Abstract:
Embodiments relate to the field of technologies of components of communications devices, and provide a dielectric filter, which resolves a problem that a solid dielectric filter has a difficulty in implementing capacitive coupling. The dielectric filter includes at least two dielectric resonators, where each of the dielectric resonators includes a body made of a solid-state dielectric material, and an adjusting hole located on a surface of the body. The adjusting hole is a blind hole, configured to adjust a resonance frequency of the dielectric resonator on which the blind hole is located. The bodies of all the dielectric resonators included by the dielectric filter form a body of the dielectric filter.

Description:
[0001]    This application is a continuation of International Application No. PCT/CN2013/076539, filed on May 31, 2013, which is hereby incorporated by reference in its entirety. 
     
    
     TECHNICAL FIELD 
       [0002]    The present invention relates to components of communications devices, and in particular, to a dielectric filter, a transceiver, and a base station. 
       BACKGROUND 
       [0003]    Radio frequency filters are components frequently used in communications devices, and have many types and forms. Metal coaxial cavity filters in the radio frequency filters are applied to radio frequency front-ends of high-power wireless communications base stations due to their desirable performance indicators (including an insertion loss and a power capacity). 
         [0004]    As wireless communications technologies develop, wireless communications base stations are distributed in an increasingly dense manner, and it is required that volumes of the base stations become increasingly small, where a radio frequency front-end filter module occupies a relatively large proportion of a volume of a base station; therefore, a filter is also required to have an increasingly small volume. However, when a volume of a metal coaxial cavity filter is reduced, it is found that a smaller volume of the filter results in a greater surface current, a greater loss, and a lower power bearing capability, that is, a smaller power capacity. That is, with a decrease in the volume of the metal coaxial cavity filter, performance indicators of the metal coaxial cavity filter deteriorate. 
         [0005]    At present, there is a miniaturized filter that uses a body made of a solid-state dielectric material and a resonator that is formed by metalizing (for example, plating silver on) a surface of the body (a solid dielectric resonator for short). Multiple resonators and coupling between the resonators form a filter (a solid dielectric filter for short). The coupling between the resonators may be classified into positive coupling (which may also be referred to as inductive coupling) and negative coupling (which may also be referred to as capacitive coupling) by polarity. A transmission zero may be formed based on a polarity of coupling between the resonators. The transmission zero refers to a frequency outside a passband of a filter, and on the frequency, a degree of suppression that is applied by the filter on a signal at the frequency is theoretically infinite. The addition of a transmission zero can effectively enhance a near-end suppression capability of the filter (that is, a suppression capability of a frequency near the passband). For example, in a three-cavity filter, if coupling between resonators  1  and  2 , coupling between resonators  2  and  3 , and coupling between resonators  1  and  3  are positive coupling, a transmission zero is formed on the right side of a passband. However, if the coupling between the resonators  1  and  2 , and the coupling between the resonators  2  and  3  are positive coupling, and the coupling between the resonators  1  and  3  is negative coupling, a transmission zero is on the left side of the passband. To implement negative coupling, structures shown in  FIG. 1   a  and  FIG. 1   b  are currently used in a solid dielectric filter. A mechanical part  10  at least a surface of which is metalized is connected between two solid dielectric resonators  11  and  12 , and the two solid dielectric resonators are separated by using a groove  13 , where the resonator  11  and the mechanical part  10  are coupled by using an electric field, to form a current on the mechanical part  10 , the current flows to the resonator  12  along the mechanical part  10 , and the mechanical part  10  and the resonator  12  are coupled by using an electric field, thereby forming capacitive coupling between the two resonators. 
         [0006]    However, because the interior of the solid dielectric resonator is a solid medium instead of air, and the solid medium is formed by die casting, an implementation technique of a metalized mechanical part inside the solid medium is very difficult, and a coupling degree of the capacitive coupling cannot be adjusted. 
       SUMMARY OF THE INVENTION 
       [0007]    Embodiments provide a dielectric filter, which resolves an existing problem that a solid dielectric filter has a difficulty in implementing capacitive coupling. 
         [0008]    To achieve the foregoing objective, the following technical solutions are used in the embodiments. 
         [0009]    According to a first aspect, the present invention provides a dielectric filter, including at least two dielectric resonators, where each of the dielectric resonators includes a body made of a solid-state dielectric material, and an adjusting hole located on a surface of the body, the adjusting hole is a blind hole, configured to adjust a resonance frequency of the dielectric resonator on which the blind hole is located. The bodies of all the dielectric resonators included by the dielectric filter form a body of the dielectric filter. The dielectric filter further includes at least one negative coupling hole, where each of the negative coupling hole is located at a position of a surface of the body, at which two dielectric resonators are connected, the position at which the negative coupling hole is located is connected to the two dielectric resonators. The negative coupling hole is a blind hole, configured to implement capacitive coupling between the two dielectric resonators. A conducting layer covering the surface of the body of the dielectric filter, a surface of the adjusting hole, and a surface of the negative coupling hole. 
         [0010]    In a first possible implementation manner according to the first aspect, a depth of the negative coupling hole is twice or more each of depths of adjusting holes of the two dielectric resonators connected to the position at which the negative coupling hole is located. 
         [0011]    In a second possible implementation manner according to the first aspect or the first possible implementation manner of the first aspect, the depth of the negative coupling hole is related to a frequency of a transmission zero of the dielectric filter. 
         [0012]    In a third possible implementation manner according to the first aspect or the first or second possible implementation manner of the aspect first, a quantity of the negative coupling holes is equal to a quantity of transmission zeros of the dielectric filter. 
         [0013]    In a fourth possible implementation manner according to the first aspect or any one of the first to third possible implementation manners of the first aspect, the two dielectric resonators connected to the position at which the negative coupling hole is located are related to the frequency of the transmission zero of the dielectric filter. 
         [0014]    In a fifth possible implementation manner according to the first aspect or any one of the first to fourth possible implementation manners of the first aspect, a surface on which the at least two dielectric resonators are connected includes a conducting layer. 
         [0015]    In a sixth possible implementation manner according to the first aspect or any one of the first to fifth possible implementation manners of the first aspect, a part of the surface of the negative coupling hole is not covered by the conducting layer. 
         [0016]    In a seventh possible implementation manner according to the sixth possible implementation manner of the first aspect, an area of the part of the surface of the negative coupling hole, which is not covered by the conducting layer, is related to a coupling degree of the capacitive coupling between the two dielectric resonators that are connected to the position at which the negative coupling hole is located. 
         [0017]    In an eighth possible implementation manner according to the first aspect or any one of the first to seventh possible implementation manners of the first aspect, a part of the surface of the adjusting hole is not covered by the conducting layer. 
         [0018]    In a ninth possible implementation manner according to the eighth possible implementation manner of the first aspect, an area of the part of the surface of the adjusting hole, which is not covered by the conducting layer, is related to the resonance frequency of the dielectric resonator on which the adjusting hole is located. 
         [0019]    In a tenth possible implementation manner according to the first aspect or any one of the first to ninth possible implementation manners of the first aspect, the solid-state dielectric material is ceramic. 
         [0020]    According to a second aspect, embodiments provide a transceiver, including the dielectric filter provided according to the first aspect or any one of the first to tenth possible implementation manners of the first aspect. 
         [0021]    According to a third aspect, embodiments provide a base station, including the transceiver provided in the second aspect. 
         [0022]    According to the dielectric filter, the transceiver, and the base station that are provided by the embodiments, because in a manner of punching a blind hole on a body made of a solid-state dielectric material, capacitive coupling is formed between resonators on two sides of the blind hole, a manufacturing technique of a structure that implements capacitive coupling is simplified. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0023]    To describe the technical solutions in the embodiments of the present invention or in the prior art more clearly, the following briefly introduces the accompanying drawings required for describing the embodiments or the prior art. 
           [0024]      FIG. 1   a  is a schematic sectional view of a structure in a solid dielectric filter that is used to implement capacitive coupling in the prior art; 
           [0025]      FIG. 1   b  is a side view of a structure in a solid dielectric filter that is used to implement capacitive coupling in the prior art; 
           [0026]      FIG. 2   a  is a schematic sectional view of a structure in a dielectric filter that is used to implement capacitive coupling according to an embodiment; 
           [0027]      FIG. 2   b  is a side view of a structure in a dielectric filter that is used to implement capacitive coupling according to an embodiment; 
           [0028]      FIG. 3  is a schematic view of a structure in a dielectric filter that is used to implement capacitive coupling according to an embodiment; 
           [0029]      FIG. 4  is a schematic view of a structure in a dielectric filter that is used to implement capacitive coupling according to an embodiment; and 
           [0030]      FIG. 5  is a schematic view of a structure in a dielectric filter that is used to implement capacitive coupling according to an embodiment. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0031]    The following clearly describes the technical solutions in the embodiments with reference to the accompanying drawings in the embodiments of the present invention. 
         [0032]    An embodiment provides a dielectric filter. As shown in  FIG. 2   a  and  FIG. 2   b , the dielectric filter includes at least two dielectric resonators ( 21 ,  22 ), where each of the dielectric resonators ( 21 ,  22 ) includes a body  201  made of a solid-state dielectric material, and a blind hole  202  located on a surface of the body and configured to adjust a resonance frequency (an adjusting hole for short), and the bodies of all the dielectric resonators included by the dielectric filter form a body of the dielectric filter. The dielectric filter further includes at least one blind hole  23  configured to implement capacitive coupling between the dielectric resonator  21  and the dielectric resonator  22  (a negative coupling hole for short), where the negative coupling hole  23  is located at a position of a surface of the body, at which the two dielectric resonators are connected, and the position at which the negative coupling hole is located is connected to the two dielectric resonators. The dielectric filter further includes a conducting layer  203  covering the surface of the body of the dielectric filter, a surface of the adjusting hole, and a surface of the negative coupling hole. Usually, a negative coupling hole is located on a surface of the body in the middle of two adjusting holes. The negative coupling hole and a body around the negative coupling hole form a structure similar to a resonator, and the negative coupling hole is similar to an adjusting hole of the resonator. A depth of the negative coupling hole is greater than each of depths of the adjusting holes on two sides of the negative coupling hole, and is usually twice or more each of the depths of the adjusting holes on the two sides of the negative coupling hole, so that a resonance frequency of the resonator may be lower than resonance frequencies of the resonators on the two sides of the negative coupling hole, and is usually a half or less than a half of the resonance frequencies of the resonators on the two sides of the negative coupling hole, thereby forming capacitive coupling between the dielectric resonator  21  and the dielectric resonator  22 . The depth of the negative coupling hole is related to a frequency of a transmission zero of the dielectric filter. Specifically, the depth of the negative coupling hole may be designed according to an actual requirement, for example, the frequency of the transmission zero, and is not limited herein. Usually, there is one negative coupling hole between the two dielectric resonators, and one transmission zero is implemented. There may be one or more negative coupling holes on the dielectric filter, and a quantity and positions of negative coupling holes (referring to between which two dielectric resonators the negative coupling holes are located) may be determined according to a quantity and frequencies of transmission zeros that are actually required. Specifically, a quantity of negative coupling holes is equal to a quantity of transmission zeros of the dielectric filter. The two dielectric resonators connected to the position at which the negative coupling hole is located are determined according to the frequency of the transmission zero of the dielectric filter. 
         [0033]    The conducting layer may be a metalized layer, and specifically, may be formed by electroplating metal on the surface of the body. The metal may be silver, or may be another metal that satisfies an actual requirement. 
         [0034]    During specific manufacturing, the body with the adjusting holes and the negative coupling hole may be obtained by means of integrated molding, and then the surface of the body is metalized, for example, the surface is electroplated, to obtain the foregoing dielectric filter. In this case, the bodies of the dielectric resonators included by the dielectric filter are continuous. The dielectric filter is obtained by means of integrated molding, so that a manufacturing technique can be easier. 
         [0035]    Further, as shown in  FIG. 3 , a surface on which the dielectric resonators that are included by the dielectric filter are connected may also include a conducting layer  301 . During specific manufacturing, a dielectric resonator with an adjusting hole and a part of a negative coupling hole may be manufactured first, where the dielectric resonator is formed by a body and a conducting layer. A dielectric filter is formed by connecting conducting layers of at least two such dielectric resonators, and a specific connection manner may be welding, sintering, or the like, which may not be limited in this embodiment of the present invention. In the formed dielectric filter, the part of the negative coupling hole of the dielectric resonator, and a part of a negative coupling hole of another dielectric resonator that is connected to the dielectric resonator form a complete negative coupling hole. 
         [0036]    Further, as shown in  FIG. 4 , a part  401  of the surface of the negative coupling hole may not be covered by the conducting layer.  FIG. 4  is a schematic view that uses the dielectric filter shown in  FIG. 2   a  as an example, and is also applicable to another dielectric filter provided by an embodiment of the present invention. An area of the part of the surface of the negative coupling hole, which is not covered by the conducting layer, is related to a coupling degree of the capacitive coupling between the two dielectric resonators that are connected to the position at which the negative coupling hole is located. That is, a part of the conducting layer inside the negative coupling hole may be removed, to adjust the resonance frequency of the structure similar to the resonator that is formed by the negative coupling hole and the body around the negative coupling hole, thereby adjusting a coupling degree between resonators that are on two sides of the negative coupling hole. By adjusting a size of an area inside the negative coupling hole, from which the conducting layer is removed, the coupling degree of the capacitive coupling between the dielectric resonator  21  and the dielectric resonator  22  may be changed. Specifically, the area of the part inside the negative coupling hole, from which the conducting layer is removed, may be adjusted in a polishing manner, which may not be limited in this embodiment of the present invention. The part from which the conducting layer is removed may be located at an inner bottom or on an inner side inside the negative coupling hole, and may be one position, or may be multiple discontinuous positions. 
         [0037]    Each of the dielectric resonators may include one or more adjusting holes, and a specific quantity may be designed according to an actual requirement. 
         [0038]    Further, as shown in  FIG. 5 , a part  501  of the surface of the adjusting hole may not be covered by the conducting layer.  FIG. 5  is a schematic view that uses the dielectric filter shown in  FIG. 4  as an example, and is also applicable to another dielectric filter provided by an embodiment. An area of the part of the surface of the adjusting hole, which is not covered by the conducting layer, is related to the resonance frequency of the dielectric resonator on which the adjusting hole is located. That is, a part of the conducting layer inside the adjusting hole may be removed, to adjust the resonance frequency of the resonator on which the adjusting hole is located. Specifically, the resonance frequency may be changed by adjusting a size of an area inside the adjusting hole, from which the conducting layer is removed. The area of the part inside the adjusting hole, from which the conducting layer is removed, may be adjusted in a polishing manner, which may not be limited in this embodiment. The part from which the conducting layer is removed may be located at an inner bottom or on an inner side inside the adjusting hole, and may be one position, or may be multiple discontinuous positions, which may be specifically designed according to an actual requirement. A conducting layer inside a blind hole on a body is removed to implement an adjustment of a resonance frequency, so that the resonance frequency is kept better. 
         [0039]    The adjusting hole or the negative coupling hole may be in a shape of a rectangle or a circle, or may be in another shape, which may not be limited in this embodiment. 
         [0040]    In the dielectric filter provided by the embodiments, because in a manner of punching a blind hole on a body made of a solid-state dielectric material, capacitive coupling is formed between resonators on two sides of the blind hole, a manufacturing technique of a structure that implements capacitive coupling is simplified. Further, an adjustment of a coupling degree of capacitive coupling may be implemented by adjusting a size of an area of a part removed from a conducting layer inside the punched blind hole. 
         [0041]    The dielectric material used in the dielectric filter that is provided by the foregoing embodiments is preferably ceramic. Ceramic has a high dielectric constant (which is 36), and has both desirable hardness and desirable high temperature resistant performance; therefore, ceramic becomes a solid-state dielectric material frequently used in the field of radio frequency filters. Certainly, other materials such as glass and electrical-insulating macromolecular polymer known by a person skilled in the art may also be selected as the dielectric material. 
         [0042]    The dielectric filter provided in the embodiments is mainly used for a radio frequency front-end of a high-power wireless communications base station. 
         [0043]    An embodiment further provides a transceiver, where the dielectric filter provided in the foregoing embodiments is used in the transceiver. The dielectric filter may be configured to filter a radio frequency signal. 
         [0044]    An embodiment further provides a base station, where the transceiver provided in the foregoing embodiment is used in the base station. 
         [0045]    The foregoing descriptions are merely specific implementation manners of the present invention, but are not intended to limit the protection scope of the present invention. Any variation or replacement readily figured out by a person skilled in the art within the technical scope disclosed in the present invention shall fall within the protection scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.