Multi-frequency bandpass filter and its design method

Abstract

The present invention relates to the field of wireless communication technology, and specifically discloses a multi-frequency bandpass filter and a design method thereof. The multi-frequency bandpass filter includes a multi-mode resonant cavity structure, a perturbation structure, a coupling slot structure and a coupling resonant cavity structure designed based on a substrate integrated gap waveguide structure. The substrate integrated gap waveguide structure includes: a first dielectric layer, a second dielectric layer and a third dielectric layer arranged in sequence from bottom to top; the lower surface of the first dielectric layer and the upper surface of the third dielectric layer are metal layers, and periodic metal sheets are etched on the upper surface of the first dielectric layer, and each metal sheet and the metal layer on the lower surface of the first dielectric layer are connected through a first metal via, and a metal strip line is etched on the upper surface of the second dielectric layer. Resonances of different frequencies are achieved through multi-mode resonant cavities, coupling resonant cavities and coupling slots, and a perturbation structure is introduced to control the working frequency band of the filter. Combined with the electromagnetic bandgap structure, a low-loss multi-frequency bandpass filter in the millimeter wave band can be realized.

Description

Technical Field

[0001] The present invention relates to the field of wireless communication technology, and in particular to a multi-frequency bandpass filter and a design method thereof. Background Art

[0002] Emerging communication modes such as semantic communication have put forward higher requirements on the performance of wireless systems. In order to meet the simultaneous transmission requirements of semantic communication and traditional communication, wireless systems need to be able to support multi-frequency operation. In this context, multi-frequency filters have become one of the key components of multi-functional communication systems. However, traditional filter theory is based on single-band design and cannot be used to design multi-passband filters. Therefore, it is urgent to develop new technologies to design multi-bandpass filters. The current multi-frequency design methods mainly include step impedance resonator technology, stub-loaded resonator technology, and multi-passband resonator technology. These methods face many challenges in designing multi-frequency filters, especially in the millimeter wave band. For example, multi-passband resonator technology requires parallel or cascade connection of multiple groups of different resonators, resulting in excessive device size; step impedance resonators are difficult to achieve high impedance strip lines in the millimeter wave band, and the design space is limited; traditional cavity filter solutions have large losses and high profile heights. Therefore, in order to meet the simultaneous communication and transmission requirements of various communication modes such as semantic communication in the millimeter wave band, it is urgent to develop new low-loss, multi-frequency filters.

[0003] The above contents are only used to assist in understanding the technical solution of the present invention and do not constitute an admission that the above contents are prior art. Summary of the invention

[0004] The main purpose of the present invention is to provide a multi-frequency bandpass filter and a design method thereof, aiming to solve the technical problem of complex design of multi-frequency bandpass filters in the prior art.

[0005] To achieve the above object, the present invention provides a multi-frequency bandpass filter, which comprises: a multi-mode resonant cavity structure, a perturbation structure, a coupling slot structure and a coupling resonant cavity structure designed based on a substrate integrated gap waveguide structure;

[0006] The substrate integrated gap waveguide structure comprises: a first dielectric layer, a second dielectric layer and a third dielectric layer arranged in sequence from bottom to top;

[0007] The lower surface of the first dielectric layer and the upper surface of the third dielectric layer are metal layers, periodic metal sheets are etched on the upper surface of the first dielectric layer, each of the metal sheets and the metal layer on the lower surface of the first dielectric layer is connected through a first metal via, and a metal strip line is etched on the upper surface of the second dielectric layer;

[0008] The multi-mode resonant cavity structure is used to control the resonant mode of the filter to be excited within the electromagnetic band gap range;

[0009] The perturbation structure is used to adjust the working frequency band of each resonant mode of the filter;

[0010] The coupled resonant cavity structure is used to adjust the number of passbands of the filter through the coupled slot structure.

[0011] Optionally, the substrate-integrated gap waveguide structure comprises: periodically arranged bandgap structural units;

[0012] Each of the bandgap structure units includes the metal sheet and the first metal via, and the width of the metal sheet is greater than the cross-sectional width of the first metal via;

[0013] The size and periodic arrangement order of the bandgap structural unit are adjusted according to the electromagnetic bandgap range.

[0014] Optionally, the equivalent circuit of the two bandgap structure units includes: a first equivalent capacitor formed by the metal sheet, a first equivalent inductor formed by the first metal via, and a second equivalent capacitor between the metal sheets of the two bandgap structure units.

[0015] Optionally, the multi-mode resonant cavity structure is arranged in the third dielectric layer;

[0016] The multi-mode resonant cavity structure comprises: a metal layer located on the upper surface of the third dielectric layer, a metal layer located on the lower surface of the third dielectric layer, and a plurality of second metal vias connecting the two metal layers;

[0017] The second metal vias are surrounded by each other to form a resonant rectangular cavity.

[0018] Optionally, the perturbation structure is arranged in the third dielectric layer;

[0019] The perturbation structure includes: a third metal via and a fourth metal via;

[0020] The fourth metal via is arranged on both sides of the third metal via;

[0021] The third metal vias and the fourth metal vias are distributed in an axisymmetric manner.

[0022] Optionally, the coupling slot structure is arranged on the metal layer on the lower surface of the third dielectric layer, and the coupling slot structure is composed of two symmetrically distributed slots.

[0023] Optionally, the multi-frequency bandpass filter is a quad-frequency bandpass filter, the coupling slot structure is arranged in the metal layer on the lower surface of the third dielectric layer, and the coupling slot structure is composed of two symmetrically distributed equilateral hexagonal slots.

[0024] Optionally, the coupled resonant cavity structure is arranged in the second dielectric layer;

[0025] The coupled resonant cavity structure comprises: a metal layer located on the upper surface of the second dielectric layer, a metal layer located on the lower surface of the third dielectric layer, and a plurality of fifth metal vias connecting the two metal layers;

[0026] The fifth metal vias are surrounded by each other to form a coupled rectangular cavity, and the coupled rectangular cavity further includes a plurality of sixth metal vias;

[0027] The sixth metal vias are arranged in a single row and axially symmetrically at the center of the coupling rectangular cavity.

[0028] Optionally, the multi-mode resonant cavity structure and the coupled resonant cavity structure are axially symmetrically distributed;

[0029] The sizes of the multi-mode resonant cavity structure and the coupled resonant cavity structure are adjusted according to the resonant frequency of the filter.

[0030] In addition, to achieve the above object, the present invention also proposes a design method of a multi-frequency bandpass filter, which is applied to the design of the above multi-frequency bandpass filter, and the method comprises the following steps:

[0031] Construct the physical model of the electromagnetic bandgap structure of the preset frequency band of the filter;

[0032] According to the physical model, a multi-mode resonant cavity structure, a perturbation structure, a coupled resonant cavity structure and a coupled slot structure are sequentially constructed.

[0033] The technical solution of the present invention proposes a multi-frequency bandpass filter and a design method thereof. The multi-frequency bandpass filter comprises: a multi-mode resonant cavity structure, a perturbation structure, a coupling slot structure and a coupling resonant cavity structure designed based on a substrate integrated gap waveguide structure; the substrate integrated gap waveguide structure comprises: a first dielectric layer, a second dielectric layer and a third dielectric layer arranged in sequence from bottom to top; the lower surface of the first dielectric layer and the upper surface of the third dielectric layer are metal layers, and periodic metal sheets are etched on the upper surface of the first dielectric layer, and each of the metal sheets and the metal layer on the lower surface of the first dielectric layer are connected through a first metal via, and a metal strip line is etched on the upper surface of the second dielectric layer; the multi-mode resonant cavity structure is used to control the resonant mode of the filter to be excited within the electromagnetic band gap range; the perturbation structure is used to adjust the working frequency band of each resonant mode of the filter; the coupling resonant cavity structure is used to adjust the number of passbands of the filter through the coupling slot structure. Resonances of different frequencies are achieved through multi-mode resonant cavities, coupled resonant cavities and coupled gaps, and a perturbation structure is introduced to control the working frequency band of the filter. Combined with the electromagnetic bandgap structure, a low-loss multi-frequency bandpass filter in the millimeter wave band can be realized. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It is a structural schematic diagram of a first embodiment of the multi-frequency bandpass filter proposed by the present invention;

[0035] Figure 2 A schematic structural diagram of a substrate-integrated gap waveguide structure in a first embodiment of a multi-frequency bandpass filter proposed by the present invention;

[0036] Figure 3 A schematic structural diagram of an electromagnetic bandgap structure in a first embodiment of a multi-frequency bandpass filter proposed by the present invention;

[0037] Figure 4 This is a schematic diagram of an equivalent structure of the electromagnetic bandgap structure in the first embodiment of the multi-frequency bandpass filter proposed by the present invention;

[0038] Figure 5 It is a schematic diagram of an equivalent circuit of an electromagnetic bandgap structure in a first embodiment of a multi-frequency bandpass filter proposed by the present invention;

[0039] Figure 6 It is a schematic diagram of parameter simulation results of the first embodiment of the multi-frequency bandpass filter proposed by the present invention;

[0040] Figure 7 The figure is a flow chart of an embodiment of a method for designing a multi-frequency bandpass filter according to the present invention.

[0041] Figure numerals: 1. first dielectric layer; 2. second dielectric layer; 3. third dielectric layer; 4. metal layer; 5. first metal via; 6. metal sheet; 7. metal strip line; 8. coupling gap structure; 9. fifth metal via; 10. sixth metal via; 11. second metal via; 12. third metal via; 13. fourth metal via.

[0042] The realization of the purpose, functional features and advantages of the present invention will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0043] It should be understood that the specific embodiments described herein are only used to explain the present invention, and are not used to limit the present invention.

[0044] 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.

[0045] It should be noted that all directional indications (such as up, down, left, right, front, back, etc.) in the embodiments of the present invention are only used to explain the relative position relationship, movement status, etc. between the components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0046] In addition, the descriptions of "first", "second", etc. in the present invention are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In addition, the technical solutions between the various embodiments can be combined with each other, but they must be based on the ability of ordinary technicians in the field to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0047] The main solution of the embodiment of the present invention is: a multi-mode resonant cavity structure, a perturbation structure, a coupled slot structure and a coupled resonant cavity structure designed based on a substrate integrated gap waveguide structure; the substrate integrated gap waveguide structure comprises: a first dielectric layer, a second dielectric layer and a third dielectric layer arranged in sequence from bottom to top; the lower surface of the first dielectric layer and the upper surface of the third dielectric layer are metal layers, and periodic metal sheets are etched on the upper surface of the first dielectric layer, and each of the metal sheets and the metal layer on the lower surface of the first dielectric layer are connected through a first metal via, and a metal strip line is etched on the upper surface of the second dielectric layer; the multi-mode resonant cavity structure is used to control the resonant mode of the filter to be excited within the electromagnetic band gap range; the perturbation structure is used to adjust the working frequency band of each resonant mode of the filter; and the coupled resonant cavity structure is used to adjust the number of passbands of the filter through the coupled slot structure.

[0048] Traditional multi-frequency design methods mainly include step impedance resonator technology, stub-loaded resonator technology, and multi-passband resonator technology. However, these methods face many challenges when designing multi-frequency filters, especially in the millimeter wave band. For example, multi-passband resonator technology requires parallel or cascade connection of multiple groups of different resonators, resulting in excessively large device size; step impedance resonators are difficult to achieve high impedance strip lines in the millimeter wave band, and the design space is limited; traditional cavity filter solutions have large losses and high profile heights. Therefore, in order to meet the simultaneous communication and transmission needs of various communication modes such as semantic communication in the millimeter wave band, it is urgent to develop new low-loss, multi-frequency filters.

[0049] Reference Figure 1 , Figure 1 This is a schematic diagram of the structure of the first embodiment of the multi-frequency bandpass filter proposed by the present invention. Figure 1A first embodiment of the multi-frequency bandpass filter of the present invention is provided.

[0050] In this embodiment, the multi-frequency bandpass filter includes: a multi-mode resonant cavity structure, a perturbation structure, a coupled slot structure and a coupled resonant cavity structure designed based on a substrate integrated gap waveguide structure.

[0051] It should be noted that the multi-mode resonant cavity structure can be used to control the excitation of the resonant mode of the filter within the electromagnetic band gap range; the perturbation structure can be used to adjust the operating frequency band of each resonant mode of the filter; and the coupled resonant cavity structure can be used to adjust the number of passbands of the filter through the coupled gap structure.

[0052] Further, see Figure 2 , Figure 2 The schematic diagram of the structure of the substrate-integrated gap waveguide structure in the first embodiment of the multi-bandpass filter proposed by the present invention is as follows: the substrate-integrated gap waveguide structure comprises: a first dielectric layer 1, a second dielectric layer 2 and a third dielectric layer 3 arranged in sequence from bottom to top.

[0053] The lower surface of the first dielectric layer 1 and the upper surface of the third dielectric layer 3 are metal layers 4, periodic metal sheets 6 are etched on the upper surface of the first dielectric layer 1, and first metal vias 5 are connected through each metal sheet 6 and the metal layer on the lower surface of the first dielectric layer 1, and metal strip lines 7 are etched on the upper surface of the second dielectric layer 2. The metal sheets can be circular metal sheets, or square or other polygonal metal sheets, and this embodiment is described using circular metal sheets.

[0054] Further, the substrate integrated gap waveguide structure comprises: periodically arranged bandgap structural units; each of the bandgap structural units comprises the metal sheet 6 and the first metal via 5, the width of the metal sheet 6 is greater than the cross-sectional width of the first metal via 5; the size of the bandgap structural unit and the periodic arrangement sequence are adjusted according to the electromagnetic bandgap range. The metal strip line 7 can be a transmission strip line for input and output of the signal to be processed, and the impedance can be set to 50 ohms to reduce the insertion loss of the filter.

[0055] Reference Figure 3 , Figure 4 as well as Figure 5 , Figure 3 This is a schematic diagram of the structure of the electromagnetic bandgap structure in the first embodiment of the multi-frequency bandpass filter proposed by the present invention. Figure 4 This is a schematic diagram of an equivalent structure of the electromagnetic bandgap structure in the first embodiment of the multi-frequency bandpass filter proposed by the present invention. Figure 5 FIG. 1 is a schematic diagram of an equivalent circuit of an electromagnetic bandgap structure in the first embodiment of the multi-frequency bandpass filter proposed by the present invention. The physical model of the electromagnetic bandgap structure array is shown in FIG. Figure 3 As shown, the equivalent physical model is as follows Figure 4 As shown, the equivalent circuit is Figure 5 As shown. The period of the electromagnetic bandgap structural unit is p , the disc spacing is g . Figure 4 The equivalent physical model includes two equivalent dielectric layers, which are the lower layer and the upper layer from bottom to top, with thicknesses of h 1. d ,in, d is the thickness of the second dielectric layer h 2 and the thickness of the third dielectric layer h 3. A metal layer is applied to the top and bottom layers of the dielectric substrate. The equivalent circuit of the two bandgap structural units includes: a first equivalent capacitor formed by the metal sheet C 1. The first equivalent inductance formed by the first metal via L and a second equivalent capacitance between the metal sheets of the two bandgap structure units C 2.

[0056] In a preferred embodiment, the electromagnetic bandgap structure calculation theory is shown in the following formula.

[0057]

[0058]

[0059]

[0060]

[0061]

[0062] In the above formula, is the dielectric constant of free space, is the period of the electromagnetic bandgap structural unit, is the thickness of the upper medium, is the radius of the metal sheet, is the radius of the metal cylinder, is the magnetic permeability of free space; the gap capacitance between the metal sheets of two adjacent electromagnetic bandgap structure units is , the capacitance from the metal sheet to the top metal layer is , the column inductance is , is the wave impedance of the lower dielectric layer, is the relative dielectric constant of the lower dielectric layer, is the electromagnetic bandgap structure electromagnetic bandgap center frequency, is the electromagnetic bandgap bandwidth of the electromagnetic bandgap structure.

[0063] The relative dielectric constant of the upper equivalent dielectric layer is calculated as follows:

[0064]

[0065] In the above formula, , and are the thicknesses of the first dielectric layer, the second dielectric layer and the third dielectric layer, respectively. is the relative dielectric constant of the second dielectric layer, is the relative dielectric constant of the third dielectric layer.

[0066] In a possible implementation, the multi-mode resonant cavity structure is established as Figure 2 As shown. The multi-mode resonant cavity structure is arranged on the third dielectric layer 3, including a metal layer 4 located on the upper surface of the third dielectric layer, a metal layer 4 on the lower surface, and a plurality of second metal vias 11 connecting the two metal layers. The multi-mode resonant cavity structure can be a resonant rectangular cavity formed by the second metal vias 11, which can generate multi-resonant modes. The multi-mode resonant cavity is axially symmetrically distributed.

[0067] In one possible implementation, the perturbation structure is established as Figure 1 As shown. The perturbation structure is arranged in the third dielectric layer 3; the perturbation structure includes: a third metal via 12 and a fourth metal via 13; the fourth metal via 13 is arranged on both sides of the third metal via 12; the third metal via 12 and the fourth metal via 13 are axially symmetrically distributed. The resonant mode operating frequency can be adjusted by changing the via position. The perturbation metal via may include a circularly arranged metal via structure (i.e., the third metal via 12 mentioned above) and two metal vias (i.e., the fourth metal via 13 mentioned above) distributed on both sides. The third metal via 12 may also be circular or arranged in any polygonal shape, etc. This embodiment is described with a circular arrangement. The mode resonant frequency can be adjusted by arranging the third metal via 12 and the fourth metal via 13, and they are axially symmetrically distributed.

[0068] In a possible implementation, the coupling gap structure is established as follows: Figure 1 As shown. The coupling slot structure 8 is arranged on the metal layer 4 on the lower surface of the third dielectric layer 3; the coupling slot structure is composed of two symmetrically distributed slots. The number of passbands can be changed by adjusting the size of the coupling slot and the spacing between the slot and the perturbation metal via. The slot can be a cross-shaped or open resonant ring. For example, the coupling slot structure can be composed of two axially symmetrically distributed hexagons, located on the metal layer on the lower surface of the third dielectric layer.

[0069] It should be understood that the coupling gap structure mainly affects the coupling coefficient of the coupling mode, and its coupling coefficient k It can be calculated according to the following formula:

[0070]

[0071] in fp and fq represents the resonant frequency of the two modes. By adjusting the size of the coupling gap, the coupling coefficient can be changed, thereby affecting the frequency and number of frequency bands.

[0072] In one possible implementation, the coupled resonant cavity structure is established as Figure 1 As shown. The coupled resonant cavity structure is arranged in the second dielectric layer 2; the coupled resonant cavity structure includes: a metal layer 4 located on the upper surface of the second dielectric layer 2, a metal layer 4 located on the lower surface of the third dielectric layer 3, and a plurality of fifth metal vias 9 connecting the two metal layers 4; each of the fifth metal vias 9 encloses a coupled rectangular cavity, and the coupled rectangular cavity also includes a plurality of sixth metal vias 10; the sixth metal vias 10 are arranged in a single row axially symmetrically at the center of the coupled rectangular cavity. The coupled resonant cavity structure is axially symmetrically distributed. Among them, the sizes of the multi-mode resonant cavity structure and the coupled resonant cavity structure are adjusted according to the resonant frequency of the filter. Specifically, they can be calculated with reference to the following formula:

[0073]

[0074] In the above formula, is the resonant frequency, is the speed of light, is the magnetic permeability of the medium, is the dielectric constant, , For the resonant mode, is the cavity length, is the width of the cavity.

[0075] Reference Figure 6 , Figure 6 Schematic diagram of parameter simulation results of the first embodiment of the multi-frequency bandpass filter proposed by the present invention. Figure 6The figure shows the S parameter simulation results of the embodiment of the present invention, with the ordinate being the S parameter in dB and the abscissa being the frequency in GHz. The figure shows the reflection coefficient and the transmission coefficient of four beam waveforms with and without connectors. It can be seen that the passband center frequencies of the filter of the embodiment of the present invention are 45.74 / 47.97 / 56.05 / 61.69 GHz, the 3 dB relative bandwidths are 3.8% / 1.04% / 5.81% / 1.52%, and the minimum insertion losses are 0.98 / 2.25 / 1.11 / 1.8 dB, respectively.

[0076] In this embodiment, the filter includes a multi-mode resonant cavity structure, a perturbation structure, a coupling slot structure, a coupled resonant cavity structure and an electromagnetic bandgap structure. The multi-mode resonant cavity includes a rectangular resonant cavity surrounded by metal vias; the perturbation includes a circularly arranged metal via in the middle and two symmetrically distributed metal vias; the coupling slot structure is two symmetrically distributed equilateral hexagonal slots; the coupled resonant cavity includes a rectangular resonant cavity surrounded by metal vias and a metal via arranged symmetrically in the middle axis. The results of simulation analysis show that the passband center frequencies are 45.74 / 47.97 / 56.05 / 61.69 GHz, the 3 dB relative bandwidths are 3.8% / 1.04% / 5.81% / 1.52%, and the minimum insertion losses are 0.98 / 2.25 / 1.11 / 1.8 dB, respectively, which are more suitable for multi-functional communications. Compared with traditional step impedance and other design methods to achieve multi-frequency filter design, the method proposed in the present invention is easier to implement. The cavity design can achieve a higher degree of freedom. Combined with the electromagnetic bandgap structure, low loss and easy integration in the millimeter wave frequency band can be achieved, effectively reducing the complexity of multi-frequency filter design.

[0077] In addition, the present invention also proposes a design method for a multi-frequency bandpass filter. Figure 7 , Figure 7 The figure is a flow chart of an embodiment of a method for designing a multi-frequency bandpass filter according to the present invention.

[0078] In this embodiment, the design method of the multi-frequency bandpass filter includes the following steps:

[0079] Step S10: constructing a physical model of the electromagnetic bandgap structure of a preset frequency band of the filter.

[0080] Step S20: constructing a multi-mode resonant cavity structure, a perturbation structure, a coupled resonant cavity structure and a coupled slot structure in sequence according to the physical model to construct a multi-frequency bandpass filter.

[0081] It should be noted that the electromagnetic bandgap structure physical model can be constructed by referring to the above electromagnetic bandgap structure calculation theoretical formula. Then, a multi-mode resonant cavity structure, a perturbation structure, a coupled resonant cavity structure and a coupled slot structure are sequentially established on the electromagnetic bandgap structure physical model constructed according to the actual use requirements of the multi-frequency bandpass filter to construct a multi-frequency bandpass filter.

[0082] Specifically, the frequency band, bandwidth and other parameters of the multi-frequency bandpass filter can be designed according to actual usage requirements to construct a physical model of the electromagnetic bandgap structure, and the multi-mode resonant cavity structure and the coupled resonant cavity structure can be constructed using the substrate integrated gap waveguide to integrate the multi-frequency bandpass filter.

[0083] In this embodiment, the multi-bandpass filter is designed to make the bandwidth as wide as possible and easy to integrate. Preferably, the degree of freedom of the metasurface should be as high as possible to meet the requirements of multi-parameter adjustment, realize controllable passband bandwidth and easy integration. The millimeter-wave-level multi-bandpass filter designed through the above steps has effectively improved performance and can better assist semantic communication and traditional communication to achieve simultaneous communication.

[0084] It should be noted that, in this article, the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or system 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 system. In the absence of further restrictions, an element defined by the sentence "comprises a ..." does not exclude the existence of other identical elements in the process, method, article or system including the element.

[0085] The above are only preferred embodiments of the present invention, and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the present invention specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A multi-frequency bandpass filter, characterized in that: The multi-frequency bandpass filter comprises: a multi-mode resonant cavity structure, a perturbation structure, a coupled slot structure and a coupled resonant cavity structure designed based on a substrate integrated gap waveguide structure; The substrate integrated gap waveguide structure comprises: a first dielectric layer, a second dielectric layer and a third dielectric layer arranged in sequence from bottom to top; The lower surface of the first dielectric layer and the upper surface of the third dielectric layer are metal layers, periodic metal sheets are etched on the upper surface of the first dielectric layer, each of the metal sheets and the metal layer on the lower surface of the first dielectric layer is connected through a first metal via, and a metal strip line is etched on the upper surface of the second dielectric layer; The multi-mode resonant cavity structure is used to control the resonant mode of the filter to be excited within the electromagnetic band gap range; The perturbation structure is used to adjust the working frequency band of each resonant mode of the filter; The coupled resonant cavity structure is used to adjust the number of passbands of the filter through the coupled slot structure; The multi-mode resonant cavity structure is arranged in the third dielectric layer; The multi-mode resonant cavity structure comprises: a metal layer located on the upper surface of the third dielectric layer, a metal layer located on the lower surface of the third dielectric layer, and a plurality of second metal vias connecting the two metal layers; The second metal vias are surrounded by each other to form a resonant rectangular cavity; The perturbation structure is arranged in the third dielectric layer; The perturbation structure includes: a third metal via and a fourth metal via; The fourth metal via is arranged on both sides of the third metal via; The third metal via and the fourth metal via are axially symmetrically distributed; The coupling slot structure is arranged on the metal layer on the lower surface of the third dielectric layer, and the coupling slot structure is composed of two symmetrically distributed slots; The coupled resonant cavity structure is arranged in the second dielectric layer.

2. The multi-frequency bandpass filter according to claim 1, characterized in that: The substrate integrated gap waveguide structure comprises: periodically arranged bandgap structural units; Each of the bandgap structure units includes the metal sheet and the first metal via, and the width of the metal sheet is greater than the cross-sectional width of the first metal via; The size and periodic arrangement order of the bandgap structural unit are adjusted according to the electromagnetic bandgap range.

3. The multi-frequency bandpass filter according to claim 2, characterized in that: The equivalent circuit of the two bandgap structural units includes: a first equivalent capacitor formed by the metal sheet, a first equivalent inductor formed by the first metal via, and a second equivalent capacitor between the metal sheets of the two bandgap structural units.

4. The multi-frequency bandpass filter according to claim 1, characterized in that: The multi-frequency bandpass filter is a quad-frequency bandpass filter, and the coupling slot structure is composed of two symmetrically distributed equilateral hexagonal slots.

5. The multi-frequency bandpass filter according to claim 4, characterized in that: The coupled resonant cavity structure comprises: a metal layer located on the upper surface of the second dielectric layer, a metal layer located on the lower surface of the third dielectric layer, and a plurality of fifth metal vias connecting the two metal layers; The fifth metal vias are surrounded by each other to form a coupled rectangular cavity, and the coupled rectangular cavity further includes a plurality of sixth metal vias; The sixth metal vias are arranged in a single row and axially symmetrically at the center of the coupling rectangular cavity.

6. The multi-frequency bandpass filter according to claim 5, characterized in that: The multi-mode resonant cavity structure and the coupled resonant cavity structure are axially symmetrically distributed; The sizes of the multi-mode resonant cavity structure and the coupled resonant cavity structure are adjusted according to the resonant frequency of the filter.

7. A multi-frequency bandpass filter design method, applied to the design of the multi-frequency bandpass filter according to any one of claims 1 to 6, characterized in that: The design method comprises the following steps: Construct the physical model of the electromagnetic bandgap structure of the preset frequency band of the filter; According to the physical model, a multi-mode resonant cavity structure, a perturbation structure, a coupled resonant cavity structure and a coupled slot structure are sequentially constructed.

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