Abstract:
The present invention can couple multiple resonances through a change in the shape of a part of a dielectric resonance element or of a cavity so as to couple energy between resonances when generating the multiple resonances, such as dual or triple resonances, of the dielectric resonance element in one cavity, thereby simplifying the shape and reducing the size thereof. In addition, a dielectric resonance element is manufactured into the shape of a doughnut so as to generate triple resonances in one cavity, thereby facilitating the manufacture of the dielectric resonance element and the emission of heat from the dielectric resonance element.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation of International Application No. PCT/KR2013/000075 filed on Jan. 7, 2013, which claims a priority to Korean Application No. 10-2012-0001631 filed on Jan. 5, 2012, which applications are incorporated herein by reference. 
     
    
     TECHNICAL FIELD 
       [0002]    The present invention relates to a high frequency filter, and more particularly, to a multi-mode bandpass filter that implements multiple resonances in a single cavity. 
       BACKGROUND ART 
       [0003]    In general, in order to implement a filter in a ultra-high frequency, a cavity filter having a cavity, a wave guide filter, a dielectric filter, or the like is implemented because a high power may be implemented and selectivity (Q: Quality factor) is high. Among them, the dielectric filter is mainly used in order to improve the selectivity in a similar cavity volume. However, such a dielectric filter has disadvantages in that a manufacturing cost is high and a weight becomes heavy since a dielectric resonance element should be introduced into a cavity. 
         [0004]    In order to overcome these disadvantages, efforts to implement multiple resonances in a single cavity have been made for a long time, as in U.S. Pat. No. 4,675,630. However, as illustrated in  FIG. 1  which is the same as the representative figure of the US patent, a plurality of coupling screws for couple energies, as indicated by reference numerals  16 ,  18 , and  20  should be fabricated in a direction of 45 degrees from edges of a cavity in order to form a filter characteristic with a plurality of resonances within a single cavity. Thus, there is a difficulty in fabricating the cavity, which causes a cost increases. In addition, because adjustment screws are distributed in various directions, a practically usable space is reduced. 
         [0005]    In  FIG. 1 , reference numeral  4  is a wave guide cavity, reference numeral  6  is a resonance element, reference numerals  8  and  10  are coaxial probes, reference numeral  14  is a low dielectric constant support, and reference numerals  22 ,  24 , and  26  are tuning screws. 
       SUMMARY 
       [0006]    An object of the present invention is to facilitate implementation of energy coupling in order to implement a filter characteristic by generating multiple resonances within a single cavity. 
         [0007]    Another object of the present invention is to reduce the manufacturing cost of a cavity by facilitating the implementation of energy coupling and to achieve additional miniaturization by reducing an implementation space. 
         [0008]    Another object of the present invention is to facilitate the manufacturing of a dielectric resonance element and dissipation of heat generated from the dielectric resonance element when multiple resonances are generated in a single cavity, by fabricating the dielectric resonance element. 
         [0009]    A multi-mode bandpass filter includes a dielectric resonance element of which the shape is partially modified for energy coupling respective resonances when multiple resonances are formed in a single cavity using a dielectric resonance element. 
         [0010]    In addition, as the same purpose, a multi-mode bandpass filter includes a cavity of which the shape is partially deformed for energy coupling of respective resonances without modifying the shape of the dielectric resonance element. 
         [0011]    A multi-mode bandpass filter includes a dielectric resonance element so as to generate triple resonances in a single cavity in which the dielectric resonance element is formed in a doughnut shape so as to facilitate the manufacturing of the dielectric resonance element and dissipation of heat. 
         [0012]    When multiple resonances are implemented using a single cavity, it is possible to simplify a coupling structure for energy coupling between respective resonance modes. 
         [0013]    Due to this, it is possible to overcome a structural restriction according to the coupling structure when implementing multiple resonances using a plurality of cavities. Thus, a multi-mode bandpass filter may be freely implemented without a structural restriction. 
         [0014]    In addition, due to the simplification of a cavity or cavities, it is possible to reduce a manufacturing cost of the cavity or cavities and to miniaturize the cavity or cavities. 
         [0015]    In addition, when triple resonances are implemented using a single cavity, the dielectric resonance element is manufactured in a doughnut shape which facilitates the manufacturing of the multi-mode bandpass filter to reduce the manufacturing cost and dissipation of heat generated from the dielectric resonance element to stably and reliably operate a product. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0016]      FIG. 1  is a perspective view of a conventional multiple resonance band filter; 
           [0017]      FIG. 2   a  is a perspective view of a multi-mode bandpass filter according to a first exemplary embodiment of the present invention; 
           [0018]      FIG. 2   b  is a transmissive perspective view of the multi-mode bandpass filter according to the first exemplary embodiment of the present invention; 
           [0019]      FIG. 2   c  is a graph representing a characteristic measured for the multi-mode bandpass filter according to the first exemplary embodiment; 
           [0020]      FIG. 3   a  is a perspective view of a multi-mode bandpass filter according to a second exemplary embodiment of the present invention; 
           [0021]      FIG. 3   b  is a transmissive perspective view of the multi-mode bandpass filter according to the second exemplary embodiment of the present invention; 
           [0022]      FIG. 3   c  is a graph representing a characteristic measured for the multi-mode bandpass filter according to the second exemplary embodiment; 
           [0023]      FIG. 4   a  is a transmissive perspective view of the multi-mode bandpass filter according to a third exemplary embodiment of the present invention; 
           [0024]      FIG. 4   b  is a characteristic simulation graph of the multi-mode bandpass filter according to the third exemplary embodiment of the present invention; 
           [0025]      FIG. 5  is a transmissive perspective view of the multi-mode bandpass filter according to a fourth exemplary embodiment of the present invention; 
           [0026]      FIG. 6  is a transmissive perspective view of the multi-mode bandpass filter according to a fifth exemplary embodiment of the present invention; 
           [0027]      FIG. 7  is a transmissive perspective view of the multi-mode bandpass filter according to a sixth exemplary embodiment of the present invention; 
           [0028]      FIG. 8  is a transmissive perspective view of the multi-mode bandpass filter according to a seventh exemplary embodiment of the present invention; and 
           [0029]      FIGS. 9   a  and  9   b  are graphs comparatively illustrating characteristics measured for multi-mode bandpass filters according to features of the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0030]      FIG. 2   a  is a perspective view of a multi-mode bandpass filter according to a first exemplary embodiment of the present invention, and  FIG. 2   b  is a transmissive perspective view of the first exemplary embodiment of the present invention, in which illustration of a cover is omitted. According to the first exemplary embodiment of the present invention, a multi-mode bandpass filter  200  includes a housing  201  and a cover  202  that shield a cavity. The housing  201  and the cover  202  are made of a metallic material so as to shield an internal signal. Occasionally, the housing  201  and the cover  202  may be used in a state where they are coated with a non-conductive material such as a plastic. 
         [0031]    In addition, input/output ports  210  and  211  are provided so as to input or output a signal to generate a resonance in the cavity. 
         [0032]    In  FIG. 2   b , which is a transmissive perspective view of  FIG. 2   a , it can be seen that first and second transmission lines  220  and  221  are provided to be connected to the input/output ports. The two transmission lines  220  and  221  serve to couple energies required by the dielectric resonance element so as to implement a desired filter. Occasionally, the two transmission lines  220  and  221  may be electrically shorted or opened with respect to the housing  201  and a desired amount of energy coupling may be implemented by changing a distance between the transmission line and the dielectric resonance element, and a length, thickness, and shape of the transmission lines. 
         [0033]    In addition, in the dielectric resonance element  230 , respective frequency resonance modes for implementing the multi-mode bandpass filter  200  are generally generated to be directly related to a ratio of the diameter and the length of the dielectric resonance element  230 . Accordingly, the respective resonance modes may be resonated at the same frequency through the adjustment of the ratio of the diameter and the length. However, in the present first exemplary embodiment, the dielectric resonance element  230  is manufactured in a doughnut shape in order to generate triple resonances as in the disclosure defined in claim  8 , thereby facilitating the manufacturing of the dielectric resonance element  230  and dissipation of heat generated from the dielectric resonance element  230 . That is, the entire external appearance of the dielectric resonance element  230  is similar to a cylindrical shape, but is formed with a through-hole is formed, for example, at the center thereof in a longitudinal direction. In addition, a dielectric resonance element  230 , which is partially modified in shape as defined in claim  1 , is provided without being provided with screws  16 ,  18 , and  20  of  FIG. 1  for energy coupling between respective frequency resonance modes of different multi-mode band resonance filters as disclosed in U.S. Pat. No. 4,675,630. Although the first exemplary embodiment executes energy coupling between multiple resonances by modifying a doughnut shape, it may also be applied to a cylindrical model and a rectangular model. The dielectric resonance element  230  used therefor typically uses a high dielectric permittivity as compared to a support  240 , is made of a dielectric having a low-loss tangent coefficient, and has a low tangent, and thus the dielectric resonance element  230  may have a high selectivity Q (Quality factor) so that the loss caused in the filter can be reduced. The dielectric resonance element  230  may not be positioned at the center of the cavity, but is positioned at the center of the cavity in order to obtain the best selectivity Q (Quality factor). 
         [0034]    Accordingly, the support  240 , having a low dielectric permittivity and a low-loss tangent coefficient, is provided so as to position the dielectric resonance element  230  at the center of the cavity. The support  240  is in contact with the dielectric resonance element at one side thereof and in contact with the housing  201  at the opposite side. Typically, alumina (Al 2 O 3 ) is used for the support because alumina has a low-loss tangent coefficient and is excellent in heat conductivity so that heat generated from the dielectric resonance element can be dissipated to the housing  201 . Besides alumina, Teflon, a plastic or the like may be used. 
         [0035]    A resonance adjustment screw  250  may be provided so as to finely adjust a resonance frequency. 
         [0036]      FIG. 2   c  is a graph representing a characteristic measured for the multi-mode bandpass filter  200  according to the first exemplary embodiment which is provided as illustrated in  FIGS. 2   a  and  2   b . As illustrated in  FIG. 2   c , it can be seen that the multi-mode bandpass filter  200  according to the present invention generates a plurality of modes. 
         [0037]    As described above with reference to  FIGS. 2   a  to  2   c , the present invention modifies a part of the doughnut-shaped dielectric resonance element  230  in order to generate multiple resonances, in which it can be seen that the modified structure is that a portion is removed in the plan structure of the dielectric resonance element  230  (i.e., in the example of  FIGS. 2   a  and  2   b , a structure obtained by cutting a portion from a circular shape). As the modified amount (the amount cut out from the circular shape) increases, a bandwidth may increase. In full measure, a semi-circle may be cut out. Such a modified amount may be properly designed in consideration of a desired filtering characteristic of the filter. 
         [0038]    At this time, the first and second transmission lines  220  and  221  illustrated in  FIG. 2   b  (and hence, the input/output ports) are configured to be positioned at an angle of 90 degrees in relation to each other with respect to the dielectric resonance element  230  on a plan view. Such an arrangement is an important configuration so as to generate two or more resonances in a single cavity. In addition, the modified portion in the dielectric resonance element  230  is formed preferably in a quadrant at an opposite side to a quadrant between the first and second transmission lines  220  and  221 , which are positioned at the angle of 90 degrees in relation to each other on the plan view. 
         [0039]      FIG. 3   a  is a perspective view of a multi-mode bandpass filter according to a second exemplary embodiment of the present invention, and  FIG. 3   b  is a transmissive perspective view of the second exemplary embodiment of the present invention. The second exemplary embodiment extends a structure in which multiple resonances are generated in a single cavity as in the first exemplary embodiment of the present invention described above, to two cavities so as to implement a multi-mode bandpass filter  300 . Although the second exemplary embodiment has been described assuming two cavities for the convenience of understanding, in practical use, the present invention may also be applied to all of two or more cavities. 
         [0040]    Referring to  FIGS. 3   a  and  3   b , the multi-mode bandpass filter  300  is provided with a housing  301  and a cover  302 . The housing and the cover are the same, in used material and use, as the housing  201  and the cover  202 , respectively. 
         [0041]    In addition, the multi-mode bandpass filter  300  includes input/output ports  310  and  311 , and first and second transmission lines  320  and  321  which are the same, in used material and use, as the input/output ports  210 ,  211 , and the first and second transmission line  220 ,  221  of the first exemplary embodiment, respectively. 
         [0042]    In order to extend the first exemplary embodiment, two dielectric resonance elements  330  and  331 , two supports  340  and  341 , and resonance adjustment screws  350 ,  351  are provided and are the same, in material and use, as the resonance element  230 , the support  240 , and the resonance adjustment screw  250  of the first exemplary embodiment of the present invention, respectively. 
         [0043]    However, third and fourth transmission lines  360  and  361  service to couple an energy required by the dielectric resonance elements  330  and  331  in order to implement a filter, and a fifth transmission line  362  is provided to interconnect the third and fourth transmission lines  360  and  361 . Occasionally, the third and fourth transmission lines  360  and  361  may be electrically shorted or opened in relation to the housing  301  similar to the first and second transmission lines, and a desired amount of energy coupling may be implemented through a modification of a distance between the transmission lines and the dielectric resonance element, and the length, thickness and shape of the transmission lines. 
         [0044]      FIG. 3   c  is a graph representing a characteristic measured for the multi-mode bandpass filter  300  according to the first exemplary embodiment which is provided as illustrated in  FIGS. 3   a  and  3   b.    
         [0045]    Hereinafter, other exemplary embodiments of the present invention will be described with reference to  FIGS. 4   a  to  8 . In the following description, for the convenience of description, illustration of the cover will be omitted, and descriptions of the functions thereof will also be omitted because they are the same as those described above. 
         [0046]      FIG. 4   a  is a transmissive perspective view of the multi-mode bandpass filter according to a third exemplary embodiment of the present invention. 
         [0047]    Referring to  FIG. 4   a , according to a third exemplary embodiment of the present invention, a multi-mode bandpass filter  400  includes a housing  401  and a cover that shield a cavity. The housing  401  and the cover are the same, in used material and use, as the housing  201  and the cover  202  of the first exemplary embodiment, respectively. 
         [0048]    However, although the shape of the dielectric resonance element is partially modified for energy coupling between respective frequency resonance modes in the first and second exemplary embodiments, in the third exemplary embodiments, a shape of the housing  401  is partially modified for energy coupling between multiple resonances. 
         [0049]    Further, the multi-mode bandpass filter  400  includes input/output ports  410  and  411 , first and second transmission lines  420  and  421 , a support  440 , and a resonance adjustment screw  450  which are the same, in used material and use, as the input/output ports  210  and  211 , first and second transmission lines  220  and  221 , a support  240 , and a resonance adjustment screw  250  of the first exemplary embodiment, respectively. 
         [0050]    However, because energy coupling is executed by modifying a part of the shape of the housing  401 , the dielectric resonance element  430  is provided in an ordinary doughnut shape (i.e., a non-modified structure). 
         [0051]      FIG. 4   b  is a characteristic simulation graph for the multi-mode bandpass filter  200  according to the third exemplary embodiment of the present invention, which is provided as illustrated in  FIG. 4   a . As illustrated in  FIG. 4   b , it can be seen that the multi-mode bandpass filter  200  according to the third exemplary embodiment generates multiple modes. 
         [0052]    As described above with reference to  FIGS. 4   a  and  4   b , in the third exemplary embodiment, an internal shape of the housing  401  (a shape of the cavity) is partially modified so as to generate multiple resonances. It can be seen that the modified structure is a structure in which a portion is added to the internal structure of the housing  401  to be opposite to the dielectric resonance element  430  (that is, in the example of  FIG. 4   a , a structure in which a corner portion in the internal structure of a rectangular view in a plan view is somewhat filled). As the modified amount (an amount filled in the corner) increases, the band width of the filter may increase. Such a modified amount may be properly designed in consideration of a desired filtering characteristic of the filter. 
         [0053]    At this time, the first and second transmission lines  420  and  421  (and hence, the input/output ports) illustrated in  FIG. 4   a  are configured to be positioned at an angle of 90 degrees in relation to each other with respect to the dielectric resonance element  230  on a plan view. At this time, the modified portion in the housing  401  is formed preferably in a quadrant at an opposite side to a quadrant between the first and second transmission lines  420  and  421  positioned at the angle of 90 in relation to each other on the plan view. 
         [0054]      FIG. 5  is a transmissive perspective view of the multi-mode bandpass filter according to a fourth exemplary embodiment of the present invention. The fourth exemplary embodiment of the present invention implements a multi-mode bandpass filter  500  by extending a structure in which multiple resonances are generated in a single cavity as in the third exemplary embodiment described above, to a structure having two cavities. Although the fourth exemplary embodiment is described assuming two cavities for the convenience of understanding, in practical use, the present invention may also be applied to all of two or more cavities. 
         [0055]    The multi-mode bandpass filter  500  includes a housing  501  and a cover. The housing and the cover are the same, in used material and use, as the housing  201  and the cover  202  of the first exemplary embodiment, respectively. 
         [0056]    In addition, the multi-mode bandpass filter  500  includes input/output ports  510  and  511 , and first and second transmission lines  520  and  521  which are the same, in used material and use, as the input/output ports  210 ,  211 , and the first and second transmission line  220 ,  221  of the first exemplary embodiment, respectively. 
         [0057]    In order to extend the third exemplary embodiment, two dielectric resonance elements  530  and  531 , two supports  540  and  541 , and resonance adjustment screws  550 ,  551  are provided and are the same, in material and use, as the resonance element  430 , the support  440 , and the resonance adjustment screw  450  of the third exemplary embodiment of the present invention, respectively. 
         [0058]    In addition, the multi-mode bandpass filter  500  includes third, fourth, and fifth transmission lines  560 ,  561 , and  562  which are the same, in used material and use, as the third, fourth, and fifth transmission lines  360 ,  361 , and  362  of the second exemplary embodiment, respectively. 
         [0059]      FIG. 6  is a transmissive perspective view of the multi-mode bandpass filter according to a fifth exemplary embodiment of the present invention. The fifth exemplary embodiment of the present invention is implemented by applying the first exemplary embodiment and the third exemplary embodiment described above to a single cavity. That is, a multi-mode bandpass filter  600  is implemented by partially modifying the shapes of both of the dielectric resonance element  630  and the housing  601  for energy coupling between multiple resonances in a single cavity. 
         [0060]    The fifth exemplary embodiment illustrated in  FIG. 6  may include input/output ports  610  and  611 , first and second transmission lines  620  and  621 , a support  640 , and a resonance adjustment screw  650  as in the foregoing exemplary embodiments. 
         [0061]      FIG. 7  is a transmissive perspective view of the multi-mode bandpass filter according to a sixth exemplary embodiment of the present invention. The sixth exemplary embodiment of the present invention implements a multi-mode bandpass filter  700  by extending a structure in which multiple resonances are generated in a single cavity as in the fifth exemplary embodiment described above, to a structure having two cavities. Although the sixth exemplary embodiment is described assuming two cavities for the convenience of understanding, in practical use, the present invention may also be applied to all of two or more cavities. 
         [0062]    The sixth exemplary embodiment illustrated in  FIG. 7  may include a housing  701 , input/output ports  710  and  711 , first and second transmission lines  720  and  721 , dielectric resonance elements  730  and  731 , supports  740  and  741 , resonance adjustment screws  750  and  751 , and third, fourth, and fifth transmission lines  760 ,  761 , and  762  as in the foregoing exemplary embodiments. 
         [0063]      FIG. 8  is a transmissive perspective view of the multi-mode bandpass filter according to a seventh exemplary embodiment of the present invention. The seventh exemplary embodiment implements multiple resonance modes in two or more cavities by implementing the first and second exemplary embodiments described above in the cavities, respectively. That is, in at least one cavity, a shape of a dielectric resonance element is modified, and in at least one other cavity, a shape of the cavity is modified to implement a multi-mode bandpass filter  800 . 
         [0064]    The seventh exemplary embodiment illustrated in  FIG. 8  may include a housing  801 , input/output ports  810  and  811 , first and second transmission lines  820  and  821 , dielectric resonance elements  830  and  831 , supports  840  and  841 , resonance adjustment screws  850  and  851 , and third, fourth, and fifth transmission lines  860 ,  861 , and  862  as in the foregoing exemplary embodiments. 
         [0065]      FIGS. 9   a  and  9   b  are graphs comparatively illustrating characteristics measured for multi-mode bandpass filters according to features of the present invention.  FIG. 9   a  represents characteristic measurement results in a case where no through-hole exists in a central portion of the dielectric resonance element, and  FIG. 9   b  represents characteristics in a case where a through-hole is formed in the central portion of the dielectric resonance element according to the present invention. As illustrated in  FIGS. 9   a  and  9   b , it can be found that when the through-hole is formed in the central portion of the dielectric resonance element, a spurious wave is generated at a frequency higher than a use frequency as compared to a structure where the through-hole is not formed, and thus forming the through-hole is more suitable in passing only a selected frequency which is a unique characteristic of a bandpass filter. 
         [0066]    As described above, when a multi-mode bandpass filter may be configured according to the exemplary embodiments. In addition, other exemplary embodiments may be implements according to various modifications and changes of the present invention. 
         [0067]    For example, a multi-mode bandpass filter structure including a single cavity or two cavities as illustrated in  FIG. 5  or the like has been described in the foregoing description for the exemplary embodiment. Besides these, other exemplary embodiments of the present invention may similarly adopt a structure which is provided with a plurality of cavities, i.e. three or more cavities. 
         [0068]    In addition, in the foregoing description, it has been described that in  FIG. 5  or the like, an interconnecting coupling structure is adapted between a plurality of (e.g., two) cavities using third to fifth transmission lines. Besides this, in other exemplary embodiments of the present invention, it is also possible to adopt a structure that connects a plurality of cavities through windows formed by partially removing partition walls between the plurality of cavities.