Design method for input coupler of convolution traveling wave amplifier

Abstract

The invention discloses an input coupler of a convolution traveling wave amplifier, and belongs to the technical field of microwave devices. The coupler for converting the rectangular waveguide TE10 mode into the circular waveguide TE11 mode structurally and mainly comprises an input rectangular waveguide, an electron beam circulation end and an output circular waveguide, the rectangular waveguide is connected with the circular waveguide, and the electron beam circulation end is completely communicated with the output circular waveguide. The electron beam circulation end is composed of a plurality of cylindrical resonant cavities, and the number, the radius and the width of the cylindrical resonant cavities are matched with the working frequency of the device. Compared with a traditional input coupler, the input coupler disclosed by the invention ensures that a TE11 mode is output by the output circular waveguide in a single direction by utilizing a multi-diffraction principle of a plurality of cylindrical resonant cavities, and the transmission and purity of the output circular waveguide TE11 mode can be improved; meanwhile, the electron beam circulation end is an open end, and a large space can be provided for electron beam circulation.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of microwave devices, in particular to a design method of a mode converter and a coupler. BACKGROUND

[0002] The gyrotron and gyrotron amplifier are tunable high frequency high power coherent radiation sources. They can be used in high resolution radar, plasma heating, electron paramagnetic resonance spectroscopy and deep space communication applications. The research on gyrotron and gyrotron amplifier based on helical waveguide has achieved good results in realizing high power and wide frequency tunability.

[0003] The gyrotron amplifier is similar in structure to the ordinary traveling wave tube, both of which are composed of an electron gun, a high frequency structure and a pair of input and output systems. The difference is that the gyrotron amplifier uses a magnetron injection electron gun to emit a gyro electron beam, and the phase velocity of the high frequency field in the gyrotron amplifier high frequency structure is greater than the speed of light in vacuum, so the gyrotron amplifier is a fast wave system.

[0004] The traditional input coupler has a geometry of a three-port T-shaped device. The T-shaped device is mainly used as a mode transducer, a polarizer and a microwave filter, and it is a basic microwave structure. Generally, port 1 of the T-shaped device is an input port, which adopts a rectangular or circular waveguide structure, and port 2 and port 3 are symmetric or asymmetric structures centered on port 1, and port 2 and port 3 are rectangular or circular waveguide structures. In addition, port 2 is a signal output end, and port 3 is a signal cutoff end.

[0005] In order to improve the electromagnetic wave transmission quality of the T-shaped device from port 1 to port 2, port 3 is usually a cutoff waveguide, and the cross section of the cutoff waveguide is usually smaller than that of the output waveguide. In order to improve the electromagnetic wave transmission quality of the T-shaped device from port 1 to port 2, port 3 is usually a cutoff waveguide, and the cross section of the cutoff waveguide is usually smaller than that of the output waveguide.

[0006] In the gyrotron amplifier, the input coupler is an important part of the gyrotron amplifier, which not only ensures the smooth transmission of the input signal from the input end to the output end, but also has a certain working bandwidth; at the same time, the cutoff end is an open end rather than a closed end, which not only ensures the good circulation of the electron beam in the cutoff waveguide, but also suppresses the transmission of the signal, prevents the electromagnetic wave from transmitting to the electron gun area and interfering with the emission and circulation of the electron beam; in addition, the gyrotron amplifier uses a magnetron injection electron gun to emit a gyro electron beam, and the electron beam needs to be compressed by a certain proportion from the gun area to the high frequency area, so the cross-sectional radius of the cutoff end is greater than that of the circular waveguide output end.

[0007] Compared with the traditional T-shaped input coupler, the input coupler in the application mainly consists of a rectangular waveguide, an electron beam flow passage, a circular waveguide output end and the like. 10 The electromagnetic wave is input in the TE 11 mode from the rectangular waveguide, and under the action of the coupler, the input signal is output in the TE 10 mode from the circular waveguide output end, and quasi-full reflection occurs at the electron beam flow passage and no output occurs from the passage. The electron beam flow passage is an important component of the high-frequency system of the gyrotron traveling wave amplifier, and is composed of multiple coaxial resonant cavities with different radii. SUMMARY

[0008] The application aims to design an input coupler applied to a gyrotron traveling wave amplifier.

[0009] To achieve the above-mentioned purpose, the application provides the following solutions.

[0010] An input coupler of a gyrotron traveling wave amplifier, comprising a rectangular waveguide, an electron beam flow passage, a circular waveguide output end and the like.

[0011] The rectangular waveguide is connected with the circular waveguide, the electron beam flow passage is connected with the circular waveguide, and the circular waveguide cavity and the electron beam flow passage are communicated.

[0012] The radius of each resonant cavity in the electron beam flow passage is greater than the radius of the output end circular waveguide.

[0013] The application ensures that the TE 10 mode of the rectangular waveguide is almost completely converted into the TE 11 mode of the circular waveguide output end by using the electron beam flow passage. 11 The radius, width and number of each resonant cavity in the electron beam flow passage are adjusted to greatly weaken the transmission of the TE 11 mode in the part, and ensure the one-way propagation of the TE

[0014] The width of the narrow side of the rectangular waveguide in the application can be comparable to the width of the cylindrical resonant cavity. BRIEF DESCRIPTION OF DRAWINGS

[0015] Figure 1 It is a three-dimensional overall structural diagram of the input coupler of the gyrotron traveling wave amplifier.

[0016] Figure 2 It is a sectional view of the input coupler of the gyrotron traveling wave amplifier.

[0017] Figure 3The internal cavity three-dimensional structure diagram of the input coupler of the gyro-TWA.

[0018] Figure 4 The input port reflection parameter S 11 curve.

[0019] Figure 5 The output port transmission parameter S 21 curve.

[0020] Figure 6 The cutoff port transmission parameter S 31 curve. DETAILED DESCRIPTION

[0021] The technical solutions in the embodiments of the present application will be described in detail below with reference to the accompanying drawings in the embodiments of the present application, so as to illustrate the technical solutions of the present application. The described embodiments are not all the embodiments, but only some embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0022] ATTACHMENT Figure 1 The three-dimensional overall structure diagram of the input coupler of the gyro-TWA; ATTACHMENT Figure 2 The sectional view of the input coupler of the gyro-TWA; ATTACHMENT Figure 3 The internal cavity three-dimensional structure diagram of the input coupler of the gyro-TWA; ATTACHMENT Figure 4 The S 11 curve of the input coupler of the gyro-TWA; ATTACHMENT Figure 5 The S 21 curve of the input coupler of the gyro-TWA; ATTACHMENT Figure 6 The S 31 curve of the input coupler of the gyro-TWA.

[0023] The input signal mode is TE 10 mode of the rectangular waveguide.

[0024] The present application takes the working frequency of 130 GHz-148 GHz as an example, and the working mode of the circular waveguide is TE 11 mode, and the center frequency is 140 GHz.

[0025] The input rectangular waveguide 1: the wide side is 1.22 mm, the narrow side is 0.45 mm, the length away from the center axis is greater than 3 mm, and the wall thickness can be valued according to actual needs.

[0026] The output circular waveguide 2: as a signal output end, and the working mode therein is TE11 The mold has an inner diameter r2 = 0.9 mm, a length greater than 3 mm, and a wall thickness that can be determined according to actual needs.

[0027] Reflecting circular waveguides 3 to 16 have equal lengths of 0.51 mm.

[0028] The inner diameter of reflecting circular waveguide 3 is r3 = 1.48 mm, the inner diameter of reflecting circular waveguide 4 is r4 = 1.25 mm, the inner diameter of reflecting circular waveguide 5 is r5 = 1.66 mm, the inner diameter of reflecting circular waveguide 6 is r6 = 1.68 mm, the inner diameter of reflecting circular waveguide 7 is r7 = 1.23 mm, the inner diameter of reflecting circular waveguide 8 is r8 = 1.42 mm, the inner diameter of reflecting circular waveguide 9 is r9 = 1.59 mm, and the inner diameter of reflecting circular waveguide 10 is r 10 = 1.34 mm, inner diameter r of reflecting circular waveguide 11 11 = 1.78 mm, inner diameter r of reflective circular waveguide 12 12 = 1.62 mm, inner diameter r of reflecting circular waveguide 13 13 =1.58 mm, inner diameter r of the reflecting circular waveguide 14 14 = 1.63 mm, inner diameter r of the reflecting circular waveguide 15 15 =1.50 mm, inner diameter r of the reflecting circular waveguide 16 16 =1.80 mm.

[0029] Circular waveguide 17: As the electron beam feed point, with a radius r 17 = 1.62 mm, length greater than 3 mm.

[0030] The outer diameters of the reflecting circular waveguides 3 and 17 can be the same, and the wall thickness can be selected according to actual needs.

[0031] The rectangular waveguide 1 and the circular waveguide 2 are not completely connected. The distance from the bottom of the rectangular waveguide 1 to the center circumference of the circular waveguide 2 is 0.8 mm.

[0032] Arc 18 is located at the root of rectangular waveguide 1. In actual fabrication, its chamfer radius r... 18 It can be any value from 0 to 0.4 mm.

[0033] The input port reflection parameters of the 140 GHz cyclotron traveling-wave amplifier input coupler provided in this example are as follows: Figure 4 As shown, the TE of this input coupler 10 The mode remains below −15 dB in the frequency range of 130 GHz to 144 GHz, S 11 Represents the input port (port 1) to TE 10 The reflectance of the mode, near 140 GHz, S 11The value can reach −30 dB, which shows that the input reflection parameter of the coupler is very low, and more than 95% of the signal can be input into the coupler.

[0034] Appendix Figure 5 TE at the output (2 ports) of the coupler 10 -TE 11 Transmission parameters, S 21 Represents the output terminal TE 11 TE mode for input port 10 The transmission coefficient of the mode, as shown in the figure, is TE in the range of 130 GHz to 145 GHz. 10 -TE 11 The transmission coefficient is greater than -0.5 dB, and over 90% of the signal can be output from the coupler; in the range of 135 GHz to 143 GHz, the transmission coefficient is less than -0.1 dB, and over 95% of the signal can be output from the coupler. This coupler can output high-purity circular waveguide TE. 11 model.

[0035] Appendix Figure 6 TE for the coupler cutoff port (3-port) 10 -TE 11 Transmission parameter S 31 (Only take r) 18 (For example, 0.4mm represents the TE at the cutoff port). 11 As shown in the figure, the transmission coefficients of the mode are all less than -13 dB in the range of 130 GHz to 148 GHz, with only about 5% of the signal being output from port 3; in the range of 133 GHz to 148 GHz, the transmission coefficients are all less than -15 dB, with only about 3% of the signal being output from port 3. This coupler has excellent cutoff and isolation performance.

[0036] The cyclotron traveling wave amplifier input coupler has a wide operating bandwidth, ranging from 130 GHz to 148 GHz, with an operating bandwidth of 18 GHz.

Claims

1. A cyclotron traveling-wave amplifier input coupler, characterized in that: The coupler includes an input rectangular waveguide, an electron beam flow terminal, and an output circular waveguide. The input coupler is connected to the circular waveguide via a rectangular waveguide, and the electron beam flow terminal is fully connected to the output circular waveguide.

2. The cyclotron traveling-wave amplifier input coupler according to claim 1, characterized in that: The electron beam flow end is composed of multiple cylindrical resonant cavities, the number, radius and width of which are adapted to the operating frequency of the device.

3. The cyclotron traveling-wave amplifier input coupler according to claim 1, characterized in that: The radius of each resonant cavity at the electron beam flow end is larger than the radius of the output circular waveguide.

4. The cyclotron traveling-wave amplifier input coupler according to claim 1, characterized in that: The input coupler's conversion mode is rectangular waveguide TE. 10 Mode conversion to circular waveguide TE 11 model.

5. The cyclotron traveling-wave amplifier input coupler according to claim 1, characterized in that: The applicable frequency bands of the input coupler include, but are not limited to, microwave, millimeter wave and terahertz frequency bands.

6. The cyclotron traveling-wave amplifier input coupler according to claim 1, characterized in that: The input coupler is not limited to the input structure of a cyclotron amplifier, but is also applicable to the output structure of a cyclotron oscillator.

7. The cyclotron traveling-wave amplifier input coupler according to claim 1, characterized in that: The input coupler is suitable for rectangular waveguide TE 10 Mode-to-circular waveguide (TE) 11 Mode or circular waveguide TE 11 Mode conversion to rectangular waveguide TE 10 Mode converter or coupler structure.

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