WO2015076212A1

WO2015076212A1 - Tunable filter apparatus

Info

Publication number: WO2015076212A1
Application number: PCT/JP2014/080281
Authority: WO
Inventors: Junya Tanaka; Hiroshi Takahashi; Toshikatsu Akiba; Takamitsu Sunaoshi; Hiroyuki Kayano; Noritsugu Shiokawa; Tamio Kawaguchi
Original assignee: Kabushiki Kaisha Toshiba
Priority date: 2013-11-20
Filing date: 2014-11-10
Publication date: 2015-05-28
Also published as: JP2015100082A; JP6430115B2

Abstract

According to an embodiment, a tunable filter apparatus includes the following elements. The dielectric substrate includes a front surface including a first area and a second area. The resonator pattern is formed of a conductive material on the first area. The characteristic adjustment member includes an opposite surface opposite to the front surface, and is formed of a dielectric material or a magnetic material or a conductive material, a volume of a space between the opposite surface and a projection plane obtained by projecting the characteristic adjustment member on the front surface being defined as a spatial volume. The driving mechanism drives the characteristic adjustment member to adjust a spatial volume ratio between the spatial volumes of the first and second areas.

Description

D E S C R I P T I O N

TUNABLE FILTER APPARATUS

CROSS-REFERENCE TO RELATED APPLICATIONS This application is based upon and claims the benefit of priority from Japanese Patent Application

No. 2013-240060, 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.

BACKGROUND

A communication apparatus for wireless or wired information communication includes various devices such as an amplifier, a mixer, and a filter (for example, a bandpass filter) . The band-pass filter is characterized by transmitting frequencies within a certain range and cutting off (attenuating) frequencies outside the range. The characteristics of the band-pass filter such as a passband width and the center frequency of the passband are designed in accordance with the specification of a communication system. A communication system needs a band-pass filter with a steep skirt characteristic (the frequency cutoff characteristic of separating the passband from the other regions) in view of effective utilization of frequencies.

An example of the band-pass filter is a planar circuit filter such as a microstrip line filter. For the planar circuit filter, a steep skirt characteristic can be

achieved by providing multiple resonant elements. When a normal conductive material is used as a wiring material for the resonant elements, the use of multiple resonant

elements leads to increased transmission loss. Thus, providing multiple resonant elements is difficult. Even when an electrically good conductor such as copper (Cu) or silver (Ag) is used as a wiring material for resonant elements, providing a large number of resonant elements is difficult. In contrast, a superconductor offers very small surface resistance even in a high frequency region compared to normal electrically good conductors. Thus, when the resonant elements are formed of a superconductor, even providing multiple resonant elements results in low

transmission loss. Therefore, forming resonant elements using a superconductor allows implementation of a band-pass filter with a steep skirt characteristic.

Furthermore, a band-pass filter with a variable characteristic (for example, the center frequency of the passband) is needed in order to construct a communication infrastructure that can deal flexibly with system changes. However, a change in the center frequency of the passband may cause the waveforms of filter characteristics to deviate from the ideal waveforms.

For the filter apparatus, there is a demand to be able to stably adjust the center frequency of the passband over a wide range while suppressing disturbance of the waveforms of the filter characteristics .

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view schematically showing an example of a tunable filter apparatus according to a first embodiment ;

FIG. 2 is a plan view showing an example of area division in which one resonator pattern is provided on a dielectric substrate;

FIG. 3 is a diagram illustrating a frequency- characteristic of a filter according to an embodiment;

FIG. 4 is a perspective view schematically showing another example of the tunable filter apparatus according to the first embodiment;

FIG. 5 is a cross-sectional view of the tunable filter apparatus in FIG. 4 including an example of a driving mechanism according to the first embodiment;

FIG. 6 is a plan view showing an example of area division in which a plurality of resonator patterns are provided on the dielectric substrate according to the embodiment ;

FIG. 7 is a perspective view schematically showing an example of a tunable filter apparatus according to a second embodiment ;

FIG. 8 is a perspective view schematically showing another example of the tunable filter apparatus according to the second embodiment; FIG. 9 is a cross-sectional view of the tunable filter apparatus in FIG. 8 including an example of a driving mechanism according to the second embodiment;

FIG. 10 is a cross-sectional view of the tunable filter apparatus in FIG. 8 including another example of the driving mechanism according to the second embodiment;

FIGS. 11A and 11B are diagrams illustrating operation of a rotation unit shown in FIG. 10;

FIG. 12 is a perspective view schematically showing an example of a tunable filter apparatus according to a third embodiment ;

FIG. 13 is a plan view showing that projection of a characteristic adjustment member shown in FIG. 12 spans both a first area and a second area;

FIG. 14 is a perspective view schematically showing another example of the tunable filter apparatus according to the third embodiment;

FIG. 15 is a cross-sectional view of the tunable filter apparatus in FIG. 14 including an example of a driving mechanism according to the third embodiment;

FIG. 16 is a perspective view schematically showing a tunable filter apparatus according to an embodiment;

FIG. 17 is a plan view showing another example of area division in which one resonator pattern is provided on a dielectric substrate according to the embodiment;

FIG. 18 is a block diagram schematically showing a water cooling system according to a fourth embodiment; FIG. 19 is a block diagram showing an example of a tunable filter apparatus according to a fifth embodiment; and

FIG. 20 is a block diagram showing another example of the tunable filter apparatus according to the fifth

embodiment .

DETAILED DESCRIPTION

In general, according to an embodiment, a tunable filter apparatus includes a dielectric substrate, a resonator pattern, a characteristic adjustment member, and a driving mechanism. The dielectric substrate includes a front surface including a first area and a second area. The resonator pattern is provided on the first area of the front surface, and is formed of a conductive material. The characteristic adjustment member includes an opposite surface opposite to the front surface, and is formed of a dielectric material or a magnetic material or a conductive material, a volume of a space sandwiched between the opposite surface and a projection plane obtained by

projecting the characteristic adjustment member on the front surface being defined as a spatial volume. The driving mechanism is configured to drive the characteristic adjustment member to adjust a spatial volume ratio between the spatial volume of the first area and the spatial volume of the second area.

Embodiments will be described hereinafter with

reference to the accompanying drawings. In the embodiments below, like reference numerals denote like elements, and a repetitive description thereof will be omitted.

(First Embodiment)

FIG. 1 schematically shows an example of a tunable filter apparatus according to a first embodiment. A tunable filter apparatus 100 shown in FIG. 1 includes a microstrip line band-pass filter. Specifically, the tunable filter apparatus 100 includes a dielectric

substrate 101 and further includes a resonator pattern 102 corresponding to a resonant element, a signal input line 103, and a signal output line 104 which are all formed on a front surface of the dielectric substrate 101 using a superconductive material. A ground film is formed all over a back surface of the dielectric substrate 101 using a superconductive material. The ground film can be used as a ground electrode. Alternatively, the ground electrode may be formed by depositing, for example, an Ag film on the ground film.

In an example shown in FIG. 1, the resonator pattern 102 is shaped like a hairpin. The resonator pattern 102 is not limited to the hairpin shape as shown in FIG. 1 but may be, for example, spiral or S-shaped. Moreover, one

resonator pattern 102 is shown in FIG. 1, but two or more resonator patterns 102 may be provided as in an example described below (for example, the example shown in FIG. 4) .

The dielectric substrate 101 is housed in a metal package 106 that blocks the high-frequency wave. In FIG. 1, a part of the metal package 106 (specifically, a bottom portion and a part of a sidewall) is showed with the other part of the metal package omitted. The metal package 106 is shaped like a box internally including a closed space. In an example, the metal package 106 includes a package main body shaped like a rectangular parallelepiped with an opening formed in an upper surface thereof and a cover that covers the opening. The package main body and the cover form the internal space . The ground electrode provided on the back surface of the dielectric substrate 101 is in contact with an inner bottom surface of the metal package 106. The front surface of the dielectric substrate 101 is directed toward the internal space in the metal package 106.

The metal package 106 is provided with a coaxial connector 108 corresponding to an output connector. The signal output line 104 is connected to a central conducting wire in the coaxial connector 108 via a connection

electrode. The signal input line 103 is connected to a central conducting wire in a coaxial connector, which corresponds to an input connector and is not shown in the drawings, via a connection electrode 107. As a connection method, wire bonding based on ultrasonic thermocompression bonding, tape bonding, or solder joint may be used. The connection electrodes may be formed using a vapor

deposition or sputtering technique with gold (Au) or silver (Ag) in order to reduce the contact resistance. In an example, the connection electrodes may be laminate films including at least either gold (Au) or silver (Ag) .

In the metal package 106, a characteristic adjustment member 105 is arranged opposite the front surface of the characteristic adjustment member 105 via a gap. More specifically, the characteristic adjustment member 105 is arranged opposite the resonator pattern 102 in a thickness direction of the resonator pattern 102 with a space formed between the characteristic adjustment member 105 and the resonator pattern 102. The characteristic adjustment member 105 may be any member that changes the distribution of magnetic and electric fields over a space near the dielectric substrate 101. The characteristic adjustment member 105 is formed of a dielectric material (for example, alumina or sapphire) or a magnetic material (for example, ferrite) . Alternatively, the characteristic adjustment member 105 may be formed of a conductive material such as metal (for example, copper) .

In the example in FIG. 1, the characteristic

adjustment member 105 is shaped like a rectangular

parallelepiped. A surface of the characteristic adjustment member 105 lying opposite the dielectric substrate 101 (hereinafter referred to as a substrate opposite surface) is parallel to the front surface of the dielectric

substrate 101. A width of the characteristic adjustment member 105 may conform to a width of the resonator pattern 102. The width as used herein refers to the dimension of the resonator pattern 102 in a transverse direction thereof. The transverse direction is perpendicular to a longitudinal direction of the resonator pattern 102. In the first embodiment, the longitudinal direction and the transverse direction of the resonator pattern 102 are perpendicular to the thickness direction of the dielectric substrate 101. The shape of the characteristic adjustment member 105 is not limited to the case of a rectangular parallelepiped as shown in FIG. 1. The characteristic adjustment member 105 may be differently shaped.

In the planar circuit filter, the resonance frequency of the resonant pattern 102 may deviate from a desired value due to a variation in the thickness or material characteristics of the dielectric substrate 101 or

deviation from the regular patterning dimensions of the resonator patterns 102. As a result, desired filter characteristics may fail to be achieved. Moreover, when the dielectric constant of the dielectric substrate 101 is increased to allow the filter to be miniaturized, a wiring pattern necessarily becomes complex in order to achieve a predetermined wiring impedance. In this case, the

thickness of the dielectric substrate 101 or the deviation from the regular patterning dimensions significantly affects the filter characteristics. According to the first embodiment, the use of the characteristic adjustment member 105 provided opposite the resonator pattern 102 enables the resonant frequency of the resonator pattern 102 to be adjusted, allowing the desired filter characteristics to be achieved.

The characteristic adjustment member 105 is supported by a driving mechanism (not shown in FIG. 1) that moves the characteristic adjustment member 105 in a direction

parallel to the front surface of the dielectric substrate 101. In this case, the distance between the substrate opposite surface of the characteristic adjustment member 105 and the front surface of the dielectric substrate 101 is kept constant. When the characteristic adjustment member 105 is moved in the direction parallel to the dielectric substrate 101, the characteristic adjustment member 105 is prevented from coming into contact with and damaging the resonator pattern 102. More specifically, the driving mechanism moves the characteristic adjustment member 105 in the longitudinal direction of the resonator pattern 102 as shown by a bidirectional arrow in FIG. 1. Moving the characteristic adjustment member 105 in the longitudinal direction of the resonator pattern 102 allows the resonant frequency of the resonator pattern 102 to be stably adjusted over a wide range.

According to the conventional technique for adjusting the resonant frequency of the resonator by moving a

dielectric member in the thickness direction of the

dielectric substrate, the waveforms of the filter

characteristics (transmission characteristic and reflection characteristic) may be rapidly disrupted. In contrast, according to the first embodiment in which the

characteristic adjustment member 105 is moved parallel to the dielectric substrate 101, the waveforms of the filter characteristics can be maintained and moderately changed. Thus, the first embodiment allows the center frequency of a passband to be stably adjusted over a wide range.

The dielectric substrate 101 is formed of a low- loss material with a small dielectric loss tangent, for example, AL2O3 (sapphire), MgO, or LaAlC>3.

A circuit pattern (specifically, the resonator pattern 102 and a pattern of the signal input line 103 and the signal output line 104) can be obtained by using a

photolithography technique to process a superconductor film formed all over the surface using a Y-Ba-Cu-0

superconductive material (hereinafter referred to as YBCO) . The material of the circuit pattern is not limited to YBCO but may be any other oxide superconductive material; for example, an R-Ba-Cu-0 material (R is Nb, Ym, Sm, or Ho) , a Bi-Sr-Ca-Cu-0 material, a Pb-Bi-Sr-Ca-Cu-0 material, a CuBapCagCu_rO_x material (1.5<p<2.5, 2.5<q<3.5 , 3.5<r<4.5 ) , or a metal superconductive material, for example, niobium or niobium tin. The material of the circuit pattern is not limited to the superconductive material but may be a normal conductive material.

The metal package 106 is formed of, for example, oxygen- free copper, which is excellent in thermal

conductivity. Alternatively, the metal package 106 may be formed of pure aluminum, an aluminum alloy, a copper alloy, or the like. Alternatively, the metal package 106 may be formed of a material with a thermal shrinkage coefficient close to the thermal shrinkage coefficient of the

dielectric substrate 101; for example, kovar, invar, or a 42-alloy.

A portion including the following is hereinafter referred to as a filter device: the dielectric substrate 101, the circuit pattern on the dielectric substrate 101 (including the resonator pattern 102, the signal input line 103, and the signal output line 104), the characteristic adjustment member 105, and the metal package 106.

FIG. 2 is a plan view schematically showing the dielectric substrate 101 shown in FIG. 1. As shown in FIG. 2, the front surface of the dielectric substrate 101 is virtually divided into two areas, that is, a first area 201 and a second area 202. The first area 201 is an area including the resonator pattern 102. The second area 202 is an area not including the resonator pattern 102, that is, the entire area of the front surface excluding the first area 201. A projection plane 110 obtained by

projecting (for example, vertically projecting) the

characteristic adjustment member 105 on the dielectric substrate 101 spans both the first area 201 and the second area 202. The first area 201 and the second area 202 may be optionally set provided that the first area 201 includes the resonator pattern 102 and that the second area does not include the resonator pattern 102.

Moving the characteristic adjustment member 105 in the direction parallel to the front surface of the dielectric substrate 101 changes the spatial volume ratio between the spatial volume of the first area 201 and the spatial volume of the second area 202 (a spatial volume difference

similarly changes) . The spatial volume refers to the volume of a space sandwiched between the projection plane 110 and the substrate opposite surface of the

characteristic adjustment member 105, that is, the volume of a pillared space in which the projection plane 110 corresponds to a bottom surface and in which the substrate opposite surface of the characteristic adjustment member 105 corresponds to a top surface. Specifically, the pillared space is a space linearly joining the projection plane 110 to the substrate opposite surface of the

characteristic adjustment member 105. In the example shown in FIG. 1, the space is shaped like a rectangular

parallelepiped, and the spatial volume is determined by multiplying the distance between the dielectric substrate 101 and the characteristic adjustment member 105 by the area of the projection plane 110.

The spatial volume of the first area 201 is the volume of a space defined (sandwiched) between a portion of the projection plane 110 positioned in the first area 201 and a portion of the substrate opposite surface located opposite the first area 201. The spatial volume of the second area 202 is the volume of a space defined (sandwiched) between a portion of the projection plane 110 positioned in the second area 202 and a portion of the substrate opposite surface located opposite the second area 202. The parallel movement of the characteristic adjustment member 105 is an example of a method for driving the characteristic

adjustment member 105 so as to change the spatial volume ratio between the spatial volume of the first area 201 and the spatial volume of the second area 202.

FIG. 3 schematically shows how the center frequency of the passband changes when the characteristic adjustment member 105 is driven. In FIG. 3, a frequency

characteristic 300 of the filter observed when the

characteristic adjustment member 105 is at a reference position is shown by a solid line. In the first embodiment and the embodiments described below, driving the

characteristic adjustment member 105 (for example, in the longitudinal direction of the resonator pattern 102) allows the center frequency of the passband to be changed

substantially without changing the passband width as shown in FIG. 3. The center frequency is shifted toward high frequencies as shown by a characteristic 301 by increasing the spatial volume of the first area 201. Furthermore, the center frequency is shifted toward low frequencies as shown by a characteristic 302 by reducing the spatial volume of the first area 201.

FIG. 4 and FIG. 5 are a perspective view and a cross- sectional view, respectively, showing another example of the tunable filter apparatus according to the first embodiment. In FIG. 4, the metal package 106 is partly omitted as in the case of FIG. 1.

A tunable filter apparatus 400 shown in FIG. 4 includes a plurality of resonator patterns 102 formed on the front surface of the dielectric substrate 101. The plurality of resonator patterns 102 are coupled together to achieve filter characteristics. In the tunable filter apparatus 400, the plurality of resonator patterns 102 are provided to achieve a steep skirt characteristic of the filter. A ground film 503 is formed on the back surface of the dielectric substrate 101 as shown in FIG. 5. The dielectric substrate 101 is housed in the metal package 106 so that a ground electrode provided on the back surface of the dielectric substrate 101 is in contact with an inner bottom surface of the metal package 106 and that the front surface of the dielectric substrate 101 is directed toward an internal space 504 of the metal package 106. The metal package 106 includes a package main body 501 and a cover 502. The internal space 504 is formed by placing a cover 502 over an opening of the package main body 501.

As shown in FIG. 4, a plurality of characteristic adjustment members 105 are arranged opposite the front surface of the dielectric substrate 101 via a gap. Each of the characteristic adjustment members 105 is provided for a corresponding one of the resonator patterns 102 and arranged opposite the corresponding resonator pattern 102 at a given distance from the resonator pattern 102 in the thickness direction of the dielectric substrate 101.

Through-holes are formed in a sidewall of the metal package 106 (specifically, the package main body 501) .

Each of the characteristic adjustment members 105 extends through the corresponding through-hole to the exterior of the metal package 106 and is supported by a driving

mechanism 510 on an opening side of the corresponding resonator pattern 102. The driving mechanism 510 is provided for each of the characteristic adjustment members 105. The driving mechanism 510 drives the characteristic adjustment member 105 so as to change the spatial volume ratio between the spatial volume of the first area

including the resonator pattern 102 and the spatial volume of the second area not including the resonator pattern 102. Specifically, the driving mechanism 510 moves the

characteristic adjustment member 105 in the longitudinal direction of the resonator pattern 102.

In an example, the driving mechanism 510 includes a spring member 511, a presser plate member 512, and a piezoelectric element 513. The piezoelectric element 513 is an example of a driving source (actuator) that drives the characteristic adjustment member 105. The driving mechanism 510 may use a magnetostrictor as a driving source. The presser plate member 512 is arranged opposite a wall surface of the metal package 106. A base portion of the characteristic adjustment member 105 is fixed to the presser plate member 512. The spring member 511 is

arranged between the metal package 106 and the presser plate member 512. The presser plate member 512 transmits the pressing force of the spring member 511 to the

piezoelectric element 513 to impose a preload on the piezoelectric element 513.

The piezoelectric element 513 is arranged between the metal package 106 and the presser plate member 512.

Specifically, one end of the piezoelectric element 513 is fixed to the metal package 106, and the other end of the piezoelectric element 513 is fixed to the presser plate member 512. A lead (not shown) is connected to the

piezoelectric element 513 so as to apply a voltage to the piezoelectric element 513. Application of a voltage to the piezoelectric element 513 extends or contracts the

piezoelectric element 513. The extension and contraction of the piezoelectric element 513 is controlled by the applied voltage. A direction in which the piezoelectric element 513 extends or contracts substantially coincides with the longitudinal direction of the resonator pattern 102. The extension and contraction of the piezoelectric element 513 moves the characteristic adjustment member 105. Adjusting the movement distances of the characteristic adjustment members 105 enables the resonant frequencies of the resonator patterns 102 to be uniformly changed. As a result, the center frequency of the passband can be adjusted without disturbing the waveforms of the filter characteristics (for example, the transmission

characteristic and reflection characteristic) .

FIG. 6 is an example of area division in which a plurality of resonator patterns 102 are provided on the dielectric substrate 101. As shown in FIG. 6, a plurality of first areas 201 and a plurality of second areas 202 are set based on the position of the resonator pattern 102. Each of the characteristic adjustment members 105 is virtually projected on the dielectric substrate 101 so as to span both the first area 201 and the second area 202. The first area 201 and the second area 202 can be

optionally set by including the resonator pattern 102 in the first area 201 and omitting the resonator pattern 102 from the second area 202.

In the example shown in FIG. 5, the substrate opposite surface of the characteristic adjustment member 105 is not a uniform plane but has a surface inclined to the front surface of the dielectric substrate 101. Specifically, a base portion side of the substrate opposite surface of the characteristic adjustment member 105 is parallel to the front surface of the dielectric substrate 101, whereas a leading end side of the substrate opposite surface is inclined to the front surface of the dielectric substrate 101. In the leading end portion, the distance between the characteristic adjustment member 105 and the dielectric substrate 101 increases toward the leading end side. Thus, this configuration increases the amount of change in the spatial volume of the first area 201 with respect to the movement of the characteristic adjustment member 105, compared to a configuration where the substrate opposite surface of the characteristic adjustment member 105 is a uniform plane. As a result, a desired amount of change in center frequency can be obtained by moving the

characteristic adjustment member 105 over a reduced

distance. Moreover, the range over which the spatial volume in the first area 201 can be changed increases to allow the center frequency of the passband to be adjusted over a wider range. At least a part of the substrate opposite surface of the characteristic adjustment member 105 may be a curved surface.

As described above, the tunable filter apparatus according to the first embodiment moves, for each resonator pattern, the characteristic adjustment member in the longitudinal direction of the resonator pattern, allowing the resonant frequency of the resonator pattern to be accurately and easily adjusted. As a result, the center frequency of the passband can be adjusted with possible disturbance of the waveforms of the filter characteristics prevented.

(Second Embodiment)

According to the first embodiment, the characteristic adjustment member is moved in a direction parallel to the front surface of the dielectric substrate (specifically, in the longitudinal direction of the resonator pattern) .

According to a second embodiment, the characteristic adjustment member is rotated around an axis parallel to a transverse direction of a resonator pattern 102.

FIG. 7 schematically shows an example of a tunable filter apparatus according to the second embodiment. In FIG. 7, a metal package 106 is partly omitted as is the case with FIG. 1. In a tunable filter apparatus 700 shown in FIG. 7, a characteristic adjustment member 105 is rotatably supported around an axis substantially parallel to the transverse direction of the resonator pattern 102. In the tunable filter apparatus 700, a first area 201 and a second area 202 can also be set on a front surface of a dielectric substrate 101 as is the case with the example shown in FIG. 2. A driving mechanism (not shown in FIG. 7) rotates the characteristic adjustment member 105 around the axis so as to change the spatial volume ratio between the spatial volume of the first area 201 and the spatial volume of the second area 202. According to the second

embodiment, the rotation quantity (rotational angle) of the characteristic adjustment member 105 is adjusted to

regulate the resonant frequency of the resonator pattern 102. Thus, the center frequency of a passband can be adjusted with possible disturbance of the waveforms of the filter characteristics prevented.

FIG. 8 and FIG. 9 are a perspective view and a cross- sectional view, respectively, schematically showing another example of the tunable filter apparatus according to the second embodiment. In FIG. 8, a metal package 106 is partly omitted as is the case with FIG. 1.

In the tunable filter apparatus 800 shown in FIG. 8, a plurality of resonator patterns 102 are provided on the front surface of the dielectric substrate 101. A plurality of characteristic adjustment members 105 are arranged over the front surface of the dielectric substrate 101 via a gap. Each of the characteristic adjustment members 105 is provided for a corresponding one of the resonator patterns 102 and arranged opposite the corresponding resonator pattern 102 at a given distance from the resonator pattern 102 in the thickness direction of the dielectric substrate 101. A width of the characteristic adjustment member 105 may conform to a width of the resonator pattern 102. In the tunable filter apparatus 800, the first area 201 and the second area 202 can be set on the front surface of the dielectric substrate 101 as is the case with the example shown in FIG . 4.

As shown in FIG. 9, through-holes are formed in a sidewall of the metal package 106. The characteristic adjustment member 105 extends through the corresponding through-hole to the exterior of the metal package 106. The characteristic adjustment member 105 is supported by a driving mechanism 910 on an opening side of the

corresponding resonator pattern 102. The driving mechanism 910 is provided for each of the characteristic adjustment members 105. The driving mechanism 910 drives the

characteristic adjustment member 105 so as to change the spatial volume ratio between the spatial volume of the first area 201 and the spatial volume of the second area 202. Specifically, the driving mechanism 910 rotates the characteristic adjustment member 105 around a support shaft 913 provided on the characteristic adjustment member 105.

In an example, the driving mechanism 910 includes a spring member 911 and a piezoelectric element 912. In the example shown in FIG. 9, a package main body 501 includes a projection portion 901 projecting in the longitudinal direction of the resonator pattern 102. A cover 502 includes a projection portion 902 projecting in the

longitudinal direction of the resonator pattern 102. The spring member 911 is arranged between the projection portion 902 of the metal package 106 and the characteristic adjustment member 105. The pressing force of the spring member 911 is applied to the piezoelectric element 912 via the characteristic adjustment member 105 as a preload.

The piezoelectric element 912 is arranged between the projection portion 901 of the metal package 106 and the characteristic adjustment member 105. Specifically, one end of the piezoelectric element 912 is fixed to the projection portion 901 of the metal package 106, and the other end of the piezoelectric element 912 is fixed to the characteristic adjustment member 105. A lead (not shown) is connected to the piezoelectric element 912 so as to apply a voltage to the piezoelectric element 912.

Application of a voltage to the piezoelectric element 912 extends or contracts the piezoelectric element 912 in the thickness direction of the dielectric substrate 101. The extension and contraction of the piezoelectric element 912 are converted into rotation by the support shaft 913. The extension and contraction of the piezoelectric element 912 rotates the characteristic adjustment member 105 around the support shaft 913, changing the orientation of the

characteristic adjustment member 105. The extension of the piezoelectric element 912 moves the characteristic

adjustment member 105 closer to the resonator pattern 102.

This reduces the spatial volume in the first area

Furthermore, the contraction of the piezoelectric element moves the characteristic adjustment member 105 away from the resonator pattern 102. This increases the spatial volume in the first area 201. Adjusting the rotation quantity of each of the characteristic adjustment members

105 enables the resonant frequencies of the resonator patterns 102 to be uniformly changed. As a result, the center frequency of the passband can be adjusted without disrupting the waveforms of the filter characteristics.

FIG. 10 schematically shows another example of the driving mechanism according to the second embodiment.

the example shown in FIG. 10, the driving mechanism

rotation unit 1002 that rotates a rotation shaft 1001 provided on the characteristic adjustment member 105. A plurality of characteristic adjustment members 105 may be coupled to one rotation shaft 1001. In this case, the characteristic adjustment members 105 are simultaneously rotated by the rotation unit 1002.

FIG. 11A and FIG. 11B schematically show an example of the structure of the rotation unit 1002. As shown in

FIG. 11A, the rotation unit 1002 includes a piezoelectric element 1101, a spring member 1102, and a rotation member 1103. The rotation member 1103 is attached to the rotation shaft 1001 and supported by the piezoelectric element 1101 and the spring member 1102 so as to rotate around the rotation shaft 1001. The rotation member 1103 transmits the pressing force of the spring member 1102 to the

piezoelectric element 1101 to impose a preload on the piezoelectric element 1101. A lead (not shown) is

connected to the piezoelectric element 1101 so as to apply a voltage to the piezoelectric element 1101. Application of a voltage to the piezoelectric element 1101 extends or contracts the piezoelectric element 1101. As shown in FIG. 11B, the extension of the piezoelectric element 1101 rotates the characteristic adjustment member 105

mechanically connected to the rotation member 1103. The contraction of the piezoelectric element 1101 rotates the characteristic adjustment member 105 in a direction

opposite to the direction in which the piezoelectric element 1101 extends. Adjusting the rotation quantity of each of the characteristic adjustment members 105 enables the resonant frequencies of the resonator patterns 102 to be uniformly changed. As a result, the center frequency of the passband can be adjusted without disturbing the

waveforms of the filter characteristics.

The rotation unit 1002 may be an actuator such as an ultrasonic motor which can directly generate a rotational driving force.

As described above, the tunable filter apparatus according to the second embodiment rotates, for each resonator pattern, the characteristic adjustment member around the axis parallel to the transverse direction of the resonator pattern, allowing the resonant frequency of the resonator pattern to be accurately and easily adjusted. As a result, the center frequency of the passband can be adjusted with possible disturbance of the waveforms of the filter characteristics prevented.

(Third Embodiment)

According to a third embodiment, a characteristic adjustment member is rotated around an axis parallel to the thickness direction of a dielectric substrate (i.e., an axis perpendicular to a front surface of a dielectric substrate) .

FIG. 12 schematically shows an example of a tunable filter apparatus according to the third embodiment. In FIG. 12, a metal package 106 is partly omitted as is the case with FIG. 1. In the tunable filter apparatus 1200 shown in FIG. 12, a characteristic adjustment member 105 is arranged in a metal package 106 and opposite the front surface of a dielectric substrate 101 via a gap. More specifically, the characteristic adjustment member 105 is arranged opposite a resonator pattern 102 in the thickness direction of the resonator pattern 102 with a space between the characteristic adjustment member 105 and the resonator pattern 102.

The characteristic adjustment member 105 is rotatably supported around an axis substantially parallel to the thickness direction of the dielectric substrate 101. The axis passes through the characteristic adjustment member 105. In an example shown in FIG. 12, the substrate opposite surface of the characteristic adjustment member 105 is inclined to the front surface of the dielectric substrate 101. The planar shape of the characteristic adjustment member 105 as viewed from the dielectric substrate 101 side is a circle.

FIG. 13 is a plan view schematically showing the dielectric substrate 101 shown in FIG. 12. The front surface of the dielectric substrate 101 is virtually divided into a first area 201 and a second area 202. The resonator pattern 102 is formed in the first area 201. The second area 202 is an area not including the resonator pattern 102. A projection plane 1210 obtained by

projecting (for example, vertically projecting) the

characteristic adjustment member 105 on the dielectric substrate 101 spans both the first area 201 and the second area 202.

A driving mechanism (not shown in FIG. 12) drives the characteristic adjustment member 105 so as to change the spatial volume ratio between the spatial volume of the first area 201 and the spatial volume of the second area 202. Specifically, the driving mechanism rotates the characteristic adjustment member 105 around an axis substantially parallel to the thickness direction of the dielectric substrate 101. This keeps the distance between the characteristic adjustment member 105 and the dielectric substrate 101 constant. When the driving mechanism rotates the characteristic adjustment member 105 around the axis substantially parallel to the thickness direction of the dielectric substrate 101, the characteristic adjustment member 105 is prevented from coming into contact with and damaging the resonator pattern 102. According to the third embodiment, the rotation quantity of the characteristic adjustment member 105 is adjusted to regulate the resonant frequency of the resonator pattern 102. Thus, the center frequency of the passband can be adjusted with possible disturbance of the waveforms of the filter characteristics prevented.

The characteristic adjustment member 105 is not limited to the example in which the characteristic

adjustment member 105 is shaped as shown in FIG. 12 but may have any shape. However, the characteristic adjustment member 105 is desirably shaped as shown in FIG. 12 so as to enable the desirable amount of change in center frequency to be achieved with a small rotation quantity.

FIG. 14 and FIG. 15 are a perspective view and a cross-sectional view, respectively, schematically showing another example of the tunable filter apparatus according to the third embodiment. In FIG. 14, the metal package 106 is partly omitted as is the case with FIG. 1.

In a tunable filter apparatus 1400 shown in FIG. 14, a plurality of resonator patterns 102 are provided on the front surface of the dielectric substrate 101. A plurality of characteristic adjustment members 105 are arranged opposite the front surface of the dielectric substrate 101 via a gap. Each of the characteristic adjustment members 105 is provided for a corresponding one of the resonator patterns 102 and arranged opposite the corresponding resonator pattern 102 at a given distance from the

resonator pattern 102 in the thickness direction of the dielectric substrate 101. A width of the characteristic adjustment member 105 may conform to a width of the

resonator pattern 102. In the tunable filter apparatus 1400, the first area 201 and the second area 202 can be set on the front surface of the dielectric substrate 101 as is the case with the example shown in FIG. 4.

As shown in FIG. 15, through-holes are formed in an upper portion (specifically, a cover 502) of the metal package 106. The characteristic adjustment member 105 extends through the corresponding through-hole to the exterior of the metal package 106. The characteristic adjustment member 105 is supported by a rotation unit 1510 serving as a driving mechanism 1510. The rotation unit 1510 is provided for each of the characteristic adjustment members 105. The rotation unit 1510 drives the

characteristic adjustment member 105 so as to change the spatial volume ratio between the spatial volume of the first area 201 and the spatial volume of the second area 202. Specifically, the rotation unit 1510 rotates the characteristic adjustment member 105 using, as a rotation axis 1511, an axis which passes through the characteristic adjustment member 105 and which is parallel to the

thickness direction of the dielectric substrate 101.

The rotation unit 1510 may be structured similarly to the rotation unit 1002 described in connection with

FIG. 11. Thus, specific description of the rotation unit 1510 is omitted. The rotation unit 1510 may be an actuator such as an ultrasonic motor which can directly generate a rotational driving force. Adjusting the rotation quantity of each of the characteristic adjustment members 105 enables the resonant frequencies of the resonator patterns 102 to be uniformly changed. As a result, the center frequency of the passband can be adjusted without

disturbing the waveforms of the filter characteristics.

As described above, the tunable filter apparatus according to the third embodiment rotates , for each

resonator pattern, the characteristic adjustment member around the axis parallel to the thickness direction of the dielectric substrate, allowing the resonant frequency of the resonator pattern to be accurately and easily adjusted. As a result, the center frequency of the passband can be adjusted with possible disturbance of the waveforms of the filter characteristics prevented.

It is possible to implement a combination of at least two of the methods for driving the characteristic

adjustment member according to the first to third

embodiments. FIG. 16 schematically shows an example of a combination of the first to third embodiments. In a tunable filter apparatus 1600 shown in FIG. 16, the

characteristic adjustment member 105 is movable in the longitudinal direction of the resonator pattern 102, rotatable around an axis parallel to the transverse

direction of the resonator pattern 102, and rotatable around an axis parallel to the thickness direction of the dielectric substrate 101. The center frequency of the passband can be more freely adjusted by combining the methods for driving the characteristic adjustment member according to the first to third embodiments.

FIG. 17 shows another example of area division in which one resonator pattern is provided on the dielectric substrate. The front surface of the dielectric substrate 101 can be virtually divided into a first area 1701

including the resonator pattern 102 and a second area 1702 not including the resonator pattern 102. (Fourth Embodiment)

When a conductor portion (a resonator pattern and the like) of a filter device is formed of an existing

superconductive material, the conductor portion is

maintained in a superconducting state by cooling the whole filter device. In a fourth embodiment, a cooling system for cooling the filter device will be described.

FIG. 18 schematically shows the cooling system according to the fourth embodiment. In the cooling system shown in FIG. 18, a filter device 1806 is sealed in a heat insulating vacuum container 1801. The filter device 1806 may be any one of the filter devices according to the above-described embodiments. The vacuum pump 1802

evacuates the inside of the heat insulating vacuum

container 1801.

The heat insulating vacuum container 1801 includes a lower container with an opening formed in an upper portion thereof and an upper container with an opening formed in a lower portion thereof . The lower container and the upper container are coupled together with the openings lying opposite each other, to define a closed space. An O-ring is interposed between the lower container and the upper container to maintain the degree of vacuum inside the heat insulating vacuum container 1801.

In the heat insulating vacuum container 1801, the filter device 1806 is held on a cold plate 1805. The cold plate 1805 is thermally coupled to a cold head 1804 of a refrigerating machine 1803. The filter device 1806 is cooled under vacuum by the refrigerating machine 1803 to a temperature at which the conductor portion of the filter device 1806 is in a superconducting state. The

superconducting characteristic is expected to be improved at lower temperatures, and thus, the temperature is desirably set to a smaller value. Any type of

refrigerating machine 1803 may be used provided that the refrigerating machine can achieve cooling. For example, the refrigerating machine 1803 may be a pulse tube

refrigerating machine, a star ring refrigerating machine, or a GM (Gifford-McMahon) refrigerating machine.

Connectors 1807, 1808, and 1809 are attached to a sidewall of the heat insulating vacuum container 1801. An input connector 1810 of the filter device 1806 is connected to a frequency signal detector 1818 via a coaxial cable 1811 inside the heat insulating vacuum container 1801, the connector 1807, and a coaxial cable 1812 outside the heat insulating vacuum container 1801. The frequency signal detector 1818 may be, for example, a network analyzer.

Furthermore, an output connector 1813 of the filter device 1806 is connected to the frequency signal detector 1818 via a coaxial cable 1814 inside the heat insulating vacuum container 1801, the connector 1808, and a coaxial cable 1815 outside the heat insulating vacuum container 1801. An actuator (not shown) of a driving mechanism is connected to a driver 1819 via a wiring cable 1816 inside the heat insulating vacuum container 1801, the connector 1809, and a wiring cable 1817 outside the heat insulating vacuum container 1801. The driver 1819 generates a driving signal (voltage signal) for driving the actuator.

In the cooling system shown in FIG. 18, vibration of the refrigerating machine 1803 acts on the filter device 1806 mainly in the vertical direction. Typically, the filter device 1806 is placed on the cold plate 1805 so that that the thickness direction of the dielectric substrate coincides with the vertical direction. In this case, according to a conventional technique for moving the characteristic adjustment member in the thickness direction of the dielectric substrate, a direction in which the characteristic adjustment member is driven coincides with the vibrating direction 1820 of the refrigerating machine 1803. This may reduce the accuracy of positioning of the characteristic adjustment member. In contrast, when the filter device 1806 is the filter device according to the first embodiment, the characteristic adjustment member is driven in the horizontal direction. The driving direction of the characteristic adjustment member is different from the vibrating direction 1820 of the refrigerating machine 1803, allowing prevention of a decrease in the accuracy of positioning of the characteristic adjustment member.

Similarly, when the filter device 1806 is the filter device according to the third embodiment, the driving direction of the characteristic adjustment member is different from the vibrating direction 1820. This allows prevention of a decrease in the accuracy of positioning of the

characteristic adjustment member.

(Fifth Embodiment)

In a fifth embodiment, a control system for a tunable filter apparatus will be described.

FIG. 19 schematically shows an example of a tunable filter apparatus according to the fifth embodiment. In the tunable filter apparatus 1900 shown in FIG. 19, an input signal (Sig. 1) is provided to the filter device 1913 via an input connector 1914. The input signal is also provided to a frequency signal detector 1916. The filter device 1913 may be any one of the filter devices according to the above-described embodiments.

The filter device 1913 filters the input signal to generate an output signal (Sig. 2) . The output signal from the filter device 1913 is transmitted to the frequency signal detector 1916 through an output connector 1915. The frequency signal detector 1916 obtains the spectrum

waveform (for example, the center frequency, transmission characteristic, and reflection characteristic) of the output signal. The spectrum waveform is transmitted to the controller 1910 as a sensor signal.

An actuator movement-distance detection sensor 1917 detects the movement distance of an actuator (for example, a piezoelectric element) 1912 included in a driving

mechanism to generate a sensor signal . The sensor signal is transmitted to the controller 1910.

The controller 1910 transmits a control signal to a driver 1911 so as to make the spectrum waveform similar to a target reference spectrum waveform based on a comparison between the spectrum waveform and the reference spectrum waveform and a comparison between the sensor signal from the actuator movement-distance detection sensor 1917 and the target movement distance of the actuator. The driver 1911 drives the actuator 1912 based on the control signal from the controller 1910. Repetition of this feedback control allows desired stable filter characteristics to be achieved. As the actuator 1912, for example, a

piezoelectric element or a magnetostrictor may be used.

Now, a sequence of operations will be described in which the controller 1910 controls the filter

characteristics of the filter device 1913 in accordance with an operation instruction 1901.

First, the operation instruction 1901 related to the series of actions of the actuator 1912 is input to an action command generator 1902. The operation instruction 1901 may be in the form of a program. An operator may input the operation instruction 1901 displayed on a panel to the controller 1910. An input device configured to input the operation instruction 1901 may be integrated with the actuator 1912 or the controller 1910 or may communicate with the actuator 1912 or the control apparatus in a wired or wireless manner. The action command generator 1902 decomposes the input operation instruction 1901 into an action procedure needed for an operation process. The action command generator 1902 expands the action procedure into a sequence of instructions at the level of action commands for the actuator 1912. A target instruction value generator 1903 calculates a target trajectory and a target value for the actuator 1912 in accordance with the generated action command. The target instruction value generator 1903 then outputs a target instruction value for driving of the actuator 1912. An actuator driving controller 1904

controls a driver 1911 in accordance with the target instruction value from the target instruction value

generator 1903 so that the actuator 1912 performs an action according to the operation.

In the controller 1910, sensor signals from the frequency signal detector 1916 and the actuator movement- distance detection sensor 1917 are provided to a signal processing circuit unit 1905. The signal processing circuit unit 1905 includes an analog-digital converter and executes various signal processes on the sensor signals. A determination unit 1906 receives the processed sensor signals from the signal processing circuit unit 1905. The determination unit 1906 executes various determination processes in accordance with the amount of deviation of the spectrum waveform from the reference spectrum waveform. The determination unit 1906 executes calculation processes such that the desired filter characteristics are obtained based on observation of the spectrum waveform performed by the frequency signal detector 1916 and adjustment of the spatial volume ratio performed by the actuator 1912. A unit including the signal processing circuit unit 1905 and the determination unit 1906 is hereinafter referred to as a spatial volume controller 1909.

The action command generator 1902 transmits action mode information associated with sequentially output and executed action commands to an action mode information unit 1907 along with information on a target operation. The action mode information unit 1907 stores spectrum waveform correction commands for the filter device 1913 defined for the respective action modes contained in various operation instructions. Furthermore, for each piece of instruction information 1908 for the corresponding action mode, the contents of output from the determination unit 1906 are set; for example, driving stop for the actuator driving controller 1904 or a return value command for the action command generator 1902. Different processes such as driving stop for the actuator 1912 or generation of a return value command are defined depending on the

respective action modes.

Thus, upon performing spectrum waveform correction, the determination unit 1906 delivers a command for stopping driving of the actuator to the actuator driving controller 1904 and even transmits a return value command for correcting a target value to the action command generator 1902, in accordance with an associated control method for the actuator 1912 associated with the defined action mode. Thus, an associated processing action suitable for the current action for spectrum waveform correction can be executed to allow driving control to be performed on the actuator 1912 so as to ensure the reliability of a spectrum waveform varying function (the function to vary the center frequency with the bandwidth maintained) .

FIG. 20 schematically shows another example of the tunable filter apparatus according to the fifth embodiment. The tunable filter apparatus shown in FIG. 20 performs driving control on an actuator 1912 using feed forward control based on table data 2001. The table data 2001 stores actuator driving information pre-acquired in

association with changes in resonant frequency. The target instruction value generator 1903 in a controller 2010 references the table data 2001 to calculate the target trajectory and the target value for the actuator 1912. The target instruction value generator 1903 outputs a target instruction value for driving of the actuator 1912. In accordance with the target instruction value from the target instruction value generator 1903, the actuator driving controller 1904 controls the driver 1911 so that the actuator 1912 performs an action associated with the operation.

The example has been described in which the piezoelectric element is used as a driving source that drives the characteristic adjustment member. However, the method for driving the characteristic adjustment member is not limited to the described example. A scheme may be adopted which involves using a threaded rod member as a characteristic adjustment member and manually driving the rod member to adjust the distance of forward and backward movement or which utilizes an electric motor, an air cylinder, or a hydraulic cylinder. Note that it is necessary to use an actuator that can adjust the distance of forward and backward movement, in order to control the stopping place of the characteristic adjustment member.

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 of the inventions .

Claims

C L A I M S

1. A tunable filter apparatus comprising:

a dielectric substrate with a front surface comprising a first area and a second area;

a resonator pattern provided on the first area of the front surface, the resonator pattern being formed of a conductive material;

a characteristic adjustment member with an opposite surface opposite to the front surface, the characteristic adjustment member being formed of a dielectric material or a magnetic material or a conductive material, a volume of a space sandwiched between the opposite surface and a

projection plane obtained by projecting the characteristic adjustment member on the front surface being defined as a spatial volume; and

a driving mechanism configured to drive the

characteristic adjustment member to adjust a spatial volume ratio between the spatial volume of the first area and the spatial volume of the second area.

2. The apparatus according to claim 1, wherein the conductive material is a superconductive material.

3. The apparatus according to claim 1, wherein the driving mechanism comprises a piezoelectric element or a magnetostrictor as a driving source.

4. The apparatus according to claim 1, wherein the driving mechanism moves the characteristic adjustment member in a direction parallel to the front surface.

5. The apparatus according to claim 1, wherein the driving mechanism rotates the characteristic adjustment member around an axis parallel to the front surface.

6. The apparatus according to claim 1, wherein the driving mechanism rotates the characteristic adjustment member around an axis perpendicular to the front surface.

7. The apparatus according to claim 1, wherein a plurality of the resonator patterns are provided on the first area of the front surface, and one characteristic adjustment member is provided for each of the plurality of resonator patterns .

8. The apparatus according to claim 1, wherein the opposite surface comprises a surface inclined to the front surface .

9. The apparatus according to claim 1, further comprising a controller configured to control the driving mechanism to make a spectrum waveform of a signal output by the resonator pattern similar to a target reference spectrum waveform.