Slow wave structure, terahertz traveling wave tube device and communication device

Abstract

The invention provides a slow wave structure, a terahertz traveling wave tube device and a communication device. According to the slow wave structure provided by the invention, the first sub slow wave structure and the second sub slow wave structure are ingeniously combined, so that the technical problem of insufficient output power in the prior art can be effectively solved. Specifically, the first sub-slow-wave structure performs cluster modulation on the electron beam through preset strong coupling impedance, so that the density and the modulation efficiency of the electron beam are improved; and the second slow wave sub-structure ensures that the electron beams subjected to cluster modulation can efficiently export microwave energy through the design of low transmission loss, so that the energy loss is obviously reduced. Through the innovative structural design, higher output power can be provided at a high frequency band, attenuation of microwave signals is effectively reduced, the overall performance of the system is improved, and the application requirements of high power and high efficiency are met.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of vacuum electron devices, in particular to a slow wave structure, a terahertz traveling wave tube device and a communication device. BACKGROUND

[0002] In the field of modern terahertz technology, terahertz traveling wave tube amplifiers (TWTs) are widely used in the amplification and processing of high-frequency signals, especially in important fields such as communication, imaging, and scientific exploration in the terahertz frequency band. Terahertz traveling wave tube amplifiers amplify input signals through the interaction between electron beams and slow wave structures, which can effectively increase the power of signals and expand the bandwidth.

[0003] In related technologies, in the application scenarios of terahertz traveling wave tubes, there is a technical problem of insufficient output power. SUMMARY

[0004] The purpose of the present application is to overcome the above technical deficiencies and provide a slow wave structure, a terahertz traveling wave tube device and a communication device to solve the technical problem of insufficient output power in the application scenarios of terahertz traveling wave tubes in related technologies.

[0005] To achieve the above technical purpose, the present application adopts the following technical solutions: In a first aspect, the present application provides a slow wave structure, comprising: A first sub-slow wave structure configured to receive an electron beam and modulate the electron beam in groups with a preset strong coupling impedance; A second sub-slow wave structure connected in series with the first sub-slow wave structure, the second sub-slow wave structure being configured to receive the electron beam modulated in groups and derive microwave energy with a preset low transmission loss.

[0006] Further, the first sub-slow wave structure includes N strong coupling slow wave units connected in series, the strong coupling slow wave units are configured as sinusoidal waveguide structures, and satisfy a first size constraint and / or a second size constraint, the first size constraint is a constraint on the height of the metal grid of the strong coupling slow wave unit to increase the height of the metal grid, and the second size constraint is a constraint on the length of the sinusoidal period of the strong coupling slow wave unit to shorten the length of the sinusoidal period; wherein N is a positive integer greater than 1.

[0007] Further, the first size constraint is that the height of the metal grid is greater than half the width of the sinusoidal waveguide and less than the width of the sinusoidal waveguide, and the second size constraint is that the length of the sinusoidal period is greater than half the height of the metal grid and less than the height of the metal grid.

[0008] Further, X size-gradually transition units are configured in series at the input end and / or the output end of the first sub-slow wave structure, where X is a positive integer greater than 1 and less than N.

[0009] Further, the second sub-slow wave structure comprises M low-loss slow wave units connected in series, the low-loss slow wave units are configured as sinusoidal waveguide structures, and satisfy a third size constraint, which is a constraint on the height of the metal grating of the low-loss slow wave unit, to shorten the height of the metal grating to reduce transmission loss.

[0010] Further, the third size constraint is that the height of the metal grating is less than 0.5 times the width of the sinusoidal waveguide.

[0011] Further, Y size-gradually transition units are configured in series at the input end and / or the output end of the second sub-slow wave structure, where Y is a positive integer greater than 1 and less than M.

[0012] Further, the application further comprises: An electron beam transmission channel configured as a vacuum metal grating channel, one end of which is connected to the output end of the first sub-slow wave structure, and the other end of which is connected to the input end of the second sub-slow wave structure.

[0013] In a second aspect, the application provides a terahertz traveling wave tube device comprising the slow wave structure described above.

[0014] In a third aspect, the application provides a terahertz communication device comprising a terahertz traveling wave tube device as described above. Advantages: The slow wave structure provided by the application can effectively solve the technical problem of insufficient output power in the prior art by ingeniously combining the first sub-slow wave structure with the second sub-slow wave structure. Specifically, the first sub-slow wave structure modulates the electron beam in groups through a pre-set strong coupling impedance, thereby improving the density and modulation efficiency of the electron beam; and the second sub-slow wave structure ensures that the electron beam modulated in groups can efficiently guide out microwave energy through the design of low transmission loss, thereby significantly reducing energy loss. Through this innovative structural design, the embodiment can provide higher output power in the high frequency band, effectively reduce the attenuation of microwave signals, improve the overall performance of the system, and meet the application requirements of high power and high efficiency. BRIEF DESCRIPTION OF DRAWINGS

[0015] Figure 1 is a structural schematic diagram of a slow wave structure provided by an embodiment of the application; Figure 2is a single period schematic diagram of a sine waveguide structure provided by an embodiment of the present application, wherein p_SineVane is the half period length of the sine waveguide, h_Vane is the height of the metal grid, W_parrel is the width in the waveguide, R_tunnel is the tunnel radius, and p_Unit is the period length of each period; Figure 3 is a dispersion characteristic schematic diagram of a strong coupling slow wave structure in a hybrid dispersion segmented sine waveguide terahertz slow wave structure provided by an embodiment of the present application; Figure 4 is a coupling characteristic schematic diagram of a strong coupling slow wave structure in a hybrid dispersion segmented sine waveguide terahertz slow wave structure provided by an embodiment of the present application; Figure 5 is a dispersion characteristic schematic diagram of a low-loss slow wave structure in a hybrid dispersion segmented sine waveguide terahertz slow wave structure provided by an embodiment of the present application; Figure 6 is a coupling characteristic schematic diagram of a low-loss slow wave structure in a hybrid dispersion segmented sine waveguide terahertz slow wave structure provided by an embodiment of the present application; Figure 7 is a whole transmission characteristic schematic diagram of a hybrid dispersion segmented sine waveguide terahertz slow wave structure provided by an embodiment of the present application; Figure 8 is a whole tube output power signal schematic diagram of a hybrid dispersion segmented sine waveguide terahertz slow wave structure provided by an embodiment of the present application; Figure 9 is a whole tube output power comparison schematic diagram of a hybrid dispersion segmented sine waveguide terahertz slow wave structure provided by an embodiment of the present application. DETAILED DESCRIPTION

[0016] In order for those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor should be within the scope of protection of the present application.

[0017] In the related art, in the electromagnetic system in the terahertz (0.1-10 THz) band, the terahertz traveling wave tube (TWT) as a core power amplifier device is widely used in radar detection, communication systems and imaging systems, and its performance directly affects the working efficiency of the system, such as radar detection distance, communication rate and imaging resolution. The existing terahertz traveling wave tube is based on the principle of vacuum electronics and is composed of an electron gun, a slow wave structure, a magnetic focusing system and a collector (such as Figure 1As shown). Among them, the slow-wave structure serves as the core carrier for energy exchange, and its design needs to meet the following two key requirements: Strong interaction strength (high coupling impedance): to efficiently modulate the electron beam density and achieve electron beam bunching.

[0018] Low transmission loss: minimize microwave energy decay to ensure efficient microwave signal transmission.

[0019] However, as the operating frequency rises above 1.03 THz, the performance of the traveling wave tube faces many challenges. Metal loss increases exponentially, and the traditional slow-wave structure faces fundamental physical conflicts in this frequency band, making it difficult to meet the requirements of high coupling impedance and low transmission loss at the same time. This physical limitation is reflected in two aspects: on the one hand, in order to increase the coupling impedance, the metal grid height (h_vane) needs to be increased, thereby improving the field confinement ability; on the other hand, the increase of the metal grid height will lead to the increase of the surface current loss, thereby aggravating the transmission loss. Therefore, although the increase of the coupling impedance can improve the modulation efficiency of the electron beam, it will increase the transmission loss to a certain extent, causing the difficulty of performance balance. These problems lead to the difficulty of meeting the actual application requirements of the power output of the high-frequency terahertz traveling wave tube.

[0020] In the related art, in the existing terahertz traveling wave tube technology, the slow-wave structure can adopt two implementation schemes: folded waveguide and uniform sinusoidal waveguide. Although these two implementation schemes have their own advantages in different application scenarios, they both face insurmountable technical defects in the operation above 1.03 THz frequency band, which makes the existing technology difficult to balance between high power output and low transmission loss.

[0021] In one implementation scheme of the related art, the folded waveguide is a slow-wave structure with high coupling impedance, which can effectively improve the modulation efficiency of the electron beam. Specifically, high coupling impedance helps to enhance the interaction between the electron beam and the high-frequency electromagnetic field, thereby improving the electron beam bunching degree. However, the defect of the folded waveguide lies in the tortuosity of its waveguide path, which leads to significant energy loss in the transmission process. As the frequency increases, the metal loss increases sharply, leading to serious decay of microwave energy in the transmission process. For high frequency bands above 1 THz, this loss is particularly prominent, and the output power of the folded waveguide often cannot meet the demand, often cannot meet the high power demand of radar and communication. Due to the excessive transmission loss, the practicability of the folded waveguide in these high-frequency applications is greatly discounted.

[0022] In another embodiment in the related art, a uniform sinusoidal waveguide, i.e., a straight-through periodic structure, is employed to reduce the transmission loss. The transmission loss of the uniform sinusoidal waveguide is generally low, which can reduce the energy attenuation and is suitable for high-frequency applications requiring low loss. However, the defect of this structure is that the field confinement ability is weak, resulting in a low coupling impedance. This seriously limits the bunching efficiency of the electron beam in the modulation stage. The low coupling impedance means that the electron beam density is not sufficiently bunched, resulting in an unsatisfactory gain of the microwave signal. Therefore, although the structure of the uniform sinusoidal waveguide can reduce the loss, it performs poorly in high-power output and cannot provide sufficient power to meet the needs of high-performance applications.

[0023] The slow wave structures in the above embodiments all face fundamental problems in the application in the terahertz band. When the frequency exceeds 1.03 THz, the output power of the folded waveguide and the uniform sinusoidal waveguide cannot meet the needs in practical applications.

[0024] It can be understood that, in the modulation process of the electron beam, strong field confinement is required to increase the electron beam density (i.e., high coupling impedance), whereas the coupling impedance of the conventional low-loss structure is generally small, resulting in insufficient bunching of the electron density. In the energy interaction stage, the bunched electron beam gives energy to the high-frequency field, but due to the high transmission loss of the high-coupling structure, a large amount of microwave energy is attenuated in the slow wave line.

[0025] In summary, in the related art, in the application scenario of the terahertz traveling wave tube, there is a technical problem of insufficient output power. To solve this technical problem, the present embodiment proposes a slow wave structure, which, by means of a partitioned slow wave structure design, spatially decouples the physical contradiction between the interaction strength and the transmission loss, significantly improves the output power and bandwidth, and reduces the energy loss.

[0026] As shown in FIGS. 1, 2, and 3, the present embodiment provides a slow wave structure comprising: Figure 1 and Figure 2 As shown in FIGS. 1, 2, and 3, the present embodiment provides a slow wave structure comprising: a first sub-slow wave structure configured to receive an electron beam and modulate the electron beam with a preset strong coupling impedance.

[0027] In the present embodiment, the first sub-slow wave structure comprises N strong coupling slow wave units connected in series, and the strong coupling slow wave units are configured as a sinusoidal waveguide structure. In the present embodiment, in order to achieve a strong coupling impedance, the height of the metal grid needs to be increased and the sinusoidal period length needs to be shortened.

[0028] Specifically, in one embodiment, the strong coupling slow wave unit needs to satisfy a first size constraint and a second size constraint, the first size constraint is a constraint for the height of the metal gate of the strong coupling slow wave unit to increase the height of the metal gate, the second size constraint is a constraint for the length of the sinusoidal period of the strong coupling slow wave unit to shorten the length of the sinusoidal period; wherein the N is a positive integer greater than 1. Specifically, the first size constraint is represented as the height of the metal gate being greater than half the width dimension of the sinusoidal waveguide and less than the width dimension of the sinusoidal waveguide; the second size constraint is represented as the length of the sinusoidal period being greater than half the height of the metal gate and less than the height of the metal gate.

[0029] In one embodiment, when designing the strong coupling slow wave unit, initial data for the height of the metal gate and initial data for the length of the sinusoidal period can be determined based on operating condition data. The initial data for the height of the metal gate is increased according to a predetermined algorithm to obtain an increased height of the metal gate, and the initial data for the length of the sinusoidal period can also be reduced according to a predetermined algorithm to obtain a shortened length of the sinusoidal period.

[0030] More specifically, in the design process, first, the initial values of the height of the metal gate and the length of the sinusoidal period need to be determined according to operating condition data. Operating condition data can include actual operating conditions, such as operating frequency band, electron beam current intensity, etc. Based on these data, appropriate initial values can be determined for the height of the metal gate and the length of the period.

[0031] The initial value of the height of the metal gate can be randomly sampled within the boundaries of the conventional design. Specifically, the initial height of the metal gate can be randomly selected between 0 and a, where a is the width dimension of the waveguide. For example, in practical applications, the initial height of the metal gate is assumed to be 0.4a, i.e. 68 microns (assuming a is 170 microns). This initial value provides a basis for subsequent adjustments.

[0032] The initial value of the length of the sinusoidal period can be determined based on the requirement of the dispersion characteristic, especially by adjusting the period length to better match the phase velocity of the system with the electron beam velocity. The initial value of the period length can be within the range of 0.5 times to 1.5 times the height of the metal gate according to operating condition requirements and frequency band data. Assuming the initial period length is 1.3 times the height of the metal gate, the period length is 88.4 microns.

[0033] After the initial parameters are determined, the present embodiment can use a double-target directional adjustment algorithm to optimize the height of the metal gate and the length of the sinusoidal period simultaneously. The goal of this algorithm is to increase the height of the metal gate and shorten the length of the sinusoidal period in order to maximize the group modulation efficiency of the electron beam and reduce the transmission loss of microwave energy.

[0034] According to the initial metal gate height, a preset increase ratio (for example, between 15% and 40%) is used to increase the height of the metal gate. The increased height of the metal gate cannot exceed the upper limit of the design (which can be 95% of a). By increasing the height of the metal gate, the coupling effect of the electron beam and the electromagnetic field can be effectively improved, thereby enhancing the efficiency of the bunching modulation. For example, assuming that the initial height is 68 microns and the increase ratio is 25%, the target metal gate height will be increased to 85 microns (i.e., the height of 0.5a), which can better modulate the electron beam.

[0035] On the basis of the increase in the height of the metal gate, the length of the sine period also needs to be shortened. The length of the period is adjusted by a preset compression ratio (for example, between 10% and 30%). Shortening the period length helps to reduce transmission loss and improve energy export efficiency. Assuming that the initial period length is 88.4 microns and the compression ratio is 20%, the final target period length is 70.7 microns. This new period length can more effectively reduce energy loss while maintaining the efficiency of the system. Through the above-mentioned dual adjustment of increasing the height of the metal gate and shortening the period length, the optimized design parameters are finally obtained, ensuring that the system can provide higher output power and lower transmission loss when operating at high frequencies.

[0036] In one specific embodiment, an oxide layer with a high dielectric constant can be generated on the surface to equivalently increase the height of the metal gate. The oxide layer can enhance the electric field binding capacity of the metal gate surface, thereby enhancing the efficiency of electron beam modulation. This method does not need to significantly change the physical shape of the metal gate, but rather increases the height by thickening the oxide layer. For example, an initial value of a metal gate can be selected first, and then an anodization method is used to grow an aluminum oxide layer.

[0037] In one specific embodiment, a laser cladding technique can be used to locally increase the thickness of the material at the top end of the metal gate. The laser cladding technique melts and sprays metal powder onto the surface of the substrate by high-energy laser to form a higher metal gate structure, thereby increasing the height of the local area.

[0038] The second sub-slow wave structure is connected in series with the first sub-slow wave structure, and is configured to receive the bunching-modulated electron beam and export microwave energy at a preset low transmission loss.

[0039] In this embodiment, the second sub-slow wave structure includes M low-loss slow wave units connected in series, and the low-loss slow wave units are configured as a sinusoidal waveguide structure. In this embodiment, in order to export microwave energy at a preset low transmission loss, the height of the metal gate needs to be shortened to reduce the transmission loss.

[0040] Specifically, in one embodiment, the low-loss slow-wave unit needs to satisfy a third size constraint, which is a constraint on the height of the metal grating for the low-loss slow-wave unit, to shorten the height of the metal grating to reduce transmission loss. Specifically, the third size constraint is expressed as the height of the metal grating being less than 0.5 times the width dimension of the sinusoidal waveguide.

[0041] In one embodiment, when designing the low-loss slow-wave unit, initial data of the height of the metal grating can be determined based on the working condition data. The initial data of the height of the metal grating is reduced according to a preset algorithm to obtain the reduced height of the metal grating.

[0042] Specifically, first, the initial height of the metal grating needs to be determined according to actual working condition data. The working condition data can include actual working conditions, such as a working frequency band, an electron beam current, and the like.

[0043] Similarly, the initial height of the metal grating can be randomly sampled from within the traditional design boundary, that is, randomly selected between 0 and the width dimension of the waveguide (a). For example, in an application, assuming that the width dimension of the waveguide is 170 microns, the initial height of the metal grating can be 68 microns, which will serve as the basis for subsequent adjustment. In order to ensure that the microwave signal can be effectively transmitted, the maximum value of the loss needs to be controlled during design. Through electromagnetic simulation, the relationship between the height of the metal grating and the transmission loss can be obtained, and a maximum loss value (for example, -80 dB) is determined as a tolerance threshold of the transmission loss. According to this loss constraint, the initial height of the metal grating is selected so that the transmission loss is closest to this value. Through calculation of the relationship between the loss and the height, a suitable initial height can also be selected.

[0044] After the initial height of the metal grating is determined, a height reduction algorithm is used to optimize the height of the metal grating. The purpose of this algorithm is to adjust the size of the metal grating according to the initial height of the metal grating, thereby reducing the loss and improving the transmission efficiency of the system. The algorithm mainly realizes optimization through two factors, a scaling factor and a compensation amount.

[0045] The scaling factor can be adjusted according to the initial height of the metal grating. If the initial height of the metal grating is large (greater than 0.6 times the width dimension of the waveguide), a larger reduction ratio is used; if the initial height of the metal grating is small, a more conservative reduction ratio is used. Specifically, if the height of the metal grating is greater than or equal to 0.6 times the width dimension of the waveguide, a larger reduction ratio (for example, 65%) is selected; if the height of the metal grating is less than 0.6 times the width dimension of the waveguide, a smaller reduction ratio (for example, 85%) is selected.

[0046] In the process of reducing the height of the metal gate, if the reduction is too large, the material yield strength of the metal gate can exceed the safe range. Therefore, a compensation amount can be introduced to prevent this situation. The size of the compensation amount is related to the initial height of the metal gate. When the initial height of the metal gate is larger, the compensation amount is larger; and when the initial height is smaller, the compensation amount is smaller. The compensation amount is used to fine-tune the final height of the metal gate to ensure that it is not excessively reduced to cause damage. Through the above two-step adjustment, the target metal gate height is finally obtained, ensuring that the transmission loss is minimized while avoiding the yield problem of the material.

[0047] In this embodiment, the influence of the optimized metal gate height on the transmission loss can be simulated by electromagnetic simulation software. The simulation results can help verify whether the reduced metal gate height can effectively reduce the transmission loss and ensure the performance of the system.

[0048] In this embodiment, after the sample is actually manufactured, actual experimental tests can be performed to check whether the adjusted metal gate height can meet the design target.

[0049] The slow wave structure provided in this embodiment can effectively solve the technical problem of insufficient output power in the prior art by ingeniously combining the first sub-slow wave structure and the second sub-slow wave structure. Specifically, the first sub-slow wave structure performs group modulation on the electron beam through a pre-set strong coupling impedance, thereby improving the density and modulation efficiency of the electron beam; and the second sub-slow wave structure ensures that the group-modulated electron beam can efficiently guide out microwave energy through the design of low transmission loss, thereby significantly reducing energy loss. Through this innovative structural design, this embodiment can provide higher output power in the high-frequency band, effectively reduce the attenuation of microwave signals, improve the overall performance of the system, and meet the application requirements of high power and high efficiency.

[0050] In some embodiments, the first sub-slow wave structure includes N strong coupling slow wave units connected in series, the strong coupling slow wave unit is configured as a sinusoidal waveguide structure, and satisfies a first size constraint and / or a second size constraint, the first size constraint is a constraint on the height of the metal gate of the strong coupling slow wave unit to increase the height of the metal gate, and the second size constraint is a constraint on the length of the sinusoidal period of the strong coupling slow wave unit to shorten the length of the sinusoidal period; wherein N is a positive integer greater than 1.

[0051] In this embodiment, the first size constraint can be represented as a constraint on the height of the metal gate of the strong coupling slow wave unit, that is, to increase the height of the metal gate, thereby enhancing the coupling effect between the electron beam and the electromagnetic field. Specifically, the height of the metal gate has a direct impact on the coupling impedance, and by increasing the height of the metal gate, the coupling impedance can be effectively improved, thereby enhancing the modulation effect of the electron beam and improving the energy exchange efficiency.

[0052] In one specific embodiment, the first size constraint can be that the height of the metal vane must be greater than 0.5 times the waveguide wide dimension and less than the waveguide wide dimension, thereby achieving a suitable metal vane height that allows for an increased coupling impedance while maintaining good transmission performance.

[0053] It can be appreciated that in conventional designs, the height of the metal vane (h_vane) is often limited to be less than the waveguide wide dimension (a), i.e., h_vane < a, typically with h_vane ∈ (0, 0.5a), to avoid short-circuiting. While this conservative design ensures safety, it also reduces the coupling impedance to some extent, thereby limiting the power output of the traveling wave tube. The present disclosure achieves a lower limit on the increase of the height of the metal vane by setting the height of the metal vane to be greater than or equal to 0.5a (i.e., h_vane ≥ 0.5a), thereby enhancing the electric field confinement and further increasing the coupling impedance.

[0054] It can be appreciated that increasing the height of the metal vane can enhance the ability of the electric field to confine the electron beam, thereby enhancing the coupling effect of the electron beam and the electromagnetic field. The lower limit of the increase of the height of the metal vane can effectively avoid the problem of insufficient coupling impedance caused by excessively low grid height in conventional designs.

[0055] In the present embodiment, the second size constraint is represented as the length of the sinusoidal period being greater than 0.5 times the height of the metal vane and less than the height of the metal vane. In the present embodiment, the second size constraint is a constraint on the length of the sinusoidal period (p_unit), i.e., the length of the sinusoidal period is shortened to optimize energy transmission efficiency and reduce transmission loss. Specifically, the second size constraint requires that the length of the sinusoidal period satisfy the following condition: 0.5h_vane ≤ p_unit < h_vane. The purpose of this constraint is to limit the range of the length of the sinusoidal period based on the height of the metal vane, in order to enhance the coupling effect of the electromagnetic field and the electron beam, and to reduce the transmission loss of the signal by shortening the period length.

[0056] It can be appreciated that in conventional designs, the design range of the length of the sinusoidal period is often wide, generally set as 0.5h_vane < p_unit < 1.5h_vane, i.e., the period length can vary from half the height of the metal vane to 1.5 times the height of the metal vane. The present embodiment narrows this design range by limiting the upper limit of the length of the sinusoidal period to be less than the height of the metal vane (h_vane), ensuring that the length of the sinusoidal period is always less than the height of the metal vane and not less than half the height of the metal vane.

[0057] It can be appreciated that shortening the length of the sinusoidal period can effectively improve the coupling strength of the electron beam and the electromagnetic field. A shorter period length allows the electron beam and the electromagnetic wave to interact more closely, thereby improving the modulation efficiency and power output.

[0058] In this embodiment, when the first size constraint and the second size constraint act together, the coupling impedance can be further improved. Specifically, the first size constraint ensures the minimum height of the metal grating, thereby enhancing the binding force of the electric field on the electron beam; the second size constraint further optimizes the coupling effect of the electromagnetic field and the electron beam by limiting the length of the sinusoidal period. The two complement each other, ensuring efficient energy conversion of the overall system.

[0059] In this embodiment, by optimizing the height of the metal grating and the length of the sinusoidal period, the coupling impedance can be effectively improved. Specifically, increasing the height of the metal grating can enhance the binding force of the electromagnetic field on the electron beam, thereby improving the coupling impedance; at the same time, shortening the length of the sinusoidal period also helps to improve the coupling impedance, enhancing the interaction between the electromagnetic field and the electron beam. These two design methods can work together to improve the coupling impedance, thereby strengthening the coupling effect of the electron beam and the electromagnetic field, improving the bunching modulation efficiency of the electron beam, and optimizing the energy exchange process. Through this optimization design, the output power and transmission efficiency of the terahertz traveling wave tube can be effectively improved, especially providing more efficient energy conversion in the high frequency band to meet the needs of high-performance terahertz systems.

[0060] In some embodiments, the first size constraint is represented as the height of the metal grating being greater than half the width dimension of the sinusoidal waveguide and less than the width dimension of the sinusoidal waveguide; the second size constraint is represented as the sinusoidal period length being greater than half the height of the metal grating and less than the height of the metal grating.

[0061] It can be understood that for a conventional sinusoidal waveguide, the relationship between the operating frequency and the width dimension of the waveguide is f>2c / a, where c represents the speed of light and a is the width dimension of the sinusoidal waveguide. In addition, the relationship between the height h_vane of the metal grating and the width dimension a is a>h_vane. The sinusoidal period length p_unit ranges from 0.5h_vane to 1.5h_vane, i.e. the period length is about 0.5 to 1.5 times the height of the metal grating.

[0062] In the segmented sinusoidal waveguide, in order to improve the coupling impedance, part of the traditional sinusoidal structure is replaced by a straight waveguide structure, which helps to improve the coupling efficiency and reduce energy loss. Specifically, in order to optimize the strong coupling unit, the height of the metal grating and the length of the sinusoidal period are analyzed in depth in the design process to explore their influence on the coupling impedance. Experimental results show that increasing the height of the metal grating or shortening the length of the sinusoidal period can effectively improve the coupling impedance.

[0063] In the design of the segmented sinusoidal waveguide, in order to improve the coupling impedance, the height of the metal grid needs to be appropriately increased. According to the design requirements, the increase of the height of the metal grid should not exceed 80% of the original height of the metal grid, and h_vane < a (that is, the height of the metal grid is always less than the width of the waveguide) must be met. By appropriately increasing the height of the metal grid, the binding force of the electric field on the electron beam can be enhanced, thereby improving the coupling impedance and optimizing the transmission of the microwave signal.

[0064] At the same time, in order to further improve the coupling impedance, the sinusoidal period length is also optimized. In the design, the sinusoidal half-period length needs to meet p_Sine = 0.5p_unit-w_parallel, where w_parallel is a parameter related to the period length. The shortening of the sinusoidal period length should not exceed 50% of the original period length. By shortening the period length, the interaction between the electromagnetic field and the electron beam can be enhanced, the group effect can be improved, and the coupling impedance can be further improved.

[0065] In the embodiment, by strictly constraining the height of the metal grid of the strong coupling slow wave unit to be between zero point five times and one time of the width of the waveguide, and by limiting the sinusoidal period length to be within zero point five times and one time of the height of the metal grid, the interaction strength between the slow wave structure and the electron beam is significantly enhanced, and the electron beam group modulation efficiency is effectively improved. On this basis, the directional compression of the period length further strengthens the high-frequency field binding effect, cooperatively solves the problem of low output power of the traditional traveling wave tube in the terahertz frequency band due to insufficient coupling impedance, while maintaining the compactness of the structure and the feasibility of processing, thereby providing a key technical guarantee for realizing a high-power terahertz radiation source. In some embodiments, X size-gradually-changing transition units are arranged in series at the input end and / or the output end of the first sub-slow wave structure, where X is a positive integer greater than 1 and less than N.

[0066] In the embodiment, by arranging X size-gradually-changing transition units in series at the input end and / or the output end of the first sub-slow wave structure, smooth transition of the signal and optimization of the energy transmission efficiency can be realized. The introduction of the size-gradually-changing transition unit effectively alleviates the reflection and energy loss caused by the sharp size change in the traditional design. By reasonably designing the size-gradual change of the transition unit, impedance matching can be realized in a shorter transition distance, thereby reducing the reflection of the signal and the loss in the transmission process.

[0067] In some embodiments, the second sub-slow wave structure includes M low-loss slow wave units connected in series, the low-loss slow wave units are configured as a sinusoidal waveguide structure, and satisfy a third size constraint, which is a constraint on the height of the metal grid of the low-loss slow wave unit, to shorten the height of the metal grid to reduce the transmission loss.

[0068] In the present embodiment, M can be greater than N, M can also be less than N, and M can also be equal to N.

[0069] In the present embodiment, the third size constraint is that the height of the metal grating is less than half the width of the sinusoidal waveguide.

[0070] Specifically, in the present embodiment, the height of the metal grating of the low-loss slow-wave unit needs to satisfy the following constraint: H_vane≤0.5a, where a is the width of the waveguide. This constraint requires that the height of the metal grating must be less than half the width of the waveguide, aiming to significantly reduce the transmission loss of the signal and improve the energy transmission efficiency by optimizing the height of the metal grating.

[0071] In traditional design schemes, the constraint on the height of the metal grating is often H_vane<a, and the main purpose of this design is to prevent short-circuiting. According to the traditional design, the typical range of the height of the metal grating is often H_vane∈(0.4a, 0.7a). However, in the present invention, the height of the metal grating is forced to be limited to H_vane≤0.5a, which significantly reduces the surface current loss. By strictly controlling the height of the metal grating, the transmission path of the current on the metal surface is reduced, thereby significantly reducing the loss of energy and optimizing the efficiency of the system.

[0072] In traditional designs, due to the large height of the metal grating, the path of the surface current is long, resulting in significant skin effect and causing large loss. By reducing the height of the metal grating, the path of the surface current can be effectively reduced, thereby improving the transmission efficiency of the microwave energy.

[0073] In some embodiments, the third size constraint is that the height of the metal grating is less than half the width of the sinusoidal waveguide.

[0074] In some embodiments, Y size-gradually-transitioning units are configured in series at the input end and / or the output end of the second sub-slow-wave structure, where Y is a positive integer greater than 1 and less than M.

[0075] In the present embodiment, by configuring Y gradually changing size transition units in series at the input end and / or the output end of the second sub-slow wave structure, smoother signal transition and optimized energy transmission can be achieved. The introduction of these gradually changing size transition units effectively avoids sharp size changes, thereby reducing reflection and energy loss. By using gradually changing size design at the input and output ends, impedance matching can be achieved, the coupling efficiency of the electron beam and the electromagnetic field can be optimized, the signal can be smoothly transmitted during the transition process, and reflection or energy attenuation caused by size mismatch can be avoided. In addition, the Y transition units (where Y is greater than 1 and less than a positive integer M) can be flexibly configured according to actual needs to achieve more precise matching effect, ensuring efficient operation of the system and lower transmission loss.

[0076] In some embodiments, the slow wave structure further comprises: an electron beam transmission channel configured as a vacuum metal grid channel, one end of which is connected to the output end of the first sub-slow wave structure, and the other end of which is connected to the input end of the second sub-slow wave structure.

[0077] In the present embodiment, by configuring an electron beam transmission channel in the slow wave structure and designing it as a vacuum metal grid channel, effective connection between the output end of the first sub-slow wave structure and the input end of the second sub-slow wave structure is achieved. This design can ensure smooth transmission of the electron beam between the two slow wave structures, minimizing energy loss and unnecessary interference. The use of a vacuum metal grid channel further optimizes the stability and focusing effect of the electron beam, improving the coupling efficiency of the electron beam and the electromagnetic field. In addition, electron beam transmission in a vacuum environment can effectively avoid energy attenuation caused by dielectric loss, ensuring efficient extraction of microwave energy. This design not only improves the power output and energy conversion efficiency of the system, but also ensures the stability and efficient operation of the overall system, especially in high-frequency applications, better meeting the requirements of high power and low loss.

[0078] The present embodiment provides a terahertz traveling wave tube device comprising the slow wave structure as described above.

[0079] The present embodiment provides a terahertz communication device comprising a terahertz traveling wave tube device as described above.

[0080] As shown in Figures 3-9 In one specific embodiment, a hybrid dispersion segmented sinusoidal waveguide terahertz slow wave structure is provided.

[0081] It can be understood that compared with solid-state amplifier devices, the terahertz traveling wave tube based on the principle of vacuum electronics has irreplaceable characteristics such as high power, wide frequency band and compact structure, and can meet the application requirements of high power and wide frequency band in the terahertz electromagnetic system, and is a very valuable high-power source. However, when the frequency rises to a frequency band above 1 THz, the excessively high microwave transmission loss makes it difficult for solid-state devices in this frequency band to achieve considerable power output, and the traditional uniform period traveling wave tube also faces the dilemma of being difficult to maintain high interaction efficiency and low transmission loss. For example, the folded waveguide traveling wave has extremely high interaction efficiency, but due to its tortuous path transmission, it also brings higher transmission loss, making it difficult for the 1 THz or above frequency band traveling wave tube based on this structure to obtain ideal power output. The traditional uniform period segmented sinusoidal waveguide traveling wave tube has excellent transmission characteristics, but for the 1 THz or above frequency band with extremely high loss, its low coupling impedance also restricts its further power amplification capability.

[0082] According to the process of beam-wave energy exchange realized by the traveling wave tube, it can be found that it first experiences an electron beam modulation process, in which the electron beam is mainly accelerated and decelerated by the high-frequency field to realize density clustering, and little microwave energy is output; and then the modulated electron beam gives its energy to the high-frequency field under suitable synchronization conditions, and the cluster center of the electron beam also gradually falls into the low-energy region, thereby losing the synchronization interaction condition with the high-frequency field, and most of the microwave energy is generated at this stage. Therefore, in the first stage, the electron beam is modulated as much as possible to achieve efficient clustering, and in the second stage, the interaction strength is maintained while the transmission loss of microwave energy is minimized, which will be the key to realizing high-power output of the 1 THz or above frequency band traveling wave tube.

[0083] The full uniform dispersion traveling wave tube is composed of the same kind of wideband slow wave structure, and since each part of the slow wave structure is completely consistent, through reasonable design, it can ensure the occurrence of interaction in a wide frequency range, and each slow wave unit can maintain good matching. Therefore, this type of traveling wave tube has the characteristics of wide frequency band and low reflection while maintaining high power. However, as the frequency rises to the terahertz frequency band, the slow wave line loss becomes the most important factor restricting the interaction efficiency of the terahertz traveling wave tube, and the traditional uniform dispersion traveling wave tube often cannot have both good interaction strength and low transmission loss, so the high transmission loss in this frequency band often leads to a decrease in interaction efficiency.

[0084] The purpose of the present embodiment is to overcome the problem that the 1 THz or above frequency band traveling wave tube is difficult to maintain high interaction strength while realizing low transmission loss, and a solution based on a mixed dispersion segmented sinusoidal waveguide is provided, which replaces the first segment of the slow wave with a strong coupling slow wave, and then connects the low-loss slow wave in a clever way to maximize the interaction efficiency while minimizing the transmission loss as much as possible.

[0085] The traveling wave tube mainly consists of a slow wave structure, an electron gun, a magnetic focusing system, a high frequency input / output structure, and a voltage reduction collecting stage. In order to maximize the interaction strength and transmission efficiency, a plurality of uniform period strong coupling slow wave units are applied in the first section of the slow wave structure, a uniform period low-loss slow wave unit is applied in the front section of the slow wave of the second section, and the last few slow wave units are evolved from the low-loss slow wave unit with a period length jump, and the period length jump is realized by shortening the length of the low-loss slow wave unit straight waveguide part, so as to realize the re-matching of the phase velocity and the electron beam, and further improve the interaction efficiency.

[0086] As shown in Figures 3-6 In the embodiment, a traveling wave tube high frequency structure working at 1.03 THz is designed, which has a circular electron beam current with a voltage of 23 kV, a current of 30 mA, and a cross-sectional size of 40 um2. According to the related formula calculation, the electron beam current has the best energy conversion state with the slow wave structure with a phase velocity of 0.285c, and has the best synchronous group state with the slow wave structure with a phase velocity of 0.290c. Therefore, 0.2876c is selected as the target slow wave structure at the working point (1030GHz) of the phase velocity requirement, and the coupling impedance of the strong coupling slow wave structure is kept above 3.5 ohms as much as possible, and the low-loss slow wave unit keeps the in-band dispersion as flat as possible while minimizing the grid height, and the coupling impedance is above 2 ohms.

[0087] The final structure parameters of the strong coupling slow wave unit are: waveguide wide side a = 170 um, channel radius R_tunnel = 27 um, unit period length p_unit = 98.5 um, grid height h_vane = 110 um, and sine structure half period length p_Sine = 27.5 um. The calculation result shows that the center frequency of the strong coupling slow wave unit is 1031GHz, the corresponding phase velocity is 0.2875c, and the coupling impedance is 3.6 ohms. At the same time, the slow wave unit has an interaction bandwidth of 10GHz, covering between 1025GHz and 1035GHz.

[0088] After optimization and iteration for the best transmission performance, the low-loss slow wave unit with the following structure parameters can be obtained: waveguide wide side A = 170 um, channel radius R_tunnel = 27 um, unit period length p_unit = 95.8 um, grid height H_vane = 85 um, and sine structure half period length p_Sine = 30 um. At this time, the low-loss slow wave unit has the following interaction characteristics: the phase velocity at the working point 1031GHz is 0.2876c, the coupling impedance is 2.5 ohms, and the interaction bandwidth is 20GHz, covering between 1020GHz and 1040GHz.

[0089] In general, through the ingenious combination of the two, the interaction bandwidth of more than 10 GHz and the coupling impedance of more than 3 ohms can be realized.

[0090] After obtaining the target slow-wave unit, X strong-coupling slow-wave units are taken as the first section of the slow-wave structure interaction region, and Nx transition units are connected at both ends for transmitting microwave energy and reducing reflection as much as possible. In this way, a complete strong-coupling slow-wave structure is obtained. Similarly, Y low-loss slow-wave units are taken as the low-loss slow-wave structure interaction region, and Ny transition units are connected at both ends. Finally, M*N phase velocity jump units are connected at the ends of the Y low-loss slow-wave units, where M is the number of phase velocity jump sections, and N is the number of each phase velocity jump unit. Finally, a complete hybrid dispersion slow-wave structure is obtained.

[0091] As shown in Figures 7-9 The copper surface conductance in the 1.03 THz band is derived according to the roughness of the copper surface, and the value is about 1.85×107 S / m. The transmission characteristics of the slow-wave system are calculated, and the calculation results show that the -15 dB return loss bandwidth of the slow-wave system is more than 70 GHz, and the in-band insertion loss is about -90 dB. Compared with the slow-wave unit at both ends using only strong-coupling units, the in-band insertion loss is increased by 20 dB, and the in-band reflection remains basically unchanged.

[0092] In addition, the particle interaction simulation determines that X=123, Y=113, M=5, and N=2 when the maximum power output state of the traveling wave tube is determined. The final calculation results show that the traveling wave tube can output a radio frequency power of up to 3700 mW at 1032 GHz, and the corresponding driving power is only 1 mW, with a gain of 35.7 dB. The 3 dB bandwidth is 12 GHz, covering between 1023 GHz and 1035 GHz. In addition, the gain characteristics calculation results show that the traveling wave tube enters the nonlinear amplification state when the input power is greater than 0.5 mW, and the maximum gain appears at an input power of 0.1 mW, about 40 dB.

[0093] Compared with the use of strong-coupling slow-wave units or low-loss units alone, the scheme of ingeniously combining the two has the best power bandwidth product. Specifically, although the strong-coupling slow-wave unit has a large bandwidth, its in-band power is low due to its high loss. Although the low-loss slow-wave unit has excellent loss characteristics, its output power is limited due to the low coupling impedance in the high-frequency region. For this embodiment, the peak power of the traveling wave tube composed of strong-coupling slow-wave structure is about 2.0 W, and the bandwidth is 16 GHz, covering 1025-1040 GHz. The peak power of the low-loss slow-wave structure traveling wave tube is 3.5 W, and the bandwidth is about 10 GHz. The scheme of ingeniously combining the two has a peak power of 3.8 W and a 3 dB bandwidth of 13 GHz. Compared with the slow wave structure using only strong coupling, the in-band output power of the former is increased by 2000mW, and the 3dB bandwidth is increased by about 4GHz compared with the slow wave structure using only low loss, and the in-band output power is close to each other. An effective way is provided for the 1.03THz traveling wave tube to achieve an observable power output.

[0094] The embodiment adopts a full-metal segmented sinusoidal slow wave structure, has excellent heat dissipation, good transmission characteristics, and a wide interaction bandwidth, and is easier to realize in the terahertz band than spiral line coupled cavities and other slow wave structures such as zigzag waveguides. Compared with other full-metal slow wave structures such as zigzag waveguides, the segmented sinusoidal slow wave structure has lower transmission loss while maintaining moderate interaction strength.

[0095] In terms of processing, the segmented sinusoidal slow wave structure has a smoother transition, is more suitable for 1.03THz NANO-CNC processing requirements than staggered double-grid waveguides, and has unique advantages in processing precision and implementation.

[0096] It should be noted that the terms "first", "second", etc. in the specification and claims of the present application and the above-described drawings are used to distinguish similar objects, and do not necessarily describe a specific order or sequence. It should be understood that the data thus used can be interchanged under appropriate circumstances, so that the embodiments of the present application described herein can be implemented in an order other than that illustrated or described herein. In addition, the terms "include" and "have" and any variations thereof are intended to cover non-exclusive inclusion, for example, a process, method, system, product or device including a series of steps or units does not have to be limited to those steps or units clearly listed, but can include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0097] Alternatively, the specific examples in the embodiments can refer to the examples described in the above-described embodiments, and the embodiments will not be described here.

[0098] The serial numbers of the above-described embodiments of the present application are only for description, and do not represent the advantages or disadvantages of the embodiments.

[0099] In the above-described embodiments of the present application, the description of each embodiment has its own focus, and the parts not described in detail in a certain embodiment can be referred to the related description of other embodiments.

[0100] The above is only the preferred embodiment of the present application, and it should be pointed out that for ordinary skilled in the art, without departing from the principle of the present application, a number of improvements and refinements can be made, which should be considered as the protection scope of the present application.

Claims

1. A slow wave structure, characterized by, The slow wave structure comprises: a first sub-slow wave structure configured to receive an electron beam and to group-modulate the electron beam with a preset strong-coupling impedance; a second sub-slow wave structure connected in series with the first sub-slow wave structure, the second sub-slow wave structure being configured to receive the group-modulated electron beam and to derive microwave energy with a preset low transmission loss.

2. A slow wave structure according to claim 1, characterised in that The first sub-slow wave structure comprises N strong-coupling slow-wave units connected in series, the strong-coupling slow-wave units being configured as sinusoidal waveguide structures and satisfying a first size constraint for increasing the height of a metal grating of the strong-coupling slow-wave units and / or a second size constraint for decreasing the length of a sinusoidal period of the strong-coupling slow-wave units, wherein N is a positive integer greater than 1.

3. A slow wave structure according to claim 2, characterised in that, The first size constraint is that the height of the metal grating is greater than 0.5 times the width of the sinusoidal waveguide and less than the width of the sinusoidal waveguide, and the second size constraint is that the length of the sinusoidal period is greater than 0.5 times the height of the metal grating and less than the height of the metal grating.

4. A slow wave structure according to claim 2, characterised in that, X size-gradual transition units connected in series are arranged at the input end and / or the output end of the first sub-slow wave structure, wherein X is a positive integer greater than 1 and less than N.

5. A slow wave structure according to claim 1, wherein The second sub-slow wave structure comprises M low-loss slow-wave units connected in series, the low-loss slow-wave units being configured as sinusoidal waveguide structures and satisfying a third size constraint for decreasing the height of a metal grating of the low-loss slow-wave units to reduce transmission loss.

6. A slow wave structure according to claim 5, characterised in that, The third size constraint is that the height of the metal grating is less than 0.5 times the width of the sinusoidal waveguide.

7. A slow wave structure according to claim 5, wherein, Y size-gradual transition units connected in series are arranged at the input end and / or the output end of the second sub-slow wave structure, wherein Y is a positive integer greater than 1 and less than M.

8. The slow wave structure of claim 1, wherein, The slow wave structure further comprises: an electron beam transmission channel configured as a vacuum metal grating channel, one end of the electron beam transmission channel being connected to the output end of the first sub-slow wave structure and the other end of the electron beam transmission channel being connected to the input end of the second sub-slow wave structure.

9. A terahertz traveling wave tube device, characterized by, The slow wave structure comprises any one of claims 1-8.

10. A terahertz communication device, characterized by, The terahertz traveling wave tube device comprises the slow wave structure of claim 9.

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