A K-band transit-time oscillator based on two-stage modulation and distributed extraction

Abstract

The application discloses a K-band transit-time oscillator based on two-stage modulation and distributed extraction, which comprises an inner cylinder and an anode outer cylinder sleeved outside the inner cylinder, a circular annular cavity is formed between the inner cylinder and the anode outer cylinder, the cavity comprises a first drift tube, a first modulation cavity, a second drift tube, a second modulation cavity, a third drift tube, an extraction cavity and a first coaxial output waveguide which are sequentially communicated, a circular annular second coaxial output waveguide is further arranged at an output end of the inner cylinder, the first coaxial output waveguide and the second coaxial output waveguide are coaxially arranged, the extraction cavity is further communicated with the second coaxial output waveguide, and the K-band transit-time oscillator is rotationally symmetrical about a central axis of the inner cylinder. The two-stage modulation structure is adopted to increase the depth of fundamental wave current modulation, so that the output efficiency is improved, and the double-side channel distributed extraction mode is adopted to improve the output power, so that the problem that the output power is limited while high efficiency output is realized at a high frequency band is overcome.

Description

Technical Field

[0001] This invention relates to microwave source devices in the field of high-power microwave technology, and more particularly to a K-band transit time oscillator based on two-stage modulation and distributed extraction. Background Technology

[0002] High-power microwaves (HPMs) are generally defined as electromagnetic waves with peak power exceeding 100 MW and wavelengths between 1 mm and 1 m (i.e., frequencies between 300 MHz and 300 GHz). In the 1970s, the rapid development of pulsed power technology enabled the generation of high-current relativistic electron beams with voltages of hundreds of kilovolts and currents of tens of kiloamperes. Applying these beams to conventional vacuum electronic microwave devices made it possible to generate HPMs with power exceeding hundreds of megawatts. Simultaneously, in-depth research in relativistic vacuum electronics and plasma physics provided theoretical support for the generation of HPMs.

[0003] High-power microwave sources are the core components for generating high-power microwave radiation. They utilize the interaction between a high-current electron beam and a resonant cavity to produce high-power microwaves. Transit-time oscillators (TSOs) exchange energy between a high-current electron beam and the intrinsic standing wave field in a resonant cavity. They are characterized by high power, high efficiency, and a single operating mode, and have attracted widespread attention from researchers.

[0004] K-band refers to electromagnetic waves with frequencies ranging from 18 to 26 GHz (corresponding wavelengths of 11.54 to 16.67 mm), belonging to the millimeter-wave category. Compared to low-frequency microwaves, K-band microwaves have advantages such as a wide spectral range, narrow beamwidth, line-of-sight propagation, all-weather operation, and high radiating antenna gain, and are currently widely used in many fields such as communications, radar, and remote sensing. Therefore, the development of K-band high-power microwave technology is very promising. However, current research mainly focuses on the L, S, C, X, Ku, and Ka bands, while publicly available results regarding the K-band are rarely reported.

[0005] In the millimeter-wave band, the internal working space of devices is small, and the power capacity is limited, thus restricting the application of these traditional microwave tubes in the high-power millimeter-wave band. Therefore, increasing the power capacity of high-frequency devices while improving output efficiency has become an urgent problem to be solved. Coaxial transit-time oscillators, due to the introduction of an inner conductor, increase the electron beam potential energy and thus increase the power capacity of the device; moreover, the coaxial structure also has the characteristic of simultaneously increasing the radii of the inner and outer conductors at equal intervals while maintaining the device characteristics unchanged, and is therefore widely used in high-frequency devices. For example, a C-band low-magnetic-field high-efficiency coaxial high-power microwave oscillator has been disclosed, see prior art 1: [Deng Rujin. Research on C-band low-magnetic-field high-efficiency coaxial high-power microwave oscillator [D]. Changsha: National University of Defense Technology, 2021]. Its structure is as follows. Figure 1As shown, the device consists of a ring cathode 101, a first modulation cavity 102, a drift section 103, a second-stage modulation cavity 104, a single-gap internal extraction cavity 105, a collector electrode 106, a coaxial output waveguide 107, and a magnetic field 108. The entire device is rotationally symmetrical about its center. This scheme achieves deep modulation of the fundamental current by introducing a two-stage modulation structure. To facilitate cooling of the collector electrode, an internal extraction method is used to output microwaves. Ultimately, under the conditions of a diode voltage of 600kV, a current of 15kA, and an external guiding magnetic field of 0.5T, a microwave output of 3.65GW was achieved at a frequency of 4.31GHz and an efficiency of 40%. It can be seen that this structure has a high output efficiency, but its application frequency band is relatively low.

[0006] Furthermore, while existing high-frequency coaxial transit-time oscillators have high output efficiency, their output power is often low. For example, research has been conducted on Ka-band high-power coaxial transit-time oscillators; see Existing Technology 2: [Song Lili. Research on Ka-band High-Power Coaxial Transit-Time Oscillators [D]. Changsha: National University of Defense Technology, 2018]. The structure is as follows... Figure 2 As shown, the device consists of a ring cathode 201, a front reflection cavity 202, a modulation cavity 203, a drift section 204, an extraction cavity 205, a coaxial output waveguide 206, and a magnetic field 207. The entire device is rotationally symmetrical about its center. This structure improves the modulation depth of the fundamental current through a four-gap modulation cavity, and then uses a single-gap extraction cavity to extract microwaves. Finally, under the conditions of 447kV, 7.4kA, and a guiding magnetic field of 0.6T, a microwave output of 1.27GW was achieved with an efficiency of 38.5% and an output microwave frequency of 26.2GHz. It can be seen that although the output frequency of this device is high, there is still room for improvement in output power and efficiency. Devices with high output power have very little experimental feasibility. In addition, compact and lightweight Ku-band long pulse transit time oscillators have also been studied. See Existing Technology 3: [Xu Weili. Research on Compact and Lightweight Ku-band Long Pulse Transit Time Oscillators [D]. Changsha: National University of Defense Technology, 2020]. The structure is as follows. Figure 3 As shown, the device consists of a ring cathode 301, a front reflector 302, a modulation cavity 303, a drift section 304, an extraction cavity 305, a bent collector 306, and a coaxial output waveguide 307. The entire device is rotationally symmetrical about its center. This structure, through a gradually curved axial design, combines the ease of axial implementation with the high power capacity of radial components. It achieves an output power of 3.37 GW, a microwave frequency of 12.43 GHz, and an efficiency of 41% under conditions of 620 kV, 13.3 kA, and an applied guiding magnetic field of 1 T. It is evident that this device has high output power and efficiency, but its experimental fabrication is challenging.

[0007] Research revealed that employing a dual-channel distributed extraction structure can increase both the device's power capacity and the output power. For example, a 50MW X-band klystron has already been developed; see Existing Technology 4: [Chu Kairong. Development of a 50MW X-band klystron [J]. High Power Laser & Particle Beams, 2020, 32(10)]. This structure is as follows... Figure 4 As shown, the device consists of a cathode 401, a modulation cavity 402, a drift section 403, a pre-terminal cavity 404, an extraction cavity 405, an electron beam 406, a first output waveguide 407a, and a second output waveguide 407b. By using dual-channel output, it achieves a microwave output of 52.1 MW with an efficiency of 60.9% under conditions of 450 kV, 190 A current, and 0.398 T magnetic field. However, this structure is designed for high-power vacuum electronic devices and is not suitable for high-power vacuum electronic devices. Furthermore, this device uses a rectangular waveguide output, while the transit-time oscillator uses a coaxial waveguide output, resulting in different microwave output modes.

[0008] Currently, there are no publicly reported technical solutions for high-frequency coaxial transit-time oscillators that simultaneously achieve high conversion efficiency, high output power, and ease of fabrication. Summary of the Invention

[0009] The technical problem this invention aims to solve is to address the shortcomings of existing technologies by providing a K-band transit-time oscillator based on two-stage modulation and distributed extraction. The two-stage modulation structure increases the modulation depth of the fundamental current, thereby improving output efficiency. Given that the K-band falls within the millimeter-wave range, the device size is relatively small, resulting in limited power capacity. Therefore, the second-stage modulation cavity is modified to a trapezoidal structure to increase the device's power capacity. Furthermore, a dual-channel distributed extraction method is employed to enhance output power, overcoming the limitation on output power while achieving high efficiency at high frequencies.

[0010] To solve the above-mentioned technical problems, the technical solution proposed by this invention is as follows:

[0011] A K-band transit-time oscillator based on two-stage modulation and distributed extraction includes an inner cylinder and an anode outer cylinder sleeved outside the inner cylinder. An annular cavity is formed between the inner cylinder and the anode outer cylinder. The cavity includes a first drift tube, a first modulation cavity, a second drift tube, a second modulation cavity, a third drift tube, an extraction cavity, and a first coaxial output waveguide connected in sequence. The output end of the inner cylinder is also provided with an annular second coaxial output waveguide. The first and second coaxial output waveguides are coaxially arranged. The extraction cavity is also connected to the second coaxial output waveguide. The K-band transit-time oscillator is rotationally symmetrical about the central axis of the inner cylinder.

[0012] Furthermore, the first modulation cavity is composed of a first modulation cavity outer cavity disposed on the inner wall of the outer cylinder of the anode, a first modulation cavity inner cavity disposed on the outer wall of the inner cylinder, and an annular space between the first modulation cavity outer cavity and the first modulation cavity inner cavity. The first modulation cavity outer cavity and the first modulation cavity inner cavity are arranged opposite to each other, and both the first modulation cavity outer cavity and the first modulation cavity inner cavity are composed of the same annular cavity with an axial gap, and the cross-section of the annular cavity is rectangular.

[0013] Furthermore, the second modulation cavity is composed of a second modulation cavity outer cavity disposed on the inner wall of the outer cylinder of the anode, a second modulation cavity inner cavity disposed on the outer wall of the inner cylinder, and an annular space between the second modulation cavity outer cavity and the second modulation cavity inner cavity. The second modulation cavity outer cavity and the second modulation cavity inner cavity are arranged opposite to each other, and both the second modulation cavity outer cavity and the second modulation cavity inner cavity are annular cavities with a trapezoidal cross-section.

[0014] Furthermore, the extraction cavity includes a first gap, a second gap, and a third gap connected sequentially along the axial direction. Each of the first, second, and third gaps is composed of a corresponding annular cavity in the outer cavity of the extraction cavity disposed on the inner wall of the anode outer cylinder, a corresponding annular cavity in the inner cavity of the extraction cavity disposed on the outer wall of the inner cylinder, and an annular space between two corresponding annular cavities. The annular cavity corresponding to the third gap in the outer cavity of the extraction cavity is connected to the input end of the first coaxial output waveguide, and the annular cavity corresponding to the second gap in the inner cavity of the extraction cavity is connected to the input end of the second coaxial output waveguide.

[0015] Furthermore, the first coaxial output waveguide includes a first output waveguide coupling slit, a first output waveguide tapered transition section, and a first output waveguide antenna connection section connected in sequence. The first output waveguide coupling slit is connected to the annular cavity corresponding to the third gap in the extraction cavity.

[0016] Furthermore, the first coaxial output waveguide also includes a circular first output waveguide adjustment block, which is disposed at the input end of the first output waveguide antenna connection section and sleeved on the outside of the inner cylinder.

[0017] Furthermore, the second coaxial output waveguide includes a second output waveguide rectangular transition section and a second output waveguide antenna connection section connected in sequence, and the second output waveguide rectangular transition section is connected to the annular cavity corresponding to the second gap in the extraction cavity.

[0018] Furthermore, the second coaxial output waveguide also includes a ring-shaped second output waveguide adjustment block, which is coaxially arranged with the inner cylinder and is located at the input end of the rectangular transition section of the second output waveguide.

[0019] Furthermore, the output end of the first coaxial output waveguide is provided with a first support rod, and the output end of the second coaxial output waveguide is provided with a second support rod. The second support rod is installed in the second coaxial output waveguide at a position corresponding to the installation position of the first support rod in the first coaxial output waveguide.

[0020] Furthermore, the inner cylinder is also provided with a trapezoidal collecting electrode, which is an annular cavity with a cross-section of a right trapezoid. The first drift tube, the first modulation cavity, the second drift tube, the second modulation cavity, the third drift tube, the extraction cavity, and the right-angled waist of the trapezoidal collecting electrode are connected in sequence to form an electron beam transmission path channel.

[0021] Compared with the prior art, the advantages of the present invention are as follows:

[0022] (1) The present invention adopts a two-stage modulation cavity cascade structure. The two-stage modulation cavities adopt a three-gap rectangular cavity + a single-gap trapezoidal cavity, which realizes two effective modulations of the electron beam, improves the modulation depth of the fundamental current, and is conducive to the device to achieve higher power output.

[0023] (2) The present invention adopts a dual-channel distributed extraction method to realize microwave extraction by two channels at the same time, which is beneficial to increase the power capacity of the device and realize higher power and higher efficiency microwave output. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the structure of a C-band low magnetic field high-efficiency coaxial high-power microwave oscillator disclosed in prior art 1.

[0025] Figure 2 This is a front cross-sectional view of the Ka-band high-power coaxial transit-time oscillator disclosed in prior art 2.

[0026] Figure 3 This is a front cross-sectional view of the compact, lightweight Ku-band long pulse transit time oscillator disclosed in prior art 3.

[0027] Figure 4 This is a partial structural schematic diagram of the X-band 50MW klystron disclosed in prior art 4.

[0028] Figure 5 This is a front cross-sectional view of the K-band coaxial transit time oscillator according to an embodiment of the present invention.

[0029] Figure 6 This is a schematic diagram of the partial structure of the dual-channel coaxial output waveguide of the K-band coaxial transit-time oscillator according to an embodiment of the present invention.

[0030] Figure 7The diagram shows the average microwave output power of the first coaxial output waveguide in the K-band coaxial transit-time oscillator of this invention.

[0031] Figure 8 This is a microwave frequency diagram of the first coaxial output waveguide in the K-band coaxial transit-time oscillator of this invention.

[0032] Figure 9 The diagram shows the average microwave output power of the second coaxial output waveguide in the K-band coaxial transit-time oscillator according to an embodiment of the present invention.

[0033] Figure 10 The microwave frequency diagram of the second coaxial output waveguide in the K-band coaxial transit-time oscillator of this embodiment of the invention.

[0034] Background Art Illustrations: 101-Ring cathode, 102-First modulation cavity, 103-Drift section, 104-Second-stage modulation cavity, 105-Extraction cavity within a single gap, 106-Collector, 107-Coaxial output waveguide, 108-Magnetic field, 201-Ring cathode, 202-Front reflector cavity, 203-Modulation cavity, 204-Drift section, 205-Extraction cavity, 206-Coaxial output waveguide, 207-Magnetic field, 301-Ring cathode, 302-Front reflector, 303-Modulation cavity, 304-Drift section, 305-Extraction cavity, 306-Bent collector, 307-Coaxial output waveguide, 401-Cathode, 402-Modulation cavity, 403-Drift section, 404-Front end cavity, 405-Extraction cavity, 406-Electron beam, 407a-First output waveguide, 407b-Second output waveguide;

[0035] Legend for the embodiments of the present invention: 501-Cathode holder, 502-Cathode, 503-Anode outer cylinder, 504-Inner cylinder, 505-First drift tube, 506-First modulation cavity, 506a-Outer cavity of the first modulation cavity, 506b-Inner cavity of the first modulation cavity, 507-Second drift tube, 508-Second modulation cavity, 508a-Outer cavity of the second modulation cavity, 508b-Inner cavity of the second modulation cavity, 509-Third drift tube, 510-Extraction cavity, 510a-Outer cavity of the extraction cavity, 510b-Inner cavity of the extraction cavity, 511 - Trapezoidal collector pole, 512- First coaxial output waveguide, 512a- First output waveguide coupling slit, 512b- First output waveguide tapered transition section, 512c- First output waveguide antenna connection section, 512d- First output waveguide adjustment block, 513- Second coaxial output waveguide, 513a- Second output waveguide rectangular transition section, 513b- Second output waveguide adjustment block, 513c- Second output waveguide antenna connection section, 514a- First support rod, 514b- Second support rod, 515- Solenoid magnetic field. Detailed Implementation

[0036] The present invention will be further described below with reference to the accompanying drawings and specific preferred embodiments, but this does not limit the scope of protection of the present invention.

[0037] This invention proposes a K-band transit-time oscillator based on two-stage modulation and distributed extraction, which can simultaneously achieve high conversion efficiency and high output at high frequencies, such as... Figure 5 As shown, the device includes a cathode holder 501 and a tubular anode outer cylinder 503. A solenoid magnetic field 515 is fitted onto the outer wall of the anode outer cylinder 503. An inner cylinder 504 is inserted into the anode outer cylinder 503, forming an annular cavity between the inner cylinder 504 and the anode outer cylinder 503. An annular cathode 502 is provided on the side of the cathode holder 501 facing the inner cylinder 504. The cathode 502 is used to emit an electron beam into the cavity between the inner cylinder 504 and the anode outer cylinder 503. The inner cylinder 504 is a cylindrical conductor with varying radii. The various cavities on its outer surface, together with the various cavities on the inner surface of the anode outer cylinder 503, form an electrodynamic structure, which interacts with the electron beam to generate HPM and radiate outwards.

[0038] like Figure 5 As shown, the K-band transit time oscillator in this embodiment is rotationally symmetrical about the central axis (OZ axis) of the inner cylinder 504. The cavity in this embodiment includes a first drift tube 505, a first modulation cavity 506, a second drift tube 507, a second modulation cavity 508, a third drift tube 509, an extraction cavity 510, and a first coaxial output waveguide 512 connected in sequence. The electron beam emitted from the cathode 502 passes through the first drift tube 505 to the extraction cavity 510 to form an electron beam transmission path. The output end of the inner cylinder 504 is also provided with a circular second coaxial output waveguide 513. The first coaxial output waveguide 512 and the second coaxial output waveguide 513 are coaxially arranged. The extraction cavity 510 is also connected to the second coaxial output waveguide 513. In addition, the inner cylinder 504 is provided with a trapezoidal collecting electrode 511 facing the electron beam transmission path. The trapezoidal collecting electrode 511 is an annular cavity with a right trapezoidal cross-section. The first drift tube 505, the first modulation cavity 506, the second drift tube 507, the second modulation cavity 508, the third drift tube 509, the extraction cavity 510 and the right-angled waist of the trapezoidal collecting electrode 511 are connected in sequence to form an electron beam transmission path channel.

[0039] In this embodiment, the cathode holder 501 is externally connected to the anode of the pulse drive source, and the left end of the anode outer cylinder 503 is externally connected to the outer conductor of the pulse drive source. The first coaxial output waveguide 512 and the second coaxial output waveguide 513 are both connected to the mode converter and the antenna. These can be designed according to the requirements of different wavelengths and application scenarios, based on general mode converter and antenna design methods, which are common methods in the high-power microwave field. The working principle of the K-band transit time oscillator in this embodiment is as follows:

[0040] A pulsed power drive source applies a high voltage to the cathode 502, which emits a high-current relativistic electron beam. This relativistic electron beam from the cathode 502 subsequently excites the TM in the first modulation cavity 506 and the second modulation cavity 508. 01 The electromagnetic waves of the mode interact with the electron beam. The first modulation cavity 506 and the second modulation cavity 508 successively perform density modulation and velocity modulation on the electron beam. Under the traction of the electron beam, the intrinsic field in the first modulation cavity 506 is excited, and the velocity of the electron beam is modulated. Then, the velocity modulation of the electron beam is converted into density modulation through the second drift tube 507 corresponding to the first modulation cavity 506, and the above process is repeated in the second modulation cavity 508. Finally, the energy of the intrinsic microwave in the modulation cavity is transferred to the electron beam. The electron beam achieves good clustering before reaching the extraction cavity 510. After the electron beam drifts to the extraction cavity 510, the energy of the electron beam is transferred to the intrinsic microwave in the extraction cavity 510. The decelerating electric field in the extraction cavity 510 interacts with the electron beam to generate HPM (high-power microwave). Finally, the generated high-power microwave is coupled outward to the mode converter and the radiating antenna through the first coaxial output waveguide 512 and the second coaxial output waveguide 513. The electron beam is then collected in the collector 511. Considering that electrons hitting the inner wall of the collector directly may generate reflected electrons that flow back into the extraction cavity and affect beam-wave interaction, the right end of the collector is set as an inclined plane. This increases the effective area on which electrons hit the collector and reduces the degree of electron reflection.

[0041] To improve output efficiency and increase the fundamental current modulation depth, this embodiment plans to employ a two-stage modulation structure. The first-stage modulation structure performs initial modulation of the electrons, with a relatively small fundamental current modulation depth, which can be achieved using a three-gap rectangular cavity commonly found in transit-time oscillators. The second-stage modulation structure, however, needs to further increase the fundamental current, thus requiring a cavity with high power capacity. Research shows that a trapezoidal cavity of the same size has a higher power capacity than a rectangular cavity. Furthermore, a larger number of cavities increases the overall tube length; therefore, a single-gap trapezoidal cavity is used as the second-stage modulation structure. This embodiment employs a two-stage modulation structure of a three-gap rectangular cavity + a single-gap trapezoidal cavity, modulating the electron beam twice to achieve a fundamental current modulation depth exceeding 130%. Figure 5As shown, in this embodiment, the first modulation cavity 506 consists of a first modulation cavity outer cavity 506a (the dotted line portion of 506a) disposed on the inner wall of the anode outer cylinder 503, a first modulation cavity inner cavity 506b (the dotted line portion of 506b) disposed on the outer wall of the inner cylinder 504, and an annular space between the first modulation cavity outer cavity 506a and the first modulation cavity inner cavity 506b. The first modulation cavity outer cavity 506a and the first modulation cavity inner cavity 506b are arranged opposite to each other, and both the first modulation cavity outer cavity 506a and the first modulation cavity inner cavity 506b are composed of annular cavities with an axial gap. The cross-sections of these annular cavities are rectangular. In this embodiment, the outer cavity 506a of the first modulation cavity is composed of a first annular cavity with a gap along the axial direction, and the inner cavity 506b of the first modulation cavity is composed of a second annular cavity with a gap along the axial direction. There are three first annular cavities and three second annular cavities, which correspond one-to-one. Each first annular cavity of the outer cavity 506a, the corresponding second annular cavity of the inner cavity 506b of the first modulation cavity, and the annular gap between the first annular cavity and the second annular cavity form a gap of the first modulation cavity 506.

[0042] Correspondingly, such as Figure 5 As shown, in this embodiment, the second modulation cavity 508 is composed of a second modulation cavity outer cavity 508a (the dotted line portion of 508a) disposed on the inner wall of the anode outer cylinder 503, a second modulation cavity inner cavity 508b (the dotted line portion of 508b) disposed on the outer wall of the inner cylinder 504, and an annular space between the second modulation cavity outer cavity 508a and the second modulation cavity inner cavity 508b. The second modulation cavity outer cavity 508a and the second modulation cavity inner cavity 508b are arranged opposite to each other, and the second modulation cavity outer cavity 508a is a third annular cavity with an isosceles trapezoidal cross-section, and the second modulation cavity inner cavity 508b is a fourth annular cavity with an isosceles trapezoidal cross-section.

[0043] To improve output power and increase power capacity, this embodiment employs a dual-channel distributed extraction method. Extensive cold-test simulations show that the maximum field strength in the three-gap output cavity often occurs in the lower half of the second gap; therefore, output is also considered in the second gap. The extraction cavity 510 also adopts a three-gap structure, using an internal extraction method in the second gap and an external extraction method in the third gap, achieving simultaneous microwave extraction from two channels. Figure 6As shown, the extraction cavity 510 in this embodiment consists of an outer extraction cavity 510a (the dotted line portion of 510a) disposed on the inner wall of the outer anode cylinder 503, an inner extraction cavity 510b (the dotted line portion of 510b) disposed on the outer wall of the inner cylinder 504, and an annular space between the outer extraction cavity 510a and the inner extraction cavity 510b. The outer extraction cavity 510a and the inner extraction cavity 510b are arranged opposite to each other, and both the outer extraction cavity 510a and the inner extraction cavity 510b are composed of annular cavities with axial gaps. In this embodiment, the outer extraction cavity 510a consists of a fifth annular cavity, a sixth annular cavity, and an annular cavity with axial gaps. The extraction cavity 510b is composed of a seventh annular cavity, and the inner cavity 510b is composed of an eighth, ninth, and tenth annular cavities spaced apart along the axial direction. The annular gaps between the fifth and eighth annular cavities, and between the fifth and eighth annular cavities, form the first gap of the extraction cavity 510. The annular gaps between the sixth and ninth annular cavities, and between the sixth and ninth annular cavities, form the second gap of the extraction cavity 510. The annular gaps between the seventh and tenth annular cavities, and between the seventh and tenth annular cavities, form the third gap of the extraction cavity 510. The input end of the first coaxial output waveguide 512 is connected to the seventh annular cavity corresponding to the third gap in the outer cavity 510a of the extraction cavity, and the input end of the second coaxial output waveguide 513 is connected to the ninth annular cavity corresponding to the second gap in the inner cavity 510b of the extraction cavity.

[0044] like Figure 6 As shown, the first coaxial output waveguide 512 in this embodiment includes a first output waveguide coupling slit 512a, a first output waveguide conical transition section 512b, and a first output waveguide antenna connection section 512c connected in sequence. The first output waveguide coupling slit 512a is connected to the seventh annular cavity corresponding to the third gap in the outer cavity 510a of the extraction cavity. Further, the first coaxial output waveguide 512 in this embodiment also includes an annular first output waveguide adjustment block 512d. The first output waveguide adjustment block 512d is a unique structure in this design for transit time, located at the input end of the first output waveguide antenna connection section 512c, and sleeved outside the inner cylinder 504. Introducing this coupling block facilitates the adjustment of the extraction cavity parameters. The Q value of the extraction cavity can be changed by adjusting the height of the coupling block; the resonant frequency of the extraction cavity can be changed by adjusting the width of the coupling block.

[0045] Correspondingly, such as Figure 6As shown, the second coaxial output waveguide 513 in this embodiment includes a second output waveguide rectangular transition section 513a and a second output waveguide antenna connection section 513c connected in sequence. The second output waveguide rectangular transition section 513a is connected to the ninth annular cavity corresponding to the second gap in the extraction cavity 510b. Further, the second coaxial output waveguide 513 in this embodiment also includes an annular second output waveguide adjustment block 513b. The second output waveguide adjustment block 513b is coaxially arranged with the inner cylinder 504, and is a unique structure of this design, located at the input end of the second output waveguide rectangular transition section 513a. Introducing this coupling block facilitates the adjustment of the extraction cavity parameters. The Q value of the extraction cavity can be changed by adjusting the height of the coupling block; the resonant frequency of the extraction cavity can be changed by adjusting the width of the coupling block.

[0046] In coaxial structures, to prevent eccentricity and misalignment of the inner and outer conductors, support rods are typically added to the coaxial output waveguide to support the inner and outer conductors. For example... Figure 5 and Figure 6 As shown, in this embodiment, the output end of the first coaxial output waveguide 512 is provided with a first support rod 514a, and the output end of the second coaxial output waveguide 513 is provided with a second support rod 514b. The second support rod 514b is installed in the second coaxial output waveguide 513 at a position corresponding to the installation position of the first support rod 514a in the first coaxial output waveguide 512.

[0047] The following is based on Figure 5 and Figure 6 The dimensions of each component are described below:

[0048] The cathode 502 is a thin-ringed cylindrical tube with a wall thickness of 1 mm and a radius R1 equal to the electron beam radius;

[0049] The first drift tube 505 is an annular cavity with an outer radius of R2 and an inner radius of R3, where R2>R1>R3, and a length of L1.

[0050] In the outer cavity 506a of the first modulation cavity, the inner and outer radii of each first annular cavity are R2 and R4, respectively, the length of each first annular cavity is L2, and the distance between adjacent first annular cavities is P1.

[0051] In the first modulation cavity 506b, the inner and outer radii of each second annular cavity are R5 and R3, respectively. The positions of the second annular cavities correspond one-to-one with the first annular cavities. The length of each second annular cavity is L2, and the distance between adjacent second annular cavities is P1.

[0052] The second drift tube 507 is an annular cavity with an outer radius of R2, an inner radius of R3, and a length of L3;

[0053] The inner and outer radii of the third circular cavity of the outer cavity 508a of the second modulation cavity are R2 and R6 respectively, where R6 > R4. The lengths of the upper and lower bases of the isosceles trapezoid in its cross-section are L4 and L5 respectively, where L5 > L4.

[0054] The inner and outer radii of the fourth circular cavity of the inner cavity 508b of the second modulation cavity are R7 and R3 respectively, where R7 < R5. The lengths of the upper and lower bases of the isosceles trapezoid in its cross-section are L4 and L5 respectively.

[0055] The third drift tube 509 is a circular cavity with an outer radius of R2 and an inner radius of R3, and a length of L6.

[0056] In the outer cavity 510a of the extraction cavity, when looking from the diode towards the output port, the lengths of the circular cavities decrease successively along the axial direction. The heights of the circular cavities at both ends are the same, and the height of the middle circular cavity is less than that of the circular cavities at both ends. Specifically, the inner and outer radii of the fifth and seventh circular cavities are R2 and R8 respectively, the inner and outer radii of the sixth circular cavity are R2 and R9 respectively, where R8 > R6 > R9. The lengths of the fifth, sixth, and seventh circular cavities are L7, L8, and L9 respectively, where L7 > L8 > L9. The interval between the fifth and sixth circular cavities is P2, and the interval between the sixth and seventh circular cavities is P3, where P2 > P3.

[0057] In the inner cavity 510b of the extraction cavity, the positions of the eighth circular cavity correspond to those of the fifth circular cavity, the positions of the ninth circular cavity correspond to those of the sixth circular cavity, and the positions of the tenth circular cavity correspond to those of the seventh circular cavity. When looking from the diode towards the output port, the lengths of the circular cavities decrease successively along the axial direction. The heights of the circular cavities at both ends are the same, and the height of the middle circular cavity is less than that of the circular cavities at both ends. Specifically, the inner and outer radii of the eighth and tenth circular cavities are R10 and R3 respectively, the inner and outer radii of the ninth circular cavity are R11 and R3 respectively, where R10 > R11. The lengths of the eighth, ninth, and tenth circular cavities are L7, L8, and L9 respectively, where L7 > L8 > L9. The interval between the eighth and ninth circular cavities is P2, and the interval between the ninth and tenth circular cavities is P3.

[0058] The outer radius of the trapezoidal collector 511 is R12, and the inner radius is R13, where R2 > R12 and R13 > R3. The length of the upper base of the right trapezoid in its cross-section is L10, the length of the lower base is L11, where L11 > L10.

[0059] The first output waveguide coupling slit 512a is a circular cavity with an outer radius of R8 and an inner radius of R14, where R14 > R2, and a length of L12.

[0060] The first output waveguide tapered transition section 512b is a circular cavity with a tapered cross-section. The upper base of the tapered cross-section is R8-R14, the lower base is R15-R14, R15>R8, and the height is L13.

[0061] The first output waveguide antenna connection section 512c is an annular cavity with an outer radius of R15, an inner radius of R14, and a length of L14.

[0062] The first output waveguide adjustment block 512d is a metal ring with an outer radius of R16 and an inner radius of R14, where R8>R16, and a length of L15. The distance between it and the right side of the seventh annular cavity in the outer cavity 510a of the extraction cavity is L16.

[0063] The second output waveguide rectangular transition section 513a is an annular cavity with an outer radius of R11, an inner radius of R17, and a length of L8.

[0064] The second output waveguide adjustment block 513b is a metal ring with an outer radius of R11 and an inner radius of R18, where R18>R17 and the length is L17, L8>L17. The distance between it and the left side of the eighth annular cavity in the extraction cavity 510b is L7+P2.

[0065] The second output waveguide antenna connection section 513c is an annular cavity with an inner radius of R17, an outer radius of R19, R18>R19, and a length of L18.

[0066] The distance between the left end of the first support rod 514a and the left end of the first output waveguide adjustment block 512d is L19, and the position of the second support rod 514b corresponds vertically to that of the first support rod 514a.

[0067] In this embodiment, the specific dimensions are set as follows: R1 = 30.5mm, R2 = 33mm, R3 = 28mm, R4 = 35.2mm, R5 = 26.2mm, R6 = 35.7mm, R7 = 25.2mm, R8 = 35.8mm, R9 = 35.6mm, R10 = 26mm, R11 = 25.6mm, R12 = 32.5mm, R13 = 28.5mm, R14 = 34mm, R15 = 39mm, R16 = 34.8mm, R17 = 17.6mm, R18 = 22.8mm, R19 = 22.6mm, L1 = 20mm. mm, L2=5.5mm, L3=11.5mm, L4=1.3mm, L5=4.3mm, L6=3.4mm, L7=4.6mm, L8=4.2mm, L9=4.0mm, L10=16.0mm, L11=32.0mm, L12=4.0 mm, L13=12.0mm, L14=26.7mm, L15=2.2mm, L16=12.0mm, L17=1.8mm, L18=48.5mm, L19=20.7mm, P1=2.5mm, P2=2.0mm, P3=1.8mm.

[0068] In particle simulation, the K-band coaxial transit-time oscillator of this embodiment was simulated under conditions of 504 kA and 9.91 kA. The simulation results are as follows. Figures 7 to 10 As shown, where:

[0069] Figure 7 This is a graph showing the average microwave power output from the first coaxial output waveguide 512. The horizontal axis represents time (ns), and the vertical axis represents average power (GW). Figure 7 It can be seen that the output microwave stabilizes after 28ns, and the average microwave output power is 1.02GW.

[0070] Figure 8 This is a frequency diagram of the output microwave from the first coaxial output waveguide 512. The horizontal axis represents frequency in nanoseconds (ns), and the vertical axis represents the voltage value at the corresponding frequency in volts per GHz (Volts / GHz). Figure 8 It can be seen that the output frequency of the first coaxial output waveguide 512 is 18.583 GHz and the spectrum is clean.

[0071] Figure 9 This is a graph showing the average microwave power output from the second coaxial output waveguide 513. The horizontal axis represents time (ns), and the vertical axis represents average power (GW). Figure 9 It can be seen that the output microwave stabilizes after 27ns, and the average microwave output power is 1.01GW.

[0072] Figure 10This is a microwave frequency diagram for the second coaxial output waveguide 513. The horizontal axis represents frequency in nanoseconds (ns), and the vertical axis represents the voltage value at the corresponding frequency in volts per GHz (Volts / GHz). Figure 10 It can be seen that the output frequency of the second coaxial output waveguide 513 is 18.583 GHz and the spectrum is clean.

[0073] Depend on Figures 7 to 10 As can be seen, the K-band coaxial transit-time oscillator in this embodiment, based on two-stage modulation and distributed extraction, achieves high-power, high-efficiency microwave output with a center frequency of 18.583 GHz (corresponding to a microwave wavelength λ = 16.14 mm). In particle simulation, with an injection power of 5 GW, the first coaxial output port outputs 1.02 GW, the second coaxial output port outputs 1.01 GW, and the total output is 2.03 GW, achieving an output efficiency of 40.6%, corresponding to an output frequency of 18.583 GHz with a clean spectrum. It achieves both high-efficiency and high-power output, and the structure of each part of the device is relatively regular, making it easy to fabricate for experiments. This provides important reference for achieving high-efficiency, high-power output of transit-time oscillators at high frequencies.

[0074] In summary, the advantages of this invention are as follows:

[0075] (1) The present invention adopts a two-stage cascaded structure of a three-gap rectangular cavity and a single-gap trapezoidal cavity, which realizes two effective modulations of the electron beam, improves the modulation depth of the fundamental current, and is conducive to the device to achieve higher power output.

[0076] (2) The present invention adopts a dual-channel distributed extraction method to realize microwave extraction by two channels at the same time, which is beneficial to increase the power capacity of the device and realize higher power and higher efficiency microwave output.

[0077] (3) The present invention outputs microwave power of 2.03GW, microwave frequency of 18.583GHz and pure spectrum, efficiency of 40.6%, high device efficiency and high output power, and the structure is conventional shape, making it easy to process in experiments.

[0078] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the invention. Therefore, any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention should fall within the protection scope of the present invention.

Claims

1. A K-band transit-time oscillator based on two-stage modulation and distributed extraction, characterized by, The device includes an inner cylinder (504) and an anode outer cylinder (503) sleeved outside the inner cylinder (504). An annular cavity is formed between the inner cylinder (504) and the anode outer cylinder (503). The cavity includes a first drift tube (505), a first modulation cavity (506), a second drift tube (507), a second modulation cavity (508), a third drift tube (509), an extraction cavity (510), and a first coaxial output waveguide (512) connected in sequence. The output end of the inner cylinder (504) is also provided with an annular second coaxial output waveguide (513). The first coaxial output waveguide (512) and the second coaxial output waveguide (513) are coaxially arranged. The extraction cavity (510) is also connected to the second coaxial output waveguide (513). The K-band transit time oscillator is rotationally symmetrical about the central axis of the inner cylinder (504). The second modulation cavity (508) is composed of a second modulation cavity outer cavity (508a) disposed on the inner wall of the anode outer cylinder (503), a second modulation cavity inner cavity (508b) disposed on the outer wall of the inner cylinder (504), and an annular space between the second modulation cavity outer cavity (508a) and the second modulation cavity inner cavity (508b). The second modulation cavity outer cavity (508a) and the second modulation cavity inner cavity (508b) are arranged opposite to each other, and both the second modulation cavity outer cavity (508a) and the second modulation cavity inner cavity (508b) are annular cavities with a trapezoidal cross-section. The extraction cavity (510) includes a first gap, a second gap, and a third gap connected sequentially along the axial direction. The first gap, the second gap, and the third gap are all composed of a corresponding annular cavity of the extraction cavity outer cavity (510a) disposed on the inner wall of the anode outer cylinder (503), a corresponding annular cavity of the extraction cavity inner cavity (510b) disposed on the outer wall of the inner cylinder (504), and an annular space between the corresponding two annular cavities. The annular cavity corresponding to the third gap in the extraction cavity outer cavity (510a) is connected to the input end of the first coaxial output waveguide (512), and the annular cavity corresponding to the second gap in the extraction cavity inner cavity (510b) is connected to the input end of the second coaxial output waveguide (513). The second coaxial output waveguide (513) includes a second output waveguide rectangular transition section (513a) and a second output waveguide antenna connection section (513c) connected in sequence. The second output waveguide rectangular transition section (513a) is connected to the annular cavity corresponding to the second gap in the extraction cavity (510b).

2. The K-band transit-time oscillator based on two-stage modulation and distributed extraction of claim 1, wherein, The first modulation cavity (506) is composed of a first modulation cavity outer cavity (506a) disposed on the inner wall of the anode outer cylinder (503), a first modulation cavity inner cavity (506b) disposed on the outer wall of the inner cylinder (504), and an annular space between the first modulation cavity outer cavity (506a) and the first modulation cavity inner cavity (506b). The first modulation cavity outer cavity (506a) and the first modulation cavity inner cavity (506b) are arranged opposite to each other, and both the first modulation cavity outer cavity (506a) and the first modulation cavity inner cavity (506b) are composed of the same annular cavity with an axial gap, and the cross-section of the annular cavity is rectangular.

3. The K-band transit-time oscillator based on two-stage modulation and distributed extraction according to claim 1, characterized in that, The first coaxial output waveguide (512) includes a first output waveguide coupling slit (512a), a first output waveguide tapered transition section (512b), and a first output waveguide antenna connection section (512c) connected in sequence. The first output waveguide coupling slit (512a) is connected to the annular cavity corresponding to the third gap in the extraction cavity (510a).

4. The K-band transit-time oscillator based on two-stage modulation and distributed extraction according to claim 3, characterized in that, The first coaxial output waveguide (512) also includes a circular first output waveguide adjustment block (512d), which is located at the input end of the first output waveguide antenna connection section (512c) and is sleeved outside the inner cylinder (504).

5. The K-band transit-time oscillator based on two-stage modulation and distributed extraction of claim 1, wherein, The second coaxial output waveguide (513) also includes an annular second output waveguide adjustment block (513b), which is coaxially arranged with the inner cylinder (504) and is located at the input end of the rectangular transition section (513a) of the second output waveguide.

6. The K-band transit-time oscillator based on two-stage modulation and distributed extraction according to claim 1, characterized in that, The output end of the first coaxial output waveguide (512) is provided with a first support rod (514a), and the output end of the second coaxial output waveguide (513) is provided with a second support rod (514b). The second support rod (514b) is installed in the second coaxial output waveguide (513) at a position corresponding to the installation position of the first support rod (514a) in the first coaxial output waveguide (512).

7. The K-band transit-time oscillator based on two-stage modulation and distributed extraction of claim 1, wherein, The inner cylinder (504) is also provided with a trapezoidal collecting electrode (511), which is an annular cavity with a right-angled trapezoidal cross-section. The ends of the first drift tube (505), the first modulation cavity (506), the second drift tube (507), the second modulation cavity (508), the third drift tube (509), the extraction cavity (510), and the trapezoidal collecting electrode (511) are connected in sequence to form an electron beam transmission path channel.

Images