Coaxial to elliptical waveguide broadband transition based on stepped impedance probes

Abstract

The application belongs to the technical field of communication and specifically relates to a coaxial-to-elliptical waveguide broadband transition device based on a step impedance probe. The application comprises an elliptical waveguide tube, a coaxial connector, a fixing seat, a short step impedance probe and a flange. The long axis side wall of the elliptical waveguide tube and the fixing seat are provided with a through hole, the fixing seat is fixed on the outer side wall of the elliptical waveguide tube, the center position of the fixing seat is consistent with the center position of the through hole, and the coaxial connector is arranged on the fixing seat. One end of the elliptical waveguide tube is provided as an elliptical waveguide tube open end, and the other end is provided as an elliptical waveguide tube closed end. The flange is fixed on the elliptical waveguide tube open end, and the open end surface is consistent with the elliptical waveguide tube open end. One end of the short step impedance probe is connected with the inner conductor of the coaxial connector, and the other end penetrates through the through hole and extends into the elliptical waveguide tube. The short step impedance probe comprises a connecting feed rod and a short step impedance feed rod. The connecting feed rod is connected with the coaxial connector and the short step impedance feed rod.

Description

Technical Field

[0001] This invention belongs to the field of communication technology, specifically relating to a broadband transition from coaxial to elliptical waveguide based on a step impedance probe. Background Technology

[0002] Elliptical waveguides have advantages such as low high-frequency loss, relatively stable waveform polarization surface, easy matching and connection with rectangular waveguides or coaxial cables, the ability to manufacture long lengths of 500m and above, good bending performance, the ability to be produced by winding, convenient transportation, and convenient installation. Currently, elliptical waveguide feeders are widely used in equipment such as terrestrial microwave relays and satellite earth stations.

[0003] Currently, elliptical waveguide connectors are composed of coaxial-to-rectangular waveguide converters and elliptical-to-rectangular waveguide converters. The conversion process is complex, the installation is cumbersome, the cost is high, and the loss is significant.

[0004] Some scholars have studied coaxial-elliptical waveguide converters, which employ a stepped impedance feed rod structure. This stepped impedance structure is a quarter-wavelength impedance transformation structure. However, the length of the feed rod inside the waveguide is limited, resulting in an indistinct stepped structure and thus limited bandwidth improvement, which cannot meet the needs of broadband systems. Summary of the Invention

[0005] This invention addresses the shortcomings of existing technologies by proposing a broadband transition from coaxial to elliptical waveguides based on a step impedance probe. Based on a short step impedance probe design, this invention achieves a wider bandwidth without increasing the length of the original feed rod by varying the high and low impedance of multiple feed rod sections. By loading a probe in the middle of the major axis of the elliptical waveguide, multiple higher-order modes of the elliptical waveguide can be effectively suppressed, enabling single-mode transmission. By selecting an appropriate elliptic eccentricity, the frequency band spacing between the fundamental mode and higher-order modes can be increased, further enhancing the single-mode bandwidth.

[0006] To achieve the above-mentioned objectives, the present invention adopts the following technical solution:

[0007] A broadband transition device from coaxial to elliptical waveguide based on a step impedance probe includes an elliptical waveguide, a coaxial connector, a mounting base, a short step impedance probe, and a flange. The elliptical waveguide has through holes on its major axis sidewall and within the mounting base. The mounting base is fixed to the outer sidewall of the elliptical waveguide, and its center position coincides with the center position of the through holes. The coaxial connector is mounted on the mounting base. One end of the elliptical waveguide is an open end, and the other end is a closed end. The flange is fixed to the open end of the elliptical waveguide, and its open end face coincides with the open end of the elliptical waveguide. One end of the short step impedance probe is connected to the inner conductor of the coaxial connector, and the other end extends into the elliptical waveguide through the through holes. The short step impedance probe includes a connecting feed rod and a short step impedance feed rod. The connecting feed rod connects to both the coaxial connector and the short step impedance feed rod.

[0008] As a further preferred embodiment of the present invention, the connecting feed rod extends into the elliptical waveguide through the through hole, and the length extending into the elliptical waveguide does not exceed 3mm, and the entire connecting feed rod is located inside the elliptical waveguide.

[0009] As a further preferred embodiment of the present invention, the short step impedance feed rod includes N thick metal cylinders and N thin metal cylinders, the number of thick metal cylinders and the number of thin metal cylinders are the same, N = 2, 3, 4...; the thick metal cylinders and the thin metal cylinders are connected in series alternately.

[0010] As a further preferred embodiment of the present invention, the lengths of the coarse metal cylinder and the fine metal cylinder are approximately λ / (4*2N), where λ is the working wavelength, and the length deviation is no greater than 4mm. The ratio of the diameters of the coarse metal cylinder and the fine metal cylinder is greater than or equal to 2.

[0011] As a further preferred embodiment of the present invention, the coaxial connector includes an outer conductor, an inner conductor, and insulation. The insulation is used to fix the inner conductor, and the outer conductor is provided with a fixing platform whose size is the same as that of the fixing base. The insulation protrudes 0.2 mm from the fixing platform.

[0012] As a further preferred embodiment of the present invention, a first stud is provided at the end of the inner conductor near the connecting feed rod, a first screw hole is provided at the end of the connecting feed rod near the coaxial connector, a second stud is provided at the end near the short step impedance feed rod, and a second screw hole is provided at the coarse metal cylindrical end of the short step impedance feed rod. The coaxial connector, the connecting feed rod, and the short step impedance feed rod are sequentially connected through the connection of the first screw hole and the first stud, and the second screw hole and the second stud. The first stud and the first screw hole are matched in size, the second stud and the second screw hole are matched in size, and neither is larger than the diameter of the connecting feed rod.

[0013] As a further preferred embodiment of the present invention, the center of the through hole is located at the center of the long axis sidewall of the elliptical waveguide, and is a quarter wavelength away from the closed end of the elliptical waveguide.

[0014] As a further preferred embodiment of the present invention, the eccentricity of the elliptical waveguide is 0.75 to 0.93.

[0015] As a further preferred embodiment of the present invention, the flange is rectangular, and its length and width are consistent with the major and minor axes of the outer wall of the elliptical waveguide.

[0016] As a further preferred embodiment of the present invention, the fixing seat is provided with a groove, the groove being 0.2 mm deep and having a diameter consistent with the insulation diameter, for the coaxial connector and the through hole to be concentric.

[0017] The coaxial-to-elliptical waveguide broadband transition based on a step impedance probe described in this invention has the following technical advantages compared with existing technologies:

[0018] (1) Based on the design of a short step impedance probe, this invention achieves a wider bandwidth by varying the high and low impedance of multiple feed rods without increasing the length of the original feed rod. By loading a probe in the middle of the long axis of the elliptical waveguide, multiple higher-order modes of the elliptical waveguide can be effectively suppressed, and single-mode transmission can be achieved. By selecting an appropriate elliptical eccentricity, the frequency band spacing between the fundamental mode and higher-order modes can be increased, further improving the single-mode bandwidth.

[0019] (2) The present invention can effectively suppress higher-order modes, while ensuring the single-mode operation of the coaxial elliptical waveguide transition, and has better matching effect and wider operating bandwidth. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the overall structure of the transition device according to an embodiment of the present invention;

[0021] Figure 2This is a side view of the short step impedance probe of the transition device and the inner conductor of the coaxial connector in an embodiment of the present invention;

[0022] Figure 3 This is a side view of the coaxial connector according to an embodiment of the present invention;

[0023] Figure 4 This is a side view of the fixing base according to an embodiment of the present invention;

[0024] Figure 5 The dispersion pattern is shown in the embodiment of the present invention;

[0025] Figure 6 This is a graph showing the |S11| and |S12| curves of an embodiment of the present invention;

[0026] In the attached diagram, 1-elliptical waveguide; 11-elliptical waveguide open end; 12-elliptical waveguide closed end; 2-coaxial connector; 21-outer conductor; 22-insulator; 23-inner conductor; 221-fixed platform; 231-first stud; 3-fixed base; 31-groove; 32-through hole; 4-short step impedance probe; 41-connecting feed rod; 42-short step impedance feed rod; 411-first screw hole; 412-second stud; 421-coarse metal cylinder; 422-fine metal cylinder; 4211-second screw hole; 5-flange. Detailed Implementation

[0027] The present invention will be further explained in detail below with reference to the accompanying drawings, so that those skilled in the art can better understand and implement the present invention. However, the following examples are only used to explain the present invention and are not intended to limit the present invention.

[0028] like Figure 1As shown, a broadband transition from coaxial to elliptical waveguide based on a step impedance probe includes: an elliptical waveguide 1, a coaxial connector 2, a mounting base 3, a short step impedance probe 4, and a flange 5. Through holes 6 are provided on the long axis sidewall of the elliptical waveguide 1 and within the mounting base 3. The mounting base 3 is fixed to the outer sidewall of the waveguide, and its center position coincides with the center position of the through hole 6. The coaxial connector 2 is mounted on the mounting base 3. One end of the elliptical waveguide 1 is an open end 11, and the other end is a closed end 12. The flange 5 is fixed to the open end 11, and its open end face coincides with the open end 11. One end of the short step impedance probe 4 is connected to the inner conductor 23 of the coaxial connector 2, and the other end extends into the elliptical waveguide 1 through the through hole 6. The short step impedance probe 4 is composed of a connecting feed rod 41 and a short step impedance feed rod 42. The connecting feed rod 41 connects the coaxial connector 2 and the short step impedance feed rod 42. The connecting feed rod 41 extends into the elliptical waveguide 1 through the through hole 6, and the length extending into the elliptical waveguide 1 does not exceed 3mm. The short step impedance feed rod 42 is entirely located inside the elliptical waveguide 1.

[0029] The eccentricity of the elliptical waveguide 1 is 0.75–0.93. The flange 5 is rectangular, and its length and width are consistent with the major and minor axes of the outer wall of the elliptical waveguide 1, which can greatly reduce the flange size and reduce costs. The center of the through hole 32 is located at the center of the major axis side wall of the elliptical waveguide 1, and is a quarter wavelength away from the closed end 12 of the elliptical waveguide.

[0030] like Figure 2 As shown, in this embodiment, the short step impedance feed rod 42 is composed of N (N = 1, 2, 3, 4) coarse metal cylinders 421 and N (N = 1, 2, 3, 4) fine metal cylinders (422). The number of coarse metal cylinders 421 and fine metal cylinders 422 is the same, and the coarse metal cylinders 421 and fine metal cylinders 422 are connected in series alternately. One end of the short step impedance feed rod 42 is a coarse metal cylinder 421, and the other end is a fine metal cylinder 422. The length of each coarse metal cylinder 421 and fine metal cylinder 422 is approximately λ / (4*2N) (λ is the operating wavelength), and the length deviation is no greater than 4mm. The ratio of the diameters of the coarse metal cylinder 421 and fine metal cylinder 422 is greater than or equal to 2.

[0031] like Figure 3 As shown, the coaxial connector 2 includes an outer conductor 21, an inner conductor 23, and an insulator 22. The insulator 22 is used to fix the inner conductor 23. The outer conductor 21 is provided with a fixing platform 211, the size of which is the same as that of the fixing base 3. The insulator 22 protrudes 0.2mm from the fixing platform 211.

[0032] The inner conductor 23 of the coaxial connector 2 is provided with a first stud 231 near the connecting feed rod 41. The end of the connecting feed rod 41 near the coaxial connector 2 is provided with a first screw hole 411, and the end near the short-step impedance feed rod 42 is provided with a second stud 412. The end of the coarse metal cylinder 421 of the short-step impedance feed rod 42 is provided with a second screw hole 4211. Through the connection of the first screw hole 411 and the first stud 231, and the second screw holes 4211 and 412, the coaxial connector 2, the connecting feed rod 41, and the short-step impedance feed rod 42 are sequentially connected together, and the connecting feed rod 41 and the short-step impedance feed rod 42 are detachable and replaceable. The first stud 231 matches the size of the first screw hole 411, and the second stud 412 matches the size of the second screw hole 4211, and neither is larger than the diameter of the connecting feed rod 41.

[0033] like Figure 4 As shown, the mounting base 3 is provided with a groove 31, which is 0.2 mm deep and has the same diameter as the insulation 22 of the coaxial connector 2, in order to ensure that the coaxial connector 2 and the through hole 6 are concentric.

[0034] The main dimensions and parameters of the transition device in this embodiment of the invention are as follows:

[0035] The internal dimensions of the elliptical waveguide are 57mm × 28mm. The distance from the through-hole to the closed end of the elliptical waveguide is 17mm, and the radius of the through-hole is 3.15mm. The length and radius of the connecting feed rod of the short stepped impedance probe are 5.9mm and 0.85mm, respectively. The radii of the first coarse metal cylinder, the first fine metal cylinder, the second coarse metal cylinder, and the second fine metal cylinder of the short stepped impedance feed rod are 2.85mm, r2 = 0.7mm, 3.1mm, and 0.6mm, respectively. The lengths of the first coarse metal cylinder, the first fine metal cylinder, the second coarse metal cylinder, and the second fine metal cylinder are 4.2mm, 3.8mm, 3.4mm, and 2.3mm, respectively.

[0036] like Figure 5 As shown in the dispersion pattern, the elliptical waveguide selected in this invention has an eccentricity of 0.82. The cutoff frequencies of TEc11, TEc21, TEc11, TMc01 and TEc21 through the elliptical waveguide are 3.14 GHz, 5.69 GHz, 6.15 GHz, 6.66 GHz and 8.02 GHz, respectively. Therefore, the frequency spacing between the TMc01 mode and the fundamental mode is relatively large, which provides a basis for using a short step impedance feed rod 42 to extend the operating frequency band.

[0037] like Figure 6As shown, the S-parameters of the coaxial-to-elliptical waveguide transition are compared under three different conditions (uniform impedance feed, two-section short step impedance feed 42, and four-section short step impedance feed 42). It can be seen that the short step impedance feed 42 can significantly extend the bandwidth compared to the uniform impedance feed. The -20dB transition bandwidth of the uniform impedance feed is 12.77% (3.985GHz-0.509GHz). Using the two-section short step impedance feed 42, the transition -20dB bandwidth is 46.48% (4.798GHz-2.23GHz). Furthermore, using the four-section short step impedance feed 42, the transition -20dB bandwidth is 53.37% (5.07GHz-2.706GHz), an extension of 14.8%. Notably, the impedance matching of the transition at high frequencies is improved. Due to the short step impedance feed rod 42 structure, the -20dB frequency range of the coaxial to elliptical waveguide transition is 3.717-6.523GHz, which exceeds the cutoff frequency of the higher-order modes TEs11 and TEc21. The transitioner based on the four short step impedance feed rods 42 only excites the main mode TEc11 of the elliptical waveguide.

[0038] The specific implementation schemes described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific implementation schemes of the present invention and are not intended to limit the scope of the present invention. Any equivalent changes and modifications made by those skilled in the art without departing from the concept and principles of the present invention should fall within the scope of protection of the present invention.

Claims

1. A broadband transition from coaxial to elliptical waveguide based on a step impedance probe, characterized in that, The system includes an elliptical waveguide (1), a coaxial connector (2), a mounting base (3), a short step impedance probe (4), and a flange (5). The elliptical waveguide (1) has a through hole (32) on its long axis sidewall and inside the mounting base (3). The mounting base (3) is fixed to the outer sidewall of the elliptical waveguide (1), and its center position coincides with the center position of the through hole (32). The coaxial connector (2) is mounted on the mounting base (3). One end of the elliptical waveguide (1) is designated as the elliptical waveguide opening end (11), and the other end is designated as the elliptical waveguide sealing end. The flange (5) is fixed to the open end (11) of the elliptical waveguide, and the open end face is consistent with the open end (11) of the elliptical waveguide. One end of the short step impedance probe (4) is connected to the inner conductor (23) of the coaxial connector (2), and the other end extends into the elliptical waveguide (1) through the through hole (32). The short step impedance probe (4) includes a connecting feed rod (41) and a short step impedance feed rod (42). The connecting feed rod (41) is connected to the coaxial connector (2) and the short step impedance feed rod (42) respectively. The short step impedance feed rod (42) includes N thick metal cylinders (421) and N thin metal cylinders (422), the number of thick metal cylinders (421) and the number of thin metal cylinders (422) are the same, N=2, 3, 4...; the thick metal cylinders (421) and the thin metal cylinders (422) are connected in series alternately; The lengths of the coarse metal cylinder (421) and the fine metal cylinder (422) are approximately λ / (4*2N), and the length deviation is no greater than 4mm. The ratio of the diameters of the coarse metal cylinder (421) and the fine metal cylinder (422) is greater than or equal to 2.

2. The broadband coaxial-to-elliptical waveguide transition based on a step impedance probe according to claim 1, characterized in that, The connecting feed rod (41) extends into the elliptical waveguide (1) through the through hole (32), and the length extending into the elliptical waveguide (1) does not exceed 3mm. The connecting feed rod (41) is entirely located inside the elliptical waveguide (1).

3. The broadband coaxial-to-elliptical waveguide transition based on a step impedance probe according to claim 1, characterized in that, The coaxial connector (2) includes an outer conductor (21), an inner conductor (23) and an insulator (22). The insulator (22) is used to fix the inner conductor (23). The outer conductor (21) is provided with a fixing platform (211), the size of which is the same as that of the fixing seat (3). The insulator (22) protrudes 0.2mm from the fixing platform (211).

4. The broadband coaxial-to-elliptical waveguide transition based on a step impedance probe according to claim 3, characterized in that, The inner conductor (23) has a first stud (231) near the end of the connecting feed rod (41), the connecting feed rod (41) has a first screw hole (411) near the end of the coaxial connector (2), and a second stud (412) near the end of the short step impedance feed rod (42). The coarse metal cylinder (421) end of the short step impedance feed rod (42) has a second screw hole (4211). Through the connection of the first screw hole (411) and the first stud (231), and the second screw hole (4211) and the second stud (412), the coaxial connector (2), the connecting feed rod (41), and the short step impedance feed rod (42) are connected in sequence. The first stud (231) and the first screw hole (411) are sized to match. The second stud (412) and the second screw hole (4211) are matched in size, and neither is larger than the diameter of the connecting feed rod (41).

5. The broadband coaxial-to-elliptical waveguide transition based on a step impedance probe according to claim 1, characterized in that, The center of the through hole (32) is located at the center of the long axis sidewall of the elliptical waveguide (1), and is a quarter wavelength away from the closed end (12) of the elliptical waveguide.

6. The broadband coaxial-to-elliptical waveguide transition based on a step impedance probe according to claim 5, characterized in that, The eccentricity of the elliptical waveguide (1) is 0.75 to 0.

93.

7. The broadband coaxial-to-elliptical waveguide transition based on a step impedance probe according to claim 1, characterized in that, The flange (5) is rectangular, and its length and width are consistent with the major and minor axes of the outer wall of the elliptical waveguide (1).

8. The broadband coaxial-to-elliptical waveguide transition based on a step impedance probe according to claim 3, characterized in that, The fixing seat (3) is provided with a groove (31) with a depth of 0.2 mm and a diameter consistent with that of the insulation (22), so that the coaxial connector (2) and the through hole (32) are concentric.

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