A filter based on a resonant single-cavity multi-mode structure

Abstract

The invention discloses a filter based on a resonant single-cavity multi-mode structure, wherein the bottom surface of a first dielectric plate and the top surface of a third dielectric plate are both provided with metal layers, and a plurality of first metal through holes are connected between the two metal layers; the input port and the output port are both connected with a coplanar waveguide feeding structure; the multi-mode resonator structure comprises two first metal patches and two second metal patches, a second metal through hole is connected between the two first metal patches, the second metal through hole passes through the third dielectric plate and is connected to the upper surface of a SIW resonant cavity, the two second metal patches are arranged at intervals, and a third metal through hole is respectively connected between the corresponding first metal patches, and the third metal through hole passes through the second dielectric plate, so that not only the resonant mode of the SIW resonant cavity itself can be excited, but also the resonant mode of the multi-mode resonator structure can be excited to obtain a desired passband, thereby achieving good effects and occupying a very small volume.

Description

Technical Field

[0001] The present invention relates to the technical field of filters, and in particular to a filter based on a resonant single-cavity multi-mode structure. Background Art

[0002] Substrate Integrated Waveguide (SIW) technology is a widely used technology in microwave and millimeter wave bands. Substrate Integrated Waveguide is achieved by opening two rows of periodic through holes on a dielectric substrate and plating metal on both sides of the through holes. In this way, the upper and lower metal surfaces are equivalent to the wide sides of a dielectric-filled rectangular waveguide. When the working wavelength is much larger than the through hole spacing, a waveguide-like propagation environment can be simulated internally. The propagation characteristics of SIW are similar to those of the corresponding dielectric-filled metal waveguide, so one feature of the SIW structure is that it has excellent characteristics similar to those of metal waveguides, namely, high quality factor, high power capacity, high isolation, low insertion loss and low radiation. On the other hand, the purpose of SIW technology is to realize the functions of traditional metal waveguides on substrates, so it has advantages that traditional metal waveguides do not have, such as small size, easy processing, and easy integration with other microwave structures in microsystems. Using SIW technology, RF passive components and active circuits can be effectively integrated on the same substrate, and the entire system can be further manufactured in the same package, truly meeting the actual requirements of RF microsystems for working performance and integration. The RF passive devices that can be constructed using SIW technology include directional couplers, power dividers, baluns, phase shifters, circulators, etc. Furthermore, some RF front-end devices such as oscillators, mixers, and amplifiers constructed using SIW passive components or resonant cavities can be used.

[0003] With the development of wireless communication systems, passive devices working in a single mode can no longer meet the needs of communication systems that require multi-functions and large bandwidths, and the demand for miniaturized broadband bandpass filters is increasing. At present, based on the research on SIW filters, the problems encountered are: the resonance frequency of the first high-order mode of the traditional SIW structure is twice that of the main mode, while the first high-order resonance frequency in the traditional SIW rectangular cavity is only 1.6 times that of the main resonance frequency, and its single-mode operation and high-order mode suppression characteristics are not as good as those of the microstrip structure; the structure of the traditional SIW rectangular and circular resonant cavity is fixed, the design lacks freedom, and it is difficult to flexibly control and adjust the coupling of multiple modes; compared with the microstrip circuit, the traditional SIW structure has no advantage in terms of lateral area. The SIW cavity has the advantage of high Q value, but the high Q value of the resonant cavity in the filter brings excellent roll-off while the bandwidth is very limited. Therefore, how to achieve broadband electromagnetic characteristics in a high-Q resonant cavity is the difficulty and focus of the filter design based on SIW technology.

[0004] There are currently several methods to address these issues:

[0005] (1) Multiple single-mode resonators are cascaded, and the horizontal cascade resonant cavity is converted into a vertical cascade using a vertical stacking structure and aperture coupling, which greatly reduces the lateral size of the resonant cavity. The disadvantage is that the vertical coupling structure makes the input and output of the filter not in the same plane, which may affect the connection between the filter and other circuit devices in the microsystem.

[0006] (2) Adding metal perturbation structures to the SIW cavity to control the various modes of the cavity. Common methods include introducing metal through holes in the cavity, that is, introducing inductive structures or capacitive structures. By designing the introduction position and structural shape of the capacitive structure or inductive structure, the various modes of the resonant cavity can be regulated, and the ideal passband can be generated through mode aggregation. The disadvantage is that it relies on the inherent mode of the resonant cavity itself for regulation, and the control range is limited.

[0007] (3) Defective Ground Structure (DGS) is introduced on the upper and lower surfaces of the SIW cavity to form a resonant unit by changing the current distribution on the metal surface. The DGS and the cavity together form working characteristics such as band gap, fast and slow waves, and left-handed propagation, achieving the effect of constructing an ideal filter. Its disadvantages are also obvious. DGS will affect the energy leakage in the cavity, which will not only greatly reduce the performance of the device constructed by the cavity itself in the microsystem, but also interfere with other circuits in the system. Summary of the invention

[0008] The purpose of the present invention is to provide a filter based on a resonant single-cavity multi-mode structure to solve the problems existing in the prior art. It can not only excite the resonant mode of the SIW resonant cavity itself, but also excite the resonant mode of the multi-mode resonator structure to obtain the desired passband, achieving good results while occupying a very small volume.

[0009] To achieve the above object, the present invention provides the following solution: The present invention provides a filter based on a resonant single-cavity multi-mode structure, comprising a SIW resonant cavity, a coplanar waveguide feeding structure and a multi-mode resonator structure;

[0010] The SIW resonant cavity comprises a first dielectric plate, a second dielectric plate and a third dielectric plate which are sequentially arranged from bottom to top, a bottom surface of the first dielectric plate and a top surface of the third dielectric plate are both provided with metal layers, and serve as the lower surface and upper surface of the SIW resonant cavity respectively, a plurality of first metal through holes are connected between the edges of the upper surface and the lower surface of the SIW resonant cavity, and the first metal through holes are sequentially distributed along the circumference of the SIW resonant cavity and form the side surface of the SIW resonant cavity;

[0011] The SIW resonant cavity is provided with an input port and an output port, the input port and the output port are symmetrically distributed on both sides of the upper surface of the SIW resonant cavity along the same straight line direction, and the coplanar waveguide feeding structure is connected between the input port and the output port and the upper surface of the SIW resonant cavity respectively;

[0012] The multimode resonator structure includes two first metal patches both arranged on the upper surface of the second dielectric plate, and two second metal patches both arranged on the upper surface of the first dielectric plate, a second metal through hole is connected between the two first metal patches, the second metal through hole passes through the third dielectric plate and is connected to the upper surface of the SIW resonant cavity, the two second metal patches are arranged at intervals, and third metal through holes are connected to the corresponding first metal patches respectively, and the third metal through hole passes through the second dielectric plate.

[0013] Preferably, the coplanar waveguide feeding structure comprises a microstrip line arranged on the top surface of the third dielectric plate, and the input port and the output port are respectively connected to the upper surface of the SIW resonant cavity through the microstrip line.

[0014] Preferably, the coplanar waveguide feeding structure further includes two slot lines for realizing coplanar waveguide excitation, each of the slot lines is opened on the upper surface of the SIW resonant cavity, and the two slot lines are located close to the microstrip line and distributed on both sides of the microstrip line.

[0015] Preferably, the slot line is in an L-shaped structure as a whole, one end of which is parallel to the arrangement direction of the input port and the output port, and the other end is perpendicular to the distribution direction of the input port and the output port.

[0016] Preferably, the first metal patch is provided with a gradient structure connected to the second metal through hole, and a shape of the gradient structure gradually decreases from the first metal patch to the second metal through hole.

[0017] Preferably, the two first metal patches are located between the input port and the output port, and are sequentially distributed along the direction in which the input port and the output port are arranged, and each of the second metal patches is correspondingly distributed below each of the first metal patches.

[0018] Preferably, the second metal through hole is located between the two third metal through holes, and the second metal through hole and the third metal through holes are distributed along the same straight line direction and are parallel to the arrangement direction of the input port and the output port.

[0019] Preferably, the first metal through holes are distributed at equal intervals along the circumference of the SIW resonant cavity to form a ring structure.

[0020] Preferably, the relationship between the radius R of the first metal through hole and the distance d between two adjacent first metal through holes satisfies: (2×R) <d<(4×R)。

[0021] Preferably, the first dielectric plate, the second dielectric plate and the third dielectric plate are all Rogers 5880 dielectric plates.

[0022] Compared with the prior art, the present invention has achieved the following technical effects:

[0023] First, the entire filter proposed in the present invention has the characteristics of miniaturization. Compared with the existing SIW filter, the structure of the entire filter proposed in the present invention has only one SIW resonant cavity, and the SIW resonant cavity can achieve the broadband filtering effect obtained by cascading multiple resonant cavities, that is, the entire filter structure proposed in the present invention can not only excite the resonant mode of the SIW resonant cavity itself, but also excite the resonant mode of the multi-mode resonator structure to obtain the desired passband, achieving good results while occupying a very small volume. Therefore, the resonator single-cavity multi-mode structure proposed in the present invention can be applied to the miniaturization and broadband design of the filter to design the required devices. Second, the entire filter proposed in the present invention has the characteristics of broadband. The entire filter proposed in the present invention is designed on the basis of the SIW structure, and a multi-mode resonator structure is introduced inside the SIW resonant cavity. The energy of the input port is simultaneously coupled to the SIW resonant cavity and the multi-mode resonator structure, generating multiple modes and obtaining a wider bandwidth. Therefore, compared with the existing single-cavity multi-mode filter design, the entire filter proposed in the present invention can not only excite the resonant mode of the SIW resonant cavity itself, but also excite the resonant mode of the multi-mode resonator structure, thereby having more resonant modes and achieving a wider working bandwidth. Third, the entire filter proposed by the present invention can be flexibly designed. By changing the shape and size parameters of the multi-mode resonator structure as a disturbance and resonance structure, the position of the resonance point can be flexibly adjusted to adapt to different operating frequencies and bandwidths. Fourth, the entire filter proposed by the present invention has a high degree of integration. Utilizing the structural characteristics of the SIW resonant cavity itself, it can be integrated into a microsystem and cascaded with other RF functional devices such as antennas and power dividers, and its self-packaging will not cause crosstalk to other circuit signals in the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0025] Figure 1An axonometric diagram of a SIW resonant cavity in one embodiment of the present invention;

[0026] Figure 2 is a schematic diagram of a multi-mode resonator structure in one embodiment of the present invention;

[0027] Figure 3 A top view of a SIW resonant cavity according to an embodiment of the present invention;

[0028] Figure 4 is a schematic diagram of the entire filter in one embodiment of the present invention;

[0029] Figure 5 A structural parameter diagram of the entire filter in one embodiment of the present invention;

[0030] Figure 6 is a side view of the entire filter in one embodiment of the present invention;

[0031] Figure 7 An exploded view of the entire filter in one embodiment of the present invention;

[0032] Figure 8 The electric field distribution diagram of each resonator of the entire filter in one embodiment of the present invention;

[0033] Fig. 9 is a performance curve diagram of the entire filter in one embodiment of the present invention;

[0034] Among them, 1-first dielectric plate, 2-metal layer, 3-first metal through hole, 4-third metal through hole, 5-first metal patch, 6-second metal patch, 7-second metal through hole, 8-input port, 9-output port, 10-slot line, 11-multi-mode resonator structure, 12-second dielectric plate, 13-third dielectric plate. DETAILED DESCRIPTION

[0035] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions 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.

[0036] The purpose of the present invention is to provide a filter based on a resonant single-cavity multi-mode structure to solve the problems existing in the prior art. It can not only excite the resonant mode of the SIW resonant cavity itself, but also excite the resonant mode of the multi-mode resonator structure to obtain the desired passband, achieving good results while occupying a very small volume.

[0037] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0038] like Figures 1 to 9 As shown, this embodiment provides a filter based on a resonant single-cavity multi-mode structure, in particular, a 5G millimeter-wave bandpass filter that meets miniaturization requirements, including a SIW resonant cavity, a coplanar waveguide feeding structure, and a multi-mode resonator structure 11; the SIW resonant cavity includes a first dielectric plate 1, a second dielectric plate 12, and a third dielectric plate 13 arranged in sequence from bottom to top. Preferably, the first dielectric plate 1, the second dielectric plate 12, and the third dielectric plate 13 are all Rogers 5880 dielectric plates, and the thickness of each dielectric plate is 0.127 mm. The bottom surface of the first dielectric plate 1 and the top surface of the third dielectric plate 13 are both provided with a metal layer 2, which serve as the lower surface and upper surface of the SIW resonant cavity respectively. The metal layer 2 is preferably made of copper and has a rectangular structure, and is respectively attached to the first dielectric plate 1 and the third dielectric plate 13. A plurality of first metal through holes 3 are connected between the edges of the upper surface and the lower surface of the SIW resonant cavity. The first metal through holes 3 are sequentially distributed along the circumference of the SIW resonant cavity and form the side of the SIW resonant cavity. The SIW resonant cavity is provided with an input port 8 and an output port 9, which are symmetrically distributed on both sides of the upper surface of the SIW resonant cavity along the same straight line direction. The input port 8 and the output port 9 are respectively connected to the upper surface of the SIW resonant cavity with a coplanar waveguide feeding structure, so that the input and output of the SIW resonant cavity are fed through the coplanar waveguide structure. The multi-mode resonator structure 11 includes two first metal patches 5, both of which are arranged on the upper surface of the second dielectric plate 12, and two second metal patches 6, both of which are arranged on the upper surface of the first dielectric plate 1, wherein the two first metal patches 5 are symmetrically distributed along the direction in which the input port 8 and the output port 9 are arranged, and the two second metal patches 6 are respectively arranged below each first metal patch 5, and a second metal through hole 7 is connected between the two first metal patches 5, and the second metal through hole 7 passes through the third dielectric plate and is connected to the upper surface of the SIW resonant cavity, that is, the second metal through hole 7 is located at the symmetry center of the multi-mode resonator structure 11, and is connected to the upper surface of the SIW resonant cavity through the second metal through hole 7, so that the multi-mode resonator structure 11 introduces a short-circuit point at the center, and the two second metal patches 6 are arranged at intervals, and are respectively connected to the corresponding first metal patches 5 with a third metal through hole 4, and the third metal through hole 4 passes through the second dielectric plate 12.

[0039] Combination Figure 7From the exploded view of the entire filter in one embodiment of the present invention, the entire filter rationally utilizes the vertical space to manufacture a resonant SIW single-cavity multi-mode filter, using a total of 3 dielectric layers and 3 metal layers 2. The working principle of the bandpass filter of the present invention is to construct a SIW resonant cavity, and introduce a multi-mode resonator structure 11 into the SIW resonant cavity. In this way, a filter based on a resonant single-cavity multi-mode structure is obtained. The filter of the present invention has a total of three resonant points in the passband. These three resonant points are respectively generated by the SIW resonant cavity and the multi-mode resonator structure 11, and their electric field distribution is shown as follows: Figure 8 The first resonance point is generated by the internal resonance of the SIW resonant cavity itself, and the second and third resonance points are generated by the multi-mode resonator structure 11. The performance of the filter of the present invention is shown in FIG. Fig. 9 shown. Fig. 9 The S parameters of the filter, i.e., the return loss of the insertion loss, are given in the millimeter wave frequency band of 24.5GHz~27.5GHz. The return loss is less than -10dB. Within the range of -10dB return loss, the lowest insertion loss is -0.9dB. The insertion loss is good and can be applied to millimeter wave systems.

[0040] In summary, first, the entire filter proposed in the present invention has the characteristic of miniaturization. Compared with the existing SIW filter, the structure of the entire filter proposed in the present invention has only one SIW resonant cavity, and the SIW resonant cavity can achieve the broadband filtering effect obtained by cascading multiple resonant cavities, that is, the entire filter structure proposed in the present invention can not only excite the resonant mode of the SIW resonant cavity itself, but also excite the resonant mode of the multi-mode resonator structure 11 to obtain the desired passband, achieving good results while occupying a very small volume. Therefore, the resonator single-cavity multi-mode structure proposed in the present invention can be applied to the miniaturized broadband design of the filter to design the required devices. Second, the entire filter proposed in the present invention has the characteristic of broadband. The entire filter proposed in the present invention is designed on the basis of the SIW structure, and the multi-mode resonator structure 11 is introduced inside the SIW resonant cavity. The energy of the input port 8 is simultaneously coupled to the SIW resonant cavity and the multi-mode resonator structure 11, generating multiple modes and obtaining a wider bandwidth. Therefore, compared with the existing single-cavity multi-mode filter design, the entire filter proposed in the present invention can not only excite the resonant mode of the SIW resonant cavity itself, but also excite the resonant mode of the multi-mode resonator structure 11, thereby having more resonant modes and achieving a wider operating bandwidth. Third, the entire filter proposed in the present invention can be flexibly designed. By changing the shape and size parameters of the multi-mode resonator structure 11 as a disturbance and resonant structure, the position of the resonance point can be flexibly adjusted to adapt to different operating frequencies and bandwidths. Fourth, the entire filter proposed in the present invention has a high degree of integration. Utilizing the structural characteristics of the SIW resonant cavity itself, it can be integrated into a microsystem and cascaded with other RF functional devices such as antennas and power dividers, and its self-packaging will not cause crosstalk to other circuit signals in the system.

[0041] In a specific embodiment, the coplanar waveguide feeding structure includes a microstrip line arranged on the top surface of the third dielectric plate 13, and the input port 8 and the output port 9 are respectively connected to the upper surface of the SIW resonant cavity through the microstrip line. And the preferred coplanar waveguide feeding structure also includes two slot lines 10 for realizing coplanar waveguide excitation, each slot line 10 is opened on the upper surface of the SIW resonant cavity, and the two slot lines 10 are located near the microstrip line and distributed on both sides of the microstrip line. Coplanar waveguide excitation is realized by the slot line 10, and the length and width of the slot line 10 can be used to adjust the coupling degree between the two ports and the SIW resonant cavity, and between the two ports and the multi-mode resonator structure 11. Further, the slot line 10 is an L-shaped structure as a whole, one end of which is parallel to the arrangement direction of the input port 8 and the output port 9, and the other end is perpendicular to the distribution direction of the input port 8 and the output port 9.

[0042] In a specific embodiment, the first metal patch 5 is provided with a tapered structure connected to the second metal via 7, and the shape of the tapered structure gradually decreases from the first metal patch 5 to the second metal via 7. Preferably, the tapered structure is a triangular structure. And preferably, the two first metal patches 5 are located between the input port 8 and the output port 9 and are sequentially distributed along the direction in which the input port 8 and the output port 9 are arranged, and each second metal patch 6 is correspondingly distributed below each first metal patch 5. Further, the second metal via 7 is located between the two third metal vias 4, and the second metal via 7 and each third metal via 4 are distributed along the same straight line direction and are parallel to the arrangement direction of the input port 8 and the output port 9.

[0043] In a specific embodiment, each first metal via 3 is equally spaced along the circumference of the SIW resonant cavity and distributed in an annular structure. As Figure 5 shown in the structural parameters of the filter of the present invention, the overall size of the filter has a length of Ly and a width of Lx. The input and output ports 9 of the filter are fed through a coplanar waveguide structure, the width of its microstrip line is pw, and the distances from the input and output ports 9 to the SIW resonant cavity are both pl. A coplanar waveguide is constructed by opening an L-shaped slot line 10 on the upper surface of the SIW resonant cavity. The two lengths of the slot line 10 are gl1 and gl2 respectively, and the width of the slot line 10 is gw. The length of the metal layer 2 on the upper surface of the SIW resonant cavity, that is, the third dielectric layer 13, is px, and its width is py. The radius of the first metal via 3 used to construct the SIW resonant cavity is R, and the distance between the vias is d. The length of the first metal patch 5 in the multimode resonator structure 11 is L1 + L3, its width is Lw, the basic length of the first metal patch 5 is L1, and it is connected to the second metal via 7 through a tapered structure with a length of L3. The length of the second metal patch 6 in the multimode resonator structure 11 is L2, and the width is Lw. The radius of the second metal via 7 in the multimode resonator structure 11 is R. Among them, the relationship between the radius R of the first metal via 3 and the distance d between two adjacent first metal vias 3 satisfies: (2×R) < d < (4×R) in order to form an SIW resonant cavity with negligible loss.

[0044] Adaptations made according to actual needs are within the protection scope of the present invention.

[0045] It should be noted that it is obvious to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the present invention can be implemented in other specific forms without departing from the spirit or essential features of the present invention. Therefore, the embodiments should be regarded as exemplary and non-restrictive from any point of view, and the scope of the present invention is defined by the appended claims rather than the above description, and it is intended that all changes falling within the meaning and scope of the equivalent elements of the claims are included in the present invention. Any reference numerals in the claims should not be regarded as limiting the claims involved.

[0046] The present invention uses specific examples to illustrate the principles and implementation methods of the present invention. The above examples are only used to help understand the method and core ideas of the present invention. At the same time, for those skilled in the art, according to the ideas of the present invention, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A filter based on a resonant single-cavity multi-mode structure, characterized in that: It includes a SIW resonant cavity, a coplanar waveguide feeding structure and a multi-mode resonator structure; The SIW resonant cavity comprises a first dielectric plate, a second dielectric plate and a third dielectric plate which are arranged from bottom to top, the bottom surface of the first dielectric plate and the top surface of the third dielectric plate are both provided with metal layers, which respectively serve as the lower surface and the upper surface of the SIW resonant cavity, and a plurality of first metal through holes are connected between the edges of the upper and lower surfaces, and each of the first metal through holes is distributed along the circumference of the SIW resonant cavity to form the side surface of the SIW resonant cavity; The SIW resonant cavity is provided with an input port and an output port, the input port and the output port are symmetrically arranged on both sides of the upper surface of the SIW resonant cavity along the same straight line direction, and the coplanar waveguide feeding structure is connected between the input port and the output port and the upper surface of the SIW resonant cavity respectively; The multimode resonator structure includes two first metal patches arranged on the upper surface of the second dielectric plate, and two second metal patches arranged on the upper surface of the first dielectric plate. A second metal through hole passing through the third dielectric plate is connected between the two first metal patches and is connected to the upper surface of the SIW resonant cavity. The two second metal patches are arranged at intervals and are respectively connected to the corresponding first metal patches by a third metal through hole passing through the second dielectric plate.

2. The filter based on the resonant single-cavity multi-mode structure according to claim 1, characterized in that: The coplanar waveguide feeding structure comprises a microstrip line arranged on the top surface of the third dielectric plate, and the input port and the output port are respectively connected to the upper surface of the SIW resonant cavity through the microstrip line.

3. The filter based on the resonant single-cavity multi-mode structure according to claim 2 is characterized in that: The coplanar waveguide feeding structure also includes two slot lines for realizing coplanar waveguide excitation, each of the slot lines is opened on the upper surface of the SIW resonant cavity, and the two slot lines are located close to the microstrip line and distributed on both sides of the microstrip line.

4. The filter based on the resonant single-cavity multi-mode structure according to claim 3 is characterized in that: The slot line is in an L-shaped structure as a whole, one end of which is parallel to the arrangement direction of the input port and the output port, and the other end is perpendicular to the distribution direction of the input port and the output port.

5. The filter based on the resonant single-cavity multi-mode structure according to any one of claims 2 to 4, characterized in that: The first metal patch is provided with a gradient structure connected to the second metal through hole, and a shape of the gradient structure gradually decreases from the first metal patch to the second metal through hole.

6. The filter based on the resonant single cavity multi-mode structure according to claim 5, characterized in that: The two first metal patches are located between the input port and the output port, and are sequentially distributed along the direction in which the input port and the output port are arranged, and each of the second metal patches is correspondingly distributed under each of the first metal patches.

7. The filter based on the resonant single-cavity multi-mode structure according to claim 6, characterized in that: The second metal through hole is located between the two third metal through holes, and the second metal through hole and each of the third metal through holes are distributed along the same straight line direction and are parallel to the arrangement direction of the input port and the output port.

8. The filter based on the resonant single-cavity multi-mode structure according to claim 7, characterized in that: The first metal through holes are evenly spaced and distributed along the circumference of the SIW resonant cavity to form a ring structure.

9. The filter based on the resonant single-cavity multi-mode structure according to claim 8, characterized in that: The relationship between the radius R of the first metal through hole and the distance d between two adjacent first metal through holes satisfies: (2×R) <d<(4×R)。 10. The filter based on the resonant single cavity multi-mode structure according to claim 9, characterized in that: The first dielectric plate, the second dielectric plate and the third dielectric plate are all Rogers 5880 dielectric plates.

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