JP2006101187A - Superconducting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent the local current concentration of a superconducting device, realize its stable high frequency transmission characteristics, and cope with both the current characteristics and the power characteristics. <P>SOLUTION: The superconducting device comprises a dielectric board (11) and a two-dimensional circuit pattern (12) made of a superconductive material on the dielectric board and the two-dimensional circuit pattern has at least a notch (20) at its part including an arc, its arc has a radius of curvature R not greater than 1/4 the effective wavelength λ. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a superconducting device, and more particularly to a dual mode superconducting device applied to a transmission front end such as a transmission filter and an antenna in the field of mobile communication and broadcasting.

  In recent years, with the spread and development of mobile phones, high-speed and large-capacity transmission technology has become indispensable. Superconductors have a very low surface resistance in the high-frequency region as compared with ordinary good electrical conductors, and therefore can be expected to have low-loss and high-Q resonators and are promising as filters for mobile communication base stations. Has been.

  For example, as shown in FIG. 1C, an RF signal received via an antenna 151 is converted into a band filter (BPF) 152R, a low noise amplifier (LNA) 153, and a down converter (D / C) After passing through 154 and demodulator (DEMOD) 155, baseband processing is performed in the baseband unit 156.

  In the transmission system, the signal processed by the baseband unit 156 passes through a modulator (MOD) 157, an up converter (U / C) 158, a high power amplifier (HPA) 159, and a band filter (BPF) 152T, and then an RF signal. As radiated from the antenna 151.

  When the superconducting filter is applied to the band filter 152R on the receiving side, a transmission loss is small and a steep frequency cutoff characteristic is expected. On the other hand, when applied to the band filter 152T on the transmission side, an effect of removing distortion generated by the high power amplifier 159 can be expected, but a large amount of power is required to transmit a high-frequency signal, miniaturization and good power characteristics. This is the current challenge.

  Conventionally, the hairpin type superconducting pattern 102 shown in FIG. 1A and the straight line type superconducting pattern 102 shown in FIG. 1B have been used as resonator patterns (for example, Patent Document 1). And 2). A superconducting ground film 104 is solidly formed on the back surface of the dielectric substrate 101, and hairpins or linear superconducting patterns 102 and feeders are formed on the front surface side of the dielectric substrate 101.

  In the case of such a microstrip line structure, there is a problem that loss increases especially when high RF power is input on the transmission side. This is because high-frequency waves such as microwaves tend to concentrate on the edge of the conductor, current concentrates on the edge or corner of the microstrip line, and the current density exceeds the critical current density of the superconductor. It is said.

  Therefore, as shown in FIG. 2A, a disk-type pattern with reduced current concentration has been proposed. That is, a disk-type superconducting pattern 112 with few corners and edges is formed on the surface of the dielectric substrate 101 to achieve a high power response as a transmission filter.

  For example, when configured as a TM11 mode resonator as shown in FIG. 2 (b), the current flows uniformly in an arc symmetric with respect to the disk diameter. The magnetic field is directed in a direction orthogonal to the current.

  However, a multistage filter or an array antenna in which a large number of such disk resonators are arranged has a drawback that the size is increased.

Therefore, as shown in FIG. 3, by providing a notch 125 in a part of the circumference of the disk-type superconducting pattern 122, the resonance frequency is separated by solving the degeneration of the electromagnetic field modes orthogonal to each other, and the dual mode filter A pattern that functions as is used. Two resonances are generated on the low frequency f1 side (current flow is in the A direction) and the high frequency f2 side (current flow is in the B direction) across the center frequency f0.
JP 2001-308603 A Japanese Patent Laid-Open No. 3-19479

  However, since the notch 125 is provided, as shown in FIG. 3, the current on the low frequency f1 side is concentrated on the corner portion of the notch and exceeds the maximum current density of the basic disk resonator without the notch. In the current density distribution diagram of FIG. 3, the region where the current density is high is a portion indicated by an arrow, and in particular, the bottom and corner portions of the U-shaped notch are high. On the contrary, the shaded portion along the circumference of the circular superconducting pattern is a portion where the current concentration is low. The frequencies f1 and f2 are out of phase by 45 ° at the maximum current density.

  As described above, as a result of current concentration at the corners and edges of the notch, in a bandpass filter or antenna using a superconducting resonator, a reduction in power resistance (allowable power) or an increase in distortion occurs.

  Therefore, an object of the present invention is to provide a superconducting device with improved power handling characteristics and reduced distortion. Such a superconducting device is suitably used for a transmission filter or an antenna.

  In order to solve the above-described problems, the present invention provides a two-dimensional circuit type superconducting resonator pattern such as a circle, an ellipse, or a polygon. Make an arc.

  Depending on the shape of the arc portion of the notch, the degree of interference between the electromagnetic field modes (coupling) differs. The larger the arc radius, the more the current concentration can be reduced. However, since the mode coupling is changed and the bandwidth is increased, the radius of curvature of the arc portion is 1/4 (λ / 4) or less of the effective wavelength. Is desirable.

Specifically, in one aspect of the present invention, the superconducting device is:
(A) a dielectric substrate;
(B) a two-dimensional circuit type resonator pattern formed of a superconductive material on the dielectric substrate, and the resonator pattern has a notch including an arc at least in part.

  By making at least a part of the notch into a curve or an arc shape, current concentration can be prevented and power characteristics and frequency characteristics can be maintained well.

  Here, the two-dimensional circuit type means not a line-shaped circuit pattern such as a hairpin type or a microstrip type, but a planar figure shape such as a circle, an ellipse, or a polygon.

  The radius of curvature R of the arc portion of the notch is desirably ¼ or less of the effective wavelength λ.

  The dielectric substrate has a dielectric constant of 8 to 10, for example, at a frequency of 3 to 5 GHz.

  The superconducting device described above further includes a ground film formed on the back surface of the dielectric substrate and a signal input / output line extending toward the resonator pattern, and the resonator pattern includes two orthogonal patterns in the 4 GHz band. Resonance is generated.

  With such a configuration, a superconducting device that operates in two resonance modes in a high-frequency region is realized.

  In a superconducting device having a two-dimensional circuit type superconducting resonator pattern, current concentration on the edge portion can be prevented, and distortion can be reduced and power characteristics can be maintained well, particularly on the high power transmission side.

  In addition, when two resonance modes are generated by one superconducting device and applied to a multistage filter or the like, the apparatus can be reduced in size.

  A preferred embodiment of the present invention will be described with reference to FIGS.

  4A is a schematic diagram of a superconducting device according to an embodiment of the present invention, and FIG. 4B is a superconducting device for transmission in a base station of a mobile communication system. It is the schematic which shows a mode that it mounted in the metal package for using for a filter.

  The superconducting device includes a dielectric substrate 11 such as an MgO single crystal substrate, a superconducting resonator pattern 12 formed in a predetermined shape with a superconducting material on the surface of the MgO dielectric substrate 11, and a superconducting filter pattern 12. A signal input / output line (feeder) 13 extending in the vicinity and a ground electrode (ground film) 14 formed on the back surface of the MgO dielectric substrate 11 are provided. In the example of FIG. 4, a YBCO (Y—Ba—Cu—O-based) material is used as the superconductive material.

  The superconducting resonator pattern 12 is a two-dimensional circuit pattern (disk pattern) having a notch 20, and the notch 20 includes an arc portion at least in part. The notch 20 couples two resonance frequencies.

  In the present specification and claims, the term “two-dimensional circuit pattern” or “two-dimensional circuit type pattern” is distinguished from a line (one-dimensional) pattern, and is circular, elliptical, or polygonal. A planar circuit pattern such as

  As the dielectric substrate 11, any dielectric substrate having a dielectric constant of 8 to 10 at a frequency of 3 to 5 GHz can be used other than the MgO single crystal substrate.

  One of the feeders 13 extending from the signal input / output electrode 15 toward the superconducting resonator pattern 12 is used as a signal input, and the other is used as a signal output.

  In FIG. 4B, a two-dimensional circuit type superconducting device is mounted on a metal package 30 whose surface is plated with gold, and a top plate (not shown) is attached. An input / output connector 31 is fixed to the metal package 30, and the electrode 15 connected to the end of the feeder 13 and the central conductor of the input / output connector 31 are electrically joined. For the electrical joining, any method such as a wire method, a tape method, or a solder method can be adopted. The ground electrode 14 made of a solid film on the back surface of the MgO dielectric substrate 11 improves the electrical connection with the metal package 30.

  FIG. 5 is a diagram showing an example of the notch shape of the superconducting resonator pattern 12. In FIG. 5A, the notch 20 is a U-shaped notch and includes a curved portion and a straight portion. The radius of curvature R of the arc (curved) portion constituting the U-shaped bottom is preferably ¼ (λ / 4) or less of the effective wavelength. This is because current concentration can be reduced as the radius of curvature R increases, but mode coupling also changes and bandwidth increases.

  In the example of FIG. 5B, the notch 20 is formed of only an arc (round cut) excluding the straight line portion. Also in this case, the radius of curvature R is λ / 4 or less.

  In order to manufacture such a superconducting device, for example, a YBCO (Y-Ba-Cu-O-based) thin film is formed on both surfaces of a 20 × 20 × 0.5 mm MgO single crystal substrate 11 using a laser deposition method. To do. The film thickness of the YBCO thin film is appropriately selected according to the filter characteristics, and is 0.5 μm, for example. The YBCO thin film on one side is patterned by a photolithography technique to form a disk-type resonator pattern 12 having an arc-shaped notch 20 and a feeder 13. The diameter of the disk type resonator pattern 12 is about 14 mm. A metal electrode 15 is formed at the end of the feeder 13. The YBCO film on the other surface of the MgO single crystal substrate 11 is left as a solid film and used as the ground electrode 14.

  This is mounted on the metal package 30 to complete the resonator. The superconducting device illustrated in FIG. 4 can be applied to, for example, fourth-generation mobile communication, and has two resonances in directions orthogonal to each other in the 4 GHz band.

  FIGS. 6A to 6C are diagrams showing still another modification of the notch portion of the superconducting resonator pattern. In the example of the notch depicted in FIG. 6, the radius of curvature R of the arc portion is preferably λ / 4 or less, and more preferably λ / 8 or less.

  FIG. 7 is a diagram showing the effect of reducing current density concentration when the superconducting pattern according to the embodiment of the present invention is used. As shown by the arrows in the figure, compared to the conventional superconducting resonator pattern having the rectangular notch of FIG. 3, the concentration of current density near the notch on the low frequency f1 side is greatly reduced. I understand that.

  Also in FIG. 7, the shaded portion of the region along the circumference of the circular superconducting pattern is a portion with a low current density.

  FIG. 8 is a graph showing the current density concentration reduction effect and frequency characteristics of the superconducting device according to the embodiment of the present invention. As a reduction effect of current density concentration, the maximum current density of a superconducting device having a rectangular notch (normal cut) and a superconducting device having a notch (round cut) including an arc portion is shown as a function of frequency. The maximum current density of the conventional normal cut is plotted with a white square, and the maximum current density of the round cut of the present invention is plotted with a white circle. In addition, as a frequency characteristic of the superconducting device according to the embodiment of the present invention, an input reflection characteristic (S11) and a transmission characteristic (S21) are shown.

  As is apparent from the graph, it is understood that the maximum current density is significantly reduced by making a round cut in which a part or all of the notches are circular arcs, as compared with a normal rectangular cut. In addition, as shown by the S11 characteristic, in the 4 GHz band, two resonance drops clearly exist, and a good frequency characteristic as a dual mode filter or a two-stage filter is shown.

  FIG. 9 is a graph showing power characteristics and distortion characteristics of the superconducting device according to the embodiment of the present invention. In order to measure the power characteristic and the distortion characteristic, a resonator sample having a round cut superconducting pattern as shown in FIG. 5B was prepared and mounted in a metal dewar. The dewar was filled with helium gas and cooled and heated in a temperature range of 70-80K. The measurement of the resonance curve at each temperature is as shown in the frequency characteristics of FIG. Under the same conditions, input / output power was measured in order to measure power durability as RF power characteristics. Further, third-order intermodulation distortion (IMD3) was measured in order to measure distortion characteristics.

  When power at the resonance frequencies f1 and f2 in the dual mode is applied, a quench phenomenon occurs at a temperature of 77.3K in the conventional superconducting pattern having a rectangular notch. That is, as indicated by the black diamonds in FIG. 9, when the power on the input side is increased, the output power of f1 on the low frequency side suddenly drops around 33.6 dMn, and the loss increases.

  On the other hand, in the superconducting pattern having the arc-shaped notch of the present invention, as shown by the black circle in FIG. 9, a power durability of 40 dBm or more is achieved without occurrence of quenching.

  In the measurement of three-dimensional intermodulation distortion (IMD3), the third-order intermodulation distortion (IMD3) caused by the nonlinear response of the resonator is measured by applying two waves adjacent to 1 MHz near the resonance frequencies f1 and f2. did. The IMD3 of the conventional superconducting pattern is represented by a white square, and the IMD3 of the superconducting pattern according to the embodiment of the present invention is represented by a white circle. As is apparent from the graph, the third-order intermodulation distortion is reduced by about 10 dBm as compared with the conventional rectangular notched superconducting pattern by using a notched superconducting pattern with a part or all of the arc. It can be confirmed.

  As described above, according to the present invention, a superconducting device with improved power resistance (allowable power) and reduced distortion is realized. Such a superconducting device is well applied to a transmitting resonator, a filter, and an antenna, and can provide a high-performance transmission / reception front end in the mobile communication and broadcasting fields.

  Although the present invention has been described based on specific embodiments, the present invention is not limited to these examples.

  For example, in the embodiment, a YBCO thin film is used as the superconducting material, but any oxide superconducting material can be used. For example, an RBCO (R—Ba—Cu—O) -based thin film, that is, a superconducting material using Nd, Gd, Sm, and Ho instead of Y (yttrium) as the R element may be used. Also, BSCCO (Bi-Sr-Ca-Cu-O) system, PBSCCO (Pb-Bi-Sr-Ca-Cu-O) system, 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.

  The dielectric substrate is not limited to the MgO single crystal substrate, and for example, a LaAlO3 substrate, a sapphire substrate, or the like may be used.

  In addition, the two-dimensional circuit pattern formed of a superconducting material is preferably circular (disk shape) from the viewpoint of reducing corners and edges as much as possible. By forming a notch including an arc, a dual mode can be realized while reducing current concentration.

Finally, the following notes are disclosed regarding the above description.
(Appendix 1) Dielectric substrate,
And a two-dimensional circuit type resonator pattern formed of a superconducting material on the dielectric substrate, wherein the resonator pattern has a notch formed at least partially in an arc. device.
(Additional remark 2) The curvature radius R of the circular arc part of the said notch is 1/4 or less of effective wavelength (lambda), The superconducting device of Additional remark 1 characterized by the above-mentioned.
(Supplementary note 3) The superconducting device according to Supplementary note 1 or 2, wherein the dielectric substrate has a frequency of 3 to 5 GHz and a dielectric constant of 8 to 10.
(Additional remark 4) It further has a ground film formed on the back surface of the dielectric substrate and a signal input / output line extending toward the resonator pattern, and the resonator pattern has two resonances orthogonal to each other in the 4 GHz band. The superconducting device according to any one of appendices 1 to 3, wherein:
(Supplementary note 5) The superconducting device according to any one of supplementary notes 1 to 4, wherein the superconducting material is an oxide superconducting material.
(Supplementary note 6) The superconducting device according to supplementary note 1, wherein the resonator pattern is a circular pattern.
(Supplementary note 7) The superconducting device according to supplementary note 1, wherein the notch is U-shaped or semicircular.

It is a figure for demonstrating the conventional superconducting filter device applied to a mobile communication system, and is a figure of the resonator which has a hairpin type and a straight line type superconducting pattern. It is a figure of the resonator which has the conventional disc type superconducting pattern. It is a figure which shows the concentration of the current density in the conventional notched disk type | mold superconducting resonator pattern. It is a schematic block diagram of the superconducting device which concerns on one Embodiment of this invention. It is a figure which shows the example of the superconducting pattern with a notch containing the circular arc part which concerns on one Embodiment of this invention. It is a figure which shows the modification of the notched superconducting pattern containing a circular arc part. It is a figure which shows the reduction effect of the current density concentration of the superconducting device of this invention. It is a graph which shows the reduction effect and frequency characteristic of the current density concentration of the superconducting device of this invention. It is a graph which shows the electric power characteristic and distortion characteristic of the superconducting device of this invention.

Explanation of symbols

10 Superconducting filter 11 Dielectric substrate 12 Superconducting pattern 13 Feeder (signal input / output line)
14 Ground film 15 Electrode

Claims (5)

A dielectric substrate;
And a two-dimensional circuit type resonator pattern formed of a superconducting material on the dielectric substrate, wherein the resonator pattern has a notch formed at least partially in an arc. device.   The superconducting device according to claim 1, wherein a radius of curvature R of the arc portion of the notch is equal to or less than ¼ of an effective wavelength λ.   The superconducting device according to claim 1 or 2, wherein the dielectric substrate has a frequency of 3 to 5 GHz and a dielectric constant of 8 to 10.   A ground film formed on a back surface of the dielectric substrate; and a signal input / output line extending toward the resonator pattern, wherein the resonator pattern generates two resonances orthogonal to each other in a 4 GHz band. The superconducting device according to any one of claims 1 to 3. The superconducting device according to claim 1, wherein the superconducting material is an oxide superconducting material.