Band-pass filter based on multilayer metal sheet waveguide

Abstract

The band-pass filter is formed by stacking multiple layers of metal sheets, a closed cavity structure is formed in the band-pass filter, and the band-pass filter comprises a first-layer metal plate, a second-layer metal plate, a third-layer metal plate, a fourth-layer metal plate, a fifth-layer metal plate and a sixth-layer metal plate which are sequentially arranged from top to bottom; all the metal plates except the last metal plate are hollowed out in different sizes to form rectangular cavities filled with air, some of the cavities serve as coupling structures for connecting different cavities, and some of the cavities serve as resonators generating resonance at a fixed frequency. The band-pass filter provided by the invention is low in loss, small in size and self-packaged.

Description

Technical Field

[0001] The invention relates to the technical field of microwave filters, and in particular to a bandpass filter based on a multi-layer metal sheet waveguide. Background Art

[0002] In modern communication systems, the increasingly tight spectrum resources have increased the demand for low-loss, high-selectivity microwave filters. Introducing a transmission zero in the stopband is considered to be a very effective way to improve selectivity. Introducing a non-resonant node can produce a transmission zero very close to the passband. There are many ways to achieve non-resonant nodes in metal foil waveguide technology, which is very meaningful for improving the rectangularity of the bandpass filter. Metal foil waveguide technology integrates multiple layers of metal plates to form a multi-layer self-encapsulated structure. Circuit design is carried out through cavities of different shapes. Electromagnetic waves propagate in the cavity. Metal has high conductivity, so the loss is small. It also acts as an electromagnetic shielding layer to prevent signal leakage. If the loss is effectively reduced in the design process of the filter, and the characteristics of self-encapsulation are also combined to reduce the complexity of filter processing and packaging, the overall performance of the filter will be greatly improved. Summary of the invention

[0003] The object of the present invention is to overcome the deficiencies and defects of the prior art and to provide a low-loss, miniaturized, self-encapsulated bandpass filter based on a multilayer metal foil waveguide.

[0004] A bandpass filter based on a multi-layer metal sheet waveguide is formed by stacking multiple layers of metal sheets and forming a closed cavity structure inside, comprising a first metal plate, a second metal plate, a third metal plate, a fourth metal plate, a fifth metal plate and a sixth metal plate arranged in sequence from top to bottom; the middle part of the first metal plate is hollowed out to form two separated first cavities for external wave port feeding; the middle part of the second metal plate is hollowed out to form two separated second cavities, the positions of the second cavities correspond to the feeding positions of the two wave ports of the first metal plate, and the second metal plate is used to control the coupling strength between the feeding port and the resonant cavity on the third metal plate; the third metal plate realizes a third cavity formed by three connected cavities, wherein the left and right cavities serve as the resonant cavity of the filter; the middle of the fourth metal plate is hollowed out to form a fourth cavity, which is used to realize the coupling between the third metal plate and the fifth metal plate, the middle of the fifth metal plate is hollowed out to form a fifth cavity as the resonant cavity of the filter, and there is no cavity formed by hollowing out on the sixth metal plate, forming a self-encapsulated structure.

[0005] Wherein, the metal sheet includes any conductive metal material.

[0006] Wherein, the size of the first cavity is determined according to wave ports of different frequency bands.

[0007] The second cavity is slightly smaller than the first cavity, and both are rectangular cavities.

[0008] The thickness of the sixth metal plate is 2 mm, and the thickness of each of the remaining metal plates is 1 mm.

[0009] Among them, multiple layers of metal plates are connected by rivets to form a self-encapsulated structure.

[0010] Therein, a plurality of through holes are punched on each metal plate and penetrate all the metal plates.

[0011] Wherein, the fourth cavity and the fifth cavity are both located at the center of the metal plate.

[0012] The area of ​​the fourth cavity is smaller than that of the fifth cavity, and both are rectangular cavities.

[0013] Among them, in the third cavity formed by the three connected cavities of the third layer of metal plate, the left and right cavities are symmetrically arranged and separated from the middle cavity by bosses that are symmetrically arranged up and down.

[0014] The present invention is based on a metal sheet waveguide structure and has a self-packaging characteristic. Multiple metal plates are stacked together, processed by high-precision laser cutting, and fixed by screws, making it easy to assemble.

[0015] The electromagnetic field of the present invention is basically distributed in the air, without dielectric loss and with small metal conductor loss, thus having the characteristic of low loss.

[0016] The present invention can effectively improve the selectivity of the filter by introducing a transmission zero point in the stop band by adopting a non-resonant node.

[0017] Compared with the coaxial resonant cavity, the metal sheet waveguide structure of the present invention is thin in thickness and small in volume, while still maintaining a relatively high Q value. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 Schematic diagram of a five-layer structure of a bandpass filter based on a metal sheet waveguide proposed in an embodiment of the present invention;

[0019] Figure 2 is a top view of the third metal plate of the bandpass filter based on the metal sheet waveguide proposed in an embodiment of the present invention;

[0020] Figure 3 It is a schematic diagram of S-parameter simulation of a bandpass filter based on a metal foil waveguide proposed in an embodiment of the present invention. DETAILED DESCRIPTION

[0021] The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0022] The bandpass filter based on the metal sheet waveguide proposed by the present invention is based on the metal sheet waveguide platform. The filter designed by utilizing a multi-layer air cavity structure has the characteristics of self-packaging, low loss and miniaturization.

[0023] The main structure of the bandpass filter based on metal sheet waveguide proposed by the present invention is as follows: Figure 1 As shown, the materials of the five metal plates from top to bottom are all copper, or any other conductive material. All metal plates except the last metal plate are hollowed out in different sizes to form air-filled rectangular cavities, some of which serve as coupling structures connecting different cavities, and some as resonators that resonate at a fixed frequency.

[0024] Specifically, the bandpass filter based on metal foil waveguide proposed in the present invention includes a first metal plate, a second metal plate, a third metal plate, a fourth metal plate, a fifth metal plate, and a sixth metal plate arranged in sequence from top to bottom; the middle part of the first metal plate is hollowed out to form two separated first cavities for external wave port feeding; the middle part of the second metal plate is hollowed out to form two separated second cavities, and the positions of the second cavities correspond to the feeding positions of the two wave ports of the first metal plate, and the second metal plate is used to control the coupling strength between the feeding port and the resonant cavity on the third metal plate; the third metal plate realizes a third cavity formed by three connected cavities, wherein the left and right cavities serve as the resonant cavities of the filter; the middle of the fourth metal plate is hollowed out to form a fourth cavity, which is used to realize the coupling between the third metal plate and the fifth metal plate, the middle of the fifth metal plate is hollowed out to form a fifth cavity, and there is no cavity formed by hollowing out on the sixth metal plate.

[0025] In order to form a closed cavity structure, multiple through holes with small diameters are punched on each metal plate and penetrate all the metal plates. The multiple layers of metal plates are connected by rivets to form a self-encapsulated structure.

[0026] In some embodiments, the sixth metal plate has a thickness of 2 mm, and the thickness of each of the remaining metal substrate layers is 1 mm.

[0027] Specifically, in the circuit design, the required operating frequency band and circuit order are determined according to actual needs, and after filter synthesis, three resonant cavities are selected to be implemented on two layers of metal plates.

[0028] by Figure 1Take the bandpass filter shown in as an example, the main circuit structure of the bandpass filter is the third metal plate and the fifth metal plate. The left and right cavities of the third metal plate are both resonant cavities that resonate within the band, and the middle cavity has a higher resonant frequency and does not resonate within or near the passband, so it can be considered as a non-resonant node near this frequency band. The cavity of the fifth metal plate is a resonant cavity that resonates within the band.

[0029] Among them, in the third cavity formed by the three connected cavities of the third metal plate, the left and right cavities are symmetrically arranged and separated from the middle cavity by symmetrically arranged upper and lower bosses. The upper and lower bosses form a coupling window for controlling the coupling strength of adjacent cavities.

[0030] In some embodiments of the present application, a plurality of (e.g., 8) large-diameter circular holes are provided on the metal plate for inserting screws to fix the flange of the waveguide port.

[0031] More preferably, each metal plate is of the same size, the centers of the third cavity, the fourth cavity and the fifth cavity are on the same straight line perpendicular to the metal plate, the first cavity and the second cavity are symmetrically arranged, and the axis of symmetry is the aforementioned straight line perpendicular to the metal plate.

[0032] The sizes of the first cavity, the second cavity, the third cavity, the fourth cavity and the fifth cavity are set according to the working frequency band of the filter and the circuit order requirements.

[0033] The S parameter simulation diagram implemented in this embodiment is as follows: Figure 3 As shown, the horizontal axis is frequency in GHz, and the vertical axis is S parameter in dB. The center frequency of this embodiment is 13.05 GHz, there are 3 transmission poles in the band, there is a transmission zero point in the upper stop band, the transmission zero point frequency is 13.23 GHz, and the return loss is less than -20 dB, achieving better filter performance.

[0034] The basic principles and main features of the present invention and the advantages of the present invention are shown and described above. It is obvious to those skilled in the art that the present invention is not limited to the details of the above exemplary embodiments, and the present invention can be implemented in other specific forms without departing from the spirit or basic features of the present invention.

[0035] Therefore, the embodiments should be considered in all respects as illustrative and non-restrictive, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is therefore intended that all changes falling within the meaning and range of equivalent elements of the claims are included in the present invention.

[0036] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A bandpass filter based on a multilayer metal foil waveguide, characterized in that: A closed cavity structure is formed by stacking multiple layers of metal sheets and forming an internal structure, including a first metal plate, a second metal plate, a third metal plate, a fourth metal plate, a fifth metal plate, and a sixth metal plate arranged in sequence from top to bottom; the middle part of the first metal plate is hollowed out to form two separated first cavities for external wave port feeding; the middle part of the second metal plate is hollowed out to form two separated second cavities, the positions of the second cavities correspond to the feeding positions of the two wave ports of the first metal plate, and the second metal plate is used to control the coupling strength between the feeding port and the resonant cavity on the third metal plate; the third metal plate realizes a third cavity formed by three connected cavities, wherein the left and right cavities serve as the resonant cavity of the filter; The fourth metal plate is hollowed out in the middle to form a fourth cavity, which is used to achieve coupling between the third metal plate and the fifth metal plate. The fifth metal plate is hollowed out in the middle to form a fifth cavity as a resonant cavity of the filter. There is no cavity formed by hollowing out on the sixth metal plate, forming a self-encapsulation structure.

2. The bandpass filter based on multilayer metal foil waveguide according to claim 1, characterized in that: The metal sheet includes any conductive metal material.

3. The bandpass filter based on multi-layer metal foil waveguide according to claim 1, characterized in that: The size of the first cavity is determined according to wave ports of different frequency bands.

4. The bandpass filter based on multilayer metal foil waveguide according to claim 1, characterized in that: The second cavity is slightly smaller than the first cavity, and both are rectangular cavities.

5. The bandpass filter based on multi-layer metal foil waveguide according to claim 1, characterized in that: The thickness of the sixth metal plate is 2 mm, and the thickness of each of the remaining metal plates is 1 mm.

6. The bandpass filter based on multi-layer metal foil waveguide according to claim 1, characterized in that: Multiple layers of metal sheets are connected by rivets to form a self-encapsulating structure.

7. The bandpass filter based on multi-layer metal foil waveguide according to claim 1, characterized in that: Multiple through holes are punched on each metal plate and penetrate all the metal plates.

8. The bandpass filter based on multi-layer metal foil waveguide according to claim 1, characterized in that: The fourth cavity and the fifth cavity are both located at the center of the metal plate.

9. The bandpass filter based on multi-layer metal foil waveguide according to claim 1, characterized in that: The area of ​​the fourth cavity is smaller than that of the fifth cavity, and both are rectangular cavities.

10. The bandpass filter based on multi-layer metal foil waveguide according to claim 1, characterized in that: In the third cavity formed by the three connected cavities of the third metal plate, the left and right cavities are symmetrically arranged and separated from the middle cavity by bosses symmetrically arranged up and down.

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