A folded waveguide slow wave structure and its design method

Abstract

This invention discloses a folded waveguide slow-wave structure and its design method. The folded waveguide slow-wave structure includes multiple upper gratings and multiple lower gratings arranged in an alternating manner, and an electron beam channel located at the central axis of the slow-wave structure. Given a fixed phase velocity ratio in the slow-wave structure, each upper grating and lower grating includes a first bend and a second bend located on the electron beam channel axis L0 with the same bending direction. Compared to a conventional folded waveguide slow-wave structure with the same phase velocity ratio, the folded waveguide slow-wave structure provided by this invention, under the condition that all other parameters are the same, can achieve dimensional compression in the diameter direction of the electron beam channel, reducing the cross-sectional size of the slow-wave structure, thereby reducing the inner diameter of the magnet, increasing the magnetic field strength, increasing the focusing current, and significantly improving the output power of the traveling wave tube. Furthermore, it achieves further miniaturization of the traveling wave tube while significantly increasing its output power.

Description

Technical Field

[0001] This invention relates to the field of microwave vacuum electronics technology. More specifically, it relates to a folded waveguide slow-wave structure and its design method. Background Technology

[0002] Short millimeter-wave and terahertz traveling wave tubes are microwave vacuum electronic devices with outstanding features of high power, wide bandwidth, and high gain. As high-power signal sources for weapon systems, they can meet the needs of high-resolution imaging radar, high-speed wireless communication, and other weapon systems.

[0003] Based on the current development status of short millimeter-wave and terahertz traveling wave tubes both domestically and internationally, folded waveguides have become one of the most commonly used slow-wave structures. Folded waveguide slow-wave structures involve bending a rectangular waveguide along an electric field to form a periodic structure consisting of a series of straight waveguide segments and waveguide connection segments. According to the morphology of the waveguide connection segments, they are generally divided into right-angle bends and "U"-shaped bends, such as... Figure 1 , Figure 2 As shown, the electron beam channel is located on the central axis of a series of straight waveguide segments arranged along the z-direction. Typically, the waveguide structure consists of multiple periodic structures defined by upper and lower gratings, each with a straight waveguide transmission segment and a waveguide connection segment. The wide side dimension of the folded waveguide is usually denoted by 'a'. Depending on the straight waveguide segment and the waveguide connection segment, the narrow side dimension of the corresponding straight waveguide segment is usually denoted by 'b', and the narrow side dimension of the corresponding waveguide connection segment is usually denoted by 'd'. 'h' is the height of the straight waveguide segment, and 'p' is the geometric period. Reducing the cross-sectional size of the folded waveguide slow-wave structure is a key research area for miniaturizing traveling wave tubes (TWTs). The height 'h' of the straight waveguide transmission segment is a crucial parameter limiting the cross-sectional size of the slow-wave structure. Currently, there is a lack of research on how to achieve miniaturization of the TWT while keeping the phase velocity ratio of the slow-wave structure and the operating voltage of the TWT constant. Summary of the Invention

[0004] In view of the above problems, one object of the present invention is to provide a folded waveguide slow wave structure that can improve the output power of a traveling wave tube without changing the operating voltage, thereby achieving further miniaturization of the traveling wave tube.

[0005] Another object of the present invention is to provide a design method for the folded waveguide slow wave structure as described above.

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

[0007] According to one aspect of the present invention, the present invention provides a folded waveguide slow wave structure, the folded waveguide slow wave structure comprising a plurality of upper gratings and a plurality of lower gratings arranged alternately with each other, and an electron beam channel located at the central axis of the slow wave structure;

[0008] When the phase light speed ratio of the slow-wave structure is determined, the upper grating and the lower grating respectively include a first bending portion and a second bending portion located on the electron beam channel axis L0 and having the same bending direction.

[0009] Furthermore, in a preferred embodiment, the folded waveguide slow wave structure comprises multiple periodic waveguide structures having waveguide transmission sections and waveguide connection sections, defined by each upper grating and each lower grating.

[0010] The waveguide transmission segment includes a first waveguide segment and a second waveguide segment. The first waveguide segment and the second waveguide segment each include a first axis L1 and a second axis L2 in their respective extension directions. The first axis L1 and the second axis L2 form a plane α, and the first axis L1 and the second axis L2 form an angle θ in the plane α.

[0011] Furthermore, a preferred embodiment is that two adjacent waveguide transmission segments have the same interaction distance.

[0012] Furthermore, in a preferred embodiment, the first waveguide segment and the second waveguide segment are arranged in a mirror image relative to the electron beam channel.

[0013] Furthermore, in a preferred embodiment, the bending direction of the upper gate body and the bending direction of the lower gate body are both opposite to or both toward the input direction of the electron beam.

[0014] Furthermore, in a preferred embodiment, the first axis L1 and the second axis L2 include an intersection point O on the electron injection channel axis L0, which has an offset Δ on the electron injection channel axis L0.

[0015] Furthermore, in a preferred embodiment, the intersection point O is offset in a direction toward or away from the input direction of the electron beam along the electron beam channel axis L0.

[0016] Furthermore, a preferred embodiment is that the included angle θ is greater than 0° and less than 180°.

[0017] According to another aspect of the present invention, the present invention provides a design method for a folded waveguide slow wave structure, the method comprising the following steps:

[0018] Under the condition that the phase light speed ratio of the slow-wave structure remains unchanged, multiple upper grating structures and multiple lower grating structures are designed to be periodically and alternately distributed. The upper grating and the lower grating each include a first bending portion and a second bending portion located on the electron beam channel axis L0 and having the same bending direction.

[0019] Furthermore, a preferred embodiment is that the folded waveguide slow wave structure constructed and defined by each upper grating and each lower grating includes multiple periodic waveguide structures having waveguide transmission sections and waveguide connection sections.

[0020] The waveguide transmission segment includes a first waveguide segment and a second waveguide segment. The first waveguide segment and the second waveguide segment each include a first axis L1 and a second axis L2 in their respective extension directions. The first axis L1 and the second axis L2 form a plane α. The first axis L1 and the second axis L2 form an angle θ in the plane α. The angle θ is greater than 0° and less than 180°.

[0021] The beneficial effects of this invention are as follows:

[0022] According to at least one aspect of the present invention, the folded waveguide slow wave structure provided by the present invention, compared with the conventional folded waveguide slow wave structure with the same phase velocity ratio (Vp / c), under the condition that all other parameters are the same, can achieve size compression of the slow wave structure in the direction of electron beam channel diameter through structural improvement, reduce the cross-sectional size of the slow wave structure, thereby reducing the inner diameter of the magnet, increasing the magnetic field strength, increasing the beam-focusing current, significantly improving the output power of the traveling wave tube, and achieving further miniaturization of the traveling wave tube while significantly improving the output power of the traveling wave tube. Attached Figure Description

[0023] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.

[0024] Figure 1 A geometric schematic diagram of a prior art right-angled folded waveguide slow-wave structure is shown.

[0025] Figure 2 This diagram illustrates the geometry of a prior art U-shaped folded waveguide slow wave structure.

[0026] Figure 3 This diagram illustrates a geometrical period of the folded waveguide slow wave structure provided by the present invention.

[0027] Figure 4 This diagram illustrates a geometrical schematic of two geometrical periods of the folded waveguide slow wave structure provided by the present invention.

[0028] Figure 5 The diagram shows a comparison of the phase velocity ratio (Vp / c) between the slow-wave structure provided by this invention and the existing folded waveguide slow-wave structure.

[0029] Figure 6 The graph shows a comparison of the effects of conventional straight waveguide transmission sections with different heights h on the phase velocity ratio (Vp / c).

[0030] Figure 7 The graph shows a comparison of the voltage effects of conventional straight waveguide transmission sections with different heights h. Detailed Implementation

[0031] To more clearly illustrate the present invention, the following description, in conjunction with preferred embodiments and accompanying drawings, further explains the invention. Similar components in the drawings are indicated by the same reference numerals. Those skilled in the art should understand that the specific description below is illustrative rather than restrictive and should not be construed as limiting the scope of protection of the present invention.

[0032] The slow-wave structure is a core component of microwave vacuum electronic devices. It is mainly used in conjunction with the electron gun, energy transfer window, and collector to form a traveling wave tube. The function of the slow-wave structure is to reduce the phase velocity of the electromagnetic waves transmitted within it, so as to keep them synchronized with the electron beam and obtain effective interaction between the beam and the wave.

[0033] Figure 1 and Figure 2 The geometric schematic diagrams of existing curved and folded waveguide slow wave structures are shown respectively, in which... Figure 1 A geometric schematic diagram of a prior art right-angled folded waveguide slow-wave structure is shown. Figure 2 The figure shows a geometric schematic diagram of a prior art U-shaped folded waveguide slow-wave structure. As illustrated, to visually represent the structural style of the slow-wave structure, its characteristics are typically defined by the shape of the grating within the folded waveguide. Figure 1 and Figure 2 The illustrated folded waveguide slow-wave structure includes upper and lower gratings of identical shape, arranged alternately to define a waveguide structure comprising multiple periodic structures, including connected straight waveguide segments and waveguide connection segments. Each upper grating is centered between two adjacent lower gratings, at equidistant distances. Similarly, each lower grating is centered between two adjacent upper gratings, at equidistant distances. This arrangement of the upper and lower gratings ensures equidistant interaction distances between adjacent straight waveguide segments.

[0034] The following will refer to Figures 3 to 5 This invention provides a detailed description of the folded waveguide slow-wave structure. In the embodiments, the electron beam propagation direction is taken from left to right as an example. Specifically, according to an inventive objective of this invention, a folded waveguide slow-wave structure is provided. This structure includes multiple upper gratings 11 and multiple lower gratings 12 arranged in an alternating manner, and an electron beam channel 4 located at the central axis of the slow-wave structure. Structurally, compared to existing slow-wave structures, the folded waveguide slow-wave structure provided by this invention, under the condition that it has the same design phase velocity ratio (Vp / c) and other design parameters as existing slow-wave structures, includes, respectively, a first bending portion and a second bending portion located on the axis L0 of the electron beam channel 4 with the same bending direction, where the upper gratings 11 and lower gratings 12 each have the same bending direction. Other design parameters, as described above, include but are not limited to the folded waveguide depth a, slot width b, and period p.

[0035] In one specific embodiment, to clearly describe the structural features of the slow-wave structure provided by the present invention, a detailed description is given using a plurality of periodic waveguide structures defined by each upper grating 11 and each lower grating 12, in conjunction with... Figure 3 as well as Figure 4 As shown, the folded waveguide slow-wave structure provided by the present invention includes multiple periodic waveguide structures having waveguide transmission sections 2 and waveguide connection sections 3, defined by upper gratings 11 and lower gratings 12. Optionally, the waveguide connection section 3 is a right-angled waveguide connection section or a U-shaped waveguide connection section.

[0036] The waveguide transmission segment 2 described in this invention includes a first waveguide segment 21 and a second waveguide segment 22. The first waveguide segment 21 and the second waveguide segment 22 each include a first axis L1 and a second axis L2 in their respective extension directions. The first axis L1 and the second axis L2 form a plane α, and the first axis L1 and the second axis L2 form an angle θ within the plane α. The angle θ is greater than 0° and less than 180°. Preferably, the first waveguide segment 21 and the second waveguide segment 22 are arranged in a mirror image relative to the electron beam channel. If the first waveguide segment and the second waveguide segment are asymmetrically distributed, a stop band will be generated at the 3π position, which can easily induce oscillations.

[0037] To illustrate the structure more vividly, the upper grating 11 and lower grating 12 are roughly "<" shaped with the same bending direction, and the waveguide transmission segment 2 defined by the upper grating 11 and lower grating 12 is also roughly "<" shaped. Furthermore, it can be determined that the electron beam channel 4 axis L0, like the first axis L1 and the second axis L2, is located within the plane α. Specifically, the electron beam channel 4 axis L0 is along the Z-direction, the width direction of the slow wave structure is along the X-direction, the height h direction of the slow wave structure is along the Y-direction, and the plane α is perpendicular to the xz plane of the electron beam channel axis L0.

[0038] Through the above design, compared with the conventional folded waveguide slow wave structure with the same phase velocity ratio (Vp / c), under the condition that all other parameters are the same, the size of the slow wave structure in the direction of the electron beam channel diameter can be compressed by structural improvement, the cross-sectional size of the slow wave structure is reduced, the inner diameter of the magnet is reduced, the beam current can be increased, the output power of the traveling wave tube is greatly improved, and the traveling wave tube can be further miniaturized while greatly improving the output power of the traveling wave tube.

[0039] In one embodiment, the present invention provides that two adjacent waveguide transmission segments 2 in a slow-wave structure have the same interaction distance. The bending direction of the upper grating 11 and the bending direction of the lower grating 12 are both away from the input direction of the electron beam. Optionally, the bending direction of the upper grating and the bending direction of the lower grating can both be towards the input direction of the electron beam.

[0040] In one embodiment, the first axis L1 and the second axis L2 include an intersection point O on the electron beam channel 4 axis L0, which has an offset Δ on the electron beam channel 4 axis L0. This offset Δ is naturally formed based on the included angle θ formed by the first waveguide segment 21 and the second waveguide segment 22. The value of the offset Δ needs to be determined according to the actual slow-wave structure dimensions, and this invention does not impose specific limitations. In this embodiment, the offset direction of the intersection point O on the electron beam channel axis L0 is towards the input direction of the electron beam. Specifically, the offset Δ is the offset of the intersection point O on the electron beam channel axis L0 compared to the intersection point O1 of a conventional straight waveguide segment in the Y-direction. In other words, the dihedral angle between plane α1 formed by the first axis L1 and the X-axis and plane α2 formed by the second axis L2 and the X-axis is the included angle θ, and the X-axis in the XZ plane is the edge of the dihedral plane α1 and plane α2.

[0041] The following examples illustrate the folded waveguide slow-wave structure provided by this invention to specifically demonstrate its advantages and characteristics. The structural dimensions (unit: mm) of the slow-wave structure provided by this invention are as follows: wide side length a = 1.9, narrow side length b = 0.2, geometric period p = 0.8, waveguide transmission section length h in the Y direction = 0.6, and electron beam channel radius r. c =0.12, Δ=0.3, corresponding included angle θ=45°.

[0042] The slow-wave structure of this invention was simulated using the 3D electromagnetic software CST Microwave Studio. Compared with a conventional folded waveguide slow-wave structure with the same phase velocity ratio (Vp / c), the simulation showed a reduction in the Y-direction dimension of the slow-wave structure under the same parameters. The dimensions (unit: mm) of the conventional folded waveguide slow-wave structure for comparison are: wide side length a = 1.9, narrow side length b = 0.2, geometric period p = 0.8, and electron beam channel radius r. c =0.12, the length of the straight waveguide in the Y direction is h0 = 0.72.

[0043] The phase velocity ratio (Vp / c) of the folded waveguide slow-wave structure determines the operating voltage of the traveling wave tube; the same phase velocity ratio (Vp / c) results in the same operating voltage. A comparison of the simulated phase velocity ratio (Vp / c) of the novel slow-wave structure and the conventional folded waveguide slow-wave structure is shown below. Figure 5 As shown, it can be seen that, under the premise that the phase velocity ratio (Vp / c) of the slow-wave structure remains unchanged, the Y-direction dimension of the slow-wave structure of the present invention can be significantly compressed, from 0.72 mm to 0.6 mm, a reduction of 16.7%, and the corresponding high-frequency cross-sectional area can be reduced by more than 20%.

[0044] According to formula (1), the output power of a traveling wave tube is equal to the product of the electronic efficiency ηe, the operating voltage V0, and the operating current I0. Under the premise that the operating voltage and electronic efficiency are constant, increasing the operating current can increase the output power P.

[0045] P out =I0V0×η e (1)

[0046] The working current is proportional to the required focusing magnetic field strength. The larger the working current, the stronger the required focusing magnetic field is to concentrate the electron beam within the electron beam channel, as shown in formula (2).

[0047]

[0048] Given a fixed magnet thickness and outer diameter, reducing the magnet's inner diameter is the most effective way to enhance the magnetic field, and the magnet's inner diameter is determined by the cross-sectional dimensions of the slow-wave circuit. As described above, using the slow-wave structure of this invention, the cross-sectional dimensions are reduced by more than 20% compared to conventional folded waveguide slow-wave structures, which can significantly reduce the magnet's inner diameter, thereby enabling the focusing of larger currents and increasing the output power of the traveling wave tube.

[0049] In conventional folded waveguide slow wave structures, if the cross-sectional size of the slow wave structure is reduced by decreasing the length h in the Y direction of the straight waveguide section, the reduction of h will significantly increase the operating voltage of the traveling wave tube. The increase in operating voltage requires a larger electron gun, which will also increase the size and weight of the power supply from the perspective of the overall structure, making it difficult to further miniaturize the traveling wave tube, which goes against the original intention of this invention.

[0050] Combination Figure 6 , Figure 7 As shown, from Figure 6 , Figure 7 It is not difficult to see that, since the operating voltage of a traveling wave tube is determined by the phase velocity ratio (Vp / c) of the slow-wave structure, when the length h of the straight waveguide section in the Y direction of a conventional folded waveguide slow-wave structure is simply reduced from 0.72 mm to 0.6 mm, the increase in the phase velocity ratio (Vp / c) is as follows: Figure 6 As shown, the corresponding operating voltage will also be as follows. Figure 7 The voltage is increased by approximately 500V. This demonstrates that the folded waveguide slow-wave structure of this invention can increase the output power of the traveling wave tube without changing the operating voltage, while also achieving the advantage of further miniaturization of the traveling wave tube.

[0051] According to another objective of the present invention, the present invention also provides a design method for a folded waveguide slow-wave structure, the method comprising the following steps:

[0052] Under the condition that the phase speed ratio (Vp / c) of the slow wave structure, i.e. the operating voltage of the traveling wave tube, remains unchanged, multiple upper gate structures and multiple lower gate structures are designed to be periodically and alternately distributed. The upper gate 11 and the lower gate 12 respectively include a first bending part and a second bending part located on the axis L0 of the electron beam channel 4 and having the same bending direction.

[0053] The folded waveguide slow-wave structure, constructed and defined by each upper grating 11 and each lower grating 12, includes multiple periodic waveguide structures with waveguide transmission sections 2 and waveguide connection sections 3. The waveguide transmission section 2 includes a first waveguide section 21 and a second waveguide section 22. The first waveguide section 21 and the second waveguide section 22 each include a first axis L1 and a second axis L2 in their respective extension directions. The first axis L1 and the second axis L2 form a plane α. The first axis L1 and the second axis L2 form an angle θ within the plane α, where the angle θ is greater than 0° and less than 180°.

[0054] The folded waveguide slow wave structure obtained by the above design method, compared with the conventional folded waveguide slow wave structure with the same phase velocity ratio (Vp / c), can achieve size compression of the slow wave structure in the direction of electron beam channel diameter under the condition that all other parameters are the same. This reduces the cross-sectional size of the slow wave structure, effectively reduces the inner diameter of the magnet, increases the beam-focusing current, and significantly improves the output power of the traveling wave tube. At the same time, it achieves further miniaturization of the traveling wave tube while significantly improving the output power of the traveling wave tube.

[0055] 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 folded waveguide slow-wave structure, comprising a plurality of upper gratings and a plurality of lower gratings arranged in an alternating pattern, and an electron beam channel located at the central axis of the slow-wave structure; characterized in that, When the phase light speed ratio of the slow-wave structure is determined, the upper grating and the lower grating respectively include a first bending portion and a second bending portion located on the electron beam channel axis L0 and having the same bending direction.

2. The slow wave structure of claim 1, wherein, The folded waveguide slow wave structure includes multiple periodic waveguide structures with waveguide transmission sections and waveguide connection sections defined by each upper grating and each lower grating. The waveguide transmission segment includes a first waveguide segment and a second waveguide segment. The first waveguide segment and the second waveguide segment each include a first axis L1 and a second axis L2 in their respective extension directions. The first axis L1 and the second axis L2 form a plane α, and the first axis L1 and the second axis L2 form an angle θ in the plane α.

3. The slow wave structure of claim 2, wherein, Two adjacent waveguide transmission segments have the same interaction distance.

4. The slow wave structure of claim 2, wherein, The first waveguide segment and the second waveguide segment are arranged in a mirror image relative to the electron beam channel.

5. The slow wave structure of claim 1, wherein, The bending directions of the upper and lower gates are either opposite to or towards the input direction of the electron beam.

6. The slow wave structure of claim 2, wherein, The first axis L1 and the second axis L2 include an intersection point O on the electron injection channel axis L0, which has an offset Δ on the electron injection channel axis L0.

7. The slow wave structure of claim 6, wherein, The direction of the offset of the intersection point O on the electron beam channel axis L0 is toward or away from the input direction of the electron beam.

8. The slow-wave structure according to claim 2, characterized in that, The included angle θ is greater than 0° and less than 180°.

9. A design method for a folded waveguide slow-wave structure, characterized in that, The method includes the following steps: Under the condition that the phase light speed ratio of the slow-wave structure remains unchanged, multiple upper grating structures and multiple lower grating structures are designed to be periodically and alternately distributed. The upper grating and the lower grating each include a first bending portion and a second bending portion located on the electron beam channel axis L0 and having the same bending direction.

10. The design method according to claim 9, characterized in that, The folded waveguide slow wave structure, constructed and defined by each upper grating and each lower grating, includes multiple periodic waveguide structures with waveguide transmission sections and waveguide connection sections. The waveguide transmission segment includes a first waveguide segment and a second waveguide segment. The first waveguide segment and the second waveguide segment each include a first axis L1 and a second axis L2 in their respective extension directions. The first axis L1 and the second axis L2 form a plane α. The first axis L1 and the second axis L2 form an angle θ in the plane α. The angle θ is greater than 0° and less than 180°.

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