Multimode dielectric resonator apparatus, filter, duplexer, and communication apparatus

Abstract: A multimode dielectric resonator apparatus is configured such that in a dielectric resonator apparatus, a TM mode and a TE mode are transformed into multiplex modes, coupling between individual resonant modes can be easily made, and a large number of sequentially coupled stages for a single dielectric core (10) can be obtained. In the multimode dielectric resonator apparatus, a dielectric core (10) is configured of a plate-like TM-mode dielectric core portion (11) and a TE-mode dielectric core portion (12) protruding therefrom in the vertical direction, for example, in a spherical shape, wherein five modes individually called a TMx mode, a TMy mode, TMy mode, a TEx mode, a TEy mode, and a TMz mode are used as multiplex modes. In addition, a filter and a duplexer use the multimode dielectric resonator apparatus, and a communication apparatus uses one of the filter and the duplexer.

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multimode dielectric resonator apparatus that operates in multiple resonant modes, to a filter and a duplexer therewith, and to a communication apparatus therewith. 2. Description of the Related Art Conventionally, a dielectric resonator having a dielectric core arranged in a cavity uses a mode such as a TE01σ mode or a TM01σ mode. In a configuration of a multistage dielectric resonator apparatus formed using the aforementioned dielectric resonators, a plurality of the dielectric cores is therefore provided in a cavity. In the aforementioned configuration using the single resonant mode generated in the single dielectric core, however, the overall size thereof is increased proportionally to the increase in the number of resonators. In addition, the plurality of dielectric cores must be positioned and fixed with high accuracy. This causes difficulties in the manufacture of dielectric resonator apparatuses, such as dielectric filters, having consistent characteristics. In view of the above, as is disclosed in Japanese Unexamined Patent Application Publication No. 11-145704, the present applicant submitted a patent application regarding a dielectric resonator apparatus in which, while only a single dielectric core is used, the multiplex number is increased. In the proposed dielectric resonator apparatus, at most six modes are generated and can be used. Specifically, with respect to resonant spaces represented by x, y, and z rectangular coordinates, the apparatus generates TMx, TMy, and TMz modes in which electric-field vectors extend toward the individual x, y, and z axes; and in addition, it generates TEx, TEy, and TEz modes in which electric-field vectors form loops in the plane directions perpendicular to the individual x, y, and z axes. However, in connection with, for example, positions for forming coupling grooves, the manufacture of the aforementioned dielectric resonator apparatus involves significant technical difficulties in coupling of the individual six modes to each other so that all the six modes can be used. Furthermore, International published document WO 99/12225 discloses a multimodal dielectric resonance device comprising dielectric cores resonating in a plurality of modes. SUMMARY OF THE INVENTION In view of the above, an object of the present invention is to provide a multimode dielectric resonator apparatus that uses the multiplex construction according to the above-described patent application, that allows individual resonant modes to be easily obtained, and that allows a large number of resonant-mode sequentially coupled stages for a single dielectric core to be obtained. Another object of the invention is to provide a filter using the aforementioned multimode dielectric resonator apparatus. Still another object of the invention is to provide a duplexer that uses the aforementioned multimode dielectric resonator apparatus. Still another object of the invention is to provide a communication apparatus using the above. According to one aspect of the present invention, a multimode dielectric resonator apparatus is formed in a dielectric resonator apparatus that comprises a dielectric core in a conductive cavity. The dielectric core comprises a TM-mode dielectric core portion primarily for determining resonant frequencies of TM modes so that at least one of the TM modes resonates in an operating frequency band, and other TM modes resonate at frequencies higher than the operating frequency band; and a TE-mode dielectric core portion primarily for determining resonant frequencies of TE modes so that the individual TE modes of a multi-TE mode resonate in the operating frequency band. According to the above-described construction, without being influenced by the TM mode to which the frequency higher than the operating frequency band is set, remaining TM modes and TE modes can be used. Furthermore, a problem can be solved which occurs when one of three TM modes used is unnecessarily coupled to another resonant mode. In addition, predetermined resonant modes can be coupled together in a predetermined condition. In addition, in the multimode dielectric resonator apparatus of the present invention, the TM-mode dielectric core portion is formed in a plate-like shape, the TE-mode dielectric core portion protrudes from a part of the TM-mode dielectric core portion, and the TM-mode dielectric core portion and the TE-mode dielectric core portion are integrated with each other. According to this construction, the resonant frequency of a TM mode in which electric-field vectors extend in the thickness direction of the plate-like TM-mode dielectric core portion is arranged to be higher than the resonant frequency of a TM mode in which electric-field vectors extend in the plane direction thereof, and the resonant frequency of the former TM mode is set to a frequency that is higher than the operating frequency band. In the above, without being influenced by the shape of the TM-mode dielectric core portion, the TE-mode dielectric core portion having the shape protruding from a part of the TM-mode dielectric core portion can be operated as a multi-TE-mode resonator. In addition, since the TM-mode dielectric core portion and the TE-mode dielectric core portion are integrated with each other, the dielectric core can be easily manufactured, and furthermore, the dielectric core can be easily arranged in the cavity. According to another aspect of the invention, a filter comprises the aforementioned multimode dielectric resonator apparatus and input/output means coupled to predetermined resonant modes arranged therein. According to this construction, the filter can be formed as a small and low-loss-type filter using multiple stages of the resonators. The filter thus formed reduces inter-resonator coupling losses, increases the Q values of the individual resonators, and uses the single dielectric core and the single cavity. More specifically, since inter-resonator coupling losses are reduced according to the multiplex resonant modes, and the dielectric core is provided in a central portion of the cavity, electromagnetic fields are concentrated at the dielectric core, conductor losses are reduced, and the Q values of the individual resonators are thereby increased. Therefore, while using the single dielectric core and the single cavity, the configuration can be used as a small and low-loss-type filter using multiple stages of the resonators. In the filter of the present invention, the aforementioned input/output means is coupled to TM modes, and means for coupling TM modes and TE modes to each other and for coupling TE modes to each other is provided. According to this construction, the input/output means is securely coupled to electromagnetic fields of TM modes in which, compared to the TE mode, a larger amount of the electromagnetic field is caused to leak to the outside of the dielectric core, and the band range can be easily increased. In addition, according to sequential coupling of TE modes, the structure of the coupling means is simplified, and the design thereof is therefore easy. According to still another aspect of the present invention, a filter comprises the aforementioned multimode dielectric resonator apparatus, either coaxial resonators or semicoaxial resonators that are coupled to predetermined modes, and input/output means coupled to the resonators. Generally, although secure coupling can be obtained when the coupling is made according to magnetic-field coupling, it is difficult to provide a coupling loop that couples only to one mode of a multimode dielectric resonator. According to the above-described construction, however, either the semicoaxial resonators or the coaxial resonators are externally coupled, and secure coupling can thereby be obtained according to coupling loops to increase the band range. In addition, a spurious mode caused by the aforementioned multimode dielectric resonator is minimized according to either the semicoaxial resonators or the coaxial resonators, and the overall spurious-mode characteristics of the filter can thereby be improved. Furthermore, since the input/output means in the multimode dielectric resonator portion is miniaturized, direct passage of signals between the input and the output is reduced. This prevents deterioration in characteristics from occurring due to the direct passage of signals. More specifically, since either the semicoaxial resonators or the coaxial resonators need not be securely coupled, the input/output means in the multimode dielectric resonator portion can be small, direct passage of signals between the input and the output is thereby reduced, and deterioration in characteristics due to the direct passage is therefore not occur. According to still another aspect of the present invention, a duplexer comprises two sets of the above-described filter. This allows the duplexer to be small overall and to be of a low-loss type. The duplexer can be used as an antenna-sharing unit. According to still another aspect of the present invention, a communication apparatus comprises at least one of the aforementioned filter and the aforementioned duplexer. The filter or the duplexer is either provided to permit transmission signals and reception signals to pass through the band in a high-frequency circuit or provided as an antenna-sharing unit. According to this, the communication apparatus can be arranged to be small overall and to be of a low-loss type. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view showing a basic configuration of a multimode dielectric resonator apparatus according to an embodiment; FIGS. 2A and 2B are an upper view and a cross-sectional view, respectively, of the multimode dielectric resonator shown in FIG. 1; FIGS. 3A to 3E show electric-field distributions in individual modes; FIG. 4 is a graph showing the relationship between the thickness dimension of a plate-like portion of a dielectric core and the resonant frequency of each of the modes; FIG. 5 is a perspective view showing a configuration of the dielectric resonator; FIG. 6 is a graph showing the relationship between the size of a spherical portion protruding from the plate-like portion of the dielectric core and the resonant frequency of each of the modes; FIGS. 7A and 7B show the relationship between a TM-mode dielectric core portion and a TE-mode dielectric core portion; FIGS. 8A and 8B show another example shape of the TE-mode dielectric core portion; FIGS. 9A and 9B show still another example shape of the TE-mode dielectric core portion; FIGS. 10A and 10B show still another example shape of the TE-mode dielectric core portion; FIGS. 11A and 11B show still another example shape of the TE-mode dielectric core portion; FIGS. 12A and 12B show still another example shape of the TE-mode dielectric core portion; FIGS. 13A and 13B show still another example shape of the TE-mode dielectric core portion; FIGS. 14A to 14C individually show example shapes of the TM-mode dielectric core portion; FIGS. 15A and 15B show an example support structure for a dielectric core in a cavity; FIGS. 16A and 16B show another example support structure for a dielectric core in a cavity; FIGS. 17A and 17B show still another example support structure for a dielectric core in a cavity; FIGS. 18A and 18B show still another example support structure for a dielectric core in a cavity; FIGS. 19A and 19B show an example filter using a quintuple mode resonator configured of the individual modes sequentially coupled to each other; FIGS. 20A and 20B individually show states of coupling between TM modes and TE modes; FIGS. 21A to 21D individually show states of coupling between TE modes; FIGS. 22A and 22B show an example filter using another quintuple mode resonator; FIGS. 23A and 23B show an example configuration of a filter using semicoaxial resonators and the quintuple mode resonator; FIGS. 24A and 24B show an example configuration of a duplexer; and FIG. 25 is a schematic view showing a configuration of a communication apparatus. DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIGS. 1 to 7B, a description will be given of a configuration of a multimode dielectric resonator apparatus according to an embodiment of the present invention. FIG. 1 is a perspective view of a basic configuration portion of the multimode dielectric resonator apparatus. Reference numeral 10 denotes a dielectric core, and reference numeral 2 denotes a cavity for housing the dielectric core 10. The dielectric core 10 is constituted of a plate-like TM-mode dielectric core portion 11 and a TE-mode dielectric core portion 12 protruding therefrom as part of a sphere. The cavity 2 is formed such that conductive films are formed on peripheral surfaces of a ceramic four-sided housing-like member. On upper and lower opening faces of the cavity 2, either dielectric plates or metal plates on which conductive films are formed, and a substantially parallelepiped shield space is thereby formed. In FIG. 1, support members for supporting the dielectric core 10 in the cavity 2 and input/output means that perform input and/or output of signals with the outside have been omitted to clearly show the arrangement of the structure of the dielectric core in the cavity. FIG. 2A is an upper view of the multimode dielectric resonator apparatus shown in FIG. 1, and FIG. 2B is a cross-sectional view of portion B-B in FIG. 2A. In these figures, reference numeral 3 denotes individual support members for connecting the TM-mode dielectric core portion 11 of the dielectric core to inner wall faces of the cavity 2. The individual support members 3 are made of a material having permittivity lower than that of the dielectric core 10. Reference numeral 15 denotes an individual groove 15 for setting mainly a TEz-mode resonant frequency to levels in the rising direction, as described below. FIGS. 3A to 3E show five example resonant-mode electric field distributions caused in the multimode dielectric resonator apparatus. FIG. 3A shows a TMx mode, and FIG. 3B shows a TMy mode. Thus, in the TMx mode, electric-field vectors extend from one of the conductive films formed on the peripheral surfaces of the cavity 2 to the opposing one of the conductive films along the x-axis. Similarly, in the TMy mode, electric-field vectors extend along the y-axis. FIG. 3C shows a TEz mode, FIG. 3D shows a TEy mode, and FIG. 3E shows a TEx mode. In the TEz mode, electric-field vectors form loops in the plane direction perpendicular to the y-axis, and electric-field vectors form loops in the plane direction perpendicular to the x-axis. A TMz mode in which electric-field vectors extend along the z-axis is also generated. However, since a dimension in the thickness direction of the plate-like TM-mode dielectric core portion 11 is less than dimensions in other directions, the resonant frequency of the TMz mode is higher than resonant frequencies of the other modes, i.e., an operating frequency band. FIG. 4 shows variations in resonant frequencies of the above-described six resonant modes in a case where a square and plate-like dielectric core is used (a state where the TE-mode dielectric core portion 12 is removed from the state shown in FIG. 1), and concurrently, the z-direction dimension thereof is varied. FIG. 5 shows an example of the apparatus in the above case. In this case, the vertical width, the horizontal width, and the height of the cavity 2 are each 40 mm. As shown in FIG. 4, by reducing the z-direction (thickness-direction) dimension of the dielectric core, the resonant frequency of the TMz mode can be separated in a direction higher in the cases of the resonant frequencies of the TMx mode and the TMy mode. In FIG. 4, the marks indicating resonant frequencies of the TMx mode overlap with the marks indicating resonant frequencies of the TMy mode. Also, the marks indicating resonant frequencies of the TEx mode overlap with the marks indicating resonant frequencies of the TEy mode. For example, by reducing the individual widths of the dielectric core in the x-axis direction and the y-axis direction to 30 mm, and by arranging the width (thickness) in the z-axis direction to be 50% thereof or less (that is, 15 mm or less), the resonant frequency of the TMz mode can be separated by 10% or more than the resonant frequencies of the TMx mode and the TMy mode. To obtain ordinary filter characteristics to meet commercial requirements, the resonant frequencies of resonant modes other than the operating frequency band must be 10% or more separated from the operating frequency band. Therefore, the thickness dimension of the TM-mode dielectric core portion must be 50% of or more than the dimensions in the other two directions. In the state as described above, however, the resonant frequency of either the TEx mode or the TEy mode also becomes higher. To solve this problem, the TE-mode dielectric core portion 12 protruding from the TM-mode dielectric core portion 11 is provided. Thereby, resonant frequencies of the TEx mode and the TEy mode are determined so as to be within the operating frequency band. FIG. 6 is a graph showing the variations in the resonant frequencies of the above-described six resonant modes in a case where the radius of the spherical portion, that is, the shape of the TE-mode dielectric core portion 12, is varied. As can be seen from the graph, according to the increase in the radius of the spherical portion of the TE-mode dielectric core portion 12, the resonant frequencies of the TEx mode and the TEy mode decrease, whereas the resonant frequencies of the TEx mode and the TEy mode almost do not vary. (In FIG. 6, the marks indicating resonant frequencies of the TMx mode overlap with the marks indicating resonant frequencies of the TMy mode. Also, the marks indicating the resonant frequencies of the TEx mode overlap with the marks indicating the resonant frequencies of the TEy mode.). In this particular example case, when the radius is about 11 mm, the TMx mode, the TMy mode, the TEx mode, and the TEy mode resonate at substantially the same frequency. Although the resonant frequency of the TMz mode is reduced by increasing the radius of the spherical portion, since it is preshifted to a high frequency, it does not influence the other modes. In the TEz mode, since the electric-field vectors in the TEz mode extend also to the plate-like TM-mode dielectric core portion, the resonant frequency thereof becomes lower than the frequencies of the TEx mode and the TEy mode. However, as shown in FIGS. 1 to 2B, since the frequency-determining grooves 15 are provided, the effective permittivity for the TEz mode is reduced, and the resonant frequency of the TEz mode is determined to be higher than in the case shown in FIG. 6. In addition, the diameter in the z-axis direction of the spherical TE-mode dielectric core portion 12 radius determines the resonant frequency of the TEy mode, and the diameters in the x-axis direction and the y-axis direction determine the resonant frequency of the TEz mode. Therefore, by increasing the diameter in the z-axis direction of the TE-mode dielectric core portion 12 to be larger than the x-axis direction and the y-axis direction, the frequencies of the TEx mode and the TEy mode can be reduced. This keeps the resonant frequency of the TEz mode constant, as shown in FIGS. 1 to 2B. As described above, depending on the size of the frequency-determining grooves 15 and the shape of the TE-mode dielectric core portion 12, the resonant frequency of the TEz mode can also be controlled to be relatively close to the resonant frequencies of the TEx mode and the TEy mode. Therefore, the overall configuration can be used as a quintuple-mode dielectric resonator apparatus. Thus, electromagnetic fields in the described individual modes of the TM mode and the TE mode coexist in the central portion of the dielectric core 10, the central portion is the TM-mode dielectric core portion 11, and concurrently, the TE-mode dielectric core portion TE-mode dielectric core portion 12. To separate these two portions completely, as shown in FIG. 7A, they can be separated into a plate-like TM-mode dielectric core portion 11 and two hemispherical TE-mode dielectric core portions 12a and 12b; alternatively, as shown in FIG. 7B, they can be separated into a plate-like TM-mode dielectric core portion 11 having an opening in the central portion and a spherical TE-mode dielectric core portion 12 to be inserted therein. Even in the case shown in FIG. 7A, TM-mode electric-field vectors still extend to the TM-mode dielectric core portion 11. Also, even in the case shown in FIG. 7B, TE-mode electric-field vectors still extend to the TE-mode dielectric core portion 12. It is to be noted that parts of the individual TM-mode dielectric core portion 11 and the TE-mode dielectric core portion 12 according to the present invention are shared in the TM modes and the TE modes in the central portion of the dielectric core. Hereinbelow, referring to FIGS. 8A to 13B, a description will be given of configurations of multimode dielectric resonator apparatuses using other dielectric cores having different shapes. In each of FIGS. 8A to 13B, similarly to the type shown in FIGS. 2A and 2B, figures having the reference symbol "A" attached thereto are upper views, and figures having the reference symbol "B" attached thereto are cross-sectional views thereof. In an example shown in FIGS. 8A and 8B, a TE-mode dielectric core portion 12 is provided to have the shape as a stepped pyramid. That is, a four-sided pyramid-like base is formed in the upper and lower direction with steps from the TM-mode dielectric core portion 11. In an example shown in FIGS. 9A and 9B, a TM-mode dielectric core portion 12 having the shape of a four-sided pyramid formed to protrude on the upper and lower sides of the TM-mode dielectric core portion 11. In an example shown in FIGS. 10A and 10B, a TM-mode dielectric core portion 12 having the shape of a four-sided column formed to protrude on the upper and lower sides of the TM-mode dielectric core portion 11. In an example shown in FIGS. 11A and 11B, a TM-mode dielectric core portion 12 having the shape of a circular column formed to protrude on the upper and lower sides of the TM-mode dielectric core portion 11. In an example shown in FIGS. 12A and 12B, a TE-mode dielectric core portion 12 having the shape of a hexagonal column is formed to protrude on the upper and lower sides of the TM-mode dielectric core portion 11. In an example shown in FIGS. 13A and 13B, a TM-mode dielectric core portion 12 having the shape of an octagonal column is formed to protrude on the upper and lower sides of the TM-mode dielectric core portion 11. In addition to the above, a polyhedral protruded portion having the shape of a polyhedral column, a polyhedral pyramid, and a polyhedral trapezoid may be used as a TE-mode dielectric core portion. With any one of these shapes, the plate-like TM-mode dielectric core portion 11 and the cavity 2 mainly function as a resonator in the TMx mode and the TMy mode. Also, the TE-mode dielectric core portion 12 mainly functions as a resonator in the TEx mode, TEy mode, and TEz modes. FIGS. 14A to 14C show examples of TM-mode dielectric core portions having other shapes. Any one of these views is a plan view of a plate-like TM-mode dielectric core portion 11. In the example in FIG. 14A, four corners of a plate-like portion are concave. In the example shown in FIG. 14B, four corners are rounded. In the example shown in FIG. 14C, the central portion of an each side is concave and tapered. As shown in FIGS. 14A to 14C, in the case where the areas where end faces of the TM-mode dielectric core oppose inner wall faces of a cavity 2 are reduced, the electrostatic capacitances therebetween are reduced. Therefore, the frequencies of the TMx mode and the TMy mode can be increased. Also, as shown in FIG. 14C, by forming the central portion of the each side of a square-plate-like portion such that a dielectric portion is removed from the end face in the internal direction, the resonant frequency of the TEz mode can be increased. In this way, depending on the shape of the plate-like TM-mode dielectric core, the frequencies of the two TM modes and the TEz mode can be individually determined. Hereinbelow, referring to FIGS. 15A to 18B, a description will be given of other example supporting structures for individual dielectric cores in individual cavities 2. In each of FIGS. 15A to 18B, similarly to the type shown in FIGS. 2A and 2B, figures having the reference symbol "A" attached thereto are upper views, and figures having the reference symbol "B" attached thereto are cross-sectional views thereof. In the example shown in FIGS. 15A and 15B, the central portion of an individual end face of a TM-mode dielectric core portion 11 of the dielectric core is supported by a support member 3. In the example shown in FIGS. 16A and 16B, four corners of a TM-mode dielectric core portion 11 of the dielectric core are individually supported by support members 3. In the example shown in FIGS. 17A and 17B, support members 3' are individually fitted with upper and lower faces of four corners of a TM-mode dielectric core portion 11, and the portions of the support members 3' are supported by support members 3 in the cavity 2. In the example shown in FIGS. 18A and 18B, a support member 3 is provided between upper and lower faces in the vicinity of each of four corners of a TM-mode dielectric core portion 11 and an opening of the cavity 2. By using materials having the permittivities lower than that of the dielectric core for these support members 3 and 3', influences therefrom the individual resonant modes are reduced. Hereinbelow, referring to FIGS. 19A and 19B, a description will be given of an example filter in which the above-described five resonant modes are sequentially coupled to each other. In FIGS. 19A and 19B, reference symbols 5a and 5b each denotes a coaxial connector, and probes 4a and 4b each jutting out in a cavity 2 are fitted with central conductors thereof. Reference symbol 13a denotes a coupling groove for coupling a TMx mode and a TEy mode, and reference symbol 13b denotes a coupling groove for coupling the TMy mode and the TEx mode together. Reference symbols 14a and 14a' denote coupling grooves for coupling the TEy mode and a TEz mode together, and in addition, reference symbols 14b and 14b' denote coupling grooves for coupling the TEx mode and the TEz mode together. FIGS. 20A and 20B illustrate the operation of the coupling groove 13a. In these figures, curved lines with arrows represent electric-field vectors in the TMx mode and the TEy mode. When the modes shown in FIG. 20A are assumed to be an even mode, and the modes shown in FIG. 20B are assumed to be an odd mode, the coupling groove 13a provides perturbations to field-intensity distributions in two modes, energy is transferred between the TMx mode, and the two modes are coupled together. Similarly, as shown in FIGS. 19A and 19B, by providing the coupling groove 13b extending in the x-axis direction, the TMy mode and the TEx mode are coupled together. FIGS. 21A to 21D individually illustrate operations of the above-described coupling grooves 14 and 14'. FIG. 21A is a perspective view illustrating electric-field vectors in the TEx mode and the TEz mode. FIG. 21B shows electric-field vectors in the two modes in an x-y-plane cross section. In this case, when a combined mode of the TEx mode and the TEz mode (that is, the TEx + z mode) is considered, the mode forms a loop on a plane perpendicular to the x + z axis direction, as shown in FIG. 21C. Also, as shown in FIG. 21D, a vector in a differential mode between the TEx mode and the TEz mode (that is, the TEx - z mode) forms a loop on a plane perpendicular to the x - z axis direction. The coupling grooves 14b and 14b' exist in a position where the electric-field vector in the TEx - z mode passes through. Therefore, they function to reduce the intensity of the electric field in the TEx - z mode, and the TEx mode and the TEz mode are coupled together according to the perturbations thereby generated. Similarly, in FIGS. 19A and 19B, the coupling grooves 14 and 14' provide perturbations to a TEy + z mode and a TEy - z mode, thereby allowing the TEy mode and the TEz mode to couple together. Thus, TMx-mode→TEy-mode coupling is caused according to the coupling groove 13a, TEy-mode→TEz-mode coupling is caused according to the coupling groove 14b, and in addition, TEx-mode→TMy-mode coupling is caused according to the coupling groove 13b. Therefore, the configuration functions as a quintuple-mode resonator in which five resonators are serially coupled to each other. In FIGS. 19A and 19B, the probe 4a couples by electric fields to the TMx mode, which is a first-stage resonator; and the probe 4b couples by electric fields to a TMy mode, which is a last-stage resonator. In this manner, the portion between the coaxial connectors 5a and 5b forms a filter presenting characteristics of a band-pass filter using five stages of resonators. Hereinbelow, referring to FIGS. 22A to 22B, a description will be given of an example in which individual coupled modes between the above-described five resonant modes and predetermined modes are rotated by 45 degrees in the xy plane. As shown in FIGS. 22A and 22B, various modes are generated. A TM-mode dielectric core portion 11 generates a TMx + y mode in which electric-field vectors extend toward the x + y axis and a TMx - y mode in which electric-field vectors extend toward the x - y axis. On the other hand, a TE-mode dielectric core portion 12 generates a TEx + y mode in which an electric-field vector forms a loop on a plane perpendicular to the x + y axis direction, a TEx - y mode in which an electric-field vector forms a loop on a plane perpendicular to the x - y axis direction, and in addition, a TEz mode in which an electric-field vector forms a loop on a plane perpendicular to the z-axis direction. Therefore, the apparatus as described above is similar to an apparatus having a construction equivalent to the construction shown in FIGS. 19A and 19B that is rotated by 45 degrees in the xy plane. In this construction, a coupling groove 13b causes the TMx + y mode and the TEx - y mode to couple together, and a coupling groove 13a causes the TMx - y mode and the TEx + y mode to couple together. Also, a coupling groove 14a causes the TEx + y mode and the TEx - y mode to couple together, and 14b causes the TEx - y mode and the TEz mode to couple together. Also, a probe 4a couples to the TMx + y mode in the electric field, and a probe 4b couples to the TMx - y mode in the electric field. As described above, in a manner similar to that shown in FIGS. 19A and 19B, the portion between coaxial connectors 5a and 5b forms a filter having characteristics of a band-pass filter using five stages of resonators sequentially coupled to each other. Hereinbelow, referring to FIGS. 23A and 23B, a description will be given of an example configuration of a filter formed by combining other resonators in the multimode dielectric resonator apparatus shown in FIGS. 22A and 22B. FIG. 23A is an upper view of a state where an upper cover is removed, and FIG. 23B is a cross-sectional view of the portion B-B in FIG. 23A. In FIGS. 23A and 23B, reference numeral 20 denotes the quintuple mode resonator 9 shown in FIG. 22A and 22B; and reference numerals 21 and 22 each denotes one of semicoaxial resonator 21 and 22. The individual semicoaxial resonators 21 and 22 have a central conductor 8 in a cavity 2, and the resonant frequency is determined according to electrostatic capacitance generated between a lower end portion of a frequency-modulating screw 9 and an upper end portion of the central conductor 8, the length of the central conductor 8, and other components. A coupling loop 7a is provided between a central conductor of a coaxial connector 5a and an inner face of the cavity 2, and external coupling is made through the coupling loop 7a. Similarly, a coupling loop 7d is provided between a central conductor of a coaxial connector 5b and an inner face of the cavity 2, and external coupling is made through the coupling loop 7d. Coupling loops 7b and 7c are connected to the probes 4a and 4b, respectively; and the coupling loops 7b and 7c are connected in magnetic field to the semicoaxial resonators 21 and 22, respectively. The above-described configuration, which has the first and last stages of resonators and five dielectric resonators therebetween, operates as a filter that has a total of seven stages of resonators and that has band-pass characteristics. As described above, since the first and last stages of resonators are arranged to be the semicoaxial resonators, and strong coupling is obtained by the coupling loops, broad-band characteristics can be easily obtained. In addition, since the spurious mode due to the quintuple mode resonator 20 are minimized by the semicoaxial resonators 21 and 22, the entire spurious characteristics are improved. Furthermore, since direct coupling to the outside is not necessary, the probes 4a and 4b in the quintuple mode resonator 20 can be small, direct passage of signals between the input and the output is reduced, and deterioration in characteristics because of the direct passage is therefore not caused. In the example shown in FIGS. 23A and 23B, although the semicoaxial resonators are used, semicoaxial resonators can be similarly used for the first stage and the last stage. Even in this case, similar effects can be obtained. Hereinbelow, referring to FIGS. 24A and 24B, a description will be given of an example configuration of a duplexer. In FIGS. 24A and 24B, reference symbols 21TX and 21RX individually denote quintuple mode resonators that are similar to those shown in FIGS. 22A and 22B; and reference symbols 21TX, 22TX, 21RX, and 22RX individually denote semicoaxial resonators that are similar to those shown in FIGS. 23A and 23B. By the two semicoaxial resonators 21TX and 22TX and the quintuple mode resonator 20TX, a transmission filter portion is configured. Similarly, by the two semicoaxial resonators 21RX and 22RX and the quintuple mode resonator 20RX, a reception filter portion is configured. Coupling loops 7e connected to a central conductor of a coaxial connector 5a are individually coupled in magnetic field to the semicoaxial resonators 22TX and 21RX, and transmission signals and reception signals are thereby separated. Thus, the duplexer as an antenna-sharing apparatus is configured. FIG. 25 is a schematic view of a configuration of a communication apparatus in which the above-described duplexer is used. As shown in the figure, a transmission circuit and a reception circuit are connected to an input port of the transmission filter and an output port of the reception filter, respectively. Also, an antenna is connected to the input and output ports of the duplexer. This allows a high frequency section of the communication apparatus to be configured. In addition to the described example, the above-described quintuple mode resonator may be provided as an independent bandpass filter. In the individual embodiments, description has been made with reference to the examples in which the TMx mode and the TMy mode are generated in the square plate-like portion of the dielectric core, and both are used. However, the arrangement may be such that, by using a rectangular plate-like state, for example, only the TMx mode is resonated in an operating frequency band, the resonant frequencies of the TMy mode and the TMz mode are increased to be higher than the operating frequency band, and only the single TM mode is used. Also, although the three modes of the TE mode are used in the embodiments, the arrangement may be such that only two TE modes thereof are used.

Claims: A multimode dielectric resonator apparatus formed in a dielectric resonator apparatus comprising a dielectric core (10) in a conductive cavity (2), characterised by the dielectric core (10) comprising: a TM-mode dielectric core portion (11) determining resonant frequencies of TM modes so that at least one of the TM modes resonates in an operating frequency band, and other TM modes resonate at frequencies higher than the operating frequency band, wherein the TM-mode dielectric core portion (11) is formed in a plate-like shape; and a TE-mode dielectric core portion (12) determining resonant frequencies of TE modes so that the individual TE modes of a multi-TE mode resonate in the operating frequency band wherein the TE-mode dielectric core portion (12) is formed in a shape protruding from a part of the TM-mode dielectric core portion (11); and wherein the TM-mode dielectric core portion (11) and the TE-mode dielectric core portion (12) are integrated with each other; and wherein support members (3, 3') supporting the dielectric core (10) in the cavity (2) connect said TM-mode dielectric core portion (11) to inner wall faces of the cavity. A filter comprising: the multimode dielectric resonator apparatus as stated in claim 1, and input/output means coupled to predetermined resonant modes in the multimode dielectric resonator apparatus. A filter as stated in Claim 2., wherein the input/output means is coupled to TM modes among a plurality of the resonant modes, further comprising: means (13a, 13b) for coupling TM modes and TE modes to each other, and means for coupling (14a, 14b, 14a', 14b') TE modes to each other. A filter comprising: the multimode dielectric resonator apparatus as stated in claim 1, either coaxial resonators or semicoaxial resonators (21, 22) that are coupled to predetermined modes, and input/output means coupled to the resonators. A duplexer comprising: two sets of the filter as stated in one of claims 2, 3, and 4. A communication apparatus comprising one of the filter as stated in one of claims 2, 3, and 4 and the duplexer as stated in claim 5.

Inventors: ABE SHIN, HATTORI JUN, ISE TOMOYUKI, WAKAMATSU HIROKI, ABE, SHIN, HATTORI, JUN, ISE, TOMOYUKI, Abe, Shin, Murata Manufacturing Co., Ltd., Hattori, Jun, Murata Manufacturing Co., Ltd., Ise, Tomoyuki, Murata Manufacturing Co., Ltd., Wakamatsu Hiroki, Murata Manufacturing Co., Ltd.
Applicants: MURATA MANUFACTURING CO, MURATA MANUFACTURING CO., LTD.
Application year: 2000
Main classification: H01P7
IPC codes: H01P7, H01P1