A trapezoidal linear slow-wave structure with a double-periodic coupled cavity

Abstract

The present invention discloses a trapezoidal linear slow-wave structure with a dual-periodic coupled cavity. The slow-wave structure comprises an upper rectangular coupled cavity, an isosceles trapezoidal subwavelength aperture, a middle rectangular resonant cavity, a strip-shaped electron injection channel, and a lower rectangular coupled cavity. At the same longitudinal position, the upper and lower rectangular coupled cavities have the same width, and are periodically alternatingly arranged at adjacent longitudinal positions. Compared to conventional trapezoidal linear slow-wave structures, the present invention's trapezoidal linear slow-wave structure with a dual-periodic coupled cavity has a greater characteristic impedance and a smaller inherent quality factor. This enhances the intensity of the injection-wave interaction and improves the output performance of an extended interaction klystron. It also better avoids parasitic oscillations, resulting in a vacuum electronic device with improved output and more stable performance.

Description

Technical Field

[0001] The present invention relates to the field of microwave vacuum electronic technology, and in particular to a trapezoidal line slow-wave structure with a double-period coupled cavity. Background Art

[0002] With the development of ultrafast laser technology, terahertz (THz) technology has experienced rapid growth. Terahertz, also known as far-infrared waves, has a frequency range of 0.1 THz to 10 THz. It lies at the transitional stage between electronics and photonics. It possesses unique properties and advantages, such as low single-photon energy, strong penetration, transient properties, and good coherence. Therefore, it holds broad application prospects in various fields, including communications, radar, and imaging. Terahertz sources are key to THz technology research, with vacuum electron devices and solid-state devices being the most common and practical. In the THz frequency band, solid-state devices are limited by current process technology and their operating principles, resulting in relatively low output power, only approaching the watt level. Vacuum electron devices, with their high power, wide bandwidth, and excellent stability, offer significant advantages over solid-state devices. Therefore, vacuum electron devices are an ideal choice for promoting the further development of THz technology.

[0003] Among numerous vacuum electronic devices, the klystron boasts high gain and efficiency due to its resonant cavity structure. The traveling-wave tube (TWT) boasts a wide bandwidth, high gain, and a high broadband gain product. The extended interaction klystron (EIK) utilizes a resonant cavity formed by reflections from the end of a slow-wave structure. Combining the advantages of both, the EIK achieves high power, high gain, and wide bandwidth while boasting a small size, light weight, and compact structure, making it ideally suited for operation in the terahertz band. The resonant slow-wave structure, serving as the high-frequency interaction circuit of the EIK, has a crucial influence on its performance, including power, gain, and bandwidth.

[0004] Theoretically, various types of slow-wave structures such as staggered gratings, coupled cavity chains, and zigzag waveguides can be used as resonant slow-wave systems for extended interaction klystrons. Compared with other slow-wave structures such as traditional coupled cavities, the trapezoidal circuit structure is simpler, has better integrity and consistency, is easier to process and assemble, has low cost, and good heat dissipation. Therefore, considering the current processing level, most extended interaction klystrons at home and abroad currently use a trapezoidal line slow-wave structure. Traditional trapezoidal line slow-wave structures such as Figure 1As shown, the trapezoidal line structure consists of an upper rectangular coupling cavity 1, an intermediate rectangular resonant cavity 3 and a lower coupled rectangular cavity 5. The upper and lower coupling cavities are connected through the intermediate resonant cavity, and the strip electron injection channel extends perpendicular to the cross section of the resonant cavity to form a trapezoidal line slow-wave structure. Compared with the traditional trapezoidal line slow-wave structure, the intermediate rectangular resonant cavity is loaded with a subwavelength hole and connected to the upper and lower rectangular coupling cavities on both sides. The hole array structure can be used to simulate the surface plasma wave to enhance the surface electric field strength, increase the injection wave interaction area, and help enhance the modulation effect of the electromagnetic wave on the electron beam. According to our previous related work on patent CN 202310111842.3, as shown in the figure, Figure 2 As shown, the middle rectangular resonant cavity is connected to the upper and lower coupling cavities via an isosceles trapezoidal subwavelength aperture. The long base of the isosceles trapezoidal subwavelength aperture is proportional to the wide side of the resonant cavity (in the x-axis direction). The strip-shaped electron injection channel extends perpendicular to the resonant cavity cross-section. The upper and lower rectangular coupling cavities use the same structure, and the structures of adjacent longitudinal coupling cavities are also identical. It is demonstrated that the use of isosceles trapezoidal subwavelength apertures in the middle rectangular resonant cavity can better increase the injection-wave interaction area, improve the characteristic impedance, and increase the interaction efficiency. However, like the traditional trapezoidal linear slow-wave structure, its inherent quality factor is still relatively large, which can easily lead to parasitic oscillations and instabilities, seriously adversely affecting the performance of the entire extended interaction klystron. Summary of the Invention

[0005] The purpose of the present invention is to address the deficiencies of the prior art and provide a trapezoidal line slow-wave structure with a dual-period coupled cavity to improve the power and gain of an extended interaction klystron while avoiding parasitic oscillations. The present invention creatively proposes a trapezoidal line slow-wave structure with a dual-period coupled cavity formed by staggered changes in the widths of adjacent coupled cavities. Compared with the traditional trapezoidal line slow-wave structure, especially the middle resonant cavity loaded with an isosceles trapezoidal subwavelength hole, the present invention, on this basis, utilizes the staggered changes in the widths of adjacent coupled cavities to further increase the characteristic impedance of the slow-wave structure, improve the interaction strength, and further reduce the inherent quality factor, which can well avoid parasitic oscillations and is more conducive to the improvement of the performance of the extended interaction klystron. The trapezoidal line slow-wave structure with a dual-period coupled cavity of the present invention has obvious advantages in the terahertz frequency band, such as easy processing, better heat dissipation, higher characteristic impedance and smaller inherent quality factor.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: a trapezoidal linear slow-wave structure with a dual-periodic coupled cavity, comprising a plurality of slow-wave cavities arranged in parallel along a longitudinal axis, each slow-wave cavity comprising an upper coupling cavity, a resonant cavity, an electron injection channel 4, and a lower coupling cavity 5. The resonant cavity comprises a middle rectangular resonant cavity 3 and subwavelength holes 2 located at the upper and lower ends of the middle rectangular resonant cavity; the subwavelength holes 2 are isosceles trapezoids, with the long base of the isosceles trapezoid connected to the middle rectangular resonant cavity, and the short base of the isosceles trapezoid connected to the coupling cavity; the resonant cavities are periodically arranged along the longitudinal axis; the electron injection channel 4 is located at the center of the middle rectangular resonant cavity 3 and extends bidirectionally perpendicular to the longitudinal cross-section of the middle rectangular resonant cavity 3, penetrating the periodically arranged resonant cavities;

[0007] The upper coupling cavity 1 is connected to the subwavelength hole on one side of the resonant cavity, and the lower coupling cavity 5 is connected to the subwavelength hole on the other side of the resonant cavity. The coupling cavity includes a W1 rectangular coupling cavity 6 and a W2 rectangular coupling cavity 7. The widths of the coupling cavities of adjacent slow-wave cavities are W1 and W2, respectively. The W1 rectangular coupling cavity 6 and the W2 rectangular coupling cavity 7 are alternately arranged adjacent to each other along the longitudinal axis to form an upper coupling cavity and a lower coupling cavity with a double-periodic structure. The upper coupling cavity 1 and the lower coupling cavity 5 have the same structure and dimensions at the same longitudinal position. The width ratio of W2 to W1 is defined as l, where W2 is larger than W1.

[0008] Furthermore, the cross-sectional shape of the upper coupling cavity and the lower coupling cavity is rectangular, circular or elliptical, preferably rectangular.

[0009] Furthermore, the length and thickness of the upper coupling cavity and the lower coupling cavity are the same.

[0010] Furthermore, the shape of the sub-wavelength hole can be a rectangle or an isosceles trapezoid, preferably an isosceles trapezoid.

[0011] Furthermore, the electron injection channel is a circular channel, an elliptical channel, or a strip-shaped injection channel, preferably a strip-shaped injection channel.

[0012] The present invention forms a trapezoidal line slow-wave structure with a double-period coupled cavity by changing the width of the coupled cavity and utilizing the staggered change of the widths of adjacent coupled cavities.

[0013] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0014] 1. The slow-wave structure with a dual-period coupled cavity of the present invention utilizes the width variation of the coupled cavity cross section and alternately changes the width dimensions of adjacent coupled cavities in the longitudinal direction to obtain a larger characteristic impedance. This allows for more effective injection-wave interaction and achieves better output performance. It also significantly reduces the inherent quality factor, avoids the generation of parasitic oscillations, and makes the output performance more stable and reliable.

[0015] 2. The resonant cavity adopts isosceles trapezoidal subwavelength holes of equal proportion, which can better increase the injection wave interaction area, improve the characteristic impedance, and increase the interaction efficiency.

[0016] 3. In the terahertz frequency band, the output power of traditional cylindrical electron injection vacuum electron devices is inversely proportional to the square of the frequency, severely limiting their power output. The present invention utilizes a strip-shaped electron injection channel, whose output power is inversely proportional to the first power of the frequency. This overcomes the limitations of geometric dimensions and operating frequency, enabling high power output in the high-frequency band. Furthermore, the strip-shaped electron injection channel has a simple structure and is easy to manufacture. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 Schematic diagram of the vacuum model of the traditional trapezoidal line slow-wave structure, where a is the main view, b is the side view, and c is the three-dimensional structure diagram.

[0018] Figure 2 Schematic diagram of the vacuum model of a trapezoidal line slow-wave structure with an isosceles trapezoidal subwavelength hole of equal proportion in the middle resonant cavity, where a is the main view, b is the side view, and c is the three-dimensional structure diagram.

[0019] Figure 3 This is a schematic diagram of the vacuum model of the trapezoidal line slow-wave structure with a dual-period coupled cavity of the present invention, where a is the main view, b is the side view, and c is the three-dimensional structure diagram.

[0020] Figure 4 This is a slope diagram of the metal model of the trapezoidal line slow-wave structure with a double-period coupled cavity of the present invention.

[0021] Figure 5 for Figure 3 Dimensional diagram of the trapezoidal line slow-wave structure with a double-periodic coupled cavity;

[0022] Figure 6 The figure shows the variation of the characteristic impedance R / Q of the trapezoidal line slow-wave structure with the double-period coupled cavity according to the present invention with the width ratio l.

[0023] Figure 7 The figure shows how the inherent quality factor Q0 of the trapezoidal line slow-wave structure with a double-period coupled cavity varies with the width ratio l.

[0024] The following description is made with reference to the accompanying drawings:

[0025] 1. Upper rectangular coupled cavity; 2. Isosceles trapezoidal subwavelength hole; 3. Middle rectangular resonant cavity; 4. Strip electron injection channel;

[0026] 5. Lower rectangular coupling cavity; 6. Rectangular coupling cavity with width W1; 7. Rectangular coupling cavity with width W2. DETAILED DESCRIPTION

[0027] In order to make the purpose, technical solutions and beneficial effects of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments.

[0028] This embodiment provides a trapezoidal linear slow-wave structure with a double-period coupled cavity, such as Figure 3 As shown, it includes an upper rectangular coupling cavity 1, an isosceles trapezoidal subwavelength hole 2, an intermediate rectangular resonant cavity 3, a strip electron injection channel 4, and a lower rectangular coupling cavity 5; the intermediate rectangular resonant cavity 3 and the isosceles trapezoidal subwavelength holes 2 located on both sides of the intermediate rectangular resonant cavity 3 constitute a resonant cavity, and the long base of the isosceles trapezoidal subwavelength hole 2 is proportionally connected to the wide side (x-axis direction) of the intermediate rectangular resonant cavity 3; the resonant cavities are periodically arranged along the longitudinal axis (z-axis direction); the strip electron injection channel 4 is a rectangular hole located at the center of the intermediate rectangular resonant cavity 3, and the strip electron injection channel 4 extends in both directions perpendicular to the cross section (xoy plane) of the intermediate rectangular resonant cavity 3, penetrating the periodically arranged resonant cavities;

[0029] The resonant cavity is connected to the upper rectangular coupling cavity 1 and the lower rectangular coupling cavity 5 via the short base of the isosceles trapezoidal subwavelength hole 2. The rectangular coupling cavity includes a rectangular coupling cavity 6 with a width of W1 and a rectangular coupling cavity 7 with a width of W2. The rectangular coupling cavities 6 and 7 are alternately arranged adjacent to each other along the longitudinal direction (z-axis direction) to form an upper rectangular coupling cavity and a lower rectangular coupling cavity of a double-periodic structure. The upper rectangular coupling cavity 1 and the lower rectangular coupling cavity 5 have the same structure and dimensions at the same longitudinal position.

[0030] Based on the trapezoidal linear slow-wave structure with isosceles trapezoidal subwavelength holes 2 of equal proportion, the width of the coupling cavity cross section is varied to keep the width of the upper rectangular coupling cavity 1 and the lower rectangular coupling cavity 5 the same at the same longitudinal position. The width of the coupling cavity is periodically alternating at adjacent longitudinal positions, represented by W1 and W2 respectively. The width ratio of W2 to W1 is defined as l, where W2 is greater than W1. When W1 is equal to W2, it is Figure 2 The traditional trapezoidal line slow-wave structure shown uses isosceles trapezoidal sub-wavelength holes 2 of equal proportions.

[0031] Figure 4 This is a cross-section of the metal model of the trapezoidal line slow-wave structure with a double-periodic coupled cavity of the present invention. It can be seen that the widths of adjacent coupled cavities in the longitudinal direction change alternately. The trapezoidal line slow-wave structure is simple and easy to assemble, which is convenient for the implementation of current micromachining technology.

[0032] In the G band, the structural dimensions of the specific scheme of the trapezoidal line slow-wave structure with a double-period coupled cavity of the present invention are as follows: Figure 5As shown, where a is the length of the upper rectangular coupling cavity 1 and the lower rectangular coupling cavity 5, a1 is the length of the middle rectangular resonant cavity 3, a2 is the length of the strip-shaped electron injection channel 4, b is the thickness of the rectangular coupling cavity, b1 is the thickness of the resonant cavity, c is the length of the short base of the isosceles trapezoidal subwavelength aperture 2, and c1 is the width of the strip-shaped electron injection channel 4. In this embodiment, a = 1.07; a1 = 0.88; a2 = 0.8; b = 0.3; b1 = 0.09; c = 0.32; c1 = 0.14; w1 = 0.86; and w2 = 1 w1 (unit: mm).

[0033] The trapezoidal line slow-wave structure with the double-period coupled cavity is simulated to obtain its characteristic impedance R / Q and inherent quality factor Q0. Figure 6 The figure shows the variation of the characteristic impedance R / Q of the trapezoidal line slow-wave structure with the double-period coupled cavity according to the present invention with the width ratio l. Figure 7 The figure shows the variation of the inherent quality factor Q0 of the trapezoidal line slow-wave structure with a dual-periodic coupled cavity according to the present invention with the width ratio l. When l = 1, the figure shows the relevant characteristic parameters of the traditional trapezoidal line slow-wave structure with an isosceles trapezoidal sub-wavelength hole of equal proportion in the middle resonant cavity.

[0034] from Figure 6 and Figure 7 As can be seen from the figure, when l = 1, that is, the width of the adjacent coupled cavities w1 = w2, this is a traditional trapezoidal line slow-wave structure with isosceles trapezoidal subwavelength holes of equal proportions in the intermediate resonant cavity. Its characteristic impedance R / Q is relatively small, and the inherent quality factor Q0 is very large. When w2 = 1 w1 (l is greater than 1), that is, the widths of the adjacent coupled cavities are different, this is the trapezoidal line slow-wave structure with a dual-period coupled cavity of the present invention. As l gradually increases from 1, the characteristic impedance R / Q gradually increases while the inherent quality factor Q0 gradually decreases. This shows that the trapezoidal line slow-wave structure with a dual-period coupled cavity of the present invention has a larger characteristic impedance and a smaller inherent quality factor, can enhance the intensity of the injection-wave interaction, improve the output performance of the extended interaction klystron, and better avoid parasitic oscillations, thereby obtaining a vacuum electronic device with better and more stable performance.

[0035] Although the above describes the illustrative specific embodiments of the present invention to facilitate understanding of the present invention by those skilled in the art, it should be clear that the present invention is not limited to the scope of the specific embodiments, and any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A trapezoidal linear slow-wave structure with a dual-period coupled cavity, comprising a plurality of slow-wave cavities arranged in parallel along a longitudinal axis, characterized in that: Each slow-wave cavity comprises: an upper coupling cavity (1), a resonant cavity, an electron injection channel (4), and a lower coupling cavity (5); the resonant cavity comprises a middle rectangular resonant cavity (3) and subwavelength holes (2) located at the upper and lower ends of the middle rectangular resonant cavity; the subwavelength hole (2) is an isosceles trapezoid, the long base of the isosceles trapezoid is connected to the middle rectangular resonant cavity, and the short base of the isosceles trapezoid is connected to the coupling cavity; the resonant cavities are periodically arranged along the longitudinal axis; the electron injection channel (4) is located at the center of the middle rectangular resonant cavity (3), and the electron injection channel (4) extends in two directions perpendicular to the longitudinal axis cross section of the middle rectangular resonant cavity (3), penetrating the periodically arranged resonant cavities; The upper coupling cavity (1) is connected to the subwavelength hole on one side of the resonant cavity, and the lower coupling cavity (5) is connected to the subwavelength hole on the other side of the resonant cavity; the coupling cavity comprises a W1 rectangular coupling cavity (6) and a W2 rectangular coupling cavity (7); the widths of the coupling cavities of adjacent slow-wave cavities are W1 and W2 respectively; the W1 rectangular coupling cavity (6) and the W2 rectangular coupling cavity (7) are alternately arranged adjacent to each other along the longitudinal axis to form an upper coupling cavity and a lower coupling cavity of a double-periodic structure; the upper coupling cavity (1) and the lower coupling cavity (5) have the same structure and adopt the same structure and size at the same longitudinal position; wherein W2 is larger than W1.

2. The trapezoidal linear slow-wave structure with a double-period coupled cavity according to claim 1, characterized in that: The longitudinal cross-section of the upper coupling cavity and the lower coupling cavity is rectangular, circular or elliptical.

3. The trapezoidal linear slow-wave structure with a double-period coupled cavity according to claim 1, characterized in that: The upper coupling cavity and the lower coupling cavity have the same length and thickness.

4. The trapezoidal linear slow-wave structure with a double-period coupled cavity according to claim 1, characterized in that: The electron injection channel is a circular channel, an elliptical channel or a strip-shaped injection channel.

5. The trapezoidal linear slow-wave structure with a double-period coupled cavity according to claim 1, characterized in that: The sub-wavelength hole is rectangular in shape.

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