Waveguide coaxial conversion device

Abstract

A waveguide coaxial conversion device, comprising a rectangular waveguide cavity, a door, an inner coaxial conductor, an outer coaxial conductor, a short-circuit waveguide, a positioning locking ring and a lifting assembly, the door is installed in the rectangular waveguide cavity; the inner coaxial conductor is connected with the lifting assembly below, and the upper part of the inner coaxial conductor passes through the center of the door and extends to form a coaxial waveguide structure with the outer coaxial conductor; the outer coaxial conductor is installed on the upper end face of the rectangular waveguide cavity; the short-circuit waveguide is installed on the opposite side of the feeding waveguide port of the rectangular waveguide cavity; the positioning locking ring is arranged in the positioning center of the bottom of the door; and the lifting assembly is installed at the bottom of the rectangular waveguide cavity.

Description

Technical Field

[0001] This invention belongs to the field of PCVD preform processing technology, and specifically relates to a waveguide coaxial conversion device. Background Technology

[0002] PCVD, or microwave plasma chemical vapor deposition, is one of the main processes for processing optical fiber preforms. The key difference between this process and other processes lies in the fact that it uses microwave plasma to directly act on the reactant gases to form a glassy state of silica or a multi-component doped silica glassy state. This is the core of the process.

[0003] Currently, microwave plasma systems used for PCVD processing consist of a microwave head mounted on a moving stage, an isolator, an adapter, a transmission waveguide, and a plasma resonant cavity. Depending on the microwave transmission mode fed into the plasma resonant cavity, existing microwave plasma systems mainly employ two implementation techniques. One approach involves directly feeding 2.45 GHz high-power microwaves generated by a magnetron within the microwave head into a cylindrical plasma resonant cavity via a rectangular waveguide in TE10 mode. High-energy electrons generated within the cylindrical resonant cavity resonate in TM010 or TE111 mode, acting on the low-pressure gas passing through the cavity to excite and form highly activated spherical plasma. This causes chemical reactions within the reaction zone, resulting in the deposition of silica glass or multi-component doped silica glass. This approach is characterized by high transmission power and low loss, but it exhibits dispersive characteristics during transmission and is prone to significant electromagnetic pollution during the feeding process into the resonant cavity. Another technical approach involves first converting high-power microwaves transmitted in TE10 mode within a rectangular waveguide into TEM mode transmitted in a coaxial waveguide via a microwave mode conversion device. The TEM mode microwaves then enter the resonant cavity via a coupling antenna, exciting spherical plasmas. This causes the gases in the reaction zone to undergo chemical reactions, ultimately forming a silica glassy state or a multi-component doped silica glassy state deposition. Its advantages include no dispersion, stable field structure, and lower electromagnetic pollution after coupling into the resonant cavity, but the transmitted power is slightly lower.

[0004] For PCVD processing of special optical fiber preforms, the required microwave power is generally relatively low. Excessively high deposition rates can negatively impact the processing quality of the optical fiber preforms and the performance of the special optical fibers. Therefore, for PCVD machines used to process special optical fiber preforms with relatively low deposition rates, using a waveguide coaxial converter to perform microwave mode conversion before excitation has a more significant advantage, which is beneficial to improving the product performance of special optical fiber preforms.

[0005] Existing waveguide-coaxial converters are mainly divided into two types: antenna type and gate type. Among them, the gate type waveguide-coaxial converter is more commonly used in high-power applications due to its advantages such as easy and secure installation of the inner conductor and easy impedance matching. Examples include the gate contact waveguide-coaxial converter structure disclosed in CN1188361C [An Optical Fiber Preform Processing Equipment Utilizing Plasma Technology]; the gate structure disclosed in CN214099836 [An Inner Conductor Assembly, Microwave Mode Converter, and Vapor Deposition System]; and the waveguide-coaxial converter disclosed in CN206992279U [A Microwave Plasma System and Its Waveguide-Coaxial Converter]. These technologies are all designed for high-power microwave plasma chemical vapor deposition applications. While they have advantages, they also have certain disadvantages, mainly: existing waveguide-coaxial converters are complex in structure and difficult to manufacture; the inner conductor of the converter is difficult to move, causing difficulties in coupling matching adjustment; or poor contact between the inner conductor and the gate can easily lead to electrical breakdown and arcing. Summary of the Invention

[0006] In view of the technical problems existing in the background art, the waveguide coaxial converter provided by the present invention is easy to process and manufacture, can easily achieve impedance matching, reduce microwave energy loss, improve coupling efficiency, and has a built-in circulating water cooling system to adapt to high temperature environment operation.

[0007] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: A waveguide-coaxial converter includes a rectangular waveguide cavity, a gate, an inner coaxial conductor, an outer coaxial conductor, a short-circuit waveguide, a positioning locking ring, and a lifting assembly. The gate is installed inside the rectangular waveguide cavity. The inner coaxial conductor is connected to the lifting assembly at its lower end and extends through the center of the gate to form a coaxial waveguide structure with the outer coaxial conductor. The outer coaxial conductor is installed on the upper end face of the rectangular waveguide cavity. The short-circuit waveguide is installed on the opposite side of the feed waveguide port of the rectangular waveguide cavity. The positioning locking ring is located in the positioning center at the bottom of the gate. The lifting assembly is installed at the bottom of the rectangular waveguide cavity and is connected to the rectangular waveguide cavity by a thread. In a preferred embodiment, the rectangular waveguide cavity is a hollow metal body with a standard rectangular waveguide through-hole. Flange structures are provided at both ends of the rectangular waveguide cavity, and both ends are threadedly connected to the flanges of the feed waveguide and the short-circuit waveguide, respectively, via these flange structures. A first threaded hole is provided at the bottom of the rectangular waveguide cavity for connection to the lifting assembly. A first circular hole is provided at the top of the rectangular waveguide cavity, the inner diameter of which is adapted to the inner diameter of the coaxial outer conductor. Specifically, the inner diameter of the first circular hole is approximately equal to and coaxial with the inner diameter of the coaxial inner conductor.

[0008] In a preferred embodiment, a first counterbore and a plurality of threaded holes are provided on the outer periphery of the first circular hole at the top of the rectangular waveguide cavity. The coaxial inner conductor is positioned through the first counterbore and connected to the rectangular waveguide cavity through the threaded holes.

[0009] In a preferred embodiment, a circulating cooling water circuit is provided at the bottom of the rectangular waveguide cavity.

[0010] In a preferred embodiment, a plurality of through holes are provided at the bottom of the rectangular waveguide cavity and fixedly connected to the door knob through screws.

[0011] In a preferred embodiment, the door knob has a rotary conical structure. A second circular hole is provided along the rotary axis and is slightly larger than the diameter of the coaxial inner conductor; a second counterbore is provided on the outer periphery of the second circular hole, and the positioning locking ring is arranged in the second counterbore; the second circular hole and the second counterbore are coaxial.

[0012] The rectangular waveguide cavity is a metal body, preferably aluminum or brass. The waveguide through hole has a standard waveguide structure, preferably BJ22 or BJ26. The door knob has a rotary conical structure perpendicular to the bottom surface. A second circular hole is provided along the rotary axis. The diameter D2 of the second circular hole is approximately equal to the diameter D1 of the top surface and is slightly larger than the diameter d of the coaxial inner conductor; a second counterbore is provided on the outer periphery of the second circular hole at the bottom surface of the door knob, and the positioning locking ring is arranged in the second counterbore; the second circular hole and the second counterbore are coaxial and perpendicular to the bottom surface of the conical body. The conical body represents the door knob.

[0013] In a preferred embodiment, the diameter D0 of the bottom surface of the door knob and the width a of the rectangular waveguide cavity satisfy the relationship: a < D0 < 2a; The diameter D0 of the bottom surface of the door knob and the waveguide length L1 of the rectangular waveguide cavity satisfy the relationship: D0 < L1. The diameter D1 of the top surface of the conical body is approximately equal to the diameter d of the coaxial inner conductor.

[0014] The height H1 of the door knob and the narrow side length b of the rectangular waveguide cavity satisfy the relationship: 0.5b < H1 < 0.9b, and the side bus length S of the door knob is 0.5λ, where λ is the vacuum wavelength of the fed microwave; Furthermore, threaded holes matching the through holes at the bottom of the rectangular waveguide cavity are provided on the bottom surface of the conical body; To ensure good contact between the bottom surface and the outer edge of the door knob and the inner cavity bottom surface of the rectangular waveguide cavity, the bottom surface of the door knob is provided with a convex platform with a thickness of h, 0 < h ≤ 2 mm; The two sides of the door knob are symmetrically cut. The cut side surface is perpendicular to the bottom surface of the door knob, and the width W of this part of the door knob after cutting is equal to the width a of the rectangular waveguide cavity.

[0015] In a preferred embodiment, the door knob is made of brass, and the surface of the door knob is coated with a coating to reduce microwave loss. The coating material is silver or gold.

[0016] In a preferred embodiment, the short-circuit waveguide is a hollow metal waveguide cavity with one end short-circuited, and its waveguide cross-sectional dimensions are consistent with the waveguide via of the rectangular waveguide cavity; the short-circuit surface of the short-circuit waveguide is planar, and the equivalent distance L between it and the gate side busbar is 0.5λ. g , where λ g The wavelength of the waveguide into which the microwaves are fed is denoted.

[0017] The positioning and locking ring 6 is a cylindrical metal ring with a section of tapered cylinder, and its inner diameter is approximately equal to the diameter of the coaxial inner conductor.

[0018] Furthermore, the conical cylinder section has several grooves circumferentially opened to increase the elasticity of the positioning locking ring; Furthermore, the outer diameter of the column portion is equivalent to the inner diameter of the second countersunk hole at the bottom of the door button, so as to accurately position the coaxial inner conductor and make it coaxial with the coaxial inner conductor.

[0019] In a preferred embodiment, the lifting assembly includes a stud, a lifting screw, an upper positioning nut, and a lower sealing plate. The outer cylindrical part of the stud has an external thread that engages with the first threaded hole of the rectangular waveguide cavity. The inner hole of the stud has an internal thread that engages with the external thread of the lifting screw. The upper positioning nut is mounted on the coaxial inner conductor, with its upper end face fitting against the lower end face of the lifting screw. The lower sealing plate is fixedly connected to the lifting screw and fits against the lower end face of the coaxial inner conductor. The upper end face of the stud has an inverted conical hole that engages with the conical cylinder of the positioning locking ring. The lifting screw has a third circular hole with a diameter D3 larger than the diameter d of the coaxial inner conductor, allowing the coaxial inner conductor to pass freely through the third circular hole. The lifting assembly is made of metal, such as brass or aluminum.

[0020] The present invention can achieve the following beneficial effects: 1. The waveguide coaxial conversion device provided by this invention can achieve high-efficiency mode conversion by changing the waveguide depth L2 of the short-circuit waveguide 5 to make the waveguide cavity on the short-circuit side stand wave.

[0021] 2. The waveguide coaxial converter provided by this invention can optimize the impedance of the gate by designing a reasonable length S of the conical side busbar, thereby minimizing the reflection of higher-order modes and improving the transmission performance of the device.

[0022] 3. The waveguide coaxial device provided by the present invention adopts a gate-type structure, the cone is easy to process, the side busbar has a gradual impedance change, the mode conversion efficiency is high, the contact area between the cone and the rectangular cavity is large, the conductivity is good, the cooling effect is good, and it can withstand high microwave power.

[0023] 4. In operation, the waveguide coaxial device provided by this invention ensures good contact between the inner conductor and the cone through the locking positioning ring, preventing adverse phenomena such as electric shock and arcing. The lifting assembly has a large contact area with the inner conductor and the rectangular waveguide cavity with water cooling structure, resulting in good cooling effect. During debugging or maintenance, the locking positioning ring can be relaxed by adjusting the depth of the stud in the rectangular waveguide cavity, facilitating the adjustment of the coupling position of the inner conductor by adjusting the position of the lifting screw, thus avoiding adjustment difficulties caused by temperature creep of the inner conductor.

[0024] 5. The waveguide coaxial device provided by this invention has an all-metal structure, and a lower sealing plate is set below the lifting component. The microwave leakage is small, and the adverse effects on the environment or human body are very small. Attached Figure Description

[0025] The present invention will be further described below with reference to the accompanying drawings and embodiments: Figure 1 This is a schematic diagram of the front cross-sectional structure of the present invention; Figure 2 This is a cross-sectional view of the front view plane of the rectangular waveguide cavity of the present invention; Figure 3 This is a schematic cross-sectional view of the rectangular waveguide cavity of the present invention from the left view plane; Figure 4 This is a cross-sectional schematic diagram of the front view plane of the cone of the present invention; Figure 5 This is a schematic cross-sectional view of the cone of the present invention in the transverse direction; Figure 6 This is a schematic diagram of the positioning and locking ring of the present invention; Figure 7 This is a cross-sectional schematic diagram of the lifting component of the present invention.

[0026] In the figure: 1-Rectangular waveguide cavity; 11-Left flange; 12-Right flange; 13-First threaded hole; 14-First round hole; 15-First countersunk hole; 16-Threaded hole; 17-Circulating cooling water circuit; 2-Door button; 21-Second round hole; 22-Second countersunk hole; 3-Coaxial inner conductor; 4-Coaxial outer conductor; 5-Short-circuit waveguide; 6-Positioning locking ring; 7-Lifting assembly; 71-Screw; 711-External thread; 712-Internal thread; 72-Lifting screw; 721-Third round hole; 73-Upper positioning nut; 74-Lower sealing plate. Detailed Implementation Example 1: Preferred solutions include Figures 1 to 7As shown, a waveguide-coaxial conversion device includes a rectangular waveguide cavity 1, a door button 2, a coaxial inner conductor 3, a coaxial outer conductor 4, a short-circuit waveguide 5, a positioning locking ring 6, and a lifting assembly 7. The door button 2 is installed inside the rectangular waveguide cavity 1. The coaxial waveguide (including the inner conductor 3 and the outer conductor 4) is installed above the rectangular waveguide cavity 1 and matches the waveguide coupling hole opened above the rectangular waveguide cavity 1. The short-circuit waveguide 5 is installed on one open side of the rectangular waveguide cavity 1. The lifting assembly 7 is located below the rectangular waveguide cavity 1, and its adjustment center is coaxial with the coaxial inner conductor opened below the rectangular waveguide cavity 1. The positioning locking ring 6 is sleeved on the outer side of the coaxial inner conductor 3 and installed between the door button 2 and the lifting assembly 7.

[0027] The rectangular waveguide cavity 1 is a hollow metal body with a standard rectangular waveguide through-hole. Flange structures are provided at both ends of the rectangular waveguide cavity 1, and both ends are threadedly connected to the flange of the feed waveguide and the flange of the short-circuit waveguide 5 respectively through the flange structures. A first threaded hole 13 is provided at the bottom of the rectangular waveguide cavity 1 for connection with the lifting assembly 7. A first circular hole 14 is provided at the top of the rectangular waveguide cavity 1. The inner diameter of the first circular hole 14 is adapted to the inner diameter of the coaxial outer conductor 4. Specifically, the inner diameter of the first circular hole 14 is approximately equal to and coaxial with the inner diameter of the coaxial inner conductor 3.

[0028] Furthermore, a first countersunk hole 15 and several threaded holes 16 are provided on the outer periphery of the first circular hole 14 at the top of the rectangular waveguide cavity 1. The coaxial inner conductor 3 is positioned through the first countersunk hole 15 and connected to the rectangular waveguide cavity 1 through the threaded holes 16.

[0029] Furthermore, a circulating cooling water circuit 17 is provided at the bottom of the rectangular waveguide cavity 1.

[0030] Furthermore, the bottom of the rectangular waveguide cavity 1 is provided with several through holes, and is fixedly connected to the door button 2 by screws.

[0031] Furthermore, the door button 2 is a rotating cone structure, with a second circular hole 21 opened along the rotation axis, which is slightly larger than the diameter of the coaxial inner conductor 3; a second countersunk hole 22 is opened on the outer periphery of the second circular hole 21, and the positioning locking ring 6 is set in the second countersunk hole 22; the second circular hole 21 and the second countersunk hole 22 are coaxial.

[0032] The rectangular waveguide cavity 1 is a metal body, preferably made of aluminum or brass, and the waveguide through-hole has a standard waveguide structure, preferably BJ22 or BJ26. The knob 2 has a structure of a rotary cone perpendicular to the bottom surface, with a second circular hole 21 opened along the rotary axis. The diameter D2 of the second circular hole is approximately equal to the diameter D1 of the top surface and is slightly larger than the diameter d of the coaxial inner conductor; a second counterbore 22 is opened on the outer periphery of the second circular hole at the bottom surface of the knob 2, and the positioning and locking ring 6 is arranged in the second counterbore 22; the second circular hole and the second counterbore are coaxial and perpendicular to the bottom surface of the cone. The said cone represents the knob 2.

[0033] Furthermore, the diameter D0 of the bottom surface of the knob 2 and the length a of the wide side of the rectangular waveguide cavity 1 satisfy the relationship: a < D0 < 2a; The diameter D0 of the bottom surface of the knob 2 and the waveguide length L1 of the rectangular waveguide cavity 1 satisfy the relationship: D0 < L1. The diameter D1 of the top surface of the cone is approximately equal to the diameter d of the coaxial inner conductor.

[0034] The height H1 of the knob 2 and the length b of the narrow side of the rectangular waveguide cavity 1 satisfy the relationship: 0.5b < H1 < 0.9b, and the length S of the side generatrix of the knob 2 is 0.5λ, where λ is the vacuum wavelength of the fed microwave; Furthermore, a threaded hole 23 matching the bottom through-hole of the rectangular waveguide cavity 1 is also provided on the bottom surface of the cone; To ensure good contact between the bottom surface and the outer edge of the knob 2 and the inner cavity bottom surface of the rectangular waveguide cavity 1, the bottom surface of the knob 2 is provided with a boss with a thickness of h, 0 < h ≤ 2 mm; On both sides of the knob 2, it is symmetrically cut, and the cut side surface is perpendicular to the bottom surface of the knob 2, and the width W of this part of the knob 2 after cutting is equal to the length a of the wide side of the rectangular waveguide cavity 1.

[0035] Furthermore, the knob 2 is made of brass, and the surface of the knob 2 is plated with a coating to reduce microwave loss, and the coating material is silver or gold.

[0036] Furthermore, the short-circuit waveguide 5 is a hollow metal waveguide cavity with one end short-circuited, and its waveguide cross-section size is the same as that of the waveguide through-hole of the rectangular waveguide cavity 1; the short-circuit surface of the short-circuit waveguide 5 is a plane, and the equivalent distance L from the short-circuit surface to the side generatrix of the knob 2 is 0.5λ g , where λ g is the waveguide wavelength of the fed microwave.

[0037] The positioning and locking ring 6 is a columnar metal ring with a section of conical cylinder, and the inner hole diameter thereof is approximately equal to the diameter of the coaxial inner conductor 3.

[0038] Furthermore, a number of slots are circumferentially opened on the conical cylinder part to increase the elasticity of the positioning and locking ring; Furthermore, the outer diameter of the column portion is equivalent to the inner diameter of the second countersunk hole 22 at the bottom of the door button 2, so as to accurately position the coaxial inner conductor 3 and make it coaxial with the coaxial inner conductor 4.

[0039] Furthermore, the lifting assembly 7 includes a stud body 71, a lifting screw 72, an upper positioning nut 73, and a lower sealing plate 74; the outer cylinder of the stud body 71 is provided with an external thread 711, which is connected to the first threaded hole 13 of the rectangular waveguide cavity 1; the inner hole of the stud body 71 is provided with an internal thread 712, which is connected to the external thread of the lifting screw 72; the upper positioning nut 73 is installed on the coaxial inner conductor 3, and its upper end face is in contact with the lower end face of the lifting screw 72; the lower sealing plate 74 is fixedly connected to the lifting screw 72 and is in contact with the lower end face of the coaxial inner conductor 3; the upper end face of the stud body 71 is provided with an inverted conical hole that cooperates with the conical cylinder of the positioning locking ring 6; the lifting screw 72 is provided with a third circular hole 721, the diameter D3 of which is larger than the diameter d of the coaxial inner conductor 3, so that the coaxial inner conductor 3 can freely pass through the third circular hole 721. The lifting component 7 is made of metal, such as brass or aluminum.

[0040] The other end of the rectangular waveguide cavity 1 is connected to the input microwave via a standard rectangular flange. The input microwave undergoes mode conversion through a gate button 2 with a gradually changing impedance, converting the horizontal transmission of the rectangular wave in TE10 mode into the vertical transmission of the circular wave in TEM mode. The wave is then output to the plasma resonant cavity (not shown in the figure) via a coaxial waveguide (including inner conductor 3 and outer conductor 4) for plasma processing.

[0041] As an embodiment of this invention patent, the gate structure is simulated using the electromagnetic simulation software HFSS. The impedance of the gate is optimized by adjusting the bottom diameter and height of the copper cone to minimize the S11 parameter and improve the transmission performance of the gate. The length of the short-circuit waveguide is also optimized using the electromagnetic simulation software HFSS to minimize the reflection from the resonant cavity (not shown in the figure) connected behind the coaxial section.

[0042] As an embodiment of this invention, when it is necessary to adjust the coupling depth of the coaxial inner conductor in the resonant cavity (not shown in the figure), the stud 71 is slightly loosened downwards so that the positioning locking ring and the coaxial inner conductor are in a relaxed state. Then, the lifting screw 72 is rotated to move up and down in the stud, which can drive the coaxial inner conductor 3 to move up and down, thereby achieving the purpose of adjusting the coupling depth. After the adjustment is completed, the stud 71 only needs to be tightened upwards.

[0043] As an embodiment of this invention patent, the large bottom surface of the gate button 2 is closely fitted to the inner wall of the rectangular waveguide cavity 1 with a water-cooled structure, which has good thermal conductivity and can withstand higher microwave power input. The coaxial inner conductor is tightly connected to the rectangular waveguide cavity 1 and the gate button 2 through the positioning locking ring, which has good conductivity and is not prone to adverse field conditions such as electrode breakdown.

[0044] As an embodiment of this invention, the input microwave uses 2.45GHz industrial microwave, and the rectangular waveguide cavity waveguide structure adopts a standard BJ26 square waveguide (long side a is 86.36mm, narrow side b is 43.18mm), the coaxial inner conductor is 8mm, and the coaxial outer conductor is 26mm, in order to achieve the ideal waveguide mode conversion and high-efficiency transmission effect of this invention.

[0045] Its main structural parameters are as follows, such as Figure 1-5 As shown: The rectangular waveguide cavity 1 has an L1 of 140 mm; the gate button 2 has an H1 of 30.8 mm, a D0 of 114.4 mm, and an h of 1.5 mm; the short-circuit waveguide 5 has an L2 of 50 mm.

[0046] As another embodiment of this invention, the input microwave uses 2.45GHz industrial microwave, and the rectangular waveguide cavity waveguide structure adopts a standard BJ26 square waveguide (long side a is 86.36mm, narrow side b is 43.18mm), the coaxial inner conductor is 8mm, and the coaxial outer conductor is 20mm, in order to achieve the ideal waveguide mode conversion and high-efficiency transmission effect of this invention.

[0047] Its main structural parameters are as follows, such as Figure 1 , Figure 2 and Figure 3 As shown: The rectangular waveguide cavity 1 has an L1 of 140 mm; the gate button 2 has an H1 of 37.5 mm, a D0 of 99 mm, and an h of 2 mm; the short-circuit waveguide 5 has an L2 of 43 mm.

[0048] In addition, for the waveguide coaxial conversion device used for PCVD processing, in one embodiment of the present invention, the coaxial outer conductor 4 is also provided with a cooling water circulation loop (not shown in the figure) and a positioning sleeve made of wave-transparent material (not shown in the figure) provided at the end of the coaxial section.

[0049] Furthermore, to reduce microwave loss during operation of the device of the present invention, a coating is provided on the surface of the gate button 2, the inner surface of the coaxial inner conductor, and the coaxial outer conductor in this embodiment. The thickness of the coating needs to take into account the skin depth of the input microwave and the allowance for oxidation and corrosion of the material in the environment. Specifically, the coating is a silver or gold plating layer with a thickness greater than 8 μm.

[0050] The above embodiments are merely preferred technical solutions of the present invention and should not be considered as limitations on the present invention. The scope of protection of the present invention should be limited to the technical solutions described in the claims, including equivalent substitutions of the technical features described in the claims. That is, equivalent substitutions and improvements within this scope are also within the scope of protection of the present invention.

Claims

1. A waveguide coaxial converter, characterized in that: The structure includes a rectangular waveguide cavity (1), a door button (2), a coaxial inner conductor (3), a coaxial outer conductor (4), a short-circuit waveguide (5), a positioning locking ring (6), and a lifting assembly (7). The door button (2) is installed inside the rectangular waveguide cavity (1). The coaxial inner conductor (3) is connected to the lifting assembly (7) at the bottom. The coaxial inner conductor (3) passes through the center of the door button (2) and extends out to form a coaxial waveguide structure with the coaxial outer conductor (4). The coaxial outer conductor (4) is installed on the upper end face of the rectangular waveguide cavity (1). The short-circuit waveguide (5) is installed on the opposite side of the feed waveguide port of the rectangular waveguide cavity (1). The positioning locking ring (6) is located in the positioning center at the bottom of the door button (2). The lifting assembly (7) is installed at the bottom of the rectangular waveguide cavity (1). The lifting assembly (7) includes a stud (71), a lifting screw (72), an upper positioning nut (73), and a lower sealing plate (74); the outer cylinder of the stud (71) is provided with an external thread (711), which is connected to the first threaded hole (13) of the rectangular waveguide cavity (1); the inner hole of the stud (71) is provided with an internal thread (712), which is connected to the external thread of the lifting screw (72); the upper positioning nut (73) is installed on the coaxial inner conductor (3), and the upper positioning nut (73) Its upper end face is in contact with the lower end face of the lifting screw (72); the lower sealing plate (74) is fixedly connected to the lifting screw (72) and in contact with the lower end face of the coaxial inner conductor (3); the upper end face of the stud body (71) is provided with an inverted conical hole that cooperates with the conical cylinder of the positioning locking ring (6); the lifting screw (72) is provided with a third circular hole (721), the diameter D3 of the third circular hole is larger than the diameter d of the coaxial inner conductor (3) so that the coaxial inner conductor (3) can freely pass through the third circular hole (721).

2. The waveguide coaxial converter according to claim 1, characterized in that: The rectangular waveguide cavity (1) is a hollow metal body with a standard rectangular waveguide through hole. Flange structures are provided at both ends of the rectangular waveguide cavity (1). The two ends of the rectangular waveguide cavity (1) are threadedly connected to the flange of the feed waveguide and the flange of the short-circuit waveguide (5) through the flange structures respectively. A first threaded hole (13) is provided at the bottom of the rectangular waveguide cavity (1) for connecting with the lifting assembly (7). A first circular hole (14) is provided at the top of the rectangular waveguide cavity (1). The inner diameter of the first circular hole (14) is adapted to the inner hole of the coaxial outer conductor (4).

3. The waveguide coaxial converter according to claim 1, characterized in that: A first countersunk hole (15) and several threaded holes (16) are provided on the outer periphery of the first circular hole (14) at the top of the rectangular waveguide cavity (1). The coaxial inner conductor (3) is positioned through the first countersunk hole (15) and connected to the rectangular waveguide cavity (1) through the threaded holes (16).

4. The waveguide coaxial converter according to claim 1, characterized in that: A circulating cooling water circuit (17) is provided at the bottom of the rectangular waveguide cavity (1).

5. The waveguide coaxial converter according to claim 1, characterized in that: The bottom of the rectangular waveguide cavity (1) has several through holes, and is fixedly connected to the door button (2) by screws.

6. The waveguide coaxial converter according to claim 1, characterized in that: The door knob (2) is of a rotary conical structure, with a second round hole (21) opened along the rotary axis, and the diameter of the second round hole (21) is slightly larger than that of the coaxial inner conductor (3); a second counterbore (22) is arranged on the outer periphery of the second round hole (21), and the positioning locking ring (6) is arranged in the second counterbore (22); the second round hole (21) and the second counterbore (22) are coaxial.

7. The waveguide coaxial converter according to claim 6, characterized in that: The bottom diameter D0 of the door knob (2) and the width a of the rectangular waveguide cavity (1) satisfy the relationship: a < D0 < 2a; The bottom diameter D0 of the door knob (2) and the waveguide length L1 of the rectangular waveguide cavity (1) satisfy the relationship: D0 < L1; The height H1 of the door knob (2) and the narrow side length b of the rectangular waveguide cavity (1) satisfy the relationship: 0.5b < H1 < 0.9b, and the side busbar length S of the door knob (2) is 0.5λ, where λ is the vacuum wavelength of the fed microwave; To ensure good contact between the bottom surface and the outer edge of the door knob (2) and the inner cavity bottom surface of the rectangular waveguide cavity (1), the bottom surface of the door knob (2) is provided with a convex platform with a thickness of h, 0 < h ≤ 2 mm; Both sides of the door knob (2) are symmetrically cut, the cut side surface is perpendicular to the bottom surface of the door knob (2), and the width W of this part of the door knob (2) after cutting is equal to the width a of the rectangular waveguide cavity (1).

8. The waveguide coaxial converter according to claim 7, characterized in that: The door knob (2) is made of brass, and the surface of the door knob (2) is plated with a coating to reduce microwave loss, and the coating material is silver or gold.

9. The waveguide coaxial converter according to claim 1, characterized in that: The short-circuit waveguide (5) is a hollow metal waveguide cavity with one end short-circuited. Its waveguide cross-sectional dimensions are consistent with the waveguide through-hole of the rectangular waveguide cavity (1). The short-circuit surface of the short-circuit waveguide (5) is a plane, and the equivalent distance L between it and the generatrix on the gate button (2) side is 0.5λ. g , where λ g The waveguide wavelength is the wavelength of the microwave feed.

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