A broadband folded all-metal slow wave structure

Abstract

The application discloses a broadband folded full-metal slow wave structure, which comprises a first grid body and a second grid body arranged in a central symmetry; the first grid body and the second grid body enclose an electron beam channel; the first grid body comprises a plurality of metal grids arranged at equal intervals along a direction of a traveling wave; a cross section of the metal grid along the direction of the traveling wave comprises a first rectangular section, a trapezoidal section and a second rectangular section connected in sequence; the first rectangular section is provided with an arc-shaped opening with an opening direction away from the trapezoidal section; the arc-shaped opening comprises a first opening and a second opening; a hollowed-out part of the first opening is a rectangular body, and a hollowed-out part of the second opening is a semi-cylindrical body. By setting the hollowed-out part of the first opening as the rectangular body and the hollowed-out part of the second opening as the semi-cylindrical body, a ring-shaped tip of the slow wave structure is prevented, the slow wave structure is easy to manufacture, the dispersion characteristic is improved to expand a bandwidth, high-frequency loss is reduced, and output power, gain, bandwidth and interaction efficiency of the traveling wave tube are improved.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of vacuum electron devices, and particularly relates to a wideband folded full-metal slow wave structure. BACKGROUND

[0002] Terahertz waves (0.1-3THz) have important research value and wide application prospects in many fields such as scientific research, communication equipment and national economy due to the characteristics of short wavelength, high frequency, low photon energy, high signal-to-noise ratio and wide bandwidth. With the increasing demand for millimeter wave terahertz power sources in the fields of radar, satellite communication, high-precision imaging, biological medicine and other fields, and the impact brought by the continuous development of solid-state power device sources in recent years, linear injection devices in vacuum electron devices are developing towards high frequency, wide bandwidth, high power and miniaturization. Traveling wave tubes have been widely used due to their wide operating bandwidth, high electron efficiency and relatively large output power.

[0003] As the core component of the traveling wave tube, the slow wave structure directly determines the device performance of the traveling wave tube. At present, the main full-metal slow wave structures in the terahertz wave band traveling wave tube mainly include folded waveguide, rectangular staggered double grid and sinusoidal waveguide structures. Due to the short working wavelength in the terahertz wave band, the structure size of the slow wave structure is small because of the size constraint, so the processing difficulty is great, and the advantages of high strength and easy processing of the folded waveguide structure have attracted widespread attention. Although the traditional folded waveguide has high coupling impedance, its dispersion characteristics are strong and the loss is large, which leads to the defects of small output power, low gain, narrow bandwidth and long saturated interaction length of the folded waveguide traveling wave tube. The slow wave structure with low high-frequency loss can greatly improve the output power, gain and electron efficiency of the traveling wave tube, and effectively reduce the tube length, which is beneficial to realize the wideband, high power and miniaturization of the traveling wave tube. Therefore, it is of great significance to develop a new slow wave structure with low high-frequency loss. SUMMARY

[0004] The technical problem to be solved by the present application is the narrow bandwidth and large loss of the traditional folded waveguide in the prior art, and the purpose is to provide a wideband folded full-metal slow wave structure. By setting the hollow part of the first opening as a rectangular body and the hollow part of the second opening as a semicircular column, the annular sharp end of the slow wave structure is prevented, which is easy to process and manufacture, improves the dispersion characteristics, expands the bandwidth, reduces the high-frequency loss, and improves the output power, gain, bandwidth and interaction efficiency of the traveling wave tube.

[0005] The present application is realized by the following technical scheme:

[0006] A wideband folded full-metal slow wave structure, comprising a first grid body and a second grid body arranged symmetrically in the center.

[0007] The first grid body and the second grid body enclose an electron beam channel.

[0008] The first grid body comprises a plurality of metal grids arranged at equal intervals along the direction of the traveling wave.

[0009] The cross section of the metal grid along the direction of the traveling wave comprises a first rectangular section, a trapezoidal section and a second rectangular section connected in sequence.

[0010] The first rectangular section is provided with an arc-shaped opening away from the trapezoidal section.

[0011] The arc-shaped opening comprises a first opening and a second opening.

[0012] The hollowed-out part of the first opening is a rectangular body, and the hollowed-out part of the second opening is a semi-cylindrical body.

[0013] The application encloses an electron beam channel by setting the first grid body and the second grid body, the first grid body comprises a plurality of metal grids arranged at equal intervals along the direction of the traveling wave, the cross section of the metal grid along the direction of the traveling wave comprises a first rectangular section, a trapezoidal section and a second rectangular section connected in sequence, the first rectangular section is provided with an arc-shaped opening away from the trapezoidal section, the hollowed-out part of the first opening is a rectangular body, and the hollowed-out part of the second opening is a semi-cylindrical body, which prevents the occurrence of a sharp tip of an electromagnetic wave, generates resonance, improves the color dispersion characteristic, expands the bandwidth, reduces the high-frequency loss, and improves the output power, gain, bandwidth and interaction efficiency of the traveling wave tube.

[0014] Further, in the first grid body, a waveguide cavity is formed between two adjacent metal grids, the bottom of the waveguide cavity is a circular arc, and the radius of the circular arc is R1.

[0015] Further, the metal grid and the adjacent waveguide cavity constitute a waveguide period of a slow wave structure.

[0016] Further, the metal grid of the second grid body is arranged at intervals with the metal grid of the first grid body.

[0017] The center line of the metal grid of the second grid body coincides with the center line of the waveguide cavity of the first grid body.

[0018] Further, the metal grid of the second grid body and the metal grid of the first grid body are staggered in the horizontal direction and the vertical direction.

[0019] Further, the depth of the vertical direction stagger is of, and R1<of<2R1, the width of the horizontal direction stagger is w2, and w2<p / 2, wherein p is the period length of the slow wave structure.

[0020] Further, the height of the first rectangular section is h1, and the width is w2.

[0021] The upper base width of the trapezoidal section is w1, the lower base width is w1+p / 2, and the height is h3.

[0022] Further, the length of the first opening is D, and the radius of the second opening is R, and 2R=D.

[0023] Further, the electron beam channel comprises a plurality of rectangular channels and arc-shaped channels arranged at both ends of the rectangular structure.

[0024] Compared with the prior art, the present application has the following advantages and beneficial effects:

[0025] The present application sets the hollowed-out part of the first opening as a rectangular body and the hollowed-out part of the second opening as a semi-cylinder, thereby preventing the occurrence of a sharp end of electromagnetic waves and resonance, improving the color dispersion characteristic, expanding the bandwidth, reducing high-frequency loss, and further improving the output power, gain, bandwidth and interaction efficiency of the traveling wave tube.

[0026] The wideband folded full-metal slow wave structure has more flat dispersion characteristics than the conventional folded waveguide slow wave structure, meaning that it has a wider cold bandwidth, and in addition, it has lower transmission loss. BRIEF DESCRIPTION OF DRAWINGS

[0027] In order to more clearly illustrate the technical solutions of the exemplary embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiments, and it should be understood that the following drawings only show some embodiments of the present application, and therefore should not be considered as a limitation on the scope, and for those skilled in the art, other related drawings can also be obtained without creative labor.

[0028] Figure 1 is a sectional view of the overall structure in the embodiment of the present application;

[0029] Figure 2 (a) is a side view of the first grid in the embodiment of the present application;

[0030] Figure 2 (b) is a side view of the waveguide cavity connection structure of the first grid and the second grid in the embodiment of the present application;

[0031] Figure 2 (c) is a side view of the second grid in the embodiment of the present application;

[0032] Figure 3(a) is a side view of the first and second grid combination in the embodiment of the present application;

[0033] Figure 3 (b) is an electron beam passage side view in the embodiment of the present application;

[0034] Figure 3 (c) is a perspective view of the embodiment of the present application; Figure 3 (a) is a reverse view;

[0035] Figure 4 is a comparison chart of the dispersion characteristics of the existing conventional folded waveguide slow wave structure and the broadband folded full-metal slow wave structure in the embodiment of the present application;

[0036] Figure 5 is a comparison chart of the dispersion characteristics of different stagger depths of the broadband folded full-metal slow wave structure in the embodiment of the present application;

[0037] Figure 6 is a comparison chart of the insertion loss characteristics of the existing conventional folded waveguide slow wave structure and the broadband folded full-metal slow wave structure in the embodiment of the present application;

[0038] Figure 7 is a comparison chart of the insertion loss characteristics of different stagger depths of the broadband folded full-metal slow wave structure in the embodiment of the present application;

[0039] Figure 8 is a comparison chart of the output power change with frequency of the conventional folded waveguide slow wave structure and the broadband folded full-metal slow wave structure in the embodiment of the present application;

[0040] Figure 9 is a comparison chart of the gain change with frequency of the conventional folded waveguide slow wave structure and the broadband folded full-metal slow wave structure in the embodiment of the present application;

[0041] Figure 10 is a comparison chart of the electron efficiency change with frequency of the conventional folded waveguide slow wave structure and the broadband folded full-metal slow wave structure in the embodiment of the present application.

[0042] Markings in the drawings and corresponding names of parts:

[0043] 1, first grid; 2, second grid; 01, metal grid; 02, waveguide cavity; 11, first rectangular section; 12, trapezoidal section; 13, second rectangular section; 011, first opening; 012, second opening; 021, rectangular passage; 022, arc-shaped passage. DETAILED DESCRIPTION

[0044] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the embodiments and accompanying drawings. The illustrative embodiments and descriptions of this invention are only for explaining this invention and are not intended to limit this invention.

[0045] In the following description, numerous specific details are set forth in order to provide a thorough understanding of the invention. However, it will be apparent to those skilled in the art that these specific details are not necessary to practice the invention. In other embodiments, well-known structures, circuits, materials, or methods have not been specifically described in order to avoid obscuring the invention.

[0046] Throughout this specification, references to "an embodiment," "an example," or "an example" mean that a particular feature, structure, or characteristic described in connection with that embodiment or example is included in at least one embodiment of the present invention. Therefore, the phrases "an embodiment," "an example," "an example," or "an example" appearing in various places throughout the specification do not necessarily refer to the same embodiment or example. Furthermore, specific features, structures, or characteristics can be combined in one or more embodiments or examples in any suitable combination and / or sub-combination. Moreover, those skilled in the art will understand that the illustrations provided herein are for illustrative purposes and are not necessarily drawn to scale. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0047] In the description of this invention, the terms "front", "rear", "left", "right", "up", "down", "vertical", "horizontal", "high", "low", "inner", and "outer" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting the scope of protection of this invention.

[0048] Example 1

[0049] like Figure 1 and Figure 2 As shown, this embodiment provides a broadband folded all-metal slow-wave structure, including a first grating 1 and a second grating 2 arranged in a centrally symmetrical manner;

[0050] The first grid 1 and the second grid 2 enclose an electron injection channel;

[0051] The first grid body 1 includes a plurality of metal grids 01 arranged at equal intervals along the traveling wave direction;

[0052] The cross section of the metal grid 01 along the traveling wave direction includes: a first rectangular segment 11, a trapezoidal segment 12, and a second rectangular segment 13 connected in sequence;

[0053] The arc-shaped opening is provided at one end of the first rectangular section 11 away from the trapezoidal section 12.

[0054] The arc-shaped opening comprises a first opening 011 and a second opening 012.

[0055] The hollowed-out part of the first opening 011 is a cuboid, and the hollowed-out part of the second opening 012 is a semicylinder.

[0056] The first grid body 1 and the second grid body 2 are arranged to enclose an electron beam channel, the first grid body 1 comprises a plurality of metal grids 01 arranged at equal intervals along the direction of the traveling wave; the cross section of the metal grid 01 along the direction of the traveling wave comprises, in sequence, a first rectangular section 11, a trapezoidal section 12, and a second rectangular section 13; the first rectangular section 11 is provided with an arc-shaped opening with an opening away from the trapezoidal section 12, the hollowed-out part of the first opening 011 is a cuboid, and the hollowed-out part of the second opening 012 is a semicylinder, which prevents the slow wave structure from having a ring-shaped sharp end, thus facilitating processing and manufacturing, improving the dispersion characteristic, expanding the bandwidth, reducing the high-frequency loss, and improving the output power, gain, bandwidth, and interaction efficiency of the traveling wave tube.

[0057] In some possible embodiments, in the first grid body 1, a waveguide cavity 02 is formed between two adjacent metal grids 01, and the bottom of the waveguide cavity 02 is a circular arc with a radius of R1.

[0058] In some possible embodiments, the metal grid 01 and the adjacent waveguide cavity 02 constitute a waveguide period of the slow wave structure.

[0059] In some possible embodiments, the metal grid 01 of the second grid body 2 is arranged at intervals with the metal grid 01 of the first grid body 1.

[0060] The center line of the metal grid 01 of the second grid body 2 coincides with the center line of the waveguide cavity 02 of the first grid body 1.

[0061] In some possible embodiments, the metal grid 01 of the second grid body 2 is arranged at intervals with the metal grid 01 of the first grid body 1 in the horizontal direction and the vertical direction.

[0062] The depth of the staggered arrangement in the vertical direction is of, and R1<of<2R1, and the width of the staggered arrangement in the horizontal direction is w2, and w2<p / 2, where p is the period length of the slow wave structure.

[0063] The staggered arrangement can increase the coupling impedance, improve the power, gain, and efficiency, and is between a semicircle and a full circle, and by limiting the parameters of the staggered arrangement, the loss is reduced and the bandwidth is increased.

[0064] In some possible embodiments, the height of the first rectangular section 11 is h1, and the width is w2.

[0065] The upper base width of the trapezoidal section 12 is w1, the lower base width is w1 + p / 2, and the height is h3.

[0066] In some possible embodiments, the length of the first opening 011 is D, the width is w2, the radius of the second opening 012 is R, and 2R = D.

[0067] In some possible embodiments, the electron beam channel includes a plurality of rectangular channels 021 and arc channels 022 correspondingly arranged at both ends of the rectangular structure.

[0068] In some possible embodiments, the width of the rectangular channel 021 is s, the length is a, and the height is h5;

[0069] The arc channel 022 is a quarter ring with an inner diameter of R3 and an outer diameter of R4, and R4 - R3 = s.

[0070] In one possible embodiment, in the 220GHz frequency band, the structural dimensions of the broadband folded all-metal slow-wave structure are: a = 0.80mm, b = 0.32mm, D = 0.20mm, h1 = 0.05mm, h2 = 0.11mm, R1 = 0.09mm, h3 = 0.197mm, h4 = 0.44mm, w1 = w2 = 0.15mm, of = 0.10mm, p = 0.503mm.

[0071] It should be particularly noted that when R1 < of < 2*R1, the electron beam channel needs to be changed to a combination of a half cylinder and a cuboid, which can avoid the resonance problem caused by the tip in the all-metal structure.

[0072] As Figure 3 shown, when viewed from the side perpendicular to the traveling wave direction, the arc openings formed after the first rectangular body of the first grid body 1 and the second rectangular body of the second grid body 2 coincide form a ring, and the radius of the ring is R2.

[0073] a is the length of the wide side of the waveguide, b is the length of the narrow side of the waveguide, h5 is the height of the straight waveguide section, p is the period length, R2 is the radius of the electron beam channel, and R4 and R3 are the large and small curvature radii of the bent part of the folded waveguide.

[0074] In one possible embodiment, in the 220GHz frequency band, the structural dimensions of the broadband folded all-metal slow-wave structure are: a = 0.75mm, b = 0.15mm, h5 = 0.25mm, p = 0.552mm, R2 = 0.10mm, s = 0.15mm, R3 = 0.06mm, R4 = 0.21mm.

[0075] The three-dimensional electromagnetic simulation software HFSS is used to calculate the dispersion characteristics and the insertion loss of the above-mentioned wideband folded full-metal slow wave structure in the 220 GHz frequency band and the conventional folded waveguide slow wave structure, and the high-frequency loss characteristics of each of the two slow wave structures are obtained by simulating 38 periods of the two slow wave structures by using the three-dimensional electromagnetic simulation software CST. Then, the PIC thermal simulation of 82 periods and 68 periods of the two slow wave structures is performed by using the three-dimensional electromagnetic simulation software CST, and the simulation results are shown in Figure 4 、 Figure 5 、 Figure 6 、 Figure 7 、 Figure 8 、 Figure 9 、 Figure 10 , wherein the solid line parts are respectively the dispersion characteristic curve, the insertion loss characteristic curve, the output power, and the gain electron efficiency curve varying with the frequency of the wideband folded full-metal slow wave structure. The dotted line parts are respectively the dispersion characteristic curve, the insertion loss characteristic curve, the output power, and the gain electron efficiency curve varying with the frequency of the wideband folded full-metal slow wave structure.

[0076] As can be seen from the dispersion characteristics of the wideband folded full-metal slow wave structure of the present application in Figure 4 and the comparative example, the normalized phase velocity curve of the wideband folded full-metal slow wave structure of the present application is relatively flat in a relatively wide frequency band (202-310 GHz), which means that it has a wider cold bandwidth, while the normalized phase velocity curve of the conventional folded waveguide slow wave structure is relatively steep, and they have basically the same normalized phase velocity at 220 GHz.

[0077] As can be clearly seen from the dispersion characteristic comparison chart of the wideband folded full-metal slow wave structure of the present application with different interlaced depths in Figure 5 , the wideband folded full-metal slow wave structure provided by the present application has a very flat dispersion characteristic curve in a relatively wide frequency band (202-310 GHz). It is shown that the cold bandwidth of the slow wave structure of the present application is greatly expanded. As can be seen from Figure 5 , as the interlaced depth of the wideband folded full-metal slow wave structure of the present application increases, the corresponding dispersion characteristic curve becomes steeper, and the normalized phase velocity value decreases, so the value of the appropriate interlaced depth of the present application is selected in combination with the needs of different bandwidths.

[0078] As can be seen from the dispersion characteristics of the wideband folded full-metal slow wave structure of the present application in Figure 6Compared with the prior art traditional folded waveguide slow wave structure, the insertion loss of the wideband folded full-metal slow wave structure of the present application is significantly lower than that of the traditional folded waveguide slow wave structure in the frequency band of 200-300 GHz. At a frequency of 220 GHz, the insertion loss of the wideband folded full-metal slow wave structure of the present application is 3.18 dB, which is about 41% lower than the insertion loss of 5.36 dB of the traditional folded waveguide slow wave structure. The lower high-frequency loss is conducive to improving the output power, gain and electronic efficiency of the traveling wave tube.

[0079] From Figure 7 As can be clearly seen from the dispersion characteristic comparison chart of the different stagger depths of the slow wave structure of the present application in the present application, the wideband folded full-metal slow wave structure provided by the present application has very low insertion loss in a relatively wide frequency band (200-300 GHz), which indicates that the high-frequency loss of the slow wave structure of the present application in the present application is greatly reduced. As can be seen from the dispersion characteristic comparison chart of the different stagger depths of the slow wave structure of the present application in the present application, Figure 7 As can be seen, with the continuous increase of the stagger depth of the wideband folded full-metal slow wave structure of the present application, i.e. of from 0.04 mm to 0.10 mm and then to 0.16 mm, the corresponding insertion loss continuously increases, i.e. from 3.18 dB to 3.68 dB and then to 4.28 dB. The increase of the insertion loss reduces the performance of the output power, gain and electronic efficiency of the traveling wave tube. Therefore, the appropriate value of the stagger depth of the slow wave structure is selected in combination with the needs of different bandwidths.

[0080] From Figure 8 As can be seen from the comparison between the present application and the comparative example in the present application, the output power of the wideband folded full-metal slow wave structure of the present application is significantly higher than that of the prior art folded waveguide slow wave structure at most frequency points in the working frequency band of 210-230 GHz, which indicates that the high-frequency loss of the slow wave structure of the present application is effectively reduced compared with the slow wave structure of the comparative example. The output power of the slow wave structure of the present application at a frequency of 220 GHz is 41.53 W, and the 3-dB power bandwidth is 12 GHz, while the 3-dB power bandwidth of the slow wave structure of the comparative example is 6 GHz, which is increased by 50%. This means that the slow wave structure of the present application has great improvement in the output power and bandwidth.

[0081] From Figure 9Compared with the prior art folded waveguide slow wave structure, the gain of the wideband folded full-metal slow wave structure of the present application is significantly higher than that of the prior art folded waveguide slow wave structure in the working frequency band of 210-230 GHz, which shows that the high frequency loss of the slow wave structure of the present application is effectively reduced compared with the slow wave structure of the comparative example. The gain of the slow wave structure in the present application at a frequency of 220 GHz is 32.47 dB, and the 3-dB gain bandwidth is 19 GHz, while the 3-dB gain bandwidth of the slow wave structure of the comparative example is 10.3 GHz, which is increased by nearly 85%, which means that the slow wave structure of the present application has great improvement in gain and bandwidth.

[0082] From Figure 10 Compared with the prior art folded waveguide slow wave structure, the electron efficiency of the wideband folded full-metal slow wave structure of the present application is significantly higher than that of the prior art folded waveguide slow wave structure at most frequency points in the working frequency band of 210-230 GHz, which shows that the high frequency loss of the slow wave structure of the present application is effectively reduced compared with the slow wave structure of the comparative example. The electron efficiency of the slow wave structure in the present application at a frequency of 220 GHz is 3.27%, and the 3-dB electron efficiency bandwidth is 12 GHz, while the 3-dB electron efficiency bandwidth of the slow wave structure of the comparative example is 6 GHz, which is increased by 50%, which means that the slow wave structure of the present application has great improvement in electron efficiency and bandwidth.

[0083] In combination with Figure 4 , Figure 5 , Figure 7 , Figure 8 , Figure 9 and Figure 10 We can see that the wideband folded full-metal slow wave structure of the present application has a more flat dispersion curve and a wider cold bandwidth than the prior art folded waveguide slow wave structure under the condition that the cutoff frequency and the 220 GHz normalized phase velocity are basically the same. PIC thermal simulation calculation shows that it has a wider 3-dB power bandwidth (increased by 50%) and a wider 3-dB bandwidth (increased by 85%), which shows that the wideband folded full-metal slow wave structure of the present application has good working performance.

[0084] The above specific embodiments further illustrate the purpose, technical solutions and beneficial effects of the present application, and it should be understood that the above description is only a specific embodiment of the present application and is not used to limit the protection scope of the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A broadband folded all-metal slow wave structure, characterized in that, The first grid (1) and the second grid (2) are arranged symmetrically; The first grid (1) and the second grid (2) form an electron beam passage; The first grid (1) and the second grid (2) comprise a plurality of metal grids (01) arranged equidistantly along the direction of the traveling wave; The cross section of the metal grid (01) along the direction of the traveling wave comprises a first rectangular section (11), a trapezoidal section (12) and a second rectangular section (13) connected in sequence; The first rectangular section (11) is provided with an arc-shaped opening at one end away from the trapezoidal section (12); The arc-shaped opening comprises a first opening (011) and a second opening (012); The hollowed-out part of the first opening (011) is a rectangular body, and the hollowed-out part of the second opening (012) is a semicylinder; In the first grid (1), two adjacent metal grids (01) form a waveguide cavity (02), the bottom of the waveguide cavity (02) is a circular arc with a radius of R1, and the metal grid (01) and an adjacent waveguide cavity (02) form a waveguide period of a slow wave structure; The metal grid (01) of the second grid (2) is arranged at intervals with the metal grid (01) of the first grid (1), and the center line of the metal grid (01) of the second grid (2) coincides with the center line of the waveguide cavity (02) of the first grid (1); The metal grid (01) of the second grid (2) and the metal grid (01) of the first grid (1) are staggered in the horizontal direction and the vertical direction, the depth of the vertical direction is of, R1<of<2R1, the width of the horizontal direction is w2, w2<p / 2, and p is the period length of the slow wave structure; The height of the first rectangular section (11) is h1, and the width is w2; The upper base width of the trapezoidal section (12) is w1, the lower base width is w1+p / 2, and the height is h3; The length of the first opening (011) is D, and the radius of the second opening (012) is R, and 2R=D.

2. The wideband folded all-metal slow wave structure according to claim 1, characterized in that, The electron beam passage comprises a plurality of rectangular passages (021) and arc-shaped passages (022) arranged at both ends of the rectangular structure.

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