CN111342172A

CN111342172A - Compact large-average-power matched load

Info

Publication number: CN111342172A
Application number: CN202010185741.7A
Authority: CN
Inventors: 王清源; 苏荣荣
Original assignee: University of Electronic Science and Technology of China
Current assignee: University of Electronic Science and Technology of China
Priority date: 2020-03-17
Filing date: 2020-03-17
Publication date: 2020-06-26

Abstract

The invention discloses a compact large-average-power matched load, which comprises a transmission line, at least one bald conical or rectangular absorber and at least one tuning screw, wherein one end of the transmission line is short-circuited, and the axis of the transmission line is along the Z direction. Compared with the traditional high-power matched load, the length of the invention is obviously shortened, the processing difficulty is greatly reduced, the average power capacity is greatly increased, and the matching of the matched load in a wider bandwidth is obviously improved. The invention is mainly used in microwave systems with high average power, in particular in the field of microwave energy industrial application.

Description

Compact large-average-power matched load

Technical Field

The invention relates to the field of low-cost high-power waveguide matched loads, in particular to a compact large-average-power matched load.

Background

The matched load is a common component in the field of radio frequency microwave. The matched load is typically formed by a length of transmission line, such as rectangular waveguide, circular waveguide, coaxial line, etc., short-circuited at one end, and one or more absorbers located in the transmission line. In order to obtain the widest possible operating bandwidth and the lowest possible reflection coefficient, the absorber is often designed as a cone. The cross-sectional dimension of the cone gradually increases from zero along the axis of the transmission line. This design suffers from several problems: 1) the length of the absorber is too long, resulting in an oversized matched load; 2) the tapered cone absorber is difficult to process (particularly, the tip thereof is easily broken), resulting in an increase in manufacturing cost; 3) the tip of the absorber absorbs microwave under high power condition to generate more heat, and is easy to be damaged.

Disclosure of Invention

The invention aims to provide a compact large-average-power matched load. In order to achieve the purpose, the technical scheme adopted by the invention is as follows:

a compact large average power matching load comprises a transmission line with one end short-circuited and an axis along the Z direction, at least one absorber positioned in the transmission line, and at least one tuning screw; the tuning screw extends into the transmission line from the outside of the transmission line, and the depth of the tuning screw in the transmission line can be adjusted from the outside of the transmission line; the X direction, the Y direction and the Z direction constitute an instructional coordinate system.

In order to facilitate the processing and to avoid damage of the absorber under high power conditions, the absorber is shaped as a rectangular body.

Alternatively, the absorber is in the shape of a cone having a minimum width and a minimum height greater than 1/50 the operating wavelength of the compact high power matched load.

The number of the absorbers is 1, the absorbers are arranged at the bottom of the transmission line and are in contact with the inner wall of the transmission line in the-Y direction.

Or the number of the absorbers is 2, the absorbers are respectively arranged on two side walls of the transmission line and are respectively contacted with the inner wall of the transmission line in the X direction and the-X direction.

The tuning screw is arranged in the Y-direction of the transmission line 1.

The number of the tuning screws may be 1 or more. A greater number of tuning screws may result in a better match but will increase the length of the compact high power match load. In a preferred design, the number of the tuning screws is 3, and the tuning screws are arranged on the transmission line along the Z direction.

The transmission line is a rectangular waveguide with a wide side along the X direction.

Or, the transmission line is a circular waveguide or a coaxial line.

The invention discloses a design scheme of a novel high-power matched load. By using a rectangular or bald cone absorber, the processing difficulty of the matched load is greatly reduced and its average power capacity is greatly increased. At the same time, the matching of the matched load over a wider bandwidth is greatly improved by the addition of one or more tuning screws. The average power capacity of conventional high power matched loads is limited primarily by the thermal performance of the absorber. The introduction of the tuning screw in the present invention will reduce the peak power capability of the matched load to some extent, but has less impact on the average power of the device. In practical application, in order to better exert the advantage of high average power, a plurality of metal radiating fins can be arranged outside the invention by referring to the structure of a common high-power matching load. The invention is mainly used in microwave systems with high average power, in particular in the field of microwave energy industrial application.

Drawings

FIG. 1 is a schematic top view of the present invention and example 1

FIG. 2 is a cross-sectional view along AA of FIG. 1

FIG. 3 is a schematic top view of example 2

FIG. 4 is a cross-sectional view along AA of FIG. 3

FIG. 5 is a schematic top view of example 3

FIG. 6 is a cross-sectional view along AA of FIG. 5

FIG. 7 is a three-dimensional simulation of the frequency-dependent reflection coefficient of example 4

The reference numbers in the drawings correspond to the names: 1-transmission line, 2-absorber, 3-tuning screw.

Some of the terms (see FIGS. 1-6) in this specification are defined as follows:

the horizontal direction, i.e., the direction lying in the horizontal plane, i.e., the direction lying in the XZ plane.

The vertical direction, or the upward direction, i.e., the Y-axis direction, i.e., the direction vertically upward from the horizontal plane,

left direction, refers to the X direction.

The right direction refers to the-X direction.

The minimum width of an arbitrary three-dimensional structure means the minimum value of the length of a projection of the line connecting two arbitrary points in the three-dimensional structure in the X direction.

The minimum height of an arbitrary three-dimensional structure refers to the minimum length of the projection of the connecting line of any two points in the three-dimensional structure in the Y direction.

Detailed Description

Example 1

As shown in fig. 1 and 2.

A compact large average power matching load comprises a transmission line 1 with a short circuit at the right end and an axis along the Z direction, an absorber 2 positioned in the

transmission line

1, and 3 tuning screws 3; the tuning screw 3 extends from the outside of the transmission line 1 into the inside of the transmission line 1, and the depth of the tuning screw 3 in the inside of the transmission line can be adjusted from the outside of the transmission line 1.

The transmission line 1 is a rectangular waveguide with its wide side in the X direction.

The absorber 2 is in the shape of a cone having a minimum width and a minimum height greater than 1/50 of the operating wavelength of the compact high power matched load.

The number of the absorbers 2 is 1, the absorbers are arranged at the bottom of the transmission line 1 and are in contact with the inner wall of the transmission line 1 in the-Y direction.

The tuning screw 3 is arranged in the Y-direction of the transmission line 1.

The number of the tuning screws is 3, and the tuning screws are arranged on the transmission line 1 along the Z direction.

Example 2

As shown in fig. 3 and 4.

The difference from example 1 is only that the absorbent body 2 has a rectangular shape. The rectangular absorber is easier to process than the pyramidal absorber, and the processing cost can be significantly reduced.

Example 3

As shown in fig. 5 and 6.

Compared with the embodiment 1, the difference is only that the number of the absorbers 2 is 2, and the absorbers are respectively arranged on two side walls of the transmission line 1 and respectively contacted with the inner wall of the transmission line 1 in the X direction and the-X direction. The number of the tuning screws 3 is 6, and the tuning screws are arranged on the transmission line 1 along the Z direction. Wherein 3 of said tuning screws 3 are arranged at the top of said transmission line 1 and the other 3 of said tuning screws 3 are arranged at the bottom of said transmission line 1.

Example 4

As shown in fig. 3, 4 and 7.

This embodiment is a specific implementation of embodiment 2. The transmission line 1 used was a BJ26 standard rectangular waveguide (86.36 mm wide and 43.18 mm high). The total length of the matched load is 150 mm and the right end is short circuited. The absorber 2 is silicon carbide (dielectric constant: epsilon '17.505, epsilon' -1.869, magnetic permeability: mu '0.97, mu' -0.034), 120.89 mm long, 86.36 mm wide and 7.22 mm high, and is arranged at the bottom of the rectangular waveguide and is in contact with the short-circuit end of the rectangular waveguide. 3 tuning screws 3 having a diameter of 8 mm are arranged in order from the short-circuited end toward the input end of the matched load along the center line of the upper surface of the rectangular waveguide. The top edge of each tuning screw facing the inside of the rectangular waveguide is chamfered by 2 mm. The distance from the central axis of each tuning screw to the short-circuited end of the rectangular waveguide is 49.2 mm, 79.94 mm and 130.91 mm respectively, and the depth of the tuning screw inserted into the rectangular waveguide is 16.62 mm, 19 mm and 10.02 mm respectively. The reflection coefficient of the matched load calculated by three-dimensional simulation is shown in fig. 7 along with the change of frequency. It can be seen from fig. 7 that the reflection coefficient of the matched load is lower than-26.8 dB and the corresponding standing wave ratio is lower than 1.1 in the 200MHz bandwidth range around the industrial microwave frequency of 2.45 GHz. The operating bandwidth of the matched load is sufficient for industrial microwave applications, whose emissions are very low.

3 embodiments of the invention are given above. The actual implementation is far more extensive than listed here. The compact high-power matched load is generally completed by adopting a rectangular waveguide section through the working procedures of cutting, drilling, tapping and the like. This matching load generally requires a heat sink to be provided outside the transmission line 1.

The compact large-average-power matching load disclosed by the invention has the characteristics of simple and compact structure, wide bandwidth realization, low processing and debugging cost and the like. By adopting the waveguide section bar, the loss of metal materials and the processing cost are greatly reduced. By adopting the bald cone absorber or the cuboid absorber, the processing difficulty of the absorber is greatly reduced, and the service life of the absorber under the condition of high average power is greatly prolonged. Low reflection coefficients over a wide operating bandwidth range are achieved by employing multiple tuning screws. Compared with the common high-power matching load, the length of the load is obviously shortened, and the use of the load is more convenient. The invention can be widely used in microwave systems with high average power, in particular in the field of microwave energy industrial application.

Claims

1. A compact large average power matching load, characterized by comprising a length of transmission line (1) with short-circuited axis at one end in Z-direction, at least one absorber (2) located inside the transmission line (1), and at least one tuning screw (3); the tuning screw (3) extends into the transmission line (1) from the outside of the transmission line (1), and the depth of the tuning screw (3) in the transmission line can be adjusted from the outside of the transmission line (1); the X direction, the Y direction and the Z direction constitute an instructional coordinate system.

2. A compact large average power matching load according to claim 1, characterized in that said absorber (2) is shaped as a rectangular body.

3. A compact high average power matching load according to claim 1, characterized in that said absorber (2) is in the shape of a cone, the minimum width and the minimum height of said cone being larger than 1/50 of the operating wavelength of said compact high power matching load.

4. A compact large average power matching load according to claim 1, characterized in that the number of absorbers (2) is 1, in contact with the inner wall of the transmission line (1) in the-Y direction.

5. A compact large average power matching load according to claim 1, characterized in that the number of absorbers (2) is 2, contacting the inner wall of the transmission line (1) in the X-direction and-X-direction, respectively.

6. A compact large average power matched load according to claim 1, characterized in that said tuning screw (3) is arranged in the Y-direction of said transmission line (1).

7. A compact large average power matching load according to claim 1, characterized in that the number of said tuning screws is 3, arranged on said transmission line (1) in Z-direction.

8. A compact large average power matching load according to claim 1, characterized in that said transmission line (1) is a rectangular waveguide with its wide side in the X-direction.

9. A compact large average power matching load according to claim 1, characterized in that said transmission line (1) is a circular waveguide or a coaxial line.

10. A compact large average power matched load according to claim 8, characterized in that all said tuning screws (3) are located on the centre line of the broadside of said transmission line (1).