Patent Publication Number: US-6211755-B1

Title: Dielectric resonator, dielectric filter, dielectric duplexer, communication device, and method of producing dielectric resonator

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a dielectric resonator, a dielectric filter, a dielectric duplexer, and a communication device each for use in a communication base station, and a method of producing a dielectric resonator. 
     2. Description of the Related Art 
     Such dielectric resonator and dielectric filter will be described with reference to FIGS. 12 through 14. FIG. 12 is a perspective view of the dielectric resonator. FIG. 13 is a partly cross sectional view of one end of the dielectric resonator. FIG. 14 is an exploded perspective view of the dielectric filter. In this case, the filter will be described by use of a two stage band-elimination dielectric filter in which two dielectrics are connected with a quarter-wave line. This filter was not a publicly known conventional technique when Japanese Patent Application No. 10-118933, which is a basis of claim of priority for the application of the present invention, was filed. 
     As shown in FIGS. 12 and 13, a dielectric resonator  110  is composed of a columnar dielectric  111 , and thin film multi-layers  112  formed on the opposite sides of the dielectric  111 . In the case that the thin film multi-layer electrodes  112  are employed as the electrodes of the dielectric resonator  110 , the nonloaded Q of the dielectric resonator  110  is enhanced. As compared with monolayer silver electrodes used as the electrodes, the dielectric resonator with high characteristics can be provided. 
     In addition, as shown in FIG. 14, a dielectric filter  120  is made up of a shield cavity  121  made of iron or the like, two dielectric resonators  110  arranged in the shield cavity  121 , and a ground plate  122 , electrical probes  123  as external coupling means, and external connectors  124  attached to the shield cavity  121 . 
     As described above, each dielectric resonator  110  is formed of the columnar dielectric  111  having the thin film multi-layer electrodes  112  formed on the opposite sides thereof. One electrode surface of the dielectric resonator  110  is soldered to the ground plate  122  having a step  122   a  and a hole  122   b  for soldering. The ground plate  122  is sandwiched between the body  121   a  of the shield cavity  121  and a lid  121   b . Thus, the dielectric resonator  110  is arranged in the shield cavity  121 . In addition, the electrical probes  123  are connected at one end to the center conductors of the external connectors  124 , respectively, and are elongated in the spaces between the dielectric resonators  110  and the shield cavity  121 . Moreover, the center conductors of the two external connectors  124  are connected through a quarter-wave line  125 . 
     In the dielectric filter  120  having the above-described configuration, an input signal, when it is input through the external connectors  124 , is transmitted to the electrical probes  123 , so that the electrical probes  123  and the dielectric resonators  110  are capacitively coupled. Then, the dielectric resonators  110  resonate at a resonant frequency determined by the shapes and sizes of the dielectric resonators  110 . Thus, the dielectric filter  120  in which the dielectric resonators are connected through the quarter-wave line  125  for connection is provided functions as a band-elimination dielectric filter for eliminating the desired frequency. 
     In general, a great number of dielectric resonators having a predetermined diameter and thickness are produced at one time. Accordingly, in order to allow the dielectric resonators to be used in dielectric filters of which the frequency characteristics are different, it is necessary to adjust the resonant frequencies of the dielectric resonators in correspondence to the frequencies. To make this adjustment, in the above-described dielectric resonator, it is possible to cut either the peripheral side-face of the dielectric resonator having thin film multi-layer electrodes formed on the opposite sides thereof, including the thin film multi-layer electrodes, to partially cut or the thin film multi-layer electrodes. 
     However, as shown in FIG. 15, if the adjustment of the resonant frequency is carried out by the above-described method, for example by cutting, the peripheral side-face of the dielectric  111 , in the thin film multi-layer electrode  112  comprising metallic layers  112   a  made of copper or the like and dielectric layers  112   b , due to the rolling properties of the metallic layers  112   a , a part of the metallic layers  112   a  of the thin film multi-layer electrode  112  will be short circuited, so that the nonloaded Q of the dielectric resonator  110  will be reduced. Therefore, after the peripheral side-face is cut to adjust the resonant frequency of the dielectric resonator, etching or the like is required to remove the short circuiting portion of the thin film multi-layer electrode. Thus, the number of production processes is increased. 
     Further, to adjust the resonant frequency of the dielectric resonator, a method of cutting the dielectric portion of the dielectric resonator excluding the thin film multi-layer electrode may be proposed. However, to adjust roughly the resonant frequency, it is required to cut an amount of the dielectric. When the dielectric of the dielectric resonator is partially removed, the symmetric structure of the dielectric resonator is unbalanced, so that the current distribution becomes uneven, and the nonloaded Q of the dielectric resonator is reduced. 
     SUMMARY OF THE INVENTION 
     In view of the foregoing, a dielectric resonator, a dielectric filter, a dielectric duplexer, a communication device, and a method of producing the dielectric resonator of the present invention have been devised. Accordingly, it is an object of the present invention to solve the above-described problems and to provide a dielectric resonator, a dielectric filter, a dielectric duplexer, and a communication device each having a high nonloaded Q. and a method of producing the dielectric resonator. 
     According to the present invention, there is provided a dielectric resonator which comprises a substantially columnar dielectric, a thin film multi-layer electrode formed on at least one of two faces opposite to each other of the dielectric, and a concave portion formed substantially evenly on the peripheral side-face of the dielectric. 
     A dielectric filter of the present invention comprises a shield cavity with conductive properties, a dielectric resonator, and an external coupling means to be coupled to the dielectric resonator, the dielectric resonator including a substantially columnar dielectric arranged in the shield cavity, a thin film multi-layer electrode formed on at least one of two faces opposite to each other of the dielectric, and a concave portion formed substantially evenly on the peripheral side face of the dielectric. 
     A dielectric duplexer of the present invention comprises a shield cavity with electroconductive properties, a dielectric resonator, an external coupling means to be coupled to the dielectric resonator, and an input-output connection means connected to the external coupling means and an antenna connection means, the dielectric resonator including a substantially columnar dielectric arranged in the shield cavity, a thin film multi-layer electrode formed on at least one of two faces opposite to each other of the dielectric, and a concave portion formed substantially evenly on the peripheral side face of the dielectric. 
     A communication device of the present invention comprises a dielectric duplexer, one of a transmission circuit and a receiving circuit connected to the dielectric duplexer, and an antenna connected to said dielectric duplexer, the dielectric duplexer including a shield cavity with conductive properties, a dielectric resonator, an external coupling means to be coupled to the dielectric resonator, an input-output connection means connected to the external coupling means and an antenna connection means, the dielectric resonator including a substantially columnar dielectric arranged in the shield cavity, a thin film multi-layer electrode formed on at least one of two faces opposite to each other of the dielectric, and a concave portion formed substantially evenly on the peripheral side-face of the resonator. 
     Accordingly, since the symmetrical structure of the dielectric resonator is kept, the current distribution is not disturbed. Further, the thin film multi-layer electrode formed in the dielectric resonator is prevented from being short-circuited. 
     Furthermore, a method of producing a dielectric resonator comprises the steps of: forming a thin film multi-layer electrode on at least one of two faces opposite to each other of a substantially columnar dielectric and an electrode on the other face, and fixing the dielectric to a rotation apparatus, and rotating the dielectric to cut substantially evenly the peripheral side-face of the dielectric by use of a cutting means. 
     Thus, the dielectric resonator of which the symmetrical structure can be easily kept can be produced without the thin film multi-layer electrode short-circuited. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is-a perspective view of a dielectric resonator according to the present invention; 
     FIG. 2 is a cross sectional view taken on line X—X of FIG. 1; 
     FIG. 3 is an illustration of a part of production process for the dielectric resonator according to the present invention; 
     FIG. 4 is a cross sectional view of a dielectric resonator according to another embodiment of the present invention; 
     FIG. 5 is an exploded perspective view of a dielectric filter of the present invention; 
     FIG. 6 is a cross sectional view taken on line Y—Y of FIG. 5; 
     FIG. 7 is an exploded perspective view of a dielectric filter according to a still further embodiment of the present invention; 
     FIG. 8 is a cross sectional view taken on line Z—Z of FIG. 7; 
     FIG. 9 is an exploded perspective view of a dielectric duplexer of the present invention; 
     FIG. 10 is a cross sectional view taken on line W—W of FIG. 9; 
     FIG. 11 is a schematic view of a communication device of the present invention; 
     FIG. 12 is a perspective view of a conventional dielectric resonator; 
     FIG. 13 is a partially cross sectional view of one end of the conventional dielectric resonator; 
     FIG. 14 is an exploded perspective view of a conventional dielectric filter: 
     FIG. 15 is a partially cross sectional view of one end of a dielectric resonator in which the metallic layers of the thin film multi-layer electrode are short-circuited. 
    
    
     PREFERRED EMBODIMENT OF THE INVENTION 
     A dielectric resonator according to an embodiment of the present invention will be now described with reference to FIGS. 1 and 2. FIG. 1 is a perspective view of the dielectric resonator, and FIG. 2 is a cross sectional view taken on line X—X of FIG.  1 . 
     As shown in FIGS. 1 and 2, dielectric resonators  10  of the instant embodiment each is made up of a columnar dielectric  11 , thin film multi-layer electrodes  12  formed on two faces opposite to each other of the dielectric  11 , and a concave portion  13  substantially evenly formed on the peripheral side-face of the dielectric  11 . With the depth and width of the concave portion  13 , the resonant frequency of the dielectric resonator  10  is adjusted. 
     A method of producing the dielectric resonator of the present invention will be now described with reference to FIG.  3 . 
     First, the dielectric resonator  10 , obtained by forming the thin film multi-layer electrodes  12  on the two faces opposite to each other of the columnar dielectric  11 , is mounted on a rotation apparatus  14 . The rotation apparatus  14  is equipped with a suction means for sucking the dielectric resonator  10  from below. The dielectric resonator  10  is fixed by means of the sucking means. After the dielectric resonator  10  is fixed, the rotation apparatus  14  is rotated in the horizontal direction, and thereby, the dielectric resonator  10  is also rotated in the horizontal direction. To cut the side face of the dielectric resonator  10 , a diamond bar  15  having a disk shape under rotation is pressed to the side-face of the dielectric resonator  10  which is also under rotation. By such a method as above described, the dielectric resonator  10  having a concave portion  13  substantially evenly formed on the peripheral side-face thereof excluding the thin film multi-layer electrodes  12 , as shown in FIGS. 1 and 2, can be easily formed. If the diamond bar  15  having a spherical shape is used as the cutting means, the dielectric resonator  10   c  with the concave portion  13 a having a concave shape as shown in the cross sectional view of FIG.  4 . 
     If the dielectric resonator  10  is produced by the above-described method, the resonant frequency of the dielectric resonator  10  can be adjusted without the thin film multi-layer electrodes  12  short-circuited, and thereby, it is unnecessary to carry out the etching of the thin film multi-layer electrodes  12  after the peripheral side-face is cut. In addition, since the concave portion  13  on the peripheral side-face of the dielectric resonator  10  is formed substantially evenly there, the symmetric structure of the dielectric resonator  10  is not unbalanced, and the current distribution is prevented from being disturbed. Accordingly, the reduction of the nonloaded Q of the dielectric resonator  10  is prevented. 
     Further, the dielectric filter according to an embodiment of the present invention will be now described with reference to FIGS. 5 and 6. FIG. 5 is an exploded perspective view of the dielectric filter of the instant embodiment. FIG. 6 is a cross sectional view taken on line Y—Y of FIG.  5 . In this case, a two-stage band-elimination filter in which two dielectrics arranged laterally are connected through a quarter-wave line. 
     A dielectric filter  20  of the instant embodiment, as shown in FIGS. 5 and 6, is made up of a shield cavity  21  made of iron plated with silver, two dielectric resonators  10  having a columnar shape arranged in the shield cavities  21 , an ground plate  22 , electrical probes  23  as external coupling means,-and external connectors  24  attached to the shield cavities  21 , respectively. 
     The thin film multi-layer electrodes  12  are formed on two faces opposite to each other of the dielectric resonator  10 . The ground plate  22  made of a copper sheet plated with silver, having steps  22   a  and holes  22   b  for soldering plated with silver is soldered to one of the two faces. The ground plate  22  is sandwiched between the body  21   a  of the shield cavity  21  and the lid  21   b  in such a manner that the ground plate  22  is in conduction with the shield cavity  21 . Thus, the dielectric resonators  10  are arranged in the shield cavities  21 . Electrical probes  23  made of metallic wires are arranged, elongating in the spaces between the electric resonators  10  and the shield cavity  21 , respectively. One end of the electrical probe  23  is attached to an external connector  24  fixed to the shield cavity  21 . Moreover, the center conductors of the two external connectors  24  are connected through the quarter-wave line  25 . 
     In the dielectric filter  20  of the instant embodiment, as shown in the cross sections of FIGS. 5 and 6, the concave portions  13  are substantially evenly formed on the peripheral side-faces of the dielectric resonators  10  arranged in the shield cavities  21 , other than the thin film multi-layer electrodes  12 . By use of such a dielectric resonators  10 , the resonant frequency of the dielectric resonators  10  can be adjusted while the symmetric structure of the dielectric resonators  10  is kept, namely, the current distribution of the dielectric resonators  10  is not prevented -from being disturbed. Thus, the reduction of the nonloaded Q is prevented. 
     In the dielectric filter  20  having the above-described structure, an input signal when it is input through the external connector  24  is fed to the electrical probe  23 , so that the electrical probe  23  and the dielectric resonator  10  are capacitive-coupled. Thus, at a resonant frequency determined by the shape and size of the dielectric resonators  10 , the dielectric resonators  10  become resonat. Thus, the dielectric filter  20  in which the dielectric resonators are connected through the quarter-wave line  25  functions as a two stage band-elimination filter for eliminating desired frequency waves. 
     To carry out the fine adjustment of the dielectric resonators  10  to such a degree that the symmetric structure of the dielectric resonator  10  is not unbalanced, after the dielectric resonators  10  are arranged in the shield cavity  21 , a fine amount of the dielectric may be cut from holes  26  provided in the shield cavity  21  by means of a fluter or the like. 
     Further, another embodiment of the dielectric filter of the present invention will be now described with reference to FIGS. 7 and 8. FIG. 7 is an exploded perspective view of the dielectric filter of the instant embodiment. FIG. 8 is a cross sectional view taken on line Z—Z of FIG.  7 . Like numerals refer to like parts in the instant and above-described embodiments, and detailed description of the like parts will be omitted below. 
     In the instant embodiment, as shown in FIGS. 7 and 8, the dielectric filter  30  is made up of a shield cavity  31  made of iron plated with silver, two columnar dielectric resonators  10  arranged in the shield cavity  31 , a ground plate  32 , an electrical probe  23  as an external coupling means, and an external connector  24  attached to the shield cavity  31 . 
     The difference between the instant and above-described embodiments lies in that the two electric resonators  10  are laterally arranged in the above-described embodiment, while in the instant embodiment, the dielectric resonators  31  are arranged on the front and back sides of the shield cavity  31 . In addition, in the above-described embodiment, the height of the dielectric filter is reduced, while in the instant embodiment, the area of the dielectric filter  30  can be reduced. These arrangements can be selected and applied, depending on the circumstances. 
     As shown in FIGS. 7 and 8, in the dielectric filter  30  of the instant embodiment, the concave portion  13  is formed substantially evenly on the peripheral side-face of the dielectric resonator  10  excluding the thin film multi-layer electrodes  12 . By use of the dielectric resonator  10 , the resonant frequency of the dielectric resonator  10  can be adjusted while the symmetrical structure of the dielectric resonator  10  is kept, that is, the current distribution of the dielectric resonator  10  is prevented from being disturbed. Thus, the reduction of the nonloaded Q is prevented. 
     In the dielectric filter  30  having the above configuration, an input signal when it is input through the external connector  24  is fed to the electrical probe  23 , so that the electrical probe  23  and the dielectric resonator  10  are capacitive-coupled. Then, at the resonant frequency determined by the shape and size of the dielectric resonator  10 , the arrangement of the dielectric resonator  10 , and the like, the dielectric resonator  10  becomes resonat. Thus, the dielectric filter  30  in which the dielectric resonators are connected to each other through the quarter-wave line  25  functions as a two-stage band-elimination dielectric filter for eliminating desired frequency waves. 
     Further, the dielectric duplexer according to an embodiment of the present invention will be now described with reference to FIGS. 9 and 10. FIG. 9 is an exploded perspective view of the dielectric duplexer of the instant embodiment. FIG. 10 is a cross sectional view taken on line W—W of FIG.  9 . Like numerals refer to like parts in the instant and above-described embodiments. Detailed description of the like parts will be omitted below. 
     As shown in FIGS. 9 and 10, the dielectric duplexer  40  of the instant embodiment includes a first dielectric filter  50   a  made up of two columnar dielectric resonators parts  10   a  arranged in the shield cavity  41 , and a second dielectric filter  50   b  made up of another two columnar dielectric resonator parts  10   b . The two dielectric resonators  10   a  making up the first dielectric filter part  50   a  are capacitive-coupled through a coupling member  27   a  whereby a transmission band pass filter is produced. The two dielectric resonators  10   b  making up the second dielectric filter part  50   b  has a resonant frequency different from the dielectric resonator  10   a  of the first dielectric filter part  50   a , and capacitive-coupled through a coupling member  27   b , whereby a receiving band-pass filter is produced. An electrical probe  23   a  as an external coupling means to be coupled to the dielectric resonator  10   a  is connected to an external connector  24   a  and further connected to an external transmission circuit. In addition, the electrical probe  23   b  to be coupled to the dielectric resonator  10   b  of the second dielectric filter part  50   b  is connected to an external connector  24   b , and further connected to an external receiving circuit. Further, the electrical probes  23   c  to be coupled to the dielectric resonator  10   a  of the first dielectric filter part  50   a , and an electrical probe  23   d  to be coupled with the dielectric resonator  10   b  of the second dielectric filter part  50   b  is connected to an external connector  24   c  and further connected to an external antenna. 
     In the dielectric duplexer  40  having the above configuration, a predetermined frequency wave is made to pass through the first dielectric filter part  50   a , and moreover, a frequency wave different from the above frequency wave is caused to pass through the second dielectric filter  50   b . Thus, the dielectric duplexer  40  functions as a band-pass dielectric duplexer. 
     As shown in FIGS. 9 and 10, also in the dielectric duplexer  40  of the present invention, the substantially even concave portion  13  is formed on the peripheral side-faces of the dielectric resonators  10   b  arranged in the shield cavity  41 , excluding the thin film multi-layer electrodes  12 . By use of the above-described dielectric resonators  10   b , the resonant frequency of the dielectric resonators  10   b  can be adjusted while the symmetrical structure of the dielectric resonator  10   b  is kept, that is, without disturbances in the current distribution of the dielectric resonators  10   b . That is, the nonloaded Q is not reduced. This is true of the dielectric resonators  10   a.    
     Furthermore, a communication device  60  according to an embodiment of the present invention will be now described with reference to FIG.  11 . FIG. 11 is a schematic view of the communication device of the instant embodiment. 
     As shown in FIG. 11, a communication device  60  of the instant embodiment is made up of a dielectric duplexer  40 , a transmitting circuit  61 , a receiving circuit  62 , and an antenna  63 . The dielectric duplexer  40  is the same that is described in the above embodiment. The external connector  24   a  connected to the first dielectric filter part  50   a  in FIG. 9 is connected to a transmitting circuit  61 . The external connector  24   b  connected to the second dielectric filter part  50   b  is connected to a receiving circuit  62 . Further, the external connector  24   c  is connected to an antenna  63 . 
     Also in the communication device  60  of the instant embodiment, a substantially even concave portion is formed on the peripheral side-face of each dielectric resonator arranged in the shield cavity, excluding the thin film multi-layer electrode. By use of the above-described dielectric resonator, the resonant frequency of the dielectric resonator can be adjusted while the symmetrical structure of the dielectric resonator is kept, that is, without the current distribution of the dielectric resonator disturbed. Thus, the nonloaded Q is not reduced. 
     As seen in the above description, the substantially even concave portion is formed on the peripheral side face of each dielectric resonator containing the columnar dielectric having the thin film multi-layer electrodes formed on the opposite sides of the dielectric, the peripheral side faces not containing the thin film multi-layer electrodes. Thus, the resonant frequency can be adjusted with the depth and width of the concave portion without the thin film multi-layer electrodes short-circuited. In addition, since the symmetrical structure of the dielectric resonators is kept, the disturbance of the current distribution is prevented. Accordingly, the dielectric resonator with a high non-loading Q factor can be provided. In addition, by use of the above-described dielectric resonator, the dielectric filter, the dielectric duplexer, and the communication device each having high characteristics can be provided. 
     Further, the method of producing the dielectric resonator comprises securing the dielectric resonator to the rotation apparatus, and substantially evenly cutting the peripheral side-face of the dielectric resonator with a cutting means. Thus, the resonant frequency can be easily adjusted without the thin film multi-layer electrodes formed on the two side opposite to each other of the dielectric resonator short-circuited. Thus, processes such as etching or the like are unnecessary.