JP4879211B2 - Tunable filter device and tuning method - Google Patents

Description

  The present invention relates to a tunable filter device used in a radio base station and the like, and a tuning method thereof.

  In recent years, with the rapid development of wireless communication, high-speed and large-capacity transmission technology has become indispensable. A microstrip line type superconducting filter using a high-temperature superconductor as a wiring material has a possibility of realizing a small and high-performance filter, and is expected to be put to practical use.

  Superconductors have a very small surface electrical resistance even in a high-frequency region such as microwaves, compared to normal electrical good conductors. Therefore, in the reception filter (resonator filter) using the superconducting material, a microstrip line type filter is configured by arranging a plurality of resonators 102a to 102i on the dielectric substrate 11, as shown in FIG. Even so, the transmission loss can be reduced. The resonators 102a to 102i are arranged so that signals propagating through the signal input / output lines 103a and 103b are electromagnetically coupled. The greater the number of resonators 102, the better the frequency cutoff characteristics, and the frequency resources can be used effectively.

  However, when used as a transmission filter, a signal having high output power is required because a signal having a high output is passed through a transmission amplifier. This is because if a signal with a large electric power is passed through a bent filter as shown in FIG. 1A, current concentrates on the bent portion of the resonator, and the superconducting state cannot be maintained due to a temperature rise due to heat generation. As a result, desired filter characteristics cannot be obtained, and the superconducting wiring itself may be broken.

  For this reason, as shown in FIG. 1B, it is conceivable that the resonator 112 is formed in a shape without a bent portion, such as a disk type, and a plurality of these are arranged (112a to 112n) to produce a filter. However, if the same number of resonators as in FIG. 1A are arranged, the filter itself becomes large, and the burden on the refrigerator is unavoidable.

  Therefore, in order to reduce the size, as shown in FIG. 1C, a groove or notch 125 is provided in a part of the disk-type resonator 122, and the positional relationship between the input / output terminals (signal input / output lines) 103a and 103b. Has been proposed to generate two resonances in one disk as shown by the orthogonal arrows in the figure (for example, see Non-Patent Document 1). By using this method, the number of resonators can be reduced.

  However, in any of the above-described methods, in order to confirm the transmission characteristics, it is necessary to prototype a superconducting filter, cool it, and actually measure the characteristics. If the characteristics are deviated, it is necessary to repeat the prototype until the desired characteristics are obtained by performing the prototype again and executing the same procedure.

On the other hand, as a tunable filter device, there is known a method of tuning a resonance frequency by applying a DC bias voltage to a nonlinear dielectric material of a parallel plate resonator and changing a dielectric constant (see, for example, Patent Document 1). ).
Special table 2000-502231 Physica C 445-448 (2006) 998-1002

  The technique of tuning by applying voltage from the outside to the dielectric material constituting the microstrip line type resonator filter requires an external power supply and a wiring structure for bias application. It is an object of the present invention to provide a filter device that can be tuned during the measurement of characteristics after trial manufacture of a filter with a simple configuration and technique without applying a voltage from the outside. It is another object of the present invention to provide such a tuning method.

  In order to solve the above problems, a tunable filter device is arranged such that a dielectric or a conductor is movable along the circumference of a superconducting disk pattern formed on a dielectric substrate. Have a configuration.

In the first aspect, the tunable filter device comprises:
A superconducting disk pattern formed on a dielectric substrate;
A dual mode generating member disposed on the circumference of the superconducting disk pattern and in close proximity to the superconducting disk pattern;
Rotating means for moving the dual mode generating member along the circumference of the superconducting disk pattern;
Is provided.

  In a preferable configuration example, the tunable filter device is accommodated in a package, and the rotating means includes a rotating shaft that can be controlled to rotate from the outside of the package, and the dual mode generating member connected to the rotating shaft. A rotating plate to be moved.

In the second aspect, the tuning method is:
A dielectric or conductor dual mode generating member is arranged on the circumference of a disk-shaped resonator formed of a superconducting material,
Transmit a signal to the resonator in a cooling environment, measure its transmission characteristics,
According to the measurement result, the dual mode generating member is moved along the circumference to adjust the transmission characteristics.
Process.

  With the above configuration and method, it is not necessary to repeat trial manufacture in order to obtain desired filter characteristics. Further, an external power supply voltage and a wiring structure for bias application are not required. By simply adjusting the position of the dual mode generating member arranged on the circumference of the superconducting pattern along the circumference, the frequency cutoff characteristic can be made variable.

  Hereinafter, preferred embodiments will be described with reference to the drawings. FIG. 2 is a basic configuration diagram of the tunable filter device 10 according to one embodiment of the present invention. As shown in the basic conceptual diagram of FIG. 2A, a resonator 12 and signal input / output lines 13a and 13b are formed on a dielectric substrate 11 with a superconducting material. The signal input line (for example, 13a) has a crescent-shaped port 18a facing the resonator 12, and the signal output line (for example, 13b) arranged at a position perpendicular to the signal input line 13a is facing to the resonator 12. A crescent-shaped port 18b. The resonator 12 and the signal input / output lines 13a and 13b are collectively referred to as a superconducting pattern. On the back surface of the dielectric substrate 11, a ground film 14 is formed of a superconducting material, as shown in FIGS. 2B and 2C.

  The resonator 12 has a disk shape in order to avoid current concentration when a high frequency signal is passed. A dual mode generating member 15 is disposed on the circumference of the resonator 12. The dual mode generating member 15 is formed of a dielectric or a conductor and is movable along the circumference of the resonator 12. In this example, the dual mode generating member 15 is configured as a dual mode generating rod 15. In the example of FIG. 2B, a rotating shaft 19 and a rotating plate 17 fixed to the rotating shaft 19 are used as a rotating mechanism that moves the dual mode generating rod 15 along the circumference of the resonator 12. The rotating shaft 19 and the rotating plate 17 are also made of a dielectric or a conductor. When the dual mode generating rod 15 and the rotating plate 17 are made of a dielectric, Al2O3, MgO, LaAlO3, sapphire, TiO2, or the like can be used.

  The dual mode generating rod 15 is fixed to the end of the rotating plate 17 and moves in the circumferential direction by the rotation of the rotating shaft 19. In this example, the height position (vertical position) of the rotating plate 17 with respect to the resonator 12 is constant regardless of the rotation of the rotating shaft 19, and the rotating plate 17 rotates in the same horizontal plane. The dual mode generating rod 15, the rotating plate 17, and the rotating shaft 19 constitute a dual mode generating adjusting mechanism 21.

  In one example, the position where the tip of the dual mode generating rod 15 touches or does not touch the surface of the resonator 12, that is, the distance between the resonator 12 and the tip of the dual mode generating rod 15 is 0.1 mm or less. The dual mode generation adjusting mechanism 21 is designed and arranged to move the dual mode generation rod 15 in the circumferential direction.

  As a good example, in order to reduce the influence of friction or the like on the resonator 12, a protective film 16 covering at least the resonator 12 portion is provided on the dielectric substrate 11, as shown in FIG. The protective film 16 is, for example, a resin thin film having a low dielectric constant such as polyimide, or any commercially available low dielectric constant film. When the rotating shaft 19 rotates as shown by the arrow A, the tip of the dual mode generating rod 15 moves on the circumference of the resonator 12 in contact with the protective film 16.

  When a foreign substance such as a dielectric or a conductor is brought close to or in contact with the disk-type resonator 12, two resonance modes are generated with one resonance pattern. By combining two resonances, the resonance peak becomes prominent, and the same effect as that obtained by arranging the disk type resonators in two stages can be obtained. A dielectric or conductor for generating two resonances is referred to as a dual mode generating member (rod) 15. When the dual mode generating rod 15 is moved along the circumference of the resonator 12, the degree of coupling between the two resonances changes, and attenuation poles appear or disappear outside the band of the filter. For this reason, the steepness of the transmission profile, that is, the bandwidth can be changed.

  FIG. 3 is a schematic diagram of the filter characteristic tuning of the tunable filter device 10 of FIG. In the tuning configuration 40, the tunable filter device 10 is accommodated in the metal package 41 so that the rotating shaft 19 of the dual mode generation adjusting mechanism 21 (see FIG. 3) passes through the upper lid of the metal package 41 for high frequency shielding. The The metal package 41 is installed on a cold plate 43 in the vacuum vessel 42. The cold plate 43 is connected to an external refrigerator (not shown) via the refrigerator expansion unit 44.

  The coaxial connector 32 of the metal package 41 is connected to one of the signal input / output lines 13 (for example, the signal input line 13a) via connection means 34 such as wire bonding. The other signal input / output line (for example, signal output line) is connected to another coaxial connector (not shown in FIG. 3) provided in the metal package 41. These coaxial connectors 32 are connected to a network analyzer (not shown) outside the vacuum vessel 42 via a coaxial cable (not shown), and the superconducting filter device 10 in the metal package 41 is cooled, so that its transmission characteristics are improved. Can be measured.

  A rotary head 22 is provided at the tip of the rotary shaft 19 that passes through the metal package 41 and protrudes to the outside. The rotation angle of the rotary shaft 19 is adjusted from the outside of the vacuum vessel 42 by adjusting means such as a driver 23 penetrating the ceiling of the vacuum vessel 42. Thereby, the dual mode generating rod 15 can be moved along the circumference of the resonator 12, and the transmission characteristic of the superconducting filter device 10 can be adjusted.

  FIG. 4 is a basic configuration diagram of a tunable filter device 20 which is a modification of FIG. In the configuration of FIG. 4, the superconducting pattern of FIG. 4A (including the resonator 12 and the input / output lines 13a and 13b having the ports 18a and 18b) is the same as that of FIG. The configuration of 31 is different. That is, the rotating shaft 29 shown in FIGS. 4B and 4C is a screw-type rotating shaft, and the height position (vertical position) of the rotating plate 27 with respect to the resonator 12 as the rotating shaft 29 rotates. ) H changes. The center frequency of the tunable filter device 20 can be adjusted by changing the height h of the rotating plate 27 with respect to the resonator 12. Specifically, when the rotating plate 27 descends and approaches the resonator 12, the dielectric constant of the space viewed from the resonator 12 changes, and the resonance frequency shifts to a lower side.

  The dual mode generating rod 25 passes through an opening 27 </ b> A provided in the vicinity of the circumference of the rotating plate 27. The diameter of the dual mode generating rod 25 is set to a size that causes slight play with respect to the opening 27A. Therefore, when the rotating shaft 29 indicated by the arrow A rotates, the rotating plate 27 descends and rises along the dual mode generating rod 25 as indicated by the arrow B, and the contact state between the dual mode generating rod 25 and the protective film 16 is as follows. The rotation plate 27 is properly maintained without hindering the vertical movement of the rotation plate 27.

  FIG. 5 is a schematic diagram of the filter characteristic tuning of the tunable filter device 20A obtained by further modifying the tunable filter device 20 of FIG. In the tuning configuration 50, the dual mode generating rod 25 of the tunable filter device 20 </ b> A has a flange 35, and a spring 26 is inserted between the flange 35 and the rotating plate 27. Even if the rotating plate 27 is lowered and raised by the rotation of the screw-type rotating shaft 29 and the rotating shaft 29, the pressure of the dual mode generating rod 25 against the resonator 12 or the protective film 16 (see FIG. 4C) by the spring 26. Can be kept constant.

  The basic configuration of tuning is the same as in FIG. 3, and the same components are denoted by the same reference numerals and description thereof is omitted. According to the transmission characteristic measurement result of the tunable filter device 20A under cooling, the screw-type rotary shaft 29 is rotated by an adjusting means such as a driver 23, and the height position of the rotary plate 27 and the dual mode generating rod 25 Both the rotational positions or only the height position of the rotating plate 27 is changed.

  When only the height position of the rotating plate 27 is changed, the dual mode generating rod 25 is set at a fixed position, for example, a point symmetrical position with respect to the orthogonal signal input / output lines 13a and 13b (see FIG. 4). , The height of the rotating plate 27 can be changed without changing the position of the dual mode generating rod 25. The amount of change in the height position due to one round of rotation is determined by the thread pitch of the screw-type rotary shaft 29. For example, the height h of the rotating plate 27 can be changed to 0.25 mm and 0.4 mm by one rotation according to the pitch dimension of the screw.

  FIG. 6 is a diagram illustrating an electromagnetic field simulation model for evaluating characteristics of the tunable filter device according to the embodiment and a measurement result thereof. The model in FIG. 6A is a simulation model for single mode evaluation in which no dual mode generating member is arranged.

  First, on a single crystal MgO substrate 11 (relative permittivity 9.7) having a thickness of 0.5 mm and a planar size of 20 mm × 20 mm, a YBCO thin film that is an oxide superconducting material is used in a 5 GHz band (diameter 11.8 mm). The superconducting pattern 61 including the disk resonator 12 and the signal input / output lines 13a and 13b is formed. The back surface of the MgO substrate 11 is covered with a complete conductor to form a ground film 14. Assuming a package for high-frequency shielding as shown by the dotted line, a complete conductor top plate 62 is installed at a height of 20 mm from the surface of the MgO substrate 11. The dielectric substrate 11 on which the superconducting pattern 61 is formed is not limited to the MgO substrate, and any dielectric substrate having a small dielectric loss can be used.

  FIG. 6B is a simulation result of the transmission characteristics by the model of FIG. As shown in FIG. 6A, when no foreign substance such as a dielectric or a conductor is disposed on the disk resonator 12 and the port 2 is disposed at a right angle to the port 1, the reflection characteristic S11 and the transmission characteristic are obtained. As indicated by S21, a resonance waveform cannot be obtained. Although not shown, when the port 2 is disposed in the horizontal direction with respect to the port 1 as shown in FIG. 1B, a resonance waveform appears at about 5 GHz with the diameter of the resonator 12 being λ / 2.

  Next, in order to generate two resonances with one resonator pattern, a position of + 45 ° counterclockwise from the extension line 71 of the input port 1 of the disk-type resonator 12 as shown in FIG. An MgO block 65 of 2 × 2 × 0.2 mm is disposed on the surface. The MgO block 65 is a dielectric block for generating a dual mode. Similar to FIG. 6A, a top plate 62 is installed at a height of 20 mm from the disk resonator 12 to make it equivalent to a high frequency shield package.

  The transmission characteristics of this model are shown in FIG. In S11 and S21, two resonance peaks appear. This is because the signal input from port 1 is degenerated in the disk, but is perturbed by the MgO block 65 to generate two resonance modes, and at port 2, the two resonances are coupled. This is because the result appears as a filter characteristic. The dielectric block 65 as the dual mode generating member 15 can generate two resonance modes as long as it has a constant dielectric constant. Particularly, the dielectric block 65 has a high dielectric constant and a low dielectric loss. TiO2 is an effective material. The generation of the two resonance modes can also be realized with a metal material.

  FIG. 8 is a diagram of a simulation model in which the position of the dielectric block 65 for generating the dual mode is different from that in FIG. In this model, the dielectric block 65 is arranged at a position of −45 ° counterclockwise with respect to the extended line 71 of the port 1 (that is, a position of 45 ° clockwise). FIG. 9 is a graph showing the result of comparing the transmission characteristics of the model of FIG. 8 with the transmission characteristics of the model of FIG. FIG. 9 shows that the steepness of the filter characteristics varies depending on the position of the dielectric block 65.

  When the dielectric block 65 is arranged at a position of + 45 ° (a point-symmetrical position with respect to the ports 1 and 2) as shown in FIG. 7 (a), attenuation poles are present at both ends of the band as shown by the dark solid lines. As shown in FIG. 8, when the dielectric block 65 is arranged at a position of −45 ° as shown in FIG. 8, the attenuation pole disappears and the characteristics become gentle as shown by a thin solid line. 7A and 8 show the case where there is one disk type resonator 12, the same effect can be obtained even if the number of disks is increased.

  FIG. 10 is a schematic diagram of a simulation model in the case where a 2 × 2 mm Au film 75 is arranged in place of the dielectric block 65 in FIGS. 7A and 8. In FIG. 10A, the Au film 75 as a conductor is disposed at a position + 45 ° from the extension line 71 of the port 1. In FIG. 10B, an Au film 75 having the same shape and size is disposed at a position of −45 °. Since the other components are the same as those in FIGS. 7A and 8, the same reference numerals are given and the description thereof is omitted.

  FIGS. 11A and 11B are graphs of transmission characteristics corresponding to the models of FIGS. 10A and 10B. When a conductor is used as the dual mode generating member, the attenuation pole appears at both ends of the band at 45 ° position, and the characteristics become steep at the position of 45 °, but the attenuation pole disappears at the position of −45 °. And the characteristic becomes gentle.

  As described above, the transmission characteristics can be changed depending on the circumferential position of the disk-type resonator 12. Even in the case where they are arranged at the same + 45 ° position, there are characteristics deviations due to patterning accuracy errors of the superconducting pattern 61 and variations in the thickness of the dielectric substrate 11, so that the tuning configuration shown in FIGS. It is possible to make adjustment while confirming actual transmission characteristics so as to show desired filter characteristics.

  The superconducting filter devices 10, 20, 20 </ b> A whose characteristics have been adjusted can contribute to miniaturization because no complicated adjustment structure remains on the metal package 41. As a method for adjusting a superconducting filter with cooling, the load on the cooler can be reduced.

  Although specific embodiments have been described above, the present invention is not limited to the above-described embodiments. For example, different characteristics can be obtained by changing the dimensions and materials of the dielectric block 65 and the conductor pattern 75. Accordingly, a plurality of types of rods having different materials and different dimensions are prepared for the dual mode generating rods 15 and 25 in the configurations of FIGS. 2 and 4 (in the case of FIG. 4, the rotating plate 27 also has different opening sizes). A plurality of types may be prepared so as to have the same), and a replaceable configuration may be adopted.

It is a figure which shows the structural example of the conventional resonator filter apparatus. It is a basic lineblock diagram of a tunable filter device of an embodiment. It is a schematic diagram of filter characteristic tuning of the embodiment. It is a basic block diagram of the modification of the tunable filter apparatus of FIG. It is a schematic diagram of filter characteristic tuning of the embodiment. It is a figure which shows the simulation model of the single mode of an Example, and its filter characteristic. It is a figure which shows the simulation model of the dual mode of an Example, and its filter characteristic. FIG. 8 is a diagram of a simulation model in which the arrangement positions of the dielectric blocks are changed in the configuration of FIG. 7. It is a figure which shows the filter transmission characteristic of the model of FIG.8 and FIG.7 (a). FIG. 9 is a diagram of a simulation model using a conductor film (Au film) instead of a dielectric block as a dual mode generating member in the models of FIG. 7A and FIG. It is a figure of the filter transmission characteristic of the model of Drawing 10 (a) and Drawing 10 (b).

Explanation of symbols

10, 20, 20A Tunable filter device 11 Dielectric substrate 12 Resonator (superconducting disk pattern)
13a, 13b Signal input / output line 14 Ground film 15, 25 Dual mode generating member (dual mode generating rod)
16 Protective films 17, 27 Rotating plate 27A Openings 18a, 18b Input / output ports 19, 29 Rotating shafts 21, 31 Dual mode generation adjusting mechanism 22 Rotating head 23 Adjusting means (driver)
40, 50 Tuning configuration 41 Metal package 42 Vacuum vessel 43 Cold plate 61 Superconducting pattern 65 Dielectric block (MgO block)
75 Conductive film (Au film)

Claims (6)

A superconducting disk pattern formed on a dielectric substrate;
A dual mode generating member disposed on the circumference of the superconducting disk pattern and in close proximity to the superconducting disk pattern;
Rotating means for moving the dual mode generating member along the circumference of the superconducting disk pattern;
The dual mode generating member is a dielectric or conductive rod extending from the rotating plate of the rotating means to the circumference of the superconducting disk pattern, and the rotating means includes a tip of the rod and the circle. A tunable filter device that moves the dual mode generating member along the circumference with a constant distance to the circumference . A package containing the tunable filter device;
Further comprising
Said rotating means includes a rotating shaft capable of rotation control from the outside of the package, that connected to said rotary shaft and a said rotary plate for movably holding said dual-mode generating member along said circumference The tunable filter device according to claim 1 . The tunable filter device according to claim 1 , wherein the rotating plate has a variable vertical position with respect to the superconducting disk pattern. 4. The tunable filter according to claim 3, wherein the rod is slidably held in a direction perpendicular to the rotating plate. A first container for holding the superconducting disk pattern and the dual mode generating member in a cooling environment;
And the rotating means moves the dual mode generating member along the circumference from the outside of the first container,
A second container containing the first container and the rotating means;
Rotation adjusting means for adjusting the rotation of the rotating means from the outside of the second container;
The tunable filter device according to claim 1, further comprising: A dual mode generating member formed of a dielectric or conductive rod extending from a rotating plate is disposed on the circumference of a disk-shaped resonator formed of a superconductive material,
Transmit a signal to the resonator in a cooling environment, measure its transmission characteristics,
According to the measurement result, the transmission characteristics are controlled by controlling the rotating plate and moving the dual mode generating member along the circumference with a constant distance between the tip of the rod and the circumference. adjust,
A tuning method characterized by that.