A hybrid gyrotron traveling wave tube high frequency system with confocal waveguide and circular waveguide cascaded

Abstract

The present invention discloses a hybrid gyrotron high-frequency system of a confocal waveguide and a circular waveguide cascaded, belonging to the technical field of microwave, millimeter wave and terahertz devices. The high-frequency system includes an axially cascaded confocal waveguide linear high-frequency band and a circular waveguide nonlinear high-frequency band. The present invention adopts a linear high-frequency band and a nonlinear high-frequency band of different waveguide structures, in which the high-frequency field has two different working modes, and the corresponding dispersion characteristic curves are different; in the confocal waveguide linear high-frequency band, a high-order mode is adopted to work to realize electron beam modulation and clustering; in the circular waveguide nonlinear section, a low-order over-mode state is adopted to work to realize the interaction and energy conversion between the electron beam and the high-frequency field. Therefore, the present invention can greatly increase the linear high-frequency size and heat dissipation area, effectively realize the operation of the millimeter-wave high average power / continuous wave power gyrotron traveling wave tube, and improve the device operating frequency, power and stability.

Description

Technical Field

[0001] The invention belongs to the technical field of microwave, millimeter wave and terahertz devices, and in particular relates to a hybrid gyrotron traveling wave tube high frequency system of a confocal waveguide and a circular waveguide cascaded. Technical Background

[0002] With the rapid development of new generation high-performance radar, communication and other technologies, the system has increasingly higher requirements for the performance of high-power signal source such as operating frequency, bandwidth and power. In the millimeter wave band, gyrotron traveling wave tubes with advantages such as high bandwidth and high power have broad application prospects and development potential.

[0003] The high-frequency system of a gyrotron traveling wave tube includes a linear high-frequency band and a nonlinear high-frequency band. The linear high-frequency band is a lossy structure that mainly realizes electron beam modulation and clustering, while the nonlinear high-frequency band mainly realizes the interaction and energy conversion between the electron beam and electromagnetic waves. In the development process of gyrotron traveling wave tubes, closed high-frequency structures such as rectangular waveguides, circular waveguides, and spiral corrugated waveguides, as well as open high-frequency structures such as confocal waveguides and photonic crystal waveguides have been produced. Usually, the linear high-frequency band and the nonlinear high-frequency band use the same waveguide structure and work in the same waveguide mode. However, as the operating frequency increases, the device size decreases, which leads to an increase in the heat loss power density of the linear high-frequency loading section (especially the end of the loading section) and a sharp drop in the device power capacity. Summary of the invention

[0004] In view of the shortcomings of the prior art, the present invention proposes a hybrid gyrotron traveling wave tube high-frequency system of cascaded confocal waveguide and circular waveguide. The high-frequency system includes a directly cascaded confocal waveguide linear high-frequency band and a circular waveguide nonlinear high-frequency band, and solves the problem of power capacity reduction caused by increased operating frequency and reduced size by adopting different types of waveguide structures.

[0005] The present invention is implemented by the following technical solutions:

[0006] A hybrid gyrotron traveling wave tube high frequency system of cascaded confocal waveguide and circular waveguide, characterized in that the high frequency system comprises an axially cascaded confocal waveguide linear high frequency section and a circular waveguide nonlinear high frequency section.

[0007] The confocal waveguide linear high frequency band comprises a square cylindrical metal shell, a confocal waveguide symmetrically arranged on the upper and lower top surfaces of the metal shell, and an absorbing medium layer arranged on the inner side wall of the metal shell.

[0008] Furthermore, wedge-shaped conductor columns with the same structure are respectively arranged on both sides of the confocal waveguide, and the cross-section of the wedge-shaped conductor column is a right-angled triangle, one of which is in contact with the metal shell, and the other is in contact with the side of the confocal waveguide.

[0009] Furthermore, the high-frequency system adopts an over-mode waveguide structure, wherein the working mode of the confocal waveguide linear high-frequency band is a high-order quasi-Gaussian mode HE 0m mode, the working mode of the circular waveguide nonlinear high frequency band is the circular waveguide TE 0n mode, and the confocal waveguide linear high frequency band and the circular waveguide nonlinear high frequency band have the same cutoff characteristics.

[0010] For linear high frequency band, the confocal waveguide works in HE 0m mode, the cutoff wave number is:

[0011]

[0012] Where m is a positive even number 2, 4, 6, etc., L t is the distance between the mirrors at the center, under confocal conditions, L t =R, R is the curvature radius of the confocal waveguide.

[0013] For nonlinear high frequency band, circular waveguide works in TE 0n mode, the cutoff wave number is:

[0014]

[0015] Where r is the radius of the circular waveguide, x n is the nth root of the first derivative of the zero-order Bessel function J0(x).

[0016] When the linear high frequency band and the nonlinear high frequency band have the same cutoff characteristics, they satisfy:

[0017]

[0018] The heat dissipation performance of the present invention is described in detail below:

[0019] The radius of the circular waveguide in the nonlinear high frequency band is r, and the length is L1, so the surface area of ​​the heat dissipation structure is:

[0020] S 圆 =2πrL1 (4)

[0021] The outer dimensions of the absorbing medium layer are a and b, and the length is L2. The surface area of ​​the heat dissipation structure is:

[0022] S 共焦 =2(a+b)L2 (5)

[0023] in,

[0024] a>b>>r (6)

[0025] Therefore, the heat dissipation area ratio of the confocal waveguide structure and the circular waveguide structure is:

[0026]

[0027] Usually in the design, a>b≈L t , from which we get:

[0028]

[0029] If the electron beam and HE 0m The mode has a total of m electric field peaks. Considering the symmetry, it is stipulated that the electron beam interacts with the i-th (i=1,2…m / 2) electric field peak counting from the center, that is, the guiding center diameter is:

[0030]

[0031] If n is fixed to 1, that is, the circular waveguide adopts TE 01 Mode, according to the principle of the strongest coupling coefficient in nonlinear high frequency, we can know:

[0032]

[0033] In summary, we can get:

[0034]

[0035] μ>>1 indicates that the high frequency of the hybrid gyrotron traveling wave tube proposed in the present invention can greatly increase the heat dissipation area and alleviate the problem of high frequency size reduction caused by high frequency operation.

[0036] At the same time, since the linear high frequency and nonlinear high frequency in the present invention adopt different waveguide structures, the high frequency field has two different working modes therein, and the corresponding dispersion characteristic curves are different; the high-order mode is adopted in the high-frequency band of the confocal waveguide to realize the modulation and clustering of the electron beam; the low-order over-mode state is adopted in the nonlinear band of the circular waveguide to realize the mutual energy conversion between the electron beam and the high frequency field. Therefore, the present invention can greatly increase the size and heat dissipation area of ​​the linear high frequency, alleviate the problems of the reduction of the high frequency size caused by high-frequency operation, the difficulty in improving the average power capacity of the device, the aggravation of the interception of the electron beam, and the aggravation of the outgassing caused by the bombardment of the loss material by the electron beam, effectively realize the operation of the millimeter wave high average power / continuous wave power gyrotron traveling wave tube, and improve the operating frequency, power and stability of the device. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 Schematic diagram of the three-dimensional structure of the traditional circular waveguide gyrotron traveling wave tube high-frequency system.

[0038] Figure 2 This is a schematic diagram of the three-dimensional structure of the hybrid gyrotron traveling wave tube high-frequency system proposed in the present invention.

[0039] Figure 3This is a side sectional view of the hybrid gyrotron traveling wave tube high frequency system proposed by the present invention.

[0040] Figure 4 This is a schematic diagram of the port mode electric field distribution of the hybrid gyrotron traveling wave tube high-frequency system proposed in the present invention, wherein Figure (a) is the electric field distribution of the confocal waveguide port, Figure (b) is the electric field distribution of the circular waveguide port, and Figure (c) is the electric field distribution of the entire high-frequency system.

[0041] Figure 5 This is a typical output signal curve of the hybrid gyrotron traveling wave tube high frequency system proposed in the present invention.

[0042] Figure 6 This is a typical output signal spectrum of the hybrid gyrotron traveling wave tube high frequency system proposed in the present invention.

[0043] Explanation of the accompanying figures: 1. Confocal waveguide, 2. Metal shell, 3. Circular waveguide, 4. Absorbing medium layer. DETAILED DESCRIPTION

[0044] The present invention is further described in detail below through a W-band hybrid gyrotron traveling wave tube high frequency system design example and accompanying drawings.

[0045] Attached Figure 1 Schematic diagram of the three-dimensional structure of the traditional circular waveguide gyrotron high-frequency system.

[0046] As attached Figure 2 , Figure 3 As shown, the hybrid gyrotron traveling wave tube high frequency system of this embodiment includes an axially cascaded confocal waveguide linear high frequency band and a circular waveguide nonlinear high frequency band.

[0047] The confocal waveguide linear high frequency band comprises a square cylindrical metal shell, a confocal waveguide symmetrically arranged on the upper and lower top surfaces of the metal shell, and an absorbing medium layer arranged on the inner wall of the metal shell; wedge-shaped conductor columns with the same structure are respectively arranged on both sides of the confocal waveguide, and the cross-section of the wedge-shaped conductor column is a right-angled triangle, one right-angled surface is in contact with the metal shell, and the other right-angled surface is completely in contact with the side surface of the confocal waveguide.

[0048] When electromagnetic waves are transmitted in a confocal waveguide, diffraction will occur, and the stray mode will affect the working mode. Therefore, a wedge-shaped conductor column is placed at the mirror of the confocal waveguide to guide the diffracted stray mode to the peripheral absorbing medium layer for full absorption.

[0049] The nonlinear high frequency section is composed of a smooth circular waveguide, and the end of the confocal waveguide linear high frequency section is directly connected to the entrance end of the nonlinear high frequency section of the circular waveguide.

[0050] Table 1 shows the main structural parameters of the W-band hybrid gyrotron high-frequency system of this embodiment. Among them, a = 14.8 mm, b = 14 mm, r = 2.5 mm, L = 140 mm, and combined with formula (1-11) for calculation, the surface area of ​​the hybrid gyrotron high-frequency is 3.7 times that of the traditional circular waveguide, which greatly increases the heat dissipation area and alleviates the electron beam interception and heat dissipation problems caused by the high-frequency size compression caused by high-frequency operation.

[0051] Table 1 Main structural parameters of the W-band hybrid gyrotron traveling wave tube high frequency system

[0052] Confocal waveguide length 140mm Circular waveguide length 20mm Confocal waveguide mirror distance R 7.0mm Circular waveguide radius r 2.1mm Absorbing medium layer width a 14.8mm Confocal waveguide bottom width w 11.2mm Height of absorbing medium layer b 14mm Confocal waveguide height h 3.2mm Absorbing medium layer thickness 0.6mm

[0053] In the present invention, different waveguide structures are used for the linear high frequency band and the nonlinear high frequency band, in which the high frequency field has two different modes. The high frequency port mode of the hybrid gyrotron traveling wave tube is as follows: Figure 4 As shown. In the linear high frequency confocal waveguide, the high order working mode is HE 04 , realize electron beam modulation and clustering; use low-order overmode state (TE) in nonlinear high-frequency circular waveguide 01 mode) to achieve the energy conversion between electron beam and high frequency field. Figure 5 and Figure 6 They are respectively the signal curves and corresponding spectrum observed at the output end after a 96 GHz sinusoidal signal is injected into the input end of the hybrid gyrotron traveling wave tube high-frequency system provided by the present invention. It can be seen that the structure can achieve stable amplification of the high-frequency field.

[0054] The above examples are only for the convenience of explaining the present invention. The hybrid high-frequency structure proposed in the present invention can be applied to high-frequency systems of gyrotron traveling wave tubes with different frequencies and different mode combinations. By changing the material size of the absorbing medium, as well as the arrangement of linear segments and nonlinear segments, etc., all belong to the scope of variation and protection of the present invention.

Claims

1. A hybrid gyrotron traveling wave tube high frequency system of confocal waveguide and circular waveguide cascade, characterized in that: The high frequency system includes an axially cascaded confocal waveguide linear high frequency section and a circular waveguide nonlinear high frequency section; The confocal waveguide linear high frequency band comprises a square cylindrical metal shell, a confocal waveguide symmetrically arranged on the upper and lower top surfaces of the metal shell, and an absorbing medium layer arranged on the inner side wall of the metal shell.

2. A hybrid gyrotron traveling wave tube high frequency system of confocal waveguide and circular waveguide cascaded as claimed in claim 1, characterized in that: Wedge-shaped conductor columns with the same structure are respectively arranged on both sides of the confocal waveguide. The cross section of the wedge-shaped conductor column is a right-angled triangle, one right-angled surface is in contact with the metal shell, and the other right-angled surface is completely in contact with the side surface of the confocal waveguide.

3. The hybrid gyrotron traveling wave tube high frequency system of confocal waveguide and circular waveguide cascaded as claimed in claim 1, characterized in that: The high-frequency system adopts an over-mode waveguide structure, wherein the working mode of the confocal waveguide linear high-frequency band is a high-order quasi-Gaussian mode HE 0m mode, the working mode of the circular waveguide nonlinear high frequency band is the circular waveguide TE 0n mode, and the confocal waveguide linear high frequency band and the circular waveguide nonlinear high frequency band have the same cutoff characteristics.

4. A hybrid gyrotron traveling wave tube high frequency system of confocal waveguide and circular waveguide cascaded as claimed in claim 3, characterized in that: When the confocal waveguide linear high frequency band and the circular waveguide nonlinear high frequency band have the same cutoff characteristics, they satisfy: Where m is a positive even number 2, 4, 6, ..., R is the curvature radius of the confocal waveguide, r is the radius of the circular waveguide, x n is the nth root of the first derivative of the zero-order Bessel function J0(x).

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