Folded waveguide slow wave structure with improved connecting waveguides and traveling wave tube

Abstract

The application relates to a folded waveguide slow wave structure with improved connecting waveguide and a traveling wave tube. The folded waveguide slow wave structure comprises a straight waveguide section and a connecting waveguide section in communication, and the width length of the connecting waveguide section is smaller than that of the straight waveguide section. According to the folded waveguide slow wave structure, the reflection of the straight waveguide section width caused by the existence of the electron beam channel is compensated by reducing the width size of the connecting waveguide, the matching performance of the slow wave structure is optimized, and the load capacity of the short millimeter wave and terahertz traveling wave tube using the folded waveguide slow wave structure is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of microwave vacuum electron technology. More particularly, it relates to a folded waveguide slow wave structure with improved connecting waveguide and a traveling wave tube. BACKGROUND

[0002] Traveling wave tubes belong to microwave vacuum electron devices, which have the characteristics of high power, wide bandwidth and high gain, and are an important class of millimeter wave or terahertz power sources to meet the application requirements of the next generation of high-speed wireless communication systems. The slow wave structure is the core part of the microwave vacuum electron device, which functions to reduce the phase velocity of the electromagnetic wave transmitted therein, so as to keep it in synchronization with the electron beam, so as to obtain effective interaction between standing waves.

[0003] According to the current development of short millimeter wave and terahertz traveling wave tubes at home and abroad, the folded waveguide has become the most commonly used slow wave structure. The folded waveguide slow wave structure is to bend the rectangular waveguide cavity along the electric field plane to form a periodic structure of a series of folded waveguide units including straight waveguide sections and connecting waveguide sections, and a circular electron beam channel is located on the central axis of the folded waveguide slow wave structure, wherein a represents the length of the wide side of the rectangular waveguide, b is the length of the narrow side of the rectangular waveguide, the geometric period is p, the height of the straight waveguide is h, and the radius of the electron beam channel is r c . The cavity of the connecting waveguide section of the folded waveguide can have a U-shaped bending structure such as Figure 1A , or a right-angle bending structure such as Figure 1B . In the conventional folded waveguide slow wave structure, the straight waveguide section and the connecting waveguide section have the same wide side length and the same narrow side length.

[0004] One of the advantages of the folded waveguide slow wave structure is that the coupling structure is simple, and it can be directly coupled in or out through the rectangular waveguide. In general cases, its matching characteristics can meet the engineering application requirements, but in special application conditions such as communication, in addition to the requirements of power, bandwidth, gain, efficiency, etc., strict requirements are also put forward for the matching characteristics of the device. As a structure formed by bending the rectangular waveguide along the E plane, the internal reflection of the folded waveguide is mainly derived from the electron beam channel area. Especially in the terahertz field, in order to realize the continuous wave operation of the device with large power, a larger electron beam channel size is often used, which will exacerbate the deterioration of the matching of the folded waveguide, and ultimately affect the communication characteristics such as the in-band consistency of the device. Therefore, the matching of the folded waveguide slow wave structure has become the primary problem to be solved in the field of application.

[0005] At present, the matching optimization of the folded waveguide is generally realized through the coupling structure, for example, by setting a gradual change or single / multiple mutations of one or two sizes on the rectangular waveguide, but the improvement is limited. At present, scholars at home and abroad have proposed a variety of new folded waveguide slow wave structures, all of which are to improve the coupling impedance of the folded waveguide slow wave structure, and there is a lack of research on new structures mainly for the optimization of the matching performance of the folded waveguide. SUMMARY

[0006] Therefore, the present application provides a folded waveguide slow wave structure with improved connecting waveguide, which comprises a straight waveguide section and a connecting waveguide section in communication, and the width length of the connecting waveguide section is less than that of the straight waveguide section, so that the folded waveguide slow wave structure with optimized matching performance is obtained.

[0007] Preferably, the electron beam channel is a circular channel.

[0008] Preferably, the width length of the straight waveguide section is 1.1-1.5 times that of the connecting waveguide section.

[0009] Preferably, the folded waveguide slow wave structure has a U-shaped connecting waveguide section or a right-angle connecting waveguide section.

[0010] In another aspect of the present application, a traveling wave tube is provided, which comprises the folded waveguide slow wave structure as described above.

[0011] In still another aspect of the present application, a folded waveguide slow wave structure device is provided, which comprises the folded waveguide slow wave structure as described above.

[0012] In yet another aspect of the present application, a design method of the folded waveguide slow wave structure as described above is provided, which comprises

[0013] designing an initial folded waveguide slow wave structure according to requirements, the initial slow wave structure comprising a straight waveguide section and a connecting waveguide section in communication, wherein the straight waveguide section and the connecting waveguide section have the same initial width length,

[0014] obtaining the folded waveguide slow wave structure with optimized matching performance by reducing the width length of the connecting waveguide section or increasing the width length of the straight waveguide section by using three-dimensional electromagnetic software.

[0015] Preferably, the folded waveguide slow wave structure has a U-shaped connecting waveguide section or a right-angle connecting waveguide section.

[0016] Preferably, the width length of the straight waveguide section is 1.1-1.5 times that of the connecting waveguide section.

[0017] The present application has the following advantages:

[0018] The folded waveguide slow wave structure of the present application, based on the conventional folded waveguide structure, compensates the reflection of the straight waveguide section wide edge due to the existence of the electron beam channel by reducing the wide edge size of the connecting waveguide or increasing the wide edge size of the connecting waveguide, improves the slow wave structure matching performance, and solves the problem that the matching performance of the conventional folded waveguide slow wave structure is difficult to be further optimized. The folded waveguide slow wave structure of the present application has the characteristics of simple structure and good compatibility with the current precision machining, can realize higher matching performance, and further improves the load capacity of the traveling wave tube.

[0019] According to the folded waveguide slow wave structure, the traveling wave tube and the device of the present application, they can be widely applied in the new generation of mobile communication equipment, the mobile communication base station equipment in the wideband wireless mobile communication technology, and the transmitting equipment in the satellite transmitting field and the broadcast television network field. BRIEF DESCRIPTION OF DRAWINGS

[0020] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed to be used in the embodiment description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0021] Figure 1A And 1B The figure shows the schematic diagram of the folded waveguide unit of the conventional folded waveguide slow wave structure.

[0022] Figure 2 The figure shows the schematic diagram of the folded waveguide slow wave structure of the first embodiment of the present application.

[0023] Figure 3 The figure shows the schematic diagram of the folded waveguide slow wave structure of the second embodiment of the present application.

[0024] Figure 4 The figure shows the VSWR comparison curve of the slow wave structure of the example 1 and the comparative example of the present application.

[0025] Figure 5 The figure shows the VSWR comparison curve of the slow wave structure of the example 2 and the comparative example of the present application. DETAILED DESCRIPTION

[0026] In order to make the technical solutions and advantages of the present application more clear, the embodiments of the present application will be further described in detail below with reference to the drawings.

[0027] The matching performance of the traveling wave tube can be measured by voltage standing wave ratio (VSWR), and the matching performance determines whether the traveling wave tube can work stably and reliably. The smaller the VSWR is, the better the matching is; the higher the VSWR is, the worse the matching is. Improving the matching of the traveling wave tube has the following two advantages: one is that the load capacity of the traveling wave tube is enhanced, and the other is that the traveling wave tube can work stably and reliably. The matching of the slow wave structure is a key factor to determine the matching of the whole tube, and the poor matching of the slow wave structure can easily cause the oscillation of the traveling wave tube. The oscillation can cause the following harms: the efficiency is reduced, the signal output power is reduced, and even the normal amplification of the traveling wave tube is destroyed; if the oscillation frequency falls within the working frequency band of the local machine, the normal work of the local machine is interfered, and even the "ringing" phenomenon occurs in the electronic countermeasure system, so that the system collapses; if the oscillation frequency falls within the working frequency band of other devices on the working platform, the corresponding devices are interfered, and the difficulty of the isolation design between the device antennas is increased

[0028] Embodiments of the present application provide a folded waveguide slow wave structure with improved connecting waveguide, which comprises a straight waveguide section and a connecting waveguide section in communication, wherein the width length of the connecting waveguide section is smaller than the width length of the straight waveguide section, so as to compensate the reflection of the straight waveguide section width caused by the existence of the electron beam channel, and optimize the matching performance of the slow wave structure. The folded waveguide slow wave structure is beneficial to improve the load capacity of the short millimeter wave and terahertz traveling wave tube using the slow wave structure.

[0029] Another embodiment of the present application provides a design method of the folded waveguide slow wave structure, which comprises designing an initial folded waveguide slow wave structure according to the requirement, the initial slow wave structure comprising a straight waveguide section, a connecting waveguide section and an electron beam channel in communication, wherein the straight waveguide section and the connecting waveguide section have the same initial width length and the same narrow length; and obtaining the folded waveguide slow wave structure with optimized matching performance by reducing the width length of the connecting waveguide section or increasing the width length of the straight waveguide section by using three-dimensional electromagnetic software. The initial slow wave structure has a U-shaped connecting waveguide section or a right-angle connecting waveguide section. The width length of the straight waveguide section of the folded waveguide slow wave structure with optimized matching performance is 1.1-1.5 times of the width length of the connecting waveguide section.

[0030] The folded waveguide slow wave structure and the design method of the present application are described below with reference to examples.

[0031] Example 1

[0032] The folded waveguide slow wave structure is designed by using three-dimensional electromagnetic software CST, and the initial folded waveguide slow wave structure is designed according to the requirement, and the obtained structure size (unit: mm) is as follows: the initial width length of the waveguide a = 2, the narrow length of the waveguide b = 0.3, the geometric period p = 1.2, the length of the straight waveguide h = 0.55, the radius of the electron beam channel r = 0.24, and the connecting waveguide section is a U-shaped structure, as shown in c Figure 2 ​As shown, the matching performance of ten geometric period slow wave structures is calculated as a comparative example. By reducing the width of the connecting waveguide segment and calculating the matching performance of ten geometric period slow wave structures, the slow wave structure of the present invention with optimized matching performance is obtained, wherein the optimized width of the connecting waveguide is a1 = 1.8 and the width of the straight waveguide segment is a = 2, as Example 1.

[0033] The simulated VSWR curves of Example 1 and the comparative example slow-wave structure are shown below. Figure 4 As shown in the figure. It can be seen that the comparative simulation results are as follows... Figure 5 As shown by the dashed line, the VSWR of the slow-wave circuit in the 85-115 GHz band is generally less than 1.6. Simulation results using the folded waveguide slow-wave structure with a reduced wide side of the connecting waveguide section, as described in this invention, are as follows. Figure 5 As shown by the solid line, the VSWR of the slow-wave circuit in the 85-115 GHz band is less than 1.4. Simulation results show that the voltage standing wave ratio of the novel structure of this invention is less than the corresponding values ​​at each frequency of a conventionally designed folded waveguide slow-wave structure with the same width, and the port matching is significantly improved.

[0034] Example 2

[0035] A folded waveguide slow-wave structure was designed using the 3D electromagnetic software CST. The initial folded waveguide slow-wave structure was designed according to requirements, and the resulting structural dimensions (unit: mm) are as follows: initial wide side length a = 1.8, narrow side length b = 0.3, geometric period p = 1.2, straight waveguide length h = 0.55, and electron beam channel radius r. c =0.24, the waveguide segment is a right-angle structure, such as Figure 3 As shown, the matching performance of ten geometric period slow wave structures is calculated as a comparative example. By increasing the width of the straight waveguide segment and calculating the matching performance of ten geometric period slow wave structures, the slow wave structure of the present invention with optimized matching performance is obtained, wherein the optimized width of the straight waveguide segment a1 = 2.2 and the width of the connecting waveguide segment a = 1.8, as Example 2.

[0036] The simulated VSWR curves of Example 2 and the comparative example slow-wave structure are shown below. Figure 5 As shown, the simulation results of the comparative slow-wave circuit show that the VSWR in the 90-115GHz band is generally less than 1.4. The simulation results of the folded waveguide slow-wave structure with a reduced width of the connecting waveguide section in this invention show that the VSWR in the 90-115GHz band is generally less than 1.1. The simulation results show that the voltage standing wave ratio of the novel structure of this invention is lower than the corresponding values ​​at each frequency of a conventionally designed folded waveguide slow-wave structure with the same width, and the port matching is significantly improved.

[0037] The folded waveguide slow wave structure according to the present application solves the problem that the matching performance of the conventional folded waveguide slow wave structure is difficult to be further optimized, and the structure can realize smaller VSWR without increasing the process complexity and precision, thereby improving the load capacity of the traveling wave tube.

[0038] In still another embodiment of the present application, a folded waveguide slow wave traveling wave tube is provided, which comprises the folded waveguide slow wave structure described above.

[0039] In still another embodiment of the present application, a folded waveguide slow wave device is provided, which comprises the folded waveguide slow wave structure described above.

[0040] The present application, on the basis of the conventional folded waveguide, compensates the reflection of the wide side of the straight waveguide section due to the existence of the electron beam channel by reducing the length of the wide side of the connecting waveguide section or increasing the length of the wide side of the straight waveguide section, realizes the optimization of the matching performance of the slow wave structure, and is suitable for improving the load capacity of the short millimeter wave and terahertz traveling wave tube using the slow wave structure.

[0041] Obviously, the above embodiments of the present application are only examples for clearly illustrating the present application, and are not intended to limit the embodiments of the present application. For those skilled in the art, other different forms of changes or variations can be made on the basis of the above description, and it is impossible to enumerate all the embodiments here. Any obvious changes or variations derived from the technical solutions of the present application are still within the protection scope of the present application.

Claims

1. A folded waveguide slow-wave structure with improved connection waveguide, characterized in that, The folded waveguide slow wave structure is a periodic structure formed by bending a rectangular waveguide cavity along an electric field to form a series of folded waveguide units, including straight waveguide segments and connecting waveguide segments. The folded waveguide slow wave structure includes connected straight waveguide segments, connecting waveguide segments, and electron beam channels. The width of the connecting waveguide segment is smaller than the width of the straight waveguide segment, resulting in a folded waveguide slow wave structure with optimized matching performance.

2. The folded waveguide slow-wave structure according to claim 1, characterized in that, The electron injection channel is a circular channel.

3. The folded waveguide slow-wave structure according to claim 1, characterized in that, The width of the straight waveguide segment is 1.1 to 1.5 times the width of the connecting waveguide segment.

4. The folded waveguide slow-wave structure according to claim 1, characterized in that, The folded waveguide slow wave structure has U-shaped or right-angle connected waveguide segments.

5. A traveling wave tube, characterized in that, The traveling wave tube includes the folded waveguide slow wave structure as described in claim 1.

6. A folded waveguide slow-wave structure device, characterized in that, The device includes the folded waveguide slow wave structure as described in claim 1.

7. A design method for a folded waveguide slow wave structure according to claim 1, characterized in that, The method includes An initial folded waveguide slow-wave structure is designed according to requirements. This initial folded waveguide slow-wave structure includes a connected straight waveguide segment, a connecting waveguide segment, and an electron beam channel, wherein the straight waveguide segment and the connecting waveguide segment have the same initial width length. By using three-dimensional electromagnetic software, a folded waveguide slow wave structure with optimized matching performance can be obtained by either reducing the width of the connecting waveguide segment or increasing the width of the straight waveguide segment.

8. The design method for folded waveguide slow wave structure according to claim 7, characterized in that, The folded waveguide slow wave structure has U-shaped or right-angle connected waveguide segments.

9. The design method for folded waveguide slow wave structure according to claim 7, characterized in that, The width of the straight waveguide segment is 1.1 to 1.5 times the width of the connecting waveguide segment.

Images