CN116666175A - K-band transit time oscillator based on last front cavity extraction structure - Google Patents
K-band transit time oscillator based on last front cavity extraction structure Download PDFInfo
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- H01J25/00—Transit-time tubes, e.g. klystrons, travelling-wave tubes, magnetrons
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Abstract
The invention discloses a K-band transit time oscillator based on a last front cavity extraction structure, which comprises an inner cylinder and an anode outer cylinder sleeved outside the inner cylinder, wherein a circular 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, the output end of the anode outer cylinder is also provided with a circular second coaxial output waveguide, the first coaxial output waveguide and the second coaxial output waveguide are coaxially arranged, the second modulation cavity is also communicated with the second coaxial output waveguide, and the K-band transit time oscillator is rotationally symmetrical about the central axis of the inner cylinder. The invention verifies the feasibility of extracting microwaves from the front cavity, and realizes higher power output while realizing higher efficiency output.
Description
Technical Field
The invention relates to a microwave source device in the technical field of high-power microwaves, in particular to a K-band transit time oscillator based on a front cavity extraction structure.
Background
High power microwaves (High Power Microwave, HPM) are generally defined as electromagnetic waves having peak powers exceeding 100MW and wavelengths between 1mm and 1m (i.e., frequencies between 300MHz and 300 GHz). In seventies of the last century, pulse power technology has been rapidly developed, and intense-current relativistic electron beams of hundreds of kilovolts and tens of kiloamperes of current are generated, which are applied to conventional vacuum electronic microwave devices, so that HPM with power exceeding hundreds of megawatts is possible to generate. Meanwhile, in the intensive research of relativity vacuum electronics, plasma physics and other subjects, theoretical support is provided for the production of HPM.
The high-power microwave source is a core component for generating high-power microwave radiation, and the interaction of the high-current electron beam and the resonant cavity is utilized to generate high-power microwaves. The transit time oscillator utilizes the strong current electron beam to exchange energy with the intrinsic standing wave field in the resonant cavity, has the characteristics of high power, high efficiency, single working mode and the like, and is widely focused by researchers.
The K band refers to electromagnetic waves with frequencies in the frequency range of 18-26 GHz (corresponding wavelengths of 11.54-16.67 mm), and belongs to the millimeter wave category. Compared with low-frequency-band microwaves, K-band microwaves have the advantages of wide frequency spectrum range, narrow wave beam, linear propagation, all-weather operation, high gain of a radiation antenna and the like, and are widely used in various fields such as communication, radar, remote sensing and the like. Therefore, the development of the K-band high-power microwave technology is very promising. However, the currently studied wave bands are mainly focused on the frequency bands such as L, S, C, X, ku, ka, and the public results about the K wave band are rarely reported.
In millimeter wave band, the internal action space of the device is smaller and the power capacity is limited, so that the application of the traditional microwave tube in high-power millimeter wave band is limited. Therefore, increasing the power capacity of the high-band device while improving the output efficiency is a problem to be solved. The coaxial transit time oscillator has the advantages that as the inner conductor is introduced, the potential energy of the electron beam is improved, and the power capacity of the device is increased; the coaxial structure also has the characteristics of simultaneously and equidistantly increasing the radius of the inner conductor and the outer conductor and keeping the characteristics of the device unchanged, and is widely used in high-frequency band devices. For example, a C-band low magnetic field high efficiency coaxial high power microwave oscillator is disclosed at present, see prior art 1: [ Deng Rujin ] C-band low-magnetic-field high-efficiency coaxial high-power microwave oscillator study [ D ]: university of defense science and technology 2021). The structure of the device is shown in fig. 1, and the device is composed of an annular cathode 101, a first modulation cavity 102, a drift section 103, a second-stage modulation cavity 104, a single-gap inner extraction cavity 105, a collector 106, a coaxial output waveguide 107 and a magnetic field 108, wherein the whole device is rotationally symmetrical about the center. The scheme realizes the depth modulation of the fundamental wave current by introducing a two-stage modulation structure. In order to facilitate the cooling of the collector, microwaves are output in an internal extraction mode, and finally, under the conditions of 600kV diode voltage, 15kA diode current and 0.5T external guide magnetic field, the microwave output of 3.65GW, the frequency of 4.31GHz and the efficiency of 40% are realized. The structure can be seen to have high output efficiency, but has a relatively low application frequency band.
In addition, the output efficiency of the existing high-frequency-band coaxial transit time oscillator is high, but the output power is often low. For example, research into Ka-band high-power coaxial time-of-flight oscillators has been conducted at present, see prior art 2: song Lili research on Ka band high power coaxial time-of-flight oscillator [ D ]. Long sand: university of defense science and technology, 2018). The structure is shown in fig. 2, and consists of an annular cathode 201, a pre-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, and the whole device is rotationally symmetrical about the center. The structure improves the modulation depth of fundamental wave current through the four-gap modulation cavity, then adopts the single-gap extraction cavity to extract microwaves, and finally realizes the microwave output of 1.27GW under the conditions of 447kV,7.4kA and 0.6T of guiding magnetic field, wherein the efficiency is 38.5%, and the output microwave frequency is 26.2GHz. It can be seen that the device has room for improvement in output power and efficiency although the output frequency is high. And the device with higher output power has little experimental feasibility. In addition, compact, lightweight Ku-band long pulse transit time oscillator studies have also been conducted at present, see prior art 3: xu Weili compact light-weight Ku band long pulse transit time oscillator study [ D ]: university of defense science and technology 2020. The structure is shown in fig. 3, and consists of an annular cathode 301, a pre-reflector 302, a modulation cavity 303, a drift section 304, an extraction cavity 305, a curved collector 306 and a coaxial output waveguide 307, the whole device being rotationally symmetric about the center. The structure combines the characteristics of easy realization in the axial direction and large radial power capacity in an axial gradual change bending mode, and realizes the output power of 3.37GW, the microwave frequency of 12.43GHz and the efficiency of 41 percent under the conditions of 620kV voltage, 13.3kA current and 1T externally applied guide magnetic field. The device has high output power and efficiency, but has high experimental processing difficulty.
At present, no technical proposal of a high-frequency-band coaxial transit time oscillator which simultaneously realizes high conversion efficiency, high output power and easy processing has been reported.
Disclosure of Invention
The invention aims to solve the technical problems: aiming at the problems in the prior art, the K-band transit time oscillator based on the last front cavity extraction structure is provided, and the problem that the output power of an extraction cavity is limited while high-efficiency output is realized in a high frequency band is solved. The increase of the modulation depth of fundamental wave current is realized by adopting a two-stage modulation structure of cascade connection of a rectangular cavity and a trapezoidal cavity, so that the output efficiency is improved; on the basis of a conventional centralized energy extraction mode, the microwave is extracted through the opening of the second-stage modulation cavity (hereinafter referred to as the last front cavity), so that high output power is realized, and meanwhile, the power capacity of the extraction cavity is increased.
In order to solve the technical problems, the invention adopts the following technical scheme:
the utility model provides a K wave band transit time oscillator based on last front chamber extraction structure, includes the inner tube and overlaps the outside positive pole urceolus of inner tube, form annular cavity between inner tube and the positive pole urceolus, the cavity is including the first drift tube, first modulation chamber, second drift tube, second modulation chamber, third drift tube, extraction chamber and the first coaxial output waveguide of intercommunication in proper order, the output of positive pole urceolus still is equipped with annular second coaxial output waveguide, first coaxial output waveguide and the coaxial setting of second coaxial output waveguide, second modulation chamber still communicates with the coaxial output waveguide of second, K wave band transit time oscillator is with the central axis rotational symmetry of inner tube.
Further, the first modulation chamber comprises a first modulation chamber outer chamber arranged on the inner wall of the anode outer cylinder, a first modulation chamber inner chamber arranged on the outer wall of the inner cylinder, and an annular space between the first modulation chamber outer chamber and the first modulation chamber inner chamber, wherein the first modulation chamber outer chamber and the first modulation chamber inner chamber are oppositely arranged, the first modulation chamber outer chamber and the first modulation chamber inner chamber are formed by the same annular cavity arranged along the axial clearance, and the cross section of the annular cavity is rectangular.
Further, the second modulation cavity comprises a second modulation cavity outer cavity arranged on the inner wall of the anode outer cylinder, a second modulation cavity inner cavity arranged 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, wherein the second modulation cavity outer cavity and the second modulation cavity inner cavity are oppositely arranged, the second modulation cavity outer cavity and the second modulation cavity inner cavity are annular cavities with trapezoid cross sections, and the second modulation cavity outer cavity is communicated with the input end of the second coaxial output waveguide.
Further, the second coaxial output waveguide comprises a second output waveguide rectangular transition section and a second output waveguide antenna connection section which are sequentially communicated, and the second output waveguide rectangular transition section is communicated with the outer cavity of the second modulation cavity.
Further, the extraction cavity comprises a first gap, a second gap and a third gap which are sequentially communicated along the axis direction, the first gap, the second gap and the third gap are corresponding annular cavities arranged in the extraction cavity outer cavity of the inner wall of the anode outer cylinder, corresponding annular cavities arranged in the extraction cavity inner cavity of the outer wall of the inner cylinder and annular spaces between the corresponding two annular cavities, and the annular cavities corresponding to the third gap in the extraction cavity outer cavity are communicated with the input end of the first coaxial output waveguide.
Further, the first coaxial output waveguide comprises a first output waveguide coupling slit, a first output waveguide conical transition section and a first output waveguide antenna connecting section which are communicated in sequence, and the first output waveguide coupling slit is communicated with a circular cavity corresponding to a third gap in the outer cavity of the extraction cavity.
Further, the first coaxial output waveguide further comprises a circular first output waveguide adjusting block, and the first output waveguide adjusting block is arranged at the input end of the first output waveguide antenna connecting section and sleeved outside the inner cylinder.
Further, the annular cavity length L7 corresponding to the first gap is greater than the annular cavity length L8 corresponding to the second gap, the annular cavity length L8 corresponding to the second gap is greater than the annular cavity length L9 corresponding to the third gap, and the interval P2 between the annular cavity corresponding to the first gap and the annular cavity corresponding to the second gap is greater than the interval P3 between the annular cavity corresponding to the second gap and the annular cavity corresponding to the third gap.
Further, the output end of the first coaxial output waveguide is provided with a first supporting rod, the output end of the second coaxial output waveguide is provided with a second supporting rod, and the second supporting rod is arranged at a position corresponding to the mounting position of the first supporting rod in the first coaxial output waveguide in the second coaxial output waveguide.
Furthermore, the inner cylinder is also provided with a trapezoid collector, the trapezoid collector is a circular cavity with a right trapezoid cross section, and the ends of the right-angle waist of 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 trapezoid collector are sequentially communicated to form an electron beam transmission path channel.
Compared with the prior art, the invention has the following advantages:
(1) The invention provides a K-band transit time oscillator based on a last front cavity extraction structure, which adopts a two-stage cascade structure of a three-gap rectangular cavity and a single-gap trapezoidal cavity, realizes twice effective modulation of electron beams, improves the modulation depth of fundamental wave current, and is beneficial to realizing higher power output of devices.
(2) The invention provides a K-band transit time oscillator based on a last front cavity extraction structure, which considers the situation that the power capacity of a second output port in distributed extraction is possibly insufficient in an internal extraction mode under the condition of small-radius high-frequency-band high-power output, and observes that the fundamental wave current modulation of the last front cavity is very large and contains abundant energy. Therefore, the microwave is output at the opening of the front cavity on the basis of the conventional centralized energy extraction mode, so that the microwave is extracted from two channels simultaneously, and the microwave output with higher power and higher efficiency is realized while the power capacity of the device is increased.
Drawings
Fig. 1 is a schematic structural diagram of a C-band low magnetic field high efficiency coaxial high power microwave oscillator disclosed in prior art 1.
Fig. 2 is a schematic diagram showing a front cross-sectional structure of a Ka-band high-power coaxial time-of-flight oscillator disclosed in prior art 2.
Fig. 3 is a schematic diagram of a front cross-sectional view of a compact lightweight Ku-band long pulse transit time oscillator as disclosed in prior art 3.
Fig. 4 is a schematic diagram showing a front cross-sectional structure of a K-band transit time oscillator according to an embodiment of the present invention.
Fig. 5 is a schematic diagram of an extraction cavity structure of a K-band transit time oscillator according to an embodiment of the present invention.
Fig. 6 is a graph of average power of microwave output from a first coaxial output waveguide in a K-band time-of-flight oscillator according to an embodiment of the present invention.
Fig. 7 is a graph of the output microwave frequency of the first coaxial output waveguide in the K-band transit time oscillator according to the embodiment of the present invention.
Fig. 8 is a graph of average power of microwave output from a second coaxial output waveguide in a K-band time-of-flight oscillator according to an embodiment of the present invention.
Fig. 9 is a graph of the output microwave frequency of the second coaxial output waveguide in the K-band transit time oscillator according to the embodiment of the present invention.
Description of the background section: 101-annular cathode, 102-first modulation cavity, 103-drift section, 104-second stage modulation cavity, 105-single gap inner extraction cavity, 106-collector, 107-coaxial output waveguide, 108-magnetic field, 201-annular cathode, 202-pre-reflection cavity, 203-modulation cavity, 204-drift section, 205-extraction cavity, 206-coaxial output waveguide, 207-magnetic field, 301-annular cathode, 302-pre-reflector, 303-modulation cavity, 304-drift section, 305-extraction cavity, 306-curved collector, 307-coaxial output waveguide;
the embodiment of the invention is illustrated in the drawings: 401-cathode mount, 402-cathode, 403-anode outer tube, 404-inner tube, 405-first drift tube, 406-first modulation cavity, 406 a-first modulation cavity outer cavity, 406 b-first modulation cavity inner cavity, 407-second drift tube, 408-second modulation cavity, 408 a-second modulation cavity outer cavity, 408 b-second modulation cavity inner cavity, 409-third drift tube, 410-extraction cavity, 410 a-extraction cavity outer cavity, 410 b-extraction cavity inner cavity, 411-trapezoidal collector, 412-first coaxial output waveguide, 412 a-first output waveguide coupling slit, 412 b-first output waveguide tapered transition section, 412 c-first output waveguide antenna connection section, 412 d-first output waveguide adjustment block, 413-second coaxial output waveguide, 413 a-second output waveguide rectangular transition section, 413 b-second output waveguide antenna connection section, 414 a-first support bar, 414 b-second support bar, 415-solenoid magnetic field.
Detailed Description
The invention is further described below in connection with the drawings and the specific preferred embodiments, but the scope of protection of the invention is not limited thereby.
The invention provides a K-band transit time oscillator based on a last front cavity extraction structure, which can realize higher power and higher efficiency microwave output while increasing the power capacity of a device, and the increase of the modulation depth of fundamental wave current is realized by adopting a two-stage modulation structure of cascade connection of a rectangular cavity and a trapezoid cavity, so that the output efficiency is improved; on the basis of a conventional centralized energy extraction mode, the microwave is extracted through the opening of the second-stage modulation cavity (hereinafter referred to as the last front cavity), so that high output power is realized, and meanwhile, the power capacity of the extraction cavity is increased. As shown in fig. 4, the cathode comprises a cathode seat 401 and an anode outer cylinder 403 with a tubular structure, a solenoid magnetic field 415 is sleeved on the outer wall of the anode outer cylinder 403, an inner cylinder 404 is inserted in the anode outer cylinder 403, a circular cavity is formed between the inner cylinder 404 and the anode outer cylinder 403, a circular cathode 402 is arranged on one side of the cathode seat 401 facing the inner cylinder 404, and the cathode 402 is used for emitting electron beams to the cavity between the inner cylinder 404 and the anode outer cylinder 403. The inner barrel 404 is a cylindrical conductor of unequal radius, the various cavities on the outer surface of which, together with the various cavities on the inner surface of the outer barrel 403 of the anode, form an electrodynamic structure, and the electron beam produces beam wave interactions to produce HPM and radiate outward.
As shown in fig. 4, the K-band transit time oscillator of the present embodiment is rotationally symmetric about the central axis (OZ axis) of the inner barrel 404, the cavity of the present embodiment includes a first drift tube 405, a first modulation cavity 406, a second drift tube 407, a second modulation cavity 408, a third drift tube 409, an extraction cavity 410, and a first coaxial output waveguide 412 that are sequentially connected, the output end of the anode outer barrel 403 is further provided with a second annular coaxial output waveguide 413, the first coaxial output waveguide 412 and the second coaxial output waveguide 413 are coaxially arranged, the second modulation cavity 408 is further communicated with the second coaxial output waveguide 413, in addition, the inner barrel 404 is further opposite to the electron beam transmission path, a trapezoidal collector 411 is provided, the trapezoidal collector 411 is a circular cavity with a right trapezoid cross section, and the right waists of the first drift tube 405, the first modulation cavity 406, the second drift tube 407, the second modulation cavity 408, the third drift tube 409, the extraction cavity 410, and the trapezoidal collector 411 are sequentially connected to form an electron beam transmission path channel.
In this embodiment, the anode of the pulse driving source is externally connected to the left end of the cathode seat 401, the outer conductor of the pulse driving source is externally connected to the left end of the anode outer cylinder 403, and the first coaxial output waveguide 412 and the second coaxial output waveguide 413 are both connected to the mode converter and the antenna, so that the method can be designed according to the general mode converter and antenna design method according to the requirements of different wavelengths and application scenarios, and is a general method in the high-power microwave field. The working principle of the K-band transit time oscillator of the present embodiment is as follows:
the pulsed power drive source applies a high voltage to the cathode 402, the cathode 402 emits a high current relativistic electron beam, the relativistic electron beam generated by the cathode 402Beam interaction occurs in the first modulation cavity 406, the second modulation cavity 408, and the extraction cavity 410 in sequence, and electron beams in the first modulation cavity 406, the second modulation cavity 408 are stimulated to generate TM 01 The electromagnetic wave of the mode and the electromagnetic wave interact with the electromagnetic wave, the first modulation cavity 406 and the second modulation cavity 408 sequentially perform density modulation and speed modulation on the electron beam, under the traction of the electron beam, an intrinsic field is excited in the first modulation cavity 406, the speed modulation is performed on the electron beam, then the speed modulation of the electron beam is converted into density modulation through the second drift tube 407 corresponding to the first modulation cavity 406, the process is repeated in the second modulation cavity 408, the electron beam drifts to the extraction cavity 410, the electromagnetic wave of the TM01 mode is excited and interacts with the electromagnetic wave, finally, the energy of the electron beam is transmitted to the intrinsic microwave of the extraction cavity 410, and the generated high-power microwave is radiated out through the output waveguide. The electron beams reach good bunching before reaching the extraction cavity 410, after the electron beams drift to the extraction cavity 410, the energy of the electron beams is transferred to the intrinsic microwaves of the extraction cavity 410, a retarding electric field in the extraction cavity 410 and the electron beams generate strong transit radiation effect to generate HPM (high power microwaves), and finally the generated high power microwaves are coupled to the mode converter and the radiation antenna through the first coaxial output waveguide 412. And the excess electron beam enters the collector 411 to be collected. Considering that electrons directly hit the inner wall of the collector may generate reflected electrons and flow back to the extraction cavity to affect beam wave interaction, the right end of the collector 411 is set to be inclined, so that the effective area of electrons hitting the collector is increased, and the degree of electron reflection is reduced.
In order to increase the output efficiency, the present embodiment proposes to employ a two-stage modulation structure by increasing the fundamental current modulation depth. The first-stage modulation structure is used for carrying out initial modulation on electrons, the modulation depth of fundamental wave current is not too large, and a common three-gap rectangular cavity in the transit time oscillator is adopted; while the second-stage modulation structure requires a further increase in fundamental current and thus requires a high power capacity cavity. Studies have shown that equally sized trapezoidal cavities have a higher power capacity than rectangular cavities. The more the number of the cavities is, the length of the whole tube is increased, so that the single-gap trapezoid cavity is adopted as a second-stage modulation structure. In the embodiment, a two-stage modulation structure of a three-gap rectangular cavity and a single-gap trapezoidal cavity is adopted, and the electron beam is modulated twice successively, so that the modulation depth of fundamental wave current is increased, and the modulation depth of the fundamental wave current is up to more than 130%.
As shown in fig. 4, in this embodiment, the first modulation cavity 406 is formed by a first modulation cavity outer cavity 406a (a dotted line portion indicated by 406 a) disposed on the inner wall of the anode outer cylinder 403, a first modulation cavity inner cavity 406b (a dotted line portion indicated by 406 b) disposed on the outer wall of the inner cylinder 404, and an annular space between the first modulation cavity outer cavity 406a and the first modulation cavity inner cavity 406b, the first modulation cavity outer cavity 406a and the first modulation cavity inner cavity 406b are disposed opposite to each other, and the first modulation cavity outer cavity 406a and the first modulation cavity inner cavity 406b are each formed by annular cavities disposed along an axial gap, and the cross sections of the annular cavities are rectangular.
Correspondingly, as shown in fig. 4, the second modulation cavity 408 in this embodiment is formed by a second modulation cavity outer cavity 408a (indicated by a dotted line portion indicated by 408 a) disposed on the inner wall of the anode outer cylinder 403, a second modulation cavity inner cavity 408b (indicated by a dotted line portion indicated by 408 b) disposed on the outer wall of the inner cylinder 404, and an annular space between the second modulation cavity outer cavity 408a and the second modulation cavity inner cavity 408b, where the second modulation cavity outer cavity 408a is disposed opposite to the second modulation cavity inner cavity 408b, and the second modulation cavity outer cavity 408a is a third annular cavity with an isosceles trapezoid cross section, the second modulation cavity inner cavity 508b is a fourth annular cavity with an isosceles trapezoid cross section, and the second modulation cavity outer cavity 408a is communicated with the input end of the second coaxial output waveguide 413. Since a large amount of energy is accumulated in the last front cavity (i.e., the second modulation cavity 408), in order to increase the output power and increase the power capacity of the extraction cavity 411, based on the conventional centralized energy extraction mode, the embodiment is opened in the last front cavity, and a part of high-power microwaves are coupled to the mode converter and the radiation antenna outwards through the second coaxial output waveguide 413, so as to realize simultaneous microwave extraction of two channels, as shown in fig. 4, the second coaxial output waveguide 413 in the embodiment includes a second output waveguide rectangular transition section 413a and a second output waveguide antenna connection section 413b which are sequentially communicated, and the second output waveguide rectangular transition section 413a is communicated with the second modulation cavity external cavity 408a, so that the output power of 1.66GW is finally obtained, and the efficiency is 33.2%.
The extraction cavity 410 of this embodiment also adopts a structure with a third gap, an outer extraction mode is adopted in the third gap of the extraction cavity 410, as shown in fig. 5, the extraction cavity 410 of this embodiment is composed of an extraction cavity outer cavity 410a (a dotted line portion indicated by 410 a) disposed on the inner wall of the anode outer cylinder 403, an extraction cavity inner cavity 410b (a dotted line portion indicated by 410 b) disposed on the outer wall of the inner cylinder 404, and an annular space between the extraction cavity outer cavity 410a and the extraction cavity inner cavity 410b, the extraction cavity outer cavity 410a and the extraction cavity inner cavity 410b are disposed opposite to each other, and each of the extraction cavity outer cavity 410a and the extraction cavity inner cavity 410b is composed of a fifth annular cavity, a sixth annular cavity and a seventh annular cavity disposed along the axial gap, the eighth annular cavity and the ninth annular cavity are formed by the eighth annular cavity disposed along the axial gap, and the seventh annular cavity are formed by the seventh annular cavity and the seventh annular cavity, and the seventh annular gap between the eighth annular cavity and the eighth annular cavity are formed by the seventh annular cavity and the seventh annular cavity. The input end of the first coaxial output waveguide 412 communicates 4 with a seventh annular cavity corresponding to the third gap in the extraction cavity outer cavity 410 a.
As shown in fig. 5, the first coaxial output waveguide 412 in this embodiment includes a first output waveguide coupling slit 412a, a first output waveguide tapered transition section 412b, and a first output waveguide antenna connection section 412c that are sequentially connected, where the first output waveguide coupling slit 412a is connected to a seventh annular cavity corresponding to the third gap in the extraction cavity outer cavity 410 a. Further, in this embodiment, the first coaxial output waveguide 412 further includes a first output waveguide adjusting block 412d having a circular ring shape, and the first output waveguide adjusting block 412d is disposed at the input end of the first output waveguide antenna connection section 412c and is sleeved outside the inner cylinder 404. The first output waveguide adjusting block 412d is introduced to facilitate adjusting parameters of the extraction cavity, and the Q value of the extraction cavity can be changed by adjusting the height of the first output waveguide adjusting block 412 d; the resonant frequency of the extraction cavity can be changed by adjusting the width of the first output waveguide adjustment block 412 d.
In order to prevent the inner and outer conductors from being eccentric and dislocated in the coaxial structure, a support rod is generally added in the coaxial output waveguide to support the inner and outer conductors. As shown in fig. 4, in the present embodiment, the output end of the first coaxial output waveguide 412 is provided with a first support rod 414a, the output end of the second coaxial output waveguide 413 is provided with a second support rod 414b, and the second support rod 414b is mounted in a position corresponding to the mounting position of the first support rod 414a in the first coaxial output waveguide 512 in the second coaxial output waveguide 413.
The dimensions of the various components are described below with reference to fig. 5 and 6:
cathode 402 is a thin annular cylinder with a wall thickness of 1mm and a radius R1 equal to the electron beam radius;
the first drift tube 405 is a circular cavity with an outer radius R2 and an inner radius R3, where R2> R1> R3, and the length is L1;
the inner radius and the outer radius of each first annular cavity in the first modulation cavity outer cavity 406a are R2 and R4 respectively, the length of each first annular cavity is L2, and the distance between adjacent first annular cavities is P1;
the inner radius and the outer radius of each second annular cavity in the first modulation cavity inner cavity 406b are R5 and R3 respectively, the positions of the second annular cavities are in one-to-one correspondence with those of the first annular cavities, the length of each second annular cavity is L2, and the distance between every two adjacent second annular cavities is P1;
the second drift tube 407 is a circular cavity with an outer radius R2 and an inner radius R3, and has a length L3;
the inner and outer radii of the third circular cavity of the second modulation cavity outer cavity 408a are R2 and R6, R6> R4, respectively, and the upper base length and the lower base length of the isosceles trapezoid of the cross section thereof are L4 and L5, respectively, L5> L4;
the inner and outer radii of the fourth annular cavity of the second modulation cavity inner cavity 408b are R7 and R3, R7< R5, and the upper base length and the lower base length of the isosceles trapezoid with the cross section are L4 and L5 respectively;
the third drift tube 409 is a circular cavity with an outer radius R2 and an inner radius R3, and has a length L6;
in the extraction cavity outer cavity 410a, the lengths of the annular cavities are sequentially reduced along the axial direction when seen from the diode to the output port, the heights of the annular cavities at the two ends are the same and different from those of the middle annular cavity, specifically, the inner and outer radiuses of the fifth annular cavity and the seventh annular cavity are R2 and R8 respectively, the inner and outer radiuses of the sixth annular cavity are R2 and R9 respectively, R8> R6> R9, the lengths of the fifth, sixth and seventh annular cavities are L7, L8 and L9 respectively, L7> L8> L9 respectively, the interval between the fifth annular cavity and the sixth annular cavity is P2, and the interval between the sixth annular cavity and the seventh annular cavity is P3 and P2> P3 respectively;
in the inner cavity 410b of the extraction cavity, the eighth annular cavity corresponds to the fifth annular cavity in position, the ninth annular cavity corresponds to the sixth annular cavity in position, the tenth annular cavity corresponds to the seventh annular cavity in position, the lengths of the annular cavities are sequentially reduced along the axial direction when seen from the diode to the output port, the annular cavities at the two ends are the same in height and different from the middle annular cavity in height, specifically, the inner radius and the outer radius of the eighth annular cavity and the tenth annular cavity are R10 and R3 respectively, the inner radius and the outer radius of the ninth annular cavity are R11 and R3 respectively, R10 is greater than R11, the lengths of the eighth annular cavity, the ninth annular cavity and the tenth annular cavity are L7, L8 and L9 respectively, the interval between the eighth annular cavity and the ninth annular cavity is P2, and the interval between the ninth annular cavity and the tenth annular cavity is P3 respectively;
the trapezoid collector 411 has an outer radius R12 and an inner radius R13, R2> R12, R13> R3; the upper bottom side length L10 and the lower bottom side length L11 and L11 of the right trapezoid with the cross section are larger than L10;
the first output waveguide coupling slit 412a is a circular cavity with an outer radius R8 and an inner radius R14, R14> R2, and a length L12;
the first output waveguide tapered transition section 412b is a circular cavity with a tapered cross section, and the tapered upper bottom length R8-R14, the lower bottom length R15-R14, R15> R8 and the height L13 of the cross section are all the same;
the first output waveguide antenna connection section 412c is a circular cavity with an outer radius R15 and an inner radius R14, and has a length L14;
the first output waveguide adjusting block 412d is a metal ring with an outer radius R16 and an inner radius R14, R8> R16, and a length L15, and a distance from the right side of the seventh annular cavity in the extraction cavity outer cavity 510a is L16;
the second output waveguide rectangular transition section 413a is a circular cavity with an outer radius of R17 and an inner radius of R6, R17 is larger than R15, and the length is L17;
the second output waveguide antenna connection section 413b is a circular cavity with an inner radius R18 and an outer radius R17, and has a length L18, where R18> R15;
the distance between the first support rod 414a and the left end of the first output waveguide adjusting block 412d is L19, and the position of the second support rod 414b corresponds to the position of the first support rod 414 a.
Specific dimensions are set in this embodiment as follows: r1=30.5 mm, r2=33 mm, r3=28 mm, r4=35.2 mm, r5=26.2 mm, r6=35.7 mm, r7=25.2 mm, r8=35.8 mm, r9=35.6 mm, r10=26 mm, r11=25.6 mm, r12=32.5 mm, r13=28.5 mm, r14=34.8 mm, r15=39 mm, r16=34.8 mm, r17=45.7 mm, r18=40.7 mm, l1=20 mm, l2=5.5 mm, l3=11.5 mm, l4=1.3 mm, l5=4.3 mm, l6=10 mm, l7=4.6 mm, l8=4.2 mm, l9=4.0 mm, l10=16.0 mm, l11=32.0 mm, l12=4.0 mm, l13=12.7=20.7 mm, l1=20.5 mm, l2=20.5 mm, l3=1.8 mm, l2.8 mm, l2=20.8 mm.
In the particle simulation, simulation results obtained by simulating the K-band coaxial transit time oscillator of the present embodiment under the 5GW injection power are shown in fig. 6 to 9, wherein:
FIG. 6 is a graph of the average power of the output microwaves from the first coaxial output waveguide 412, with time on the abscissa, in ns; the ordinate is average power in GW. From fig. 7, the output microwaves tend to stabilize after 28ns, resulting in a microwave output with an average power of 0.37 GW.
FIG. 7 is a graph of the output microwave frequency of the first coaxial output waveguide 412, with the abscissa being frequency in ns; the ordinate is the voltage value at the corresponding frequency in Volts/GHz. As can be seen from fig. 8, the output frequency of the first coaxial output waveguide 412 is 18.65GHz and the frequency spectrum is clean.
Fig. 8 is a graph of the average power of the output microwaves of the second coaxial output waveguide 413, with time on the abscissa and ns on the unit; the ordinate is average power in GW. From fig. 8, the output microwaves tend to stabilize after 27ns, resulting in a microwave output with an average power of 1.29 GW.
Fig. 9 is a graph of the frequency of the output microwaves of the second coaxial output waveguide 413, with the abscissa being frequency in ns; the ordinate is the voltage value at the corresponding frequency in Volts/GHz. As can be seen from fig. 9, the output frequency of the second coaxial output waveguide 413 is 18.65GHz and the frequency spectrum is clean.
As can be seen from fig. 6 to 9, the K-band coaxial transit time oscillator of the present embodiment performs distributed extraction based on the last front cavity, so as to achieve high-power and high-efficiency microwave output with a center frequency of 18.65GHz (corresponding microwave wavelength λ=16.08 mm). In the particle simulation, under the 5GW injection power, the output power of the first coaxial output port is 0.37GW, the output power of the second coaxial output port is 1.29GW, the total output is 1.66GW, the output efficiency reaches 33.2%, and the corresponding output frequency is 18.65GHz and the frequency spectrum is pure.
From the above results, the method of the embodiment verifies the feasibility of extracting microwaves from the front cavity, realizes higher power output while realizing higher efficiency output, has more regular structure of each part of the whole device, is easy to process in experiments, and has important reference significance for realizing high efficiency and high power output of the transit time oscillator in a high frequency band.
In summary, the invention has the following advantages:
(1) The invention adopts a two-stage cascade structure of three-gap rectangular cavity and single-gap trapezoidal cavity, realizes twice effective modulation of electron beams, improves the modulation depth of fundamental current, and is beneficial to realizing higher power output of devices.
(2) On the basis of a conventional centralized energy extraction mode, microwaves are output at the opening of the front cavity, so that the microwaves are extracted from two channels simultaneously, the power capacity of the device is increased, and the microwaves with higher power and higher efficiency are output.
(3) The microwave power output by the microwave oven is 1.66GW, the microwave frequency is 18.65GHz, the frequency spectrum is pure, the efficiency is 33.2%, the output power of the last front cavity is 1.29GW, and the feasibility of extracting microwaves from the last front cavity is fully proved.
The foregoing is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. While the invention has been described with reference to preferred embodiments, it is not intended to be limiting. Therefore, any simple modification, equivalent variation and modification of the above embodiments according to the technical substance of the present invention shall fall within the scope of the technical solution of the present invention.
Claims (10)
1. The utility model provides a K wave band transit time oscillator based on last front chamber extraction structure, its characterized in that includes inner tube (404) and cover and locate outside positive pole urceolus (403) of inner tube (404), form annular cavity between inner tube (404) and positive pole urceolus (403), the cavity is including first drift tube (405), first modulation chamber (406), second drift tube (407), second modulation chamber (408), third drift tube (409), extraction cavity (410) and first coaxial output waveguide (412) that communicate in proper order, the output of positive pole urceolus (403) still is equipped with annular second coaxial output waveguide (413), first coaxial output waveguide (412) and second coaxial output waveguide (413) coaxial setting, second modulation chamber (408) still communicates with second coaxial output waveguide (413), K wave band transit time oscillator is rotationally symmetrical about the central axis of inner tube (404).
2. The K-band time-of-flight oscillator based on a last front cavity extraction structure according to claim 1, wherein the first modulation cavity (406) consists of a first modulation cavity outer cavity (406 a) provided at an inner wall of the anode outer cylinder (403), a first modulation cavity inner cavity (406 b) provided at an outer wall of the inner cylinder (404), and an annular space between the first modulation cavity outer cavity (406 a) and the first modulation cavity inner cavity (406 b), the first modulation cavity outer cavity (406 a) and the first modulation cavity inner cavity (406 b) are arranged opposite to each other, and the first modulation cavity outer cavity (406 a) and the first modulation cavity inner cavity (406 b) are each composed of the same annular cavity provided along an axial gap, and the cross section of the annular cavity is rectangular.
3. The K-band time-of-flight oscillator based on the last-front-cavity extraction structure according to claim 1, wherein the second modulation cavity (408) is composed of a second modulation cavity outer cavity (408 a) provided on an inner wall of the anode outer cylinder (403), a second modulation cavity inner cavity (408 b) provided on an outer wall of the inner cylinder (404), and an annular space between the second modulation cavity outer cavity (408 a) and the second modulation cavity inner cavity (408 b), the second modulation cavity outer cavity (408 a) and the second modulation cavity inner cavity (408 b) are oppositely arranged, and the second modulation cavity outer cavity (408 a) and the second modulation cavity inner cavity (408 b) are annular cavities each having a trapezoid cross section, and the second modulation cavity outer cavity (408 a) is communicated with an input end of the second coaxial output waveguide (413).
4. A K-band time-of-flight oscillator based on a last front cavity extraction structure according to claim 3, characterized in that the second coaxial output waveguide (413) comprises a second output waveguide rectangular transition section (413 a) and a second output waveguide antenna connection section (413 b) in turn, the second output waveguide rectangular transition section (413 a) being in communication with a second modulation cavity external cavity (408 a).
5. The K-band transit time oscillator based on the last forecavity extraction structure according to claim 1, wherein the extraction cavity (410) comprises a first gap, a second gap and a third gap which are sequentially communicated along the axis direction, the first gap, the second gap and the third gap are each formed by a corresponding annular cavity of an extraction cavity outer cavity (410 a) arranged on the inner wall of the anode outer cylinder (403), a corresponding annular cavity of an extraction cavity inner cavity (410 b) arranged on the outer wall of the inner cylinder (404), and an annular space between the corresponding two annular cavities, and the annular cavity corresponding to the third gap in the extraction cavity outer cavity (410 a) is communicated with the input end of the first coaxial output waveguide (412).
6. The K-band time-of-flight oscillator based on a last-front-cavity extraction structure of claim 5, wherein the first coaxial output waveguide (412) comprises a first output waveguide coupling slit (412 a), a first output waveguide tapered transition section (412 b), and a first output waveguide antenna connection section (412 c) that are sequentially communicated, the first output waveguide coupling slit (412 a) being in communication with a circular cavity corresponding to a third gap in the extraction cavity outer cavity (410 a).
7. The K-band time-of-flight oscillator based on the last-front-cavity extraction structure of claim 6, wherein the first coaxial output waveguide (412) further comprises a first output waveguide adjusting block (412 d) in a circular shape, and the first output waveguide adjusting block (412 d) is disposed at an input end of the first output waveguide antenna connecting section (412 c) and is sleeved outside the inner barrel (404).
8. The K-band transit time oscillator based on a last forecavity extraction structure according to claim 5, wherein a length L7 of the annular cavity corresponding to the first gap is greater than a length L8 of the annular cavity corresponding to the second gap, the length L8 of the annular cavity corresponding to the second gap is greater than a length L9 of the annular cavity corresponding to the third gap, and a spacing P2 between the annular cavity corresponding to the first gap and the annular cavity corresponding to the second gap is greater than a spacing P3 between the annular cavity corresponding to the second gap and the annular cavity corresponding to the third gap.
9. The K-band time-of-flight oscillator based on the last-forecavity extraction structure according to claim 1, wherein the output end of the first coaxial output waveguide (412) is provided with a first support rod (414 a), the output end of the second coaxial output waveguide (413) is provided with a second support rod (414 b), and the second support rod (414 b) is mounted in a position in the second coaxial output waveguide (413) corresponding to the mounting position of the first support rod (414 a) in the first coaxial output waveguide (412).
10. The K-band transit time oscillator based on the last front cavity extraction structure according to claim 1, wherein the inner cylinder (404) is further provided with a trapezoid collector (411), the trapezoid collector (411) is a circular cavity with a right trapezoid cross section, and ends of the first drift tube (405), the first modulation cavity (406), the second drift tube (407), the second modulation cavity (408), the third drift tube (409), the extraction cavity (410) and the right-angle waist of the trapezoid collector (411) are sequentially communicated to form an electron beam transmission path channel.
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