JP2008172652A - Superconductive tunable filter using piezoelectric element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To control a resonance frequency over a wide range without being affected by characteristics of a piezoelectric element, related to a superconductive tunable filter using the piezoelectric element. <P>SOLUTION: The superconductive tunable filter has a resonator pattern 2 formed of a two-dimensional figure on a dielectric base substrate 1 by using a superconductive material, a dielectric 3 disposed opposite above the resonator pattern 2, and a mechanism which moves up and down a support rod 4 holding the dielectric 3 atop by displacing the piezoelectric element 7. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a superconducting tunable filter using a piezoelectric element capable of controlling a resonance frequency without depending on the characteristics of the piezoelectric element.

  Microwave filters using superconducting wiring have been developed for a long time. However, since cellular phones have become widespread in recent years, a microwave filter capable of controlling the cut-off frequency is required.

  In controlling the cut-off frequency in such a microwave filter, a method of controlling the effective magnetic permeability or effective permittivity of the superconducting wiring has become the mainstream.

  As a method for controlling the effective dielectric constant, a method is known in which a dielectric is disposed on a superconducting wiring and the position of the dielectric is changed.

  In recent years, a method has been considered in which a piezo element is attached to this dielectric, the position is precisely controlled, and the effective dielectric constant is accurately controlled (see, for example, Patent Document 1 and Patent Document 2).

  However, when these known methods are used, there is a problem that the resonance frequency that can be controlled is determined by the characteristics of the piezoelectric element.

In general, since the characteristics of a piezo element are reduced to 1/3 to 1/10 at a low temperature, the resonance frequency cannot be controlled over a wide range.
JP 2001-211004 A JP 2002-204102 A Eiji Omichi, “Stick and slip method”, Solid Physics, Vol. 37 No. 1 11 (2002)

  The present invention seeks to be able to control the resonance frequency over a wide range without being affected by the characteristics of the piezoelectric element.

  In a superconducting tunable filter using a piezo element according to the present invention, a resonator pattern formed of a superconducting material on a dielectric base substrate and made of a two-dimensional figure is opposed to the resonator pattern. And a mechanism for moving a support rod holding the dielectric at the tip up and down by the displacement of the piezo element.

  By adopting the above means, precise position control of the dielectric and a wide range of movement distance are realized, and the resonance frequency can be controlled over a wide range without depending on the characteristics of the piezoelectric element.

  The superconducting tunable filter of the present invention falls within the category of controlling the superconducting resonance frequency by changing the position of the dielectric disposed on the superconducting resonator, but precisely controlling the position of the dielectric. Therefore, the position is changed by utilizing the displacement of the piezo element and transmitting the displacement to the dielectric through a mechanism for moving the dielectric up and down.

  In this case, the piezo element is driven by applying, for example, a stick and slip method (for example, see Non-Patent Document 1), thereby realizing precise position control and a wide range of movement distance. can do.

  1A and 1B are explanatory diagrams showing an example of a superconducting tunable filter according to the present invention, where FIG. 1A is a main part plane, FIG. 1B is a main part cut side surface, and FIG. 1C is a direction orthogonal to FIG. The main part cutting | disconnection side surface which looked at from the right side is each shown.

  In the figure, 1 is a dielectric base substrate made of MgO, 2 is a superconducting resonator pattern, 3 is a dielectric, 4 is a support bar, 5 is a signal input / output line, 6 is a screw, 6A is a spring, 7 is Piezoelectric elements, 8 is a metal package, and 9 is a ground electrode. The dielectric 3 may be replaced with a magnetic material.

  Since the superconducting tunable filter is used as, for example, a transmission filter in a base station of a mobile communication system, noise removal or reduction is an important issue, and is thus mounted on the metal package 8.

  The superconducting tunable filter includes, for example, a dielectric base substrate 1 made of an MgO single crystal substrate, a superconducting resonator pattern 2 formed in a predetermined shape with a superconducting material on the surface of the dielectric base substrate 1, and a superconducting filter. A signal input / output line 5 extending in the vicinity of the resonator pattern 2, a dielectric 3 mounted on the dielectric base substrate 1, and a mechanism for moving the dielectric 3 up and down by the piezoelectric element 7 are supported. The displacement of the piezoelectric element 7 is supported It is transmitted to the dielectric 3 via the bar 4. The spring 6A plays a role of restraining the support bar 4.

  The piezo element 7 is manufactured on the assumption that it is used at room temperature. However, when it is used at a low temperature, the characteristics are lowered, but it has been confirmed that it operates (see, for example, Non-Patent Document 1).

  In the superconducting tunable filter shown in FIG. 1, a YBCO (Y—Ba—Cu—O-based) material is used as a superconducting material, and the superconducting resonator pattern 2 is formed as a two-dimensional circuit pattern.

  As the dielectric base substrate 1, a substrate made of an arbitrary dielectric material having a dielectric constant of 8 to 10 at a frequency of 3 to 5 GHz other than the MgO single crystal substrate can be used.

  One of the signal input / output lines 5 is used for signal input, and the other is used for signal output. A ground electrode 9 is formed on the back surface of the dielectric base substrate 1.

  FIG. 2 is a main part slope view showing a model for simulating the adjustment of the resonance frequency in the superconducting tunable filter. The parts indicated by the same symbols as those used in FIG. 1 are the same or effective. This part is represented.

As the dielectric 3 in the model, single crystal LaAlO ₃ was used, and a simulation was performed on transmission characteristics (S21) when the dielectric 3 was moved in the vertical direction.

  FIG. 3 is an explanatory view of the main part showing a superconducting tunable filter for explaining the movement of the piezo element and the support rod. FIG. 3A shows the waveform of the voltage applied to the piezo element, and FIG. The main part cutting side surface explaining the effect | action with respect to the support rod of a piezo element is each shown.

  As can be seen from (A), the waveform of the voltage for displacing the piezo element is a kind of sawtooth wave. The bar 4 operates as seen in (B) and (C).

  That is, when the sawtooth wave rises as A → B, the piezo element 7 is displaced as indicated by the broken line in (B), and the support bar 4 frictionally coupled to the piezo element 7 is also indicated by the broken line. As shown, it moves by a length L corresponding to the displacement of the piezo element 7.

  Next, when the sawtooth wave falls as B → C, the piezo element 7 is restored as indicated by the solid line in (C), but the support rod 4 is frictionally coupled to the piezo element 7. Slips and stays at the position moved by the length L. Eventually, the dielectric 3 is moved accordingly. In order to reverse the operation direction of the support rod 4, the voltage applied to the piezo element may be reversed.

  FIG. 4 is a diagram showing the result of the simulation, with the vertical axis representing the resonance frequency (GHz) and the horizontal axis representing the distance (mm), from the dielectric base substrate 1 to the dielectric 3. The change of the resonance frequency when changing the distance is shown.

From the figure, it can be seen that when single crystal LaAlO ₃ is used for the dielectric 3, about 4% of the resonance frequency can be controlled.

  FIG. 5 is a cut-away side view of a main part showing a superconducting tunable filter using a plurality of sets of dielectric up-and-down mechanisms described with reference to FIG. 1, and the parts indicated by the same symbols as those used in FIG. It shall represent the same or equivalent part.

  As can be seen in FIG. 5, by installing the vertical mechanism of the dielectric 3 at a plurality of locations and controlling each independently, the angular deviation in the height direction of the dielectric 3 can be accurately corrected, The control of the resonance frequency can be performed more precisely, and a desired filter characteristic can be realized.

  In each of the above-described embodiments, the case where the stick-and-slip method depending on the piezo element is applied as the mechanism for raising and lowering the dielectric has been described. However, the present invention is not limited to this. By using this, the dielectric may be moved up and down by changing the displacement of the piezo element into a vertical movement.

  Further, although the YBCO thin film is used as the material of the superconducting resonator pattern 2, any oxide superconducting material can be used. For example, an RBCO (R—Ba—Cu—O) -based thin film, that is, a superconducting material in which Y (yttrium) is replaced with Nd, Sm, Gd, Dy, Ho or the like as an R element, or BSCCO (Bi -Sr-Ca-Cu-O), PBSCCO (Pb-Bi-Sr-Ca-Cu-O), CBCCO (Cu-Bap-Caq-Cur-Ox, 1.5 <p <2.5, 2 .5 <q <3.5, 3.5 <r <4.5) may be used for the superconducting material.

Furthermore, the dielectric base substrate 1 is not limited to the MgO single crystal substrate, and for example, a LaAlO ₃ substrate, a sapphire substrate, or the like may be used.

Furthermore, the dielectric 3 is not limited to a LaAlO ₃ single crystal, but is a single crystal SrTiO ₃ , MgO, NdGaO ₃ , LaSrAlO ₄ , LaSrGaO ₄ , YAlO ₃ , Si, GaAs, LiNbO ₃ , LiTaO ₃ , BaB ₂ O. ₄ , YbO ₄ , TiO ₂ , CaCO ₃ , KTiOPO ₄ , LiB ₃ O ₅ , KH ₂ PO ₄ , LiIO ₃ , sapphire, or the like can be used, and a polycrystalline material can also be used.

  In general, it is known that the filter band in a high frequency filter shifts depending on an error of an electrode pattern or a filter mounting method. Usually, ten filters are manufactured, of which 9 The target is obtained in the target band, but one is lost.

  Therefore, since the filter band can be corrected by using the tunable mechanism of the present invention described above, all of the manufactured high frequency filters can be used normally in the target filter band. This is effective not only for selecting a band but also for normal filter correction.

It is explanatory drawing showing an example of the superconducting tunable filter using a piezo element. It is a principal part slope figure showing the model in the case of simulating. It is principal part explanatory drawing showing the superconducting tunable filter for demonstrating a motion of a piezoelectric element and a support rod. It is a diagram showing the result of having performed simulation. It is explanatory drawing showing an example of the superconducting tunable filter using a piezo element.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Dielectric base board which consists of MgO 2 Superconducting resonator pattern 3 Dielectric 4 Support rod 5 Signal input / output line 6 Screw 6A Spring 7 Piezo element 8 Metal package 9 Ground electrode

Claims (4)

A resonator pattern composed of a two-dimensional figure formed of a superconducting material on a dielectric base substrate; and a dielectric positioned opposite to the resonator pattern;
A superconducting tunable filter using a piezo element, comprising a mechanism for moving a support rod holding the dielectric at the tip thereof up and down by displacement of the piezo element. A resonator pattern composed of a two-dimensional figure formed of a superconducting material on a dielectric base substrate; and a dielectric positioned opposite to the resonator pattern;
A superconducting tunable filter using a piezo element, comprising a plurality of mechanisms for moving up and down a plurality of support rods holding the dielectric at the tip by displacement of the corresponding piezo element. A resonator pattern composed of a two-dimensional figure formed of a superconducting material on a dielectric base substrate; and a dielectric positioned opposite to the resonator pattern;
A superconducting tuner using a piezo element, comprising: a plurality of mechanisms for vertically moving a plurality of support rods holding the dielectric at the tip thereof by independent displacements of the corresponding piezo elements. Bull filter. Single-crystal LaAlO ₃ , SrTiO ₃ , MgO, NdGaO ₃ , LaSrAlO ₄ , LaSrGaO ₄ , YAlO ₃ , Si, GaAs, LiNbO ₃ , LiTaO ₃ , BaB ₂ O ₄ , YbO ₄ , TiO ₂ , CaCO ₃ , _{KTiOPO 4, LiB 3 O 5,} KH 2 PO 4, LiIO 3, superconducting tuner using a piezoelectric element of any one of claims 1 to claim 3, characterized in that one selected from sapphire Bull filter.

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