A High-Power Filter for Circular Waveguide Based on the Mechanism of Deep Periodic Perturbation at the Boundary

Abstract

The present invention discloses a high-power circular waveguide filter based on a deep periodic perturbation mechanism of the boundary. The first, second, third, and fourth-order resonators are constructed by using a circular waveguide six-petal deformed structure resonator. Six cylinders uniformly distributed in the circular waveguide six-petal deformed structure resonator introduce deep periodic perturbation to the circular waveguide boundary. By greatly perturbing the metal boundary condition of the circular waveguide, the spacing between the waveguide eigenmode spectra is widened, thereby realizing the high isolation characteristic between the waveguide resonance modes. In addition, the window opening, i.e., the coupling position, between the waveguide input port and the first-order resonator is at the center position of a single cylinder on the boundary of the first-order resonator. The center of the bottom surface of the second-order resonator is window-coupled with the center of the top surface of the first-order resonator. The coupling positions of the second-order resonator and the third-order resonator are at the center position between two cylinders on the boundary at the rear of the second-order resonator and at the center position between a single cylinder and another single cylinder on the boundary of the third-order resonator. The center of the bottom surface of the third-order resonator is window-coupled with the center of the top surface of the fourth-order resonator, so that the field strength in the coupling structure region of the filter is reduced, and the power capacity of the filter is further increased.

Description

Technical Field

[0001] The present invention belongs to the technical field of filters. More specifically, it relates to a high-power circular waveguide filter based on the mechanism of deep periodic perturbation at the boundary. Background Art

[0002] Currently, with the continuous development of wireless communication technologies, more and more devices need to transmit high-power signals. For example, devices such as radars and satellite communications need to transmit high-power signals to achieve long-distance communication. In addition, the development of high-power microwave (HPM) synthesis technologies has also put forward the requirement for filters with a high-power capacity in the order of hundreds of MW. In the design of traditional high-power filters, it is often necessary to balance frequency selectivity and power capacity, so a trade-off is required. For HPM synthesis technologies, power capacity is a crucial factor because it requires the microwave link to operate stably during high-power transmission and requires wide stopband characteristics to effectively achieve incoherent power synthesis of multiple HPM sources.

[0003] In high-power filter applications, the main choices for traditional microwave transmission lines are microstrip lines and waveguides, etc. Microstrip filters have become the main choice in many communication devices due to their miniaturization advantages. However, due to the small volume and loss problems of microstrip transmission lines, the power capacity of microstrip filters is limited. For high-power applications, waveguide filters with larger volumes are more suitable because they have higher power capacities. However, there are some problems in the structural design of currently known waveguide filters. For example, there are many screw adjustment structures in waveguide resonant units and tuning units. A large number of tuning and coupling adjustment structures greatly increase the complexity of filter design, processing, and debugging. In the high-frequency band, especially above the X-band, with the sharp decrease in the volume of waveguide transmission lines, it is difficult for the high-frequency structure design of traditional filters to meet the application requirements in the MW order.

[0004] The TE011 mode of a circular waveguide is suitable for high-power device applications. However, classic filters operating in the TE011 mode of a circular waveguide have low mode isolation due to degenerate modes, resulting in a narrow stopband for the device, making it difficult to meet the stopband bandwidth requirements for multi-channel synthesis. Moreover, there are high electric field concentration regions in the coupling units, and the power capacity is greatly limited. Summary of the Invention

[0005] In view of the technical principle defects of insufficient power capacity and insufficient stopband width in existing high-power circular waveguide filters, the present invention provides a high-power circular waveguide filter based on the mechanism of deep periodic perturbation at the boundary, which can effectively separate the resonant mode TE011 from its degenerate mode TM111 to a high degree, improve the mode isolation from other adjacent interfering oscillation modes, enable it to have wide stopband characteristics, and at the same time have a high power capacity.

[0006] To achieve the above-mentioned invention object, the high-power filter of circular waveguide based on the boundary deep periodic perturbation mechanism of the present invention is characterized in that it includes a waveguide input port, first, second, third, and fourth-order resonant cavities, and a waveguide output port;

[0007] The first, second, third, and fourth-order resonant cavities are all circular waveguide six-petal deformed structure resonant cavities. The circular waveguide six-petal deformed structure resonant cavity is a cavity formed by six identical arc-shaped columnar pieces evenly distributed around the central circle and sealed up and down, so that six cylinders are evenly distributed inside the cavity;

[0008] The waveguide input port is coupled with the first-order resonant cavity through a rectangular coupling window, and the coupling position is at the center position of a single cylinder at the boundary of the first-order resonant cavity;

[0009] The second-order resonant cavity is located directly above the first-order resonant cavity, i.e., the centers coincide, and are staggered by 30°. The first-order resonant cavity is coupled with the second-order resonant cavity through a cross coupling window, and the coupling position is at the center positions of the top surface of the first-order resonant cavity and the bottom surface of the second-order resonant cavity;

[0010] The third-order resonant cavity is located at the same horizontal position behind the second-order resonant cavity. The second-order resonant cavity is coupled with the third-order resonant cavity through a rectangular coupling window, and the coupling positions are at the center position between two cylinders at the boundary of the rear position of the second-order resonant cavity and at the center position between a single cylinder and a single cylinder at the boundary of the third-order resonant cavity;

[0011] The fourth-order resonant cavity is located directly below the third-order resonant cavity, i.e., the centers coincide, and are staggered by 30°. The third-order resonant cavity is coupled with the fourth-order resonant cavity through a cross coupling window, and the coupling position is at the center positions of the bottom surface of the third-order resonant cavity and the top surface of the fourth-order resonant cavity;

[0012] The waveguide output port is coupled with the fourth-order resonant cavity through a rectangular coupling window, and the coupling position is at the center position of a single cylinder at the boundary of the rear position of the fourth-order resonant cavity.

[0013] The object of the present invention is achieved in this way.

[0014] The high-power filter for circular waveguide based on the mechanism of deep periodic perturbation of the boundary of the present invention uses a circular waveguide six-petal deformed structure resonator to construct the first, second, third, and fourth-order resonators. The six cylinders evenly distributed in the circular waveguide six-petal deformed structure resonator introduce deep periodic perturbation to the circular waveguide boundary. By greatly perturbing the metal boundary condition of the circular waveguide, the spacing between the waveguide eigenmode spectra is broadened, thereby realizing the high isolation characteristic between waveguide resonance modes. In addition, the input port of the waveguide and the window opening of the first-order resonator, that is, the coupling position, is at the center position of a single cylinder on the boundary of the first-order resonator. The center of the bottom surface of the second-order resonator is window-coupled with the center of the top surface of the first-order resonator. The coupling positions of the second-order resonator and the third-order resonator are at the center position between two cylinders on the boundary behind the second-order resonator and at the center position between a single cylinder on the boundary of the third-order resonator. The center of the bottom surface of the third-order resonator is window-coupled with the center of the top surface of the fourth-order resonator, which reduces the field strength in the coupling structure area of the filter and further increases the power capacity of the filter.

[0015] In addition, the input coupling window is a rectangular coupling window opened at the position of a single cylinder on the boundary of the resonator, exciting the TE011 mode in the first-order resonator. The coupling window between the first-order resonator and the second-order resonator adopts a cross-coupling window structure and is respectively opened at the center positions of the top surface and the bottom surface to suppress the coupling propagation of the main TE resonance interference modes. The coupling window between the second-order resonator and the third-order resonator adopts a rectangular coupling window structure and is opened at the center position between two cylinders on the boundaries of the two resonators to suppress the coupling propagation of the main TM resonance interference modes. The coupling window between the third-order resonator and the fourth-order resonator is symmetric with the coupling window between the first-order resonator and the second-order resonator, and the output coupling window and the input coupling window are also symmetric structures.

[0016] Compared with the prior art, the present invention has the following advantages:

[0017] 1. The proposed circular waveguide six-petal deformed structure resonator is a circular waveguide resonator with a deep periodic deformed boundary, having a higher isolation degree of the TE011 mode;

[0018] 2. The present invention simultaneously has a higher power capacity and a wider stopband width;

[0019] 3. The structure of the present invention is simple, and the design and processing are convenient;

[0020] 4. Tests prove that compared with the "X-band high-power circular waveguide cavity filter" disclosed in the Chinese invention patent application with the patent publication number CN109687069 in the prior art, the power capacity of which exceeds 2000W, the power capacity of the present invention exceeds 0.45GW, and the power capacity is increased by more than five orders of magnitude. Description of the Drawings

[0021] Figure 1It is a schematic structural diagram of a specific embodiment of the circular waveguide high-power filter based on the boundary deep periodic perturbation mechanism of the present invention;

[0022] Figure 2 is Figure 1 a schematic cross-sectional view of the shown resonant cavity;

[0023] Figure 3 is Figure 1 a schematic structural diagram of the coupling between the waveguide input port and the first-order resonant cavity through a rectangular coupling window as shown;

[0024] Figure 4 is Figure 1 a schematic structural diagram of the cross coupling window between the first-order resonant cavity and the second-order resonant cavity as shown;

[0025] Figure 5 is Figure 1 a schematic structural diagram of the coupling between the second-order resonant cavity and the third-order resonant cavity through a rectangular coupling window as shown;

[0026] Figure 6 is Figure 1 a diagram of the calculation results of the S parameters of the circular waveguide high-power filter as shown;

[0027] Figure 7 is Figure 1 a schematic diagram of the cross-sectional electric field distribution of the circular waveguide high-power filter as shown. Specific Embodiment

[0028] The following describes the specific embodiments of the present invention in conjunction with the accompanying drawings so that those skilled in the art can better understand the present invention. It should be particularly noted that in the following description, when the detailed description of known functions and designs may dilute the main content of the present invention, these descriptions will be omitted here.

[0029] Figure 1 It is a schematic structural diagram of a specific embodiment of the circular waveguide high-power filter based on the boundary deep periodic perturbation mechanism of the present invention.

[0030] In this embodiment, as Figure 1 shown, the circular waveguide high-power filter based on the boundary deep periodic perturbation mechanism of the present invention includes a waveguide input port 1, first, second, third, and fourth-order resonant cavities 2, 3, 4, 5, and a waveguide output port 6.

[0031] In an embodiment, the high-power circular waveguide filter of the present invention based on the boundary deep periodic perturbation mechanism can operate in the X band, with a passband center frequency of 9.25 GHz, a bandwidth of 200 MHz, and an in-band return loss greater than 28 dB. The waveguide input port 1 uses a rectangular waveguide (with a wide-side length a = 28.5 mm and a narrow-side length b = 15 mm) of the standard rectangular waveguide BJ84 with an increased narrow side, and the material is aluminum. The heights of the first-order resonator 2 and the third-order resonator 4 are the same, both being h1 = 23.87 mm. The height of the second-order resonator 3 is the same as that of the fourth-order resonator 5, both being h2 = 23.8 mm.

[0032] The first, second, third, and fourth-order resonators 2, 3, 4, and 5 are all circular waveguide six-petal deformed structure resonators. As Figure 2 shown, the circular waveguide six-petal deformed structure resonator is a cavity formed by six identical arc-shaped cylinder sheets evenly distributed around a central circle and sealed up and down, so that six cylinders are evenly distributed on the inner side of the cavity. The resonator uses six evenly distributed cylinders to introduce perturbations to the circular waveguide boundary, and by greatly perturbing the metal boundary conditions of the circular waveguide, the spacing between the waveguide eigenmode spectra is broadened, and the resonant mode TE011 and its degenerate mode TM111 are effectively separated by a large margin, thereby realizing the high isolation characteristic between waveguide resonant modes.

[0033] In the embodiment, through the selection of dimensions, the TE011 mode of the resonator has the maximum mode isolation degree, with a central large circle radius R = 16 mm, a small circle radius r = 9.87 mm, and a spacing d = 18.37 mm between the centers of the large circle and the small circle.

[0034] As Figure 3 shown, the waveguide input port 1 and the first-order resonator 2 are coupled through a rectangular coupling window 7, and the coupling position is at the center position of a single cylinder on the boundary of the first-order resonator. This structure can excite the TE011 resonant mode in the first-order resonator 2. According to the calculation of the input group delay: the length l1 of the rectangular coupling window 7 is 9.51 mm, the narrow-side length b1 is 10.5 mm, and the wide-side length is the same as the height of the first-order resonator 2, both being h1 = 23.87 mm.

[0035] As Figure 1 shown, the second-order resonator 3 is located directly above the first-order resonator 2, that is, the centers coincide, and they are staggered by 30°. The first-order resonator 2 and the second-order resonator 3 are coupled through a cross-coupling window 8, and the coupling position is at the center positions of the top surface of the first-order resonator 2 and the bottom surface of the second-order resonator 3, so as to suppress the coupling propagation of the main TE resonant interference modes.

[0036] Figure 4 Is Figure 1 a schematic structural diagram of the cross-coupling window between the first-order resonator and the second-order resonator shown.

[0037] As Figure 4 shown, the cross-coupling window 8 is located at the center of the top surface of the first-order resonator 2 and the bottom surface of the second-order resonator 3. In this embodiment, the cross-coupling window 8 is aligned with the transmission direction and the direction perpendicular to the transmission direction. According to the design specifications of the filter, the coupling coefficient between the first-order resonator and the second-order resonator is calculated to be 0.0244, and the input group delay is 2.13 ns. According to the coupling coefficient between the first-order resonator 2 and the second-order resonator 3: the length of the wide side a1 of the cross-coupling window 8 is 27.9 mm, the length of the narrow side b3 is 7 mm, and the height l3 is 2.5 mm.

[0038] Figure 5 is Figure 1 a schematic structural diagram of the coupling between the second-order resonator and the third-order resonator through a rectangular coupling window as shown.

[0039] The third-order resonator 4 is located at the same horizontal position behind the second-order resonator 3. The second-order resonator 3 and the third-order resonator 4 are coupled through a rectangular coupling window 9 to suppress the coupling propagation of the main TM resonance interference mode. The coupling position is the center position between two cylinders at the rear position boundary of the second-order resonator 3 and the center position between a single cylinder at the boundary of the third-order resonator 4. The coupling coefficient between the second-order resonator 3 and the third-order resonator 4 is 0.0178, and the input group delay is 2.13 ns.

[0040] According to the coupling coefficient between the second-order resonator 3 and the third-order resonator 4: the length of the narrow side b2 of the rectangular coupling window 9 is 10.7 mm, the length of the wide side is the same as the height of the second-order resonator, both are h2 = 23.8 mm, and the center distance l2 between the second-order resonator 3 and the third-order resonator 4 is 57.5 mm. In order to reduce the magnitude of the electric field strength at the rectangular coupling window 9 and avoid the concentration of the electric field strength to improve the power capacity of the filter, the connection where the electric field of the rectangular coupling window 9 is concentrated is chamfered, and the chamfer radius rr at the connection of the rectangular coupling window 9 is 1.5 mm.

[0041] The high-power filter of circular waveguide based on the mechanism of deep periodic perturbation of the boundary of the present invention adopts a symmetric structure and is axisymmetric about the plane where the center of the rectangular coupling window 9 between the second-order resonator 3 and the third-order resonator 4 is located.

[0042] The fourth-order resonator 5 is located directly below the third-order resonator 4, that is, the centers coincide and are staggered by 30°. The third-order resonator 4 and the fourth-order resonator 5 are coupled through a cross-coupling window 10. The coupling position is the center position of the bottom surface of the third-order resonator 4 and the top surface of the fourth-order resonator 5. The cross-coupling window 10 is aligned with the transmission direction and the direction perpendicular to the transmission direction.

[0043] The waveguide output port 6 is coupled to the fourth-order resonator 5 through a rectangular coupling window 11, and the coupling position is at the center position of a single cylinder at the rear position boundary of the fourth-order resonator 5.

[0044] Figure 6 Yes Figure 1 It is a graph showing the calculation results of the S parameters of the circular waveguide high-power filter shown. From Figure 6 it can be seen that the center frequency of the filter is 9.25 GHz, the bandwidth is 200 MHz, the return loss in the passband is greater than 28 dB, and the out-of-band rejection is greater than 20 dB in the frequency ranges of 8.5 - 9.0 GHz and 9.5 - 10.0 GHz. Therefore, the filter has a relatively wide stopband width.

[0045] Figure 7 Yes Figure 1 It is a schematic diagram of the cross-sectional electric field distribution of the circular waveguide high-power filter shown. Figure 7 The maximum field strength in it is 0.999 MV / cm (input 0.45 GW). Taking the typical microwave breakdown threshold of 1 MV / cm in the HPM system for calculation, the power capacity of the filter can reach more than 0.45 GW. Therefore, the filter has a high power capacity.

[0046] Although the above describes the illustrative specific embodiments of the present invention for the convenience of those skilled in the art to understand the present invention, it should be clear that the present invention is not limited to the scope of the specific embodiments. For those of ordinary skill in the art, as long as various changes are within the spirit and scope of the present invention defined and determined by the appended claims, these changes are obvious, and all inventions created using the concept of the present invention are within the scope of protection.

Claims

1. A high-power filter for circular waveguide based on the boundary deep periodic perturbation mechanism, characterized in that It includes a waveguide input port, first, second, third, and fourth-order resonant cavities, and a waveguide output port; The first, second, third, and fourth-order resonant cavities are all circular waveguide six-petal deformed structure resonant cavities. The circular waveguide six-petal deformed structure resonant cavity is a cavity formed by six identical arc-shaped columnar sheets evenly distributed around the central circle and sealed up and down, so that six cylinders are evenly distributed on the inner side of the cavity; The waveguide input port is coupled to the first-order resonant cavity through a rectangular coupling window, and the coupling position is at the center position of a single cylinder at the boundary of the first-order resonant cavity; The second-order resonant cavity is located directly above the first-order resonant cavity, i.e., the centers coincide, and they are staggered by 30°. The first-order resonant cavity and the second-order resonant cavity are coupled through a cross-coupling window, and the coupling position is at the center positions of the top surface of the first-order resonant cavity and the bottom surface of the second-order resonant cavity; The third-order resonant cavity is located at the same horizontal position behind the second-order resonant cavity. The second-order resonant cavity and the third-order resonant cavity are coupled through a rectangular coupling window, and the coupling positions are at the center position between two cylinders at the rear position boundary of the second-order resonant cavity and at the center position between two single cylinders at the boundary of the third-order resonant cavity; The fourth-order resonant cavity is located directly below the third-order resonant cavity, i.e., the centers coincide, and they are staggered by 30°. The third-order resonant cavity and the fourth-order resonant cavity are coupled through a cross-coupling window, and the coupling position is at the center positions of the bottom surface of the third-order resonant cavity and the top surface of the fourth-order resonant cavity; The waveguide output port is coupled to the fourth-order resonant cavity through a rectangular coupling window, and the coupling position is at the center position of a single cylinder at the rear position boundary of the fourth-order resonant cavity.

2. The high-power filter for circular waveguide based on the boundary deep periodic perturbation mechanism according to claim 1, wherein The cross-coupling windows between the first-order resonant cavity and the second-order resonant cavity, and between the third-order resonant cavity and the fourth-order resonant cavity are all aligned with the transmission direction and the direction perpendicular to the transmission direction.

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