A cross-section channel-opening folded waveguide slow wave structure

Abstract

This invention provides a cross-section channel-opening folded waveguide slow-wave structure. The folded waveguide slow-wave structure includes two first structural parts arranged along the wide side of the slow-wave structure; a second structural part disposed between the two first structural parts; and an electron beam channel. The first structural part includes a first straight waveguide segment and a first waveguide connecting segment. The second structural part includes a second straight waveguide segment and a second waveguide connecting segment. The first waveguide connecting segment includes a second outer arc boundary, and the second outer arc boundary and the first straight waveguide segment include a second outer arc junction. The second outer arc junction and the electron beam channel axis form a second spacing height in the radial direction of the electron beam channel. The second waveguide connecting segment includes a third outer arc boundary, and the third outer arc boundary and the second straight waveguide segment include a third outer arc junction. The third outer arc junction and the electron beam channel axis form a third spacing height in the radial direction of the electron beam channel. The third spacing height is greater than the second spacing height.

Description

Technical Field

[0001] This invention relates to the field of microwave vacuum electronics technology. More specifically, it relates to a cross-section channel-opening folded waveguide slow-wave structure. Background Technology

[0002] A traveling wave tube (TWT) is a vacuum electronic device capable of generating or amplifying microwave signals, and it has broad development prospects in fields such as communications, electronic warfare, and radar systems. A TWT mainly consists of an electron gun, a slow-wave structure, a collector, input / output devices, and a magnetic focusing system. The slow-wave structure is the site of beam-wave interaction, i.e., the key component for generating or amplifying microwave signals. Currently, folded waveguide-type slow-wave structures are one of the main slow-wave structures used in millimeter-wave / terahertz band TWTs. This structure is an all-metal waveguide structure, with advantages such as simple structure, ease of fabrication, and high power capacity. However, open-type folded waveguide slow-wave structures with the same operating bandwidth have higher coupling impedance than conventional folded waveguide slow-wave structures.

[0003] The open-type folded waveguide slow-wave structure is based on the conventional folded waveguide slow-wave structure. The parameter h controlling the height of the straight waveguide is split into an inner height h1 and an outer height h2. By adjusting the size of h1, the height of the inner arc of the waveguide is made smaller than the electron beam channel radius rc. An opening appears in the radial direction between two adjacent straight waveguide segments, directly connecting to the arc-shaped portion of the waveguide, forming an open-type folded waveguide slow-wave structure. Figures 1A-1C As shown in the figure. In this structure, because the electron beam channel is directly connected to the arc-shaped waveguide, the boundary conditions of the electromagnetic field are changed, resulting in a new field distribution and dispersion characteristics.

[0004] Although the open-type folded waveguide slow-wave structure has a larger coupling impedance than the conventional folded waveguide slow-wave structure, it is still relatively small for millimeter-wave terahertz traveling wave tubes. To achieve greater output power and higher efficiency, the coupling impedance of the slow-wave structure needs to be further improved. Summary of the Invention

[0005] To address the aforementioned problems, this invention provides a cross-section channel-opening folded waveguide slow-wave structure to improve the coupling impedance of the slow-wave structure, thereby enhancing the output power, gain, and electronic efficiency of the broadband traveling wave tube.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] The present invention provides a cross-section channel opening type folded waveguide slow wave structure, including a multi-periodic structure defined by a plurality of upper gratings and a plurality of lower gratings that are staggered with each other;

[0008] The folded waveguide slow wave structure includes:

[0009] Within one cycle, two first structural parts are arranged along the wide side of the slow wave structure;

[0010] Within one cycle, a second structural portion is disposed between the two first structural portions along the wide side direction of the slow-wave structure; and

[0011] Electronic injection channel;

[0012] The first structural part includes a first straight waveguide segment and a first waveguide connection segment connected in series; the second structural part includes a second straight waveguide segment and a second waveguide connection segment connected in series.

[0013] Both the first waveguide connection segment and the second waveguide connection segment include the same first inner circular arc boundary, which is located within the boundary defined by the electron beam channel;

[0014] The first waveguide connection segment includes a second outer arc boundary, and there is a second outer arc junction between the second outer arc boundary and the first straight waveguide segment. A second gap height is formed between the second outer arc junction and the electron beam channel axis in the radial direction of the electron beam channel.

[0015] The second waveguide connection segment includes a third outer arc boundary. The third outer arc boundary and the second straight waveguide segment include a third outer arc junction. The third outer arc junction and the electron beam channel axis form a third gap height in the radial direction of the electron beam channel. The third gap height is greater than the second gap height.

[0016] A preferred embodiment is that the first inner arc boundary and the first straight waveguide segment include a first inner arc junction, and the first inner arc junction and the electron beam channel axis form a first gap height in the radial direction of the electron beam channel; the second gap height is greater than the first gap height.

[0017] The preferred embodiment is defined as follows: the electron beam channel radius is rc, the slow wave structure half-cycle length is p, and the narrow side length of the straight waveguide segment is b; the value range of the first interval height is: greater than 0 and less than rc-(pb) / 2; the value of the second interval height is: greater than rc-(p+b) / 2.

[0018] In a preferred embodiment, in the radial direction of the electron beam channel, the first inner arc junction is located between the electron beam channel axis and the second outer arc junction, and the second outer arc junction is located between the electron beam channel axis and the third outer arc junction.

[0019] The preferred scheme is to define the electron beam channel radius as rc, the width of the slow wave structure as a1, and the width of the second structure as a2; the range of a2 is: 2rc < a2 < a1.

[0020] A preferred embodiment is that the folded waveguide slow wave structure is applied to traveling wave tubes in the millimeter wave and terahertz frequency bands.

[0021] The present invention also provides a traveling wave tube comprising the folded waveguide slow wave structure described above.

[0022] This invention also provides a design method for a cross-section channel-opening folded waveguide slow wave structure, the method comprising:

[0023] An initial folded waveguide slow wave structure is designed according to requirements. This initial folded waveguide slow wave structure includes a connected straight waveguide section, a curved waveguide connecting section, and an electron beam channel.

[0024] Using three-dimensional electromagnetic field simulation software, the first inner circular arc boundary was moved down to the boundary defined by the electron beam channel;

[0025] Using three-dimensional electromagnetic field simulation software, the boundary of the third outer arc is moved upward so that the height of the third gap formed between the intersection of the third outer arc and the axis of the electron beam channel in the radial direction of the electron beam channel is greater than the height of the second gap formed between the intersection of the second outer arc and the axis of the electron beam channel in the radial direction of the electron beam channel.

[0026] The preferred embodiment is that the electron beam channel radius is rc, the width of the slow wave structure is a1, the width of the second structure is a2, and the value range of a2 is: 2rc < a2 < a1.

[0027] The preferred approach is to adjust the normalized phase velocity and coupling impedance of the folded waveguide slow wave structure by changing the height of the second spacing, the height of the third spacing, and the width of the second structural part, thereby optimizing the performance of the folded waveguide slow wave structure.

[0028] The beneficial effects of this invention are as follows:

[0029] Compared to conventional channel-opening folded waveguide slow-wave structures, this invention, based on this, splits the outer folded waveguide into two first structural sections and a second structural section located between the two first structural sections, ensuring that the second structural section is higher than the first structural section in the slow-wave structure height direction, thus forming a new slow-wave structure. The resulting cross-section channel-opening folded waveguide slow-wave structure, when applied to millimeter-wave / terahertz traveling wave tubes, can significantly improve the electron beam channel axial coupling impedance under the premise of the same operating frequency band and similar in-band normalized phase velocity, thereby significantly improving the traveling wave tube's output power, gain efficiency, and electronic efficiency.

[0030] Furthermore, by designing the cross-section of the slow wave structure as a cross, the area of ​​the waveguide circumcircle can be reduced while maintaining the bandwidth of the folded waveguide slow wave structure. This reduces the actual cross-sectional size of the slow wave structure, providing space in terms of structural dimensions to improve the focusing performance of the traveling wave tube focusing system.

[0031] The cross-section channel-opening folded waveguide slow wave structure and traveling wave tube provided by this invention can be widely used in next-generation mobile communication equipment, mobile communication base station equipment in broadband wireless mobile communication technology, and transmission equipment in the fields of satellite launch and broadcast television networks. Attached Figure Description

[0032] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.

[0033] Figures 1A-1C This is a schematic diagram of a conventional channel-opening type folded waveguide slow wave structure.

[0034] Figures 2A-2C This is a schematic diagram of a conventional folded waveguide slow wave structure.

[0035] Figures 3A-3C This is a schematic diagram of the cross-section channel-opening folded waveguide slow wave structure of the present invention.

[0036] Figure 4 This is a graph showing the dispersion characteristics of the cross-section channel-opening folded waveguide slow wave structure of the present invention.

[0037] Figure 5 This is a comparison diagram of the normalized phase velocity of the cross-section channel-opening folded waveguide slow wave structure of the present invention, the channel-opening folded waveguide slow wave structure with similar in-band phase velocity, and the conventional folded waveguide slow wave structure.

[0038] Figure 6 This is a comparison diagram of the coupling impedance of the cross-section channel-opening folded waveguide slow wave structure of the present invention, the channel-opening folded waveguide slow wave structure with similar in-band phase velocity, and the conventional folded waveguide slow wave structure.

[0039] Figure 7 This is a normalized phase velocity curve of the cross-section channel-opening folded waveguide slow wave structure of the present invention under different h2 conditions.

[0040] Figure 8 This is a coupling impedance curve of the cross-section channel-opening folded waveguide slow wave structure of the present invention under different h2 conditions.

[0041] Figure 9 This is a normalized phase velocity curve of the cross-section channel-opening folded waveguide slow wave structure of the present invention under different h3 conditions.

[0042] Figure 10 This is a coupling impedance curve of the cross-section channel-opening folded waveguide slow wave structure of the present invention under different h3 conditions.

[0043] Figure 11This is a normalized phase velocity curve of the cross-section channel-opening folded waveguide slow wave structure of the present invention under different a2 conditions.

[0044] Figure 12 This is a coupling impedance curve of the cross-section channel-opening folded waveguide slow wave structure of the present invention under different a2 conditions. Detailed Implementation

[0045] Various exemplary embodiments of the present invention will now be described in detail with reference to the accompanying drawings. It should be noted that, unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps set forth in these embodiments do not limit the scope of the invention.

[0046] The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the invention or its application or use.

[0047] Technologies and equipment known to those skilled in the art may not be discussed in detail, but where appropriate, such technologies and equipment should be considered part of the specification.

[0048] In all the examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values.

[0049] It should be noted that similar labels and letters in the following figures indicate similar items; therefore, once an item is defined in one figure, it does not need to be discussed further in subsequent figures.

[0050] Further improving the coupling impedance of slow-wave structures. This invention provides a cross-section channel-opening folded waveguide slow-wave structure, which is applied to traveling-wave tubes in the millimeter-wave and terahertz frequency bands, combined with... Figures 1A to 12As shown, the cross-section channel-opening folded waveguide slow-wave structure specifically includes a multi-periodic structure defined by multiple upper gratings and multiple lower gratings that are staggered together; the folded waveguide slow-wave structure includes: two first structural portions 10 arranged along the wide side direction of the slow-wave structure within one period; a second structural portion 20 disposed between the two first structural portions 10 within one period along the wide side direction of the slow-wave structure; and an electron beam channel 30; the first structural portion 10 includes a first straight waveguide section and a first waveguide connecting section connected together; the second structural portion 20 includes a second straight waveguide section and a second waveguide connecting section connected together; both the first waveguide connecting section and the second waveguide connecting section include the same first inner circular arc boundary C. 1. The first inner arc boundary C1 is located within the boundary defined by the electron beam channel 30; the first waveguide connecting segment includes a second outer arc boundary C2, and a second outer arc junction Q2 is included between the second outer arc boundary C2 and the first straight waveguide segment, and a second spacing height h2 is formed between the second outer arc junction Q2 and the electron beam channel axis L0 in the radial direction of the electron beam channel; the second waveguide connecting segment includes a third outer arc boundary C3, and a third outer arc junction Q3 is included between the third outer arc boundary C3 and the second straight waveguide segment, and a third spacing height h3 is formed between the third outer arc junction Q3 and the electron beam channel axis L0 in the radial direction of the electron beam channel, and the third spacing height h3 is greater than the second spacing height h2. The novel folded waveguide slow-wave structure provided by this invention is based on a channel-opening folded waveguide slow-wave structure. It involves splitting the waveguide cavity of the folded waveguide into two first structural portions 10 on either side and a second structural portion 20 in the middle. The second structural portion 20 protrudes outward from the first structural portions 10, resulting in a cross-shaped cross-section for the slow-wave structure, thus forming the cross-section channel-opening folded waveguide slow-wave structure of this invention. Compared to channel-opening folded waveguide slow-wave structures and conventional folded waveguide slow-wave structures, this structure provides a higher axial coupling impedance.

[0051] For traveling wave tubes (TWTs), a circular inner-hole periodic permanent magnet focusing system is a classic electron beam focusing method. For two sets of periodic permanent magnet focusing systems with identical parameters except for the inner hole size, a smaller inner hole results in a stronger focusing magnetic field and a stronger electron beam focusing ability, which is more beneficial for improving the performance of the TWT. For folded waveguide-type slow-wave structures, their radial cross-section is usually circular to match the circular inner-hole periodic permanent magnet focusing system. Therefore, the smaller the circumcircle corresponding to the radial cross-section of the slow-wave structure, the more beneficial it is to reduce the inner hole of the focusing system, thereby improving the electron beam focusing effect. Currently, the cross-sectional size of the slow-wave structure in millimeter-wave and terahertz TWTs limits the focusing performance of the electron beam focusing system, preventing further increases in current density and thus limiting the output power of the TWT. To improve the focusing performance of the electron beam focusing system, it is necessary to further reduce the radial cross-sectional size of the slow-wave structure. Compared to channel-opening folded waveguide slow-wave structures and conventional folded waveguide slow-wave structures, the structure provided by this invention has a smaller radial cross-sectional dimension. The electron beam channel axis is in the X direction, the width direction of the slow-wave structure is in the Y direction, and the height direction of the slow-wave structure is in the Z direction. Here, the radial cross-section refers to the cross-section of the slow-wave structure located in the plane formed by the Y and Z directions. The cross-section channel-opening folded waveguide slow-wave structure provided by this invention can improve the coupling impedance, thereby enhancing the output power, gain, and electronic efficiency of the broadband traveling wave tube, while reducing the radial cross-sectional dimension of the slow-wave structure improves the focusing performance of the matching electron beam focusing system.

[0052] In one specific embodiment, a first inner arc junction Q1 is included between the first inner arc boundary C1 and the first straight waveguide segment. A first interval height h1 is formed between the first inner arc junction Q1 and the electron beam channel axis L0 in the radial direction of the electron beam channel. The second interval height h2 is greater than the first interval height h1.

[0053] Furthermore, the electron beam channel radius is rc, the slow wave structure half-cycle length is p, and the narrow side length of the straight waveguide segment is b; the first gap height h1 ranges from 0 to 1.

[0054] In one specific embodiment, in the radial direction of the electron beam channel, the first inner arc junction Q1 is located between the electron beam channel axis L0 and the second outer arc junction Q2, and the second outer arc junction Q2 is located between the electron beam channel axis L0 and the third outer arc junction Q3.

[0055] In one specific embodiment, the electron beam channel radius is rc, the width of the slow wave structure is a1, the width of the second structure is a2, and the value range of a2 is: 2rc < a2 < a1.

[0056] ​The folded waveguide slow wave structure provided in this embodiment of the invention is a broadband slow wave structure; this folded waveguide slow wave structure is applied to traveling wave tubes in the millimeter wave / terahertz band.

[0057] Specifically, refer to Figures 1A-1C The diagram shows a single-period geometric schematic of a channel-opening type folded waveguide slow-wave structure. 'a' represents the width of the waveguide, 'b' represents the width of the waveguide, the geometric half-period is 'p', the straight waveguide height is 'h', and the electron beam channel radius is 'rc'. The straight waveguide is divided into an inner height 'h1' and an outer height 'h2'. By adjusting the dimension of 'h1', the height of the inner arc of the waveguide is made smaller than the electron beam channel radius 'rc'. An opening appears in the radial direction between two adjacent straight waveguide segments, directly connecting to the arc-shaped portion of the waveguide. The geometric period includes two interaction gaps of unequal length.

[0058] The structural dimensions of the specific scheme of the channel-opening folded waveguide slow wave structure used for comparison are as follows (unit: mm): a = 0.870, b = 0.160, p = 0.260, h1 = 0.030, h2 = 0.140, rc = 0.120.

[0059] Furthermore, the circumcircle area corresponding to the radial cross-section of this channel-opening folded waveguide slow-wave structure is 0.979 mm². 2 .

[0060] Reference Figures 2A-2C The figure shows a single-period geometric schematic diagram of a conventional folded waveguide slow wave structure. In the figure, a represents the width of the waveguide, b represents the width of the waveguide, p represents the geometric half-period, h represents the height of the straight waveguide, and rc represents the radius of the electron beam channel.

[0061] The structural dimensions of the conventional folded waveguide slow wave structure used for comparison are as follows (unit: mm): a = 0.86, b = 0.16, p = 0.305, h = 0.26, rc = 0.12.

[0062] Furthermore, the circumcircle area corresponding to the radial section of this conventional folded waveguide slow-wave structure is 0.994 mm. 2 .

[0063] Reference Figures 3A-3C The diagram shown is a single-cycle geometric schematic of a cross-section channel-opening folded waveguide slow-wave structure provided by the present invention. This structure is based on the channel-opening folded waveguide slow-wave structure, by splitting the waveguide cavity of the folded waveguide into a first structural part 10 and a second structural part 20 to form a new slow-wave structure. The outer height of the straight waveguide in the first structural part is h2, and the outer height of the straight waveguide in the second structural part is h3; the total waveguide width is a1, and the width of the second structural part is a2.

[0064] Within the G-band region, the specific structural dimensions of the cross-section channel-opening folded waveguide slow wave structure of this invention are as follows (unit: mm): a1=0.89, a2=0.52, b=0.16, p=0.26, h1=0.03, h2=0.04, h3=0.22mm, rc=0.12.

[0065] Furthermore, the circumcircle area corresponding to the radial section of this cross-section channel-opening folded waveguide slow-wave structure is 0.818 mm². 2 It is 83.55% of the circumcircle area of ​​the radial section of the channel-opening folded waveguide slow wave structure, and 82.29% of the circumcircle area of ​​the radial section of the conventional folded waveguide slow wave structure.

[0066] The cross-section channel-opening folded waveguide slow wave structure, the channel-opening folded waveguide slow wave structure with similar in-band phase velocity, and the conventional folded waveguide slow wave structure of the present invention were simulated using three-dimensional electromagnetic software. The correlation dispersion characteristics, field distribution, normalized phase velocity, axial coupling impedance and high-frequency loss characteristics were calculated.

[0067] Reference Figure 4 The figure shows the dispersion characteristics of a cross-section channel-opening folded waveguide slow wave structure, with the operating point selected as the -1st spatial harmonic of intrinsic mode 3.

[0068] Reference Figure 5 The figure shows the normalized phase velocities of a cross-section channel-aperture folded waveguide slow-wave structure, a channel-aperture folded waveguide slow-wave structure with similar in-band phase velocities, and a conventional folded waveguide slow-wave structure. Within the 200GHz–230GHz operating frequency band, the maximum difference among the three is less than 0.001.

[0069] Reference Figure 6 The figure shows a comparison of the coupling impedance of the cross-section channel-aperture folded waveguide slow-wave structure, the channel-aperture folded waveguide slow-wave structure, and the conventional folded waveguide slow-wave structure. Within the 200GHz–230GHz operating frequency band, the axial coupling impedance of the cross-section channel-aperture folded waveguide slow-wave structure of this invention is 3.25% greater than that of the channel-aperture folded waveguide slow-wave structure with similar in-band phase velocity, and 47.82% greater than that of the conventional folded waveguide slow-wave structure.

[0070] Reference Figure 7 The figure shows the normalized phase velocity of the cross-section channel-opening folded waveguide slow-wave structure under different h2 values. In the 200GHz to 230GHz operating frequency band, an increase of 0.01mm in h2 results in a decrease of approximately 0.003 in the normalized phase velocity.

[0071] Reference Figure 8The figure shows the coupling impedance of a cross-section channel-opening folded waveguide slow-wave structure under different h2 values. In the 200GHz to 230GHz operating frequency band, for the low-frequency end (around 200GHz), an increase of 0.01mm in h2 reduces the coupling impedance by approximately 0.2Ω; for the high-frequency end (around 230GHz), h2 has almost no effect on the coupling impedance.

[0072] Reference Figure 9 The figure shows the normalized phase velocity of the cross-section channel-opening folded waveguide slow wave structure under different h3 values. In the 200GHz to 230GHz operating frequency band, for the low-frequency end (around 200GHz), h3 has almost no effect on the normalized phase velocity; for the high-frequency end (around 230GHz), an increase of 0.01mm in h3 reduces the normalized phase velocity by approximately 0.0006.

[0073] Reference Figure 10 The figure shows the coupling impedance of a cross-section channel-opening folded waveguide slow-wave structure under different h3 values. Within the 200GHz–230GHz operating frequency band, h3 has almost no effect on the coupling impedance.

[0074] Reference Figure 11 The figure shows the normalized phase velocity of a cross-section channel-opening folded waveguide slow-wave structure under different a2 values. Within the 200GHz–230GHz operating frequency band, the effect of a2 variation on the normalized phase velocity at the low-frequency end (around 200GHz) is smaller than at the high-frequency end (around 230GHz). For the low-frequency end (around 200GHz), an increase of 0.01mm in a2 reduces the normalized phase velocity by approximately 0.0003; for the high-frequency end (around 230GHz), an increase of 0.01mm in a2 reduces the normalized phase velocity by approximately 0.0006.

[0075] Reference Figure 12 The figure shows the coupling impedance of a cross-section channel-opening folded waveguide slow wave structure under different a2 values. Within the 200GHz to 230GHz operating frequency band, a2 has almost no effect on the coupling impedance.

[0076] Therefore, the above characteristics can be used to specifically adjust the normalized phase velocity and coupling impedance at each frequency point within the band.

[0077] According to another aspect of the invention, the invention also provides a traveling wave tube comprising the folded waveguide slow wave structure described above.

[0078] According to another aspect of the present invention, the present invention also provides a design method for a cross-section channel-opening folded waveguide slow-wave structure. The method includes: designing an initial folded waveguide slow-wave structure as needed, the initial folded waveguide slow-wave structure including a connected straight waveguide section, a curved waveguide connecting section, and an electron beam channel; using three-dimensional electromagnetic field simulation software, moving the first inner arc boundary C1 downward to within the boundary defined by the electron beam channel; using three-dimensional electromagnetic field simulation software, moving the third outer arc boundary C3 upward so that the third interval height h3 formed between the third outer arc junction Q3 and the electron beam channel axis L0 in the radial direction of the electron beam channel is greater than the second interval height h2 formed between the second outer arc junction Q2 and the electron beam channel axis L0 in the radial direction of the electron beam channel.

[0079] The further electron beam channel radius is rc, the width of the slow wave structure is a1, the width of the second structure is a2, and the value range of a2 is: 2rc < a2 < a1.

[0080] Optionally, by changing the second interval height h2, the third interval height h3, and the wide side length a2, the normalized phase velocity and coupling impedance of the folded waveguide slow wave structure can be adjusted to optimize the performance of the folded waveguide slow wave structure. This can improve the coupling impedance of the slow wave structure while reducing the radial cross-sectional size of the slow wave structure, thus providing space in terms of structural size to improve the focusing performance of the traveling wave tube focusing system.

[0081] More specifically, an initial folded waveguide slow-wave structure is designed as needed. This initial folded waveguide slow-wave structure includes a connected straight waveguide section, a curved waveguide connecting section, and an electron beam channel. Using three-dimensional electromagnetic field simulation software, the first inner arc boundary C1 is moved down to the boundary defined by the electron beam channel to obtain an open-type folded waveguide slow-wave structure. Based on the obtained open-type folded waveguide slow-wave structure, the folded waveguide is divided into two first structural parts on both sides and a second structural part in the middle. Among them, the second outer arc boundary C2 of the first structural part and the second outer arc junction Q2 between the second outer arc boundary C2 and the first straight waveguide section are designed with a second spacing height h2 in the radial direction of the electron beam channel axis L0. The third outer arc boundary C3 of the second structural part is moved up. The third outer arc junction Q3 of the second structural part and the second straight waveguide section are designed with a third spacing height h3 in the radial direction of the electron beam channel axis L0. h3 is greater than h2, thereby improving the coupling impedance of the folded waveguide slow-wave structure.

[0082] In summary, compared to conventional channel-opening folded waveguide slow-wave structures, this invention, based on this, splits the outer folded waveguide into two first structural sections and a second structural section located between the two first structural sections, ensuring that the second structural section is higher than the first structural section in the slow-wave structure height direction, thus forming a new slow-wave structure. The resulting cross-section channel-opening folded waveguide slow-wave structure, when applied to millimeter-wave / terahertz traveling wave tubes, can significantly improve the electron beam channel axial coupling impedance under the premise of the same operating frequency band and similar in-band normalized phase velocity, thereby significantly improving the traveling wave tube's output power, gain efficiency, and electronic efficiency.

[0083] Furthermore, by designing the cross-section of the slow wave structure as a cross, the area of ​​the waveguide circumcircle can be reduced while maintaining the bandwidth of the folded waveguide slow wave structure. This reduces the actual cross-sectional size of the slow wave structure, providing space in terms of structural dimensions to improve the focusing performance of the traveling wave tube focusing system.

[0084] The cross-section channel-opening folded waveguide slow wave structure and traveling wave tube provided by this invention can be widely used in next-generation mobile communication equipment, mobile communication base station equipment in broadband wireless mobile communication technology, and transmission equipment in the fields of satellite launch and broadcast television networks.

[0085] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. For those skilled in the art, other variations or modifications can be made based on the above description. It is impossible to exhaustively list all the implementation methods here. All obvious variations or modifications derived from the technical solutions of the present invention are still within the protection scope of the present invention.

Claims

1. A cross-section channel-opening type folded waveguide slow wave structure, characterized in that, It includes a multi-periodic structure defined by multiple upper grids and multiple lower grids that are staggered with each other; The folded waveguide slow wave structure includes: Within one cycle, two first structural parts are arranged along the wide side of the slow wave structure; Within one cycle, a second structural portion is disposed between the two first structural portions along the wide side direction of the slow-wave structure; the second structural portion protrudes outward from the first structural portions, making the cross-section of the slow-wave structure cross-shaped; and Electronic injection channel; The first structural part includes a first straight waveguide segment and a first waveguide connection segment connected in series; the second structural part includes a second straight waveguide segment and a second waveguide connection segment connected in series. Both the first waveguide connection segment and the second waveguide connection segment include the same first inner circular arc boundary, which is located within the boundary defined by the electron beam channel; The first waveguide connection segment includes a second outer arc boundary, and there is a second outer arc junction between the second outer arc boundary and the first straight waveguide segment. A second gap height is formed between the second outer arc junction and the electron beam channel axis in the radial direction of the electron beam channel. The second waveguide connection segment includes a third outer arc boundary. The third outer arc boundary and the second straight waveguide segment include a third outer arc junction. The third outer arc junction and the electron beam channel axis form a third gap height in the radial direction of the electron beam channel. The third gap height is greater than the second gap height.

2. The cross-section channel-opening folded waveguide slow-wave structure according to claim 1, characterized in that, The first inner arc boundary and the first straight waveguide segment include a first inner arc junction, and a first gap height is formed between the first inner arc junction and the electron beam channel axis in the radial direction of the electron beam channel; the second gap height is greater than the first gap height.

3. The cross-section channel-opening folded waveguide slow-wave structure according to claim 2, characterized in that, Defined as follows: the electron beam channel radius is rc, the slow wave structure half-cycle length is p, and the narrow side length of the straight waveguide segment is b; the value range of the first interval height is: greater than 0 and less than rc-(pb) / 2; the value of the second interval height is: greater than rc-(p+b) / 2.

4. The cross-section channel-opening folded waveguide slow-wave structure according to claim 2, characterized in that, In the radial direction of the electron injection channel, the first inner arc junction is located between the electron injection channel axis and the second outer arc junction, and the second outer arc junction is located between the electron injection channel axis and the third outer arc junction.

5. The cross-section channel-opening folded waveguide slow-wave structure according to claim 1, characterized in that, Defined as follows: the electron beam channel radius is rc, the width of the slow wave structure is a1, and the width of the second structure is a2; the range of a2 is: 2rc < a2 < a1.

6. The cross-section channel-opening folded waveguide slow-wave structure according to claim 1, characterized in that, The folded waveguide slow wave structure is applied to traveling wave tubes in the millimeter wave and terahertz frequency bands.

7. A traveling wave tube, characterized in that, The traveling wave tube includes the folded waveguide slow wave structure as described in any one of claims 1 to 6.

8. A design method for a slow-wave structure of a cross-section channel-opening folded waveguide based on claim 1, characterized in that, The method includes: An initial folded waveguide slow wave structure is designed according to requirements. This initial folded waveguide slow wave structure includes a connected straight waveguide section, a curved waveguide connecting section, and an electron beam channel. Using three-dimensional electromagnetic field simulation software, the first inner circular arc boundary was moved down to the boundary defined by the electron beam channel; Using three-dimensional electromagnetic field simulation software, the boundary of the third outer arc is moved upward so that the height of the third gap formed between the intersection of the third outer arc and the axis of the electron beam channel in the radial direction of the electron beam channel is greater than the height of the second gap formed between the intersection of the second outer arc and the axis of the electron beam channel in the radial direction of the electron beam channel.

9. The design method for folded waveguide slow wave structure according to claim 8, characterized in that, The electron beam channel radius is rc, the width of the slow wave structure is a1, the width of the second structure is a2, and the value of a2 is in the range of 2rc < a2 < a1.

10. The design method for folded waveguide slow wave structure according to claim 9, characterized in that, By changing the height of the second and third gaps, the height of the second gap, the width of the second structural section, and the normalized phase velocity and coupling impedance of the folded waveguide slow wave structure, the performance of the folded waveguide slow wave structure is optimized.

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