Cavity Filter

Abstract

To provide a cavity filter which is easily manufactured and of which the capacitive cross-coupling design is easily performed.SOLUTION: A cavity filter includes: a cavity at one side and a cavity at the other side that require capacitive cross-coupling design; resonance rods respectively provided in the cavity at the one side and the cavity at the other side; a vertical post extended from any one of the resonance rods to be disposed and extended vertically upward and downward within an inner wall that is a boundary between the cavity at the one side and the cavity at the other side; a horizontal part mediating coupling of the vertical post and the resonant bars; and a filter upper cover which performs covering so as to cover opened upper parts of the cavity at the one side and the cavity at the other side. An upper part of the vertical post is in contact with a bottom face of the filter upper cover in the range of assembly tolerance. A lower end of the horizontal part is separated from bottom faces of the cavity at the one side and the cavity at the other side by a predetermined distance.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a cavity filter and a manufacturing method thereof, and more particularly to a cavity filter which is easy to manufacture and in which transmission zero point design by coupling is easy, and a manufacturing method thereof. [Background technology]

[0002] Generally, in order to improve the attenuation characteristics of the stopband of a Band Pass Filter (BPF), a transmission-zero design is used that uses electric or magnetic coupling or mixed coupling between non-adjacent odd number (cascaded triplet) or even number (cascaded quardruplet) of resonant elements.

[0003] Cross coupling across an even number of resonant elements generally results in symmetrical transmission zeros in the filter passband, whereas cross coupling across an odd number of resonant elements generally results in one transmission zero on the left or right side of the passband depending on the type of coupling (i.e., electric or magnetic coupling).

[0004] Using electric coupling, the left or right side of the passband The transmission zeros that occur symmetrically on the left and right are called capacitive cross-coupling, and the transmission zeros that occur on the right side of the passband using magnetic coupling are called inductive cross-coupling.

[0005] The common method used to realize the capacitive cross-coupling of cavity filters is to insert components that maximize the electric field coupling of the two components of coupling. In the case of ultra-miniature cavity filters, the components here are realized by PCB type and the recently developed and used Notch R / B type. Summary of the Invention [Problem to be solved by the invention]

[0006] An object of the present invention is to provide a cavity filter that is easy to manufacture and a method for manufacturing the same.

[0007] Another object of the present invention is to provide a cavity filter designed to suppress magnetic field coupling and to excite electric field coupling relatively strongly, and a manufacturing method thereof.

[0008] Another object of the present invention is to provide a cavity filter including a vertical post formed integrally with a resonator bar without a separate component for maximizing electric field coupling, and a method for manufacturing the same. The technical problems of the present invention are not limited to the technical problems mentioned above, and other technical problems not mentioned will be clearly understood by those skilled in the art from the following description. [Means for solving the problem]

[0009] One embodiment of the cavity filter according to the present invention requires a capacitive cross-coupling design. a notch vertical post extending from one of the resonating rods and vertically extending up and down within an inner wall that is a boundary between the one-side cavity and the other-side cavity, and the notch vertical post and one of the resonating rods connected to the notch vertical post are integrally formed.

[0010] Here, the resonator may further include a horizontal portion mediating a connection between the notch vertical post and the resonator rod, the horizontal portion being integrally formed with the notch vertical post.

[0011] The resonator rod, the notch vertical post and the horizontal portion are integrally injection molded and then partially cut away to form the resonator rod, the vertical post and the horizontal portion.

[0012] The filter may further include a filter upper cover for covering the open upper portions of the one-side cavity and the other-side cavity, and an upper portion of the notch vertical post may contact a lower surface of the filter upper cover within an assembly tolerance.

[0013] In addition, from the moment that the distance between the upper end of the notch vertical post and the filter upper cover goes outside the assembly tolerance range, the one-side cavity and the other-side cavity are coupled by inductive cross-coupling instead of capacitive cross-coupling, so that the frequency filtering characteristics can be inverted.

[0014] The separation distance is set to less than 0.1 mm.

[0015] In addition, a lower end of the horizontal portion including a lower end of the notch vertical post may be spaced apart from the bottom surfaces of the one-side cavity and the other-side cavity by a predetermined distance.

[0016] In addition, when the lower end of the horizontal part including the lower end of the vertical post for notch comes into contact with the bottom surfaces of the one-side cavity and the other-side cavity, the one-side cavity and the other-side cavity are coupled by inductive cross coupling instead of capacitive cross coupling, and from the moment when the lower end of the horizontal part including the lower end of the vertical post for notch is separated from the bottom surfaces of the one-side cavity and the other-side cavity, the phase value is inverted to a negative (negative) value and coupled by capacitive cross coupling.

[0017] In addition, as the distance between the lower end of the horizontal portion including the lower end of the notch vertical post and the bottom surface of the one-side cavity and the other-side cavity increases, the coupling bandwidth of the capacitive cross-coupling becomes larger.

[0018] In addition, the vertical post for the notch is formed in a rod or bar shape having a circular or polygonal horizontal cross section, and the horizontal portion is formed in a square bar shape having a width corresponding to the outer diameter of the vertical post for the notch and forming a predetermined thickness on the top and bottom.

[0019] In addition, a spacing adjustment post is further formed integrally with the notch vertical post so as to extend a predetermined length toward the unconnected resonator rods among the resonator rods involved in the capacitive cross-coupling.

[0020] In addition, the extending direction of the horizontal portion and the extending direction of the notch vertical post may be perpendicular to each other.

[0021] One embodiment of a method for manufacturing a cavity filter according to the present invention is to provide a method for manufacturing a cavity filter by providing a plurality of resonating rods each of which is involved in one side cavity and another side cavity that require a capacitive cross-coupling design, and a method for manufacturing a cavity filter by providing a plurality of resonating rods each of which is involved in a capacitive cross-coupling design. a cavity separating step of cutting out a part of a bottom surface connecting the two cavities after the injection molding step to separate the horizontal part from the bottom surface of the two cavities; a parts installation step of coupling a tuning plate that interacts with a tuning screw for frequency tuning to an upper end of each resonator rod after the cavity separating step; and a cover coupling step of covering the part cut out by the cavity separating step with a filter lower cover and coupling the open upper part of each cavity with a filter upper cover after the parts installation step.

[0022] Here, the injection molding step may be a step of integrally injection molding through a lower fixed mold and an upper movable mold which is movable downward from an upper portion of the lower fixed mold and has a shaped frame having a space between the lower fixed mold and into which a predetermined molten material is injected and hardened. Effect of the Invention

[0023] According to an embodiment of the cavity filter and the manufacturing method thereof according to the present invention, the following various effects can be achieved.

[0024] First, the need for separate component manufacturing and assembly processes for the capacitive cross-coupling design is eliminated, which has the advantage of facilitating the manufacture of the product.

[0025] Second, since it is possible to derive frequency filtering characteristics comparable to the design values ​​of capacitive cross-coupling that is produced and assembled using separate components, the filter can be very easily designed. [Brief description of the drawings]

[0026] [Figure 1] 1 is a plan view showing a conventional cavity filter to be compared with an embodiment of a cavity filter according to the present invention; [Diagram 2] 1 is a projected perspective view showing an embodiment of a cavity filter according to the present invention. [Diagram 3] FIG. 2 is a plan view of FIG. [Figure 4] 4 is a perspective view showing a second resonator and a fourth resonator involved in capacitive cross-coupling in the configurations of FIGS. 2 and 3. FIG. [Diagram 5] FIG. 5 is a front view of FIG. [Figure 6] FIG. 5 is a plan view of FIG. [Figure 7A] 3A to 3C are perspective projection views showing various embodiments of vertical posts for notches in the configuration of FIG. 2. [Figure 7B] 3A to 3C are perspective projection views showing various embodiments of vertical posts for notches in the configuration of FIG. 2. [Figure 8A] It is a comparison diagram of the electric field distribution diagram realized by the cavity filter of the comparative example. [Figure 8B] It is a comparison diagram of the magnetic field distribution diagram realized by the cavity filter of the comparative example. [Figure 9A] It is a comparison diagram of the electric field distribution diagram realized by an embodiment of the cavity filter according to the present invention. [Figure 9B] It is a comparison diagram of the magnetic field distribution diagram realized by an embodiment of the cavity filter according to the present invention. [Figure 10A] It is a graph showing the change in frequency filtering characteristics due to the shape of the notch vertical post in the configuration of FIG. 5. [Figure 10B] It is a graph showing the change in frequency filtering characteristics due to the shape of the notch vertical post in the configuration of FIG. 5. [Figure 11] It is a graph for comparing the frequency filtering characteristics of each cavity filter according to FIGS. 1 and 3. [Figure 12] It is a graph for comparing the level deviations of each cavity filter according to FIGS. 1 and 3. [Figure 13A] It is a front cross-sectional view showing a method for manufacturing a cavity filter according to the present invention. [Figure 13B] It is a front cross-sectional view showing a method for manufacturing a cavity filter according to the present invention. [Figure 13C] It is a front cross-sectional view showing a method for manufacturing a cavity filter according to the present invention. [Figure 13D] It is a front cross-sectional view showing a method for manufacturing a cavity filter according to the present invention.

Embodiments for Carrying Out the Invention

[0027] Hereinafter, an embodiment of the cavity filter and its manufacturing method according to the present invention will be described in detail with reference to the accompanying drawings. When attaching reference numerals to the components of each drawing, it should be noted that for the same components, they are given as identical numerals as much as possible even if they are shown on other drawings. Further, when explaining the embodiments of the present invention, if it is determined that a specific explanation of such a known configuration or function hinders the understanding of the embodiments of the present invention, the detailed explanation thereof will be omitted.

[0028] When explaining the components of the embodiments of the present invention, terms such as first, second, A, B, (a), (b), etc. can be used. Such terms are merely for distinguishing the components from other components, and the essence, order, or sequence of the components are not limited by such terms. Also, unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by those having ordinary knowledge in the technical field to which the present invention pertains. Terms defined in commonly used dictionaries should be interpreted as having a meaning consistent with the meaning in the context of the related art, and in this application, unless clearly defined, they are not interpreted in an ideal or overly formal sense.

[0029] FIG. 1 is a plan view showing a conventional cavity filter compared with an embodiment of the cavity filter according to the present invention. Prior to specifically explaining an embodiment of the cavity filter and its manufacturing method according to the present invention, for the understanding of an embodiment of the present invention, the cavity filter 1a according to the comparative example will be described first.

[0030] Referring to FIG. 1, the cavity filter 1a of the comparative example has a structure in which dielectric or metallic resonators are connected in multiple stages in a plurality of cavities 11a to 16a in which a space is formed by a metal housing (and a lid, etc.). For convenience of explanation, the illustration of the configuration related to the metal housing is omitted in the explanation. However, it may be understood that the appearance of the cavity filter 1a of the comparative example or the inner wall 10 of the cavity is defined by the metal housing.

[0031] More specifically, the cavity filter 1a of the comparative example has a structure in which a first cavity 11a, a second cavity 12a, a third cavity 13a, a fourth cavity 14a, a fifth cavity 15a and a sixth cavity 16a are coupled to each other, and a first resonating rod 51a, a second resonating rod 52a, a third resonating rod 53a, a fourth resonating rod 54a, a fifth resonating rod 55a and a sixth resonating rod 56a are vertically installed in each of the cavities 11a to 16a. Hereinafter, for convenience, each of the cavities 11a to 16a functions as a first resonator, a second resonator, a third resonator, a fourth resonator, a fifth resonator and a sixth resonator.

[0032] The first resonator of the first cavity 11a is coupled to an input connector 21a for receiving an input signal, and the sixth resonator of the sixth cavity 16a is coupled to an output connector 22a for providing an output signal, such that a signal input to the input connector 21a passes through the first, second, third, fourth, fifth and sixth resonators in that order, as indicated by arrows in FIG. The signal is then output to the output connector 22a.

[0033] Generally, in a filter without a separate cutout structure, coupling occurs only between adjacent resonators, which are essentially open sections between the resonators. However, as shown in FIG. 1, the cutout structure (metal rod, 50a) located between the second cavity 12a and the fourth cavity 14a allows cross-coupling to occur between non-adjacent resonators between the second and fourth resonators.

[0034] However, in the cavity filter 1a of the comparative example, the metal bar 50a must be provided in a structure penetrating between the inner wall 10 in order to form a capacitive cross-coupling between the second cavity 12a and the fourth cavity 14a. At this time, in order to electrically isolate the metal bar 50a from the inner wall 10, the outside of the metal bar 50a must be surrounded by a support made of a dielectric material (not shown) such as Teflon (registered trademark) and then coupled to the inner wall 10. Here, the part of the inner wall 10 where the metal bar 50a is provided may be formed as a through-hole structure and provided at the lower end. However, since it may not be easy to form a through-hole in the inner wall 10 in the manufacturing process of the cavity filter, a complicated process must be performed in which the upper end of the inner wall 10 is cut out, the metal bar 50a surrounded by the support so as to be insulated is provided at the cut-out part, and then the shape of the cut-out part of the inner wall 10 is fixed in a form that engages with the support.

[0035] The cavity filter 1 according to the present invention and its manufacturing method derive frequency filter characteristics equivalent or similar to those of the cavity filter 1a described in the comparative example above, but offer the advantage that the manufacturer can manufacture the cavity filter much more easily than the cavity filter 1a according to the comparative example above.

[0036] FIG. 2 is a projection perspective view showing one embodiment of a cavity filter according to the present invention, FIG. 3 is a plan view of FIG. 1, FIG. 4 is a perspective view showing the second and fourth resonators involved in cross-coupling in the configurations of FIGS. 2 and 3, FIG. 5 is a front view of FIG. 4, FIG. 6 is a plan view of FIG. 4, and FIGS. 7A and 7B are projection perspective views showing various embodiments of vertical posts for cutouts in the configuration of FIG. 2.

[0037] As shown in Fig. 2 and Fig. 3, a first embodiment of a cavity filter according to the present invention includes cavities 11-16 formed in a plurality of block units. The cavities 11-16 are formed in a space or block form that is empty or filled with a dielectric having a predetermined dielectric constant, and in the following description, the cavities are limited to being formed in a space form considering that air also corresponds to a dielectric having a predetermined dielectric constant. In addition, the material of the portion that divides or partitions the space is a metal housing made of a metal material, but in the present invention, the specific structure of the metal housing is not shown. However, a simple description will be given with reference to Figs. 13A to 13D while describing an embodiment of a method for manufacturing a cavity filter according to the present invention.

[0038] A first embodiment of the cavity filter according to the present invention includes a first cavity 11 located in the upper left part of FIG. 3, a second cavity 12 arranged to form an open section in the diagonal direction of the lower right part of the first cavity 11, a third cavity 13 arranged to form an open section in the diagonal direction of the upper right part of the second cavity 12, a fourth cavity 14 arranged to form an open section in the diagonal direction of the lower right part of the third cavity 13, a fifth cavity 15 arranged to form an open section in the diagonal direction of the upper right part of the fourth cavity 14, and a sixth cavity 16 arranged to form an open section in the diagonal direction of the lower right part of the fifth cavity 15.

[0039] The first cavity 11 to the sixth cavity 16 have resonating rods 51 to 56 disposed in the center of the bottom surface thereof, respectively. For convenience, these resonating rods 51 to 56 are named the first resonating rod to the sixth resonating rod 51 to 56. In addition, the block shape of the portion including the first cavity 11 in which the first resonating rod 51 is provided can be named the first resonating block 31, and the other cavities 12 to 16 are named in order, such as the second resonating block 32.

[0040] An input connector 21 for inputting an input signal is connected to the first resonating rod 51 of the first cavity 11 corresponding to the first resonating block 31, and an output connector 22 for providing an output signal is connected to the sixth resonating rod 56 of the sixth cavity 16 corresponding to the sixth resonating block 36.

[0041] Circular first to sixth tuning plates 61 to 66 are provided at the upper ends of the first to sixth resonator rods 51 to 56, respectively, and are provided at a predetermined distance from the lower surface of a filter upper cover 90 described later.

[0042] In addition, tuning plates 61'-66' are provided on the tops of the first to sixth resonating rods 51-56, respectively, which are assembled to a filter upper cover 90 arranged to cover the upper parts of the first to sixth cavities 11-16, as shown in Fig. 4, and enable frequency tuning via tuning screws (not shown). The tuning plates 61'-66' may be integrally formed with the filter upper cover 90, or may be manufactured separately and coupled to the corresponding parts of the filter upper cover 90. Here, the spacing between the lower surfaces of the tuning plates 61'-66' and the first to sixth tuning plates 61-66 allows fine frequency tuning adjustment according to the change in the fine shape of the tuning plates 61'-66', which changes according to the tuning process of the designer.

[0043] Meanwhile, one embodiment of the cavity filter according to the present invention may further include a notched vertical post 80 arranged to be positioned within the inner wall 10 between the second cavity 12 and the fourth cavity 14 for forming capacitive cross-coupling between the second cavity 12 and the fourth cavity 14, as shown in Figures 2 and 3.

[0044] In the embodiment of the present invention, the notch vertical post 80 is formed at a position for forming capacitive cross-coupling between the second cavity 12 and the fourth cavity 14, but as long as the resonators are not connected via an open section and cross-coupled across an odd number of resonators, the notch vertical post 80 may be located between the first cavity 11 and the third cavity 13, between the third cavity 13 and the fifth cavity 15, and between the fourth cavity 14 and the sixth cavity 16. In this case, it is natural that the design of the partitions 40, 40a, and 40b described below for forming the boundaries or open sections between the resonator blocks 31 to 36 may be different. As shown in Figures 2 and 3, the partition 40 can include an outer partition 40a formed so that a portion of the side wall flows into the interior, and an inner partition 40b formed so that the portions flow in the vertical direction inside the cavities 11-16.

[0045] The notch vertical post 80 is defined as a part located between any one-side cavity 12 (see "second cavity 12" in Figures 2 and 3) and the inner wall 10 of any other-side cavity 14 (see "fourth cavity 14" in Figures 2 and 3) that is not connected to the one-side cavity 12 via an open section and is located across an odd number of resonators, in the multiple resonator blocks 31 to 36.

[0046] More specifically, as shown in Figs. 4 to 6, the notch vertical post 80 is provided between one side cavity (second cavity 12) and the other side cavity (fourth cavity 14) and is arranged in the vertical direction. Here, the notch vertical post 80 is arranged between any boundary line connecting the inner wall 10 and the inner partition wall 40b (see Fig. 3), which corresponds to the boundary between the one side cavity (second cavity 12) and the other side cavity (fourth cavity 14). Also, as shown in Figs. 4 to 6, the notch vertical post 80 is , provided in a rod shape having a circular horizontal cross section.

[0047] Here, as shown in Figures 4 and 5, it is preferable that the extension direction of the tip of the horizontal portion 70 and the extension direction of the upper end of the notch vertical post 80 are mutually perpendicular. As shown in Figures 4 to 6, the notch vertical post 80 has a lower end that is perpendicular to the tip of the horizontal portion 70 that extends horizontally on part of the outer circumferential surface of the resonator rod (second resonator rod 52) of one cavity (second cavity 12). As shown in Figure 4, the horizontal portion 70 has a width that corresponds approximately to the outer diameter of the second resonator rod 52 and is formed in a square bar shape that forms a predetermined thickness on the top and bottom.

[0048] On the other hand, the notch vertical posts 80-1, 80-2 are formed to have a square horizontal cross section as shown in Figures 7A and 7B. That is, the shape of the horizontal cross section of the notch vertical posts 80-1, 80-2 is not necessarily limited to a circular horizontal cross section as shown in Figures 2 to 6, but can have a polygonal horizontal cross section, that is, a square horizontal cross section, or a specific cross-sectional shape not shown, as shown in Figures 7A and 7B, and the same characteristics can be derived to the extent that the upper ends of the notch vertical posts 80-1, 80-2 contact the lower surface of the filter upper cover 90.

[0049] 7B, a spacing adjustment post 80-2' is further formed integrally with the notch vertical post 80-2 so as to extend a predetermined length toward the opposite resonator (i.e., the fourth resonating rod 54) in order to adjust the spacing between the opposite resonator (i.e., the fourth resonating rod 54) involved in the capacitive cross-coupling. The capacitive cross-coupling can be adjusted to an appropriate magnitude by adjusting the spacing between the spacing adjustment post 80-2' and the fourth resonating rod 54.

[0050] In a cavity filter according to an embodiment of the present invention, the resonator rod (second resonator rod 52) of one cavity (second cavity 12), the horizontal portion 70, and the vertical post 80 for cutting out are made of the same material and are injection molded as a single unit. At the same time, the resonator rod (second resonator rod 52), the horizontal portion 70, and the vertical post 80 for cutting out are made of the same material as the material of the metal housing (not shown), and are injection molded as a single unit at the same time when the metal housing is manufactured, as shown in Figs. 13A to 13D described later. This will be described in more detail while explaining the manufacturing method of the cavity filter according to an embodiment of the present invention.

[0051] Figures 8A and 8B are comparative diagrams of electric field distribution diagrams and magnetic field distribution diagrams realized by a comparative example cavity filter 1a, Figures 9A and 9B are comparative diagrams of electric field distribution diagrams and magnetic field distribution diagrams realized by one embodiment of a cavity filter according to the present invention, and Figures 10A and 10B are graphs showing the change in frequency filtering characteristics depending on the shape of the cutout vertical post 80 in the configuration of Figure 5.

[0052] As shown in Figures 4 to 6, in one embodiment 1 of the cavity filter according to the present invention, when a horizontal portion 70 is interposed between the second resonant rod 52 of either one of the one side cavity (second cavity 12) and the other side cavity (fourth cavity 14) (in this embodiment, the second cavity 12) and a vertical post 80 for notching is extended vertically up and down between each cavity, the following changes in the electric field distribution diagram and the magnetic field distribution diagram can be confirmed compared to the cavity filter 1a according to the comparative example.

[0053] 8A and 8B are electric field distribution diagrams and magnetic field distribution diagrams of the cavity filter 1a of the comparative example, which show that the second cavity 12 and the fourth cavity 14 are mutually uniformly coupled with each other when electric field coupling and magnetic field coupling are respectively performed between the second cavity 12 and the fourth cavity 14.

[0054] Here, Figures 9A and 9B are electric field distribution diagrams and magnetic field distribution diagrams realized in one embodiment 1 of the cavity filter according to the present invention, and it can be seen that strong magnetic field coupling occurs between the second cavity 12 having the second resonant rod 52 connected to the notch vertical post 80 and the notch vertical post 80, and the magnetic field coupling component with the fourth resonant rod 54 of the opposite fourth cavity 14 where cross-coupling should originally occur is suppressed to the maximum extent, and only a relatively strong electric field coupling component mainly exists.

[0055] As described above, the cavity filter according to the present invention has an advantage that it is easy to realize capacitive cross-coupling by merely designing the horizontal portion 70 and the notch vertical post 80 integrally formed with the second resonator rod 52 without adding any specific parts. Meanwhile, the notch vertical post 80 is extended to a height such that its upper end contacts the lower surface of the filter upper cover 90 located at the upper part, as shown in FIG. 5. However, it is not necessary for the upper end of the notch vertical post 80 to physically contact the lower surface of the filter upper cover 90, and a distance is allowed in consideration of the assembly tolerance with respect to the filter upper cover 90. However, the distance from the lower surface of the filter upper cover 90 due to the assembly tolerance should not exceed a preset distance.

[0056] As a result of the test conducted by the applicant of the present invention, when the upper end of the notch vertical post 80 contacts the lower surface of the filter upper cover 90 as shown in the left diagram of Fig. 10A, the phase value is formed as a negative value, and the coupling is performed by the capacitive cross coupling (i.e., electric coupling) desired by the designer, but when the separation distance between the upper end of the notch vertical post 80 and the filter upper cover 90 is in an area that is out of the minimum assembly tolerance as shown in the right diagram of Fig. 10A, the phase value is inverted to +, and instead of the capacitive cross coupling desired by the designer, the coupling is performed by the inductive cross coupling (i.e., magnetic coupling), and the frequency filtering characteristics can be inverted. Here, the allowable range of the assembly tolerance must be set to less than 0.1 mm before the phase value is inverted to a positive value.

[0057] Meanwhile, it is preferable that the lower end of the vertical post 80 for cutting out and the lower end of the horizontal part 70 including the same are spaced a predetermined distance from the inner bottom surface of the cavity (second cavity 12) as shown in Fig. 5. The predetermined distance here may mean a distance at which the lower end of the vertical post 80 for cutting out and the lower end of the horizontal part 70 including the same do not physically come into contact with the inner bottom surface of the cavity (second cavity 12).

[0058] As a result of a test conducted by the applicant of the present invention, as shown in FIG. 10B, when the lower end of the vertical post 80 for notching and the lower end of the horizontal part 70 including it come into contact with the bottom surface of the cavity (second cavity 12) (i.e., when the separation distance is 0), the Phase value is formed to be a positive value, and coupling is performed by inductive cross coupling (i.e., magnetic coupling) instead of the capacitive cross coupling desired by the designer. However, from the moment when the lower end of the vertical post 80 for notching and the lower end of the horizontal part 70 including it separate from the bottom surface of the cavity (second cavity 12) (i.e., when the separation distance is 0.1 mm or more), the Phase value is inverted to be a negative value, and coupling is performed by capacitive cross coupling (i.e., electric field coupling) desired by the designer. In addition, it can be seen that as the distance between the lower end of the notch vertical post 80 and the lower end of the horizontal part 70 including the notch vertical post 80 and the cavity (second cavity 12) increases, the electric coupling is excited more strongly, and the coupling bandwidth becomes larger.

[0059] In this manner, in the cavity filter according to the embodiment of the present invention, the upper end of the notch vertical post 80 does not necessarily contact the lower surface of the filter upper cover 90 within the range of the assembly tolerance. (hereinafter referred to as the "first condition"), and the lower end of the vertical post 80 for notching and the lower end of the horizontal portion 70 including it are separated from the bottom surface of the cavity (second cavity 12) (hereinafter referred to as the "second condition") must be simultaneously satisfied in order to realize capacitive cross-coupling (C-coupling) through electric coupling.

[0060] In contrast, when at least one of the first and second conditions is not satisfied (i.e., when the first condition is satisfied but the second condition is not satisfied, when the second condition is satisfied but the first condition is not satisfied, or when both the first and second conditions are not satisfied), a difference occurs in that inductive cross coupling (L-coupling) is realized by magnetic coupling rather than capacitive cross coupling (C-coupling).

[0061] FIG. 11 is a graph for comparing the frequency filtering characteristics of the cavity filters according to FIG. 1 and FIG. 3, and FIG. 12 is a graph for comparing the level deviations of the cavity filters according to FIG.

[0062] 11 (particularly FIG. 11(b)), it can be seen that in the cavity filter 1 according to the embodiment of the present invention, C-notches and L-notches are formed on the left and right sides of the band due to the electric coupling and magnetic coupling between the second cavity 12 and the fourth cavity 14, respectively, and compared with the graph showing the frequency filtering characteristics of the cavity filter 1a of the comparative example, the difference in insertion loss is very similar. This can be inferred from the fact that the comparative example 1a and the cavity filter 1 according to the embodiment of the present invention have the same level of quality factor (Q) value.

[0063] 12, it can be seen that the cavity filter (b) according to an embodiment of the present invention has a very uniform level deviation in capacitive cross-coupling compared to the cavity filter (a) of the comparative example. This is because the assembly tolerance of parts is eliminated, and a constant level of capacitive cross-coupling can be achieved compared to the cavity filter (a) of the comparative example.

[0064] 13A to 13D are front cross-sectional views showing a method for manufacturing a cavity filter according to an embodiment of the present invention. Hereinafter, the method for manufacturing a cavity filter according to an embodiment of the present invention configured as above will be described with reference to the attached drawings (particularly, FIGS. 13A to 13D).

[0065] As shown in Figures 13A to 13D, a method of manufacturing a cavity filter according to one embodiment of the present invention includes the steps of: manufacturing a molten material by injection molding so that the horizontal portion 70 and the vertical post 80 for cutting out, which are made of the same material as the resonator rods, are integrally manufactured (the injection molding step described below); cutting out a portion so that the elements of one cavity (particularly, the second cavity 12) and the other cavity (particularly, the fourth cavity 14) are separated (the cavity separation step described below); fixing the tuning plate to the upper end of the resonator rod of each cavity (i.e., the upper end of the second resonator rod 52 of the second cavity 12 and the fourth resonator rod 54 of the fourth cavity 14) (the component installation step described below); and then combining a filter lower cover 95 covering the cut out portion and a filter upper cover 90 covering the upper portion of each cavity 12, 14 (the cover combining step described below).

[0066] That is, the manufacturing method of the cavity filter according to the embodiment of the present invention includes an injection molding step in which each resonator rod, the horizontal portion 70, and the notch vertical post 80, which are involved in at least two cavities requiring the capacitive cross-coupling design, are integrally injection-molded so as not to be separated. and a cavity separating step of, after the injection molding step, cutting out a portion of the bottom surface connecting the two cavities to separate each cavity; a component installation step of, after the cavity separating step, connecting tuning plates 61-66, which are the main components, to the upper ends of each resonating rod; and a cover joining step of, after the component installation step, covering the portions cut out in the cavity separating step to separate each of the cavities 12, 14 with a filter lower cover 95 and joining the open upper portions of each of the cavities 12, 14 to be covered with a filter upper cover 90.

[0067] More specifically, the injection molding step is a step of producing a casting in which each resonator rod, horizontal portion 70, and vertical post 80 for cutout are injection molded as a single unit through a lower fixed mold 100a and an upper movable mold 100b which is movable downward from the top of the lower fixed mold 100a and has a shaped frame having a space between the lower fixed mold 100a and the upper movable mold 100b into which a predetermined molten material is injected and hardened, as shown in Figures 13A and 13B.

[0068] The cavity separation step is a step of forming the lower end of the horizontal portion 70, including the lower end of the notch vertical post 80, so as to be spaced a predetermined distance from the bottom surface of the cavity (particularly, the second cavity 12) (see reference numeral "5" in FIG. 13C), as well as cutting and separating the one side cavity (the second cavity 12) and the other side cavity (the fourth cavity 14) so ​​that they are not interconnected, as shown in FIG. 13C.

[0069] Next, the component installation step is a step of connecting separately manufactured tuning plates 61 to 66 to the upper end of each resonator bar so that frequency tuning can be performed in combination with tuning screws (not shown).

[0070] Finally, the cover joining step is a step in which a filter lower cover 95 is used to form the bottom of the cavities 12, 14, and the cutout portions of the bottom formed by the cavity separation step (see reference numeral "5" in FIG. 13C) are sealed so that they are not open to the bottom side, and a filter upper cover 90 is used to seal the open tops of each of the cavities 12, 14, and the above-mentioned tuning screws (not shown) are provided.

[0071] An embodiment of the cavity filter and its manufacturing method according to the present invention has been described in detail above with reference to the accompanying drawings. However, the present invention is not necessarily limited to the above embodiment, and it is obvious that various modifications and equivalents can be made by those skilled in the art to which the present invention pertains. Therefore, the true scope of the present invention is defined by the following claims. [Industrial Applicability]

[0072] The present invention provides a cavity filter and a method for manufacturing the same that includes a vertical post formed integrally with a resonating rod, which is easy to manufacture and designed to suppress magnetic field coupling and excite relatively strong electric field coupling without the need for a separate component that maximizes electric field coupling. [Explanation of symbols]

[0073] 1a: Comparative example cavity filter 1: Cavity filter of the present invention 11-16: Cavity 21: Input connector 22: Output connector 31-36: Resonance block 40: Bulkhead 51~56: Resonance rod 61-66: Tuning plate 70: Horizontal section 80: Vertical post for cutout 90: Filter top cover 95: Filter bottom cover

Claims

1. One-side and other-side cavities that require capacitive cross-coupling design; a resonating rod provided in each of the one side cavity and the other side cavity; a vertical post extending from any one of the resonating rods and extending vertically up and down within an inner wall that is a boundary between the one-side cavity and the other-side cavity; A horizontal portion that mediates the connection between the vertical post and the resonating rod; a filter upper cover for covering the open upper portions of the one-side cavity and the other-side cavity; an upper portion of the vertical post contacts a lower surface of the filter upper cover within an assembly tolerance; A cavity filter, wherein a lower end of the horizontal portion is spaced a predetermined distance from the bottom surfaces of the one-side cavity and the other-side cavity.

2. The cavity filter of claim 1 , wherein said horizontal portion is integrally formed with said vertical post.

3. 2. The cavity filter according to claim 1, wherein the resonating rod, the vertical post and the horizontal portion are integrally injection molded and then partially cut out.

4. 2. The cavity filter of claim 1, wherein, from the moment when the separation distance between the upper end of the vertical post and the filter upper cover goes outside the assembly tolerance range, the one-side cavity and the other-side cavity are coupled by inductive cross-coupling instead of capacitive cross-coupling, and the frequency filtering characteristics are inverted.

5. The vertical posts are formed in the shape of rods or bars having a circular or polygonal horizontal cross section; 2. The cavity filter according to claim 1, wherein the horizontal portion is formed in a square bar shape having a width corresponding to an outer diameter of the vertical post and a predetermined thickness at the top and bottom.

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