A metal plate coupled coaxial resonant cavity and electromagnetic hybrid coupled bandpass filter

Abstract

A metal plate coupled coaxial resonant cavity, comprising a metal resonant cavity, a cover plate, and two metal resonant plates; the metal resonant cavity is in the shape of a column, and the cover plate is located on the top of the metal cavity, so that the metal cavity becomes a closed space; a pair of metal resonant plates are arranged inside the metal resonant cavity, and a gap is left between the upper ends of the pair of metal resonant plates and the metal resonant cavity to form an open circuit end; the lower ends of the pair of metal resonant plates are directly connected to the metal resonant cavity to form a short circuit end; the size of the filter cavity depends on the specific frequency requirements. The present invention is applied to electromagnetic hybrid coupled bandpass filters. The open circuit, short circuit structure and the gap between the above-mentioned metal resonant plates together constitute a 1 / 4 wavelength metal plate coupling mode, which can provide an independent electric and magnetic hybrid coupling path.

Description

Technical Field

[0001] The invention belongs to the technical field of wireless communication, and in particular relates to a metal plate coupled coaxial resonant cavity and an electromagnetic hybrid coupled bandpass filter. Background Art

[0002] Coaxial cavity filters have the characteristics of good stability, moderate Q value (passband insertion loss / power capacity), good heat dissipation, etc., and are widely used in communication base stations and radar systems. Frequency selection performance is an important indicator of coaxial cavity filters. The frequency selection performance of the filter can be effectively improved by introducing a transmission zero. Traditionally, coaxial cavity filters introduce transmission zeros by a cross-coupling topology method, which has the disadvantages of large filter size and high design difficulty. The recently developed electromagnetic hybrid coupling cavity filter can introduce a transmission zero in a linear topology by constructing an electric and magnetic hybrid coupling dual path between adjacent resonant cavities. Moreover, the position of the transmission zero can be controlled by adjusting the relative size of the electric and magnetic coupling components in the hybrid coupling.

[0003] In the existing electromagnetic hybrid coupled coaxial cavity filter, the construction of electric and magnetic hybrid coupled dual paths requires the introduction of additional circuit structures, which increases the complexity of filter design and in-band loss.

[0004] CN2023113151028 is a prior application of the present application, which is a miniaturized high-Q coaxial resonant cavity, comprising: a metal cavity, a cover plate, and a metal resonant rod; the metal cavity is a three-dimensional geometric shape of a cylinder or a cuboid, and the cover plate is located at the top of the metal cavity, so that the metal cavity becomes a closed space to reduce radiation loss; a metal resonant rod is arranged inside the metal cavity, the upper end of the metal resonant rod is a circular plane, the lower end is a circular plane, and the side surface is a gradually concave structure; the central axis of the metal resonant rod coincides with the central axis of the metal shell; a gap is left between the upper end of the metal resonant rod and the metal cavity to form an open circuit; the lower end of the metal resonant rod is directly connected to the metal cavity to form a short circuit; the size of the filter cavity depends on the specific frequency and Q value requirements. Summary of the invention

[0005] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a metal plate coupled coaxial resonant cavity with independently constructed electric and magnetic hybrid coupling dual paths, which can be suitable for the design of electromagnetic hybrid coupling filters and realize the generation of transmission zero points (when the numerator of the filter transmission function is zero) without introducing additional structures.

[0006] To achieve the above-mentioned purpose, the present invention adopts the following technical scheme: a metal plate coupled coaxial resonant cavity, comprising: a metal cavity, a cover plate, a first metal resonant plate, and a pair of second metal resonant plates; the metal cavity is in a three-dimensional (cylindrical, rectangular, etc.) shape, and the cover plate is located at the top of the metal cavity, so that the metal cavity becomes a closed space to reduce radiation loss; a first and a second metal resonant plate are arranged inside the metal cavity, both of which are composed of irregular square metal blocks and curved hexahedrons, and a gap is left between the two metal resonant plates; a gap is left between the upper ends of the two metal resonant plates and the metal cavity, which is regarded as an open circuit, and the lower ends are directly connected to the metal cavity, which is regarded as a short circuit; the open circuit, short circuit structure and the gap between the above-mentioned metal resonant plates together constitute a 1 / 4 wavelength metal plate coupling mode (wavelength = light speed / resonance frequency), which can provide an independent electric and magnetic hybrid coupling path, and is suitable for the design of electromagnetic hybrid coupled coaxial cavity filter.

[0007] The size of the metal cavity depends on the specific frequency requirements. Normally, the metal cavity shell, the two metal resonant plates in the cavity, the gap between the metal resonant plates, and the gap between the metal resonant plates and the top of the metal cavity comprehensively determine the frequency of the metal plate coupling mode. When the size of the external metal shell is constant, the gap between the two metal resonant plates has a greater influence on the plate coupling resonant frequency. The smaller the gap, the lower the resonant frequency. However, considering the processing accuracy, the gap width should be at least greater than 0.2mm in any case; when the size of the external metal shell is constant, the gap between the upper end of a pair of metal resonant plates and the metal cavity should be greater than 3mm to facilitate the tuning process after processing. Regarding specific dimensions, if for the following embodiments or for a specific frequency, we can give each specific dimension, please refer to the following embodiments. If it covers the entire microwave band, the size range is very large.

[0008] The two metal resonant plates are composed of an upper part and a lower part; the irregular square metal plate is the upper part of the metal resonant plate, which is formed by chamfering the inner corners of a rectangular metal block, and the curved plate is the lower part of the metal resonant plate, which is provided with a gradual curved surface (the longitudinal section is a concave arc curve function), and the arc-shaped gradual curved surface is formed by lateral pressing, stretching, etc.;

[0009] The gradual curved surface is formed by lateral stretching of a concave curve function;

[0010] The concave curve function is represented by f(x), which is any function that satisfies the following formula, where x1 and x2 are any two values ​​in the domain:

[0011]

[0012] The concave curve function includes parabolic function, hyperbolic function, hemispherical function, elliptical curve, oval, involute, catenary; or concave curve synthesized from several concave curve functions; any concave function, whether it is a single one or a combination of several, meets the definition of the formula. Or the concave curve can be an arc that cannot be expressed analytically (discrete multi-point fitting), or it can be a concave arc drawn or programmed. The concave arc curves of a pair of resonant plates, that is, the arc-shaped gradient surface and the chamfered inner fillet of the rectangular metal block are back to back and outward, and the back arc of the concave arc curve is convex, and a pair of convex places form the smallest gap size. If it is for a certain embodiment, the domain of x can be [0, h1], h1 is the length of the lower end of the metal resonance rod, and the coordinate origin is at the bottom point of the lower end of the metal resonance rod.

[0013] The gap between the two metal resonant plates is composed of the upper gap between the irregular square metal blocks and the lower gap between the curved hexahedrons;

[0014] Furthermore, the width of the upper gap in the upper part of the two metal resonant plates must be smaller than the width of the lower gap (the R of the arc-shaped gradual surface is smaller) to ensure that the first and second metal resonant plates form capacitive coupling at the upper gap and inductive coupling at the lower gap; the central axes of the two metal resonant plates coincide with the central axis of the metal cavity.

[0015] The metal plate coupled coaxial resonant cavity has independent electric and magnetic hybrid coupling dual-path characteristics.

[0016] The capacitive coupling and the inductive coupling together constitute a plate coupling resonance mode;

[0017] The plate coupling resonance mode can directly form an electric and magnetic hybrid coupling dual path when the metal plate coupling coaxial resonant cavity is cascaded, thereby achieving the generation of a transmission zero point;

[0018] Furthermore, a coaxial cavity electromagnetic hybrid coupling bandpass filter is provided, comprising a filter cavity cover, a filter cavity, an SMA connector (joint), and four pairs of metal resonant plates are arranged in the filter cavity (each pair is similar to the above-mentioned pair of metal resonant plates coupled to the coaxial resonant cavity), namely a first pair of metal resonant plates, a second pair of metal resonant plates, a third pair of metal resonant plates, and a fourth pair of metal resonant plates; the above-mentioned upper and lower gaps are left between each pair of metal resonant plates; the filter cavity is a three-dimensional (rectangular) geometric figure, and the filter cavity cover is located at the top of the filter cavity to form a closed cavity; the first pair of metal resonant plates, the second pair of metal resonant plates, the third pair of metal resonant plates, and the fourth pair of metal resonant plates are all connected to the filter cavity to form a short circuit, and have gaps with the filter cover to form an open circuit; the coaxial cavity electromagnetic hybrid coupling bandpass filter uses two SMA connectors for energy input and output.

[0019] Furthermore, the coaxial cavity electromagnetic hybrid coupling bandpass filter is formed by directly cascading four metal plate coupled coaxial resonant cavities; by simply adjusting the distance between adjacent resonant cavities, the bandwidth and transmission zero point can be controlled simultaneously.

[0020] Furthermore, the coaxial cavity bandpass filter is an axisymmetric structure, so the four metal plate coupled coaxial resonant cavities have the same symmetric size;

[0021] Furthermore, the SMA connector is placed on both sides of the input and output of the coaxial cavity bandpass filter, and the coaxial cavity bandpass filter is connected to an external circuit and matched with the external circuit through the SMA connector and a 50Ω characteristic impedance transmission line.

[0022] Beneficial effects:

[0023] (1) The metal plate coupled coaxial resonant cavity provided by the present invention can independently provide dual paths of electric and magnetic coupling, and is very suitable for the design of electromagnetic hybrid coupling filters.

[0024] (2) The electromagnetic hybrid coupling bandpass filter provided by the present invention can realize the control of the transmission zero point by simply adjusting the distance between adjacent resonant cavities. Compared with the prior art, there is no need to introduce additional structures to construct the electric and magnetic coupling paths, which reduces the complexity of the structure and design while retaining the high quality factor of the filter.

[0025] (3) The present invention can be combined with the existing cross-coupling technology to create a coaxial cavity filter with smaller size and better performance.

[0026] (4) The metal plate coupled coaxial resonant cavity provided by the present invention can be applied to the design of a duplexer and can flexibly generate transmission zero points, so that the duplexer has a simple structure but can obtain good isolation performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a schematic diagram of the metal plate coupled coaxial resonant cavity structure provided by the present invention.

[0028] Figure 2 Schematic diagram of the structure of the fourth-order electromagnetic hybrid coupled coaxial cavity filter in Example 2 of the present invention.

[0029] Figure 3 Schematic diagram of the top view of the structure of the fourth-order electromagnetic hybrid coupled coaxial cavity filter in Example 2 of the present invention.

[0030] Figure 4 This is a simulation waveform curve diagram of the fourth-order electromagnetic hybrid coupled coaxial cavity filter in Example 2 of the present invention.

[0031] Figure 5This is a simulation waveform curve diagram of the fourth-order electromagnetic hybrid coupled coaxial cavity filter in Example 2 of the present invention. DETAILED DESCRIPTION

[0032] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0033] Example 1

[0034] like Figure 1 As shown, the metal plate coupled coaxial resonant cavity of the embodiment of the present invention comprises: a metal cavity 2, a cavity cover 1, a first metal resonant plate composed of an irregular rectangular metal block 3 and a curved hexahedron 4; a second metal resonant plate composed of an irregular rectangular metal block 5 and a curved hexahedron 6; the metal cavity 2 is a rectangular parallelepiped geometric shape, and the cover 1 is located on the top of the metal cavity 2, so that the metal cavity becomes a closed space to reduce radiation loss; a first and a second pair of metal resonant plates are arranged inside the metal cavity 2, and two gaps of different widths are left between the pair of metal resonant plates, and an upper gap 7 is between the irregular square metal block 3 and the irregular square metal block 5; a lower gap 8 is between the curved hexahedron 4 and the curved hexahedron 6; the irregular square metal block 3 and the irregular square metal block 5 are 5 is formed by chamfering the inner rounded corners of a rectangular metal block; the curved hexahedron 4 and the curved hexahedron 6 are formed by lateral stretching of a gradual curved surface; the width of the gap 7 on the two metal resonant plates must be smaller than the width of the lower gap 8 to ensure that the first and second metal resonant plates form capacitive coupling in the upper gap 7 and inductive coupling in the lower gap 8; the central axis of the two metal resonant plates coincides with the central axis of the metal cavity 2; a gap is left between the upper ends of the two metal resonant plates and the metal cavity 2, and the gap height is h-h1mm, forming an open circuit; the lower ends of the first metal resonant rod and the second metal resonant rod are directly connected to the metal cavity 2 to form a short circuit; the open circuit and short circuit structure together with the upper gap 7 and the lower gap 8 constitute a plate coupling resonance mode with independent electric and magnetic hybrid coupling capabilities. The open circuit and short circuit structure together with the gap between the above metal resonant plates constitute a 1 / 4 wavelength metal plate coupling mode, which is suitable for electromagnetic hybrid coupling coaxial cavity filters.

[0035] like Figure 1 As shown, the gradual change surface of the curved hexahedron 4 and the curved hexahedron 6 is formed by the concave curve function f(x)=px 2+b, x∈[0, h1] is formed by transverse stretching, where p is a concave coefficient greater than 0, b is half the length of the gap 7 on the metal resonant plate, and h1 is the height of the curved hexahedron 4 and the curved hexahedron 6. The change of the concave coefficient p can control the resonant frequency of the metal plate coupled coaxial resonant cavity.

[0036] Example 2

[0037] like Figure 2 , Figure 3 As shown, on the basis of the above-mentioned embodiment 1, the embodiment of the present invention provides an electromagnetic hybrid coupling bandpass filter without introducing additional structures, including: a filter cavity cover plate 9, a filter cavity 10, and an SMA connector 11; the filter cavity 10 contains four pairs of metal resonant plates, which are respectively composed of a curved hexahedron 12, a curved hexahedron 13, a curved hexahedron 14, a curved hexahedron 15, an irregular rectangular metal block 16, an irregular rectangular metal block 17, an irregular rectangular metal block 18, and an irregular rectangular metal block 19; the curved hexahedron 12, the curved hexahedron 13, the curved hexahedron 14, the curved hexahedron 15 and the filter cavity 10 are directly connected to form a short circuit; there is a gap between the irregular rectangular metal block 16, the irregular rectangular metal block 17, the irregular rectangular metal block 18, the irregular rectangular metal block 19 and the filter cavity cover plate 9. A gap with a length of h-h1 forms an open circuit; an upper gap 20 is left between the irregular rectangular metal block 16 and the irregular rectangular metal block 17; an upper gap 21 is left between the irregular rectangular metal block 18 and the irregular rectangular metal block 19; there is a plate capacitive coupling between the upper gap 20 and the upper gap 21, and its width can greatly affect the cavity resonance frequency; a lower gap 22 is left between the curved hexahedron 12 and the curved hexahedron 13; a lower gap 23 is left between the curved hexahedron 14 and the curved hexahedron 15; there is an inductive coupling around the plate between the lower gap 22 and the lower gap 23, and its width can greatly affect the cavity resonance frequency; the above-mentioned open circuit and short circuit structure and the upper gap 20, the upper gap 21, the lower gap 22, and the lower gap 23 together constitute a fourth-order electromagnetic hybrid coupling bandpass filter; the width of the upper gap must be smaller than the width of the lower gap to ensure the formation of the electric and magnetic hybrid coupling dual paths.

[0038] While keeping the resonant frequency unchanged, the transmission zero point can be adjusted to move from left to right by increasing the upper gap 20 and the upper gap 21; the transmission zero point can be adjusted to move from right to left by increasing the lower gap 22 and the lower gap 23. There are spacings 24 and 25 between the adjacent metal plate coupling pairs. By increasing the spacings 24 and 25, the filter coupling bandwidth can be increased and the transmission zero point can be adjusted to move from left to right at the same time.

[0039] The SMA connector 11 is placed on both sides of the input and output of the electromagnetic hybrid coupling coaxial cavity filter, and the filter is connected to the external circuit and matched with the external circuit through the SMA connector and the 50Ω characteristic impedance transmission line. Like the SMA connector, the present invention can be applied to the microwave field with a frequency range up to 26.5GHz. The specific cavity size can be determined by the specific filter index.

[0040] Figure 4 , Figure 5 The simulation results of the fourth-order electromagnetic hybrid coupling bandpass filter S are shown in Figure 2. From the simulation results, it can be seen that without introducing any additional structure, the transmission zero point is one more than the traditional fourth-order cross-coupled bandpass filter and the existing electromagnetic hybrid coupling filter, and the transmission zero point position can be flexibly adjusted.

[0041] The above description is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Any modifications, equivalent substitutions and improvements made by any technician familiar with the technical field within the technical scope disclosed by the present invention and within the spirit and principle of the present invention should be covered by the protection scope of the present invention.

Claims

1. A metal plate coupled coaxial resonant cavity, characterized in that: It includes a metal resonant cavity, a cover plate, and two metal resonant plates; the metal resonant cavity is in the shape of a column, and the cover plate is located on the top of the metal cavity, so that the metal cavity becomes a closed space; a pair of metal resonant plates are arranged inside the metal resonant cavity, and a gap is left between the upper ends of the pair of metal resonant plates and the metal resonant cavity to form an open circuit end; the lower ends of the pair of metal resonant plates are directly connected to the metal resonant cavity to form a short circuit end; the size of the filter cavity depends on the specific frequency requirements; the pair of metal resonant plates are composed of an upper part and a lower part; the irregular square metal plate is the upper part of the metal resonant plate, which is formed by the chamfered inner fillet of a rectangular metal block, and a curved hexahedron is provided as the lower part of the metal resonant plate, and a gradual curved surface is provided, and an arc-shaped gradual curved surface is formed by lateral pressing or stretching; the gradual curved surface is formed by lateral stretching of a concave curve function; The concave curve function is represented by f(x), which is any function that satisfies the following formula, where x1 and x2 are any two values ​​in the domain: The concave curve function is a parabola function, a hyperbola function, a hemispherical function, an elliptical curve, an oval line, an involute, a catenary, a concave curve synthesized by several concave curve functions, or a concave curve is a discrete multi-point fitting arc; the concave arc curves of a pair of resonant plates, i.e., the arc-shaped gradual curved surface and the chamfered inner fillet of the rectangular metal block are back to back and outward, the back arc of the concave curve is convex, and a pair of convex places form a minimum gap size; The gap between the pair of metal resonant plates is composed of an upper gap between the irregular square metal plates and a lower gap between the curved hexahedrons; The width of the upper gap of the upper part of a pair of metal resonant plates should be smaller than the width of the lower gap, so as to ensure that the pair of metal resonant plates form capacitive coupling at the upper gap and inductive coupling at the lower gap.

2. The metal plate coupled coaxial resonant cavity according to claim 1, characterized in that: The central axis of the pair of metal resonant plates coincides with the central axis of the metal cavity; and an independent electric and magnetic hybrid coupling dual path is provided.

3. The fourth-order electromagnetic hybrid coupled coaxial cavity filter prepared by the metal plate coupled coaxial resonant cavity according to claim 1 or 2, characterized in that: The invention comprises a filter cavity cover plate, a filter cavity, an SMA connector and four pairs of metal resonant plates arranged in the filter cavity, wherein the four pairs of metal resonant plates are a first pair of metal resonant plates, a second pair of metal resonant plates, a third pair of metal resonant plates and a fourth pair of metal resonant plates; the upper and lower gaps are left between each pair of metal resonant plates; the filter cavity is a rectangular parallelepiped geometric figure, and the filter cavity cover plate is located at the top of the filter cavity to form a closed cavity; the first pair of metal resonant plates, the second pair of metal resonant plates, the third pair of metal resonant plates and the fourth pair of metal resonant plates are all connected to the filter cavity to form a short circuit, and gaps are left with the filter cover plate to form an open circuit; the coaxial cavity electromagnetic hybrid coupling bandpass filter adopts two SMA connectors for energy input and output; the fourth-order electromagnetic hybrid coupling coaxial cavity filter is formed by directly cascading four metal plates coupled to coaxial resonant cavities.

4. The fourth-order electromagnetic hybrid coupled coaxial cavity filter according to claim 3, characterized in that: The fourth-order electromagnetic hybrid coupled coaxial cavity filter is an axisymmetric structure, so the four metal plate coupled coaxial resonant cavities are symmetrical and have the same size.

5. The fourth-order electromagnetic hybrid coupled coaxial cavity filter according to claim 3 or 4, characterized in that: The SMA connectors are placed on both sides of the input and output of the coaxial cavity bandpass filter, and the coaxial cavity bandpass filter is connected to and matched with an external circuit through the SMA connector and a 50Ω characteristic impedance transmission line.

6. The fourth-order electromagnetic hybrid coupled coaxial cavity filter according to claim 3 or 4, characterized in that: By adjusting the distance between adjacent resonant cavities, the bandwidth and transmission zero point can be controlled simultaneously.

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