Patent Publication Number: US-10333191-B2

Title: Ceramic block RF filter having a first plurality of through-hole resonators and a second plurality of through-holes for blocking RF signal coupling

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This patent application claims priority and benefit of the filing date of U.S. Provisional Patent Application Ser. No. 62/399,018 filed on Sep. 23, 2016, the disclosure and contents of which are expressly incorporated herein in its entirety by reference. 
    
    
     TECHNICAL FIELD 
     This invention relates to a radio-frequency (RF) filter and, more specifically, to a ceramic monoblock RF filter with grounded through-holes in the filter block unwanted RF signal coupling and provide additional RF signal rejection outside of the bandwidth of the RF filter without an increase in the length or size of the filter. 
     BACKGROUND OF THE INVENTION 
     Ceramic monoblock radio-frequency (RF) filters provide for the attenuation/rejection of RF signals with frequencies outside of a particular frequency range or band and little rejection/attenuation to RF signals with frequencies within a particular range or band of interest. 
     These filters most typically take the form of a six sided block of ceramic material having a plurality of resonators/poles in the form of through-holes extending through the interior of the block and terminating in openings in the opposed top and bottom surfaces or sides of the block such as, for example, as shown in U.S. Pat. No. 4,431,977 to Sokola et al. and U.S. Pat. No. 4,692,726 to Green et al, the disclosures and descriptions of which are incorporated herein by reference. 
     The bandpass of such a ceramic monoblock filter can be designed for specific bandpass requirements. Typically, the tighter or narrower the bandpass, the higher the insertion loss becomes, i.e., an important electrical parameter. A wider bandwidth, however, reduces the filter&#39;s capacity to attenuate/reject unwanted frequencies, i.e., frequencies which are known in the art as rejection frequencies. 
     Moreover, the reactive RF signal coupling between adjacent and non-adjacent resonators, and thus the level of rejection outside of a bandwidth and performance of such filters is dictated at least to some extent by the physical dimensions of each resonator, by the orientation and location of the resonators relative to each other, and by aspects of the top metallization pattern that is applied to the top surface or side of the block of the filter. Interactions of the electric and electromagnetic fields within and around the resonators and the block are complex and difficult to predict. 
     Currently, increased levels of rejection of the RF signal outside of a filter&#39;s bandwidth and thus improved filter performance can be achieved by adding resonators to the ends of the block. Increasing the length or size of the block however is not desirable in applications where space is limited on, for example, a customer&#39;s motherboard. 
     The present invention is directed to a ceramic monoblock RF filter providing increased levels of rejection outside of a filter&#39;s bandwidth and increased performance through the use of structure which in one embodiment comprises grounded RF signal blocking through-holes located and positioned in the filter in a manner that blocks unwanted RF signal coupling between resonators but does not require an increase in the length or size of the RF filter. 
     SUMMARY OF THE INVENTION 
     The present invention relates generally to an RF filter for the transmission of an RF signal comprising a block of dielectric material including opposed top and bottom surfaces, opposed longitudinal side surfaces, and opposed transverse side surfaces, at least first and second RF signal input/outputs defined on the block of dielectric material, a first plurality of resonators defined on the block of dielectric material, and means on the block of dielectric material for blocking the coupling of the RF signal between the first and/or second RF signal input/outputs and respective ones of the first plurality of resonators or between respective non-adjacent ones of the first plurality of resonators. 
     In one embodiment, the first plurality of resonators comprise a first plurality of through-hole resonators extending through the block of dielectric material and terminating in respective openings in the top and bottom surfaces of the block of dielectric material, the means for blocking the coupling of the RF signal comprising one or more grounded RF signal blocking through-holes extending through the block of dielectric material and terminating in respective openings in the top and bottom surfaces of the block of dielectric material and located in a relationship spaced and off-set from one or more of the first plurality of through-hole resonators. 
     In one embodiment, the one or more RF signal blocking through-holes are located between and spaced from the first plurality of through-hole resonators and the respective opposed longitudinal side surfaces. 
     In one embodiment, a plurality of RF signal blocking through-holes are located on opposed sides of and spaced from the first plurality of through-hole resonators. 
     The present invention is also directed to an RF filter for the transmission of an RF signal comprising a block of dielectric material including opposed top and bottom surfaces, opposed longitudinal side surfaces, and opposed transverse side surfaces, a first plurality of through-holes extending through the block and terminating in respective openings in the top and bottom surfaces of the block and defining a first plurality of through-hole resonators, and a second plurality of through-holes extending through the block and terminating in respective openings in the top and bottom surfaces of the block, the second plurality of through-holes being located and positioned relative to the first plurality of through-holes for blocking the coupling of the RF signal between selected ones of the first plurality of through-hole resonators. 
     In one embodiment, the second plurality of through-holes are positioned on the block of dielectric material in a relationship spaced and off-set from the first plurality of through-holes. 
     In one embodiment, the openings of the respective first and second plurality of through-holes defined in the top and bottom surfaces of the block of dielectric material are surrounded by pads of metallization and a layer of metallization respectively and the interior surface of the respective first and second plurality of through-holes are covered with a layer of metallization to define the first plurality of through-hole resonators and the second plurality of through-holes defining a second plurality of grounded through-holes. 
     The present invention is further directed to an RF filter for the transmission of an RF signal comprising a block of dielectric material including opposed top and bottom surfaces, opposed longitudinal side surfaces, and opposed transverse side surfaces, first, second, and third RF signal input/outputs defined on the block of dielectric material, a first plurality of through-holes extending through the block and terminating in respective openings in the top and bottom surfaces of the block and defining a first plurality of through-hole resonators, and a second plurality of grounded through-holes extending through the block and terminating in respective openings in the top and bottom surfaces of the block, the second plurality of through-holes being located and positioned on opposite sides of and spaced from the first plurality of through-holes and further in a relationship off-set from the first plurality of through-holes for blocking the coupling of the RF signal between non-adjacent ones of the first plurality of through-hole resonators and between the first, second, and/or third RF signal input/outputs and selected ones of the first plurality of through-hole resonators. 
     In one embodiment, a first one of the second plurality of grounded through-holes is positioned adjacent the first RF signal input/output and between first and second ones of the first plurality of through-hole resonators for blocking the coupling of the RF signal between the first RF signal input/output and the first one and a third one of first plurality of through-hole resonators. 
     In one embodiment, a second one of the second plurality of grounded through-holes is positioned between the third one and a fourth one of the first plurality of through-hole resonators for blocking the coupling of the RF signal between the second one and a fourth one of the first plurality of through-hole resonators. 
     In one embodiment, a third one of the second plurality of grounded through-holes is positioned adjacent to the second RF signal input/output and between the fifth and a sixth one of the first plurality of through-hole resonators for blocking the coupling of the RF signal between the fifth one of the first plurality of through-hole resonators and the second RF signal input/output. 
     In one embodiment, a fourth one of the second plurality of grounded through-holes is positioned between the third and fourth ones of the first plurality of through-holes resonators for blocking the coupling of the RF signal between the third one and the fifth one of the first plurality of through-hole resonators. 
     In one embodiment, a fifth one of the second plurality of grounded through-holes is positioned between the sixth one and a seventh one of the first plurality of through-hole resonators for blocking the coupling of the RF signal between the sixth one and the seventh one of the first plurality of through-hole resonators. 
     In one embodiment, a sixth one of the second plurality of grounded through-holes is positioned adjacent the second RF signal input/output for blocking the coupling of the RF signal between the seventh one and an eight one of the first plurality of through-hole resonators. 
     In one embodiment, a seventh one of the second plurality of grounded through-holes is positioned adjacent the third RF signal input/output and between eleventh and twelfth ones of the first plurality of through-hole resonators for blocking the coupling of the RF signal between the third RF signal input/output and the eleventh one of the first plurality of through-hole resonators. 
     There are other advantages and features of this invention, which will be more readily apparent from the following detailed description of the embodiment of the invention, the drawings, and the appended claims. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
       In the accompanying drawings that form part of the specification, and in which like numerals are employed to designate like parts throughout the same: 
         FIG. 1  is a perspective view of a ceramic monoblock filter in accordance with the present invention; 
         FIG. 2  is a plan view of the top surface of the ceramic monoblock RF filter shown in  FIG. 1 ; 
         FIG. 3  is a plan view of the bottom surface of the ceramic monoblock RF filter shown in  FIG. 1 ; and 
         FIG. 4  is a graph depicting the performance of the ceramic monoblock RF filter as a function of Frequency (MHz) and Insertion Loss (dB) in accordance with the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENT 
       FIGS. 1, 2, and 3  depict a ceramic monoblock radio-frequency (RF) filter  100 , and more specifically a duplexer RF filter, in accordance with the present invention that includes an elongate, parallelepiped (or “box shaped”) solid core or body or monoblock  130  composed of ceramic dielectric material and including three sets of opposing side surfaces: a top longitudinal surface  132  ( FIGS. 1 and 2 ), a bottom longitudinal surface  133  ( FIGS. 1 and 3 ) opposed, spaced, and parallel to the top surface  132 ; opposing, spaced apart, and parallel long or longitudinally extending sides or surfaces  134  and  136 ; and opposed short or transversely extending sides or surfaces  138  and  140 . The interface between the sides  134 ,  136 ,  138 , and  140  define four vertical, parallel, and spaced apart edges extending between the top surface  132  and the bottom surface  133 . The core  130  has a length, a width, and a height. 
     The core  130  defines a first plurality of generally cylindrically shaped and generally centrally located through-hole passageways or through-holes  150 A,  150 B,  150 C,  150 D,  150 E,  150 F,  150 G,  150 H,  150 I,  150 J,  150 K,  150 L,  150 M and  150 N which extend between, and terminating in, openings in the top surface  132  and openings in the bottom surface  133 . In the embodiment shown, the through-hole passageways  150 A- 150 N are generally centrally located on the core  130 ; extend along and in the same direction as the longitudinal central axis L ( FIG. 2 ) of the core  130  in a spaced apart relationship between the transverse sides  138  and  140 ; and are spaced from and generally parallel to and located between the opposed longitudinal sides  134  and  136 . 
     In accordance with the present invention, the core  130  additionally defines a second plurality of generally cylindrically shaped through-hole passageways or through-holes  160 A,  160 B,  160 C,  160 D,  160 E,  160 F and  160 G also extending between, and terminating in, openings in the top surface  132  and openings in the bottom surface  133  respectively. 
     In the embodiment shown, the through-hole passageways  160 A,  160 B,  160 C,  160 D, and  160 G extend in a spaced apart and generally co-linear relationship in the same direction as the core longitudinal axis L and more specifically extend along and spaced from and adjacent to the longitudinal side  134  and still more specifically extend between and spaced from and generally parallel to the central longitudinal axis L and the longitudinal side  134  and, yet still more specifically, between and spaced from the through-hole passageways  150 A- 150 N and the longitudinal side  134 . 
     Further, in the embodiment shown, the through-hole passageways  160 E and  160 F extend in a spaced apart and generally co-linear relationship in the same direction as the core longitudinal axis L and more specifically extend along and spaced from and adjacent to and spaced from the opposed longitudinal side  136  and still more specifically extend between and spaced from and generally parallel to the central longitudinal axis L and the longitudinal side  136  and yet still more specifically, between and spaced from the through-hole passageways  150 A- 150 N and the longitudinal side  136 . 
     Thus, in the embodiment shown, the plurality of through-hole passageways  160 A,  160 B,  160 C,  160 D, and  160 G and the plurality of through-hole passageways  160 E and  160 F are respectively located on opposite sides of and spaced from and generally parallel to and offset from the core central longitudinal axis L and further in a relationship spaced from and on opposite sides of and offset from and parallel to the plurality of central trough-hole passageways  150 A- 150 N. 
     Still further, in the embodiment shown in  FIGS. 1 and 2 , the through-hole passageway  160 A is positioned adjacent and to the right of the RF signal input/output port  190 A, between RF signal input/output ports  190 A and  190 B, and further is located and positioned in the longitudinal direction and orientation between and off-set from the through-hole passageways  150 B and  150 C; the through-hole passageway  160 B is located and positioned between the RF signal input/output ports  190 A and  1906  and further is located and positioned in the longitudinal direction and orientation between and offset from the through-hole passageways  150 D and  150 E; the through-hole passageway  160 C is located and positioned adjacent and to the left of the RF signal input/output port  1906 , between and spaced from the RF signal input/output ports  190 A and  1906 , and further is located and positioned in the longitudinal direction and orientation between and off-set from the through-hole passageways  150 F and  150 G; and the through-hole passageway  160 D is located and positioned adjacent and to the right of the RF signal input/output port  1906 , between and spaced from the input/output ports  190   b  and  190 C, and further is located and positioned in the longitudinal direction and orientation between and off-set from the through-hole passageways  150 G and  150 H. 
     Moreover, the through-hole passageway  160 E is positioned and located between and spaced from the RF signal input/output ports  190 A and  1906  and further is located and positioned in the longitudinal direction and orientation between and off-set from the through-hole passageways  150 D and  150 E; the through-hole passageway  160 F is positioned and located opposite and spaced from the input/output port  1906  and further is located and positioned in the longitudinal direction and orientation between and spaced from the through-hole passageways  150 G and  150 H; and the through-hole passageway  160 G is locates adjacent and to the left of the input/output port  190 C, between and spaced from the RF signal input/output ports  190 B and  190 C, and further is located and positioned in the longitudinal direction and orientation between and off-set from the through-hole passageways  150 L and  150 M. 
     The core  130  is rigid and is preferably made of a ceramic material selected for mechanical strength, dielectric properties, plating compatibility, and cost. 
     The filter  100  includes a pattern of metallized and unmetallized areas or regions and, more specifically, an expansive area or region of metallization on the top surface  132  that defines the respective input/output ports or pads  190 A,  1906  and  190 C and includes respective portions extending from the top surface  132  onto the side surface  134 . The pattern on the top surface  132  additionally defines respective pads or regions of metallization  170  surrounding each of the plurality of through-hole passageways  150 A- 150 N and further respective additional strips or regions of metallization  174  and  176  extending along the side  134  and into the expansive area or region of metallization  162  covering the side  134  and also a strip or region of metallization  178  extending along the opposed side  136  and into the expansive area or region of metallization  162  covering the side  136 . 
     In the embodiment shown in  FIGS. 1 and 2 , the through-hole passageways  160 A,  160 B, and  160 C are located in the metallized region  174 ; the through-hole passageways  160 E and  160 F are located in the metallized region  176 ; and the through-hole passageways  160 D and  160 G are located in the metallized region  178 . 
     Thus, the expansive metallized area covers portions of the top surface  132  and side surface  134  and substantially all of the side surfaces  136 ,  138 , and  140  and the bottom surface  133  in  FIGS. 1 and 3  and the interior sidewalls or surfaces of the plurality of through-hole passageways  150 A- 150 M and  160 A- 160 G. The expansive metallized area extends contiguously from within the interior surface of the plurality of through-hole passageways  150 A- 150 M and  160 A- 160 G towards both the top surface  132  and bottom surface  133  to define and serve as local electrical ground. 
     In particular, the metallized area extending contiguously from within the interior surface of the plurality of through-hole passageways  160 A- 160 G towards and in contiguous electrical coupling relationship with the respective metallization areas  174 ,  176 , and  178  ( FIG. 1 ) in the top surface  132  that surround the top openings of the respective through-hole passageways  160 A- 160 G and the metallization on the bottom surface  133  that surrounds the bottom openings of the respective through-hole passageways  160 A- 160 G define and form respective electrically grounded or ground through-hole passageways  160 A- 160 G. 
     The core  130 , the pattern of metallized and unmetallized regions or areas including the respective regions or pads of metallization on the top surface  132 , and the plurality of through-hole passageways  150 A- 150 M together form and define a series of through-hole resonators  180 A,  180 B,  180 C,  180 D,  180 E,  180 F,  180 G,  180 H,  180 I,  180 J,  180 K,  180 L,  180 M and  180 N for the transmission of an RF signal through the duplexer RF filter  100  including, for example, the transmission of a transmit RF signal that is inputted through the RF signal input/output port  190 A, travels and is filtered through respective through-hole resonators  180 A- 180 G and is outputted through the antenna RF signal input/output port  1906  and an RF signal that is received through the antenna RF signal input/output port  1906 , travels and is filtered through respective through-hole resonators  180 M- 180 H and is outputted through the RF signal input/output port  190 C. 
     Thus, in the embodiment shown, the through-hole resonator  180 A is located on the block  130  between the transverse side surface  138  and the first RF signal input/output pad  190 A; the through-hole resonators  180 B- 180 G and the grounded through-holes  160 A,  160 B,  160 C, and  160 E are located on the block  130  between the first end RF signal input/output pad  190   a  and the second center RF signal antenna input/output pad  190 B; the grounded through-hole  160 F is located on the block  130  opposite the RF signal antenna input/output pad  190 B; the through-hole resonators  180 H- 180 L and the grounded through-hole  160 G are located between the second RF signal antenna input/output pad  1906  and the third end RF signal input/output pad  190 C; the through-hole resonator  180 M is located on the block  130  opposite the third end RF signal input/output pad  190 C; and the through-hole resonator  180 N is located on the block  30  between the third end RF signal input/output pad  190   c  and the transverse side surface  140  of the block  30 . 
     In accordance with the present invention, the addition of the grounded through-hole passageways  160 A- 160 G advantageously creates additional electrical capacitors and define means or structures on the block  130  and the filter  100  that block unwanted electric coupling between the input/output ports  190 A,  1906 , and  190 C and selected ones of the through-hole resonators  180 A- 180 N and also unwanted electromagnetic couplings between non-adjacent selected ones of the plurality of through-hole resonators  180 A- 180 N which in turn provides and allows for an added or increased levels of rejection of the RF signal outside of the high and low bandpass of the filter  100  which in turn provides and allows for increased filter performance without adding resonators to the ends of the filter  100  and increasing the length or size of the filter  100 . 
     More specifically, in the embodiment shown in  FIGS. 1 and 2 , the grounded through-hole passageway  160 A blocks the direct electrical coupling and transmission of the RF signal between the RF signal input/output port  190 A and the through-hole resonator  180 C and also block the direct electromagnetic coupling and transmission of the RF signal between non-adjacent through-hole resonators  180 B and  180 D (i.e., the through-hole passageway  160 A prevents the RF signal from bypassing the adjacent through-hole resonator  180 C); the grounded through-hole passageway  160 B blocks the direct electromagnetic coupling and transmission of the RF signal between non-adjacent through-hole resonators  180 C and  180 E (i.e., the grounded through-hole passageway  160 B prevents the RF signal from bypassing the adjacent through-hole resonator  180 D); the grounded through-hole passageway  160 E blocks the direct electromagnetic coupling and transmission of the RF signal between non-adjacent through-hole resonators  180 D and  180 F (i.e., the grounded through-hole passageway  160 E prevents the RF signal from bypassing the adjacent through-hole resonator  180 E); and the grounded trough-hole passageway  160 C blocks the direct electrical coupling and transmission of the RF signal between the through-hole resonator  180 F and the RF signal antenna input/output port  190 B (i.e., the through-hole passageway  160 C prevents the RF signal from bypassing the adjacent through-hole resonator  180 G). 
     Moreover, the grounded through-hole passageway  160 D blocks the direct electrical coupling and transmission of the RF signal between the RF signal input/output port  190 B and the through-hole resonator  180 I (i.e., the through-hole passageway  160 D prevents the RF signal from bypassing the through-hole resonator  180 H); and the grounded through-hole passageway  160 G blocks the direct and electrical coupling and transmission of the RF signal between the through-hole resonator  180 L and the RF signal input/output port  190 C (i.e., the through-hole passageway  160 G prevents the RF signal from bypassing the adjacent resonator  180 M). 
       FIG. 4  depicts the improved performance of the ceramic RF filter  100  in accordance with the present invention. More specifically, the dotted line generally designated with the numeral  200 A in  FIG. 4  depicts the high band performance of an RF filter without the grounded RF signal blocking through-holes of the present invention while the solid line generally designated with the numeral  300 A in  FIG. 4  depicts the improved high band performance and increased levels of rejection of the RF signal outside of the high band of the duplexer RF filter  100  incorporating the grounded RF signal blocking through-holes  160 A- 160 G in accordance with the present invention. 
     Further, the dotted line generally designated with the numeral  200 B in  FIG. 4  depicts the low band performance of an RF filter without the grounded RF signal blocking through-holes of the present invention while the solid line generally designated with the numeral  300 B in  FIG. 4  depicts the improved low band performance and increased levels of rejection of the RF signal outside of the low band of the duplexer RF filter  100  incorporating the grounded RF signal blocking through-holes  160 A- 160 G in accordance with the present invention 
     Numerous variations and modifications of the ceramic monoblock RF filter of the present invention may be effected without departing from the spirit and scope of the novel features of the invention. 
     It is also to be understood that no limitations with respect to the embodiment illustrated herein are intended or should be inferred. It is, of course, intended to cover by the appended claims all such modifications as fall within the scope of the claims. 
     For example, it is understood that the present invention extends to a structure or means other than the grounded RF signal blocking through-hole passageways  160 A- 160 G for blocking unwanted RF signal coupling including, for example slits or slots covered with metallization and extending between the top and bottom surfaces  132  and  133  of the filter  100 .