Bandpass filter based on multilayer metallic flake waveguide

Abstract

The application discloses a band-pass filter based on a multilayer metal sheet waveguide, which is stacked by multilayer metal sheets and internally forms a closed cavity structure, and comprises first, second, third, fourth, fifth and sixth layers of metal sheets arranged in sequence from top to bottom; all the metal sheets except the last layer of metal sheet are hollowed out in different sizes to form air-filled rectangular cavities, some of which serve as coupling structures for connecting different cavities, and some of which serve as resonators resonating at a fixed frequency. The band-pass filter is low-loss, miniaturized and self-packaged.

Description

Technical Field

[0001] This invention relates to the field of microwave filter technology, and in particular to a bandpass filter based on a multilayer metal thin-film waveguide. Background Technology

[0002] In modern communication systems, the increasingly scarce spectrum resources drive the growing demand for low-loss, high-selectivity microwave filters. Introducing transmission zeros in the stopband is considered a highly effective way to improve selectivity. Introducing a non-resonant node can generate a transmission zero very close to the passband. Non-resonant nodes can be implemented in various ways using thin-film metal waveguide technology, which is significant for improving the rectangularity of bandpass filters. Thin-film metal waveguide technology integrates multiple metal plates, forming a multi-layered self-encapsulated structure. Circuit design utilizes cavities of different shapes, allowing electromagnetic waves to propagate within the cavities. The high conductivity of the metal results in low loss and also acts as an electromagnetic shielding layer to prevent signal leakage. If losses are effectively reduced during filter design, while also incorporating self-encapsulation characteristics and minimizing the complexity of filter fabrication and packaging, the overall performance of the filter will be significantly improved. Summary of the Invention

[0003] The purpose of this invention is to overcome the shortcomings and defects of the prior art and provide a low-loss, miniaturized, self-encapsulated bandpass filter based on a multilayer metal thin-film waveguide.

[0004] A bandpass filter based on a multilayer metal sheet waveguide is constructed by stacking multiple layers of metal sheets to form a closed cavity structure. The structure includes, from top to bottom, 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. The first metal plate has two spaced-apart cavities hollowed out in the middle for external waveport feeding. The second metal plate also has two spaced-apart cavities hollowed out in the middle, their positions corresponding to the two waveport feeding positions on the first metal plate. The second metal plate controls the coupling strength between the feeding ports and the resonant cavities on the third metal plate. The third metal plate forms a third cavity with three interconnected cavities, the left and right cavities serving as the filter's resonant cavities. The fourth metal plate has a hollowed-out middle cavity for coupling between the third and fifth metal plates, and the fifth metal plate has a hollowed-out middle cavity serving as the filter's resonant cavity. The sixth metal plate has no hollowed-out cavities, forming a self-encapsulated structure.

[0005] The metal sheet may be any conductive metal material.

[0006] The size of the first cavity is determined according to the different frequency bands of the port.

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

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

[0009] The multi-layered metal plates are connected by rivets to form a self-encapsulating structure.

[0010] Multiple through holes are drilled in each metal plate, penetrating all the metal plates.

[0011] The fourth and fifth cavities 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] In the third cavity formed by the three interconnected cavities of the third metal plate, the left and right cavities are symmetrically arranged and separated from the middle cavity by symmetrically arranged bosses.

[0014] This invention is based on a metal thin-film waveguide structure, which has self-encapsulation characteristics. Multiple metal plates are stacked together, processed by high-precision laser cutting, and fixed with screws, making it easy to assemble.

[0015] The electromagnetic field of this invention is basically distributed in the air, with no dielectric loss and low loss in the metal conductor, thus exhibiting low-loss characteristics.

[0016] This invention introduces transmission zeros within the stopband by employing non-resonant nodes, which can effectively improve the selectivity of the filter.

[0017] Compared to coaxial resonant cavities, the metal sheet waveguide structure of this invention is thinner and smaller in size, while still maintaining a relatively high Q value. Attached Figure Description

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

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

[0020] Figure 3 This is a schematic diagram of the S-parameter simulation of the bandpass filter based on a thin metal waveguide proposed in an embodiment of the present invention. Detailed Implementation

[0021] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0022] The bandpass filter proposed in this invention is based on a thin metal waveguide platform. The filter designed using a multi-layer air cavity structure has the characteristics of self-encapsulation, low loss, and miniaturization.

[0023] The main structure of the bandpass filter based on a thin metal waveguide proposed in this invention is as follows: Figure 1 As shown, the five metal plates from top to bottom are all made of copper, or any other conductive material. Hollows of different sizes are cut out from all the metal plates except the last one to form air-filled rectangular cavities. Some of these cavities serve as coupling structures connecting different cavities, while others act as resonators that resonate at a fixed frequency.

[0024] Specifically, the bandpass filter based on a thin metal waveguide proposed in this invention includes, from top to bottom, 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. The middle portion of the first metal plate is hollowed out to form two spaced-apart first cavities for external waveport feeding. The middle portion of the second metal plate is hollowed out to form two spaced-apart second cavities, the positions of which correspond to the two waveport feeding positions of the first metal plate. The second metal plate is used to control the coupling strength between the feeding ports and the resonant cavities on the third metal plate. The third metal plate forms a third cavity formed by three interconnected cavities, with the left and right cavities serving as the filter's resonant cavities. The middle portion of the fourth metal plate is hollowed out to form a fourth cavity for coupling between the third and fifth metal plates. The middle portion of the fifth metal plate is hollowed out to form a fifth cavity. The sixth metal plate has no hollowed-out cavities.

[0025] To form a closed cavity structure, multiple small-diameter through holes are drilled in each metal plate, penetrating all the metal plates. The multiple metal plates are connected by rivets to form a self-encapsulating structure.

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

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

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

[0029] In the third cavity formed by the three interconnected 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 coupling windows to control the coupling strength between adjacent cavities.

[0030] In some embodiments of this application, multiple (e.g., eight) large-diameter circular holes on the metal plate are used to insert screws to secure the flange of the waveguide port.

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

[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 operating frequency band and circuit order requirements of the filter.

[0033] The S-parameter simulation graph achieved in this embodiment is as follows: Figure 3 As shown, the horizontal axis represents frequency in GHz, and the vertical axis represents S-parameters in dB. This embodiment has a center frequency of 13.05 GHz, three transmission poles in the in-band, one transmission zero in the upper stopband at 13.23 GHz, and a return loss of less than -20 dB, achieving good filter performance.

[0034] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. It will be apparent to those skilled in the art that the present invention is not limited to the details of the above exemplary embodiments, and that 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 regarded as exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of the equivalents of the claims be included within the invention.

[0036] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A bandpass filter based on a multilayer metal thin-film waveguide, characterized in that, The structure is composed of multiple layers of stacked metal sheets forming a closed cavity. It includes, from top to bottom, 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. The middle portion of the first metal plate is hollowed out to form two spaced-apart cavities for external waveport feeding. The middle portion of the second metal plate is also hollowed out to form two spaced-apart cavities. The positions of these cavities correspond to the two waveport feeding positions of the first metal plate, and the second metal plate controls the coupling strength between the feeding ports and the resonant cavities on the third metal plate. The third metal plate forms a third cavity composed of three interconnected cavities, with the left and right cavities serving as the resonant cavities of the filter. The fourth metal plate has a cavity formed by hollowing out the middle, which is used to couple the third and fifth metal plates. The fifth metal plate has a cavity formed by hollowing out the middle, which serves as the resonant cavity for the filter. The sixth metal plate has no cavity formed by hollowing out the middle, forming a self-encapsulating structure.

2. The bandpass filter based on a multilayer metal thin-film waveguide according to claim 1, characterized in that, The metal sheet may be any conductive metal material.

3. The bandpass filter based on a multilayer metal thin-film waveguide according to claim 1, characterized in that, The size of the first cavity is determined according to the different frequency band wave ports.

4. The bandpass filter based on a multilayer metal thin-film 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 a multilayer metal thin-film waveguide according to claim 1, characterized in that, The sixth metal plate has a thickness of 2mm, and the thickness of each of the remaining metal plates is 1mm.

6. The bandpass filter based on a multilayer metal thin-film waveguide according to claim 1, characterized in that, Multi-layered metal plates are connected by rivets to form a self-encapsulating structure.

7. The bandpass filter based on a multilayer metal thin-film waveguide according to claim 1, characterized in that, Multiple through holes are drilled in each metal plate, penetrating all the metal plates.

8. The bandpass filter based on a multilayer metal thin-film waveguide according to claim 1, characterized in that, Both the fourth and fifth cavities are located at the center of the metal plate.

9. The bandpass filter based on a multilayer metal thin-film 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 a multilayer metal thin-film waveguide according to claim 1, characterized in that, In the third cavity formed by the three interconnected cavities of the third metal plate, the two cavities on the left and right are symmetrically arranged and separated from the middle cavity by symmetrically arranged bosses.

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