Patent Publication Number: US-7898367-B2

Title: Ceramic monoblock filter with metallization pattern providing increased power load handling

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of the filing date of U.S. Provisional Application Ser. No. 60/934,863 filed on Jun. 15, 2007, which is explicitly incorporated herein by reference as are all references cited therein. 
    
    
     FIELD OF THE INVENTION 
     This invention relates to electrical filters and, in particular, to a dielectric ceramic monoblock filter which incorporates a metallization pattern on the top surface thereof adapted and structured to provide an increase in a filter&#39;s power load handling capability. 
     BACKGROUND OF THE INVENTION 
     Ceramic dielectric block filters offer several advantages over air-dielectric cavity filters. The blocks are relatively easy to manufacture, rugged, and relatively compact. In the basic ceramic block filter design, resonators are formed by cylindrical passages called through-holes which extend between opposed top and bottom surfaces of the block. The block is substantially plated with a conductive material (i.e., metallized) on all but one of its six (outer) sides and on the interior walls of the resonator through-holes. 
     The top surface is not fully metallized but instead bears a metallization pattern designed to couple input and output signals through the series of resonators. In some designs, the pattern may extend to the sides of the block, where input/output electrodes or pads are formed. 
     The reactive coupling between adjacent resonators is dictated, at least to some extent, by the physical dimensions of each resonator, by the orientation of each resonator with respect to the other resonators, and by aspects of the top surface metallization pattern. 
     Although such RF signal filters have received widespread commercial acceptance since the 1970s, efforts at improvement on this basic design have continued to the present. 
     For example, there continues to exist a need to increase power-handling capabilities of ceramic filters for higher power applications. Currently, increasing the ceramic body size and/or the top pattern gaps to their maximum is the primary method used to increase the power handling capability of monoblock filters. Increasing the gaps in some cases, however, reduces the electrical performance of the filter and creates manufacturing sensitivity issues. Moreover, and where size and space is a limitation, increasing the size of the ceramic body is not an option. 
     Therefore, the need continues for an improved RF monoblock filter which can offer improved and increased power handling capabilities without either an increase in the size of the filter or an increase in the size of the gaps in the top metallization pattern. 
     SUMMARY OF THE INVENTION 
     It is a feature of the invention to provide a ceramic monoblock filter comprising a block of dielectric material defined by top, bottom, and side surfaces wherein the side and bottom surfaces are substantially covered with a conductive material. 
     A plurality of spaced-apart resonators are defined by a plurality of spaced-apart resonator through-holes extending between the top and bottom surfaces of the block and surrounded on the top surface by conductive material defining conductive resonator plates. A pattern of conductive material on the top surface defines at least an input/output transmission line defined by a first elongate strip of conductive material extending on the top surface between, and spaced from, first and second ones of the plurality of resonators. 
     The pattern additionally defines a bar on the top surface defined by a second strip of conductive material. The bar extends above and is spaced from the resonator plates defining the first and second resonators. The bar is located generally opposite and spaced from a top edge of the input/output transmission line. 
     The pattern still further defines a ground plate defined by one or more additional strips of conductive material on the top surface. The ground plate is coupled to the conductive material covering the side surfaces and is located generally opposite and spaced from the bar. 
     In one embodiment, the ground plate and the bar include respective interdigitated extension strips of conductive material defining a load splitting capacitor between the bar and the ground plate. In one embodiment, the respective interdigitated spaced-apart extension strips are generally spiral-shaped. 
     The input/output transmission line and the bar may additionally define respective interdigitated spaced-apart extension strips of conductive material defining a load splitting capacitor between the bar and the input/output transmission line. 
     Additional load splitting capacitors may be defined by extending terminal end portions of the bar over respective portions of the first and second resonators. 
     There are other advantages and features of this invention, which will be more readily apparent from the following detailed description of preferred embodiments of the invention, the 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 and the accompanying FIGURES as follows: 
         FIG. 1  is an enlarged perspective view of a ceramic monoblock filter incorporating the features of the present invention; 
         FIG. 2  is a top plan view of the top face of a filter incorporating a prior art input port capacitive loading metallization pattern; 
         FIG. 3  is an enlarged top plan view of the metallization pattern on the top surface of the ceramic monoblock filter shown in  FIG. 1 ; 
         FIG. 4  is an enlarged, broken, top plan view of the input port capacitive loading metallization pattern of the filter shown in  FIG. 1 ; 
         FIG. 5  is a schematic of the electrical circuit defined by the input port metallization pattern of the prior art filter shown in  FIG. 2 ; 
         FIG. 6  is a schematic of the electrical circuit defined by the input port metallization pattern of the filter of the present invention shown in  FIGS. 1 and 4 ; 
         FIG. 7  is a graph depicting the power handling characteristics of the prior art filter of  FIG. 2 ; 
         FIG. 8  is a graph depicting the power handling characteristics of the filter of  FIG. 1 ; 
         FIG. 9  is a graph comparing the performance characteristics of the filters of  FIGS. 1 and 2 ; and 
         FIG. 10  is a graph comparing the delay characteristics of the filters of  FIGS. 1 and 2 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     While this invention is susceptible to embodiment in many different forms, this specification and the accompanying FIGURES disclose only one preferred form as an example of the invention. The invention is not intended to be limited to the embodiment so described, however. The scope of the invention is identified in the appended claims. 
       FIGS. 1 ,  3 , and  4  show a preferred embodiment of a filter  100  ( FIGS. 1 ,  3 ) which incorporates the increased and improved power handling metallization pattern features of the present invention. 
     Filter  100  includes a block  110  ( FIG. 1 ) composed of a dielectric material and selectively plated with a conductive material. Block  110  has a top surface or face  112 , a bottom surface (not shown) and four side surfaces or faces  116  ( FIGS. 3 ,  4 ),  117 ,  120  ( FIGS. 1 ,  3 ), and  129  ( FIGS. 3 ,  4 ). Filter  100  can be constructed of a suitable dielectric material that has low loss, a high dielectric constant, and a low temperature coefficient. 
     The plating or material on block  110  is electrically conductive, preferably copper, silver or an alloy thereof. Such plating or material preferably covers all surfaces of the block  110  to define ground with the exception of top surface  112 , the plating of which is described in some detail below. 
     In the embodiment of  FIGS. 1 ,  3 , and  4 , block  110  includes eight ( 8 ) through-holes  101 ,  102 ,  103 ,  104 ,  105 ,  106 ,  107 , and  108  ( 101 - 108 ) as shown in  FIGS. 1 and 3 , each extending from the top surface  112  to the bottom surface (not shown). The interior walls defining through-holes ( 101 - 108 ) are likewise plated with an electrically conductive material. Each of the plated through-holes  101 - 108  is essentially a transmission line resonator/pole comprised of a short-circuited coaxial transmission line having a length selected for desired filter response characteristics. For an additional description of the through-holes  101 - 108 , reference may be made to U.S. Pat. No. 4,431,977, to Sokola et al. Although block  110  is shown with eight plated through-holes  101 - 108 , the present invention is not so limited and encompasses filters with more or fewer through-holes. 
     Top surface  112  of block  110  defines opposed peripheral longitudinal edges  130  and  133 , opposed peripheral side edges  115  ( FIGS. 1 ,  3 ) and  119 , and is selectively plated with an electrically conductive material similar to the plating on block  110 . The selective plating includes and defines respective RF signal input-output (I/O) transmission lines/ pads/plates, specifically input electrode/port/line  114  and output electrode/port/line  118  ( FIGS. 1 ,  3 ). Also included are conductive resonator plates  121 ,  122 ,  123 ,  124 ,  125 ,  126 ,  127 , and  128  ( 121 - 128 ) that surround respective through-holes   101 ,  102 ,  103 ,  104 ,  105 ,  106 ,  107 , and  108  and in combination define respective resonators. Each of the plates  121 ,  122 ,  123 ,  124 ,  125 ,  126 ,  127 , and  128  are separated by regions devoid of conductive material and each defines respective opposed and spaced-apart plate edges such as, for example, as depicted in  FIG. 3  which identifies edge  126 A of plate  126 , edge  127 A of plate  127  and unmetallized region  112 A therebetween. 
     Top surface  112  additionally defines at least four ground plates  131 ,  132 ,  134 , and  135  as shown in  FIG. 3 . Plates  121 - 128  are used to capacitively couple the transmission line resonators, provided by the plated through-holes  101 - 108 , to ground plating or strips  131 ,  132 ,  137 , and  135  which are coupled to the ground material which covers the respective side and bottom surfaces. Portions of plates  121 - 128  also couple the associated resonators of through-holes  101 - 108  to the input electrode  114  and the output electrode  118 . 
     Ground plate or strip  131  is located on the top filter surface  112  and extends along a central portion of the peripheral lower edge of top surface  112  generally longitudinally between the input and output ports  114  and  118 . Opposed terminal ends of plate  131  are spaced from the ports  114  and  118 . Ground plate  132  is also located on the filter top surface  112  and extends generally longitudinally along the lower edge of top surface  112  generally between the edge  115  of side surface  120  and the output port  118 . Plate  132  is spaced from the port  118 . Ground plate  137  is located on the top filter surface  112  and extends along the lower edge of surface  112  generally between the edge  119  of opposed side surface  129  and the input port  114 . Plate  137  is spaced from the port  114 . Ground plate or strip  135  is located on the top surface  112  and extends the full length of the filter along the top longitudinal edge  133  of the filter  100 . 
     Coupling between the transmission line resonators, provided by the plated through-holes  101 - 108 , is accomplished at least in part through the dielectric material of block  110  and is varied by varying the width of the dielectric material and the distance between adjacent transmission line resonators. The width of the dielectric material between adjacent through-holes  101 - 108  can be adjusted in any suitable regular or irregular manner as is known in the art, such as, for example, by the use of slots, cylindrical holes, square or rectangular holes, or irregular-shaped holes. 
     The present invention is directed to the metallization pattern on the top surface  112  of filter  100  and, more specifically, the portion of the metallization pattern in the region of the input pad or port  114  which, as described in more detail below, is adapted to improve input capacitive coupling to ground which, in turn, increases the power load characteristics and abilities of the filter. 
     Referring to  FIGS. 1 and 4 , it is understood that input transmission port or pad or line  114  is defined by an elongate strip of metallized/conductive material which bridges the top and side surfaces  112  and  117  ( FIG. 1 ) respectively. More specifically, input port  114  defines a first portion of a strip of conductive material located on the side surface  117 ; a second strip which wraps around and bridges the edge  130  between side surface  117  and top surface  112 ; and a third elongate strip portion which extends generally between and spaced from the metallized resonator plates  127  and  128 . Input port or pad  114  preferably extends in a relationship spaced from and parallel to the resonator plates  127  and  128  and a relationship generally transverse to the top lower and upper longitudinal filter edges  130  and  133  respectively. 
     As shown in  FIG. 4 , the input pad  114  additionally defines strips of metallized material defining a plurality of fingers  136 ,  138 , and  140  extending generally perpendicularly outwardly from opposed sides of the top portion of input pad  114  extending between respective resonator plates  127  and  128 . Fingers  136 ,  138 , and  140  are interdigitated into (i.e., protrude into) respective grooves  142 ,  144 , and  146  defined in respective resonator plates  127  and  128 . The grooves  142 ,  144 , and  146  of course define regions devoid of metallized material. The fingers  136 ,  138 ,  140  are spaced from the metallized material defining the plates  127  and  128 . 
     The top portion of input pad  114  extending between respective resonator plates  127  and  128  still further defines a central elongate groove  143  defining a fork having at least two tines  145  and  147  extending in a direction generally perpendicular to the upper top longitudinal filter edges  130  and  133 . Groove  143  defines a region devoid of conductive material. 
     The metallization pattern on the input side of the filter  100  is still further defined by an elongate strip or bar  148  ( FIGS. 3 ,  4 ) of metallized conductive material located above the respective resonator plates  127  and  128  and extending in an orientation and placement generally parallel to and spaced from the upper edges of respective resonator plates  127  and  128 . Bar  148  extends in a direction parallel to the lower and upper longitudinal filter edges  130  and  133 . 
     Bar  148  more specifically defines a central portion and respective opposed terminal end portions  150  and  152 . The central portion is located and positioned generally opposite the ends of bar tines  145  and  147 , and the respective end portions  150  and  152  extend and overlap at least about ¼ of the length of the respective resonator plates  127  and  128  in a generally spaced-apart and parallel relationship thereto. Bar  148  is spaced from the top of the plates  127  and  128 . 
     Resonator plate  127  additionally defines a strip or finger or extension  154  of metallized conductive material protruding generally perpendicularly outwardly and upwardly from the top longitudinal edge thereof in a generally transverse relationship to the bar  148  and spaced from the terminal end portion  150  of bar  148 . The resonator plate  128  in turn defines an upper shoulder  156  which is spaced from the opposed terminal end portion  152  of bar  148 . 
     Bar  148  still further defines a generally centrally located elongate first extension or strip or finger  157  of metallized conductive material extending generally perpendicularly outwardly and downwardly from a lower edge of the bar  148 . Extension  157  is interdigitated into (i.e., protrudes into) the elongate groove  143  defined in the top portion of input pad  114 . Extension  157  is spaced from the conductive material defining input pad  114 . 
     Bar  148  still further defines a pair of second and third elongate metallization extensions/strips/fingers  158  and  160  protruding and extending generally perpendicularly upwardly and outwardly from a top longitudinal edge of each of the respective bar terminal end portions  150  and  152 . Bar extensions  158  and  160  are oriented and located relative to each other in a spaced-apart, parallel relationship. A pair of further metallization extensions/strips/fingers  162  and  164  protrude generally normally inwardly from the opposed respective inner edges of bar extensions  158  and  160 . Extensions  162  and  164  define bent, curved, or spiral-shaped fingers. 
     Bar  148  still further defines a plurality of grooves  166 ,  168 , and  170  protruding into the top edge thereof and extending along the length thereof in a generally spaced-apart and parallel relationship. Grooves  166 ,  168 , and  170  define regions devoid of conductive material. 
     The metallization pattern in accordance with the present invention still further comprises a grounded plate extension  172  ( FIG. 3 ) composed of one or more strips or bars or extensions or fingers of metallized material on the top filter surface  112  which protrude unitarily inwardly and outwardly from the grounding plate  135  extending along the top edge  133  of filter  100 . 
     The grounded plate extension  172  is located generally opposite and spaced from the bar  148 . In the embodiment of  FIG. 4 , grounded plate extension  172  is defined by respective strips  174 ,  176 , and  178  of metallized material which in combination define an “I-beam” shaped metallization pattern. Strip  176  is a unitary, integral extension of plate  135 , extends along the top filter edge  133  of filter  100  and preferably has a width greater than the width of the ground plate  135 . Strip  178  is spaced from the strip  176  and is intercoupled thereto by the strip  174  which extends therebetween in a generally transverse relationship. 
     In accordance with the present invention, grounded plate extension  172  and, more specifically, strips  174  and  178  thereof, are spaced and split from the bar  148 . 
     Grounded plate extension  172  is still further defined by a pair of strips, extensions, or fingers of metallized material extending downwardly and inwardly from opposed terminal end portions of the strip  174  and defining respective curved or spiral-shaped terminal fingers  180  and  182  which, in the embodiment shown, are similar in shape and configuration to, but mirror images of, the fingers  162  and  164  defined on bar  148 . 
     Spiral-shaped fingers  162  and  164  and fingers  180  and  182  are respectively meshed/interwoven/interconnected/interdigitated together in a spaced-apart relationship and are separated and surrounded by regions devoid of conductive material so as to define an indirect capacitive coupling between the bar  148  and ground plate  135  as described in more detail below. 
     In the embodiment of  FIG. 4 , grounded plate extension  172  is located generally in the space defined between the fingers  158  and  160  of bar  148  in a relationship wherein the strip  178  of grounded plate extension  172  is spaced from and parallel to the bar  148 ; tabs or fingers  200  on strip  178  are interdigitated into (i.e., protrude into) the respective grooves  166 ,  168 , and  170  defined in bar  148  in a relationship spaced from the conductive material defining the bar  148  and the fingers  180  and  182  of grounded plate extension  172  are spaced from the respective fingers  158  and  160  of bar  148 . Taps  200  extend generally normally outwardly from the strip  178 . 
     Top surface  112  defines an additional strip  202  of conductive material extending normally inwardly from the top ground plate  135 . Strip  202  is located between and spaced from bar extension  160  on one side and the left side edge of resonator plate  128  on the other side. Strip  202  and bar extension  160  are disposed relative to each in a parallel relationship. 
     By way of background, it is known that the power handling of filters is directly related to the component with the greatest increase in stored energy. In ceramic monoblock filters, the circuit pattern incorporated onto the ceramic block forms capacitors to ground and capacitors between resonators. The capacitors with the most stored energy are the components with the greatest likelihood of arcing from high power. The input pad metallization pattern of the present invention increases the power handling of ceramic monoblock filters by modifying the components with the greatest chance of arcing. This is done by splitting the stored energy among two or more series connected capacitors. 
     Illustration A below shows a 1 Farad capacitor with 1 volt applied. In this example, the stored energy “E” is equal to the ½ CV 2  where C corresponds to capacitance and V corresponds to voltage. This calculates to (½)*(1F)*(1V)=½ Joule. If the circuit of Illustration A is changed to the equivalent electrical circuit shown in Illustration B, the arcing potential is reduced. 
     Illustration A 
     
       
         
         
             
             
         
       
     
     In Illustration B below, the total stored energy in the circuit is still ½ Joule. However, the stored energy in each of the capacitors (C 1  and C 2 ) is equal to ½ C 1  *V 1   2 =½ C 2 *V 2   2  where C 1  and C 2  corresponds to capacitance and V 1  and V 2  corresponds to voltage. This calculates to (½)*(2F)*(½) 2 =¼ Joule. Each capacitor now has ½ the stored energy of the Illustration A capacitor. Note that the stored energy is related to the squared voltage (V 2 ). In electromagnetic theory, the electric field strength is directly related to the voltage. Arcing occurs when the electric field strength increases such that the breakdown voltage of air (29000V/cm) is exceeded, creating a conductive path between the two metallic plates of the capacitor. The breakdown of air has units of volts-per-centimeter which, of course, means that the spacing of the capacitive plates is an important variable in arcing. As the capacitive plates are moved closer together, the probability of arcing increases. 
     Illustration B 
     
       
         
         
             
             
         
       
     
     The Illustration B capacitive values are greater than the Illustration A capacitor value. The larger the capacitive value, the closer the metallic plates have to be located. This decreases the power handling. However, where space permits on the monoblock filter, the plate&#39;s surface area can be increased to maintain the desired capacitive value and still keep the wider plate spacing. The wide plate spacing in combination with the lower capacitive stored energy can increase the power handling of a filter. 
     In accordance with the present invention and referring to  FIGS. 4 and 6  in particular, it is understood that input transmission line or port  114 , resonators  127  and  128 , and grounded plate extension  172  ( FIG. 4 ) in combination define multiple sources of capacitive loading to the input transmission line or port  114  via the power load distribution bar  148 . More specifically, it is understood that the polarity of ground extension plate  172  is negative and that the polarity of the input pad  114  is positive. When a load is applied to the filter  100 , the polarity of the metallization pattern defining bar  148  will change to positive. Because the bar  148  is capacitively loaded to multiple sources as described above, the effect is the same as directly loading the input to ground as is known in the art and shown in the input port metallization pattern  302  of the prior art filter  300  shown in  FIG. 2  and briefly described below. 
     Filter  300  shown in  FIG. 2  includes a block  310  composed of a dielectric material and selectively plated with a conductive material. Block  310  has a top surface or face  312 , a bottom surface (not shown) and four side surfaces or faces  316 ,  317 ,  320 , and  329 . Filter  300  can be constructed of a suitable dielectric material that has low loss, a high dielectric constant, and a low temperature coefficient. 
     The plating or material on block  310  is electrically conductive, preferably copper, silver or an alloy thereof. Such plating or material preferably covers all surfaces of the block  310  to define ground with the exception of top surface  312 , the plating of which is described in some detail below. 
     The block  310  includes eight ( 8 ) through-holes including through-holes  307  and  308 , each extending from the top surface  312  to the bottom surface (not shown). The interior walls defining each of the through-holes including through-holes  307  and  308  are likewise plated with an electrically conductive material and serve the same purpose as the through-holes  101 - 108  of filter  100 . 
     Top surface  312  of block  310  defines respective RF signal input-output (I/O) transmission lines/pads/plates including specifically an input electrode/port/line  314 . Also included on the top surface  312  are a plurality of conductive resonator plates that surround the respective through-holes. Plates  327  and  328  surround the through-holes  307  and  308  and in combination define respective resonators. Each of the plates, including the plates  327  and  328 , are separated by regions devoid of conductive material. Top surface  312  additionally defines at least three ground plates  331 ,  335 , and  337  similar in placement and purpose to the ground plates  131 ,  135 , and  137  on the top surface  112  of filter  100 . 
     Input transmission port or pad or line  314  is defined by an elongate strip of metallized/conductive material  334  which bridges the top and side surfaces  312  and  317  respectively and extends on the top surface  312  generally between and spaced from the metallized resonator plates  327  and  328 . The input pad  314  additionally defines a strip of metallized material defining a finger  338  extending generally normally outwardly from one of the sides of the input pad  314 . Finger  338  is interdigitated into (i.e., protrudes into) a groove  344  defined in the resonator plate  327 . Groove  344  defines a region devoid of metallized material and finger  338  is spaced from the metallized material defining the plate  327 . 
     The top portion of input pad  314  still further defines a central elongate groove  343  devoid of conductive material and defining a fork having at least two tines  345  and  347 . 
     The top surface  312  of filter  300  also includes a ground plate extension  372  of metallized material which extends unitarily outwardly from the ground plate  335 , is located generally opposite and spaced from the input transmission pad  314 , and is defined by respective strips of metallized material  374  and  376 . Strip  376  is a unitary, integral extension of the strip  335 . Strip  374  extends downwardly from the strip  376  between the resonator plates  327  and  328  and into the groove  343  in the input pad  314 . 
       FIG. 5  is a schematic diagram of the electrical methodology and circuit of the input metallization pattern  302  of the prior art filter  300  shown in  FIG. 2  and thus the reference numerals identified in  FIG. 5  correspond to like reference numerals identified in  FIG. 2  with the exception of the reference numerals  401 ,  402 ,  403 ,  404 , and  410  in  FIG. 5  and are not further described herein which identify the respective capacitors defined by the input metallization pattern  302  of filter  300 .  FIG. 6  is a schematic diagram of the splitting electrical methodology and circuit of the input metallization pattern of the filter  100  of the present invention as shown in  FIGS. 3 and 4  and thus the reference numerals identified in  FIG. 6  correspond to like reference numerals identified in  FIGS. 3 and 4  and are not further described herein with the exception of the reference numerals  210 ,  212 ,  214  and  216  and, more specifically, the reference numerals  212 ,  214  and  216  which identify the power load splitting capacitors defined by the filter  100  of the present invention. 
     The metallization pattern in accordance with the present invention, however, affords the advantage of facilitating the distribution of the power load over the full length of the bar  148 , thus increasing the amount of power load which the filter can handle. 
     Specifically, and still with reference to  FIGS. 4 and 6  in particular, it is understood that, in accordance with the principles shown in Illustration B: downward extension  157  ( FIG. 4 ) of bar  148  ( FIGS. 4 ,  6 ) defines a capacitor  210  ( FIG. 6 ) between bar  148  and input port  114  ( FIGS. 4 ,  6 ) for splitting the power load between bar  148  and input port  114 ; terminal end portions  150  ( FIGS. 4 ,  6 ) and  152  ( FIGS. 4 ,  6 ) of bar  148  extend and overlie portions of respective resonator plates  127  ( FIGS. 4 ,  6 ) and  128  ( FIGS. 4 ,  6 ) to define additional respective capacitors  212  ( FIGS. 6) and 214  ( FIG. 6 ) between the bar  148  and resonator plates  127  and  128  for splitting the load between the respective resonator plates  127  and  128 ; and extensions  158  ( FIGS. 4 ,  6 ) and  160  ( FIGS. 4 ,  6 ) of bar  148  in combination with ground plate extension  172  ( FIGS. 4 ,  6 ) define an additional capacitor  216  ( FIG. 6 ) which splits the load between the input port  114  and ground plate  135  ( FIGS. 4 ,  6 ). 
     In accordance with a preferred embodiment of the metallization pattern of the present invention, the distance, generally designated X in  FIG. 4  between the finger  154  ( FIGS. 4 ,  6 ) on resonator plate  127  and the terminal edge  150  ( FIGS. 4 ,  6 ) of bar  148  is about 0.007 inches; the distance generally designated Y in  FIG. 4 , between the ground bar  178  ( FIGS. 4 ,  6 ) and the power load distribution bar  148  is also preferably about 0.007 inches; and the distance, generally designated Z in  FIG. 4 , between the ground bar  178  and the top terminal edge of input transmission port  114  is preferably about 0.03 inches. 
       FIGS. 7 and 8  in combination illustrate that the metallization pattern in accordance with the present invention has been shown to provide an increase in the filter power level from a reference power level of about 46 dBm and an actual power level of about 47 dBm/50 watts (as shown in  FIG. 7  for the  FIG. 2  prior art filter) to a reference power level of about 48 dBm and an actual power level of about 49 dBm/79 watts (as shown in  FIG. 8  for the  FIG. 1  filter) before there is a catastrophic failure. 
       FIG. 9  in turn illustrates that the metallization pattern in accordance with the present invention has also been shown to create a filter exhibiting “in band” performance characteristics similar to the prior art filter of  FIG. 2  while, however, providing increased “out of band” rejection resulting from heavier loading to ground and source splitting via the bar  148 . Line  400  in  FIG. 9  represents the performance of the filter shown in  FIG. 2 . Line  402  in  FIG. 9  represents the performance of the filter of the present invention. 
       FIG. 10  illustrates that the metallization pattern in accordance with the present invention not only allows the filter to handle increased power loads but also additionally advantageously causes an increase in the delay experienced by the filter  100  thus, of course, allowing the filter  100  to handle a higher power load for a longer period of time. Lines  500  in  FIG. 10  represent the performance of the filter shown in  FIG. 2 . Lines  502  in  FIG. 10  represent the performance of the filter of the present invention. 
     Numerous variations and modifications of the embodiment described above may be effected without departing from the spirit and scope of the novel features of the invention. No limitations with respect to the specific module illustrated herein are intended or should be inferred.