TUNABLE FILTER APPARATUS

CROSS-REFERENCE TO RELATED APPLICATIONS This application is based upon and claims the benefit of priority from prior Japanese Patent Application No.

2013-240403, filed November 20, 2013, the entire contents of which are incorporated herein by reference.

FIELD

Embodiments described herein relate generally to a tunable filter apparatus capable of accurately adjusting the frequency characteristics of a filter at high speed.

BACKGROUND

A filter apparatus used for a communication device system or the like, more specifically, a bandpass filter is required to have frequency characteristics including a very sharp skirt characteristic so that no interference occurs between adjacent frequency bands by passing only a desired frequency band. To construct infrastructure which can flexibly cope with a change in system, a bandpass filter capable of changing the frequency characteristics such as the center frequency and bandwidth is essential.

In consideration of such situation, there has

conventionally been proposed a tunable filter apparatus capable of setting the frequency characteristics to be variable by changing the gap length between a filter substrate and a dielectric. BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view showing the arrangement of a tunable filter apparatus according to the first embodiment ;

FIG. 2 is a front view showing a tunable filter apparatus according to the first embodiment ,-

FIG. 3A is a view for explaining the operation of a tunable mechanism according to the first embodiment ,-

FIG. 3B is a view for explaining the operation of the tunable mechanism according to the first embodiment;

FIG. 3C is a view for explaining the operation of the tunable mechanism according to the first embodiment;

FIG. 4 is a view showing the configuration of a control system of the tunable mechanism constituted by using a distortion sensor according to the first

embodiment ;

FIG. 5 is a perspective view showing the arrangement of a tunable filter apparatus according to a modification of the first embodiment;

FIG. 6 is a front view showing the tunable filter apparatus according to the modification of the first embodiment ;

FIG. 7 is a perspective view showing the arrangement of a tunable filter apparatus according to the second embodiment ;

FIG. 8 is a front view showing the tunable filter apparatus according to the second embodiment;

FIG. 9A is a view for explaining the operation of a tunable mechanism used for the tunable filter apparatus according to the second embodiment;

FIG. 9B is a view for explaining the operation of the tunable mechanism used for the tunable filter apparatus according to the second embodiment;

FIG. 9C is a view for explaining the operation of the tunable mechanism used for the tunable filter apparatus according to the second embodiment ;

FIG. 10 is a perspective view showing the arrangement of a tunable filter apparatus according to a modification of the second embodiment;

FIG. 11 is a front view showing the tunable filter apparatus according to the modification of the second embodiment ;

FIG. 12 is a view showing the arrangement of a tunable mechanism according to the third embodiment;

FIG. 13 is a view showing the arrangement of a tunable mechanism according to the fourth embodiment;

FIG. 14 is a view showing a practical connection example of a multilayered member according to the fourth embodiment ;

FIG. 15 is a view showing the arrangement of a tunable mechanism according to the fifth embodiment ,-

FIG. 16 is a view showing the arrangement of a tunable mechanism according to the sixth embodiment; and FIG. 17 is a view showing the arrangement of a tunable mechanism according to the seventh embodiment .

DETAILED DESCRIPTION

In general, according to one embodiment, a tunable filter apparatus includes a substrate fixing portion, a filter substrate, a member, a first supporting portion, a driving element, and a second supporting portion. The substrate fixing portion is supported an apparatus base. The filter substrate is provided in part of the substrate fixing portion, and includes a circuit with a resonant element formed by a conductive film. The member includes an opposite surface opposing the circuit, and is formed by at least one of a dielectric, a magnetic material, and a conductive material. The first supporting portion movably supports the member between a first state and a second state. The first state is state in which the opposite surface is close to the circuit. The second state is state in which the opposite surface is farther away from the circuit as compared with the first state. The driving element applies a driving force to the first supporting portion. The second supporting portion connects the first supporting portion and the driving element. The first supporting portion is arranged in the substrate fixing portion. The driving element is arranged on the apparatus base .

Prior to a description of the embodiments, a general tunable filter apparatus will be explained. In the embodiments, a tunable filter apparatus that sets the frequency characteristics to be variable by changing the gap length between a filter substrate and a dielectric is proposed.

A general tunable filter apparatus is configured to drive a dielectric by mainly using a piezoelectric element as a driving element. It is, therefore, possible to relatively readily downsize a tunable mechanism, and obtain high positioning accuracy.

In the general tunable filter apparatus, however, the filter characteristics may become unstable due to the temperature effect caused by heat generated by the

piezoelectric element.

(First Embodiment)

A tunable filter apparatus 1 according to the first embodiment will be described below with reference to

FIGS. 1, 2, 3A, 3B, 3C, and 4. FIG. 1 is a perspective view showing the arrangement of the tunable filter

apparatus 1 according to this embodiment. FIG. 2 is a front view showing the tunable filter apparatus 1.

The tunable filter apparatus 1 includes a cold plate. 2, a superconducting filter substrate 3 that contacts and is fixed to part of the cold plate 2, a dielectric 4 such as alumina or sapphire, tunable mechanisms (#1, #2, and #3) 5, an apparatus base 6, and a refrigerator 7. The

dielectric 4 is attached to the tunable mechanisms (#1, #2, and #3) 5 so as to oppose a circuit (not shown) including a resonant element formed by a superconducting film on the surface of the superconducting filter substrate 3.

The tunable mechanisms (#1, #2, and #3) 5 movably drives the dielectric 4 between the first state in which the dielectric 4 is close to the circuit (not shown) of the superconducting filter substrate 3 and the second state in which the dielectric 4 is farther away from the circuit as compared with the first state. Note that in this

embodiment, the tunable mechanisms (#1, #2, and #3) 5 drive the dielectric 4 in a direction (arrow A) almost

perpendicular to the surface of the superconducting filter substrate 3.

The apparatus base 6 supports the cold plate 2 via, for example, the refrigerator 7. The refrigerator 7 maintains the cold plate 2 in a low-temperature state. The low-temperature state indicates a state in which the cold plate 2 is cooled to a temperature within a range in which the superconducting filter substrate 3 (superconducting film) can be maintained in a superconducting state.

Furthermore, each tunable mechanism 5 includes two piezoelectric elements 8 and 9, a dielectric driving lever 10 for movably supporting and driving the dielectric 4 in the direction of the arrow A, and a piezoelectric driving force transmission lever 11 that is connected to the dielectric driving lever 10 and transmits the driving forces of the piezoelectric elements 8 and 9 to. the

dielectric driving lever 10. Each of the piezoelectric elements 8 and 9 has one terminal fixed to the apparatus base 6 and the other terminal connected and fixed to the piezoelectric driving force transmission lever 11 via a corresponding one of elastic hinges 12 and 13 having an arc-shaped notch

structure. This allows the piezoelectric driving force transmission lever 11 to be movable between the first state in which the piezoelectric driving force transmission lever 11 is close to at least part of the piezoelectric elements 8 and 9 and the second state in which the piezoelectric driving force transmission lever 11 is farther away from the piezoelectric elements 8 and 9 as compared with the first state. In the first embodiment, the piezoelectric driving force transmission lever 11 is movable in the direction of an arrow Al or A2 with respect to the

piezoelectric elements 8 and 9.

The dielectric driving lever 10 has one terminal fixed to the dielectric 4 and the other terminal that contacts and is fixed to the cold plate 2 via an elastic hinge 14. The dielectric driving lever 10 and the piezoelectric driving force transmission lever 11 are mechanically coupled via two elastic hinges 15 and 16 that are arranged to be series-connected.

The tunable filter apparatus 1 shown in FIG. 1 has an arrangement in which three tunable mechanisms (#1, #2, and #3) 5 are arranged. The present invention is not limited to this, and the number of tunable mechanisms 5 and their installation positions are determined according to the circuit conditions of the resonant element (not shown) formed on the superconducting filter substrate 3, and depend on the design of a filter. A gap length G indicates the initial gap length between the superconducting filter substrate 3 and the dielectric 4, and is variable in the direction of the arrow A along with the operation of the piezoelectric elements 8 and 9.

The operation of the tunable filter apparatus 1 will be described next. FIG. 3 is a view for explaining the operation of the tunable mechanism 5. FIG. 3A is a view showing the initial state in which no driving voltages are applied to the piezoelectric elements 8 and 9. FIG. 3B shows an analysis example indicating the overall

deformation when a driving voltage is applied to the piezoelectric element 9 to give a driving displacement x2. FIG. 3C shows an analysis example indicating deformation when a driving voltage is applied to the piezoelectric element 8 to give a driving displacement xl . Furthermore, points a to g are defined in FIG. 3A, and the concept of a displacement magnification operation will be explained below .

In the operation example shown in FIG. 3B, the

displacement magnification functions of the dielectric driving lever 10 and piezoelectric driving force

transmission lever 11 magnify the driving displacement x2 of the piezoelectric element 9 based on a predetermined displacement magnification ratio, thereby causing the dielectric 4 to move in almost the direction of the arrow Al . This can change the gap length G.

More specifically, the tunable mechanism 5 forms a displacement magnification mechanism having a two-stage configuration formed from the first displacement

magnification function of the piezoelectric driving force transmission lever 11 with the point a as the fulcrum, the point b as the power point, and the point d as the point of action, and the second displacement magnification function of the dielectric driving lever 10 with the point e as the fulcrum, the point f as the power point, and the point g as the point of action. With the displacement magnification mechanism having a two-stage configuration, it is possible to obtain a displacement amount larger than that obtained by, for example, a one- stage displacement magnification mechanism of a virtual lever with the point a as the fulcrum, the point b as the power point, and the point g as the point of action.

Under the dimensional conditions in FIGS. 1, 2, 3A, 3B, and 3C, it is possible to obtain about twice the displacement amount of the one-stage displacement

magnification mechanism. The displacement magnification ratio of the piezoelectric driving force transmission lever 11 is about 3.8, and that of the dielectric driving lever 10 is about 2.7, resulting in about 10 as the displacement magnification ratio of the two-stage configuration. On the other hand, since the one-stage displacement magnification ratio of the virtual lever is 5, it is possible to obtain about twice the displacement amount of the one-stage displacement magnification mechanism.

As a result, based on the features of the mechanism capable of readily obtaining a large displacement amount, downsizing of the tunable mechanism can be expected. Note that the concept of the function of the displacement magnification mechanism has been explained above, and no correct moving amount has been indicated. The actual moving amount of the dielectric 4 is not determined based on only the distances between the fulcrum and the force point and point of action, and is largely influenced by the dielectric driving lever 10, the piezoelectric driving force transmission lever 11, and the mechanical rigidities and drive frequencies of the elastic hinges 12 to 16. It is, therefore, necessary to estimate a moving amount by performing fine design evaluation by structure analysis and the like.

In the operation example shown in FIG. 3C, the driving displacement xl of the piezoelectric element 8 is magnified based on a predetermined displacement magnification ratio, thereby causing the dielectric 4 to move in almost the direction of the arrow A2. This can change the gap length G. In the concept of the displacement magnification mechanism at this time, the tunable mechanism 5 forms the first displacement magnification function of the piezoelectric driving force transmission lever 11 by setting the point b as the fulcrum, the point a as the power point, and the point d as the point of action.

As another operation example, the piezoelectric elements 8 and 9 may be driven at the same time. In the concept of the displacement magnification mechanism when so-called push-pull driving is performed, the tunable mechanism 5 forms the first displacement magnification function of the piezoelectric driving force transmission lever 11 by setting the point c as the fulcrum, the points a and b as the power points, and the point d as the point of action.

Note that the elastic hinges 12 to 16 have low

rigidity in at least the movable direction of the

dielectric 4 (the direction of the arrow Al or A2) , and high rigidities in directions other than the movable direction.

FIG. 4 is a view showing the configuration of a control system 18 of the tunable mechanism 5 constituted by using a distortion sensor 17.

The distortion sensor 17 is adhered near the position of the elastic hinge 14. The distortion sensor 17 measures a distortion amount generated by elastic deformation of the elastic hinge 14. Information indicating the measured distortion amount is supplied to the control system 18.

More specifically, a sensor signal of the distortion sensor 17 is supplied to a distortion sensor signal processing circuit 19. The distortion sensor signal processing circuit 19 performs predetermined signal processing on the input sensor signal, and outputs an output signal to a controller 21. The controller 21 obtains an operation signal 22 for the piezoelectric elements 8 and 9 based on the output signal of the

distortion sensor signal processing circuit 19 and a command value input by an operator .

A piezoelectric element driving circuit 23 generates a driving voltage 24a for the piezoelectric element 8 and a driving voltage 24b for the piezoelectric element 9 based on the operation signal 22, and applies the driving

voltages to the piezoelectric elements 8 and 9,

respectively. This can construct dielectric position feedback control of the tunable mechanism 5 for indirectly measuring (estimating) a dielectric position with the distortion amount obtained by the distortion sensor 17.

Therefore, high accuracy of the variable gap length is obtained by correcting the nonlinear characteristics and the influence of the dielectric driving lever 10, the piezoelectric driving force transmission lever 11, and the mechanical rigidities of the elastic hinges 12 to 16. It is also possible to deal with a change in gap length due to the vibration effect and the temperature effect (thermal expansion) caused by heat generated by the piezoelectric elements 8 and 9 and the like along with a change in environmental temperature, long-term driving, and high- speed driving. It can thus be expected that the

positioning stability of the variable gap length further improves .

(Modification of First Embodiment)

FIGS. 5 and 6 each show a tunable filter apparatus 100 according to a modification of the first embodiment.

FIG. 5 is a perspective view showing the arrangement of the tunable filter apparatus 100. FIG. 6 is a front view showing the tunable filter apparatus 100. Note that the tunable filter apparatus 100 has a portion common to the tunable filter apparatus 1 shown in FIGS. 1, 2, 3A, 3B, 3C, and 4. A detailed description of the already described contents will be omitted and only the difference will be explained. The same applies to FIG. 7 and subsequent drawings .

The tunable filter apparatus 100 includes a plurality of columns (#1 and #2) 101 for mechanically coupling a cold plate 2 and an apparatus base 6. This can improve the supporting rigidity of the cold plate 2, and decrease the vibration amplitude of the cold plate 2 caused by an adverse mechanical vibration generated by a refrigerating means, thereby obtaining high accuracy of a variable gap length.

Note that the cold plate 2 is in a predetermined low- temperature state to maintain the superconducting filter substrate 3 in the superconducting state. However, the columns 101 also have predetermined adiabatic characteristics to sufficiently thermally insulate the cold plate 2 from the apparatus base 6 that is not in the low- temperature state but at room temperature. That is, the material properties, shape, dimensions, and the like of each column 101 are configured by general mechanical strength design and thermal design with predetermined mechanical characteristics and sufficient adiabatic

characteristics .

(Second Embodiment)

FIGS. 7, 8, and 9 each show a tunable filter apparatus 200 according to the second embodiment. FIG. 7 is a perspective view showing the arrangement of the tunable filter apparatus 200. FIG. 8 is a front view showing the tunable filter apparatus 200.

The tunable filter apparatus 200 includes a cold plate 2, a superconducting filter substrate 3 that contacts and is fixed on the cold plate 2, a dielectric 4, tunable mechanisms (#1, #2, and #3) 205, an apparatus base 6, and a refrigerator 7. The dielectric 4 is attached to the tunable mechanisms (#1, #2, and #3) 205 so as to oppose a circuit (not shown) including a resonant element formed by a superconducting film on the surface of the

superconducting filter substrate 3.

The tunable mechanisms (#1, #2, and #3) 205 movably drive the dielectric 4 between the first state in which the dielectric 4 is close to the circuit (not shown) of the superconducting filter substrate 3 and the second state in which the dielectric 4 is farther away from the circuit as compared with the first state. Note that in the second embodiment, the tunable mechanisms (#1, #2, and #3) 205 drive the dielectric 4 in a direction (arrow A) almost perpendicular to the surface of the superconducting filter substrate 3.

The apparatus base 6 supports the cold plate 2 via, for example, the refrigerator 7. The refrigerator 7 maintains the cold plate 2 in a low-temperature state.

Furthermore, each tunable mechanism 205 includes two piezoelectric elements 8 and 9, a dielectric driving lever 210 for movably supporting and driving the dielectric 4 in the direction of the arrow A, and a piezoelectric driving force transmission lever 211 that is connected to the dielectric driving lever 210 and transmits the driving forces of the piezoelectric elements 8 and 9 to the

dielectric driving lever 210.

Each of the piezoelectric elements 8 and 9 has one terminal fixed to the apparatus base 6 and the other terminal connected and fixed to the piezoelectric driving force transmission lever 211 via a corresponding one of elastic hinges 212 and 213. Each of the elastic hinges 212 and 213 has an arc-shaped notch structure. Furthermore, the dielectric driving lever 210 has one terminal connected to the piezoelectric driving force transmission lever 211 via two elastic hinges 215 and 216 that are arranged to be series-connected, and the other terminal that contacts and is fixed to the cold plate 2 via an elastic hinge 214. The dielectric 4 contacts and is fixed to the dielectric driving lever 210 at a position between the elastic hinges 214 and 215.

FIG. 9 is a view for explaining the operation of the tunable mechanism 205 used for the tunable filter apparatus 200. FIG. 9A is a view showing the initial state in which no driving voltages are applied to the piezoelectric elements 8 and 9. FIG. 9B shows an analysis example indicating the overall deformation when a driving voltage is applied to the piezoelectric element 9 to give a driving displacement x4. FIG. 9C shows an analysis example

indicating deformation when a driving voltage is applied to the piezoelectric element 8 to give a driving displacement x3.

Referring to FIG. 9A, points a to g are defined, and the concept of a displacement magnification operation and displacement reduction operation will be explained below. In the operation example shown in FIG. 9B, the displacement reduction function (displacement reduction lever) of the dielectric driving lever 210 and the displacement

magnification function (displacement magnification lever) of the piezoelectric driving force transmission lever 211 magnify the driving displacement x4 of the piezoelectric element 9 based on a predetermined displacement

magnification ratio, thereby causing the dielectric 4 to move in almost the direction of an arrow A3. This can change a gap length G.

More specifically, the tunable mechanism 205 forms a two-stage displacement conversion mechanism constituted by the displacement magnification function of the

piezoelectric driving force transmission lever 211 with the point a as the fulcrum, the point b as the power point, and the point d as the point of action, and the displacement reduction function of the dielectric driving lever 210 with the point e as the fulcrum, the point f as the power point, and the point g as the point of action.

While ensuring predetermined adiabatic characteristics with the lever length of the piezoelectric driving force transmission lever 211, it is possible to implement a predetermined driving resolution, and optimize a driving range by the displacement reduction function of the

dielectric driving lever 210 for the displacement amount magnified by the displacement magnification function of the piezoelectric driving force transmission lever 211, thereby almost individually, separately designing the adiabatic characteristics and driving characteristics. The

displacement magnification ratio of the piezoelectric driving force transmission lever 211 is 5, and that of the dielectric driving lever 210 is about 0.6, resulting in about 3 as the displacement magnification ratio of the two- stage arrangement. Consequently, it is possible to

implement function optimization.

In the operation example shown in FIG. 9C, the driving displacement x3 of the piezoelectric element 8 is magnified based on a predetermined displacement magnification ratio, thereby causing the dielectric 4 to move in almost the direction of an arrow A4. This can change the gap length G. In the concept of the displacement magnification mechanism at this time, the tunable mechanism 205 forms the displacement magnification function of the piezoelectric driving force transmission lever 211 by setting the point b as the fulcrum, the point a as the power point, and the point d as the point of action. As another operation example, in the concept of the displacement magnification mechanism when push-pull driving is performed to drive the piezoelectric elements 8 and 9 at the same time, the tunable mechanism 205 forms the displacement magnification function of the piezoelectric driving force transmission lever 211 by setting the point c as the fulcrum, the points a and b as the power points, and the point d as the point of action.

(Modification of Second Embodiment)

FIGS. 10 and 11 each show a tunable filter apparatus 300 according to a modification of the second embodiment. FIG. 10 is a perspective view showing the arrangement of the tunable filter apparatus 300. FIG. 11 is a front view showing the tunable filter apparatus 300.

The tunable filter apparatus 300 includes a plurality of columns (#1 and #2) 301 for mechanically coupling a cold plate 2 and an apparatus base 6. This can improve the supporting rigidity of the cold plate 2, and decrease the vibration amplitude of the cold plate 2 caused by an adverse mechanical vibration generated by a refrigerating means, thereby obtaining high accuracy of a variable gap length. Note that the material properties, shape,

dimensions, and the like of the columns 301 are configured by general mechanical strength design and thermal design with predetermined mechanical characteristics and

sufficient adiabatic characteristics, similarly to the columns 101.

(Third Embodiment)

FIG. 12 is a view showing the arrangement of a tunable mechanism 405 according to the third embodiment.

The tunable mechanism 405 includes a first member 450 integrally formed by the first material properties, and a second member 451 integrally formed by the second material properties, and is configured so that the thermal

conductivity of the first member 450 is higher than that of the second member 451.

The first member 450 is formed from constituent members including a dielectric driving lever 410 and elastic hinges 414, 415, and 416. The second member 451 is formed from constituent members including a piezoelectric driving force transmission lever 411 and elastic hinges 412 and 413. The first member 450 and the second member 451 are connected at a contact fixing surface 452.

According to the aforementioned third embodiment, the first member 450 is configured to have material properties with a thermal conductivity higher than that of the second member 451. Therefore, it is possible to reduce, by excellent adiabatic characteristics of the second member 451, a change in temperature of the dielectric 4 caused by heat generated along with driving of piezoelectric elements 8 and 9, and also stably maintain the dielectric 4 in the low-temperature state by the high thermal conductivity of the first member 450 arranged on a cold plate 2a and thermally coupled to it. It can thus be expected that the temperature stability of the filter characteristics further improves .

Note that the following arrangement (not shown) may be adopted. The first member 450 is formed from constituent members including the dielectric driving lever 410 and the elastic hinge 414, and the second member 451 is formed from constituent members including the piezoelectric driving force transmission lever 411 and the elastic hinges 412, 413, 415, and 416. The first member 450 and the second member 451 are connected at a contact fixing surface.

Alternatively, the constituent members can be replaced without departing from the scope of the constituent

elements of the present invention.

(Fourth Embodiment)

FIG. 13 is a view showing the arrangement of a tunable mechanism 505 according to the fourth embodiment.

In the tunable mechanism 505, part of a piezoelectric driving force transmission lever 511 includes a

multilayered member 511a with respect to a heat

transmission direction. Assume that the heat transmission direction is a direction in which heat generated by driving of piezoelectric elements 8 and 9 is transmitted to the piezoelectric driving force transmission lever 511 via elastic hinges 512 and 513, and flows to a dielectric driving lever 510 via elastic hinges 515 and 516. The dielectric driving lever 510 is connected to a cold plate 2a via an elastic hinge 514. The multilayered member 511a may have a multilayered structure with the same material properties, a multilayered structure with different

material properties, or a combination thereof, and forms a high contact thermal resistance by the multilayered

structure.

Referring to FIG. 14, for example, the multilayered member 511a is made of a material A, a material B having material properties different from those of the material A, the material A, the material A, and the material A, which form a plurality of divided members. With a combination of different materials A and B, it is possible to obtain a contact thermal resistance. Even with a combination of the materials A having the same material properties, it is possible to obtain a contact thermal resistance.

As described above, according to the fourth

embodiment, the adiabatic characteristics, that is, the heat insulation performance of the piezoelectric driving force transmission lever 511 further improve, and it is possible to reduce, at a high level, a change in

temperature of a dielectric 4 caused by heat generated along with driving of the piezoelectric elements 8 and 9. It can thus be expected that the temperature stability of the filter characteristics further improves.

(Fifth Embodiment)

FIG. 15 is a view showing the arrangement of a tunable mechanism 605 according to the fifth embodiment. The tunable mechanism 605 includes elastic hinges 612, 613,

614, 615, and 616 having a leaf spring structure, instead of the arc-shaped elastic hinges.

According to the fifth embodiment, such elastic hinge is readily designed to have low rotation spring rigidity, as compared with the arc-shaped elastic hinge, thereby increasing the variable width of a gap length G.

(Sixth Embodiment)

FIG. 16 is a view showing the arrangement of a tunable mechanism 705 according to the sixth embodiment.

The tunable mechanism 705 includes leaf spring members

712a, 713a, 714a, 715a, and 716a respectively forming elastic hinges 712, 713, 714, 715, 716 having a leaf spring structure. Each of the leaf spring members 712a and 713a has one terminal that contacts and is fixed to a

corresponding one of pedestals 720 and 721 respectively provided in the piezoelectric elements 8 and 9, and the other terminal that contacts and is fixed to a piezoelectric driving force transmission lever 711.

The leaf spring member 714a has one terminal that contacts and is fixed to a pedestal 722 provided on a cold plate 2a, and the other terminal that contacts and is fixed to a dielectric driving lever 710. Furthermore, the leaf spring members 715a and 716a are arranged in series via a connecting member 723. The leaf spring members 715a and 716a have one terminal that contacts and is fixed to the dielectric driving lever 710, and the other terminal that contacts and is fixed to the piezoelectric driving force transmission lever 711.

As described above, according to the sixth embodiment, since the dielectric driving lever 710, the piezoelectric driving force transmission lever 711, and the leaf spring members 712a, 713a, 714a, 715a, and 716a are formed from separate members, it is possible to select material

properties appropriate for the respective roles, thereby- implementing high performance of the tunable mechanism 705.

That is, the thermal conductivity of the dielectric driving lever 710 is set to be higher than that of the piezoelectric driving force transmission lever 711. It is possible to reduce, by excellent adiabatic characteristics of the piezoelectric driving force transmission lever 711, a change in temperature of the dielectric 4 caused by heat generated along with driving of piezoelectric elements 8 and 9, and also stably maintain the dielectric 4 in the low- temperature state by the high thermal conductivity of the dielectric driving lever 710 arranged on a cold plate 2a and thermally coupled to it. It can thus be expected that the temperature stability of the filter

characteristics further improves.

It is possible to select, for the leaf spring members

712a, 713a, 714a, 715a, and 716a, material properties appropriate for the elastic hinges 712, 713, 714, 715, and 716 without any influence of selection of material

properties for the dielectric driving lever 710 and

piezoelectric driving force transmission lever 711. It is, therefore, possible to improve or optimize the strength reliability along with the deformation operation of the elastic hinges 712, 713, 714, 715, and 716. As a result, it can be expected that the operational reliability of the filter apparatus improves.

(Seventh Embodiment)

FIG. 17 is a view showing the arrangement of a tunable mechanism 805 according to the seventh embodiment. Note that in FIG. 17, the same reference numerals as those in FIG. 3 denote the same parts and a detailed description thereof will be omitted.

The tunable mechanism 805 includes an elastic hinge 814 having one terminal connected to a cold plate 2a and the other terminal integrally formed with a dielectric driving lever 810. Note that the tunable mechanism 805 is arranged so that an opposite surface 4a of a dielectric 4 arranged to oppose a filter substrate almost coincides with the rotation center of an elastic hinge 814. This forms the displacement magnification mechanism of the dielectric driving lever 810 with a point e as the fulcrum, a point f as the power point, and a point g as the point of action. The dielectric 4 moves in the direction of an arrow A along with driving of piezoelectric elements 8 and 9. At this time, since the opposite surface 4a of the dielectric 4 is arranged so as to almost coincide with the rotation center of the elastic hinge 814, the opposite surface 4a of the dielectric 4 along with driving of the piezoelectric elements 8 and 9 can change a gap length G while

maintaining a parallel state with respect to a

superconducting filter substrate 3, as compared with the above-described tunable mechanisms 5, 205, 405, and 505 which are not arranged so that the opposite surfaces of the dielectrics 4 coincide with the rotation centers of the elastic hinges 14, 214, and 414, respectively. This can reduce a horizontal shift between the dielectric 4 and the circuit on the superconducting filter substrate 3, thereby providing more stable filter characteristics.

(Other Embodiments)

In the tunable mechanisms 5, 205, 405, 505, 605, 705, and 805 described in the first to seventh embodiments shown in FIGS. 1, 2, 3A, 3B, 3C, 4, 5, 6, 7, 8, 9A, 9B, 9C, 10, 11, 12, 13, 14, 15, 16, and 17, the two piezoelectric elements 8 and 9 are used. However, one of the

piezoelectric elements may be used. In this case, instead of the other piezoelectric element, another member may be arranged to connect and fix the elastic hinge and the apparatus base, or a member integrally formed with the elastic hinge or apparatus base may be used to connect and fix the elastic hinge and the apparatus base. The number of piezoelectric elements is decided based on design specifications such as the drive frequency, and design conditions such as the mechanical strength of a

piezoelectric element.

As the elastic hinges 12, 13, 14, 15, 16, 212, 213,

214, 215, 216, 412, 413, 414, 415, 416, 612, 613, 614, 615, 616, 712, 713, 714, 715, 716, and 814, elastic hinges having an arc -shaped notch structure or leaf spring

structure are used. The present invention is not limited to them. For example, the elastic hinge may have a cone- shaped notch structure, or may be formed from an elastic element having at least lower rigidity in the movable direction of the dielectric than in directions other than the movable direction, and may be deformed, as needed, without departing from the spirit of the arrangement.

Furthermore, the elastic hinge may be formed from an elastic element having at least high rigidity in the operation displacement direction in which the driving force of the piezoelectric element is transmitted, as compared with rigidities in directions other than the operation displacement direction, and may be deformed, as needed, without departing from the spirit of the arrangement. With such arrangement, the first connecting member that contacts and is fixed to the dielectric, and is connected to the substrate fixing portion via the first elastic element is included, and thus the motion of the dielectric along with the operation of the driving element includes no mechanical sliding. It is, therefore, possible to implement high accuracy of the variable gap length by removing the strong nonlinear characteristics caused by a static friction force, and reduce heat generated due to sliding friction heat at the time of high-speed driving. It can thus be expected that the temperature stability of the filter characteristics improves.

According to each of the aforementioned embodiments, it is possible to adjust the gap length at predetermined speed with predetermined accuracy by lowering the

temperature of the dielectric, and improving the adiabatic characteristics of the dielectric and driving element, that is, by improving the heat isolation performance, and magnifying or reducing the operation displacement of a driving element. It is then possible to provide a tunable filter apparatus according to stabilization of the filter characteristics and high-speed, high-accuracy control of a variable gap length while suppressing the temperature effect .

By providing a high-speed tunable filter apparatus, it is possible to flexibly cope with the frequency

characteristics (the center frequency, bandwidth, skirt characteristic, and the like) of a bandpass filter

necessary for an information communication device system in accordance with various application specifications. In addition, especially, a high-speed tunable superconducting filter apparatus can be expected to be used as a technique of solving the frequency interference in a next-generation high-speed mass data communication system.

Furthermore, in each of the aforementioned

embodiments, a case in which the dielectric 4 is used has been explained. Any member which changes the magnetic field distribution or electric field distribution in a space near the superconducting filter substrate 3 may be used, and a magnetic material such as ferrite or a

conductor such as copper can be used as a material . In each of the aforementioned embodiments, the superconducting filter substrate 3 has been exemplified. However, a filter substrate other than the superconducting filter substrate 3 may be used.

While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions.

Indeed, the novel embodiments described herein may be embodied in a variety of other forms; furthermore various omissions, substitutions and changes in the form of the embodiments described herein may be made without departing from the spirit of the inventions. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit the inventions.