Patent Publication Number: US-9431690-B2

Title: Dielectric waveguide filter with direct coupling and alternative cross-coupling

Description:
CROSS-REFERENCE TO RELATED AND CO-PENDING APPLICATIONS 
     This application is a continuation patent application which claims the benefit of the filing date of U.S. patent application Ser. No. 14/088,471 filed on Nov. 25, 2013 now U.S. Pat. No. 9,130,255 issued on Sep. 8, 2015, entitled “Dielectric Waveguide Filter with Direct Coupling and Alternative Cross-Coupling”, the disclosure of which is incorporated herein by reference as are all references cited therein, which claimed the benefit of the filing date and disclosure of U.S. Provisional Application Ser. No. 61/730,615 filed on Nov. 28, 2012, the contents of which are entirely incorporated herein by reference as are all of references cited therein, and further claimed the benefit of the filing date and disclosure of, and is a continuation-in-part of, U.S. application Ser. No. 13/103,712 filed on May 9, 2011 now U.S. Pat. No. 8,823,470 issued on Sep. 2, 2014 and titled “Dielectric Waveguide Filter with Structure and Method for Adjusting Bandwidth”, U.S. application Ser. No. 13/373,862 filed on Dec. 3, 2011 now U.S. Pat. No. 9,030,279 issued on May 12, 2015 and titled “Dielectric Waveguide Filter with Direct Coupling and Alternative Cross-Coupling”, and U.S. application Ser. No. 13/564,822 filed on Aug. 2, 2012 now U.S. Pat. No. 9,030,278 issued on May 12, 2015 and titled “Tuned Dielectric Waveguide Filter and Method of Tuning”, the contents of which are also entirely incorporated herein by reference as are all of the references cited therein. 
    
    
     FIELD OF THE INVENTION 
     The invention relates generally to dielectric waveguide filters and, more specifically, to a dielectric waveguide filter with direct coupling and alternative cross-coupling. 
     BACKGROUND OF THE INVENTION 
     This invention is related to a dielectric waveguide filter of the type disclosed in U.S. Pat. No. 5,926,079 to Heine et al. In which a plurality of resonators are spaced longitudinally along the length of a monoblock and in which a plurality of slots/notches are spaced longitudinally along the length of the monoblock and define a plurality of bridges between the plurality of resonators which provide a direct inductive/capacitive coupling between the plurality of resonators. 
     The attenuation characteristics of a waveguide filter of the type disclosed in U.S. Pat. No. 5,926,079 to Heine et al. can be increased through the incorporation of zeros in the form of additional resonators located at one or both ends of the waveguide filter. A disadvantage associated with the incorporation of additional resonators, however, is that it also increases the length of the filter which, in some applications, may not be desirable or possible due to, for example, space limitations on a customer&#39;s motherboard. 
     The attenuation characteristics of a filter can also be increased by both direct and cross-coupling the resonators as disclosed in, for example, U.S. Pat. No. 7,714,680 to Vangala et al. which discloses a monoblock filter with both inductive direct coupling and quadruplet cross-coupling of resonators created in part by respective metallization patterns which are defined on the top surface of the filter and extend between selected ones of the resonator through-holes to provide the disclosed direct and cross-coupling of the resonators. 
     Direct and cross-coupling of the type disclosed in U.S. Pat. No. 7,714,680 to Vangala et al. and comprised of top surface of metallization patterns is not applicable in waveguide filters of the type disclosed in U.S. Pat. No. 5,926,079 to Heine et al. which includes only slots and no top surface metallization patterns. 
     The present invention is thus directed to a dielectric waveguide filter with both direct and optional cross-coupled resonators which allow for an increase in the attenuation characteristics of the waveguide filter without an increase in the length of the waveguide filter or the use of metallization patterns on the top surface of the filter. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to a dielectric waveguide filter comprising a block of dielectric material including a plurality of exterior surfaces covered with an exterior layer of conductive material, a plurality of stacked resonators defined in the block of dielectric material by one or more slots extending into the block of dielectric material and an interior layer of conductive material that separates the plurality of stacked resonators, at least a first RF signal input/output electrode defined on the block of dielectric material, and a first RF signal transmission window defined in the interior layer of conductive material and defining a direct path for the transmission of an RF signal between the plurality of stacked resonators. 
     In one embodiment, first and second slots extend into one or more of the exterior surfaces of the block of dielectric material and separate the block of dielectric material into at least first and second stacked resonators and third and fourth stacked resonators, the first RF signal transmission window being defined in the interior layer of conductive material between the first and second stacked resonators and a second RF signal transmission window is defined in the interior layer of conductive material and defines an indirect path for the transmission of the RF signal between the third and fourth stacked resonators. 
     In one embodiment, a second RF signal input/output electrode is defined in the block of dielectric material in a relationship relative to the first RF signal input/output electrode to define a generally oval shaped direct path for the transmission of the RF signal through the dielectric waveguide filter. 
     In one embodiment, the block of dielectric material defines a longitudinal axis and the first and second RF signal input/output electrodes are defined by respective first and second through-holes extending through the block of dielectric material, the first and second slots and the first and second through-holes extending in a direction transverse to the direction of the longitudinal axis, and the first and second through-holes being disposed in a diametrically opposed and co-linear relationship on opposite sides of the interior layer of conductive material. 
     In one embodiment, the block of dielectric material is comprised of first and second separate blocks of dielectric material each including a plurality of exterior surfaces covered with an exterior layer of conductive material and defining the interior layer of conductive material when the first and second separate blocks of dielectric material are stacked on each other, the first slot being defined in the first block of dielectric material and separating the first block of dielectric material into the first and third resonators, the second slot being defined in the second block of dielectric material and separating the second block of dielectric material into the second and fourth resonators, the respective first and second RF signal transmission windows being defined by respective windows in the layer of conductive material which covers the exterior surface of each of the first and second blocks of dielectric material. 
     The present invention is also directed to a dielectric waveguide filter comprising a first block of dielectric material including a plurality of exterior surfaces covered with a layer of conductive material and at least a first slot extending into one or more of the exterior surfaces and separating the first block of dielectric material into at least first and second resonators, a first RF signal input/output electrode defined at one end of the first block of dielectric material, and a second block of dielectric material including a plurality of exterior surfaces covered with a layer of conductive material and at least a second slot extending into one or more of the exterior surfaces and separating the second block of dielectric material into at least third and fourth resonators, the second block of dielectric material being stacked on the first block of dielectric material in a relationship wherein the first and fourth resonators are stacked on each other and the second and third resonators are stacked on each other and a first direct generally oval shaped RF signal transmission path is defined through the waveguide filter. 
     In one embodiment, the first direct RF signal transmission path is defined in part by a first RF signal transmission window located between the second and third stacked resonators. 
     In one embodiment, the first direct RF signal transmission window is defined by respective first and second windows in the layer of conductive material covering the exterior surface of the respective first and second blocks of dielectric material. 
     In one embodiment, a second RF signal transmission window located is between the first and fourth stacked resonators for providing an indirect path for the transmission of the RF signal between the first and fourth resonators. 
     In one embodiment, the second RF signal transmission window is defined by respective third and fourth windows in the layer of conductive material covering the exterior surface of the respective first and second blocks of dielectric material. 
     In one embodiment, a second RF signal input/output electrode is defined at one end of the second block of dielectric material and positioned in a relationship diametrically opposed to the first RF signal input/output electrode defined at the one end of the first block of dielectric material, the first and second RF signal input/output electrodes being defined by respective first and second through-holes extending through the respective first and second blocks of dielectric material. 
     In one embodiment, respective first and second steps are defined in the respective one ends of the first and second blocks of dielectric material, the respective first and second through-holes extending through the respective first and second steps. 
     The present invention is further directed to a dielectric waveguide filter comprising a first block of dielectric material defining a first longitudinal axis and including a plurality of exterior surfaces covered with a layer of conductive material, a first plurality of slots defined in the first block of dielectric material and extending in a direction opposite the direction of the first longitudinal axis and separating the first block of dielectric material into a first plurality of resonators extending along the first longitudinal axis, and a first step defined at one end of the first block of dielectric material, a first RF signal input/output through-hole defined in the step of the first block of dielectric material, a second block of dielectric material seated against the first block of dielectric material, the second block of dielectric material defining a second longitudinal axis and including a plurality of exterior surfaces covered with a layer of conductive material, a second plurality of slots defined in the second block of dielectric material and extending in a direction opposite the direction of the second longitudinal axis and separating the second block of dielectric material into a second plurality of resonators extending along the second longitudinal axis, and a second step defined at one end of the second block of dielectric material, a second RF signal input/output through-hole defined in the step of the second block of dielectric material, and a first direct RF signal transmission path defined by the combination of the first and second RF signal input/output through-holes and the plurality of resonators in the first and second blocks of dielectric material. 
     In one embodiment, the first direct RF signal transmission path is defined in part by a first direct RF signal transmission means located between a first one of the first plurality of resonators in the first block of dielectric material and a first one of the second plurality of resonators in the second block of dielectric material. 
     In one embodiment, the first direct RF signal transmission means is defined by respective first and second windows defined in the layer of conductive material covering the exterior surface of the respective first and second blocks of dielectric material. 
     In one embodiment, a first indirect RF signal transmission means defines a first indirect coupling path for the transmission of the RF signal from a second one of the first plurality of resonators in the first block of dielectric material to a second one of the second plurality of resonators in the second block of dielectric material. 
     In one embodiment, the first indirect RF signal transmission line means is defined by respective third and fourth windows defined in the layer of conductive material covering the plurality of exterior surfaces of the respective first and second blocks of dielectric material. 
     In one embodiment, the first direct RF signal transmission path is generally oval in shape. 
     Other advantages and features of the present invention will be more readily apparent from the following detailed description of the preferred embodiment of the invention, the accompanying drawings, and the appended claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and other features of the invention can best be understood by the following description of the accompanying FIGURES as follows: 
         FIG. 1  is an enlarged perspective view of a dielectric waveguide filter according to the present invention; 
         FIG. 2  is an enlarged, part phantom, perspective view of the dielectric waveguide filter shown in  FIG. 1 ; 
         FIG. 3  is an enlarged, exploded, part phantom, perspective view of the two blocks of the dielectric waveguide filter shown in  FIG. 1 ; 
         FIG. 4  is a graph depicting the performance of the dielectric waveguide filter shown in  FIG. 1 ; 
         FIG. 5  is an enlarged, part phantom, perspective view of another embodiment of a dielectric waveguide filter according to the present invention; and 
         FIG. 6  is an enlarged, exploded, broken, part phantom, perspective view of the two blocks of the dielectric waveguide filter shown in  FIG. 5 . 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
       FIGS. 1, 2, and 3  depict a waveguide filter  1100  incorporating both direct and alternative cross-coupling/indirect coupling features and characteristics in accordance with the present invention. 
     In the embodiment shown, the waveguide filter  1100  is made from a pair of separate generally parallelepiped-shaped monoblocks of dielectric material  1101  and  1103  which have been coupled together in a stacked relationship to form the waveguide filter  1100 . 
     The bottom monoblock  1101  is comprised of a suitable solid block or core of dielectric material, such as for example ceramic, and includes opposed longitudinal horizontal exterior surfaces  1102   a  and  1104   a , opposed longitudinal side vertical exterior surfaces  1106   a  and  1108   a  that are disposed in a relationship normal to and extend between the horizontal exterior surfaces  1102   a  and  1104   a , and opposed transverse end side vertical exterior end surfaces  1110   a  and  1112   a  that are disposed in a relationship generally normal to and extend between the longitudinal horizontal exterior surfaces  1102   a  and  1104   a  and the longitudinal vertical exterior surfaces  1102   a  and  1102   b.    
     Thus, in the embodiment shown, each of the surfaces  1102   a ,  1104   a ,  1106   a , and  1108   a  extends in the same direction as the longitudinal axis L 1  ( FIG. 3 ) of the monoblock  1101  and each of the end surfaces  1110   a  and  1112   a  extends in a direction transverse or normal to the direction of the longitudinal axis L 1  of the monoblock  1101 . 
     The top monoblock  1103  is also comprised of a suitable solid block or core of dielectric material, such as for example ceramic, and includes opposed longitudinal horizontal exterior surfaces  1102   b  and  1104   b , opposed longitudinal side vertical exterior surfaces  1106   b  and  1108   b  disposed in a relationship normal to and extending between the horizontal exterior surfaces  1102   b  and  1104   b , and opposed transverse end side vertical exterior surfaces  1110   b  and  1112   b  disposed in a relationship normal to and extending between the horizontal exterior surfaces  1102   b  and  1104   b  and the longitudinal side vertical exterior surfaces  1106   b  and  1108   b.    
     Thus, in the embodiment shown, each of the surfaces  1102   b ,  1104   b ,  1106   b , and  1108   b  extends in the same direction as the longitudinal axis L 2  ( FIG. 3 ) of the monoblock  1103  and each of the surfaces  1110   b  and  1112   b  extends in a direction transverse or normal to the direction of the longitudinal axis L 2  of the monoblock  1103 . 
     The monoblocks  1101  and  1103  include respective first and second pluralities of resonant sections (also referred to as cavities or cells or resonators)  1114 ,  1116 , and  1118  and  1120 ,  1121 , and  1122  which are spaced longitudinally along the length of, and extend co-linearly with and in the same direction as the longitudinal axis L 1  and L 2  of, the respective monoblocks  1101  and  1103  and are separated from each other by a plurality of (and more specifically a pair in the embodiment of  FIGS. 1, 2, and 3 ) spaced-apart and generally parallel vertical slits or slots  1124   a  in the monoblock  1101  that are cut into the vertical exterior surface  1106   a  and, more specifically, are cut into the surfaces  1102   a ,  1104   a , and  1106   a  of the monoblock  1101 , and a pair of spaced-apart and generally parallel vertical slits or slots  1124   b  in the monoblock  1103  that are cut into the vertical exterior surface  1106   b  and, more specifically, are cut into the surfaces  1102   b ,  1104   b , and  1106   b  of the monoblock  1103 . 
     Thus, in the embodiment shown, each of the vertical slits or slots  1124   a  and  1124   b  extend in a direction generally transverse or normal to the direction of the longitudinal axis L 1  and L 2  of the respective monoblocks  1101  and  1103 . 
     As shown in  FIG. 3 , the one of the slits  1124   a  in the bottom monoblock  1101  defines a first bridge or through-way or pass  1128  on the monoblock  1101  for the passage and transmission of an RF signal between the resonator  1114  and the resonator  1116  while the other of the slits  1124   a  in the monoblock  1101  defines a second bridge or through-way or pass  1130  on the monoblock  1101  for the passage and transmission of an RF signal between the resonator  1116  and the resonator  1118 . 
     Similarly, and as also shown in  FIG. 3 , the one of the slits  1124   b  in the monoblock  1103  defines a first bridge or through-way or pass  1134  on the monoblock  1103  for the passage and transmission of an RF signal between the resonator  1122  and the resonator  1121  while the other of the slits  1124   b  in the monoblock  1103  defines a second bridge or through-way or pass on the monoblock  1103  for the passage and transmission of an RF signal between the resonator  1121  and the resonator  1120 . 
     The monoblock  1101 , and more specifically the end resonator  1114  of the monoblock  1101 , additionally comprises and defines an end step  1136   a  comprising, in the embodiment shown, a generally L-shaped recessed or grooved or shouldered or notched region or section of the longitudinal surface  1102   a , opposed side surfaces  1106   a  and  1108   a , and side end surface  1112   a  of the monoblock  1101  from which dielectric ceramic material has been removed or is absent. 
     The monoblock  1103 , and more specifically the end resonator  1122  of the monoblock  1103 , similarly additionally comprises and defines an end step  1136   b  comprising, in the embodiment shown, a generally L-shaped recessed or grooved or shouldered or notched region or section of the longitudinal surface  1104   b , opposed side surfaces  1106   b  and  1108   b , and side end surface  1112   b  of the monoblock  1103  from which dielectric material has been removed or is absent. 
     Stated another way, in the embodiment shown, the respective steps  1136   a  and  1136   b  are defined in and by an end section or region of the respective monoblocks  1101  and  1103  having a height or thickness less than the height or thickness of the remainder of the respective monoblocks  1101  and  1103 . 
     Further, in the embodiment shown, the respective end steps  1136   a  and  1136   b  each comprise a generally L-shaped recessed or notched portion of the respective end resonators  1114  and  1122  defined on the respective monoblocks  1101  and  1103  which include respective first generally horizontal surfaces  1140   a  and  1140   b  located or directed inwardly of, spaced from, and parallel to the surfaces  1102   a  and  1104   b  of the respective monoblocks  1101  and  1103  and respective second generally vertical surfaces or walls  1142   a  and  1142   b  located or directed inwardly of, spaced from, and parallel to, the respective side end surfaces  1110   a  and  1112   a  and  11100   b  and  1112   b  of the respective monoblocks  1101  and  1103 . 
     Further, and although not shown or described herein in any detail, it is understood that the end steps  1136   a  and  1136   b  could also be defined by an outwardly extending end section or region of the respective monoblocks  1101  and  1103  having a height or thickness greater than the height or thickness of the remainder of the respective monoblocks  1101  and  1103 . 
     The monoblocks  1101  and  1103  additionally each comprise an electrical RF signal input/output electrode which, in the embodiment shown, is in the form of respective cylindrically shaped through-holes  1146   a  and  1146   b  ( FIGS. 2 and 3 ) which extend through the body of the respective monoblocks  1101  and  1103  and, more specifically, extend through the respective steps  1136   a  and  1136   b  thereof and, still more specifically, through the body of the respective end resonators  1114  and  1122  defined in the respective monoblocks  1101  and  1103  between, and in relationship generally normal to, the respective surfaces  1140   a  and  1140   b  of the respective steps  1136   a  and  1136   b  and the respective surfaces  1104   a  and  1102   b  of the respective monoblocks  1101  and  1103 . 
     Still more specifically, the respective input/output through-holes  1146   a  and  1146   b  are spaced from and generally parallel to the respective transverse side end surfaces  1112   a  and  1112   b  of the respective monoblocks  1101  and  1103  and define respective generally circular openings  1147   a  and  1147   b  located and terminating in the respective step surfaces  1140   a  and  1140   b  and respective opposed openings  1148   a  and  1148   b  terminating in the respective block surfaces  1104   a  and  1102   b  ( FIG. 3 ). 
     The respective RF signal input/output through-holes  1146   a  and  1146   b  are also located and positioned in and extend through the interior of the respective monoblocks  1101  and  1103  in a relationship generally spaced from and parallel to the respective step wall or surfaces  1142   a  and  1142   b  and in a relationship and direction generally normal or transverse to the longitudinal axis of the respective monoblocks  1101  and  1103 . 
     All of the external surfaces  1102   a ,  1104   a ,  1106   a ,  1108   a ,  1108   a ,  10   a , and  1112   a  of the monoblock  1101 , the external surfaces of the monoblock  1101  defining the slits  1124   a , and the interior cylindrical surface of the monoblock  1101  defining the RF signal input/output through-hole  1146   a  are covered with a suitable conductive material, such as for example silver, with the exception of the regions described in more detail below including a ring shaped region  1170   a  ( FIGS. 2 and 3 ) on the surface  1140   a  and surrounding the opening  1147   a  defined in the surface  1140   a  by the through-hole  1146   a.    
     Similarly, all of the exterior surfaces  1102   b ,  1104   b ,  1106   b ,  1110   b , and  1112   b  of the monoblock  1103 , the external surfaces of the monoblock  1103  defining the slits  1124   b , and the interior cylindrical surface of the monoblock  1103  defining the RF signal input/output through-hole  1146   b  are covered with a suitable conductive material, such as for example silver, with the exception of the regions described in more detail below including a ring shaped region  1170   b  ( FIGS. 1, 2, and 3 ) on the surface  1140   b  and surrounding the opening  1147   b  defined in the surface  1140   b  by the through-hole  1146   b.    
     The monoblocks  1101  and  1103  still further comprise respective RF signal input/output connectors  1400  protruding outwardly from the respective openings  1147   a  and  1147   b  defined in the respective surfaces  1140   a  and  1140   b  by the respective through-holes  1146   a  and  1146   b.    
     As shown in  FIGS. 1 and 2 , the separate monoblocks  1101  and  1103  are coupled to and stacked on each other in an overlying and abutting and stacked relationship to define and form the waveguide filter  1100  in a manner in which the separate monoblocks  1101  and  1103 , and more specifically the respective resonators thereof, are arranged in an overlying, abutting, and stacked relationship against each other as described in more detail below. 
     Specifically, the monoblocks  1101  and  1103  are coupled to each other in a relationship wherein, as shown in  FIGS. 1, 2, and 3 , the longitudinal horizontal exterior surface  1102   b  of the top monoblock  1103  is seated on and abutted against the longitudinal horizontal exterior surface  1104   a  of the bottom monoblock  1101 . 
     Still more specifically, the monoblocks  1101  and  1103  are stacked against each other in a relationship wherein the horizontal surface  1104   a  of the monoblock  1101  is abutted against the horizontal surface  1102   b  of the monoblock  1103 ; a central interior layer  1150  of conductive material ( FIGS. 1 and 2 ) which extends the length and width of the interior of the waveguide filter  1100  is sandwiched between the surface  1104   a  of the monoblock  1101  and the surface  1102   b  of the monoblock  1103 , and is defined by the layer of conductive material covering the length and width of the external surfaces  1104   a  and  1102   b  of the respective monoblocks  1101  and  1103 ; the longitudinal side vertical exterior surface  1106   a  of the monoblock  1101  is co-planarly aligned with the longitudinal side vertical exterior surface  1106   b  of the monoblock  1103 ; the slots  1124   a  on the monoblock  1101  are co-linearly aligned with the slots  1124   b  on the monoblock  1103 ; the opposed longitudinal side vertical exterior surface  1108   a  of the monoblock  1101  is co-planarly aligned with the longitudinal side vertical exterior surface  1108   b  of the monoblock  1103 ; the transverse end side vertical exterior surface  1110   a  of the monoblock  1101  is co-planarly aligned with the transverse side vertical exterior surface  1110   b  of the monoblock  1103 ; and the opposed transverse end side vertical exterior surface  1112   a  of the monoblock  1101  is co-planarly aligned with the opposed transverse end side vertical exterior surface  1112   b  of the monoblock  1103 . 
     Thus, in the relationship as shown in  FIGS. 1 and 2 , the respective end steps  1136   a  and  1136   b  on the respective monoblocks  1101  and  1103  are disposed in an opposed, abutting, and stacked relationship; the respective resonators  1114  and  1122  on the respective monoblocks  1101  and  1103  are disposed in an opposed, abutting, and stacked relationship; the respective resonators  1116  and  1121  on the respective monoblocks  1101  and  1103  are disposed in an opposed, abutting, and stacked relationship; and the respective resonators  1118  and  1120  on the respective monoblocks  1101  and  1103  are disposed in an opposed, abutting, and stacked relationship. 
     Thus, and as shown in  FIG. 2 , the waveguide filter  1100  is a generally parallelepiped-shaped block of dielectric material defining a longitudinal axis L 3  and includes opposed, spaced-apart, and parallel bottom and top longitudinal horizontal exterior surfaces  1102  and  1104  that correspond to the respective exterior surfaces  1102   a  and  1102   b  of the respective monoblocks  1101  and  1103  and extend in the same direction as, and below and above and generally parallel to, the longitudinal axis L 3 ; a central interior layer  1150  of conductive material that corresponds to the layer of conductive material on each of the surfaces  1104   a  and  1102   b  of the respective monoblocks  1101  and  1103  and extends through the full length and width of the interior of the waveguide filter  1100  in a generally horizontal co-planar relationship with the longitudinal axis L 3  and further in a relationship spaced from and generally parallel to, the bottom and top horizontal longitudinal exterior surfaces  1102  and  1104 ; opposed, spaced-apart and parallel side vertical exterior surfaces  1106  and  1108  that correspond to the vertically co-planarly aligned surfaces  1106   a  and  1106   b  and  1108   a  and  1108   b  respectively of the respective monoblocks  1101  and  1103  and extending in the same direction as, and on opposite sides of and generally parallel to, the longitudinal axis L 3 ; opposed, spaced-apart and parallel end side vertical exterior surfaces  1110  and  1112  corresponding to the vertically co-planarly aligned surfaces  1110   a  and  1110   b  and  1112   a  and  1112   b  of the respective monoblocks  1101  and  1103  and extend in a direction transverse or normal to, and intersecting, the longitudinal axis L 3 ; a pair of spaced-apart and parallel slits or slots  1124  in the waveguide filter  1100  corresponding to the vertically co-linearly aligned slits or slots  1124   a  and  1124   b  in the respective monoblocks  1101  and  1103  and extending into the waveguide filter  1100  from the exterior vertical longitudinal surface  1106  and into the body of the waveguide filter  1100  in a relationship and direction transverse or normal to the longitudinal axis L 3  and terminating in respective apertures or cut-outs in the bottom and top longitudinal horizontal surfaces  1102  and  1104 ; and an end section or region  1136  that is unitary with the resonators  1114  and  1122  and, in the embodiment shown, has a thickness or height less than the thickness or height of the remainder of the waveguide filter  1100 . 
     In the embodiment shown, the end section or region  1136  defines a first generally L-shaped step or shoulder  1136   a  corresponding to the step  1136   a  defined in the monoblock  1101 , which is located below and spaced from the longitudinal axis L 3 , and includes an exterior surface  1140   a  extending inwardly and spaced from and parallel to the bottom exterior surface  1102  of the waveguide filter  1100 ; and a diametrically opposed second generally L-shaped step or shoulder  1136   b  corresponding to the step  1136   b  in the monoblock  1103 , which is located above and spaced from the longitudinal axis L 3  and including an exterior surface  1140   b  extending inwardly and spaced from and parallel to the top exterior surface  1104  of the waveguide filter  1100 . 
     A generally cylindrically shaped through-hole  1146   a  corresponding to the through-hole  1146   a  defined in the monoblock  1101  extends through the end section  1136 , in a relationship and direction transverse and normal to and below the longitudinal axis L 3 , between a generally cylindrically shaped opening  1147   a  defined in the step surface  1140   a  and the central layer  1150  of conductive material. 
     A generally cylindrically shaped through-hole  1146   b  corresponding to the through-hole  1146   b  in the monoblock  1103  extends through the end section  1136 , in a relationship co-linear with and diametrically opposed to the through-hole  1146   b  and in a relationship and direction transverse and normal to and above the longitudinal axis L 3 , between a generally cylindrically shaped opening  1147   b  defined in the step surface  1140   b  and the central layer  1150  of conductive material. 
     Thus, in the embodiment shown, the through-holes  1146   a  and  1146   b  are located in a diametrically opposed and co-linear relationship on opposite sides of, and in a relationship generally normal to, the central layer  1150  of conductive material and the longitudinal axis L 3  of the waveguide filter  1100 .ip 
     Thus, in the embodiment of  FIG. 2 , each of the exterior surfaces  1102 ,  1104 ,  1106 ,  1108 ,  1110 ,  1112  of the waveguide filter  1100 , the interior surface of the waveguide filter  1100  defining the respective slits/slots  1124 , and the interior surface of the waveguide filter  1100  defining the respective through-holes  1146   a  and  1146   b  are covered or coated with a layer of conductive material with the exception of respective circular or ring shaped regions  1170   a  and  1170   b    1151  surrounding the respective openings  1147   a  and  1147   b  defined by the respective through-holes  1146   a  and  1146   b  in the respective step surfaces  1140   a  and  1140   b  of the end section  1136 . 
     The waveguide filter  1100  further comprises a first interior or internal RF signal transmission window or means or coupling  1622  ( FIGS. 2 and 3 ), which in the embodiment shown is in the shape of a rectangle extending in a direction transverse to and intersecting the longitudinal axis L 3 , that provides for a direct inductive path or window or coupling for the transmission of the RF signal between the respective resonators  1118  and  1120  of the waveguide filter  1100  and, more specifically, between the resonators  1118  and  1120  of the respective monoblocks  1101  and  1103  coupled together to define the waveguide filter  1100 . 
     In the embodiment shown, the window  1622  comprises a generally rectangularly shaped aperture or void or opening or window that is defined in the central layer  1150  of conductive material and is formed in the region of the central layer  1150  located between the resonators  1118  and  1120 . More specifically, the window  1622  is defined by respective generally rectangularly shaped apertures or voids or openings or windows  1622   a  and  1622   b  that are formed in the layer of conductive material that covers the respective exterior surfaces  1104   a  and  1102   b  of the respective monoblocks  1101  and  1103  and located thereon in the region of the respective resonators  1118  and  1120 . The windows  1622   a  and  1622   b  are aligned with each other when the monoblocks  1101  and  1103  are coupled together to define the central layer  1150  of conductive material and the window  1622  therein. 
     Stated another way, the window  1622  is defined by respective generally rectangularly shaped regions  1622   a  and  1622   b  of dielectric material on the respective exterior surfaces  1104   a  and  1102   b  of the respective monoblocks  1101  and  1103  which upon alignment with each other when the monoblocks  1101  and  1103  are coupled together defines the interior RF signal transmission window  1622 . 
     In accordance with this embodiment, the window  1622  located in the interior of the waveguide filter  1100  between the resonators  1118  and  1120  allows for the internal or interior direct inductive passage or transmission of an RF signal from the resonator  1118  into the resonator  1120  of the waveguide filter  1100 . 
     The waveguide filter  1100  additionally comprises a first indirect or cross-coupling interior or internal capacitive RF signal transmission window or means or coupling  1722  located in the interior of the waveguide filter  1100  between the resonators  1116  and  1121 , which in the embodiment shown is in the shape of a rectangle extending in the same direction as and co-linear with the longitudinal axis L 3  and the window  1622 , for transmitting an RF transmission signal between the respective resonators  1116  and  1121  of the waveguide filter  1100  and, more specifically, between the resonators  1116  and  1121  of the respective monoblocks  1101  and  1103  coupled together to define the waveguide filter  1100 . 
     In the embodiment shown, the window  1722  comprises a generally rectangularly shaped aperture or void or opening or window that is defined in the central layer  1150  of conductive material and is formed in the region of the central layer  1150  located between the resonators  1116  and  1121 . Thus, the window  1722  is defined by respective generally rectangularly shaped apertures or voids or openings or windows  1722   a  and  1722   b  that are formed in the layer of conductive material that covers the respective exterior surfaces  1104   a  and  1102   b  of the respective monoblocks  1101  and  1103  and are located in the region of the respective resonators  1116  and  1121 . The windows  1722   a  and  1722   b  are aligned with each other when the monoblocks  1101  and  1103  are coupled together to define the central layer  1150  of conductive material and the window  1722  therein. 
     Stated another way, the window  1722  is defined by respective generally rectangularly shaped regions  1722   a  and  1722   b  of dielectric material on the respective exterior surfaces  1104   a  and  1102   b  of the respective monoblocks  1101  and  1103  which upon alignment with each other when the monoblocks  1101  and  1103  are coupled together defines the interior RF signal transmission window  1722 . 
     In accordance with the invention, the waveguide filter  1100  defines a first magnetic or inductive generally oval-shaped direct coupling RF signal transmission path for RF signals, generally designated by the arrows d in  FIG. 2 , as described below. 
     Initially, the RF signal is transmitted into the connector  1400  and the through-hole  1146   a  in the embodiment where the through-hole  1146   a  in the monoblock  1101  defines the RF signal input through-hole. Thereafter, the RF signal is transmitted into the end section  1136  and, more specifically, the end step  1136   a  on the monoblock  1101 ; then into the resonator  1114  in monoblock  1101 ; then into the resonator  1116  in monoblock  1101  via the RF signal transmission bridge or pass  1128 ; and then into the resonator  1118  in monoblock  1101  via the RF signal transmission bridge or pass  1130 . 
     Thereafter, the RF signal is transmitted from the monoblock  1101  into the monoblock  1103  and, more specifically, from the resonator  1118  in the monoblock  1101  into the resonator  1120  in the monoblock  1103  via the interior inductive RF signal transmission window  1622  located in the interior of the waveguide filter  1100  between the resonators  1118  and  1120 . 
     Thereafter, the RF signal is transmitted into the resonator  1121  in the monoblock  1103  via the RF signal transmission bridge or pass  1132 ; then into the resonator  1122  in monoblock  1103  via the RF signal transmission bridge or pass  1134 ; then into the end section  1136  of monoblock  1103  and, more specifically, into the step  1136   b  of monoblock  1103 ; and then out through the through-hole  1146   b  and the connector  1400  in the end section  1136  of monoblock  1103  in the embodiment where the through-hole  1146   b  in the monoblock  1103  defines the RF signal output through-hole. 
     In accordance with this embodiment of the present invention, the waveguide filter  1100  also defines and provides an alternate or indirect- or cross-coupling RF signal transmission path for RF signals generally designated by the arrow c in  FIG. 2 . 
     Specifically, the cross-coupling or indirect capacitive RF signal transmission path c is defined and created by the interior RF signal transmission means or window  1722  located between the resonators  1116  and  1121  which allows for the transmission of a small portion of the direct RF signal being transmitted through the resonator  1116  of the monoblock  1101  directly into the resonator  1121  of the monoblock  1103 . 
     In accordance with the present invention and as shown in  FIG. 3  wherein the area or size of the RF signal transmission window  1622  is larger than the area or size of the RF signal transmission window  1722 , the internal RF signal transmission window  1622  between and interconnecting the respective resonators  1118  and  1120  of the respective monoblocks  1101  and  1103  of waveguide filter  1100  is designed/sized to create an inductive direct RF signal coupling stronger than the indirect, capacitive cross-coupling created and defined by the internal RF transmission window  1722  between and interconnecting the respective resonators  1116  and  1121  of the respective monoblocks  1101  and  1103  of waveguide filter  1100 . 
       FIG. 4  is a graph which shows the calculated frequency response of the high performance dielectric waveguide filter  1100  which, in the embodiment shown, is comprised of and includes the following performance characteristics: monoblocks  1103  and  1103  each comprised of a high quality C14 ceramic material with a dielectric constant of about 37 or above; monoblocks  1101  and  1103  each being approximately 2 inches in length, 0.5 inches in width, and 1.1 inches in height; a bandwidth up to five percent (5%) of the center frequency; power handling up to two hundred watts (200 W); resonators having a Q in the range between about one thousand to two thousand (1000-2000); insertion loss of about minus two dB (−2 dB); out of band rejection of about minus seventy dB (−70 dB); bandwidth in the range of between about forty to one hundred Megahertz (40-100 MHz); and a center frequency of about two Gigahertz (2 GHz). 
       FIG. 5  is another embodiment of a dielectric waveguide filter  2100  in accordance with the present invention which is identical, in all but one respect as discussed below, to the structure, elements, and function of the dielectric waveguide filter  1100 , and thus the numerals used to designate the various elements of the waveguide filter  1100  in  FIGS. 1-3  have been used to identify and designate the same elements in the waveguide filter  2100  shown in  FIG. 5  and thus the earlier description of the structure and function of each of the elements of the waveguide filter  1100  is incorporated herein by reference and applies to and is repeated herein with respect to each of the elements identified in  FIG. 5  with respect to the waveguide filter  2100  as though such description was fully set forth herein. 
     The waveguide filter  2100  shown in  FIG. 5  differs from the waveguide filter  1100  shown in  FIGS. 1-3  in that the rectangularly shaped indirect or cross-coupling interior or internal capacitive RF signal transmission window or means or coupling  1722  located in the interior of the waveguide filter  1100  between the resonators  1116  and  1121  has been substituted in the waveguide filter  2100  shown in  FIG. 5  with a round or circular shaped indirect or cross-coupling interior or internal capacitive RF signal transmission window or means or coupling  2722  located in the interior of the waveguide filter  2100  between the resonators  1116  and  1121 . 
     In the embodiment shown, the window  2722  comprises a generally round or circular shaped region or portion or patch or pad of the conductive or metal material defining the central interior layer  1150  of conductive material that is surrounded by a generally ring shaped region  2723  which is devoid of conductive material (i.e., a region of dielectric material) that isolates the window or patch of conductive material  2722  from the remainder of the conductive material of the central interior layer  1150  of conductive material and is formed in the region of the central layer  1150  located between the resonators  1116  and  1121 . 
     Thus, and as shown in  FIG. 6 , the window  2722  is defined by respective generally circular shaped regions or portions or patches or pads  2722   a  and  2722   b  of the conductive material on the respective exterior surfaces  1104   a  and  1102   b  of the respective monoblocks  1101  and  1103  that are surrounded by respective ring shaped regions  2723   a  and  2723   b  of the respective exterior surfaces  1104   a  and  1102   b  which are devoid of conductive material (i.e., respective regions of dielectric material) that isolate the respective windows or patches of conductive material  2722   a  and  2722   b  from the remainder of the layer of conductive material covering the respective exterior surfaces  1104   a  and  1102   b . The respective windows  2722   a  and  2722   b  are located on the respective exterior surfaces  1104   a  and  1102   b  of the respective monoblocks  1101  and  1103  in the region of the respective resonators  1116  and  1121 . 
     The windows  2722   a  and  2722   b  are aligned with and connected to each other when the monoblocks  1101  and  1103  are coupled together to define the central layer  1150  of conductive material and the window  2722  therein. 
     In this embodiment, a cross-coupling or indirect capacitive RF signal transmission path c is defined and created by the interior RF signal transmission means or window  2722  located between the resonators  1116  and  1121  which allows for the transmission of a small portion of the direct RF signal being transmitted through the resonator  1116  of the monoblock  1101  directly into the resonator  1121  of the monoblock  1103 . 
     While the invention has been taught with specific reference to the embodiments shown, it is understood that a person of ordinary skill in the art will recognize that changes can be made in form and detail without departing from the spirit and the scope of the invention. The described embodiments are to be considered in all respects only as illustrative and not restrictive. 
     For example, it is understood that the configuration, size, shape, and location of several of the elements of the waveguide filter including, but not limited to, the windows, steps, through-holes, and slits/slots of the waveguide filter may be adjusted depending upon the particular application or desired performance characteristics of the waveguide filter.