CN101127412B - A coupling output structure for gyrotron traveling wave amplifier - Google Patents

Abstract

A coupling output structure of a gyrotron traveling wave tube amplifier in the present invention has an input port; an output port: the radius of the output port is greater than the radius of the input port; a first-stage tapered circular waveguide and a second-stage gradient circular waveguide are cascaded between the input port and the output port N-level tapered circular waveguide. Two sections of modified Dorff-Chebyshev tapered circular waveguides are cascaded, or two sections of modified Dorff-Chebyshev tapered circular waveguides are cascaded in the middle to a transitional circular waveguide. The coupled output structure solves the problems of the prior art that the size is too large, the reflection coefficient of the input port is not low enough, the mixed mode suppression ability is not strong enough, and the like. The coupling output structure has been applied to the cyclotron traveling wave tube amplifier and achieved positive results, which has important practical engineering significance for the development of high-power microwave sources used in long-range radar and electronic information countermeasures in my country.

Description

A Coupling Output Structure of Contronic TWT Amplifier

technical field

The invention belongs to the field of microwave technology, and particularly relates to high-power microwave devices.

Background technique

There is a big gap between my country and foreign countries in the development of long-range radar, mainly because there is no suitable high-power microwave source, and the power of the high-power microwave source developed in China is far from meeting the needs of ultra-long-range radar systems. Amplifiers are one of the high power microwave sources most likely to meet this requirement.

Fundamentally speaking, the coupling output structure of the gyrotron amplifier is a circular waveguide gradient structure, and its main function is to match the circular waveguide with a smaller radius to the circular waveguide with a larger radius. There are many gradient methods for the gradient structure that can accomplish this function, such as linear gradients, exponential gradients, and Chebyshev gradients. Different gradient methods have different performances in different applications. In the application of the gyro-traveling-wave tube amplifier, a single-stage taper structure is usually used.

In the accompanying drawings, Fig. 1A, Fig. 1B, Fig. 1C and Fig. 1D show a kind of coupling output structure of the gyrotron traveling wave tube amplifier designed according to the solution of the prior art, which adopts a single-segment modified Dolf—— Chebyshev tapered circular waveguide references: [1] H.Flugel, E.Kuhn, "Computer-Aided Analysis and Design of Circular Waveguide Tapers". IEEE trans., Microwave Theory and Techniques, vol.36, no.2, Feb. 1988, pp 332-336. For ease of comparison with embodiments of the present invention, the prior art solutions shown in Fig. 1A, Fig. 1B, Fig. 1C and Fig. 1D have the same input port radius and output port radius as the embodiment of the present invention, which are 5.82mm and 5.82mm respectively. 20mm.

Fig. 1A is a diagram of the variation of the radius of a single-segment modified Dolf-Chebyshev tapered circular waveguide with the axial position. The meanings represented by the curves in Fig. 1D, Fig. 2D and Fig. 3D are respectively: Curve S11 represents the reflection coefficient of input port 1 of the coupling output structure; Curve S121 represents the transmission curve of the first miscellaneous mode TM11 of the working main mode TE11 coupled from the input port to the output port; curve S122 represents the second miscellaneous mode TE31 of the working main mode TE11 coupled from the input port 1 to the output port 2 the transmission curve. Fig. 1C, Fig. 1D, Fig. 2C, Fig. 2D, Fig. 3C and Fig. 3D are calculated by finite element numerical calculation method.

From Figure 1A, it can be seen that under the current parameter conditions, the length of the coupling output structure is 195.798mm; Figure 1B is a cross-sectional view of the coupling output structure corresponding to Figure 1A; Figure 1C is a standing wave ratio diagram corresponding to the structure of Figure 1B, where The standing wave ratio at 16GHz is about 1.4, and the standing wave ratio is about 1.1 or less in the frequency range greater than 17.5GHz; Figure 1D shows the situation of mixed mode suppression corresponding to the structure of Figure 1B. It can be seen from the figure that the mixed mode suppression The curves S121 and S122 are between -15dB and -20dB above the high frequency band 17.5GHz. These all show that the solutions based on the prior art and the coupling output structure designed based on the current structural parameters are not ideal in terms of structural size, standing wave ratio, and ability to suppress mixed modes.

Contents of the invention

The purpose of the present invention is to solve the problems of the single-segment modified Dolf-Chebyshev tapered circular waveguide structure in the prior art, such as the size is too large, the reflection coefficient of the input port is not low enough, and the mixed mode suppression ability is not strong enough. The invention provides a coupling output structure of a gyrotron traveling wave tube amplifier.

In order to achieve the stated purpose, the technical scheme of the coupling output structure of the multi-stage cascaded traveling wave tube amplifier provided by the present invention is as follows:

It has an input port; it has an output port: the radius of the output port is greater than the radius of the input port; between the input port and the output port, there are a first-level tapered circular waveguide and an N-level tapered circular waveguide cascaded.

According to an embodiment of the present invention, the first-level tapered circular waveguide and the N-th stage tapered circular waveguide use a modified Dolf-Chebyshev tapered circular waveguide.

According to the embodiment of the present invention, two-stage waveguide cascading is adopted, that is, the first-stage tapered circular waveguide is cascaded with the second-stage tapered circular waveguide; one end of the first-stage tapered circular waveguide is the input port, and the second-stage tapered circular waveguide One end is an output port.

According to an embodiment of the present invention, the first-stage tapered circular waveguide and the second-stage tapered circular waveguide are modified Dolf-Chebyshev tapered circular waveguides.

According to an embodiment of the present invention, a three-stage waveguide cascade is adopted, that is, a second-stage transitional circular waveguide is cascaded between the first-stage tapered circular waveguide and the third-stage tapered circular waveguide; one end of the first-stage tapered circular waveguide is An input port, and one end of the third-stage tapered circular waveguide is an output port.

According to an embodiment of the present invention, the first-stage tapered circular waveguide and the third-stage tapered circular waveguide are modified Dolf-Chebyshev tapered circular waveguides, and the second-stage transitional circular waveguide is a section of cylindrical waveguide.

According to an embodiment of the present invention, the overall radius change of the first-stage tapered circular waveguide is smaller than the overall radius change of the N-stage tapered circular waveguide; the first reference complex mode suppression degree of the first-stage tapered circular waveguide is smaller than that of the N-stage tapered The first reference noise-mode rejection for a circular waveguide.

Positive effects of the present invention: the coupling output structure of multi-stage cascaded cyclotron traveling wave tube amplifiers of the present invention solves the single-stage modified Dolf-Chebyshev tapered circular waveguide structure [1] of the prior art solution. Large, the input port reflection coefficient is not low enough, the mixed mode suppression ability is not strong enough and so on. In the embodiment of the present invention, the coupling output structure has a working frequency band close to the cut-off frequency of its input port of 15.1 GHz, which is characterized by relatively low standing wave in the working frequency band, high ability to suppress mixed modes, compact structure, and smooth inner wall. Compared with the single-segment modified Dolf-Chebyshev tapered circular waveguide structure designed under the same structural parameters in the prior art, the coupling output structure has better transmission performance, and it has a more compact structure, Lower VSWR and better ability to suppress mixed modes, and better meet the assembly requirements of the whole tube of the gyro-traveling-wave tube amplifier.

The present invention is applied to the high-power microwave source of the cyclotron traveling wave tube amplifier, and is used in national defense fields such as radar target imaging, radar anti-low flying target, missile defense and electronic countermeasures, as well as civil fields such as deep space detection, remote sensing, meteorology and navigation. It has a good application prospect.

Description of drawings

Fig. 1A is the variation of the radius of the coupled output structure of the gyrotron traveling wave tube amplifier with the axial position in the prior art;

Fig. 1B is a sectional view of the structure corresponding to the structure of Fig. 1A;

Fig. 1C is the standing wave ratio corresponding to the structure of Fig. 1A;

Fig. 1D is the situation of heterogeneous mode suppression corresponding to the structure of Fig. 1A;

Fig. 2A is the variation of the radius with the axial position in Embodiment 1 of the present invention;

Fig. 2B is a sectional view of the structure corresponding to the embodiment of Fig. 2A;

Fig. 2C is the standing wave ratio corresponding to the embodiment of Fig. 2A;

Fig. 2D is the situation of heterogeneous mode suppression corresponding to the embodiment of Fig. 2A;

Fig. 3 A is the variation of the radius with the axial position according to Embodiment 2 of the present invention;

Fig. 3B is a sectional view of the structure corresponding to the embodiment of Fig. 3A;

Fig. 3 C is the standing wave ratio corresponding to the embodiment of Fig. 3A;

Fig. 3D is the situation of heterogeneous mode suppression corresponding to the embodiment of Fig. 3A;

specific implementation plan

In order to help a better understanding of the present invention, the specific implementation of the present invention will be described below with reference to the accompanying drawings, and the coupling output structure of multi-stage cascaded gyrotron amplifiers will be described in detail below with reference to the accompanying drawings.

The high-power and wide-bandwidth capabilities of the cyclotron traveling-wave tube amplifier in the millimeter wave band make it a coherent radiation source that has attracted much attention among high-power microwave sources, and has been widely used in radar and communication systems. The waveguide radius used in the main interaction section of the gyrotron TWT amplifier does not meet the electron heat injection load requirements or the collector voltage limit. Therefore, a tapered waveguide needs to be used to connect the interaction section and the output window, that is, the coupling output structure. The coupling output structure of the gyrotron amplifier can couple the high-energy microwave in the main interaction waveguide working near the cutoff frequency to the external microwave power transmission system. At the same time, the coupled output structure must have a low standing wave ratio and high rejection of heterogeneous modes.

The working characteristics of the gyrotron TWT amplifier put forward the following two restrictions on the design of its coupling output structure: First, structurally, the operating frequency of the high-power gyrotron TWT amplifier is usually close to the cut-off frequency of its main interaction waveguide, and the main interaction waveguide The active waveguide has a relatively small radius; in order to transmit higher powers, the outer transmission waveguide is required to have a relatively large radius. Therefore, the radius of the circular waveguide at the output end of the coupled output structure is usually 2 to 3 times larger than the input radius. The length of the coupling output structure should be as short as possible to reduce the requirements on the volume of the gyrotron and the working magnetic field. The inner wall of the coupling output structure should be smooth to prevent sparking. It is necessary to ensure that the change gradient of the waveguide radius between the output of the coupling output structure and the input port should be as low as possible, so as to prevent the transmission performance from changing when the output waveguide is connected to an external system.

Second, in terms of transmission performance, the coupling output structure must have a low standing wave ratio to avoid reflected waves affecting the normal operation of the main interaction loop; it is also required that the high-energy microwave transmission mode in the coupling output structure has high stability and the output circle The waveguide must have a good ability to suppress mixed modes. These two limitations pose a great challenge to the design of the coupling output structure of the gyro TWT amplifier.

Modified Dolf-Chebyshev tapered circular waveguide has been widely used in waveguide tapering. Compared with other tapering methods (such as linear tapering, exponential tapering, etc.), the change gradient of waveguide radius with input and output ports is zero. It has the advantages of smooth inner wall and strong suppression ability of mixed modes [1]. However, the working frequency range of the modified Dolf-Chebyshev tapered circular waveguide is usually far away from the cut-off frequency of the port. However, in the application of the gyrotron traveling wave tube amplifier, the working frequency band of the coupled output structure needs to be close to the cutoff frequency of its input port. In this case, if a single-segment modified Dolf-Chebyshev tapered circular waveguide is used as the coupling output structure of the convoluted traveling wave tube amplifier, the size and structure will not be compact enough, the reflection will not be low enough, and the ability to suppress mixed modes will not be strong enough. question. Therefore, the coupling output structure of the single-section modified Dolf-Chebyshev tapered circular waveguide cannot meet the actual needs well, and the coupling output structure of the multi-section cascaded convolution traveling wave amplifier proposed by the present invention can be more compact Smaller size structure, smaller reflection coefficient and better ability to suppress miscellaneous modes.

Figures 1A, 1B, 1C and 1D show a prior art solution using a single segment modified Dolf-Chebyshev tapered circular waveguide. In order to more accurately illustrate the performance superiority of the design scheme of the present invention, a single-segment modified Dolf-Chebyshev tapered circular waveguide with the same structural parameters as the present invention is specially designed and calculated as a reference. Comparing the radius change Fig. 1A, structure Fig. 1B, standing wave ratio Fig. 1C and heterogeneous mode suppression Fig. 1D of this reference design scheme with the two embodiments of the present invention, it is easier to distinguish the differences and the performance of the present invention superiority.

The relevant theory [1] shows that the three design parameters of the modified Dolf-Chebyshev tapered circular waveguide can be described by the following equations:

${\mathrm{<span\; class="notranslate">\; W</span>}}_{\mathrm{<span\; class="notranslate">\; max</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; dB</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span><span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 20</span>}{\mathrm{<span\; class="notranslate">\; log</span>}}_{\mathrm{<span\; class="notranslate">\; 10</span>}}<span\; class="notranslate">\; [</span>\mathrm{<span\; class="notranslate">\; 2</span>}\frac{{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}}{{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}\mathrm{<span\; class="notranslate">\; ln</span>}<span\; class="notranslate">\; (</span>\frac{{\mathrm{<span\; class="notranslate">\; a</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}}{{\mathrm{<span\; class="notranslate">\; a</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; \&CenterDot;</span>\frac{\mathrm{<span\; class="notranslate">\; \&theta;</span>}}{\mathrm{<span\; class="notranslate">\; sinh</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&theta;</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 0.21723</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; ]</span>$

$\mathrm{<span\; class="notranslate">\; a</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&theta;</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; a</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}\mathrm{<span\; class="notranslate">\; exp</span>}<span\; class="notranslate">\; \{</span>\mathrm{<span\; class="notranslate">\; ln</span>}<span\; class="notranslate">\; (</span>\frac{{\mathrm{<span\; class="notranslate">\; a</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}}{{\mathrm{<span\; class="notranslate">\; a</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}}<span\; class="notranslate">\; )</span>{<span\; class="notranslate">\; \&Integral;</span>}_{<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; \&theta;</span>}}^{\mathrm{<span\; class="notranslate">\; \&theta;</span>}}\frac{{\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&theta;</span>}\sqrt{\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&xi;</span>}<span\; class="notranslate">\; /</span>\mathrm{<span\; class="notranslate">\; \&theta;</span>}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; )</span>}{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; sinh</span>}\mathrm{<span\; class="notranslate">\; \&theta;</span>}}\mathrm{<span\; class="notranslate">\; d\&xi;</span>}<span\; class="notranslate">\; \}</span>$

$\mathrm{<span\; class="notranslate">\; z</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&theta;</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 2</span>}{\mathrm{<span\; class="notranslate">\; k</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}}{{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}{<span\; class="notranslate">\; \&Integral;</span>}_{<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; \&theta;</span>}}^{\mathrm{<span\; class="notranslate">\; \&theta;</span>}}{\mathrm{<span\; class="notranslate">\; a</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&xi;</span>}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; d\&xi;</span>}$

Among them, a and z are the radius and length of the tapered waveguide respectively; W _max is the first reference mixed-mode suppression degree in the design process. I ₀ is the zero-order modified Bessel function of the first kind. a ₁ and a ₂ are the radii of the input and output waveguides, respectively. _k0 is the free-space wavenumber at the center frequency of the operating frequency band. x _n and x _m are the roots of the Bessel function derivatives corresponding to the working principal mode and the first reference miscellaneous mode respectively. It should be noted that the first reference noise-mode suppression degree W _max is only a reference value for determining the integral boundary θ. The design parameters, design process and achieved performance will be described in detail below.

In the two specific implementations of the prior art and the present invention, the radius of the input port 1 is 5.82 mm, the radius of the output port 2 is 20 mm, and the radius of the output port is 3.44 times the radius of the input port. According to the calculation, it can be obtained that the ratio of the radius of the output port to the radius of the input port is 1, or as large as 5 times, that is, the ratio of the radius is 1 to 5 times, and good performance can be obtained.

In order to illustrate the superiority in the structure and performance of the multi-stage cascaded gyro-traveling wave tube amplifier coupling output structure of the present invention and the existing single-stage modified Dolf-Chebyshev tapered circular waveguide, the following description will Adopt the method of comparison, with embodiment 1 of the present invention, as shown in Figure 2A, Figure 2B, Figure 2C and Figure 2D, embodiment 2, as shown in Figure 3A, Figure 3B, Figure 3C and Figure 3D, and existing The techniques are shown in Figure 1A, Figure 1B, Figure 1C and Figure 1D for comparative illustration.

Please refer to Fig. 1A, Fig. 1B, Fig. 1C and Fig. 1D, which show the details of the coupled output structure of the convoluted TWT amplifier using the prior art single-segment modified Dolf-Chebyshev tapered circular waveguide structure design. Design parameters: the radius of input port 1 is 5.82mm, the radius of output port 2 is 20mm, the first reference mixed mode suppression degree W _max is -60dB, and the overall length is 195.798mm. Figure 1A shows the variation of radius with axial position for a solution (single-segment modified Dolf-Chebyshev tapered circular waveguide structure). Figure 1B shows a cross-sectional view of the structure corresponding to Figure 1A. FIG. 1C shows the standing wave ratio corresponding to the structure of FIG. 1B , wherein the standing wave ratio is about 1.4 at 16 GHz, and is about 1.1 or less in the frequency range greater than 17.5 GHz. Figure 1D is the mixed mode suppression corresponding to the structure of Figure 1B. It can be seen from the figure that the curves S121 and S122 are between -15dB and -20dB in the high frequency band (above 17.5GHz); the curve S11 represents the input port of the coupling output structure 1 reflection coefficient, the curve S12 represents the transmission curve of the working main mode TE11 coupled into the waveguide from the input port 1 to the output port 2. Figure 1A, Figure 1C and Figure 1D illustrate that the single-segment modified Dolf-Chebyshev tapered circular waveguide structure based on the existing solutions has the advantages of large structure size, insufficient reflection coefficient of input port 1, and insufficient suppression of mixed modes, etc. question.

Embodiment 1: Please refer to Fig. 2A, Fig. 2B, Fig. 2C and Fig. 2D, the details of the coupling output structure of the convoluted traveling wave tube amplifier designed by cascading two sections of modified Dolf-Chebyshev tapered circular waveguides . Please refer to FIG. 2A , which shows the variation of the radius with the axial distance in Embodiment 1. Referring to FIG. In Figure 2B, the coupling output structure adopts two-stage waveguide cascading, that is, the first-stage tapered circular waveguide 3 is cascaded with the second-stage tapered circular waveguide 4; one end of the first-stage tapered circular waveguide 3 is the input port 1, and the second stage tapered circular waveguide One end of the tapered circular waveguide 4 is the output port 2 . Both the first-stage tapered circular waveguide 3 and the second-stage tapered circular waveguide 4 are modified Dolf-Chebyshev tapered circular waveguides. The design parameters of this embodiment are: the radius of the input port 1 is 5.82 mm, the radius of the output port 2 is 20 mm, and the overall length is 174.487 mm. Among them, the input radius of the first-stage tapered circular waveguide 3 is 5.82mm, the output radius is 7.5mm, and the length is 54.27mm, and the W _max is -75dB during design; the input radius of the second-stage tapered waveguide 4 is 7.5mm, the output radius is 20mm, and the length is 130.317mm , W _max is -35dB during design.

According to the above design parameters, the overall radius change of the first-stage tapered circular waveguide 3 is smaller than the overall radius change of the second-stage tapered circular waveguide 4, that is, the overall radius change of the first-stage tapered circular waveguide 3 is small, only 1.68mm, and the second The overall radius of the gradually tapered circular waveguide 4 varies greatly, which is 12.5 mm. After calculation, the overall radius change of the first-stage tapered circular waveguide 3 is 0.8 mm, or 2 mm, and the overall radius change of the second-stage tapered circular waveguide 4 is 13.38 mm, or as small as 12.18 mm. Design within the range can get good transmission performance. The first reference mixed-mode suppression degree of the first-stage tapered circular waveguide 3 is 30 dB smaller than the first reference mixed-mode suppression degree of the second-stage tapered circular waveguide 4 . After calculation, the first reference mixed-mode suppression degree of the first-stage tapered circular waveguide 3 is 20dB or 40dB lower than the first reference mixed-mode suppression degree of the second-stage tapered circular waveguide 4. Designs within such a value range are all Good transmission performance can be obtained.

Compared with the structure of the existing solution under the same structural parameters, that is, the radii of the input port 1 and the output port 2 , that is, compared with FIG. 1B , it can be found that the overall length of this embodiment is shorter and the structure is more compact.

Please refer to Figure 2C, which shows the VSWR of this scheme. The specific situation is: the frequency band with standing wave ratio less than 1.15 is 16GHz to 18.5GHz; the frequency band with standing wave ratio less than 1.05 is 16.37GHz to 18.5GHz; The ISWR curve is very flat. The center frequency of 17.25 GHz of the operating frequency band is 1.14 times the cutoff frequency of 15.1 GHz of the operating mode of the input end. Compared with the standing wave ratio of the structure under the same structural parameters, that is, the radius of the input port 1 and the output port 2, that is, compared with Fig. 1C, the embodiment 1 has a lower Standing wave ratio, that is, embodiment 1 has lower reflection and better transmission performance than the prior art solution. Please refer to FIG. 2D , which shows the suppression of mixed modes in Embodiment 1 of the present invention. In the entire frequency range of 15.5GHz-18.5GHz, the first miscellaneous mode TM11 is suppressed below -28.5dB as shown by the curve S121; the second miscellaneous mode TE31 is suppressed below -33.5dB as shown by the curve S122. Comparing the solution of the prior art as shown in FIG. 1C , it can be seen that the mixed mode suppression capability of this embodiment is better. The curve S11 represents the reflection coefficient of the input port 1 of the coupling-out structure, and the curve S12 represents the transmission curve of the working main mode TE11 coupled into the waveguide from the input port 1 to the output port 2 . Through the elaboration of Embodiment 1 of the present invention and the system comparison with the prior art solution, it can be seen that the embodiment 1 of the present invention has a more compact structure, lower standing wave ratio and better mode suppression ability than the prior art solution .

Embodiment 2: Please refer to Fig. 3A, Fig. 3B, Fig. 3C and Fig. 3D, which shows the design of two sections of modified Dolf - Chebyshev tapered circular waveguide loaded with a section of uniform circular waveguide cascaded in the middle. Details of the coupling output structure of the gyrotron traveling wave tube amplifier. Please refer to FIG. 3A , which shows the variation of the radius with the axial distance in Embodiment 2 of the present invention. In FIG. 3B, the coupling output structure adopts three-stage waveguide cascading, that is, there is a cascade connection between the first-stage tapered circular waveguide 5 and the third-stage tapered circular waveguide 7; one end of the first-stage tapered circular waveguide 5 is an input port 1. One end of the third-stage tapered circular waveguide 7 is the output port 2 . The first-stage tapered circular waveguide 5 and the third-stage tapered circular waveguide 7 are both modified Dolf-Chebyshev tapered circular waveguides; the second-stage transitional circular waveguide 6 is a section of cylindrical waveguide between the first-stage tapered circular waveguide 5 and the third grade tapered circular waveguide 7. The design parameters of this embodiment are: the radius of the input port 1 is 5.82 mm, the radius of the output port 2 is 20 mm, and the overall length is 180.397 mm. Among them, the first-stage tapered circular waveguide 5 has an input radius of 5.82mm, an output radius of 7mm, and a length of 47.923mm, and the W _max is -75dB during design; the second-stage transition circular waveguide 6 is a uniform circular waveguide with a length of 17mm and a radius of 7mm; The three-stage tapered circular waveguide 7 has an input radius of 7mm, an output radius of 20mm, a length of 115.474mm, and a W _max of -32dB during design.

According to the above design parameters, the overall radius change of the first-stage tapered circular waveguide 5 is smaller than the overall radius change of the second-stage tapered circular waveguide 7, that is, the overall radius change of the first-stage tapered circular waveguide 5 is small, only 1.18 mm, and the third The overall radius of the graded tapered circular waveguide 7 varies greatly, which is 13mm; After calculation, the overall radius change of the first-stage tapered circular waveguide 5 is 0.8mm, or to 2mm, and the overall radius change of the second-stage tapered circular waveguide 7 is 13.38mm, or to 12.18mm, such a value range Internal design can get good transmission performance. The first reference mixed-mode suppression degree of the first-stage tapered circular waveguide 5 is 33 dB smaller than the first reference mixed-mode suppression degree of the third-stage tapered circular waveguide 7 . After calculation, the first reference mixed-mode suppression degree of the first-stage tapered circular waveguide 5 is 20dB or 40dB lower than the first reference mixed-mode suppression degree of the second-stage tapered circular waveguide 7. Designs within such a value range are all Good transmission performance can be obtained.

Compared with the structure of the existing technical solution with the same structural parameters, that is, the radius of the input port 1 and the output port 2, that is, compared with FIG. 1B, it can be seen that the overall length of embodiment 2 is shorter and the structure is more compact.

Referring to Figure 3C, the standing wave ratio of this embodiment is shown. The specific situation is: the frequency range of the VSWR less than 1.1 is 15.8GHz-18.5GHz; the frequency range of the VSWR less than 1.05 is 16.44GHz-18.5GHz. Compared with the standing wave ratio of the structure with the same structural parameters, that is, the radius of the input port 1 and the output port 2, compared with the prior art solution, that is, compared with FIG. 1C, it can be seen that the embodiment 2 has a better Low standing wave ratio, that is, embodiment 2 has lower reflection and better transmission performance than the prior art solution. Please refer to Fig. 3D, which shows the mixed mode suppression of this scheme. Please refer to Fig. 3D, which shows the mixed mode suppression of this scheme. The first miscellaneous mode TM11 (curve S121 ) is suppressed below -25dB in the entire frequency range of 15.5GHz-18.5GHz; the second miscellaneous mode TE31 (curve S121 ) is suppressed below -32dB. The curve S11 represents the reflection coefficient of the input port 1 of the coupling-out structure, and the curve S12 represents the transmission curve of the working main mode TE11 coupled into the waveguide from the input port 1 to the output port 2 . Comparing Fig. 1C of the prior art solution, it can be seen that Embodiment 2 has a better capability of suppressing complex modes. Through the elaboration of Embodiment 2 of the present invention and the system comparison with the prior art solution, it can be seen that the embodiment 2 of the present invention has a more compact structure, lower standing wave ratio and better mode suppression ability than the prior art solution .

The lowest mode cut-off frequency corresponding to the input port 1 circular waveguide radius of 5.82 mm is calculated to be about 15.1 GHz in the design schemes of the above two embodiments. Therefore, comparing Embodiment 1 and Embodiment 2 of the present invention with the prior art solutions, Comparing Fig. 2C, Fig. 3C and Fig. 1C, it can be found that the present invention has a lower standing wave ratio in the working frequency band 16GHz-18.5GHz close to the cutoff frequency, that is, better transmission performance.

The above is only a specific implementation mode in the present invention, but the scope of protection of the present invention is not limited thereto. Anyone familiar with the technology can understand the conceivable transformation or replacement within the technical scope disclosed in the present invention. All should be covered within the scope of the present invention, therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims (5)

1. A coupling output structure of a gyro-traveling-wave tube amplifier, characterized in that the structure is used to connect the interaction section and the output window of the gyro-traveling-wave tube amplifier, and the high-energy microwave in the interaction section of the gyro-traveling-wave tube amplifier coupled to an external microwave power delivery system where: Has an input port; has an output port: The output port radius is greater than the input port radius; Between the input port and the output port, a first-level circular waveguide to an N-th-level circular waveguide are cascaded; wherein the first-level circular waveguide and the N-level circular waveguide are the first-level tapered circular waveguide and the N-level tapered circular waveguide; The first-stage tapered circular waveguide and the N-stage tapered circular waveguide adopt a modified Dolf-Chebyshev tapered circular waveguide, and N is equal to 2 or 3. 2. According to the coupling output structure of the gyrotron traveling wave tube amplifier according to claim 1, it is characterized in that a two-stage waveguide cascade connection is adopted, that is, the first stage tapered circular waveguide is cascaded with the second stage tapered circular waveguide; the first stage tapered circular waveguide is cascaded; One end of the waveguide is an input port, and one end of the second-stage tapered circular waveguide is an output port. 3. According to the coupling output structure of the gyrotron traveling wave tube amplifier according to claim 1, it is characterized in that three-stage waveguide cascading is adopted, that is, the second stage cascaded between the first stage tapered circular waveguide and the third stage tapered circular waveguide The one-stage circular waveguide is the second-stage transitional circular waveguide; one end of the first-stage tapered circular waveguide is an input port, and one end of the third-stage tapered circular waveguide is an output port. 4. According to the coupling output structure of the cyclotron traveling wave tube amplifier according to claim 3, it is characterized in that, the first-stage tapered circular waveguide and the third-stage tapered circular waveguide adopt a modified Dolf-Chebyshev tapered circular waveguide, The second-stage transition circular waveguide is a section of cylindrical waveguide. 5. according to claim 1 described gyrotron traveling wave tube amplifier coupling output structure, it is characterized in that, the overall radius change of the first stage tapered circular waveguide is smaller than the overall radius change of the Nth stage tapered circular waveguide; the first stage tapered circular waveguide The first reference heterogeneous mode suppression degree is smaller than the first reference heterogeneous mode suppression degree of the Nth grade tapered circular waveguide.

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