Double-frequency broadband large-angular-domain high-gain antenna based on cavity structure

Abstract

The utility model discloses a double-frequency broadband large-angular-domain high-gain antenna based on a cavity structure, and mainly solves the problems that the existing antenna cannot meet the requirements of wide frequency band, high gain of a large angular domain near an end-fire direction and conformal installation at the same time. The antenna comprises a radome (1), a metal cavity (2), three sealing rings (3, 7 and 8), two radiators (4 and 5) and a connector (6), the radome comprises a radome front end, a radome flange and an air conditioning cavity from top to bottom, and the influence of the size non-uniformity of the radome on the antenna performance can be eliminated by changing the shape and size of the air conditioning cavity; the two radiators are located in the metal cavity and jointly adjust the angular domain range of the antenna; the first sealing ring (3) is positioned between the antenna housing and the metal cavity; second and third sealing rings (7, 8) are located between the metal cavity and the connector. The antenna has the characteristics of wide frequency band, high gain of a large angular domain near an end-fire direction and easy conformal performance, is high in water pressure resistance and sealing performance, and is suitable for ground radar equipment and submarine radar equipment.

Description

Technical Field

[0001] This utility model belongs to the field of radar equipment antennas, specifically relating to a dual-band broadband large-angle domain high-gain antenna that can be used on mobile platforms. Background Technology

[0002] With the continuous development of modern radar equipment, the requirements for antennas in radar equipment are becoming increasingly stringent. Antennas not only need to meet the requirements of wide bandwidth and conformal installation, but also need to meet the requirements of high gain in specific angular domains under different installation environments. K-band and Ka-band antennas have the advantages of small size and light weight, and have broad application prospects on mobile platforms.

[0003] The main types of antennas include waveguide slot antennas, parabolic antennas, microstrip antennas, and horn antennas. Among them, waveguide slot antennas and parabolic antennas have relatively high profiles, resulting in relatively large size and weight, making them inconvenient to conform to equipment. Microstrip antennas have low profiles, small size, light weight, and are easy to conform to equipment, but they have high feed line losses, low gain and narrow bandwidth in the large-angle region near the antenna end-fire direction, resulting in spatial dead zones and failing to meet the communication requirements of radar equipment. Horn antennas have simple structure and feeding, wide bandwidth, and high efficiency, but they also have low gain in the large-angle region near the end-fire direction, resulting in spatial dead zones and failing to meet the communication requirements of radar equipment.

[0004] Utility model patent CN 218997080 U discloses a high-power antenna element with a vacuum design. It achieves a simple and easy-to-install sealed structure by adding an radome, sealing ring, and sealing groove to a horn antenna. While this antenna element boasts a wide bandwidth and high gain, its maximum gain points towards the normal direction, resulting in low gain in the large angular region near the end-fire direction. This creates a spatial dead zone during use, failing to meet communication requirements. Utility Model Content

[0005] The purpose of this invention is to address the shortcomings of the existing technology by proposing a dual-band broadband large-angle high-gain antenna based on a cavity structure. This antenna can extend the large-angle coverage near the antenna end-fire direction while meeting bandwidth and conformal installation requirements, thereby avoiding spatial blind spots in communication and meeting the communication needs of the equipment.

[0006] To achieve the above objectives, this utility model provides a dual-band broadband large-angle high-gain antenna based on a cavity structure, comprising an antenna radome, a metal cavity, three sealing rings, two radiators, and a connector, characterized in that:

[0007] The radome, from top to bottom, includes a front end of the radome, a flange of the radome, and an air conditioning cavity. The influence of the radome size non-uniformity on the antenna performance is eliminated by changing the shape and size of the air conditioning cavity.

[0008] The metal cavity includes, from top to bottom, a sealing groove, an upper flange of the cavity, an air cavity, and a lower flange of the cavity;

[0009] Both radiators are located within the air cavity, and the three together adjust the angular range of the antenna.

[0010] The connector (6) includes, from top to bottom, a mounting flange (61), two connector sealing grooves (62, 63) and two waveguide coaxial converters (64, 65). The mounting flange (61) is aligned with the outer contour of the lower flange (24) of the metal cavity and is securely connected. The first sealing ring (3) is installed in the sealing groove (21), and the second sealing ring (7) and the third sealing ring (8) are respectively installed in the two connector sealing grooves (62, 63) to seal the upper and lower ends of the metal cavity (2) and protect its internal environment.

[0011] Preferably, both radiators are modified designs based on a pyramidal horn, and their deflection angles are 0.3 to 0.7 times the maximum radiation angle in the angular domain.

[0012] Preferably, the front end of the radome is conformally designed according to the shape of the mounting platform and the size of the opening, so as to meet the conformal installation requirements of any platform while ensuring antenna performance.

[0013] Preferably, the radome mounting flange has the same outer dimensions as the flange on the metal cavity and is fastened together so that the upper surface of the metal cavity fits tightly against the lower surface of the radome.

[0014] Preferably, the air cavity contains multiple adjustable parameters, including: cavity width B5, cavity length B6, cavity height B8, and distance B4 between the two radiators; by adjusting these adjustable parameters and the deflection angle of the two radiators, the angular range of the antenna can meet the design requirements.

[0015] This invention features an antenna radiator designed with two independent functional variations based on a pyramidal horn. By optimizing the radiator and adjusting the size of the metal cavity to adjust the antenna gain within a specific angular range, the antenna not only possesses a wide operating bandwidth but also meets the communication requirements of radar equipment in different angular domains, enabling simultaneous signal transmission and reception. Furthermore, the antenna's uppermost layer utilizes a wave-transparent radome, facilitating conformal installation on different platforms. Additionally, the use of sealing rings between the radome and the metal cavity, and between the metal cavity and the connector, provides strong water pressure resistance and sealing performance, making it suitable not only for ground-based radar equipment but also for submarine radar equipment, thus broadening its application platform. Attached Figure Description

[0016] Figure 1This is a schematic diagram of the overall structure of this utility model;

[0017] Figure 2 This is an exploded view of the structure of this utility model;

[0018] Figure 3 This is a schematic diagram of the antenna radome 1 in this utility model;

[0019] Figure 4 This is a schematic diagram of the structure of the metal cavity 2 in this utility model;

[0020] Figure 5 This is a schematic diagram of the structure of the first radiator 4 in this utility model;

[0021] Figure 6 This is a schematic diagram of the structure of the second radiator 5 in this utility model;

[0022] Figure 7 This is a schematic diagram of the connector 6 in this utility model;

[0023] Figure 8 This is a simulation result diagram of the K-band standing wave coefficient of this utility model embodiment;

[0024] Figure 9 This is a simulation result of the K-band radiation pattern of an embodiment of this utility model;

[0025] Figure 10 This is a simulation result diagram of the Ka-band standing wave coefficient of an embodiment of this utility model;

[0026] Figure 11 This is a simulation result of the Ka-band radiation pattern of an embodiment of this utility model. Detailed Implementation

[0027] The embodiments and effects of this utility model are described in detail below with reference to the accompanying drawings.

[0028] Reference Figure 1 and Figure 2 In this embodiment, the antenna includes an antenna cover 1, a metal cavity 2, a first sealing ring 3, a first radiator 4, a second radiator 5, a connector 6, a second sealing ring 7, and a third sealing ring 8, and can be divided into three layers from top to bottom. The antenna cover 1 is located in the uppermost layer, the metal cavity 2 is located in the middle layer, and the connector 6 is located in the lowermost layer. The first sealing ring 3 is located between the antenna cover 1 and the metal cavity 2. The first radiator 4 and the second radiator 5 are located inside the metal cavity 2. The second sealing ring 7 and the third sealing ring 8 are located between the metal cavity 2 and the connector 6.

[0029] The aforementioned radome 1 is used for conformal antenna design with the mounting platform; the metal cavity 2 and the two radiators work together to form a specific radiation angular domain; the first radiator 4 is used to transmit the energy signal of the first operating frequency band of the antenna, and the second radiator 5 is used to transmit the energy signal of the second operating frequency band of the antenna. The two operating frequency bands of the antenna are selected according to the requirements of the radar system; the connector 6 is used for the transmission and conversion of dual-band signals; and the three sealing rings work together to isolate the inner and outer spaces of the metal cavity 2 and seal and protect the two radiators.

[0030] When the antenna is working, it can transmit and receive on both frequency bands simultaneously, or it can transmit on one frequency band and receive on the other; its working principle is as follows:

[0031] When the antenna is in the transmitting state, the electrical signal transmitted by the back-end radar equipment is converted into electromagnetic waves through connector 6, and then the electromagnetic waves are radiated outward through the first radiator 4 and the second radiator 5. When the electromagnetic waves reach the wall structure of the metal cavity 2, they will be reflected, changing the propagation path of the electromagnetic waves. These reflected electromagnetic waves and the directly radiated electromagnetic waves are vector superimposed at the opening of the metal cavity 2 to form the phase plane pointing to the required angular domain. The electromagnetic waves that have completed the vector superposition are radiated outward through the antenna cover 1.

[0032] When the antenna is in receiving mode, the incoming electromagnetic waves pass through the antenna cover 1 and enter the metal cavity 2. Part of the electromagnetic waves are reflected by the wall structure of the metal cavity 2 and then reach the openings of the first radiator 4 and the second radiator 5. The other part of the electromagnetic waves directly reach the openings of the first radiator 4 and the second radiator 5. After the two are vectored and superimposed, they enter the first radiator 4 and the second radiator 5. Then, the electromagnetic waves are converted into electrical signals through the connector 6 and input to the back-end radar equipment.

[0033] In this embodiment, the first operating frequency band is set to, but is not limited to, 23GHz to 26.5GHz; the second operating frequency band is set to, but is not limited to, 26.8GHz to 35GHz; and the angular domain range of the first and second frequency bands is set to, but is not limited to, -75° to 0°.

[0034] refer to Figure 3 3(a) is the front view, 3(b) is the top view, and 3(c) is the side view. The radome 1 includes, from top to bottom, the radome front end 11, the radome flange 12, and the air conditioning cavity 13. The radome thickness h is an initial value calculated according to the optimal wave transmission formula of the material, under the premise of satisfying the structural strength. The calculation formula is as follows:

[0035]

[0036] In the formula, λ0 represents the wavelength of the antenna's operating center frequency, and ε r θ represents the dielectric constant of the material, θ represents the incident angle of the electromagnetic wave, i.e., the deflection angle of the radiator, and m represents any positive integer;

[0037] In this example, the antenna has two operating frequency bands. The initial value is taken as the center frequency of the high-frequency band. By changing the shape and size of the air conditioning cavity 13, both operating frequency bands meet the wave transmission requirements.

[0038] The shape and size of the radome front end 11 and radome flange 12 are determined based on the surface equation corresponding to the mounting platform and the antenna installation position. Specifically, the outer length A1 and outer width A2 of the mounting flange 12, the length A3 and width A4 of the radome front end, the distance A5 from the edge of the radome front end to the highest point of the radome flange, and the distance A6 from the edge of the radome front end to the lowest point of the radome flange are determined. The radome determined according to the surface equation provided by the mounting platform meets the conformal requirements of the platform. By adjusting the size of the air conditioning cavity 13 and the radome thickness h through modeling and simulation, the influence of the uneven overall size of the radome caused by the different curvatures between different mounting platforms on the antenna performance can be eliminated, thus determining the final size of the radome.

[0039] In some embodiments, the curvature of the mounting platform is larger, the bulge of the radome is more pronounced, its shape is closer to a part of a sphere, the overall non-uniformity of the radome is stronger, and the surface of the corresponding air conditioning cavity also needs to be adjusted to a curved surface; in other embodiments, the curvature of the mounting platform is smaller, the surface of the corresponding radome is flatter, its shape is closer to a rectangle, and the surface of the corresponding air conditioning cavity can also be adjusted to a plane.

[0040] In this embodiment, the radome material is set to, but is not limited to, cyanate quartz fiber preform with a dielectric constant of 3.1 and a loss tangent of 0.007. Material; the shape of the front end of the radome and the upper surface of the radome flange is set to, but is not limited to, satisfying the surface equation x. 2 +y 2 +z 2 =R 2 R represents the radius of the sphere.

[0041] refer to Figure 4 4(a) is a top view and 4(b) is a cross-sectional view. The metal cavity 2 includes a sealing groove 21, an upper flange 22, an air cavity 23, and a lower flange 24 from top to bottom.

[0042] The sealing groove 21 contains a first sealing ring 3, which is used to seal the upper end of the metal cavity and protect the internal environment of the cavity.

[0043] The outer length B1 and outer width B2 of the flange 22 on the cavity are the same as the outer length A1 and outer width A2 of the radome mounting flange 12, and the two are tightly connected, so that the upper surface of the metal cavity fits tightly with the lower surface of the radome.

[0044] The air cavity 23 contains two radiators. The installation position of the first radiator 4 from the edge of the metal cavity, the distance B3, the distance B4 between the second radiator 5 and the first radiator 4, the inner length B5, the inner width B6, and the inner depth B8 of the air cavity are adjusted by modeling and simulation to optimize the radiation performance of the antenna in a specific angular domain.

[0045] The lower flange 24 of the cavity is located on the central axis of the cavity and is used to install the connector 6;

[0046] refer to Figure 5 The first radiator 4 is fixed on the lower surface of the inner wall of the metal cavity and includes an excitation waveguide 41 and a radiation waveguide 42. The size of the excitation waveguide 41 is selected according to the requirements of the selected first operating frequency band and the standard waveguide size table is referenced. The initial value of the deflection angle θ1 of the excitation waveguide 41 is calculated according to the required angular domain range. Then, by modeling and simulating the radiation pattern of a specific angular domain, the deflection angle θ1, bending radius r1 of the excitation waveguide, and the height C1, aperture length C2, and aperture width C3 of the radiation waveguide are optimized to make the angular domain range and radiation performance of the antenna meet the design requirements. The optimized parameter values ​​are the final values.

[0047] In this example, the excitation waveguide 41 is selected, but is not limited to, the standard BJ260 rectangular waveguide, i.e., C4 is 8.636mm and C5 is 4.318mm; the initial value of the deflection angle θ1 of the excitation waveguide 41 is set to, but is not limited to, 50°, based on the maximum angular range of the end-fire direction being -75°.

[0048] refer to Figure 6 In this embodiment, the second radiator 5 is composed of an excitation waveguide 51 and a radiation waveguide 52, which is fixed on the lower surface of the inner wall of the metal cavity and is on the same horizontal plane as the first radiator 4. The initial values ​​of the size and deflection angle θ2 of the excitation waveguide 51 are selected according to the same principle as the initial values ​​of the size and deflection angle θ1 of the excitation waveguide 41. The final values ​​of the deflection angle θ2, bending radius r2 of the excitation waveguide 51, and the height D1, aperture length D2, and aperture length D3 of the radiation waveguide 52 are determined by modeling and simulation.

[0049] In this example, based on the operating frequency requirements, the excitation waveguide 51 is selected, but not limited to, a standard BJ320 rectangular waveguide, i.e., D4 is 7.112mm and D5 is 3.556mm; the initial value of the deflection angle θ2 of the excitation waveguide 51 is set to, but not limited to, 50° according to the angular domain range.

[0050] refer to Figure 7 The connector 6 is used to coaxially integrate two waveguides and is designed to be water pressure resistant and sealed. From top to bottom, it includes a mounting flange 61, two connector sealing grooves 62 and 63, and two waveguide coaxial converters 64 and 65.

[0051] The outer dimensions of the mounting flange 61 are the same as those of the lower flange 24 of the cavity, and they are fastened together so that the upper surface of the connector fits tightly with the lower surface of the lower flange of the cavity.

[0052] The connector sealing groove 63 is used to install the second sealing ring 7, and the connector sealing groove 62 is used to install the third sealing ring 8; the two sealing rings work together to seal the lower end of the metal cavity and protect the internal environment of the cavity.

[0053] The inner wall size of the cavity of the first waveguide coaxial converter 64 is the same as the inner wall size of the radiator excitation waveguide 41, and the inner wall size of the cavity of the second waveguide coaxial converter 65 is the same as the inner wall size of the radiator excitation waveguide 51.

[0054] In this example, the inner wall dimensions of waveguide cavity 64 are set to, but are not limited to, 8.636mm × 4.318mm; the inner wall dimensions of waveguide cavity 65 are set to, but are not limited to, 7.112mm × 3.556mm.

[0055] The effectiveness of this invention can be further illustrated by the following simulation results.

[0056] I. Simulation Conditions

[0057] An electromagnetic simulation model of an embodiment of this utility model was established using HFSS electromagnetic simulation software.

[0058] The electromagnetic simulation model of this invention includes two operating frequency bands: the K-band and the Ka-band. Its structural parameters are set as follows:

[0059] Radome: Its outer length A1 is 74.5mm, outer width A2 is 65.0mm, length A3 of the front end of the radome is 58.5mm, width A4 is 49mm, distance A5 from the edge of the front end of the radome to the highest point of the radome flange is 1.51mm, distance A6 from the edge of the front end of the radome to the lowest point of the radome flange is 1.85mm, and thickness h of the radome is 6.0mm; the dimensions of the air conditioning cavity are 20mm × 10mm × 0.35mm.

[0060] Metal cavity: The outer length B1 of the upper flange 22 of the cavity is 74.5mm, the outer width B2 is 65mm, the distance B3 from the installation position of the first radiator 4 to the edge of the metal cavity is 36.35mm, the distance B4 between the second radiator 5 and the first radiator 4 is 23.70mm, the inner length B5 of the air cavity 23 is 39mm, the inner width B6 is 51.5mm, the inner depth B8 is 18.9mm, and the thickness B7 of the lower flange 24 of the cavity is 4.0mm.

[0061] The first radiator 4 has the following characteristics: the deflection angle θ1 of the excitation waveguide 41 is 50°, the bending radius r1 is 4.23 mm, the height C1 of the radiation waveguide 42 is 12 mm, the aperture length C2 is 10.0 mm, the aperture width C3 is 9.0 mm, and the length C4 of the excitation waveguide 41 is 8.636 mm and the width C5 is 4.318 mm.

[0062] The second radiator 5 has the following characteristics: the deflection angle θ2 of the excitation waveguide 51 is 50°, the bending radius r2 is 18.4 mm, the height D1 of the radiating waveguide 52 is 9.0 mm, the aperture length D2 is 7.5 mm, the aperture length D3 is 5.0 mm, the length D4 of the excitation waveguide 51 is 7.112 mm, and the width D5 is 3.556 mm.

[0063] II. Simulation Content

[0064] Simulation 1: The K-band standing wave coefficient of the antenna electromagnetic simulation model of the above embodiment of this utility model is simulated, and the results are as follows: Figure 8 .from Figure 8 It can be seen that the standing wave ratio (SWR) of the antenna is 1.2943 at 23 GHz and 1.2645 at 26.45 GHz. The maximum SWR in the 23 GHz to 26.5 GHz band is 1.3196, corresponding to a frequency of 25.15 GHz. Therefore, it can be concluded that the SWR of the antenna in the K band is less than 1.35 in the 23 GHz to 26.5 GHz range.

[0065] Simulation 2: The K-band radiation pattern of the antenna electromagnetic simulation model of the above embodiment of this utility model is simulated, and the results are as follows. Figure 9 .from Figure 9 As can be seen, the antenna has a gain of 6.3709dB at an angle of -75° and a gain of 8.7782dB at an angle of 0°. The minimum gain in the -75° to 0° angle range is 3.9169dB, corresponding to an angle of -9°. Therefore, it can be concluded that the antenna gain is greater than 3.9dB in the K-band -75° to 0° angle range.

[0066] Simulation 3: The Ka-band standing wave coefficient of the antenna electromagnetic simulation model of the above embodiment of this utility model is simulated, and the results are as follows: Figure 10 .from Figure 10 It can be seen that the standing wave ratio (SWR) of the antenna is 1.2968 at a frequency of 26.8 GHz and 1.2598 at a frequency of 35 GHz. The maximum SWR in the 26.8 GHz to 35 GHz frequency band is 1.2968, corresponding to a frequency of 26.8 GHz. Therefore, it can be concluded that the Ka-band SWR of the antenna is less than 1.35 in the range of 26.8 GHz to 35 GHz.

[0067] Simulation 4: The Ka-band radiation pattern of the antenna electromagnetic simulation model of the above embodiment of this utility model is simulated, and the results are as follows: Figure 11 .from Figure 11 As can be seen, the antenna has a gain of 3.2011dB at an angle of -75° and a gain of 4.2605dB at an angle of 0°. The minimum gain in the -75° to 0° angle range is 2.8592dB, corresponding to an angle of -14°. Therefore, it can be concluded that the antenna gain in the Ka-band end-fire direction in the -75° to 0° angle range is greater than 2.8dB.

[0068] The simulation results above show that the dual-band broadband large-angle high-gain antenna based on cavity structure of this invention has a standing wave ratio of less than 1.35 with a K-band standing wave ratio greater than 14% and a Ka-band standing wave ratio greater than 26%; the gain is greater than 2.8dB in the -75° to 0° angle range, indicating that this invention has wide-bandwidth radiation performance with high gain in the large angle range near the end-fire direction.

[0069] The above description is merely a specific example of this utility model and does not constitute any limitation on this utility model. Obviously, those skilled in the art, after understanding the content and principle of this utility model, may make various modifications and changes in form and details without departing from the principle and structure of this utility model. However, these modifications and changes based on the concept of this utility model are still within the protection scope of the claims of this utility model.

Claims

1. A dual-band wideband large-angle-domain high-gain antenna based on a cavity structure, comprising a radome (1), a metal cavity (2), three sealing rings (3, 7, 8), two radiators (4, 5), and a connector (6), characterized in that: the radome (1) comprises, from top to bottom, a radome front end (11), a radome flange (12), and an air conditioning cavity (13), and the influence of unevenness of the radome size on the performance of the antenna is eliminated by changing the shape and size of the air conditioning cavity (13); the metal cavity (2) comprises, from top to bottom, a sealing groove (21), a cavity upper flange (22), an air cavity (23), and a cavity lower flange (24); the two radiators (4, 5) comprise a first radiator (4) and a second radiator (5), both of which are arranged in the air cavity (23), and the three together adjust the angular range of the antenna; the connector (6) comprises, from top to bottom, a mounting flange (61), two connector sealing grooves (62, 63), and two waveguide coaxial converters (64, 65), the mounting flange (61) is consistent with the outer contour of the cavity lower flange (24) of the metal cavity and is tightly connected; the first sealing ring (3) is installed in the sealing groove (21), the second sealing ring (7) and the third sealing ring (8) are installed in the two connector sealing grooves (62, 63) respectively, so that the upper and lower ends of the metal cavity (2) are sealed, and the internal environment is protected; the radome front end (11) is conformally designed according to the shape and opening size of the mounting platform, so as to meet the conformal installation requirements of any platform under the premise of ensuring the performance of the antenna; the radome flange (12) is consistent with the outer contour size of the cavity upper flange (22) of the metal cavity, and is tightly connected, so that the upper surface of the metal cavity and the lower surface of the radome are tightly fitted; the total thickness h of the radome (1) is given an initial value according to the best wave transmission formula of the material used by the radome at two working frequency bands under the premise of meeting the structural strength, and then the final value is determined through simulation optimization combined with the adjustment of the size and shape of the air conditioning cavity (13); the two radiators (4, 5) have the following structure: the first radiator (4) comprises, from bottom to top, a first excitation waveguide (41) and a first radiation waveguide (42), and the performance of the first working frequency band of the antenna is optimized by adjusting the bending radius r1 of the first excitation waveguide (41), and the height C1, the mouth length C2, and the mouth width C3 of the first radiation waveguide (42); the second radiator (5) comprises a second excitation waveguide (51) and a second radiation waveguide (52), and the performance of the second working frequency band of the antenna is optimized by adjusting the bending radius r2 of the second excitation waveguide (51), and the height D1, the mouth length D2, and the mouth length D3 of the second radiation waveguide (52). ​ ​ ​ ​ 2. The antenna according to claim 1, characterized in that The two radiators (4, 5) are both deformed designs on the basis of corner horn loudspeakers, the deflection angle of the first radiator (4) and the deflection angle of the second radiator (5) are both 0.3-0.7 times the maximum radiation angle in the angular domain.

3. The antenna according to claim 1, wherein, ​ 4. The antenna according to claim 1, wherein, ​ 5. The antenna according to claim 1, wherein, ​ 6. The antenna according to claim 1, wherein, The air cavity (23) contains multiple adjustable parameters, including: inner cavity width B5, inner cavity length B6, inner cavity height B8, first radiator (4) installation position distance from metal cavity edge size B3, distance B4 between the second radiator (5) and the first radiator (4); by adjusting these adjustable parameters and the deflection angles of the first radiator (4) and the second radiator (5) 、 , the angular domain range of the antenna meets the design requirements.

7. The antenna according to claim 1, wherein, ​ ​ ​ 8. The antenna according to claim 1, characterized in that: The two waveguide coaxial converters (64, 65) include a first waveguide coaxial converter (64) and a second waveguide coaxial converter (65), wherein the waveguide inner wall size of the first waveguide coaxial converter (64) is consistent with the inner wall size of the first excitation waveguide (41); the waveguide inner wall size of the second waveguide coaxial converter (65) is consistent with the inner wall size of the second excitation waveguide (51).

Images