A pi-shaped folded waveguide slow wave structure

Abstract

This invention provides a π-shaped folded waveguide slow-wave structure, comprising multiple upper and lower gates arranged in an alternating pattern, and an electron beam channel located at the central axis of the slow-wave structure. The folded waveguide slow-wave structure also includes a waveguide structure defined by each upper and lower gate. The waveguide structure includes straight waveguide segments forming multiple periodic structures and waveguide connection segments. The waveguide connection segments include expansion portions formed at both ends of the waveguide connection segments. This slow-wave structure can alter the internal field strength distribution of existing rectangular folded waveguides, improve the coupling impedance amplitude of the slow-wave structure, and effectively enhance the power and efficiency of the device.

Description

Technical Field

[0001] This invention relates to the field of microwave vacuum electronics technology. More specifically, it relates to a π-shaped folded waveguide slow-wave structure. Background Technology

[0002] Slow-wave structures are the core component of microwave vacuum electronic devices. Their function is to reduce the phase velocity of electromagnetic waves transmitted within them, ensuring that a certain spatial harmonic and the electron beam meet the synchronization condition. An interaction occurs between the electron beam and the electromagnetic field, amplifying the electromagnetic wave through energy exchange. In the short millimeter-wave and terahertz frequency bands, helical slow-wave structures are extremely difficult to fabricate, and their power handling capacity is low at high frequencies, with significant heat dissipation challenges. Therefore, all-metal folded waveguide slow-wave structures are commonly used in short millimeter-wave and terahertz traveling-wave tube devices. Folded waveguide slow-wave structures offer advantages such as high mechanical strength, good heat dissipation, large power capacity, wide bandwidth, ease of fabrication, and compatibility with microfabrication techniques, making them widely studied by vacuum electronic research institutions both domestically and internationally.

[0003] like Figure 1 and Figure 2 As shown, a conventional rectangular folded waveguide slow-wave structure is formed by arranging rectangular waveguides into a periodic structure along an electric field. The electron beam channel is a cylindrical structure located on the transverse central axis of the folded waveguide slow-wave structure. The electron beam channel (denoted as 10) and the rectangular folded waveguide (denoted as 20) are filled with a vacuum, while the rest is made of metallic material. The radius of the electron beam channel is denoted as r. c The width dimension of the rectangular folded waveguide is denoted by a, the geometric period of the slow wave structure is denoted by p, the height of the straight waveguide (denoted as 201) is denoted by h, the narrow side is denoted by b, and the narrow side of the transverse straight waveguide (denoted as 202) is denoted by d.

[0004] In the short millimeter and terahertz frequency bands, conventional rectangular folded waveguide slow wave structures have low axial coupling impedance and low interaction efficiency between electron beams and electromagnetic waves. This limits the performance improvement of device gain, power and efficiency, and to some extent affects the application of such slow wave structures. Summary of the Invention

[0005] To address the aforementioned problems, this invention provides a π-shaped folded waveguide slow-wave structure. This slow-wave structure can alter the internal field strength distribution of existing rectangular folded waveguides, increase the coupling impedance amplitude of the slow-wave structure, and effectively improve device power and efficiency.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] The present invention provides a π-shaped folded waveguide slow wave structure, the folded waveguide slow wave structure comprising multiple upper gratings and multiple lower gratings distributed interleaved with each other, and an electron beam channel located at the central axis of the slow wave structure;

[0008] The folded waveguide slow wave structure also includes a waveguide structure defined by each upper grating and each lower grating;

[0009] The waveguide structure includes straight waveguide segments forming multiple periodic structures and waveguide connection segments; the waveguide connection segments include expansion portions formed at both ends of the waveguide connection segments.

[0010] Furthermore, a preferred embodiment is that the two expansion sections are arranged symmetrically with respect to the centerline of the waveguide connection section.

[0011] Furthermore, in a preferred embodiment, the waveguide connection segment includes an end boundary that protrudes beyond the side boundary of the electron beam channel in the direction of the straight waveguide segment axis.

[0012] Furthermore, in a preferred embodiment, the end boundary includes a vertical boundary and arc-shaped transition boundaries symmetrically arranged on the upper and lower sides of the vertical boundary.

[0013] Furthermore, in a preferred embodiment, the waveguide connection segment includes an inner arc boundary, which comprises at least two arc-shaped boundaries.

[0014] Furthermore, a preferred solution is,

[0015] Defined as b, the narrow side length of the straight waveguide segment, and p, the geometric period length of the slow wave structure;

[0016] The radius R corresponding to the arc-shaped boundary n The length is 0 < R n <(p / 4-b / 2).

[0017] Furthermore, a preferred solution is,

[0018] The narrow side length of the waveguide connection segment is defined as d;

[0019] The radius R corresponding to the arc-shaped transition boundary w The length is 0 < R w <d.

[0020] Furthermore, a preferred solution is,

[0021] The geometric period length of a slow-wave structure is defined as p;

[0022] The length L of the waveguide connection segment along the axial direction of the electron beam channel is 0 < L < p.

[0023] The beneficial effects of this invention are as follows:

[0024] Compared with the traditional rectangular folded waveguide slow wave structure, the π-shaped folded waveguide slow wave structure provided by the present invention improves the end structure of the waveguide connection segment by forming expansion sections at both ends of the waveguide connection segment. These expansion sections can increase the internal cavity volume of the waveguide connection segment, change the field strength distribution inside the folded waveguide, effectively increase the coupling impedance amplitude of the slow wave structure, and achieve effective improvement in device power and efficiency.

[0025] Furthermore, by combining the inner arc boundary of the waveguide connection segment with its inferior arc structure, the present invention increases the internal cavity volume of the waveguide connection segment, changes the field strength distribution inside the folded waveguide, and enhances the field strength near the electron beam channel, thereby improving the overall axial coupling impedance of the slow wave structure.

[0026] Compared to conventional rectangular folded waveguide slow wave structures, the π-shaped folded waveguide slow wave structure of this invention increases the axial coupling impedance by more than 30% in the 91-101 GHz frequency band. Attached Figure Description

[0027] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.

[0028] Figure 1 A schematic diagram of an existing rectangular folded waveguide slow wave structure is shown.

[0029] Figure 2 The diagram shows the structure of an existing single-period rectangular folded waveguide slow wave structure.

[0030] Figure 3 This is a front view of a single geometric period of the π-shaped folded waveguide provided by the present invention.

[0031] Figure 4 This diagram illustrates the structure of a single geometric period of the π-shaped folded waveguide provided by the present invention.

[0032] Figure 5 A schematic diagram of the π-shaped folded waveguide slow wave structure provided by the present invention is shown.

[0033] Figure 6 The diagram shows a comparison of the phase velocity ratio (Vp / c) between the slow-wave structure provided by this invention and the existing rectangular folded waveguide slow-wave structure.

[0034] Figure 7 The diagram shows a comparison of the axial coupling impedance between the slow-wave structure provided by this invention and the existing rectangular folded waveguide slow-wave structure. Detailed Implementation

[0035] Various exemplary embodiments of the present invention will now be described in detail with reference to the accompanying drawings. It should be noted that, unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps set forth in these embodiments do not limit the scope of the invention.

[0036] The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the invention or its application or use.

[0037] Technologies and equipment known to those skilled in the art may not be discussed in detail, but where appropriate, such technologies and equipment should be considered part of the specification.

[0038] In all the examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values.

[0039] It should be noted that similar labels and letters in the following figures indicate similar items; therefore, once an item is defined in one figure, it does not need to be discussed further in subsequent figures.

[0040] To improve the interaction efficiency between electron beams and electromagnetic waves in existing rectangular folded waveguide slow-wave structures, thereby enhancing device power and efficiency, this invention provides a π-shaped folded waveguide slow-wave structure, combined with... Figures 3 to 5 As shown, the folded waveguide slow wave structure specifically includes multiple upper gratings 4 and multiple lower gratings 5 ​​that are staggered with each other, and an electron beam channel 1 located at the central axis of the slow wave structure; the folded waveguide slow wave structure also includes a waveguide structure (also called a waveguide cavity) defined by each upper grating 4 and each lower grating 5; the waveguide structure includes straight waveguide segments 2 forming multiple periodic structures and waveguide connection segments 3.

[0041] It should be noted that, as shown in the figure, the π-shaped folded waveguide slow wave structure provided by this invention is a further improvement on the waveguide connection segment of the rectangular folded waveguide based on the existing rectangular folded waveguide slow wave structure. Those skilled in the art will understand that a folded waveguide typically includes multiple upper gratings 4 and multiple lower gratings 5 ​​arranged in an alternating pattern, and the straight waveguide segment 2 and waveguide connection segment 3 are defined by the upper gratings 4 and lower gratings 5 ​​into multiple geometrically periodic structures. Based on the structural style of the folded waveguide, combined with... Figure 4 The schematic diagram of the single geometric period of the π-shaped folded waveguide provided by the present invention is illustrated in this embodiment. However, those skilled in the art will understand that the improvement of the structure of the waveguide connection segment 3 in the present invention includes the waveguide connection segment 3 located above the electron beam channel 1 and the waveguide connection segment 3 located below the electron beam channel 1.

[0042] For ease of description, this invention defines the following: in the figures, 'a' represents the width of the waveguide, 'd' represents the width of the waveguide connection segment, 'b' represents the width of the straight waveguide segment, 'h' represents the height of the straight waveguide segment, and the electron beam channel radius is represented by 'r'. c The geometric period of the slow-wave structure is represented by p. This invention addresses an improvement to the folded waveguide slow-wave structure in a periodic structure where two straight waveguide segments have the same interaction distance; that is, the narrow side length b of the waveguides corresponding to two adjacent straight waveguide segments is equal.

[0043] Compared to existing technologies, the improvement of the waveguide connection segment structure in this invention lies in that the waveguide connection segment 3 includes expansion portions 31 formed at both ends of the waveguide connection segment 3. That is, based on a conventional rectangular folded waveguide, the waveguide connection segment 3 is extended laterally to form two connected cavity structures at its two ends. Preferably, the two expansion portions 31 are arranged along the axial direction of the electron beam channel 1. Specifically, the expansion portions 31 are formed by an inward recess of the sidewall surface of the gate perpendicular to the axial direction of the electron beam channel.

[0044] In the above description, the grating includes an upper grating 4 corresponding to the waveguide connection section 3 above the electron beam channel 1, and a lower grating 5 corresponding to the waveguide connection section 3 below the electron beam channel 1. That is, when the waveguide connection section 3 above the electron beam channel 1 is taken as the object of description, the grating actually refers to the upper grating 4, and when the waveguide connection section 3 below the electron beam channel 1 is taken as the object of description, the grating actually refers to the lower grating 5.

[0045] Compared with the traditional rectangular folded waveguide slow wave structure, the π-shaped folded waveguide slow wave structure provided by the present invention improves the end structure of the waveguide connection section by forming expansion portions 31 at both ends of the waveguide connection section 3. The expansion portions 31 can increase the internal cavity volume of the waveguide connection section 3, change the field strength distribution inside the folded waveguide, effectively increase the coupling impedance amplitude of the slow wave structure, and achieve effective improvement in device power and efficiency.

[0046] Specifically, two expansion sections 31 are formed at both ends of the waveguide connection section 3 along the axial direction of the electron beam channel 1; the two expansion sections 31 are symmetrically arranged with respect to the center line 32 of the waveguide connection section 3 to avoid the generation of a stop band at the 3π phase shift.

[0047] Furthermore, the waveguide connection segment 3 includes an end boundary, which is the outer boundary of the expansion portion 31. This end boundary is formed by an outward bulge from the position corresponding to the side boundary of the straight waveguide segment 2, meaning the end boundary protrudes beyond the side boundary of the electron beam channel 1 of the straight waveguide segment 2, and the side boundary is perpendicular to the axis of the electron beam channel 1. Even further, the end boundary includes a vertical boundary 311 and arc-shaped transition boundaries 312 symmetrically arranged on the upper and lower sides of the vertical boundary 311; specifically, the radius R corresponding to the arc-shaped transition boundary 312 is... w The length is 0 < R w <d.

[0048] In one specific embodiment, the waveguide connecting segment 3 further includes an inner arc boundary, which comprises at least two arc-shaped boundaries 33, the two arc-shaped boundaries 33 being symmetrically arranged with respect to the centerline 32 of the waveguide connecting segment 3. By utilizing the inferior arc structure of the inner arc boundary of the waveguide connecting segment 3, this invention increases the internal cavity volume of the waveguide connecting segment 3, alters the field strength distribution inside the folded waveguide, and enhances the field strength near the electron beam channel, thereby improving the overall axial coupling impedance of the slow-wave structure.

[0049] In one specific embodiment, the structure of the arcuate boundary 33 of the present invention is defined, but not limited thereto, wherein the radius R corresponding to the arcuate boundary 33 is... n The length is 0 < R n <(p / 4-b / 2).

[0050] In addition, in order to ensure the integrity of the slow wave structure, reduce the difficulty of the process, and facilitate the manufacturing, in this invention, the start and end points of one end of the inner arc boundary coincide with the start and end points of the corresponding straight waveguide segment 2 sidewall, and the start and end points of the other end coincide with the start and end points of the corresponding straight waveguide segment 2 sidewall.

[0051] Compared with the traditional rectangular folded waveguide slow wave structure, the π-shaped folded waveguide slow wave structure provided by this invention improves the end structure of the waveguide connection segment and utilizes the inner arc boundary of the waveguide connection segment with a minor arc structure. This increases the internal cavity volume of the waveguide connection segment, changes the field strength distribution inside the folded waveguide, improves the field strength near the electron beam channel, effectively increases the coupling impedance amplitude of the slow wave structure, and achieves effective improvement in device power and efficiency.

[0052] In one specific embodiment, in order to avoid the impact of communication between adjacent cavities on the slow wave performance, the length L of the waveguide connection segment 3 in the axial direction of the electron injection channel 1 is 0 < L < p.

[0053] When the dimensions of the π-shaped folded waveguide slow-wave structure are set (unit: mm) a = 1.9, b = 0.3, d = 0.4, p = 1.32, h = 0.52, rc =0.22, L=1.08, R w =0.2, R n =0.2. A folded waveguide model was established using the 3D electromagnetic software CST. Modeling and simulation were performed on both a conventional rectangular folded waveguide and a π-shaped folded waveguide, and their performance was compared and analyzed. To increase the magnitude of the coupling impedance (Kc) of the slow-wave structure of the π-shaped folded waveguide, the period p or parameter L was adjusted so that its center frequency phase velocity ratio (Vp / c) was the same as that of the conventional folded waveguide. Figure 6 and Figure 7 The figures show a comparison of dispersion and coupling impedance for a π-shaped folded waveguide slow-wave structure and a conventional rectangular waveguide slow-wave structure, respectively. Compared to the conventional rectangular folded waveguide slow-wave structure, the π-shaped folded waveguide slow-wave structure exhibits an increase in axial coupling impedance of over 30% in the 91-101 GHz frequency band. Therefore, under otherwise unchanged conditions, using the π-shaped folded waveguide slow-wave structure as the interaction circuit, microwave vacuum tubes can achieve higher gain, higher power, and higher efficiency due to the increased coupling impedance.

[0054] The π-shaped folded waveguide slow wave structure provided by this invention is simple. It only requires milling an additional cavity structure on the basis of a conventional rectangular waveguide and chamfering the right angle of the grating. The manufacturing process is very easy to implement, and the performance improvement is significant. Compared with the conventional structure, the axial coupling impedance increases by more than 30%, which can improve the gain and efficiency of short millimeter wave and terahertz devices.

[0055] Specifically, in combination Figure 3 , Figure 4 and Figure 5 As shown, this invention is an optimization based on a conventional rectangular folded waveguide. During machine processing of the folded waveguide, the waveguide connection section is extended laterally, and to improve processing performance, the upper and lower right angles of the cavity structure are chamfered. The chamfer radii are denoted as R. w (0 < R) w <d), forming a cavity structure with a lateral dimension of L (0 < L < p). Simultaneously, the right-angled boundaries at the connection points between the waveguide connecting section and the straight waveguide section within the folded waveguide are chamfered, with the chamfer radii denoted as R. n (0 < R) nBy subtracting (p / 4-b / 2), the π-shaped folded waveguide slow-wave structure of this invention can be obtained. Compared with the conventional rectangular right-angle folded waveguide slow-wave structure, this invention increases the internal cavity volume of the waveguide connection section, thereby enlarging the internal cavity and altering the field strength distribution inside the existing rectangular right-angle folded waveguide. This increases the field strength near the electron beam channel, thereby improving the coupling impedance amplitude of the slow-wave structure. The axial coupling impedance can be increased by more than 30% in the 91-101 GHz frequency band. This slow-wave structure has a simple manufacturing process, is easy to process and manufacture, and does not reduce the processing accuracy of each dimension. It is applicable to short millimeter and terahertz traveling wave tube slow-wave structures.

[0056] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. For those skilled in the art, other variations or modifications can be made based on the above description. It is impossible to exhaustively list all the implementation methods here. All obvious variations or modifications derived from the technical solutions of the present invention are still within the protection scope of the present invention.

Claims

1. A π-shaped folded waveguide slow wave structure, the folded waveguide slow wave structure comprising multiple upper gratings and multiple lower gratings arranged in an alternating manner, and an electron beam channel located at the central axis of the slow wave structure; The folded waveguide slow wave structure also includes a waveguide structure defined by each upper grating and each lower grating; The waveguide structure includes straight waveguide segments forming multiple periodic structures and waveguide connection segments; characterized in that, The waveguide connection segment includes expansion portions formed at both ends of the waveguide connection segment; The waveguide connection section includes an end boundary that protrudes beyond the side boundary of the electron beam channel in the direction of the straight waveguide section. The end boundary includes a vertical boundary and arc-shaped transition boundaries symmetrically arranged on the upper and lower sides of the vertical boundary.

2. The π-shaped folded waveguide slow-wave structure according to claim 1, characterized in that, The two expansion sections are symmetrically arranged with respect to the centerline of the waveguide connection section.

3. The π-shaped folded waveguide slow-wave structure according to claim 1, characterized in that, The waveguide connection segment includes an inner arc boundary, which includes at least two arc-shaped boundaries.

4. The π-shaped folded waveguide slow-wave structure according to claim 3, characterized in that, Defined as b, the narrow side length of the straight waveguide segment, and p, the geometric period length of the slow wave structure; The radius R corresponding to the arc-shaped boundary n The length is 0 < R n < (p / 4-b / 2).

5. The π-shaped folded waveguide slow-wave structure according to claim 1, characterized in that, The narrow side length of the waveguide connection segment is defined as d; The radius R corresponding to the arc-shaped transition boundary w The length is 0 < R w <d.

6. The π-shaped folded waveguide slow-wave structure according to claim 1, characterized in that, The geometric period length of a slow-wave structure is defined as p; The length L of the waveguide connection segment along the axial direction of the electron beam channel is 0 < L < p.

Images