Dielectric resonator device and manufacturing method thereof

Abstract: A dielectric resonator device in which inner electrodes (2a-2d;8a-8d) are provided in a dielectric block (1), and an other electrode (3) is formed on an outer face of the dielectric block. lengths (L1-L4) of the inner electrodes are determined according to resonance frequencies of the respective resonators, while widths (S1-S4) of non-electrode formed regions (7a-7d) are determined according to the amounts of coupling between the respective resonators. Since the dielectric block may be standardized, various kinds of dielectric resonator devices different in characteristics can be obtained without increasing the kinds of molding metal molds.

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention generally relates to a dielectric resonator arrangement, and more particularly, to a dielectric resonator device constructed by forming a plurality of resonator electrodes on a dielectric substrate or in a dielectric block. Conventionally, there have been employed a multi-stage dielectric resonator device constituted by forming a plurality of resonance electrodes (inner electrodes) within a dielectric block, and a ground electrode over the outer face of said dielectric block, and a strip-line type multi-stage resonator device having a plurality of resonance electrodes formed on the surface of a dielectric substrate, and a ground electrode formed on a confronting surface of said dielectric substrate, for example, as a band-pass filter, etc. in a microwave band region. In the dielectric resonator device having a plurality of inner electrodes formed within the dielectric block, coupling bores or holes are formed to achieve coupling among respective resonators for setting of the amount of coupling by the size of such coupling bores. However, in this type of the resonator device in which the coupling bores are to be provided, not only the productivity is low in the manufacture, but it has been difficult to adjust the coupling amount properly. Therefore, it has been considered to control resonator characteristics by adjusting the range of formation of the inner electrodes as shown in Fig. 4(A) which is a top plan view of a conventional dielectric resonator device, and Fig. 4(B) representing a side sectional view taken along the line IV(B)-IV(B) in Fig. 4(A). In Figs. 4(A) and 4(B), the known resonator device, for example, in the form of a symmetrical 4 stage band-pass filter, includes a dielectric block 1' formed therein with four through-holes, and inner electrodes 2a', 2b', 2c' and 2d' formed in the inner peripheral faces of said through-holes. The dielectric resonator device as referred to above may be represented by an equivalent circuit as shown in Fig. 5, in which R1, R2, R3 and R4 denote the resonators formed by the inner electrodes 2a', 2b', 2c' and 2d' as shown in Figs. 4(A) and 4(B), with symbols K1 and K2 representing the coupling amounts between the respective neighboring resonators. In the dielectric resonator device having the construction as illustrated in Figs. 4(A) and 4(B), for example, the resonance frequency of the resonator R2 is determined by a length L2' of the inner electrode 2b' at a second stage, while the coupling amount K2 is determined by a length S2' of a region not formed with the inner electrode, and an interval P2' between the inner electrodes 2b'-2c'. When a filter is to be designed in a relation represented by f1>f2 and K1>K2 on the assumption that the dielectric resonator device shown in Figs. 4(A) and 4(B) is constructed as the symmetrical 4 stage band-pass filter, and the resonance frequencies of the resonators R1 and R4 are represented by f1, and those of the resonators R2 and R3, by f2, the procedure for the design will be as follows. (i) To determine the length L2' of the inner electrodes 2b' and 2c' according to the resonance frequencies f2. (ii) To determined the length S2' of the inner electrode non-formed region and/or the interval P2' between the inner electrodes 2b'-2c' according to the coupling amount K2, with consequent determination of the axial length L thereby. (iii) To determine the length L1' of the inner electrodes 2a' and 2b' according to the resonance frequency f1, with consequent determination of S1'. (iv) To determine the interval P1' between the inner electrodes 2a'- 2b' and 2c'- 2d' according to the coupling amount K1. Although the symmetrical 4 stage band-pass filter may be designed in the manner as described above, since the interval P1' and P2' between the inner electrodes are not constant according to the filter characteristics aimed at, different metal molds are required for each kind of the filters, thus resulting in high manufacturing cost. 2. Description of the Prior Art SUMMARY OF THE INVENTION Accordingly, an essential object of the present invention is to provide a dielectric resonator device constituted by providing resonance electrodes on a dielectric member, which is arranged to obtain necessary characteristics without changing intervals between the neighboring resonance electrodes. Another object of the present invention is to provide the dielectric resonator device of the above described type in many kinds which are different in characteristics without increasing kinds of molding metal mods for manufacturing thereof. A further object of the present invention is to provide a method of manufacturing the dielectric resonator device of the above described type in an efficient manner at low cost. These objects, according to the present invention, are accomplished by the device according to claim 1 and by the method according to claim 2. A device according to the preamble of claim 1 is known from document JP-A-36090201. Document JP-A-36090201 relates to a dielectric filter which comprises a dielectric block 40 in which a plurality of through-holes 14 is provided. The respective inside peripheral surfaces of the through-holes 14 are coated with inner conductors 30. The length of these inner conductors 30 is about 1/4 wavelength and the one-side ends of the inner conductors 30 are connected to a outer conductor 10 and the other ends are open ends. Document GB-A-2240432 relates to a strip line filter including a laminate of a plurality of dielectric substrates having conducting resonator means provided between each of the adjacent two dielectric substrates. BRIEF DESCRIPTION OF THE DRAWINGS These and other objects and features of the present invention will become apparent form the following description taken in conjunction with the preferred embodiment thereof with reference to the accompanying drawings, in which; Fig. 1(A) is a front elevational view of a dielectric resonator device according to one preferred embodiment of the present invention, Fig. 1(B) is a cross section taken along the line I(B)-I(B) in Fig. 1(A), Fig. 2 is a perspective view of the dielectric resonator device of Fig. 1(A), Fig. 3(A) is a top plan view of a dielectric resonator device according to a second embodiment of the present invention, Fig. 3(B) is a cross section taken along the line III(B)-III(B) in Fig. 3(A), Fig. 4(A) is a front elevational view of a conventional dielectric resonator device (already referred to), Fig. 4(B) is a cross section taken along the line IV(B)-IV(B) in Fig. 4(A) (already referred to), Fig. 5 is an equivalent circuit diagram of a symmetrical 4 stage band-pass filter, and Fig. 6 is an equivalent circuit diagram of a 2 stage comb-line type filter. 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. Referring now to the drawings, there is shown in Figs. 1(A), 1(B) and 2, a dielectric resonator device RA according to one preferred embodiment of the present invention, which generally includes a dielectric block 1 in the form of a hexahedron or in a rectangular cubic box-like configuration having a first face A and a second face B which are generally parallel to each other and side faces C, D, E and F contiguously provided between said first and second faces, four through-holes Ha, Hb, Hc and Hd formed to extend through the dielectric block 1 from the first face A to the second face B, first inner electrodes 2a, 2b, 2c and 2d and second inner electrodes 8a, 8b, 8c and 8d respectively formed in the inner peripheral faces of the respective through-holes Ha to Hd, and an outer electrode 3 formed on the first face A, the second face B, and the side faces C, D, E and F. The dielectric block 1 is formed through employment of a molding metal mold which serves as a standard (not particularly shown). Although the dielectric block to be obtained by one metal mold has the same shape and same dimensions on the whole, including positions of the through-holes Ha to Hd, resonator devices having different resonator characteristics may be obtained by the lengths of the first inner electrodes 2a to 2d and the second inner electrodes 8a to 8d to be formed on the respective inner peripheral faces of said through-holes Ha to Hd. By way of example, it becomes possible to constitute a plurality of kinds of band-pass filters different in center frequencies and band widths, etc. by the use of the dielectric block produced by the common molding metal mold. Subsequently, referring to Fig. 6, showing an equivalent circuit diagram of a general 2 stage comb-line type filter, factors determining the center frequencies and band widths will be explained. In the first place, the center frequency fo is represented by an equation as follows from the resonance condition. 2πfoCs = Ya·cot o o = {√(εr)/C} · 2πfoL where εr is a dielectric constant of a resonator surrounding substance, Cs is a straight capacity, L is a resonator length, Ya is admittance of the resonator, and C is a light velocity. Meanwhile, a coupling coefficient k is represented by a following equation, and is determined by each admittance and . k = {(Yo-Ye)/Ya} {(1 + o/(sin o·cos o)} 1 where Yo is an admittance in the odd mode, and Ye is an admittance in the even mode. Subsequently, specific examples will be shown by referring to Figs. 1(A) and 1(B). In Figs. 1(A) and 1(B), there is shown a dielectric resonator device RA according to one preferred embodiment of the present invention, which comprises a dielectric block 1 having a first face and a second face B generally parallel to each other, side faces continuous between the first and second faces A and B, and through-holes Ha, Hb, Hc and Hd extending from the first face A to the second face B through the dielectric block 1, an outer electrode 3 formed over the first face A, the second face B, and the side faces of said dielectric block 1, and first inner electrodes 2a, 2b, 2c and 2d and second inner electrodes 8a, 8b, 8c, and 8d formed, through gaps 7a, 7b, 7c and 7d at least in the vicinity of opening portions at one side, on inner peripheral faces of said through-holes Ha to Hd. More specifically, the first inner electrodes 2a, 2b, 2c, and 2d, and the second inner electrodes 8a, 8b, 8c, and 8d are each formed on the inner peripheral faces of the respective through-holes Ha, Hb, Hc and Hd through the gaps, i.e. non-electrode forming regions 7a, 7b, 7c and 7d provided therebetween, and one end of each of the inner electrodes 2a to 2d and 8a to 8d is conducted to the outer electrode 3. The first inner electrodes 2a to 2d act as resonance electrodes, with the first face A of the dielectric block 1 functioning as a short-circuiting face. Lengths of the first inner electrodes 2a, 2b, 2c and 2d are represented by L1, L2, L3 and L4, and widths of the gaps 7a, 7b, 7c and 7d are denoted by S1, S2, S3 and S4 respectively. Meanwhile, the lengths of the respective sides of the dielectric block are represented by La, Lb and Lc, and the intervals between the respective inner electrodes are represented by P1 between 2a and 2b, P2 between 2b and 2c, and P3 between 2c and 2d. Here. the relation for the respective internals may be set as P1=P2=P3 or P1≠P2≠P3≠P1. Although the resonance frequency of each resonator is determined by various factors, in the embodiment as shown in Figs. 1(A) and 1(B), the resonance frequency of the first resonator by the first inner electrode 2a is determined by L1 and S1, the resonance frequency of the second resonator by the first inner electrode 2b is determined by L2 and S2, the resonance frequency of the third resonator by the first inner electrode 2c is determined by L3 and S3, and further, the resonance frequency of the fourth resonator by the first inner electrode 2d is determined by L4 and S4. Meanwhile, the coupling amounts between the neighboring resonators are determined by P1, P2 and P3, and S1, S2, S3 and S4, and in this case, the intervals P1, P2 and P3 between the inner electrodes to be set by the metal mold dimensions are fixed. The dielectric resonator device RA as shown in Figs. 1(A) and 1(B) functions as a band-pass filter "F1" having a center frequency of f1, and a band width of BW1, but in order to produce on a large scale, band-pass filters with different characteristics by the dimensions of the first and second inner electrodes within the respective through-holes through employment of dielectric blocks prepared by the same metal mold, such band-pass filters may be manufactured after designing in the manner as described hereinbelow. Firstly, in the case where a band-pass filter "F2" with the band width equal to BW1, and the center frequency of f2 higher than f1 (f2>f1) is to be produced on a large scale, the length of the first inner electrode 2a is set to be L12 shorter than L1, that of the first inner electrode 2b is set to be L22 shorter than L2, that of the first inner electrode 2c is set to be L32 shorter than L3, and that of the first inner electrode 2d is set to be L42 shorter than L4. The widths S1, S2, S3 and S4 of the gaps 7a to 7d between the first inner electrodes 2a to 2d, and the second inner electrodes 8a to 8d, are set to be the same as in the case where the center frequency is f1 in principle, and accordingly, the lengths of the second inner electrodes 8a to 8d are set to be longer than those in the case of the band-pass filter "F1". As described above, when the center frequency is higher, each length of the second inner electrodes 8a to 8d becomes generally longer. However, in the case where the center frequency f2 of this filter "F2" is spaced away from he center frequency f1 of the filter "F1" too far to neglect the variation in the pass-band width, the widths S1, S2, S3 and S4 of the gaps are slightly increased, with corresponding slight increase of the lengths L12, L22, L32, and L42 of the first inner electrodes in design for manufacturing. Then, for mass-production of the filter having the pass-band width narrower than BW1, with the center frequency set at f2, the widths S1, S2, S3 and S4 are each increased at the designing stage. In the above case, if the influence over the resonance frequency of each resonator can not be neglected due to the alternation of the values for S1, S2, S3 and S4, the values for the lengths L12, L22, L32 and L42 of the respective first inner electrodes are altered in the directions towards L12 → L1, L22 → L2, L32 → L3, and L42 → L4 respectively, and simultaneously, the lengths of the second inner electrodes 8a, 8b, 8c and 8d are reduced by the amounts in which the lengths of the first inner electrodes L12, L22, L32 and L42 are increased respectively in the designing. Conversely, for mass-production of the filter having the pass-band width wider than BW1, with the center frequency set at f2, the widths S1, S2, S3 and S4 are each reduced at the designing stage. In the above case, if the influence over the resonance frequency of each resonator can not be neglected due to the alternation of the values for S1, S2, S3 and S4, the values for the lengths L12, L22, L32 and L42 of the respective first inner electrodes are further reduced and simultaneously, the lengths of the second inner electrodes 8a, 8b, 8c and 8d are increased. As described above, various kinds of filters as desired are manufactured on a large scale by determining the lengths of the first and second inner electrodes and the widths of the gaps at the stage of designing. It is to be noted here that the lengths of the respective electrodes and the widths of the gaps as referred to above may be set at the predetermined values by grinding the inner electrodes at the gap portions through employment of a grained stone. In the case where a band-pass filter "F3" with the band width equal to BW1, and the center frequency of f3 lower than f1 (f3<f1) is to be produced on a large scale, the length of the first inner electrode 2a is set to be L13 longer than L1, that of the first inner electrode 2b is set to be L23 longer than L2, and that of the first inner electrode 2c is set to be L33 longer than L3, and that of the first inner electrode 2d is set to be L43 longer than L4. The widths S1, S2, S3 and S4 of the gaps 7a to 7d between the first inner electrodes 2a to 2d, and the second inner electrodes 8a to 8d, are set to be the same as in the case where the center frequency is f1 in principle, and accordingly the lengths of the second inner electrodes 8a to 8d are set to be shorter than those in the case of the band-pass filter "F1". As described above, when the center frequency is lower, each length of the second inner electrodes 8a to 8d becomes generally shorter. However, in the case where the center frequency f3 of this filter "F3" is spaced away from the center frequency f1 of the filter "F1" too far to neglect the variation in the pass-band width, the widths S1, S2, S3 and S4 of the gaps are slightly decreased, with corresponding slight decrease of the lengths L13, L23, L33, and L43 of the first inner electrodes in design for manufacturing. Then, for mass-production of the filter having the pass band width narrower than BW1, with the center frequency set at f3, the widths S1, S2, S3 and S4 are each increased at the designing stage. In the above case, if the influence over the resonance frequency of each resonator can not be neglected due to the alternation of the values for S1, S2, S3 and S4, the values for the lengths L13, L23, L33 and L43 of the respective first inner electrodes are further increased, and simultaneously, the lengths of the second inner electrodes 8a, 8b, 8c and 8d are reduced in the designing. Conversely, for mass-production of the filter having the pass and width wider than BW1, with the center frequency st at f3, the widths S1, S2, S3 and S4 are each decreased at the designing stage. In the above case, if the influence over the resonance frequency of each resonator can not be neglected due to the alternation of the values for S1, S2, S3 and S4, the values for the lengths L13, L23, L33 and L43 of the respective first inner electrodes are altered in the directions towards L13 → L1, L23 → L2, L33 → L3, and L43 → L4 respectively, and simultaneously, the lengths of the second inner electrodes 8a, 8b, 8c and 8d are increased by the amounts in which the lengths of the first inner electrodes L12, L22, L32 and L42 are decreased respectively in the designing. As described above, various kinds of filter as desired are manufactured on a large scale by determining the lengths of the first and second inner electrodes and the widths of the gaps at the stage of designing. In the manners as described so far, it may be so arranged to obtain the dimensional data for each part which will provide the desired characteristics at the stage of designing or trial production, sand to carry out mass production on the basis of such data. However, in the case where dielectric resonator devices different in the resonance frequencies, etc. to a large extent can not be constituted by a single common dielectric block, it may be, for example, so arranged to classify the resonance frequencies, etc. into ranks for common use of the dielectric blocks according to each rank. Thus, it becomes possible to produce various band-pass filters having center frequencies and pass-band widths as desired by dielectric blocks formed through employment of common metal molds. This is made possible by the presence of the second inner electrodes 8a, 8b, 8c and 8d contiguous from the outer electrode 3 on the second surface B of the dielectric block shown in Figs. 1(A) and 1(B), and this is the effect peculiar to the present invention which is not available by the conventional dielectric resonator device as shown in Figs. 4(A) and 4(B). It is to be noted here that in the embodiment as shown in Figs. 1(A) and 1(B), although input and output terminals of the signals are omitted in the drawings, known constructions disclosed, for example, in Japanese Patent Laid-Open Publications Tokkaisho Nos. 59-51606, 60-114004, or Japanese Utility Model Laid-Open Publications Jikkaisho No. 58-54102 or 63-181002 may be adopted. It should be noted here that in the dielectric resonator device RA according to the foregoing embodiment, the dielectric block in the hexahedron shape is employed, the concept of the present invention is to limited in its application to the dielectric block of such shape. Moreover, the dielectric block to be employed is not limited to those molded by one-piece molding, but may be one as disclosed, for example in Japanese Patent Publication Tokkohei No. 3-15841, in which two dielectric substrates are employed, and by joining these two dielectric substrates, through-holes are formed in the joined faces. In the first embodiment of Figs. 1(A) and 1(B), although the present invention has been described as applied to the dielectric resonator device of 1/4 wavelength type, it may be so modified as applied to a dielectric resonator device in which the respective resonance electrodes resonate to 1/2 wavelength by providing spaces in the both opening portions of the respective through-holes. Additionally, in the first embodiment, although the inner diameter of each through-hole is set to be constant in its axial direction, the shape of the through-hole may be modified, for example, into a tapered shape or stepped shape. Referring further to Figs. 3(A) and 3(B), there is shown a dielectric resonator device RB according to a second embodiment of the present invention, which includes a dielectric substrate 4 having resonance electrodes 5a, 5b, 5c and 5d on its first main surface 4a and a ground electrode 6 on its second main surface 4b, with the resonance electrodes 5a to 5d being conducted to the ground electrode 6 in the vicinity of an edge portion at one side of said dielectric substrate 4, and auxiliary electrodes 9a, 9b, 9c and 9d conducted to the ground electrode 5 and extending from the other edge portion of said dielectric substrate which confronts said one edge portion thereof, towards position near open ends of said resonance electrodes 5a to 5d. More specifically, the electrodes 5a, 5b, 5c and 5d and 9a, 9b, 9c and 9d are formed on the first main surface 4a through non-electrode forming regions 7a, 7b, 7c and 7d provided therebetween as shown. In these electrodes, the electrodes 5a, 5b, 5c and 5d function as strip lines for the resonant electrodes, while the electrodes 9a, 9b, 9c and 9d act as the auxiliary electrodes. Moreover, the ground electrode 6 is formed from the second main face 4b (i.e. the reverse face) of the dielectric substrate 4 towards the edge portion at the short-circuited end sides of the resonance electrodes 5a, 5b, 5c and 5d, and the edge portion at the forming side of the auxiliary electrodes 9a, 9b, 9c an 9d. By the above structure, the resonator device RB functions as the strip-line type dielectric resonator device, and can be used as the four stage band-pass filter. In this case also, the filter characteristics can be set by the length of the strip-line from the short-circuited end, and the length of the non-electrode formed portions 7a, 7b, 7c and 7d. It is to be noted here that in the first and second embodiments as described so far, although the present invention has been described with reference to the comb-line type filter as one example, the concept of the present invention is not limited in its application to the above, but may be applied to a filter of an inter-digital type as well. As is clear from the foregoing description, according to the present invention, various kinds of dielectric resonator devices different in the characteristics may be readily obtained without increasing the kinds or variations of the dielectric blocks or dielectric substrates, with a marked reduction in the manufacturing cost.

Claims: A dielectric resonator device comprising a dielectric block (1) having a first face (A) and a second face (B) generally parallel to each other, side faces (C-F) continuous between said first and second faces (A,B), and through-holes (Ha-Hd) extending from the first face (A) to the second face (B) through the dielectric block (1), an outer electrode (3) formed over said first face (A), said second face (B) and said side faces (C-F) of said dielectric block (1), and first inner electrodes (2a-2d) formed on inner peripheral faces of said through-holes; characterized by second inner electrodes (8a-8d) formed on inner peripheral faces of said through-holes; and gaps (7a-7d) formed in the vicinity of either the first face (A) or the second face (B) separating said first inner electrodes and said second inner electrodes. A method for manufacturing a dielectric resonator device comprising the steps of: forming a dielectric block (1) having a first face (A) and a second face (B) generally parallel to each other, side faces (C-F) continuous between said first and second faces (A,B) and through-holes (Ha-Hd) extending from the first face (A) to the second face (B) through the dielectric block (1), applying through formation an outer conductor film (3) on said first face (A), second face (B) and side faces (C-F) of said dielectric block (1), and applying through formation first inner conductor films (2a-2d) onto inner peripheral faces of said through-holes; characterized by the following step applying through formation second inner conductor films (8a-8d) onto inner peripheral faces of said through-holes; wherein said first and said second inner conductor films are applied such that gaps (7a-7d) are formed between said first and said second inner conductor films in the vicinity of either said first face (A) or said second face (B). A method of manufacturing a dielectric resonator device as claimed in claim 2, wherein said dielectric block (1) is formed through employment of common molding metal molds, thereby to produce dielectric resonator devices having various resonator characteristics by differentiating positions of the gaps (7a-7d) within the respective through-holes (Ha-Hd). A method of manufacturing a dielectric resonator device as claimed in claim 2, wherein said dielectric block (1), is formed through employment of common molding metal molds, thereby to produce dielectric resonator devices having various resonator characteristics by differentiating widths (S1-S4) of the gaps (7a-7d) within the respective through-holes (Ha-Hd). A method of manufacturing a dielectric resonator device as claimed in claim 2, wherein said dielectric block (1), is formed through employment of common molding metal molds, thereby to produce dielectric resonator devices having various resonator characteristics by differentiating positions and widths of the gaps (7a-7d) within the respective through-holes (Ha-Hd).

Inventors: KITAICHI YUKIHIRO, YAMADA YASUO, KITAICHI,YUKIHIRO, YAMADA, YASUO
Applicants: MURATA MANUFACTURING CO, MURATA MANUFACTURING CO., LTD.
Application year: 1992
Main classification: H01P1
IPC codes: H01P7, H01P1, H01P11