A terahertz single-ridge waveguide bandpass filter based on high-order modes

Abstract

The present application discloses a terahertz single-ridge waveguide bandpass filter based on high-order modes, comprising a metal waveguide with a hollow structure, a metal ridge structure arranged in the metal waveguide, and a plurality of perturbation metal pillars, wherein the bottom of the metal ridge structure is connected to the bottom inner wall of the metal waveguide, the top of the perturbation metal pillar is connected to the top inner wall of the metal waveguide, and the bottom of the perturbation metal pillar is spaced apart from the metal ridge structure. The RWG to SRW conversion structure and the ridge structure transition section are mirror-distributed between the input port and the output port of the filter with the SRW filter structure as the center. The present application adopts air filling to reduce loss and utilizes the high-order modes of the SRW filter structure for bandpass filtering. The selection of high-order modes ensures that the filter has a good bandpass response within the target frequency band, avoiding the size and performance limitations brought by low-order modes. The perturbation metal pillars can further improve the out-of-band suppression performance of the filter.

Description

Technical Field

[0001] The present application relates to the technical field of bandpass filters, and in particular to a terahertz single-ridge waveguide bandpass filter based on a high-order mode. Background Art

[0002] Existing substrate integrated waveguide (SIW) filters based on dielectric materials, while highly integrated and easily miniaturized, are common in the D-band. However, at D-band frequencies, dielectric loss increases significantly, leading to high insertion loss, which severely limits their application in high-frequency, high-performance systems. Similarly, microstrip structures face performance bottlenecks in the D-band due to radiation and conductor losses, making them unsuitable for this frequency band.

[0003] To reduce insertion loss, some research has employed air-dielectric cavity filters or rectangular waveguide filters. While these designs have achieved certain performance breakthroughs, the traditional rectangular waveguide structure has limited parameter freedom, making it difficult to balance multimode tuning and impedance matching, thus presenting limitations. Furthermore, some D-band cavity filters are fabricated using micromachining processes, which are complex and costly.

[0004] To address these issues, some researchers have attempted to use a single-ridge waveguide (SRW) structure. SRW structures offer more design freedom than traditional waveguides and are particularly suitable for constructing periodic structure filters with specific frequency responses. However, existing SRW filters are still primarily used in low-frequency bands (such as the S-band) and are based on dielectric-filled structures, resulting in high losses. While some work has attempted to reduce losses by filling SRW with air, these efforts only utilize the fundamental mode of the SRW for filtering, failing to fully exploit the potential of higher-order modes, limiting bandwidth control capabilities and potential for performance improvement. Furthermore, the ridge structure typically employs a simple rectangular design, without in-depth optimization of the ridge morphology, resulting in a relatively simple filtering response.

[0005] Typical application scenarios for 6G technology place extremely high demands on the capacity, speed, latency, and reliability of communication systems. To support terabit-per-second data transmission rates, the D-band, as one of the potential key frequency bands for 6G, has garnered widespread attention due to its abundant spectrum resources.

[0006] In 6G communication systems, filters, as core components in RF front-end modules, are primarily responsible for signal passband selection and out-of-band interference suppression, directly impacting system performance. Due to the high frequency and short wavelength of the D-band, filters face challenges such as high insertion loss, small structural dimensions, and high processing precision requirements. Traditional low-frequency filter design methods and processing techniques are difficult to directly apply. Furthermore, to reduce system size and power consumption, D-band filters must achieve high selectivity, low loss, and strong out-of-band suppression. Therefore, designing filters that achieve low insertion loss, high performance, and process feasibility in the D-band is crucial for the implementation of 6G communication technology.

[0007] In recent years, single-ridge waveguide structures have been used in low-frequency filter design due to their excellent impedance control capabilities and compactness. Research has shown that the introduction of a periodic structure can achieve better frequency response and offer significant advantages in out-of-band suppression. However, due to its dielectric-filled structure, insertion loss remains relatively high. Subsequent research has employed air-filled SRWs to reduce loss, with some success. However, these efforts typically only utilize the fundamental mode and operate at relatively low frequencies, leaving development of higher-order modes and high-frequency applications unexplored.

[0008] In terms of manufacturing, although micromachining technology can achieve high-precision, complex structures in D-band filters, its process is complex and costly. In contrast, high-precision computer numerical control (CNC) machining is particularly suitable for meeting the production requirements of D-band metal SRW filters due to its ease of operation and high efficiency.

[0009] In summary, the existing D-band filter solutions still have shortcomings in terms of insertion loss, bandwidth adjustment, structural controllability and manufacturing process, and it is difficult to fully meet the comprehensive requirements of 6G communication systems for high performance, low loss, miniaturization and flexible regulation. Summary of the Invention

[0010] The purpose of this application is to provide a terahertz single-ridge waveguide bandpass filter based on a high-order mode to solve the above-mentioned technical problems existing in the prior art. The various technical effects that can be produced by the preferred technical solution among the many technical solutions provided in this application are described in detail below.

[0011] To achieve the above objectives, this application provides the following technical solutions:

[0012] The present application provides a terahertz single-ridge waveguide bandpass filter based on a high-order mode, comprising a metal waveguide with a hollow structure, a metal ridge structure arranged in the metal waveguide, and a plurality of perturbation metal pillars, wherein the bottom of the metal ridge structure is connected to the bottom inner wall of the metal waveguide, the top of the perturbation metal pillar is connected to the top inner wall of the metal waveguide, and the bottom of the perturbation metal pillar is spaced apart from the metal ridge structure;

[0013] One end opening of the metal waveguide is set as an input port, and the other end opening is set as an output port; the bottom of the metal waveguide, the metal ridge structure, and the perturbation metal column are combined to form an RWG-to-SRW conversion structure, a ridge structure transition section, and an SRW filtering structure that are connected in sequence, and the RWG-to-SRW conversion structure and the ridge structure transition section are mirror-distributed between the input port and the output port with the SRW filtering structure as the center.

[0014] In some embodiments, the number of the RWG to SRW conversion structure and the number of the ridge structure transition sections are both 2, the number of the SRW filtering structure is 1, and from the input port to the output port, the RWG to SRW conversion structure, the ridge structure transition section, the SRW filtering structure, the ridge structure transition section, and the RWG to SRW conversion structure are connected in sequence.

[0015] In some embodiments, the SRW filtering structure includes two symmetrical filtering units, each filtering unit including a pair of first L-shaped ridge structures and four first perturbation metal pillars; in one of the filtering units, the two first L-shaped ridge structures are arranged in a mirror image, and the openings are all facing the top inner wall of the metal waveguide, forming a first top open structure; the four first perturbation metal pillars are evenly surrounded on the first top open structure.

[0016] In some embodiments, the first L-shaped ridge structure includes a first horizontal cuboid and a first vertical cuboid, the first horizontal cuboid is perpendicular to the first vertical cuboid, and the two first perturbation metal columns are distributed on both sides of the first vertical cuboid; at the junction of the two filtering units, the two first vertical cuboids are spliced, and the two first perturbation metal columns are spliced; the central axis of the first horizontal cuboid coincides with the central axis of the metal waveguide.

[0017] In some embodiments, the size of the first horizontal cuboid is , the size of the first vertical cuboid is , the distance S0 between the first perturbation metal column and the inner side wall of the metal waveguide is 144.1 , the size of the first perturbative metal column is .

[0018] In some embodiments, the ridge structure transition section includes a first transition unit and a second transition unit, the first transition unit includes a pair of second ridge structures and four second perturbation metal pillars, the two second ridge structures are arranged in a mirror image, and the openings are all facing the top inner wall of the metal waveguide, forming a second top open structure, and the four second perturbation metal pillars are evenly surrounded by the second top open structure; the second transition unit includes a pair of third ridge structures and four third perturbation metal pillars, the two third ridge structures are arranged in a mirror image, and the openings are all facing the top inner wall of the metal waveguide, forming a third top open structure, and the four third perturbation metal pillars are evenly surrounded by the third top open structure.

[0019] In some embodiments, the second ridge structure includes a second horizontal cuboid, a second vertical cuboid and a first bottom cuboid, the first bottom cuboid is located below the second horizontal cuboid, the second horizontal cuboid is perpendicular to the second vertical cuboid, and two second perturbation metal columns are distributed on both sides of the second vertical cuboid; the third ridge structure includes a third horizontal cuboid, a third vertical cuboid and a second bottom cuboid, the second bottom cuboid is located below the third horizontal cuboid, the third horizontal cuboid is perpendicular to the third vertical cuboid, and two third perturbation metal columns are distributed on both sides of the third vertical cuboid, and the central axis of the second horizontal cuboid and the central axis of the third horizontal cuboid both coincide with the central axis of the metal waveguide.

[0020] In some embodiments, at the junction of the first transition unit and the second transition unit, the second vertical cuboid and the third vertical cuboid are spliced ​​together, and the second perturbation metal column and the third perturbation metal column are spliced ​​together.

[0021] In some embodiments, the size of the second horizontal cuboid is , the size of the third horizontal cuboid is , the size of the second vertical cuboid is , the size of the third vertical cuboid is , the size of the first bottom cuboid is , the size of the second bottom cuboid is The distance S0 between the second perturbation metal column and the third perturbation metal column and the inner side wall of the metal waveguide is 144.1 μm, and the size of the second perturbation metal column is , the size of the third perturbation metal column is .

[0022] In some embodiments, the RWG to SRW conversion structure is a three-step structure, and the width of each step is c=550.33 , the length and height of the first step from bottom to top are: tx1=510.04 ,tz1=141.45 The length and height of the second step are tx2=510.04 ,tz2=216.37 , the length and height of the third step are tx3=697.51 ,tz3=141.45 .

[0023] The implementation of one of the above-mentioned technical solutions of the present application has the following advantages or beneficial effects: the terahertz single-ridge waveguide bandpass filter based on high-order modes of the present application includes a metal waveguide with a hollow structure, which is filled with air to reduce loss, and uses the high-order modes of the SRW filter structure for bandpass filtering. The selection of high-order modes ensures that the filter has a good bandpass response within the target frequency band, avoiding the size and performance limitations brought by low-order modes. At the same time, a number of perturbation metal columns are connected to the top inner wall of the metal waveguide, which can further improve the out-of-band suppression performance of the filter. The positions and sizes of these perturbation metal columns are precisely designed to effectively suppress the propagation of undesirable out-of-band modes by perturbing the high-order Floquet modes of the ridge waveguide structure, while keeping the high-order modes that provide bandpass performance unaffected. Specifically, the change in electromagnetic field distribution caused by the metal columns suppresses the transmission of high-order modes, significantly improving the out-of-band suppression bandwidth.

[0024] At the same time, the input and output ports achieve impedance matching and mode conversion through a specific RWG to SRW conversion structure, ensuring a smooth transition of the electromagnetic field distribution from SRW to RWG. This enables the terahertz single-ridge waveguide bandpass filter based on high-order modes to achieve efficient electromagnetic energy transmission with the standard waveguide port, ensuring good impedance matching.

[0025] By rationally utilizing the high-order modes of SRW and introducing perturbed metal pillars, highly selective, low-loss signal transmission is achieved within the target frequency band, significantly improving the out-of-band rejection bandwidth. Furthermore, the increased size brought about by the high-order modes facilitates machining precision control and reduces manufacturing complexity. The proposed structure exhibits excellent reconfigurability and design flexibility, is amenable to CNC processing, and simplifies the manufacturing process. It combines high performance with a high cost-effectiveness, possessing broad engineering application prospects and promotional value. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present application. Those skilled in the art can also derive other drawings based on these drawings without inventive work. In the drawings:

[0027] Figure 1 Schematic diagram of the structure of a terahertz single-ridge waveguide bandpass filter based on a high-order mode according to an embodiment of the present application;

[0028] Figure 2 This is a schematic structural diagram of a terahertz single-ridge waveguide bandpass filter based on a high-order mode according to an embodiment of the present application, in which the upper wall and side walls of the metal waveguide are hidden;

[0029] Figure 3 2 is a schematic diagram of a RWG to SRW conversion structure according to an embodiment of the present application;

[0030] Figure 4 This is another structural schematic diagram of the terahertz single-ridge waveguide bandpass filter based on the high-order mode in an embodiment of the present application, in which the upper wall and side walls of the metal waveguide are hidden;

[0031] Figure 5 is a cross-sectional view of a terahertz single-ridge waveguide bandpass filter based on a high-order mode according to an embodiment of the present application;

[0032] Figure 6 Schematic diagram of the SRW filter structure of an embodiment of the present application;

[0033] Figure 7 is a structural diagram of the first transition unit in an embodiment of the present application;

[0034] Figure 8 is a structural diagram of the second transition unit in an embodiment of the present application;

[0035] Figure 9 It is a schematic diagram of S parameters of an embodiment of the present application. DETAILED DESCRIPTION

[0036] In order to make the purpose, technical solutions and advantages of the present application clearer, the various exemplary embodiments to be described below will refer to the corresponding drawings, which constitute a part of the exemplary embodiments, in which various exemplary embodiments that may be used to implement the present application are described. Unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The implementation methods described in the following exemplary embodiments do not represent all implementation methods consistent with the present disclosure. It should be understood that they are only examples of processes, methods and devices that are consistent with some aspects disclosed in the present application as detailed in the appended claims, and other embodiments may also be used, or structural and functional modifications may be made to the embodiments listed herein without departing from the scope and essence of the present application.

[0037] In the description of this application, it should be understood that the terms "center", "longitudinal", "transverse" and the like indicate the orientation or positional relationship based on the figures, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the elements referred to must have a specific orientation, be constructed and operated in a specific orientation. The terms "first", "second" and the like are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. The term "multiple" means two or more. The terms "connected" and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, an integral connection, a mechanical connection, an electrical connection, a communication connection, a direct connection, an indirect connection through an intermediate medium, and can be the internal connection of two elements or the interaction relationship between two elements. The term "and / or" includes any and all combinations of one or more related listed items. For those of ordinary skill in the art, the specific meanings of the above terms in this application can be understood according to the specific circumstances.

[0038] In order to illustrate the technical solution described in this application, a specific embodiment is provided below, and only the parts related to the embodiment of this application are shown.

[0039] like Figure 1-8 As shown, the present application provides a terahertz single-ridge waveguide bandpass filter 100 based on a high-order mode, comprising a metal waveguide 10 with a hollow structure, a metal ridge structure 1 arranged in the metal waveguide 10, and a plurality of perturbation metal pillars 2, wherein the bottom of the metal ridge structure 1 is connected to the bottom inner wall of the metal waveguide 10, the top of the perturbation metal pillar 2 is connected to the top inner wall of the metal waveguide 10, and the bottom of the perturbation metal pillar 2 is spaced apart from the metal ridge structure 1;

[0040] One end opening of the metal waveguide 10 is set as the input port 101, and the other end opening is set as the output port 102; the bottom of the metal waveguide 10, the metal ridge structure 1 and the perturbation metal column 2 are combined to form a RWG-to-SRW conversion structure 3, a ridge structure transition section 4 and an SRW filtering structure 5 connected in sequence, and the RWG-to-SRW conversion structure 3 and the ridge structure transition section 4 are mirror-distributed between the input port 101 and the output port 102 with the SRW filtering structure 5 as the center.

[0041] Specifically, the metal waveguide 10 has a rectangular waveguide structure in its overall appearance and a hollow structure inside. The metal ridge structure 1 and the perturbation metal column 2 are both arranged in the hollow structure. Figure 1 From the current perspective, the bottom of the metal ridge structure 1 is fixed to the bottom inner wall of the metal waveguide 10, and the tops of several perturbation metal pillars 2 are connected to the top inner wall of the metal waveguide 10. The bottoms of the perturbation metal pillars 2 do not contact the top of the metal ridge structure 1. The left end opening of the metal waveguide 10 is set as the input port 101 of the terahertz single-ridge waveguide bandpass filter 100 based on the high-order mode, and the right end opening is set as the output port 102 of the terahertz single-ridge waveguide bandpass filter 100 based on the high-order mode.

[0042] From left to right, the bottom of the metal waveguide 10, the metal ridge structure 1 and the perturbation metal column 2 form a sequentially connected RWG to SRW conversion structure 3, a ridge structure transition section 4 and an SRW filtering structure 5, where the RWG is a rectangular waveguide and the SRW is a ridge waveguide.

[0043] In some embodiments, the number of RWG to SRW conversion structures 3 is 2, the number of ridge structure transition sections 4 is 2, the number of SRW filter structures 5 is 1, and the RWG to SRW conversion structures 3 and the ridge structure transition sections 4 are mirror-distributed with the SRW filter structure 5 as the center. Figure 2 As shown, Figure 2 The top and sidewalls of the metal waveguide 10 are hidden, and from the input port 101 to the output port 102, that is, from left to right, it can be divided into the RWG to SRW conversion structure 3, the ridge structure transition section 4, the SRW filtering structure 5, the ridge structure transition section 4 and the RWG to SRW conversion structure 3, which are connected in sequence.

[0044] Furthermore, one end of the first RWG to SRW conversion structure 3 is an input port 101, and the other end is connected to one end of the first ridge structure transition section 4, the other end of the first ridge structure transition section 4 is connected to one end of the SRW filter structure 5, the other end of the SRW filter structure 5 is connected to the other end of the second ridge structure transition section 4, one end of the second ridge structure transition section 4 is connected to the other end of the second RWG to SRW conversion structure 3, and one end of the second RWG to SRW conversion structure 3 is an output port 102.

[0045] It can be understood that one end of the first RWG-to-SRW conversion structure 3 has the same structure as one end of the second RWG-to-SRW conversion structure 3, and the other end of the first RWG-to-SRW conversion structure 3 has the same structure as the other end of the second RWG-to-SRW conversion structure 3. Similarly, one end of the first ridge structure transition section 4 has the same structure as one end of the second ridge structure transition section 4, and the other end of the first ridge structure transition section 4 has the same structure as the other end of the second ridge structure transition section 4. The SRW filter structure 5 has the same structure at both ends. This allows the RWG-to-SRW conversion structure 3 and the ridge structure transition section 4 to be mirror-imaged and distributed between the input port 101 and the output port 102, centered around the SRW filter structure 5. Furthermore, the combination of several perturbation metal pillars 2 and metal waveguides 10, along with the high-order mode operating mechanism, achieves a high-performance bandpass filter function.

[0046] Both input port 101 and output port 102 utilize standard rectangular waveguide interfaces, based on the WR-6.5 dimensions commonly used in the D-band. To achieve efficient mode conversion and impedance matching from RWG to SRW, RWG-to-SRW conversion structures 3 are installed at both input port 101 and output port 102. This structure utilizes a multi-step metal transition layer, which gradually shifts the electric field from a concentrated state at the center of the RWG cavity to a high-impedance mode concentrated at the ridge of the SRW. This creates a smooth transition from low-impedance to high-impedance mode, reducing reflections and improving transmission efficiency.

[0047] A ridge structure transition section 4 is provided between the RWG-to-SRW conversion structure 3 and the SRW filter structure 5. This section gradually changes the geometric parameters of the ridges within the metal waveguide 10, aligning the SRW electromagnetic field distribution with that within the filter structure, thereby achieving improved electromagnetic continuity and frequency selectivity. By adjusting the height of each ridge, the ridge structure transition section 4 compresses or expands the ridge shape, effectively connecting the RWG-to-SRW conversion structure 3 and the SRW filter structure 5.

[0048] The SRW filter structure 5 is arranged at the center of the waveguide to excite and control the propagation characteristics of a specific Floquet mode. The second Floquet mode can be selected as the main passband operating mode, which has good transmission performance in the D band.

[0049] In order to suppress high-order spurious modes outside the passband, a number of perturbation metal pillars 2 are provided in the metal waveguide 10. The SRW filter structure 5 includes the perturbation metal pillars 2. By setting the parameters of the perturbation metal pillars 2, perturbations are formed to achieve effective interference of high-order modes and continue to work in the second Floquet mode, so that the working frequency band of the next mode is shifted upward, thereby widening the 20 dB cutoff bandwidth and achieving better out-of-band suppression performance.

[0050] In some embodiments, such as Figure 3 As shown, the RWG to SRW conversion structure 3 is a three-step structure, and the width of each step is c=550.33 , the length and height of the first step from bottom to top are: t x1 =510.04 , t z1 =141.45 , the length and height of the second step are t x2 =510.04 , t z2 =216.37 , the length and height of the third step are t x3 =697.51 , t z3 =141.45 .

[0051] Specifically, since both the input port 101 and the output port 102 are provided with a three-step structure RWG to SRW conversion structure 3, the lateral length thereof is t x1 , t x2 , t x3 , and the longitudinal height t z1 , t z2 , t z3 The first RWG to SRW conversion structure 3 changes step by step, causing the electric field to gradually transition from being concentrated at the center of the ridge waveguide cavity (the center of the hollow structure) to a high-impedance mode concentrated at the ridge waveguide ridge, completing a smooth transition from low-impedance to high-impedance mode, reducing reflections and improving transmission efficiency.

[0052] The second RWG-to-SRW conversion structure 3, which is mirror-symmetrical to the first RWG-to-SRW conversion structure 3, realizes the mode inverse conversion from RWG to SRW. By gradually reducing the size of the metal ridge and gradually reducing the height of the ridge structure to zero, the mode transition from high impedance to low impedance is achieved, and finally the electromagnetic field is evenly distributed in the center of the RWG cavity, achieving efficient output.

[0053] In some embodiments, as Figure 4-5 As shown, the SRW filtering structure 5 includes two symmetrical filtering units 51, each filtering unit 51 includes a pair of first L-shaped ridge structures 511 and four first perturbation metal pillars 21; in one filtering unit 51, the two first L-shaped ridge structures 511 are arranged in a mirror image, and the openings are all facing the top inner wall of the metal waveguide 10, forming a first top open structure; the four first perturbation metal pillars 21 are evenly surrounded on the first top open structure.

[0054] Specifically, the SRW filtering structure 5 is the main filtering structure, and its two filtering units 51 have completely identical structures. Its core is a waveguide structure with a double-layer stepped metal ridge, and is symmetrically distributed along the central axis of the entire terahertz single-ridge waveguide bandpass filter 100 based on high-order modes. Each filtering unit 51 is configured with four first perturbation metal columns 21, which can further improve the out-of-band suppression performance of the terahertz single-ridge waveguide bandpass filter 100 based on high-order modes.

[0055] In some embodiments, the first L-shaped ridge structure 511 includes a first horizontal cuboid 512 and a first vertical cuboid 513, the first horizontal cuboid 512 is perpendicular to the first vertical cuboid 513, and the two first perturbation metal columns 21 are distributed on both sides of the first vertical cuboid 513; at the junction of the two filtering units 51, the two first vertical cuboids 513 are spliced, and the two first perturbation metal columns 21 are spliced; the central axis of the first horizontal cuboid 512 coincides with the central axis of the metal waveguide 10.

[0056] Specifically, if Figure 6 As shown, Figure 6 is a schematic diagram of the structure of the SRW filter structure 5, wherein the size of the first horizontal cuboid 512 is , the size of the first vertical cuboid 513 is The distance S0 between the first perturbation metal column 21 and the inner side wall of the metal waveguide 10 is 144.1 , the size of the first perturbation metal column 21 is The width a of the metal waveguide 10 is 1.651 mm, and the height b is 8.255 mm. The period length p of the filter unit 51 is 1800 .

[0057] The filter unit 51 adopts an L-shaped ridge structure design, so that the terahertz single-ridge waveguide bandpass filter 100 based on the high-order mode can accurately control the frequency and bandwidth of the passband.

[0058] By setting the first perturbation metal column 21 on the first L-shaped ridge structure 511, perturbation is formed, and the design parameters of the first perturbation metal column 21 can achieve effective interference with the high-order mode, and keep the second Floquet mode working, so that the working frequency band of the next mode is shifted upward, thereby widening the 20 dB cutoff bandwidth and achieving better out-of-band suppression performance.

[0059] In some embodiments, the ridge structure transition section 4 includes a first transition unit 41 and a second transition unit 42. The first transition unit 41 includes a pair of second ridge structures 411 and four second perturbation metal pillars 22. The two second ridge structures 411 are arranged in a mirror image, and the openings are all facing the top inner wall of the metal waveguide 10, forming a second top open structure, and the four second perturbation metal pillars 22 are evenly surrounded by the second top open structure; the second transition unit 42 includes a pair of third ridge structures 421 and four third perturbation metal pillars 23. The two third ridge structures 421 are arranged in a mirror image, and the openings are all facing the top inner wall of the metal waveguide 10, forming a third top open structure, and the four third perturbation metal pillars 23 are evenly surrounded by the third top open structure.

[0060] In some embodiments, the second ridge structure 411 includes a second horizontal cuboid 412, a second vertical cuboid 413 and a first bottom cuboid 414, the first bottom cuboid 414 is located below the second horizontal cuboid 412, the second horizontal cuboid 412 is perpendicular to the second vertical cuboid 413, and the two second perturbation metal columns 22 are distributed on both sides of the second vertical cuboid 413; the third ridge structure 421 includes a third horizontal cuboid 422, a third vertical cuboid 423 and a second bottom cuboid 424, the second bottom cuboid 424 is located below the third horizontal cuboid 422, the third horizontal cuboid 422 is perpendicular to the third vertical cuboid 423, and the two third perturbation metal columns 23 are distributed on both sides of the third vertical cuboid 423, and the central axis of the second horizontal cuboid 412 and the central axis of the third horizontal cuboid 422 both coincide with the central axis of the metal waveguide 10.

[0061] In some embodiments, at the junction of the first transition unit 41 and the second transition unit 42 , the second vertical cuboid 413 and the third vertical cuboid 423 are spliced ​​together, and the second perturbation metal column 22 and the third perturbation metal column 23 are spliced ​​together.

[0062] In some embodiments, as Figure 7-8 As shown, Figure 7 is a schematic structural diagram of the first transition unit 41, Figure 8 is a schematic structural diagram of the second transition unit 42. The size of the second horizontal cuboid 412 is , the size of the third horizontal cuboid 422 is , the size of the second vertical cuboid 413 is , the size of the third vertical cuboid 423 is , the size of the first bottom cuboid 414 is , the size of the second bottom cuboid 424 is ; p is the period length of the first transition unit 41 or the second transition unit 42, which is consistent with the period length of the filter unit 51. The distance S0 between the second perturbation metal column 22 and the third perturbation metal column 23 and the inner side wall of the metal waveguide 10 is 144.1 μm, and the size of the second perturbation metal column 22 is , the size of the third perturbation metal column 23 is .

[0063] Specifically, the ridge structure transition section 4 is similar to the structural design of the SRW filter structure 5, with only the longitudinal dimensions changing. The first ridge structure transition section 4 is set between the RWG to SRW conversion structure of the input port 101 and the SRW filter structure 5. Its main function is to gradually change the geometric parameters of the ridge inside the waveguide so that the electromagnetic field distribution of the SRW matches the distribution of the SRW filter structure 5, thereby achieving better electromagnetic continuity and frequency selectivity control. This transition section is adjusted by adjusting the parameter h 11 、h 21 、h 31 、h 12 、h 22 、h 32 The compression or expansion of the ridge shape is achieved, and the RWG to SRW conversion structure 3 and the SRW filtering structure 5 are effectively connected.

[0064] The second ridge structure transition section 4, which is symmetrical to the first ridge structure transition section 4, is arranged at the end of the SRW filtering structure 5. Its structure is similar to that of the first ridge structure transition section 4. Its function is to reversely adjust the ridge parameters so that the electromagnetic field gradually recovers from the filtering area to a field distribution matching the traditional rectangular SRW structure, ensuring that the energy is smoothly output to the next conversion structure.

[0065] In the high-order mode-based terahertz single-ridge waveguide bandpass filter 100 of the present application, at passband frequencies, the electromagnetic field can be smoothly transmitted from the input port 101 to the RWG-to-SRW conversion structure 3, then enter the SRW filter structure 5 via the conversion of the RWG-to-SRW conversion structure 3 and the ridge structure transition section 4. It then propagates in the target Floquet mode, achieving frequency selectivity through metal ridge perturbations, and finally outputted via a symmetrical structure to the ridge structure transition section 4, the RWG-to-SRW conversion structure 3, and the output port 102. However, at out-of-band frequencies, the electromagnetic field will rapidly attenuate due to mode mismatch, out-of-band cutoff, or high-order mode perturbations, and will not effectively pass through the filter, thereby achieving the desired bandpass characteristics.

[0066] In summary, the filter constructs a high-performance, low-insertion-loss, broadband-suppression metal ridge waveguide bandpass filter suitable for D-band applications through conversion structure design, ridge morphology control, periodic perturbation loading and high-order mode suppression mechanism.

[0067] The terahertz single-ridge waveguide bandpass filter 100 based on high-order modes of the present application includes a metal waveguide 10 with a hollow structure, which is filled with air to reduce loss and uses the high-order modes of the SRW filter structure 5 for bandpass filtering. The selection of high-order modes ensures that the filter has a good bandpass response within the target frequency band, avoiding the size and performance limitations brought by low-order modes. At the same time, a number of perturbation metal columns 2 are connected to the top inner wall of the metal waveguide 10, which can further improve the out-of-band suppression performance of the filter. The positions and sizes of these perturbation metal columns 2 are precisely designed to effectively suppress the propagation of undesirable out-of-band modes by perturbing the high-order Floquet modes of the ridge waveguide structure, while keeping the high-order modes that provide bandpass performance unaffected. Specifically, the change in electromagnetic field distribution caused by the metal columns suppresses the transmission of high-order modes, significantly improving the out-of-band suppression bandwidth.

[0068] At the same time, the input port 101 and the output port 102 achieve impedance matching and mode conversion through a specific RWG to SRW conversion structure 3, ensuring a smooth transition of the electromagnetic field distribution from SRW to RWG, so that the terahertz single-ridge waveguide bandpass filter 100 based on the high-order mode can achieve efficient electromagnetic energy transmission with the standard waveguide port, ensuring good impedance matching.

[0069] By rationally utilizing the high-order modes of SRW and introducing a perturbative metal pillar 2, highly selective, low-loss signal transmission is achieved within the target frequency band, significantly improving the out-of-band rejection bandwidth. Furthermore, the increased size brought about by the high-order modes facilitates machining precision control and reduces manufacturing complexity. The proposed structure exhibits excellent reconfigurability and design flexibility, is amenable to CNC processing, and simplifies the manufacturing process. It combines high performance with a high cost-effectiveness, promising broad engineering applications and potential for widespread adoption.

[0070] The S parameters of this application are as follows Figure 9 As shown in the figure, its center frequency is 136.15 GHz, 3-dB bandwidth is 18.2 GHz, relative bandwidth is 13.37%, in-band return loss is greater than 21 dB, minimum insertion loss is 0.2 dB, and out-of-band 20-dB stopband bandwidth is 48.1 GHz, achieving excellent out-of-band suppression while taking into account excellent filtering performance.

[0071] The above are merely preferred embodiments of the present application. Those skilled in the art will appreciate that various changes or equivalent substitutions may be made to these features and embodiments without departing from the spirit and scope of the present application. Furthermore, under the guidance of this application, these features and embodiments may be modified to adapt to specific circumstances and materials without departing from the spirit and scope of the present application. Therefore, the present application is not limited to the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this application are intended to be protected by this application.

Claims

1. A terahertz single-ridge waveguide bandpass filter based on high-order modes, characterized in that: A metal waveguide comprising a hollow structure, a metal ridge structure and a plurality of perturbation metal pillars arranged in the metal waveguide, wherein the bottom of the metal ridge structure is connected to the bottom inner wall of the metal waveguide, the top of the perturbation metal pillar is connected to the top inner wall of the metal waveguide, and the bottom of the perturbation metal pillar is spaced apart from the metal ridge structure; One end opening of the metal waveguide is set as an input port, and the other end opening is set as an output port; the bottom of the metal waveguide, the metal ridge structure, and the perturbation metal column are combined to form an RWG-to-SRW conversion structure, a ridge structure transition section, and an SRW filtering structure that are connected in sequence, and the RWG-to-SRW conversion structure and the ridge structure transition section are mirror-distributed between the input port and the output port with the SRW filtering structure as the center; The SRW filter structure includes two symmetrical filter units, each of which includes a pair of first L-shaped ridge structures and four first perturbation metal pillars. In one of the filter units, the two first L-shaped ridge structures are arranged in a mirror image, and the openings of both face the top inner wall of the metal waveguide, forming a first top open structure. The four first perturbation metal pillars are evenly surrounded on the first top open structure. The first L-shaped ridge structure includes a first horizontal cuboid and a first vertical cuboid, the first horizontal cuboid is perpendicular to the first vertical cuboid, and the two first perturbation metal columns are distributed on both sides of the first vertical cuboid; at the junction of the two filtering units, the two first vertical cuboids are spliced, and the two first perturbation metal columns are spliced; the central axis of the first horizontal cuboid coincides with the central axis of the metal waveguide.

2. The terahertz single-ridge waveguide bandpass filter based on high-order modes according to claim 1, characterized in that: The number of the RWG-to-SRW conversion structure and the number of the ridge structure transition sections are both 2, the number of the SRW filtering structure is 1, and from the input port to the output port, the RWG-to-SRW conversion structure, the ridge structure transition section, the SRW filtering structure, the ridge structure transition section, and the RWG-to-SRW conversion structure are connected in sequence.

3. The terahertz single-ridge waveguide bandpass filter based on high-order modes according to claim 1, characterized in that: The size of the first horizontal cuboid is , the size of the first vertical cuboid is , the distance S0 between the first perturbation metal column and the inner side wall of the metal waveguide is 144.1 , the size of the first perturbative metal column is ; Among them, h 11 、h 12 All represent adjustment parameters; the RWG to SRW conversion structure is a three-step structure, and the width of each step is c=550.33 .

4. The terahertz single-ridge waveguide bandpass filter based on high-order modes according to claim 1, characterized in that: The ridge structure transition section includes a first transition unit and a second transition unit, the first transition unit includes a pair of second ridge structures and four second perturbation metal pillars, the two second ridge structures are arranged in a mirror image, and the openings are all facing the top inner wall of the metal waveguide, forming a second top open structure, and the four second perturbation metal pillars are evenly surrounded by the second top open structure; the second transition unit includes a pair of third ridge structures and four third perturbation metal pillars, the two third ridge structures are arranged in a mirror image, and the openings are all facing the top inner wall of the metal waveguide, forming a third top open structure, and the four third perturbation metal pillars are evenly surrounded by the third top open structure.

5. The terahertz single-ridge waveguide bandpass filter based on high-order modes according to claim 4, characterized in that: The second ridge structure includes a second horizontal cuboid, a second vertical cuboid and a first bottom cuboid, the first bottom cuboid is located below the second horizontal cuboid, the second horizontal cuboid is perpendicular to the second vertical cuboid, and the two second perturbation metal columns are distributed on both sides of the second vertical cuboid; the third ridge structure includes a third horizontal cuboid, a third vertical cuboid and a second bottom cuboid, the second bottom cuboid is located below the third horizontal cuboid, the third horizontal cuboid is perpendicular to the third vertical cuboid, and the two third perturbation metal columns are distributed on both sides of the third vertical cuboid, and the central axis of the second horizontal cuboid and the central axis of the third horizontal cuboid both coincide with the central axis of the metal waveguide.

6. The terahertz single-ridge waveguide bandpass filter based on high-order modes according to claim 5, characterized in that: At the junction of the first transition unit and the second transition unit, the second vertical cuboid and the third vertical cuboid are spliced ​​together, and the second perturbation metal column and the third perturbation metal column are spliced ​​together.

7. The terahertz single-ridge waveguide bandpass filter based on high-order modes according to claim 1, characterized in that: The RWG to SRW conversion structure is a three-step structure, and the width of each step is c=550.33 , the length and height of the first step from bottom to top are: t x1 =510.04 , t z1 =141.45 , the length and height of the second step are t x2 =510.04 , t z2 =216.37 , the length and height of the third step are t x3 =697.51 , t z3 =141.45 .

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