Dielectric filter capable of realizing double CT zero points

Abstract

The invention discloses a dielectric filter capable of realizing double CT zero points, and the dielectric filter comprises a body made of a solid dielectric material, the surface of the body is provided with a circuit surface and an electrode surface which are adjacent, the circuit surface is provided with two groups of resonance through holes which are arranged in a triangular manner, and a grounding column is formed between every two resonance through holes in each group in a protruding manner. An isolation groove is formed between the two resonance through holes in the top, and the two groups of resonance through holes respectively form a CT zero point. According to the improved scheme, on the basis of a filter of a conventional structure, double CT zero points can be achieved by properly utilizing the size space in the height direction.

Description

Technical Field

[0001] The present application belongs to the field of communication technology, and in particular relates to a dielectric filter capable of realizing dual CT zero points. Background Art

[0002] The one-piece dielectric filter is a single dielectric with N (N≥2) resonant through holes opened in sequence. The dielectric surface is composed of an electrode surface, a circuit surface (open surface) and a short surface. The dielectric surface and the resonant through hole are coated with a certain silver layer. The electrode surface is composed of an input and output electrode silver layer and a grounding silver layer. The electrode is connected to the electrode of the circuit surface to form an input and output port. A coupling capacitor is formed between the silver layer of the input and output port and the silver layer of the first and last resonant cavity on the circuit surface. The signal can enter the filter through the input and output port to realize the filtering function. There are two coupling modes for realizing the passband of the dielectric filter, one is positive coupling (inductive coupling) and the other is negative coupling (capacitive coupling). The zero point mode of the dielectric filter with a conventional structure can be designed as a CT zero point on the left between the three cavities, or as a CQ zero point between the four cavities, but the CT zero point on the right side of the passband is not easy to realize. The CT zero point is usually generated between the three cavities, and the CQ zero point is usually generated between the four resonant cavities. Both the CT zero point and the CQ zero point can be called cross-coupling zero points, which can improve the out-of-band suppression of the filter.

[0003] Conventional one-piece dielectric filters are not easy to realize CT zero points due to structural limitations. If the CT zero point on the right side of the passband needs to be designed, cavities 12 and 23 need to be designed as positive coupling (inductive coupling). When cavity 13 is designed as positive coupling (inductive coupling), a CT zero point will be formed on the right side of the passband to improve the out-of-band suppression index. However, the resonant cavities of the conventional one-piece structure are arranged in a straight row, and the distance between cavities 13 is relatively far, so the inductive coupling is not easy to realize. Usually, capacitive coupling can only be realized in a specific way. In this case, it is difficult to generate a CT zero point on the right side. Summary of the invention

[0004] The purpose of the present invention is to provide a dielectric filter capable of realizing double CT zero points. The improved scheme can realize double CT zero points by properly utilizing the dimension space in the height direction on the basis of a conventional structural filter.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] The embodiment of the present application discloses a dielectric filter capable of realizing dual CT zero points, comprising a body made of solid dielectric material, wherein the surface of the body is respectively formed with adjacent circuit surfaces and electrode surfaces, wherein two groups of resonant through holes are arranged in a triangular pattern, wherein grounding posts are protruded between two of the resonant through holes in each group, and an isolation groove is formed between the two resonant through holes at the top, and the two groups of resonant through holes respectively form a CT zero point.

[0007] Preferably, in the above-mentioned dielectric filter capable of realizing double CT zero points, there is / is not the grounding column between the two groups of the resonant through holes.

[0008] Preferably, in the above-mentioned dielectric filter capable of realizing double CT zero points, two input and output electrodes are symmetrically arranged on the electrode surface, and a U-shaped solder resist groove is formed on the periphery of the input and output electrodes.

[0009] Preferably, in the above-mentioned dielectric filter capable of realizing double CT zero points, the input and output electrodes extend to the two resonant through holes on the circuit surface close to the outer side.

[0010] Preferably, in the above-mentioned dielectric filter capable of realizing dual CT zero points, the length of the grounding column between the two bottom resonant through holes in each group of the resonant through holes arranged in a triangular shape controls the strength of the CT zero point.

[0011] Preferably, in the above-mentioned dielectric filter capable of realizing double CT zero points, the top width of the body is smaller than the bottom width.

[0012] Compared with the prior art, the advantage of the present invention is that the improved solution can realize double CT zero points by properly utilizing the dimension space in the height direction based on the conventional structure filter. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0014] Figure 1 Shown is a circuit diagram of a dielectric filter in a conventional embodiment;

[0015] Figure 2 Shown is a simulation curve diagram of a dielectric filter in a conventional embodiment;

[0016] Figure 3 It is a circuit diagram of a dielectric filter capable of realizing double CT zero points in a specific embodiment of the present invention;

[0017] Figure 4 It is a schematic diagram of the electrode surface of the dielectric filter capable of realizing double CT zero points in a specific embodiment of the present invention;

[0018] Figure 5The figure shows the coupling of the dielectric filter capable of realizing double CT zero points and the schematic diagram of realizing CT zero points in a specific embodiment of the present invention;

[0019] Figure 6 Shown is a simulation curve diagram of a dielectric filter capable of realizing double CT zero points in a specific embodiment of the present invention.

[0020] Figure 7 It is a schematic diagram showing the numbering of the resonant through holes of the dielectric filter capable of realizing double CT zero points in a specific embodiment of the present invention. DETAILED DESCRIPTION

[0021] The following will describe the technical solutions in the embodiments of the present invention in detail in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0022] like Figure 1-2 As shown, a dielectric filter with a 6-cavity structure is used as an example. The center frequency of the filter is 1960MHz, the bandwidth is 60MHz, and there needs to be a certain suppression of the out-of-band 2010MHz. The solder resist groove on the electrode surface is designed as a U-shaped structure. The length*width*height of the dielectric filter is 11*5.3*3.5mm. It is designed as a 6-cavity structure, arranged in sequence. Among them, cavities 12, 23, 45, and 56 are designed as positive coupling, and cavities 34 are designed as negative coupling. Due to the structure, it is difficult to design the CT zero point on the right side of the passband for cavities 13 and 46. The suppression on the right side of the passband of this structure cannot achieve a good effect. Reference Figure 2 According to the simulation curve, the suppression at 2010MHz on the right side of the passband is only about 24dB, and the insertion loss within the band is about 3.5dB.

[0023] For conventional one-piece dielectric filters, the structure is to open N (N≥2) resonant through holes in sequence on a dielectric body. The advantages of this structure are simple mold implementation, multiple products can be shared, and processing is convenient. However, there are certain limitations in the design of zero points. For example, it is difficult to design a CT zero point on the right side of the passband. The CT zero point on the right side needs to satisfy the situation that all three cavities are positively coupled. The first and last cavities of the three cavities of the conventional one-piece dielectric filter can only produce negative coupling (capacitive coupling), and cannot form the effect of a CT zero point. This brings difficulties to the realization of the zero point on the right side of the passband of the dielectric filter.

[0024] like Figure 3-7As shown in the figure, we have designed a new scheme to realize a dielectric filter with double CT zero points, including a body made of solid dielectric material, the surface of the body is respectively formed with adjacent circuit surfaces 101 and electrode surfaces 102, two groups of resonant through holes 103 are arranged in a triangular pattern on the circuit surface 101, and grounding posts 104 are formed between each group of resonant through holes 103, and an isolation groove 105 is formed between the two top resonant through holes 103, and the two groups of resonant through holes 103 respectively form a CT zero point. Two input and output electrodes 106 are symmetrically arranged on the electrode surface 102, and U-shaped solder resist grooves 107 are formed on the periphery of the input and output electrodes 106. The input and output electrodes 106 extend to the two resonant through holes 103 near the outside on the circuit surface 101. The length of the grounding post 104 between the two bottom resonant through holes 103 of each group controls the strength of the CT zero point. The top width of the body is smaller than the bottom width. There is / is no grounding post 104 between the two groups of resonant through holes 103. (The grounding post can be designed between the resonant through holes 3 and 4 or not. In this case, a capacitive coupling, also called negative coupling, is designed between the two groups of resonant through holes. This design can properly balance the passband flatness when the right suppression can be satisfied.)

[0025] The improvement scheme can be achieved by increasing the height dimension on the conventional structure, and the cavity arrangement adopts the upper and lower parallel method. The advantage of this structure is that it is convenient to realize the CT zero point, and the height dimension is properly utilized. The single cavity Q value of the dielectric filter will also be improved to a certain extent, which can reduce the insertion loss index of the filter and is more flexible in design. The filter of this structure can also adjust the frequency of the resonant cavity and the coupling amount between the two resonant cavities by processing the electrode on the electrode surface and designing the circuit on the circuit surface, which is convenient for fine-tuning the performance indicators.

[0026] We take a 6-cavity dielectric filter as an example. The center frequency of the filter is 1960MHz, the bandwidth is 60MHz, and there is a certain suppression of the out-of-band 2010MHz. The electrode surface design is the same as the conventional structure filter. The length*width*height of the filter is 11*5.8*5.4mm. Among them, the 12th, 23rd, 45th and 56th cavities are designed as positive coupling, and the 34th cavity is designed as negative coupling. Since the resonant cavities are arranged up and down, the 13th and 46th cavities can be designed with the CT zero point on the right side. The right-side suppression of this structure can achieve better results. By opening an isolation slot between the 25 cavities, the signal crosstalk can be reduced.

[0027] refer to Figure 6 The simulation curve shows that the suppression at 2010MHz on the right side of the passband can reach about 35dB, and the insertion loss in the band is 2.8-2.9dB. The CT zero point position of the 13-cavity is about 2027.5MHz, and the CT zero point position of the 46-cavity is about 2010MHz. The performance is much better than the conventional solution.

[0028] The improved scheme can realize multiple CT zero points by properly utilizing the dimensional space in the height direction on the basis of the conventional structural filter, thereby improving the out-of-band suppression and the in-band insertion loss index. After the length dimension is fixed, the Q value of the single cavity will be higher because the cavity row of the structure adopts an upper and lower structure.

[0029] The design of the new structure is more flexible, and the resonant cavity can be arranged up and down, which is convenient for realizing multiple CT zero points and enriching the zero point design of the dielectric filter. Because the design of the CT zero point needs to ensure a certain amount of coupling between the head and tail cavities, it can be adjusted by the position of the head and tail resonant cavities and the circuit surface coupling structure design. The structural design is all through-holes, including isolation grooves, which are easy to process and do not have any process difficulties.

[0030] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprise a ..." do not exclude the existence of other identical elements in the process, method, article or device including the elements.

[0031] The above is only a specific implementation of the present application. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present application. These improvements and modifications should also be regarded as the scope of protection of the present application.

Claims

1. A dielectric filter capable of realizing double CT zero points, comprising a body made of solid dielectric material, wherein the surface of the body is respectively formed with adjacent circuit surfaces and electrode surfaces, characterized in that: Two groups of resonant through holes are arranged in a triangle shape on the circuit surface, a grounding column is formed between each two of the resonant through holes in each group, an isolation groove is formed between the two resonant through holes at the top, and the two groups of resonant through holes respectively form a CT zero point.

2. The dielectric filter capable of realizing double CT zero points according to claim 1, characterized in that: There is / is not the grounding post between the two groups of the resonant through holes.

3. The dielectric filter capable of realizing double CT zero points according to claim 1, characterized in that: Two input and output electrodes are symmetrically arranged on the electrode surface, and a U-shaped solder resist groove is formed on the periphery of the input and output electrodes.

4. The dielectric filter capable of realizing double CT zero points according to claim 3, characterized in that: The input and output electrodes extend to the two resonant through holes on the circuit surface close to the outer side.

5. The dielectric filter capable of realizing double CT zero points according to claim 1, characterized in that: The length of the grounding column between the two bottom resonant through holes in each group of the resonant through holes arranged in a triangle shape controls the strength of the CT zero point.

6. The dielectric filter capable of realizing double CT zero points according to claim 1, characterized in that: The top width of the body is smaller than the bottom width.

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