Ceramic cover plate cavity filter

Abstract

The utility model 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 loading of the ceramic capacitors between the resonators and the ceramic silver layers, 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] This utility model relates to the field of wireless communication, and in particular to a ceramic cover plate cavity filter. Background Technology

[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 air capacitance between the resonator and the metal cover. Among them, the volume of metal cavity filters is still relatively large, which does not conform to the trend of filter miniaturization. On the other hand, all-dielectric filters have a low single-cavity Q value, high insertion loss, and the parasitic passband is close to the main passband, which often leads to poor far-end suppression. Utility Model Content

[0003] To address the aforementioned issues, this invention provides a ceramic cover plate cavity filter, which reduces the filter height by loading a ceramic capacitor between the resonator and the ceramic silver layer. Since the dielectric constant of ceramic materials is 2 to 200 times that of air, the filter volume can be significantly reduced compared to traditional metal cavity filters, resulting in a significant miniaturization effect. Compared to traditional all-dielectric filters, it has a higher single-cavity Q value, lower insertion loss, a parasitic passband further from the main passband, and better far-end suppression.

[0004] According to one aspect of the present invention, a ceramic cover plate cavity filter is provided, 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] The top of the ceramic cover plate is provided with a plurality of recessed silver-plated blind holes, and the surface of the ceramic cover plate has a silver-plated layer that extends into the silver-plated blind holes;

[0006] The cavity has multiple protruding and hollow cavity pillars, each cavity pillar is located directly below each silver-plated blind hole, and each cavity pillar has a hollow resonant pillar installed inside, and each resonant pillar has a tuning screw installed inside.

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

[0008] The ceramic cover plate is provided with at least one through metallized via. The bottom end of the metallized via is connected to the top end of the cavity column through a silver cantilever. The cavity column is also connected to the resonant column inside it through a coupling rib, forming a capacitive coupling structure.

[0009] At least one of the cavity columns has a coupling column installed in its hollow portion. The resonant column inside the cavity column is electrically connected to a capacitor ring. At least one silver ring is provided on the inner wall of the ceramic cover plate. The silver ring is connected to the capacitor ring to form an input-output coupling structure.

[0010] In some embodiments, the ceramic cover plate is soldered to the cavity using solder paste. The advantage is that the connection method between the ceramic cover plate and the cavity is described; however, they can also be connected using other conductive materials.

[0011] In some embodiments, the cavity is made of Kovar alloy, Invar steel, or silver-plated ceramic material, and its coefficient of thermal expansion is close to or the same as that of the ceramic cover plate. The advantage of this is that describing the material selection for the cavity and setting the coefficient of thermal expansion can improve the reliability of the electrical connection under varying high and low temperature environments.

[0012] In some embodiments, the bottom of the silvered blind via is provided with a polishing hole, and the silvered layer does not extend into the polishing hole. Its advantage lies in that it further describes the specific structure of the silvered blind via, and the polishing hole can be used for frequency tuning.

[0013] In some embodiments, the coupled cantilever has an adjustment hole at its lower part. This is advantageous because the adjustment hole can accommodate the stress deformation of the coupled cantilever.

[0014] In some embodiments, one end of the silver cantilever is electrically connected to a 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 configured as an open circuit. Its advantage lies in describing several variations of the capacitive coupling structure.

[0015] In some embodiments, there are two or more silvered cantilevers, each electrically connected to two resonant disks on the inner surface of the ceramic cover plate. An advantage is that, in various modified structures, the amount of capacitive coupling can be increased by increasing the number of silvered cantilevers.

[0016] In some embodiments, the cavity is made of aluminum, and a thin layer made of Kovar alloy or Invar is disposed between the ceramic cover and the cavity. This is advantageous because it allows the thermal stress between the ceramic cover and the aluminum cavity to be transferred between the thin layer and the aluminum cavity, thereby improving the reliability of the weld. Attached Figure Description

[0017] Figure 1 This is an exploded structural diagram of a ceramic cover plate cavity filter according to one embodiment of the present invention;

[0018] Figure 2 for Figure 1The diagram shows a partial cross-sectional structure of a ceramic cover plate cavity filter.

[0019] Figure 3 for Figure 1 A schematic diagram of the cross-sectional structure of the coupled cantilever of the filter shown.

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

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

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

[0023] Figure 7 for Figure 6 A schematic diagram of the cross-sectional structure of another type of deformed structure of the capacitive coupling structure of the filter shown.

[0024] Figure 8 for Figure 1 The diagram shows a cross-sectional view of the input-output coupling structure of the filter.

[0025] Figure 9 for Figure 5 A schematic diagram of the cross-sectional structure related to the input-output coupling structure of the filter shown.

[0026] Figure 10 This is an exploded structural diagram of a ceramic cover plate cavity filter according to another embodiment of the present invention.

[0027] In the figure: 1. Ceramic cover plate; 2. Cavity; 3. Silver-coated blind hole; 4. Silver-coated layer; 5. Polished hole; 6. Cavity pillar; 7. Resonant pillar; 8. Tuning screw; 9. Coupling cantilever; 10. Tuning hole; 11. Metallized via; 12. Silver-coated cantilever; 13. Coupling rib; 14. Coupling pillar; 15. Capacitor ring; 16. Silver-coated ring; 17. Thin layer; 18. Resonant disk. Detailed Implementation

[0028] The present invention will now be described in further detail with reference to 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 is electrically connected to the cavity 2.

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

[0031] The cavity 2 can be made of Kovar alloy, Invar steel or silvered ceramic material. In addition, in order to improve the reliability of electrical connection under high and low temperature environmental changes, the coefficient of thermal expansion of the cavity 2 material needs to be close to or the same as that of the ceramic cover plate 1.

[0032] The top of the ceramic cover plate 1 is provided with multiple recessed but not through silver blind holes 3, and the bottom of the silver blind holes 3 is provided with polishing holes 5.

[0033] The cavity 2 has multiple protruding and hollow cavity pillars 6, each cavity pillar 6 is located directly below each silvered blind hole 3, and each cavity pillar 6 has a hollow resonant pillar 7 installed inside, and each resonant pillar 7 has a tuning screw 8 installed inside, thus forming multiple resonators.

[0034] The surface of the ceramic cover plate 1 has a silver layer 4 that extends into the silver blind hole 3 but does not extend into the polished hole 5, while the silver layer 4 does not cover the top of the cavity pillar 6 and the resonant pillar 7.

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

[0036] like Figure 3 As shown, at least one pair (two in each pair) of cavity pillars 6 are connected by a coupling cantilever 9, and an adjustment hole 10 is provided below the coupling cantilever 9. The coupling amount can be adjusted by pressing the coupling cantilever 9 through the ceramic cover plate 1 with an external ejector pin, causing it to deform toward the adjustment hole 10. The larger the protrusion of the coupling cantilever 9, the greater the coupling amount.

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

[0038] Furthermore, in the capacitive coupling structure, the cavity pillar 6 and its internal resonant pillar 7 are connected by a coupling rib 13. The higher the height of the coupling rib 13 (denoted as 'a' in the figure), the stronger the capacitive coupling, and vice versa; the smaller the distance between the cavity pillar 6 and the resonant pillar 7 (denoted as 'b' in the figure), the stronger the coupling, and vice versa; the smaller the distance between the metallized via 11 and the resonant pillar 7 (denoted as 'c' in the figure), the stronger the coupling, and vice versa.

[0039] Preferably, there are two capacitive coupling structures arranged symmetrically, so that the simultaneous use of the two capacitive coupling structures can significantly enhance the amount of capacitive coupling.

[0040] like Figure 6 As shown, in order to obtain a stronger capacitive coupling, a type of deformation can be made to the above capacitive coupling structure, wherein... Figure 6 a, 6b, and 6c show three different structures of this type of deformation. For example... Figure 6 As shown in Figure a, 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 configured to be electrically connected to the resonant disk 18 on the inner surface of the ceramic cover plate 1.

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

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

[0043] like Figure 7 As shown, where Figure 7 a, 7b, and 7c respectively show the... Figure 6 a, 6b, and 6c are another type of modified structure. In this type of modification, 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, while the other end is not connected to the metallized via 11, but is set as an open circuit. This type of modification simplifies the capacitive coupling structure, but reduces the amount of capacitive coupling.

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

[0045] like Figure 10As shown, considering that the material density of cavity 2 is often high and its weight is large, resulting in greater difficulty in welding, cavity 2 can be made of lighter aluminum. A thin layer 17 made of Kovar alloy or Invar is provided between ceramic cover plate 1 and cavity 2. This thin layer 17 does not affect the installation and function of the above structures. Thus, the thermal stress between ceramic cover plate 1 and aluminum cavity 2 can be transferred between thin layer 17 and aluminum cavity 2, thereby improving the reliability of welding.

[0046] The above descriptions are merely some embodiments of this utility model. For those skilled in the art, various modifications and improvements can be made without departing from the inventive concept of this utility model, and all such modifications and improvements fall within the protection scope of this utility model.

Claims

1. A ceramic cover plate cavity filter characterized by: It includes 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); The top of the ceramic cover plate (1) is provided with a plurality of recessed silver-plated blind holes (3), and the surface of the ceramic cover plate (1) has a silver-plated layer (4) that extends into the silver-plated blind holes (3). The cavity (2) has multiple protruding and hollow cavity pillars (6), each cavity pillar (6) is located directly below each silver-plated blind hole (3), and each cavity pillar (6) has a hollow resonant pillar (7) installed inside, and each resonant pillar (7) has a tuning screw (8) installed inside. At least one pair of the cavity columns (6) are also connected by a coupling cantilever (9); The ceramic cover plate (1) is provided with at least one through metallized via (11). The bottom end of the metallized via (11) is connected to the top end of the cavity column (6) through a silver cantilever (12). The cavity column (6) is also connected to the resonant column (7) inside it through a coupling rib (13) to form a capacitive coupling structure. At least one cavity column (6) has a coupling column (14) installed in its hollow part. The resonant column (7) inside the cavity column (6) is electrically connected to a capacitor ring (15). At least one silver ring (16) is provided 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-lid cavity filter of claim 1, wherein: The ceramic cover plate (1) is soldered to the cavity (2) using solder paste.

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

4. The ceramic-lid cavity filter of claim 1, wherein: The bottom of the silvered blind hole (3) is provided with a polishing hole (5), and the silvered layer (4) does not extend into the polishing hole (5).

5. The ceramic-lid cavity filter of claim 1, wherein: The coupling cantilever (9) has an adjustment hole (10) at its lower part.

6. The ceramic-lid cavity filter of claim 1, wherein: 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 as an open circuit.

7. The ceramic-lid cavity filter of claim 6, wherein: The silvered cantilever (12) has two or more, which are electrically connected to two resonant disks (18) on the inner surface of the ceramic cover plate (1).

8. The ceramic-lid cavity filter of claim 1, wherein: The cavity (2) is made of aluminum, and a thin layer (17) made of Kovar alloy or Invar is disposed between the ceramic cover plate (1) and the cavity (2).

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