Dielectric resonator apparatus

Abstract: A dielectric resonator apparatus is provided with a dielectric resonator (100) which has a spherical or approximately spherical dielectric placed within the shield case (10) of the rectangular cavity, and uses each resonance of a x mode, a y mode and a z mode of TE₁₀₁ where an electric field is caused respectively around an x axis, a y-axis and a z-axis of a rectangular coordinate system predetermined in the dielectric, and external coupling means (Lo,Li) for coupling the above described resonator to an external circuit, whereby the dielectric resonator apparatus which has no-load Q larger than in the conventional embodiment, can be made smaller in size, and also, can realize three resonators with one apparatus.

Description: The present invention generally relates to a dielectric resonator apparatus for using resonances of spherical TE 101 modes (hereinafter referred to as spherical TE 101 modes) within a shield case of a rectangular cavity. Conventionally a dielectric resonator for microwave filter use (hereinafter referred to as a first conventional embodiment) which is cylindrical in shape and uses a TE 013 mode is disclosed in, for example, Japanese Utility Model Laid-Open Publication No. 51-35946 as a dielectric resonator. When a microwave filter was constructed with the use of a dielectric resonator in the first conventional embodiment, one dielectric resonator was required to use with respect to one filter. When many filters were constructed, many dielectric resonators were required, with a problem that volume to be occupied with many dielectric resonators, and the weight became great. A smaller and lighter dielectric resonator apparatus (hereinafter referred to as to a second conventional embodiment) for using the resonances of TM 110 modes or their modified modes is disclosed in Japanese Patent Laid-Open Publication No. 61-157101 and in corresponding US-A-4 623 857, which is shown in Fig. 12. As shown in Fig. 12, a composite dielectric 202 which is made of ceramic, integrated with three pillar-shaped dielectrics 202a, 202b, 202c being orthogonal to one another, is placed within a shield case 201 of a rectangular cavity. Resonances of three TM modes, namely, a TM 110 mode, a TM 011 mode and a TM 101 mode exist in a xyz rectangular coordinate system with an axial direction of one pillar-shaped dielectric being in conformity with a z axis. In order to prevent the electromagnetic fields of three TM modes from interfering with one another, coupling adjusting members 204, 205 composed of a pair of screw metallic bodies within a plane with pillar shaped dielectrics 202a, 202b being both included in it are projected into the shield case 201 towards the center of the composite dielectric 202 from the ridge line portions 206, 207 of the shield case 101. In order to couple the above described dielectric resonator to an external circuit, for example, two coupling loops (not shown) for coupling a pillar-shaped dielectric 202a only are provided with the pillar-shaped dielectric 202a being grasped therebetween. In a dielectric resonator apparatus of a second conventional embodiment constructed as described hereinabove, three resonators which are orthogonal electrically into one shield case 201 can be accommodated, and independent three microwave filters can be realized when the above described three modes are set not to be interfered with one another. Three modes are coupled by the adjustment of the above described coupling adjusting members 204, 205 in inserting degree so that, for example, a three stage of microwave filter can be realized. As the composite dielectric 202 is placed in contact against the shield case 201 in the above described second conventional embodiment, the energies within the dielectric resonator are not concentrated to the center of the composite dielectric 202 so that the electromagnetic field is distributed even on the side inner immediately to the shield case 201. The surface current flows to the inner wall of the shield case 201, thus resulting in large conductor loss. No-loads Q (Q 0 ) of the respective pillar-shaped dielectrics 202a, 202b, 202c are comparatively small. Accordingly, there is a problem in that the passing band width is difficult to be made narrower when the microwave band passing filter is constructed with the use of the dielectric resonator apparatus. SU-A-1058014 discloses a segmented dielectric resonator having several spherical layers which are mutually perpendicular and differ in thickness. The dielectric resonator is formed by a plurality of mutually perpendicular spherical layers. Accordingly, the present invention has been developed with a view to substantially eliminating the above discussed drawbacks inherent into the prior art and has for its essential object to provide an improved dielectric resonator apparatus. Another important object of the present invention is to provide an improved dielectric resonator apparatus which has no-load Q larger than in the conventional embodiment, can be made smaller in size, and also, can realize three resonators with one apparatus. These objects are achieved by a dielectric resonator apparatus as defined in claim 1. BRIEF DESCRIPTION OF THE DRAWINGS These and other objects and features of the present invention will become apparent from the following description taken in conjunction with the preferred embodiment thereof with reference to the accompanying drawings, in which; Fig. 1 is an oblique view of a dielectric resonator apparatus in a first embodiment in accordance with the present invention; Fig. 2 is an oblique view of the dielectric resonator of Fig. 1; Fig. 3 is a circuit diagram of an equivalent circuit in the dielectric resonator apparatus of Fig. 1; Fig. 4 is an oblique view in a modified embodiment of a dielectric resonator of Fig. 2; Fig. 5 is an oblique view of the dielectric resonator apparatus in a second embodiment in accordance with the present invention; Fig. 6 is an oblique view of the dielectric resonator of Fig. 5; Fig. 7 is a circuit diagram of an equivalent circuit of the dielectric resonator apparatus of Fig. 5; Fig. 8 is an oblique view in a modified embodiment of the dielectric resonator of Fig. 6; Figs. 9a, 9b and 9c are oblique views showing respective electric force lines of a x mode, a y mode and a z mode in a dielectric resonator in first and second embodiments; Figs. 10a, 10b and 10c are oblique views showing respective electric force lines of a xy- even mode, a yz- even mode, and a zx- even mode in the dielectric resonator in the first and second embodiments; Figs. 11a, 11b and 11c are oblique views showing respective electric force lines of a xy- odd mode, a yz- odd mode and a zx- odd mode in the first and second embodiments; and Fig. 12 is an oblique view of a dielectric resonator apparatus in the second conventional embodiment. DETAILED DESCRIPTION OF THE INVENTION Before the description of the present invention proceeds, it is to be noted that like parts are designated by like reference numerals throughout the accompanying drawings. (First Embodiment) Fig. 1 shows a dielectric resonator apparatus in a first embodiment in accordance with the present invention. Fig. 2 shows a dielectric resonator using the dielectric resonator apparatus. A dielectric resonator apparatus in a first embodiment has an approximately spherical dielectric resonator 100 placed within a shield case 10 of a rectangular cavity, the dielectric resonator 100 integrated with three ring shaped dielectrics 51, 52, 53 being orthogonal to one another, and also, and has loops Lix, Lox, Liy, Loy, Liz, Loz for input, output coupling use provided so as to be inductively coupled to the magnetic fields of mutually independent respective resonators REx, REy, REz (see Fig. 3) by the resonance of three modes when the polar axis of the TE 101 mode is put into conformity with mutually orthogonal a x axis, a y axis and a z axis with the use of the resonance of the TE 101 mode which is a basic mode of the dielectric resonator 100. Three modes with three modes when the polar axis of the TE 101 mode being in conformity with a x axis, a y axis and a z axis which are orthogonal to one another with the center of the dielectric resonator 100 being as a center are as follows. The distribution of the electric force lines 41, 42, 43 in each mode is shown in the (a), (b) and (c) of Fig. 9. (a) TE 101 (x) mode (hereinafter referred to as x mode) (b) TE 101 (y) mode (hereinafter referred to as y mode) (c) TE 101 (z) mode (hereinafter referred to as z mode) As shown in Fig. 1, an approximately spherical-shaped dielectric resonator 100 is placed on a cylindrical shaped support stand 11 which is comparatively as low as, for example, approximately 4 through 6 in specific inductive capacity and has a linear expansion coefficient the same as that in the dielectric resonator 100, in the central portion within the shield case 10 of the metallic rectangular cavity. Each of the dielectrics 51, 52, 53 of the dielectric resonator 100 is composed of a ceramic dielectric with ZrSn being mixed with, for example, TiO 2 as a main component. In order to prevent a spurious mode, which is a high order mode except for the spherical 101 mode, from being caused, a spherical shaped cavity portion 101 is formed in the central portion of the spherical dielectric as shown in Fig. 2, in the approximately spherical dielectric resonator 100. Four, approximately triangle cone trapezoidal, notch portions 102 are formed in the upper side portion of the above described sphere and four, approximately triangle cone trapezoidal, notch portion 103 are formed in the lower side portion of the above described sphere so that only a portion of the given thickness may remain from the above described spherical surface where the respective electric force lines (see Fig. 9) of the above described x mode, the y mode and the z mode, and may extend through to the cavity portion 101 from the above described spherical surface. Namely, the above described dielectric resonator 100 is approximately spherical so that the shafts of the respective rings of three ring shaped dielectrics 51, 52, 53 may be in conformity with the above described x axis, y axis and z axis and be integrated in mutually orthogonal condition. As the above described respective ring shaped dielectrics 51, 52, 53 respectively can distinguish among the respective electromagnetic field distribution of the x mode, the y mode and the z mode, the dielectric resonators REx, REy, REz of the above described x mode, the y mode and the z mode where the mode couplings mutually are not substantially provided as shown in the equivalent circuit in Fig. 3 can be constructed. In a process where the spurious mode of a higher order mode except for the spherical 101 mode can be removed, and also, in a process to be formed by the burning of the dielectric resonator 100, uneven burning can be reduced, with an advantage that possibility of being cracked is reduced. The shield case 10 may be a metallic electrode film for shield use formed on the inner face or the outer face of a rectangular cavity composed of ceramic of a material the same as, for example, the dielectric resonator 100. In order to make different the respective resonance frequencies of the respective dielectric resonators REx, REy, REz, a concave portion 21 for frequency adjusting use which is provided with a given thickness from the outer peripheral surface and is approximately rectangular in shape is formed respectively in the external peripheral surface of four positions each being separated by ninety degrees with the shaft of the ring shaped dielectric 51 being provided as a center, and also, four concave portions 22, 23 for frequency adjusting use respectively are formed in ring shaped dielectrics 52, 53. The respective concave portions 21, 22, 23 are made larger in thickness so that the resonance frequencies of the above described respective resonators REx, REy, REz can be made higher. In the present embodiment, the respective concave portions 21, 22, 23 are made different mutually in thickness so that the respective resonance frequencies of the respective dielectric resonators REx, REy, REz can be made different. Generally the x mode, the y mode and the z mode are coupled with one another. The following six modes are defined as modes in these cases. (a) A xy- even mode is a mode of an electromagnetic field in a case where each electromagnetic field of a x mode and a y mode is superposed with the same sign. The electromagnetic field of the mode is expressed with the next "Numerical Equation 1" and electric force lines 44 are distributed in the dielectric resonator 100 as shown in (a) of Fig. 10. (Numerical Equation 1) (electromagnetic field of xy - even mode) = C 0 {(electromagnetic field of x mode) + (electromagnetic field of y mode)} wherein C 0 is a normalized constant, in the present embodiment it is an inverse number of a square root of 2. (b) A xy- odd mode is a mode of an electromagnetic field in a case where each electromagnetic field of a x mode and a y mode is superposed with an inverse sign. The electromagnetic field of the above described mode is expressed with the next "Numerical Equation 2" and electric force lines 47 are distributed in the dielectric resonator 100. (Numerical Equation 2) (electromagnetic field of xy- odd mode) = C 0 {(electromagnetic field of x mode) - (electromagnetic field of y mode)} (C) A yz- even mode is a mode of an electromagnetic field in a case where each electromagnetic field of the y mode and the z mode are superposed with the same sign. The electromagnetic field of the mode is expressed with the next "Numerical Equation 3" and electric force lines 45 are distributed in the dielectric resonator 100 as shown in (b) of Fig. 10. (Numerical Equation 3) (electromagnetic field of yz- even mode) = C 0 {(electromagnetic field of y mode) + (electromagnetic field of z mode)} (d) A yz- odd mode is a mode of an electromagnetic field in a case where each electromagnetic field of the y mode and the z mode is superposed with an inverse sign. The electromagnetic field of the mode is expressed with the next "Numerical Equation 4" and the electric force lines 48 are distributed in the dielectric resonator 100 as shown in the (b) of Fig. 11. (Numerical Equation 4) (electromagnetic field of yz- odd mode) = C 0 {(electromagnetic field of y mode ) - (electromagnetic field of z mode)} (e) A zx- even mode is a mode of an electromagnetic field in a case where each electromagnetic field of a z mode and a x mode is superposed with the same sign. The electromagnetic field of the mode is expressed with the next "Numerical Equation 5". Electric force lines 46 are distributed in the dielectric resonator 100. (Numerical Equation) (electromagnetic field of xk- even mode) = C 0 {(electromagnetic field of z mode) + (electromagnetic field of x mode)} (f) A zx- odd mode is a mode of an electromagnetic field in a case where each electromagnetic field of a z mode and a x mode is superposed with an inverse sign. The electromagnetic field of the mode is expressed with the next "Numerical Equation 6". Electric force lines 49 are distributed in the dielectric resonator 100 as shown in the (c) of Fig. 11. (Numerical Equation 6) (electromagnetic field of zx- odd mode) = C 0 {(electromagnetic field of z mode) - (electromagnetic field of x mode)} In order to prevent the respective electromagnetic fields of the x mode, the y mode and the z mode from being interfered with on another, the coupling adjusting member 12a composed of a screw shaped metallic conductor, a dielectric or a magnetic material is provided to form one side of the upper surface of the shield case 10 parallel to the xy plane and to project into the shield case 10 towards the center of the dielectric resonator 100 from the central portion of the ridge line portion 121 parallel to the x axis. A coupling adjusting member 12b composed of a similar material is provided to form one side of the upper surface of the shield case 10 parallel to the xy plane and to project into the shield case 10 towards the center of the dielectric resonator 100 from the central portion of the ridge line portion 122 parallel to the y axis. Further, a coupling adjusting member 12c composed of a similar material is provided to form one side on the side face of the shield case 10 parallel to the xz plane and to project into the shield case 10 towards the center of the dielectric resonator 100 from the central portion of the ridge line portion 123 parallel to the z axis. The coupling between the y mode and the z mode can be adjusted by the insertion of the coupling adjusting member 12a into the shield case 10 so as to mainly give influences to the resonance frequency of the dielectric resonator REx of the x mode. The coupling between the z mode and the x mode can be adjusted by the insertion of the coupling adjusting member 12 into the shield case 10 so as to mainly give influences to the resonator frequency of the dielectric resonator REy of the y mode. Further, the coupling between the x mode and the y mode can be adjusted by the insertion of the coupling adjusting member 12c into the shield case 10 so as to mainly give influences to the resonance frequency of the dielectric resonator REz of the z mode. When the respective coupling adjusting members 12a, 12b, 12c are inserted into the shield case 10, the x mode, the y mode and the z mode which are independent mutually when they are not inserted are adapted to be coupled with respect to one another. The resonance frequencies of the respective dielectric resonators REx, REy, REz are changed as follows in accordance with the division between a case where materials of the coupling adjusting materials 12a, 12b, 12c are metallic conductors and a case where they are a dielectric or a magnetic material. (A) When the coupling adjusting member is a metallic conductor, the variation δω in the resonance angle frequency ω of the respective dielectric resonators REx, REy, REz is expressed with the next "Numerical Equation 7". (Numerical Equation 7) δω ω = ΔWm - ΔWe Wm + We where Wm is an magnetic energy to be included in the dielectric resonator, We is an electric energy to be included in the dielectric resonator. ΔWm is an magnetic energy to be included in a region to be occupied by a coupling adjusting member, and ΔWe is an electric energy to be included in a region to be occupied by a coupling adjusting member. In the dielectric resonator apparatus, the resonance electromagnetic field of the spherical 101 mode has the magnetic energy larger than electric energy, namely, ΔWm - ΔWe > 0 on the side inner immediately to the shield case 10. Therefore, when the coupling adjusting member which is a metallic conductor is inserted into the shield case 10, the resonance frequency of the dielectric resonator corresponding to the coupling adjusting member rises. (B) When the coupling adjusting member is a dielectric or a magnetic material, the change δω in the resonance angle frequency ω of the respective dielectric resonators REx, REy, REz is expressed with the next "Numerical Equation 8". (Numerical Equation 8) δω ω = ΔWm + ΔWe Wm + We When the coupling adjusting member which is a dielectric or a magnetic material is inserted into a shield case 10 as clear from the "Numerical Equation 8", the resonance frequency of the dielectric resonator corresponding to the coupling adjusting member is lowered. The respective coupling adjusting members 12a, 12b, 12c are operated similarly in any position when if it is in the central portion of the ridge line portion of a side parallel to a side of a ridge line portion 121, 122 or 123 where it is placed. A coupling adjusting member may be placed in the central portion of the ridge line portion of all the sides of the shield case 10. In the dielectric resonator apparatus of the present embodiment, three pairs of loops Lix, Lox, Liy, Loy, Liz, Loz for input output coupling use are provided as follows so as to be inductively coupled to the magnetic fields of the respective resonators REx, REy, REz of the above described x mode, y mode and z mode and to be separated by given distances from the dielectric resonator 100. In the loops Lix, Lox for input output coupling use of the x mode, a face these loops form conforms to a plane the ring of the ring shaped dielectric 51 forms, and vertical to the shaft of the ring, namely, a face the electric force line of the x mode forms. The loop Lix, Lox for input, output coupling use of the x mode are provided to be inductively coupled to the magnetic field of the resonator REx of the x mode and to be opposed with the dielectric resonator 100 being grasped mutually between. Both the ends of the loop Lix for input coupling use are connected with the input terminals T11, T12 (see Fig. 3) and also, both the ends of the loop Lox for output coupling use are connected with the output terminals T21, T22 (see Fig. 3). It is to be noted that the loop Lox for output coupling use is accommodated within a cylinder of the support stand 11. In the loops Liy, Loy for input output coupling use of the y mode, a face these loops form conforms to a plane the ring of the ring shaped dielectric 52 forms, and vertical to the shaft of the ring, namely, a face the electric force line of the y mode forms. The loops Liy, Loy for input, output coupling use of the y mode are provided to be inductively coupled to the magnetic field of the resonator REx of the y mode and to be opposed with the dielectric resonator 100 being grasped mutually between. Both the ends of the loop Liy for input coupling use are connected with the input terminals T31, T32 (see Fig. 3) and also, both the ends of the loop Lox for output coupling use are connected with the output terminals T41, T42 (see Fig. 3). In the loops Liz, Loz for input output coupling use of the z mode, a face these loops form conforms to a plane the ring of the ring shaped dielectric 53 forms, and vertical to the shaft of the ring, namely, a face the electric force line of the z mode forms. The loops Liz, Loz for input, output coupling use of the z mode are provided to be inductively coupled to the magnetic field of the resonator REz of the z mode and to be opposed with the dielectric resonator 100 being grasped mutually between. Both the ends of he loop Liz for input coupling use are connected with the input terminals T51, T52 (see Fig. 3) and also, both the ends of the loop Loz for output coupling use are connected with the output terminals T61, T62 (see Fig. 3). Here a plane the loops LIx, Lox for input output, coupling use of the x mode form, a plane the loops Liy, Loy for input, output coupling use of the y mode, and a plane the loops Liz, Loz for input, output coupling use of the z mode form are orthogonal to one another. Accordingly, they are not inductively coupled to one another. The coupling among the resonators of the respective modes can be adjusted to zero by the adjustment of the respective insertion lengths of the coupling adjusting members 12a, 12b, 12c even when the respective resonators of the x mode, the y mode and the z mode are somewhat inductively coupled actually. The equivalent circuit of the dielectric resonator apparatus in the present embodiment constructed as described hereinabove is shown in Fig. 3. As clear from Fig. 3, the respective circuits of the x mode, the y mode and the z mode are independent to one another and are in a trebly degenerated condition. In a circuit of the x mode, a resonator REx of the x mode is composed of one capacitor Cx and two inductors Lx 1 , Lx 2 . The resonance frequency of the resonator REx is determined with these component elements. Here the inductor Lx 1 is inductively coupled (+M) to a loop Lix for input coupling use, while the inductor Lx 2 is inductively coupled (+M) to the output coupling loop Lox. In the circuit of the y mode, the resonator REy of the y mode is composed of one capacitor Cy and two inductors Ly 1 , Ly 2 . The resonance frequency of the resonator REy is determined by the component elements. Here the inductor Ly 1 is inductively coupled (+M) to a loop Liy for input coupling use, while the inductor Ly 2 is inductively coupled (+M) to the output coupling loop Lox. In the circuit of the z mode, the resonator REz of the z mode is composed of one capacitor Cz and two inductors Lz 1 , Lz 2 . The resonance frequency of the resonator REz is determined by the component elements. Here the inductor Lz 1 is inductively coupled (+M) to a loop Liz for input coupling use, while the inductor Lz 2 is inductively coupled (+M) to the output coupling loop Loz. Electrostatic capacity of capacitors Cx, Cy, Cz to be included in the respective resonators REx, REy, REz respectively corresponds to the volume of concave portions 21, 22, 23 for frequency adjusting use. When the volume of the concave portions 21, 22, 23 is increased, the respective electrostatic capacity of the above described capacitors Cx, Cy, Cz becomes smaller and the resonator frequencies of the respective resonators REx, REy, REz rise. Inductances for each mode of the inductances Lx 1 , Lx 2 , Ly 1 , Ly 2 , Lz 1 , Lz 2 to be included in the respective resonators REx, REy, REz respectively correspond to the insertion lengths of the coupling adjusting members 12a, 12b, 12c. If each insertion lengths of the coupling adjusting members 12a, 12b, 12c become long when, for example, the coupling adjusting members 12a, 12b, 12c are metallic conductors, inductance for each mode becomes smaller, and the resonance frequencies of the respective resonators REx, REy, REz rise. The inductances Ly 1 , Ly 2 ,Lz 1 > Lz 2 are made somewhat smaller by the longer insertion length of the coupling adjusting member 12a as described hereinabove and influences are given even to the coupling between the y mode and the z mode. The inductances Lz 1 , Lz 2 , Lx 1 , Lx 2 are made somewhat smaller by the long insertion length of the coupling adjusting member 12b and also influences are given even to the coupling between the z mode and the x mode. Further, the inductances Lx 1 , Lx 2 , Ly 1 , Ly 2 are made somewhat smaller by the longer insertion length of the coupling adjusting member 12c, and influences are give even to the coupling between the x mode and the y mode. In a dielectric resonator apparatus constructed as described hereinabove, the circuits of the resonators REx, REy, REz of three modes of the x mode, y mode and z mode are made independent to one another and also, the resonance frequencies of the respective resonators REx, REy, REz are made mutually different so that three independent microwave band passing filters which are mutually different in the central frequency in the passing band can made be constructed with one dielectric resonator apparatus. As the dielectric resonator 100 is approximately spherical, it can be made considerably smaller in size and lighter in weight as compared with the second conventional embodiment formed with three pillar-shaped dielectrics being integrated. As the dielectric of the dielectric resonator 100 is concentrated near the central portion within the above described shield case, the electromagnetic field energies in each mode of the TE 101 are distributed near the central portion of the above described shield case 10. Higher no-load Q (Q 0 ) is provided as compared with the second conventional embodiment where the electromagnetic field energies are not concentrated in the central portion. Therefore, there is an advantage in that three microwave band passing filters having narrower passing band than in the conventional embodiment can be realized. In the above described first embodiment, although resonator frequencies of the resonators REx, REy, REz of each mode are mutually made different, the present invention is not restricted to it. The resonator frequencies of the two or all the resonators may be made the same. A modified embodiment 100a of the dielectric resonator 100 of Fig. 2 will be shown in Fig. 4. It is to be noted that like parts in Fig. 2 are designated by like reference numerals throughout the accompanying drawing in Fig. 4. The dielectric resonator 100a in the present embodiment is characterised to have a ]-shaped section and a given length in a tangential direction of the ring so that the respective frequency adjusting concave portions 21a, 22a, 23a have the respective surface central portions of the respective ring shaped dielectrics 51, 52, 53 remained as compared with the dielectric resonator 100 of Fig. 2. The respective frequency adjusting concave portions 21a, 22a, 23a may be optionally shaped on the conditions where one portion of the ring may remain so as to pass the electric force lines of each mode into the rings. (Second Embodiment) A dielectric resonator apparatus in a second embodiment in accordance with the present invention will be shown in Fig. 5. A dielectric resonator 110 to be used by the dielectric resonator apparatus is shown in Fig. 6. Referring to Fig. 5 and Fig. 6, it is to be noted that like parts in Fig. 1 and Fig. 2 are designated by like reference numerals throughout the accompanying drawings in Fig. 5 and Fig. 6. The dielectric resonator apparatus in the second embodiment is characterized to have a mode coupling between the x mode and the y mode, and between the y mode and the z mode as compared with the first embodiment of Fig. 1, and has a Lix and a Loz only provided as an input, output coupling loop. The difference point between the first embodiment and the second embodiment will be described in detail hereinafter. As shown in Fig. 6, a mode coupling concave portion 31xy having a longitudinal length parallel to an angle direction of 45 degrees with respect to the plane of each ring, and a given depth is formed at the top portion of the dielectric resonator 110 which is a cross portion between the ring shaped dielectric 51 of the x mode and the ring shaped dielectric 52 of the y mode as shown in Fig. 6. The resonator REx of the x mode is coupled electromagnetically to the resonator REy of the y mode so as to cause the mode coupling as a mode coupling concave portion 31xy is formed at the cross portion of the electric force line of the x mode and the electric force line of the y mode. A mode coupling concave portion 31yz having a length in the longitudinal direction parallel to an angle direction of 45 degrees with respect to the plane of each ring, and a given depth is formed on the side face portion of the dielectric resonator 110 which is the cross portion between the ring shaped dielectric 52 of the y mode and the ring shaped dielectric 53 of the z mode. The resonator REy of the y mode and the resonator REz of the z mode are electromagnetically coupled so as to cause the mode coupling as the mode coupling concave portion 31yz is formed in the cross portion between the electric force line of the y mode and the electric force line of the z mode. In the present embodiment, the insertion length of the coupling adjusting member 12b is adjusted so that the resonator REx of the x mode is not coupled mutually to the resonator REz of the z mode. The equivalent circuit of the dielectric resonator apparatus in the present embodiment constructed as described hereinabove is shown in Fig. 7. As clear from Fig. 7, a mode coupling is caused between the respective resonators REx, REy of the x mode and the y mode, and a mode coupling is caused between the respective resonators REy and REz of the y mode and the z mode. The inductance Lx 2 of the resonator REx of the x mode and the inductance Ly 2 of the y mode are inductively coupled with the inductive coupling coefficient kxy and the inductance Ly 1 of the resonator REx of the y mode and the inductance Lz 1 of the y mode are inductively coupled with the inductive coupling coefficient kyz. The inductive coupling coefficient kzx between the z mode and the x mode is set to zero. In the dielectric resonator apparatus constructed as described hereinabove, a three-stage of microwave band passing filter, with the circuits of the resonators REx, REy, REz of three modes, a x mode, a y mode and a z mode, being connected in concatenation, can be composed of one dielectric resonator apparatus. The resonance frequencies of the resonators REx, REy, REz of each mode can be optionally set as in the first embodiment. A modified embodiment 110a of the dielectric resonator 110 of Fig. 6 is shown in Fig. 8. Referring to Fig. 8, it is to be noted that like parts in Fig. 6 are designated by like reference numerals throughout the accompanying drawings in Fig. 8. In the dielectric resonator 110a in the modified embodiment, as compared with the dielectric resonator 110 of Fig. 6, each frequency adjusting concave portions 21a, 22a, 23a has a ]-character shaped section and a given length in the tangential direction of the ring so that the respective surface central portions of the respective ring shaped dielectrics 51, 52, 53 may be left. Also, the mode coupling concave portions 32xy, 32yz have ]-character shaped section so that the respective surface central portions of the respective ring shaped dielectrics 51, 52, 53 may be left. The respective frequency adjusting concave portions 21a, 22a, 23a and the mode coupling concave portions 32xy, 32yz may be optionally shaped on the conditions that one portion of the ring may remain so as to pass the electric force lines of the respective modes into the rings. In the above described second embodiment, a dielectric resonator apparatus is shown where a x mode is coupled in mode to a y mode, and a y mode is coupled in mode to a z mode. The present invention may be composed of, in addition to the above description, for example, a dielectric resonator apparatus where a x mode is coupled to a y mode, a z mode is independent, a dielectric resonator apparatus where a z mode is coupled to a x mode in addition to the mode coupling in the second embodiment. (Other embodiments) In the above described respective embodiments, a cavity portion 101 and notches 102, 103 are formed in the dielectric resonators 100, 100a, 110, 110z. The present invention may remain spherical in shape without formation of the cavity portion 101 and the notch portions 102, 103 in addition to it. According to a dielectric resonator apparatus in accordance with the present invention as described hereinabove, a dielectric resonator which has a spherical or approximately spherical dielectric placed within the shield case of the rectangular cavity, and uses the respective resonances of the x mode, the y mode and the z mode of the TE 101 where the electric fields are caused respectively around the x axis, the y axis and the z axis of the rectangular coordinate system predetermined in the above described dielectric, and an external coupling means for coupling the above described dielectric resonator to the external circuit are provided. Three pillar-shaped resonators using the respective resonances of the x mode, the y mode and the z mode of the above described TE 101 are realized by one apparatus and the shape is spherical or approximately spherical. Therefore, the size can be made considerably smaller, the weight considerably lighter as compared with the second conventional embodiment formed through the integration of the three pillar-shaped dielectric. The electromagnetic energies are also distributed near the central portion of the above described shield case in each mode of the TE 101 as the above described dielectric is concentrated near the central portion within the above described shield case in the dielectric resonator apparatus in accordance with the present invention. No-load Q (Q 0 ) is higher as compared with the above described conventional embodiment where the electromagnetic field energies are not concentrated in the central portion. Therefore, there is an advantage in that three microwave band passing filters having a passing band narrower than in the conventional embodiment can be realized.

Claims: Dielectric resonator apparatus comprising: a shielded case (10) forming a rectangular cavity; a spherical dielectric resonator (100) arranged in said case (10) wherein said resonator (100) is formed by three ring-shaped dielectrics (51,52,53) being mutually orthogonal, wherein said ring-shaped dielectrics (51,52,53) are formed in a xz-plane, a yz-plane and xy-plane, respectively, of a rectangular coordinate system such that each ring-shaped dielectric is operable in a resonance condition of a x mode, y mode and z mode of the TE 101 -mode; and an external coupling means (L ix , L ox , L iy , L oy , L iz , L oz ) for coupling said resonator (100) to an external circuit. The dielectric resonator apparatus defined in claim 1, wherein each resonance of a x mode, a y mode and a z mode of the TE 101 is mutually in a non-coupling condition. The dielectric resonator apparatus defined in claim 1 or 2, where the non-coupling condition is achieved with a coupling adjusting member (12a,12b,12c) projecting into the shielded case (10) operable with respect to each pair of two resonances in the mutually non-coupling condition. The dielectric resonator apparatus defined in claim 2 or 3, where respective resonances of a x mode, a y mode and a z mode of the TE 101 have mutually different resonance frequencies. The dielectric resonator apparatus defined in claim 4, where respective resonances of a x mode, a y mode and a z mode of the TE 101 have mutually different resonance frequencies defined by concave portions formed respectively in the three ring shaped dielectrics corresponding to the resonances. The dielectric resonator apparatus defined in claim 2, 3, 4 or 5, where the external coupling means (L ix ,L ox ,L iy ,L oy ,L iz , L oz ) is provided with pairs of coupling loops which are arranged in accordance with each resonance of a x mode, a y mode and a z mode of the TE 101 so as to be separated by a given distance from each of the ring shaped dielectrics (51,52,53) to grasp each of the ring shaped dielectrics (51,52,53), and to be interlinked with a magnetic field of the resonance of a x mode, a y mode or a z mode of the TE 101 . The dielectric resonator apparatus defined in any of claims 1 to 6, where two resonances of each pair of at least two pairs among three pairs of the respective resonances of a x mode, a y mode and a z mode of the TE 101 are mutually in a coupling condition. The dielectric resonator apparatus defined in claim 7, where the coupling condition is achieved with a concave portion (21,22,23) formed in a cross portion where the two ring shaped dielectrics corresponding to two resonances in the coupling condition are crossed. The dielectric resonator apparatus defined in claim 7 or 8, where two resonances of at least one pair among three pairs of the respective resonances of a x mode, a y mode and a z mode of the TE 101 are mutually in a non-coupling condition. The dielectric resonator apparatus defined in any of claims 1 to 9, where the external coupling means is provided with a first coupling loop (L oz ) which is separated by a given distance from the first ring shaped dielectric (51) and is adapted to be interlinked with the magnetic field of the resonance caused by the first ring shaped dielectric, and a second coupling loop (L ox ) which is separated by a given distance from the second ring shaped dielectric (52) and is adapted to be interlinked with the magnetic field of the resonance caused by the second ring shaped dielectric.

Inventors: HIDAKA SEIJI, ISHIKAWA YOUHEI, NISHIDA HIROSHI, WADA HIDEKAZU, HIDAKA, SEIJI, ISHIKAWA, YOUHEI, NISHIDA, HIROSHI, WADA, HIDEKAZU
Applicants: MURATA MANUFACTURING CO, MURATA MANUFACTURING CO., LTD.
Application year: 1992
Main classification: H01P7
IPC codes: H01P1, H01P7