Waveguide band-pass filter

Abstract

The invention provides a waveguide band-pass filter. The waveguide band-pass filter comprises a rectangular waveguide; the first dielectric substrate is arranged in the rectangular waveguide, is in contact with two oppositely arranged waveguide side walls of the rectangular waveguide and is used for forming artificial surface plasmon polaritons so as to regulate and control the upper cut-off frequency of a passband; and the second dielectric substrate is arranged in the rectangular waveguide, is crossed with the first dielectric substrate at intervals, is in contact with four waveguide side walls at the periphery of the rectangular waveguide, and is used for regulating and controlling the lower cut-off frequency of the passband. According to the rectangular waveguide band-pass filter, combination of the SSPP and the rectangular waveguide is achieved, independent regulation and control of the upper cut-off frequency and the lower cut-off frequency of the pass band of the rectangular waveguide band-pass filter are achieved, and the excellent sideband selection characteristic is guaranteed.

Description

TECHNICAL FIELD

[0001] The disclosed embodiments of the present application relate to the technical field of wireless communication, and more specifically, to a waveguide bandpass filter. BACKGROUND

[0002] Rectangular waveguide bandpass filters employ a full-metal enclosed structure, offering significant advantages such as low insertion loss, high quality factor, and excellent mechanical stability and power capacity. These characteristics enable them to effectively meet the stringent requirements of radar, satellite communication, and other systems for low loss and high power handling capability, providing reliable filtering solutions for related fields. Therefore, for high-frequency application scenarios, it is of great engineering value and practical significance to research and design tunable passband, high-performance rectangular waveguide filters.

[0003] Currently, the research on traditional rectangular waveguide filters mainly focuses on full-metal structure design. Such devices generally have the problems of large size and heavy weight, making it difficult to meet the urgent needs of modern communication systems for device miniaturization and high integration. More critically, due to the fixed size characteristics of standard rectangular waveguides, the lower cutoff frequency of their bandpass filters often lacks adjustability, which severely restricts their flexibility in complex application scenarios. SUMMARY

[0004] According to embodiments of the present application, a waveguide bandpass filter is proposed to solve the above problems.

[0005] According to aspects of the present application, an example waveguide bandpass filter is disclosed, comprising: a rectangular waveguide; a first dielectric substrate disposed inside the rectangular waveguide and in contact with two oppositely disposed waveguide side walls of the rectangular waveguide, for forming an artificial surface plasmon polariton to regulate the upper cutoff frequency of the passband; and a second dielectric substrate disposed inside the rectangular waveguide, spaced apart from the first dielectric substrate, and in contact with four waveguide side walls around the rectangular waveguide, for regulating the lower cutoff frequency of the passband.

[0006] In some embodiments, the first dielectric substrate is in vertical contact with the two oppositely disposed waveguide side walls of the rectangular waveguide, the second dielectric substrate is in vertical contact with the four waveguide side walls around the rectangular waveguide, and the first dielectric substrate and the second dielectric substrate are vertically spaced apart, so that the width of the first dielectric substrate and the width of the second dielectric substrate are equal to the height of the rectangular waveguide, and the length of the second dielectric substrate is equal to the width of the rectangular waveguide.

[0007] In some embodiments, the second dielectric substrate is symmetrically vertically disposed with respect to the first dielectric substrate.

[0008] In some embodiments, the first dielectric substrate is provided with artificial surface plasmon polariton structures symmetrically arranged with respect to a horizontal middle line and a vertical middle line of the first dielectric substrate, the artificial surface plasmon polariton structures comprising a first preset number of artificial surface plasmon polariton units and artificial surface plasmon polariton transition structures located on both sides of the first preset number of artificial surface plasmon polariton units; wherein the first preset number of artificial surface plasmon polariton units are arranged at intervals.

[0009] In some embodiments, the artificial surface plasmon polariton unit is a rectangular microstrip line with a slot in the middle.

[0010] In some embodiments, the artificial surface plasmon polariton transition structure comprises a second preset number of artificial surface plasmon polariton transition units gradually increasing towards the artificial surface plasmon polariton unit to adapt to the artificial surface plasmon polariton unit; wherein the second preset number of artificial surface plasmon polariton transition units are arranged at intervals.

[0011] In some embodiments, the artificial surface plasmon polariton transition unit is a rectangular microstrip line with a slot in the middle, and the size of the rectangular microstrip line and the slot of the second preset number of artificial surface plasmon polariton transition units gradually increase towards the artificial surface plasmon polariton unit.

[0012] In some embodiments, a first resonator and a second resonator are arranged on a second dielectric substrate to regulate the lower cutoff frequency of the passband, wherein the first resonator is arranged on a first surface of the second dielectric substrate, the second resonator is arranged on a second surface of the second dielectric substrate, and the first surface and the second surface are arranged opposite to each other.

[0013] In some embodiments, the first resonator faces the first dielectric substrate; and the second resonator and the first resonator are symmetrically arranged with respect to the first dielectric substrate.

[0014] In some embodiments, the first resonator is a U-shaped microstrip line symmetrically arranged with respect to the first dielectric substrate; and the second resonator is an inverted H-shaped microstrip line symmetrically arranged with respect to the first dielectric substrate.

[0015] The beneficial effects of the present application are: the first dielectric substrate is arranged in the rectangular waveguide and in contact with two opposite waveguide side walls of the rectangular waveguide, used for forming an SSPP, for regulating the upper cutoff frequency of the passband, realizing the combination of the SSPP and the rectangular waveguide, breaking through the limitation of large volume of the traditional rectangular waveguide filter, perfectly adapting to the miniaturization demand of the modern communication system, and providing a new scheme for regulating the performance of the filter. Meanwhile, the second dielectric substrate is arranged in the rectangular waveguide and is arranged in a staggered manner with the first dielectric substrate, and is in contact with the four waveguide side walls around the rectangular waveguide, used for regulating the lower cutoff frequency of the passband, effectively solving the technical problem that the lower cutoff frequency of the traditional rectangular waveguide filter is not adjustable. In addition, the first dielectric substrate and the second dielectric substrate are used to independently regulate the upper and lower cutoff frequencies of the passband of the rectangular waveguide bandpass filter, and ensure excellent sideband selection characteristics.

[0016] These and other objects of the present application will no doubt become apparent to those skilled in the art after reading the following detailed description of the preferred embodiments, illustrated in the accompanying drawings. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 is a perspective split schematic diagram of a waveguide bandpass filter according to an embodiment of the present application.

[0018] Figure 2 is another perspective split schematic diagram of a waveguide bandpass filter according to an embodiment of the present application.

[0019] Figure 3 is a front perspective schematic diagram of a waveguide bandpass filter according to an embodiment of the present application.

[0020] Figure 4 is a back perspective schematic diagram of a waveguide bandpass filter according to an embodiment of the present application.

[0021] Figure 5 is a left perspective schematic diagram of a waveguide bandpass filter according to an embodiment of the present application.

[0022] Figure 6 is a right perspective schematic diagram of a waveguide bandpass filter according to an embodiment of the present application.

[0023] Figure 7 is a dispersion curve diagram of an SSPP in a waveguide bandpass filter 100.

[0024] Figure 8 is a response S parameter curve diagram of a bandpass filter according to an embodiment of the present application. DETAILED DESCRIPTION

[0025] The scheme of the embodiments of the present application will be described in detail below in conjunction with the drawings of the specification.

[0026] In the following description, specific details such as particular system architectures, interfaces, and technologies are presented for illustrative purposes rather than for limiting purposes, in order to provide a thorough understanding of this application.

[0027] In this document, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " generally indicates that the preceding and following related objects have an "or" relationship. Furthermore, "many" in this document means two or more. Moreover, the term "at least one" in this document means any combination of at least two of any one or more of a plurality of objects. For example, including at least one of A, B, and C can mean including any one or more elements selected from the set consisting of A, B, and C.

[0028] like Figures 1-6 The diagram shown is a schematic representation of a waveguide bandpass filter 100 according to an embodiment of this application. The waveguide bandpass filter 100 includes a rectangular waveguide 110, a first dielectric substrate 120, and a second dielectric substrate 130.

[0029] Since the waveguide bandpass filter 100 includes a rectangular waveguide 110, it can also be called a rectangular waveguide bandpass filter. The rectangular waveguide 110 is a hollow metal tube with a rectangular cross-section, serving as a high-pass structure and exhibiting high-pass characteristics. The rectangular waveguide 110 includes waveguide sidewalls 111-114, which are connected to form a hollow metal tube. The waveguide sidewalls 111-114 can be made of the same metal. The rectangular waveguide 110 can be a WR-28 rectangular waveguide 110.

[0030] A first dielectric substrate 120 is disposed inside a rectangular waveguide 110 and contacts two opposing waveguide sidewalls 111 and 112 of the rectangular waveguide 110. That is, the first dielectric substrate 120 is in contact with the waveguide sidewalls 111 and 112 of the rectangular waveguide 110 to form artificial surface plasmon polaritons (SSPPs) to modulate the upper cutoff frequency of the passband. The artificial surface plasmon polaritons have low-pass characteristics. In other words, the first dielectric substrate 120 implements a low-pass filter through SSPPs. The first dielectric substrate 120 can be a Rogers RT5880 dielectric substrate.

[0031] The second dielectric substrate 130 is arranged inside the rectangular waveguide 110, is arranged in cross with the first dielectric substrate 120, and is in contact with the four waveguide side walls 111-114 around the rectangular waveguide 110, and is used to regulate the lower cutoff frequency of the passband. That is, the second dielectric substrate 130 is used to form a band-stop filter to regulate the lower cutoff frequency of the passband. The second dielectric substrate 130 is in contact with the waveguide side walls 111-114 of the rectangular waveguide 110, that is, the second dielectric substrate 130 is connected to the rectangular waveguide 110 as a whole from the inside, and occupies the cross section of the rectangular waveguide 110. The second dielectric substrate 130 can be made of the same material as the first dielectric substrate 120, that is, the second dielectric substrate 130 can also be a Rogers RT5880 dielectric substrate.

[0032] In the waveguide band-pass filter 100, based on the high-pass characteristic of the rectangular waveguide 110 and the low-pass characteristic of the fundamental mode of the SSPP formed by the first dielectric substrate 120, a band-pass characteristic is formed to generate a passband. Specifically, the first dielectric substrate 120 forms an SSPP, and the upper cutoff frequency of the passband of the waveguide band-pass filter 100 can be realized and regulated by the SSPP on the first dielectric substrate 120. Moreover, the second dielectric substrate 130 is used to form a band-stop filter, and the lower cutoff frequency of the passband of the waveguide band-pass filter 100 can be realized and regulated by the second dielectric substrate 130.

[0033] In this embodiment, the first dielectric substrate 120 is arranged inside the rectangular waveguide 110 and in contact with two oppositely arranged waveguide side walls of the rectangular waveguide 110, and is used to form an SSPP to regulate the upper cutoff frequency of the passband, realizing the combination of the SSPP and the rectangular waveguide 110, breaking through the limitation of large volume of traditional rectangular waveguide filters, perfectly adapting to the miniaturization demand of modern communication systems, and providing a new scheme for regulating the performance of filters. At the same time, the second dielectric substrate 130 is arranged inside the rectangular waveguide 110, is arranged in cross with the first dielectric substrate 120, and is in contact with the four waveguide side walls 111-114 around the rectangular waveguide 110, and is used to regulate the lower cutoff frequency of the passband, effectively solving the technical problem that the lower cutoff frequency of the traditional rectangular waveguide filter cannot be adjusted. In addition, by the first dielectric substrate 120 and the second dielectric substrate 130, the upper and lower cutoff frequencies of the passband of the rectangular waveguide band-pass filter 100 are independently regulated, and excellent sideband selection characteristics are ensured.

[0034] In some embodiments, as Figures 1-6As shown, the first dielectric substrate 120 is vertically in contact with two opposite waveguide side walls 111 and 112 of the rectangular waveguide 110, the second dielectric substrate 130 is vertically in contact with four waveguide side walls 111-114 around the rectangular waveguide 110, and the first dielectric substrate 120 and the second dielectric substrate 130 are vertically arranged in a spaced manner, so that the width of the first dielectric substrate 120 and the width of the second dielectric substrate 130 are equal to the height of the rectangular waveguide 110, and the length of the second dielectric substrate 130 is equal to the width of the rectangular waveguide 110.

[0035] The first dielectric substrate 120 is vertically in contact with the waveguide side wall 111 and the waveguide side wall 112 of the rectangular waveguide 110, which means that the first dielectric substrate 120 is arranged inside the rectangular waveguide 110 along the length direction of the rectangular waveguide 110 and is arranged in parallel with the waveguide side wall 113 and the waveguide side wall 114 of the rectangular waveguide 110. That is, the first dielectric substrate 120 is arranged in parallel with the E plane of the rectangular waveguide 110, and the E plane of the rectangular waveguide 110 is a plane parallel to the electric field direction of the rectangular waveguide 110. The second dielectric substrate 130 is vertically in contact with the four waveguide side walls 111-114 around the rectangular waveguide 110, which means that the second dielectric substrate 130 is consistent with the size of the rectangular cross section of the rectangular waveguide 110, that is, the length and width of the second dielectric substrate 130 are the same as the length and width of the cross section, that is, the length and width of the rectangular waveguide 110 are the same. That is, the second dielectric substrate 130 is arranged in parallel with the H plane of the rectangular waveguide 110, and the H plane of the rectangular waveguide 110 is a plane parallel to the magnetic field direction of the rectangular waveguide 110.

[0036] In some embodiments, as shown in Figure 1 、 Figure 2 and Figure 5 , the second dielectric substrate 130 is vertically arranged symmetrically about the first dielectric substrate 120.

[0037] That is, the second dielectric substrate 130 corresponds to the rectangular cross section of the rectangular waveguide 110, so that the first dielectric substrate 120 is located on the plane where the center line of the rectangular waveguide 110 is located.

[0038] In some embodiments, as shown in Figures 1-4 , the first dielectric substrate 120 is provided with an artificial surface plasmon structure 120' arranged symmetrically about the horizontal middle line and the vertical middle line of the first dielectric substrate 120, the artificial surface plasmon structure 120' includes a first preset number of artificial surface plasmon units 121 and artificial surface plasmon transition structures 122 located on both sides of the first preset number of artificial surface plasmon units 121. Among them, the first preset number of artificial surface plasmon units 121 are arranged in a spaced manner.

[0039] The artificial surface plasmon polariton structure 120' is a periodic structure, i.e., forming an SSPP, and is disposed on one surface 120a of the first dielectric substrate 120, parallel to the E-plane of the rectangular waveguide 110. The other surface 120b of the first dielectric substrate 120 has no metal layer. These two surfaces 120a and 120b of the first dielectric substrate 120 are arranged opposite each other.

[0040] exist Figures 1-4 The structure includes three artificial surface plasmon polariton units 121, which are equally spaced, meaning that the distance between any two adjacent artificial surface plasmon polariton units 121 is equal. The artificial surface plasmon polariton structure 120' also includes artificial surface plasmon polariton transition structures 122 on both sides of the three artificial surface plasmon polariton units 121.

[0041] Furthermore, in some embodiments, such as Figure 3 As shown, the artificial surface plasmon polariton unit 121 is a rectangular microstrip line 121 with a central slot 121g.

[0042] The rectangular microstrip line 121 with a central slot 121g is a rectangular metal layer with a central slot.

[0043] In some embodiments, such as Figures 1-4 As shown, the artificial surface plasmon transition structure 122 includes a second predetermined number of artificial surface plasmon transition units that gradually increase in size toward the artificial surface plasmon unit 121, for example... Figures 1-4 The figure shows three artificial surface plasmon transition units 122a-122c, adapted to the artificial surface plasmon unit 121.

[0044] Among them, the second preset number of artificial surface plasmon polariton transition units, for example Figures 1-4 The three artificial surface plasmon transition units 122a-122c are spaced apart.

[0045] exist Figures 1-4 In the middle, the second quantity is also 3, the same as the number of artificial surface plasmon polariton units 121. Facing the artificial surface plasmon polariton units 121, the three artificial surface plasmon polariton transition units 122a-122c gradually increase in size, thereby adapting to the three artificial surface plasmon polariton units 121.

[0046] Three artificial surface plasmon polariton transition units 122a-122c are equally spaced, meaning the distance between any two adjacent artificial surface plasmon polariton transition units is equal. For example, the distance between artificial surface plasmon polariton transition units 122a-122b is equal to the distance between artificial surface plasmon polariton transition units 122b-122c. The distance between any two adjacent artificial surface plasmon polariton transition units (e.g., 122a-122b, 122b-122c) is equal to the distance between any two adjacent artificial surface plasmon polariton units 121, to better accommodate the artificial surface plasmon polariton units 121.

[0047] In some embodiments, such as Figures 1-4 As shown, the artificial surface plasmon polariton transition unit 122a is a rectangular microstrip line 122a with a central slot 122ag, the artificial surface plasmon polariton transition unit 122b is a rectangular microstrip line 122b with a central slot 122bg, and the artificial surface plasmon polariton transition unit 122c is a rectangular microstrip line 122c with a central slot 122cg. The dimensions of the rectangular microstrip lines 122a-122c and the slots 122ag-122cg of the second preset number of artificial surface plasmon polariton transition units all gradually increase towards the artificial surface plasmon polariton unit 121.

[0048] In other words, artificial surface plasmon polariton transition unit 122a has a slot 122ag, artificial surface plasmon polariton transition unit 122b has a slot 122bg, and artificial surface plasmon polariton transition unit 122c has a slot 122cg. Facing the artificial surface plasmon polariton unit 121, the dimensions of the rectangular microstrip lines and slots 122ag-122cg of the three artificial surface plasmon polariton transition units 122a-122c gradually increase. Specifically, the lengths of the rectangular microstrip lines 122a-122c and slots 122ag-122cg of the three artificial surface plasmon polariton transition units 122a-122c gradually increase, while keeping the widths of the rectangular microstrip lines and slots 122ag-122cg of the three artificial surface plasmon polariton transition units 122a-122c constant. Meanwhile, the widths of the rectangular microstrip lines and slots 122ag-122cg of the three artificial surface plasmon polariton transition units 122a-122c are the same as the widths of the rectangular microstrip lines and slots 121g of the artificial surface plasmon polariton unit 121, so as to adapt to the artificial surface plasmon polariton unit 121.

[0049] In some embodiments, such as Figures 1-2 and Figures 5-6As shown, a first resonator 131 and a second resonator 132 are disposed on the second dielectric substrate 130 to control the lower cutoff frequency of the passband. The first resonator 131 is disposed on the first surface 130a of the second dielectric substrate 130, and the second resonator 132 is disposed on the second surface 130b of the second dielectric substrate 130. The first surface 130a and the second surface 130b are disposed opposite to each other.

[0050] The first resonator 131 and the second resonator 132 form a band-stop filter, that is, the band-stop filter is a second-order band-stop filter. By setting the resonant frequencies of the first resonator 131 and the second resonator 132 to a lower frequency band, the lower cutoff frequency of the waveguide bandpass filter 100 can be adjusted, that is, the lower cutoff frequency of the passband of the waveguide bandpass filter 100 can be controlled.

[0051] The first resonator 131 is disposed on the first surface 130a of the second dielectric substrate 130, and the second resonator 132 is disposed on the second surface 130b of the second dielectric substrate 130. Since the first surface 130a and the second surface 130b are disposed opposite each other, the first resonator 131 and the second resonator 132 are disposed opposite each other and partially opposite each other, that is, the projection of the first resonator 131 on the second surface 130b falls into the second resonator 132.

[0052] Furthermore, in some embodiments, such as Figures 5-6 As shown, the first resonator 131 faces the first dielectric substrate 120; the second resonator 132 and the first resonator 131 are both symmetrically arranged about the first dielectric substrate 120.

[0053] The first resonator 131 is symmetrically arranged about the first dielectric substrate 120, so the distance from the first resonator 131 to both sides of the second dielectric substrate 130 that contacts the waveguide sidewalls 113 and 114 is equal. Similarly, the second resonator 132 is symmetrically arranged about the first dielectric substrate 120, so the distance from the second resonator 132 to both sides of the second dielectric substrate 130 that contacts the waveguide sidewalls 113 and 114 is equal. However, the distance from the second resonator 132 to both sides of the second dielectric substrate 130 that contacts the waveguide sidewalls 113 and 114 may differ from the distance from the first resonator 131 to both sides of the second dielectric substrate 130 that contacts the waveguide sidewalls 113 and 114.

[0054] The distances from the first resonator 131 to both sides of the second dielectric substrate 130 that contacts the waveguide sidewalls 111 and 112 are unequal, while the distances from the second resonator 132 to both sides of the second dielectric substrate 130 that contacts the waveguide sidewalls 111 and 112 are equal. Specifically, the distance from the first resonator 131 to one side of the second dielectric substrate 130 that contacts the waveguide sidewall 111 is less than the distance from the second resonator 132 to one side of the second dielectric substrate 130 that contacts the waveguide sidewall 111.

[0055] It should be noted that all distances described here refer to vertical distances.

[0056] In some embodiments, the first resonator 131 is a U-shaped microstrip line symmetrically arranged with respect to the first dielectric substrate 120; the second resonator 132 is an H-shaped microstrip line symmetrically arranged with respect to the first dielectric substrate 120 and inverted.

[0057] If the U-shaped microstrip lines are symmetrically arranged about the first dielectric substrate 120, then the distances from the U-shaped microstrip lines to both sides of the second dielectric substrate 130 that contacts the waveguide sidewalls 113 and 114 are equal. In other words, the two branches of the U-shaped microstrip lines are equidistant from both sides of the second dielectric substrate 130 that contacts the waveguide sidewalls 113 and 114. Similarly, if the inverted H-shaped microstrip lines are symmetrically arranged about the first dielectric substrate 120, then the distances from the inverted H-shaped microstrip lines to both sides of the second dielectric substrate 130 that contacts the waveguide sidewalls 113 and 114 are equal. In other words, the four branches of the inverted H-shaped microstrip lines are equidistant from both sides of the second dielectric substrate 130 that contacts the waveguide sidewalls 113 and 114. The distance from the inverted H-shaped microstrip line to both sides of the second dielectric substrate 130 that contacts the waveguide sidewalls 113 and 114 may be different from the distance from the U-shaped microstrip line to both sides of the second dielectric substrate 130 that contacts the waveguide sidewalls 113 and 114.

[0058] The distances from the U-shaped microstrip line to both sides of the second dielectric substrate 130 in contact with waveguide sidewalls 111 and 112 are not equal; that is, the distance from the two branches of the U-shaped microstrip line to one side of the second dielectric substrate 130 in contact with waveguide sidewall 112 is not equal to the distance from the middle portion of the U-shaped microstrip line to one side of the second dielectric substrate 130 in contact with waveguide sidewall 111. The distances from the inverted H-shaped microstrip line to both sides of the second dielectric substrate 130 in contact with waveguide sidewalls 111 and 112 are equal; that is, the distance from the inverted H-shaped microstrip line to one side of the second dielectric substrate 130 in contact with waveguide sidewall 111 is equal to the distance from the inverted H-shaped microstrip line to both sides of the second dielectric substrate 130 in contact with waveguide sidewall 112. The distance from the U-shaped microstrip line to one side of the second dielectric substrate 130 that contacts the waveguide sidewall 111 is less than the distance from the inverted H-shaped microstrip line to one side of the second dielectric substrate 130 that contacts the waveguide sidewall 111.

[0059] like Figure 7 and Figure 8 As shown, it describes Figures 1-6 The electromagnetic simulation results of the waveguide bandpass filter 100 shown are as follows: Figure 7 This is the dispersion curve of the SSPP in the waveguide bandpass filter 100. Figure 8 This is a graph of the S-parameters of the waveguide bandpass filter 100. It can be seen that the center frequency of this waveguide bandpass filter 100 is 32.2 GHz, belonging to the Ka band. Its 3-dB relative bandwidth reaches 20%, or 6.44 GHz bandwidth. There are transmission zeros on both sides of the passband, and the suppression depth is >35 dB. It possesses excellent frequency selectivity and out-of-band suppression capability, thus maintaining the advantages of traditional rectangular waveguides such as low loss and high power capacity while achieving a significant weight reduction effect, greatly expanding its applicability in weight-sensitive applications such as airborne and spaceborne applications.

[0060] Those skilled in the art will readily recognize that numerous modifications and variations can be made to the apparatus and method while maintaining the teachings of this application. Therefore, the above disclosure should be considered limited only by the scope of the appended claims.

Claims

1. A waveguide bandpass filter, characterized in that, include: Rectangular waveguide; A first dielectric substrate is disposed inside the rectangular waveguide and in contact with two oppositely disposed waveguide sidewalls of the rectangular waveguide to form artificial surface plasmons to control the upper cutoff frequency of the passband. The second dielectric substrate is disposed inside the rectangular waveguide, intersecting with the first dielectric substrate at intervals, and in contact with the four waveguide sidewalls around the rectangular waveguide, for controlling the lower cutoff frequency of the passband.

2. The waveguide bandpass filter according to claim 1, characterized in that, The first dielectric substrate is in perpendicular contact with the two oppositely arranged waveguide sidewalls of the rectangular waveguide, and the second dielectric substrate is in perpendicular contact with the four waveguide sidewalls around the rectangular waveguide. The first dielectric substrate and the second dielectric substrate are arranged perpendicularly at intervals, so that the width of the first dielectric substrate and the width of the second dielectric substrate are equal to the height of the rectangular waveguide, and the length of the second dielectric substrate is equal to the width of the rectangular waveguide.

3. The waveguide bandpass filter according to claim 2, characterized in that, The second dielectric substrate is arranged symmetrically and perpendicularly to the first dielectric substrate.

4. The waveguide bandpass filter according to claim 3, characterized in that, The first dielectric substrate is provided with an artificial surface plasmon polariton structure that is symmetrically arranged with respect to both the horizontal and vertical center lines of the first dielectric substrate. The artificial surface plasmon polariton structure includes a first preset number of artificial surface plasmon polariton units and artificial surface plasmon polariton transition structures located on both sides of the first preset number of artificial surface plasmon polariton units. The first preset number of artificial surface plasmon polariton units are spaced apart.

5. The waveguide bandpass filter according to claim 4, characterized in that, The artificial surface plasmon polariton unit is a rectangular microstrip line with a central slot.

6. The waveguide bandpass filter according to claim 4 or 5, characterized in that, The artificial surface plasmon polariton transition structure includes a second preset number of artificial surface plasmon polariton transition units that gradually increase in size toward the artificial surface plasmon polariton unit, in order to adapt to the artificial surface plasmon polariton unit. The second preset number of artificial surface plasmon transition units are spaced apart.

7. The waveguide bandpass filter according to claim 6, characterized in that, The artificial surface plasmon polariton transition unit is a rectangular microstrip line with a central slot. The dimensions of the rectangular microstrip line and the slot of the second preset number of artificial surface plasmon polariton transition units gradually increase toward the artificial surface plasmon polariton unit.

8. The waveguide bandpass filter according to claim 3, characterized in that, A first resonator and a second resonator are disposed on the second dielectric substrate to control the lower cutoff frequency of the passband. The first resonator is disposed on a first surface of the second dielectric substrate, and the second resonator is disposed on a second surface of the second dielectric substrate. The first surface and the second surface are disposed opposite to each other.

9. The waveguide bandpass filter according to claim 8, characterized in that, The first resonator faces the first dielectric substrate; Both the second resonator and the first resonator are symmetrically arranged about the first dielectric substrate.

10. The waveguide bandpass filter according to claim 8 or 9, characterized in that, The first resonator is a U-shaped microstrip line symmetrically arranged with respect to the first dielectric substrate; the second resonator is an H-shaped microstrip line symmetrically arranged with respect to the first dielectric substrate and inverted.

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