Coaxial relativistic magnetron outputting TEM mode

Abstract

The application relates to a coaxial relativistic magnetron outputting TEM modes, belonging to the technical field of high-power microwaves, which comprises an anode, a cathode and a magnet, the anode comprises an inner cavity cylinder and an outer cavity cylinder which are coaxially nested, long anode blocks and short anode blocks are alternately arranged on the inner wall of the inner cavity cylinder in the angular direction, the long anode blocks and the short anode blocks are alternately distributed in the axial direction of the inner cavity cylinder to form symmetrical sector edge cavities inside the inner cavity cylinder, an edge cavity angular coupling slot is arranged on the inner cavity cylinder and corresponds to the sector edge cavities, and an inner cavity axial coupling slot is arranged on the inner cavity cylinder and located between the long anode blocks and the short anode blocks, the application has the advantages of simple and compact structure, suitable permanent magnet packaging and low-order mode output, and can realize high-power and high-efficiency microwave output.

Description

A coaxial relativistic magnetron that outputs TEM mode Technical Field

[0001] This invention belongs to the field of high-power microwave technology, and specifically relates to a coaxial relativistic magnetron that outputs a TEM mode. Background Technology

[0002] High-power microwaves (HPM) refer to electromagnetic waves with peak power greater than 100 MW and frequencies between 300 MHz and 300 GHz. It is an interdisciplinary research field that has developed since the 1970s along with advancements in pulsed power technology, relativistic electronics, and plasma physics. Currently, high-power microwaves have wide applications in satellites, radar, and high-energy electron radio frequency accelerators.

[0003] High-power microwave sources are devices that utilize relativistic electron beams to generate high-power microwave radiation and are one of the key components in high-power microwave systems. Among them, the relativistic magnetron (RM) has advantages such as simple structure, low operating magnetic field, and the ability to operate with high power and repetitive pulses, making it one of the most practically valuable miniaturized high-power microwave sources. Current research on relativistic magnetrons focuses on improving power, conversion efficiency, reducing the overall system size and weight, and achieving miniaturized designs. The relativistic magnetron is essentially an extension of the conventional magnetron to a high-current electron beam. To generate such a large current, a relativistic high voltage is required. The main difference between it and the conventional magnetron, besides the higher voltage and current, is the replacement of the hot cathode in the conventional magnetron with a field emission cold cathode. Furthermore, the electron motion in the relativistic magnetron must take relativistic effects into account. Due to its high voltage and high current characteristics, relativistic magnetrons are generally designed between the P and C bands to prevent arcing and breakdown.

[0004] The coaxial magnetron is developed based on the conventional magnetron. Compared to the conventional magnetron, it adds a coaxial resonant cavity (usually called the outer cavity) outside the general magnetron resonant cavity (usually called the inner cavity in the coaxial magnetron). The inner cavity cylinder has a coupling slit at every small cavity, which couples the inner and outer cavities together. Therefore, the coaxial magnetron resonant cavity is a composite cavity, with most of its energy stored in the outer cavity, which is beneficial for increasing the overall power capacity of the tube. However, the π mode in the inner cavity and the TE011 mode in the outer cavity of the coaxial magnetron are tightly coupled. The TE011 mode is a higher-order mode, and the outer cavity is relatively large, typically designed in the C~Ku band, with the number of cavities in the inner cavity mostly between 20 and 40. Therefore, if the traditional coaxial magnetron is directly extrapolated to relativistic conditions, problems arise such as the inapplicability of microwave output methods and difficulties in microwave extraction; furthermore, magnet design is difficult, and miniaturization is challenging.

[0005] In 2006, Greenwood and Hoff et al. proposed a full-cavity extraction relativistic magnetron. This structure features axial slots on the outer walls of all resonant cavities for radial energy output, with adjacent resonant cavities symmetrically coupled to a sector-shaped output waveguide along the centerline. When the magnetron operates in π-mode, the TE11 mode is excited within the sector-shaped output waveguide and propagates axially. This structure is periodically symmetrical, exhibits good mode stability, and high conversion efficiency. While similar to a coaxial magnetron, the external sector-shaped waveguide in this structure only serves as an energy extraction channel and does not store energy. Therefore, it cannot fully utilize the external cavity's energy storage capabilities to increase power capacity, unlike a traditional coaxial magnetron. Summary of the Invention

[0006] A coaxial relativistic magnetron with output TEM mode is proposed, which improves the overall power capacity of the tube by setting a coaxial external cavity.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] A coaxial relativistic magnetron for outputting a TEM mode includes an anode, a cathode, and a magnet. The anode comprises an inner cavity cylinder and an outer cavity cylinder coaxially nested together. Long anode blocks and short anode blocks are alternately arranged along the angular direction on the inner wall of the inner cavity cylinder. The long anode blocks and the short anode blocks are distributed alternately in length along the axial direction of the inner cavity cylinder to form a symmetrical fan-shaped side cavity inside the inner cavity cylinder. An angular coupling seam is provided on the inner cavity cylinder corresponding to the fan-shaped side cavity, and the angular coupling seam extends along the angular direction of the inner cavity cylinder. An axial coupling seam is provided on the inner cavity cylinder between the long anode blocks and the short anode blocks, and the axial coupling seam extends along the axial direction of the inner cavity cylinder.

[0009] The technical solution is further configured such that there are N long anode blocks and N short anode blocks, where N is a positive integer not less than 2. A gap is provided between adjacent long anode blocks and short anode blocks to form a resonant cavity. The number of resonant cavities is twice the number of long anode blocks, and all resonant cavities participate in the full cavity coupling extraction of microwave energy.

[0010] The technical solution is further configured such that a gap is provided between the inner cavity cylinder and the outer cavity cylinder to form an outer cavity, and the outer cavity is located on the periphery of the long anode block.

[0011] The technical solution is further configured such that a short road surface is connected between one end of the outer cavity cylinder and the inner cavity cylinder, and the other end is connected to an output waveguide coaxial with it. The short road surface and the output waveguide are located on different sides of the long anode block.

[0012] The technical solution is further configured such that the outer conductor of the output waveguide is connected to the outer cavity cylinder, and the inner conductor of the output waveguide is connected to the inner cavity cylinder.

[0013] The technical solution is further configured such that the angle of the angular coupling seam of the side cavity is less than or equal to the angle of the sector-shaped side cavity in which it is located.

[0014] The technical solution is further configured such that the number of the fan-shaped side cavities is twice the number of the short anode blocks.

[0015] The technical solution is further configured such that the axial length of the axial coupling seam in the inner cavity is less than the axial length of the short anode block.

[0016] This technical solution is further configured such that, when the coaxial relativistic magnetron operates in π mode, the magnetic fields of adjacent resonant cavities have a 180° phase difference. The axial coupling slot in the inner cavity magnetically couples the adjacent out-of-phase axial magnetic fields of the resonant cavity, coupling a pair of degenerate TEn1 modes in the outer cavity. The outer cavity cuts off the TEn1 modes, and the TEn1 modes achieve coaxial energy storage in the outer cavity. There are in-phase angular magnetic fields in the same-side fan-shaped side cavity, which couple out the TEM mode in the outer cavity through the side cavity angular coupling slot. The coaxial TEM mode is not cut off, realizing energy extraction.

[0017] The technical solution is further configured such that the magnet is a permanent magnet, an electromagnet, or a combination of both, and the inner radius of the magnet is not less than the outer radius of the outer cavity cylinder.

[0018] The beneficial effects of this invention are:

[0019] An axial coupling seam connects the inner and outer cavities, enabling energy storage in the outer cavity, effectively reducing the electric field strength in the inner cavity and increasing power capacity. An angular coupling seam is used on the side cavity to couple the output coaxial TEM mode, ensuring that the angular periodic symmetry of the resonant cavity is almost unaffected by the output structure. The overall structure is uniquely designed, with functional partitions for the inner cavity resonant system, the outer cavity energy storage system, and the coaxial output system, ensuring that they do not interfere with each other. The structure is compact and facilitates miniaturization. Attached Figure Description

[0020] Figure 1 is an axial view of the coaxial relativistic magnetron that outputs the TEM mode in an embodiment of the present invention;

[0021] Figure 2 is a side view of the coaxial relativistic magnetron that outputs the TEM mode in an embodiment of the present invention;

[0022] Figure 3 is a cross-sectional view of AA in Figure 2;

[0023] Figure 4 is a cross-sectional view of BB in Figure 3;

[0024] Figure 5 is a cross-sectional view of CC in Figure 3;

[0025] Figure 6 is a cross-sectional diagram of the electric field of the coaxial relativistic magnetron outputting the TEM mode in an embodiment of the present invention;

[0026] Figure 7 is a diagram showing the electric field distribution at the output port of the coaxial relativistic magnetron in an embodiment of the present invention, which outputs the TEM mode.

[0027] Figure 8 is a diagram of the total output power signal of the coaxial relativistic magnetron in the output TEM mode in an embodiment of the present invention.

[0028] Figure 9 is a microwave spectrum of the coaxial relativistic magnetron output TEM mode in an embodiment of the present invention.

[0029] In the attached diagram: 1. Long anode block; 2. Short anode block; 3. Inner cavity cylinder; 4. Outer cavity cylinder; 5. Inner cavity axial coupling seam; 6. Side cavity angular coupling seam; 7. Output waveguide; 8. Cathode; 9. Magnet; 10. Resonant cavity; 11. Short road surface; 12. Fan-shaped side cavity. Detailed Implementation

[0030] To enable those skilled in the art to better understand the technical solutions of the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings. Based on the embodiments in this application, other similar embodiments obtained by those skilled in the art without creative effort should all fall within the scope of protection of this application. Furthermore, directional terms mentioned in the following embodiments, such as "up," "down," "left," and "right," are only for reference to the directions in the accompanying drawings; therefore, the directional terms used are for illustrative purposes and not for limiting the invention.

[0031] According to an embodiment of the present invention, a coaxial relativistic magnetron with output TEM mode is provided, as shown in Figures 1 to 5, including an anode, a cathode 8 and a magnet 9, wherein the anode includes a long anode block 1, a short anode block 2, an inner cavity cylinder 3, an outer cavity cylinder 4, an inner cavity axial coupling slit 5, a side cavity angular coupling slit 6 and an output waveguide 7.

[0032] Optionally, the inner cavity cylinder 3 and the outer cavity cylinder 4 are coaxially nested. The long anode block 1 and the short anode block 2 are alternately arranged around the inner wall of the inner cavity cylinder 3 along the angular direction. The long anode block 1 and the short anode block 2 are distributed alternately in length along the axial direction of the inner cavity cylinder 3 to form a symmetrical fan-shaped side cavity 12 inside the inner cavity cylinder 3.

[0033] It is understood that the end of the short anode block 2, the adjacent long anode block 1, and the inner cavity cylinder 3 together constitute the fan-shaped side cavity 12. The design of the double-sided symmetrical fan-shaped side cavity 12 ensures the angular symmetry of energy extraction, effectively suppresses non-π mode oscillations that may be caused by structural asymmetry, and enables the device to work stably in the designed π mode.

[0034] Optionally, the angular coupling seam 6 is located on the inner cavity cylinder 3 and corresponds to the fan-shaped side cavity 12. The angular coupling seam 6 extends along the inner cavity cylinder 3 in the angular direction. That is, the angular coupling seam 6 is located on the outer wall (inner cavity cylinder 3) of the fan-shaped side cavity 12.

[0035] It is understandable that when the magnetron operates in π mode, a magnetic field distribution dominated by angular magnetic fields will exist within the fan-shaped cavity 12 formed by the short anode block 2 and the adjacent long anode block 1. Directly opening the angular coupling slot 6 on the outer wall of the fan-shaped cavity 12—the region with the strongest magnetic field—and extending it angularly, means that the orientation of the coupling slot is optimally matched with the direction of the magnetic field. This arrangement achieves highly efficient magnetic coupling. The angularly extending slot cuts through the outer wall current, exciting high-frequency currents and electric fields at the slot, which in turn excite electromagnetic waves in the outer cavity. Since the angular magnetic fields of all the fan-shaped cavities 12 on one side of the short anode block 2 are in phase, the energy coupled through all the angular coupling slots 6 is also in phase. The superposition of these in-phase energies directly excites a coaxial TEM mode with a matched field distribution. Since the angular magnetic fields on both sides of the short anode block 2 are out of phase, a pair of out-of-phase TEM modes are excited. However, the axial distances on both sides differ by half a wavelength, resulting in spatial phase inversion, which precisely cancels out the effect of the out-of-phase angular magnetic fields. This "in-situ, in-phase" coupling method avoids complex mode switching, significantly reduces energy loss, and thus improves the overall conversion efficiency of the device. Furthermore, the cavity corner coupling slot 6 achieves magnetic coupling, and the electric field strength in the slot region is relatively low, making it less prone to breakdown. This design allows energy to be uniformly and distributedly extracted from the interaction region to the output waveguide 7 through multiple cavity corner coupling slots 6, avoiding the problem of excessively high power density caused by single-point or localized concentrated extraction. This significantly improves the power handling capability (i.e., power capacity) of the entire output structure, enabling the device to operate reliably at higher power levels.

[0036] It should be noted that the interaction region refers to the annular vacuum region jointly enclosed by the cathode 8, the long anode block 1, and the short anode block 2. It is the core region for the conversion of electron beam kinetic energy into microwave energy.

[0037] In a coaxial relativistic magnetron with an output TEM mode in this embodiment, as shown in Figures 1 to 5, there are N long anode blocks 1 and N short anode blocks 2, where N is a positive integer not less than 2. A gap is provided between adjacent long anode blocks 1 and short anode blocks 2 to form a resonant cavity 10. The number of resonant cavities 10 is twice the number of long anode blocks 1, and all resonant cavities 10 participate in the full cavity coupling extraction of microwave energy.

[0038] Understandably, full-cavity coupling means that the microwave energy generated by each resonant cavity 10 can be effectively coupled and output, realizing the in-phase superposition and power synthesis of the energy of all resonant cavities 10. At the same time, the participation of all resonant cavities 10 in extraction means that the energy is transferred out uniformly and symmetrically from the entire circumference. This design maintains the angular periodic symmetry of the electromagnetic field in the interaction region and eliminates disturbances caused by uneven extraction.

[0039] In a coaxial relativistic magnetron with an output TEM mode in this embodiment, as shown in Figures 1 to 5, a gap is provided between the inner cavity cylinder 3 and the outer cavity cylinder 4 to form an outer cavity, which is located on the periphery of the long anode block 1.

[0040] It is understandable that the internal space of the inner cylinder 3 serves as the inner cavity. By designing the radial dimension (i.e., the gap width) of the outer cavity, it can be made to cut off the TEn1 mode coupled from the inner cavity through the axial coupling seam 5. Due to the cutoff effect, microwave energy cannot dissipate rapidly and is "trapped" in the outer cavity, forming a strong electromagnetic standing wave, thus achieving energy storage. This results in some energy being stored in the relatively large outer cavity, rather than in the highly concentrated inner cavity interaction region. At the same time, the outer cavity is located on the periphery of the long anode block 1 and surrounds the entire interaction region, providing a uniform physical space and electromagnetic environment for opening the angular coupling seam 6 and achieving symmetrical coupling. In other words, since the angular magnetic fields on both sides of the short anode block 2 are out of phase, they excite a pair of out-of-phase TEM modes. However, the axial distances on both sides differ by half a wavelength, and the spatial phase is out of phase, which cancels out the effect of the out-of-phase angular magnetic fields. This ensures that they do not conflict in the output waveguide 7, but are superimposed in phase, thus enhancing the output power.

[0041] In a coaxial relativistic magnetron with an output TEM mode in this embodiment, as shown in Figures 1 to 5, one end of the outer cavity cylinder 4 is connected to the inner cavity cylinder 3 via a short road surface 11, and the other end is connected to an output waveguide 7 coaxial with it. The short road surface 11 and the output waveguide 7 are located on different sides of the long anode block 1.

[0042] It is understandable that a short-circuit surface 11 is set at the left end of the outer cavity to form a total reflection boundary. When microwave energy is coupled from the interaction region to the outer cavity, the wave propagating to the left will be completely reflected back into the cavity when it encounters the short-circuit surface 11.

[0043] Optionally, the outer conductor of the output waveguide 7 is connected to the outer cavity cylinder 4, and the inner conductor of the output waveguide 7 is equal to the inner cavity cylinder 3. Preferably, the radius of the outer conductor of the output waveguide 7 is equal to the radius of the outer cavity cylinder 4, and the radius of the inner conductor of the output waveguide 7 is equal to the radius of the inner cavity cylinder 3. This means that the radii of the inner and outer conductors are continuous and consistent from the outer cavity to the output waveguide 7, without any abrupt changes, which ensures that the characteristic impedance of the transmission line is continuous, thus achieving perfect impedance matching.

[0044] It is understood that since the short surface is located to the left of the long anode block 1, the portion of the inner cavity cylinder 3 located to the right of the long anode block 1 serves as the inner conductor of the output waveguide 7, and the portion of the outer cavity cylinder 4 located to the right of the outer cavity serves as the outer conductor of the output waveguide 7. In other words, the inner and outer conductors of the output waveguide 7 are directly derived axially from the inner and outer conductors of the outer cavity, reusing the cavity structure. This not only simplifies the structure and reduces connection points and potential energy losses, but more importantly, it ensures the continuity of the electromagnetic field distribution, making the transition from the outer cavity energy storage mode to the output transmission mode very smooth. Simultaneously, the defined boundary conditions formed by the short surface, together with the matched output to its right, define the resonant characteristics of the outer cavity, giving the system a high Q value (quality factor) and stabilizing the oscillation frequency. Integrating energy storage, frequency stabilization, and output functions into a compact axial structure eliminates the need for additional mode converters or transition structures, greatly simplifying the overall design and facilitating system miniaturization.

[0045] In a coaxial relativistic magnetron with an output TEM mode in this embodiment, as shown in Figures 1 to 5, the number of the sector-shaped side cavities 12 is twice the number of the short anode blocks 2, that is, the number of the side cavity angular coupling slots 6 is twice the number of the short anode blocks 2; the opening angle of the side cavity angular coupling slot 6 is less than or equal to the opening angle of the sector-shaped side cavity 12 in which it is located, and the axial length of the side cavity angular coupling slot 6 is greater than, less than or equal to the axial length of the sector-shaped side cavity 12.

[0046] Understandably, to most effectively couple the magnetic field energy within the sector-shaped side cavities 12, the angular coupling slots 6 cover the region with the strongest magnetic field as much as possible. The dimensions of the angular coupling slots 6 are designed to maximize the magnetic coupling area within the limits allowed by the mechanical structure, thereby improving the efficiency of energy extraction. A one-to-one correspondence between the 2N sector-shaped side cavities 12 and the 2N angular coupling slots 6 ensures that the energy generated by all resonant cavities 10 of the magnetron can be extracted through their adjacent sector-shaped side cavities 12 and angular coupling slots 6.

[0047] In a coaxial relativistic magnetron with an output TEM mode in this embodiment, as shown in Figures 1 to 5, the inner cavity axial coupling seam 5 is located on the inner cavity cylinder 3 and between the long anode block 1 and the short anode block 2. The inner cavity axial coupling seam 5 extends axially along the inner cavity cylinder 3, and the axial length of the inner cavity axial coupling seam 5 is less than the axial length of the short anode block 2.

[0048] It is understandable that a strong axial magnetic field exists within the resonant cavity 10 formed by the gap between the long anode block 1 and the short anode block 2. Placing the axial coupling slot 5 on the inner cavity cylinder 3 between the long anode block 1 and the short anode block 2 means it is directly located in the region of strongest magnetic field within the resonant cavity 10. The axial coupling slot 5 extends axially, matching its orientation with the axial magnetic field direction of the resonant cavity 10, achieving the highest efficiency in magnetic coupling. The axial slot cuts through the wall current, most effectively coupling the energy out of the resonant cavity 10. Since the outer cavity is designed to cut off the TEn1 mode, energy is stored there, significantly reducing the electric field strength in the inner cavity interaction region, thereby greatly improving the overall tube's ability to withstand high power (i.e., power capacity) and avoiding the risk of inner cavity breakdown.

[0049] When the coaxial relativistic magnetron operates in π mode, the magnetic fields of adjacent resonant cavities 10 have a 180° phase difference. The axial coupling slit 5 in the inner cavity magnetically couples the adjacent out-of-phase axial magnetic fields of the resonant cavity 10, coupling a pair of degenerate TEn1 modes in the outer cavity. The outer cavity cuts off the TEn1 modes, and the TEn1 modes achieve coaxial energy storage in the outer cavity. There is an in-phase angular magnetic field in the same-side fan-shaped side cavity 12, which couples out the TEM mode in the outer cavity through the side cavity angular coupling slit 6. Unlike the TE mode, the TEM mode has no cutoff frequency in the coaxial structure. This means that at any frequency, as long as the size of the coaxial structure can guarantee the mechanical strength, the TEM mode can be transmitted without loss, that is, the coaxial TEM mode is not cut off, realizing energy extraction. In other words, there are four magnetic field regions on both sides of the short anode block 2 and at both ends of the axial direction. The axial coupling seam 5 of the inner cavity is responsible for feeding energy from the resonant cavity 10 into the outer cavity for energy storage, and the angular coupling seam 6 of the side cavity is responsible for extracting energy from the outer cavity in the form of TEM mode. This division of labor makes the three major functional modules of inner cavity, outer cavity and output system independent of each other and highly efficient and coordinated, without interfering with each other, so as to achieve more comprehensive magnetic coupling extraction, thereby achieving higher power and efficiency extraction output.

[0050] In a coaxial relativistic magnetron with an output TEM mode in this embodiment, as shown in Figures 1 to 5, the cathode 8 is located on the central axis of the anode, and the emitted electron beam undergoes cycloidal motion in the gap between the cathode and anode. The magnet 9 is configured as a permanent magnet, an electromagnet, or a combination of both. The inner radius of the magnet 9 is not less than the outer radius of the outer cavity cylinder 4, and the magnet 9 provides a static magnetic field for guiding and confining the electron beam.

[0051] Referring to Figures 1 to 9, the structural composition of the coaxial relativistic magnetron outputting the TEM mode in this invention will be illustrated below with specific examples:

[0052] The coaxial relativistic magnetron in this example consists of an anode, a cathode 8, and a magnet 9. The anode is made of non-magnetic stainless steel, titanium alloy, or other materials. The magnet 9 is a permanent magnet made of hard magnetic material or an electromagnetic coil, depending on the actual needs. The cathode 8 is made of non-magnetic stainless steel, titanium alloy, or other materials. As needed, a cathode emitting material is set in a certain area between the cathode end caps to emit electrons. The emitting material can be graphite, velvet, or other materials.

[0053] Specifically, it includes a long anode block 1, a short anode block 2, an inner cavity cylinder 3, an outer cavity cylinder 4, an inner cavity axial coupling seam 5, a side cavity angular coupling seam 6, an output waveguide 7, a cathode 8, and a magnet 9. Three long anode blocks 1 and three short anode blocks 2 alternately surround the cathode 8 along the angular direction and are tightly attached to the inner cavity cylinder 3, forming six resonant cavities 10. The long anode block has an inner radius of 33 mm, an outer radius of 60 mm, an axial length of 100 mm, and an angle of 40°. The short anode block 2 has an inner radius of 33 mm, an outer radius of 60 mm, an axial length of 75 mm, and an angle of 40°. The long anode blocks 1 and short anode blocks 2 are distributed alternately in length, with the left end of the short anode block 2 12.5 mm away from the left end of the long anode block 1. The long anode blocks 1, short anode blocks 2, and inner cavity cylinder 3 together form six fan-shaped side cavities 12 with an angle of 80° at the left and right ends of the short anode blocks 2. The outer cavity cylinder 4 and the inner cavity cylinder 3 are coaxially and concentrically nested, connected together by an inner cavity axial coupling seam 5 and a side cavity angular coupling seam 6. There are six inner cavity axial coupling seams 5, located on the inner cavity cylinder 3 corresponding to the six resonant cavities 10. Each inner cavity axial coupling seam 5 has an inner radius of 60mm, an outer radius of 68mm, an angle of 18°, and an axial length of 60mm. There are also six side cavity angular coupling seams 6, located on the inner cavity cylinder 3 corresponding to the six fan-shaped side cavities 12. Each side cavity angular coupling seam 6 has an inner radius of 60mm, an outer radius of 68mm, an angle of 80°, and an axial length of 12.5mm. The output waveguide 7 is axially and concentrically connected to the outer cavity cylinder 4, with an inner radius of 68mm, an outer radius of 88mm, and a wall thickness of 3mm. A short path is provided to connect the outer cavity cylinder 4 and the inner cavity cylinder 3. The cathode 8 is a transparent cathode, consisting of three parts: a cathode base post, end caps, and three identical metal pillars. The cathode base post is a cylinder with a radius of 15.5 mm and a length of 80 mm; the cathode end caps are two cylinders with a radius of 23.5 mm and a thickness of 20 mm; the three metal pillars all have a sector-shaped cross-section with an inner radius of 10 mm, an outer radius of 15.5 mm, and an included angle of 30°, and are 80 mm long. The magnet 9 can be a permanent magnet, an electromagnetic coil, or a combination of both.

[0054] Figure 6 shows the electric field distribution on the cross-section of the interaction region of the coaxial relativistic magnetron outputting the TEM mode in this embodiment during normal operation (π-mode oscillation). Figure 6 clearly shows that the electric field lines radially point from the inner surfaces of the long anode block 1 and the short anode block 2 towards the central cathode 8. The electric field directions of two adjacent resonant cavities 10 are opposite (i.e., a phase difference of 180 degrees), verifying that the magnetron operates in π mode. Most of the energy is stored in the outer cavity, verifying the external cavity energy storage. Figure 7 shows the electric field distribution of microwave energy at the output waveguide 7 (output port). Figure 7 clearly shows that the electric field lines are radially distributed, pointing from the inner conductor (the extension of the inner cavity cylinder 3) to the outer conductor (the extension of the outer cavity cylinder 4). This is the most fundamental and typical electric field configuration of the coaxial TEM mode (transverse electromagnetic mode). Simultaneously, the electric field distribution across the entire cross-section is very uniform and symmetrical, without any distorted or locally enhanced regions. This indicates that the output mode is very pure, with almost no unnecessary higher-order modes (such as TE or TM modes) doped. This pure and regular TEM mode distribution proves that the design of coupling energy from the external cavity to the output waveguide through the "side cavity angular coupling slot" is extremely successful and efficient.

[0055] The coaxial relativistic magnetron of the output TEM mode under the above-mentioned structural dimensions was calculated using particle simulation software under the conditions of an input voltage of approximately 630 kV and a guiding magnetic field of approximately 0.38 T. The results are shown in Figures 8 and 9. Figure 8 shows the instantaneous output power and average output power as a function of time. The black curve represents the instantaneous output power, showing the instantaneous value of the output power at different time points, while the red curve represents the average output power, reflecting the average value of the output power over a certain time period. As can be seen from the figure, an L-band TEM mode output with a resonant frequency of 1.417 GHz, an output power of 2.02 GW, and a power conversion efficiency of 72.3% was obtained. Figure 9 shows the voltage amplitude within a unit frequency bandwidth, reflecting the density distribution of voltage energy in the frequency domain. The voltage energy is mainly concentrated in the frequency range of approximately 1.3 GHz to 1.5 GHz, while the energy distribution in other frequency ranges is lower. This indicates that under uniform magnetic field conditions, this invention can maintain relatively high output power and beam conversion efficiency, and can be applied to high-power microwave systems with stringent high efficiency requirements.

[0056] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of this application described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0057] Optionally, specific examples in this embodiment can refer to the examples described in the above embodiments, and will not be repeated here.

[0058] The sequence numbers of the embodiments in this application are for descriptive purposes only and do not represent the superiority or inferiority of the embodiments.

[0059] In the above embodiments of this application, the descriptions of each embodiment have different focuses. For parts not described in detail in a certain embodiment, please refer to the relevant descriptions of other embodiments.

[0060] The above description is only a preferred embodiment of this application. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of this application, and these improvements and modifications should also be considered within the scope of protection of this application.

Claims

1. A coaxial relativistic magnetron outputting a TEM mode, comprising an anode, a cathode, and a magnet, characterized in that, The anode comprises an inner cavity cylinder and an outer cavity cylinder coaxially nested together. Long anode blocks and short anode blocks are alternately arranged along the angular direction on the inner wall of the inner cavity cylinder. The long and short anode blocks are distributed alternately in length along the axial direction of the inner cavity cylinder to form a symmetrical fan-shaped side cavity inside the inner cavity cylinder. An angular coupling seam is provided on the inner cavity cylinder corresponding to the fan-shaped side cavity, extending along the angular direction of the inner cavity cylinder. An axial coupling seam is provided on the inner cavity cylinder between the long and short anode blocks, extending along the axial direction of the inner cavity cylinder. Adjacent long and short anode blocks are coupled together. A resonant cavity is formed by a gap, and an outer cavity is formed by a gap between the inner and outer cylinders. The number of sector-shaped side cavities is twice the number of short anode blocks. When the coaxial relativistic magnetron operates in π mode, the magnetic fields of adjacent resonant cavities have a 180° phase difference. The axial coupling seam in the inner cavity magnetically couples the adjacent out-of-phase axial magnetic fields of the resonant cavity, coupling a pair of degenerate TEn1 modes in the outer cavity. The outer cavity cuts off the TEn1 modes, and the TEn1 modes achieve coaxial energy storage in the outer cavity. There are in-phase angular magnetic fields in the same-side sector-shaped side cavities, which couple out TEM modes in the outer cavity through the angular coupling seams of the side cavities. The coaxial TEM modes are not cut off, realizing energy extraction.

2. A coaxial relativistic magnetron for outputting a TEM mode according to claim 1, characterized in that, Both the long anode block and the short anode block are provided in N, where N is a positive integer not less than 2. The number of resonant cavities is twice the number of long anode blocks, and all resonant cavities participate in the full-cavity coupling extraction of microwave energy.

3. A coaxial relativistic magnetron for outputting a TEM mode according to claim 2, characterized in that, The outer cavity is located on the periphery of the long anode block.

4. A coaxial relativistic magnetron for outputting a TEM mode according to claim 1, characterized in that, One end of the outer cavity cylinder is connected to the inner cavity cylinder by a short road surface, and the other end is connected to an output waveguide coaxial with it. The short road surface and the output waveguide are located on different sides of the long anode block.

5. A coaxial relativistic magnetron for outputting a TEM mode according to claim 4, characterized in that, The outer conductor of the output waveguide is connected to the outer cavity cylinder, and the inner conductor of the output waveguide is connected to the inner cavity cylinder.

6. A coaxial relativistic magnetron for outputting a TEM mode according to claim 1, characterized in that, The angle of the angular coupling seam of the cavity is less than or equal to the angle of the sector-shaped cavity in which it is located.

7. A coaxial relativistic magnetron for outputting a TEM mode according to claim 1, characterized in that, The axial length of the axial coupling seam in the inner cavity is less than the axial length of the short anode block.

8. A coaxial relativistic magnetron for outputting a TEM mode according to claim 1, characterized in that, The magnet is configured as a permanent magnet, an electromagnet, or a combination of both, and the inner radius of the magnet is not less than the outer radius of the outer cavity cylinder.

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