A method for solving attenuation of a G-band edge-aligned interdigital line high-frequency structure of a traveling wave tube

Abstract

The application belongs to the field of vacuum electron devices, and particularly relates to a kind of attenuation solving method of G-band edge alignment staggered grid row wave tube high-frequency structure.The attenuation quantity definition of passive device is introduced into the high-frequency structure of active device-G-band edge alignment staggered grid row wave tube for the first time, and the solving method of the change rate of time-averaged radio frequency power P along the axial direction used in the solving of attenuation constant of existing high-frequency structure is deviated, the solving formula of attenuation constant of G-band edge alignment staggered grid row wave tube high-frequency structure is obtained by starting from the basic theory of attenuation and transmission, deduction and numerical verification, the attenuation constant solved can support 3-dimensional large signal nonlinear beam-wave interaction solver BWISFW calculation, and compared with CST-PIC, the calculation results are consistent.The attenuation constant calculation method provided by the application is especially suitable for G-band edge alignment staggered grid row wave tube high-frequency structure, and is helpful to shorten the development cycle and reduce the production cost.

Description

Technical Field

[0001] The present invention belongs to the field of vacuum electronic devices, and in particular relates to a method for solving the attenuation of a high-frequency structure of a G-band edge-aligned staggered-grid traveling wave tube. Background Art

[0002] The interleaved double-gate traveling wave tube has broad application prospects in fields such as terahertz high-power coherent radiation sources due to its advantages of high power, wide bandwidth, and easy processing.

[0003] The main physical processes in the operation of an interleaved dual-grid traveling-wave tube (TWT) include the generation, formation, and focusing of an electron beam; its interaction with electromagnetic waves in high-frequency structures; and the dissipation and cooling of the electron beam energy. The beam-wave interaction process is central to this process, and in-depth research into its fundamental theory and nonlinear phenomena is highly significant, guiding the design and optimization of TWTs, shortening development cycles, reducing production costs, and saving development funds.

[0004] Currently, there are two main types of solvers in the field for calculating the interaction process of interleaved dual-gate traveling wave tubes: one is the time-domain particle simulation solver, which describes the electromagnetic field, particle motion state and output signal changes over time in the device, represented by CST-PIC and MAGIC3D; the other is the frequency-domain solver, which is divided into small-signal analytical theory and large-signal semi-numerical and semi-analytical theory.

[0005] When performing calculations using a time-domain particle simulation solver, the device is first modeled in three dimensions, followed by solution settings and meshing. The particle simulation solver then proceeds from the most basic Maxwell's electromagnetic equations and Newton's equations of motion in their relativistic form, without introducing any additional approximations or assumptions. It solves for field variations and port output signals at all locations within the device, using a so-called "first principles" approach. High-frequency intrinsic parameters are not required before the calculation. While particle simulation programs can accurately process the interaction between electromagnetic fields and charged particles, the computational overhead is significant due to the typically long beam-wave interaction period and the large number of particles required to be tracked. Even with GPU acceleration and the use of high-performance computers or servers, a single beam-wave interaction calculation can still take several hours with a small number of mesh divisions and a short device simulation run time, such as 5ns or 10ns. With a large number of mesh divisions and a long device simulation run time, such as 50ns or 200ns, a single beam-wave interaction calculation can take approximately a day.

[0006] In the frequency-domain solver, small-signal analytical theory simulates the device's linear operation, including kinematic theory and space charge wave theory. It is only used for preliminary analysis during the device design process. In large-signal theory, the device operates in a nonlinear state, with extremely high charge density within the electron beam and severe transcendence between particles. Traditional analytical methods are inadequate in this situation, requiring a combination of analytical and numerical methods, performed by a computer. Based on the electron beam model and space charge field calculation method, models are primarily categorized as 1D disk models, 2D electron ring models, and 3D circular fan models. The number of dimensions is determined by particle velocity and position: the 1D disk model considers only the axial velocity and position; the 2D ring model considers the particle's axial velocity, radial velocity, axial position, and radial position; and the 3D circular fan model considers the particle's axial velocity, radial velocity, angular velocity, as well as the axial position, radial position, and angular position. Additionally, there are 1.5D models that consider radial velocity based on the 1D model; and 2.5D models that consider angular velocity based on the 2D model. Among the different types of frequency-domain solvers mentioned above in China, the 3D large-signal nonlinear beam-wave interaction solver BWISFW is a software with relatively good calculation results for the beam-wave interaction process of folded waveguide traveling wave tubes and interleaved double-grating traveling wave tubes. It has high accuracy and is recognized by the industry. The calculation results are consistent with CST-PIC, and its core contains complete and rigorous analytical theory, which can provide a good analytical description of the physical process of the device.

[0007] Based on the characteristics of the aforementioned time-domain particle simulation and frequency-domain solvers, the industry generally agrees that CST-PIC can accurately simulate the changing physical processes of a device, accurately solving the electromagnetic fields, particle motion states, and temporal variations of output signals at each location within the device. BWISFW is a frequency-domain solver that combines analytical theory with numerical algorithms. Its numerical solution utilizes a relatively simple fourth-order Runge-Kutta algorithm, primarily used to solve partial differential equations. BWISFW's analytical theory is rigorous, providing a comprehensive analytical description of the device's physical processes. However, due to the high computational overhead of CST-PIC, industry designers often first perform device design and injection-wave interaction calculations using a frequency-domain solver, before performing final refinement using particle simulation.

[0008] Therefore, based on the above background, BWISFW can be used to verify the solution method of the high-frequency structure intrinsic parameters of the G-band edge-aligned staggered grating traveling wave tube, and CST-PIC is used as a comparison.

[0009] Accurately determining the intrinsic parameters of high-frequency structures, such as impedance, attenuation constant, and normalized phase velocity, is fundamental to the beam-wave interaction process and a crucial reference for designers when designing high-frequency structures. Therefore, the accuracy of determining the attenuation constant of high-frequency structures is closely linked to the accuracy of beam-wave interaction calculations for traveling wave tubes (TWTs), ultimately impacting the quality of TWT designs.

[0010] The current method for calculating the attenuation constant of high-frequency structures of G-band edge-aligned staggered-grating traveling-wave tubes (TWTs) is to take the partial derivative of the time-averaged RF power P with respect to axial distance, divide it by 2P, and multiply it by 8.686 to convert it to dB / m. However, research has revealed that this method still has problems. When the attenuation constant calculated using this method is substituted into the BWISFW beam-wave interaction solution, the result is inconsistent with the CST-PIC. Therefore, a new method is urgently needed to solve the attenuation constant of high-frequency structures of G-band edge-aligned staggered-grating TWTs. Summary of the Invention

[0011] In response to the above-mentioned problems or shortcomings, in order to accurately solve the attenuation constant of the high-frequency structure of the G-band edge-aligned staggered grating traveling wave tube, the present invention provides an attenuation solution method for the high-frequency structure of the G-band edge-aligned staggered grating traveling wave tube. Based on the basic theory of attenuation and signal transmission, a solution formula for the attenuation constant of the high-frequency structure of the G-band edge-aligned staggered grating traveling wave tube is obtained. The solved attenuation constant can support the BWISFW calculation of the injection-wave interaction process of the G-band edge-aligned staggered grating traveling wave tube, and the calculation results are consistent with the CST-PIC solution results.

[0012] When solving the attenuation constant of the high-frequency structure of the traveling wave tube, it is necessary to use the intrinsic loss power P of the high-frequency structure. loss Calculation is based on P loss The definition is as formula (1), where H t is the tangential component of the magnetic field of the high-frequency structure of the traveling wave tube, S is the surface area of ​​the inner wall of the high-frequency structure of the traveling wave tube, R s is the surface resistance of the high-frequency structure of the traveling wave tube. t The size of the high-frequency structure and the conductivity of the material are different. At the same time, the conductivity of the material will also vary with the material properties, the surface roughness of the device processing, and the operating frequency band of the device. t The distribution of very complex functions is very complex and it is difficult to obtain the calculation results using analytical formulas. Therefore, it is necessary to use numerical simulation software to solve the eigenmode of high-frequency structures to obtain P loss .

[0013]

[0014] A method for solving the attenuation of a high-frequency structure of a G-band edge-aligned staggered grating traveling wave tube comprises the following steps:

[0015] S1. In a 3D electromagnetic simulation software (such as CST) with an eigenmode solver, perform 3D modeling based on the dimensions of the G-band edge-aligned staggered-grid traveling wave tube high-frequency structure.

[0016] S2. According to the working state of the G-band edge-aligned staggered grating traveling wave tube, the pre-processing solution is set up, and the field distribution of the high-frequency structure is calculated using the eigenmode solver to obtain the frequency f of the high-frequency structure. The relevant pre-processing solution settings include the frequency range of the eigenmode solution, the conductivity of the background material, the boundary conditions, and the phase shift parameters. Units, material settings for meshing models.

[0017] S3. After the eigenmode calculation of the high-frequency structure is performed using the 3D electromagnetic simulation software, the P is calculated using the post-processing function of the 3D electromagnetic simulation software. loss .

[0018] S4. In the CST eigenmode solver, change the phase shift parameter Then re-solve and calculate to get the corresponding f and P loss . Get at least n sets of phase shift parameters Corresponding f and P loss , n≥5.

[0019] S5. Use formula (2) to obtain the time-averaged RF power P of the high-frequency structure of the traveling wave tube, where l is the period length of the high-frequency structure, W T is the normalized energy of the eigenmode solution, v g is the group velocity. In the CST eigenmode solver, W T is 1 joule. Group velocity v g The angular frequency ω and propagation constant β are obtained by performing forward difference, center difference and backward difference on them.

[0020]

[0021] S6. Derive the calculation formula of the attenuation constant α of high-frequency structures from the basic theory of attenuation and signal transmission.

[0022] According to the definition of attenuation of passive components, the attenuation L is the ratio of the input microwave power to the output microwave power under the condition of matching the attenuator terminal load. For the high-frequency structure of the traveling wave tube, the input microwave power is P and the output microwave power is (PP loss ), as shown in formula (3):

[0023]

[0024] The attenuation L actually includes two factors: one is the microwave loss within the system or component, which absorbs a portion of the input microwave power. This attenuation is called "absorption" attenuation. The other is caused by a mismatch at the input of the system or component, which causes a portion of the input microwave power to be reflected, reducing the power entering the system or component. This corresponding attenuation is called "reflection attenuation." When solving the attenuation constant for high-frequency structures, the calculation is based on a single-cycle eigenmode. There is no input-output matching issue. Therefore, the attenuation constant refers to absorption attenuation, which is determined by the device material conductivity and the surface roughness of the device processing.

[0025] The attenuation constant α represents the loss of microwave power per unit length in the signal transmission direction, then:

[0026]

[0027] Converting the unit of α to nepers gives the exact calculation method of the decay constant:

[0028]

[0029] Furthermore, the three-dimensional electromagnetic simulation software with the eigenmode solver is CST; the loss power P is calculated in CST loss Specifically, the Loss and Q in the post-processing is used to fill in the conductivity determined by the working frequency band, material properties, and surface roughness of the current high-frequency structure, and calculate the loss power P of the current high-frequency structure under this phase shift parameter. loss .

[0030] The solution principle of the present invention: For the first time, the present invention introduces the definition of the attenuation of passive devices into the high-frequency structure of the active device - the edge-aligned staggered grating traveling wave tube of the G band. This deviates from the existing high-frequency structure attenuation constant solution method of the time-averaged RF power P with the axial change rate. Starting from the basic theory of attenuation and transmission, the invention derives and numerically verifies the formula for solving the attenuation constant of the high-frequency structure of the G band edge-aligned staggered grating traveling wave tube. The attenuation constant obtained by the solution can support the calculation of the 3D large-signal nonlinear beam-wave interaction solver BWISFW, and is compared with the commercial 3D electromagnetic simulation software CST-PIC. The calculated results are consistent. However, when the attenuation constant obtained by the existing theoretical solution is used for BWISFW solution, the calculated results are inconsistent with CST-PIC. The main reason is that the existing theory is to calculate the partial derivative of the time-averaged RF power P with respect to the axial distance z, and then divide it by 2P to obtain the attenuation constant. The physical meaning of this theory is the ratio of the rate of change of energy loss of the time-averaged RF power P at each position in the signal propagation direction to the input energy; while the physical meaning of the attenuation constant calculation formula derived by the present invention is the ratio of the initial energy of the signal to the energy at any position during the propagation process, which is more consistent with the physical meaning of the attenuation constant of microwave devices. Therefore, it can be proved that the attenuation constant calculation method derived by the present invention reflects the physical meaning of attenuation more accurately, is suitable for the attenuation analysis of the high-frequency structure of the edge-aligned staggered grating traveling wave tube of the G band, and can provide accurate theoretical guidance for the design and manufacture of the edge-aligned staggered grating traveling wave tube of the G band, which helps to shorten the development cycle and reduce its production cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 3D model of the beam-wave interaction region simulated for the control group particles;

[0032] Figure 2 The TWT output power simulated for the control group particles;

[0033] Figure 3 This is the time domain power flow curve of CST-PIC in the control group;

[0034] Figure 4 is the phase space diagram of CST-PIC of the control group;

[0035] Figure 5 The high-frequency structural three-dimensional model of the first interaction region of the embodiment and the control group;

[0036] Figure 6 3D electric field distribution diagrams obtained for the eigenmodes of the embodiment and the control group;

[0037] Figure 7 The phase shift parameters of Example 17 are and the dispersion curve corresponding to f;

[0038] Figure 8is the output power of the BWISFW wave injection interaction in the embodiment;

[0039] Figure 9 This is a phase space diagram of the BWISFW beam-wave interaction in the embodiment;

[0040] Figure 10 is the BWISFW beam-wave interaction output power obtained by the existing attenuation constant calculation method for the control group. DETAILED DESCRIPTION

[0041] To make the objectives, technical solutions and advantages of the present invention more clear, the present invention is further described in detail below by taking a dual-segment 220 GHz edge-aligned staggered grating traveling wave tube as an example, in combination with the implementation manner and the accompanying drawings. The operating frequency of the traveling wave tube in the embodiment is 220 GHz.

[0042] A method for solving the attenuation of a high-frequency structure of a G-band edge-aligned staggered grating traveling wave tube, the specific steps of which are as follows:

[0043] S1. Perform 3D modeling and pre-processing of a 220 GHz edge-aligned staggered-grating traveling-wave tube in CST-PIC. This includes setting up solution parameters, meshing, field monitors, power flow monitors, and other calculations. A particle simulation solution is then performed, and the results are used as control data.

[0044] Figure 1 This is a three-dimensional model diagram of the beam-wave interaction area simulated for the control group particles. Figure 2 This is the traveling wave tube output power simulated by the control group particles. Since CST-PIC is a time domain solver, its output power is expressed as a time domain diagram of the port signal. Figure 2 The power is 0.5 times the square of the signal amplitude in the stable region after 2ns. Therefore, the output power of the 220GHz edge-aligned staggered grating traveling wave tube solved by CST particle simulation is 21.125W. Figure 3 The CST-PIC time-domain power flow curve for the control group is shown in Figure 2. Due to the noise and mode competition during the operation of the microwave tube, and the fact that the time-domain calculation shows the power flow at the current moment, the CST time-domain power flow monitor does not average the power flow over a time period. Therefore, the amplitude of the power flow obtained at different simulation times varies slightly with the axis. The final output power of the traveling wave tube is still based on the output port signal (i.e. Figure 2 ), but the time domain power flow curve can still more accurately describe the change of signal power with propagation distance. Figure 4This is the phase space diagram of the control group CST-PIC. The ordinate is the normalized phase velocity, which is the ratio of the particle axial velocity to the speed of light. It represents the energy distribution of the particles in the electron beam as they propagate axially. At the end of the traveling wave tube, the particle velocity distribution is discrete, and the velocity of most particles is reduced. The energy is used for signal output amplification. Table 1 lists the parameters related to the beam-wave interaction.

[0045] Table 1 Beam-wave interaction parameters

[0046]

[0047] S2. In the CST eigenmode solution, the eigenmode of the high-frequency structure of the first interaction region of the dual-segment 220GHz edge-aligned staggered grating traveling wave tube is solved to obtain the phase shift parameters. The corresponding three-dimensional electric field distribution and f. Pre-processing solution settings include three-dimensional modeling, pre-processing settings, including solution settings, meshing settings, etc. Figure 5 The high-frequency structural three-dimensional model of the first interaction region of the embodiment and the control group, Figure 6 Table 2 shows the 3D electric field distribution diagram of the eigenmode solution of the embodiment and the control group. Table 2 shows the eigenmode solution parameters.

[0048] Table 2 Eigensolution parameters

[0049]

[0050]

[0051] S3. Open the "Loss and Q" in the CST post-processing software, enter the conductivity of the background material, and calculate the loss power P of the current high-frequency structure under this phase shift parameter. loss The high-frequency structure of the dual-segment 220GHz edge-aligned staggered-grid traveling wave tube is made of oxygen-free copper. Considering the loss effect of the surface roughness of the device processing at 220GHz, the conductivity of the background material is set to 2*10 7 S / m.

[0052] S4. In the CST eigenmode solver, change the phase shift parameter Re-execute S2 and S3 to obtain a total of 17 sets of phase shift parameters Corresponding f and P loss , Figure 7 17 sets of phase shift parameters in this embodiment And the dispersion curve corresponding to f.

[0053] S5. The 17 sets of phase shift parameters obtained in S4 are f、P loss , and the high-frequency structure period length l, substitute into formula (6) to calculate the phase shift parameters The corresponding attenuation constant α1 of the high-frequency structure in the first beam-wave interaction region is shown in Table 3.

[0054] Table 3 Attenuation constants corresponding to phase shifts of high-frequency structures in the first beam-wave interaction region

[0055]

[0056]

[0057] S6. Repeat steps S2-S5 to calculate the phase shift parameters The corresponding high-frequency structure attenuation constant α2 in the second segment of the beam-wave interaction region is shown in Table 4.

[0058] Table 4 Attenuation constants corresponding to phase shifts of high-frequency structures in the second beam-wave interaction region

[0059]

[0060] S7. Calculate each phase shift parameter The calculation methods of other intrinsic parameters of the high-frequency structures in the corresponding first and second wave injection interaction regions, including total impedance, are well known in the industry and will not be repeated here.

[0061] The current solution for the attenuation constant of the high-frequency structure of the G-band edge-aligned staggered grating traveling wave tube is shown in formula (7):

[0062]

[0063] The results obtained from the two attenuation constant calculation methods, formula (5) and formula (7), were imported into BWISFW for verification. It was found that the attenuation constant calculated by formula (5) supports the BWISFW beam-wave interaction calculation and its calculation result is consistent with CST-PIC, while the attenuation constant calculated by formula (7) supports the BWISFW beam-wave interaction calculation and its calculation result is inconsistent with CST-PIC. This proves that the attenuation constant calculation method provided by the present invention more accurately reflects the physical meaning of attenuation and is suitable for attenuation analysis of high-frequency structures of edge-aligned staggered grating traveling wave tubes in the G band.

[0064] S8. Set each phase shift parameter The corresponding eigenvalues ​​of the high-frequency structure in the dual-segment beam-wave interaction region and the data of the electron beam channel region in the eigenmode field distribution in the high-frequency structure are imported into BWISFW, and the beam-wave interaction calculation of the dual-segment 220GHz edge-aligned staggered grating traveling wave tube is performed. Figure 8 is the output power of the BWISFW beam interaction in the embodiment, Figure 9 This is the phase space diagram of the BWISFW beam-wave interaction in the embodiment.

[0065] S9. Change the calculation method of the attenuation constant α in formula (6) to formula (7), repeat steps S2-S8, and use the attenuation constant calculated in the existing method to support BWISFW to perform injection-wave interaction calculation on a dual-segment 220 GHz edge-aligned staggered grating traveling wave tube. Figure 10 The BWISFW beam-wave interaction output power for the control group is obtained using the existing attenuation constant calculation method. Table 5 shows the attenuation constants calculated using the existing method.

[0066] Table 5 Attenuation constants solved by existing methods

[0067]

[0068] S10. By analyzing the BWISFW calculation results in S8 and S9, it is found that the BWISFW beam-wave interaction calculation results supported by the attenuation constant calculated by formula (6) are consistent with those of CST-PIC. The BWISFW output power is 22.0861W, and the output power of the CST particle simulation is 21.125W. The peak values ​​of the BWISFW and CST particle simulations that vary with axial power also have the same coordinates on the z-axis. The BWISFW power peak position is z = 50.24 mm ( Figure 8 ), CST is z=52.115mm( Figure 3 ). This shows that the calculation method of the attenuation constant derived in this paper is correct.

[0069] However, the calculation results of the BWISFW beam-wave interaction supported by the attenuation constant calculated by formula (7) are inconsistent with those of the CST-PIC, and its output power is not well stimulated and is only 9.709W.

[0070] Through the above experiments, it can be seen that the present invention introduces the definition of the attenuation of passive devices for the first time into the high-frequency structure of the active device - the edge-aligned staggered grating traveling wave tube of the G band. It deviates from the solution method of the time-averaged RF power P with the axial change rate used to solve the attenuation constant of the existing high-frequency structure. Starting from the basic theory of attenuation and transmission, it is deduced and numerically verified to obtain the solution formula of the attenuation constant of the high-frequency structure of the edge-aligned staggered grating traveling wave tube of the G band. The attenuation constant obtained by solving the solution can support the calculation of the 3D large-signal nonlinear beam-wave interaction solver BWISFW, and is compared with the commercial 3D electromagnetic simulation software CST-PIC. The calculation results are consistent. The physical meaning of the attenuation constant calculation formula derived by the present invention is the ratio of the initial energy of the signal to the energy at any position during the propagation process, which is more in line with the physical meaning of the attenuation constant of the microwave device. Therefore, it can be proved that the attenuation constant calculation method derived by the present invention reflects the physical meaning of attenuation more accurately, is suitable for the attenuation analysis of the high-frequency structure of the edge-aligned staggered grating traveling wave tube of the G band, and can provide accurate theoretical guidance for the design and manufacture of the edge-aligned staggered grating traveling wave tube of the G band, which helps to shorten the development cycle and reduce its production cost.

Claims

1. A method for solving the attenuation of a high-frequency structure of a G-band edge-aligned staggered grating traveling wave tube, characterized in that: The following steps are involved: S1. Build a 3D model of the G-band edge-aligned staggered-grating traveling-wave tube high-frequency structure using 3D electromagnetic simulation software with an eigenmode solver. S2. Perform pre-processing and solution settings based on the operating state of the G-band edge-aligned staggered grating traveling wave tube, and use the eigenmode solver to calculate the field distribution of the high-frequency structure to obtain the frequency f of the high-frequency structure; S3. After the eigenmode calculation of the high-frequency structure is performed using the 3D electromagnetic simulation software, the P loss ; S4. In the CST eigenmode solver, change the phase shift parameter Then re-solve and calculate to get the corresponding f and P loss ; Get at least n sets of phase shift parameters Corresponding f and P loss , n≥5; S5. Use formula (2) to obtain the time-averaged RF power P of the high-frequency structure of the traveling wave tube; Where l is the period length of the high-frequency structure, W T is the normalized energy of the eigenmode solution, v g is the group velocity; in the CST eigenmode solver, W T is 1 joule; group velocity v g The angular frequency ω and the propagation constant β are obtained by performing forward difference, center difference and backward difference on them. S6. Derive the formula for calculating the attenuation constant α of high-frequency structures from the basic theories of attenuation and signal transmission; According to the definition of attenuation of passive components, the attenuation L is the ratio of the input microwave power to the output microwave power under the condition of matching the attenuator terminal load. For the high-frequency structure of the traveling wave tube, the input microwave power is P and the output microwave power is (PP loss ), as shown in formula (3): The attenuation constant α represents the loss of microwave power per unit length in the signal transmission direction, then: Converting the unit of α to nepers gives the exact calculation method of the decay constant:

2. The attenuation solution method for the G-band edge-aligned staggered-grating traveling wave tube high-frequency structure according to claim 1, characterized in that: The pre-processing solution settings of step 2 include the frequency range of the eigenmode solution, the conductivity of the background material, the boundary conditions, and the phase shift parameters. Unit and material settings for meshing the model.

3. The attenuation solution method for the G-band edge-aligned staggered-grid traveling wave tube high-frequency structure according to claim 1, characterized in that: The three-dimensional electromagnetic simulation software with the eigenmode solver is CST.

4. The attenuation solution method for the G-band edge-aligned staggered-grating traveling wave tube high-frequency structure according to claim 3, characterized in that: The power loss P is calculated in the CST loss Specifically, the Loss and Q in the post-processing is used to fill in the conductivity determined by the working frequency band, material properties, and surface roughness of the current high-frequency structure, and calculate the loss power P of the current high-frequency structure under this phase shift parameter. loss .

5. The attenuation solving method for the high-frequency structure of a G-band edge-aligned staggered-grating traveling wave tube according to claim 1, characterized in that: n＝17。

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