Improved trapezoidal line slow wave structure and traveling wave tube

Abstract

The application discloses an improved trapezoidal line slow wave structure and a traveling wave tube. The slow wave structure comprises a straight waveguide section, the straight waveguide section comprises a first coupling groove, a second coupling groove and an electron beam channel located in the middle of the first coupling groove and the second coupling groove along the direction of the central axis of the straight waveguide section; the width of the first coupling groove and the second coupling groove alternately changes on two adjacent metal plates of the slow wave structure, the transmission path of electromagnetic waves in the slow wave structure is prolonged, the phase velocity of electromagnetic waves in the slow wave structure is reduced, and then the bandwidth is extended. The traveling wave tube comprises the improved trapezoidal line slow wave structure. The application has the advantages of easy processing, good heat dissipation, wider bandwidth, higher coupling impedance and lower ohmic loss in the terahertz wave band, and solves the problems of narrow bandwidth, lower coupling impedance and larger loss of the traditional trapezoidal line slow wave structure.

Description

Technical Field

[0001] This invention relates to the field of microwave vacuum electronics technology, and more specifically to a modified trapezoidal line slow wave structure for use in traveling wave tubes. Background Technology

[0002] The millimeter-wave (MMW) region has garnered increasing attention from academia and industry, particularly in applications such as space communication, chemical spectroscopy, and biomedical imaging. However, the lack of high-performance millimeter-wave sources limits its widespread application. High power, a wide operating bandwidth, and high electronic efficiency are highly advantageous, even essential, for millimeter-wave power amplifiers, highlighting the strengths of vacuum electronic devices (VEDs) compared to solid-state circuits.

[0003] Among the various components of a traveling wave tube (TWT), the slow-wave structure, as the primary site for energy exchange between electromagnetic waves and the electron beam, largely determines the TWT's amplification performance. Among the many high-frequency characteristics of the slow-wave structure, the interaction impedance indicates the degree of energy exchange between the electromagnetic waves and the electron beam, ohmic loss represents the loss of electromagnetic waves during transmission, and the dispersion bandwidth represents the operating frequency range.

[0004] Trapezoidal slow-wave lines, as a type of coupled-cavity slow-wave structure, have the advantages of simple structure, low cost, large power capacity, and good heat dissipation, making them very suitable for use in high-power traveling-wave tubes in the millimeter-wave band.

[0005] However, the biggest drawback of traditional trapezoidal slow-wave lines is their extremely narrow bandwidth; furthermore, as the operating frequency reaches the millimeter wave or even terahertz band, the coupling impedance of the slow-wave structure decreases and the ohmic loss increases, which greatly reduces the amplification performance of the traveling wave tube. Summary of the Invention

[0006] The technical problem this invention aims to solve is the narrow bandwidth, low coupling impedance, and high loss inherent in traditional trapezoidal slow-wave lines. The purpose of this invention is to provide an improved trapezoidal slow-wave structure and traveling-wave tube. Based on the traditional trapezoidal structure, this invention utilizes the characteristic that the width of the cross-sectional dimension affects the cutoff frequency of electromagnetic wave propagation. By alternately changing the widths of the upper and lower coupling slots, the phase velocity of the electromagnetic wave in the slow-wave structure is reduced, thereby achieving bandwidth extension. This structure offers advantages in the terahertz band, including ease of fabrication, good heat dissipation, wider bandwidth, higher coupling impedance, and lower ohmic loss.

[0007] This invention is achieved through the following technical solution:

[0008] In a first aspect, the present invention provides an improved trapezoidal slow-wave structure, which includes a straight waveguide section, the straight waveguide section including a first coupling slot, a second coupling slot, and an electron beam channel located between the first coupling slot and the second coupling slot along the central axis of the straight waveguide section; on two adjacent metal plates of the slow-wave structure, the widths of the first coupling slot and the second coupling slot alternately change, thereby extending the transmission path of electromagnetic waves in the slow-wave structure, reducing the phase velocity of electromagnetic waves in the slow-wave structure, and thus achieving bandwidth extension.

[0009] Building upon the traditional trapezoidal line structure, this invention leverages the characteristic that the width of the cross-sectional dimension affects the cutoff frequency of electromagnetic wave propagation. By alternately altering the widths of the upper and lower coupling slots (i.e., the first coupling slot and the second coupling slot), the propagation path of electromagnetic waves in the slow-wave structure is extended, and the phase velocity of electromagnetic waves in the slow-wave structure is reduced, thereby achieving bandwidth extension. This solves the problems of narrow bandwidth, low coupling impedance, and high loss in traditional trapezoidal slow-wave lines.

[0010] Furthermore, the straight waveguide segment is a straight rectangular waveguide.

[0011] Furthermore, the first coupling slot and the second coupling slot are rectangular, elliptical, or polygonal in shape.

[0012] Furthermore, when the first coupling slot and the second coupling slot are rectangular in shape, the widths of the first coupling slot and the second coupling slot on two adjacent metal plates of the slow-wave structure are:

[0013] On the first metal plate, the width of the first coupling groove is A1, and the width of the second coupling groove is A2;

[0014] On the second metal plate, the width of the first coupling groove is A2, and the width of the second coupling groove is A1;

[0015] In this case, A1 is not equal to A2.

[0016] Furthermore, the first coupling slot is located at the top of the straight waveguide section, and the second coupling slot is located at the bottom of the straight waveguide section;

[0017] Alternatively, the first coupling slot can be located at a certain distance from the metal at the top of the straight waveguide section, and the second coupling slot can be located at a certain distance from the metal at the bottom of the straight waveguide section.

[0018] Furthermore, the number of first coupling slots is at least one, and the number of second coupling slots is at least one.

[0019] Furthermore, the electron beam channel is a strip-shaped channel, which has significant performance advantages and potential application value compared to the traditional circular electron beam channel. The strip-shaped electron beam channel has a larger electron beam cross-sectional area, which can carry a larger operating current and increase the output power capacity of the device. Moreover, the strip-shaped electron beam channel has a simple structure and is easy to assemble, which is conducive to the implementation of current microfabrication technology.

[0020] Furthermore, the electron beam channel is either a circular channel or an elliptical channel.

[0021] Furthermore, there is at least one electron beam channel.

[0022] Secondly, the present invention provides a traveling wave tube, which includes the aforementioned modified trapezoidal slow wave structure.

[0023] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0024] 1. Based on the traditional trapezoidal structure, this invention utilizes the characteristic that the width of the cross-sectional dimension affects the cutoff frequency of electromagnetic wave transmission. By alternating the widths of the upper and lower coupling slots, the phase velocity of electromagnetic waves in the slow-wave structure is reduced. It is foreseeable that the slow-wave structure of this invention can achieve a wider bandwidth when used in traveling wave tubes.

[0025] 2. Simulation data shows that the present invention can achieve high coupling impedance over a wide bandwidth. It is foreseeable that the slow-wave structure of the present invention, when used in traveling-wave tubes, can achieve more efficient beam-wave interaction, resulting in greater power output and higher electronic efficiency.

[0026] 3. Simulation data shows that this invention can achieve lower ohmic losses over a wider bandwidth. It is foreseeable that the slow-wave structure of this invention, when used in traveling-wave tubes, can achieve greater power output and higher electronic efficiency.

[0027] 4. This invention employs a strip-shaped electron beam channel, which offers significant performance advantages and potential application value compared to traditional circular electron beam channels. The strip-shaped electron beam channel has a larger electron beam cross-sectional area, allowing for the loading of larger operating currents and increasing the device's output power capacity. Furthermore, the strip-shaped electron beam channel has a simple structure and is easy to assemble, facilitating implementation with current microfabrication technologies. Attached Figure Description

[0028] The accompanying drawings, which are included to provide a further understanding of embodiments of the invention and form part of this application, do not constitute a limitation thereof. In the drawings:

[0029] Figure 1 A diagram of a single-period vacuum model of a traditional trapezoidal slow-wave line;

[0030] Figure 2This is a single-period vacuum model diagram of the improved trapezoidal slow-wave structure of the present invention;

[0031] Figure 3 A single-period metal model diagram of a traditional trapezoidal slow wave line;

[0032] Figure 4 This is a single-period metal model diagram of the improved trapezoidal slow-wave structure of the present invention;

[0033] Figure 5 A three-layer anatomical diagram of a single-period metallic model of a traditional trapezoidal slow wave line;

[0034] Figure 6 This is a three-layer anatomical diagram of a single-period metal model of the improved trapezoidal slow-wave structure of the present invention.

[0035] Figure 7 This is a top sectional view of the single-layer modified trapezoidal slow-wave structure of the present invention;

[0036] Figure 8 This is a three-dimensional diagram of the improved trapezoidal line slow wave structure of the present invention;

[0037] Figure 9 This is a diagram showing the electric field intensity distribution of a traditional trapezoidal slow-wave line.

[0038] Figure 10 This is a diagram showing the electric field intensity distribution of the improved trapezoidal slow-wave structure of the present invention.

[0039] Figure 11 Dispersion characteristic curves of traditional trapezoidal slow-wave lines and modified trapezoidal slow-wave structures;

[0040] Figure 12 The coupling impedance curves are those of a traditional trapezoidal slow-wave line and a modified trapezoidal slow-wave structure.

[0041] Figure 13 The loss characteristic curves are those of the traditional trapezoidal slow wave line and the improved trapezoidal slow wave line structure.

[0042] Figure reference numerals and corresponding component names:

[0043] 1-First coupling slot, 2-Second coupling slot, 3-Electron beam channel, 4-Metal grid. Detailed Implementation

[0044] In the following, the terms “comprising” or “may include” as used in various embodiments of the invention indicate the presence of an inventive function, operation, or element, and do not limit the addition of one or more functions, operations, or elements. Furthermore, as used in various embodiments of the invention, the terms “comprising,” “having,” and their cognates are intended only to indicate a specific feature, number, step, operation, element, component, or combination of the foregoing, and should not be construed as primarily excluding the presence of one or more other features, numbers, steps, operations, elements, components, or combinations of the foregoing, or adding one or more combinations of the foregoing.

[0045] In various embodiments of the invention, the expression "or" or "at least one of A and / or B" includes any combination or all combinations of the words listed simultaneously. For example, the expression "A or B" or "at least one of A and / or B" may include A, may include B, or may include both A and B.

[0046] The expressions used in the various embodiments of the present invention (such as "first," "second," etc.) may modify various constituent elements in the various embodiments, but do not limit the corresponding constituent elements. For example, the above expressions do not limit the order and / or importance of the elements. The above expressions are only used for the purpose of distinguishing one element from other elements. For example, a first user device and a second user device refer to different user devices, although both are user devices. For example, a first element may be referred to as a second element without departing from the scope of the various embodiments of the present invention, and similarly, a second element may also be referred to as a first element.

[0047] It should be noted that if a description is made of "connecting" one component to another, then the first component can be directly connected to the second component, and a third component can be "connected" between the first and second components. Conversely, when a component is "directly connected" to another component, it can be understood that there is no third component between the first and second components.

[0048] The terminology used in the various embodiments of the invention is for the purpose of describing particular embodiments only and is not intended to limit the various embodiments of the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which the various embodiments of the invention pertain. The terms (such as those defined in a generally used dictionary) are to be interpreted as having the same meaning as in the context of the relevant technical field and are not to be interpreted as having an idealized or overly formal meaning, unless clearly defined in the various embodiments of the invention.

[0049] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the embodiments and accompanying drawings. The illustrative embodiments and descriptions of the present invention are only used to explain the present invention and are not intended to limit the present invention.

[0050] Example 1

[0051] like Figures 1 to 13 As shown, Figure 1 This is a traditional trapezoidal slow-wave line, which is a straight line. A traditional trapezoidal slow-wave line includes a straight waveguide section, which is a straight rectangular waveguide. The straight waveguide section consists of two coupling slots (first coupling slot 1 and second coupling slot 2) running vertically through a series of metal plates, and an electron beam channel 3 located between the first coupling slot 1 and the second coupling slot 2, along the central axis of the straight waveguide section. The remaining portion of the metal plate after the slots are cut out forms a metal grid 4. The electron beam propagates along the electron beam channel 3. The width of both the first coupling slot 1 and the second coupling slot 2 is A1.

[0052] Building upon the traditional trapezoidal line structure, this invention leverages the characteristic that the width of the cross-sectional dimension affects the cutoff frequency of electromagnetic wave propagation. By alternately altering the widths of the upper and lower coupling slots (i.e., the first coupling slot and the second coupling slot), the propagation path of electromagnetic waves in the slow-wave structure is extended, and the phase velocity of electromagnetic waves in the slow-wave structure is reduced, thereby achieving bandwidth extension. This solves the problems of narrow bandwidth, low coupling impedance, and high loss in traditional trapezoidal slow-wave lines.

[0053] like Figure 2 As shown, this invention discloses an improved trapezoidal slow-wave structure. The slow-wave structure includes a straight waveguide section, comprising a first coupling slot 1, a second coupling slot 2, and an electron beam channel 3 located between the first coupling slot 1 and the second coupling slot 2 along the central axis of the straight waveguide section. On two adjacent metal plates of the slow-wave structure, the widths of the first coupling slot 1 and the second coupling slot 2 alternate. Specifically, on the first metal plate, the widths of the first coupling slot 1 and the second coupling slot 2 are: A1 and A2 on the first metal plate; and A2 and A1 on the second metal plate. Wherein, A1 is not equal to A2. This extends the transmission path of electromagnetic waves in the slow-wave structure, reduces the phase velocity of electromagnetic waves in the slow-wave structure, and thus achieves bandwidth extension. This solves the problems of narrow bandwidth, low coupling impedance, and high loss in traditional trapezoidal slow-wave lines.

[0054] As a further implementation, the first coupling groove 1 and the second coupling groove 2 are rectangular, elliptical, or polygonal in shape.

[0055] As a further implementation, the first coupling groove 1 is located at the top of the straight waveguide section, and the second coupling groove 2 is located at the bottom of the straight waveguide section; or the first coupling groove 1 is located at a certain distance from the metal at the top of the straight waveguide section, and the second coupling groove 2 is located at a certain distance from the metal at the bottom of the straight waveguide section.

[0056] As a further implementation, the electron beam channel is a strip channel, which has significant performance advantages and potential application value compared to the traditional circular electron beam channel. The strip electron beam channel has a larger electron beam cross-sectional area, can load a larger operating current, and increases the output power capacity of the device. Moreover, the strip electron beam channel has a simple structure and is easy to assemble, which is conducive to the implementation of current microfabrication technology. Of course, circular or elliptical channels can also be used.

[0057] As a further implementation, the number of first coupling slots 1 is at least one, and the number of second coupling slots 2 is at least one. This invention... Figure 2 , Figure 4 , Figure 6 , Figure 7 and Figure 8 This illustration only shows the case where there is one first coupling slot 1 and one second coupling slot 2. Of course, it is also possible for there to be multiple first coupling slots 1 and multiple second coupling slots 2.

[0058] As a further implementation, there is at least one electron beam channel. This invention Figure 2 , Figure 4 , Figure 6 , Figure 7 and Figure 8 This illustration only shows the case with one electron beam channel. Of course, the electron beam channel is not limited to one; two or more channels are also possible. When there are two electron beam channels, the two electron beam channels are axially symmetrical along the central axis of the straight waveguide section.

[0059] Building upon the traditional trapezoidal slow-wave line, this invention leverages the characteristic that the width of the cross-sectional dimension affects the cutoff frequency of electromagnetic wave propagation. By alternately altering the widths of the upper and lower coupling slots, the phase velocity of the electromagnetic wave in the slow-wave structure is reduced, thereby achieving bandwidth extension. High-frequency characteristic calculations show that this invention significantly offers advantages such as wider bandwidth, higher coupling impedance, and lower ohmic loss. It overcomes the shortcomings of traditional trapezoidal slow-wave lines, which suffer from narrow bandwidth, low coupling impedance, and high loss.

[0060] This embodiment also proposes a traveling wave tube, which includes the aforementioned modified trapezoidal slow wave structure.

[0061] Example 2

[0062] like Figures 1 to 13As shown, this embodiment compares the high-frequency electromagnetic characteristics of an improved trapezoidal slow-wave structure proposed in Embodiment 1 with those of a traditional trapezoidal slow-wave line through simulation.

[0063] Among them, the simulation data includes the traditional ladder circuit (TLC) and the improved ladder circuit (NLC).

[0064] Figure 1 This is a single-period vacuum model of a traditional trapezoidal slow wave line. Figure 1 The model shown is made of vacuum material. Figure 1 In the diagram, W represents the maximum width of the structure (0.2 mm), H represents the maximum height of the structure (0.87 mm), B1 represents the hole depth of the first coupling groove 1 and the second coupling groove 2 (0.225 mm), S1 represents the thickness of the first coupling groove 1 and the second coupling groove 2 (0.3 mm), S2 represents the thickness of the metal grid (0.25 mm), Tx represents the width of the electron beam channel (0.8 mm), Ty represents the height of the electron beam channel (0.15 mm), and the width of both the first coupling groove 1 and the second coupling groove 2 is A1, which is 0.17 mm.

[0065] Figure 2 This is a single-period vacuum model for an improved trapezoidal slow-wave structure. Figure 2 The model shown is made of vacuum material. Figure 2 In the diagram, W represents the maximum width of the structure (0.2 mm), H represents the maximum height of the structure (0.87 mm), B1 represents the hole depth of the first coupling groove 1 and the second coupling groove 2 (0.225 mm), S1 represents the thickness of the first coupling groove 1 and the second coupling groove 2 (0.3 mm), S2 represents the thickness of the metal grid 4 (0.25 mm), Tx represents the electron beam channel width (0.8 mm), Ty represents the electron beam channel height (0.15 mm), A1 represents the maximum width of the first coupling groove 1 (1.7 mm), and A2 represents the maximum groove width of the second coupling groove 2 (0.4 mm).

[0066] Figure 3 This is a single-period metal model of a traditional trapezoidal slow wave line. Figure 3 The model shown is made of high-conductivity oxygen-free copper with a surface roughness of 1 μm.

[0067] Figure 4 This is a single-period metal model of an improved trapezoidal slow-wave structure. Figure 4 The model shown is made of high-conductivity oxygen-free copper with a surface roughness of 1 μm.

[0068] Figure 5 This is a three-layer anatomical diagram of a single-period metal model of a traditional trapezoidal slow wave line. Figure 6 A three-layer anatomical diagram of a single-period metallic model of a modified trapezoidal slow-wave structure, and... Figure 5The difference is that the widths of the first coupling groove 1 and the second coupling groove 2 change alternately.

[0069] Figure 7 A top-view cross-sectional view of a modified trapezoidal slow-wave structure. The widths of the first coupling groove 1 alternately change between A1 and A2, and the widths of the second coupling groove 2 alternately change between A2 and A1. Figure 8 This is a three-dimensional diagram of the improved trapezoidal line slow wave structure of the present invention.

[0070] Figure 9 This is a diagram showing the electric field intensity distribution of a traditional trapezoidal slow-wave line. Figure 10 This is the electric field intensity distribution diagram of the improved trapezoidal slow-wave structure, and... Figure 9 The comparison reveals that, within the same scale range, the present invention clearly exhibits an electromagnetic wave cutoff state, proving that the present invention can extend the electromagnetic wave transmission path and reduce the phase velocity of electromagnetic waves in the slow-wave structure by alternating the widths of the upper and lower coupling slots.

[0071] Figure 11 The figures show the dispersion characteristics of a traditional trapezoidal slow-wave line and a modified trapezoidal slow-wave line structure. The results show that the bandwidth of the comparative structure is approximately 81 GHz to 86 GHz (5 GHz), while the bandwidth of this invention is 83 GHz to 131 GHz (48 GHz), demonstrating that dispersion can occur over a wider frequency range. Furthermore, the normalized phase velocity is relatively flat in the 95 GHz to 125 GHz frequency range, proving that this invention can amplify electromagnetic waves over a wider frequency range.

[0072] Figure 12 The figures show the coupling impedance curves of a traditional trapezoidal slow-wave line and a modified trapezoidal slow-wave line structure. The results show that the present invention exhibits significantly higher coupling impedance in the 84GHz-131GHz frequency band, demonstrating that the invention not only has a wider operating bandwidth but also achieves higher gain, greater output power, and higher electronic efficiency.

[0073] Figure 13 The figures show the loss characteristics of a traditional trapezoidal slow-wave line and a modified trapezoidal slow-wave line structure. The results show that the present invention exhibits significantly lower ohmic loss in the 84GHz-131GHz frequency band, demonstrating that the invention can achieve higher gain, greater output power, and higher electronic efficiency when operating in millimeter-wave and even terahertz frequency bands.

[0074] Therefore, through simulation comparison calculations, the present invention clearly has the advantages of wider bandwidth, higher coupling impedance and lower ohmic loss.

[0075] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. An improved trapezoidal slow-wave structure, the slow-wave structure comprising a straight waveguide section, the straight waveguide section comprising a first coupling slot (1), a second coupling slot (2), and an electron beam channel (3) located between the first coupling slot (1) and the second coupling slot (2) along the central axis of the straight waveguide section; characterized in that, On two adjacent metal plates of the slow wave structure, the widths of the first coupling slot (1) and the second coupling slot (2) change alternately, which prolongs the transmission path of electromagnetic waves in the slow wave structure, reduces the phase velocity of electromagnetic waves in the slow wave structure, and thus realizes bandwidth extension. The first coupling groove (1) and the second coupling groove (2) are rectangular in shape. On two adjacent metal plates of the slow wave structure, the widths of the first coupling groove (1) and the second coupling groove (2) are: On the first metal plate, the width of the first coupling groove (1) is A1, and the width of the second coupling groove (2) is A2; On the second metal plate, the width of the first coupling groove (1) is A2, and the width of the second coupling groove (2) is A1; In this case, A1 is not equal to A2.

2. The improved trapezoidal line slow-wave structure according to claim 1, characterized in that, The straight waveguide segment is a straight rectangular waveguide.

3. A modified trapezoidal line slow-wave structure according to any one of claims 1-2, characterized in that, The first coupling groove (1) is located at the top of the straight waveguide section, and the second coupling groove (2) is located at the bottom of the straight waveguide section.

4. A modified trapezoidal line slow-wave structure according to any one of claims 1-2, characterized in that, The number of the first coupling slot (1) is at least one, and the number of the second coupling slot (2) is at least one.

5. A modified trapezoidal line slow-wave structure according to any one of claims 1-2, characterized in that, The electron beam channel is a strip channel.

6. A modified trapezoidal line slow-wave structure according to any one of claims 1-2, characterized in that, The electron beam channel is either a circular channel or an elliptical channel.

7. A modified trapezoidal line slow-wave structure according to any one of claims 1-2, characterized in that, The electron beam channel is at least one.

8. A traveling wave tube, characterized in that, The traveling wave tube includes a modified trapezoidal slow wave structure as described in any one of claims 1-7.

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