A low coupling directional coupler

Abstract

The application discloses a low-coupling directional coupler, which comprises a plate-shaped cavity, a main coupling line, a secondary coupling line, two main connecting lines, two secondary connecting lines and four coaxial ports. The cross section of the cavity of the plate-shaped cavity is in the shape of, the main coupling line and the secondary coupling line are consistent in size and are arranged side by side with narrow surfaces opposite to each other in the horizontal cavity of the plate-shaped cavity, the inner ends of the two main connecting lines are connected to the two ends of the main coupling line and are coaxial with the main coupling line, the two secondary connecting lines are arranged in the two vertical cavities respectively and the inner ends thereof are connected to the two ends of the secondary coupling line respectively, the two end surfaces of the secondary coupling line are both chamfered surfaces, and the outer conductors of the four coaxial ports are mounted on the plate-shaped cavity and the inner conductors thereof are connected to the wide surfaces of the outer ends of the two main connecting lines and the two secondary connecting lines respectively. The application realizes accurate adaptation in the low-coupling range by designing and calculating the parameters of the narrow-edge coupling structure, and effectively controls the volume of the directional coupler while ensuring the directivity to be greater than 30 dB.

Description

Technical Field

[0001] This invention relates to the field of directional coupler technology, specifically a low-coupling directional coupler. Background Technology

[0002] A coupler is a common microwave device used for power distribution or power combining, and it has a wide range of applications in microwave circuit systems. Couplers can be lossy or lossless three-port or four-port devices. When there are only three ports, they mainly adopt a T-type structure, with the Wilkinson power divider as a representative structure. When there are four ports, the ports are isolated from each other and the energy coupling is directional, which is called a directional coupler.

[0003] Regarding directional couplers, in 1955, SB Cohn, using conformal mapping and combining it with the odd-even mode impedance analysis theory of TEM waves, first derived the design formula for narrow-side coupled striplines, considering the influence of stripline thickness on coupling performance, thus laying the foundation for the theoretical design of narrow-side directional couplers. However, for the specific requirements of low-frequency bands (40-100 MHz), high power (≥1.5 MW), and low coupling (-40 dB), the parameter design of existing narrow-side coupled structures lacks targeted solutions, making it difficult to simultaneously meet the comprehensive indicators of directivity, VSWR, field strength limitation, and port adaptability. In particular, the problems of signal reflection suppression and over-coupling under high-power transmission have not been effectively solved.

[0004] In addition, traditional couplers often use side-fed or dielectric-filled designs, which have problems such as excessive size, poor port matching, severe signal reflection, and easy breakdown under high power. The discontinuity of the inter-section transition in multi-section couplers can also lead to a decrease in directivity. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a low-coupling directional coupler that designs and calculates the parameters of the narrow-side coupling structure to achieve accurate adaptation within the low coupling range, while ensuring that the directivity is greater than 30dB and effectively controlling the size of the directional coupler.

[0006] The technical solution of this invention is as follows:

[0007] A low-coupling directional coupler includes a plate-shaped cavity, a main coupling line, a secondary coupling line, two main connecting lines, two secondary connecting lines, and four coaxial ports. The cross-section of the cavity of the plate-shaped cavity is [missing information]. The plate-shaped cavity includes an interconnected horizontal cavity and two vertical cavities. The main coupling line and the secondary coupling line are of the same size and are arranged side by side with their narrow faces facing each other in the horizontal cavity of the plate-shaped cavity, forming a narrow-side coupling structure. The inner ends of the two main connecting lines are connected to the two ends of the main coupling line and are coaxial with the main coupling line. The two secondary connecting lines are respectively arranged in the two vertical cavities and their inner ends are respectively connected to the two ends of the secondary coupling lines. Both ends of the secondary coupling lines are beveled, and the beveled ends are symmetrical along the central section of the secondary coupling line. The angle between each beveled end and the axial section of the main connecting line is an acute angle. The outer conductors of the four coaxial ports are installed on the plate-shaped cavity, and their inner conductors are respectively connected to the wide faces of the outer ends of the two main connecting lines and the two secondary connecting lines.

[0008] The cavity height of the plate-shaped cavity is Cavity height Thickness of the main coupling line and the secondary coupling line Width of primary and secondary coupling lines Spacing between primary and secondary coupling lines Satisfy the following equation (1):

[0009] (1);

[0010] In equation (1), Represents the coupling coefficient of the even mode; The coupling coefficient representing the odd mode; , , The intermediate parameters representing the even mode. The intermediate parameter representing the odd modulus. and The calculation formula is shown in the following formula (2); This represents the line thickness correction factor, with a value range of 1.02 to 1.05. Represents the even-mode impedance correction factor. ;

[0011] (2);

[0012] In equation (2), Represents the characteristic impedance of even mode; Represents the characteristic impedance of odd mode; It represents the relative permittivity of the air inside the cavity of the plate-shaped cavity.

[0013] The coupling coefficient of the even mode The coupling coefficient of the odd mode is calculated using the following formula (3). The following formula (4) is used to calculate:

[0014] (3);

[0015] (4).

[0016] The even-mode characteristic impedance and odd-mode characteristic impedance The calculation formula is shown in the following formula (5):

[0017] (5);

[0018] In equation (5), The characteristic impedance representing a low-coupling directional coupler. This represents the coupling degree of a low-coupling directional coupler.

[0019] Triangular isolation blocks are provided on the sides of both ends of the secondary coupling line. The top and bottom ends of the triangular isolation blocks are in close contact with the top and bottom surfaces of the plate-shaped cavity, respectively. The triangular isolation blocks are right-angled triangles. The inclined surface of the triangular isolation block is parallel to the inclined tangent surface at the end of the secondary coupling line and there is a gap between the two. One of the right-angled surfaces of the triangular isolation block is parallel to the main connecting line.

[0020] A metal partition wall is provided between one of the right-angled faces of the triangular isolation block and the main connecting line.

[0021] Of the four coaxial ports, the outer conductors of the two coaxial ports connected to the main connecting line are installed on the bottom of the plate-shaped cavity, and the outer conductors of the two coaxial ports connected to the secondary connecting line are installed on the top of the plate-shaped cavity.

[0022] All four coaxial ports are either 9-inch or 12-inch coaxial ports.

[0023] Advantages of this invention:

[0024] (1) The coupling line of the present invention adopts a narrow-side coupling structure, which can cover the entire frequency band of 40-100 MHz without the need for multi-stage cascading, and meets the coupling requirements of -40dB to -60dB;

[0025] (2) Based on the odd and even mode impedance, the present invention optimizes the size parameters of the low-coupling directional coupler, achieves accurate adaptation of the low coupling range, achieves main path loss of less than 0.05 dB, standing wave ratio of less than 1.05, and controllable field strength under high power.

[0026] (3) Both ends of the secondary coupling line of the present invention are beveled surfaces, which can directly suppress signal reflection at the discontinuity of the transmission line (coupled line and connecting line). The bevel of the triangular isolation block is parallel to the bevel of the end of the secondary coupling line, further optimizing the field distribution inside the cavity. At the same time, the triangular isolation block reduces electromagnetic interference between lines and prevents the discontinuous part of the transmission line from participating in coupling, making the directivity greater than 30dB. The synergistic effect of the two can effectively avoid excessive coupling. At the same time, by setting a metal partition wall, the influence of the triangular isolation block on the main connecting line can be effectively avoided.

[0027] (4) The four coaxial ports of the present invention are connected to the top and bottom of the plate-shaped cavity in pairs, which greatly reduces the overall volume of the directional coupler and reduces the reflection at the coaxial port connection. Attached Figure Description

[0028] Figure 1 This is a perspective view of the present invention.

[0029] Figure 2 This is a plan view of the interior of the plate-shaped cavity of the present invention.

[0030] Reference numerals: 1-plate-shaped cavity, 2-main coupling line, 3-secondary coupling line, 4-main connecting line, 5-secondary connecting line, 6-9-inch coaxial port, 7-triangular isolation block, 8-metal partition wall. Detailed Implementation

[0031] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0032] See Figure 1 and Figure 2 A low-coupling directional coupler includes a plate-shaped cavity 1, a main coupling line 2, a secondary coupling line 3, two main connecting lines 4, two secondary connecting lines 5, and four 9-inch coaxial ports 6. The cross-section of the cavity of the plate-shaped cavity 1 is [missing information]. The plate-shaped cavity 1 includes an interconnected horizontal cavity and two vertical cavities. The main coupling line 2 and the secondary coupling line 3 are of the same size and are arranged side-by-side within the horizontal cavity of the plate-shaped cavity 1, forming a narrow-side coupling structure. The inner ends of the two main connecting lines 4 are connected to both ends of the main coupling line 2 and are coaxial with the main coupling line 2. The two secondary connecting lines 5 are respectively arranged within the two vertical cavities, with their inner ends connected to both ends of the secondary coupling lines 3. Both ends of the secondary coupling lines 3 are beveled surfaces, and the beveled surfaces at both ends are symmetrical along the central section of the secondary coupling line 3. The angle between each beveled surface and the axial tangent of the main connecting line 4 is an acute angle. Triangular isolation blocks 7 are provided on the sides of both ends of the secondary coupling lines 3. The top and bottom ends of the triangular isolation blocks 7... The triangular isolation block 7 is a right triangle, with its inclined surface parallel to the oblique cut surface at the end of the secondary coupling line 3 and a gap between them. One of the right angles of the triangular isolation block 7 is parallel to the main connecting line 4, and a metal partition wall 8 is provided between one of the right angles of the triangular isolation block and the main connecting line. Four 9-inch coaxial ports 6 are installed on the plate-shaped cavity 1 and are respectively connected to the outer ends of the two main connecting lines 4 and the two secondary connecting lines 5. Among the four coaxial ports, the two 9-inch coaxial ports 6 connected to the main connecting lines 4 are installed on the bottom end of the plate-shaped cavity 1, and the two 9-inch coaxial ports 6 connected to the secondary connecting lines 5 are installed on the top end of the plate-shaped cavity 1.

[0033] The plate-shaped cavity 1 is grounded, so the distance between the two grounding plates is... That is, the cavity height of plate-shaped cavity 1 is Cavity height Thickness of main coupling line 2 and secondary coupling line 3 Width of main coupling line 2 and secondary coupling line 3 The spacing between the main coupling line 2 and the secondary coupling line 3 Satisfy the following equation (1):

[0034] (1);

[0035] In equation (1), Represents the coupling coefficient of the even mode; The coupling coefficient representing the odd mode; , , The intermediate parameters representing the even mode. The intermediate parameter representing the odd modulus. and The calculation formula is shown in the following formula (2); This represents the line thickness correction factor, with a value range of 1.02 to 1.05. Represents the even-mode impedance correction factor. ;

[0036] (2);

[0037] In equation (2), Represents the characteristic impedance of even mode; Represents the characteristic impedance of odd mode; This represents the relative permittivity of the air inside the plate-shaped cavity. When the dielectric plate inside the plate-shaped cavity is made of high-temperature resistant alumina ceramic suitable for high power, or dielectrically stable and low-loss polytetrafluoroethylene, it is considered to be suitable for this cavity. That is, the relative permittivity of alumina ceramics or polytetrafluoroethylene;

[0038] The coupling coefficient of the even mode in equation (1) The coupling coefficient of the odd mode is calculated using the following formula (3). The following formula (4) is used to calculate:

[0039] (3);

[0040] (4);

[0041] Even-mode characteristic impedance in equation (2) and odd-mode characteristic impedance The calculation formula is shown in the following formula (5):

[0042] (5);

[0043] In equation (5), The characteristic impedance representing a low-coupling directional coupler. This represents the coupling degree of a low-coupling directional coupler.

[0044] Based on the above formula, the thicknesses of the main coupling line 2 and the secondary coupling line 3 are... Set to 3 mm, the distance between the two media plates The spacing between the main coupling line 2 and the secondary coupling line 3 is set to 36 mm. The width of the main coupling line 2 and the secondary coupling line 3 is set to 18 mm. The setting is 36mm to meet the requirements of low frequency band 40~100 MHz and low coupling -40 dB, ensuring that the maximum electric field strength under 1.5 MW input is ≤1.8×10. 6 V / m, while ensuring that the main path loss is less than 0.05 dB, the standing wave ratio (VSWR) is less than 1.05, and the directivity is greater than 30 dB, so that long-term reliable operation can be achieved without additional heat dissipation devices.

[0045] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A low-coupling directional coupler, characterized in that: It includes a plate-shaped cavity, a main coupling line, a secondary coupling line, two main connecting lines, two secondary connecting lines, and four coaxial ports. The cross-section of the cavity of the plate-shaped cavity is [missing information]. The plate-shaped cavity includes an interconnected horizontal cavity and two vertical cavities. The main coupling line and the secondary coupling line are of the same size and are arranged side by side with their narrow faces facing each other in the horizontal cavity of the plate-shaped cavity, forming a narrow-side coupling structure. The inner ends of the two main connecting lines are connected to the two ends of the main coupling line and are coaxial with the main coupling line. The two secondary connecting lines are respectively arranged in the two vertical cavities and their inner ends are respectively connected to the two ends of the secondary coupling lines. Both ends of the secondary coupling lines are beveled, and the beveled ends are symmetrical along the central section of the secondary coupling line. The angle between each beveled end and the axial section of the main connecting line is an acute angle. The outer conductors of the four coaxial ports are installed on the plate-shaped cavity, and their inner conductors are respectively connected to the wide faces of the outer ends of the two main connecting lines and the two secondary connecting lines. Triangular isolation blocks are provided on the sides of both ends of the secondary coupling line. The top and bottom ends of the triangular isolation blocks are in close contact with the top and bottom surfaces of the plate-shaped cavity, respectively. The triangular isolation blocks are right-angled triangles. The inclined surface of the triangular isolation block is parallel to the inclined surface of the end of the secondary coupling line and there is a gap between the two. One of the right-angled surfaces of the triangular isolation block is parallel to the main connecting line. A metal partition wall is provided between one of the right-angled faces of the triangular isolation block and the main connecting line.

2. The low-coupling directional coupler according to claim 1, characterized in that: The cavity height of the plate-shaped cavity is Cavity height Thickness of the main coupling line and the secondary coupling line Width of primary and secondary coupling lines Spacing between primary and secondary coupling lines Satisfy the following equation (1): （1）； In equation (1), Represents the coupling coefficient of the even mode; The coupling coefficient representing the odd mode; , , The intermediate parameters representing the even mode. The intermediate parameter representing the odd modulus. and The calculation formula is shown in the following formula (2); This represents the line thickness correction factor, with a value range of 1.02 to 1.

05. Represents the even-mode impedance correction factor. ; （2）； In equation (2), Represents the characteristic impedance of even mode; Represents the characteristic impedance of odd mode; It represents the relative permittivity of the air inside the cavity of the plate-shaped cavity.

3. A low-coupling directional coupler according to claim 2, characterized in that: The coupling coefficient of the even mode The coupling coefficient of the odd mode is calculated using the following formula (3). The following formula (4) is used to calculate: （3）； （4）。 4. A low-coupling directional coupler according to claim 2, characterized in that: The even-mode characteristic impedance and odd-mode characteristic impedance The calculation formula is shown in the following formula (5): （5）； In equation (5), The characteristic impedance representing a low-coupling directional coupler. This represents the coupling degree of a low-coupling directional coupler.

5. A low-coupling directional coupler according to claim 1, characterized in that: Of the four coaxial ports, the outer conductors of the two coaxial ports connected to the main connecting line are installed on the bottom of the plate-shaped cavity, and the outer conductors of the two coaxial ports connected to the secondary connecting line are installed on the top of the plate-shaped cavity.

6. A low-coupling directional coupler according to claim 1, characterized in that: All four coaxial ports are either 9-inch or 12-inch coaxial ports.

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