A side-coupled absorption cavity and coupling structure for suppressing oscillation of a strip beam traveling wave tube

Abstract

The application discloses a side edge coupling absorption cavity and a coupling structure for inhibiting oscillation of a strip beam traveling wave tube, and relates to the technical field of vacuum electron. The technical scheme is as follows: a shell is provided with a coupling hole in a side wall, the coupling hole is used for being connected with a side edge of a slow wave structure and inputting an oscillation signal of a specific frequency, an absorption medium is arranged in the center of an inner cavity of the shell and used for absorbing the oscillation signal, part of the oscillation signal generated in the slow wave structure is input into the absorption cavity in the side edge through the coupling hole and is absorbed by the absorption medium in the absorption cavity, and the oscillation signal is inhibited in a mode of absorption filtering, thus the absorption of part of self-excitation oscillation is realized without increasing the length of the tube, and the stability of high-power output of the strip beam traveling wave tube is improved.

Description

Technical Field

[0001] This invention relates to the field of vacuum electronics technology, and more specifically, to a side-coupled absorption cavity and coupling structure for suppressing oscillations in a ribbon traveling wave tube. Background Technology

[0002] Traveling wave tubes (TWTs) are the most widely used and largest-market O-type devices in vacuum electronic devices. They are important terahertz wave emission sources, possessing a series of advantages such as high power capacity, wide operating bandwidth, high efficiency, and relatively high gain. Compared to the circular electron beams used in traditional TWTs, strip electron beams, at the same current density, have a larger cross-sectional area, weaker space charge effect, and higher conductivity. This allows for increased beam-wave interaction area, reduced cathode emission density, and lower RF intensity, making them more suitable for planar and integrated design schemes.

[0003] However, traveling wave tubes with strip bundle structures also face traditional stability problems. In high-power output designs, traveling wave tubes are prone to self-oscillation due to their high operating current and feedback path issues. The high gain results in very high oscillation power, which can easily generate strong radio frequency fields that can lead to device breakdown.

[0004] Traditional oscillation suppression methods employ phase velocity jumps and mid-section cutoffs to add concentrated attenuators. However, under high-power output conditions, the required phase velocity jump cycles increase, making fabrication more difficult, and self-excited oscillations still occur after prolonged operation. Mid-section cutoffs, on the other hand, increase the inhomogeneity within the slow-wave structure, causing heat accumulation at the cutoff point. This results in extremely high heat load per unit area for the concentrated attenuator, placing a severe burden on the attenuation material and further increasing the tube length, thus placing higher demands on the focusing system. Therefore, a novel attenuation structure is urgently needed to suppress self-excited oscillations with minimal alteration to the slow-wave channel structure and tube length. Summary of the Invention

[0005] The purpose of this application is to provide a side-coupled absorption cavity and coupling structure for suppressing oscillations in a strip-beam traveling wave tube (TBV). This structure suppresses oscillation signals through absorption filtering, achieving partial absorption of self-excited oscillations while avoiding increasing the tube length, thereby increasing the stability of the high-power output of the TPV.

[0006] The above-mentioned technical objective of this application is achieved through the following technical solution: a side-coupled absorption cavity for suppressing the oscillation of a band beam traveling wave tube, comprising: a housing, wherein a coupling hole is provided on the side wall of the housing, the coupling hole is used to connect to the side of a slow wave structure to receive an oscillation signal of a specific frequency, and an absorption medium is provided in the center of the inner cavity of the housing for absorbing the oscillation signal.

[0007] Using the above technical solution, part of the oscillation signal generated in the slow wave structure is connected to the absorption cavity on the side through the coupling hole and absorbed by the absorption medium in the absorption cavity. When the absorption cavity is applied to the slow wave structure, it is only necessary to open the hole in the side wall of the slow wave structure without changing the overall structure of the slow wave structure, and there is no need to increase the tube length. Moreover, the absorption cavity absorbs waves in the oscillation frequency range through the frequency selection characteristics of the inner cavity and the coupling hole, which has little impact on the transmission performance of the slow wave structure. The oscillation energy is absorbed by the absorption cavity, which disperses the heat burden of the slow wave structure.

[0008] Furthermore, the cross-section of the inner cavity of the housing is rectangular.

[0009] Furthermore, the cross-section of the coupling hole is rectangular with rounded corners.

[0010] Furthermore, the absorption medium is cylindrical, and has a through cylindrical hole in the middle.

[0011] Secondly, the present invention provides a coupling structure for suppressing the oscillation of a band beam traveling wave tube, comprising: a slow wave structure and a plurality of absorption cavities as described above; the absorption cavities are disposed on the side of the spacer region between two adjacent metal grids of the slow wave structure and are staggered vertically along the axis of the slow wave structure, and the absorption cavities are connected to the slow wave structure through coupling holes.

[0012] Furthermore, the slow-wave structure is an interleaved dual-grid slow-wave structure.

[0013] Furthermore, the center of the absorption cavity is aligned with the center of the adjacent metal grid spacing region of the slow wave structure.

[0014] Furthermore, the height of the metal grid in the slow-wave structure is equal to the internal height of the absorption cavity.

[0015] Furthermore, the actual size of the absorption cavity is obtained through the following steps: performing Fourier analysis on the output signal of the traveling wave tube to obtain the oscillation frequency; calculating the initial size of the absorption cavity using the resonant frequency calculation formula and the oscillation frequency; treating the absorption medium as a perturbation and correcting the initial size of the absorption cavity until the resonant point is corrected to the oscillation frequency to obtain the actual size of the absorption cavity.

[0016] Furthermore, the loss tangent of the absorbing medium is 0.4, and the relative permittivity is 8.

[0017] Compared with the prior art, this application has the following beneficial effects:

[0018] 1. During coupling, only a coupling hole needs to be opened on the side of the slow wave structure, without changing the channel of the slow wave structure, and no additional tube length is required;

[0019] 2. The absorption cavity has little impact on the transmission performance of the traveling wave tube. It utilizes the frequency selectivity of the resonant cavity and coupling hole to absorb waves within the oscillation frequency range, without affecting normal interaction.

[0020] 3. The coupling structure absorbs the energy of the oscillation into the side structure, dispersing the heat burden on the slow wave line. At the same time, the absorption cavity is loaded on the side of the slow wave structure axis by magnetic coupling, which does not affect the magnetic system designed and installed above and below the slow wave line. Attached Figure Description

[0021] 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:

[0022] Figure 1 This is a schematic diagram of the absorption cavity provided in Embodiment 1 of the present invention;

[0023] Figure 2 These are the front and side views of the absorption cavity provided in Embodiment 1 of the present invention;

[0024] Figure 3 These are the front and side views of the staggered dual-grid slow-wave structure provided in Embodiment 2 of the present invention;

[0025] Figure 4 The interleaved dual-grid slow-wave structure of the coupling absorption cavity provided in Embodiment 2 of the present invention;

[0026] Figure 5 This is a comparison diagram of the transmission performance of the staggered dual-grid slow-wave structure before and after the coupling absorption cavity provided in Embodiment 3 of the present invention.

[0027] Figure 6 The output signal intensity diagram and Fourier analysis of the output signal of the interleaved dual-grid traveling wave tube in front of the coupling absorption cavity provided in Embodiment 3 of the present invention under no input signal.

[0028] Figure 7 The output power diagram and Fourier analysis of the output signal of the interleaved dual-grid traveling wave tube in front of the coupling absorption cavity provided in Embodiment 3 of the present invention under an input signal of 29.5 GHz.

[0029] Figure 8 The output signal intensity diagram of the interleaved dual-grid traveling wave tube after the coupled absorption cavity provided in Embodiment 3 of the present invention under no input signal.

[0030] Figure 9 The output power diagram and Fourier analysis of the output signal of the interleaved dual-grid traveling wave tube after the coupled absorption cavity provided in Embodiment 3 of the present invention under an input signal of 29.5 GHz.

[0031] The attached diagram shows the markings and corresponding component names:

[0032] 1. Absorption cavity; 11. Shell; 12. Coupling hole; 13. Absorption medium; 2. Slow wave structure; 21. Metal shell; 22. Electron beam channel; 23. Metal grid. Detailed Implementation

[0033] In the following, the terms “comprising” or “may include” as used in the various embodiments of this application indicate the presence of the claimed function, operation, or element, and do not limit the addition of one or more functions, operations, or elements. Furthermore, as used in the various embodiments of this application, 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 the possibility of adding one or more combinations of the foregoing.

[0034] In various embodiments of this application, the expression "or" or "at least one of B and / or C" includes any combination or all combinations of the words listed simultaneously. For example, the expression "B or C" or "at least one of B and / or C" may include B, may include C, or may include both B and C.

[0035] The terms used in the various embodiments of this application (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 terms do not limit the order and / or importance of the elements. The above terms 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, without departing from the scope of the various embodiments of this application, a first element may be referred to as a second element, and similarly, a second element may be referred to as a first element.

[0036] It should be noted that if a description refers to "connecting" a component to another component or "connecting" it to another component, 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 or "directly connected" to another component, it can be understood that there is no third component between the first and second components.

[0037] The terminology used in the various embodiments of this application is for the purpose of describing particular embodiments only and is not intended to limit the various embodiments of this application. 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 this application 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 this application.

[0038] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the embodiments and accompanying drawings. The illustrative embodiments and descriptions of this application are only for explaining this application and are not intended to limit this application.

[0039] In high-power output designs, traveling wave tubes (TWTs) with strip bundle structures are prone to self-excited oscillations due to their high operating current and inherent feedback path issues. Traditional oscillation suppression methods employ phase velocity jumps and mid-section cutoffs to add concentrated attenuators. However, under high-power output conditions, the number of phase velocity jumps increases, making fabrication more difficult, and self-excited oscillations still occur after prolonged operation. Furthermore, mid-section cutoffs increase the inhomogeneity within the slow-wave structure, causing heat accumulation at the cutoff point. This results in extremely high heat load per unit area for the concentrated attenuator, placing a severe burden on the attenuation material and further increasing the tube length, thus placing higher demands on the banding system.

[0040] In view of this, to overcome the application problems of existing oscillation technology in the high-power field, the applicant proposes a side-coupled absorption cavity and coupling structure for suppressing oscillations in a strip-beam traveling wave tube (SWT). This structure suppresses the oscillation signal through absorption filtering, achieving partial absorption of self-excited oscillations while avoiding increasing the tube length, thus increasing the stability of the SWT's high-power output. The absorption cavity and coupling structure of this application are further described below with reference to embodiments and accompanying drawings.

[0041] Example 1

[0042] Please see Figure 1-2 As shown, this embodiment provides a side-coupled absorption cavity structure, including: a housing 11, the side wall of the housing is provided with a coupling hole 12, the coupling hole 12 is used to connect to the side of the slow wave structure to receive an oscillation signal of a specific frequency, and the inner cavity center of the housing 11 is provided with an absorption medium 13 for absorbing the oscillation signal.

[0043] Specifically, some of the oscillation signals generated in the slow wave structure are connected to the absorption cavity on the side through the coupling hole 12 and absorbed by the absorption medium 13 in the absorption cavity. The absorption medium 13 suppresses the oscillation signals by absorption filtering.

[0044] It should be noted that the principle of absorption cavity filtering is a reflective stopband filtering. Frequency points within the stopband enter the resonant cavity (the interior of the absorption cavity) and form standing waves. These waves are reflected between the input port and the resonant cavity and will not continue to interact with the electron beam on the slow wave line. However, considering that the gain of the slow wave line is relatively large, the back-and-forth reflection of the wave on the slow wave line is very likely to increase the heat loss of the slow wave line between the input port and the resonant cavity. Therefore, an absorption medium is designed in the resonant cavity to consume the standing waves in the resonant cavity, increase the insertion loss, reduce reflection, increase the Q value of the resonant cavity, and consume the energy of the wave in the absorption cavity.

[0045] In this embodiment, a specific structure of housing 11, coupling hole 12, and absorbing medium 13 is provided for the staggered double-grid slow-wave structure. The inner cavity of housing 11 is a resonant cavity, the shape of which is designed according to the slow-wave structure. Considering that the electric field distribution of the staggered double-grid slow-wave structure and the electric field distribution of the base film of the cuboid resonant cavity are similar, the similar field distributions of the two structures result in higher coupling efficiency, and it is more convenient to use a cuboid resonant cavity to fabricate into the slow-wave structure. Therefore, preferably, the cross-section of the inner cavity of housing 11 is rectangular.

[0046] In this embodiment, to allow the absorbing medium to better absorb wave energy, the electric field energy distribution when the cuboid resonant cavity generates standing waves was analyzed. It was found that the energy is generally concentrated in the central region and is circular. Therefore, preferably, the absorbing medium 13 at the center of the inner cavity is cylindrical. Furthermore, considering the ease of assembly of the absorbing medium and the separation of standing wave modes, a through cylindrical hole is provided in the center of the absorbing medium 13.

[0047] In this embodiment, to maximize the area of ​​the opening within the limited staggered dual-gate cavity region, while avoiding excessive right angles and reducing the accumulation of electric field at the tips during coupling, the coupling hole 12 preferably has a cross-section that is a rectangle with rounded corners; wherein, a rectangle with rounded corners means that the three sides of the rectangle are transformed from straight lines into smooth arc curves.

[0048] The side-coupled absorption cavity for suppressing oscillations in a ribbon-beam traveling wave tube (TWT) provided in this embodiment only requires openings in the sidewall of the slow-wave structure when applied to slow-wave structures, without altering the overall structure or increasing the tube length. Furthermore, the absorption cavity utilizes the frequency selectivity of the resonant cavity and coupling aperture to absorb waves within the oscillation frequency range, minimizing its impact on the transmission performance of the slow-wave structure. The absorption of oscillation energy by the cavity disperses the heat load on the slow-wave structure, reducing the risk of thermal breakdown. The absorption cavity in this embodiment can serve as a partial attenuator structure and is widely applicable in slow-wave structures of TWTs operating in the submillimeter-wave and terahertz bands.

[0049] Example 2

[0050] Please see Figure 3-4 As shown, this embodiment provides a coupling structure for suppressing the oscillation of a ribbon traveling wave tube, based on the absorption cavity in Embodiment 1.

[0051] The coupling structure includes a slow wave structure 2 and a plurality of absorption cavities 1 as described in Embodiment 1; the absorption cavities 1 are disposed on the side of the spaced area between two adjacent metal grids 23 of the slow wave structure 2, and are staggered vertically along the axis of the slow wave structure 2, and the absorption cavities 1 are connected to the slow wave structure 2 through coupling holes 12.

[0052] In this embodiment, the slow wave structure 2 is an interleaved double-grid slow wave structure, including: a metal shell 21, an electron beam channel 22 and a metal grid plate 23, with the metal grids 23 arranged vertically; the center of the absorption cavity 1 is aligned with the center of the spaced area between two adjacent metal grids 23 of the slow wave structure 2, and the height of the metal grids 23 in the slow wave structure 2 is equal to the internal height of the absorption cavity 1.

[0053] To facilitate implementation, this embodiment also provides a method for calculating the actual size of the absorption cavity 1 (resonant cavity). The actual size of the absorption cavity 1 is obtained through the following steps: performing Fourier analysis on the output signal of the traveling wave tube to obtain the oscillation frequency; calculating the initial size of the absorption cavity 1 using the resonant frequency calculation formula and the oscillation frequency; treating the absorption medium 13 as a perturbation and correcting the initial size of the absorption cavity 1 until the resonant point is corrected to the oscillation frequency, thus obtaining the actual size of the absorption cavity 1.

[0054] Specifically, the oscillation frequency is obtained from the Fourier analysis of the output signal of the traveling wave tube, and the initial size of the absorption cavity 1 is calculated using the resonant frequency calculation formula and the oscillation frequency:

[0055]

[0056] In the formula, f mnlis the resonant frequency, a is the short side of the rectangular absorption cavity in the horizontal direction, d is the long side in the horizontal direction, b is the height in the vertical direction, and m, n, l are the modes of the fundamental mode (the fundamental mode of the rectangular absorption cavity is the TE101 mode, and m, n, l correspond to 1, 0, 1).

[0057] An absorption medium 13 is added to the initial-sized absorption cavity, and the change in the resonant point is observed. The absorption medium 13 is considered as a small perturbation, and the initial size of the absorption cavity 1 is corrected using a formula until the resonant point is placed at the oscillation frequency. The actual size of the absorption cavity is then obtained, as shown in the following formula:

[0058]

[0059] In the formula, ω is the resonant frequency of the absorption cavity after the perturbation is added, ω0 is the resonant frequency of the initial absorption cavity, ΔV is the volume of the perturbation object, and V0 is the volume of the original absorption cavity.

[0060] It should be noted that the dimensions of the absorbing medium can initially be set to a / 5, b / 5, d / 5. After analyzing the changes in the resonant point, the dimensions of the absorbing medium can be appropriately increased and the dimensions of the absorbing cavity reduced. Then, the absorbing cavity is coupled into the slow-wave line. The size of the coupling aperture mainly affects the insertion loss at the resonant point; a larger size results in higher insertion loss and a wider absorption bandwidth. After the absorbing cavity is coupled into the slow-wave line, the boundary conditions will change, and the resonant point will shift. At this point, it is necessary to further optimize the actual dimensions of absorbing cavity 1 using simulation software to bring the absorption frequency back to the resonant frequency.

[0061] Please see Figure 3 As shown, for slow-wave structure 2, the width is a, the height is b, and the single-cycle length is p. It has longitudinally arranged rectangular metal grids with a width of a, a height of h, a thickness of g, and a spacing of l. The electron beam channel height is hb, where hb ≤ b / 4. Where b = hb + 2h, and l = pg. The interleaved double-grid slow-wave structure operates in the Ka band and has an output power of 4kW.

[0062] Please see Figure 2 As shown, for the absorption cavity 1, its inner cavity is a cuboid with a long side of lc, a short side of ac, and a height of bc. A cylindrical absorbing medium 13 is placed at the center of the inner cavity. The absorbing medium has a height of rh, an outer radius of rm, and an inner radius of rn. The loss tangent of the absorbing medium 13 is 0.4, and its relative permittivity is 8. The material uses commonly used laboratory test data. The absorption cavity 1 is connected to the side of the slow wave structure 2 through a rectangular coupling hole 12 with a rounded corner. The thickness of the coupling hole 12 is a0, the width of the coupling hole 12 is 2*b0, the radius of the rounded corner is r0, and the height of the coupling hole 12 is 2*r0.

[0063] Please see Figure 4As shown, for the staggered double-grid slow-wave structure coupled with the absorption cavity, Figure 4 includes absorption cavity 1 (only the vacuum structure inside the absorption cavity is shown in the figure) and slow-wave structure 2 (only the vacuum structure inside the slow-wave structure is shown in the figure). Absorption cavity 1 contains absorption medium 13. Absorption cavity 1 is placed on the side of the space between two adjacent metal grids 23, and is staggered vertically. The horizontal distance between adjacent absorption cavities is 2.5*p, so that the center of the absorption cavity corresponds to the center of the staggered double-grid cavity region.

[0064] Compared to conventional oscillation suppression designs, the coupling structure with an absorption cavity in this embodiment offers several advantages: First, it only requires opening a coupling hole on the side of the slow-wave structure, without altering the channel of the slow-wave structure or requiring additional tube length. Second, the absorption cavity has minimal impact on the transmission performance of the traveling wave tube. Utilizing the frequency selectivity of the resonant cavity and coupling hole, it absorbs waves within the oscillation frequency range, without affecting normal interactions, and only absorbs oscillation signals at the corresponding frequencies. Third, it absorbs the energy of the oscillation into the side structure, dispersing the heat load on the slow-wave line. Simultaneously, by using magnetic coupling to load the absorption cavity on the side of the slow-wave structure axis, it does not affect the magnetic system designed and installed above or below the slow-wave line.

[0065] Example 3

[0066] Please see Figure 5-9 As shown, this embodiment uses simulation software to analyze the oscillation suppression effect of the interlaced double-gate slow-wave structure (referred to as the original structure) before coupling absorption cavity and the interlaced double-gate slow-wave structure (referred to as the optimized structure) after coupling in Embodiment 2.

[0067] The following is combined Figure 5-9 As shown, the oscillation changes of the traveling wave tube before and after adding the absorption cavity were analyzed using microwave simulation software. In the particle simulation settings, the electron gun voltage was 28.6kV and the current was 0.8A. Under input conditions, the input signal frequency was 29.5GHz and the input power was 20W.

[0068] Figure 5 This is a comparison diagram of the transmission performance of the staggered dual-grid slow-wave structure before and after the coupling absorption cavity. Figure 5 (a) is a comparison chart of S11. Figure 5 (b) shows the S21 comparison diagram, with the horizontal axis representing frequency and the vertical axis representing decibels. In the diagram, "original structure" represents the original structure and "optimized structure" represents the optimized structure. Figure 5(a) In the S11 comparison diagram, the original structure operates in the frequency band of 26.51GHz-30.20GHz with a voltage drop of less than -20dB. The transmission performance of the optimized structure coupled with the absorption cavity is basically less than -20dB in this range. However, the S11 of 29.14GHz-29.40GHz is greater than -20dB, and it is significantly affected. The worst frequency is 29.29GHz, with an S11 of -16.42dB. All of these frequencies exceed -15dB in the operating frequency band, but the overall impact on transmission performance is relatively small. Figure 5 (b) In the S21 comparison diagram, the original structure has an S21 of less than -1dB in the operating frequency band, while the optimized structure has an S21 of less than -1dB in the range of 26.90GHz-31.5GHz. After further analysis of the oscillation signal and the addition of the absorption cavity, the optimized structure has an S21 of less than -6dB in the out-of-band range of 25.42GHz-25.71GHz. The minimum S21 at the frequency point of 25.58GHz reaches -19.6dB. This part is the absorption frequency range, and the original structure will generate an oscillation signal in this range.

[0069] Figure 6 It shows the output signal intensity diagram and Fourier analysis diagram of the interleaved dual-grid traveling wave tube in front of the coupling absorption cavity under no input signal. Figure 6 (a) is the output signal strength graph, with the horizontal axis representing simulation time and the vertical axis representing signal strength. Figure 6 (b) is the Fourier analysis plot, with the horizontal axis representing frequency and the vertical axis representing the Fourier analysis results. The simulation time was 150 ns. When the original structure had no signal input, it could only amplify the self-excited oscillation signal, with a signal frequency of 25.56 GHz. The oscillation started at 70 ns and reached an output of 5352 W at 150 ns. The oscillation frequency was outside the operating frequency band, with high loss and high coupling impedance at low frequencies, most likely indicating that the oscillation signal was generated by the combined effect of reflected oscillation and lower sideband oscillation.

[0070] Figure 7 The output power diagram and Fourier analysis diagram of the output signal of the interleaved dual-grid traveling wave tube in front of the coupling absorption cavity under the input of a 29.5 GHz signal are shown. Figure 7 (a) is the output signal strength graph, with the horizontal axis representing simulation time and the vertical axis representing signal strength. Figure 7 (b) is the Fourier analysis plot, with the horizontal axis representing frequency and the vertical axis representing the Fourier analysis results. The input signal frequency is 29.5 GHz and the power is 20 W. The original structure outputs normally up to 65 ns, at which point the oscillation signal begins to have an effect, and the oscillation amplitude gradually increases. At 140 ns, the signal strength reaches 7304 W, which is greater than the normal output signal power. The spectrum shows one amplified signal at 29.499 GHz and two oscillation signals. It is found that 25.67 GHz is the oscillation signal, while 33.33 GHz is the intermodulation signal of the amplified signal and the oscillation signal.

[0071] Figure 8 This is a graph showing the output signal intensity of the interleaved dual-grid traveling wave tube after coupling the absorption cavity under no input signal. The horizontal axis represents the simulation time, and the vertical axis represents the signal intensity. The simulation time is 150 ns. It can be seen that the output signal intensity of the optimized structure is much smaller than that of the original structure, and the suppression effect on self-excited oscillation is very obvious.

[0072] Figure 9 The output power diagram and Fourier analysis diagram of the output signal of the interleaved dual-grid traveling wave tube after coupling absorption cavity under the input of 29.5 GHz signal. Figure 9 (a) is the output signal strength graph, with the horizontal axis representing simulation time and the vertical axis representing signal strength. Figure 9 (b) is the Fourier analysis plot, with the horizontal axis representing frequency and the vertical axis representing the Fourier analysis results. The input signal frequency is 29.5 GHz, the power is 20 W, the simulation time is 200 ns, the optimized structure output is increased to at least 200 ns, the spectrum is clean, and the amplified signal is 29.499 GHz.

[0073] Combination Figure 5-9 Simulation analysis data shows that, compared with the original interlaced double-grid structure, the coupled absorption cavity structure in this embodiment has a significant effect on suppressing self-excited oscillations and has little impact on the transmission performance of the traveling wave tube, absorbing only the oscillation signal of the corresponding frequency.

[0074] 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. A coupling structure for suppressing oscillations in a strip beam traveling wave tube, characterized in that it comprises: Slow wave structure (2) and multiple absorption cavities (1); The slow wave structure (2) is an interleaved double-grid slow wave structure; The absorption cavity (1) is disposed on the side of the space between two adjacent metal grids (23) of the slow wave structure (2), and is staggered up and down along the axis of the slow wave structure (2). The absorption cavity (1) is connected to the slow wave structure (2) through the coupling hole (12). The absorption cavity includes: a housing (11), the side wall of which is provided with a coupling hole (12), the coupling hole (12) is used to connect to the side of the slow wave structure (2) to receive an oscillation signal of a specific frequency, and an absorption medium (13) is provided in the center of the inner cavity of the housing (11) to absorb the oscillation signal; the cross-section of the inner cavity of the housing (11) is rectangular; the cross-section of the coupling hole (12) is rectangular with rounded corners; the absorption medium (13) is cylindrical, and the middle of the absorption medium (13) has a through cylindrical hole; The center of the absorption cavity (1) is aligned with the center of the spaced region between the two adjacent metal grids (23) of the slow wave structure (2).

2. The coupling structure for suppressing oscillations of a strip beam traveling wave tube according to claim 1, characterized in that: The height of the metal grid (23) in the slow wave structure (2) is equal to the internal height of the absorption cavity (1).

3. The coupling structure for suppressing oscillations of a strip beam traveling wave tube according to claim 1, characterized in that: The actual dimensions of the absorption cavity (1) are obtained through the following steps: The oscillation frequency is obtained by performing Fourier analysis on the output signal of the traveling wave tube. The initial dimensions of the absorption cavity (1) are calculated using the resonant frequency calculation formula and the oscillation frequency. The absorption medium (13) is treated as a perturbation, and the initial size of the absorption cavity (1) is corrected until the resonant point is corrected to the oscillation frequency, so as to obtain the actual size of the absorption cavity (1).

4. The coupling structure for suppressing oscillations of a strip beam traveling wave tube according to claim 3, characterized in that: The loss tangent of the absorption medium (13) is 0.4 and the relative permittivity is 8.

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