Abstract:
A resonator pattern made of superconductive material is disposed over a first surface of a base substrate made of dielectric. An adjustment substrate made of dielectric is disposed facing the first surface at a distance from the first surface. The adjustment substrate is supported by a support mechanism for supporting the adjustment substrate in such a manner capable of changing an angle between the first surface and a surface of the adjustment substrate facing the base substrate. A superconductive filter is provided which can shift a center frequency of a filter band and suppress disturbance of a waveform of a filter characteristic, with a simple method.

Description:
CROSS REFERENCE TO RELATED APPLICATION  
       [0001]     This application is based on and claims priority of Japanese Patent Application No. 2006-265292 filed on Sep. 28, 2006, the entire contents of which are incorporated herein by reference.  
       BACKGROUND OF THE INVENTION  
       [0002]     A) Field of the Invention  
         [0003]     The present invention relates to a superconductive filter and a filter characteristic adjusting method, and more particularly to a superconductive filter and a filter characteristic adjusting method, capable of changing a filter bandwidth without changing the shape of resonator patterns formed on a dielectric substrate.  
         [0004]     B) Description of the Related Art  
         [0005]     A recent spread of mobile phones has made it essential to use high speed and large capacity transmission technologies. A superconductor has a very small surface resistance even in a high frequency area, as compared to a general electric conductor. Therefore, the superconductor is suitable for the material of a conductive pattern of a planar circuit type filter. The discovery of high temperature oxide superconductors and the development of refrigerators have greatly mitigated an issue of cooling a superconductor.  
         [0006]     JP-A-HEI-10-209722 discloses a technique of adjusting impedance by forming a dielectric film on a strip line made of superconductive material or trimming a width of the strip line. JP-A-2004-64359 discloses a technique of changing a filter band-pass characteristic by controlling temperature of a superconductive filter. JP-A-2005-354657 discloses a technique of adjusting a filter characteristic by moving up or down an adjustment plate made of a normal conductor or a superconductor and disposed above a superconductive filter pattern.  
         [0007]     JP-A-2002-204102 discloses a technique of adjusting a filter characteristic by moving up or down a dielectric plate disposed above a superconductive filter pattern by using a piezoelectric actuator. A superconductive filter disclosed in JP-A-2002-57506 is constituted of a plurality of half wavelength hair pin type patterns disposed along a straight line generally at an equal pitch. Each hair pin type pattern is slid transversally by a piezoelectric actuator to adjust a coupling coefficient of respective stages.  
       SUMMARY OF THE INVENTION  
       [0008]     With the method disclosed in JP-A-HEI-10-209722, the dielectric film is formed on the strip line or the width of the strip line is trimmed. It is therefore necessary to add a dielectric film forming process and a laser abrasion process. The method disclosed in JP-A-2004-64359 requires a temperature adjusting apparatus.  
         [0009]     The methods disclosed in JP-A-2005-354657 and JP-A-2002-204102 can change the center frequency of a passband width simply by moving up or down the adjustment plate. However, there is a case in which the waveform of a filter characteristic varies from an ideal waveform as the center frequency is shifted.  
         [0010]     The method disclosed in JP-A-2002-57506 can adjust the characteristic of a filter having hair pin type patterns coupled at multiple stages. This method cannot be applied to a filter having other structures.  
         [0011]     It is an object of the present invention to provide a superconductive filter capable of shifting the center frequency of a filter bandwidth while suppressing disturbance of the waveform of a filter characteristic. It is another object of the present invention to provide a filter characteristic adjusting method capable of shifting the center frequency of a filter bandwidth while suppressing disturbance of the waveform of a filter characteristic.  
         [0012]     According to one aspect of the present invention, there is provided a superconductive filter comprising:  
         [0013]     a base substrate made of dielectric;  
         [0014]     a resonator pattern made of superconductive material and formed over a first surface of the base substrate;  
         [0015]     an adjustment substrate made of dielectric and disposed facing the first surface at a distance from the first surface; and  
         [0016]     a support mechanism for supporting the adjustment substrate in such a manner capable of changing an angle between the first surface and a surface of the adjustment substrate facing the base substrate.  
         [0017]     According to another aspect of the present invention, there is provided a method of adjusting filter characteristic of a superconductive filter comprising:  
         [0018]     a base substrate made of dielectric;  
         [0019]     a resonator pattern made of superconductive material and formed over a first surface of the base substrate; and  
         [0020]     an adjustment substrate made of dielectric and disposed facing the first surface at a distance from the first surface, wherein the method comprises a step of:  
         [0021]     changing an attitude of the adjustment substrate with reference to the first surface of the base substrate.  
         [0022]     The filter characteristic can be adjusted by changing an angle between the first surface and a surface of the adjustment substrate facing the base substrate. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0023]      FIGS. 1A  to  1 C are cross sectional views of a superconductive filter according to a first embodiment.  
         [0024]      FIG. 2A  is a plan view of a base substrate of the superconductive filter of the first embodiment,  FIG. 2B  is a plan view of an additional substrate, and  FIG. 2C  is a plan view of the base substrate and the additional substrate stacked on the base substrate.  
         [0025]      FIG. 3A  is a cross sectional view of a superconductive filter according to a first reference example, and  FIG. 3B  is a graph showing transmission and reflection characteristics of the filter.  
         [0026]      FIG. 4A  is a cross sectional view of a superconductive filter according to a second reference example, and  FIG. 4B  is a graph showing transmission and reflection characteristics of the filter.  
         [0027]      FIG. 5A  is a cross sectional view of the superconductive filter of the first embodiment, and  FIG. 5B  is a graph showing transmission and reflection characteristics of the filter.  
         [0028]      FIG. 6A  is a front view of a superconductive filter according to a second embodiment, and  FIG. 6B  is a cross sectional view thereof.  
         [0029]      FIG. 7  is a cross sectional view of an adjusting apparatus for a superconductive filter.  
         [0030]      FIGS. 8A  to  8 C are plan views showing other examples of the structure of a resonator pattern.  
         [0031]      FIG. 9A  is a plan view of a superconductive filter according to a third embodiment, and  FIG. 9B  is a cross sectional view thereof taken along one-dot chain line B 9 -B 9  shown in  FIG. 9A .  
         [0032]      FIGS. 10A and 10B  are a cross sectional view and a plan view, respectively, of an actuator used for the superconductive filter of the third embodiment.  
         [0033]      FIG. 11  is a block diagram showing a control system for the superconductive filter of the third embodiment.  
         [0034]      FIGS. 12A  to  12 E are cross sectional plan views showing other examples of the structure of the superconductive filter of the third embodiment. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0035]      FIG. 1A  is a cross sectional view of a superconductive filter according to the first embodiment.  FIGS. 1B and 1C  are a cross sectional view taken along one-dot chain line B 1 -B 1  shown in  FIG. 1A  and a cross sectional view taken along one-dot chain line C 1 -C 1  shown in  FIG. 1A , respectively. A cross sectional view taken along one-dot chain lines A 1 -A 1  shown in  FIGS. 1B and 1C  corresponds to  FIG. 1A .  
         [0036]     A base substrate  10  is disposed on the bottom of a main body  30 A of a package  30 . Resonator patterns are formed on the front surface of the base substrate  10  and a ground film  15  is formed on the back surface. The ground film  15  contacts the bottom of the package main body  30 A. An additional substrate  17  is disposed on the base substrate  10 .  
         [0037]     The package main body  30 A is a container having a cuboid shape whose top is opened. This opening is closed by a ceiling plate  30 B. The package main body  30 A and ceiling plate  30 B constitute the package  30  defining an inner closed space. The package  30  is made of oxygen free copper. Instead of oxygen free copper, the package may be made of pure aluminum, aluminum alloy, copper alloy or the like. The package may be made of kovar, invar,  42  alloy or the like having a thermal contraction coefficient near to that of the base substrate  10 .  
         [0038]      FIG. 2A  is a plan view of the base substrate  10 . The base substrate  10  is made of dielectric such as single crystal MgO, has a rectangle plan shape with a longer side length of 36 mm and a shorter side length of 22 mm, and has a thickness of 0.5 mm. Resonator patterns  13  and  14  having a circular shape with a diameter of about 12.8 mm and a thickness of 500 nm are formed on the surface of the base substrate  10 , being arranged parallel to the longer side. Signal input/output feeders  11  and  12  are coupled to the resonator pattern  13 . A line width of each of the feeders  11  and  12  is 0.5 mm and the width of an end portion of each of the feeders  11  and  12  facing the resonator pattern  13  is broadened. The feeder  11  is disposed along a first virtual straight line L 1  passing through the centers of the resonator patterns  13  and  14 . The other feeder  12  is disposed along a second virtual straight line L 2  crossing the first virtual straight line L 1  at a right angle and passing through the center of the resonator pattern  13 . Position alignment marks  16  are formed on the surface of the base substrate  10  at predetermined positions.  
         [0039]     These patterns are made of Y—Ba—Cu—O based superconductive material (hereinafter, represented by YBCO). The patterns may be made of oxide superconductive material other than YBCO, for example, R—Ba—Cu—O based material (R is Nb, Ym, Sm or Ho), Bi—Sr—Ca—Cu—O based material, Pb—Bi—Sr—Ca—Cu—O based material and CuBa p Ca q Cu r O x  based material (1.5&lt;p&lt;2.5, 2.5&lt;q&lt;3.5, 3.5&lt;r&lt;4.5) or the like. The ground film  15  is formed on the whole back surface of the base substrate  10 .  
         [0040]     In the following, description will be made on a manufacture method for the base substrate  10 , resonator patterns  13  and  14 , feeders  11  and  12  and ground film  15 .  
         [0041]     First, a film of YBCO is formed on both surfaces of a single crystal MgO substrate having a diameter of 2 inches (50.8 mm) and a thickness of 0.5 mm, by laser vapor deposition. The YBCO film on one surface is patterned by usual photolithography techniques to form the resonator patterns  13  and  14 , feeders  11  and  12  and position alignment marks  16 . An electrode is formed on the surface of the end portion of each of the feeders  11  and  12  on the side opposite to the resonator pattern  13 , by a lift-off method. The electrode is made of a lamination of a Cr film, a Pd film and an Au film laminated in this order. Ag is vapor-deposited on the whole surface of the YBCO film formed on the opposite surface (back surface). Lastly, the MgO substrate is cut into a predetermined size with a dicing saw.  
         [0042]      FIG. 2B  is a plan view of the additional substrate  17 . The additional substrate  17  is made of dielectric such as LaAlO 3 , has a rectangle plan shape with a longer side length of 33 mm and a shorter side length of 20 mm, and has a thickness of 0.5 mm. Namely, the additional substrate  17  is slightly smaller than the base substrate  10 . An additional pattern  18  is formed on the surface of the additional substrate  17 , having a diameter of about 2.8 mm and a thickness of 500 nm. Position alignment marks  19  are formed at predetermined positions. These patterns are made of superconductive material such as YBCO.  
         [0043]     Next, description will be made on a manufacture method for the additional substrate  17  and additional pattern  18 .  
         [0044]     First, a YBCO film having a thickness of 500 nm is formed on one surface of a LaAlO 3  substrate having a diameter of 2 inches (50.8 mm) and a thickness of 0.5 mm. The YBCO film is patterned by usual photolithography techniques to form the additional pattern  18  and position alignment marks  19 . Lastly, the substrate is cut into a predetermined size with a dicing saw.  
         [0045]      FIG. 2C  is a plan view showing the base substrate  10  and additional substrate  17  stacked on the base substrate  10 . These two substrates are aligned in position by superposing the position alignment marks  16  formed on the base substrate  10  upon the position alignment marks  19  formed on the additional substrate  17 . In this state, the additional pattern  18  is superposed upon the outer circumferential line of the resonator pattern  14  at a position spaced from the first virtual straight line L 1 . For example, the additional pattern  18  is disposed at a cross point between a straight line extending from the center of the resonator pattern  14  at 45 degrees to the first virtual straight line L 1  and the outer circumferential line of the resonator pattern  14 . The end portions of the feeders  11  and  12  are not in contact with the additional substrate  17 , but are exposed.  
         [0046]     Description will continue reverting to  FIGS. 1A  to  1 C. The base substrate  10  and additional substrate  17  are loaded in the package main body  30 A in the state maintaining the positional relation shown in  FIG. 2C . The positions of the base substrate  10  and additional substrate  17  are fixed by retainer springs  38 . The surface of the package main body  30 A is plated with gold.  
         [0047]     An adjustment substrate  20  is disposed above the additional substrate  17 . The adjustment substrate  20  is made of dielectric such as LaAlO 3 , has a rectangle plan shape with a longer side length of 36 mm and a shorter side length of 22 mm, and has a thickness of 0.5 mm. Namely, the adjustment substrate  20  has the same size as that of the base substrate  10 .  
         [0048]     The adjustment substrate  20  is supported by the package main body  30 A via a support shaft  21 , facing the additional substrate  17 . The support shaft  21  is made of dielectric having a dielectric constant lower than that of the adjustment substrate  20 . The support shaft  21  is disposed crossing the longer sides of the adjustment substrate  20  at a right angle and passing through the centers of the longer sides, and fixed to the surface of the adjustment substrate  20  on the side opposite to the surface facing the additional substrate  17 .  
         [0049]     The support shaft  21  protrudes to the outside of the package main body  30 A via through holes  37  formed in the wall of the package main body  30 A. As the support shaft  21  is rotated, the attitude of the adjustment substrate  20  changes in a way of changing an angle between the surface of the adjustment substrate  20  facing the additional substrate  17  and the surface of the base substrate  10 .  
         [0050]     An input connector  35  and an output connector  36  are mounted on the sidewalls of the package main body  30 A. A center conductor of the input connector  35  and a center conductor of the output connector  36  are connected to the feeders  11  and  12 , respectively, via Au wires having a diameter of 25 μm. An Au ribbon or an Al wire may be used instead of the Au wire. They may be connected to the feeders  11  and  12  by bonding or using solder.  
         [0051]     In the superconductive filter of the first embodiment, the resonator pattern  13  constitutes a first stage disc type resonator, and the other resonator pattern  14  constitutes a second stage disc type resonator. The additional pattern  18  superposed upon the outer circumferential line of the resonator pattern  14  releases degeneracy of electromagnetic field modes perpendicular to each other. In the result, resonance frequencies are separated and the superconductive filter operates as a dual mode filter.  
         [0052]     The center frequency and a degree of interference between electromagnetic field modes perpendicular to each other (coupling), i.e., a bandwidth depend on a mutual positional relation between the resonance pattern  14  and additional pattern  18 . For example, as the additional pattern  18  moves toward the outside of the resonator pattern  14 , coupling becomes strong and the bandwidth becomes broad. Conversely, as the additional pattern  18  moves toward the inside of the resonator pattern  14 , coupling becomes weak and the bandwidth becomes narrow. In order to realize resonance in the dual mode, the additional pattern  18  and resonator pattern  14  are required not to place in a concentric fashion.  
         [0053]     The superconductive filter of the first embodiment has a target center frequency of 4 GHz and a target bandwidth of 0.08 GHz.  
         [0054]     Next, with reference to  FIGS. 3A  to  5 B, description will be made on a function of the adjustment substrate  20  of the superconductive filter of the first embodiment.  
         [0055]      FIG. 3A  is a cross sectional view of a superconductive filter in which adjustment substrate  20  is not disposed. This superconductive filter has the same structure as that of the superconductive filter of the first embodiment, excepting that the adjustment substrate  20  is not disposed.  
         [0056]      FIG. 3B  shows transmission and reflection characteristics of the superconductive filter shown in  FIG. 3A . The characteristics were measured under the condition that the superconductive filter was cooled to 70 K. The abscissa represents a frequency in the unit of “GHz” and the ordinate represents signal intensity in the unit of “dB”. This relation is also applied to the graphs shown in  FIGS. 4B and 5B  to be described later. Curves T 1  and R 1  shown in  FIG. 3B  represent intensities of transmission and reflection waves, respectively. As seen from  FIG. 3B , the center frequency is about 4.03 GHz shifted by about 0.03 GHz from the target center frequency.  
         [0057]      FIG. 4A  is a cross sectional view of a superconductive filter in which the adjustment substrate  20  is disposed in parallel to the surface of the base substrate  10 . A height from the upper surface of the additional substrate  17  to the adjustment substrate  20  was set to 3.5 mm.  
         [0058]      FIG. 4B  shows transmission and reflection characteristics of the superconductive filter shown in  FIG. 4A . Curves T 2  and R 2  shown in  FIG. 4B  represent intensities of transmission and reflection waves, respectively. The center frequency lowers slightly and comes close to the target center frequency. However, waveforms of the transmission and reflection characteristics are distorted and symmetry thereof is lost.  
         [0059]      FIG. 5A  is a cross sectional view of the superconductive filter of the first embodiment in which the adjustment substrate  20  is slanted by 5° to raise the edge on the side of the first stage resonator pattern  13 . A height from the upper surface of the additional substrate  17  to the center of the adjustment substrate  20  was set to 3.5 mm.  
         [0060]      FIG. 5B  shows transmission and reflection characteristics of the superconductive filter shown in  FIG. 5A . Curves T 3  and R 3  shown in  FIG. 5B  represent intensities of transmission and reflection waves, respectively. The center frequency is nearly the target center frequency of 4 GHz. The waveforms of the transmission and reflection characteristics maintain almost symmetry.  
         [0061]     The center frequency can be shifted by disposing the adjustment substrate  20  in parallel to the base substrate  10  and additional substrate  17  and adjusting a distance between the adjustment substrate  20  and additional substrate  17 . However, if the distance only is adjusted without changing the attitude of the adjustment substrate  20 , the waveforms of the transmission and reflection characteristics are distorted as shown in  FIG. 4B . By changing the attitude of the adjustment substrate  20 , the center frequency can be shifted while suppressing distortion of the waveforms.  
         [0062]      FIG. 6A  is a front view of a superconductive filter according to the second embodiment, and  FIG. 6B  is a cross sectional view taken along one-dot chain line B 6 -B 6  shown in  FIG. 6A . Description will be made by paying attention to different points from the superconductive filter of the first embodiment shown in  FIGS. 1A  to  2 C, and it is omitted to describe the components having the same structure as that of the superconductive filter of the first embodiment.  
         [0063]     Slits  32  are formed in a pair of sidewalls of the package  30 , and the support shaft  21  protrudes to the outside of the package  30  via the slits  32 . The inner circumferential surface of each slit  32  includes a guide surface extending along a direction perpendicular to the surface of the base substrate  10 . The support shaft  21  is guided by the guide surfaces and can move along a direction (up/down direction) with respect to a height from the base substrate  10  to the support shaft  21 .  
         [0064]     In the sidewalls of the package  30 , through holes  45  extending from the upper ends of the slits  32  to the upper surfaces of the package  30  are formed, and recesses  46  having bottoms and extending from the lower ends of the slits  32  to some depth are formed. A part of a coil spring  40  is inserted into the recess  46  and a remaining part thereof is disposed in the slit  32  to support the support shaft  21 . An adjusting screw  42  is inserted into the through hole  45  and a top end of the adjusting screw contacts the support shaft  21  in the slit  32 . By adjusting an insertion depth of the adjusting screw  42 , a height to the end of the support shaft  21  can be changed. The adjustment substrate  20  can be tilted by setting opposite ends of the support shaft  21  to different heights.  
         [0065]     In the second embodiment, a height to the adjustment substrate  20  can be adjusted by maintaining the attitude thereof unchanged. Further, the adjustment substrate  20  can be tilted not only in one direction but also in mutually perpendicular two directions. It is therefore possible to increase the degree of freedom of adjusting the center frequency and bandwidth of the superconductive filter.  
         [0066]      FIG. 7  is a cross sectional view of an adjusting apparatus for the superconductive filters of the first and second embodiments. A superconductive filter  1  is accommodated in an adiabatic vacuum container  50 . The adiabatic vacuum container  50  includes a lower container having an upper opening and an upper container having a lower opening. By abutting the openings of both the containers upon each other, a tightly air-shielded space can be defined. By involving an O ring between both the containers, an inner vacuum degree can be maintained.  
         [0067]     The superconductive filter  1  is held on a cold plate  53  disposed in the adiabatic vacuum container  50 . The cold plate  53  is thermally coupled to a cold head of a refrigerator, and cooled to a temperature at which the superconductive filter takes a superconductive phase. A vacuum pump  52  evacuates the inside of the adiabatic vacuum container  50 .  
         [0068]     Connectors  58  and  59  are mounted in the wall of the adiabatic vacuum container  50 . The input connector  35  of the superconductive filter  1  is coupled to a network analyzer  65  via a coaxial cable  60  in the container, the connector  58  and a coaxial cable  60  outside the container. The output connector  36  of the superconductive filter  1  is coupled to the network analyzer  65  via a coaxial cable  60  in the container, the connector  59  and a coaxial cable  60  outside the container.  
         [0069]     A height adjusting driver  55  passes through the upper wall of the adiabatic vacuum container  50  and is inserted into the container. The distal end of the driver is meshed with the adjusting screw  42  of the superconductive filter  1 . An attitude adjusting driver  56  passes through the sidewall of the adiabatic vacuum container  50  and is inserted into the container. The distal end of the driver couples the end of the support shaft  21  via a flexible coupling tube  57 .  
         [0070]     A height to the end of the support shaft  21  can be changed by adjusting an insertion depth of the adjusting screw  42  by using the height adjusting driver  55 . The attitude of the adjustment substrate  20  can be changed by rotating the support shaft  21  using the attitude adjusting driver  56 .  
         [0071]     Desired filter characteristics can be obtained by adjusting the height to the adjustment substrate  20  and the attitude of the adjustment substrate  20  using the height adjusting driver  55  and attitude adjusting driver  56  while the center frequency and the waveforms of the transmission and reflection characteristics of the superconductive filter  1  are observed with the network analyzer  65 .  
         [0072]      FIGS. 8A  to  8 C show other examples of the structure of the resonator pattern.  
         [0073]     In the example of the structure shown in  FIG. 8A , a hair pin type filter pattern  71  is formed on the surface of a base substrate  70 . Feeders  72  and  73  are coupled to opposite ends of the hair pin type filter pattern.  
         [0074]     In the example of the structure shown in  FIG. 8B , a circular resonator pattern  78  is formed on the surface of a base substrate  75 , the pattern having a notch  79 . Feeders  76  and  77  are coupled to the resonator pattern  78 . The feeders  76  and  77  are disposed respectively on lines extending from a pair of radii constituting a sector having a center angle of 90°. The notch  79  is disposed at a position facing the feeders  76  and  77  across the center of the resonator pattern  78 . Since the notch  79  is formed, dual mode resonances are generated in the resonator pattern  78 .  
         [0075]     In the example of the structure shown in  FIG. 8C , a circular resonator pattern  81  is formed on the surface of a base substrate  80 . Feeders  82  and  83  are coupled to the resonator pattern  81 . An additional substrate  84  is disposed on the base substrate  80 , and a circular additional pattern  85  is formed on the surface of the additional substrate  84 . The feeders  82  and  83  and additional pattern  85  are disposed at positions corresponding to those of the feeders  76  and  77  and notch  79  shown in  FIG. 8B .  
         [0076]     Also in the superconductive filters having the resonator patterns shown in  FIGS. 8A  to  8 C instead of the resonator patterns of the superconductive filters of the first and second embodiments, the center frequency can be shifted by adjusting the attitude of the adjustment substrate  20 , while a change in the waveforms of the transmission and reflection characteristics is suppressed.  
         [0077]     The resonator patterns of the superconductive filters of the first and second embodiments and the resonator pattern shown in  FIG. 8C  do not have a curved portion having a small curvature of radius and a sharp corner. If curved portions or sharp corners are formed, current concentrates upon the curved portion or sharp corner, and the superconductive phase may not be maintained because of heat generation or the like. The resonator patterns of the superconductive filters of the first and second embodiments and the resonator pattern shown in  FIG. 8C  can suppress local current concentration so that these resonator patterns are suitable for high power filters.  
         [0078]     With reference to  FIGS. 9A  to  11 , description will be made on a superconductive filter according to the third embodiment.  
         [0079]      FIG. 9A  is a cross sectional view of the superconductive filter of the third embodiment, and  FIG. 9B  is a cross sectional view taken along one-dot chain line B 9 -B 9  shown in  FIG. 9A . A cross sectional view taken along one-dot chain line A 9 -A 9  shown in  FIG. 9B  corresponds to the cross sectional view shown in  FIG. 9A . Description will be made by paying attention to different points from the superconductive filter of the first embodiment shown in  FIGS. 1A  to  1 C, and it is omitted to describe the components having the same structure as that of the superconductive filter of the first embodiment.  
         [0080]     In the first embodiment, the adjustment substrate  20  is supported by the support shaft  21 , whereas in the third embodiment, the adjustment substrate  20  is supported by two piezoelectric thin film actuators  90  at generally the center positions of a pair of mutually parallel sides of the adjustment substrate  20 . A base portion of the piezoelectric thin film actuator  90  is fixed to the package main body  30 A, and a flexible potion of the actuator protrudes from the inner surface of the package main body  30 A into the inside space of the package  30  like a beam. Lead wires  91  extend to the outside of the package  30  to apply a voltage to the piezoelectric thin film actuator  90 . A distal end of the flexible portion of the piezoelectric thin film actuator  90  is fixed to the adjustment substrate  20 . The attitude of the adjustment substrate  20  can be changed by changing the deflection degree of the flexible portion.  
         [0081]      FIGS. 10A and 10B  are respectively a cross sectional view and a plan view of the piezoelectric thin film actuator  90 . The piezoelectric thin film actuator  90  is constituted of a stainless steel substrate  95 , a lower electrode  96 , a piezoelectric film  97  and an upper electrode  98 . The lower electrode  96 , the piezoelectric film  97  and the upper electrode  98  are laminated on the surface of the flexible portion. A thickness of the substrate  95  is 10 nm for example.  
         [0082]     The lower electrode  96  is made of refractory metal such as platinum (Pt), conductive nitride such as TiN, conductive oxide such as SrRuO 3  or the like, and a thickness thereof is 200 n m for example. These materials can be deposited on the substrate  95  by sputtering or a vacuum deposition method. The piezoelectric film  97  is made of piezoelectric material such as lead zirconate titanate (PZT) and lead lanthanum zirconate titanate (PLZT), and a thickness thereof is 2 to 3 μm for example. The piezoelectric film  97  can be formed by sputtering, a sol-gel method, a metal organic chemical vapor deposition (MOCVD) method, a pulse laser deposition (PLD) method, a hydrothermal synthesis method, an aerosol deposition (AD) method or the like. The upper electrode  98  as well as the lower electrode  96  is made of refractory metal such as platinum (Pt), conductive nitride such as TiN, conductive oxide such as SrRuO 3  or the like, and a thickness thereof is 200 nm for example.  
         [0083]     Patterning the lower electrode  96 , piezoelectric film  97  and upper electrode  98  can be achieved by lift-off, wet etching, dry etching or the like using a photoresist pattern. If a pattern size is large, a metal through mask may be used to form films.  
         [0084]     The distal end of the flexible portion of the substrate  95  is fixed to the adjustment substrate  20  by solder  99 . The lead wires  91  are connected to the lower electrode  96  and upper electrode  98 , respectively, by wire bonding or the like. The lead wires  91  extend to the outside of the package in an electrically isolated state. A length of the flexible portion of the substrate  95  is 50 mm for example.  
         [0085]     Instead of connecting the lead wires  91  to the lower electrode  96  and upper electrode  98  by wire bonding or the like, wiring patterns may be formed on the substrate to use them as the lead wires. In this case, an insulating film of alumina, silica or the like having a thickness of 300 nm is formed by sputtering, CVD or the like, covering the whole surface of the substrate (actuator), and wiring patterns are formed on the insulating film. The wiring patterns are connected to the lower electrode  96  and upper electrode  98  via openings formed in the insulating film.  
         [0086]     As a dc voltage is applied between the lower electrode  96  and upper electrode  98 , the flexible portion of the substrate  95  deflects. The deflection degree can be adjusted by changing amplitude of voltage.  
         [0087]     Although a unimorph type actuator is shown in  FIGS. 10A and 10B , a bimorph type actuator may also be used.  
         [0088]      FIG. 11  is a block diagram showing a control system for the superconductive filter of the third embodiment. An input signal sig 1  is input to a resonant circuit  25  via an input connector  35 . The resonant circuit  25  is constituted of the base substrate  10 , feeders  11  and  12 , resonator patterns  13  and  14 , additional substrate  17  and additional pattern  18  shown in  FIG. 2C , the ground line shown in  FIG. 1A  and the like. An output signal sig 2  is output from an output connector  36 .  
         [0089]     A controller  100  includes a network analyzer  101 , an operational circuit  102  and a driver  103 . The output signal sig 2  from the resonant circuit  25  is input to the network analyzer  101 . The network analyzer  101  acquires a spectrum waveform (e.g., the waveform T 1  in  FIG. 3B , the waveform T 2  in  FIG. 4B  or the waveform T 3  in  FIG. 5B ) of the output signal sig 2 . This spectrum waveform is input to the operational circuit  102 .  
         [0090]     The operational circuit  102  compares the spectrum waveform of the output signal sig 2  with the target standard waveform, and sends a control signal to the driver  103  to make the spectrum waveform of the output signal sig 2  have a waveform like the target standard waveform. The driver  103  drives the actuator  90  in accordance with the control signal received from the operational circuit  102 . This feedback control is repeated so that a stable filter characteristic can be obtained.  
         [0091]     In the third embodiment, the adjustment substrate  20  is supported by two piezoelectric thin film actuators  90  at generally the center positions of a pair of mutually parallel sides of the adjustment substrate  20 . Therefore, although the tilt angle in one direction can be changed, the tilt angle in a direction perpendicular to the one direction cannot be changed. Next, description will be made on examples capable of changing the tilt angle in two directions.  
         [0092]     In the examples shown in  FIGS. 12A  to  12 E, an adjustment substrate  20  has a plan shape including first and second sides  20   a  and  20   b  parallel to each other and third and fourth sides  20   c  and  20   d  perpendicular to the first side  20   a.    
         [0093]     As shown in  FIG. 12A , four actuators  90   a  to  90   d  are mounted at generally the centers of the first to fourth sides  20   a  to  20   d . By supporting the adjustment substrate  20  by four actuators  90   a  to  90   d , the tilt angle can be changed in two directions.  
         [0094]     In the example shown in  FIG. 12B , a width of each of four actuators  90   a  to  90   d  is wider than that shown in  FIG. 12A . The top end portion mounted on the adjustment substrate  20  is narrower than the other portion. Since the width of each of the actuators  90   a  to  90   d  is made wider, a large drive force can be generated. By narrowing the top end portion mounted on the adjustment substrate  20 , the attitude of the adjustment substrate  20  can be changed easily.  
         [0095]     In the example shown in  FIG. 12C , two actuators are mounded on each side of the adjustment substrate  20 . For example, actuators  90   a   1  and  90   a   2  are mounted on the first side  20   a  at positions symmetrical with respect to the center of the side. By increasing the number of actuators  90 , the attitude can be controlled more stably.  
         [0096]     In the example shown in  FIG. 12D , each of actuators  90   a  to  90   d  is mounted on the adjustment substrate  20  only at opposite ends in a width direction of the actuators  90   a  and  90   d , and the central portion does not contact the adjustment substrate  20 . With this arrangement, the attitude of the adjustment substrate  20  can be changed easily.  
         [0097]     In the example shown in  FIG. 12E , the plan shape of the adjustment substrate  20  is a square or a rectangle, and actuators  90   a  to  90   d  support the adjustment substrate  20   a  at its four corners. Also with this arrangement supporting the adjustment substrate  20  at four corners, the tilt angle of the adjustment substrate  20  can be changed in two directions.  
         [0098]     The present invention has been described in connection with the preferred embodiments. The invention is not limited only to the above embodiments. It will be apparent to those skilled in the art that other various modifications, improvements, combinations, and the like can be made.