A bimodal cosh waveguide slow wave structure, a traveling wave tube and a design method

Abstract

This invention provides a bimodal hyperbolic cosine waveguide slow-wave structure, a traveling wave tube, and a design method. The bimodal hyperbolic cosine waveguide slow-wave structure includes multiple upper gratings and multiple lower gratings arranged in an alternating pattern; and an electron beam channel. The slow-wave structure also includes a cavity structure defined by each upper grating and each lower grating. The cavity structure includes upper and lower curved waveguide segments forming multiple periodic structures. The connected upper and lower curved waveguide segments are arranged in a centrally symmetrical manner. Each segment includes a boundary line, which is a hyperbolic cosine curve; the boundary line satisfies the following functional relationship: ((-cosh(2×(-t) / (p-b)))+cosh(1)) / (cosh(1)-cosh(0))×H, where t∈[-(p+b) / 2,(p+b) / 2], p is the half-cycle length of the slow wave structure, b is the cavity width of the cavity structure on the electron beam channel axis, and H is the vertical distance between the peak endpoint of the boundary line and the electron beam channel axis.

Description

Technical Field

[0001] This invention relates to the field of microwave vacuum electronics technology. More specifically, it relates to a double-peak hyperbolic cosine waveguide slow-wave structure, a traveling wave tube, and a design method thereof. 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 electrode, input / output devices, and a magnetic focusing system. The slow-wave structure is the site of interaction between the electron beam and electromagnetic waves, and is a key component for microwave signal amplification. Currently, folded waveguide-type slow-wave structures are one of the mainstream slow-wave structures for TWTs in the millimeter-wave / terahertz band. This structure is an all-metal waveguide structure, possessing advantages such as simple structure, ease of fabrication, high power capacity, and good heat dissipation.

[0003] A conventional folded waveguide slow-wave structure is a periodic structure formed by bending a rectangular waveguide along an electric field, creating a series of straight waveguide segments and waveguide connection segments. The electron beam channel is located on the central axis of the folded waveguide slow-wave structure, and the radial direction is closed between adjacent straight waveguide segments, such as... Figures 1A-1C As shown.

[0004] When conventional folded waveguide slow-wave structures are applied to traveling wave tubes (TWTs), the -1st spatial harmonic is typically chosen as the operating point, corresponding to a phase shift of 360°–720°. Generally, the smaller the phase shift corresponding to the operating frequency of the TWT, the greater the coupling impedance. Therefore, selecting the operating frequency at a position with a relatively early phase shift during design is more beneficial for improving output power, gain, and electronic efficiency. However, for conventional folded waveguide slow-wave structures, the earlier the phase shift of the operating point, the greater the dispersion intensity, resulting in a narrower operating bandwidth. Furthermore, the dispersion intensity is proportional to the ratio of the electron beam channel radius (rc) to the waveguide width (a). In the millimeter-wave / terahertz band, due to the limitation of electron beam focusing capability, the electron beam channel radius (rc) accounts for a larger proportion of the waveguide width (a), leading to more intense dispersion. Therefore, when conventional folded waveguide slow-wave structures are applied to broadband millimeter-wave / terahertz band TWTs, in order to obtain sufficient bandwidth, the operating point is usually chosen after a phase shift of 540°. This results in a smaller coupling impedance, limiting the output power, gain, and electronic efficiency of the TWT. Summary of the Invention

[0005] To address the aforementioned problems, this invention provides a bimodal hyperbolic cosine waveguide slow wave structure to solve the problem that conventional folded waveguide slow wave structures, in order to ensure sufficient operating bandwidth, have a relatively late phase shift corresponding to the operating point, resulting in low coupling impedance and limiting the output power, gain, and electronic efficiency of the traveling wave tube.

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

[0007] This invention provides a bimodal hyperbolic cosine waveguide slow wave structure, comprising multiple upper gratings and multiple lower gratings arranged in an alternating manner; and an electron beam channel; the slow wave structure further includes a cavity structure defined by each upper grating and each lower grating; the cavity structure includes upper curved waveguide segments and lower curved waveguide segments forming multiple periodic structures; the connected upper curved waveguide segments and lower curved waveguide segments are arranged in a centrally symmetrical manner;

[0008] Both the upper curved waveguide segment and the lower curved waveguide segment include a boundary line, which is a hyperbolic cosine curve.

[0009] The boundary line satisfies the following functional relationship:

[0010] ((-cosh(2×(-t) / (pb)))+cosh(1)) / (cosh(1)-cosh(0))×H,

[0011] Where t∈[-(p+b) / 2,(p+b) / 2], p is the half-cycle length of the slow wave structure, b is the cavity width of the cavity structure on the electron beam channel axis, and H is the vertical distance between the peak endpoint of the boundary line and the electron beam channel axis.

[0012] In a preferred embodiment, the upper curved waveguide segment is connected to the lower curved waveguide segment at both ends along the axial direction of the electron beam channel, and the connection point is on the axial direction of the electron beam channel.

[0013] A preferred embodiment is that the boundary line includes an outer boundary and an inner boundary, the vertical distance between the peak endpoint of the outer boundary and the axis of the electron beam channel is H1, the vertical distance between the peak endpoint of the inner boundary and the axis of the electron beam channel is H2, and the radius of the electron beam channel is r. c H1>H2≥r c .

[0014] The preferred solution is,

[0015] The outer boundary satisfies the following functional relationship:

[0016] ((-cosh(2×(-t) / (pb)))+cosh(1)) / (cosh(1)-cosh(0))×H1;

[0017] The inner boundary satisfies the following functional relationship:

[0018] ((-cosh(2×(-t) / (pb)))+cosh(1)) / (cosh(1)-cosh(0))×H2.

[0019] A preferred embodiment is that the line connecting the peak endpoints of the inner boundary and the peak endpoints of the outer boundary is orthogonal to the axis of the electron injection channel.

[0020] A preferred embodiment is that the electron injection channel is a circular cross-section channel.

[0021] A preferred embodiment is that the slow-wave structure is applied to traveling-wave tubes in the millimeter-wave and terahertz frequency bands.

[0022] The present invention also provides a traveling wave tube, comprising the slow wave structure of the bimodal hyperbolic cosine waveguide described above.

[0023] This invention also provides a method for designing a slow-wave structure of a bimodal hyperbolic cosine waveguide, the method comprising:

[0024] Design an initial folded waveguide slow wave structure, which includes a connected upper folded waveguide segment, a lower folded waveguide segment, and an electron beam channel. The connected upper folded waveguide segment and lower folded waveguide segment are arranged in a centrally symmetrical manner.

[0025] Using three-dimensional electromagnetic field simulation software, the boundary lines of the upper and lower curved waveguide segments are designed as hyperbolic cosine curves, and the boundary lines satisfy the following functional relationship:

[0026] ((-cosh(2×(-t) / (pb)))+cosh(1)) / (cosh(1)-cosh(0))×H,

[0027] Where t∈[-(p+b) / 2,(p+b) / 2], p is the half-cycle length of the slow wave structure, b is the cavity width of the cavity structure on the electron beam channel axis, and H is the vertical distance between the peak endpoint of the boundary line and the electron beam channel axis.

[0028] A preferred embodiment is that the boundary line includes an outer boundary and an inner boundary, the vertical distance between the peak endpoint of the outer boundary and the axis of the electron beam channel is H1, the vertical distance between the peak endpoint of the inner boundary and the axis of the electron beam channel is H2, and the radius of the electron beam channel is r. c H1>H2≥r c .

[0029] The beneficial effects of this invention are as follows:

[0030] For broadband millimeter-wave / terahertz traveling wave tubes (TWTs), compared to conventional folded waveguide slow-wave structures, the slow-wave structure of this invention can operate before a phase shift of 540° while maintaining the same operating frequency band, thus exhibiting greater coupling impedance and improving the TWT's output power, gain, and electronic efficiency. Within the 207 GHz to 232 GHz operating frequency band, the axial coupling impedance of the bimodal hyperbolic cosine waveguide slow-wave structure of this invention is more than 60% higher than that of a conventional folded waveguide slow-wave structure with the same in-band phase velocity.

[0031] The bimodal hyperbolic cosine waveguide slow wave structure 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] Figure 1A This is one of the structural schematic diagrams of a conventional folded waveguide slow wave structure.

[0034] Figure 1B This is the second schematic diagram of a conventional folded waveguide slow wave structure.

[0035] Figure 1C This is the third schematic diagram of a conventional folded waveguide slow wave structure.

[0036] Figure 2A This is one of the structural schematic diagrams of the slow wave structure of the bimodal hyperbolic cosine waveguide of the present invention.

[0037] Figure 2B This is the second schematic diagram of the slow wave structure of the bimodal hyperbolic cosine waveguide of the present invention.

[0038] Figure 2C This is the third schematic diagram of the slow wave structure of the bimodal hyperbolic cosine waveguide of the present invention.

[0039] Figure 3 This is a graph showing the dispersion characteristics of the slow-wave structure of the bimodal hyperbolic cosine waveguide of the present invention.

[0040] Figure 4 This is a comparison diagram of the phase light velocity ratio between the bimodal hyperbolic cosine waveguide slow wave structure of the present invention and a conventional folded waveguide slow wave structure with the same in-band phase velocity.

[0041] Figure 5 This is a comparison diagram of the dispersion characteristics of the bimodal hyperbolic cosine waveguide slow wave structure of the present invention and a conventional folded waveguide slow wave structure with the same in-band phase velocity.

[0042] Figure 6 This is a comparison diagram of the coupling impedance of the bimodal hyperbolic cosine waveguide slow wave structure of the present invention and a conventional folded waveguide slow wave structure with the same in-band phase velocity. Detailed Implementation

[0043] 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.

[0044] 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.

[0045] 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.

[0046] 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.

[0047] 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.

[0048] To improve the output power, gain, and electronic efficiency of a traveling wave tube (TWT) by achieving a relatively forward operating point and higher coupling impedance without increasing structural complexity or fabrication difficulty, and while maintaining the same bandwidth, this invention provides a bimodal hyperbolic cosine waveguide slow-wave structure. This slow-wave structure is applied to TWTs in the millimeter-wave and terahertz frequency bands, combined with… Figures 2A to 6 As shown, the bimodal hyperbolic cosine waveguide slow-wave structure specifically includes multiple upper gratings and multiple lower gratings arranged in an alternating pattern, as well as an electron beam channel 13, which is a circular cross-section channel. The slow-wave structure also includes a cavity structure defined by each upper grating and each lower grating. The cavity structure includes upper curved waveguide segments 11 and lower curved waveguide segments 12 forming multiple periodic structures. The connected upper curved waveguide segments 11 and lower curved waveguide segments 12 are arranged in a centrally symmetrical manner.

[0049] Furthermore, both the upper curved waveguide segment 11 and the lower curved waveguide segment 12 include boundary lines, which are hyperbolic cosine curves. The boundary lines satisfy the following functional relationship:

[0050] ((-cosh(2×(-t) / (pb)))+cosh(1)) / (cosh(1)-cosh(0))×H,

[0051] Where t∈[-(p+b) / 2,(p+b) / 2], p is the half-cycle length of the slow wave structure, b is the cavity width of the cavity structure on the electron beam channel axis L, and H is the vertical distance between the peak endpoint of the boundary line and the electron beam channel axis L.

[0052] In the above embodiment, the upper curved waveguide segment 11 is connected to the lower curved waveguide segment 12 at both ends along the electron beam channel axis, and the connection point is on the electron beam channel axis L. More specifically, refer to... Figure 2B As shown, the connection points between one end of the upper curved waveguide segment 11 and the lower curved waveguide segment 12 are Q1 and Q2, respectively, and both Q1 and Q2 are located on the electron beam channel axis L. Similarly, the connection points between the other end of the upper curved waveguide segment and the lower curved waveguide segment are also located on the electron beam channel axis L.

[0053] In one specific embodiment, combined with Figure 2B As shown, the boundary line includes an outer boundary C1 and an inner boundary C2. The perpendicular distance between the peak endpoint of the outer boundary C1 and the electron beam channel axis L is H1, and the perpendicular distance between the peak endpoint of the inner boundary C2 and the electron beam channel axis L is H2. The radius of the electron beam channel is r. c H1>H2≥r c .

[0054] Furthermore, the line M connecting the peak endpoints of the inner boundary C2 and the outer boundary C1 is orthogonal to the electron beam channel axis. Within one period 2p, the slow wave structure is symmetrical about this line M.

[0055] The vertical distance between the peak endpoint of the outer boundary C1 and the electron beam channel axis L corresponds to the hyperbolic cosine curve function of the outer boundary C1, and the vertical distance between the peak endpoint of the inner boundary C2 and the electron beam channel axis L corresponds to the hyperbolic cosine curve function of the inner boundary C2.

[0056] More specifically, the outer boundary satisfies the following functional relationship:

[0057] ((-cosh(2×(-t) / (pb)))+cosh(1)) / (cosh(1)-cosh(0))×H1;

[0058] The inner boundary satisfies the following functional relationship:

[0059] ((-cosh(2×(-t) / (pb)))+cosh(1)) / (cosh(1)-cosh(0))×H2.

[0060] The inner and outer boundaries of the bimodal hyperbolic cosine waveguide slow-wave structure of this invention are both composed of deformation functions based on hyperbolic cosine functions. Here, 'a' represents the width of the wider side of the bimodal hyperbolic cosine waveguide slow-wave structure. 'b' represents the cavity width of the cavity structure on the electron beam channel axis L, which is the distance between the outer boundary C1 and the inner boundary C2 on the electron beam channel axis L, i.e., the distance between connection points Q1 and Q2. 'H1' represents the perpendicular distance between the peak endpoint of the outer boundary C1 and the electron beam channel axis L. 'H2' represents the perpendicular distance between the peak endpoint of the inner boundary C2 and the electron beam channel axis L. The geometric half-period of the bimodal hyperbolic cosine waveguide slow-wave structure is p, and the electron beam channel radius is r. c .

[0061] The specific structural dimensions (unit: mm) of the bimodal hyperbolic cosine waveguide slow-wave structure of this invention are listed below: Located in the G-band region, the dimensions of the bimodal hyperbolic cosine waveguide slow-wave structure are a = 0.844, b = 0.14, p = 0.26, H1 = 0.29, H2 = 0.14, r... c =0.12.

[0062] Reference Figures 1A-1C As shown in the figure, 'a' represents the wide side length of the conventional folded waveguide, 'b' represents the narrow side length of the conventional folded waveguide, the geometric half-period is 'p', the straight waveguide height is 'h', and the electron beam channel radius is 'r'. c The specific structural dimensions of a conventional folded waveguide slow-wave structure are as follows (unit: mm): a = 0.90, b = 0.16, p = 0.31, h = 0.26, r c =0.12.

[0063] The bimodal hyperbolic cosine waveguide slow-wave structure of this invention was simulated using the 3D electromagnetic software CST Microwave Studio. The dispersion curve and axial coupling impedance were calculated and compared with the cold characteristic parameters of a conventional folded waveguide slow-wave structure with the same phase velocity ratio within the operating frequency band. The simulation results and field distribution of the cold characteristics have been presented in [reference needed]. Figures 3-6 The Chinese side indicated that...

[0064] Figure 3 The dispersive characteristics of the slow-wave structure of the bimodal hyperbolic cosine waveguide of the present invention are illustrated. When the slow-wave structure of the present invention is used in a traveling wave tube operating in the dominant mode, and the operating mode is selected as the -1st spatial harmonic of intrinsic mode 2 with the operating point located between 360° and 720° phase shift, the optimal operating point is located before 540° phase shift, resulting in a higher coupling impedance at the same operating bandwidth. It is understood that this is only a preferred embodiment, and the selection of the operating mode includes, but is not limited to, intrinsic mode 2. When used in other types of devices, other operating modes and operating points can be selected as needed.

[0065] Figure 4 The diagram shows the phase velocity ratio between a bimodal hyperbolic cosine waveguide slow-wave structure and a conventional folded waveguide slow-wave structure with the same in-band phase velocity. Within the operating frequency band of 207 GHz to 232 GHz, the maximum difference between the two is less than 0.0003. Therefore, their operating bandwidths and operating voltages are essentially the same.

[0066] Figure 5This paper compares the dispersion characteristics of a bimodal hyperbolic cosine waveguide slow-wave structure and a conventional folded waveguide slow-wave structure with the same in-band phase velocity. For the bimodal hyperbolic cosine waveguide slow-wave structure, the operating frequency band of 207 GHz to 232 GHz lies between a phase shift of 475° and 535°; for the conventional folded waveguide slow-wave structure, the operating frequency band of 207 GHz to 232 GHz lies between a phase shift of 550° and 630°. Under the same operating bandwidth conditions, the operating point of this invention is further forward than that of the conventional folded waveguide slow-wave structure, resulting in higher coupling impedance.

[0067] Figure 6 The diagram shows a comparison of the coupling impedance between a bimodal hyperbolic cosine waveguide slow-wave structure and a conventional folded waveguide slow-wave structure with the same in-band phase velocity. Within the 207 GHz to 232 GHz operating frequency band, the axial coupling impedance of the bimodal hyperbolic cosine waveguide slow-wave structure is more than 60% higher than that of the conventional folded waveguide slow-wave structure with the same in-band phase velocity.

[0068] According to another aspect of the present invention, a traveling wave tube is also provided, which includes the bimodal hyperbolic cosine waveguide slow wave structure described above.

[0069] According to another aspect of the present invention, the present invention also provides a method for designing a bimodal hyperbolic cosine waveguide slow wave structure. The method includes: designing an initial folded waveguide slow wave structure, the initial folded waveguide slow wave structure including a connected upper curved waveguide segment 11, a lower curved waveguide segment 12, and an electron beam channel 13, wherein the connected upper curved waveguide segment 11 and lower curved waveguide segment 12 are arranged in a centrally symmetrical manner; and using three-dimensional electromagnetic field simulation software, designing the boundary lines of the upper curved waveguide segment 11 and the lower curved waveguide segment 12 as hyperbolic cosine curves and ensuring that the boundary lines satisfy the following functional relationship:

[0070] ((-cosh(2×(-t) / (pb)))+cosh(1)) / (cosh(1)-cosh(0))×H,

[0071] Where t∈[-(p+b) / 2,(p+b) / 2], p is the half-cycle length of the slow wave structure, b is the cavity width of the cavity structure on the electron beam channel axis L, and H is the vertical distance between the peak endpoint of the boundary line and the electron beam channel axis L.

[0072] Furthermore, the boundary line includes an outer boundary C1 and an inner boundary C2. The perpendicular distance between the peak endpoint of the outer boundary C1 and the electron beam channel axis L is H1, and the perpendicular distance between the peak endpoint of the inner boundary C2 and the electron beam channel axis L is H2. The electron beam channel radius is r. c H1>H2≥r c .

[0073] In summary, for broadband millimeter-wave / terahertz traveling wave tubes, compared to conventional folded waveguide slow-wave structures, the slow-wave structure of this invention can operate before a phase shift of 540° while maintaining the same operating frequency band, thus exhibiting greater coupling impedance and improving the traveling wave tube's output power, gain, and electronic efficiency. Within the 207GHz–232GHz operating frequency band, the axial coupling impedance of the bimodal hyperbolic cosine waveguide slow-wave structure of this invention is more than 60% higher than that of a conventional folded waveguide slow-wave structure with the same in-band phase velocity.

[0074] The bimodal hyperbolic cosine waveguide slow wave structure 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.

[0075] 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 slow-wave structure for a bimodal hyperbolic cosine waveguide, characterized in that, It includes multiple upper gratings and multiple lower gratings that are staggered with each other; and an electron beam channel; the slow wave structure also includes a cavity structure defined by each upper grating and each lower grating; the cavity structure includes upper curved waveguide segments and lower curved waveguide segments that form multiple periodic structures; the connected upper curved waveguide segments and lower curved waveguide segments are arranged in a centrally symmetrical manner; Both the upper curved waveguide segment and the lower curved waveguide segment include a boundary line, which is a hyperbolic cosine curve. The boundary line satisfies the following functional relationship: ， Where t∈[-(p+b) / 2,(p+b) / 2], p is the half-cycle length of the slow wave structure, b is the cavity width of the cavity structure on the electron beam channel axis, and H is the vertical distance between the peak endpoint of the boundary line and the electron beam channel axis. The upper curved waveguide segment is connected to the lower curved waveguide segment at both ends along the axial direction of the electron beam channel, and the connection point is on the axial direction of the electron beam channel. The boundary line includes an outer boundary and an inner boundary. The perpendicular distance between the peak endpoint of the outer boundary and the axis of the electron beam channel is H1, and the perpendicular distance between the peak endpoint of the inner boundary and the axis of the electron beam channel is H2. The radius of the electron beam channel is r. c H1>H2≥r c .

2. The slow-wave structure of the bimodal hyperbolic cosine waveguide according to claim 1, characterized in that, The outer boundary satisfies the following functional relationship: ； The inner boundary satisfies the following functional relationship: 。 3. The slow-wave structure of the bimodal hyperbolic cosine waveguide according to claim 1, characterized in that, The line connecting the peak endpoints of the inner boundary and the peak endpoints of the outer boundary is orthogonal to the axis of the electron injection channel.

4. The slow-wave structure of the bimodal hyperbolic cosine waveguide according to claim 1, characterized in that, The electron injection channel is a circular cross-section channel.

5. The slow-wave structure of the bimodal hyperbolic cosine waveguide according to claim 1, characterized in that, The slow-wave structure is applied to traveling-wave tubes in the millimeter-wave and terahertz frequency bands.

6. A traveling wave tube, characterized in that, Including the bimodal hyperbolic cosine waveguide slow wave structure as described in any one of claims 1-5.

7. A method for designing a slow-wave structure of a bimodal hyperbolic cosine waveguide, characterized in that, The method includes: Design an initial folded waveguide slow wave structure, which includes a connected upper folded waveguide segment, a lower folded waveguide segment, and an electron beam channel. The connected upper folded waveguide segment and lower folded waveguide segment are arranged in a centrally symmetrical manner. Using three-dimensional electromagnetic field simulation software, the boundary lines of the upper and lower curved waveguide segments are designed as hyperbolic cosine curves, and the boundary lines satisfy the following functional relationship: ， Where t∈[-(p+b) / 2,(p+b) / 2], p is the half-cycle length of the slow wave structure, b is the cavity width of the cavity structure on the electron beam channel axis, and H is the vertical distance between the peak endpoint of the boundary line and the electron beam channel axis. The upper curved waveguide segment is connected to the lower curved waveguide segment at both ends along the axial direction of the electron beam channel, and the connection point is on the axial direction of the electron beam channel. The boundary line includes an outer boundary and an inner boundary. The perpendicular distance between the peak endpoint of the outer boundary and the axis of the electron beam channel is H1, and the perpendicular distance between the peak endpoint of the inner boundary and the axis of the electron beam channel is H2. The radius of the electron beam channel is r. c H1>H2≥r c .

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