Dielectric resonator

Abstract: A dielectric resonator comprises a dielectric block (21) having an outer surface including first and second end surfaces substantially parallel to each other and a side surface extending between the first and second end surfaces. An external conductor (25) is formed on the outer surface of the dielectric block (21). At least one through hole (23) extends through the dielectric body (21) and an internal conductor (24) is provided in the at least one through hole. A predetermined portion of the side surface of the dielectric block (21) is shaped so that a first portion of the external conductor (25) at the shaped portion of the side surface is closer to the internal conductors (24) in the at least one through hole (23) as compared with a second portion of the external conductor on portions of the outer surface of the dielectric block other than the shaped portion. A non-conductive portion is provided at an inner surface of the at least one through hole wherein a surface of said non-conductive portion is flush with said inner surface of the at least one through hole. Signal input and output electrodes are provided on the outer surface of the dielectric body for providing capacitive connection with the internal conductor of the at least one through hole.

Description: The present invention generally relates to a dielectric resonator, with an internal conductor being formed within a dielectric, and an external conductor being formed on the outside face of the dielectric, and its characteristic adjusting method. A dielectric resonator, where a resonator electrode is formed within a dielectric block, an earth electrode is formed on the outside face of the dielectric block, and a so-called tri-plate type of dielectric resonator with strip lines being opposite to each other by the use of a dielectric basic plate with a strip line being formed on one main face, and an earth electrode being formed on the other main face are used as a band passing filter and so on in, for example, the microwave band. Fig. 18 shows as an explosive perspective view the construction of the conventional general dielectric resonator using the dielectric block. In Fig. 18, reference numeral 40 is approximately six-face unit shaped dielectric block with three internal conductor shaped holes 46, 47, 48 and coupling holes 49, 50 being provided among the respectively internal conductor formed holes. The internal conductor is formed on the inside face of the internal conductor formed holes 46, 47, 48, and an external conductor is formed on the other five faces except for an open face 52. Reference numerals 53, 54 are so-called resin pins each being composed of resin portions 53a, 54a and signal input, output terminals 53b, 54b. Two resin pins 53, 54 are inserted into the internal conductor formed holes 46, 48 from the open face side of the dielectric block so that the terminals 53b, 54b are coupled in capacity to the internal conductor within the internal conductor formed holes 46, 48. Reference numeral 55 is a case for retaining the dielectric block 40 and the resin pins 53, 54 and also, covering the open face portion of the dielectric block. The resin pins 53, 54 are respectively inserted into the dielectric block 40 so as to cover the case 55, and also, the whole is integrated by the soldering of the dielectric block 40 with the external conductor 51. In the mounting operation of the dielectric resonator, the projection portions 55a, 55b of the case 55 are functioned as an earth terminal. As shown in Fig. 18, many components such as input, output terminals, case and so on are necessary if a plurality of resonators are formed on a single dielectric block. The assembling steps thereof become complicated and also, completed products have to be mounted as electronic components with a lead wire attached to it having to be mounted even in the mounting operation of the completed product on the circuit basic plate. The surface mounting operation can not be effected as in the other electronic components to be mounted on the same circuit basic plate so that a lower height operation is hard to effect. If the case 55 is adapted not to be used by the direct connection of the external conductor 51 of the dielectric block 40 on the earth electrode on the circuit basic plate, the open face 52 is exposed, and the electromagnetic field leakage is caused in this portion. When the metallic member approaches to the open face, the influences by the metallic member is received. Also, the resonator is connected with the electromagnetic field of the outside so that the given characteristics as the dielectric resonator can be obtained no more. JP-A-57013801 relates to an interdigital band-pass filter in which a hollow gap is made in the center of an inductive body wherein a metallic film is adhered to a proper depth on the internal wall of the hole to form a resonator. WO-A-8500929 relates to a microwave circuit device and its fabrication. A band-pass filter is formed of a solid block of a high dielectric constant material provided with a number of holes wherein the block and the hole walls are plated with a material having an electrical conductivity much higher than that of the material of the block. The plated exterior surface of the block comprises a resonance cavity for the device and the plated walls of the through holes form a plurality of interdigital resonator rods extending into the cavity from opposite walls. WO-A-8302853 relates to a ceramic band path filter which includes a block which is comprised of a dielectric material which, in turn, is covered or plated with an electrically-conductive material. The block includes holes which extend from the top surface to the bottom surface thereof. These holes are plated with electrically-conductive material wherein the conductive plating on the dielectric material partially extends into the through hole, leaving a part of the hole unplated. Further, plated or unplated slots on side surfaces of the filter are provided to adjust the coupling between the respective coaxial resonators. Starting from this prior art, it is the object underlying the present invention to provide a dielectric resonator having an improved characteristic. This object is achieved by a dielectric resonator according to claim 1. These, and other features of the present invention will become apparent from the following description of the preferred embodiments with reference to the drawings, in which: Fig. 1 (a), (b) are a perspective view and a sectional view of the dielectric resonator in a first embodiment of the present invention; Fig. 2 is a perspective view of a dielectric resonator of a second embodiment of the present invention; Fig. 3 (a), (b) are a perspective view and an essential portion sectional view of a dielectric resonator of a third embodiment; Fig. 4 (a), (b) are a perspective view and an essential portion sectional view of a dielectric resonator of a fourth embodiment; Fig. 5 (a), (b) are a perspective view and an essential portion sectional view of a dielectric resonator of a fifth embodiment; Fig. 6 (a), (b) are a perspective view and an essential portion sectional view of a dielectric resonator of a sixth embodiment of the present invention; Fig. 7 is a perspective view of a dielectric resonator of a seventh embodiment thereof; Fig. 8 is a perspective view of a dielectric resonator of an eighth embodiment thereof; Fig. 9 is a perspective view of a dielectric resonator of a nineth embodiment of the present invention; Fig. 10 is a perspective view of a dielectric resonator of a thenth embodiment thereof; Fig. 11 is a sectional view of a dielectric resonator of Fig. 10; Fig. 12 is a front view of the dielectric resonator in accordance with a further embodiment; Fig. 13 is a front view showing a conductor deleted embodiment for the characteristics measurement of the dielectric resonator of Fig. 25; Fig. 14 is a partial front face view showing the conductor deleted embodiment for the characteristics measurement of the dielectric resonator of Fig. 25; Fig. 15 is a graph showing the measurement result in the coupling coefficient changes of the dielectric resonator of Fig. 25; Fig. 16 is a graph showing the measurement result in the resonance frequency changes of the dielectric resonator of Fig. 25; Fig. 17 is a front face view of a dielectric resonator in accordance with a further embodiment; and Fig. 18 is an explosive perspective view of a conventional resonator. Before the description of the present invention proceeds, it is noted that like parts are designated by like reference numerals throughout the drawings. (First Embodiment) Fig. 1 shows an embodiment one. Groove shaped concave portions 28 are formed in approximately parallel with the end face 22a side of the dielectric 22 on both the sides of the hole 23 with inside conductor 24 of the dielectric 22 being formed on the inside face. An outside conductor 25 is formed across the outside face whole of the dielectric 22 including the concave portion 28. Accordingly, the interval between the outside conductor 25, which becomes an earth electrode of the bottom portion of the groove shaped concave portion 28, and the inside conductor 24 becomes shorter as shown in Fig. 1 (b), so that floating capacity Cs can be easily obtained. The concave portion 28 can work the dielectric 22 or form it by a molding operation. Accordingly, the floating capacity Cs can be obtained by the comparatively simple working operation or the molding operation. The adjustment of the floating capacity Cs (size of the floating capacity Cs) can be easily effected by the deletion of the size and depth of the concave portion 28 or one portion of the outside conductor 25. In the comb-line type, the band width of the filter can be made larger by provision of, for example, the larger floating capacity Cs. The resonator length becomes shorter and the size can be made smaller by provision of, for example, the larger floating capacity Cs. Further, the floating capacity Cs can be easily obtained, and also, the adjustment of the floating capacity Cs can be easily effected even in the filter of the construction of interdigital coupling. (Second Embodiment) Fig. 2 shows an embodiment two, is different from the prior embodiment, with the groove shaped concave portion 28 being provided on the single side of the dielectric 22. Even in the embodiment, the floating capacity Cs can be easily obtained and the adjustment can be easily effected as in the prior embodiment. (Third Embodiment) Fig. 3 shows an embodiment three. In the present embodiment, the groove shaped concave portion 28 is formed on one side face of the dielectric 22. The outside conductor 25 of the bottom portion of the concave portion 28 is approached towards the inside conductor 24 within the hole 23 of the dielectric 22 so as to easily obtain the floating capacity Cs. The interval t between the outside conductor 25 which becomes an earth electrode and the inside conductor 24, the width w of the concave portion 28, the depth d and so on are changed so as to control the floating capacity Cs. The coupling between the resonators can be adjusted by the adjustment of the floating capacity Cs. The passing zone of the filter can be controlled without changes. The above described floating capacity Cs can be provided larger by the concave portion 28. The shape can be standardized, a metal mold cost and a management cost can be reduced. In the embodiment shown in Fig. 3, the concave portion 28 is formed on one side face of the dielectric 22, and can be formed on both the side faces of the dielectric 22. In this case, the floating capacity Cs can be provided larger. (Fourth Embodiment) Fig. 4 shows an embodiment four. Round hole shaped concave portions 28 are opened, in the same direction, near the hole 23. The concave portions 28 are respectively formed in accordance with the holes 23. The hole may become one or may be formed by the number of the holes 23 or more. The concave portion 28 may be provided correspondingly on both the sides of the hole 23. Many concave portions 28 may be formed. (Fifth Embodiment) Fig. 5 shows an embodiment five. In the embodiment, the round hole shaped concave portion 28 is formed on the side face of the dielectric 22. The outside conductor 25 of the bottom portion of the concave portion 28 is near-by in parallel to the inside conductor 24. Even in the embodiment, the concave portion 28 is formed correspondingly to the hole 23. The number of the holes 23 may be one or may be three or more. In addition, the concave portion 28 may be formed in either face of the dielectric 22. (Sixth Embodiment) Fig. 6 shows an embodiment six. Taper portions 29 are formed on both the sides of the corner portion on the open face 23 of the dielectric 22. The taper portion 29 is formed so that the interval between the inside conductor 24 within the hole 23 and the outside conductor 25 as an earth electrode of the taper portion 29 becomes shorter, and the floating capacity Cs can be easily obtained as in the above described embodiment. The size of the floating capacity Cs can be easily adjusted by the angle of the above described taper portion 29 and the size of the taper portion 9. The taper portion 29 is formed on the angle portion of the other face so that the floating capacity Cs may be obtained. (Seventh Embodiment) Fig. 7 shows an embodiment seven where the taper portion 29 is formed on the single side of the dielectric 22. Even in the embodiment, the floating capacity Cs can be easily obtained by the taper portion 29. (Eighth Embodiment) Fig. 8 shows an embodiment eight. In the present embodiment, a taper portion 29 is formed with one portion instead of the whole face of the angle portion of the dielectric 22 being notched. In Fig. 8, a concave portion 30 with a taper portion 29 being formed is formed by only one portion. Concave portions 30 may be formed by plurality on the single side or both the sides in accordance with the respective hole 23. The number of the concave portions 30 is not restricted. The floating capacity Cs can be easily adjusted by the position and size of the concave portion 30. (Nineth Embodiment) Fig. 9 is an embodiment nine, where a concave portion 31 of approximately L type in a stage shaped section, instead of such a taper shaped section as in the prior embodiment, is formed on the single side of the corner portion on the top face of the dielectric 22. Even in this case, the interval between the inside conductor 24 within the hole 23 and the outside conductor 25 which becomes an earth electrode of the concave stage portion 31 becomes shorter so that the floating capacity Cs can be easily obtained. Although the concave stage portion 31 is continuously formed in Fig. 9, it may be formed not continuously, in one portion or intermittent portions, in the corner portions on both the side portions of the dielectric 22. The size of the floating capacity can be easily adjusted by the size or the like of the concave stage portion 31. (Tenth Embodiment) The present embodiment ten in Fig. 10 and Fig. 11 is an embodiment where the concave stage portion 31 is further made deeper as compared with the case of the above described embodiment 18. In an integrated type of dielectric resonator, the floating capacity Cs is obtained by the inside conductor 24 and the concave stage portion 31 is formed by a dielectric filter comb-line connected so that the outside conductor 25 is approached to the inside conductor 24 within the hole 23 so as to increase the floating capacity Cs. The approached size W and the depth X of the concave stage portion 31 are adjusted so as to adjust the coupling. When the size of the dielectric 22 in the axial direction of the hole 23 is made L, 0 ≤ X < L. The coupling coefficients of the dielectric resonator can be changed by the change in the above described size X, W so that the passing band of the filter can be controlled without the shape (metal mold). The shape of the dielectric resonator can be standardized, and the metallic cost and the management cost can be reduced. As the large coupling coefficient can be obtained without the pitch between the holes 3 being narrowed, the pole of the high pass becomes far from the passing band, and the damping of the low pass is improved. The resonance electrode length becomes shorter with the floating capacity Cs being increased, so that the filter can be made smaller in size. Further, the filter larger in the specific band is obtained. The dielectric resonator in each of the above described embodiments is not restricted to the number of the stages although the three-stage construction has been described. Namely, it can be applied to the dielectric resonator of one stage or three-stage or more. The dielectric resonator of the present invention can be applied to a case where all the filters such as band pass filter, band elimination filter, high-pass filter, low-pass filter and so on are formed. As is clear from the foregoing description, according to the arrangement of the present invention, the dielectric resonator of the present invention can be mounted on the surface on the circuit basic plate without the use of a special individual signal input, output terminals as the signal input, output electrodes are provided on one portion of the external conductor. As the conductor exists on the open face of the internal conductor formed hole so as to provide no open face, the electromagnetic field leakage is less so that influences by the electromagnetic field leakage are less if the dielectric resonator is mounted on the circuit basic plate in a condition as it is. According to the dielectric resonator of the present invention, a dielectric resonator without coupling coefficients being adjusted between the resonator frequency of the resonator and the resonance without coating addition and so on with respect to the non-formed portion of the internal conductor. According to the dielectric resonator of the present invention, the open portion of the internal conductor is formed in a location secluded from the open face of the internal conductor formed holes, the influences by the electromagnetic field leakage is less. Therefore, no couplings among the resonator, the other object near the resonator and the circuit are provided so that stable resonator characteristics are provided. As is clear from the characteristic adjusting method of the dielectric resonator of the present invention, there are steps of providing an open portion in one portion of the internal conductor only by the movement of a grinding tool in the axial direction of the internal conductor formed hole with the deletion locations of the internal conductor and the dielectric being restricted, and also, easily adjusting the tip end capacity by the moving amount. Further, a dielectric resonator having given resonance frequency and coupling amount can be easily obtained without the higher size accuracy to be demanded in the grinding working operation, because the tip end capacity is gradually lowered in spite of much grinding amount of the whole. In a dielectric resonator for making resonant with the given frequency by an inside conductor formed on the inside face of the hole of the dielectric and an outside conductor formed on the outside face of the above described dielectric, the concave portion is formed on the surface of the above described dielectric, the outside conductor of the bottom portion of the concave portion is approached to the above described inside conductor so that the interval between the inside conductor of the hole interior of the dielectric and the outside conductor which becomes an earth electrode becomes shorter so as to easily obtain the floating capacity by the approaching operation between the outside conductor of the bottom portion of the concave portion formed on the surface of the dielectric and the above described inside conductor. The floating capacity can be adjusted by the comparatively simple working or molding operation of the size, depth and so on of the concave portion. In the comb-line type, the band width of the filter can be made larger by provision of, for example, larger floating capacity. Resonator length becomes shorter by the provision of, for example, the larger floating capacity with an effect that the size may be made smaller. In the present invention, the taper portion is formed in the corner portion of the dielectric, and the outside conductor of the taper portion is approached to the inside conductor, the interval between the inside conductor of the hole interior of the dielectric and the outside conductor which becomes an earth electrode becomes shorter as in the case of the claim 1 so that the floating capacity is easier to obtain. The floating capacity can be adjusted by comparatively simple working or molding operation of the size, inclination and so on of the taper portion of the corner portion. In the comb-line type, the band width of the filter can be made larger by the provision of, for example, the larger floating capacity. The resonator length becomes shorter by provision of, for example, the larger floating capacity so that the size may be made smaller. In the present invention, approximately L type of concave stage portion in section is provided in the corner portion of the dielectric, and the outside conductor of the concave stage portion is approached to the inside conductor so that the interval between the inside conductor of the hole interior of the dielectric and the outside conductor which becomes an earth electrode becomes shorter so as to easily obtain the floating capacity. The floating capacity can be adjusted by comparatively simple working or molding operation of the size, depth and so on of the concave portion of the corner portion. In the comb-line type, the band width of the filter can be widened by provision of, for example, the larger floating capacity. The resonator length becomes shorter by provision of, for example, the larger floating capacity so that the size may be made smaller. The construction of the dielectric resonator in accordance with a further embodiment where the resonance frequency and the coupling degree have been adjusted by the provision of the deletion portion of the conductor and the dielectric in one portion of the short-circuit face is shown in Fig. 12. Fig. 12 is a front face view seen from the short-circuit face side, with reference characters C, D being deletion portions of the conductor and the dielectric of the short-circuit faces. The resonance frequency of the resonator by the internal conductor formed hole 5 is lowered by the partial deletion of the conductor and the dielectric in the region of the SI in Fig. 12. Similarly, if the conductor and the dielectric are partially deleted in the region of the S2, the resonance frequency of the resonator is lowered by the internal conductor formed hole 6. The coupling degree between both the resonators is lowered if the conductor and the dielectric are partially deleted in the region of the S12. Modified embodiment of the coupling coefficients by the deletion of the conductor and the dielectric are shown in Fig. 13 and Fig. 15. A conductor deletion portion of a width d is provided in the middle position of two coupling holes as shown in Fig. 13. Changes in the coupling coefficients are measured when the area S has been changed. In Fig. 13, a = 2.0 mm, b = 4.0 mm, c = 5.0 mm. Fig. 15 shows the change ratio of the coupling coefficients with the axis of abscissas being a conductor deletion area S, the axis of ordinates being Ko in the coupling coefficient in the case of S = 0, the coupling coefficient after the conductor deletion being Ka. The coupling coefficient can be adjusted by the conductor deletion area among the internal conductor formed holes on the short-circuit face. Fig. 14 and Fig. 15 show the adjustment example of the resonance frequency. A conductor deletion portion of a length g with a width f is provided in a location away at a given interval from the internal conductor formed hole as in Fig. 14 so as to measure the resonance frequency when the length g has been changed. In Fig. 14, a = 2.0 mm, e = 3.0 mm, f = 0.5 mm. In Fig. 16, the axis of abscissas is a length g, the axis of ordinates shows the variation amount in the resonance frequency with the resonance frequency in the case of g = 0 being a reference. The resonance frequency can be adjusted by the conductor deletion of the internal conductor formed periphery on the short-circuit face. A embodiment shown in Figs. 12 through Fig. 16 is that one portion of the conductor and the dielectric is deleted on the short-circuit face, and the capacity Cs is decreased, if the conductor and the dielectric on the open face on the internal conductor non-formed portion side are deleted, so that the resonance frequency can be adjusted in a higher direction. Although two stages of dielectric resonator is shown in the examples shown in Fig. 12 through Fig. 16, the same things can be applied even to the dielectric resonator of three stairs or more. The coupling degree between the resonators are adjusted by the partial deletion of the conductor and the dielectric in the area S12, S23, ... S n-1 n among the open portions of the internal conductor formed holes on the short-circuit face as described in Fig. 17 in this case. The resonance frequency of the respective resonators can be adjusted by the partial deletion of the conductor and the dielectric in the regions of S1, S2, S3 ... Sn.

Claims: A dielectric resonator, comprising: a dielectric body (21) having at least one through hole (23); an internal conductor (24) on the inside of the at least one through hole (23); an external conductor (25) on the outside face of the dielectric body (21); and a predetermined portion of a side surface of the dielectric block (21) so shaped that a first portion of the external conductor (25) at the shaped portion of the side surface is closer to the internal conductor (24) in the at least one through hole (23) when compared with a second portion of the external conductor on portions of the outer surface of the dielectric body (21) other than the shaped portion; characterized in that said at least one through hole (23) has two sections of internal conductor and a section free of internal conductor extending between the first and second sections, thus dividing said at least one through hole by a non-conductive portion, the surface of said non-conductive portion being flush with said inner surface of the at least one through hole. The dielectric resonator as claimed in claim 1, comprising a plurality of through holes. The dielectric resonator as claimed in claim 1, wherein the dielectric body (21) is a rectangular block, said outer surface of the dielectric body defined by at least one face being a circuit base plate mounting face for mounting and electrically connecting the dielectric resonator to a circuit base plate, signal input and output electrodes being provided on said at least one face of said outer surface of the dielectric body. The dielectric resonator as claimed in claim 1, wherein said outer surface of the dielectric body (21) defines a face and respective side faces, signal input and output electrodes being on the face of said outer surface and extend from the face to said respective side faces of the dielectric body (21). The dielectric resonator as claimed in claim 2, wherein at least two said holes (23) have a respective pair of internal conductors separated by a corresponding non-conductive portion. The dielectric resonator as claimed in claim 5, wherein said pair of non-conductive portions are spaced unequally from the ends of the holes. The dielectric resonator as claimed in claim 6, wherein said pair of non-conductive portions have unequal axial lengths. The dielectric resonator as claimed in claim 5, wherein said two non-conductive portions have unequal axial lengths. The dielectric resonator as claimed in claim 1, further comprising a short-circuit face, a portion of the external conductor being removed in one portion of the short-circuit face for adjusting at least one of the resonance frequency and the coupling degree of the resonator. The dielectric resonator as claimed in claim 1, further comprising a short-circuit face, a portion of the dielectric body being removed in one portion of the short-circuit face for adjusting at least one of the resonance frequency and the coupling degree of the resonator. The dielectric resonator as claimed in claim 1, wherein the dielectric body (21) includes an end face, a pair of recesses (28) in the dielectric body at the end face thereby defining a pair of side portions of the end face, the recesses being generally parallel with the side portions and being located on respective sides of the plurality of holes (23). The dielectric resonator as claimed in claim 1, wherein the dielectric body (21) includes a side face, a recess (28) in the dielectric body at the side face. The dielectric resonator as claimed in claim 1, wherein the dielectric body (21) includes a side face, a recess (28) in the dielectric body at the side face, the external conductor extending into the recess in the dielectric body and over a bottom surface of the recess. The dielectric resonator as claimed in claim 1, further comprising a plurality of generally circular recesses (28) at locations proximate to the plurality of holes (23), the generally circular recesses extending into the dielectric body in the same direction as the plurality of holes. The dielectric resonator as claimed in claim 1, wherein the dielectric body (21) includes a side face, a generally circular recess (28) in the dielectric body at the side face, the external conductor extending into the generally circular recess in the dielectric body and over a bottom surface of the recess, a portion of the external conductor on the bottom surface of the generally circular recess being generally parallel to the internal conductor in a corresponding one of the plurality of holes. The dielectric resonator as claimed in claim 1, wherein the dielectric block (21) comprises a shaped portion (29), said shaped portion (29) of the dielectric block (21) comprising tapered portions provided on at least one corner of the dielectric block so that portions of the external conductor on the tapered portions are closer to the internal conductors in the plurality of holes. The dielectric resonator as claimed in claim 1, wherein the dielectric block (21) comprises a shaped portion (31), said shaped portion of the dielectric block comprising stepped portions of generally L-shape provided on at least one corner of the dielectric block so that portions of the external conductor on the stepped portions are closer to the internal conductors in plurality of holes.

Inventors: KATO HIDEYUKI, KITAICHI YUKIHIRO, MATSUMOTO HARUO, MORI HISASHI, TADA HITOSHI, TSUJIGUCHI TATSUYA, YAMADA YASUO, YORITA TADAHIRO, KATO, HIDEYUKI, KITAICHI, YUKIHIRO, MATSUMOTO, HARUO, MORI, HISASHI, TADA, HITOSHI, TSUJIGUCHI, TATSUYA, YAMADA, YASUO, YORITA, TADAHIRO
Applicants: MURATA MANUFACTURING CO, MURATA MANUFACTURING CO., LTD.
Application year: 1993
Main classification: H01P1
IPC codes: H01P1