CN201540945U - meander slot waveguide slow wave line - Google Patents

Abstract

A serpentine groove guide slow-wave line belongs to the technical field of electronic microwave tubes, in particular to a structure of a slow-wave line in a microwave tube high-frequency system. The structure is formed by bending the groove back and forth along the direction of a groove guide crossheading, the electric field of a groove guide middle ground mode is the strongest in a slow-wave line vertical shaft, and just generates the strongest interaction with an electron beam; a gap is formed between the upper metal plate and the lower metal plate of the groove guide without special electron beam channel, and the side wall for supporting the gap of the upper and the lower metal plates is made of metal material, insulating material or microwave absorption material. The serpentine groove guide provided by the utility model reserves the advantages of large size, low loss and broad band of the groove guide, and the serpentine groove guide slow-wave line has higher output power and efficiency due to the through allowance of the electron beam with a large size, and at the same time, the slow-wave line has the characteristics of relatively simple structure, low requirement on the processing precision and easy processing. The serpentine groove guide slow-wave line provided by the utility model is particularly suitable for being used in traveling wave tubes in the wave bands of millimeter wave and submillimeter wave.

Description

meander slot waveguide slow wave line

technical field

The utility model belongs to the technical field of microwave electron tubes, and relates to a slow wave line structure in a microwave tube high-frequency system.

Background technique

When the ordinary waveguide used as a microwave transmission line works in the millimeter wave, especially the short millimeter wave band, the size will become very small, which greatly limits the power capacity of microwave transmission, and at the same time, the loss increases rapidly. For example, at 200GHz frequency, rectangular The size of the waveguide is only 1.092mm×0.546mm, the theoretical loss reaches 9.7dB/m, and the actual measured loss is as high as 40dB/m. Although the overmode waveguide can increase the size of the waveguide, there is serious high-order mode competition.

Slot waveguide is a waveguide transmission line proposed in the 1960s. As shown in Figure 1, it consists of upper and lower metal plates 1, 2, and a slot 3 processed on the metal plate. The shape of slot 3 can be Arc shape, semicircle, rectangle, ellipse, triangle, trapezoid etc., also can be any other shapes. Figure 2 shows the cross-sectional view of several slot-shaped slot waveguides. The figure also shows the distribution of the fundamental mode high-frequency field in the slot waveguide. The thin solid line is the electric force line, and the dotted line is the magnetic force line. Other slot shapes The fundamental high-frequency field distribution in a slot waveguide is similar. It can be seen that this field distribution is similar to the TE ₁₁ mode in the circular waveguide, which has the following characteristics:

(1) In the direction of the central axis of the cross-section of the slot waveguide, the electric field has a lateral maximum value, and when the electron beam passes along this direction, it will interact with the field most effectively;

(2) The field is mainly concentrated in the groove area. As the distance away from the groove area increases, the fundamental mode field will decay rapidly, so that when the distance away from the groove area reaches a certain distance, the fundamental mode field actually tends to zero.

The slot waveguide overcomes the shortcomings of ordinary waveguides in size and loss, and has the advantages of large size, small loss, and wide single-mode operating frequency range, so it is especially suitable for applications in the millimeter wave and submillimeter wave bands. Taking the comparison between the circular waveguide and the semicircular groove waveguide as an example, the TE _11- mode single-mode working range of the ordinary circular waveguide is 2.61R<λ<3.14R, where R is the radius of the circular waveguide, and λ is the microwave wavelength; while the semicircular groove The single-mode operating range of the waveguide can reach 0.99R<λ<3.27R, which is much larger than the operating frequency range of the circular waveguide, where R is the radius of curvature of the semicircular groove; on the contrary, if the single-mode operating frequency range remains unchanged, the semicircular The size of the shaped slot waveguide can be much larger than that of the circular waveguide, so that the power capacity is also increased accordingly; as for the loss, at the same frequency of 200GHz, according to the difference in the distance between the two metal plates 1 and 2, the loss of the rectangular slot waveguide It is between 1 and 5dB/m, which is much smaller than the theoretical loss of 9.7dB/m of the rectangular waveguide at the same frequency.

The rectangular narrow waveguide is bent back and forth along its broad side (E surface) to form a meandering rectangular waveguide (bending can be done at right angles or arcs). Fig. 3 shows a three-dimensional schematic diagram of an ordinary meandering rectangular waveguide with an arc bend, and 4 in the figure is a rectangular narrow waveguide. When bending, in addition to the arc bending part 5, there is also a section of straight waveguide part 6, along the central axis of the ordinary meandering waveguide, a longitudinally penetrating circular hole is opened, and the circular passages of the straight waveguides of the two adjacent meandering units The holes are connected by metal tubes with the same diameter as the circular through holes to form the electron injection channel 7, thereby forming the meandering waveguide slow wave line. Fig. 3 also draws the electric force line distribution of the TE ₁₀ mode in the rectangular waveguide.

The meandering waveguide slow-wave line can be divided into two by cutting along the central plane passing through the central axis of the meandering waveguide slow-wave line and parallel to the narrow side of the rectangular waveguide. Therefore, the existing meandering waveguide slow wave line is usually made of two and a half metal plates: one half of the metal plate is shown in Figure 4 (the other half of the metal plate is completely symmetrical to it), and half metal plates are processed on the two half metal plates. A meandering rectangular waveguide and a semicircular metal through hole 8, and then two metal plates are combined to form a complete meandering rectangular waveguide slow wave line (two semicircular through holes 8 are combined to just form a circular electron injection channel 7).

Since the electric force line of the fundamental mode TE ₁₀ mode in the rectangular waveguide is perpendicular to the wide side of the waveguide, after the rectangular waveguide is bent to form a meander waveguide, the direction of the force line will be exactly in the longitudinal direction of the meander waveguide (that is, the direction of the central axis). When passing through the channel 7, the direction of electron movement and the direction of the high-frequency electric field will be the same or opposite, thereby interacting to generate energy exchange, and under certain conditions, the microwave field is amplified; at the same time, the microwave is transmitted along the rectangular waveguide in a zigzag manner. The phase velocity in the longitudinal direction of the waveguide slows down. It can be seen that the meandering waveguide can become one of the most important high-frequency systems for beam-wave interaction in the microwave tube - the slow wave line, and the meandering rectangular waveguide slow wave line has been widely used in millimeter wave traveling wave tubes.

Since the ordinary rectangular waveguide works in the millimeter wave, especially the short millimeter wave band, the size will become very small, which greatly limits the power capacity of the transmitted microwave, and at the same time, the loss increases rapidly; therefore, the meandering rectangular waveguide slow wave based on the rectangular waveguide When the line works in the millimeter wave, especially the short millimeter wave band, it also has the defects of small size, low power capacity for transmitting microwaves, and increased loss, which greatly limits the application of the meandering rectangular waveguide slow wave line.

Contents of the invention

The utility model provides a meandering groove waveguide slow wave line, which has the characteristics of wide frequency band, large size and low loss compared with the existing meandering rectangular waveguide slow wave line, and has higher output power and efficiency ; At the same time, the slow wave line also has the characteristics of relatively simple structure, low processing precision requirements and easy processing.

The utility model is based on the same principle as the ordinary zigzag rectangular waveguide slow wave line, and bends the slots in the slot waveguide back and forth into a zigzag slot waveguide (the bending method can also be right-angle bending or arc bending), that is The meander groove waveguide slow wave line of the utility model is formed.

The technical scheme of the utility model is as follows:

The meander groove waveguide slow wave line, as shown in Figure 5, includes an upper metal plate 1 and a lower metal plate 2 parallel to each other, both metal plates have a meander groove 3, and the meander groove 3 consists of a series of bent groove parts 9 and The straight groove part 10 is connected end to end, and the zigzag groove 3 of the upper and lower metal plates is mirror-symmetrical with respect to the central plane between the upper and lower metal plates; The supporting walls 11 (as shown in FIG. 7 ) at the edge positions are fixed together. The whole zigzag slot waveguide is equivalent to bending the slot in the slot waveguide back and forth, and the bending method can be right-angle bending or arc bending; that is, the curved slot part 9 of the zigzag slot 3 can be a right-angle curved slot , can also be arc curved groove.

In the above solution, the cross-sectional shape of the zigzag groove 3 can be arc, semicircle, rectangle, ellipse, triangle or trapezoid, or any other shape. The material of the supporting wall 11 can be metal, insulating material or microwave absorbing material.

It should be noted that since the electric force lines of the high-frequency field in the slot waveguide are nearly parallel to the upper and lower metal plates rather than perpendicular to the metal plates, when bending, the metal plates cannot be bent, but along the direction of the groove. The groove is bent back and forth. The shape of the meander groove waveguide monolithic metal plate is shown in Figure 6, and the shape of the other piece is also completely symmetrical to it. It is not difficult to see that if the slot is rectangular, the shape of the single metal plate of the meandering slot waveguide is basically the same as that of the half metal plate of the ordinary meandering rectangular waveguide, except that the meandering slot waveguide does not have a half plate dedicated to the electron injection channel. Circular through hole 8. This is because, when the two metal plates of the zigzag slot waveguide are combined to form a complete slow wave line, the two metal plates do not touch, and a certain distance is left in the middle, and this distance naturally forms the path of the electron beam; while ordinary When the two halves of the meandering rectangular waveguide are combined, they must be completely closed and firmly combined to form a complete meandering rectangular waveguide slow wave line. Obviously, at this time, a special circular through hole is opened separately on the central axis to form In addition, because there is a gap between the upper and lower metal plates of the slot waveguide, the groove depth on the single metal plate of the meandering rectangular waveguide is deeper than that on the half-metal plate of the ordinary meandering rectangular waveguide. shallower.

The advantage of the meander groove waveguide slow wave line provided by the utility model lies in:

(1) The characteristics of broadband, large size, and low loss that slot waveguides have are also available in meandering slot waveguides;

(2) In the meander groove waveguide, the fundamental mode high-frequency field has the strongest longitudinal electric field on the central symmetry plane between the upper and lower metal plates, so the interaction with the electron beam is the most effective, which is conducive to improving the output of the microwave tube power and efficiency;

(3) In the zigzag waveguide, the separated upper and lower metal plates will naturally form electron beam channels, and allow the ribbon electron beam to pass through. When the diameter of the cylindrical electron beam is the same, the width of the ribbon-shaped electron beam can be much larger than the thickness. Therefore, under the condition of constant current density, the total current of the ribbon-shaped electron beam can be much larger than that of the cylindrical electron beam. As the applied current increases, the output power of the microwave tube can be increased. It can be seen that the meandering slot waveguide slow wave line traveling wave tube can obtain greater output power than the ordinary meandering waveguide traveling wave tube with the same size.

(4) Since in the slot waveguide, the fundamental mode field will be attenuated to a small value as long as it is a certain distance away from the slot, therefore, in the meandering slot waveguide slow wave line, we can conveniently use The support wall is used to support and fix the upper and lower metal plates. As shown in Figure 7, the support wall 11 can be metal, or insulating material or microwave absorbing material. As long as the meandering slot waveguide is designed correctly, no matter what support wall will affect the slot waveguide pair The transfer of the schema.

(5) Due to the separation of the upper and lower metal plates of the zigzag slot waveguide, there is a gap between the upper and lower metal plates when they are put together, thus reducing the alignment requirements for the slots in the upper and lower metal plates. The plates are closed into a whole, which requires that the waveguide grooves on the two metal plates must be strictly aligned to form a complete rectangular narrow waveguide with smooth inner walls, and the two half-metal plates must be tightly and firmly combined by a special method. Therefore, the processing accuracy requirements are very strict, and the process is relatively complicated.

Based on these advantages of the meander groove waveguide, it is more suitable for slow wave line application in millimeter wave and submillimeter wave band traveling wave tubes.

Description of drawings

Figure 1 is a schematic diagram of a slot waveguide, in which (a) is an arc-shaped slot waveguide, and (b) is a rectangular slot waveguide.

Fig. 2 is a cross-sectional view of the slot waveguide of four slot shapes, respectively: (a) triangle, (b) trapezoid, (c) semicircle and (d) rectangle. The figure shows the distribution of the fundamental mode high-frequency electromagnetic field in the slot waveguide, the thin solid line is the electric force line, and the dotted line is the magnetic force line.

Figure 3 is a three-dimensional schematic diagram of the slow wave line of a common meandering rectangular waveguide, and the distribution of TE ₁₀ -mode electric force lines in the rectangular waveguide is also shown in the figure.

Fig. 4 is the pattern of the half-metal plate of the ordinary meandering rectangular waveguide slow wave line actually processed.

Fig. 5 is a three-dimensional structural schematic diagram of the meandering arc groove waveguide slow wave line provided by the utility model.

Fig. 6 is the semi-metallic plate pattern of the waveguide slow wave line of the meandering arc groove waveguide actually processed.

Fig. 7 is a schematic structural view of the meandering rectangular slot waveguide slow wave line provided by the present invention.

In the above figures, 1 is the upper metal plate of the slot waveguide; 2 is the lower metal plate of the slot waveguide; 3 is the slot of the slot waveguide; 4 is the rectangular narrow waveguide shape and the distribution of the TE _10- mode electric force line forming the meandering rectangular waveguide; 5 is the ordinary meandering waveguide The curved waveguide part in the rectangular waveguide slow wave line; 6 is the straight waveguide part in the ordinary meandering rectangular waveguide slow wave line; 7 is the electron injection channel; Hole; 9 is the curved groove waveguide part in the meander groove waveguide slow wave line; 10 is the straight groove waveguide part in the meander groove waveguide slow wave line; 11 is the support side wall between the upper and lower metal plates of the meander groove waveguide slow wave line.

Detailed ways

Fig. 5 and Fig. 7 show two specific implementations of meandering slot waveguide slow wave lines.

Fig. 5 is a three-dimensional structural schematic diagram of a meandering arc groove waveguide slow wave line. Here, in order to clearly see the meandering situation of the groove, the thickness of the metal plate is ignored; at the same time, the support wall between the upper and lower metal plates is ignored.

Fig. 7 is a three-dimensional structural schematic diagram of a meandering rectangular slot waveguide slow wave line. The upper and lower metal plates should be formed by directly digging zigzag grooves on the metal plate with a certain thickness, similar to Fig. 6 . Here, the thickness of the metal plate is ignored in order to clearly see the twists and turns of the groove. Beryllium oxide ceramic strips 11 are used for support between the upper and lower metal plates.

Claims (5)

1. curved channel waveguide slow-wave line comprises the last metallic plate (1) and the following metallic plate (2) that are parallel to each other, all has tortuous groove (3) on two metallic plates; It is characterized in that described tortuous groove (3) is formed by connecting by set of flex slot part (9) and straight trough part (10) head and the tail, and the tortuous groove (3) of upper and lower metallic plate is the minute surface symmetry with respect to the central plane between the upper and lower metallic plate; Be fixed together by the supporting walls (11) that is positioned at the long limit of upper and lower metallic plate marginal position between the upper and lower metallic plate; Groove during whole curved channel waveguide is equivalent to slot wave led bending back and forth forms.

2. curved channel waveguide slow-wave line according to claim 1 is characterized in that, the curved slot part (9) of described tortuous groove (3) is the quarter bend crank slot.

3. curved channel waveguide slow-wave line according to claim 1 is characterized in that, the curved slot part (9) of described tortuous groove (3) is the arc bend crank slot.

4. according to claim 1,2 or 3 described curved channel waveguide slow-wave lines, it is characterized in that the shape of cross section of described tortuous groove (3) is circular arc, semicircle, rectangle, ellipse, triangle or trapezoidal.

5. curved channel waveguide slow-wave line according to claim 1 is characterized in that, the material of described supporting walls (11) is metal, insulating material or microwave absorbing material.

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