A hybrid slow-wave structure based on transmission bandgap modulation to suppress back-wave oscillations

Abstract

This invention discloses a hybrid slow-wave structure for suppressing back-wave oscillations based on transmission bandgap modulation. It comprises two unit structures: a working unit and a modulation unit. Both unit structures consist of a rectangular coupling cavity, a circular electron beam channel, and a grating gap. The y-axis length of the grating gap in the modulation unit is greater than that in the working unit. This shifts the bandgap between modes 1 and 2 of the modulation unit downwards compared to the working unit. Consequently, the back-wave competition frequency of the working unit is modulated to a position close to the bandgap in the modulation unit. Even if the back-wave competition frequency of the working unit is located within the modulation unit's bandgap in the hybrid slow-wave structure, while the working frequency of the working unit is outside the modulation unit's bandgap, it still exhibits good transmission characteristics in the modulation unit, thereby suppressing back-wave competition oscillations without affecting signal transmission at the working frequency. This hybrid slow-wave structure possesses the characteristic of modulating the transmission bandgap and has significant application value in the field of terahertz vacuum electronic devices.

Description

Technical Field

[0001] This invention belongs to the field of vacuum electronic device technology. More specifically, it relates to a hybrid slow wave structure based on transmission bandgap modulation to suppress backwave oscillations, which can be used in backwave tubes and traveling wave tubes, and is especially suitable for terahertz backwave tubes operating in high-order modes. Background Technology

[0002] Slow-wave structures are the core of traveling-wave tubes (TWTs) and backward-wave tubes (WRTBs), which have wide applications in communications, spectral imaging, plasma diagnostics, and many other fields. For a beam-wave interaction circuit composed of a single slow-wave structure, the operating voltage line intersects not only with the operating mode at the operating point but also with other modes. When the intersection of these other modes is located in the backward-wave region, backward-wave oscillations are easily generated. Common methods to solve backward-wave oscillations include cutting off the circuit or adding attenuators. While these methods cut off the backward-wave oscillation loop, they also cut off the operating mode signal loop, making them unsuitable for WRTBs. To suppress the backward-wave competing oscillation mode without affecting the operating mode, a circuit with special control functions needs to be inserted into the operating circuit. This circuit only affects the oscillation loop at the backward-wave competing frequency.

[0003] Chinese invention patent CN112216579B, authorized on March 15, 2022, discloses a high-order backward wave oscillation suppression structure for a strip-beam traveling wave tube. This structure includes a shell, rectangular grids staggered on the top and bottom surfaces of the shell's inner cavity, and a row of periodically arranged rectangular coupling waveguides of the same size on each side of the shell. The two rows of rectangular coupling waveguides are offset along the axial direction by half a slow-wave period and also offset in the longitudinal direction, so that one rectangular coupling waveguide corresponds to one rectangular cavity. This invention, by loading staggered rectangular coupling waveguides on both sides of the slow-wave structure, simultaneously achieves the suppression and absorption of higher-order modes without affecting or disrupting the operating mode.

[0004] This invention patent is only applicable to strip-shaped traveling wave tubes, and the rectangular coupled waveguides are placed on both sides of the slow wave structure in an alternating manner, which makes the structural design more complex and difficult to process and manufacture. Summary of the Invention

[0005] The purpose of this invention is to solve the problem of back-wave competition oscillation in a single slow-wave structure. It proposes a hybrid slow-wave structure based on transmission bandgap modulation to suppress back-wave oscillation. A certain number of periodic modulation unit slow-wave structures are inserted into the circuit composed of working unit slow-wave structures. This improves signal transmission attenuation and disrupts excitation conditions at the back-wave competition frequency points in the working unit, thereby cutting off its back-wave oscillation loop without affecting the signal transmission at the working frequency point. This achieves the goal of stable operation of the hybrid slow-wave structure in its working mode.

[0006] To achieve the above-mentioned objectives, this invention provides a hybrid slow-wave structure based on transmission bandgap modulation to suppress back-wave oscillations, comprising:

[0007] A working unit circuit consisting of working units with a certain number of cycles;

[0008] Its characteristic is that it further includes:

[0009] A control unit circuit consisting of control units with a certain number of cycles is inserted into the working unit circuit;

[0010] Both the working unit and the control unit include a rectangular coupling cavity, a circular electron beam channel and a grating gap. The grating gap is connected to the rectangular coupling cavity and has the same x-direction depth as the rectangular coupling cavity. The circular electron beam channel passes through the center of the grating gap in the x-direction.

[0011] The y-axis length of the grating gap in the control unit is longer than that in the working unit.

[0012] The objective of this invention is achieved as follows.

[0013] This invention relates to a hybrid slow-wave structure based on transmission bandgap modulation to suppress back-wave oscillations. It comprises two unit structures: a working unit and a modulation unit. Both unit structures consist of a rectangular coupling cavity, a circular electron beam channel, and a grating gap. The y-axis length of the grating gap in the modulation unit is greater than that in the working unit. This shifts the bandgap between modes 1 and 2 of the modulation unit downwards compared to the working unit. Consequently, the back-wave competition frequency of the working unit is modulated to a position close to the bandgap in the modulation unit. Even if the back-wave competition frequency of the working unit is located within the modulation unit's bandgap in the hybrid slow-wave structure, while the working frequency of the working unit is outside the modulation unit's bandgap, it still exhibits good transmission characteristics in the modulation unit. This suppresses back-wave competition oscillations without affecting the signal transmission at the working frequency. This hybrid slow-wave structure possesses the characteristic of modulating the transmission bandgap and has significant application value in the field of terahertz vacuum electronic devices. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of a single slow-wave structure circuit;

[0015] Figure 2 This is a schematic diagram of a specific embodiment of the hybrid slow wave structure for suppressing back-wave oscillation based on transmission bandgap modulation of the present invention;

[0016] Figure 3 yes Figure 1 The diagram shows the vacuum structure of the working unit and the control unit, where (a) is the working unit and (b) is the control unit.

[0017] Figure 4This is a dispersion diagram of the working unit and control unit structure in this invention;

[0018] Figure 5 This is the phase velocity synchronization voltage diagram of the working unit and control unit structure in this invention;

[0019] Figure 6 This is a comparison diagram of the transmission loss of the hybrid slow-wave circuit and the single slow-wave circuit in this invention.

[0020] Figure 7 This is a comparison diagram of the operating spectra of the hybrid slow-wave circuit and the single slow-wave circuit in this invention. Detailed Implementation

[0021] The specific embodiments of the present invention will now be described with reference to the accompanying drawings to enable those skilled in the art to better understand the invention. It should be particularly noted that in the following description, detailed descriptions of known functions and designs that might obscure the main content of the invention will be omitted here.

[0022] In this embodiment, as Figure 1 As shown, the single slow wave structure consists of only the working unit circuit 4a.

[0023] Figure 2 This is a schematic diagram of a specific implementation of the hybrid slow wave structure based on transmission bandgap modulation to suppress back-wave oscillations according to the present invention.

[0024] In this embodiment, as Figure 2 As shown, this invention is based on a hybrid slow-wave structure that suppresses back-wave oscillations by controlling the transmission bandgap. It comprises a working unit circuit 4a consisting of working units with a certain number of cycles and a control unit circuit 4b consisting of control units with a certain number of cycles. The control unit circuit 4b is inserted into the working unit circuit 4a. In this embodiment, compared to... Figure 1 The single slow wave structure shown in this invention is based on a hybrid slow wave structure that suppresses back-wave oscillation by controlling the transmission bandgap. The control unit circuit 4b is inserted into the working unit circuit 4a from the middle position. The working unit circuit 4a includes a working unit with 8 cycles on the left and a working unit with 8 cycles on the right. The control unit circuit 4b includes a control unit with 4 cycles.

[0025] In this embodiment, as Figure 3 As shown, both the working unit and the control unit include a rectangular coupling cavity 1, a circular electron beam channel 2, and grating gaps 3a and 3b. The grating gaps 3a and 3b are connected to the rectangular coupling cavity 1 and have the same x-direction depth as the rectangular coupling cavity 1. The circular electron beam channel 2 passes through the center of the grating gaps 3a and 3b in the x-direction.

[0026] In this embodiment, as Figure 3As shown, the grating gaps 3a and 3b between the circular electron beam channel 2 and the rectangular coupling cavity 1 are arc-shaped, and the bottom surface of the grating gaps 3a and 3b in the y direction is semi-circular.

[0027] The grating gap 3a of the control unit has a longer y-direction length than the grating gap 3b of the working unit. Thus, as... Figure 4 As shown, the bandgap between mode 1 (mode 1-b) and mode 2 (mode 2-b) of the control unit is shifted downwards compared to the working unit. This causes the backwave competition frequency of the working unit to be controlled to a position close to the bandgap in the control unit. Even if the backwave competition frequency of the working unit is located in the bandgap of the control unit in the hybrid slow wave structure, while the working frequency of the working unit is located outside the bandgap of the control unit, it still has good transmission characteristics in the control unit, thereby suppressing backwave competition oscillation and not affecting the signal transmission of the working frequency.

[0028] In addition, such as Figure 2 As shown, the hybrid slow-wave structure of this invention, which suppresses back-wave oscillations based on transmission bandgap modulation, is connected to the standard waveguide 6 via a coupling structure 5, thereby transitioning the input and output of the hybrid slow-wave structure from the coupling structure to the standard waveguide. 7 represents the metal casing.

[0029] Figure 5 These are the phase velocity synchronization voltage curves for the two unit structures in this invention. For example... Figure 5 As shown, since the backwave competition frequency of the working unit is located near the bandgap of the control mode, the phase velocity synchronization voltage difference between the working unit and the control unit is large, while the working frequency is very small. This causes the excitation condition of the backwave competition frequency of the working unit to be destroyed in the control unit, while having little impact on the working frequency.

[0030] Figure 6 These are the transmission loss curves of the hybrid slow-wave circuit and the single slow-wave circuit in this invention. For example... Figure 6 As shown, the transmission loss of the working unit's backwave contention frequency is significantly increased in the hybrid slow-wave circuit, thereby attenuating and absorbing the backwave contention signal, while the transmission loss of the working frequency does not change significantly in the two circuits.

[0031] Figure 7 This refers to the operating spectrum of the hybrid slow-wave circuit and the single slow-wave circuit in this invention. For example... Figure 7 As shown, the operating spectrum of the single slow-wave structure circuit has both the back-wave competition frequency and the operating frequency, resulting in competitive oscillation. In contrast, the operating spectrum of the hybrid slow-wave circuit is pure and operates stably at the operating frequency, indicating that the control unit suppresses the back-wave competition frequency.

[0032] In summary, this invention, based on a hybrid slow-wave structure for suppressing back-wave oscillations through transmission bandgap modulation, can control the transmission bandgap of a single slow-wave structure, thereby increasing the transmission loss at the back-wave competition frequency and disrupting the excitation conditions, thus suppressing back-wave competition oscillations and ensuring stable operation. This hybrid slow-wave structure possesses the characteristic of controlling the transmission bandgap and has significant application value in the field of terahertz vacuum electronic devices.

[0033] Although the illustrative specific embodiments of the present invention have been described above to enable those skilled in the art to understand the invention, it should be understood that the invention is not limited to the scope of the specific embodiments. For those skilled in the art, various changes are obvious as long as they are within the spirit and scope of the invention as defined and determined by the appended claims, and all inventions utilizing the concept of the present invention are protected.

Claims

1. A hybrid slow-wave structure based on transmission bandgap modulation to suppress back-wave oscillations, comprising: A working unit circuit consisting of working units with a certain number of cycles; Its characteristic is that it further includes: A control unit circuit consisting of control units with a certain number of cycles is inserted into the working unit circuit; Both the working unit and the control unit include a rectangular coupling cavity, a circular electron beam channel and a grating gap. The grating gap is connected to the rectangular coupling cavity and has the same x-direction depth as the rectangular coupling cavity. The circular electron beam channel passes through the center of the grating gap in the x-direction. The y-axis length of the grating gap in the control unit is longer than the y-axis length of the grating gap in the working unit; The grating gap between the circular electron beam channel and the rectangular coupling cavity is arc-shaped, and the bottom surface of the grating gap in the y-direction is semi-circular.

2. The hybrid slow-wave structure based on transmission bandgap modulation to suppress back-wave oscillations according to claim 1, characterized in that, The control unit circuit is inserted into the working unit circuit from the middle position.

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