All-metal slow wave structure of periodically slotted flat plate structure loaded rectangular waveguide

Abstract

The invention discloses an all-metal slow-wave structure with a periodically slotted flat plate structure loaded with a rectangular waveguide, which is characterized in that a double-F-shaped slot structure is periodically etched on a metal flat plate, and the periodically slotted flat plate is embedded into the rectangular waveguide to form an all-metal slow-wave structure, so that a double-strip electron beam channel is formed. The structure greatly enhances the longitudinal field intensity at an electron beam channel, has higher coupling impedance than that of a conventional slow wave structure at the frequency band, keeps lower synchronous voltage, and can simultaneously realize synchronization of forward wave / backward wave regions. In addition, the structure also has the advantages of all-metal structure, open internal space, heat dissipation convenience, simple structure and easiness in processing. Therefore, the structure provided by the invention is particularly suitable for designing W-band traveling wave tube amplifiers or backward wave oscillators with relatively high interaction electron efficiency and output power.

Description

Technical Field

[0001] This invention relates to a microwave vacuum electronic device suitable for wireless communication, and more particularly to a slow-wave structure made entirely of metal. Background Technology

[0002] With the evolution of wireless communication systems towards millimeter wave and even submillimeter wave frequency bands, especially in application scenarios such as 5G / 6G base station front-end, wireless backhaul links, fixed point-to-point microwave access, and airborne / vehicle-mounted high-speed data links, stringent requirements have been placed on radio frequency power sources, namely "low voltage drive, large bandwidth, high output power, miniaturization, and high reliability".

[0003] Among various millimeter-wave power sources, vacuum electronic devices exhibit a clear advantage over solid-state devices due to their high power, high efficiency, high gain, and excellent bandwidth performance. Millimeter-wave traveling wave tubes (TWTs) or back-wave tubes (BWOs) have consistently been core components of RF power sources in point-to-point 5G / 6G wireless links due to their superior high-power transmission capabilities. Especially in the W-band around 94 GHz, atmospheric attenuation is minimal and interference immunity is excellent, making it highly suitable for high data rate transmissions.

[0004] Traveling wave tubes (TWTs) and back-wave tubes (BWOs) are two typical microwave vacuum electronic devices designed based on the slow wave structure (SWS) working principle. The slow wave structure (SWS) is the key core component for energy exchange in TWTs and BWOs.

[0005] Currently, commonly used slow wave structures (SWS) include folded waveguides, sinusoidal waveguides, staggered double-grating waveguides, and corrugated waveguides. To achieve high output power, these structures often require operating voltages above 20kV, corresponding to coupling impedances of approximately 1.5-3Ω. This limits the energy exchange efficiency between the electron beam and the electromagnetic field, making it difficult to exceed 200W in output power. Furthermore, the high operating voltage significantly increases the size, weight, and cost of the devices, hindering the development of wireless communication systems towards lightweight, low-power, and high-reliability designs.

[0006] In addition, these structures generally suffer from problems such as complex three-dimensional structure, high processing difficulty, and poor reliability. In particular, the electron injection channel poses a great challenge to the processing and assembly process under harsh process conditions such as sub-millimeter period and micron-level processing tolerance and surface roughness.

[0007] Therefore, there is an urgent need for a novel W-band slow-wave structure that is simple in structure, all-metal, with significantly reduced normalized phase velocity and greatly improved coupling impedance, in order to overcome the limitations of existing slow-wave structures in terms of manufacturing complexity and low-voltage operation, and to provide technical support for the widespread application of next-generation millimeter-wave and even terahertz band traveling-wave tubes / returning-wave tubes in wireless communication. Summary of the Invention

[0008] Purpose of the invention: In view of the above-mentioned prior art, an all-metal slow wave structure with a periodically slotted flat plate structure loaded with a rectangular waveguide is proposed, which is suitable for low-voltage high-power traveling wave tubes / returning wave tubes in the W-band.

[0009] Technical solution: An all-metal slow-wave structure for loading a rectangular waveguide with a periodically slotted flat plate structure, comprising: a rectangular waveguide and a periodically slotted flat plate; the periodically slotted flat plate is disposed within the rectangular waveguide along the length of the waveguide, dividing the inner cavity of the rectangular waveguide into two upper and lower strip-shaped electron beam channels.

[0010] Furthermore, the periodically slotted plate includes a metal plate and double F-shaped slots periodically arranged along the length of the metal plate.

[0011] Furthermore, the double F-shaped groove is composed of a vertical groove arranged along the width direction of the metal plate and two parallel transverse grooves near each end of the vertical groove; wherein, the two transverse grooves at one end face the same direction and face the opposite direction to the two transverse grooves at the other end; the width of each part of the double F-shaped groove is the same, and the overall structure is centrally symmetrical.

[0012] Furthermore, the inner walls of the rectangular waveguide have grooves that are opened opposite each other along the length of the waveguide, and the two sides of the periodically slotted plate are respectively embedded in the grooves on both sides.

[0013] Beneficial Effects: Existing W-band slow-wave structures, such as sinusoidal waveguides, folded waveguides, interlaced double-grid waveguides, and corrugated waveguides, have high normalized phase velocities and coupling impedances of only 1.5-3Ω, which greatly limits operating efficiency and output power. Furthermore, operating voltages exceeding 20kV significantly increase the size, weight, and cost of the electron gun insulation and high-voltage power supply. In addition, their complex structures generally lead to low consistency and stability in mass production of traditional EDM, ultra-precision milling, and LIGA processes. In summary, existing W-band slow-wave structures struggle to simultaneously meet the requirements of low voltage, high power, wide bandwidth, miniaturization, and high reliability.

[0014] This invention utilizes a periodically etched double F-groove structure on a metal plate to create an all-metal slow-wave structure by embedding the periodically slotted plate into a rectangular waveguide. This structure naturally possesses dual-strip electron beam channels. This structure significantly enhances the longitudinal field strength at the electron beam channels, exhibits a higher coupling impedance than conventional slow-wave structures in this frequency band, and maintains a lower synchronization voltage, enabling simultaneous synchronization in both forward and backward wave regions. Furthermore, the structure of this invention offers advantages such as an all-metal structure, open internal space for heat dissipation, simple structure, and ease of fabrication. Therefore, this structure is particularly suitable for designing W-band traveling-wave tube amplifiers or backward-wave oscillators with high interaction electron efficiency and output power. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the all-metal slow-wave structure of the periodically slotted flat plate structure loaded with a rectangular waveguide according to the present invention. Figure 2 This is a schematic diagram of the rectangular waveguide structure of the all-metal slow-wave structure of the present invention; Figure 3 This is a schematic diagram of the periodically slotted plate of the all-metal slow-wave structure of the present invention. Figure 4 This is a schematic diagram of the unit structure dimensions of the all-metal slow-wave structure of the present invention; Figure 5 This is a schematic diagram of the working of the strip electron beam of the all-metal slow-wave structure of the present invention; Figure 6 The Brillouin curve of the single-period slow-wave structure in the embodiment is shown. Figure 7 The high-frequency characteristic curve of the forward wave region in the embodiment is shown. Figure 8 The high-frequency characteristic curve of the backwave region in the embodiment is shown. Detailed Implementation

[0016] The invention will now be further explained with reference to the accompanying drawings.

[0017] An all-metal slow-wave structure of a periodically slotted flat-plate loaded rectangular waveguide is proposed, suitable for W-band low-voltage high-power traveling-wave tubes / returning-wave tubes. Its specific structure is as follows: Figure 1 As shown. To better demonstrate its internal structure, Figure 1 A partial rectangular waveguide structure is hidden within it. For example... Figure 1 As shown, it consists of a rectangular waveguide 1 and a periodically slotted plate 2, wherein the periodically slotted plate 2 is arranged inside the rectangular waveguide 1 along the length of the waveguide, forming a complete all-metal slow wave circuit structure.

[0018] like Figure 2As shown, the rectangular waveguide 1 is composed of a rectangular waveguide 11 and grooves 12 formed by relatively opening on the inner walls on both sides of the waveguide along the waveguide length direction. Specifically, a groove 12 with a certain depth is opened at the middle position of the inner cavity side wall of the rectangular waveguide 1, and the two side edges of the periodically slotted plate 2 are respectively inserted into the grooves 12 on both sides to achieve the insertion and assembly of the plate structure.

[0019] As Figure 3 shown, the periodically slotted plate 2 is composed of a metal plate 22 and double F-shaped grooves 21 arranged periodically in the length direction of the metal plate 22. Specifically, the double F-shaped groove 21 is composed of a vertical groove arranged along the width direction of the metal plate 22 and two parallel horizontal grooves near both ends of the vertical groove. Among them, the orientations of the two horizontal grooves at one end are the same and opposite to those of the two horizontal grooves at the other end. The widths of each part of the double F-shaped groove 21 are the same, and the overall structure is centrosymmetric.

[0020] Among them, the width of the metal plate 22 is w3, the groove period is p; the groove width of the double F-shaped groove 21 is t1, the width of the horizontal groove is w1, the distance between the two horizontal grooves at one end is w2, and the distance from the horizontal groove relatively close to the center point at one end to the other end of the vertical groove is L2. Among the parameters L2, w2, t1, the relationship w2 + 2t1 < L2 is satisfied; between the period parameter p and the parameters t2, w1, p = 2w1 + t1 is satisfied.

[0021] As Figure 4 shown, the inner cavity width of the rectangular waveguide 1 is wa, the outer height of the rectangular waveguide 1 is wb, and the thickness of the metal plate 22 is t.

[0022] As Figure 5 shown, the periodically slotted plate 2 divides the inner cavity of the rectangular waveguide 1 into two natural strip electron beam channels above and below. Therefore, strip electron beam one 31 and strip electron beam two 32 can be respectively loaded at the upper and lower surface positions of the periodically slotted plate 2. When the strip electron beam is injected into the slow-wave structure, the electron beam will interact with the high-frequency electric field signal in the slow-wave structure. The high-frequency signal modulates the density of the strip electron beam, causing some electrons to accelerate and some electrons to decelerate, and obtaining energy from the kinetic energy of the electron beam to achieve energy amplification.

[0023] In this embodiment, its structural parameters are as follows: Rectangular waveguide 1: wa = 1.27 mm, wb = 2.15 mm; Periodically slotted plate 2: t = 0.2 mm, t1 = 0.1 mm, w2 = 0.12 mm, L2 = 0.83 mm, w1 = 0.23 mm, w3 = 2.27 mm, p = 0.55 mm. The slow-wave structures of other frequency bands can be obtained by scaling the slow-wave structure in this embodiment.

[0024] Figure 6 This is the Brillouin curve of phase shift and frequency relationship obtained in this embodiment. The Brillouin curve is the curve of free space wavenumber and phase constant. The ratio of the ordinate to the abscissa of any point on the Brillouin curve is the ratio of phase velocity to the speed of light. It can be seen that it is a fast wave and a slow wave. Among them, 0 to π is the zeroth space harmonic (fundamental wave), π to 2π is the -1st harmonic, 2π to 3π is the 1st harmonic, and 3π to 4π is the 2nd harmonic. Figure 6 The diagram shows a light speed line, a 10kV voltage line, and a 6kV voltage line. The region to the left of the light speed line represents fast waves, and the region to the right represents slow waves. Therefore, from... Figure 6 As can be seen, most of the data falls within the slow wave region. The 10kV operating voltage line has a synchronization region with the forward wave of the -1st space harmonic, which can be used to design a traveling wave tube amplifier. The 6kV voltage line intersects with the backward wave region of the 1st harmonic, so under this voltage condition, it can be used to design a backward wave oscillator. Both devices have a lower synchronization voltage than conventional slow wave structures.

[0025] Figure 7 The high-frequency characteristic curves of the forward wave region are given. Figure 6 The horizontal axis represents frequency, the left vertical axis represents the normalized phase velocity (ratio of phase velocity to the speed of light), and the right vertical axis represents coupling impedance. As can be seen from the figure, in this embodiment, the normalized phase velocity in the 90-98 GHz frequency band is... V pc / C 0 = 0.1889 - 0.2183, coupling impedance K c =11.45-35Ω, and the normalized phase velocity at a typical frequency of 94GHz is V pc / C 0 = 0.1973, corresponding to a synchronization voltage of 10.26 kV, and coupling impedance K c =13.7, compared with the traditional slow wave structure, it not only has a lower synchronization voltage, but also a higher coupling impedance, making it very suitable for designing a new type of low-voltage, high-power, high-efficiency traveling wave tube amplifier.

[0026] Figure 7 The high-frequency characteristic curves of the return wave region are given, from Figure 7 As can be seen from the data, in this embodiment, the normalized phase velocity is within the 90-98GHz frequency band. V pc / C 0 = 0.1369 - 0.1738, Coupling impedance K c=7.03-9.64Ω, and the normalized phase velocity at a typical frequency of 94GHz is V pc / C 0 = 0.1553, corresponding to a synchronization voltage of 6.28kV, and coupling impedance K c =6.32Ω. Therefore, even in the backwave region of the first harmonic, it not only has a lower synchronization voltage but also a higher coupling impedance compared to the traditional slow-wave structure, making it very suitable for designing a low-voltage, high-power, and high-efficiency backwave oscillator.

[0027] The structure of this invention has a higher coupling impedance than conventional slow-wave structures and can operate with dual-strip electron beams, reducing electron beam density and improving interaction efficiency. It can fully utilize the longitudinal field component of the electromagnetic wave for energy exchange with the electron beam, thereby increasing the output power and electronic efficiency of the traveling-wave device. Furthermore, as described above, the all-metal slow-wave structure of the periodically slotted flat-plate loaded rectangular waveguide of this invention provides a more open energy exchange space, which helps solve the problems of heat dissipation and electron accumulation, ensuring the tube's service life and operational stability.

[0028] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. An all-metal slow-wave structure with a periodically slotted flat plate structure loading a rectangular waveguide, characterized in that, include: A rectangular waveguide (1) and a periodically slotted plate (2); the periodically slotted plate (2) is arranged in the rectangular waveguide (1) along the length of the waveguide, dividing the inner cavity of the rectangular waveguide (1) into two strip-shaped electron beam channels.

2. The all-metal slow-wave structure according to claim 1, characterized in that, The periodically slotted plate (2) includes a metal plate (22) and double F-shaped slots (21) periodically arranged along the length of the metal plate (22).

3. The all-metal slow-wave structure according to claim 2, characterized in that, The double F-shaped groove (21) is composed of a vertical groove arranged along the width direction of the metal plate (22) and two parallel transverse grooves near each end of the vertical groove; wherein, the two transverse grooves at one end are oriented in the same direction and are oriented in the opposite direction to the two transverse grooves at the other end; the width of each part of the double F-shaped groove (21) is the same and the overall structure is centrally symmetrical.

4. The all-metal slow-wave structure according to any one of claims 1-3, characterized in that, The inner walls of the rectangular waveguide (1) have grooves (12) that are opened opposite each other along the length of the waveguide. The two sides of the periodically slotted plate (2) are respectively embedded in the grooves (12) on both sides.

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