CN111144050A - Design method of strip traveling wave tube slow wave structure working in high-order mode - Google Patents
Design method of strip traveling wave tube slow wave structure working in high-order mode Download PDFInfo
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- CN111144050A CN111144050A CN201911393575.3A CN201911393575A CN111144050A CN 111144050 A CN111144050 A CN 111144050A CN 201911393575 A CN201911393575 A CN 201911393575A CN 111144050 A CN111144050 A CN 111144050A
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J23/00—Details of transit-time tubes of the types covered by group H01J25/00
- H01J23/16—Circuit elements, having distributed capacitance and inductance, structurally associated with the tube and interacting with the discharge
- H01J23/24—Slow-wave structures, e.g. delay systems
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J25/00—Transit-time tubes, e.g. klystrons, travelling-wave tubes, magnetrons
- H01J25/34—Travelling-wave tubes; Tubes in which a travelling wave is simulated at spaced gaps
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Abstract
The invention discloses a design method of a low-wave structure of a ribbon traveling-wave tube working in a high-order mode, and relates to the technical field of microwave electronics and terahertz. The design method has the advantages that the strip-shaped traveling wave tube can successfully work in a high-order mode, the limitation of cut-off frequency on the width of an electronic channel is removed, the advantage of large strip-shaped beam electron width is fully exerted, and the power capacity of the strip-shaped traveling wave tube is greatly increased. Meanwhile, due to the expansion of the size, the difficulty of processing and assembling is further reduced, the device can work under high voltage, the interaction impedance is improved, and the energy conversion efficiency of electron beams and electromagnetic waves is improved. Compared with the traveling wave tube with the circular section electron beam in the traditional working mode, the power capacity of the traveling wave tube is improved by nearly one order of magnitude.
Description
Technical Field
The invention relates to the technical field of microwave electronics and terahertz, in particular to a design method of a staggered grid strip traveling wave tube working in a high-order mode.
Background
As is well known, terahertz waves have a series of excellent characteristics, so that they have very important academic and application values (some of which are already in practical use). This has also led to great attention being paid to terahertz scientific and technical research and application in all countries of the world, mainly in the united states, europe and japan. A general consensus is reached in China: the terahertz technology provides an excellent opportunity for the innovation of scientific technology, the development of national economy, the national security construction and the like, and can possibly cause the revolutionary development of the scientific technology.
The most important factor limiting the development of terahertz technology at present is the lack of a terahertz source with enough power. Terahertz sources can be currently generated by solid state devices, electro-vacuum devices, and optoelectronic devices. Among which electric vacuum devices are considered to be the most practical and reliable solution. Especially in the fields of military countermeasure, satellite borne, airborne communication, radar and the like, and even the only solution. However, with the continuous development of communication technology, the advantages of millimeter wave and terahertz frequency bands become targets generally pursued in various countries. With the increase of frequency, the size sharing effect further reduces the volume of the device, greatly reduces the power capacity, seriously limits the radar transmission and communication transmission performance, and how to improve the power becomes a key problem which needs to be solved urgently in the national defense field and the communication field.
At present, traveling wave tubes are one kind of electro-vacuum devices, and are especially suitable for electronic countermeasure, satellite-borne communication and vehicle-mounted communication because of the incomparable broadband and miniaturization characteristics of other devices, so that the traveling wave tubes are popular in various countries. Considering the processing and assembling difficulty of millimeter wave and terahertz frequency bands, a zigzag waveguide structure or a rectangular staggered grid structure is widely adopted as a slow wave structure of a traveling wave tube. The staggered grid structure has a natural ribbon beam channel and potential broadband operating characteristics, so that the staggered grid structure has unique advantages in the research of ribbon beam traveling wave tubes. Compared with the traditional cylindrical electron beam, the ribbon traveling wave tube has larger current and power capacity. However, as the frequency increases to millimeter waves, the size sharing effect greatly reduces the width of the electronic channel of the ribbon traveling wave tube, thereby greatly limiting the power capacity and causing the ribbon traveling wave tube to encounter a bottleneck in the development of the millimeter wave field.
Disclosure of Invention
In order to solve the problem of power capacity limitation, the invention provides a design method of a staggered grid strip traveling wave tube working in a high-order mode. The design scheme has the advantages that the strip-shaped traveling wave tube can successfully work in a high-order mode, the limitation of cut-off frequency on the width of an electronic channel is eliminated, the advantage of large strip-shaped beam electron width is fully played, and the power capacity of the strip-shaped traveling wave tube is greatly increased. Meanwhile, due to the expansion of the size, the difficulty of processing and assembling is further reduced, the device can work under high voltage, the interaction impedance is improved, and the energy conversion efficiency of electron beams and electromagnetic waves is improved. Compared with the traveling wave tube with the circular section electron beam in the traditional working mode, the power capacity of the traveling wave tube is improved by nearly one order of magnitude.
The invention is realized by the following technical scheme: a design method of a strip traveling wave tube slow wave structure working in a high-order mode comprises the following steps:
s1, providing an initial model of a slow wave structure of the ribbon beam traveling wave tube, modeling by utilizing HFSS software, calculating a dispersion curve, and modifying electronic channels, staggered gate width and height parameters to ensure that the maximum electron beam width is obtained while the required bandwidth is met on a working frequency band.
S2, selecting a working voltage matched with the phase speed of the electromagnetic waves in the dispersion curve according to the step S1, and drawing an electron beam speed straight line. The designed working voltage is more than 2kV and exceeds the traditional design voltage.
S3, further optimizing the size parameters of the initial model, enabling the dispersion curve of the high-order mode and the electron beam velocity to linearly meet the synchronous condition in the working frequency band, namely the electron beam velocity is 5% -10% higher than the electromagnetic wave phase velocity, and utilizing the passband of the high-order mode to realize the interaction between the electron beam and the electromagnetic wave, thereby realizing the high-order mode working of the slow wave structure of the strip-shaped traveling wave tube. The designed electron beam straight line has larger slope and passes through the dispersion curve, and compared with the electron beam straight line which is parallel to the dispersion curve in the traditional design, the electron beam straight line avoids low-frequency sideband oscillation, which cannot be realized by the traditional structure.
And S4, adjusting the width of the slow wave structure staggered grid to obtain the maximum coupling impedance at the working frequency section. After the step is completed, the designed slow wave structure of the ribbon traveling wave tube working in the high-order mode is obtained.
And S5, adopting software CST Studio Suite to perform PIC particle simulation and simulation analysis and verify the wave-filling interaction strength.
The invention provides a design method of a staggered grid slow wave structure for high-order mode work, which is based on the following principle: in order to remove the limit of the cut-off frequency on the width of the electronic channel, the dispersion characteristic analysis of the staggered grid slow wave structure finds that the first high-order mode of the staggered grid slow wave structure is similar to a rectangular waveguide TM11Distribution of the modes. According to the formula of the cut-off frequency of the rectangular waveguide:
wherein f iscThe cut-off frequency of the rectangular waveguide, c the speed of light in vacuum, a the length of the long side of the waveguide, b the length of the short side of the waveguide, and m and n are natural numbers and are different from 0.
Conventional mode of operation TE10In the mode, the cut-off frequency is only related to the long side a, when the frequency is increased, the value of a is reduced, and the width of an electronic channel corresponding to a slow-wave structure is reduced, so that the power capacity is reduced. By working at higher order TM11Under the mode, its cutoff frequency is controlled by long limit a and short side b, through reducing the b value properly, can realize the increase of an value to under the unchangeable condition of cutoff frequency, electron channel width obviously increases, and the advantage of banding notes can full play, and power capacity has obvious promotion than traditional scheme.
Compared with the prior art, the invention has the advantages that:
1. the design method provided by the invention provides a brand-new design method of the ribbon traveling wave tube working in a high-order mode, greatly increases the power capacity, solves the problem of low-order oscillation commonly existing in the traveling wave tube, and has important academic and application values.
2. The design method provided by the invention has short design period, can be directly optimized on the traditional design of the existing low-order mode work, accelerates the design process and increases the practicability.
3. The design method provided by the invention adopts the high-order mode to work, so that the structure size is further increased, and the size sharing effect is relieved. The processing, calibration and assembly difficulty of the whole structure is reduced, and the method has high industrial value.
Drawings
FIG. 1 is a schematic flow diagram of a scheme of the invention,
FIG. 2 is a schematic diagram of a structure of a slow wave with staggered gates
FIG. 3 is a schematic diagram of the size of the slow wave structure designed in this embodiment
Figure 4 is a schematic diagram of the dispersion comparison of the present scheme with the conventional scheme,
figure 5 is a diagram comparing the coupling impedance of the present solution with that of the conventional solution,
fig. 6 is a final output power result diagram according to the present scheme.
The reference numbers illustrate: reference numeral 1 denotes a slow wave structure of the staggered grid-strip traveling wave tube, and reference numeral 2 denotes a gradual change matching structure.
Detailed Description
The invention is further described below with reference to the accompanying drawings:
referring to fig. 1, a method for designing a slow-wave structure of a ribbon traveling-wave tube operating in a high-order mode according to this embodiment includes the following steps: an initial model (with a cross-sectional width W of the slow-wave structure and a height TH of the electron channel of 770 μm and 150 μm, respectively.) is given, the period length P of the slow-wave structure is 468 μm, the spacing VL between two adjacent gates on the same side is 351 μm, and the gate height VH is 320 μm), and the dispersion curve is modeled and calculated by software HFSS. On the basis, parameters of the electronic channel, the width of the staggered gate and the height are modified, the maximum electron beam width is ensured while the required bandwidth is met on the working frequency band, the width W of the cross section of the adjusted slow wave structure and the height TH of the electronic channel are 900 micrometers and 150 micrometers respectively, and the width is increased by 17%. And selecting a working voltage matched with the phase velocity of the electromagnetic waves in the dispersion curve in the step S1, selecting the working voltage as 27600V and drawing an electron beam velocity straight line. The electron beam straight line of the slow wave structure designed by the invention has larger slope and passes through the dispersion curve, and compared with the electron beam straight line parallel to the dispersion curve in the traditional design, the electron beam straight line of the slow wave structure avoids low-frequency sideband oscillation, which can not be realized by the traditional structure. Adjusting the size parameters of the model to enable the dispersion curve of a high-order mode and an electron beam to meet the synchronous condition, namely the electron velocity is slightly larger than the electromagnetic wave phase velocity, and realizing the interaction between the electron beam and the electromagnetic wave by utilizing the passband of the high-order mode, thereby realizing the high-order mode work of the device, wherein the cycle length P of the adjusted slow wave structure is 650 mu m, the distance VL between two adjacent grids on the same side is 433 mu m, and the height VH of the grid is 330 mu m; and adjusting the width of the staggered grids to obtain the maximum coupling impedance at the working frequency section as far as possible, wherein the distance VL between two adjacent grids is 450 mu m, and the designed slow wave structure of the high-order mode working ribbon traveling wave tube is obtained after the step is completed. Elliptical electron beams with an axial ratio of 7:1(700 μm 100 μm) are adopted corresponding to the width and height of the slow wave structure, PIC particle simulation and simulation analysis are carried out in CST software, and the interaction strength of the injected waves is verified.
In this example: the working center frequency of the slow wave structure of the ribbon traveling wave tube is 220GHz, and the slow wave structure is shown in figure 2 and comprises 76 period uniform slow wave structures, gradient structures with 3 periods at two ends, an input port and an output port. The whole structure is made of all-metal oxygen-free copper, the width W of the cross section of the slow wave structure and the height TH of an electron channel are 900 micrometers and 150 micrometers respectively, and an elliptical electron beam with an axial ratio of 7:1(700 micrometers by 100 micrometers) is adopted correspondingly. The period length P of the slow wave structure is 650 mu m, the distance VL between two adjacent grids on the same side is 450 mu m, and the height VH of each grid is 330 mu m. By adopting the design scheme provided by the invention, the dispersion and the coupling impedance (parameters for reflecting the interaction strength of electrons and electromagnetic waves) of the designed slow-wave structure are respectively shown in fig. 3 and 4, and the comparison with the traditional structure is added. Fig. 5 shows the output power result of the traveling wave tube under the design of the scheme. At the frequency of 220GHz, under the condition that the input power is 100mW, the output power exceeds 340W, and the gain is as high as 35 dB. The example shows that the design method of the slow wave structure of the ribbon traveling wave tube working in the high-order mode has the effect of remarkably improving the power capacity and has wide application prospect and practical value.
The above example is only for convenience of explaining the scheme of the present invention, and the design method of the slow wave structure of the ribbon traveling wave tube operating in the high-order mode provided by the present invention can be used for designing the staggered grid ribbon traveling wave tubes of different frequency bands such as X, Ku, Ka, etc. The idea flow of the scheme of the invention is protected by changing all parameters mentioned in the scheme of the invention.
Claims (1)
1. A design method of a slow wave structure of a strip traveling wave tube working in a high-order mode is characterized by comprising the following steps:
s1, providing an initial model of a slow wave structure of a ribbon beam traveling wave tube, modeling by utilizing HFSS software, calculating a dispersion curve, modifying electronic channels, staggered gate width and height parameters, and ensuring that the maximum electron beam width is obtained while the required bandwidth is met on a working frequency band;
s2, selecting a working voltage matched with the phase speed of the electromagnetic waves in the dispersion curve according to the step S1, and drawing an electron beam speed straight line;
s3, further optimizing the size parameters of the initial model to enable the dispersion curve of the high-order mode and the electron beam velocity line in the working frequency band to meet the synchronous condition, namely the electron beam velocity is 5-10% higher than the electromagnetic wave phase velocity;
s4, adjusting the width of the slow wave structure staggered grid to obtain the maximum coupling impedance at the working frequency section; after the step is completed, the designed slow wave structure of the ribbon traveling wave tube working in the high-order mode is obtained.
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Cited By (2)
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| CN112216579A (en) * | 2020-09-28 | 2021-01-12 | 电子科技大学 | High-order backward wave oscillation suppression structure for ribbon beam traveling wave tube |
| CN113035672A (en) * | 2021-03-05 | 2021-06-25 | 电子科技大学 | Double-electron-beam expansion interaction circuit based on gap high-order mode |
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| CN113035672A (en) * | 2021-03-05 | 2021-06-25 | 电子科技大学 | Double-electron-beam expansion interaction circuit based on gap high-order mode |
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