Metal sheet filter based on path separation electromagnetic coupling

Abstract

The invention discloses a metal sheet filter based on path separation electromagnetic coupling, and relates to the technical field of microwave devices. The filter comprises eleven layers of metal sheets which are arranged in a cascading manner, wherein each metal sheet is provided with hollow windows with different sizes; wherein the first layer of metal sheets and the eleventh layer of metal sheets are used for realizing connection with a waveguide according to the size of an interface cut by a window; the second layer and the tenth layer of metal sheets are used for realizing transition from the rectangular waveguide to the cavity structure according to the size of an interface cut by the window; the third layer, the fifth layer, the seventh layer and the ninth layer are of cavity structures and are used for controlling the positions of filter poles according to the size of a window cut interface; and the fourth layer, the sixth layer and the eighth layer are used for realizing coupling between adjacent cavities according to the size and the position of a window cut interface. According to the invention, the cavity filter with high integration level and low loss can be realized through the multilayer vertical metal sheet waveguide structure, and the condition of high selectivity is met.

Description

Technical Field

[0001] The invention relates to the technical field of microwave devices, and in particular to a metal foil filter based on path separation electromagnetic coupling. Background Art

[0002] At present, filters are needed in millimeter wave communication systems to achieve highly selective transmission or suppression of signals, and satellite systems also require support from highly integrated, low-loss waveguide filters.

[0003] The selectivity of the filter is its key indicator. In a complex communication environment, the filter needs to have high selectivity to ensure that only signals within a specific frequency range are transmitted, while other interference signals are effectively suppressed. Therefore, how to obtain high selectivity is a difficult problem that needs to be overcome. With the rapid development of communication technology, modern communication systems have an increasing demand for highly integrated filters. Low integration not only increases space and cost, but may also cause connection and coupling problems in the system, reducing the reliability and stability of the system. Summary of the invention

[0004] The purpose of the present invention is to provide a metal foil filter based on path separation electromagnetic coupling, which can realize a high-integration, low-loss cavity filter through a multi-layer vertical metal foil waveguide structure, meet the conditions of high selectivity, and improve the reliability and stability of the system.

[0005] To achieve the above object, the present invention provides the following solutions: A metal foil filter based on path separation electromagnetic coupling comprises: eleven layers of metal foils arranged in cascade, and each of the metal foils has a hollow window of different sizes; wherein the metal foils of the first and eleventh layers are used to achieve connection with a waveguide according to the interface size of the window cut-out; the metal foils of the second and tenth layers are used to achieve transition from a rectangular waveguide to a cavity structure according to the interface size of the window cut-out; the third, fifth, seventh and ninth layers are cavity structures, and are used to achieve control of the position of the filter pole according to the interface size of the window cut-out; and the fourth, sixth and eighth layers are used to achieve coupling between adjacent cavities according to the interface size and position of the window cut-out.

[0006] Optionally, the coupling relationship between the adjacent cavities is: , Where k is the total coupling coefficient, is the magnetic coupling coefficient, is the electrical coupling coefficient.

[0007] Optionally, the total coupling coefficient k is proportional to the electrical coupling coefficient and the magnetic coupling coefficient The gap between them decreases, thus narrowing the bandwidth.

[0008] Optionally, based on the frequency relationship, when the electrical coupling coefficient Greater than the magnetic coupling coefficient When the transmission zero frequency Greater than the center frequency , the transmission zero is located in the upper stop band; when the magnetic coupling coefficient Greater than the electrical coupling coefficient When the transmission zero frequency Less than the center frequency , the transmission zero is located in the lower stop band.

[0009] Optionally, the frequency relationship is: , in, is the transmission zero frequency, is the center frequency.

[0010] Optionally, the metal foil filter is an N-order filter with N-1 zero points.

[0011] According to the specific embodiments provided by the present invention, the present invention discloses the following technical effects: The present invention discloses a metal foil filter based on path separation electromagnetic coupling, the filter comprises eleven layers of metal foils arranged in cascade, and each metal foil has a hollow window of different sizes; wherein the metal foils of the first and eleventh layers are used to realize connection with the waveguide according to the interface size of the window cut; the metal foils of the second and tenth layers are used to realize the transition from the rectangular waveguide to the cavity structure according to the interface size of the window cut; the third, fifth, seventh and ninth layers are cavity structures, which are used to realize the position of the control filter pole according to the interface size of the window cut; the fourth, sixth and eighth layers are used to realize coupling between adjacent cavities according to the interface size and position of the window cut. The present invention can realize a cavity filter with high integration and low loss through a multi-layer vertical metal foil waveguide structure, and meet the conditions of high selectivity. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0013] Figure 1The schematic diagram of the structure of the metal foil filter based on path separation electromagnetic coupling of the present invention; wherein, part (a) is a schematic diagram of the structure from a first perspective; and part (b) is a schematic diagram of the structure from a second perspective; Figure 2 Schematic diagram of M4, M6, and M8 metal sheets, i.e., coupling windows of adjacent cavities in this embodiment; Figure 3 FIG. 4 is a schematic diagram of the fourth-order response of the filter in this embodiment. DETAILED DESCRIPTION

[0014] 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.

[0015] The purpose of the present invention is to provide a metal foil filter based on path separation electromagnetic coupling, which can realize a high-integration, low-loss cavity filter through a multi-layer vertical metal foil waveguide structure, meet the conditions of high selectivity, and improve the reliability and stability of the system.

[0016] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0017] like Figure 1 As shown, the present invention provides a metal foil filter based on path separation electromagnetic coupling, comprising: eleven layers of metal foils arranged in cascade, and each of the metal foils has a hollow window of different sizes; wherein the metal foils of the first and eleventh layers are used to achieve connection with the waveguide according to the interface size of the window cut-out; the metal foils of the second and tenth layers are used to achieve transition from a rectangular waveguide to a cavity structure according to the interface size of the window cut-out; the third, fifth, seventh and ninth layers are cavity structures, which are used to control the position of the filter pole according to the interface size of the window cut-out; the fourth, sixth and eighth layers are used to achieve coupling between adjacent cavities according to the interface size and position of the window cut-out.

[0018] Based on the above technical solution, the following embodiments are provided.

[0019] The filter can be realized by laser cutting or CNC technology, and the specific structure is composed of eleven layers of metal sheets. Among them, the first and eleventh layers cut the waveguide cross-section size to achieve connection with the waveguide, the second and tenth layers cut a specific window size in the middle position to achieve the transition from the rectangular waveguide to the cavity structure, the third, fifth, seventh and ninth layers are cavity structures, and the position of the filter pole can be controlled by changing the size of the cavity. The fourth, sixth and eighth layers are used to achieve coupling between adjacent cavities by adjusting the size and position of the coupling window.

[0020] The high selectivity based on path separation electromagnetic coupling is mainly achieved by adjusting the size and position of the coupling windows of the fourth, sixth and eighth layers. The two adjacent cavities and their coupling windows are analyzed to obtain the total coupling coefficient k and the electrical coupling coefficient and magnetic coupling coefficient The relationship is: , It is not difficult to find from the above formula that for the total coupling coefficient k, the electrical coupling coefficient and the magnetic coupling coefficient The effects of are mutually offset, and the electrical coupling coefficient and the magnetic coupling coefficient The smaller the gap, the smaller the total coupling coefficient k, which makes the bandwidth narrower.

[0021] In addition, the transmission zero frequency With center frequency , electrical coupling coefficient and the magnetic coupling coefficient The relationship is: , From the above formula, we can know that in order to make the transmission zero frequency With center frequency Close, that is, the zero point is close to the passband to obtain better suppression, the electrical coupling coefficient and the magnetic coupling coefficient The gap should be smaller. At the same time, when the electrical coupling coefficient Greater than the magnetic coupling coefficient When the transmission zero frequency Greater than the center frequency , the transmission zero is located in the upper stop band; when the magnetic coupling coefficient Greater than the electrical coupling coefficient When the transmission zero frequency Less than the center frequency , the transmission zero is located in the lower stop band.

[0022] Combining the above two relationships, we can get that the bandwidth and frequency selection ability of the filter should be a pair of contradictory indicators, so when designing and simulating, we need to control the relative size of electromagnetic coupling to balance the bandwidth and frequency selection ability of the filter. When actually designing and simulating, we can observe the distribution of the electromagnetic field of the main mode of the cavity used, so as to roughly determine the position and size of the coupling window, and then fine-tune the relevant parameters to get the response we need.

[0023] The above mainly analyzes the coupling between the two cavities. On this basis, the structure can be further cascaded to realize an N-order filter with N-1 zero points.

[0024] In this embodiment, the metal foil filter composed of multiple layers of metal foil couples adjacent cavities at different positions to achieve position control of the transmission zero point. Based on the coupling principle described above, the filter design mainly includes the following steps: (1) Select the center frequency and determine the filter operating frequency band.

[0025] (2) Determine the required filter order, zero point position, etc. based on actual needs.

[0026] (3) Determine the cavity size and operating mode through the selected center frequency, and determine the dimensions of the connected standard waveguide and the waveguide-to-cavity transition structure.

[0027] (4) Design the coupling windows of adjacent cavities, change the size, shape, and position of the windows according to actual conditions, and fine-tune related parameters to achieve the ideal response.

[0028] Taking the fourth-order filter shown in the present invention as an example, the operating frequency band of the filter is selected as the Ku band, and the center frequency is selected as 17.5GHz. The selection of the order needs to be combined with actual needs. At the same time, since the zero point position and bandwidth are a pair of contradictory technical indicators, it is necessary to balance the two according to specific needs. The present invention selects the fourth order, and requires the zero point to be as close to the passband as possible.

[0029] According to the selected frequency band and center frequency, the cavity size used is determined to be 18mm. The specific structure of the cavity is as follows: Figure 1 In addition, the standard waveguide selected is WR-51, which can be determined Figure 1 The dimensions of M1 and M11 in the figure can then be obtained through simulation calculation to obtain the transition structure from waveguide to cavity, that is, Figure 1 Available in M2 and M10 sizes.

[0030] The electromagnetic field distribution of the main mode of the cavity is obtained through eigenmode simulation. The position and size of the coupling window are roughly determined according to the required electromagnetic coupling strength. Then, the coupling window can be obtained by fine-tuning the parameters. Figure 2As shown, the ideal simulation results can be obtained as follows Figure 3 shown.

[0031] Therefore, the present invention has the following beneficial effects: (1) The position of the introduced transmission zero can be adjusted by adjusting the size and position of the coupling window to improve the selectivity of the filter. This mechanism can improve the filter stopband suppression and effectively improve the system signal-to-noise ratio.

[0032] (2) The vertical structure is adopted to reduce the footprint of the filter.

[0033] (3) The structure with multi-layer metal sheets as the main body is easy to process and assemble, which solves the problem of waveguide integrated processing and also reduces the cost.

[0034] (4) The electromagnetic field is mainly distributed in the air, and the effective dielectric constant is small, which avoids the introduction of dielectrics, thereby reducing dielectric loss and achieving a low-loss effect.

[0035] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0036] This article uses specific examples to illustrate the principles and implementation methods of the present invention. The above examples are only used to help understand the core idea of ​​the present invention. At the same time, for those skilled in the art, according to the idea of ​​the present invention, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A metal foil filter based on path separation electromagnetic coupling, characterized in that: include: Eleven layers of cascaded metal sheets, each of which has a hollow window of different sizes; wherein the metal sheets of the first and eleventh layers are used to achieve connection with the waveguide according to the size of the interface cut out of the window; the metal sheets of the second and tenth layers are used to achieve transition from a rectangular waveguide to a cavity structure according to the size of the interface cut out of the window; the third, fifth, seventh and ninth layers are cavity structures, which are used to control the position of the filter pole according to the size of the interface cut out of the window; the fourth, sixth and eighth layers are used to achieve coupling between adjacent cavities according to the size and position of the interface cut out of the window.

2. The metal foil filter based on path separation electromagnetic coupling according to claim 1, characterized in that: The coupling relationship between the adjacent cavities is: ， Where k is the total coupling coefficient, is the magnetic coupling coefficient, is the electrical coupling coefficient.

3. The metal foil filter based on path separation electromagnetic coupling according to claim 2, characterized in that: The total coupling coefficient k increases with the electrical coupling coefficient and the magnetic coupling coefficient The gap between them decreases, thus narrowing the bandwidth.

4. The metal foil filter based on path separation electromagnetic coupling according to claim 3, characterized in that: Based on the frequency relationship, when the electrical coupling coefficient Greater than the magnetic coupling coefficient When the transmission zero frequency Greater than the center frequency , the transmission zero is located in the upper stop band; when the magnetic coupling coefficient Greater than the electrical coupling coefficient When the transmission zero frequency Less than the center frequency , the transmission zero is located in the lower stop band.

5. The metal foil filter based on path separation electromagnetic coupling according to claim 4, characterized in that: The frequency relationship is: ， in, is the transmission zero frequency, is the center frequency.

6. The metal foil filter based on path separation electromagnetic coupling according to claim 1, characterized in that: The metal foil filter is an N-order filter with N-1 zero points.

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