Novel ceramic waveguide filter with transmission zero point

Abstract

The utility model discloses a novel ceramic waveguide filter with a transmission zero point, comprising a ceramic housing which is composed of a first frequency resonant cavity, a second frequency resonant cavity, a third frequency resonant cavity, a fourth frequency resonant cavity, a fifth frequency resonant cavity, a sixth frequency resonant cavity, a first zero cavity and a second zero cavity. Wherein the first frequency resonant cavity and the sixth frequency resonant cavity are port resonant cavities; the first frequency resonant cavity, the second frequency resonant cavity, the third frequency resonant cavity, the fourth frequency resonant cavity, the fifth frequency resonant cavity, the sixth frequency resonant cavity, the first zero cavity and the second zero cavity are each provided with a first frequency resonant hole, a second frequency resonant hole, a third frequency resonant hole, a fourth frequency resonant hole, a fifth frequency resonant hole, a sixth frequency resonant hole, a first zero cavity resonant hole and a second zero cavity resonant hole. The resonant frequency of the resonant cavity with the corresponding frequency and the resonant frequency of the zero cavity are respectively generated. According to the utility model, through the innovative design, the use of a traditional cross coupling structure is avoided so as to realize the transmission zero point.

Description

Technical Field

[0001] The utility model relates to the technical field of filters in microwave communication, and particularly relates to a novel ceramic waveguide filter with transmission zeros. Background Technique

[0002] With the continuous development of modern communication technology, the requirements for filters are getting higher and higher. Therefore, filter technologies with small size, light weight, high performance and low cost are extremely important for filters in modern wireless communication applications. At present, in the application scenario of 5G communication array antennas, traditional metal cavity filters can no longer meet the requirements of wireless communication systems in terms of volume or weight.

[0003] Due to the characteristic of high relative permittivity of ceramic materials, at microwave frequencies, the wavelength of electromagnetic waves in ceramic materials varies with the relative permittivity of the materials. The relationship between the wavelength of electromagnetic waves and the relative permittivity of ceramic materials can be expressed as:

[0004]

[0005] λ: The wavelength of microwaves in ceramic materials, in meters (m); λ 0 : The wavelength of microwaves in vacuum, in meters (m); ε r : The relative permittivity of ceramic materials. It can be seen from the formula that:

[0006] When electromagnetic waves of the same frequency pass through, the greater the relative permittivity of the ceramic material, the shorter the wavelength of the electromagnetic waves in the ceramic material. Generally, the sizes of ceramic waveguide resonators are integer multiples of half-wavelengths. Therefore, the sizes of ceramic material waveguide resonators with high relative permittivity can be designed to be smaller, thus realizing the miniaturization and light weight of the filter. Therefore, ceramic filters have become the mainstream filter design scheme in the contemporary communication field.

[0007] At present, most ceramic waveguide filters basically need to have transmission zeros to achieve better technical indicators to meet the current overall machine usage requirements. In order to achieve transmission zeros, in the prior art, a cross-coupling structure is usually adopted to achieve transmission zeros, which involves designing coupling holes, coupling slots, isolation slots and other structures between three or four non-adjacent resonators. Therefore, the overall structure is mostly two rows of resonators arranged in parallel, in a ring or U-shaped structure; in the case of more transmission zeros, a double-layer ring or U-shaped structure will also be adopted. In this way, the port input and output are mostly on the same side and close to each other, which will not only increase the installation cost, but also cause low port isolation and signal crosstalk and other problems, and cannot well meet the high integration requirements of the "direct input and direct output" structure of signals in contemporary communication systems. The following are two existing patents on ceramic waveguide filters:

[0008] Existing Patent 1: CN 114762183 A. This patent discloses a ceramic waveguide filter, which is a common ceramic waveguide filter on the market currently. It uses a cross-coupling form to achieve a pair of transmission zeros. The specific solution is as follows: Four resonators 132, 133, 134, and 135 are arranged in sequence. These four resonators form a cross-coupling topology of a CQ (cascaded quadruplet), where the solid lines represent the main coupling between adjacent resonators, and the dashed lines represent the cross-coupling between non-adjacent resonators. At the same time, 133 and 134 form a capacitive coupling through the coupling hole 140, an inductive coupling is formed between the two non-adjacent resonators 132 and 135, and all other cavities are inductively coupled, thus achieving one transmission zero at the low end and one at the high end. There are some deficiencies in this ceramic waveguide filter:

[0009] 1. The input and output ports 151 and 152 are located on the same side of the filter, with a short distance, low port isolation, and signal crosstalk is likely to occur.

[0010] 2. In order to separate the port resonators 131 and 136 and eliminate the parasitic coupling between them, a separation window 121 is opened between the two end cavities 131 and 136 of this filter. The 121 separation window cannot penetrate the side wall of the ceramic housing, otherwise the mechanical strength of the entire filter will be greatly reduced. Therefore, this separation window cannot well eliminate the parasitic coupling between 131 and 136, and there are great limitations.

[0011] 3. Since the ceramic waveguide filter is debugged by grinding the key dimensions such as the resonant holes, coupling holes, and separation windows on the ceramic, there is irreversibility, making debugging the core difficulty of the current ceramic waveguide filter. For the four resonators forming the CQ cross-coupling topology, the resonant frequency of each cavity and the coupling between any two cavities will affect the transmission zeros. Therefore, there are many factors affecting the position of the transmission zeros, the debugging difficulty is large, and the debugging cost is high.

[0012] Existing Patent 2: CN117638435 A. A ceramic waveguide filter disclosed in this patent also generates a pair of transmission zeros through a cross-coupling structure; a "T"-shaped coupling window structure is added between the four resonators 2-3-4-5 (301), dividing the four resonators into two isosceles triangle structures 2-3-5 and 2-4-5, forming two CT (cascaded triplet) cross-coupling topologies. In the 2-3-5 CT structure, the coupling between 3 and 5 is capacitive, and the couplings between 2-3 and 2-5 are inductive, achieving one transmission zero at the low end; similarly, in the 2-4-5 CT structure, the couplings between 2-4, 4-5, and 2-5 are all inductive, achieving one transmission zero at the high end.

[0013] Furthermore, it places ports 201 and 701 on both sides of the entire filter, improving the port isolation, reducing signal crosstalk, and optimizing the parasitic coupling between the two port resonators. However, this filter design has structural deficiencies:

[0014] 1. The filter has a hexahedron unconventional structure, which will create a large gap during installation in actual base station applications, resulting in low space utilization of the entire base station and being impractical;

[0015] 2. If it is changed to a common cuboid structure, the volume of the entire filter will increase, and the useless volume will also increase accordingly, greatly reducing the utilization rate of the ceramic shell itself and increasing the cost.

[0016] 3. To meet the coupling between resonators, there are too many through holes 10 and 13 in the structure of this filter. Not only is the structure complex, the processing cost high, and the consistency poor, but it also increases the factors affecting the frequency, coupling, and transmission zeros of the resonator cavity. Similar to Patent 1, the debugging difficulty is large and the debugging cost is high. Summary of the Utility Model

[0017] The purpose of the present utility model is to provide a new type of ceramic waveguide filter with transmission zeros to solve the problems raised in the above background technology.

[0018] To achieve the above purpose, the present utility model provides the following technical solution: A new type of ceramic waveguide filter with transmission zeros, including a ceramic shell, the ceramic shell is composed of frequency resonator cavity one, frequency resonator cavity two, frequency resonator cavity three, frequency resonator cavity four, frequency resonator cavity five, frequency resonator cavity six, zero cavity one, and zero cavity two, where frequency resonator cavity one and frequency resonator cavity six are port resonator cavities;

[0019] Frequency resonator cavity one, frequency resonator cavity two, frequency resonator cavity three, frequency resonator cavity four, frequency resonator cavity five, frequency resonator cavity six, zero cavity one, and zero cavity two are all provided with frequency resonator holes one, frequency resonator holes two, frequency resonator holes three, frequency resonator holes four, frequency resonator holes five, frequency resonator holes six, zero cavity resonator holes one, and zero cavity resonator holes two, which respectively generate the resonant frequencies of the corresponding frequency resonator cavities and the resonant frequency of the zero cavity; among them, frequency resonator hole one and frequency resonator hole six are port resonator holes; zero cavity resonator hole one resonates to generate a low-end transmission zero, and its resonant frequency is equal to the frequency point at the low-end transmission zero position, and zero cavity resonator hole two resonates to generate a high-end transmission zero, and its resonant frequency is equal to the frequency point at the high-end transmission zero position;

[0020] A capacitive coupling square groove is provided between zero cavity two and the adjacent frequency resonator cavity six, and the capacitive coupling square groove is a blind groove, the opening direction is opposite to the opening direction of the resonator hole, and the depth of the square groove is greater than one-half of the ceramic shell;

[0021] A coupling isolation window is provided between the zero cavity one and the frequency resonance cavity one;

[0022] Coupling isolation windows one, two, three, four, and five are provided between adjacent two of the frequency resonance cavities one, two, three, four, five, and six;

[0023] Frequency resonance holes one and six are designed on the frequency resonance cavity one and the frequency resonance cavity six, and port feed probe holes one and two are opened at precise positions directly below the frequency resonance holes one and six.

[0024] Preferably, the ceramic housing is made from a ceramic powder raw material ratio through a firing process.

[0025] Preferably, the relative dielectric constant of the ceramic housing is selected to be 23.

[0026] Preferably, the frequency resonance holes one, two, three, four, five, six, the zero cavity resonance holes one and two are shallow blind holes, and their depth is designed not to exceed half of the total thickness of the ceramic housing.

[0027] Preferably, the frequency resonance holes one, two, three, four, five, six, the zero cavity resonance holes one and two, and the capacitive coupling square groove are designed on the same horizontal line.

[0028] Preferably, a conductive coating is attached to the surface of the ceramic housing and the inner walls of the frequency resonance holes one, two, three, four, five, six, the zero cavity resonance holes one and two, the port feed probe holes one and two, and the capacitive coupling square groove.

[0029] Compared with the prior art, the beneficial effects of the present utility model are:

[0030] 1. This patent does not adopt the current technical solution of using a cross-coupling structure to achieve transmission zeros, but innovatively introduces a zero cavity on the side of the frequency resonance cavity of the ceramic waveguide filter, realizing a new type of ceramic waveguide filter with transmission zeros.

[0031] 2. This filter overcomes the difficulty that the currently "direct in and direct out" structure on the market is difficult to achieve transmission zeros, and optimizes the deficiencies such as low port isolation and easy signal crosstalk caused by the cross-coupling structure, which results in the ports of the ceramic waveguide filter with a ring-shaped or U-shaped structure being on the same side.

[0032] 3. By coupling the zero cavity to the side of the resonant cavity, the present utility model can achieve an innovative design of transmission zeros only through the resonant frequency of the zero cavity and the coupling between the zero cavity and the adjacent resonant cavity. This design not only simplifies the structure of the filter, making the design of transmission zeros simpler and more flexible, but also reduces the similarity with the prior art, thereby reducing the risk of infringement.

[0033] 4. The filter has a common cuboid structure, with a simple structure, low installation cost, high space utilization, and high integration in base station layout, without causing space waste.

[0034] 5. If the resonant frequency of the zero cavity of the filter of the present utility model decreases, the frequency point of the transmission zero position realized by this zero cavity will move towards the low end. Conversely, if the resonant frequency of the zero cavity increases, the frequency point of the transmission zero position realized by this zero cavity will move towards the high end. However, no matter how it changes, the frequency point of the transmission zero position realized by the zero cavity is always equal to the resonant frequency of this zero cavity.

[0035] 6. Since the frequency point of each transmission zero position of the novel ceramic waveguide filter of the present utility model is only related to the resonant frequency of the corresponding zero cavity, independent adjustment of each transmission zero is achieved, avoiding mutual influence between zeros. This design significantly reduces the debugging difficulty and cost of the filter, while improving production efficiency.

[0036] 7. The input and output ports of the filter are distributed on different sides of the filter, with high port isolation and no signal crosstalk, which can better meet the integrated application of 5G communication systems.

[0037] 8. The coupling windows between two adjacent resonant cavities are not opened on the same side of the ceramic housing, but are alternately distributed on both sides, effectively reducing the parasitic coupling between non-adjacent resonant cavities of the entire filter and reducing the influence of parasitic coupling on transmission zeros.

[0038] 9. The capacitive coupling square groove is designed between the zero cavity and the resonant cavity adjacent to the zero cavity. While achieving the coupling between the zero cavity and the resonant cavity adjacent to the zero cavity, changing the distance between the inner wall of the square groove and the adjacent resonant holes can also play a role in optimizing the resonant frequency of the resonant cavity or zero cavity adjacent to it. When the distance becomes closer, the resonant frequency of the resonant cavity will become higher. The advantage of this design is that when the realized transmission zero is at the high end of the passband, the frequency requirements of this zero cavity and the frequency resonant cavity adjacent to this zero cavity will become higher. At this time, this design can well avoid the risk of being unable to achieve high frequencies.

[0039] 10. The probe hole opened directly below the port resonator can not only achieve signal input and output and the time delay requirements of the entire filter, but also play a role in assisting the adjustment of the resonant frequency of the port resonator; by adjusting the distance between the bottom of the probe hole opening and the bottom of the port resonator hole, the equivalent capacitance of the resonator hole can be adjusted, thereby adjusting the resonant frequency generated by the resonator hole. Description of the Drawings

[0040] Figure 1 : Schematic diagram of the CQ cross-coupling principle. The solid line represents the main coupling between adjacent resonators, and the dashed line represents the cross-coupling between non-adjacent resonators. Two transmission zeros can be achieved through the resonant frequencies of the four cavities and the coupling between them. The positions of the two transmission zeros can both be at the high end or the low end, or one at the low end and one at the high end.

[0041] Figure 2 : Schematic diagram of the CT cross-coupling principle. The solid line represents the main coupling between adjacent resonators, and the dashed line represents the cross-coupling between non-adjacent resonators. One transmission zero can be achieved through the resonant frequencies of the three cavities and the coupling between them. The position of the transmission zero can be at the low end or the high end.

[0042] Figure 3 : Schematic diagram of the transmission zero principle of the zero cavity. TZ (transmission zero) represents the transmission zero achieved by the zero cavity or the zero cavity. By coupling a zero cavity to any one resonator, taking the resonant frequency of the zero cavity as the transmission zero, and further through the specific coupling between the zero cavity and the resonator, one transmission zero can be achieved. One zero cavity achieves one transmission zero, and two zero cavities achieve two transmission zeros, and so on.

[0043] Figure 4 : Topological structure diagram of this embodiment. This embodiment uses six frequency resonators, and a zero cavity is respectively coupled to the head and tail cavities 1 and 6 shown in the figure, achieving one transmission zero at the low end and one at the high end.

[0044] Figure 5 : Front view of the 3D structure of this embodiment.

[0045] Figure 5.1 : Front view of the 3D structure of this embodiment.

[0046] Figure 6 : Rear view of the 3D structure of this embodiment.

[0047] Figure 7 : Top view of the 3D structure of this embodiment.

[0048] Figure 8 : Front view of the 3D structure of this embodiment.

[0049] Figure 9 : S-parameter waveform diagram of this embodiment Detailed implementation manner

[0050] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0051] The present invention provides a novel ceramic waveguide filter. This filter avoids the use of traditional cross-coupling structures through innovative design to achieve transmission zeros. The specific innovative points include coupling a zero cavity to the side of a certain resonator cavity. Only by the resonant frequency of the zero cavity and the specific coupling between the zero cavity and the adjacent resonator cavity can a transmission zero be achieved. Further, by coupling a zero cavity to each of the N resonator cavities, N transmission zeros can be achieved. At the same time, the resonant frequency of the zero cavity is always equal to the frequency point where the transmission zero is located. Each zero cavity independently controls the corresponding zero, and the zeros do not affect each other, making the design of the transmission zeros more free and flexible. Compared with the traditional cross-coupling form of ceramic waveguide filters in Patent 1 and Patent 2, the complexity and debugging difficulty of the filter are greatly reduced. It has a very large cost advantage and practical value.

[0052] Further, the input and output ports of the filter of this utility model are on both sides of the filter, presenting a highly integrated structure of "direct input and direct output", overcoming the difficulty that the "direct input and direct output" structure of the current ceramic waveguide filter cannot well achieve transmission zeros, improving the port isolation, reducing signal crosstalk, and improving the stability of the filter; compared with Patent 2, the overall structure of the ceramic waveguide filter provided by this patent has a better external structure, which is a conventional cuboid, and the internal structure is simpler, with a low processing cost. In practical applications, it can more efficiently utilize the space of the base station, with a higher space utilization rate, saving the installation cost, and better meeting the integrated application requirements.

[0053] The following is a specific embodiment of the present invention, which realizes the technical index requirements of a 3.5G frequency band filter for 5G communication released by a certain communication company:

[0054] Passband: 3400 MHz - 3600 MHz

[0055] Insertion loss: < 1.0 dB

[0056] Return loss: > 20 dB

[0057] Out-of-band rejection: 3200 - 3300 MHz > 51 dB

[0058] 3300 - 3350 MHz > 25 dB

[0059] 3650 - 3700 MHz > 25 dB

[0060] 3700 - 3800 MHz > 51 dB.

[0061] Please refer to Figure 3-9 , the present utility model provides a technical solution: a novel ceramic waveguide filter with transmission zeros, comprising a ceramic housing 1, the ceramic housing 1 is composed of a frequency resonance cavity one 2, a frequency resonance cavity two 4, a frequency resonance cavity three 5, a frequency resonance cavity four 6, a frequency resonance cavity five 7, a frequency resonance cavity six 8, a zero cavity one 3 and a zero cavity two 9, wherein the frequency resonance cavity one 2 and the frequency resonance cavity six 8 are port resonance cavities;

[0062] The frequency resonance cavity one 2, the frequency resonance cavity two 4, the frequency resonance cavity three 5, the frequency resonance cavity four 6, the frequency resonance cavity five 7, the frequency resonance cavity six 8, the zero cavity one 3 and the zero cavity two 9 are all provided with a frequency resonance hole one 201, a frequency resonance hole two 401, a frequency resonance hole three 501, a frequency resonance hole four 601, a frequency resonance hole five 701, a frequency resonance hole six 801, a zero cavity resonance hole one 301 and a zero cavity resonance hole two 901, which respectively generate the resonance frequencies of the corresponding frequency resonance cavities and the resonance frequencies of the zero cavities; among them, the frequency resonance hole one 201 and the frequency resonance hole six 801 are port resonance holes; the zero cavity resonance hole one 301 resonates to generate a low - end transmission zero, and its resonance frequency is equal to the frequency point at the low - end transmission zero position, and the zero cavity resonance hole two 901 resonates to generate a high - end transmission zero, and its resonance frequency is equal to the frequency point at the high - end transmission zero position;

[0063] A capacitive coupling square groove 10 is arranged between the zero cavity two 9 and the adjacent frequency resonance cavity six 8, and the capacitive coupling square groove 10 is a blind groove, the opening direction is opposite to the opening direction of the resonance hole, and the depth of the square groove is greater than one - half of the ceramic housing 1;

[0064] A coupling partition window 11 is arranged between the zero cavity one 3 and the frequency resonance cavity one 2;

[0065] Coupling partition windows one 12, coupling partition windows two 13, coupling partition windows three 14, coupling partition windows four 15 and coupling partition windows five 16 are arranged between adjacent two of the frequency resonance cavity one 2, the frequency resonance cavity two 4, the frequency resonance cavity three 5, the frequency resonance cavity four 6, the frequency resonance cavity five 7 and the frequency resonance cavity six 8;

[0066] The frequency resonance cavity one 2 and the frequency resonance cavity six 8 are designed with a frequency resonance hole one 201 and a frequency resonance hole six 801, and port feed probe holes one 17 and port feed probe holes two 18 are opened at precise positions directly below the frequency resonance hole one 201 and the frequency resonance hole six 801.

[0067] In the present utility model, the ceramic housing 1 is made from a ceramic powder raw material ratio through a firing process.

[0068] In the present utility model, the relative dielectric constant of the ceramic housing 1 is selected to be 23.

[0069] In the present utility model, the first frequency resonance hole 201, the second frequency resonance hole 401, the third frequency resonance hole 501, the fourth frequency resonance hole 601, the fifth frequency resonance hole 701, the sixth frequency resonance hole 801, the first zero - cavity resonance hole 301, and the second zero - cavity resonance hole 901 are shallow blind holes, and their depth design does not exceed half of the total thickness of the ceramic housing.

[0070] In the present utility model, the first frequency resonance hole 201, the second frequency resonance hole 401, the third frequency resonance hole 501, the fourth frequency resonance hole 601, the fifth frequency resonance hole 701, the sixth frequency resonance hole 801, the first zero - cavity resonance hole 301, the second zero - cavity resonance hole 901, and the capacitive coupling square groove 10 are designed on the same horizontal line.

[0071] In the present utility model, a conductive coating is attached to the surface of the ceramic housing 1 and the inner walls of the first frequency resonance hole 201, the second frequency resonance hole 401, the third frequency resonance hole 501, the fourth frequency resonance hole 601, the fifth frequency resonance hole 701, the sixth frequency resonance hole 801, the first zero - cavity resonance hole 301, the second zero - cavity resonance hole 901, the first port feeding probe hole 17, the second port feeding probe hole 18, and the capacitive coupling square groove 10.

[0072] The present utility model proposes a ceramic waveguide filter, which includes a plurality of frequency resonance cavities and at least one zero - cavity. The design of the zero - cavity is used to generate a transmission zero at the resonance frequency generated by the zero - cavity, without relying on a traditional cross - coupling structure; by introducing a zero - cavity on the side of at least one frequency resonance cavity, at least one transmission zero is achieved, overcoming the difficulty that the "straight - in and straight - out" structure on the market is difficult to achieve a transmission zero, and solving the deficiencies such as low port isolation and easy signal crosstalk caused by the cross - coupling structure in the ceramic waveguide filter with a ring - shaped or U - shaped structure where the ports are on the same side. It has extremely high application value and prospects in the current and future ceramic filter industries.

[0073] Traditional ceramic waveguide filters require the resonance frequencies of multiple resonance cavities and mutual and cross - coupling through a cross - coupling structure to achieve a transmission zero, as shown in Figure 1 and Figure 2, the utility model innovatively adopts a zero-cavity structure to achieve the transmission zeros of the ceramic waveguide filter. This method simplifies the complexity of the traditional cross-coupling structure. Since the frequency of the transmission zero position is always equal to the resonant frequency of the corresponding zero cavity, by precisely controlling the resonant frequency of the zero cavity and the coupling strength with adjacent resonant cavities, the independent control of the transmission zeros is effectively achieved. Therefore, the transmission zeros can be designed more flexibly.

[0074] The number of zero cavities is equal to the number of transmission zeros. Only one zero cavity needs to be introduced to achieve one transmission zero, and two zero cavities need to be introduced to achieve two transmission zeros, and so on. Up to N zero cavities can be introduced into N resonant cavities to achieve N zeros, and the zeros do not affect each other.

[0075] The position of the zero cavity can be flexibly located on the side of any frequency resonant cavity, not limited to the arrangement on the leftmost and rightmost sides of both sides of the filter in the embodiment. This embodiment is just an optimal arrangement scheme based on the case of achieving two transmission zeros.

[0076] The resonant frequency of the zero cavity is always equal to the frequency of the position where its corresponding transmission zero is located. The resonant frequency of the zero cavity introducing the low-end transmission zero is equal to the frequency of the low-end transmission zero position, so the resonant frequency of this zero cavity is lower than the center frequency of the filter passband; on the contrary, the resonant frequency of the zero cavity introducing the high-end transmission zero is equal to the frequency of the high-end transmission zero position, so the resonant frequency of this zero cavity is higher than the center frequency of the filter passband.

[0077] Different from the traditional ceramic waveguide filter, in the traditional ceramic waveguide filter, the frequencies of all frequency resonant cavities are the same and equal to the center frequency of the filter passband. In the ceramic waveguide filter of the utility model, the resonant frequency of the resonant cavity adjacent to the zero cavity realizing the low-end transmission zero is lower than the center frequency of the filter passband. Similarly, the resonant frequency of the resonant cavity adjacent to the zero cavity realizing the high-end transmission zero is higher than the center frequency of the filter passband.

[0078] An innovative design of capacitive coupling is used for the coupling between the zero cavity realizing the high-end transmission zero and the adjacent frequency resonant cavity. It is realized through a capacitive coupling square groove. Because when realizing the high-end transmission zero, the frequency requirements of these two cavities will become higher. At this time, the capacitive coupling square groove can not only achieve the expected coupling amount between the two cavities, but also assist in adjusting the frequencies of the two resonant cavities by adjusting the distance between the inner wall of the capacitive coupling square groove and the resonant hole. When the distance gets closer, the frequency of the resonant cavity will become higher, avoiding the risk that the frequency is too high to be achieved.

[0079] The coupling windows between adjacent two frequency resonant cavities are not opened on the same side of the ceramic housing. Instead, they are alternately distributed on both sides of the filter, effectively reducing the parasitic coupling of the entire filter.

[0080] The overall design of the ceramic waveguide filter is an "in-and-out" arrangement structure. The port feeding positions are located on both sides of the filter, with high port isolation and little crosstalk between signals. This avoids the problems of poor port isolation and easy signal crosstalk caused by ceramic waveguide filters with ports on the same side using cross-coupling design to transmit zeros.

[0081] A probe hole is designed directly below the resonant hole at the port position. Its main function is to perform port feeding. Another function is to change the equivalent capacitance by changing the diameter and depth of the probe hole or the resonant hole directly above it, thereby changing the resonant frequency or the port time delay value. It can achieve the balance between the time delay value and the resonant frequency, keeping the sizes of the probe hole and the resonant hole within the optimal range, which is beneficial for processing, plating metallization, etc.

[0082] Different from traditional ceramic waveguide filters, the coupling amount between two resonant cavities in traditional ceramic waveguide filters generally does not exceed the passband bandwidth. In the present utility model, the coupling amount between the zero cavity and the adjacent resonant cavity is greater than that between any other adjacent frequency resonant cavities, and is greater than the passband bandwidth.

[0083] The content not described in detail in this specification belongs to the prior art well-known to those skilled in the art. Although the embodiments of the present utility model have been shown and described, for those of ordinary skill in the art, it can be understood that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principle and spirit of the present utility model. The scope of the present utility model is defined by the appended claims and their equivalents.

Claims

1. A novel ceramic waveguide filter with transmission zero, characterized in that: The invention comprises a ceramic shell (1), wherein the ceramic shell (1) is composed of a frequency resonant cavity 1 (2), a frequency resonant cavity 2 (4), a frequency resonant cavity 3 (5), a frequency resonant cavity 4 (6), a frequency resonant cavity 5 (7), a frequency resonant cavity 6 (8), a zero cavity 1 (3) and a zero cavity 2 (9), wherein the frequency resonant cavity 1 (2) and the frequency resonant cavity 6 (8) are port resonant cavities; The frequency resonance cavity 1 (2), frequency resonance cavity 2 (4), frequency resonance cavity 3 (5), frequency resonance cavity 4 (6), frequency resonance cavity 5 (7), frequency resonance cavity 6 (8), zero cavity 1 (3) and zero cavity 2 (9) are all provided with frequency resonance hole 1 (201), frequency resonance hole 2 (401), frequency resonance hole 3 (501), frequency resonance hole 4 (601), frequency resonance hole 5 (701), frequency resonance hole 6 (801), zero cavity resonance hole 1 (301) and zero cavity resonance hole 2 (901), which respectively generate the resonance frequency of the corresponding frequency resonance cavity and the resonance frequency of the zero cavity; wherein the frequency resonance hole 1 (201) and the frequency resonance hole 6 (801) are port resonance holes; the zero cavity resonance hole 1 (301) resonates to generate a low-end transmission zero point, and its resonance frequency is equal to the frequency point of the low-end transmission zero point position; the zero cavity resonance hole 2 (901) resonates to generate a high-end transmission zero point, and its resonance frequency is equal to the frequency point of the high-end transmission zero point position; A capacitive coupling square groove (10) is provided between the second zero cavity (9) and the adjacent sixth frequency resonance cavity (8), and the capacitive coupling square groove (10) is a blind groove, the opening direction of which is opposite to the opening direction of the resonance hole, and the depth of the square groove is greater than half of the ceramic housing (1); A coupling window (11) is provided between the zero cavity one (3) and the frequency resonance cavity one (2); Two adjacent frequency resonant cavities among the frequency resonant cavity one (2), the frequency resonant cavity two (4), the frequency resonant cavity three (5), the frequency resonant cavity four (6), the frequency resonant cavity five (7) and the frequency resonant cavity six (8) are provided with a coupling partition window one (12), a coupling partition window two (13), a coupling partition window three (14), a coupling partition window four (15) and a coupling partition window five (16); Frequency resonance cavity one (2) and frequency resonance cavity six (8) are designed with frequency resonance hole one (201) and frequency resonance hole six (801), and port feeding probe hole one (17) and port feeding probe hole two (18) are opened at precise positions directly below frequency resonance hole one (201) and frequency resonance hole six (801).

2. A novel ceramic waveguide filter with a transmission zero according to claim 1, characterized in that: The ceramic shell (1) is made of ceramic powder raw materials through a sintering process.

3. The novel ceramic waveguide filter with transmission zero according to claim 1, characterized in that: The relative dielectric constant of the ceramic housing (1) is selected to be 23.

4. The novel ceramic waveguide filter with transmission zero according to claim 1, characterized in that: The frequency resonance hole 1 (201), the frequency resonance hole 2 (401), the frequency resonance hole 3 (501), the frequency resonance hole 4 (601), the frequency resonance hole 5 (701), the frequency resonance hole 6 (801), the zero cavity resonance hole 1 (301) and the zero cavity resonance hole 2 (901) are shallow blind holes, and their depth is designed not to exceed half of the total thickness of the ceramic shell.

5. The novel ceramic waveguide filter with transmission zero according to claim 1, characterized in that: The frequency resonance hole 1 (201), the frequency resonance hole 2 (401), the frequency resonance hole 3 (501), the frequency resonance hole 4 (601), the frequency resonance hole 5 (701), the frequency resonance hole 6 (801), the zero cavity resonance hole 1 (301), the zero cavity resonance hole 2 (901) and the capacitive coupling square slot (10) are designed to be on the same horizontal line.

6. The novel ceramic waveguide filter with transmission zero according to claim 1, characterized in that: Conductive coatings are attached to the surface of the ceramic shell (1) and the inner wall of the frequency resonance hole 1 (201), the frequency resonance hole 2 (401), the frequency resonance hole 3 (501), the frequency resonance hole 4 (601), the frequency resonance hole 5 (701), the frequency resonance hole 6 (801), the zero cavity resonance hole 1 (301), the zero cavity resonance hole 2 (901), the port feeding probe hole 1 (17), the port feeding probe hole 2 (18) and the capacitive coupling square slot (10).

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