Ceramic cover plate cavity filter

Abstract

The invention discloses a ceramic cover plate cavity filter. The filter comprises a ceramic cover plate and a cavity, wherein the ceramic cover plate is connected to the top of the cavity and is electrically connected with the cavity; a plurality of sunken silver-coated blind holes are formed in the top of the ceramic cover plate, a silver-coated layer is arranged on the surface of the ceramic cover plate, and the silver-coated layer extends into the silver-coated blind holes; a plurality of protruding hollow cavity columns are arranged in the cavity, all the cavity columns are located under all the silver-coated blind holes respectively, hollow resonant columns are installed in all the cavity columns, and tuning screw rods are installed in all the resonant columns. According to the ceramic cover plate cavity filter, the height of the filter is reduced through ceramic capacitor loading between the resonator and the ceramic silver layer, and compared with a traditional cavity filter, the ceramic cover plate cavity filter is lower in height, smaller in size, smaller in insertion loss and better in far-end suppression effect.

Description

Technical Field

[0001] The invention relates to the field of wireless communications, and in particular to a ceramic cover plate cavity filter. Background Art

[0002] Traditional base station RF filters generally use cavity filters, mainly including metal cavity filters and all-dielectric filters. Traditional cavity filters reduce the filter height and size by loading the air capacitor between the resonator and the metal cover. The volume of the metal cavity filter is still large, which does not conform to the trend of filter miniaturization. The single-cavity Q value of the all-dielectric filter is low, the insertion loss is large, and the parasitic passband is close to the main passband, which often leads to poor far-end suppression effect. Summary of the invention

[0003] To solve the above problems, the present invention provides a ceramic cover plate cavity filter, which reduces the height of the filter by loading a ceramic capacitor between the resonator and the ceramic silver layer. Since the dielectric constant of the ceramic material is 2 to 200 times that of air, compared with the traditional metal cavity filter, the volume of the filter can be significantly reduced, which has a significant effect on the miniaturization of the filter; compared with the traditional all-dielectric filter, the single cavity Q value is higher, the insertion loss is smaller, the parasitic passband is farther away from the main passband, and the far-end suppression effect is better.

[0004] According to one aspect of the present invention, there is provided a ceramic cover plate cavity filter, comprising a ceramic cover plate and a cavity, wherein the ceramic cover plate is connected to the top of the cavity and is electrically connected to the cavity;

[0005] A plurality of recessed silvered blind holes are arranged on the top of the ceramic cover plate, and a silvered layer is provided on the surface of the ceramic cover plate, and the silvered layer extends into the silvered blind holes;

[0006] The cavity body has a plurality of protruding and hollow cavity columns, each of which is located directly below each of the silver blind holes, each of which has a hollow resonant column installed inside, and each of which has a tuning screw installed inside;

[0007] At least one pair of the cavity columns are also connected via a coupling cantilever;

[0008] At least one through metallized via is provided on the ceramic cover plate, the bottom end of the metallized via is connected to the top end of one of the cavity columns through a silver cantilever, and the cavity column and the resonant column inside it are also connected through a coupling rib to form a capacitive coupling structure;

[0009] A coupling column is installed in the hollow part of at least one of the cavity columns, and the resonant column inside the cavity column is electrically connected to a capacitor ring. At least one silver ring is arranged on the inner wall of the ceramic cover plate, and the silver ring is connected to the capacitor ring to form an input-output coupling structure.

[0010] In some embodiments, the ceramic cover plate and the cavity are soldered by solder paste. The benefit lies in that the connection method between the ceramic cover plate and the cavity is described, and the two can also be connected by other conductive materials.

[0011] In some embodiments, the cavity is made of kovar, invar or silver-coated ceramic material, and the expansion coefficient is close to or consistent with the ceramic cover plate. The benefit is that the cavity material selection is described, and setting the expansion coefficient can improve the reliability of the electrical connection under high and low temperature environment changes.

[0012] In some embodiments, a polished hole is provided at the bottom of the silvered blind hole, and the silvered layer does not extend into the polished hole. The benefit is that the specific structure of the silvered blind hole is further described, and the polished hole can be used for frequency tuning.

[0013] In some embodiments, a debugging hole is provided below the coupling cantilever, which is beneficial in that the debugging hole can be used to adapt to the force deformation of the coupling cantilever.

[0014] In some embodiments, one end of the silver cantilever is electrically connected to the resonant disk on the inner surface of the ceramic cover plate, and the other end is electrically connected to the outer surface of the cavity through the metallized via or is set to an open circuit. The benefit is that several variant structures of the capacitive coupling structure are described.

[0015] In some embodiments, the silvered cantilever has more than two, which are electrically connected to the two resonant disks on the inner surface of the ceramic cover plate. The advantage is that it further describes that in various deformation structures, the capacitive coupling amount can be increased by increasing the number of silvered cantilever.

[0016] In some embodiments, the cavity is made of aluminum, and a thin layer made of Kovar or Invar is provided between the ceramic cover and the cavity. This is beneficial in that the temperature-dependent stress between the ceramic cover and the aluminum cavity can be transferred to between the thin layer and the aluminum cavity, thereby improving the reliability of welding. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 A schematic diagram of the exploded structure of a ceramic cover plate cavity filter according to an embodiment of the present invention;

[0018] Figure 2 for Figure 1A schematic diagram of a partial cross-sectional structure of a ceramic cover plate cavity filter is shown;

[0019] Figure 3 for Figure 1 A schematic diagram of a cross-sectional structure of the coupling cantilever of the filter shown;

[0020] Figure 4 for Figure 1 A schematic cross-sectional structure diagram of the capacitive coupling structure of the filter shown;

[0021] Figure 5 for Figure 1 A schematic cross-sectional structure diagram of the capacitive coupling structure of the filter shown;

[0022] Figure 6 for Figure 5 A schematic cross-sectional view of a type of deformed structure of the capacitive coupling structure of the filter shown;

[0023] Figure 7 for Figure 6 A schematic cross-sectional view of another type of deformation structure of the capacitive coupling structure of the filter shown;

[0024] Figure 8 for Figure 1 A schematic cross-sectional view of the input and output coupling structures of the filter shown;

[0025] Fig. 9 for Figure 5 A schematic cross-sectional view of the input and output coupling structures of the filter shown;

[0026] Fig.10 The figure is a schematic diagram of the exploded structure of a ceramic cover plate cavity filter according to another embodiment of the present invention.

[0027] In the figure: ceramic cover plate 1, cavity 2, silvered blind hole 3, silver layer 4, polished hole 5, cavity column 6, resonance column 7, tuning screw 8, coupling cantilever 9, debugging hole 10, metallized via 11, silvered cantilever 12, coupling rib 13, coupling column 14, capacitor ring 15, silver ring 16, thin layer 17, resonance disk 18. DETAILED DESCRIPTION

[0028] The present invention will be further described in detail below in conjunction with the accompanying drawings.

[0029] like Figure 1-2 As shown, the filter includes a ceramic cover plate 1 and a cavity 2 , the ceramic cover plate 1 is connected to the top of the cavity 2 , and the ceramic cover plate 1 is electrically connected to the cavity 2 .

[0030] Preferably, the ceramic cover plate 1 and the cavity 2 are connected by soldering or other conductive materials.

[0031] The material of the cavity 2 can be Kovar alloy, Invar steel or silver-coated ceramic material. In addition, in order to improve the reliability of the electrical connection under high and low temperature environment changes, the material expansion coefficient of the cavity 2 needs to be close to or consistent with that of the ceramic cover plate 1.

[0032] A plurality of silver blind holes 3 which are recessed but not penetrated are arranged on the top of the ceramic cover plate 1 , and polished holes 5 are arranged at the bottom of the silver blind holes 3 .

[0033] There are multiple protruding and hollow cavity columns 6 in the cavity 2, and each cavity column 6 is located directly below each silver blind hole 3. A hollow resonance column 7 is installed inside each cavity column 6, and a tuning screw 8 is installed inside each resonance column 7, thereby forming multiple resonators.

[0034] A silver layer 4 is provided on the surface of the ceramic cover plate 1 . The silver layer 4 extends into the silver blind hole 3 but does not extend into the polished hole 5 . Meanwhile, the silver layer 4 does not cover the top of the cavity column 6 and the resonance column 7 .

[0035] The deeper the silver blind hole 3 is, the stronger the capacitance loading is and the lower the resonance frequency is, and vice versa. The polished hole 5 is used for frequency tuning, and the larger its diameter is, the higher the resonance frequency is, and vice versa. The closer the tuning screw 8 is to the ceramic cover plate 1, the lower the resonance frequency is, and vice versa.

[0036] like Figure 3 As shown, at least one pair (two in each pair) of cavity columns 6 are connected by a coupling cantilever 9, and a debugging hole 10 is left below the coupling cantilever 9. The coupling cantilever 9 is squeezed by an external ejector through the ceramic cover plate 1 to deform toward the debugging hole 10, so that the coupling amount can be adjusted, and the larger the protrusion of the coupling cantilever 9 is, the greater the coupling amount is.

[0037] like Figure 4-5 As shown, at least one through metallized via 11 is provided on the ceramic cover plate 1, and the bottom end of the metallized via 11 is connected to the top end of a cavity column 6 through a silver cantilever 12, so that one end of the silver cantilever 12 can be electrically connected to the cavity column 6, and the other end can be electrically connected to the outer surface of the cavity 2 through the metallized via 11, thereby forming a capacitive coupling structure. The capacitive coupling structure can achieve capacitive coupling by flipping the magnetic field phase by 90 degrees.

[0038] In addition, in the capacitive coupling structure, the cavity column 6 and the resonant column 7 inside it are connected by a coupling rib 13. The higher the height of the coupling rib 13 (indicated by a in the figure), the stronger the capacitive coupling, and vice versa; the smaller the distance between the cavity column 6 and the resonant column 7 (indicated by b in the figure), the stronger the coupling, and vice versa; the smaller the distance between the metallized via 11 and the resonant column 7 (indicated by c in the figure), the stronger the coupling, and vice versa.

[0039] Preferably, there are two capacitive coupling structures and they are arranged axially symmetrically, so that the capacitive coupling amount can be significantly enhanced by using the two capacitive coupling structures simultaneously.

[0040] like Figure 6 As shown, in order to obtain a stronger capacitive coupling, the above capacitive coupling structure can be deformed into a type of deformation, where Figure 6 6a, 6b, and 6c show three structures of this type of deformation respectively. Figure 6 As shown in FIG. 1 , one end of the silver cantilever 12 is still electrically connected to the outer surface of the cavity 2 through the metallized via 11 , but the other end is electrically connected to the resonant disk 18 on the inner surface of the ceramic cover plate 1 .

[0041] In addition, the amount of capacitive coupling can be further increased by increasing the number of silver cantilevers 12, such as Figure 6 As shown in b, the silver cantilever 12 has two ends, and they are electrically connected to the two resonant disks 18 on the inner surface of the ceramic cover plate 1 respectively.

[0042] And as Figure 6 As shown in FIG. c, the number of silver cantilevers 12 can also be increased to three or more.

[0043] like Figure 7 As shown, Figure 7 a, 7b, and 7c show the Figure 6 a, 6b, and 6c have undergone another type of deformation structure. In this type of deformation, one end of the silver cantilever 12 is still electrically connected to the resonant disk 18 on the inner surface of the ceramic cover plate 1, and the other end is not connected to the metallized via 11, but is set to an open circuit. This type of deformation simplifies the capacitive coupling structure, but reduces the capacitive coupling amount.

[0044] like Figure 8-9 As shown, a coupling column 14 is installed in the hollow part of at least one cavity column 6, and the resonant column 7 inside the cavity column 6 is electrically connected to a capacitor ring 15, and at least one silver ring 16 is arranged on the inner wall of the ceramic cover plate 1, and each silver ring 16 is connected to each capacitor ring 15, thereby forming an input-output coupling structure. The larger the angle (indicated by d in the figure) between the coupling column 14 and the silver ring 16 is, the greater the coupling amount is, and vice versa.

[0045] like Fig.10As shown, considering that the material density of the cavity 2 is often high and the weight is large, the welding process is also difficult. For this reason, the cavity 2 can be made of lighter aluminum, and a thin layer 17 made of Kovar alloy or Invar steel is provided between the ceramic cover plate 1 and the cavity 2. The thin layer 17 does not affect the installation and function of the above-mentioned structures. Thus, the temperature-dependent stress between the ceramic cover plate 1 and the aluminum cavity 2 can be transferred to between the thin layer 17 and the aluminum cavity 2, thereby improving the reliability of welding.

[0046] The above are only some embodiments of the present invention. For those skilled in the art, several modifications and improvements can be made without departing from the creative concept of the present invention, which all belong to the protection scope of the present invention.

Claims

1. A ceramic cover plate cavity filter, characterized in that: It comprises a ceramic cover plate (1) and a cavity (2), wherein the ceramic cover plate (1) is connected to the top of the cavity (2) and is electrically connected to the cavity (2); A plurality of recessed silvered blind holes (3) are arranged on the top of the ceramic cover plate (1); a silvered layer (4) is provided on the surface of the ceramic cover plate (1); and the silvered layer (4) extends into the silvered blind holes (3); The cavity (2) has a plurality of protruding and hollow cavity columns (6), each of the cavity columns (6) is located directly below each of the silver blind holes (3), each of the cavity columns (6) is equipped with a hollow resonant column (7), and each of the resonant columns (7) is equipped with a tuning screw (8); At least one pair of cavity columns (6) are connected via a coupling cantilever (9); The ceramic cover plate (1) is provided with at least one through-going metallized via hole (11), the bottom end of the metallized via hole (11) is connected to the top end of one of the cavity columns (6) via a silver cantilever (12), and the cavity column (6) and the resonant column (7) therein are also connected via a coupling rib (13), thereby forming a capacitive coupling structure; A coupling column (14) is installed in the hollow part of at least one of the cavity columns (6); a resonant column (7) inside the cavity column (6) is electrically connected to a capacitor ring (15); and at least one silver ring (16) is arranged on the inner wall of the ceramic cover plate (1); the silver ring (16) is connected to the capacitor ring (15) to form an input-output coupling structure.

2. The ceramic cover plate cavity filter according to claim 1, characterized in that: The ceramic cover plate (1) and the cavity (2) are welded by solder paste.

3. The ceramic cover plate cavity filter according to claim 1, characterized in that: The material of the cavity (2) is Kovar alloy, Invar steel or silver-coated ceramic material, and its expansion coefficient is close to or consistent with that of the ceramic cover plate (1).

4. The ceramic cover plate cavity filter according to claim 1, characterized in that: A polished hole (5) is provided at the bottom of the silvered blind hole (3), and the silvered layer (4) does not extend into the polished hole (5).

5. The ceramic cover plate cavity filter according to claim 1, characterized in that: A debugging hole (10) is provided below the coupling cantilever (9).

6. The ceramic cover plate cavity filter according to claim 1, characterized in that: One end of the silvered cantilever (12) is electrically connected to the resonant disk (18) on the inner surface of the ceramic cover plate (1), and the other end is electrically connected to the outer surface of the cavity (2) through the metallized via (11) or is set to an open circuit.

7. The ceramic cover plate cavity filter according to claim 6, characterized in that: The silvered cantilever (12) has more than two and is electrically connected to two resonant disks (18) on the inner surface of the ceramic cover plate (1) respectively.

8. The ceramic cover plate cavity filter according to claim 1, characterized in that: The cavity (2) is made of aluminum, and a thin layer (17) made of Kovar or Invar is arranged between the ceramic cover plate (1) and the cavity (2).

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