Cavity filter filled with medium
Technical Field
The invention relates to the technical field of communication equipment, in particular to a dielectric-filled cavity filter.
Background
Filters are important components in communication devices, and the types and forms of the filters are different according to index requirements. The metal cavity filter has excellent insertion loss and power capacity performance, and is widely applied to the radio frequency front end of a wireless communication base station.
With the development of the 5G technology, the distribution of wireless communication base stations is more and more intensive, the base stations are required to be smaller and smaller, and the loss is increased when the size of the metal cavity filter is reduced. Therefore, the performance index is deteriorated when the volume of the metal cavity filter is reduced.
Disclosure of Invention
Aiming at the defects of the prior art, the invention provides a dielectric-filled cavity filter to solve the problems in the prior art.
In order to realize the purpose, the technical scheme adopted by the invention is as follows:
a dielectric-filled cavity filter comprising: at least two dielectric-filled cavity resonators and at least one connecting body;
the dielectric filling cavity resonator and the connecting body are rectangular and have the same height, the width of the connecting body is smaller than or equal to that of the dielectric filling cavity resonator, the side face of the dielectric filling cavity resonator is fixedly connected with one side face of the connecting body, and the other side face of the connecting body is fixedly connected with the side face of the other dielectric filling cavity resonator.
The upper surface or the lower surface of the dielectric filling cavity resonator is provided with a tuning hole for tuning the resonant frequency, and the tuning hole is a blind hole.
The surfaces of the dielectric-filled cavity resonator and the connecting body and the inner wall of the tuning hole are covered with a layer of silver as a conductive layer.
The surfaces of the dielectric-filled cavity resonator and the connecting body are removed with a rectangular shaped conductive layer, the rectangular area being located between the two tuning holes and not touching the tuning holes. The middle part of the rectangular area is provided with a negative coupling sheet in a rectangular shape, and the negative coupling sheet covers the surfaces of the dielectric filling cavity resonator and the connecting body at the same time.
The negative coupling sheet is realized in a silver plating mode and is used for realizing capacitive coupling between the two dielectric-filled cavity resonators;
a surface conductive layer covering the body surface, tuning hole surface and negative coupling of the dielectric-filled cavity filter.
Further, the length and width of the negative coupling foil are related to the frequency of the transmission zero of the dielectric filled cavity filter.
Further, the number of the negative coupling sheets is less than or equal to the number of transmission zeros of the dielectric filled cavity filter.
Further, the two dielectric-filled cavity resonators connected with the negative coupling sheet at the position are related to the frequency of the transmission zero of the dielectric-filled cavity filter.
Further, the area of the negative coupling sheet is related to the coupling amount of capacitive coupling of the two dielectric-filled cavity resonators at which the negative coupling sheet is connected.
Under the condition that the width of the negative coupling sheet is not changed, the length of the negative coupling sheet is related to the coupling quantity of capacitive coupling of two dielectric-filled cavity resonators connected at the position of the negative coupling sheet.
Under the condition that the length of the negative coupling sheet is not changed, the width of the negative coupling sheet is related to the coupling quantity of capacitive coupling of two dielectric-filled cavity resonators connected at the position of the negative coupling sheet.
The area of the negative coupling sheet is related to the resonant frequency of the dielectric-filled cavity resonator where the negative coupling sheet is located.
Furthermore, the dielectric filling cavity resonator and the connecting body are made of ceramic.
Further, the connecting body between the two dielectric-filled cavity resonances is at the middle position of the side of the dielectric-filled cavity resonance or at the edge position of the side.
Compared with the prior art, the invention has the advantages that:
the capacitive coupling between the resonators on the two sides is realized by changing the way of brushing silver on the body made of the solid dielectric material, and the manufacturing process of the structure for realizing the capacitive coupling is simplified. The method can be integrally formed in the aspect of processing and production, has simple process realization and is beneficial to large-scale batch production.
Drawings
Fig. 1 is a schematic cross-sectional view of a dielectric-filled cavity filter for implementing a capacitive coupling structure according to an embodiment of the present invention;
fig. 2 is a top view of a dielectric-filled cavity filter for implementing a capacitive coupling structure according to an embodiment of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be further described in detail below with reference to the accompanying drawings by way of examples.
There is a miniaturized filter using a body made of a solid dielectric material and metallizing (e.g. silver plating) the surface of the body to form a resonator. The plurality of resonators and the resonators are coupled to form a filter, namely, a dielectric-filled cavity filter. Wherein the coupling between the respective resonators can be divided into positive coupling (which may also be referred to as inductive coupling) and negative coupling (which may also be referred to as capacitive coupling) according to polarity. Transmission zeros may be formed based on the coupling polarities of the respective resonators. The transmission zero is a frequency point outside the passband of the filter, the signal suppression of the filter on the frequency point at the frequency point theoretically reaches infinity, and the transmission zero is increased, so that the suppression capability of the near end of the filter (namely, the suppression capability of the frequency point closer to the passband) can be effectively increased. For example, in a three-cavity filter, the coupling between the resonators a and b, b and c, and a and c is positive, and the transmission zero is formed on the right side of the passband. If the coupling between resonators a and b, b and c is positive and the coupling between a and c is negative, the transmission zero is to the left of the passband. To achieve negative coupling, structures as shown in fig. 1 and 2 are currently employed in solid dielectric filled cavity filters: a structural member 12 having an incompletely metallized surface is connected between dielectric-filled cavity resonator a10 and dielectric-filled cavity resonator B11, dielectric-filled cavity resonator a10 and dielectric-filled cavity resonator B11 are coupled to structural member 12 by an electric field, and a current is generated in structural member 12, and flows along structural member 12 to dielectric-filled cavity resonator B11, and structural member 12 is coupled to dielectric-filled cavity resonator B11 by an electric field, thereby forming a capacitive coupling between the two resonators.
Embodiment 1 of the present invention provides a dielectric-filled cavity filter, as shown in fig. 1 and 2, the dielectric-filled cavity filter includes at least two dielectric-filled cavity resonators, in this embodiment, a dielectric-filled cavity resonator a10 and a dielectric-filled cavity resonator B11; the side surface of each dielectric filling cavity resonator is connected with a connecting body 12 made of a solid dielectric material, and a tuning hole 101 which is positioned on the surface of the dielectric filling cavity resonator and is used for debugging the resonant frequency is formed, wherein the tuning hole 101 is a blind hole;
the dielectric-filled cavity resonator A10, the dielectric-filled cavity resonator B11 and the connecting body 12 form a body of the dielectric-filled cavity filter; the dielectric-filled cavity filter further comprises at least one negative coupling foil 103 for achieving a capacitive coupling between the dielectric-filled cavity resonator a10 and the dielectric-filled cavity resonator B11,
the upper surface or the lower surface of the dielectric filling cavity resonator is provided with a tuning hole 101 for tuning the resonant frequency, and the tuning hole 101 is a blind hole.
The surfaces of the dielectric-filled cavity resonator and the connecting body 12 and the inner walls of the tuning hole 101 are covered with a layer of silver as a conductive layer.
The surfaces of the dielectric-filled cavity resonator and the connecting body 12 are stripped of the rectangular shaped conductive layer to form a rectangle. The rectangle is located between the two tuning holes 101 and does not touch the tuning holes 101.
A negative coupling sheet 103 is arranged in the middle of the rectangle, and the negative coupling sheet 103 covers the surfaces of the dielectric-filled cavity resonator A10, the dielectric-filled cavity resonator B11 and the connecting body 12 at the same time
The negative coupling sheet 103 is attached to the surfaces of the dielectric-filled cavity resonator A10, the dielectric-filled cavity resonator B11 and the connector, and the negative coupling sheet 103 is positioned between and connected with the dielectric-filled cavity resonator A10 and the dielectric-filled cavity resonator B11;
the connecting body 12 can be located in the middle part or in the edge part, as desired, while usually a negative coupling foil 103 is located between two tuning holes 101.
The length of the negative coupling foil 103 is related to the frequency of the transmission zero of the dielectric filled cavity filter. Specifically, the length of the negative coupling sheet 103 can be designed according to practical requirements, such as the frequency of the transmission zero, and is not limited herein.
The number of negative coupling flakes 103 between two dielectric-filled cavity resonators is typically one, achieving one transmission zero. The number of the negative coupling sheets 103 on the dielectric-filled cavity filter may be 1 or more than 1, and the number and the positions of the negative coupling sheets 103 (which means between which two dielectric-filled cavity resonators are located) may be determined according to the number and the frequency of transmission zeros actually required. Specifically, the number of the negative coupling sheets 103 is equal to the number of transmission zeros of the dielectric filled cavity filter, and when symmetric zeros are set, one negative coupling sheet 103 corresponds to two out-of-band transmission zeros. The two medium-filled cavity filters connected with the negative coupling sheet 103 are determined according to the frequency of the transmission zero of the medium-filled cavity filters.
The conductive layer may be a metallization layer, and may be formed by electroplating metal on the surface of the body. The metal can be silver, and can also be other metals meeting the actual requirement.
In particular, the body of the tuning hole may be obtained by integral forming, and the negative coupling sheet 103 may be manufactured during surface metallization of the body, such as surface plating, to obtain the dielectric-filled cavity filter. The dielectric-filled cavity filter comprises a dielectric-filled cavity resonator having a continuous body. The dielectric filter is obtained by adopting an integrated forming mode, so that the processing technology is simpler.
The number of tuning holes included in each dielectric-filled cavity resonator may be 1 or more than 1, and the specific number may be designed according to actual needs.
In the dielectric-filled cavity filter provided by the embodiment of the invention, the capacitive coupling is formed between the resonators on two sides of the blind hole in the mode of plating the silver negative coupling sheet 103 on the body made of the solid dielectric material, so that the manufacturing process of the structure for realizing the capacitive coupling is simplified. And further, the adjustment of the coupling amount of the capacitive coupling can be realized by adjusting the size of the area of the silver-plated negative coupling sheet 103, preferably the length of the negative coupling sheet 103.
The dielectric material used in the dielectric filter provided in the above embodiment is preferably ceramic, which has a high dielectric constant (20.5) and good hardness and high temperature resistance, and thus becomes a solid dielectric material commonly used in the field of radio frequency filters. Of course, other materials known to those skilled in the art, such as glass, electrically insulating polymers, etc., may be used as the dielectric material.
It will be appreciated by those of ordinary skill in the art that the examples described herein are intended to assist the reader in understanding the manner in which the invention is practiced, and it is to be understood that the scope of the invention is not limited to such specifically recited statements and examples. Those skilled in the art can make various other specific changes and combinations based on the teachings of the present invention without departing from the spirit of the invention, and these changes and combinations are within the scope of the invention.