Slow-wave structure and backward wave oscillator

Abstract

This application relates to a slow-wave structure and a backward-wave oscillator. The slow-wave structure includes a periodic waveguide; the periodic waveguide includes a first structure and a second structure arranged oppositely, wherein, in a first direction, the end faces of the first structure and the second structure arranged oppositely are end faces with periodically varying undulations, the projections of the peak portions of the first structure and the second structure in the first direction coincide, and the distance between the peak portion of the first structure and the peak portion of the second structure is a minimum value. Injection channels are formed at the trough portion of the first structure and the peak portion of the second structure, and the injection channels communicate with each other in the first direction to form an electron beam channel. Using this slow-wave structure can provide a larger working current and improve the interaction coupling impedance, thereby enhancing the output performance of the backward-wave oscillator.

Description

Technical Field

[0001] This application relates to the field of vacuum electron technology, and particularly to a slow-wave structure and a backward-wave oscillator. Background Art

[0002] The frequency of terahertz waves is between the infrared band and the microwave band, with a frequency range of 0.1 - 10 THz (wavelength in 0.03 - 3 mm). Electromagnetic waves in this frequency range have important research value and broad application prospects in the fields of high-speed space communication, ultra-high-resolution weapon guidance, medical imaging, terahertz spectral feature analysis of substances, security inspection, material detection, etc.

[0003] The backward-wave oscillator operates in the terahertz band and can quickly achieve tuning of the operating frequency point within a wide frequency range by adjusting the synchronization voltage. The operation of the backward-wave oscillator does not require an additional excitation signal. Just by injecting a high-energy electron beam through an electron gun, a stable output signal can be generated through self-excited oscillation in the slow-wave structure. It has a high output power and can operate at room temperature.

[0004] There is a problem of conductivity loss in the slow-wave structure of existing backward-wave oscillators, and it will increase rapidly with the increase of the operating frequency. And the slow-wave structure with small loss has a problem of small coupling impedance, resulting in defects such as low output power, low gain, and low interaction efficiency. Summary of the Invention

[0005] Based on this, in view of the above technical problems, it is necessary to provide a slow-wave structure and a backward-wave oscillator with small conductivity loss and large coupling impedance.

[0006] To achieve the above object and other objects, in a first aspect, a slow-wave structure is provided, including a periodic waveguide; the periodic waveguide includes a first structure and a second structure arranged oppositely, wherein,

[0007] In a first direction, the end faces of the first structure and the second structure arranged oppositely are end faces with periodically varying undulations. The projections of the peak portions of the first structure and the peak portions of the second structure in the first direction coincide, and the distance between the peak portion of the first structure and the peak portion of the second structure is a minimum value. Injection channels are provided at the trough portion of the first structure and the peak portion of the second structure, and the injection channels communicate with each other in the first direction to form an electron beam channel.

[0008] In one embodiment, it includes a plurality of the periodic waveguides, and the periodic waveguides are arranged along a second direction, and the distances between the periodic waveguides are the same.

[0009] In one embodiment, the end face of the first structure has the same shape, the same fluctuation amplitude, and the same fluctuation period as the end face of the second structure.

[0010] In one embodiment, the distance between the peak portions of the first structure and the peak portions of the second structure is equal to twice the fluctuation amplitude.

[0011] In one embodiment, the distance between the peak portions of the first structure and the peak portions of the second structure is less than twice the fluctuation amplitude.

[0012] In one embodiment, the injection channels are coaxially arranged in the first direction to form the electron beam channel.

[0013] In one embodiment, the shape of the injection channel in the cross-sectional plane is circular, and the injection channels communicate with each other to form a circular electron beam channel; wherein, the cross-sectional plane is a plane perpendicular to the first direction.

[0014] In one embodiment, the diameter of the circular electron beam channel is less than or equal to the width of the periodic waveguide.

[0015] In one embodiment, the end face with periodically varying fluctuations includes at least one of a sine wave end face, a triangular wave end face, and a square wave end face.

[0016] In a second aspect, a backward wave oscillator is provided, including an electron gun, a focusing system, an input / output device, a collector, and the slow wave structure according to any one of the above embodiments. Among them,

[0017] The input end of the slow wave structure is connected to the output end of the electron gun, and the output end of the slow wave structure is connected to the collector;

[0018] The focusing system is arranged near the slow wave structure;

[0019] The input end of the input / output device is arranged near the input end of the slow wave structure, and the output end of the input / output device is arranged near the output end of the slow wave structure.

[0020] The above slow-wave structure and backward-wave oscillator reduce the conductivity loss of the slow-wave structure and are easy to process by forming a periodic waveguide with the first structure and the second structure. By overlapping the projections of the peak parts of the first structure and the second structure in the first direction, the first structure and the second structure are oppositely arranged, so as to form a regular undulating strip-shaped channel in the gap between the first structure and the second structure. Then, by arranging the first structure and the second structure close to each other, the height of the channel is compressed. Then, injection channels are arranged at the trough part of the first structure and the peak part of the second structure, and the injection channels are connected to form a regular electron beam channel, so that the focusing ability of the electron beam passing through the electron beam channel is stronger, the coupling impedance is increased, and the beam-wave interaction efficiency is improved, so as to facilitate the improvement of the output power level, gain and interaction efficiency. Description of the Drawings

[0021] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0022] Figure 1 The front view of the slow-wave structure provided in an embodiment of the present application;

[0023] Figure 2 The side view of the slow-wave structure provided in another embodiment of the present application;

[0024] Figure 3 The front view of the slow-wave structure provided in another embodiment of the present application;

[0025] Figure 4 The structural schematic diagram of the slow-wave structure provided in another embodiment of the present application;

[0026] Figure 5 The schematic diagram of the electron beam in the slow-wave structure provided in an embodiment of the present application;

[0027] Figure 6 The dispersion characteristic diagram of the slow-wave structure provided in an embodiment of the present application.

[0028] Explanation of the reference numerals:

[0029] 1. The first structure; 2. The second structure; 3. The electron beam channel; 4. The periodic waveguide; 5. The electron beam. Detailed Embodiments

[0030] To facilitate the understanding of this application, the following will provide a more comprehensive description of this application with reference to the relevant accompanying drawings. Embodiments of this application are shown in the drawings. However, this application can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, these embodiments are provided to make the disclosure of this application more thorough and comprehensive.

[0031] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the technical field to which this application belongs. The terms used in the description of this application herein are only for the purpose of describing specific embodiments and are not intended to limit this application.

[0032] It can be understood that the terms "first", "second", etc. used in this application may be used herein to describe various elements, but these elements are not limited by these terms. These terms are only used to distinguish a first element from another element.

[0033] Spatial relationship terms such as "under", "below", "beneath", "underneath", "above", "over", etc. can be used herein to describe the relationship of one element or feature shown in the drawings with other elements or features. It should be understood that, in addition to the orientation shown in the drawings, spatial relationship terms also include different orientations of the device during use and operation. For example, if the device in the drawing is flipped, an element or feature described as "under other elements" or "beneath it" or "under it" will be oriented "above" the other elements or features. Therefore, the exemplary terms "under" and "beneath" can include both upward and downward orientations. In addition, the device may also include additional orientations (such as rotating 90 degrees or other orientations), and the spatial descriptors used herein are accordingly interpreted.

[0034] As used herein, the singular forms "a", "an" and "the" may also include the plural forms unless the context clearly dictates otherwise. It should also be understood that the terms "comprising" or "having", etc. specify the presence of the stated features, wholes, steps, operations, components, parts, or combinations thereof, but do not preclude the presence or addition of one or more other features, wholes, steps, operations, components, parts, or combinations thereof.

[0035] In one embodiment, a slow-wave structure is provided, which includes a periodic waveguide; the periodic waveguide includes a first structure and a second structure arranged oppositely, wherein, in a first direction, the end faces of the first structure and the second structure arranged oppositely are end faces with periodically varying undulations, the projections of the peak portions of the first structure and the peak portions of the second structure in the first direction coincide, and the distance between the peak portions of the first structure and the peak portions of the second structure is a minimum value. Injection channels are formed at the trough portions of the first structure and the peak portions of the second structure, and the injection channels communicate with each other in the first direction to form an electron beam channel.

[0036] The slow-wave structure includes two metal plates arranged parallel and oppositely, and two side walls arranged oppositely and perpendicular to the metal plates. The side walls can be metal walls or dielectric walls. The two metal plates and the two side walls together form a cuboid. The distance between the metal plates arranged oppositely up and down of the cuboid is the narrow side b, and the distance between the side walls arranged oppositely front and back of the cuboid is the wide side a.

[0037] Optionally, the end face with periodically varying undulations includes at least one of a sine-wave end face, a triangular-wave end face, and a square-wave end face.

[0038] Optionally, the end faces of the first structure and the second structure have the same shape, the same undulation amplitude, and the same undulation period. That is, the end faces of both the first structure and the second structure are sine-wave end faces, triangular-wave end faces, or square-wave end faces. In some embodiments, the end faces of the first structure and the second structure can also be different. For example, the end face of the first structure is a sine-wave end face, and the end face of the second structure is a triangular end face. The end faces of the first structure and the second structure can also be cosine-wave end faces, that is, the same waveform as the sine wave, both are smooth circular-arc-shaped periodically undulating waveforms, and the difference is only in the starting point position.

[0039] Taking the example that the end faces of the first structure 1 and the second structure 2 are the same and both are sine-wave end faces for illustration, as Figure 1 shown, the periodic waveguide includes a first structure 1 and a second structure 2, and the first structure 1 and the second structure 2 are arranged oppositely up and down. It can be that the first structure 1 is above and the second structure 2 is below, or the first structure 1 is below and the second structure 2 is above, which is not limited herein. The first structure 1 is formed on the upper metal plate, and the second structure 2 is formed on the lower metal plate. The first direction is the projection direction from one side wall of the slow-wave structure to the other side wall. In the first direction, the end faces of the first structure 1 and the second structure 2 arranged oppositely are sine-wave end faces. The undulation amplitude of the sine-wave end face, that is, the undulation height, is h, and the undulation period of the sine-wave end face is p. The distance x from the peak of the first structure 1 to the trough of the second structure 2 is less than or equal to the length a of the wide side of the slow-wave structure: x = b + 2h ≤ a.

[0040] The first structure and the second structure each include a plurality of sinusoidal structures arranged oppositely to Figure 1 illustrate the leftmost first sinusoidal structure of the first structure 1 and the leftmost second sinusoidal structure of the second structure 2. The projection of the peak portion of the first sinusoidal structure in the first direction coincides with the projection of the peak portion of the second sinusoidal structure in the first direction, and the distance between the peak portion of the first sinusoidal structure and the peak portion of the second sinusoidal structure is at a minimum value. Therefore, the first structure and the second structure are arranged close to each other. A first notch is formed by cutting or other processes at the trough portion of the first sinusoidal structure, and a second notch is formed by cutting or other processes at the peak portion of the second sinusoidal structure. The first notch and the second notch are combined to form a first injection channel. There are a plurality of sinusoidal structures arranged oppositely between the first structure 1 and the second structure 2. An injection channel is formed between the trough portion of the first structure 1 and the peak portion of the second structure 2 in each pair of oppositely arranged sinusoidal structures. The injection channels are connected in the first direction to form an electron beam channel 3 leading from the input end to the output end of the slow-wave structure.

[0041] For the above slow-wave structure, the periodic waveguide is formed by the first structure 1 and the second structure 2, which reduces the conductivity loss of the slow-wave structure and is easy to process. By making the projections of the peak portions of the first structure 1 and the second structure 2 coincide in the first direction, the first structure 1 and the second structure 2 are arranged oppositely, so as to form a regular undulating strip-shaped channel in the gap between the first structure 1 and the second structure 2. Then, by arranging the first structure 1 and the second structure 2 close to each other, the height of the channel is compressed. Then, injection channels are formed at the trough portion of the first structure 1 and the peak portion of the second structure 2, and the injection channels are connected to form a regular electron beam channel 3, so that the focusing ability of the electron beam passing through the electron beam channel is stronger, the coupling impedance is increased, and thus the beam-wave interaction efficiency is improved, so as to facilitate the improvement of the output power level, gain and interaction efficiency.

[0042] In one embodiment, as Figure 2 , it includes a plurality of periodic waveguides 4, and the periodic waveguides 4 are arranged along the second direction. The second direction is Figure 1 the extending direction from one side wall to the other side wall, that is, the periodic waveguides 4 are arranged in sequence along the wide side a of the slow-wave structure. The slow-wave structure may include y periodic waveguides 4. The widths of the periodic waveguides 4 are all the same and are w. There are gaps between the periodic waveguides 4, and the distances between the periodic waveguides 4 are all the same and are t. There are also gaps between the periodic waveguides 4 and the side walls of the slow-wave structure, and the gap widths are also t, that is, a = y * w + (y + 1) * t.

[0043] Each periodic waveguide 4 includes a first structure and a second structure that are oppositely arranged. Notches are formed in the trough portions of each oppositely arranged first structure and the peak portions of the second structure to form injection channels. All the injection channels of each periodic waveguide 4 are connected to form an electron beam channel 3. Each periodic waveguide 4 forms an electron beam channel 3 respectively, and the number of electron beam channels 3 is the same as the number of periodic waveguides 4. The multiple electron beam channels 3 are respectively connected to the input end and the output end of the slow-wave structure, and an electron beam can be placed in each electron beam channel 3.

[0044] Optionally, the shape of the injection channel in the cross-sectional plane is circular, and the injection channels are connected to form a circular electron beam channel 3; wherein, the cross-sectional plane is a plane perpendicular to the first direction. The diameter r of the circular electron beam channel 3 is less than or equal to the width w of the periodic waveguide 4, as Figure 4 shown. The cross-section of the injection channel can also be triangular, rectangular, square, etc.

[0045] In the above-mentioned slow-wave structure, the periodic waveguide 4 is formed by the first structure and the second structure, which reduces the conductivity loss of the slow-wave structure and is easy to process. By making the projections of the peak portions of the first structure and the second structure coincide in the first direction, the first structure and the second structure are oppositely arranged, so as to form a regular undulating strip-shaped channel in the gap between the first structure and the second structure. Then, by setting the first structure and the second structure close to each other, the height of the channel is compressed. Then, injection channels are opened in the trough portion of the first structure and the peak portion of the second structure, and the injection channels are connected to form a regular circular electron beam channel 3. The focusing technology of the circular electron beam is more mature. By setting multiple periodic waveguides 4, multiple regular electron beam channels 3 can be formed, further enhancing the focusing ability of the electron beam, and the multi-electron beam structure can provide a larger working current to increase the coupling impedance, thereby improving the beam-wave interaction efficiency, so as to facilitate the improvement of the output power level, gain and interaction efficiency.

[0046] In one embodiment, the distance between the peak portion of the first structure and the peak portion of the second structure is equal to twice the fluctuation amplitude.

[0047] As Figure 3 , taking the end faces of the first structure 1 and the second structure 2 being the same and both being sine-wave end faces as an example for illustration, both the first structure 1 and the second structure 2 include multiple sine structures. Taking the leftmost first sine structure of the first structure 1 and the leftmost second sine structure of the second structure 2 for illustration, the projections of the peak portions of the first sine structure and the second sine structure coincide in the first direction.

[0048] The distance between the peak portions of the first structure 1 and the peak portions of the second structure 2 is equal to twice the fluctuation amplitude, which means that the projection of the trough point of the first structure and the peak point of the second structure in the second direction coincides. If the channel of the electron beam is circular, the trough portion of the first sine structure of the first structure forms a first semi-circular notch, and the peak portion of the second sine structure of the second structure forms a second semi-circular notch. The first semi-circular notch and the second semi-circular notch are combined to form a first injection channel, and multiple input and output channels are coaxially arranged to form a circular electron beam channel. When the first structure 1 and the second structure 2 are arranged oppositely, a strip-shaped channel will be formed. In the prior art, the width hp of this strip-shaped channel is greater than or equal to 0. In this embodiment, the first structure 1 and the second structure 2 are arranged close enough, and there will be an overlapping part between the trough portion of the first structure 1 and the peak portion of the second structure 2. At this time, hp is equal to 0, that is, a complete and unbroken strip-shaped channel cannot be formed.

[0049] Optionally, the distance between the peak portions of the first structure and the peak portions of the second structure is less than twice the fluctuation amplitude, that is, hp is less than or equal to 0.

[0050] The above slow-wave structure reduces the conductivity loss of the slow-wave structure and is easy to process by forming a periodic waveguide with the first structure 1 and the second structure 2. By making the projections of the peak portions of the first structure 1 and the second structure 2 coincide in the first direction, the first structure 1 and the second structure 2 are arranged oppositely, so as to form a regular undulating strip-shaped channel in the gap between the first structure 1 and the second structure 2. Then, by arranging the first structure and the second structure close to each other, the height of the channel is compressed to the amplitude, and then injection channels are opened in the trough portion of the first structure and the peak portion of the second structure. Each injection channel is connected to form a regular electron beam channel. The focusing ability of the electron beam is enhanced through the regular electron beam channel 3 to increase the coupling impedance, thereby improving the beam-wave interaction efficiency, so as to facilitate the improvement of the output power level, gain and interaction efficiency.

[0051] In one embodiment, as Figure 4, the narrow side b and the wide side a of the slow-wave structure. The slow-wave structure may include 3 periodic waveguides. The width w and the interval t of the periodic waveguides. Each periodic waveguide includes a first structure 1 and a second structure 2 arranged opposite to each other. The end faces of the first structure 1 and the second structure 2 may be sinusoidal end faces. The fluctuation period of the sinusoidal end face is p, and the fluctuation amplitude is h. The projection of the peak part of the second structure 2 in the first direction coincides with the peak part of the first structure 1, and the second structure 2 and the first structure 1 are arranged close to each other until the distance between the peak part of the first structure 1 and the peak part of the second structure 2 is less than 2h, that is, there is a partial overlapping area in the projection of the trough part of the first structure in the second direction with the peak part of the second structure. The electron beam channel is arranged in the overlapping area. The cross-sectional width of the electron beam channel is less than the width of the periodic waveguide. Each periodic waveguide generates an electron beam channel 3 corresponding to it. The cross-section of the electron beam channel 3 may be circular. The diameter of the circular electron beam channel is less than the width of the periodic waveguide. Therefore, the slow-wave structure includes 3 circular electron beam channels 3 connecting the input end and the output end. The electron beam 5 may be arranged in the circular electron beam channel 3. The diameter of the electron beam 5 is less than or equal to the diameter of the electron beam channel 3. For example Figure 5 . The narrow side of the slow-wave structure may be b = 68um. The width w of the periodic waveguide may be equal to the diameter r of the circular electron beam channel 3, that is, w = r = 40um. The number of periodic waveguides may be 3. The fluctuation period of the periodic waveguide may be p = 80um. The fluctuation amplitude of the periodic waveguide may be h = 42um. The gap between each periodic waveguide is t = 20um. The wide side of the slow-wave structure may be a = 4*t + 3*w = 4*20 + 3*40 = 200um. Using the three-dimensional electromagnetic simulation software HFSS for calculation, its dispersion characteristics are obtained as Figure 6 shown in the figure. In the figure, phase shift is the phase deviation, the unit is degree, frequency is the frequency, the unit is gigahertz, and dispersion curve is the dispersion curve. The results show that the slow-wave structure has a relatively wide operating bandwidth, and the operating bandwidth is approximately 380GHz - 990GHz.

[0052] The above slow-wave structure is composed of the first structure 1 and the second structure 2 to form a periodic waveguide, which reduces the conductivity loss of the slow-wave structure and is easy to process. By relatively arranging the first structure 1 and the second structure 2, a regular undulating strip-shaped channel is formed between the first structure 1 and the second structure 2. The first structure 1 and the second structure 2 are arranged close to each other, so that the trough part of the first structure 1 and the peak part of the second structure 2 overlap in the projection in the second direction to form an overlapping area. Then, injection channels are opened in the trough part and the peak part corresponding to the overlapping area, and the injection channels are connected to form a regular electron beam channel 3. The focusing technology of the circular electron beam is more mature. By setting multiple periodic waveguides, multiple regular electron beam channels 3 can be formed, further enhancing the focusing ability of the electron beam. Moreover, the multi-electron beam structure can provide a larger working current to increase the coupling impedance, thereby improving the beam-wave interaction efficiency, facilitating the improvement of the output power level, gain, and interaction efficiency.

[0053] In one embodiment, a backward-wave oscillator is provided, which includes an electron gun, a focusing system, an input-output device, a collector, and the slow-wave structure according to any one of the above embodiments.

[0054] The electron gun is used to provide energy to make the backward-wave oscillator work. It exchanges energy with the backward wave generated by self-excited oscillation in the slow-wave structure after accelerating the electron beam to a certain speed. According to the requirements of the slow-wave structure, the electron gun can also adjust the shape, energy, speed, etc. of the electron beam injected into the backward-wave oscillator. By changing the voltage of the electron gun, the moving speed of the electrons can be adjusted, so as to excite electromagnetic waves of different frequencies in the slow-wave structure.

[0055] The focusing system is arranged near the slow-wave structure and is a device for overcoming the space charge force between electrons to maintain a certain shape of the electron beam. After the electron beam enters the high-frequency system from the electron gun, due to the space charge force existing between the internal electrons, the electron beam will gradually diverge and deform during travel, which will lead to insufficient energy exchange with the high-frequency field and there is also a risk that individual electrons will hit the high-frequency structure and cause device damage.

[0056] The slow-wave structure is connected to the output end of the electron gun for energy exchange. In order to ensure that the electron beam and the high-frequency field can continuously and efficiently exchange energy during the beam-wave interaction, the traveling speed of the electrons should be slightly greater than the phase velocity of the electromagnetic wave, which is called synchronization. The function of the slow-wave structure is to slow down the phase velocity of the high-frequency field to the synchronization speed to ensure the effective interaction. The return wave oscillator operates in the terahertz band. In the case of beam-wave interaction, the conductivity loss of the slow-wave structure itself must be considered, and the loss will increase rapidly with the increase of the operating frequency. Compared with other slow-wave structures, the sinusoidal waveguide has low loss and is easy to process. However, the electric field strength of this structure in the direction of electromagnetic wave transmission is relatively weak, so its coupling impedance is small, which leads to the defects of low output power and gain, low interaction efficiency, etc. of the sinusoidal waveguide traveling wave tube. Therefore, in this embodiment, the slow-wave structure in the above embodiment can well avoid the defects of low output power and gain, low interaction efficiency, etc.

[0057] The input end of the input-output device is located near the input end of the slow-wave structure, and the output end of the input-output device is located near the output end of the slow-wave structure, so as to achieve good impedance matching between the slow-wave structure and the subsequent device, thereby more efficiently coupling the amplified output signal to the output loop. At the same time, the outside world is isolated to maintain the vacuum environment in the backward wave oscillator.

[0058] The collector is connected to the output end of the slow-wave structure, and is used to collect electrons output from the output end of the electron injection channel of the slow-wave structure and recover part of the remaining energy of the electrons, thereby improving the energy utilization of the backward wave oscillator, thereby improving the working efficiency and significantly improving the thermal state of the device.

[0059] The above-mentioned backward wave oscillator forms a regular undulating band channel between the first structure and the second structure by relatively arranging the first structure and the second structure in the slow wave structure. The first structure and the second structure are arranged close to each other, and then injection channels are opened at the trough part of the first structure and the peak part of the second structure. The injection channels are connected to form a regular electron injection channel, so that the focusing ability of the electron beam is stronger, so as to improve the coupling impedance, thereby improving the injection-wave interaction efficiency, so as to improve the output power level, gain and interaction efficiency of the backward wave oscillator.

[0060] In the description of this specification, the description with reference to the terms "some embodiments", "other embodiments", "ideal embodiments", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic descriptions of the above terms do not necessarily refer to the same embodiment or example.

[0061] The technical features of the above embodiments can be combined arbitrarily. For the sake of concise description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope recorded in this specification.

[0062] The above-described embodiments merely represent several implementation manners of the present application. The description is relatively specific and detailed, but it should not be construed as a limitation on the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present application, several modifications and improvements can still be made, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application shall be subject to the appended claims.

Claims

1. A slow-wave structure, characterized in that, comprising y periodic waveguides; the periodic waveguides include a first structure and a second structure arranged oppositely, wherein, in a first direction, the end faces of the first structure and the second structure arranged oppositely are respectively end faces with periodically varying undulations, the projections of the peak portions of the first structure and the peak portions of the second structure in the first direction coincide, and the distance between the peak portion of the first structure and the peak portion of the second structure is at a minimum value. Injection channels are provided at the trough portion of the first structure and the peak portion of the second structure, and the injection channels communicate with each other in the first direction to form an electron beam channel; wherein, y is a positive integer greater than or equal to 2, each of the periodic waveguides is arranged along a second direction, and the spacing between each of the periodic waveguides in the second direction is the same and is all t, and the widths of each of the periodic waveguides in the second direction are the same and are all w. Wherein, the width a of the slow-wave structure in the second direction = y * w + (y + 1) * t, and both t and w are greater than zero.

2. The slow wave structure according to claim 1, characterized in that, The end face of the first structure and the end face of the second structure have the same shape, the same undulation amplitude, and the same undulation period.

3. The slow wave structure according to claim 2, characterized in that, The distance between the peak portion of the first structure and the peak portion of the second structure is equal to twice the undulation amplitude.

4. The slow wave structure according to claim 2, wherein The distance between the peak portion of the first structure and the peak portion of the second structure is less than twice the undulation amplitude.

5. The slow wave structure according to claim 1, wherein Each of the injection channels is coaxially arranged in the first direction to form the electron beam channel.

6. The slow wave structure according to claim 1, characterized in that, The shape of the injection channel on the cross-sectional plane is circular, and each of the injection channels communicates to form a circular electron beam channel; wherein, the cross-sectional plane is a plane perpendicular to the first direction.

7. The slow wave structure according to claim 6, characterized in that The diameter of the circular electron beam channel is less than or equal to the width of the periodic waveguide.

8. The slow wave structure according to claim 1, characterized in that The end face with periodically varying undulations includes at least one of a sine wave end face, a triangular wave end face, and a square wave end face.

9. A backward wave oscillator, characterized in that, comprising an electron gun, a focusing system, an input / output device, a collector, and the slow-wave structure according to any one of claims 1-8, wherein, the input end of the slow-wave structure is connected to the output end of the electron gun, and the output end of the slow-wave structure is connected to the collector; the focusing system is arranged near the slow-wave structure; the input end of the input / output device is arranged near the input end of the slow-wave structure, and the output end of the input / output device is arranged near the output end of the slow-wave structure.

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