Flat-top ridge loading electron beam channel opening type folded waveguide slow wave structure

Abstract

The invention provides a flat-top ridge loading electron beam channel opening type folded waveguide slow-wave structure, which comprises a multi-periodic cavity structure defined by grid bodies arranged in an up-down staggered manner, and comprises a straight waveguide section, a connecting waveguide section and an electron beam channel which are communicated with each other, the inner boundary of the connecting waveguide section is located in the boundary limited by the electron beam channel; the grid body comprises a first structure surface forming the inner boundary of the connecting waveguide section, a second structure surface forming the outer boundary of the connecting waveguide section, and a third structure surface forming the side boundary of the straight waveguide section; the first structure surface is an arc surface, and the second structure surface is a flat and straight surface; the grid body comprises a ridge loading structure, and the ridge loading structure comprises a first ridge loading part which protrudes towards the interior of the cavity structure from a first structure surface and a second ridge loading part which protrudes towards the interior of the cavity structure from a third structure surface; the ridge loading structure is a continuous extension structure on the first structure surface and the third structure surface.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of microwave vacuum electron technology. More particularly, it relates to a flat-top ridge-loaded electron beam channel opening type folded waveguide slow wave structure. BACKGROUND

[0002] A traveling wave tube is a kind of vacuum electron device, which can realize microwave signal generation or amplification, and has broad development prospects in the fields of communication, electronic countermeasures, radar systems, etc. The traveling wave tube mainly consists of an electron gun, a slow wave structure, a collector, an input / output device and a focusing system. The slow wave structure is the place for beam-wave interaction, i.e. the key component for realizing microwave signal generation or amplification. At present, the folded waveguide slow wave structure is one of the main slow wave structures adopted by the millimeter wave / terahertz band traveling wave tube. This structure is a full-metal waveguide structure, which has the advantages of simple structure, easy processing and large power capacity.

[0003] Since the development of the traveling wave tube towards high power is one of the industry trends. In order to further improve the output power, the electron beam current needs to be increased, which leads to the need to improve the focusing performance of the traveling wave tube focusing system. The cross-sectional size of the millimeter wave terahertz traveling wave tube slow wave structure currently limits the focusing performance of the electron beam traveling wave tube focusing system, making it impossible to further improve the current density, thereby limiting the output power of the traveling wave tube. SUMMARY

[0004] In view of the above problems, the present application provides a flat-top ridge-loaded electron beam channel opening type folded waveguide slow wave structure to solve the problem that the cross-sectional size of the existing slow wave structure limits the focusing performance of the electron beam traveling wave tube focusing system, making it impossible to further improve the current density, thereby limiting the output power of the traveling wave tube.

[0005] To achieve the above purpose, the present application adopts the following technical solutions:

[0006] The present application provides a flat-top ridge-loaded electron beam channel opening type folded waveguide slow wave structure, which comprises a multi-periodic cavity structure formed by upper and lower staggered grid bodies, and the slow wave structure comprises a straight waveguide section, a connecting waveguide section and an electron beam channel; the inner boundary of the connecting waveguide section is located within the boundary defined by the electron beam channel.

[0007] The grid body comprises:

[0008] a first profile constituting the inner boundary of the connecting waveguide section,

[0009] a second profile constituting the outer boundary of the connecting waveguide section, and

[0010] a third profile constituting the side boundary of the straight waveguide section.

[0011] The first profile is a circular arc profile, and the second profile is a flat profile.

[0012] The grid body comprises a ridge loading structure, which comprises:

[0013] a first ridge loading protruding into the cavity structure from the first profile, and

[0014] a second ridge loading protruding into the cavity structure from the third profile.

[0015] The ridge loading structure is in a continuous extension structure on the first profile and the third profile.

[0016] Preferably, the ridge loading structure is in a U shape, the first ridge loading protrudes towards the connecting waveguide section, and the second ridge loading protrudes towards the straight waveguide section; an end of the second ridge loading away from the first ridge loading penetrates the connecting waveguide section along the axial direction of the straight waveguide section.

[0017] Preferably, a first interface portion is included between the inner boundary of the connecting waveguide section and the straight waveguide section, and a first interval height is formed between the first interface portion and the electron beam channel axis in the radial direction of the electron beam channel; a second interface portion is included between the outer boundary of the connecting waveguide section and the straight waveguide section, and a second interval height is formed between the second interface portion and the electron beam channel axis in the radial direction of the electron beam channel; the second interval height is greater than the first interval height.

[0018] Preferably, the center line of the ridge loading structure in the width direction coincides with the width center line of the folded waveguide slow wave structure.

[0019] Preferably, the height of the slow wave structure is h3, the radius of the electron beam channel is r, the half-period length of the slow wave structure is p, and the length of the narrow side of the straight waveguide section is b; h3>max(r×2, p-b-r×2).

[0020] Preferably, the first ridge loading and the second ridge loading have the same thickness and width; the thickness of the ridge loading structure is j, 0

[0021] Preferably, the sum of the first interval height and the second interval height is h4; 0

[0022] Preferably, the length of the second ridge loading in the axial direction of the straight waveguide section is h5; 0

[0023] Preferably, the ridge loading structure further comprises a third ridge loading protruding into the cavity structure from the second surface; the ridge loading structure is continuously extended on the first surface, the second surface and the third surface; the first ridge loading, the second ridge loading and the third ridge loading have the same thickness and width.

[0024] The application also provides a design method of the flat-top ridge loading electron beam channel opening type folded waveguide slow wave structure, comprising the following steps:

[0025] According to the requirement, an initial folded waveguide slow wave structure is designed, which comprises a multi-periodic cavity structure defined by alternately arranged upper and lower grid bodies, and the slow wave structure comprises a straight waveguide section, a connecting waveguide section and an electron beam channel;

[0026] The inner boundary of the connecting waveguide section is lowered to be within the boundary defined by the electron beam channel;

[0027] The grid body comprises a first surface constituting the inner boundary of the connecting waveguide section, a second surface constituting the outer boundary of the connecting waveguide section, and a third surface constituting the side boundary of the straight waveguide section; the first surface is a circular arc surface, and the second surface is a flat surface; the grid body comprises a ridge loading structure, which comprises a first ridge loading protruding into the cavity structure from the first surface, and a second ridge loading protruding into the cavity structure from the third surface; the ridge loading structure is continuously extended on the first surface and the third surface.

[0028] The application has the following beneficial effects:

[0029] The application provides a flat-top ridge-loaded electron beam channel opening type folded waveguide slow wave structure, which comprises a multi-period cavity structure formed by upper and lower staggered grids, and the slow wave structure comprises a straight waveguide section, a connecting waveguide section and an electron beam channel; the inner boundary of the connecting waveguide section is located in the boundary defined by the electron beam channel; the grid comprises a first profile constituting the inner boundary of the connecting waveguide section, a second profile constituting the outer boundary of the connecting waveguide section and a third profile constituting the side boundary of the straight waveguide section; the first profile is a circular arc surface, and the second profile is a flat surface; the grid comprises a ridge loading structure, the ridge loading structure comprises a first ridge loading protruding into the cavity structure from the first profile and a second ridge loading protruding into the cavity structure from the third profile; the ridge loading structure continuously extends on the first profile and the third profile. Through the above arrangement, the cross-sectional size of the slow wave structure can be reduced without changing the basic performance of the dispersion, the phase-light velocity ratio and the coupling impedance of the slow wave structure, so that the inner diameter of the focusing channel of the magnet focusing system of the traveling wave tube can be further reduced, thereby helping to improve the focusing performance of the magnet focusing system and the overall performance of the traveling wave tube. In addition, the outer straight boundary forming the flat-top structure is easier to realize in the processing technology compared with the arc-shaped outer boundary of the conventional slow wave structure, which helps to reduce the processing difficulty of the slow wave structure and improve the processing precision, thereby realizing better actual performance. The slow wave structure and the traveling wave tube provided by the application can be widely applied to a new generation of mobile communication equipment, mobile communication base station equipment in wideband wireless mobile communication technology, and transmitting equipment in the field of satellite transmission and the field of broadcast television network. BRIEF DESCRIPTION OF DRAWINGS

[0030] The specific embodiments of the application will be further described in detail below with reference to the accompanying drawings.

[0031] Figures 1A-1C Fig. 1 is a single period structure schematic diagram of a flat-top ridge-loaded electron beam channel opening type folded waveguide slow wave structure provided by the application.

[0032] Figures 2A-2C Fig. 2 is a single period structure schematic diagram of an existing arc-top ridge-loaded electron beam channel opening type folded waveguide slow wave structure.

[0033] Figure 3 Fig. 3 is a dispersion characteristic curve diagram of the flat-top ridge-loaded electron beam channel opening type folded waveguide slow wave structure provided by the application.

[0034] Figure 4 Fig. 4 is a phase-light velocity ratio curve comparison diagram of the flat-top ridge-loaded electron beam channel opening type folded waveguide slow wave structure provided by the application and an arc-top ridge-loaded electron beam channel opening type folded waveguide slow wave structure with similar in-band phase velocity.

[0035] Figure 5is a dispersion characteristic curve comparison chart of the flat-top-ridge-loaded electron beam channel opening type folded waveguide slow wave structure and the arc-top-ridge-loaded electron beam channel opening type folded waveguide slow wave structure with similar phase velocities in the band.

[0036] Figure 6 is a coupling impedance curve comparison chart of the flat-top-ridge-loaded electron beam channel opening type folded waveguide slow wave structure and the arc-top-ridge-loaded electron beam channel opening type folded waveguide slow wave structure with similar phase velocities in the band. DETAILED DESCRIPTION

[0037] Various exemplary embodiments of the present application will now be described in detail with reference to the accompanying drawings. It should be noted that the relative arrangements, numerical expressions, and numerical values of the components and steps set forth in these embodiments are not limiting to the scope of the present application unless specifically stated otherwise.

[0038] The following description of at least one exemplary embodiment is merely exemplary in nature and is in no way intended to limit the scope of the application its application or uses.

[0039] Techniques and equipment known to those of ordinary skill in the relevant art can not be discussed in detail, but should be considered part of the specification where appropriate.

[0040] In all of the examples shown and discussed herein, any specific values should be interpreted as merely exemplary and not as a limitation. Thus, other examples of the exemplary embodiments can have different values.

[0041] It should be noted that like reference numerals and letters refer to like items in the several views of the drawings, and as such, further discussion of them is not necessary in the subsequent drawings.

[0042] In order to improve the focusing performance of the magnetic focusing system, it is necessary to reduce the cross-sectional size of the slow wave structure in the magnetic focusing channel, thereby correspondingly reducing the inner diameter of the magnetic focusing channel. In general, the overall size of the folded waveguide slow wave structure or the size of certain structures (such as the height of the straight waveguide or the length of the wide side) is reduced to reduce the cross-sectional size of the slow wave structure and improve the focusing performance of the magnetic focusing system, but this will change the basic performance of the slow wave structure and affect the overall performance of the traveling wave tube. Therefore, in order to maintain the basic performance of the slow wave structure unchanged, improve the focusing performance of the traveling wave focusing system, and further improve the output power of the traveling wave tube, the present application provides a flat-top-ridge-loaded electron beam channel opening type folded waveguide slow wave structure, which combines Figures 1A to 6As shown, specifically, the flat-top ridge-loaded electron beam channel opening type folded waveguide slow wave structure includes a multi-period cavity structure defined by the upper and lower staggered grids, and the slow wave structure includes a straight waveguide section 1, a connecting waveguide section 2, and an electron beam channel 3. The inner boundary of the connecting waveguide section 2 is located within the boundary defined by the electron beam channel 3. The grid includes a first surface constituting the inner boundary of the connecting waveguide section 2, a second surface constituting the outer boundary of the connecting waveguide section 2, and a third surface constituting the side boundary of the straight waveguide section 1. The first surface is a circular arc surface, and the second surface and the third surface are both flat surfaces. The grid includes a ridge loading structure 4, which includes a first ridge loading 41 protruding inward from the first surface toward the cavity structure and a second ridge loading 42 protruding inward from the third surface toward the cavity structure. The ridge loading structure 4 is continuously extended on the first surface and the third surface. It should be noted that the first surface and the third surface both have ridge loadings. The first surface being a circular arc surface means that the surface of the first surface except the first ridge loading is a circular arc surface, and the surface of the first ridge loading formed on the first surface is also a circular arc surface. The third surface being a flat surface means that the surface of the third surface except the second ridge loading is a flat surface, and the surface of the second ridge loading formed on the third surface is also a flat surface. Preferably, in the specific embodiments of the present application, the cross section of the ridge loading structure is rectangular. Those skilled in the art can understand that, without affecting the overall performance of the slow wave structure, the surface of the ridge loading structure can also have a certain curvature, and the cross-sectional shape can also be other shapes besides rectangular, which is not limited by the present application.

[0043] Further, the connecting waveguide section 1 includes an inner boundary and an outer boundary. The inner boundary is an inner circular arc boundary 5, and the outer boundary is an outer straight line boundary 6. The inner circular arc boundary 5 is located within the boundary defined by the electron beam channel 3. The straight waveguide section 1 includes an inner side boundary 7 and an outer side boundary 8. Both the inner side boundary 7 and the outer side boundary 8 are vertical boundaries. The first ridge loading 41 and the second ridge loading 42 are connected. The first ridge loading 41 extends with the inner circular arc boundary 5. One grid includes one first ridge loading 41 and two second ridge loadings 42. The two second ridge loadings 42 respectively extend along the straight waveguide section axis from the two ends of the first ridge loading 41 along the electron beam channel axis, i.e., the ridge loading structure 4 is a continuously extended structure. The straight waveguide section axis is perpendicular to the electron beam channel axis. Figure 1C As shown, the straight waveguide section axis is the Y direction, and the electron beam channel axis is the X direction. The extension direction of the outer straight line boundary 6 is consistent with the extension direction of the electron beam channel axis. Figure 2ACompared to the ridge-loaded electron beam channel open-type folded waveguide slow-wave structure shown in the diagram, where both the inner and outer boundaries of the connecting waveguide section are arc-shaped, this application, through the aforementioned configuration, enables the flat-top ridge-loaded electron beam channel open-type folded waveguide slow-wave structure to reduce the cross-sectional size of the slow-wave structure while maintaining its basic performance. This allows for a further reduction in the focusing channel of the magnetic focusing system, creating space for improving the focusing performance of the focusing magnetic field. Simultaneously, it also reduces the manufacturing difficulty of the slow-wave structure. (Referring to the accompanying drawings, in...) Figure 1C In the view, the position between the two straight waveguide segments 1 and the connecting waveguide segment 2 is the location of the grating. The outer boundary of the ridge loading structure 4 is represented by a dashed line in the figure. The first ridge loading 41 is formed between the inner arc boundary 5 and the arc dashed line above it, and the second ridge loading 42 is formed between the inner side boundary 7 and the vertical dashed line connected to the arc dashed line.

[0044] In one specific embodiment, the inner boundary of the connecting waveguide segment is an inner circular arc boundary 5, and the outer boundary of the connecting waveguide segment is an outer straight boundary 6. The inner circular arc boundary 5 is entirely located within the boundary defined by the electron beam channel 3. At this time, the slow wave structure forms a flat-top ridge loaded electron beam channel opening type folded waveguide slow wave structure with an electron beam channel opening. The inner circular arc boundary 5 and the straight waveguide segment 1 include a first junction, and the first junction and the electron beam channel axis form a first spacing height h1 in the radial direction of the electron beam channel; the outer straight boundary 6 and the straight waveguide segment 1 include a second junction, and the second junction and the electron beam channel axis form a second spacing height h2 in the radial direction of the electron beam channel; the second spacing height h2 is greater than the first spacing height h1.

[0045] More specifically, the parameter controlling the height of the straight waveguide is divided into a first interval height h1 and a second interval height h2. By adjusting the size of h1, the inner circular arc boundary 5 can be entirely located within the boundary defined by the electron beam channel 3. An opening appears in the electron beam channel 3 between two adjacent straight waveguide segments 1, directly connecting to the connecting waveguide segment 2, forming a flat-top ridge-loaded electron beam channel-opening folded waveguide slow-wave structure with an open electron beam channel. In this structure, because the electron beam channel 3 is directly connected to the connecting waveguide segment 2, the boundary conditions of the electromagnetic field change, resulting in a new field distribution and dispersion characteristics. Compared to a conventional folded waveguide slow-wave structure without an opening, the flat-top ridge-loaded electron beam channel-opening folded waveguide slow-wave structure with an open opening has a higher coupling impedance, even with the same operating bandwidth.

[0046] Further, in a specific embodiment, the slow wave structure comprises an upper ridge and a lower ridge, and a ridge loading structure 4 is formed on the upper ridge and the lower ridge, the ridge loading structure 4 is in a U shape, a first ridge loading 41 protrudes towards the connecting waveguide section 2, and a second ridge loading 42 protrudes towards the straight waveguide section 1. The extension end of each of the two second ridge loadings 42 penetrates the connecting waveguide section 2 along the axis of the straight waveguide section respectively. The extension end of the second ridge loading 42 refers to the end of the second ridge loading 42 away from the first ridge loading 41. In a folded waveguide unit, the ridge loading structure 4 protrudes towards the straight waveguide section 1 and the connecting waveguide section 2, and the ridge loading structure 4 extends from one side of the ridge to the other side along the outer contour of the ridge. Specifically, in the vertical cross section of the slow wave structure in the Figure 1C the ridge loading structure 4 is in a U shape. The ridge loading structure formed on the upper ridge is in a positive U shape, and the ridge loading structure formed on the lower ridge is in an inverted U shape. The flat top of the flat-top ridge-loaded electron beam channel opening type folded waveguide slow wave structure of the application is penetrated by the ridge loading structure 4 along the axis of the straight waveguide section. Based on Figure 1A From the perspective of top view, the two side edges of the flat top at the top end of the slow wave structure along the axis of the electron beam channel form symmetrical concave parts due to the existence of the ridge loading structure 4, becoming a H-shaped flat top structure. Compared with the electron beam channel opening type folded waveguide slow wave structure without loading, the slow wave structure matching performance can be optimized by setting the ridge loading structure on the ridge based on the electron beam channel opening type folded waveguide slow wave structure without loading, and the slow wave structure obtained by this method is applied to a wideband millimeter wave / terahertz traveling wave tube. Under the premise of the same working frequency band and similar in-band phase velocity ratio, the electron beam channel axis coupling impedance can be greatly improved, and the output power, gain efficiency and electron efficiency of the traveling wave tube can be obviously improved. The flat-top ridge-loaded electron beam channel opening type folded waveguide slow wave structure described above can reduce the process difficulty of the slow wave structure and reduce the cross-sectional size of the slow wave structure under the premise of keeping the basic performances such as dispersion, phase velocity ratio and coupling impedance unchanged, thereby creating space for improving the performance of the focusing magnetic field.

[0047] Further, the application provides a flat-top ridge-loaded electron beam channel opening type folded waveguide slow wave structure with an electron beam channel opening and a ridge loading structure, the height of the slow wave structure is h3, the electron beam channel radius is r, the half-period length of the slow wave structure is p, and the narrow edge length of the straight waveguide section is b; h3>max(r*2, p-b-r*2). The height h3 of the slow wave structure is bisected by the electron beam channel axis. The sum of the first interval height h1 and the second interval height h2 is h4; 0 Figure 1C The two vertical dashed lines in FIG. 4 are the vertical boundaries of the second ridge loading 41, and the curved dashed lines connected to the two vertical dashed lines at both ends are the curved boundaries of the first ridge loading 41. In the application, by loading the ridge loading structure 4 with a width of a2 and a thickness of j, the waveguide width a1 and the second interval height h2 can be reduced while the bandwidth of the folded waveguide slow wave structure remains unchanged, thereby reducing the cross-sectional size of the slow wave structure and providing space for improving the focusing performance of the traveling wave tube focusing system. There are high-order terms, cross terms and transcendental function relationships among the above parameters of the folded waveguide slow wave structure of the application, the correlation between the core performance and the parameters is based on nonlinear equations, and the nonlinear characteristics of the high-dimensional parameter space cause the performance to change with the parameters, which does not satisfy the superposition principle. Therefore, the parameter change is nonlinear, and the rules cannot be exhausted or fitted through a finite number of experiments. The scheme of the application must be realized through theoretical modeling and simulation optimization, rather than experimental trial and error.

[0048] More specifically, referring to FIG. 4, Figures 1A-1CFig. 1 shows a schematic diagram of a single period structure of a flat-top ridge-loaded electron beam channel opening type folded waveguide slow wave structure provided in Example 1 of the present application, a represents the length of the wide side of the waveguide, b represents the length of the narrow side of the waveguide, p represents the geometric half period, the vertical distance between the connecting point of the inner boundary and the straight waveguide section and the outer boundary is h4, the overall height of the slow wave structure is h3, the straight waveguide has a protruding ridge load with a width of a2 and a thickness of j, the vertical boundary of the ridge load structure has a length of h5 in the axial direction of the straight waveguide section; the vertical distance between the connecting point of the inner boundary and the straight waveguide section and the electron beam channel axis is h1, the vertical distance between the connecting point of the outer boundary and the straight waveguide section and the electron beam channel axis is h2. The radius of the electron beam channel is r, by adjusting the size of h1, the height of the circular arc in the waveguide is less than the radius r of the electron beam channel, and the electron beam channel between the adjacent two straight waveguide sections appears an opening in the radial direction, which is directly connected to the connecting waveguide section.

[0049] In the G-band region, the specific structural dimensions of the flat-top ridge-loaded electron beam channel opening type folded waveguide slow wave structure provided in Example 1 of the present application are as follows (unit: mm): a = 0.765, b = 0.16, p = 0.26, h1 = 0.03, h2 = 0.24; h3 = 0.48, h4 = 0.27, h5 = 0.27, r = 0.12, j = 0.03. The cross-sectional size is: 0.765 mm x 0.48 mm; the circumscribed circle area is: 0.64 mm 2 .

[0050] Further, on the basis of the structure of Example 1, the ridge load structure provided in Example 2 of the present application further comprises a third ridge load protruding from the second profile towards the cavity structure; the ridge load structure continuously extends on the first profile, the second profile and the third profile; the first ridge load, the second ridge load and the third ridge load have the same thickness and width.

[0051] In the G-band region, the specific structural dimensions of the flat-top ridge-loaded electron beam channel opening type folded waveguide slow wave structure provided in Example 2 of the present application are as follows (unit: mm): a = 0.7545, b = 0.16, p = 0.26, h1 = 0.03, h2 = 0.2645; h3 = 0.529, h4 = 0.27, h5 = 0.2345, r = 0.12, j = 0.03. The cross-sectional size is: 0.7545 mm x 0.529 mm; the circumscribed circle area is: 0.667 mm 2 .

[0052] Reference Figures 2A-2CAs shown in the figure, it is a single period structure schematic diagram of an existing arc top ridge loaded electron beam channel opening type folded waveguide slow wave structure. The ridge loading of the arc top ridge loaded electron beam channel opening type folded waveguide slow wave structure extends along with the bending of the slow wave structure, and the ridge loading is formed on both sides of the slow wave structure. a represents the wide side length of the waveguide, b is the narrow side length of the straight waveguide, the geometric half period is p, the vertical distance between the connecting point of the inner boundary and the straight waveguide section and the electron beam channel axis is h1, and the vertical distance between the connecting point of the outer boundary and the straight waveguide section and the electron beam channel axis is h2. The straight waveguide section and the connecting waveguide section have ridge loading with a protruding ridge with a width of a2 and a thickness of j on both sides of the extension direction, and the electron beam channel radius is r.

[0053] The structure size of the existing arc top ridge loaded electron beam channel opening type folded waveguide slow wave structure for comparison is as follows (unit: mm): a = 0.76, a2 = 0.3, b = 0.16, p = 0.26, h1 = 0.03, h2 = 0.1, r = 0.12, j = 0.03. The cross-sectional size is: 0.76mm x 0.62mm; the circumscribed circle area is: 0.755mm 2 .

[0054] The flat top ridge loaded electron beam channel opening type folded waveguide slow wave structure and the arc top ridge loaded electron beam channel opening type folded waveguide slow wave structure with similar phase velocity in the band provided by the present application are simulated by using three-dimensional electromagnetic software, and the relevant dispersion characteristics, phase-light velocity ratio, axial coupling impedance and high-frequency loss characteristics are calculated.

[0055] Referring to Figure 3 As shown in the figure, it is the dispersion characteristics of the flat top ridge loaded electron beam channel opening type folded waveguide slow wave structure of the present application, and the operating point is selected at the-1 spatial harmonic of the intrinsic mode 3.

[0056] Referring to Figure 4 As shown in the figure, it is the phase-light velocity ratio curve comparison of the flat top ridge loaded electron beam channel opening type folded waveguide slow wave structure example 1 and example 2 of the present application and the arc top ridge loaded electron beam channel opening type folded waveguide slow wave structure with similar phase velocity in the band. In the 200GHz-230GHz operating frequency band, the phase-light velocity ratios of the three are basically the same.

[0057] Referring to Figure 5 As shown in the figure, it is the dispersion characteristics comparison of the flat top ridge loaded electron beam channel opening type folded waveguide slow wave structure example 1 and example 2 of the present application and the arc top ridge loaded electron beam channel opening type folded waveguide slow wave structure with similar phase velocity in the band. For the 200GHz-230GHz operating frequency band, the corresponding phase shifts of the present application and the arc top ridge loaded electron beam channel opening type slow wave structure are both between 460° and 530°, and the operating intervals are basically consistent.

[0058] Referring to Figure 6As shown in the figure, the coupling impedance of the flat-top ridge loaded electron beam channel opening type folded waveguide slow wave structure of the present application and the in-band phase velocity similar arc-top ridge loaded electron beam channel opening type folded waveguide slow wave structure is compared. In the 200GHz-230GHz operating frequency band, the coupling impedances of the three are also basically the same.

[0059] In combination Figures 3-6 As shown in the figure, the dispersion, phase-light velocity ratio, coupling impedance and other cold characteristics of the flat-top ridge loaded electron beam channel opening type folded waveguide slow wave structure of the present application and the in-band phase velocity similar arc-top ridge loaded electron beam channel opening type folded waveguide slow wave structure for comparison are very small in the 200GHz-230GHz operating frequency band, but the cross-sectional circumscribed circle area of the present application is only 84.78% of that of the arc-top ridge loaded electron beam channel opening type folded waveguide slow wave structure for comparison, so it is more conducive to reducing the inner diameter of the traveling wave tube focusing system, thereby achieving the purpose of improving the focusing magnetic field strength and improving the focusing ability.

[0060] The present application also provides a design method of a flat-top ridge loaded electron beam channel opening type folded waveguide slow wave structure, which comprises the following steps: designing an initial folded waveguide slow wave structure according to needs, the slow wave structure comprising a multi-periodic cavity structure defined by upper and lower staggered grid bodies, the slow wave structure comprising a straight waveguide section, a connecting waveguide section and an electron beam channel; using a three-dimensional electromagnetic field simulation software, moving the inner boundary of the connecting waveguide section downward to the boundary defined by the electron beam channel; using a three-dimensional electromagnetic field simulation software, designing a ridge loading structure protruding towards the cavity structure on the grid body; the grid body comprises a first surface constituting the inner boundary of the connecting waveguide section, a second surface constituting the outer boundary of the connecting waveguide section, and a third surface constituting the side boundary of the straight waveguide section; the first surface is a circular arc surface, and the second surface is a flat surface; the grid body comprises a ridge loading structure, the ridge loading structure comprising a first ridge loading protruding towards the cavity structure from the first surface, and a second ridge loading protruding towards the cavity structure from the third surface; the ridge loading structure is continuously extended on the first surface and the third surface.

[0061] The present application also provides a traveling wave tube comprising the slow wave structure as described above.

[0062] In summary, the application provides a flat-top ridge loaded electron beam channel opening type folded waveguide slow wave structure, which comprises a multi-period cavity structure formed by upper and lower staggered grids, and the slow wave structure comprises a connected straight waveguide section, a connecting waveguide section and an electron beam channel; the inner boundary of the connecting waveguide section is located within the boundary defined by the electron beam channel; the grid comprises a first profile constituting the inner boundary of the connecting waveguide section, a second profile constituting the outer boundary of the connecting waveguide section, and a third profile constituting the side boundary of the straight waveguide section; the first profile is a circular arc surface, and the second profile is a flat surface; the grid comprises a ridge loading structure, which comprises a first ridge loading protruding into the cavity structure from the first profile, and a second ridge loading protruding into the cavity structure from the third profile; the ridge loading structure continuously extends on the first profile and the third profile. Through the above arrangement, the cross-sectional size of the slow wave structure can be reduced without changing the basic performance of the dispersion, the phase-light velocity ratio and the coupling impedance of the slow wave structure, which can create space for further reduction of the inner diameter of the focusing channel of the magnet focusing system of the traveling wave tube, thereby helping to improve the focusing performance of the magnet focusing system and further improving the overall performance of the traveling wave tube. In addition, the outer straight boundary forming a flat-top structure adopted by the application is easier to realize in the processing technology than the arc-shaped outer boundary of the conventional slow wave structure, which helps to reduce the processing difficulty of the slow wave structure and improve the processing precision, thereby realizing better actual performance. The slow wave structure and the traveling wave tube provided by the application can be widely applied to new generation mobile communication equipment, mobile communication base station equipment in wideband wireless mobile communication technology, and transmitting equipment in satellite transmitting field and broadcast television network field.

[0063] Obviously, the above embodiments of the application are only examples for clearly illustrating the application, and are not intended to limit the implementation modes of the application. For those skilled in the art, other different forms of changes or modifications can be made on the basis of the above description, and it is impossible to enumerate all the implementation modes here. Any obvious changes or modifications derived from the technical solutions of the application still fall within the protection scope of the application.

Claims

1. A flat-topped ridge-loaded electron beam channel open-type folded waveguide slow-wave structure, characterized in that, The slow-wave structure includes a multi-periodic cavity structure defined by vertically staggered gratings, and the slow-wave structure includes a connected straight waveguide section, a connecting waveguide section, and an electron beam channel. The inner boundary of the connecting waveguide segment is located within the boundary defined by the electron beam channel; The gate body includes: The first surface that forms the boundary of the waveguide segment. The second surface that forms the outer boundary of the waveguide segment, and The third surface that forms the side boundary of the straight waveguide segment; The first surface is a circular arc, and the second surface is a flat surface; The gate includes a ridge-loaded structure, the ridge-loaded structure comprising: Loading is applied from the first surface toward the first ridge protruding into the cavity structure, and Load is applied from the third surface toward the second ridge protruding into the cavity structure; The ridge-loaded structure extends continuously on the first and third planes.

2. The flat-top ridge loaded electron beam channel open-type folded waveguide slow-wave structure according to claim 1, characterized in that, The ridge loading structure is U-shaped, with the first ridge loading protruding towards the connecting waveguide section and the second ridge loading protruding towards the straight waveguide section; the end of the second ridge loading away from the first ridge loading passes through the connecting waveguide section axially along the straight waveguide section.

3. The flat-top ridge loaded electron beam channel open-type folded waveguide slow-wave structure according to claim 1, characterized in that, The connection between the inner boundary of the waveguide segment and the straight waveguide segment includes a first junction, and a first gap height is formed between the first junction and the axis of the electron beam channel in the radial direction of the electron beam channel; the connection between the outer boundary of the waveguide segment and the straight waveguide segment includes a second junction, and a second gap height is formed between the second junction and the axis of the electron beam channel in the radial direction of the electron beam channel; the second gap height is greater than the first gap height.

4. The flat-top ridge loaded electron beam channel open-type folded waveguide slow wave structure according to claim 1, characterized in that, The centerline of the ridge-loaded structure in the width direction coincides with the centerline of the folded waveguide slow wave structure.

5. The flat-top ridge loaded electron beam channel open-type folded waveguide slow wave structure according to claim 3, characterized in that, The slow wave structure has a height of h3, an electron beam channel radius of r, a half-cycle length of p, and a narrow side length of b for the straight waveguide segment; h3 > max(r×2, pbr×2).

6. The flat-top ridge loaded electron beam channel open-type folded waveguide slow-wave structure according to claim 5, characterized in that, The first ridge loading and the second ridge loading have the same thickness and width; the thickness of the ridge loading structure is j, 0 < j < b / 2; the width of the ridge loading structure is a2, and the length of the wide side of the straight waveguide segment is a, 2r < a2 < a.

7. The flat-top ridge loaded electron beam channel open-type folded waveguide slow-wave structure according to claim 6, characterized in that, The sum of the height of the first interval and the height of the second interval is h4; 0 < h4 ≤ r + (h3 + bp) / 2 - j.

8. The flat-top ridge loaded electron beam channel open-type folded waveguide slow-wave structure according to claim 6, characterized in that, The length of the second ridge loaded on the axial direction of the straight waveguide segment is h5; 0 < h5 ≤ r + (h3 + bp) / 2 - j.

9. The flat-top ridge loaded electron beam channel open-type folded waveguide slow-wave structure according to claim 1, characterized in that, The ridge loading structure further includes a third ridge loading that protrudes from the second surface toward the cavity structure; the ridge loading structure is a continuous extension structure on the first, second, and third surfaces; the first, second, and third ridge loadings have the same thickness and width.

10. A design method for a flat-topped ridge-loaded electron beam channel open-type folded waveguide slow-wave structure, characterized in that, Includes the following steps: Design an initial folded waveguide slow wave structure as needed. The slow wave structure includes a multi-periodic cavity structure defined by staggered grids. The slow wave structure includes a connected straight waveguide section, a connecting waveguide section, and an electron beam channel. The inner boundary of the connecting waveguide segment is moved down to the boundary defined by the electron beam channel; The grating includes: a first surface forming the inner boundary of the waveguide segment, a second surface forming the outer boundary of the waveguide segment, and a third surface forming the side boundary of the straight waveguide segment; the first surface is an arc surface, and the second surface is a straight surface; the grating includes a ridge loading structure, the ridge loading structure including: a first ridge loading protruding from the first surface toward the cavity structure, and a second ridge loading protruding from the third surface toward the cavity structure; the ridge loading structure is a continuous extension structure on the first surface and the third surface.

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