Trapezoidal staggered gate slow wave structure of circular electron beam channel

Abstract

The utility model relates to the technical field of vacuum electronics, in particular to a trapezoidal staggered gate slow-wave structure of a circular electron beam channel, which comprises a metal shell, trapezoidal upper metal gates and trapezoidal lower metal gates which are symmetrically arranged in a staggered manner are arranged in the metal shell, and the upper metal gates and the lower metal gates are respectively provided with arc-shaped concave holes; along the electron transmission direction, the concave holes respectively penetrate through the upper metal gate and the lower metal gate, and the upper and lower concave holes are enclosed to form a circular electron beam channel. Through the slow-wave structure, the bandwidth of the slow-wave structure can be increased, so that the longitudinal electric field in the slow-wave structure is enhanced.

Description

Technical Field

[0001] This utility model relates to the field of vacuum electronics technology, and in particular to a slow-wave structure with trapezoidal staggered grids for a circular electron beam channel. Background Technology

[0002] The function of a traveling wave tube (TWT) is to amplify microwave signals. The microwave signal to be amplified enters the slow-wave circuit through an input energy coupler and travels along the slow-wave circuit. Electrons exchange energy with the traveling microwave field, amplifying the microwave signal. However, the introduction of higher-order modes causes instability in operation. The slow-wave structure is one of the key components of the TWT, and its high-frequency performance is crucial to the efficiency of the TWT. Common slow-wave structures include coupler slow-wave structures, helical slow-wave structures, zigzag waveguides, positive waveguides, and interlaced-grid slow-wave structures. Coupled-cavity slow-wave structures, zigzag waveguides, sinusoidal waveguides, and interlaced-grid slow-wave structures have all-metal structures and good heat dissipation. Helical slow-wave structures, due to their structural characteristics, have poor heat dissipation. Coupled-cavity slow-wave structures have high coupling impedance but narrow operating bandwidth. Furthermore, at high frequencies, the size of the slow-wave structure decreases. Due to its complex structure, coupled-cavity slow-wave structures are difficult to manufacture and assemble in small sizes, resulting in low yield. The tortuous waveguide has a wide operating bandwidth, is easy to manufacture, and has a simple input and output structure, but as the frequency band increases, the loss is high and the coupling impedance is not high.

[0003] Currently, millimeter-wave and terahertz devices based on vacuum electronics have significant advantages in terms of output power, operating bandwidth, and electronic efficiency, and are irreplaceable in high-frequency electronic equipment and other application systems. However, as the frequency increases, the wavelength becomes smaller, resulting in smaller device size and smaller size of high-frequency interaction systems. The design of critical dimensions affects the efficiency of the entire traveling wave tube.

[0004] Both helical and coupled cavity structures face challenges in fabrication due to their structural characteristics. Therefore, finding a high-performance traveling wave tube (TWT) slow-wave structure that can operate at high frequencies is crucial. The zigzag waveguide, as an all-metal slow-wave structure, offers advantages such as good heat dissipation, high power capacity, relatively simple input / output structure, and ease of fabrication, making it a promising high-power, small-scale radiation source in the terahertz range. However, the existing zigzag waveguide structure limits the bandwidth of its fundamental mode. Interlaced-grid slow-wave structures offer high coupling impedance and wide operating bandwidth, but the strip-shaped electron beam places high demands on the TWT's focusing system.

[0005] In the prior art, a Chinese invention patent document with publication number CN116598178A and publication date of August 15, 2023, was proposed. The technical solution disclosed in this patent document is as follows: a slow-wave device with a semi-periodic staggered trapezoidal concave end face grating, comprising: a rectangular waveguide housing, a periodic diffuse wave structure formed by gratings of semi-periodic staggered trapezoidal concave end faces loaded on the inner sides of the two wide sides of the rectangular waveguide housing, and an electron beam channel formed by the overlapping of the concave end faces of the gratings loaded on the inner sides of the two wide sides of the rectangular waveguide housing; when the slow-wave device is working, the phase velocity of the radio frequency signal input to the device along the central axis of the device is reduced by the gratings on both sides of the upper and lower wide sides of the rectangular waveguide housing, so that the radio frequency signal and the electron beam have similar travel speeds, thereby realizing that the electron beam exchanges DC energy during the interaction between the electron beam and the radio frequency signal, thereby completing the amplification of the radio frequency signal.

[0006] In the above technical solutions, the electron beam channel on a single metal grid is a complete rectangle or a complete circle, and the bandwidth of the slow-wave structure needs to be enhanced. Summary of the Invention

[0007] To address the aforementioned technical problems, this invention proposes a circular electron beam channel trapezoidal staggered grid slow-wave structure. Breaking with conventional thinking, the circular electron beam channel is formed by enclosing upper and lower concave holes, which can increase the bandwidth of the slow-wave structure. On the other hand, it can change the electric field distribution in the slow-wave structure, thereby enhancing the longitudinal electric field in the slow-wave structure.

[0008] This utility model is achieved by adopting the following technical solution:

[0009] A circular electron beam channel trapezoidal staggered grid slow wave structure includes a metal shell. Inside the metal shell are trapezoidal and staggered symmetrically arranged upper and lower metal grids. The upper and lower metal grids are respectively provided with arc-shaped concave holes. Along the electron transport direction, the concave holes pass through the upper and lower metal grids respectively, and the upper and lower concave holes enclose each other to form a circular electron beam channel.

[0010] The upper and lower metal grids overlap in the longitudinal direction.

[0011] The overlap distance b between the upper and lower metal grids in the longitudinal direction is less than the radius r of the circular electron beam channel.

[0012] The radius r of the circular electron beam channel satisfies the following condition: b <r<2*b。

[0013] The arrangement period of the upper and lower metal gates is p, and adjacent upper and lower metal gates are staggered by 1 / 4 of the arrangement period.

[0014] It also includes an input structure and an output structure, and both the input structure and the output structure respectively include two straight waveguide segments and a bent waveguide segment located between the two straight waveguide segments.

[0015] Compared with the prior art, the beneficial effects of the present utility model are manifested in:

[0016] 1. The present utility model breaks the conventional idea and the characteristic of setting a complete electron beam channel on a single metal grid, that is, the electron beam channel on a single metal grid is no longer a complete circle, but based on the symmetry of the upper metal grid and the lower metal grid, arc-shaped concave holes are respectively provided on the upper metal grid and the lower metal grid. From the propagation direction, the upper and lower concave holes enclose to form a complete circular electron beam channel. This structure can, on the one hand, increase the bandwidth of the slow-wave structure, and on the other hand, change the electric field distribution in the slow-wave structure, making the longitudinal electric field in the slow-wave structure enhanced. In addition, this kind of structure can have multiple modes and can also be used for the multi-mode operation of a traveling wave tube.

[0017] Based on the above structure, the effective area of the circular electron beam channel introduced in the present utility model is larger than that of the existing staggered grid ribbon electron beam channel, and is also larger than the electron beam channel radius of the meander waveguide. Moreover, compared with the electron beam channels in the prior art, it can focus better, has lower requirements for the magnetic field of the externally applied focusing system, and can solve the problems of high concentricity requirements for the externally applied magnetic field by the existing electron beam channels, easy electron beam distortion and splitting, and excessive edges during long-distance transmission.

[0018] 2. The upper metal grid and the lower metal grid overlap in the longitudinal direction, which can also increase the coupling impedance. In summary, the structure of the present utility model can not only increase the radius of the circular electron beam channel, but also is beneficial to increasing the bandwidth and coupling impedance of the slow-wave structure.

[0019] 3. In the present utility model, the overlapping distance of the upper metal grid and the lower metal grid in the longitudinal direction is less than the radius r of the circular electron beam channel, making the size of the circular electron beam channel in the present utility model larger and the effective area larger. At the same time, this structure can alleviate the problem of the need for excessive structure in the staggered grid traveling wave tube. This slow-wave structure has the characteristics of a part of the meander waveguide, which is beneficial to the transmission of electromagnetic waves, enabling its input structure and output structure to borrow the input and output structures of the meander waveguide, being simpler, having a smaller required length, and thus making the entire traveling wave tube smaller, which is beneficial to the miniaturization of the device.

[0020] 4. In the present utility model, the radius r of the circular electron beam channel satisfies the following condition: b < r < 2*b, which is set after comprehensively considering the influence of the coupling impedance, bandwidth and device processing difficulty of the slow-wave structure, and has strong practicability.

[0021] 5. In this utility model, the adjacent upper and lower metal gates are staggered by 1 / 4 of their arrangement period, which can reduce the overlap between high-order and low-order electric field modes in the staggered gate device. This allows only the required operating mode to be selected without other interfering electric field modes.

[0022] 6. The input and output structures of this utility model are simple and have good transmission performance. Attached Figure Description

[0023] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments, wherein:

[0024] Figure 1 This is a schematic diagram of the structure of the present invention. Figure 1 ;

[0025] Figure 2 This is a schematic diagram of the structure of the present invention. Figure 2 ;

[0026] Figure 3 This is a schematic diagram of the upper and lower metal grids in this utility model;

[0027] Figure 4 This is a schematic diagram showing the dimensions of the vacuum section model in this utility model;

[0028] Figure 5 This is a side view of the vacuum section model in this utility model;

[0029] Figure 6 This is a schematic diagram of the input structure in this utility model;

[0030] Figure 7 This is a schematic diagram of an interleaved grating slow wave structure in the prior art;

[0031] Figure 8 This is a tortuous waveguide diagram in the prior art;

[0032] Figure 9 This is a schematic diagram of the electric field distribution in an existing staggered-gate slow-wave structure.

[0033] Figure 10 This is a schematic diagram of the electric field distribution of the slow-wave structure of this utility model;

[0034] Figure 11 This is a schematic diagram of the electric field distribution in a tortuous waveguide in the prior art;

[0035] Figure 12 The simulation results of the dispersion characteristics of this utility model are shown in the figure.

[0036] Figure 13 The simulation results of the transmission characteristics of the traveling wave tube of this utility model are shown in the figure.

[0037] Figure 14 This is a schematic diagram comparing the coupling impedance of the slow wave structure, the staggered grating slow wave structure, and the tortuous waveguide in this embodiment;

[0038] Marked in the image:

[0039] 1. Metal shell, 2. Upper metal grid, 3. Lower metal grid, 4. Electron injection channel, 5. Recessed hole. Detailed Implementation

[0040] Example 1

[0041] As a basic embodiment of this utility model, the utility model includes a circular electron beam channel trapezoidal staggered grid slow wave structure, comprising a metal shell 1, within which are arranged trapezoidal upper metal grid 2 and lower metal grid 3 in a staggered and symmetrical manner. The upper metal grid 2 and lower metal grid 3 are each provided with an arc-shaped recess 5. Along the electron transport direction, the recess 5 penetrates both the upper metal grid 2 and lower metal grid 3. The central angle of each recess 5 is greater than or equal to 180° and less than 360°. Along the electron transport direction, the upper and lower recesses 5 enclose a circular electron beam channel 4.

[0042] Example 2

[0043] In a preferred embodiment of this utility model, the utility model includes a circular electron beam channel trapezoidal staggered grid slow wave structure, comprising a metal shell 1, within which are trapezoidal and symmetrically arranged upper metal grid 2 and lower metal grid 3. The upper metal grid 2 and lower metal grid 3 are each provided with an arc-shaped recess 5. The longitudinal distance between the upper metal grid 2 and lower metal grid 3 is 0, and the recess 5 is semi-circular with a central angle of 180°. Along the electron transport direction, the recess 5 penetrates both the upper metal grid 2 and lower metal grid 3, and the upper and lower semi-circular recesses 5 together form a circular electron beam channel 4.

[0044] Example 3

[0045] In another preferred embodiment of this utility model, the utility model includes a trapezoidal staggered grating slow-wave structure for a circular electron beam channel, comprising a metal shell 1, within which are trapezoidal and symmetrically arranged upper metal grating 2 and lower metal grating 3. The upper metal grating 2 and lower metal grating 3 overlap in the longitudinal direction. Arc-shaped recesses 5 are respectively provided on the upper metal grating 2 and lower metal grating 3. More specifically, the overlap distance b between the upper metal grating 2 and lower metal grating 3 in the longitudinal direction is less than the radius r of the circular electron beam channel 4.

[0046] Along the electron transport direction, the concave holes 5 penetrate the upper metal grid 2 and the lower metal grid 3 respectively, and the upper and lower concave holes 5 enclose a circular electron injection channel 4.

[0047] Example 4

[0048] As the best implementation mode of the present utility model, refer to the attached drawings of the specification Figure 1 and the attached drawings of the specification Figure 2 , the present utility model includes a circular electron beam channel trapezoidal staggered grid slow wave structure, including a metal shell 1, and upper metal grids 2 and lower metal grids 3 which are staggered and symmetrically arranged are provided inside the metal shell 1. Both the upper metal grid 2 and the lower metal grid 3 are trapezoidal, and the tops of the upper metal grid 2 and the lower metal grid 3 close to the electron beam channel 4 are the narrow sides of the trapezoid. The arrangement period of the upper metal grid 2 and the lower metal grid 3 is p, and the adjacent upper metal grid 2 and lower metal grid 3 are staggered by 1 / 4 of the arrangement period. Through the above arrangement, the overlap of the high-order mode and the low-order mode of the electric field in the staggered grid device can be reduced, so that only the required working mode can be selected, and there will be no other interfering electric field modes.

[0049] Refer to the attached drawings of the specification Figure 3 , the upper metal grid 2 and the lower metal grid 3 overlap in the longitudinal direction, so that the original electron beam disappears, which is convenient for increasing the coupling impedance. Further, a circular electron beam channel 4 with a large radius can be introduced to solve the focusing problem of the high-frequency band strip electron beam. The effective area of the introduced circular electron beam channel 4 is larger than that of the staggered grid strip electron beam channel 4, and also larger than the radius of the electron beam channel 4 of the zigzag waveguide. Specifically, openings are formed at the central positions of the tops of the upper metal grid 2 and the lower metal grid 3 to form arc-shaped concave holes 5. The central angle of the concave hole 5 is greater than 180° and less than 360°. Along the electron transmission direction, the concave hole 5 also penetrates through the upper metal grid 2 and the lower metal grid 3 respectively. Along the electron transmission direction, the upper and lower concave holes 5 enclose to form a circular electron beam channel 4 with a large radius.

[0050] Among them, the radius r of the circular electron beam channel 4 satisfies the following conditions: b < r < 2*b. Where b is the overlapping distance of the upper metal grid 2 and the lower metal grid 3 in the longitudinal direction. More specifically, refer to the attached drawings of the specification Figure 4 and the attached drawings of the specification Figure 5 , in this embodiment, the arrangement period p can be 4.1 mm, the height h of the upper metal grid 2 and the lower metal grid 3 is 3.4 mm, the inclined transverse value t of the upper metal grid 2 and the lower metal grid 3 is 0.6 mm, the width w of the slow wave structure is 7.8 mm, the width g of the upper metal grid 2 and the lower metal grid 3 close to the electron beam channel 4 is 0.8 mm, the overlapping distance b of the upper metal grid 2 and the lower metal grid 3 in the longitudinal direction is 0.6 mm, and the radius r of the electron beam channel 4 is 1.1 mm.

[0051] Through the above structure, the bandwidth range of the large circular electron beam channel 4 trapezoidal staggered grid slow wave structure is 22 - 28 GHz.

[0052] The dispersion characteristics of the slow-wave structure in this embodiment are simulated, as shown in the appendix to the specification. Figure 12 As can be seen, the bandwidth of the slow-wave structure in this embodiment can reach 5 GHz. The transmission characteristics of the traveling-wave tube in this embodiment are simulated, as shown in the appendix to the specification. Figure 13 It can be seen that the slow-wave structure in this embodiment has better transmission characteristics. Comparing the coupling impedance of the slow-wave structure in this embodiment with that of the interleaved time grating and the tortuous waveguide, see the appendix to the specification. Figure 14 It can be seen that the coupling impedance of the slow-wave structure in this embodiment is improved.

[0053] Furthermore, it also includes input and output structures. Through the overlapping structure of the upper metal grid 2 and the lower metal grid 3 in the longitudinal direction, and the introduction of a large-radius circular electron beam channel 4, the slow-wave structure of this invention possesses some characteristics of a tortuous waveguide, which is beneficial for electromagnetic wave transmission. The input and output structures can draw upon the input and output structures of tortuous waveguides and be modified accordingly. For details, please refer to the appendix to the specification. Figure 6 Both the input and output structures include two straight waveguide segments and a curved waveguide segment located between them. The curved waveguide segment has an inner radius of 2.85 mm, an outer radius R of 4.75 mm, and a width of 7.8 mm. The straight waveguide segment has a length of 3 mm, a width of 7.8 mm, and a height of 1.9 mm. This shorter required length results in a smaller overall traveling wave tube, which is beneficial for device miniaturization.

[0054] The slow-wave structure, the interlaced grating slow-wave structure, and the tortuous waveguide in this embodiment are compared with those in the appendix to this application specification. Figure 7 ~Instruction manual included Figure 11 In this embodiment, the slow-wave structure has a greater longitudinal electric field component within the electron beam channel 4, thus exhibiting a higher coupling impedance. Specifically, from the perspective of the electric field distribution of the staggered-gate slow-wave structure, the electric field energy of the staggered gates is mainly concentrated in the electron beam channel 4 between the upper and lower metal gates 3, as shown in the appendix to the specification. Figure 9 ~Instruction manual included Figure 11In region A, the electric field has a strong longitudinal component, while in region B, the electric field is mainly transverse. To increase the longitudinal electric field, one could: 1. Reduce the spacing between the upper and lower metal grids 3. However, this would reduce the electron beam size, hindering its transmission and causing many electrons to hit the metal walls, thus reducing the efficiency of the traveling wave tube. 2. Increase the area of ​​region A and decrease the area of ​​region B to obtain a greater longitudinal electric field. Therefore, this embodiment reduces the spacing between the upper and lower metal grids 3, causing them to overlap in the opposite longitudinal direction. Simultaneously, the shape of the upper and lower metal grids 3 is altered, causing the naturally occurring electron beam between the interlaced grids to disappear. Considering the high requirements of the focusing system for the strip electron beam, a large-radius circular electron beam channel 4 is introduced. Through the cooperation of the above structures, not only can the problem of strip electron beam aggregation be solved, but the performance of the traveling wave tube can also be improved.

[0055] In summary, any other corresponding modifications made by those skilled in the art based on the technical solution and concept of this utility model without creative mental effort after reading this utility model document are all within the scope of protection of this utility model.

Claims

1. A circular electron beam channel trapezoidal staggered grid slow wave structure, comprising a metal shell (1), wherein a trapezoidal and staggered symmetrical upper metal grid (2) and a lower metal grid (3) are arranged in the metal shell (1), characterized in that: The upper metal gate (2) and the lower metal gate (3) overlap in the longitudinal direction; the upper metal gate (2) and the lower metal gate (3) are respectively provided with a circular-arc-shaped recess (5); along the electron transmission direction, the recess (5) penetrates the upper metal gate (2) and the lower metal gate (3) respectively, and the upper and lower recesses (5) enclose a circular electron beam channel (4).

2. A circular electron beam channel trapezoidal interleaved grating slow wave structure according to claim 1, characterized in that: The overlapping distance b of the upper metal gate (2) and the lower metal gate (3) in the longitudinal direction is less than the radius r of the circular electron beam channel (4).

3. A circular electron beam channel trapezoidal interleaved grating slow wave structure according to claim 2, characterized in that: The radius r of the circular electron beam channel (4) satisfies the following condition: b < r < 2*b.

4. A circular electron beam channel trapezoidal interleaved grating slow wave structure according to claim 2, characterized in that: The arrangement period of the upper metal gate (2) and the lower metal gate (3) is p, and adjacent upper metal gates (2) and lower metal gates (3) are staggered by 1 / 4 of the arrangement period.

5. A circular electron beam channel trapezoidal interleaved grid slow wave structure according to any one of claims 1 to 4, characterized in that: Further comprising input structure and output structure, the input structure and the output structure all respectively include two straight waveguide sections and a bent waveguide section between the two straight waveguide sections.

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