Miniaturized periodic permanent magnet focused metamaterial backward wave oscillator

Abstract

The application discloses a miniaturized periodic permanent magnet focusing super-structured material backward wave oscillator, which comprises a super-structured material slow wave structure, a coupling cavity, a periodic permanent magnet focusing system and a coaxial output interface; the super-structured material slow wave structure comprises a waveguide shell, a periodic resonant structure and a first real space gap; the coupling cavity comprises a coupling cavity shell, a coupling cavity inner conductor and a second real space gap, the coupling cavity inner conductor is connected with the periodic resonant structure and the coaxial output interface; the periodic permanent magnet focusing system comprises a first permanent magnet focusing structure and a second permanent magnet focusing structure which are asymmetrically arranged upwards and downwards, and the super-structured material slow wave structure is arranged between the first permanent magnet focusing structure and the second permanent magnet focusing structure. The super-structured material slow wave structure and the periodic permanent magnet focusing system are arranged, and the coupling cavity is multiplexed as a collector, so that the size of the backward wave oscillator is reduced. The asymmetrically arranged periodic permanent magnet focusing system generates an asymmetric focusing magnetic field, and energy exchange of an electron beam is facilitated.

Description

Technical Field

[0001] This invention relates to the field of vacuum electronic devices, and more particularly to a miniaturized metamaterial backward wave oscillator with periodic permanent magnet focusing. Background Technology

[0002] Vacuum electronic devices, such as backward-wave oscillators (WROS) and traveling-wave tubes (TWTs), have been applied in accelerators, plasma science, radar, and other fields due to their high output power. It is well known that the output power of WROS is always higher than that of solid-state devices. In a vacuum environment, electrons exhibit higher mobility, and coupled with the excellent heat dissipation performance of vacuum electronic devices, they can achieve high power output even at high frequencies. In contrast, the efficiency and power of solid-state devices decrease significantly with increasing operating frequency. Attempting to achieve the power level of a single vacuum electronic tube through integration would severely hinder the overall system efficiency due to heat dissipation issues, and the miniaturization advantages of solid-state devices in terms of size and weight would also disappear. Therefore, in current high-power, high-frequency applications, microwave vacuum electronic devices maintain an unparalleled advantage.

[0003] Miniaturization is a long-term development goal and trend for vacuum electronic devices. To achieve this miniaturization, it is necessary to gradually reduce the size of components, including but not limited to slow-wave structures, output structures, electron guns, and magnetic focusing systems. High-power microwave sources are one of the important applications of backward-wave oscillators (ROS). Miniaturized ROS can reduce costs and equipment size. Furthermore, the slow-wave structure of traditional ROS is relatively large, which is not conducive to the overall miniaturization of the device. Moreover, current metamaterial ROS typically use a uniform magnetic field generated by a solenoid or permanent magnet to focus the electron beam, which is not conducive to the miniaturization of the focusing system and results in poor electron beam focusing performance. Summary of the Invention

[0004] To address the issues of large size and poor electron beam focusing in conventional backward wave oscillators, this invention proposes a miniaturized metamaterial backward wave oscillator with periodic permanent magnet focusing. It employs a metamaterial as the slow-wave structure and a novel periodic permanent magnet focusing system, reusing the coupling cavity as the collecting electrode, resulting in a smaller size. Furthermore, the asymmetrically configured periodic permanent magnet focusing system generates an asymmetric focusing magnetic field, facilitating better energy exchange of the electron beam and thus resolving the aforementioned problems.

[0005] This application discloses a miniaturized metamaterial backward wave oscillator with periodic permanent magnet focusing, including a metamaterial slow wave structure, a coupling cavity, a periodic permanent magnet focusing system, and a coaxial output interface; The metamaterial slow-wave structure includes a waveguide shell, and a periodic resonant structure and a first vacuum gap are disposed inside the waveguide shell. One end of the coupling cavity is connected to the slow-wave structure of the metamaterial, and the other end is connected to the coaxial output interface. The coupling cavity includes a coupling cavity shell, and an inner conductor and a second vacuum gap are provided inside the coupling cavity shell. The inner conductor includes a first inner conductor segment, a second inner conductor segment, and a third inner conductor segment. The first inner conductor segment is connected to the periodic resonant structure, and the third inner conductor segment is connected to the coaxial output interface. The periodic permanent magnet focusing system includes a first permanent magnet focusing structure and a second permanent magnet focusing structure arranged asymmetrically at the top and bottom, and a metamaterial slow-wave structure is disposed between the first permanent magnet focusing structure and the second permanent magnet focusing structure.

[0006] Preferably, the coaxial output interface includes an interface housing, a dielectric layer is disposed inside the interface housing, an interface probe is disposed inside the dielectric layer, and the interface probe is connected to the third segment of the inner conductor.

[0007] Preferably, one end of the metamaterial slow-wave structure is provided with an electron injection port for connecting an external electron gun.

[0008] Preferably, the periodic resonant structure comprises a plurality of periodically arranged metamaterial unit structures.

[0009] Preferably, the periodic resonant structure is biased on the inner wall of the waveguide housing.

[0010] Preferably, the first vacuum gap is connected to the second vacuum gap, one end of the coupling cavity shell is connected to the waveguide shell, and the other end is connected to the interface shell.

[0011] Preferably, the radius of the second segment of the inner conductor is larger than that of the first segment and the third segment of the inner conductor.

[0012] Preferably, both the first permanent magnet focusing structure and the second permanent magnet focusing structure include a fourth iron pole shoe. The second iron pole shoe is disposed opposite to the side of the fourth iron pole shoe. The first iron pole shoe and the third iron pole shoe are arranged alternately in a periodic manner between the second iron pole shoes. Iron pole shoe pads are disposed below the first iron pole shoe and below the third iron pole shoe in the first permanent magnet focusing structure, and above the first iron pole shoe and above the third iron pole shoe in the second permanent magnet focusing structure.

[0013] Preferably, multiple cavities are formed between the first, second, third, and fourth iron pole shoes, and a central magnet is disposed in each cavity, while periodically arranged edge magnets are disposed on the outer side of the second iron pole shoe.

[0014] Preferably, the lateral dimension of the edge magnet in the first permanent magnet focusing structure is smaller than the lateral dimension of the edge magnet in the second permanent magnet focusing structure.

[0015] The beneficial effects of this invention are: (1) The present invention uses metamaterials as slow wave structures. Compared with traditional backwave oscillators, metamaterials have smaller dimensions due to their subwavelength characteristics.

[0016] (2) The coupling cavity of the present invention can achieve good matching of the signal output structure and can also be reused as the collector of the backward wave oscillator. Compared with the traditional backward wave oscillator, it realizes structural reuse and further reduces the size of the device.

[0017] (3) The present invention employs a novel periodic permanent magnet focusing system. Compared with the solenoid focusing system, the present invention does not require an additional power supply and auxiliary coils and their fixing devices, thereby greatly reducing weight and size. At the same time, under the same electron beam parameters, the peak magnetic field required by the periodic magnetic field is smaller than that of the uniform magnetic field. Therefore, the periodic permanent magnet focusing system is also smaller in size than the uniform permanent magnet focusing system.

[0018] (4) The edge magnets of the periodic permanent magnet focusing system of the present invention are asymmetrically set, which can balance and cancel the asymmetrical distribution of space charge field on the upper and lower surfaces of the electron beam caused by the periodic resonance structure, so as to better focus the electron beam. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the miniaturized metamaterial backward wave oscillator with periodic permanent magnet focusing according to an embodiment of the present invention; Figure 2 This is a cross-sectional view of the miniaturized metamaterial backward wave oscillator with periodic permanent magnet focusing according to an embodiment of the present invention. Figure 3 This is a cross-sectional view of the slow-wave structure of the metamaterial according to an embodiment of the present invention; Figure 4 This is a schematic diagram of the metamaterial unit structure according to an embodiment of the present invention; Figure 5 This is a cross-sectional view of the coupling cavity and coaxial output interface according to an embodiment of the present invention; Figure 6 This is a schematic diagram of the periodic permanent magnet focusing system according to an embodiment of the present invention; Figure 7 This is a cross-sectional view of the periodic permanent magnet focusing system according to an embodiment of the present invention; Figure 8 This is a schematic diagram of the electron focusing result of a miniaturized periodic permanent magnet focused metamaterial backward wave oscillator according to an embodiment of the present invention.

[0020] The attached figures are labeled as follows: 1-Metamaterial slow-wave structure, 101-Periodic resonant structure, 102-Waveguide shell, 103-First vacuum gap, 104-Electron injection port, 2-Coupled cavity, 201-Coupled cavity shell, 202-First segment of inner conductor, 203-Second segment of inner conductor, 204-Third segment of inner conductor, 205-Second vacuum gap, 3-Periodic permanent magnet focusing system, 301-First iron pole shoe, 302-Second iron pole shoe, 303-Third iron pole shoe, 304-Fourth iron pole shoe, 305-Central magnet, 306-Edge magnet, 307-Iron pole shoe gasket, 4-Coaxial output interface, 401-Interface probe, 402-Dielectric layer, 403-Interface shell. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided with reference to the accompanying drawings and embodiments.

[0022] This application discloses a miniaturized metamaterial backward wave oscillator with periodic permanent magnet focusing, the structure of which is as follows: Figure 1 The metamaterial slow-wave structure 1, coupling cavity 2, periodic permanent magnet focusing system 3, and coaxial output interface 4 are all components of the back-wave oscillator. The back-wave oscillator interacts with the slow-wave structure through the electron beam, causing the electron beam to decelerate and release energy, thereby exciting high-power coherent electromagnetic radiation. The metamaterial back-wave oscillator comprises the following main components: a metamaterial slow-wave structure: formed by periodically arranging metamaterial units in the direction of electron beam travel, providing a site for energy exchange; a signal output structure (including the coupling cavity and the SMA coaxial output structure): outputting the high-power signal generated by the system; a periodic permanent magnet focusing system, ensuring that the electron beam is not dispersed by the space charge field; and a collecting electrode (multiplexed by the coupling cavity), used to collect the remaining electrons after the interaction.

[0023] like Figure 2As shown, the metamaterial slow-wave structure 1 includes a periodic resonant structure 101, a waveguide shell 102, a first vacuum gap 103, and an electron injection port 104. The periodic resonant structure 101 is disposed on the inner wall of the waveguide shell 102, the first vacuum gap 103 is disposed inside the waveguide shell 102, and the electron injection port 104 is disposed on the left side of the waveguide shell 102. The periodic resonant structure 101 includes multiple periodically arranged metamaterial unit structures, the number of which is adjustable; in this embodiment, there are 12. An electron gun is connected to the electron injection port 104, and electrons are emitted from the opening into the metamaterial slow-wave structure 1. The tail end of the periodic resonant structure 101 is connected to a conductor inside the coupling cavity 2 and extends into the cavity a certain distance to enhance the impedance matching of the coupling cavity 2. By biasing the periodic resonant structure 101 on the inner wall of the waveguide shell 102, the electron injection can avoid the periodic resonant structure 101, thus realizing that the magnetic field generated by the periodic permanent magnet focusing system 3 can produce the same magnetic force on the upper and lower surfaces of the electron beam, reducing the difficulty of magnetic field focusing.

[0024] In this embodiment, the cross-sectional view of the metamaterial slow-wave structure 1 and the dimensions of each structure are as follows: Figure 3 As shown in the figure, the dimensions (unit: mm) are: a =14.5, by =4, ty =2, tz =2.5, ar =5, wl =131, wge =4.5, offs =3, t =1.2, gap =2. Among them, the transverse dimension of the inner cavity of the metamaterial slow-wave structure 1 is... a × a . bx The height of the cathode inlet (electron injection port 104) for emitting electron beams ty and tz These represent the thicknesses of the cavity walls of the metamaterial slow-wave structure 1 in the vertical and horizontal planes, respectively. ar The distance between the periodic resonant structure 101 and the cathode inlet. offs The distance between the periodic resonant structure 101 and the center of the electron beam (i.e., the position where the periodic resonant structure 101 is biased on the inner wall of the waveguide housing 102). gap The distance between the periodic resonant structure 101 and the upper surface of the electron beam is denoted as ... t The thickness of the periodic resonant structure 101 is given. wl The cavity length of the slow-wave structure 1 in the metamaterial is given. wge The length of the periodic resonant structure 101 extending into the coupling cavity 2. Figure 4(a) is a schematic diagram of the periodic resonant structure 101 composed of periodic arrangements of metamaterial unit structures in this embodiment. Figure 4 (b) is a schematic diagram of the metamaterial unit structure used in this embodiment.

[0025] One end of the coupling cavity 2 is connected to the metamaterial slow-wave structure 1, and the other end is connected to the coaxial output interface (Sub-Miniatureversion A, SMA) 4. The coaxial output interface 4 includes an interface housing 403, a dielectric layer 402 disposed within the interface housing 403, and an interface probe 401 disposed within the dielectric layer. The coupling cavity 2 includes a coupling cavity housing 201, an inner conductor, and a second vacuum gap 205. The inner conductor is disposed inside the coupling cavity housing 201 and includes a first inner conductor segment 202, a second inner conductor segment 203, and a third inner conductor segment 204. The first inner conductor segment 202 is connected to the periodic resonant structure 101, and the third inner conductor segment 204 is connected to the interface probe 401 of the coaxial output interface 4 for signal output. The second inner conductor segment 203 is disposed between the first inner conductor segment 202 and the third inner conductor segment 204, and the radius of the second inner conductor segment 203 is slightly larger than that of the first inner conductor segment 202 and the third inner conductor segment 204, which allows for impedance matching adjustment of the signal output structure and facilitates assembly. The first vacuum gap 103 is connected to the second vacuum gap 205. One end of the coupling cavity housing 201 is connected to the waveguide housing 102, and the other end is connected to the interface housing 403 of the coaxial output interface 4.

[0026] The cross-sectional view of the coupling cavity 2 and the coaxial output interface 4 in this embodiment, as well as the dimensions of each structure, are shown below. Figure 5 As shown in the figure, the dimensions (unit: mm) are: li1 =33, li2 =10, el =52.5, ri1 =0.8, lo =4, ro =2.1, ri =0.6, t =2. Wherein, the internal dimensions of coupling cavity 2 are... ea × ea ×e l . l The total length of the cavity. li1 The length of the first segment 202 of the inner conductor. li2 The length is the sum of the lengths of the first segment 202 and the second segment 203 of the inner conductor. ri1 The radius of the second segment 203 of the inner conductor. ri The radii of the first inner conductor segment 202, the third inner conductor segment 204, and the interface probe 401 are given. lo The length of coaxial output interface 4. roThe radius of the dielectric layer 402 inside the coaxial output interface 4. t The thickness of the interface housing 403 for the coaxial output interface 4 is 403.

[0027] like Figure 6 As shown, the periodic magnetic focusing (PMF) system 3 includes a first permanent magnetic focusing structure disposed above the metamaterial slow wave structure 1 and a second permanent magnetic focusing structure disposed below the metamaterial slow wave structure 1. The metamaterial slow wave structure 1 is disposed between the first permanent magnetic focusing structure and the second permanent magnetic focusing structure, and the first permanent magnetic focusing structure and the second permanent magnetic focusing structure are asymmetrically disposed.

[0028] Both the first and second permanent magnet focusing structures include a fourth iron pole piece 304. A second iron pole piece 302 is positioned opposite each other on the right side of the fourth iron pole piece 304. A first iron pole piece 301 and a third iron pole piece 303 are arranged in a periodically alternating pattern between the second iron pole pieces 302. Iron pole piece spacers 307 are provided below the first and third iron pole pieces 301 in the first permanent magnet focusing structure, and above the first and third iron pole pieces 301 in the second permanent magnet focusing structure. Multiple cavities are formed between the first, second, third, and fourth iron pole pieces 304. A central magnet 305 is placed in each cavity. Periodically arranged edge magnets 306 are arranged on the outer front and rear sides of the second iron pole pieces 302, thereby generating a periodic magnetic field to control the focusing of electrons. The third iron pole piece 303 passes through the second iron pole piece 302 to limit the movement of the edge magnets 306. The edge magnets 306 in the first and second permanent magnet focusing structures are asymmetrically arranged. The lateral dimension of the edge magnets 306 in the first permanent magnet focusing structure is smaller than that in the second permanent magnet focusing structure. This is used to generate an asymmetrical magnetic field to counteract the interference magnetic field generated by the periodic resonant structure 101, facilitating better energy exchange of the electron beam. The period of each structure and the magnetic field strength of each material in the periodic permanent magnet focusing system 3 can be adjusted as needed to control the focusing position and degree of electrons. In this embodiment, the first iron pole shoe 301, the third iron pole shoe 303, the second iron pole shoe 302, and the fourth iron pole shoe 304 in the first and second permanent magnet focusing structures form 15 periods, the central magnet 305 has 14 periods, and the edge magnets 306 have 7 periods. Furthermore, the magnetic field strength of the first and last central magnets 305 is different, which facilitates focusing during the initial and final stages of electron beam energy exchange.

[0029] In this embodiment, the cross-sectional view of the periodic permanent magnet focusing system and the dimensions of each structure are as follows: Figure 7 As shown in the figure, the dimensions (unit: mm) are: y1 =15.5,z1 =2.5, tz =4, y =15, iz =1, mz1 =8, my1 =15, mz2 =17, my2 =15.5, gz =126, ty =0.5, x =30, x1 =38, gx =1, xt =1.5, xb =3. Among them, the dimensions of the fourth iron pole shoe 304 on the far left are: x1 × y1 × z1 The dimensions of the first iron pole shoe 301 are x × my1 × iz The dimensions of the third iron pole shoe 303 are gx × y × gz The dimensions of the second iron pole shoe 302 are xt × y × iz The dimensions of the 307 iron pole shoe gasket are x × ty × tz The dimensions of the upper and lower center magnets 305 are as follows: x × my1 × mz1 The dimensions of the edge magnet 306 on the outer side of the first permanent magnet focusing structure are: xt × my2 × mz2 The dimensions of the edge magnet 306 on the outer side of the second permanent magnet focusing structure are as follows: xb × my2 × mz2 The distance from the first central magnet 305 on the left to the last first iron pole piece 301 is... gz .

[0030] The miniaturization advantage of this embodiment lies in the fact that the size of the metamaterial slow-wave structure 1 is on the subwavelength order, smaller than that of traditional slow-wave structures. The coupling cavity 2 can be reused as a collector, eliminating the need for an additional collector and further reducing the device size. Compared to other metamaterial backwave oscillators that place the periodic resonant structure in the center of the waveguide and the electron injection port at the bottom, this embodiment shifts the bias of the periodic resonant structure 1 upwards and places the electron injection port 104 in the center of the metamaterial waveguide. This allows the upper and lower surfaces of the electron injection port to obtain the same focusing magnetic field under the focusing of the periodic permanent magnet system. Because of this, this application can employ the periodic permanent magnet focusing system 3, thus achieving a miniaturization advantage. By introducing the periodic permanent magnet focusing system 3, the disadvantage of a large focusing system size caused by using a solenoid is solved. By periodically arranging the magnets and iron pole shoes and adjusting the relevant parameters of the periodic permanent magnet focusing system 3, a magnetic field for focusing electrons can be generated, while also achieving the goal of reducing the system size. Furthermore, the periodic permanent magnet focusing system 3 employs an asymmetric design to generate an asymmetric focusing magnetic field, which balances and cancels the asymmetric space charge field on the electron beam surface caused by the periodic resonant structure, facilitating better focusing of the electron beam. Finally, the high-power signal coupled by the coupling cavity 2 is output through the SMA coaxial output interface 4.

[0031] In summary, the backward-wave oscillator shown in this application embodiment uses a metamaterial slow-wave structure 1. Based on the subwavelength characteristics of the metamaterial, the slow-wave structure of the backward-wave oscillator is miniaturized. A periodic permanent magnet focusing system 3 is also introduced. Compared to traditional solenoid focusing systems, this avoids the use of large-sized solenoids, reduces the system size, and enhances the overall system integrity. Furthermore, the upper and lower outer edge magnets 306 are asymmetrically arranged to generate an asymmetrical magnetic field to balance and counteract the asymmetrical space charge field on the upper and lower surfaces of the electron beam caused by the periodic resonant structure 101, facilitating better focusing of the electron beam. Figure 8 As shown, the miniaturized periodic permanent magnet focusing metamaterial backward wave oscillator proposed in this application realizes the focusing of the electron beam through simulation.

[0032] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. A miniaturized metamaterial backward wave oscillator with periodic permanent magnet focusing, characterized in that, It includes a metamaterial slow-wave structure (1), a coupling cavity (2), a periodic permanent magnet focusing system (3), and a coaxial output interface (4). The metamaterial slow wave structure (1) includes a waveguide shell (102), a periodic resonant structure (101) and a first vacuum gap (103) are provided inside the waveguide shell (102), and the periodic resonant structure (101) is biased on the inner wall of the waveguide shell (102); The coupling cavity (2) is connected at one end to the metamaterial slow wave structure (1) and at the other end to the coaxial output interface (4). The coupling cavity (2) includes a coupling cavity shell (201). The coupling cavity shell (201) is provided with a coupling cavity inner conductor and a second vacuum gap (205). The coupling cavity inner conductor includes an inner conductor first segment (202), an inner conductor second segment (203) and an inner conductor third segment (204). The inner conductor first segment (202) is connected to the periodic resonant structure (101), and the inner conductor third segment (204) is connected to the coaxial output interface (4). The first vacuum gap (103) is connected to the second vacuum gap (205). One end of the coupling cavity shell (201) is connected to the waveguide shell (102), and the other end is connected to the interface shell (403). The periodic permanent magnet focusing system (3) includes a first permanent magnet focusing structure and a second permanent magnet focusing structure arranged asymmetrically at the top and bottom. A metamaterial slow wave structure (1) is arranged between the first permanent magnet focusing structure and the second permanent magnet focusing structure. The lateral dimension of the edge magnet (306) in the first permanent magnet focusing structure is smaller than the lateral dimension of the edge magnet (306) in the second permanent magnet focusing structure.

2. The miniaturized metamaterial backward wave oscillator with periodic permanent magnet focusing according to claim 1, characterized in that, The coaxial output interface (4) includes an interface housing (403), a dielectric layer (402) is provided inside the interface housing (403), an interface probe (401) is provided inside the dielectric layer, and the interface probe (401) is connected to the third segment (204) of the inner conductor.

3. The miniaturized periodic permanent magnet focused metamaterial backward wave oscillator according to claim 2, characterized in that, The metamaterial slow wave structure (1) has an electron injection port (104) at one end for connecting an external electron gun.

4. The miniaturized metamaterial backward wave oscillator with periodic permanent magnet focusing according to claim 3, characterized in that, The periodic resonant structure (101) comprises multiple metamaterial unit structures arranged periodically.

5. The miniaturized metamaterial backward wave oscillator with periodic permanent magnet focusing according to claim 4, characterized in that, The radius of the second segment (203) of the inner conductor is greater than that of the first segment (202) and the third segment (204) of the inner conductor.

6. The miniaturized metamaterial backward-wave oscillator with periodic permanent magnet focusing according to claim 5, characterized in that, Both the first permanent magnet focusing structure and the second permanent magnet focusing structure include a fourth iron pole shoe (304). The second iron pole shoe (302) is arranged opposite to the side of the fourth iron pole shoe (304). The first iron pole shoe (301) and the third iron pole shoe (303) are arranged alternately in a periodic manner between the second iron pole shoes (302). Iron pole shoe pads (307) are arranged below the first iron pole shoe (301) and below the third iron pole shoe (303) in the first permanent magnet focusing structure, and above the first iron pole shoe (301) and above the third iron pole shoe (303) in the second permanent magnet focusing structure.

7. The miniaturized metamaterial backward wave oscillator with periodic permanent magnet focusing according to claim 6, characterized in that, Multiple cavities are formed between the first iron pole piece (301), the second iron pole piece (302), the third iron pole piece (303) and the fourth iron pole piece (304), and a central magnet (305) is provided in the cavity. A periodically arranged edge magnet (306) is provided on the outside of the second iron pole piece (302).

Images