin film coils, and the upper layer coil 31 moves the second comb electrode 34 by electrostatic force. By being attached to the two comb-teeth electrodes 34, the actuator 31 moves the coil 31 in the direction parallel to the film surface (front / rear / left / right) to change the horizontal distance of the conductors constituting the two-layer coil. Can be made. Further, since the opposing areas of the coils change, the amount of magnetic flux generated from one coil passes through the other coil changes.
Thereby, the mutual inductance of the two layers of coils can be changed, and the inductance of the entire variable inductor 30 can be changed.

  Further, the actuator 32 is configured to move the second comb electrode 34 by generating an electrostatic force due to a potential difference between potentials applied to the first comb electrode 33 and the second comb electrode 34, respectively. The electrostatic force is adjusted by urging the second comb-teeth electrode 34 in an opposite direction to the electrostatic force by an elastic material and adjusting the magnitude of the potential difference between the potentials applied to the electrodes 33 and 34. By adjusting the movement amount of the second comb electrode 34, that is, the movement amount of the coil 31 of the second layer, the inductance of the variable inductor 30 can be arbitrarily set within the movable range of the second comb electrode 34 of the actuator 32. It becomes possible to change continuously.

Furthermore, the actuator 32 of the variable inductor 30 of the present embodiment can be manufactured using the MEMS technology.
Thus, by manufacturing the actuator 32 using the MEMS technology, the variable inductor 30 can be manufactured on a semiconductor substrate, for example, a silicon substrate.
As a result, it is possible to realize the variable inductor 30 that has a simple configuration and can be integrated, downsized, reduced in power consumption, and reduced in cost. For example, an integrated circuit including the variable inductor 30 can be formed on one chip.

  In addition to the configuration of the variable inductor 30 shown in FIG. 8, as in the embodiment shown in FIG. 6, a third layer coil is arranged on the second layer coil 31, and the variable inductor is It is also possible to configure.

  In FIG. 8, the second layer coil 31 is directly attached to the second comb electrode 34 of the actuator 32. For example, a frame similar to the frame 4 shown in FIG. It is good also as a structure which attached to this 2nd comb-tooth electrode and formed the coil of the 2nd layer on this frame.

Next, FIG. 11 shows a schematic configuration diagram (plan view) of still another embodiment of the variable inductor of the present invention.
The variable inductor 40 includes a first layer coil (not shown) formed on a substrate and a second layer coil 41 provided thereon, as in the previous embodiment.
In the second layer coil 41, a thin film coil is formed in a spiral shape, a first terminal T1 is provided on the outside, and a second terminal is provided at the tip of the wiring that extends from the inside to the outside through the coil 41. A terminal T2 is provided.

The second-layer coil 41 is attached to the actuator 42 in the vicinity of its four corners.
The actuator 42 includes a first comb-tooth electrode 43 and a second comb-tooth electrode 44, and the first comb-tooth electrode 43 is fixed to the substrate, and two layers are provided on the second comb-tooth electrode 44. An eye coil 41 is attached.
The second comb-tooth electrode 44 is disposed in the vicinity of the four corners of the coil 41 in FIG. 11, and the first comb-tooth electrode 43 is disposed to face the second comb-tooth electrode 44 in FIG.

The second comb-tooth electrode 44 is also attached to a conductive elastic material such as the spring 113 shown in FIG. 14A, and is attached in a direction away from the first comb-tooth electrode 43 by the elastic material when there is no electrostatic force. It is energized.
Since the actuator 42 is configured in this manner, the actuator 42 operates in the same manner as the actuator shown in FIGS. 14A to 14C. That is, when a voltage is applied, the second comb electrode 44 enters between the first comb electrodes 43 due to electrostatic force. When no voltage is applied, the first comb electrode 44 is caused by the elastic force of the elastic material. The second comb electrode 44 is separated from the comb electrode 43.

  In addition, since the second comb electrode 44 is stationary at the place where the elastic force and the electrostatic force of the elastic material are balanced by connecting the elastic material as described above, it is applied to the two comb electrodes 43 and 44. If the magnitude of the electrostatic force is adjusted according to the potential difference, the position where the second comb electrode 44 is stationary can be adjusted. As a result, the amount of movement of the second layer coil 41 attached to the second comb electrode 44 can be adjusted.

  In the present embodiment, as shown in FIGS. 11 and 12A, the longitudinal directions of the first comb-tooth electrode 43 and the second comb-tooth electrode 44 of the actuator 42 are oblique with respect to the front-rear direction and the left-right direction. It has become the direction.

Then, as shown in FIG. 12B, for example, by applying a relatively negative potential to the first comb electrode 43 and applying a relatively positive potential to the second comb electrode 44, the second The comb-tooth electrode 44 moves obliquely so as to approach the support material of the first comb-tooth electrode 43.
As a result, the second layer coil 41 connected to the second comb-tooth electrode 44 moves along the longitudinal direction of the second comb-tooth electrode 44 in an oblique direction indicated by a thick arrow in FIG.

In the case of the configuration of the present embodiment, the movement in the left-right direction X depends on the angle between the longitudinal direction of the first comb-tooth electrode 43 and the second comb-tooth electrode 44 and the left-right direction X and the front-back direction Y. The ratio between the amount ΔX and the movement amount ΔY in the front-rear direction Y is determined, and ΔX / ΔY is substantially constant.
In this case, unlike the variable inductor 30 of the previous embodiment, it cannot be arbitrarily moved in the left-right direction and the front-rear direction. However, the elastic material only needs to be provided in one direction, and there is no need to provide in three directions. Have.

According to the configuration of the variable inductor 40 of the present embodiment described above, the first layer of the actuator 42 is provided with two layers of coils made of thin film coils, and the upper layer coil 41 moves the second comb-teeth electrode 44 by electrostatic force. By being attached to the two comb-teeth electrodes 44, the actuator 42 is operated to move the coil 41 in a direction parallel to the film surface (a direction oblique to the left-right direction X and the front-rear direction Y). It is possible to change the horizontal distance of the conductor constituting the coil. Further, since the opposing areas of the coils change, the amount of magnetic flux generated from one coil passes through the other coil changes.
Thereby, the mutual inductance of the two layers of coils can be changed, and the inductance of the entire variable inductor 40 can be changed.

  Further, the actuator 42 has a configuration in which the second comb electrode 44 moves by generating an electrostatic force due to a potential difference between potentials applied to the first comb electrode 43 and the second comb electrode 44, respectively. The electrostatic force is adjusted by urging the second comb electrode 44 in an opposite direction to the electrostatic force with an elastic material and adjusting the magnitude of the potential difference between the potentials applied to the electrodes 43 and 44. By adjusting the amount of movement of the second comb electrode 44, that is, the amount of movement of the second layer coil 41, the inductance of the variable inductor 40 can be arbitrarily set within the movable range of the second comb electrode 44 of the actuator 42. It becomes possible to change continuously.

  In addition to the configuration of the variable inductor 40 shown in FIG. 11, a third layer coil is arranged on the second layer coil 41 as in the embodiment shown in FIG. It is also possible to configure.

  In FIG. 11, the second layer coil 41 is directly attached to the second comb-teeth electrode 44 of the actuator 42. For example, a frame similar to the frame 4 shown in FIG. It is good also as a structure which attached to this 2nd comb-tooth electrode and formed the coil of the 2nd layer on this frame.

Note that the elastic material for biasing the comb-tooth electrode is not limited to the conductive spring 113 shown in FIG. 14, and other elastic materials can be used.
Further, instead of configuring the elastic material with a conductive material, a wiring is connected to the support material for the second comb electrode separately from the elastic material, and a potential is applied from the wiring to the second comb electrode. It doesn't matter if you do.

In each of the above-described embodiments, two or three layers of thin film coils are provided, and only one layer (second layer thin film coil) is moved by the actuator.
In the present invention, other configurations are possible as long as a plurality of thin film coils are provided and some or all of the layers are moved by an actuator.

  Moreover, the structure of the thin film coil of each layer is not limited to the structure similar to the thin film coil 51 shown in FIG. 2, and another structure is also possible.

In each of the above embodiments, the coil is configured to move in a direction perpendicular to the film surface of the coil or in a direction parallel to the film surface by the actuator, but from a direction perpendicular to the film surface or a direction parallel to the film surface. Even if it is slightly deviated, that is, in the direction substantially perpendicular to the film surface of the coil or in the direction substantially parallel to the film surface, the same effect can be obtained.
In the present invention, the moving direction of the coil may be moved in other directions such as obliquely upward, and even in such a configuration, the mutual inductance between the coils is changed to change the inductance of the variable inductor. be able to.

In addition to the configuration in which the coil of the variable inductor according to the present invention is moved by an actuator, it is also possible to combine a configuration in which a coil for passing current is switched by switching, a configuration in which the amount of current flowing in each coil is different, and the like. is there.
By combining the configurations in this way, it is possible to widen the range in which the inductance of the variable inductor changes.

The variable inductors of the present invention, such as the variable inductors 1, 20, 30, 40 of the above-described embodiments, are used in, for example, a VCO (voltage controlled oscillator) whose circuit configuration is shown in FIGS. 15A and 15B. it can.
In the VCO (Voltage Controlled Oscillator) shown in FIGS. 15A and 15B, two coils are provided in the upper part of each figure, and the variable inductor of the present invention is applied to these two coils to change the inductance of the coil. be able to.

  This VCO (Voltage Controlled Oscillator) is used, for example, in a PLL circuit that generates a reference frequency in an electronic device for wireless communication such as a mobile phone, and the output frequency can be controlled by voltage.

  The present invention is not limited to the above-described embodiment, and various other configurations can be taken without departing from the gist of the present invention.

  The inductor of the present invention can be applied to, for example, electronic devices such as mobile phones and LSI testers, and DC-DC converters represented by switching power supply circuits.

It is a schematic block diagram (perspective view) of one embodiment of the variable inductor of the present invention. It is sectional drawing of the thin film coil which comprises the coil of each layer of FIG. FIGS. 2A to 2C are diagrams illustrating a detailed configuration of the actuator of FIG. A and B are diagrams for explaining the operation of the actuator of FIG. A, B It is a figure explaining the movement of the coil by the actuator of FIG. It is a schematic block diagram (perspective view) of other embodiment of the variable inductor of this invention. It is a figure which shows the relationship between the moving distance of the coil of the variable inductor of FIG. 6, and the magnitude | size of an inductance. It is a schematic block diagram (plan view) of further another embodiment of the variable inductor of the present invention. It is a schematic block diagram of the comb-tooth electrode which comprises the actuator of FIG. AC is a figure explaining operation | movement of the actuator of FIG. It is a schematic block diagram (plan view) of still another embodiment of the variable inductor of the present invention. A and B are diagrams for explaining the operation of the actuator of FIG. A, B It is a figure explaining the structure and operation | movement of an actuator using an electrostatic action. FIGS. 14A to 14C are diagrams illustrating the configuration and operation of an actuator using the principle of FIG. A and B are circuit configuration diagrams of a VCO (voltage controlled oscillator) to which the variable inductor of the present invention can be applied. It is a figure explaining changing the whole inductance by changing A and B mutual inductance. It is a figure explaining the relationship between the relative position of the thin film coil of A and B 2 layers, and the magnitude | size of a mutual inductance.

Explanation of symbols

1, 20, 30, 40 Variable inductor, 2, 3, 8, 31, 41 Coil, 5, 32, 42 Actuator, 6 Substrate, 7 Support base, 33, 43 First comb electrode, 34, 44 Second Comb electrode, 51 thin film coil, 60 comb electrode

Claims (3)

With multiple thin film coils,
Among the plurality of thin film coils, an actuator is provided for at least one thin film coil,
Wherein the actuator, by bending due to thermal expansion, the thin film in a direction substantially perpendicular to the film plane of the coil to move the thin film coil, the interval of the plurality of thin-film coil in a direction substantially perpendicular to the film surface of the thin film coil A variable inductor characterized by having a configuration in which the current is changed . The variable inductor according to claim 1, wherein the actuator has a structure in which a first wiring layer, an insulating layer, and a second wiring layer are stacked. A plurality of thin-film coils in which spiral coils are formed in a rectangular shape as a whole ,
Actuators are provided near the four corners of at least one thin film coil among the plurality of thin film coils,
The actuator includes a fixed first comb-tooth electrode and movable second comb-tooth electrodes arranged alternately, and the first comb-tooth electrode and the second comb-tooth electrode By applying a potential difference therebetween, the second comb electrode moves, and the thin film coil moves in a direction substantially parallel to the film surface of the thin film coil.
The variable inductor , wherein the longitudinal direction of the first comb-tooth electrode and the second comb-tooth electrode is formed obliquely with respect to the longitudinal direction and the lateral direction of the rectangular thin-film coil .

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