HIGH-FREQUENCY CIRCUIT ELEMENT

Abstract: In a small transmission line type high-frequency circuit element that has small loss due to conductor resistance and has a high Q value, an error in the dimension of a pattern, etc. can be corrected to adjust element characteristics . An elliptical shape resonator (12) that is formed of an electric conductor is formed on a substrate (11a), while a pair of input-output terminals (13) are formed on a substrate (11b). Substrate (11a) on which resonator (12) is formed and substrate (11b) on which input-output terminal (13) is formed are located parallel to each other, with a surface on which resonator (12) is formed and a surface on which input-output terminal (13) is formed being opposed. Substrates (11a) and (11b) that are located parallel to each other are relatively moved by a mechanical mechanism that uses a screw and moves slightly. Also, substrate (11a) is rotated by the mechanical mechanism that uses a screw and moves slightly around the center axis of resonator (12) as a rotation axis (18).

Description: Technical Field The present invention relates to a high-frequency circuit element that basically comprises a resonator, such as a filter or a channel combiner, used for a high-frequency signal processor in communication systems, etc. Background Art A high-frequency circuit element that basically comprises a resonator, such as a filter or a channel combiner, is an essential component in high-frequency communication systems. Especially, a filter that has a narrow band is required in mobile communication systems, etc. for the effective use of a frequency band. Also, a filter that has a narrow band, low loss, and small size and can withstand large power is highly desired in base stations in mobile communication and communication satellites. The main examples of high-frequency circuit elements such as resonator filters presently used are those using a dielectric resonator, those using a transmission line structure, and those using a surface accoustic wave element. Among them, those using a transmission line structure are small and can be applied to frequencies as high as microwaves or milliwaves. Furthermore, they have a two-dimensional structure formed on a substrate and can be easily combined with other circuits or elements, and therefore they are widely used. Conventionally, a half-wavelength resonator with a transmission line is most widely used as this type of resonator. Also, by coupling a plurality of these half-wavelength resonators, a high-frequency circuit element such as a filter is formed. (Laid-open Japanese Patent Application No. (Tokkai hei) 5-267908) However, in a resonator that has a transmission line structure, such as a half-wavelength resonator, high-frequency current is concentrated in a part in a conductor. Therefore, loss due to conductor resistance is relatively large, resulting in degradation in Q value in the resonator, and also an increase in loss when a filter is formed. Also, when using a half-wavelength resonator that has a commonly used microstrip line structure, the effect of loss due to radiation from a circuit to space is a problem. These effects are more significant in a smaller structure or at high operating frequencies. A dielectric resonator is used as a resonator that has relatively small loss and is excellent in withstanding high power. However, the dielectric resonator has a solid structure and large size, which are problems in implementing a smaller high-frequency circuit element. Also, by using a superconductor that has a direct current resistance of zero as a conductor of a high-frequency circuit element using a transmission line structure, lower loss and an improvement in high frequency characteristics in a high-frequency circuit can be achieved. An extremely low temperature environment of about 10 kelvins was required for a conventional metal type superconductor. However, the discovery of a high-temperature oxide superconductor has made it possible to utilize the superconducting phenomena at relatively high temperatures (about 77 kelvins). Therefore, an element that has a transmission line structure and uses the high-temperature superconducting materials has been examined. However, in the above elements that have conventional structures, superconductivity is lost due to excessive concentration of current, and therefore it is difficult to use a signal having large power. Thus, the inventors, etc. have implemented a small transmission line type high-frequency circuit element that has small loss due to conductor resistance and a high Q value, by using a resonator that is formed of a conductor formed on a substrate and has two dipole modes orthogonally polarizing without degeneration as resonant modes. Here, "two dipole modes orthogonally polarizing without degeneration" will be explained. In a common disk type resonator, a resonant mode in which positive and negative charges are distributed separately in the periphery of the disk is called a "dipole mode" and therefore is similarly called herein. When considering a two-dimensional shape, any dipole mode is resolved into two independent dipole modes in which the directions of current flow are orthogonal. If the shape of a resonator is a complete circle, the resonance frequencies of two dipole modes orthogonally polarizing are the same. In this case, the energy of two dipole modes is the same, and the energy is degenerated. Generally, in the case of a resonator having any shape, the resonance frequencies of these independent modes are different, and therefore the energy is not degenerated. For example, when considering a resonator having an elliptical shape, two independent dipole modes orthogonally polarizing are respectively in the directions of the long axis and short axis of the ellipse, and the resonance frequencies of both modes are respectively determined by the lengths of the long axis and short axis of the ellipse. The "two dipole modes orthogonally polarizing without degeneration" refers to these resonant modes in a resonator having an elliptical shape, for example. When using a resonator that has thus two dipole modes orthogonally polarizing without degeneration as resonant modes, by separately using both modes, one resonator can be operated as two resonators that have different resonance frequencies. Therefore, the area of a resonator circuit can be effectively used, that is, a smaller resonator can be implemented. Also, when using this resonator, the resonance frequencies of two dipole modes are different, and therefore the coupling between both modes rarely occurs, rarely resulting in unstable resonance operation and degradation in Q value. In addition, this resonator has such a high Q value that the loss due to conductor resistance is small. Generally, a resonator that has a transmission line structure and uses a thin film electrode pattern, regardless of whether a superconductor is used or not, has a two-dimensional structure formed on a substrate. Therefore, variations in element characteristics (for example, a difference in center frequency) due to an error in the dimension of a pattern etc. in patterning a transmission line structure occurs. Also, in the case of a resonator that has a transmission line structure and uses a superconductor, there is a problem that element characteristics are changed due to temperature change and input power, which is specific to superconductors, in addition to the problem of variations in element characteristics due to an error in the dimension of a pattern, etc. Therefore, the ability to adjust variations in element characteristics due to an error in the dimension of a pattern, etc. as well as a change in element characteristics due to temperature change and input power is required. Laid-open Japanese Patent Application No. (Tokkai hei) 5-199024 discloses a mechanism that adjusts element characteristics. This adjusting mechanism disclosed in this official gazette comprises a structure in which a conductor piece, a dielectric piece, or a magnetic piece is located so that it can enter into the electromagnetic field generated by a high frequency flowing through a resonator circuit in a high-frequency circuit element comprising a superconducting resonator and a superconducting grounding electrode. According to this mechanism, by locating the conductor piece, the dielectric pice, or the magnetic piece close to or away from the superconducting resonator, a resonance frequency which is one of element characteristics can be easily adjusted. However, in the high-frequency circuit element disclosed in the above Laid-open Japanese Patent Application No. (Tokkai hei) 5-199024, the shape of the superconducting resonator is a complete circle, and the resonance frequencies of two dipole modes orthogonally polarizing are the same. Therefore, both modes can not be utilized separately, and a smaller superconducting resonator and a smaller high-frequency circuit element can not be implemented. The preferred embodiment aims to provide a small transmission line type high-frequency circuit element that has small loss due to conductor resistance and has a high Q value, wherein an error in the dimension of a pattern, etc. can be corrected to adjust element characteristics. According to the present invention There is provided a high-frequency circuit element as claimed in claim 1. The substrate having the resonator formed and a substrate having the input-output terminal formed are preferably located parallel to each other, with a substrate surface on which the resonator is formed and a substrate surface on which the input-output terminal is formed being opposed. A substrate on which the resonator is formed is preferably formed into a disk-like shape, and the substrate on which the resonator is formed is preferably fitted in a hole having a circular section which is provided in a substrate on which the input-output terminal is formed. The electric conductor preferably has a smooth outline. The electric conductor preferably has an elliptical shape. The structure of the entire element preferably has a structure selected from a microstrip line structure, a triplate line structure, and a coplaner wave guide structure. By changing the relative positions of the substrate having the resonator formed and the other substrate, the input-output terminal and the resonator can be optimally coupled so that high frequencies can be processed. Also, by relatively changing the coupling position of each input-output terminal to the resonator, the coupling strength of the pair of input-output terminals and each two modes orthogonally polarizing can be changed to adjust a center frequency in operation as the resonator. As a result, variations in element characteristics (for example, a difference in center frequency) due to an error in the dimension of a pattern, etc. in patterning a transmission line structure can be adjusted after manufacturing the high-frequency circuit element to implement a high-frequency circuit element that has high performance. In this case, element characteristics can be adjusted by mechanically correcting positions, and therefore element characteristics can be adjusted while the high-frequency circuit element is operated. As a result, practical adjustment can be achieved compared with trimming a resonator pattern, etc. Furthermore, when forming one of the input-output terminals on the substrate on which the resonator is formed, element characteristics can be adjusted by changing the interval between the input-output coupling points of one input-output terminal and of the other input-output terminal. According to the preferable example that a substrate on which the resonator is formed and a substrate on which the input-output terminal is formed are located parallel to each other, with a substrate surface on which the resonator is formed and a substrate surface on which the input-output terminal is formed being opposed, the coupling between the input-output terminal and the resonator is good. According to the preferable example that a substrate on which the resonator is formed is formed into a disk-like shape and that the substrate on which the resonator is formed is fitted in a hole having a circular section which is provided in a substrate on which the input-output terminal is formed, a small size element can be implemented. According to the preferable example that the electric conductor has a smooth outline, high-frequency current is excessively concentrated in a part, and a signal wave is not radiated to space. Therefore, a decrease in Q value due to an increase in radiation loss is prevented, and as a result, high Q (unloaded Q) is obtained. Also, since high-frequency current is distributed in two dimensions, maximum current density at which resonance operation is performed by a high-frequency signal having the same power can be lowered. Therefore, when a high-frequency signal having large power is processed, negative effects due to the excessive concentration of high-frequency current, such as degradation of a conductor material due to exothermic reaction, etc., can be prevented, and as a result, a high-frequency signal having larger power can be processed. According to the preferable example that the electric conductor has an elliptical shape, a resonator that has two dipole modes orthogonally polarizing without degeneration as resonant modes can be easily implemented. According to the preferable example that the structure of the entire element has a structure selected from a microstrip line structure, a triplate line structure, and a coplaner-wave guide structure, the following advantages are obtained. The microstrip line structure is simple in structure and has good coherency with other circuits. The triplate line structure has extremely small radiation loss, and therefore a high-frequency circuit element that has small loss can be obtained. In the coplanar wave guide structure, the entire structure including a grounded plane can be manufactured on one surface of a substrate, and therefore manufacturing processes can be simplified, and the structure is especially effective when using a high-temperature superconducting thin film which is difficult to form on both surfaces of a substrate as a conductor material. Embodiments of the present invention will now be described, by way of example only, and with reference to the accompanying drawings in which: Fig. 1 is a cross-sectional view showing a first embodiment of a high-frequency circuit element; Fig. 2 (a) is a plan view showing a second embodiment of a high-frequency circuit element; Fig. 2 (b) is a cross-sectional view of Fig. 2 (a); and Fig. 2 (c) is an exploded perspective view of Fig. 2 (a). Fig. 1 is a cross-sectional view showing a first embodiment of a high-frequency circuit element. As shown in Fig. 1, a resonator 12 having an elliptical shape which is formed of an electric conductor is formed on and at the center of a substrate 11a which is formed of monocrystal of a dielectric, etc., by using a vacuum evaporation method and etching, for example. A pair of input-output terminals 13 are formed on a substrate 11b which is formed of monocrystal of a dielectric, etc., by using a vacuum evaporation method and etching, for example. Substrate 11a on which resonator 12 is formed and substrate 11b on which input-output terminal 13 is formed are located parallel to each other, with a surface on which resonator 12 is formed and a surface on which input-output terminal 13 is formed being opposed. By thus locating the substrate surface having resonator 12 formed and the substrate surface having input-output terminal 13 formed opposed and parallel to each other, the coupling of input-output terminal 13 and resonator 12 is good. In this case, if a gap exists between substrates 11a and 11b, there are no problems in principle. However, in order to improve the characteristics of the high-frequency circuit element, substrates 11a and 11b are in contact with each other. Thereby, one end of input-output terminal 13 is coupled to the outer periphery of resonator 12 by capacitance. Also, grounded planes 14 are formed on the entire back surfaces of substrates 11a and 11b, and a high-frequency circuit element that has a strip line structure as a whole is implemented. When thus using the strip line structure, radiation loss is extremely small, and therefore a high-frequency circuit element that has small loss is obtained. In the high-frequency circuit element that is formed as mentioned above, resonance operation can be performed by coupling a high-frequency signal. When considering a resonator having an elliptical shape as in this example, two independent dipole modes orthogonally polarizing are respectively in the directions of the long axis and short axis of the ellipse. The resonance frequencies of both modes are respectively determined by the lengths of the long axis and short axis of the ellipse. Therefore, in this case, the energies of two dipole modes are different and are not degenerated. When using a resonator that has such two dipole modes orthogonally polarizing without degeneration as resonant modes, both modes can be separately used, and therefore one resonator can be operated as two resonators that have different resonance frequencies. As a result, the area of a resonator circuit can be effectively used, that is, a small-size resonator can be implemented. Also, when using this resonator, the resonance frequencies of two dipole modes are different, and therefore the coupling between both modes rarely occurs, rarely resulting in unstable resonance operation or degradation in Q value. In addition, such a high Q value leads to small loss due to conductor resistance. Substrates 11a and lib which are located parallel to each other can be relatively moved by a mechanical mechanism that uses a screw and moves slightly. Thereby, resonator 12 and input-output terminal 13 can be adjusted to be optimally coupled so that high frequencies can be processed. Also, substrate 11a can be rotated around the center axis (vertical direction) of resonator (ellipse) 12 as a rotation axis 18 by the mechanical mechanism that uses a screw and moves slightly. Thereby, the coupling positions of the pair of input-output terminals 13 and the outer peripheral part of resonator 12 can be changed, and therefore, by changing the coupling strength of the pair of input-output terminals 13 and each two modes orthogonally polarizing, a center frequency in operation as the resonator can be adjusted. Therefore, by suitably adjusting the relative positions of substrates 11a and 11b as well as the coupling position of resonator 12 and input-output terminal 13, element characteristics can be adjusted to implement a high-frequency circuit element that has high performance. Thus, according to the structure of this example, variations in element characteristics (for example, a difference in center frequency) due to an error in the dimension of a pattern, etc. in patterning a transmission line structure can be adjusted after manufacturing the high-frequency circuit element. Therefore, practical adjustment is possible compared with trimming a resonator pattern, etc. While resonator 12 is formed on substrate 11a, and the pair of input-output terminals 13 are formed on substrate 11b in this example, a structure need not be limited to this structure. One input-output terminal 13 may be formed on substrate 11a having resonator 12 formed. In this structure, element characteristics can be adjusted by changing the interval between the input-output coupling points of one input-output terminal 13 and of the other input-output terminal 13. Fig. 2 is a structural view showing a second embodiment of a high-frequency circuit element. As shown in Fig. 2, a hole having a circular section 19a is provided at the center of a substrate 19 which is formed of monocrystal of a dielectric, etc. A pair of input-output terminals 13 are formed on substrate 19 sandwiching hole 19a by using a vacuum evaporation method and etching, for example. A substrate 20 which is formed of the same material as that of substrate 19 is formed into a disk-like shape so that it can be fitted in hole 19a of substrate 19. A resonator having an elliptical shape 12 which is formed of an electric conductor is formed on substrate 20 by using a vacuum evaporation method and etching, for example. Substrate 20 is fitted in hole 19a of substrate 19 to be integrated. Thereby, one end of input-output terminal 13 is coupled to the outer peripheral part of resonator 12 by capacitance. Also, grounded planes 14a and 14b are respectively formed on the entire back surfaces of substrates 19 and 20, and a high-frequency circuit element that has a microstrip line structure as a whole is implemented. This microstrip line structure is simple in structure and has good coherency with other circuits. Substrate 20 can be relatively rotated around the center axis (vertical direction) of resonator (ellipse) 12 as a rotation axis 18 by a mechanical mechanism that uses a screw and moves slightly. Thereby, the coupling positions of the pair of input-output terminals 13 and the outer peripheral part of resonator 12 can be changed, and therefore, by changing the coupling strength of the pair of input-output terminals 13 and each two modes orthogonally polarizing, a center frequency in operation as the resonator can be similarly adjusted as in the above first example. While the high-frequency circuit element that has a microstrip line structure is illustrated in this example, a structure need not be limited to this structure. A strip line structure may be formed by locating a substrate that has a grounded plane opposed to resonator 12 in this high-frequency circuit element. Also, a coplanar wave guide structure may be formed by manufacturing the entire structure including a grounded plane on one surface of a substrate. By using this coplanar wave guide structure, manufacturing processes can be simplified, and the structure is especially effective when using a high-temperature superconducting thin film which is difficult to form on both surfaces of a substrate as a conductor material. As mentioned above, according to the high-frequency circuit element according to the present invention, in a small transmission line type high-frequency circuit element that has a high Q value, an error in the dimension of a pattern, etc. can be corrected to adjust element characteristics. Therefore, this high-frequency circuit element can be used for a base station in mobile communication or a communication satellite which requires a filter that can withstand large power.

Claims: A high-frequency circuit element comprising a resonator (12) that is formed of an electric conductor and has two dipole modes orthogonally polarizing without degeneration as resonant modes, and input-output terminals (13), wherein said resonator (12) and at least one of said input-output terminals (13) are formed on different substrates (11a;11b;19;20), and wherein the high-frequency circuit element comprises a mechanism that relatively rotates the substrate (11a;20) on which the resonator (12) is formed around a rotation axis that is perpendicular to the substrate (11b;19) on which at least one of said input-output terminals (13) is formed. The high-frequency circuit element according to claim 1, wherein the substrate (11a) on which the resonator (12) is formed and the substrate (11b) on which at least one of said input-output terminals (13) is formed are located parallel to each other, with the substrate surface on which said resonator (12) is formed and the substrate surface on which at least one of said input-output terminals (13) is formed being opposed. The high-frequency circuit element according to claim 1, wherein the substrate (20) on which the resonator (12) is formed is formed into a disk-like shape, said substrate (20) being fitted in a hole (19a) having a circular section which is provided in the substrate (19) on which the input-output terminal (13) is formed. The high-frequency circuit element according to claim 1, 2 or 3, wherein the electric conductor has a smooth outline. The high-frequency circuit element according to any preceding claim, wherein the electric conductor has an elliptical shape. The high-frequency circuit element according to any preceding claim, wherein the structure of the entire element has a structure selected from a microstrip line structure, a triplate line structure, and a coplanar wave guide structure.

Inventors: ENOKIHARA AKIRA, HIGASHINO HIDETAKA, MIZUNO KOICHI, SETSUNE KENTARO, ENOKIHARA, AKIRA, HIGASHINO, HIDETAKA, MIZUNO, KOICHI, SETSUNE, KENTARO
Applicants: MATSUSHITA ELECTRIC IND CO LTD, MATSUSHITA ELECTRIC INDUSTRIAL CO., LTD
Application year: 1995
Main classification: H01P7
IPC codes: H01P7, H01P1