Slit-type staggered double-gate waveguide slow wave structure

Abstract

The invention discloses a slit-type staggered double-gate waveguide slow-wave structure, each single-cycle structure comprises a metal shell, an upper metal gate and a lower metal gate, the upper metal gate and the lower metal gate are staggered in a half-cycle manner, and a rectangular electron beam channel exists between the upper metal gate and the lower metal gate. The lower edge of the upper metal gate and the upper edge of the lower metal gate are respectively provided with a gap, N is equal to 1, 2,..., the shapes and the sizes of the gaps are the same, the N gaps of the upper metal gate or the lower metal gate are symmetrically distributed, and the N gaps of the upper metal gate and the N gaps of the lower metal gate are also symmetrically distributed. The notches are formed in the vertically staggered metal gates to form the vacuum slits communicated with the electron beam channels, so that the loss and dispersion characteristics of the staggered double-gate waveguide slow wave structure are reduced, and the output power and bandwidth of the traveling wave tube are further improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of waveguide slow-wave structures, and more specifically, relates to a slit-type staggered double-grid waveguide slow-wave structure. Background Art

[0002] Terahertz (THz) waves refer to electromagnetic waves in the frequency range of 0.1 - 10 THz, and their unique properties have brought far-reaching impacts to fields such as communication (broadband communication), radar, electronic countermeasure, electromagnetic weapons, astronomy, medical imaging, nondestructive testing, and security inspection. However, the further development of current terahertz technology is limited by terahertz radiation sources that can be practically applied. Therefore, the exploration of terahertz radiation sources is extremely urgent.

[0003] Combined with the frequency range of terahertz waves, the generation of terahertz radiation sources can be explored from the perspectives of photonics and electronics respectively. Among them, from the electronics perspective, terahertz radiation sources can be divided into solid-state electronics and vacuum electronics terahertz radiation sources. Terahertz radiation sources based on vacuum electronics mainly include electro-vacuum devices such as traveling wave tubes, backward wave tubes, extended interaction devices, gyrotrons, and Oro tubes. Among these, traveling wave tubes have advantages such as wide bandwidth, high gain, high efficiency, high stability, and long life.

[0004] The main module that determines the performance of a traveling wave tube is the slow-wave structure. Among many different types of slow-wave structures, the staggered double-grid waveguide slow-wave structure, as a common slow-wave structure for sheet beams, not only has high gain characteristics and a relatively wide operating frequency band, but its all-metal structure can significantly improve the power capacity and stability of the traveling wave tube, thereby obtaining higher output power. Figure 1 is a schematic diagram of a traditional staggered double-grid waveguide slow-wave structure. Figure 1 (a) is a schematic diagram of a single-period three-dimensional structure. To better show the internal structure, the upper half of the structure is hidden by half. p represents the period length, and s represents the thickness of the upper metal grid / lower metal grid. Figure 1 (b) is a front view of a single-period structure. hg represents the height of the upper metal grid / lower metal grid, ht represents the height of the electron beam channel, and wg represents the width of the upper metal grid / lower metal grid. Figure 2 is a schematic diagram of the dispersion curves of a traditional staggered double-grid waveguide slow-wave structure at different metal grid heights. Figure 2 The traditional staggered double-grid waveguide slow-wave structure with zero slits (0-slit) is adopted in Figure 2As shown in the figure, the upper cut-off frequency of the traditional staggered double-gate waveguide slow-wave structure decreases with the increase of the metal gate height hg, and the lower cut-off frequency does not change with hg. Through research, it is found that with the increase of the operating frequency, especially when the frequency increases to the terahertz band, the output power of the traveling-wave tube with the staggered double-gate waveguide slow-wave structure will decrease sharply due to the increase of the surface metal loss. In this case, in order to meet the high output power characteristics, it is often impossible to take into account the bandwidth characteristics of the traveling-wave tube. Summary of the Invention

[0005] The purpose of the present invention is to overcome the deficiencies of the prior art and provide a double-slit staggered double-gate waveguide slow-wave structure. By setting notches on the upper and lower staggered metal gates to form vacuum slits connected to the electron beam channel, the loss and dispersion characteristics of the staggered double-gate waveguide slow-wave structure are reduced, thereby further improving the output power and bandwidth of the traveling-wave tube.

[0006] In order to achieve the above invention purpose, the slit-type staggered double-gate waveguide slow-wave structure of the present invention, each single-period structure includes a metal shell, an upper metal gate, and a lower metal gate. The upper metal gate and the lower metal gate are staggered in a semi-period, and there is a rectangular electron beam channel between the upper metal gate and the lower metal gate. Its characteristics are:

[0007] N notches are respectively arranged on the lower edge of the upper metal gate and the upper edge of the lower metal gate, N = 1, 2, …, and the shape and size of each notch are the same; in the single-period structure, with the center of the electron beam channel as the origin, the horizontal direction as the X-axis, the vertical direction as the Y-axis, and the electron beam direction as the Z-axis, a coordinate system is constructed. The projections of the N notches of the upper metal gate or the lower metal gate on the X-Y plane are symmetrically distributed about the Y-axis, and the projections of the N notches of the upper metal gate and the N notches of the lower metal gate on the X-Y plane are axially symmetric about the X-axis.

[0008] The slit-type staggered double-gate waveguide slow-wave structure of the present invention, each single-period structure includes a metal shell, an upper metal gate, and a lower metal gate. The upper metal gate and the lower metal gate are staggered in a semi-period, and there is a rectangular electron beam channel between the upper metal gate and the lower metal gate. 1 notch is respectively arranged on the lower edge of the upper metal gate and the upper edge of the lower metal gate, N = 1, 2, …, and the shape and size of each notch are the same. The N notches of the upper metal gate or the lower metal gate are symmetrically distributed, and the N notches of the upper metal gate and the N notches of the lower metal gate are also symmetrically distributed.

[0009] The present invention has the following beneficial effects:

[0010] 1) By setting notches on the upper metal gate and the lower metal gate to form vacuum slits connected to the electron beam channel, the lower cut-off frequency of the staggered double-gate waveguide slow-wave structure can be reduced. The method of further reducing the gate height to increase the upper cut-off frequency can be combined to significantly improve the passband of the entire slow-wave structure;

[0011] 2) The present invention can reduce the loss of the staggered double-gate waveguide slow-wave structure, thereby achieving an increase in output power, which has particularly significant advantages in the terahertz frequency band where loss attenuation is the dominant factor;

[0012] 3) The structure of the present invention is simply designed and easy to process. By changing the slit size, the output characteristics of the traveling-wave tube can also be significantly changed, which has certain engineering application significance;

[0013] 4) Under the same working conditions, whether the metal gate width wg is kept constant or the metal gate height hg is kept constant, the high-frequency characteristics and PIC simulation results show that the slit-type staggered double-gate waveguide slow-wave structure has lower loss and wider bandwidth characteristics, fully proving the feasibility of enhancing the bandwidth of the traveling-wave tube based on this slow-wave structure. Description of the Drawings

[0014] Figure 1 is a schematic diagram of the traditional staggered double-gate waveguide slow-wave structure;

[0015] Figure 2 is a schematic diagram of the dispersion curves of the traditional staggered double-gate waveguide slow-wave structure under different metal gate heights;

[0016] Figure 3 is a structural diagram of the specific implementation manner of the slit-type staggered double-gate waveguide slow-wave structure of the present invention;

[0017] Figure 4 is a schematic diagram of the dispersion curves of the zero-slit and double-slit staggered double-gate waveguide slow-wave structures under different metal gate widths;

[0018] Figure 5 is a vacuum model diagram of the traveling-wave tube based on the double-slit staggered double-gate waveguide slow-wave structure in this embodiment;

[0019] Figure 6 is a schematic diagram of the parameters of five slow-wave structures in this embodiment;

[0020] Figure 7 is a comparison diagram of the dispersion curves of five slow-wave structures in this embodiment;

[0021] Figure 8 is a comparison diagram of the normalized phase velocity curves of five slow-wave structures in this embodiment;

[0022] Figure 9 is a comparison diagram of the interaction impedance curves of five slow-wave structures at the center point of the electron beam channel in this embodiment;

[0023] Figure 10 is a comparison diagram of the dispersion characteristics of the 2-slit staggered double-gate waveguide slow-wave structure under different slit distances in this embodiment;

[0024] Figure 11 It is a comparison diagram of the dispersion characteristics of the 2-slit staggered dual-gate waveguide slow-wave structure in different slit heights in this embodiment;

[0025] Figure 12 It is a comparison diagram of the dispersion characteristics of the 2-slit staggered dual-gate waveguide slow-wave structure in different slit widths in this embodiment;

[0026] Figure 13 It is a comparison diagram of the dispersion curves of three traveling wave tubes in this embodiment;

[0027] Figure 14 It is a comparison diagram of the normalized phase velocity curves of three traveling wave tubes in this embodiment;

[0028] Figure 15 It is a comparison diagram of the interaction impedance curves of three traveling wave tubes;

[0029] Figure 16 It is a comparison diagram of the normalized group velocity curves of three traveling wave tubes in this embodiment;

[0030] Figure 17 It is a comparison diagram of the reflection coefficient S11 of three traveling wave tubes in the case of 20 periods in this embodiment;

[0031] Figure 18 It is a comparison diagram of the transmission coefficient S21 of three traveling wave tubes in the case of 20 periods in this embodiment;

[0032] Figure 19 It is a comparison diagram of the relationship curves between the output power and frequency of three traveling wave tubes in this embodiment;

[0033] Figure 20 It is a comparison diagram of the relationship curves between the output gain and frequency of three traveling wave tubes in this embodiment. Specific implementation manners

[0034] The following describes the specific implementation manners of the present invention with reference to the accompanying drawings, so that those skilled in the art can better understand the present invention. It should be particularly noted that in the following description, when the detailed descriptions of known functions and designs may dilute the main content of the present invention, these descriptions will be omitted here.

[0035] Embodiment

[0036] Figure 3 It is a structural diagram of the specific implementation manner of the slit-type staggered dual-gate waveguide slow-wave structure of the present invention. Figure 3 In (a), it is a three-dimensional structure diagram of a single period. In order to better show the internal structure, half of the upper part structure is hidden. (b) is a front view of the single period structure. As Figure 3As shown, the slit-type staggered double-gate waveguide slow-wave structure of the present invention is similar to the traditional staggered double-gate waveguide slow-wave structure, including a metal housing 1, an upper metal gate 2, and a lower metal gate 3. The upper metal gate 2 and the lower metal gate 3 are staggered in a semi-period, and there is a rectangular electron beam channel 4 between the upper metal gate 2 and the lower metal gate 3. The difference is that in the present invention, N notches 5 are respectively arranged on the lower edge of the upper metal gate 2 and the upper edge of the lower metal gate 3, where N = 1, 2, …, and the shapes and sizes of each notch 5 are the same. In a single-period structure, taking the center of the electron beam channel as the origin, the horizontal direction as the X-axis, the vertical direction as the Y-axis, and the electron beam direction as the Z-axis, a coordinate system is constructed. The projections of the N notches of the upper metal gate 2 or the lower metal gate 3 on the X-Y plane are symmetrically distributed about the Y-axis, and the projections of the N notches of the upper metal gate 2 and the N notches of the lower metal gate 3 on the X-Y plane are axially symmetric about the X-axis.

[0037] According to the above description, by arranging the notches 5 on the upper metal gate 2 and the lower metal gate 3, N vacuum slits communicating with the rectangular electron beam channel 4 can be respectively formed above and below the rectangular electron beam channel 4. Figure 3 In [the figure], the number N of the notches 5 is 2. Therefore, two vacuum slits are respectively formed above and below the rectangular electron beam channel 4.

[0038] Taking into comprehensive consideration the processing difficulty and technical effects, in this embodiment, the notch 5 is set as a cuboid, and the preferred value range of its width ws is where wg represents the width of the upper metal gate 2 / lower metal gate 3; the preferred value range of the height is 5μm ≤ hs ≤ ws, where ws represents the width of the cuboid notch. In addition, the number N of the notches 5 is preferably set as an even number, and the better values are 2, 4. The preferred value range of the distance ds between the notches 5 is

[0039] Figure 4 It is a schematic diagram of the dispersion curves of the zero-slit and double-slit staggered double-gate waveguide slow-wave structures with different metal gate widths. From Figure 4 it can be seen that the cut-off frequency of the traditional zero-slit (0-slit) staggered double-gate waveguide slow-wave structure decreases as wg increases. When the metal gate width wg is fixed, the cut-off frequency of the double-slit (2-slit) staggered double-gate waveguide slow-wave structure is lower than that of the zero-slit (0-slit) staggered double-gate waveguide slow-wave structure. That is, the effect of inserting double slits on the original metal gate is not much different from the effect of increasing the metal gate width wg. However, after inserting the double slits, the decrease amplitude of the lower cut-off frequency of the slow-wave structure is greater than that of the upper cut-off frequency. That is, compared with increasing the gate width wg, the double-slit (2-slit) staggered double-gate waveguide slow-wave structure has a wider passband and more gentle dispersion, which will further enhance the bandwidth.

[0040] Figure 5 This is the vacuum model diagram of the traveling wave tube based on the double-slit staggered double-gate waveguide slow-wave structure in this embodiment. As Figure 5 shown, the vacuum model of the traveling wave tube includes a high-frequency signal input port 51, an input rectangular coupling hole 52, an electron beam emission extreme port 53, a slow-wave structure 54, an electron collection extreme port 55, an output rectangular coupling hole 56, a high-frequency signal output port 57, a double-slit channel 58, and an elliptical electron beam channel 59. The specific dimensions of the high-frequency signal input port 51 are consistent with the standard rectangular waveguide WR-1.5. Using the elliptical electron beam channel 59 can ensure that signals within the operating frequency band are always cutoff when passing through the electron beam emission extreme port 53 and the electron collection extreme port 55, thus avoiding affecting the input and output signals. Figure 5 The number of periods of the slow-wave structure in

[0041] To better illustrate the technical effects of the present invention, specific examples are used to simulate and verify the present invention. In this embodiment, the high-frequency characteristics of different slow-wave structures are compared and verified. In this embodiment, the phase of the slow-wave structure is fixed at 450°, that is, phase = 450°, and the eigenfrequency corresponding to this phase is 670 GHz. Under this condition, the designed traveling wave tubes will have the same synchronous voltage. On this basis, five slow-wave structures are designed based on the zero-slit (0-slit) and slit-type (N-slit) staggered double-gate waveguide slow-wave structures. Figure 6 This is the parameter schematic diagram of the five slow-wave structures in this embodiment. As Figure 6 shown, while keeping other parameters fixed, in order to make the eigenfrequency 670 GHz when phase = 450°, the 1st slow-wave structure uses the traditional 0-slit staggered double-gate waveguide slow-wave structure, and the metal gate height is hg = 210 μm; the 2nd to 5th slow-wave structures use the N-slit staggered double-gate waveguide slow-wave structure, the number of slits N = 1, 2, 3, 4, and the metal gate height is hg = 110 μm; the slit heights hs are 100 μm, 52 μm, 27 μm, and 16 μm respectively. This means that compared with the 0-slit staggered double-gate waveguide slow-wave structure, at the same center frequency, the metal gate height hg value of the N-slit (N = 1 - 4) staggered double-gate waveguide slow-wave structure is lower, which is beneficial to reducing the aspect ratio of the processing size, thus making the device structure easier to process. In addition, Figure 6 as shown, the inserted slits in the N-slit (N = 1 - 4) staggered double-gate waveguide slow-wave structure have the same slit width ws and slit spacing ds, and ws = ds = 30 μm. It can be seen from the figure that in order to meet the condition that the eigenfrequency is 670 GHz when phase = 450°, the slit height hs gradually decreases as the number of inserted slits N increases.

[0042] Figure 7 It is a comparison diagram of the dispersion curves of the five slow-wave structures in this embodiment. From Figure 7 it can be seen that under the conditions of satisfying phase = 450° and the eigenfrequency being 670 GHz, the passband of the N-slit (N = 1 - 4) staggered double-gate waveguide slow-wave structure is larger than that of the 0-slit, and the more slits are inserted, the wider the passband.

[0043] Figure 8 It is a comparison diagram of the normalized phase velocity curves of the five slow-wave structures in this embodiment. From Figure 7 it can be seen that under the conditions of satisfying phase = 450° and the eigenfrequency being 670 GHz, the dispersion of the N-slit (N = 1 - 4) staggered double-gate waveguide slow-wave structure is flatter than that of the 0-slit, and the more slits are inserted, the flatter the normalized phase velocity curve, which has obvious advantages for obtaining a wider bandwidth.

[0044] Figure 9 It is a comparison diagram of the interaction impedance curves at the center point of the electron beam channel of the five slow-wave structures in this embodiment. From Figure 9 it can be seen that under the conditions of satisfying phase = 450° and the eigenfrequency being 670 GHz, due to the flatter dispersion curve, the interaction impedance of the N-slit (N = 1 - 4) staggered double-gate waveguide slow-wave structure at the center point of the electron beam channel is generally smaller than that of the 0-slit, and the more slits are inserted, the smaller the obtained interaction impedance. It should be noted that the interaction impedance when N is even is greater than that when N is odd, and the interaction impedance of the 1-slit staggered double-gate waveguide slow-wave structure at the center point of the electron beam channel is close to 0. Calculating the average interaction impedance in the electron beam interaction region, it is found that its distribution law is the same as above, but the value of the interaction impedance increases slightly.

[0045] It is found through research that by appropriately changing the size parameters of the inserted slits, the dispersion curve can be made flatter. Since the more slits are inserted, the higher the processing requirements and the more complex the structure, in this embodiment, the simulation of the slit size parameters only considers the case of inserting 2 slits (2-slit). In order to fully illustrate the influence of each size parameter of the slits described in the present invention on the staggered double-gate waveguide slow-wave structure, similarly, the phase is fixed at phase = 450°, and the eigenfrequency corresponding to this phase is 670 GHz. While keeping other size parameters unchanged, the dispersion characteristics under different slit-to-slit distances ds, slit heights hs, and slit widths ws are simulated.

[0046] Figure 10 It is a comparison diagram of the dispersion characteristics of the 2-slit staggered double-gate waveguide slow-wave structure under different slit-to-slit distances. Figure 10The height hs of the middle slit = the width ws of the slit = 30 μm. Kc represents the interaction impedance, and Vp / c represents the normalized phase velocity. From Figure 10 it can be seen that as the distance ds between the slits gradually increases, the entire interaction impedance curve and the normalized phase velocity curve of the slow-wave structure gradually shift to the left, and the dispersion curve becomes flatter.

[0047] Figure 11 It is a comparison diagram of the dispersion characteristics of the 2-slit staggered double-gate waveguide slow-wave structure at different slit heights. Figure 11 In it, the distance ds between the slits = the width ws of the slit = 30 μm. From Figure 11 it can be seen that as the height hs of the slit gradually increases, the entire interaction impedance curve and the normalized phase velocity curve of the slow-wave structure gradually shift to the left, and the interaction impedance gradually increases.

[0048] Figure 12 It is a comparison diagram of the dispersion characteristics of the 2-slit staggered double-gate waveguide slow-wave structure at different slit widths. Figure 12 In it, the distance ds between the slits = the height hs of the slit = 30 μm. From Figure 12 it can be seen that as the width ws of the slit gradually increases, the entire interaction impedance curve and the normalized phase velocity curve of the slow-wave structure gradually shift to the left, the dispersion curve becomes flatter, and the decrease amplitude of the lower cut-off frequency is greater than that of the upper cut-off frequency.

[0049] Based on the above analysis results, it can be known that increasing the distance ds between the slits or the width ws of the slit can make the dispersion curve flatter, so as to obtain a wider bandwidth.

[0050] To fully illustrate the bandwidth enhancement method described in the present invention, based on the above analysis, three traveling wave tubes are designed respectively using the input-output structure design scheme shown in Figure 5 for the 0-slit and 2-slit staggered double-gate waveguide slow-wave structures: The first one: 0-slit: wg = 235 μm, hg = 210 μm; the second one: 0-slit: wg = 247 μm, hg = 120 μm; the third one: 2-slit: wg = 235 μm, hg = 120 μm. It can be noted that the first and the third traveling wave tubes have the same gate width wg, and the second and the third traveling wave tubes have the same gate height hg. Table 1 is the specific structure size and parameter table of the third 2-slit staggered double-gate waveguide slow-wave structure in this embodiment.

[0051] Symbol Parameter Value (μm) ds Distance between slits 100 hg Height of metal grid 120 hs Height of slit 16 ht Height of electron beam channel 60 p Period length 150 s Thickness of metal grid 40 wg Width of metal grid 235 ws Width of slit 35

[0052] Table 1

[0053] Figure 13It is a comparison chart of the dispersion curves of three traveling wave tubes in this embodiment. From Figure 13 it can be seen that when the phase of the three traveling wave tubes is 450°, the corresponding eigenfrequencies are all 670 GHz, and it can be clearly seen that the bandwidth between the upper and lower cut-off frequencies of the third traveling wave tube (2-slit: wg = 235 μm, hg = 120 μm) is significantly larger than that of the first traveling wave tube (0-slit: wg = 235 μm, hg = 210 μm) with the same grid width wg and the second traveling wave tube (0-slit: wg = 247 μm, hg = 120 μm) with the same grid height hg.

[0054] Figure 14 It is a comparison chart of the normalized phase velocity curves of three traveling wave tubes. From Figure 14 it can be seen that the three traveling wave tubes have the same synchronous voltage at 670 GHz, and it can be clearly seen that the dispersion of the third traveling wave tube (2-slit: wg = 235 μm, hg = 120 μm) is significantly weaker than that of the first and second traveling wave tubes, that is, the third traveling wave tube will have a wider bandwidth.

[0055] Figure 15 It is a comparison chart of the interaction impedance curves of three traveling wave tubes. From Figure 15 it can be seen that due to the weaker dispersion characteristics, the interaction impedance of the third traveling wave tube (2-slit: wg = 235 μm, hg = 120 μm) is the weakest, while the first traveling wave tube (0-slit: wg = 235 μm, hg = 210 μm) with the same grid width wg has the strongest dispersion characteristics and has the largest interaction impedance, meaning it has a stronger interaction energy conversion ability.

[0056] Figure 16 It is a comparison chart of the normalized group velocity curves of three traveling wave tubes in this embodiment. From Figure 16 it can be seen that due to the insertion of the double slit, compared with the first and second traveling wave tubes without slit insertion, the third traveling wave tube (2-slit: wg = 235 μm, hg = 120 μm) has the largest normalized group velocity, while the first traveling wave tube has the smallest normalized group velocity although it has the largest interaction impedance. The expression of the attenuation constant α in the traveling wave tube is:

[0057]

[0058] where ω 0 is the angular frequency, v g is the group velocity, and Q is the quality factor.

[0059] As can be seen from the above formula, the attenuation constant α is inversely proportional to the normalized group velocity. Further research shows that when the phase of the first traveling wave tube is 450°, its quality factor is 279, while that of the third traveling wave tube is 277. Combining Figure 16 with the above formula, it can be seen that, in comparison, the third traveling wave tube has weaker attenuation loss, while the first traveling wave tube has stronger attenuation loss.

[0060] Figure 17 Figure 6 is a comparison chart of the reflection coefficient S11 of the three traveling wave tubes in this embodiment under 20 periods. From Figure 17 it can be seen that the bandwidth of the first traveling wave tube (0-slit: wg = 235μm, hg = 210μm) is 20GHz (660 - 680GHz); the bandwidth of the second traveling wave tube (0-slit: wg = 247μm, hg = 120μm) is 66GHz (645 - 711GHz); when the frequency is greater than 648GHz, the reflection coefficient S11 of the third traveling wave tube (2-slit: wg = 235μm, hg = 120μm) is less than -15dB, and it has the widest bandwidth.

[0061] Figure 18 Figure 7 is a comparison chart of the transmission coefficient S21 of the three traveling wave tubes in this embodiment under 20 periods. From Figure 18 it can be seen that although the first traveling wave tube (0-slit: wg = 235μm, hg = 210μm) has the largest interaction impedance, its transmission loss attenuation is also the largest, while the transmission loss attenuation of the third traveling wave tube is slightly greater than that of the second.

[0062] To compare and verify the interaction performance of the three traveling wave tubes, it is necessary to ensure that the three traveling wave tubes have the same working conditions. Therefore, the working current of the three traveling wave tubes is set to 0.018A, the electron beam width is 120μm, the electron beam height is 40μm, and the focusing magnetic field is 1.2T. The conductivity of the lossy oxygen-free copper is set to 2×10 7 S / m, and the output characteristics of the three traveling wave tubes are compared. Table 2 is a comparison table of the parameters and output characteristics of the three traveling wave tubes in this embodiment.

[0063] Parameter 0-slit 0-slit 2-slit wg (μm) 235 247 235 hg (μm) 210 120 120 Number of saturation periods 190 210 210 Operating voltage (kV) 19.6 19.5 19.3 Frequency (GHz) 671 672 669 Output power (W) 1.91 2.66 2.74 Gain (dB) 32.81 34.24 34.38 Electron efficiency 0.54％ 0.76％ 0.79％ 3-dB bandwidth (GHz) 3 17 22

[0064] Table 2

[0065] As shown in Table 2, since the first traveling wave tube (0-slit: wg = 235 μm, hg = 210 μm) has the maximum interaction impedance, its saturation period number is the smallest, which is 190 periods; the interaction impedances of the second and third traveling wave tubes are similar, and they have the same saturation period number, which is 210 periods. Also, because the third traveling wave tube (2-slit: wg = 235 μm, hg = 120 μm) has the lowest loss attenuation, its output power and saturation gain are the largest, which are 2.74 W and 34.38 dB respectively, and the corresponding electron efficiency is 0.79%.

[0066] Figure 19 is a comparison diagram of the relationship curves between the output power and frequency of the three traveling wave tubes in this embodiment. From Figure 19 it can be seen that the third traveling wave tube (2-slit: wg = 235 μm, hg = 120 μm) has the widest bandwidth, and its 3-dB bandwidth reaches 22 GHz (654 - 676 GHz). The 3-dB bandwidth of the second traveling wave tube (0-slit: wg = 247 μm, hg = 120 μm) is 17 GHz (661 - 678 GHz). The 3-dB bandwidth of the first traveling wave tube (0-slit: wg = 235 μm, hg = 210 μm) is 3 GHz (668 - 671 GHz).

[0067] Figure 20 is a comparison diagram of the relationship curves between the output gain and frequency of the three traveling wave tubes in this embodiment. From Figure 13 it can be seen that when the frequency is 670 GHz, the output gains of the three traveling wave tubes are such that the third traveling wave tube is greater than the second and greater than the first, and the third traveling wave tube has the widest bandwidth.

[0068] Although the above describes the illustrative specific embodiments of the present invention for the convenience of those skilled in the art to understand the present invention, it should be clear that the present invention is not limited to the scope of the specific embodiments. For those of ordinary skill in the art, as long as various changes are within the spirit and scope of the present invention defined and determined by the appended claims, these changes are obvious, and all inventions and creations using the concept of the present invention are within the scope of protection.

Claims

1. A slit-type staggered double-grating waveguide slow-wave structure, each single-period structure comprises a metal shell (1), an upper metal grid (2), and a lower metal grid (3), the upper metal grid (2) and the lower metal grid (3) are staggered in a half-period, and there is a rectangular electron injection channel (4) between the upper metal grid (2) and the lower metal grid (3), characterized in that: N notches (5) are respectively arranged at the lower edge of the upper metal grid (2) and the upper edge of the lower metal grid (3), N = 1, 2, ..., and each notch (5) has the same shape and size; in a single-period structure, a coordinate system is constructed with the center of the electron injection channel (4) as the origin, the horizontal direction as the X-axis, the vertical direction as the Y-axis, and the electron injection direction as the Z-axis, and the projections of the N notches of the upper metal grid (2) or the lower metal grid (3) on the XY plane are symmetrically distributed about the Y-axis, and the projections of the N notches of the upper metal grid (2) and the N notches of the lower metal grid (3) on the XY plane are symmetrically distributed about the X-axis.

2. The slot-type staggered double-grating waveguide slow-wave structure according to claim 1, characterized in that: The notch (5) is a rectangular parallelepiped.

3. The slot-type staggered double-grating waveguide slow-wave structure according to claim 2, characterized in that: The width ws of the notch (5) ranges from Wherein wg represents the width of the upper metal grid (2) / lower metal grid (3).

4. The slot-type staggered double-grating waveguide slow-wave structure according to claim 2, characterized in that: The height hs of the notch (5) has a value range of 5 μm≤hs≤ws, wherein ws represents the width of the notch.

5. The slot-type staggered double-grating waveguide slow-wave structure according to claim 1, characterized in that: The number of the notches (5) is N=2,4.

6. The slot-type staggered double-grating waveguide slow-wave structure according to claim 1, characterized in that: The distance ds between the notches (5) in the upper metal grid (2) or the lower metal grid (3) has a value range of

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