Structure-reused dual-band cavity filter

Abstract

This invention provides a dual-band cavity filter with a multiplexed structure, belonging to the field of filter technology. It includes: a filter body; a first waveguide interface at each end of the filter body; a first waveguide resonant cavity coupled to each of the two first waveguide interfaces; and multiple sequentially coupled second waveguide resonant cavities coupled between the two first waveguide resonant cavities; both the first and second waveguide resonant cavities are connected to a second waveguide interface. This invention combines filters from two frequency bands through resonant cavity multiplexing, achieving both dual-band filtering and filter miniaturization. By utilizing a gap waveguide structure to divide the microwave frequency band into rectangular waveguide resonant cavities, it achieves a high frequency ratio for the dual-band filter while also possessing the advantage of controllable frequency ratio. The gap waveguide resonant cavity and the rectangular waveguide resonant cavity are structurally complementary, making the dual-band filter structurally compatible with both millimeter-wave and microwave frequency bands.

Description

Technical Field

[0001] This invention relates to the field of filter technology, and specifically to a dual-band cavity filter with a multiplexed structure. Background Technology

[0002] Filters provide channel selection, noise attenuation, and frequency division multiplexing functions for wireless communication systems, making them indispensable components in the radio frequency (RF) front-end. Metal cavity filters, in particular, are widely used in microwave, millimeter-wave, and terahertz communication bands due to their advantages such as high Q-value, low loss, and high power capacity. However, as operating frequencies increase to millimeter-wave and higher bands, the requirements for manufacturing precision and tight electrical contact between structural components in existing metal cavity filters become increasingly stringent. Gap waveguides, as a novel electromagnetic wave transmission and shielding structure, effectively compensate for the performance deficiencies caused by air gaps between the metal components of cavity filters due to their non-electrical contact characteristics. Therefore, cavity filters based on gap waveguide technology have broad application prospects in millimeter-wave communication systems.

[0003] On the other hand, with the rapid development of wireless communication technology, modern wireless communication devices often need to have dual-band or even multi-band operating characteristics. The frequency selection function of filters makes them play a crucial role in the dual-band operation of wireless communication systems. However, common methods for implementing dual-band filters have many drawbacks. For example, paralleling different single-band filters leads to excessive size; inserting transmission zeros within the passband is limited to low-frequency ratio applications; and using multimode resonators results in complex designs. Furthermore, the millimeter-wave communication frequency bands currently under extensive research differ significantly from the commercially available 5G frequency bands. The size and precision requirements of devices used in these two frequency bands differ, and if dual-band filters operate under these conditions, their structural characteristics must be compatible with both frequency bands.

[0004] Due to the superior performance of cavity filters using gapped waveguide technology, such as non-tight electrical contact characteristics, low insertion loss, and high Q value, their application research in the microwave and millimeter-wave bands is increasing. However, most of the gapped waveguide filters reported so far are single-frequency filters, and some studies have proposed dual-frequency filters using gapped waveguide structures, which have drawbacks such as small frequency ratio, incompatibility between microwave and millimeter-wave bands, and complex filter design processes. Summary of the Invention

[0005] The purpose of this invention is to provide a dual-band cavity filter that achieves dual-band operation while having a large frequency ratio and structural multiplexing capability compatible with both microwave and millimeter-wave frequency bands, thereby solving at least one of the technical problems existing in the background art.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A dual-band cavity filter with a reusable structure includes a filter body and a cover plate covering the filter body, characterized in that:

[0008] The filter body is provided with a first waveguide interface at each of its two ends;

[0009] Each of the two first waveguide interfaces is coupled to a first waveguide resonant cavity; multiple second waveguide resonant cavities are coupled sequentially between the two first waveguide resonant cavities.

[0010] Both the first waveguide resonant cavity and the second waveguide resonant cavity are connected to a second waveguide interface.

[0011] Preferably, the first waveguide interface couples the first waveguide resonant cavity through a first coupling window, and the first waveguide resonant cavity and the second waveguide resonant cavity, as well as the plurality of sequentially coupled second waveguide resonant cavities, are all coupled through a second coupling window.

[0012] Preferably, multiple gap waveguide structures are provided in the first waveguide resonant cavity, the second waveguide resonant cavity, and the second coupling window.

[0013] Preferably, the first waveguide resonant cavity is divided into multiple first gap waveguide resonant cavities by multiple gap waveguide structures within the first waveguide resonant cavity; the multiple first gap waveguide resonant cavities are sequentially coupled and connected to each other through a first coupling structure.

[0014] Preferably, in the plurality of sequentially coupled first gap waveguide resonant cavities, the first gap waveguide resonant cavities at both ends are connected to a second waveguide interface through a third coupling window.

[0015] Preferably, the second waveguide resonant cavity is divided into multiple second gap waveguide resonant cavities by multiple gap waveguide structures within the second waveguide resonant cavity; the multiple second gap waveguide resonant cavities are sequentially coupled and connected to each other through a second coupling structure.

[0016] Preferably, in the plurality of sequentially coupled second gap waveguide resonant cavities, the second gap waveguide resonant cavities at both ends are connected to a second waveguide interface through a fourth coupling window.

[0017] Preferably, the filter body has a groove, and the groove has a second stepped structure; the groove and the cover plate together form the second waveguide interface.

[0018] Preferably, a rectangular notch is provided at both ends of the cover plate and at both ends of the filter body, and a first stepped structure is provided in the rectangular notch; the two rectangular notches at the same end of the cover plate and the filter body together form the first waveguide interface.

[0019] Preferably, a rectangular notch is provided at both ends of the filter body to serve as the first waveguide interface.

[0020] The beneficial effects of this invention are as follows: By multiplexing resonant cavities, filters of two frequency bands are combined together, achieving both dual-frequency filtering and miniaturization; by using a gap waveguide structure to divide the microwave frequency band into rectangular waveguide resonant cavities, a high frequency ratio of the dual-frequency filter is achieved, while also having the advantage of controllable frequency ratio; the gap waveguide resonant cavity and the rectangular waveguide resonant cavity are structurally complementary, making the structure of the dual-frequency filter compatible with both millimeter-wave and microwave frequency bands.

[0021] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and will become apparent from the description or may be learned by practice of the invention. Attached Figure Description

[0022] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 This is a three-dimensional structural diagram of the dual-band cavity filter with multiplexed structure described in an embodiment of the present invention.

[0024] Figure 2 This is an internal structural diagram of the dual-band cavity filter with multiplexed structure described in an embodiment of the present invention.

[0025] Figure 3 This is a diagram of the cover plate structure of the dual-band cavity filter with multiplexed structure according to an embodiment of the present invention.

[0026] Figure 4 This is a structural diagram of the dual-band cavity filter with multiplexed structure according to an embodiment of the present invention.

[0027] Figure 5 This is a top view of the filter body of the dual-band cavity filter with multiplexed structure according to an embodiment of the present invention.

[0028] Figure 6 This is a topology diagram of a dual-band cavity filter with multiplexed structure as described in an embodiment of the present invention.

[0029] Figure 7 This is a schematic diagram of the simulation curve of the filtering characteristics of the microwave band rectangular waveguide filter described in an embodiment of the present invention.

[0030] Figure 8 This is a schematic diagram of the simulated filter characteristic curves of the millimeter-wave band gapped waveguide filter according to an embodiment of the present invention. Figure 8 (a) is a transmission curve of a third-order gapped waveguide filter. Figure 8 (b) is the transmission curve of a fourth-order gap waveguide filter.

[0031] Figure 9 This is a schematic diagram of the isolation curves between the input / output ports of the third-order gap waveguide filter and the input / output ports of the rectangular waveguide filter according to an embodiment of the present invention.

[0032] Figure 10 This is a schematic diagram of the isolation curve between the third-order gap waveguide filter and the fourth-order gap waveguide filter according to an embodiment of the present invention.

[0033] Figure 11 Frequency ratio variation curves for different forms of the second waveguide resonant cavity provided in embodiments of the present invention. Figure 11 (a) to (d) represent different ways of dividing the first or second waveguide resonant cavity using gap waveguide structures (dividing it into 4, 6, 8, and 9 gap waveguide resonators, respectively). Figure 11 (e) is a schematic diagram of the frequency ratio curve.

[0034] Wherein: 1-Filter body; 2-First waveguide interface; 3-First waveguide resonant cavity; 4-Second waveguide resonant cavity; 5-Second waveguide interface; 6-First coupling window; 7-Second coupling window; 8-Gap waveguide structure; 9-First gap waveguide resonant cavity; 10-First coupling structure; 11-Third coupling window; 12-Second gap waveguide resonant cavity; 13-Second coupling structure; 14-Fourth coupling window; 15-Cover plate; 17-Rectangular notch; 18-First stepped structure; 19-Groove; 20-Second stepped structure. Detailed Implementation

[0035] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0036] It will be understood by those skilled in the art that, unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0037] It should also be understood that terms such as those defined in general dictionaries should be understood to have meanings consistent with their meanings in the context of the prior art, and should not be interpreted in an idealized or overly formal sense unless defined as here.

[0038] Those skilled in the art will understand that, unless specifically stated otherwise, the singular forms “a,” “an,” “the,” and “the” used herein may also include the plural forms. It should be further understood that the term “comprising” as used in this specification means the presence of the stated features, integers, steps, operations, elements, and / or components, but does not exclude the presence or addition of one or more other features, integers, steps, operations, elements, and / or groups thereof.

[0039] In the description of this specification, references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of those different embodiments or examples.

[0040] In the description of this specification, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0041] In the description of this specification, the terms “center,” “upper,” “lower,” “front,” “rear,” “left,” “right,” “vertical,” “horizontal,” “top,” “bottom,” “inner,” and “outer,” etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this technology and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this technology.

[0042] Unless otherwise expressly specified and limited, the terms "installation," "connection," "linking," and "setting" should be interpreted broadly. For example, they can refer to a fixed connection or setting, a detachable connection or setting, or an integral connection or setting. Those skilled in the art can understand the specific meaning of these terms in this art according to the specific circumstances.

[0043] To facilitate understanding of the present invention, the present invention will be further explained and described below with reference to the accompanying drawings and specific embodiments. However, the specific embodiments do not constitute a limitation on the embodiments of the present invention.

[0044] Those skilled in the art should understand that the accompanying drawings are merely schematic diagrams of embodiments, and the components in the drawings are not necessarily essential for implementing the present invention.

[0045] Example 1

[0046] like Figure 1 , Figure 2 As shown in Embodiment 1, a dual-band cavity filter with a reusable structure is provided. The structure includes: a filter body 1, with a cover plate 15 covering the top of the filter body 1; a first waveguide interface 2 at each end of the filter body 1; a first waveguide resonant cavity 3 coupled to each of the two first waveguide resonant cavities 2; a plurality of second waveguide resonant cavities 4 coupled sequentially between the two first waveguide resonant cavities 3; and a second waveguide interface 5 connected to both the first waveguide resonant cavity 3 and the second waveguide resonant cavity 4.

[0047] The first waveguide interface 2 is coupled to the first waveguide resonant cavity 3 through a first coupling window 6. The first waveguide resonant cavity 3 and the second waveguide resonant cavity 4, as well as the plurality of sequentially coupled second waveguide resonant cavities 4, are coupled through a second coupling window 7. A plurality of gap waveguide structures 8 are provided within the first waveguide resonant cavity 3, the second waveguide resonant cavity 4, and the second coupling window 7.

[0048] Multiple gap waveguide structures 8 within the first waveguide resonant cavity 3 divide the first waveguide resonant cavity 3 into multiple first gap waveguide resonant cavities 9; the multiple first gap waveguide resonant cavities 9 are sequentially coupled and connected through a first coupling structure 10. Among the multiple sequentially coupled first gap waveguide resonant cavities 9, the first gap waveguide resonant cavities 9 at both ends are connected to a second waveguide interface 5 through a third coupling window 11.

[0049] Multiple gap waveguide structures 8 within the second waveguide resonant cavity 4 divide the second waveguide resonant cavity 4 into multiple second gap waveguide resonant cavities 12; the multiple second gap waveguide resonant cavities 12 are sequentially coupled and connected through a second coupling structure 13. Among the multiple sequentially coupled second gap waveguide resonant cavities 12, the first and last second gap waveguide resonant cavities 12 are all connected to a second waveguide interface 5 through a fourth coupling window 14.

[0050] In this embodiment 1, both the first waveguide resonant cavity 3 and the second waveguide resonant cavity 4 are rectangular. A gap waveguide structure 8 is set in the rectangular waveguide resonant cavity (i.e., the first waveguide resonant cavity 3 and the second waveguide resonant cavity 4) to realize the reuse of the cavity. That is, the gap waveguide structure is used to divide the rectangular waveguide resonant cavity to form a gap waveguide resonant cavity (i.e., the first gap waveguide resonant cavity 9 and the second gap waveguide resonant cavity 12). The rectangular waveguide resonant cavity (i.e., the first waveguide resonant cavity 3 and the second waveguide resonant cavity 4) and its coupling structure (i.e., the first coupling window 6 and the second coupling window 7) form a microwave frequency band filter. The gap waveguide resonant cavity (i.e., the first gap waveguide resonant cavity 9 and the second gap waveguide resonant cavity 12) and its coupling structure (i.e., the first coupling structure 10, the second coupling structure 13, the third coupling window 11, and the fourth coupling window 14) form a millimeter wave frequency band filter.

[0051] Example 2

[0052] like Figures 1 to 5 As shown in Embodiment 2, a dual-band cavity filter with a multiplexed structure is provided. Its structure includes: a filter body 1, with a cover plate 15 covering the top of the filter body 1. Each end of the filter body 1 is provided with a first waveguide interface 2; each of the two first waveguide interfaces 2 is coupled to a first waveguide resonant cavity 3; a second waveguide resonant cavity 4 is coupled between the two first waveguide resonant cavities 3; both the first waveguide resonant cavity 3 and the second waveguide resonant cavity 4 are connected to a second waveguide interface 5.

[0053] In this embodiment, both ends of the cover plate 15 and both ends of the filter body 1 are provided with a rectangular notch 17, and a first stepped structure 18 is provided within the rectangular notch 17; the two rectangular notches 17 on the same end of the cover plate 15 and the filter body 1 together form the first waveguide interface 2. The filter body 1 is provided with a groove 19, and a second stepped structure 20 is provided within the groove 19; the groove 19 and the cover plate 15 together form the second waveguide interface 5. In this embodiment, the rectangular notches 17 may also be provided only at both ends of the filter body 1 as the first waveguide interface 2.

[0054] The first waveguide interface 2 is coupled to the first waveguide resonant cavity 3 through a first coupling window 6, and the first waveguide resonant cavity 3 and the second waveguide resonant cavity 4 are coupled through a second coupling window 7. Multiple gap waveguide structures 8 are provided within the first waveguide resonant cavity 3, the second waveguide resonant cavity 4, and the second coupling window 7.

[0055] Multiple gap waveguide structures 8 within the first waveguide resonant cavity 3 divide the first waveguide resonant cavity 3 into multiple first gap waveguide resonant cavities 9; the multiple first gap waveguide resonant cavities 9 are sequentially coupled and connected through a first coupling structure 10. Among the multiple sequentially coupled first gap waveguide resonant cavities 9, the first gap waveguide resonant cavities 9 at both ends are connected to a second waveguide interface 5 through a third coupling window 11.

[0056] Multiple gap waveguide structures 8 within the second waveguide resonant cavity 4 divide the second waveguide resonant cavity 4 into multiple second gap waveguide resonant cavities 12; the multiple second gap waveguide resonant cavities 12 are sequentially coupled and connected through a second coupling structure 13. Among the multiple sequentially coupled second gap waveguide resonant cavities 12, the first and last second gap waveguide resonant cavities 12 are all connected to a second waveguide interface 5 through a fourth coupling window 14.

[0057] like Figure 5 As shown, in this embodiment 2, there are three waveguide resonators: two first waveguide resonators 3 and one second waveguide resonator 4 in the middle. The first waveguide resonator 3 contains three first gap waveguide resonators 9. The uppermost first gap waveguide resonator 9 is connected to a second waveguide interface 5 through a third coupling window 11. The upper and lower ends of the middle first gap waveguide resonator 9 are coupled to the upper and lower first gap waveguide resonators 9 respectively through a first coupling structure. The second waveguide resonator 4 contains four second gap waveguide resonators 12, which are sequentially connected through a second coupling structure 13.

[0058] In this embodiment 2, the entire structure of the dual-band cavity filter with multiplexed structure is made of metal material. For example, the cover plate 15, the filter body 1, the gap waveguide structure 8, the first coupling structure 10 and the second coupling structure 13 are all made of metal material.

[0059] In this embodiment 2, by controlling the structural parameters of the gapped waveguide and the division of the rectangular waveguide resonant cavity, a controllable frequency ratio can be achieved, thus providing a simple implementation method for high-frequency ratio filters. Simultaneously, after loading the gapped waveguide structure into the rectangular waveguide resonant cavity, the size of the original rectangular waveguide resonant cavity is significantly reduced due to the capacitance shortening effect, achieving miniaturization of the dual-frequency filter. On the other hand, a gapped waveguide filter is used as the implementation method for the dual-frequency filter in the millimeter-wave band, while a rectangular waveguide filter is used in the microwave band. The two are structurally complementary and compatible with the characteristics of both frequency bands. By multiplexing the resonant cavities, the filters of the two frequency bands are combined, achieving both dual-frequency filtering and filter miniaturization. Utilizing the gapped waveguide structure to divide the rectangular waveguide resonant cavity in the microwave band achieves a high frequency ratio for the dual-frequency filter while also possessing the advantage of a controllable frequency ratio. The complementary structure of the gapped waveguide resonant cavity and the rectangular waveguide resonant cavity allows the dual-frequency filter structure to be compatible with both millimeter-wave and microwave frequency bands. Since a single rectangular waveguide resonator already includes the topology of the entire gap waveguide filter, it can also be applied to multi-band filters by changing the topology of the gap waveguide filter within each rectangular waveguide resonator.

[0060] Example 3

[0061] like Figures 1 to 10 As shown in Embodiment 3, a dual-band cavity filter with a reusable structure is provided. The entire filter structure is manufactured using all-metal machining, including an upper metal cover plate (i.e., cover plate 15) and a lower metal filter body (i.e., filter body 1). The upper metal cover plate has a cuboid structure, and a first stepped transition structure (rectangular notch 17 and the first stepped structure 18 inside it) is symmetrically arranged at the left and right ends of the upper metal cover plate about the X-axis. The X-axis direction is parallel to the narrow side of the upper metal cover plate. The length and width of the lower metal filter body are the same as those of the upper metal cover plate. Three rectangular slots are symmetrically distributed on the upper surface of the lower metal filter body about the X-axis. The rectangular slots and the upper metal cover plate form a rectangular waveguide resonant cavity (i.e., the first waveguide resonant cavity 3 at both ends and the second waveguide resonant cavity 4 located between the two first waveguide resonant cavities 3). The rectangular waveguide resonant cavities are connected by a first rectangular window coupling structure (i.e., the second coupling window 7). The rectangular waveguide resonant cavities at the left and right ends are connected to the first stepped transition structures at both ends of the lower metal filter body through a second rectangular window coupling structure (i.e., the first coupling window 6). The rectangular waveguide resonant cavities at the left and right ends are connected to the second stepped transition structures in the X-axis direction through a third rectangular window coupling structure (i.e., the third coupling window 11). The rectangular slot in the middle is only connected to the two second stepped transition structures (groove 19 and the second stepped structure 20 inside it) through a second rectangular window coupling structure in the positive X-axis direction.

[0062] The first rectangular window coupling structure is formed by a cuboid metal groove in the lower metal filter body, a gap waveguide structure loaded within the groove, and an upper metal cover plate; the second and third rectangular window coupling structures are formed by the cuboid metal groove in the lower metal filter body and the upper metal cover plate. The rectangular waveguide resonant cavity, the first rectangular window coupling structure, and the second rectangular window coupling structure together constitute a rectangular waveguide filter; the middle rectangular waveguide resonant cavity is connected to the left and right rectangular waveguide resonant cavities through the first rectangular window coupling structure.

[0063] A gap waveguide structure 8 is loaded along both the X and Y axes within the rectangular waveguide resonant cavity, dividing the rectangular waveguide resonant cavity into multiple gap waveguide resonant cavities. The gap waveguide filter consists of gap waveguide resonant cavities, metal ridge coupling structures (i.e., the first coupling structure 10 and the second coupling structure 13), and a third rectangular window coupling structure. The input and output gap waveguide resonant cavities (i.e., the gap waveguide resonant cavities connected to the second interface) are connected to the third rectangular window coupling structure, and the gap waveguide resonant cavities are connected to each other via the metal ridge coupling structure.

[0064] In this embodiment 3, the first stepped transition structure of the lower metal filter body and the first stepped transition structure of the upper metal cover plate together form a transition conversion structure between the rectangular waveguide filter and the WR-159 waveguide interface (i.e., the first waveguide interface 2). The second stepped transition structure is connected to the direct chamfered waveguide transmission line structure and together with the upper metal cover plate forms a transition conversion structure between the gap waveguide filter and the WR-28 waveguide interface (i.e., the second waveguide interface 5). The gap waveguide structure is composed of metal pillars of equal length and width and an upper metal plate, wherein there are at least two rows of metal pillars and an air gap exists between the metal pillars and the upper metal plate.

[0065] like Figure 1 As shown, the dual-band cavity filter based on a gap waveguide structure provided in this embodiment includes an upper metal cover plate (i.e., cover plate 15) and a lower metal filter body (i.e., filter body 1); as Figure 3 As shown, a first-step transition structure is symmetrically arranged at both ends of the upper metal cover plate about the X-axis. Figure 4 As shown, a first-step transition structure is also set at both ends of the lower metal filter body about the X-axis. The first-step transition structure of the upper metal cover plate and the first-step transition structure of the lower metal filter body together form the transition conversion structure between the rectangular waveguide filter and the WR-159 waveguide interface. The second-step transition structure is connected to the direct chamfered waveguide transmission line structure and together with the upper metal cover plate, forms the transition conversion structure between the gap waveguide filter and the WR-28 waveguide interface.

[0066] like Figure 5As shown, the rectangular waveguide filter structure for the microwave band is symmetrical about the X-axis, including a first rectangular waveguide resonator (i.e., the first waveguide resonator 3 on the left), a second rectangular waveguide resonator (i.e., the second waveguide resonator 4 in the middle), a third rectangular waveguide resonator (i.e., the first waveguide resonator 3 on the right), a first coupling window structure (i.e., the second coupling window 7), and a second coupling window structure (i.e., the first coupling window 6). A millimeter-wave band gapped waveguide filter is formed by loading gapped waveguide structures into the three rectangular waveguide resonators and the first coupling window structure, including a third-order gapped waveguide filter (i.e., the first waveguide resonator 3 has three gapped waveguide resonators) and a fourth-order gapped waveguide filter (i.e., the second waveguide resonator 4 in the middle has four gapped waveguide resonators). Each third-order gapped waveguide filter consists of three gapped waveguide resonators, a first metal ridge coupling structure (i.e., the first coupling structure 10), and a third coupling window structure (the third coupling window 11). The fourth-order gap waveguide filter consists of four identical gap waveguide resonant cavities, a second metal ridge coupling structure (i.e., the second coupling structure 13), and a fourth coupling window structure (i.e., the fourth coupling window 14).

[0067] Figure 6 The diagram shows the filter topologies corresponding to embodiments of the present invention. The rectangular waveguide filter topology for the microwave band corresponds to the dashed box portion, while the gapped waveguide filter for the millimeter-wave band corresponds to the solid box portion. As can be seen from the diagram, the input and output ports of the filters are different in the two frequency bands, and the main topology of the gapped waveguide filter is loaded into each rectangular waveguide resonant cavity.

[0068] In Embodiment 3 of this invention, the length, width, and height of the second resonant cavity (i.e., the middle second waveguide resonant cavity 4) of the rectangular waveguide filter are 31mm, 19mm, and 4mm, respectively. The length, width, and height of the first and third resonant cavities (i.e., the first waveguide resonant cavities 3 at both ends) are the same, at 27.4mm, 18mm, and 4mm. The length and width of the first coupling window structure (i.e., the second coupling window 7) are 10.2mm and 7mm, respectively, and the length and width of the second coupling window structure (i.e., the first coupling window 6) are 14.47mm and 2mm, respectively. The coupling strength can be changed by changing the length of the coupling window. The metal pillars used in the gap waveguide structure 8 are all 1mm long and 1mm wide, and 3mm high. The air gap between the metal pillar and the upper metal cover plate is 1mm. The metal ridge coupling structure of the third-order gap waveguide filter has the same width and height as the metal pillar, but a length of 2.33mm. The metal ridge coupling structure of the fourth-order gap waveguide filter also has the same width and height as the metal pillar, with lengths of 2.3mm and 2.65mm, respectively. The length, width, and height of the second coupling window structure in the gap waveguide filter are 3.8 mm, 1 mm, and 4 mm, respectively.

[0069] The coupling strength can be controlled by changing the length of the aforementioned metal ridge and the lengths of the first and second coupling windows. The resonant frequency of a rectangular waveguide resonator is mainly determined by its cavity size, while the resonant frequency of a gapped waveguide resonator can be changed by moving the position of the metal pillars around the cavity. Moving the position of the metal pillars or adjusting the coupling structure of the gapped waveguide filter does not affect the resonant frequency of the rectangular waveguide resonator. Therefore, gapped waveguide filters in the millimeter-wave band and rectangular waveguide filters in the microwave band can be tuned independently.

[0070] Figure 7 The simulated filtering characteristics curves of the microwave band rectangular waveguide filter corresponding to the embodiment of the present invention are shown. The results show that the passband frequency range is 5.74-5.85 GHz, the relative bandwidth is 1.9%, and the insertion loss within the passband is better than -0.81 dB.

[0071] Figure 8 The simulated filtering characteristics curves of the millimeter-wave band gapped waveguide filter corresponding to the embodiments of the present invention are shown. The results show that the passband frequency range is 26.7GHz-27.3GHz, the relative bandwidth is 2.2%, and the insertion loss within the passband is better than -0.48dB.

[0072] Figure 9 The isolation between the input / output ports of the third-order gap waveguide filter and the input / output ports of the rectangular waveguide filter corresponding to the embodiments of the present invention is shown. The results show that the isolation between the high- and low-frequency filter ports is better than -40dB. Figure 10 The isolation between the third-order and fourth-order gap waveguide filters corresponding to the embodiments of the present invention is shown in the results, which indicate that the isolation between the ports of the two high-frequency filters is also better than -40dB.

[0073] Figure 11 Frequency ratio variation curves for different forms of the second waveguide resonant cavity provided in embodiments of the present invention. Figure 11 (a) to (d) represent different ways of dividing the first or second waveguide resonant cavity using gap waveguide structures (dividing it into 4, 6, 8, and 9 gap waveguide resonators, respectively). Figure 11 (e) is a schematic diagram of the frequency ratio curve. Figure 11 It is known that the frequency ratio variation range can be controlled by changing the number of divisions in the gap waveguide cavity and the height of the metal pillars in the gap waveguide. Simultaneously, the isolation between the filters in the two frequency bands is high. Therefore, the design process of the dual-band filter of this invention can be summarized as follows: first, determine the division form of the gap waveguide structure according to the required frequency ratio; then, design the gap waveguide filter first according to the traditional filter design method; and finally, design the rectangular waveguide filter after loading the gap waveguide filter structure.

[0074] The dual-band filter based on gapped waveguides provided in Embodiment 3 can achieve two operating frequency bands of 5.74-5.85GHz and 26.7GHz-27.3GHz, with center frequencies of 5.8GHz and 27GHz, and relative bandwidths of 1.9% and 2.2%, respectively. The insertion losses in the two operating frequency bands are better than -0.81dB and -0.48dB, respectively. The isolation between the high-frequency and low-frequency filters, as well as the isolation between the high-frequency filters themselves, are both better than -40dB.

[0075] In this embodiment 3, cavity multiplexing is achieved by loading a gap waveguide structure into a rectangular waveguide resonant cavity. Specifically, the gap waveguide structure is used to divide the rectangular waveguide resonant cavity to form a gap waveguide resonant cavity. The rectangular waveguide resonant cavity and its coupling structure constitute a microwave frequency band filter, while the gap waveguide resonant cavity and its coupling structure constitute a millimeter-wave frequency band filter. Therefore, by controlling the structural parameters of the gap waveguide and the division of the rectangular waveguide resonant cavity, the frequency ratio can be controlled, thus providing a simple implementation method for high frequency ratio filters. Simultaneously, after loading the gap waveguide structure into the rectangular waveguide resonant cavity, the size of the original rectangular waveguide resonant cavity is significantly reduced due to the capacitance shortening effect, achieving miniaturization of the dual-frequency filter. Furthermore, using a gap waveguide filter as the implementation method for the dual-frequency filter in the millimeter-wave band, and a rectangular waveguide filter as the implementation method in the microwave band, the two filter structures are complementary and compatible with the device size requirements of both frequency bands.

[0076] In summary, in this embodiment of the invention, the first waveguide resonant cavity and the second waveguide resonant cavity can be referred to as first-type waveguide resonant cavities, the first gap waveguide resonant cavity and the second gap waveguide resonant cavity can be referred to as second-type waveguide resonant cavities, the first coupling window, the third coupling window and the fourth coupling window can be referred to as first-type coupling structures, the second coupling window is a second-type coupling structure, and the first coupling structure and the second coupling structure are referred to as third-type coupling structures. After the cover plate and the filter body are closed, a structure can be formed as follows: Figure 11The cavities shown in (a) to (d) are formed by a surrounding structure (the surrounding structure is a schematic diagram of the cover plate and the filter body after being closed, and the coupling window structure in the above embodiments is not shown) and a schematic diagram of the gap waveguide structure inside the cavity. In the figures, the upper and lower boundaries plus the surrounding boundaries can form a resonant cavity. For the upper and lower boundaries of the resonant cavity: both the first and second type of resonant cavities are metal walls; for the surrounding boundaries of the resonant cavity: the first type of resonant cavity is still a metal wall, while the second type of resonant cavity is composed of a gap waveguide structure and a metal wall, or is composed entirely of a gap waveguide structure. Among them, the second type of resonant cavity is located inside the first type of resonant cavity; the second type of resonant cavity reuses the metal wall of the first type of resonant cavity. The first type of coupling structure is constructed by opening a coupling window on the metal wall. In the embodiments of the present invention, an inductive coupling window is used, as well as a capacitive coupling window, a coupling hole of mixed coupling form, etc., so the first type of coupling structure is not limited to the form of a coupling window. The third type of coupling structure in the embodiments of the present invention uses a metal ridge, and coupling can also be achieved by changing the spacing between two rows of metal pins, so the third type of coupling structure is not limited to the form of a metal ridge.

[0077] The aforementioned dual-band cavity filter with multiplexed structure forms two frequency band filters. The first frequency band filter is composed of a first type of resonant cavity, and the second frequency band filter is composed of a second type of resonant cavity. Specifically, the first frequency band filter consists of: a first waveguide interface + a first stepped structure + a first type of coupling structure + multiple (first type of resonant cavity + second type of coupling structure) + a first type of coupling structure + a first stepped structure + a first waveguide interface. The second frequency band filter consists of: a second waveguide interface + a second stepped structure + a first type of coupling structure + multiple (second type of resonant cavity + third type of coupling structure) + a first type of coupling structure + a second stepped structure + a second waveguide interface.

[0078] While the specific embodiments of the present invention have been described above in conjunction with the accompanying drawings, this is not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that, based on the technical solutions disclosed in the present invention, various modifications or variations that can be made by those skilled in the art without creative effort should be included within the scope of protection of the present invention.

Claims

1. A dual-band cavity filter with a reusable structure, comprising a filter body (1) and a cover plate (21) covering the filter body (1), characterized in that: The filter body (1) is provided with a first waveguide interface (2) at each end; Each of the two first waveguide interfaces (2) is coupled to a first waveguide resonant cavity (3); multiple second waveguide resonant cavities (4) are coupled sequentially between the two first waveguide resonant cavities (3); Both the first waveguide resonant cavity (3) and the second waveguide resonant cavity (4) are connected to a second waveguide interface (5); The first waveguide interface (2) is coupled to the first waveguide resonant cavity (3) through the first coupling window (6), and the first waveguide resonant cavity (3) and the second waveguide resonant cavity (4) and the plurality of sequentially coupled second waveguide resonant cavities (4) are coupled through the second coupling window (7); Multiple gap waveguide structures (8) are provided in the first waveguide resonant cavity (3), the second waveguide resonant cavity (4), and the second coupling window (7); Multiple gap waveguide structures (8) within the first waveguide resonant cavity (3) divide the first waveguide resonant cavity (3) into multiple first gap waveguide resonant cavities (9); the multiple first gap waveguide resonant cavities (9) are sequentially coupled and connected through a first coupling structure (10); In the plurality of sequentially coupled first gap waveguide resonant cavities (9), the first gap waveguide resonant cavities (9) at both ends are connected to a second waveguide interface (5) through a third coupling window (11); Multiple gap waveguide structures (8) within the second waveguide resonant cavity (4) divide the second waveguide resonant cavity (4) into multiple second gap waveguide resonant cavities (12); the multiple second gap waveguide resonant cavities (12) are sequentially coupled and connected through a second coupling structure (13); The first waveguide interface (2), the first coupling window (6), the first waveguide resonator (3), the second coupling window (7), and the second waveguide resonator (4) together constitute the first frequency band filter; the second waveguide interface (2), the first gap waveguide resonator (9), the first coupling structure (10), and the third coupling window (11) together constitute the second frequency band filter.

2. The dual-band cavity filter with multiplexed structure according to claim 1, characterized in that, In the plurality of sequentially coupled second gap waveguide resonant cavities (12), the second gap waveguide resonant cavities (12) at both ends are connected to a second waveguide interface (5) through a fourth coupling window (14).

3. The dual-band cavity filter with multiplexed structure according to claim 2, characterized in that, The filter body (1) is provided with a groove (19), and a second stepped structure (20) is provided in the groove (19); the groove (19) and the cover plate (15) together form the second waveguide interface (5).

4. The dual-band cavity filter with multiplexed structure according to any one of claims 1-3, characterized in that, A rectangular notch (17) is provided at both ends of the cover plate (15) and at both ends of the filter body (1). A first stepped structure (18) is provided in the rectangular notch (17). The two rectangular notches (17) on the same end of the cover plate (15) and the filter body (1) together form the first waveguide interface (2).

5. The dual-band cavity filter with multiplexed structure according to any one of claims 1-3, characterized in that, The filter body (1) has a rectangular notch (17) at both ends, which serves as the first waveguide interface (2).

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