S-band transit time oscillator and method thereof

Abstract

The invention discloses an S-band transit time oscillator and a method thereof, and belongs to the technical field of high-power microwave devices. Comprising an anode structure, an annular cathode and an output circular waveguide, the anode structure is a wheel-shaped metamaterial unit array which is coaxially arranged up and down, an electron drift channel and three electromagnetic regulation and control cavities are formed through unit arrangement, and the drift channel among the cavities is in a cut-off state for working electromagnetic waves and is coupled only through bunching electrons; the annular cathode and the anode are vertically arranged to generate radial current, a cut-off cavity is arranged at a cathode port, the output circular waveguide is connected with the electromagnetic regulation and control cavity to form a single port, a TM01 mode is radiated, and the maximum size is smaller than the wavelength of the mode. An external magnetic field is not needed, the output power can reach 1.03 GW under the external 460kV voltage and 2.8 kA current, the highest conversion efficiency is 80%, the device compactness is high, light and small equipment is adapted, and the problems that traditional dual-port deployment is difficult and the size is large are solved.

Description

Technical Field

[0001] This invention belongs to the field of high-power microwave device technology, specifically relating to an S-band transit time oscillator and its method. Background Technology

[0002] Radial transit-time oscillators (RTOs) were proposed by Arman, Mostron, and Kwan in 1995 and 1996, respectively. They feature a large cathode emitting area, and the radial movement of electrons reduces current density, facilitating the realization of magnetic field-free high-power microwave devices. Currently, the S-band three-cavity radial transit-time oscillator proposed by Xiao Renzhen of the Northwest Institute of Nuclear Technology achieves a power conversion efficiency of up to 53%, but it requires two output ports, which is difficult to implement in engineering, and the cavity radius must be larger than the operating mode cutoff wavelength, which is unfavorable for deployment in current lightweight equipment systems. This invention proposes utilizing the novel electromagnetic properties of metamaterials to achieve a radial three-cavity transit-time oscillator operating below the cutoff frequency, with electromagnetic waves output at a single port, improving the device's compactness. Specifically, a novel type of wheel-shaped metamaterial unit is proposed. By designing the arrangement of the units to form an electron drift channel, the wheel-shaped metamaterial unit array is loaded in a circular waveguide, forming three electromagnetically controlled cavities, achieving a power conversion efficiency of up to 80%.

[0003] For magnetic field guiding systems, solenoid coils and permanent magnets are common. Solenoid coils have several drawbacks: first, they require an additional power supply to generate a magnetic field, and the energy consumption of this supply reduces the overall system efficiency; second, under high repetition rate and long pulse conditions, the coil generates a large amount of heat, necessitating an additional cooling system. These additional systems not only reduce the overall efficiency of the HPM system but also increase its size and weight. The main reason is that, given a certain weight and volume, the magnitude of the guiding magnetic field generated by a permanent magnet is limited. Therefore, to address the generally low efficiency problem of permanent magnet-encapsulated HPM sources, two approaches are needed: first, to research low-magnetic-field, high-efficiency HPM sources; and second, to optimize the design of permanent magnets to generate the highest possible magnetic field within a given weight and volume. Consequently, further development of lightweight and miniaturized HPM sources using guiding magnetic field systems is hindered. Magnetic field-free relativistic transit-time oscillators, as a highly promising high-power microwave source for narrowband directed-energy weapons, have broad application prospects.

[0004] A transit-time oscillator (TTO) is a microwave device based on the interaction between electromagnetic waves and an electron beam, commonly used in radar systems, electronic countermeasures, plasma heating, and basic scientific research. In 2025, He Yufang et al. from the National University of Defense Technology (NUDT) proposed an X-band low-magnetic-field transit-time oscillator. Employing a distributed magnet design method, they reduced the size and weight of the magnetic field system to approximately 5.67 kg, operating at 8 GHz with a power output of 1.17 GW and a power conversion efficiency of approximately 40.67%. In 2023, Yu Zhuang and Ju Jinchuan et al. from NUDT proposed a K-band coaxial transit-time oscillator. This oscillator uses a two-stage modulation structure cascaded with a high appearance quality factor three-gap rectangular modulation cavity and a low appearance quality factor single-gap trapezoidal modulation cavity. This resulted in a microwave output power of 2.2 GW with a beam-to-wave power conversion efficiency of 44% and an output microwave frequency of 18.55 GHz, exhibiting a clean spectrum, all while maintaining a high magnetic field strength of 0.74 T. These methods have made it possible to reduce the weight of the magnetic field system and improve the power conversion efficiency of transit-time oscillators. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to address the shortcomings of the prior art by providing an S-band transit time oscillator. By designing and arranging a wheel-shaped metamaterial unit array to form an electron drift channel, the efficiency of the interaction between drift electrons and electromagnetic waves is improved and miniaturization is achieved. This solves the technical problem that traditional transit time oscillators require external high voltage and magnetic field to generate GW-level output power.

[0006] The present invention adopts the following technical solution: An S-band transit-time oscillator includes an anode structure, a ring cathode, and an output circular waveguide. The anode structure is an array of wheel-shaped metamaterial units arranged coaxially. The wheel-shaped metamaterial unit array forms an electron drift channel and three electromagnetic control cavities through the unit arrangement. The electron drift channel between the cavities is cut off from the working electromagnetic wave, and the cavities are coupled through electron clustering. The ring cathode is placed perpendicular to the anode structure and is used to generate radial current. A cutoff cavity is provided at the cathode port of the anode structure. The output circular waveguide is connected to the electromagnetic control cavities to form a single-power output port. The output circular waveguide radiates a forward TM01 mode, and the maximum size of the output circular waveguide is smaller than the wavelength of the TM01 mode. The wheel-shaped metamaterial unit array constitutes a slow-wave interaction structure, which is used to adjust the equivalent dielectric parameters of the device to realize energy exchange between electrons and electromagnetic waves and electron clustering.

[0007] Preferably, the wheel-shaped metamaterial unit array includes an upper wheel-shaped metamaterial unit and a lower wheel-shaped metamaterial unit, and the axial spacing between the upper and lower units constitutes the electron drift channel.

[0008] Preferably, the upper unit and / or lower unit of the wheel-shaped metamaterial are provided with a central cavity.

[0009] Preferably, the bottom of the lower unit of the wheel-shaped metamaterial has a central through hole.

[0010] Preferably, the upper unit and / or lower unit of the wheel-shaped metamaterial include an inner annular groove and an outer annular groove.

[0011] Preferably, the upper unit of the wheel-shaped metamaterial and the lower unit of the wheel-shaped metamaterial are connected by at least one unit connecting rod.

[0012] Preferably, the central axis of the unit connecting rod forms an angle θ with the horizontal direction.

[0013] Preferably, the maximum dimension of the output circular waveguide is its inner radius Rw, and Rw < λ, where λ is the operating wavelength of the TM01 mode.

[0014] Preferably, the transit time oscillator operates at a frequency of 2.19 GHz and has an output power of 1.03 GW when the applied voltage is 460 kV and the operating current is 2.8 kA.

[0015] Another technical solution of the present invention is a microwave generation method based on an S-band transit time oscillator, comprising the following steps: A high-voltage pulse is applied between the annular cathode and the anode structure, causing the annular cathode to emit explosive electrons, forming an electron beam that moves radially. The electron beam enters the electromagnetic control cavity through the electron drift channels between the wheel-shaped metamaterial unit arrays; Within the electromagnetically controlled cavity, the electron beam interacts with the intrinsic mode field controlled by the slow-wave interaction structure, realizing the conversion of electron energy into microwave energy and speed modulation of the electron beam; the speed-modulated electron beam clusters in the electron drift channel and achieves energy coupling between cavities through the clustered electrons; Ultimately, the excited microwaves are radiated from the single power output port in TM01 mode by the output circular waveguide connected to the electromagnetic control cavity, and the radiation process is constrained by the cutoff cavity at the cathode port.

[0016] Compared with the prior art, the present invention has at least the following beneficial effects: An S-band transit time oscillator is presented. An electron drift channel formed by a wheel-shaped metamaterial unit array and three electromagnetically controlled cavities utilize the novel electromagnetic properties of the metamaterial to cut off the working electromagnetic wave in the drift channel between cavities, achieving coupling only through focused electrons. This avoids the coupling interference problems of traditional cavities and improves the accuracy of beam-wave interaction. A ring cathode and anode are placed perpendicularly to ensure stable radial current generation, providing sufficient "energy carrier" for the interaction between the electron beam and electromagnetic wave. The cutoff cavity at the cathode port, in conjunction with a single-output circular waveguide, achieves TM01 mode radiation with a waveguide size smaller than the wavelength, completely solving the drawbacks of traditional dual-port oscillators, such as difficult engineering implementation and excessively large cavity radii, achieving both miniaturization and practicality. The slow-wave interaction structure allows adjustment of the equivalent dielectric parameter, effectively reducing the oscillation threshold current and improving the energy exchange efficiency between electrons and electromagnetic waves. GW-level output can be achieved without an external magnetic field, simplifying system design and reducing energy consumption and size. Furthermore, the array is divided into upper and lower units, with axial spacing forming an electron drift channel. This structured and controllable electron beam path avoids energy loss due to electron scattering. This segmented structure facilitates optimization of unit spacing based on operating frequency, adapting to different electromagnetic dispersion characteristics and creating favorable conditions for electron velocity modulation and clustering. Compared to an integrated structure, the segmented design is easier to manufacture and assemble, while allowing independent optimization of individual unit structural parameters, improving the overall adjustability of the device's performance. The drift channel formed by the axial spacing precisely matches the radial trajectory of the electron beam, ensuring smooth entry of the electron beam into the electromagnetic control cavity, enhancing the stability of beam-wave interaction, and laying the structural foundation for efficient energy conversion.

[0017] Furthermore, the central cavity provides a smooth radial movement path for the electron beam, reducing collision losses between electrons and the unit structure and ensuring the integrity and energy density of the electron beam. Simultaneously, the central cavity allows for adjustment of the equivalent permittivity and permeability distribution of the unit, enabling more precise electromagnetic control of the metamaterial and adapting to the magnetic and electric field distribution requirements of the operating mode. The flexible design of cavities in the upper and / or lower units allows for structural adjustments based on actual electromagnetic control needs, ensuring basic functionality while reserving space for performance optimization. The cavity structure also reduces unit weight, further contributing to device miniaturization, while reducing material usage and processing costs, balancing practicality and economy.

[0018] Furthermore, the central through-hole, in conjunction with the central cavity, forms a through-channel, ensuring that the electron beam, emitted from the cathode, smoothly enters the drift channel and electromagnetic control cavity through the through-hole, avoiding energy loss or structural heating caused by electron accumulation at the bottom of the unit. The through-hole size can be optimized according to the electron beam current density to ensure electron transmission efficiency, while also facilitating the construction of a vacuum environment inside the device, adapting to the vacuum requirements of the anode structure. The through-hole structure also balances the electromagnetic distribution inside the unit, reduces edge field distortion, and improves the uniformity of beam-wave interaction, thereby ensuring the spectral purity of the output microwave and further enhancing the device's operational stability.

[0019] Furthermore, the design of the annular grooves can alter the geometric parameters of the metamaterial units, thereby flexibly adjusting the equivalent dielectric parameters and permeability, enabling the cavity to excite and stably maintain the target operating mode. The electromagnetic boundary conditions formed by the double annular groove structure are beneficial for confining the propagation of electromagnetic waves within the cavity, reducing energy leakage, and improving energy utilization. The design of setting annular grooves in the upper and / or lower units can achieve differentiation in the electromagnetic characteristics of different units. By arranging them in an array, a gradient electromagnetic environment can be formed, enhancing the electron velocity modulation effect, providing better electromagnetic conditions for electron aggregation, and helping to improve power conversion efficiency.

[0020] Furthermore, the inclusion of at least one connecting rod ensures a stable overall structure between the upper and lower units, preventing unit displacement due to electromagnetic forces or thermal effects during operation. This guarantees the dimensional accuracy of the electron drift channel and cavity structure, thereby maintaining the stability of beam-wave interaction. The connection method of the connecting rods does not compromise the electromagnetic characteristics of the units. By optimizing the number and position of the connecting rods, structural strength and electromagnetic distribution can be balanced, avoiding interference with electromagnetic wave propagation. Compared to a separate structure without connections, the connecting rod design improves the mechanical reliability of the device, adapts to high-power, long-pulse operating scenarios, and facilitates overall assembly and debugging, reducing the difficulty of engineering applications.

[0021] Furthermore, the angle θ can be designed to adjust the spatial orientation of the connecting rod within the unit array, preventing it from obstructing the electron beam transmission path and ensuring smooth electron beam passage. Simultaneously, the angle setting can alter the electromagnetic boundary conditions of the unit structure, fine-tuning the equivalent electromagnetic parameters of the metamaterial, making the electromagnetic dispersion characteristics of the cavity more aligned with the design objectives, and further improving beam-wave interaction efficiency. A specific angle can balance the structural mechanical strength and electromagnetic compatibility, allowing the connecting rod to both provide stability and minimize the scattering effect on electromagnetic waves, ensuring the spectral purity and power stability of the output microwave.

[0022] Furthermore, by leveraging the electromagnetic modulation properties of metamaterials, this limitation is overcome, enabling stable radiation of the TM01 mode even when Rw < λ. This significantly reduces the device's radial size, making it suitable for deployment in lightweight and compact equipment. This design does not sacrifice output power or efficiency, ensuring core device performance while achieving miniaturization, thus resolving the inherent trade-off between high power and miniaturization in traditional devices.

[0023] Furthermore, the clearly defined operating frequency is locked to S-band application scenarios, adapting to actual needs such as radar and electronic countermeasures; specific voltage and current parameters provide a basis for power supply system design, ensuring that the device can be engineered; the 1.03GW output power and stable operating parameters prove that the oscillator can still achieve high power output without an external magnetic field, and its performance is better than traditional low-magnetic-field or magnetic-field oscillators, highlighting its advantages of high power conversion efficiency and strong operating stability, providing reliable performance support for practical applications.

[0024] A microwave generation method based on an S-band time-of-flight oscillator is presented. This method employs a coherent process involving high-voltage pulse excitation of the electron beam, precise transmission via a drift channel, beam-wave interaction within the cavity, focused electron coupling, and single-port output in TM01 mode. This process is deeply integrated with the oscillator's core structure, yielding significant results. It not only stably generates a radial electron beam, reducing transmission loss, but also enhances energy conversion through a metamaterial slow-wave structure, achieving a power conversion efficiency of 80% and outputting pure microwaves with a high power of 1.03 GW and a stable frequency of 2.19 GHz. The single-port design and cutoff cavity constraint solve the challenges of traditional dual-port deployments. Combined with a miniaturized waveguide design, it adapts to the needs of lightweight and compact equipment, eliminating the need for an external magnetic field, simplifying system structure and reducing energy consumption, and balancing high efficiency, stability, and engineering practicality.

[0025] In summary, the method of this invention achieves single-port output and miniaturization through metamaterial unit arrays and optimized structural design, enabling high-power output of 1.03GW without the need for an external magnetic field, with a conversion efficiency of 80%. It features strong structural adjustability, convenient processing and assembly, and stable operating parameters. It solves the deployment challenges of traditional devices, improves beam-wave interaction efficiency, and is suitable for the needs of lightweight and compact equipment, showing broad application prospects.

[0026] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the following description of the relative embodiments will be briefly introduced. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 The diagram shows the structure of the S-band transit time oscillator of the present invention, wherein (a) is a schematic diagram of the radial three-cavity cross-section, (b) is a schematic diagram of the upper unit cross-section of the wheel-shaped metamaterial structure unit, and (c) is a schematic diagram of the lower unit cross-section of the wheel-shaped metamaterial structure unit. Figure 2 The figure shows that (a) is the equivalent permittivity and (b) is the equivalent permeability. Figure 3 This is a schematic diagram of the cross-section of a radial three-cavity transit-time oscillator; Figure 4 A schematic diagram of the wheel-shaped metamaterial structural unit that constitutes the radial three-cavity body; Figure 5 A schematic diagram of electron clustering at different times in a radial three-cavity transit-time oscillator; Figure 6 The diagram shows the electrical structure of a radial three-cavity transit-time oscillator with an applied operating voltage of 460kV and an operating current of 2.8kA. In the diagram, (a) represents the operating electric field, (b) represents the output power, (c) represents the operating frequency of 2.19GHz, and (d) represents the operating current. Figure 7 The electron energy distribution at different times is given by an applied voltage of 460kV and an operating current of 2.8kA. Figure 8 The electric field distribution in a radial three-cavity transit-time oscillator with an output power of 1.03 GW is shown. Figure 9 TM in a radial three-cavity transit-time oscillator 01 Schematic diagram; Figure 10 A schematic diagram of the thermal load of the wheel-shaped metamaterial structure unit of the radial three-cavity transit time oscillator with an output power of 1.03GW; Figure 11 The curves show the output power and conversion efficiency of the radial three-cavity transit-time oscillator. (a) shows the current changing from 2.0kA to 2.8kA when the applied voltage is U=460kV, and (b) shows the voltage changing from 420kV to 460kV when the current is I=2.8kA. Detailed Implementation

[0029] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0030] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "one side," "one end," and "one side," etc., indicating orientation or positional relationships based on the orientation or positional relationships shown in the accompanying drawings, are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined with "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0031] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0032] It should be understood that, when used in this specification and the appended claims, the terms "comprising" and "including" indicate the presence of the described features, integrals, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or collections thereof.

[0033] It should also be understood that the terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the invention. As used in this specification and the appended claims, the singular forms “a,” “an,” and “the” are intended to include the plural forms unless the context clearly indicates otherwise.

[0034] It should also be further understood that the term "and / or" as used in this specification and the appended claims refers to any combination of one or more of the associated listed items and all possible combinations, and includes such combinations.

[0035] The accompanying drawings illustrate various structural schematic diagrams according to embodiments disclosed in this invention. These drawings are not to scale, and some details have been enlarged for clarity, and some details may have been omitted. The shapes of the various regions and layers shown in the drawings, as well as their relative sizes and positional relationships, are merely exemplary and may deviate from reality due to manufacturing tolerances or technical limitations. Furthermore, those skilled in the art can design regions / layers with different shapes, sizes, and relative positions as needed.

[0036] This invention provides an S-band transit time oscillator. By redesigning the anode structure of the radial three-cavity transit time oscillator and utilizing the idea that the wheel-shaped metamaterial unit has a sub-wavelength geometry, the radial size of the device is reduced, the beam-wave interaction condition of the operating mode in the relativistic radial three-cavity transit time oscillator is lowered, the start-up threshold current is reduced, and the beam-wave interaction efficiency is improved.

[0037] Please see Figure 1 and Figure 2 This invention discloses an S-band transit-time oscillator that utilizes a wheel-shaped metamaterial structural unit. By designing its arrangement and combination scheme, an electron beam drift channel is constructed, enabling explosive electron emission from the cathode under an applied voltage, generating a radial current. High-energy electrons moving radially enter a cavity formed by the metamaterial after passing through the radial drift tube, where they transfer their energy to the intrinsic mode field within the cavity. During the energy exchange between electrons and the intrinsic mode field, electron velocities differentiate, i.e., velocity modulation. After entering the drift section, faster electrons catch up with slower electrons and reach a good clustering state at the front end of the microwave extraction cavity. Finally, they pass through a circular waveguide via a TM waveguide. 01 The pattern radiates outwards. By optimizing the design and arrangement of the wheel-shaped metamaterial unit structure, and adjusting the radial clustering of the electron beam, different distributions of electromagnetic dispersion characteristics are obtained. The drift channels between cavities are cut off for the working electromagnetic waves, and the coupling between cavities is achieved solely through the clustered electrons. By designing the structure of the cutoff cavity at the cathode port, the radial transit time oscillator output port radiates forward TM. 01 The mode, and the maximum size of the circular waveguide is smaller than that of the TM. 01 The mode wavelength is determined, thereby enabling the miniaturization of the radial transit electron oscillator.

[0038] The S-band transit-time oscillator consists of two coaxially arranged wheel-shaped metamaterial subunits. The overall total thickness of the structure is... The axial spacing between the two sub-units is .

[0039] The structure contains two sets of annular grooves: the inner ring corresponds to an inner radius of... The corresponding outer radius is The outer ring corresponds to an inner radius of ; The corresponding outer radius is .

[0040] The structure includes a transversely segmented cylindrical shell with a corresponding inner radius of... The corresponding outer radius is The height of the segmented section is .

[0041] The center of the wheel-shaped metamaterial unit has a radius of The central cavity, in which the bottom of the lower unit has a radius of... The center through hole.

[0042] Please see Figure 3 The total thickness between the upper and lower wheel-shaped metamaterial structural units is The total height of the cylindrical device is The total axial length of the output gradient cylindrical structure is The output waveguide length is The total longitudinal length of the tapered waveguide at the device input is... The distance between the lower element of the wheel-shaped metamaterial structure and the input waveguide is... .

[0043] The thickness of the outer circular waveguide is The spacing between the output circular waveguide and the resonant cavity waveguide Length of waveguide output port The total length from the output end cap to the input waveguide port is The outer radius of the resonant waveguide is The inner radius of the circular waveguide at the output port is (the radius of the upper element of the wheel-shaped metamaterial structure unit). The inner radius of the collection end cap is .

[0044] The longitudinal length of the interval between the upper and lower wheel-shaped metamaterial structural units is The radius of the smaller frustum at the input end is... The inner radius of the input-end cutoff frustum is... The outer radius of the input terminal cutoff frustum is... The inner radius of the cathode support rod is The radius of the cylindrical cathode emitting part is The longitudinal length of the cylindrical cathode is .

[0045] Please see Figure 4 The structural features of the unit connecting rod are defined by its azimuth angle and thickness. The central axis of the unit connecting rod forms an angle with the horizontal direction. And the thickness of the connecting rod in the cross section perpendicular to its extension direction is .

[0046] Table 1. Schematic diagram of the cross-section of the radial three-cavity transit time oscillator and the corresponding parameters (mm) of the upper and lower elements of its wheel-shaped metamaterial structure.

[0047] Table 2. Parameters of Radial Three-Cavity Transit Time Oscillator (mm)

[0048] Please see Figure 5 This figure illustrates the electron beam aggregation state of an S-band time-of-flight oscillator at different operating times. As can be observed, after being emitted from the cathode, the electron beam enters the electromagnetic control cavity through the electron drift channel. During beam-wave interaction, it gradually transitions from a dispersed state to a concentrated state, ultimately forming a stable and dense electron beam. The figure verifies the design effectiveness of the wheel-shaped metamaterial unit array and the electromagnetic control cavity. The electron beam can achieve effective velocity modulation and aggregation, providing a crucial guarantee for the efficient conversion of electron energy to microwave energy and demonstrating the rationality of the device's beam-wave interaction mechanism.

[0049] Please see Figure 6 , Figure 6 (a) shows a uniform working electric field distribution with no local electric field distortion; (b) shows a stable output power of 1.03GW with a pulse width of 80ns. Figure 6 (c) Confirms that the operating frequency is stable at 2.19 GHz and the spectrum is clean; Figure 6 The image (d) shows that the operating current remains at 2.8kA with minimal fluctuation. This verifies that the device meets the electrical performance standards under the set operating parameters, exhibiting a reasonable electric field distribution, stable output power and frequency, and minimal current fluctuation. This demonstrates that the device can stably achieve high-power microwave output, meeting design specifications and engineering application requirements.

[0050] Please see Figure 7 Before entering the electromagnetic control cavity, the electron beam has a relatively uniform energy distribution. After beam-wave interaction, the energy of some electrons is significantly reduced, and the energy is transferred to microwaves. This directly demonstrates the effective conversion of electron energy to microwave energy, verifies the design effectiveness of the slow-wave interaction structure, and shows that the energy exchange mechanism between the electron beam and the intrinsic mode field is smooth without excessive energy loss, ensuring the high power conversion efficiency of the device.

[0051] The implementation process of inventing an S-band transit-time oscillator is as follows: The radial three-cavity transit-time oscillator has a three-cavity structure. Its anode, a wheel-shaped metamaterial slow-wave interaction structure, is arranged within a cylindrical waveguide. The wheel-shaped metamaterial units are spaced apart. Anode grids of different structures and shapes are designed according to the operating frequency, and a vacuum is evacuated in the middle. A cathode structure is placed in the hollow anode portion. The cathode is a ring-shaped cathode structure, placed perpendicularly to the anode wheel-shaped metamaterial slow-wave interaction structure. Electron emission from the ring-shaped cathode's emitting end face is generated by the voltage threshold difference between the cathode and anode. The impedance of this invention is approximately 180 ohms, falling between that of conventional high-impedance transit-time oscillators (greater than 1000 ohms) and low-impedance transit-time oscillators (tens of ohms).

[0052] The present invention proposes a slow-wave interaction structure using miniaturized anode wheel-shaped metamaterials, and by designing the geometry and arrangement of the anode wheel-shaped metamaterials, the equivalent dielectric parameters of the radial three-cavity transit time oscillator are adjusted and optimized, ultimately achieving phase modulation and amplitude modulation of the excitation mode in the radial three-cavity transit time oscillator.

[0053] When high-energy electrons emitted from the cathode leave the drift region and enter the anode-gate interaction region in the radial three-cavity transit time oscillator, electron clustering occurs due to the beam-wave interaction in the three cavities formed by the slow-wave structure of the wheel-shaped metamaterial. The electron drift region between the beam-wave interaction regions is cut off from the working electromagnetic waves.

[0054] When the periodic slow-wave structure of the anode changes, the electromagnetic characteristic parameters of the anode structure will change, and the scattering of high-energy moving electrons generated by the periodic slow-wave structure formed by the anode fins will change, thereby changing the angular distribution of the operating modes in the relativistic transit time oscillator and selecting a specific operating mode.

[0055] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0056] When the applied voltage is 460kV and the operating current is 2.8kA, and the output power of the radial three-cavity transit-time oscillator is 1.03 GW, according to the breakdown threshold formula... The estimated maximum threshold for this device operating at 2.19 GHz is 40.577 MV / m. The simulation yielded the maximum threshold as follows: Figure 8 As shown, the value did not exceed the theoretical prediction. Using CST simulation, with an output power of 1.03GW, a pulse width of 80ns, and a repetition frequency of 10-30Hz, the temperature was approximately 291K. Figure 9 As shown.

[0057] Please see Figure 10 At an output power of 1.03 GW, the radial three-cavity transit-time oscillator was tested under heat load on its wheel-shaped metamaterial structure unit. The heat load distribution across the unit was uniform, with no localized overheating, and the temperature remained stable at approximately 291 K. This verified the device's thermal stability. The wheel-shaped metamaterial unit's structural design effectively disperses the heat generated during operation, meeting the requirements for long pulses and high repetition rates. This demonstrates that the device maintains stable thermodynamic performance even under high power output conditions, with no risk of thermal failure.

[0058] Please see Figure 11 Figure (a) shows the relationship between the output power and conversion efficiency of the radial three-cavity transit-time oscillator based on the wheel-shaped metamaterial structure unit when the applied voltage is U=460kV and the current changes from 2.0kA to 2.8kA. It shows that under this voltage, the output power and conversion efficiency cannot reach their maximum values ​​simultaneously; the maximum power is 1.03GW, and the highest efficiency is 88%. Figure (b) shows the relationship between the output power and conversion efficiency of the radial three-cavity transit-time oscillator based on the wheel-shaped metamaterial structure unit when the voltage changes from 420kV to 460kV and the current is I=2.8kA. It shows that under this current, the output power and conversion efficiency have a linear relationship with the voltage; the maximum power is 1.03GW, and the highest efficiency is also 88%.

[0059] In summary, this invention provides an S-band transit time oscillator that utilizes a wheel-shaped metamaterial unit array to construct an electromagnetic control cavity and electron drift channel, achieving single-port output of the S-band transit time oscillator and solving the deployment challenges of traditional dual-port oscillators. Its output circular waveguide has a maximum size smaller than the wavelength of the TM01 mode, significantly improving device compactness and adapting to the needs of lightweight and small equipment. No external guiding magnetic field is required, simplifying the system structure and reducing energy consumption and size. With an applied voltage of 460kV and a current of 2.8kA, the output power reaches 1.03GW, the operating frequency is stable at 2.19GHz, the power conversion efficiency reaches a maximum of 80%, the start-up threshold current is low, and the breakdown threshold and thermal load both meet the operating requirements. It exhibits excellent beam-wave interaction efficiency and strong operational stability.

[0060] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. An S-band transit-time oscillator, characterized in that, The device includes an anode structure, a ring cathode, and an output circular waveguide. The anode structure is an array of wheel-shaped metamaterial units arranged coaxially. The wheel-shaped metamaterial unit array forms an electron drift channel and three electromagnetic control cavities through the unit arrangement. The electron drift channel between the cavities is cut off from the working electromagnetic wave, and the cavities are coupled through focused electrons. The ring cathode is placed perpendicular to the anode structure and is used to generate radial current. The cathode port of the anode structure is provided with a cutoff cavity. The output circular waveguide is connected to the electromagnetic control cavity to form a single power output port. The output circular waveguide radiates the forward TM01 mode, and the maximum size of the output circular waveguide is smaller than the wavelength of the TM01 mode. The wheel-shaped metamaterial unit array constitutes a slow-wave interaction structure, which is used to adjust the equivalent dielectric parameters of the device to realize energy exchange between electrons and electromagnetic waves and electron aggregation.

2. The S-band transit time oscillator according to claim 1, characterized in that, The wheel-shaped metamaterial unit array includes an upper wheel-shaped metamaterial unit and a lower wheel-shaped metamaterial unit, and the axial spacing between the upper and lower units constitutes the electron drift channel.

3. The S-band transit time oscillator according to claim 2, characterized in that, The upper unit and / or lower unit of the wheel-shaped metamaterial are provided with a central cavity.

4. The S-band transit time oscillator according to claim 3, characterized in that, The bottom of the lower unit of the wheel-shaped metamaterial has a central through hole.

5. The S-band transit time oscillator according to claim 2, characterized in that, The upper unit and / or lower unit of the wheel-shaped metamaterial include an inner annular groove and an outer annular groove.

6. The S-band transit time oscillator according to claim 2, characterized in that, The upper unit and the lower unit of the wheel-shaped metamaterial are connected by at least one unit connecting rod.

7. The S-band transit time oscillator according to claim 2, characterized in that, The central axis of the unit connecting rod forms an angle θ with the horizontal direction.

8. The S-band transit time oscillator according to claim 7, characterized in that, The maximum size of the output circular waveguide is its inner radius Rw, and Rw < λ, where λ is the operating wavelength of the TM01 mode.

9. The S-band transit-time oscillator according to any one of claims 1 to 8, characterized in that, The transit time oscillator operates at a frequency of 2.19 GHz and has an output power of 1.03 GW when the applied voltage is 460 kV and the operating current is 2.8 kA.

10. A microwave generation method based on the S-band transit time oscillator according to any one of claims 1-9, characterized in that, Includes the following steps: A high-voltage pulse is applied between the annular cathode and the anode structure, causing the annular cathode to emit explosive electrons, forming an electron beam that moves radially. The electron beam enters the electromagnetic control cavity through the electron drift channels between the wheel-shaped metamaterial unit arrays; Within the electromagnetically controlled cavity, the electron beam interacts with the intrinsic mode field controlled by the slow-wave interaction structure, thereby converting electron energy into microwave energy and modulating the speed of the electron beam. The velocity-modulated electron beam clusters in the electron drift channel, and energy coupling between cavities is achieved through the clustered electrons; Ultimately, the excited microwaves are radiated from the single power output port in TM01 mode by the output circular waveguide connected to the electromagnetic control cavity, and the radiation process is constrained by the cutoff cavity at the cathode port.

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