Patent Grant
7825751
This application is based upon and claims the benefit of priority from the prior Japanese Patent Applications No. 2006-143602, filed on May 24, 2006; the entire contents of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to a resonant circuit, a filter circuit, and an antenna device.
2. Related Art
A communication apparatus which performs information communication by radio or wire is constituted by various high frequency components such as an antenna, an amplifier, a mixer, and a filter. Among these components, a band pass filter (BPF), in which a plurality of resonant elements are arranged, has a function of passing only a signal in a specific frequency band. In today's communication systems, from a viewpoint of effective use of frequency, a sharp cut-off characteristic is preferred as a filter characteristic so as to enable the maximum use of the available band width. Further, to meet a demand for miniaturization of communication apparatuses, a filter having a smaller size is preferred.
In order to realize the filter characteristics, it is necessary to make a plurality of resonant elements coupled by electromagnetic fields, and the circuit constant of the filter consists of the resonant frequency fi of each resonant element, the coupling coefficient between resonant elements Mij, and the external quality factor Qe.
Methods for realizing the coupling coefficient between resonant elements in a filter circuit can be roughly classified into the following two kinds. The first method is a gap coupling by which a desired coupling is realized only on the basis of the positional relation between resonant elements without adding a coupling element in addition to the resonant elements. The gap coupling is suitable for a filter circuit which is constituted only by the coupling between adjacent resonant elements, such as in the Chebyshev's function type filter. The second method is a cross coupling by which a coupling is realized by adding a transmission line as described in the Patent Document 1 and the Patent Document 2. The cross coupling is suitable for a filter circuit which makes the steep skirt characteristics by the attenuation pole, and improving the planarity in group delay.
In a planar filter in which all resonant elements are arranged on a same plane, it is difficult to take a sufficient interval between adjacent resonant elements when promoting the miniaturization of the filter, as a result of which undesirable cross couplings exist in addition to desired couplings. By the influence of the undesirable cross couplings, the filter performance or the symmetry of the filter cut-off characteristic is deteriorated, which is one of the causes of the difficulty in realizing the filter characteristics.
As a measure against the undesirable cross coupling, there are a method for making the magnitude of the undesirable cross coupling small by devising the shape and arrangement of the resonant elements, and a method for effecting electromagnetic shielding between resonant elements which are coupled with each other by an undesirable cross coupling, by inserting a metal plate or the like between the resonant elements, as described in the Patent Document 3 and the Patent Document 4.
Patent Document 1: JP-A 2004-530391 (Kokai)
Patent Document 2: JP-A 2000-341071 (Kokai)
Patent Document 3: JP-A 2001-308603 (Kokai)
Patent Document 4: JP-A 2004-349966 (Kokai)
As described above, the undesirable cross coupling is not controlled by the prior art, and in the case where there are structural restrictions, such as those in miniaturizing a filter and an antenna, there are problems that the filter characteristic, the voltage standing wave ratio (VSWR), and the gain of the antenna are deteriorated by the undesirable cross coupling.
An object of the present invention is to provide a resonant circuit, a filter circuit, and an antenna device, in which the above described performance is improved by eliminating the above described disadvantages of the prior art, and by controlling the uncontrolled cross coupling between resonant elements which constitute the filter and the antenna.
A resonant circuit according to an aspect of the present invention,
in which resonant elements of a plurality of orders of at least four or more are arranged by forming a predetermined conductor pattern on a dielectric substrate, is characterized
in that among the resonant elements of the plurality of orders, a first to fourth resonant elements forming a desired four orders are arranged so as to effect electromagnetic field couplings between the first and second resonant elements, between the second and third resonant elements, between the third and fourth resonant elements, and between the fourth and first resonant elements,
by including at least either a first coupling element which is arranged between the second and fourth resonant elements, in a region on the dielectric substrate except element forming regions in which the resonant elements are formed, so as to intersect a first line segment formed by removing from a line segment connecting a center of gravity of a first region in which the first resonant element is formed to a center of gravity of a third region in which the third resonant element is formed, parts of the line segment included in the first and third regions in which the first and third resonant elements are formed, or
a second coupling element which is arranged between the first and third resonant elements, in a region on the dielectric substrate except the element forming regions in which the resonant elements are formed, so as to intersect a second line segment formed by removing from a line segment connecting a center of gravity of a second region in which the second resonant element is formed to a center of gravity of a fourth region in which the fourth resonant element is formed, parts of the line segment included in the second and fourth regions in which the second and fourth resonant elements are formed, and
in that electrical lengths of the first and second coupling elements are selected from a range except electrical lengths of integer multiples of a half wavelength of a wavelength in a range corresponding to a frequency range determined on the basis of a center frequency and a band width of the resonant circuit.
Further, a filter circuit according to an aspect of the present invention,
in which resonant elements of a plurality of orders of at least four or more, and an input section and an output section which are connected to the feed line, are arranged by forming a predetermined conductor pattern on a dielectric substrate, is characterized
in that among the resonant elements of the plurality of orders, a first to fourth resonant elements forming a desired four orders are arranged so as to effect electromagnetic field couplings between the first and second resonant elements, between the second and third resonant elements, between the third and fourth resonant elements, and between the fourth and first resonant elements,
by including at least either a first coupling element which is arranged between the second and fourth resonant elements, in a region on the dielectric substrate except element forming regions in which the resonant elements are formed, so as to intersect a first line segment formed by removing from a line segment connecting a center of gravity of a first region in which the first resonant element is formed to a center of gravity of a third region in which the third resonant element is formed, parts of the line segment included in the first and third regions in which the first and third resonant elements are formed, or
a second coupling element which is arranged between the first and third resonant elements, in a region on the dielectric substrate except the element forming regions in which the resonant elements are formed, so as to intersect a second line segment formed by removing from a line segment connecting a center of gravity of a second region in which the second resonant element is formed to a center of gravity of a fourth region in which the fourth resonant element is formed, parts of the line segment included in the second and fourth regions in which the second and fourth resonant elements are formed, and
in that electrical lengths of the first and second coupling elements are selected from a range except electrical lengths of integer multiples of a half wavelength of a wavelength in a range corresponding to a frequency range determined on the basis of a center frequency and a band width of the resonant circuit.
Further, an antenna device according to an aspect of the present invention,
in which resonant elements of a plurality of orders of at least four or more and an input section as a feeding line are arranged by forming a predetermined conductor pattern on a dielectric substrate, is characterized
in that among the resonant elements of the plurality of orders, a first to fourth resonant elements forming a desired four orders are arranged to effect electromagnetic field couplings between the first and second resonant elements, between the second and third resonant elements, between the third and fourth resonant elements, and between the fourth and first resonant elements,
by including at least either a first coupling element which is arranged between the second and fourth resonant elements, in a region on the dielectric substrate except element forming regions in which the resonant elements are formed, so as to intersect a first line segment formed by removing from a line segment connecting a center of gravity of a first region in which the first resonant element is formed to a center of gravity of a third region in which the third resonant element is formed, parts of the line segment included in the first and third regions in which the first and third resonant elements are formed, or
a second coupling element which is arranged between the first and third resonant elements, in a region on the dielectric substrate except the element forming regions in which the resonant elements are formed, so as to intersect a second line segment formed by removing from a line segment connecting a center of gravity of a second region in which the second resonant element is formed to a center of gravity of a fourth region in which the fourth resonant element is formed, parts of the line segment included in the second and fourth regions in which the second and fourth resonant elements are formed, and
in that electrical lengths of the first and second coupling elements are selected from a range except electrical lengths of integer multiples of a half wavelength of a wavelength in a range corresponding to a frequency range determined on the basis of a center frequency and a band width of the resonant circuit.
In the following, embodiments according to the present invention will be described with reference to the accompanying drawings.
The filter 10 has a dense structure formed in such a manner that these resonant elements 102 to 105 are brought close to each other for miniaturization. The respective resonant elements 102 to 105 are constituted by bending an open ends microstrip line, and have an electrical length which is about an integer multiple of a half wavelength within a frequency range from fc−df/2 to fc+df/2, which is defined by a center frequency fc and a filter band width df according to a filter specification.
The four resonant elements 102, 103, 104 and 105 are numbered counterclockwise from the resonant element 102 in FIG. 1 such that the resonant element 102 is designated as the first resonant element, the resonant element 103 is designated as the second resonant element, the resonant element 104 is designated as the third resonant element, and the resonant element 105 is designated as the fourth resonant element. In the numbering, an arbitrary element is set to be designated as the first resonant element among the four resonant elements, and the other elements are successively numbered clockwise or counterclockwise.
The respective resonant elements 102 to 105 are coupled between the first and second resonant elements, between the second and third resonant elements, between the third and fourth resonant elements, and between the first and fourth resonant elements, so that one block is formed by the four resonant elements. The coupling value between the resonant elements is, for example, approximately 10−2 to 10−5, and is controllable by changing the distance between the resonant elements. Each coupling between the resonant elements is effected by the gap coupling based on an interval between the resonant elements, or the cross coupling based on a transmission line.
Since the filter 10 according to the present embodiment has a dense structure in which the four resonant elements 102 to 105 are brought close to each other, there exist uncontrolled cross couplings between the first and third resonant elements and between the second and fourth resonant elements. In order to selectively control the cross couplings, a coupling element 106 for controlling the cross coupling is provided between the first and third resonant elements.
The electrical length t of the coupling element 106, when defined so as to correspond to fc, is set in a range where an electrical length tfc of a half wavelength in a frequency range from fc−df/2 to fc+df/2 which is defined by fc and df, and integer multiples of the electrical length of this range are excluded, and is, for example, set in a range 0°<t<tfc and tfc<t<2tfc. With this, the cross coupling is controlled by changing the electrical length and arrangement of the coupling elements.
Note that in this case, one wavelength is calculated by multiplying a reciprocal of a frequency existing in the above described frequency range (for example, a frequency existing in each predetermined step width) by the speed of electromagnetic wave, and has a range corresponding to the above described frequency range.
In an actual filter circuit, the electrical length t of a coupling element can be calculated in such a manner that the dielectric constant of the substrate and the dimension of the line are inputted into an electromagnetic field simulator so as to make the calculation performed. The electrical length of the coupling element 106 shown in
On the basis of ranges (regions) 107, 108, 109 and 110 where patterns of the respective resonant elements exist, as shown in
A range of a resonant element is defined as a range obtained by connecting a plurality of apexes which are selected so as to make the range of the resonant element maximally expanded from an apex of the pattern of the resonant element. In the case where the pattern of the resonant element has a circular form, the range of the resonant element is defined as the range where the pattern exists.
The filter 10 can be made of a conductive material formed on an insulating substrate (not shown) as a dielectric substrate. The insulating substrate has a ground conductor on one face of the substrate, and a line conductor on the opposite face. The conductive material includes metals such as copper and gold, superconductors such as niobium and niobium-tin, and Y system copper oxide high-temperature superconductors. The substrate is made of various suitable materials such as magnesium oxide, sapphire, and lanthanum aluminate. For example, a superconducting microstrip line is formed on a magnesium oxide substrate (not shown) with a thickness of about 0.43 mm and a relative dielectric constant of about 10. Here, a Y system copper oxide high-temperature superconducting thin film having a thickness of about 500 nm is used as the superconductor of the microstrip line, and the line width of the strip conductor is about 0.4 mm. The superconducting thin film can be formed by a laser vapor deposition method, a sputtering method, a co-vapor deposition method, and the like. Further, various suitable structures such as a strip line and a coplanar line, can be adopted as the filter structure in addition to the microstrip line.
In a filter 11 shown in
The coupling elements 106 and 114 may have various shapes. For example, they may have a line shape opened at both ends, and square, rectangular, cross, circular, elliptic shapes. Alternatively, they may have a line shape with a plurality of open ends, or other suitable shapes.
Specifically, in the transmission coefficient S21, it is possible to make the frequency characteristic almost symmetrical with respect to the center frequency of 2.00 GHz, while in the reflection coefficient S11, it is possible to lower the reflection coefficient S11 to approximately −30 dB within a range of band width df around the center frequency of 2.00 GHz.
In this way, according to the present embodiment, the uncontrolled cross couplings, which exist between two resonant elements among the resonant elements 102 to 105 constituting the resonant circuit, are controlled by using the coupling element 106 which is newly arranged between the two resonant elements. As a result, it is possible to create a state where two resonant elements are not coupled with each other or a state where the amount of coupling between the two resonant elements is reduced, which states are difficult to realize on a plane, and to thereby improve the characteristics of a planar filter.
The filter 60 has a dense structure in which these resonant elements 602 to 607 are brought close to each other for miniaturization. The respective resonant elements 602 to 607 are constituted by bending an open ends microstrip line, and have an electrical length which is an integer multiple of a half wavelength within a frequency range from fc−df/2 to fc+df/2, which is defined by a center frequency fc and a filter band width df according to a filter specification.
In a block consisting of four resonant elements 603, 604, 605 and 606 which are selected from the six resonant elements 602, 603, 604, 605, 606 and 607, the four resonant elements are numbered counterclockwise from the resonant element 604 on the top left in the figure such that the resonant element 604 is designated as the first resonant element, the resonant element 603 is designated as the second resonant element, the resonant element 606 is designated as the third resonant element, and the resonant element 605 is designated as the fourth resonant element. In the numbering, an arbitrary element is selected from the four resonant elements so as to be designated as the first resonant element, and the other elements are successively numbered clockwise or counterclockwise.
The four resonant elements are selected in such a manner that in the respective resonant elements selected and numbered, the couplings are effected between the first and second resonant elements, between the second and third resonant elements, between the third and fourth resonant elements, and between the first and fourth resonant elements, respectively, and the coupling value between the two resonant elements is, for example, approximately 10−2 to 10−5. Further, the four resonant elements are selected in such a manner that a line segment connecting the centers of gravity of the ranges where the first and third resonant elements exist, intersect a line segment connecting the centers of gravity of the ranges where the second and fourth resonant element exist.
Coupling elements 608 and 609 are a coupling element which couples the first resonant element 604 with the second resonant element 603, and a coupling element which couples the third resonant element 606 with the second resonant element 605, respectively. The couplings between the first and second resonant elements, between the second and third resonant elements, between the third and fourth resonant elements, and between the first and fourth resonant elements are effected by the gap coupling based on an interval between the resonant elements or the cross coupling based on a transmission line.
Since the filter 60 according to the present embodiment has a dense structure in which the resonant elements 603 to 606 are brought close to each other, there exist uncontrolled cross couplings between the first and third resonant elements, and between the second and fourth resonant elements. In order to selectively control the magnitude of the cross couplings, for example, a coupling element 610 for controlling the cross coupling is provided between the first and third resonant elements.
The electrical length t of the coupling element 610, when defined so as to correspond to fc, is set in a range where an electrical length tfc of a half wavelength in a frequency range from fc−df/2 to fc+df/2 which is defined by fc and df, and integer multiples of the electrical length of this range are excluded, and is, for example, set in a range 0°<t<tfc and tfc<t<2tfc. With this, the cross coupling is controlled by changing the electrical length and arrangement of the coupling elements.
In a block consisting of four resonant elements 602, 603, 606 and 607 which are selected from the six resonant elements 602, 603, 604, 605, 606 and 607, the four resonant elements are numbered counterclockwise from the resonant element 603 on the top left in the figure such that the resonant element 603 is designated as the first resonant element, the resonant element 602 is designated as the second resonant element, the resonant element 607 is designated as the third resonant element, and the resonant element 606 is designated as the fourth resonant element. In the respective resonant elements 602, 603, 606 and 607 which are selected and numbered, the couplings between the first and second resonant elements, between the second and third resonant elements, between the third and fourth resonant elements, and between the first and fourth resonant elements are effected, respectively. The coupling value between the two resonant elements is, for example, approximately 10−2 to 10−5.
In order to control the magnitude of the uncontrolled cross couplings between the first and third resonant elements and between the second and fourth resonant elements, a coupling element 611 for controlling the cross coupling is provided. It is possible to control the cross coupling by changing the shape and arrangement of the coupling element 611.
The filter 60 can be made of a conductive material formed on an insulating substrate (not shown) as a dielectric substrate. The insulating substrate has a ground conductor on one face of the substrate, and a line conductor on the opposite face. The conductive material includes metals such as copper and gold, superconductors such as niobium and niobium-tin, and Y system copper oxide high-temperature superconductors. The substrate is made of various suitable materials such as magnesium oxide, sapphire, and lanthanum aluminate. For example, a superconducting microstrip line is formed on a magnesium oxide substrate (not shown) with a thickness of about 0.43 mm and a relative dielectric constant of about 10. Here, a Y system copper oxide high-temperature superconducting thin film having a thickness of about 500 nm is used as the superconductor of the microstrip line, and the line width of the strip conductor is about 0.4 mm. The superconducting thin film can be formed by a laser vapor deposition method, a sputtering method, a co-vapor deposition method, and the like.
In the block 1, the four resonant elements are numbered counterclockwise from the resonant element 702 in the figure such that the resonant element 702 is designated as the first resonant element, the resonant element 703 is designated as the second resonant element, the resonant element 704 is designated as the third resonant element, and the resonant element 705 is designated as the fourth resonant element. In the block 2, the four resonant elements are numbered counterclockwise from the resonant element 706 in the figure such that the resonant element 706 is designated as the first resonant element, the resonant element 707 is designated as the second resonant element, the resonant element 708 is designated as the third resonant element, and the resonant element 709 is designated as the fourth resonant element.
In order to selectively control the magnitude of the cross couplings in the filter 70, for example, a coupling element 710 for controlling the cross coupling is provided between the second and fourth resonant elements of the block 1, and a coupling element 711 for controlling the cross coupling is provided between the first and third resonant elements of the block 2. The electrical length t of the coupling elements 710 and 711, when defined so as to correspond to fc, is set in a range where an electrical length tfc of a half wavelength in a frequency range from fc−df/2 to fc+df/2 which is defined by fc and df, and integer multiples of the electrical length of this range are excluded, and is set, for example, in a range 0°<t<tfc and tfc<t<2tfc. With this, it is possible to control the cross coupling by changing the electric length and arrangement of the coupling elements. Further, it is possible to selectively control the cross coupling having a great influence on the filter characteristics.
It is also possible to control undesirable cross couplings between the blocks, by providing coupling elements between the third resonant element of the block 1 and the first resonant element of the block 2, between the fourth resonant element of the block 1 and the second resonant element of the block 2, and between the third resonant element of the block 1 and the fourth resonant element of the block 2.
The filter 70 can be made of a conductive material formed on an insulating substrate (not shown) as a dielectric substrate. The insulating substrate has a ground conductor on one face of the substrate, and a line conductor on the opposite face. The conductive material includes metals such as copper and gold, superconductors such as niobium and niobium-tin, and Y system copper oxide high-temperature superconductors. The substrate is made of various suitable materials such as magnesium oxide, sapphire, and lanthanum aluminate. For example, a superconducting microstrip line is formed on a magnesium oxide substrate (not shown) with a thickness of about 0.43 mm and a relative dielectric constant of about 10. Here, a Y system copper oxide high-temperature superconducting thin film having a thickness of about 500 nm is used as the superconductor of the microstrip line, and the line width of the strip conductor is about 0.4 mm. The superconducting thin film can be formed by a laser vapor deposition method, a sputtering method, a co-vapor deposition method, and the like.
Specifically, in the transmission coefficient S21, it is possible to make the frequency characteristic almost symmetrical with respect to the center frequency of 2.00 GHz, while in the reflection coefficient S11, it is possible to lower the reflection coefficient S11 to approximately −20 dB within a range of band width df around the center frequency of 2.00 GHz.
The filter 80 is constituted by two blocks of block 1 which consists of four resonant elements 802, 803, 804 and 805, and block 2 which consists of four resonant elements 806, 807, 808 and 809, and by making the resonant element 805 of the block 1 cascade-connected to the resonant element 806 of the block 2 by a coupling element 814 for coupling between the blocks. Here, the coupling element 814 is directly connected to the resonant elements to realize the coupling. It is possible to control the magnitude of the coupling by changing the connecting position and the electrical length t of the coupling element.
In the block 1, the four resonant elements are numbered clockwise from the resonant element 802 in the figure such that the resonant element 802 is designated as the first resonant element, the resonant element 803 is designated as the second resonant element, the resonant element 804 is designated as the third resonant element, and the resonant element 805 is designated as the fourth resonant element. Here, in the block 1, the coupling between the first resonant element 802 and the fourth resonant element 805 is realized by a coupling element 810 for coupling between the resonant elements, and the coupling between the second resonant element 803 and the third resonant element 804 is realized by a coupling element 811 for coupling between the resonant elements.
Further, in the block 2, the four resonant elements are numbered clockwise from the resonant element 806 in the figure such that the resonant element 806 is designated as the first resonant element, the resonant element 807 is designated as the second resonant element, the resonant element 808 is designated as the third resonant element, and the resonant element 809 is designated as the fourth resonant element. Here, in the block 2, the coupling between the first resonant element 806 and the fourth resonant element 809 is realized by a coupling element 812 for coupling between the resonant elements, and the coupling between the second resonant element 807 and the third resonant element 808 is realized by a coupling element 813 for coupling between the resonant elements.
In order to selectively control the magnitude of the undesirable cross couplings in the filter 80, for example, a coupling element 816 for controlling the cross coupling is provided between the first and third resonant elements of the block 1, and a coupling element 817 for controlling the cross coupling is provided between the first and third resonant elements of the block 2.
The electrical length t of the coupling elements 816 and 817, when defined so as to correspond to fc, is set in a range where an electrical length tfc of a half wavelength in a frequency range from fc−df/2 to fc+df/2 which is defined by fc and df, and integer multiples of the electrical length of this range are excluded, and is set, for example, in a range 0°<t<tfc and tfc<t<2tfc. With this, it is possible to control the cross coupling by changing the electrical length and arrangement of the coupling elements.
Further, the undesirable cross couplings between the blocks is controlled by providing a coupling element 815 between the third resonant element of the block 1 and the second resonant element of the block 2.
The filter 80 can be made of a conductive material formed on an insulating substrate (not shown) as a dielectric substrate. The insulating substrate has a ground conductor on one face of the substrate, and a line conductor on the opposite face. The conductive material includes metals such as copper and gold, superconductors such as niobium and niobium-tin, and Y system copper oxide high-temperature superconductors. The substrate is made of various suitable materials such as magnesium oxide, sapphire, and lanthanum aluminate. For example, a superconducting microstrip line is formed on a magnesium oxide substrate (not shown) with a thickness of about 0.43 mm and a relative dielectric constant of about 10. Here, a Y system copper oxide high-temperature superconducting thin film having a thickness of about 500 nm is used as the superconductor of the microstrip line, and the line width of the strip conductor is about 0.4 mm. The superconducting thin film can be formed by a laser vapor deposition method, a sputtering method, a co-vapor deposition method, and the like.
The filter 90 is constituted by two blocks of block 1 which consists of four resonant elements 902, 903, 904 and 905, and block 2 which consists of four resonant elements 906, 907, 908 and 909, and by making the resonant element 905 of the block 1 cascade-connected to the resonant element 906 of the block 2 by a coupling element 914 for coupling between the blocks. It is possible to control the magnitude of the coupling by changing the arranging position and the electrical length t of the coupling element.
In the block 1, the four resonant elements are numbered clockwise from the resonant element 902 in the figure such that the resonant element 902 is designated as the first resonant element, the resonant element 903 is designated as the second resonant element, the resonant element 904 is designated as the third resonant element, and the resonant element 905 is designated as the fourth resonant element. Here, in the block 1, the coupling between the first resonant element 902 and the fourth resonant element 905 is realized by a coupling element 910 for coupling between the resonant elements, and the coupling between the second resonant element 903 and the third resonant element 904 is realized by a coupling element 911 for coupling between the resonant elements.
Further, in the block 2, the four resonant elements are numbered clockwise from the resonant element 906 in the figure such that the resonant element 906 is designated as the first resonant element, the resonant element 907 is designated as the second resonant element, the resonant element 908 is designated as the third resonant element, and the resonant element 909 is designated as the fourth resonant element. Here, in the block 2, the coupling between the first resonant element 906 and the fourth resonant element 909 is realized by a coupling element 912 for coupling between the resonant elements, and the coupling between the second resonant element 907 and the third resonant element 908 is realized by a coupling element 913 for coupling between the resonant elements.
In order to selectively control the magnitude of the undesirable cross couplings in the filter 90, for example, a coupling element 916 for controlling the cross coupling is provided between the second and fourth resonant elements of the block 1, and a coupling element 917 for controlling the cross coupling is provided between the first and third resonant elements of the block 2.
The electrical length t of the coupling elements 916 and 917, when defined so as to correspond to fc, is set in a range where an electrical length tfc of a half wavelength in a frequency range from fc−df/2 to fc+df/2 which is defined by fc and df, and integer multiples of the electrical length of this range are excluded, and is set, for example, in a range 0°<t<tfc and tfc<t<2tfc. With this, it is possible to control the cross coupling by changing the electrical length and arrangement of the coupling elements.
Further, the undesirable cross couplings between the blocks is controlled by providing a coupling element 915 between the third resonant element of the block 1 and the second resonant element of the block 2.
The filter 90 can be made of a conductive material formed on an insulating substrate (not shown) as a dielectric substrate. The insulating substrate has a ground conductor on one face of the substrate, and a line conductor on the opposite face. The conductive material includes metals such as copper and gold, superconductors such as niobium and niobium-tin, and Y system copper oxide high-temperature superconductors. The substrate is made of various suitable materials such as magnesium oxide, sapphire, and lanthanum aluminate. For example, a superconducting microstrip line is formed on a magnesium oxide substrate (not shown) with a thickness of about 0.43 mm and a relative dielectric constant of about 10. Here, a Y system copper oxide high-temperature superconducting thin film having a thickness of about 500 nm is used as the superconductor of the microstrip line, and the line width of the strip conductor is about 0.4 mm. The superconducting thin film can be formed by a laser vapor deposition method, a sputtering method, a co-vapor deposition method, and the like.
Here, the respective resonant elements are coupled with each other, and numbered counterclockwise from the resonant element 1002 in the figure such that the resonant element 1002 is designated as the first resonant element, the resonant element 1003 is designated as the second resonant element, the resonant element 1004 is designated as the third resonant element, and the resonant element 1005 is designated as the fourth resonant element. In order to selectively control the magnitude of the coupling between the resonant elements, for example, a coupling element 1006 for controlling the cross coupling is provided between the second and fourth resonant elements.
The coupling element 1006 may have various shapes. For example, the coupling element 1006 may have a line shape opened at both ends, and square, rectangular, cross, circular, elliptic shapes. Further, the coupling element 1006 may also have a line shape with a plurality of open ends, or other suitable shapes. It is possible to control the coupling between the resonant elements by changing the electrical length and arrangement of the coupling element.
The filter 1000 can be made of a conductive material formed on an insulating substrate (not shown) as a dielectric substrate. The insulating substrate has a ground conductor on one face of the substrate, and a line conductor on the opposite face. The conductive material includes metals such as copper and gold, superconductors such as niobium and niobium-tin, and Y system copper oxide high-temperature superconductors. The substrate is made of various suitable materials such as magnesium oxide, sapphire, and lanthanum aluminate. For example, a superconducting microstrip line is formed on a magnesium oxide substrate (not shown) with a thickness of about 0.43 mm and a relative dielectric constant of about 10. Here, a Y system copper oxide high-temperature superconducting thin film having a thickness of about 500 nm is used as the superconductor of the microstrip line, and the line width of the strip conductor is about 0.4 mm. The superconducting thin film can be formed by a laser vapor deposition method, a sputtering method, a co-vapor deposition method, and the like.
In this way, according to the present embodiment, the undesirable cross couplings which exist between the two resonant elements among the resonant elements 1002 to 1005 constituting the resonant circuit are controlled by using the coupling element 1006 which is newly arranged between the two resonant elements. Thus, it is possible to create a state where two resonant elements are not coupled with each other or a state where the amount of coupling between the two resonant elements is reduced, which states are difficult to realize on a plane, and to thereby improve the characteristics of the planar antenna.
The antenna 1500 is an eight element array antenna constituted by the eight resonant elements 2003 to 2010. The resonant element is capable of taking various shapes such as a linear structure, circular and elliptic shapes, in addition to a rectangular patch structure as shown in
Here, the respective resonant elements 2003 to 2010 are coupled with each other, and four adjoining resonant elements 2003 to 2006 selected from the eight resonant elements 2003 to 2010 are numbered counterclockwise from the resonant element 2003 in the figure such that the resonant element 2003 is designated as the first resonant element, the resonant element 2004 is designated as the second resonant element, the resonant element 2005 is designated as the third resonant element, and the resonant element 2006 is designated as the fourth resonant element.
In order to selectively control the magnitude of the coupling between the resonant elements, for example, a coupling element 2011 for controlling the cross coupling is provided between the first and third resonant elements and between the second and fourth resonant elements. It is possible to control the coupling between the resonant elements by changing the electrical length, the arrangement, and the shape of the coupling element 2011. Further, the coupling element 2011 may have various shapes. For example, the coupling element 2011 may have a line shape opened at both ends, and square, rectangular, cross, circular, elliptic shapes. Further, the coupling element 2011 may have a line shape with a plurality of open ends, or other suitable shapes.
Similarly, the coupling between the resonant elements 2005 to 2008, which form another combination of adjoining resonant elements, can be controlled by a coupling element 2012 for controlling the cross coupling, and the coupling between the resonant elements 2007 to 2010 can be controlled by a coupling element 2013 for controlling the cross coupling.
The antenna 1500 can be made of a conductive material formed on the dielectric substrate 2000. The conductive material includes metals such as copper and gold, superconductors such as niobium and niobium-tin, and Y system copper oxide high-temperature superconductors. The substrate is made of various suitable materials such as magnesium oxide, sapphire, and lanthanum aluminate.
Note that the above described embodiments are examples, and the present invention is not limited to these examples. For example, the resonant elements may be arranged in multi-order with at least four or more, instead of four, six, and eight orders.
Additional advantages and modifications will readily occur to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details and representative embodiments shown and described herein. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2006-143602 | May 2006 | JP | national |
| Number | Name | Date | Kind |
|---|---|---|---|
| 5608363 | Cameron et al. | Mar 1997 | A |
| 5805034 | Evans et al. | Sep 1998 | A |
| 6300849 | Takeda et al. | Oct 2001 | B1 |
| 6370404 | Shen | Apr 2002 | B1 |
| 6496710 | Tsuzuki | Dec 2002 | B1 |
| 6529750 | Zhang et al. | Mar 2003 | B1 |
| 6633207 | Hidaka et al. | Oct 2003 | B1 |
| 6734760 | Tsujiguchi | May 2004 | B2 |
| 7215225 | Fuke et al. | May 2007 | B2 |
| 7471173 | Hidaka et al. | Dec 2008 | B2 |
| 20040233022 | Tsuzuki et al. | Nov 2004 | A1 |
| 20050007210 | Fuke et al. | Jan 2005 | A1 |
| Number | Date | Country |
|---|---|---|
| 2000-341071 | Dec 2000 | JP |
| 2001-308603 | Nov 2001 | JP |
| 2004-530391 | Sep 2004 | JP |
| 2004-349966 | Dec 2004 | JP |
| 2005-265721 | Sep 2005 | JP |
| Number | Date | Country | |
|---|---|---|---|
| 20080055181 A1 | Mar 2008 | US |
