Abstract:
The present invention provides a dielectric filter and a dielectric duplexer, each including a plurality of dielectric resonators. The dielectric filter and the dielectric duplexer each comprising: a dielectric block having a first surface and a second end surface opposite to each other; at least three resonator holes passing through the first end surface to the second end surface of the dielectric block; inner conductors disposed on the inner wall surfaces of the resonator holes; an outer conductor disposed on the external surface of the dielectric block; the outer conductor on the first end surface of the dielectric block being separated into an inner part and a peripheral part by a nonconductive portion; the inner part including the openings of at least three of the resonator holes adjacent to each other; a peripheral part being arranged around the inner part; and the inner part and the peripheral part being connected by a microinductance-generating means.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a dielectric filter, a dielectric duplexer, and a transceiver. 
     2. Description of the Related Art 
     Recently, a small, light in weight, and thin-type of radio communication equipment such as a mobile phone have been rapidly popular. In addition to this tendency, electronic components which are to be mounted on such a type of radio communication equipment are required to have a small size and a reduced height. Furthermore, a dielectric duplexer, which is an antenna-shared unit for performing reception and transmission by a single antenna, is required to be small-sized, lightweight, and lower in height. 
     Conventionally, a dielectric duplexer used as an antenna-shared unit in a mobile phone or the like adopts a structure in which resonator holes of a plurality of dielectric resonators are aligned in a straight line in a single dielectric block. However, generally, both a filter on the transmitting side and a filter on the receiving side, which are composed of dielectric resonators formed on the dielectric block, are allowed to block a pass band of the counter-side filter by band-pass filter characteristics, so that it is difficult to obtain sufficient attenuation in an attenuation band, as long as the number of the dielectric resonators is not increased. Thus, the dielectric duplexer having a structure in which the resonator holes are aligned in a straight line, needs to be large overall. 
     As a result, it is considerable, for example, that the transmitting filter may be formed by a band-block filter. When a single dielectric block is used, a transmission-line conductor is disposed for coupling adjacent resonators by setting a phase difference of π/2 (rad) between them. In this case, since the transmission line is a microstrip line whose half-face is dielectric and its other half-face is air, the electrical length of the line is longer than the resonator length of the dielectric resonator, so that the dimension of the aligning direction of the resonators is very large. 
     In addition, for example, even though the transmitting filter is used as a band-block filter in the case of an antenna-shared unit, when the transmitting filter side is viewed from the side of the receiving filter, in the pass band of the receiving filter, namely, in the block band of the transmitting filter, impedance is substantially zero, so that receiving signals from the antenna flow to the side of the transmitting filter. In order to avoid such a situation, it is necessary to dispose a phase unit having the electrical length of π/2 between the transmitting filter and an antenna terminal so as to make the impedance in the block band of the transmitting filter viewed from the side of the receiving filter infinite. However, this arrangement increases the number of components in the radio communication equipment, thereby leading to rising in cost. 
     In order to solve the above-mentioned problems in the conventional dielectric duplexer, for example, a duplexer shown in FIGS. 9A to  9 C is presented. The duplexer comprises rectangular-parallelepiped formed dielectric block  1 , and with respect to it, various holes, and an electrode film are formed. In other words,  2   a ,  2   b ,  2   c ,  5   a ,  5   b , and  5   c  are resonator holes on the side of the transmitting filter of the dielectric duplexer; and  4   a ,  4   b ,  4   c , and  4   d  are resonator holes on the side of the receiving filter. Numeral reference  3  is an input-output coupling resonator hole. 
     Each of the respective resonator holes  2   a  through  5   c  is a step hole whose internal diameters of the upper half part and the lower half part in FIG. 9B mutually differ. In order not to make the figure complicated, resonator holes  5   b  and  5   c  are not shown in FIG.  9 B. In this figure,  12   a ,  12   b , and  12   c  are inner conductors formed on the inner wall surfaces of the resonator holes  2   a ,  2   b , and  2   c ;  15   a  is an inner conductor formed on the inner wall surface of the resonator hole  5   a ;  14   a ,  14   b ,  14   c , and  14   d  are inner conductors formed on the inner wall surfaces of the resonator holes  4   a ,  4   b ,  4   c , and  4   d ; and  13  is an inner conductor formed on the inner wall surface of the input-output coupling resonator hole  3 . 
     In addition, in each of the inner conductors except for the inner conductors  12   a  and  13 , a nonconductive portion indicated by g is disposed near the extremity of a step hole having a longer internal diameter so as to use this part as a disconnection end. Holes  6   a ,  6   b , and  6   c  shown in FIG. 9A are ground holes, in which inner conductors are formed on the entire inner peripheral surfaces of the straight holes with fixed internal diameters. On the external surface of the dielectric block  1  are formed a transmitting terminal Tx and an antenna terminal ANT, respectively connecting to the inner conductors  12   a  and  13  of the resonator holes  2   a  and  3 ; and a receiving terminal Rx is formed to make capacitance between it and the inner conductor  14   d  of the resonator hole  4   d . Furthermore, an outer conductor  10  is formed on the substantially entire surface except for these terminals Tx, Rx, and ANT. 
     Meanwhile, in the dielectric duplexer having the aforementioned structure, as shown in FIGS. 9A to  9 C, since the resonator holes  2   a  through  2   c ,  3 ,  5   a  through  5   c  and the ground holes  6   a  through  6   c  of the dielectric resonators comprising a filter on the transmitting side are aligned in a staggering form in the dielectric block  1 , the dimension w of the aligning direction of the resonator holes  2   a  through  2   c  is reduced, whereas the height h is increased when it is mounted on a print circuit board, or the like. In addition, in the conventional dielectric duplexer, arrangement of the resonator holes  2   a  through  2   c  and the ground holes  6   a  through  6   c  are complicated, and also it is difficult to form and manufacture the dielectric block  1 . 
     Furthermore, in the dielectric duplexer shown in FIG. 9, only Q 0  characteristics of approximately ⅔ is obtainable as compared with the one having the same height as that in which the resonator holes are aligned in a line in the dielectric block; and when the height h is reduced, the characteristics are deteriorated. 
     SUMMARY OF THE INVENTION 
     To overcome the above described problems, the present invention provides a dielectric filter, a dielectric duplexer, and a transceiver, which have a lower height and good characteristics, and can be easily manufactured. 
     One preferred embodiment of the present invention provides a dielectric filter or a dielectric duplexer including a plurality of dielectric resonators, the dielectric filter comprising: a dielectric block having a first surface and a second end surface opposite to each other; at least three resonator holes passing through the first end surface to the second end surface of the dielectric block; inner conductors disposed on the inner wall surfaces of the resonator holes; an outer conductor disposed on the external surface of the dielectric block; the outer conductor on the first end surface of the dielectric block being separated into an inner part and a peripheral part by a nonconductive portion; the inner part including the openings of at least three of the resonator holes adjacent to each other; a peripheral part being arranged around the inner part; and the inner part and the peripheral part being connected by a microinductance-generating means. 
     The microinductance-generating unit is, for example, a conductor pattern integrated with the outer conductor, or a metallic lead wire. 
     In the dielectric filter and the dielectric duplexer having such a structure, among the respective dielectric resonators formed by at least three resonator holes surrounded by the nonconductive portion, the dielectric resonator using the first end surface side as a short-circuit end is grounded through the microinductance generating unit. This arrangement permits mutual comb-line coupling between the dielectric resonators using the first end surface side as a short-circuit end among the three dielectric resonators. As a result, it is not necessary to dispose mutually coupling dielectric resonators in a staggering form in the dielectric block. 
     In the above described dielectric duplexer or dielectric duplexer, the openings of the resonator holes included in the inner part may be disposed in a recess provided on the first end surface of the dielectric block, and the nonconductive portion may be disposed on the inner wall surface of the recess. 
     Since the recess allows the nonconductive portion and the openings of the resonator holes to be recessed from a first end surface of the dielectric block, influence of the leaking electromagnetic field on the other electronic components mounted on a circuit board can be suppressed. Similarly, influence of the electromagnetic field leaking from the other electronic components on the dielectric filter and the dielectric duplexer can be also suppressed. 
     In the above described dielectric filter or dielectric duplexer, a coupling-block ground hole may be disposed between the resonator holes which the openings thereof are included in the inner part. Such a coupling-block ground hole between the resonator holes surrounded by the nonconductive portion permits the coupling-block ground hole to cut off mutual electromagnetic coupling between the resonator holes disposed on both sides of the coupling-block ground hole by the blocking action. 
     Further, a transceiver employed in the present invention includes at least either one of the dielectric filter or the dielectirc duplexer having the aforementioned characteristics, so that the device can be flexible in reducing the height thereof. 
     Other features and advantages of the present invention will become apparent from the following description of preferred embodiments of the invention which refers to the accompanying drawings, wherein like reference numerals indicate like elements to avoid duplicative description. 
    
    
     BRIEF DESCRIPTION OF DRAWINGS 
     FIGS. 1A,  1 B to  1 C show a structure of a first preferred embodiment of a dielectric duplexer according to the present invention, in which FIG. 1A is a back view; FIG. 1B is a plan view; and FIG. 1C is a front view. 
     FIG. 2 is an electric equivalent circuit diagram of the dielectric duplexer shown in FIG.  1 . 
     FIG. 3 is a transmitting-side filter characteristic view of the dielectric duplexer shown in FIG.  1 . 
     FIG. 4 is a receiving-side filter characteristic view of the dielectric duplexer shown in FIG.  1 . 
     FIG. 5 is an electric equivalent circuit diagram showing a second preferred embodiment of the dielectric duplexer according to the present invention. 
     FIG. 6 is a partially cut-away perspective view showing a structure of a third preferred embodiment of the dielectric duplexer according to the present invention. 
     FIG. 7 is a front view showing a fourth preferred embodiment of the dielectric duplexer according to the present invention. 
     FIG. 8 is a block diagram showing one preferred embodiment of a transceiver according to the present invention. 
     FIGS. 9A,  9 B and  9 C show a structure of a conventional dielectric duplexer, in which FIG. 9A is a back view; FIG. 9B is a plan view; and FIG. 9C is a front view. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     [First Preferred Embodiment, FIGS.  1 A through  4 ] 
     A first preferred embodiment of the dielectric duplexer according to the present invention is shown in FIGS. 1A,  1 B and  1 C. In the dielectric duplexer  20 , the transmitting side comprises two band-block filters, and the receiving side comprises two band-pass filters and a trap. In a dielectric block  21  of a rectangular parallelepiped form are formed resonator holes  22   a  through  22   d  of the transmitting filter side, resonator holes  23   a  through  23   d  of the receiving filter side, an input-output coupling resonator hole  24 , and a ground hole  25 . The resonator holes  22   a  through  22   d ,  23   a  through  23   d ,  24 , and the ground hole  25  are aligned in a straight line in the dielectric block  21 ; and this arrangement is different from the dielectric duplexer shown in FIG.  9 . 
     Each of the resonator holes  22   a  through  22   d ,  23   a  through  23   d ,  24 , and the ground hole  25 , as shown in FIG. 1B, are step holes which pass through a first surface  26  of the dielectric block  21  to an opposing second surface  27 , and the respective step holes have internal diameters of different lengths in the upper half part and the lower half part thereof. Inner conductors  32   a  through  32   d  are formed on the inner wall surfaces of the resonator holes  22   a  through  22   d ; and inner conductors  33   a  through  33   d  are formed on the inner wall surfaces of the resonator holes  23   a  through  23   d . An inner conductor  34  is formed on the inner wall surface of the input-output coupling resonator hole  24 . The ground hole  25  is a straight hole having an internal diameter of a fixed length; and an inner conductor  35  is formed on the entire inner peripheral surface thereof. 
     In each of the inner conductors except for the inner conductors  32   b ,  33   c , and  34 , a nonconductive portion indicated by g is formed near the extremity of a step hole with a longer internal diameter, and this part (which is, in other words, the part electrically separated from an outer conductor  36 ) is a disconnection end. Meanwhile, the part of the inner conductor opposing the disconnection part, (which is, in other words, the part electrically connected to the outer conductor  36 ), is a short-circuit end. On the external surface of the dielectric block  21  are formed a transmitting terminal Tx connected to the inner conductor  32   b  of the resonator hole  22   b , a receiving terminal Rx connected to the inner conductor  33   c  of the resonator hole  23   c , and an antenna terminal ANT connected to the inner conductor  34  of the resonator hole  24 ; and furthermore, the outer conductor  36  is formed on the substantially entire surface except for the transmitting terminal Tx, the receiving terminal Rx, and the antenna terminal ANT. 
     As shown in FIG. 1C, in the inner part  41  on a first end surface  26  of the dielectric block  21 , the outer conductor  36  is cut away in a letter-C form to dispose a nonconductve portion  43  in such a manner that the resonator holes  22   c  and  22   d , the input-output coupling resonator hole  24 , and the ground hole  25  are surrounded. A conductor pattern  44  left near the center of the nonconductive portion  43  is integrated with the outer conductor  36 ; and it is a microinductance generating means for mutually connecting the inner part  41  and the outer part  42  which are electrically separated by the nonconductive portion  43 . 
     In the dielectric duplexer  20  having the aforementioned structure, the disconnection ends and the short-circuit ends of the inner conductor  33   a  formed in the resonator hole  23   a  and the inner conductor  33   b  formed in the resonator hole  23   b  are disposed in the mutually same direction so as to produce a comb-line coupling between the inner conductors  33   a  and  33   b , whereas the disconnection ends and the short-circuit ends of the inner conductor  33   a  formed in the resonator hole  23   a  and the inner conductor  34  formed in the input-output coupling resonator hole  24  are disposed in the mutually reversed direction so as to produce an inter-digital coupling between the inner conductors  33   a  and  33   b , and similarly, so as to produce an inter-digital coupling between the inner conductor  33   b  formed in the resonator hole  23   b  and the inner conductor  33   c  formed in the resonator hole  23   c . This permits formation of two band-pass filters between the antenna terminal ANT and the receiving terminal Rx. In addition, an inter-digital coupling occurs between the inner conductor  33   c  formed in the resonator hole  23   c  and the inner conductor  33   d  formed in the resonator hole  23   d . This permits formation of a trap on the receiving side. 
     Meanwhile, a comb-line coupling occurs between the inner conductor  32   c  formed in the resonator hole  22   c  and the inner conductor  34  formed in the input-output coupling resonator hole  24  by the nonconductive portion  43 , whereas an inter-digital coupling occurs between the inner conductor  32   b  formed in the resonator hole  22   b  and the inner conductor  32   c  formed in the resonator hole  22   c . This permits formation of a wide-band band-block filter between the transmitting terminal Tx and the antenna terminal ANT. Furthermore, an inter-digital coupling occurs between the inner conductors  32   a  formed in the resonator hole  22   a  and  32   b  formed in the resonator hole  22   b , and between the inner conductor  32   c  formed in the resonator hole  22   c  and the inner conductor  32   d  formed in the resonator hole  22   d . This permits formation of two traps on the transmitting side. 
     FIG. 2 shows an electric equivalent circuit diagram of the dielectric duplexer  20 . In the dielectric block  21  are disposed dielectric resonators R 1  through R 4  formed by the respective resonator holes  22   a  through  22   d  on the transmitting filter side, a dielectric resonator R 5  formed by the input-output coupling resonator hole  24 , and respective dielectric resonators R 6  through R 9  formed by the resonator holes  23   a  through  23   d  on the receiving filter side. Between the dielectric resonators R 1  and R 3  is disposed the dielectric resonator R 2  which is connected to the transmitting terminal Tx; between the dielectric resonators R 4  and R 6  is disposed the dielectric resonator R 5  which is connected to the antenna terminal ANT; and furthermore, between the dielectric resonators R 7  and R 9  is disposed the dielectric resonator R 8  which is connected to the receiving terminal Rx. The dielectric resonator R 4  and the dielectric resonator R 5  connected to the antenna terminal ANT are electromagnetically mutually shielded by the inner conductor  35  of the ground hole  25 . 
     In the transmitting side, a wide-band band-block filter is formed by the dielectric resonators R 2 , R 3 , and R 5 , and the trap formed by the dielectric resonators R 2  and R 4  is combined with this to comprise two band-block filters. The dielectric resonators R 3  and R 5  are grounded through a microinductance L 1  (see FIG. 2) formed of a conductor pattern  44  which is located near the center of the nonconductive portion  43  shown in FIG.  1 C. Namely, regarding the dielectric resonators R 3  and R 5 , the part on the side of a first end surface  26  is a short-circuit end. This allows a comb-line coupling between the dielectric resonators R 3  and R 5 . Furthermore, modifications in the form and pattern of the conductor pattern  44  permit changing of values of the microinductance, so that electromagnetic coupling between the dielectric resonators R 3  and R 5  can be easily adjusted. 
     In this arrangement, the dielectric duplexer  20  is different from the conventional dielectric duplexer shown in FIG. 9, since it is not necessary to dispose the resonator holes  22   a  through  22   d ,  23   a  through  23   d , and  24  in the dielectric block  21  in a staggering form. This allows the mounting height h of the dielectric duplexer  20  to be significantly lower than that of the conventional dielectric duplexer, so that the dielectric block  21  can be easily manufactured. 
     Under the condition in which the mounting height h is equal, characteristics of the dielectric duplexer  20  are improved more than those of the dielectric duplexer shown in FIG.  9 . The measured values of pass characteristics S 21  and reflection characteristics S 1  of the transmitting filter in the dielectric duplexer  20  are shown in FIG. 3; and the measured values of pass characteristics S 21  and reflection characteristics S 11  of the receiving filter in the dielectric duplexer  20  are shown in FIG.  4 . 
     [Second Preferred Embodiment, FIG.  5 ] 
     The electric equivalent circuit of a second preferred embodiment of the dielectric duplexer according to the present invention is shown in FIG.  5 . In a dielectric duplexer  30 , the dielectric resonator R 4  and the dielectric resonator R 2  which is connected to the transmitting terminal Tx are grounded through a microinductance L 2 . In other words, the structure is equivalent to that in which the nonconductive portion  43  is disposed on a first end surface  26  of the dielectric duplexer  20  employed in the first embodiment by cutting away the outer conductor  36  in a letter-C form so as to surround the resonator holes  22   b ,  22   c ,  22   d , and the ground hole  25  which is disposed between the resonator holes  22   b  and  22   c , on the inner part  41 . The microinductance L 2  is formed by the conductor pattern  44 , which is located near the center of the nonconductive portion  43 . The dielectric resonator R 3  and the dielectric resonator R 2  which is connected to the transmitting terminal Tx are electrically shielded to each other by the inner conductor  35  formed in the ground hole  25  formed therebetween. 
     In the dielectric duplexer  30 , similar to the first embodiment, the dielectric resonators R 2  and R 4  are grounded through the microinductance L 2  to produce a comb-line coupling, so that the mounting height h can be significantly lower than that of the conventional art, and the characteristics can be enhanced. 
     [Third Preferred Embodiment, FIG.  6 ] 
     A third preferred embodiment of the dielectric duplexer according to the present invention is shown in FIG. 6. A dielectric duplexer  40  has such an arrangement that, in the dielectric duplexer  20  of the first embodiment, respective openings of the resonator holes  22   c ,  22   d , and  24 , and the ground hole  25  are formed in a recess  51  on a first end surface  26  of the dielectric block  21 ; and the outer conductor  36  is cut away on the inner peripheral wall of the recess  51  so as to dispose the nonconductive portion  43 . 
     When such an arrangement is provided, since the openings of the resonator holes  22   c ,  22   d , and  24 , and the ground hole  25  are recessed from the first end surface  26  of the dielectric block  21 , in addition to the effects created by the dielectric duplexer  20  of the first embodiment, high frequencies generated in the dielectric duplexer  40  are unlikely to leak outside. Moreover, influence due to high frequencies from the outside on the dielectric duplexer  40  can be reduced. 
     [Fourth Embodiment, FIG.  7 ] 
     A front view of a fourth preferred embodiment of the dielectric duplexer according to the present invention is shown in FIG. 7. A dielectric duplexer  50  has such an arrangement that the nonconductive portion  43  of the dielectric duplexer  20  shown in FIG. 1 is formed in a ring-shape, in which the inner part  41  and the outer part  42  are mutually connected through a metallic lead wire  44   a  so as to use the metallic lead wire  44   a  as a microinductance. Such an arrangement permits easy adjustment of inductance-values of the microinductance by modifying the length and shape of the metallic lead wire  44   a.    
     [Fifth Preferred Embodiment: FIG.  8 ] 
     A fifth preferred embodiment shows an embodiment of a transceiver according to the present invention, in which an example of a mobile phone is illustrated. 
     FIG. 8 is an electric circuit block diagram of RF section of a mobile phone  120 . In FIG. 8, reference numeral  122  denotes an antenna device; reference numeral  123  denotes an antenna-shared filter (duplexer); reference numeral  131  denotes a transmitting-side isolator; reference numeral  132  denotes a transmitting-side amplifier; reference numeral  133  denotes a transmitting-side inter-stage band-pass filter; reference numeral  134  denotes a transmitting-side mixer; reference numeral  135  denotes a receiving-side amplifier; reference numeral  136  denotes a receiving-side inter-stage band-pass filter; reference numeral  137  denotes a receiving-side mixer; reference numeral  138  denotes a voltage-controlled oscillator (VCO); and reference numeral  139  denotes a local band-pass filter. In this case, it is possible to use, for example, the duplexer  20 ,  30 ,  40 , or  50  of the first through fourth embodiments as an antenna-shared filter (duplexer)  123 . Mounting of the dielectric duplexer  20 ,  30 ,  40 , or  50  can reduce the height of the RF section so as to obtain a slim mobile phone. [Other Embodiments] 
     A dielectric filter, a dielectric duplexer, and a transceiver according to the present invention should not be construed to the above-described embodiments, and various changes and modifications are possible without departing from the spirit and scope of the present invention. More particularly, although a description has been given of a dielectric dupulexer and a transceiver in the embodiments above, it is to be understood that a dielectric filter such as a band-block filter or the like can be applied. 
     As clearly seen from the given description above, according to the present invention, since among respective dielectric resonators formed by at least three resonator holes surrounded by a nonconductive portion, a dielectric resonator, whose part of a first end surface side being a short-circuit end, is grounded through a microinductance to produce a comb-line coupling, it is not necessary to dispose the mutually coupling dielectric resonators in a staggering form in a dielectric block, so that the mounting height is significantly lower than that of the conventional art, and the characteristics are also improved. Moreover, since the present invention adopts a simple alignment of the resonator holes formed in the dielectric block, manufacturing of the dielectric block is easy. 
     In addition, when at least three resonator holes surrounded by the nonconductive portion are disposed in a recess formed on the short-circuit surface of the dielectric block to form a nonconductive portion on the inner wall surface of the recess, the short-circuit surfaces of the dielectric resonators are recessed from a first end surface of the dielecric block so as to strengthen shielding of the openings of the dielectric resonators in the recess. This not only makes high frequencies generated in the dielectric resonators unlikely to leak out, but also permits influence due to high frequencies from the outside on the dielectric resonators to be reduced. Furthermore, mounting a dielectric filter and a dielectric duplexer according to the present invention allows the height of a transceiver to be reduced. 
     While the invention has been particularly shown and described with reference to preferred embodiments thereof, it will be understood by those skilled in the art that the forgoing and other changes in form and details may be made therein without departing from the spirit of the invention.