Slow wave structure, traveling wave tube, electronic equipment and communication system

Abstract

The invention discloses a slow wave structure, a traveling wave tube, electronic equipment and a communication system. The slow wave structure comprises a folded wave guide structure, the wave guide structure has a period in the longitudinal direction and an amplitude in the transverse direction perpendicular to the longitudinal direction, and at least one of the amplitude of a first part of the wave guide structure and the period of the first part is gradually changed in the longitudinal direction. Therefore, reflection of the slow wave structure can be reduced, backward wave oscillation can be effectively suppressed, and a wider working bandwidth can be obtained.

Description

Slow-wave structures, traveling wave tubes, electronic equipment, and communication systems

[0001] The present application relates to the field of communications, and more specifically, to a slow-wave structure, a traveling wave tube, an electronic device, and a communication system.

[0002] Traveling wave tubes (TWTs) are one of the most important types of vacuum electronic devices. They offer high power, wide bandwidth, compact size, and lightweight design, making them widely used in communications, radar imaging, and electronic countermeasures. As a key component of TWTs, slow-wave structures (SWSs) convert the DC energy of an electron beam into electromagnetic wave energy through the interaction between the electron beam and the electromagnetic wave propagating along the SWS.

[0003] Improving the electronic efficiency of a traveling wave tube (TWT) not only increases the tube's overall efficiency but also improves output power and gain. This efficiency can be improved by synchronizing the phase velocity of the electromagnetic wave propagating along the slow-wave structure with the velocity of the electron beam. Because the velocity of the electron beam does not vary linearly, conventional slow-wave structures typically achieve this synchronization through multiple discrete phase velocity jumps. This structural design increases the complexity of the slow-wave structure and leads to overall performance instability.

[0004]

[0005] The embodiments of the present application provide a slow-wave structure, a traveling wave tube, an electronic device, and a communication system to reduce reflection of the slow-wave structure, suppress return wave oscillation, improve electronic efficiency, and obtain a wider operating bandwidth.

[0006] In a first aspect, a slow-wave structure is provided. The slow-wave structure comprises a folded waveguide structure having a period in a longitudinal direction and an amplitude in a transverse direction perpendicular to the longitudinal direction, wherein at least one of the amplitude and the period of a first portion of the waveguide structure gradually varies along the longitudinal direction. This structure can reduce reflections from the slow-wave structure, effectively suppress backward oscillations, and achieve a wider operating bandwidth.

[0007] In some implementations of the first aspect, the first portion of the waveguide structure may satisfy at least one of the following: an amplitude of the first portion continuously increases along the longitudinal direction; or a period of the first portion continuously decreases along the longitudinal direction. Thus, the phase velocity of the electromagnetic wave can be continuously reduced along the longitudinal direction.

[0008] In some implementations of the first aspect, the amplitude or period of the first portion may satisfy any of the following functional relationships: an exponential function, a logarithmic function, a polynomial function, or a trigonometric function. In this way, a full-period phase velocity gradient can be achieved in the entire slow-wave structure with fewer variable parameters.

[0009] In some implementations of the first aspect, the transverse amplitude and longitudinal period of the second portion of the waveguide structure can be constant along the longitudinal direction, and the second portion is closer to the input end of the slow-wave structure than the first portion. This allows the electromagnetic wave phase velocity to better match the electron beam velocity, thereby improving interaction efficiency.

[0010] In some implementations of the first aspect, the amplitude of the second portion of the waveguide structure in the transverse direction may be smaller than the amplitude of the first portion, the amplitude of the second portion may continuously increase in the longitudinal direction at a rate of amplitude change that is smaller than the rate of amplitude change of the first portion, and the second portion is closer to the input end of the slow-wave structure than the first portion. This allows the phase velocity of the electromagnetic wave to better match the velocity of the electron beam, thereby improving interaction efficiency.

[0011] In some implementations of the first aspect, the period of the second portion of the waveguide structure in the longitudinal direction may be greater than the period of the first portion, the period of the second portion may continuously decrease along the longitudinal direction at a rate of change that is smaller than the rate of change of the period of the first portion, and the second portion is closer to the input end of the slow-wave structure than the first portion. This allows the phase velocity of the electromagnetic wave to better match the velocity of the electron beam, thereby improving interaction efficiency.

[0012] In some implementations of the first aspect, the slow-wave structure may further include an attenuator disposed between the first portion and the second portion, thereby further suppressing backward oscillation.

[0013] In some implementations of the first aspect, the waveguide structure may include a folded waveguide, thereby realizing an improved waveguide-type slow-wave structure.

[0014] In some implementations of the first aspect, the waveguide structure may include a folded line, thereby realizing an improved folded line slow-wave structure.

[0015] In some implementations of the first aspect, the slow-wave structure may further include: a metal tube shell extending in a longitudinal direction; and a dielectric support member insulated from the metal tube shell and supporting the waveguide structure. Thus, an improved folded-line slow-wave structure may be realized.

[0016] In some implementations of the first aspect, the fold line may include a double-layer fold line, thereby improving electronic efficiency.

[0017] In some implementations of the first aspect, the slow-wave structure may include a first ridge structure and a second ridge structure located on opposite sides of a double-layer fold line, with the first ridge structure and the second ridge structure respectively being parallel to a plane in which the double-layer fold line lies. The ridge structures can be used to adjust the impedance of the fold line, thereby adjusting the dispersion characteristics of the slow-wave structure.

[0018] In a second aspect, a traveling wave tube (TWT) is provided. The beneficial effects of the TWT are described in the first aspect and are not further elaborated here. The TWT comprises an input / output device, an electronic transceiver assembly, a focusing assembly, and a slow-wave structure according to any one of the first aspects. The input / output device is configured to input electromagnetic waves to the input end of the slow-wave structure and output electromagnetic waves from the output end of the slow-wave structure. This reduces reflections from the slow-wave structure, effectively suppresses backward oscillations, achieves a wider operating bandwidth, and improves the operating stability of the TWT.

[0019] In some implementations of the second aspect, the electronic transceiver assembly may be configured to emit electron beams on the planar cathode emission surface, thereby simplifying the manufacturing process and saving manufacturing costs.

[0020] In some implementations of the second aspect, the electron beam may be a strip-shaped electron beam or a transversely divergent electron beam, thereby improving the flexibility of the traveling wave tube structure design.

[0021] In a third aspect, an electronic device is provided. The beneficial effects can be found in the description of the first aspect and are not further elaborated here. The electronic device comprises: a power supply; and a traveling wave tube according to any one of the second aspects, powered by the power supply. This provides an electronic device with wide bandwidth, high electronic efficiency, and high stability.

[0022] In a fourth aspect, a communication system is provided. The beneficial effects of the communication system can be found in the description of the first aspect and are not further elaborated here. The communication system includes a traveling wave tube according to any one of the second aspects. This enables the communication system to have wide bandwidth, high electronic efficiency, and high stability.

[0023] In some implementations of the fourth aspect, the communication system may further include at least one of the following: a baseband, a mid-range radio frequency module, and an antenna.

[0024] The above and other features, advantages and aspects of the embodiments of the present application will become more apparent with reference to the following detailed description in conjunction with the accompanying drawings. In the accompanying drawings, the same or similar reference numerals represent the same or similar elements, wherein:

[0025] FIG1A shows a schematic block diagram of a communication system to which embodiments of the present disclosure may be applied;

[0026] FIG1B shows a schematic structural diagram of a traveling wave tube to which embodiments of the present disclosure may be applied;

[0027] FIG2A shows a schematic diagram of a multi-segment phase velocity jump slow wave structure;

[0028] FIG2B is a schematic diagram showing the phase velocity of electromagnetic waves transmitted on the slow-wave structure in FIG2A ;

[0029] FIG3A shows a schematic diagram of a radial line slow-wave structure;

[0030] FIG3B shows a schematic diagram of another radial line slow-wave structure;

[0031] 4A to 4D are schematic diagrams showing a slow-wave structure including folded lines provided in an embodiment of the present application;

[0032] FIG5 is a schematic diagram showing a folding line of a slow-wave structure provided in an embodiment of the present application;

[0033] 6A to 6E are schematic diagrams showing a slow-wave structure including a double-layer folded line provided in an embodiment of the present application;

[0034] 7A to 7D show simulation results of the slow-wave structure in FIG. 6A to FIG. 6E ;

[0035] 8A and 8B are schematic diagrams showing a slow-wave structure including multiple folding lines provided by an embodiment of the present application;

[0036] FIG8C is a schematic diagram showing the phase velocity of the electromagnetic wave transmitted on the slow-wave structure in FIG8A to FIG8B ;

[0037] FIG9A is a schematic diagram of a traveling wave tube including a slow-wave structure of a V-shaped folded line provided in an embodiment of the present application;

[0038] FIG9B shows a schematic diagram of a traveling wave tube including an S-shaped folded line slow wave structure provided by an embodiment of the present application; and

[0039] FIG10 shows a schematic diagram of a slow-wave structure including a folded waveguide provided in an embodiment of the present application.

[0040] The following describes embodiments of the present application in more detail with reference to the accompanying drawings. Although certain embodiments of the present application are shown in the accompanying drawings, it should be understood that the present application can be implemented in various forms and should not be construed as being limited to the embodiments described herein. Instead, these embodiments are provided to provide a more thorough and complete understanding of the present application. It should be understood that the drawings and embodiments of the present application are for illustrative purposes only and are not intended to limit the scope of protection of the present application.

[0041] In the description of the embodiments of this application, the term "including" and similar terms should be understood as open inclusion, that is, "including but not limited to." The term "based on" should be understood as "based at least in part on." The term "one embodiment" or "the embodiment" should be understood as "at least one embodiment." The terms "first," "second," etc. can refer to different or the same objects. Other explicit and implicit definitions may also be included below.

[0042] Traveling wave tubes are the most important type of devices in vacuum electronic devices. They have the characteristics of high power, wide bandwidth, small size and light weight. They are widely used in communications, radar imaging, electronic countermeasures and other aspects. The technical solutions of the embodiments of the present application are mainly used in application scenarios of wireless communication systems such as RF / microwave / millimeter wave and THz base stations, vehicle-mounted equipment, satellite payloads, etc. Figure 1A shows a schematic block diagram of a communication system to which the embodiments of the present disclosure can be applied. A communication system (for example, a base station system) using a traveling wave tube amplifier consists of an input signal, a baseband, an intermediate radio frequency module, a traveling wave tube and an antenna, and is mainly used to meet applications such as point-to-point (P2P) or point-to-multiple point (P2MP) backhaul. The baseband is used to implement encoding, pre-distortion and other processing of the input signal. The intermediate radio frequency module is used to implement functions such as digital-to-analog conversion, signal up-conversion, amplification, filtering and the like of the baseband phase signal, and outputs a constant envelope phase modulated radio frequency signal that meets the saturation operation of the traveling wave tube. The traveling wave tube (TWT) amplifies the constant envelope phase modulated signal from the RF module and transmits the amplified signal to the antenna. The antenna radiates the amplified signal into free space.

[0043] FIG1B shows a schematic diagram of the structure of a traveling wave tube (TWT) applicable to embodiments of the present disclosure. The TWT primarily consists of an electron gun, an input / output device, a slow-wave structure, a focusing system, and a collector. The electron gun emits electrons, which are focused by a magnetic focusing system and pass through a slow-wave circuit before ultimately entering the collector. The slow-wave structure is the core component of the TWT's transducer structure, converting the kinetic energy of the electrons into electromagnetic wave energy by interacting with an electron beam transmitted through the slow-wave structure, thereby amplifying the electromagnetic wave. The input device converts the TE10 mode into a (quasi-)TEM mode, inputting the signal to be amplified into the slow-wave line for modulating the electron beam; the output device couples the amplified signal to an external circuit. Electrons emitted by the electron gun, focused by the focusing system, enter the slow-wave circuit. Modulated by the signal fed from the input device, they cluster along the direction of interaction between the electromagnetic wave and the electron beam (i.e., the direction of electron beam transmission) and gradually transfer energy to the electromagnetic wave. In other words, the kinetic energy of the electron beam is converted into electromagnetic wave energy. The collector is used to recover the remaining energy of the electrons after interacting with the electromagnetic waves.

[0044] To improve the efficiency of traveling wave tubes (TWTs), improvements are typically made to enhance electronic efficiency and collector efficiency. On the one hand, a specific transducer structure (i.e., a TWT slow-wave structure) can be designed to meet the research objectives, allowing the TWT to convert the DC energy of the electron beam into electromagnetic wave energy through the slow-wave structure. On the other hand, collector efficiency can be improved by designing a multi-stage step-down collector. Improving the electronic efficiency of a TWT not only increases the TWT's overall efficiency but also improves output power and gain. Therefore, in the field of vacuum electronics, various improvements have been made to various types of slow-wave structures (including helical slow-wave structures, coupled cavity slow-wave structures, folded waveguide and folded linear slow-wave structures, etc.). Their goal is to maximize electronic efficiency while meeting the gain and bandwidth requirements of the TWT amplifier and ensuring long-term operational stability.

[0045] During this exploration, phase-velocity jump technology has been widely applied in the design of slow-wave structures. Its theoretical basis is as follows: the interaction between an electron beam and the electromagnetic wave propagating along the slow-wave structure causes the electron beam to continuously convert its kinetic energy into electromagnetic wave energy, gradually reducing its velocity. This causes the beam's velocity to shift from slightly greater than the electromagnetic wave's phase velocity to less than it. Consequently, the electromagnetic wave propagating along the slow-wave structure is no longer amplified, indicating a dynamic equilibrium in the energy conversion between the electron beam and the electromagnetic wave. Phase-velocity jump technology modulates the dimensions of the slow-wave structure so that the phase velocity of the electromagnetic wave propagating along the structure changes in sync with the electron beam's velocity. This allows the electromagnetic wave and the electron beam to resynchronize and improve electronic efficiency. Because the electron beam's velocity reduction is not linear, phase-velocity jump technology typically employs multiple structural changes to achieve this synchronization.

[0046] FIG2A is a schematic diagram of a related multi-segment phase velocity jump slow-wave structure. FIG2B is a schematic diagram of the phase velocity Vp of an electromagnetic wave transmitted on the slow-wave structure in FIG2A . As shown in FIG2A , the slow-wave structure of the traveling wave tube uses a dielectric substrate etched with a metal folded slow-wave line. Because during the interaction between the electron beam and the slow-wave structure, the electron beam is subjected to the longitudinal (z-direction) electric field force, causing some electrons to accelerate while others to decelerate. Therefore, the phase velocity of the electromagnetic wave transmitted along the slow-wave line may experience a positive or negative phase velocity jump. In the slow-wave structure shown in FIG2A , discrete changes in the phase velocity are achieved by changing the period of the slow-wave line. The entire slow-wave line is divided into several segments (in FIG2A , five segments are taken as an example), and the period length (p1, p2, p3, p4, p5) and number of periods (N1, N2, N3, N4, N5) of each segment are different. The phase velocity of the electromagnetic wave transmitted along the slow-wave line is directly related to the period length of the corresponding slow-wave line. The shorter the period length of the slow-wave line, the smaller the phase velocity of the electromagnetic wave transmitted along the slow-wave line. In order to match the phase velocity of the electromagnetic wave with the velocity of the electron beam, as the velocity of the electron beam gradually decreases, the period length of the slow-wave line decreases discretely along the direction of electron beam transmission (z direction), that is, p2>p3>p4>p5. In addition, since the velocity change of the electron beam in the initial stage is small, the period length of the first section of the slow-wave line can be slightly shorter than the period length of the second section of the slow-wave line, that is, p1<p2. As shown in Figure 2B, the phase velocity of the electromagnetic wave transmitted along the slow-wave line varies discretely along the direction of electron beam transmission (z direction), so that the phase velocity of the electromagnetic wave matches the velocity of the electron beam. By dividing the slow-wave line into several sections along the longitudinal direction (z direction), the electromagnetic wave has a fixed phase velocity in each section, and the phase velocity increases (or decreases) discretely along the slow-wave line, the electron beam and the electromagnetic wave transmitted along the slow-wave line are better synchronized. This is called phase velocity resynchronization technology. By using multiple structural jumps (usually period, pitch or radius, etc.) to achieve changes in phase velocity, the electromagnetic wave and the electron beam are synchronized again, allowing the electromagnetic wave to exchange energy with the electron beam more effectively, thereby improving electronic efficiency.

[0047] To achieve multiple changes in the phase velocity of electromagnetic waves, some solutions employ a multi-segment discrete phase velocity jump slow-wave structure. Specifically, the slow-wave structure consists of multiple segments with discrete phase velocity jumps. This complicates the slow-wave structure, increasing the difficulty of processing and assembly. Furthermore, it inevitably introduces multiple reflection points within the slow-wave circuit, increasing the risk of reflection oscillations within the traveling wave tube and impacting overall performance. For example, when electromagnetic waves propagate along the slow-wave line, they are reflected at discontinuities. The propagation direction of the reflected wave (-z direction) is opposite to the forward direction of the electron beam (z direction). The reversely propagating electromagnetic wave and the electron beam do not meet synchronization conditions and therefore do not interact. However, when the reflected wave propagates toward the input, if it encounters a discontinuity, it will produce a secondary reflection. The secondary reflected signal propagates along the slow-wave line toward the output. If the secondary reflected wave is larger than the weak electromagnetic wave input at the input, repeated cycles of this process may generate oscillations at a suitable frequency. Even if no oscillation occurs, the secondary or even tertiary reflected waves can vectorially superimpose with the input electromagnetic wave, causing fluctuations in gain and phase, leading to unstable operation of the traveling wave tube. The presence of multiple reflection points on the slow-wave line further increases the instability of the traveling wave tube.

[0048] In the slow-wave circuit, the reverse oscillation can be suppressed by cutting off and setting an attenuator. However, this will further complicate the slow-wave structure, reduce the gain of the traveling wave tube, and increase the length of the traveling wave tube.

[0049] In addition to the above-mentioned implementation of non-uniform slow wave lines through multi-stage jumps, some related technologies also use radial slow wave line solutions. Figure 3A shows a schematic diagram of a related radial line slow wave structure. As shown in Figure 3A, the change relationship of the slow wave line is a logarithmic periodic change, and its functional relationship is The angular angle is θ, the radius of the nth segment is dn, and the normalized phase velocity is vpc = 1 / (π / 2+θ / (e πb -e -πb )). It can be found that when the opening angle θ and the exponential variation coefficient b of this slow wave line are constant, its phase velocity is a constant. In other words, although this slow wave line changes along the radial direction, it has a constant electromagnetic wave phase velocity. This slow wave line that diffuses along the angular direction is conducive to interacting with the laterally divergent electron beam, but it cannot achieve phase velocity resynchronization to improve electron efficiency. Figure 3B shows a schematic diagram of another related radial line slow wave structure. As shown in Figure 3B, the slow wave line is composed of concentric circular arcs. The electromagnetic wave phase velocity of this slow wave line is constant and is determined by the opening angle and the adjacent concentric circular arcs.

[0050] Since the phase velocity of the electromagnetic wave transmitted along the radial slow-wave line is constant, it is not conducive to the energy exchange between the electromagnetic wave and the electron beam, and therefore is not conducive to improving the electronic efficiency. Although other methods (such as adding ridges, changing the structural parameters (period) of the radial line, etc.) can be used to improve the electronic efficiency, these methods will lead to the disadvantages of the slow-wave structure shown in Figure 2A. That is, the complexity of the slow-wave structure is increased, and the continuous change of the phase velocity throughout the entire cycle is not achieved. This reduces the operating bandwidth and increases the risk of traveling wave tube oscillation.

[0051] In addition, in this radial slow-wave structure, if a conventional planar cathode is used to emit an electron beam, the phases of the electron beams on the same cross section at a specific longitudinal position will be inconsistent, resulting in extremely low electron efficiency. In order for electromagnetic waves to interact with the electron beam, the radial line slow-wave structure requires that the cathode emission surface of the electron gun be angularly conformal to the slow-wave line. That is, the cathode emission surface of the electron beam and the arc of the slow-wave line have the same curvature to ensure that the electron beam emitted from the cathode emission surface can simultaneously interact with the interaction field along the radial direction, realizing energy exchange between the electron beam and the electromagnetic wave. However, the constraint of the cathode emission surface being conformal to the slow-wave line makes the design, processing and assembly of the electron gun electrode more complicated.

[0052] Currently, there is a lack of effective solutions to achieve the goals of wide bandwidth, high electronic efficiency, and high stability for traveling wave tubes (TWTs) without increasing the complexity of the TWT system. On the one hand, conventional TWTs employ a discrete phase-velocity jump slow-wave structure to improve electronic efficiency, which increases structural complexity, reduces operating bandwidth, and increases the risk of TWT oscillation. On the other hand, TWTs employing radial slow-wave lines cannot achieve a balanced performance, including the trade-offs between bandwidth, electronic efficiency, gain, stability, and structural and process complexity.

[0053] In order to achieve the goals of wide bandwidth, high efficiency and high stability of the traveling wave tube without increasing the complexity of the traveling wave tube system, the embodiment of the present application provides a slow-wave structure with a full-period phase velocity gradient and a traveling wave tube based on this slow-wave structure. In this solution, the slow-wave structure has a folded waveguide structure, the waveguide structure has a period in the longitudinal direction and an amplitude in the transverse direction perpendicular to the longitudinal direction, and at least one of the amplitude of the first part of the waveguide structure and the period of the first part changes gradually along the longitudinal direction. Using the above method, the slow-wave structure can achieve continuous change of the phase velocity of the electromagnetic wave, thereby enabling the electromagnetic wave to fully interact with the electron beam while achieving wide-band matching. On this basis, a planar traveling wave tube with high electronic efficiency and high stability can be constructed.

[0054] As mentioned above, the embodiments disclosed in this application can be applied to any other implementations without any limitation. In order to more clearly discuss the embodiments disclosed in this application, the embodiments disclosed in this application are described with reference to FIG. 4A to FIG. 10 .

[0055] Figures 4A to 4D illustrate, in different views, the schematic structure of a slow-wave structure 1 including folded lines, provided by one embodiment of the present application. Specifically, Figure 4A illustrates the schematic structure of the slow-wave structure 1 including folded lines, provided by one embodiment of the present application, in a side view in the xz plane; Figure 4B illustrates the schematic structure of the slow-wave structure 1 including folded lines, provided by one embodiment of the present application, in a perspective view; Figure 4C illustrates the schematic structure of the slow-wave structure 1 including folded lines, provided by one embodiment of the present application, in a cross-sectional view in the xy plane; and Figure 4D illustrates a schematic structure of a portion of the slow-wave structure 1 including folded lines, provided by one embodiment of the present application, in a perspective view. The slow-wave structure 1 includes a folded slow-wave line 13. In the present disclosure, a folded slow-wave line can include a folded coaxial metal line. When electromagnetic waves propagate along the metal line, the phase velocity is reduced due to the folded path. Therefore, a folded metal line is also referred to as a "folded slow-wave line." The folded slow-wave line 13 has an amplitude in the transverse direction (i.e., the x-direction) and a period in the longitudinal direction (i.e., the z-direction). The amplitude, period, or both of the folded slow-wave line 13 can continuously and gradually change in the longitudinal direction. In the present disclosure, the longitudinal direction represents the transmission direction of the electron beam, and the transverse direction represents the direction perpendicular to the longitudinal direction. Unlike the angular and radial directions in Figures 3A and 3B, the transverse and longitudinal directions are defined based on a Cartesian coordinate system. In some embodiments, the slow-wave structure 1 may include a metal waveguide tube shell 11 extending in the longitudinal direction, a dielectric support 12 insulated from the metal waveguide tube shell 11, an input device 15, and an output device 16. The dielectric support 12 is used to support the folded slow-wave line 13. In some embodiments, the slow-wave structure 1 may also include a ridge 14 on one side of the folded slow-wave line 13, with the ridge 14 and the folded slow-wave line 13 both extending in the z-direction in the xz plane. By adjusting the height of the ridge 14, the impedance of the folded slow-wave line 13 can be adjusted, thereby adjusting the dispersion characteristics of the slow-wave structure 1. An electron beam channel can be provided on the side of the folded slow-wave line 13 opposite the ridge 14. The folded slow-wave line 13 can be made of a high-temperature resistant and non-deformable metal material, such as molybdenum, molybdenum alloy, tungsten, oxygen-free copper, etc. The metal waveguide shell 11 can be made of a metal material suitable for vacuum environments, such as nickel-copper alloy, molybdenum-copper alloy, or oxygen-free copper. The dielectric support 12 can be made of a ceramic material, such as boron nitride (BN), beryllium oxide (BeO), silicon carbide (SiC), or aluminum nitride (AlN). The above examples of metals, alloys, and ceramics are merely illustrative; the folded slow-wave line 13 and dielectric support 12 are not limited to these materials.

[0056] FIG5 shows some schematic implementations of the folded slow-wave line 13, such as folded slow-wave lines 13a, 13b, and 13c. The amplitude of the folded slow-wave line 13a in the transverse direction gradually increases along the longitudinal direction, and the period of the folded slow-wave line 13b in the longitudinal direction gradually decreases along the longitudinal direction. The amplitude of the folded slow-wave line 13c in the transverse direction gradually increases along the longitudinal direction, and the period in the longitudinal direction gradually decreases along the longitudinal direction.

[0057] In some embodiments, the folded slow-wave line 13 may satisfy a sine or cosine function relationship:

[0058] or

[0059] Wherein A(z) represents the variation relationship of the lateral amplitude of the folded slow-wave line 13 along the longitudinal direction (i.e., the z direction), and p(z) represents the variation relationship of the longitudinal period of the folded slow-wave line 13 along the longitudinal direction. By optimizing the parameters of the amplitude variation function A(z) and the period variation function p(z), the phase velocity of the electromagnetic wave transmitted in the folded slow-wave line 13 along the longitudinal direction can be continuously varied, and thus can be kept consistent with the velocity of the electron beam when passing through the slow-wave structure for energy exchange. In other words, by optimizing the parameters of the amplitude variation function A(z) and the period variation function p(z), the phase velocity of the electromagnetic wave transmitted along the slow-wave line can always be synchronized with the electron beam moving along the z direction, thereby achieving a higher energy conversion efficiency.

[0060] In some embodiments, A(z) represents a function that increases along the longitudinal direction. For example, A(z) may satisfy an exponential function, such as A(z)=A0*e αz , or A(z)=A0*2 αz , 0≤z≤L, L represents the length of the folded slow-wave line 13 in the longitudinal direction, A0 represents the initial amplitude of the folded slow-wave line 13, that is, the transverse amplitude of 3 at the input end, α is the amplitude growth factor, α>0 makes the transverse amplitude of the folded slow-wave line 13 increase along the longitudinal direction. The transverse amplitude of the folded slow-wave line 13 can also satisfy other functional relationships. As another example, A(z) can satisfy a logarithmic function, such as A(z)=A0*log a (a+αz), where a>1. As another example, A(z) may satisfy a polynomial function, such as A(z)=A0*(1+αz). As another example, A(z) may satisfy a trigonometric function, such as

[0061] In some embodiments, p(z) represents a function that decreases along the longitudinal direction. For example, p(z) may satisfy an exponential function, such as p(z)=p0*e -βz , or p(z)=p0*2 -βz , 0≤z≤L, L represents the length of the folded slow-wave line 13 along the longitudinal direction, p0 represents the initial period of the folded slow-wave line 13, that is, the longitudinal period of 3 at the input end, β represents the period decreasing factor, -β<0 makes the longitudinal period of the folded slow-wave line 13 decrease along the longitudinal direction. The longitudinal period of the folded slow-wave line 13 can also satisfy other functional relationships. As another example, p(z) can satisfy a logarithmic function, such as p(z)=p0*log a (a-βz), where a>1+βL. As another example, p(z) may satisfy a polynomial function, such as p(z)=p0*(1-βz), where β<1 / L. As another example, p(z) may satisfy a trigonometric function, such as Where β>1.

[0062] Figures 6A to 6E show schematic diagrams of a slow-wave structure 1' including a double-layer folding line provided by an embodiment of the present application in different views. Specifically, Figure 6A shows a schematic structure of a slow-wave structure 1' including a double-layer folding line provided by an embodiment of the present application in a side view in the xz plane; Figure 6B shows a schematic structure of a slow-wave structure 1' including a double-layer folding line provided by an embodiment of the present application in a stereoscopic view; Figure 6C shows a schematic structure of a slow-wave structure 1' including a double-layer folding line provided by an embodiment of the present application in a cross-sectional view in the xy plane; Figure 6D shows a schematic structure of a portion of a slow-wave structure 1' including a double-layer folding line provided by an embodiment of the present application in a perspective view; Figure 6E shows a schematic structure of a portion of a slow-wave structure 1' including a double-layer folding line provided by an embodiment of the present application in a cross-sectional view in the xz plane. The slow-wave structure 1' of Figures 6A to 6E is similar to the slow-wave structure 1 of Figures 4A to 4D, except that the folded slow-wave line 13' in the slow-wave structure 1' includes a double-layer folding line. The folded slow-wave line 13' is supported on both sides by dielectric supports 12, and the dielectric supports 12 are insulated from the outer metal waveguide shell 11. It can be understood that this is only exemplary, and the slow-wave structure 1' can also include more layers of folded lines. Since the even mode (mode 2) of the double-layer folded line structure has a strong axial electric field component, it is conducive to interaction with the electron beam; while the fundamental mode shows that the axial electric fields of the upper and lower layers are opposite, and the total electric field is 0, and it cannot interact with the electron beam. Therefore, in order to better realize the mode conversion from waveguide to double-layer folded line slow-wave structure, a double-layer microstrip coupling method with ridges added from top to bottom is designed. In some embodiments, the slow-wave structure 1' can also include two ridges 14 on both sides of the double-layer folded line, and the ridges 14 and the double-layer folded line extend along the z direction in the xz plane. By adjusting the height of the two ridges 14, the impedance of the double-layer folded line can be adjusted, thereby adjusting the dispersion characteristics of the slow-wave structure 1'. An electron beam channel can be provided between the double-layer folded lines.

[0063] Figures 7A to 7D show the simulation results of the slow-wave structure 1' in Figures 6A to 6E. For the double-layer slow-wave structure 1' in Figures 6A to 6E, the function change relationship of the slow-wave line is a sinusoidal line. The amplitude change function is A(z)=A0*e αz The periodic variation function is p(z) = p0*(1-βz), α = 0.005, and β = 0. That is, the lateral amplitude of the folded slow-wave line 13' gradually increases along the longitudinal direction, while the longitudinal period of the folded slow-wave line 13' remains unchanged. Assume that the number of periods n of the folded slow-wave line 13' is 70, the longitudinal period p = 0.3 mm, and the interaction length (i.e., the length of the slow-wave line along the z direction) is L = n*p = 21 mm. Simulations were performed with an electron beam voltage of 5.5 kV, an injection current of 0.1 A, and a focusing magnetic field of 0.28 T.

[0064] Figure 7A shows a schematic diagram of the variation of the phase velocity Vp of an electromagnetic wave propagating in the slow-wave structure 1' along the z direction. By optimizing the parameters of the amplitude variation function A(z) and the period variation function p(z) of the fold lines in the slow-wave structure 1', the phase velocity can be made to decrease continuously and monotonically overall.

[0065] Figure 7B shows a schematic diagram of the transmission characteristics of the slow-wave structure 1'. As shown in Figure 7B, this slow-wave structure with a continuously gradient phase velocity can achieve good matching between the port and the slow-wave line, as well as the continuous variation of the slow-wave line, over a wide frequency range. The return loss is less than -20dB, and the insertion loss is approximately -5dB at 40GHz, laying the foundation for the development of broadband traveling-wave tubes.

[0066] FIG7C shows a schematic diagram of the simulated output power of the slow-wave structure 1'. As shown in FIG7C , the 3dB bandwidth of the slow-wave structure 1' is within the frequency range of 36.5GH-43GHz, the maximum output power is 107W@39GHz, and the electronic efficiency reaches 19.5%. FIG7D shows a schematic diagram of the frequency spectrum of the output signal of the slow-wave structure 1'. As shown in FIG7D , the amplitude difference between the fundamental wave and the higher-order mode of the output signal spectrum exceeds 40dB, that is, within the range of 70 cycles, through the continuous phase velocity gradient, no backward oscillation and reflection oscillation occur. The simulation results confirm that the planar traveling wave tube can achieve high electronic efficiency, wide bandwidth and high stability through the above-mentioned continuously gradient slow-wave structure.

[0067] Figures 8A to 8B show schematic diagrams of a slow-wave structure 1" including multiple folding lines provided in an embodiment of the present application. Specifically, Figure 8A shows a schematic structure of a slow-wave structure 1" including multiple folding lines provided in an embodiment of the present application in a side view in the xz plane; Figure 8B shows a schematic structure of a slow-wave structure 1" including multiple folding lines provided in an embodiment of the present application in a stereoscopic view. The slow-wave structure 1" of Figures 8A to 8B is similar to the slow-wave structure 1 of Figures 4A to 4D, except that the folded slow-wave line 13" in the slow-wave structure 1" includes multiple folding lines. In the example of Figures 8A to 8B, the slow-wave structure 1" includes two folding lines 131 and 132, but it can be understood that this is merely exemplary, and the slow-wave structure 1" may also include more folding lines. Similar to the slow-wave structure 1' in Figures 6A to 6E, each fold line of the slow-wave structure 1" can be composed of one or more layers of fold lines. In the examples of Figures 8A to 8B, the fold lines 131 and 132 are each composed of two layers of fold lines. The fold lines 131 and 132 are supported on both sides by dielectric support members 12, and the dielectric support members 12 are insulated from the outer metal waveguide shell 11. An electron injection channel can be provided between the two layers of fold lines.

[0068] As shown in Figure 8A , one end of fold line 132 is connected to input device 15, while the other end is truncated and suspended in the air. One end of fold line 131 is connected to output device 16, while the other end is truncated and suspended in the air. Attenuator 17 is disposed on dielectric support member 12 at the suspended portion between fold lines 131 and 132. Attenuator 17 can be vaporized carbon on fold lines 131 and 132 or on dielectric support member 12, or directly replaced by lossy ceramic. It primarily attenuates electromagnetic waves fed from input device 15 to prevent reflection at the truncated portion, and attenuates electromagnetic waves reflected at the port of output device 16.

[0069] In some embodiments, the relationship between the amplitude variation function A(z) and the period variation function p(z) of the two fold lines 131 and 132 can be different. The amplitude growth factor and period reduction factor of fold line 131 are α1 and β1, respectively, and the longitudinal length of fold line 131 is L1. The amplitude growth factor and period reduction factor of fold line 132 are α2 and β2, respectively, and the longitudinal length of fold line 132 is L2. Fold line 131 is closer to input device 15 than fold line 132. In one embodiment, α1 = 0, β1 = 0, and at least one of α2 and β2 is not equal to 0. In other words, the lateral amplitude and longitudinal period of fold line 131 near input device 15 remain unchanged, while fold line 132 near output device 16 is implemented as shown in FIG5 . In another embodiment, 0 < α1 < α2. In other words, the rate of change of the lateral amplitude of fold line 131 is smaller than the rate of change of the lateral amplitude of fold line 132. In another embodiment, 0 < β1 < β2. In other words, the rate of change of the longitudinal period of fold line 131 is smaller than the rate of change of the longitudinal period of fold line 132. Optionally, the transverse amplitude of fold line 131 at the truncation is equal to or slightly smaller than the transverse amplitude of fold line 132 at the truncation. Optionally, the longitudinal period of fold line 131 at the truncation is equal to or slightly larger than the longitudinal period of fold line 132 at the truncation.

[0070] FIG8C is a schematic diagram showing the phase velocity of the electromagnetic wave transmitted on the slow-wave structure 1″ shown in FIG8A and FIG8B . As shown in FIG8C , the phase velocity of the electromagnetic wave transmitted in the fold line 132 continuously decreases, and the phase velocity of the electromagnetic wave transmitted in the fold line 131 is constant, or slowly decreases at a rate of change smaller than that of the fold line 132. Since the velocity change of the electron beam is small in the initial stage, the electron beam can be better synchronized with the electromagnetic wave transmitted along the fold line. In addition, unlike the jump shown in FIG2B , the phase velocity of the electromagnetic wave changes continuously at the truncation point between the fold line 131 and the fold line 132. In this way, the reflection of the electromagnetic wave generated at the truncation point can be reduced.

[0071] Although the folded slow-wave lines in the embodiments shown in FIG. 4A to FIG. 8C are shown to satisfy a sine or cosine function relationship, the embodiments of the present application are not limited thereto. The folded slow-wave lines can be of any folded shape, including but not limited to V-shaped, S-shaped, and U-shaped, as long as the lateral amplitude of the folded slow-wave line gradually increases, or the longitudinal period gradually decreases, or both are satisfied at the same time, so that the phase velocity of the electromagnetic wave transmitted in the folded slow-wave line along the longitudinal direction continuously changes gradually. Therefore, the embodiments of the present application aim to propose an extended full-period phase velocity gradient slow-wave structure, which only constrains the amplitude variation function A(z) and the period variation function p(z) of the folded slow-wave line. The folded slow-wave line can be represented by the general function relationship l SWS (z)=A(z)P(z), where the change relationship of the slow wave line in the transverse direction (i.e., x direction) is A(z), and the change relationship in the longitudinal direction (i.e., z direction) is P(z). A(z) can be a function that continuously increases along the z direction, and P(z) can be a function that continuously decreases along the z direction.

[0072] FIG9A shows a schematic diagram of a traveling wave tube (TWT) including a slow-wave structure with a V-shaped fold line, according to an embodiment of the present application. The TWT includes an electron gun, input / output devices, a magnetic focusing system, a slow-wave structure, and a collector. The slow-wave structure includes a metal fold line, a metal tube shell, and a dielectric support block. The dielectric support block is insulated from the metal tube shell and serves to support the fold line. Electrons emitted by the electron gun, under the focusing action of the focusing system, pass through the slow-wave circuit and ultimately enter the collector. An electromagnetic wave signal is input into the slow-wave structure via an input device. The electromagnetic wave transmitted along the metal fold line interacts with the electron beam passing through the slow-wave circuit, converting the electron's kinetic energy into electromagnetic wave energy, thereby amplifying the electromagnetic wave signal. The amplified electromagnetic wave signal is coupled to an external circuit via an output device. The fold line of the slow-wave structure is V-shaped. Along the direction of electron beam transmission (i.e., the longitudinal direction, z-direction), the lateral amplitude of the fold line gradually increases, while the longitudinal period gradually decreases. The electron beam in FIG9B is illustrated as a laterally divergent electron beam. On the one hand, the parameters of the fold line can be optimized to make the phase velocity of the electromagnetic wave transmitted along the fold line match the velocity of the electron beam, thereby improving the electron efficiency; on the other hand, the expansion of the lateral dimension of the fold line can match the laterally divergent electron beam, which not only reduces the electron beam density but also avoids the stability of the traveling wave tube caused by electron bombardment of the slow-wave structure in the output section.

[0073] Figure 9B shows a schematic diagram of a traveling wave tube including a slow-wave structure with an S-shaped folded line provided in an embodiment of the present application. The traveling wave tube includes an electron gun, an input and output device, a magnetic focusing system, a slow-wave structure, and a collector. The traveling wave tube of Figure 9A is similar to the traveling wave tube of Figure 9B, except that the folded line of the slow-wave structure of the traveling wave tube of Figure 9B is an S-shaped folded structure, and the electron beam of Figure 9B is illustrated as a strip-shaped electron beam. Along the direction of electron beam transmission (i.e., the longitudinal direction, the z-direction), the lateral amplitude of the folded line gradually increases, and the longitudinal period gradually decreases. The traveling wave tube shown in Figure 9B can improve electron efficiency, expand bandwidth, and increase the stability of the traveling wave tube operation. Although the electron beam of Figure 9B is illustrated as a strip-shaped electron beam, it can also be a transversely divergent electron beam or multiple circular electron beams, depending on the design of the magnetic focusing system. For a transversely divergent electron beam, a magnetic focusing system can be easily designed, and it is also beneficial to further improve electron efficiency and operating stability.

[0074] Although the embodiments shown in FIG. 4A to FIG. 9B are folded line slow-wave structures, the embodiments of the present application are not limited thereto, and the features of the folded lines described in FIG. 4A to FIG. 9B can also be applied to folded waveguides.

[0075] Figure 10 shows a schematic diagram of a slow-wave structure 2 including a folded waveguide provided in an embodiment of the present application. The slow-wave structure 2 includes a folded waveguide 23. The folded waveguide 23 has an amplitude in the transverse direction and a period in the longitudinal direction. The amplitude, period, or both of the folded waveguide 23 can be continuously and gradually changed in the longitudinal direction. The slow-wave structure 2 may further include a metal waveguide wall 21 and an electron beam channel 22. The folded waveguide 23 may have a sine-cosine shape, a V-shape, an S-shape, a U-shape, etc. In some embodiments, the transverse amplitude of the folded waveguide 23 increases along the longitudinal direction. In some embodiments, the longitudinal period of the folded waveguide 23 decreases along the longitudinal direction. In some embodiments, the transverse amplitude of the folded waveguide 23 increases along the longitudinal direction, and the longitudinal period decreases along the longitudinal direction. In some embodiments, the change in the transverse amplitude of the folded waveguide 23 along the longitudinal direction may satisfy an exponential function, a logarithmic function, a polynomial function, or a trigonometric function. In some embodiments, the change in the longitudinal period of the folded waveguide 23 along the longitudinal direction may satisfy an exponential function, a logarithmic function, a polynomial function, or a trigonometric function.

[0076] In some embodiments, the folded waveguide 23 may include multiple sections of folded waveguide. In one embodiment, the folded waveguide section near the input end may have a constant transverse amplitude and longitudinal period. In another embodiment, the period-decreasing factor of the longitudinal period of the folded waveguide section near the input end may be smaller than the period-decreasing factor of the longitudinal period of the folded waveguide section near the input end. In another embodiment, the amplitude-increasing factor of the transverse amplitude of the folded waveguide section near the input end may be smaller than the amplitude-increasing factor of the transverse amplitude of the folded waveguide section near the input end. In another embodiment, the transverse amplitude and longitudinal period of adjacent ends of two folded waveguide sections are the same or vary continuously.

[0077] The embodiment of the present application proposes a slow-wave structure and a planar traveling wave tube constructed by the slow-wave structure. By gradually increasing the lateral amplitude of the folded waveguide structure, or gradually reducing the longitudinal period, or satisfying both at the same time, the phase velocity of the electromagnetic wave transmitted in the folded slow-wave line along the longitudinal direction can be continuously and gradually changed. This continuously and gradually changing slow-wave structure can reduce the reflection of the slow-wave structure, while effectively suppressing the back-wave oscillation, and obtaining a wider working bandwidth. In addition, through the lateral amplitude and / or longitudinal period of the waveguide structure, the electromagnetic wave transmitted in the folded slow-wave line can be continuously changed to better match the speed of the electron beam, thereby improving the interaction efficiency. On the other hand, the slow-wave structure of the embodiment of the present application is simpler and easier to manufacture. By using fewer variable parameters (for example, amplitude growth factor and period decrement factor), the phase velocity gradient of the entire period can be achieved in the entire slow-wave structure, which is conducive to achieving global optimization through optimization algorithm to achieve higher electronic efficiency.

[0078] In addition, the present application provides various example embodiments, as described and as shown in the accompanying drawings. However, the present application is not limited to the embodiments described and illustrated herein, but can be extended to other embodiments. Many modifications and changes are obvious to those of ordinary skill in the art without departing from the scope of each implementation described. The choice of terms used in this article is intended to explain the principles of each implementation, practical application or improvement to the technology in the market, or to enable other ordinary technicians in this technology to understand the various implementations disclosed herein. References in the specification to "one embodiment", "the embodiment", "these embodiments" or "some embodiments" mean that the specific features, structures or characteristics described are included in at least one embodiment, and the appearance of these phrases in various places in the specification do not necessarily all refer to the same embodiment.

[0079] Although various embodiments have been described in language specific to structural features and / or methodological acts, it should be understood that the subject matter defined in the accompanying representations is not necessarily limited to the specific features or acts described. Rather, the specific features and acts are disclosed as example forms of implementing the claimed subject matter.

Claims

A slow-wave structure, comprising: A folded waveguide structure having a period in a longitudinal direction and an amplitude in a transverse direction perpendicular to the longitudinal direction, wherein at least one of the amplitude of a first portion of the waveguide structure and the period of the first portion gradually changes along the longitudinal direction. The slow-wave structure according to claim 1, wherein the first portion of the waveguide structure satisfies at least one of the following: an amplitude of the first portion continuously increases along the longitudinal direction; or a period of the first portion continuously decreases along the longitudinal direction. The slow-wave structure according to claim 2, wherein the amplitude or period of the first part satisfies any of the following functional relationships: exponential function, logarithmic function, polynomial function or trigonometric function. The slow-wave structure according to any one of claims 1 to 3, wherein the amplitude of the second portion of the waveguide structure in the transverse direction and the period in the longitudinal direction remain unchanged along the longitudinal direction, and the second portion is closer to the input end of the slow-wave structure than the first portion. The slow-wave structure according to any one of claims 1 to 3, wherein the amplitude of the second portion of the waveguide structure in the transverse direction is smaller than the amplitude of the first portion, the amplitude of the second portion continuously increases along the longitudinal direction at an amplitude change rate that is smaller than the amplitude change rate of the first portion, and the second portion is closer to the input end of the slow-wave structure than the first portion. The slow-wave structure according to any one of claims 1 to 3, wherein the period of the second portion of the waveguide structure in the longitudinal direction is greater than the period of the first portion, the period of the second portion continuously decreases along the longitudinal direction at a period change rate smaller than the period change rate of the first portion, and the second portion is closer to the input end of the slow-wave structure than the first portion. The slow-wave structure according to any one of claims 4 to 6, further comprising an attenuator arranged between the first portion and the second portion. The slow-wave structure according to any one of claims 1 to 7, wherein the waveguide structure comprises a folded waveguide. The slow-wave structure according to any one of claims 1 to 7, wherein the waveguide structure comprises a fold line. The slow-wave structure according to claim 9, further comprising: a metal tube shell extending in the longitudinal direction; and a dielectric support member insulated from the metal tube shell and supporting the waveguide structure. The slow-wave structure according to claim 9 or 10, wherein the folding line comprises a double-layer folding line. The slow-wave structure according to claim 11, wherein the slow-wave structure comprises a first ridge structure and a second ridge structure located on opposite sides of the double-layer folding line, and the first ridge structure and the second ridge structure are respectively parallel to the plane where the double-layer folding line is located. A traveling wave tube, comprising: An input-output device, an electronic transceiver component, a focusing component, and a slow-wave structure according to any one of claims 1 to 12; wherein the input-output device is configured to input electromagnetic waves to the input end of the slow-wave structure and output the electromagnetic waves from the output end of the slow-wave structure. The traveling wave tube according to claim 13, wherein the electron transceiver assembly is configured to emit the electron beam at a planar cathode emitting surface. The traveling wave tube according to claim 14, wherein the electron beam is a ribbon electron beam or a transversely divergent electron beam. An electronic device, comprising: Power supply device; And the traveling wave tube according to any one of claims 13 to 15, powered by the power supply device. A communication system comprising: A traveling wave tube according to any one of claims 13 to 15. The communication system according to claim 17, further comprising at least one of the following: a baseband, a mid-range radio frequency module, and an antenna.

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