A half-slot gap waveguide based tri-band metasurface bandpass filter

Abstract

The application discloses a three-passband metasurface band-pass filter based on a half-slot gap waveguide, which comprises a lower metal base plate and an upper metal base plate, the lower metal base plate is arranged below the upper metal base plate, and one side of the lower metal base plate towards the upper metal base plate is provided with a periodic metal peg array; when the upper metal base plate is buckled on the lower metal base plate, an air gap is formed between the periodic metal peg array and the upper metal base plate to form a half-slot gap waveguide working space; the two side ends of the upper metal base plate are connected with flanges through a rectangular waveguide connecting shell, and the flanges are provided with feed waveguide cavities; the hollow cavities of the rectangular waveguide connecting shell are communicated with the feed waveguide cavities; the upper metal base plate is provided with a gap waveguide cavity at the middle position of the end face towards the periodic metal peg array, and the gap waveguide cavity is communicated with the hollow cavities of the rectangular waveguide connecting shell at two ends.

Description

Technical Field

[0001] This invention belongs to the field of millimeter-wave passive device technology, and in particular relates to a three-band metasurface bandpass filter based on a half-mode slot gap waveguide. Background Technology

[0002] With the rapid development of 5G mobile communication, satellite internet, vehicle-mounted radar, and high-speed wireless transmission systems, the millimeter-wave band has gradually become an important operating frequency band for modern wireless communication systems due to its abundant spectrum resources, high transmission rate, and large system capacity. In millimeter-wave front-end systems, bandpass filters are key passive devices for achieving signal frequency selection, suppressing out-of-band interference, and improving the system's anti-interference capability. Their performance directly affects the transmission quality and integration level of the entire RF front-end.

[0003] Currently, various types of millimeter-wave bandpass filters have been proposed, including those based on microstrip lines, substrate integrated waveguides, metallic cavities, and gapped waveguides, to meet the needs of high-frequency, high-performance, and miniaturized wireless communication systems. However, research on millimeter-wave filters that can simultaneously achieve three-band operation, have a compact structure, and offer flexible bandwidth adjustment is still relatively lacking, especially in achieving multi-mode cooperative resonance and three-band integration in a single-cavity structure. Therefore, to address these issues, there is an urgent need to develop a novel millimeter-wave three-band bandpass filter that can achieve good filtering response across multiple frequency bands in a compact structure, and possesses advantages such as low loss, high integration, and adjustable bandwidth to meet the application requirements of future multi-band, high-performance wireless communication systems. Summary of the Invention

[0004] The purpose of this invention is to address the shortcomings of existing millimeter-wave multi-passband filters, such as complex structure, large size, and difficulty in achieving a three-passband filtering response. This invention proposes a three-passband metasurface bandpass filter based on a half-mode slotted gap waveguide. This filter achieves a three-passband bandpass filtering response by incorporating a resonant cavity and perturbation metal pillars within a single half-mode slotted gap waveguide cavity, and constructs an electromagnetic bandgap operating environment through a periodic metal pin array. It offers advantages such as compact structure, low loss, good frequency selectivity, and ease of integration and fabrication.

[0005] To address the aforementioned technical problems and achieve the aforementioned objectives, this invention proposes a three-band metasurface bandpass filter based on a half-mode slotted gap waveguide. The filter includes a lower metal base plate and an upper metal base plate. The lower metal base plate is disposed below the upper metal base plate, and a periodic metal pin array is provided on the side of the lower metal base plate facing the upper metal base plate. When the upper metal base plate is fastened to the lower metal base plate, an air gap is formed between the periodic metal pin array and the upper metal base plate to constitute the working space of the half-mode slotted gap waveguide.

[0006] The upper metal base plate is connected to flanges on both sides by rectangular waveguide connecting housings, and a feeding waveguide cavity is provided on the flanges; the hollow cavity of the rectangular waveguide connecting housing is connected to the feeding waveguide cavity.

[0007] The upper metal base plate is provided with a gap waveguide resonant cavity at the middle position of the end face of the periodic metal pin array, and the two ends of the gap waveguide resonant cavity are connected to the hollow cavity of the rectangular waveguide connecting shell.

[0008] Furthermore, the gap waveguide resonant cavity includes a first notch and a second notch, which are symmetrically arranged on both sides of the end face of the upper metal base plate facing the periodic metal pin array. A gap is provided at the center of the end face. One end of the gap is connected to the first notch through a first groove, and the other end is connected to the second notch through a second groove. The depth of the gap is greater than the depth of the first and second notches. Metal pillars are respectively provided at both ends inside the gap, below the lower ends of the first and second grooves, and the lower ends of the metal pillars are lower than the lower end faces of the first and second notches. Furthermore, the first and second notches are respectively connected to the hollow cavities of the rectangular waveguide connecting shells on both sides of the upper metal base plate.

[0009] Furthermore, the first and second notches are cubic notches, and the hollow cavity of the rectangular waveguide connecting shell is a cubic cavity.

[0010] Furthermore, the lower end face of the rectangular waveguide connecting housing is flush with the lower end face of the lower metal base plate.

[0011] Furthermore, the spacing between the periodic metal pin array and the upper metal base plate is less than 1 / 4λ, where λ is the wavelength corresponding to the lowest operating center frequency of the filter.

[0012] Furthermore, the periodic metal pin array comprises multiple periodically arranged cuboid metal pins.

[0013] Furthermore, the end face of the upper metal base plate that is fastened to the lower metal base plate is the same size as the end face of the lower metal base plate, and the other end face of the upper metal base plate is smaller than the end face of the lower metal base plate.

[0014] Beneficial effects: Compared with the prior art, the technical solution of the present invention has the following beneficial technical effects:

[0015] (1) This invention achieves a three-passband filtering function within a single gap waveguide cavity by coordinating the size of the gap with the parameters of the metal pillar. This results in high integration and a high passband bandwidth for the filter. Test results show that the center frequencies of the three passbands of this filter are 25.14 GHz, 30.60 GHz, and 37.05 GHz, respectively, with corresponding 3dB fractional bandwidths of 11.67%, 10.26%, and 3.14%.

[0016] (2) This invention uses a periodic metal needle array and upper and lower metal boundaries to form an electromagnetic bandgap structure, which effectively suppresses the propagation of non-target modes and electromagnetic leakage. Test results show that the insertion loss of this filter in the three passbands is 0.59dB, 0.43dB and 0.90dB, respectively, and the signal isolation between passbands is high, which can effectively avoid mutual interference between signals in each passband and has high signal transmission efficiency.

[0017] (3) The present invention uses a single half-mode slot gap waveguide cavity to realize three-pass band filtering. The final prototype resonant cavity size is 1.17λg×0.75λg×0.21λg. Compared with the multi-cavity cascaded structure, it has better miniaturization advantages and is very suitable for modern multi-standard wireless communication systems with high space requirements. Attached Figure Description

[0018] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments, so as to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art. The advantages and implementation methods of the present invention will become more apparent. The content of the accompanying drawings is only used to illustrate and explain the present invention, but does not constitute any limitation on the present invention. In the accompanying drawings:

[0019] Figure 1 This is a schematic diagram of the overall structure of a three-band metasurface bandpass filter based on a half-mode slotted waveguide according to the present invention.

[0020] Figure 2 Schematic diagram of a periodic metal pin array;

[0021] Figure 3 This is a schematic diagram of the end face of the upper metal base plate;

[0022] Figure 4 This is a schematic diagram of a gap waveguide cavity on an upper metal substrate.

[0023] Figure 5 This is a schematic diagram of the internal structure of the gap waveguide cavity on the upper metal substrate.

[0024] Figure 6 This is a comparison chart of simulation and test results of the frequency response of a filter provided in an embodiment of the present invention. Detailed Implementation

[0025] The embodiments of the present invention will be further described below with reference to the accompanying drawings. It should be noted that the following embodiments are only used to explain the technical solutions of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

[0026] like Figures 1 to 3 As shown, this invention proposes a three-band metasurface bandpass filter based on a half-mode slotted gap waveguide. The filter includes a lower metal base plate 10 and an upper metal base plate 11. The lower metal base plate 10 is disposed below the upper metal base plate 11. A periodic metal pin array 12 is provided on the side of the lower metal base plate 10 facing the upper metal base plate 11. When the upper metal base plate 11 is fastened to the lower metal base plate 10, an air gap is formed between the periodic metal pin array 12 and the upper metal base plate 11 to form the working space of the half-mode slotted gap waveguide.

[0027] The upper metal base plate 11 is connected to flanges 13 at both ends via rectangular waveguide connecting housing 14. A feeding waveguide cavity 15 is provided on the flange 13. The hollow cavity of the rectangular waveguide connecting housing 14 is connected to the feeding waveguide cavity 15.

[0028] like Figure 1 and Figure 4 As shown, the upper metal base plate 11 is provided with a gap waveguide resonant cavity 16 at the middle position of the end face of the periodic metal pin array 12, and the two ends of the gap waveguide resonant cavity 16 are connected to the hollow cavity of the rectangular waveguide connecting shell 14.

[0029] Furthermore, the gap waveguide resonant cavity 16 includes a first notch 17 and a second notch 18. The first notch 17 and the second notch 18 are symmetrically arranged on both sides of the end face of the upper metal base plate 11 facing the periodic metal pin array 12. A gap 19 is provided at the center of the end face. One end of the gap 19 is connected to the first notch 17 through a first groove 20, and the other end is connected to the second notch 18 through a second groove 21. The depth of the gap 19 is greater than the depth of the first notch 17 and the second notch 18. Metal pillars 22 are respectively provided at both ends inside the gap 19 and below the lower ends of the first groove 20 and the second groove 21. The lower ends of the metal pillars 22 are lower than the lower end faces of the first notch 17 and the second notch 18. Furthermore, the first notch 17 and the second notch 18 are respectively connected to the hollow cavities of the rectangular waveguide connecting housing 14 on both sides of the upper metal base plate 11.

[0030] Furthermore, the first notch 17 and the second notch 18 are cubic notches, and the hollow cavity of the rectangular waveguide connecting housing 14 is a cubic cavity.

[0031] Furthermore, the lower end face of the rectangular waveguide connecting housing 14 is flush with the lower end face of the lower metal base plate 10.

[0032] Furthermore, the distance between the periodic metal pin array 12 and the upper metal base plate 11 is less than 1 / 4λ, where λ is the wavelength corresponding to the lowest operating center frequency of the filter.

[0033] Furthermore, the periodic metal pin array 12 comprises multiple periodically arranged cuboid metal pins.

[0034] Furthermore, the end face of the upper metal base plate 11 that is fastened to the lower metal base plate 10 is the same size as the end face of the lower metal base plate 10, and the other end face of the upper metal base plate 11 is smaller than the end face of the lower metal base plate 10.

[0035] like Figure 2 As shown, the periodic metal needle array 12 is a two-dimensional periodically arranged array of metal needle units, wherein the period p of the metal needle array is set to 1.4 mm, the width a of the metal needles is set to 1.2 mm, and the height h of the metal needles is set to 2.5 mm. According to the full-wave simulation analysis results of the two-dimensional metasurface unit, the electromagnetic bandgap formed by this structure covers 20.5 GHz to 48.3 GHz, which can cover the operating frequency band of the three-pass band filter of this invention, thereby providing a stable electromagnetic boundary environment for the gapped waveguide cavity 16.

[0036] like Figure 5 As shown, the core coupling and resonance geometric parameters inside the gap waveguide resonant cavity 16 were optimized by full-wave simulation. The specific dimensional parameters are set as follows: the width qw of the first groove 20 and the second groove 21, which serve as coupling irises, is 2.1 mm and the depth is 3.6 mm; the length w of the gap 19, which serves as the resonant cavity, is 14 mm, the width th is 2.5 mm, and the depth l is 9 mm; the metal pillars 22, which are symmetrically arranged at both ends inside the gap 19 to introduce perturbation responses, have a length b is 2.3 mm, a height d is 1.9 mm, an upper surface depth c is 4.4 mm, and a width th is 2.5 mm; the edge step height f of the upper metal base plate 11 is 2 mm.

[0037] In this embodiment, through the aforementioned global and local parameter configurations, independent control and decoupling of the six-mode frequency response excited within a single cavity are achieved. Specifically, the spatial physical position of the metal pillar 22 coincides precisely with the electric field regions of the resonant modes corresponding to the low-frequency and high-frequency passbands, and is simultaneously located within the electric field region of the resonant mode corresponding to the mid-frequency passband. Therefore, by adjusting the size parameters b and d and the spatial arrangement position parameter c of the perturbation of the metal pillar 22, the center frequencies of the low-frequency and high-frequency passbands can be independently controlled and moved without affecting the in-band response of the mid-frequency passband.

[0038] Meanwhile, by adjusting the length w and depth l of the gap 19, the bandwidth and bandwidth ratio of the three passbands can be independently controlled. Full-wave simulation results show that as the depth l increases, the bandwidth of the high-frequency passband remains almost constant, while the bandwidth of the low-frequency passband decreases and the bandwidth of the mid-frequency passband increases. Similarly, when the length w increases, the bandwidth of the low-frequency passband remains almost constant, while the bandwidth of the mid-frequency passband decreases and the bandwidth of the high-frequency passband increases. In summary, by controlling the geometric parameters of the gap waveguide cavity 16, the bandwidth ratio of the three passbands can be adjusted to better meet the asymmetric bandwidth requirements of different communication frequency bands.

[0039] like Figure 6 The figure shows a comparison of simulation and test results of the frequency response of a filter provided in an embodiment of the present invention. Based on the proposed structure and parameters, after full-wave simulation optimization and prototype fabrication, the measured center frequencies of the three passbands of the filter are 25.14 GHz, 30.60 GHz, and 37.05 GHz, respectively, with corresponding 3dB fractional bandwidths of 11.67%, 10.26%, and 3.14%, and corresponding insertion losses of 0.59 dB, 0.43 dB, and 0.90 dB, respectively. The final prototype resonant cavity size is 14 mm × 9 mm × 2.5 mm, i.e., 1.17λg × 0.75λg × 0.21λg, where λg is the waveguide wavelength at the center frequency of the low-frequency passband. The measured results are generally consistent with the simulation results, indicating that the proposed three-passband metasurface bandpass filter structure based on a half-mode slotted gap waveguide is feasible and can achieve the expected three-passband bandpass filtering function.

[0040] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention are included within the scope of protection of the present invention.

Claims

1. A three-band metasurface bandpass filter based on a half-mode slotted gap waveguide, characterized in that, The filter includes a lower metal base plate and an upper metal base plate. The lower metal base plate is located below the upper metal base plate. A periodic metal pin array is provided on the side of the lower metal base plate facing the upper metal base plate. When the upper metal base plate is fastened to the lower metal base plate, an air gap is formed between the periodic metal pin array and the upper metal base plate to form a semi-mode slot gap waveguide working space. The upper metal base plate is connected to flanges on both sides by rectangular waveguide connecting housings, and a feeding waveguide cavity is provided on the flanges; the hollow cavity of the rectangular waveguide connecting housing is connected to the feeding waveguide cavity. The upper metal base plate is provided with a gap waveguide resonant cavity at the middle position of the end face of the periodic metal pin array, and the two ends of the gap waveguide resonant cavity are connected to the hollow cavity of the rectangular waveguide connecting shell.

2. A three-band metasurface bandpass filter based on a half-mode slotted gap waveguide according to claim 1, characterized in that, The gap waveguide resonant cavity includes a first notch and a second notch, which are symmetrically arranged on both sides of the end face of the upper metal base plate facing the periodic metal pin array. A gap is provided at the center of the end face. One end of the gap is connected to the first notch through a first groove, and the other end is connected to the second notch through a second groove. The depth of the gap is greater than the depth of the first and second notches. Metal pillars are respectively provided at both ends inside the gap, below the lower ends of the first and second grooves, and the lower ends of the metal pillars are lower than the lower end faces of the first and second notches. Furthermore, the first and second notches are respectively connected to the hollow cavities of the rectangular waveguide connecting shells on both sides of the upper metal base plate.

3. A three-band metasurface bandpass filter based on a half-mode slotted gap waveguide according to claim 2, characterized in that, The first and second notches are cubic notches, and the hollow cavity of the rectangular waveguide connecting shell is a cubic cavity.

4. A three-band metasurface bandpass filter based on a half-mode slotted gap waveguide according to claim 1 or 2, characterized in that, The lower end face of the rectangular waveguide connecting housing is flush with the lower end face of the lower metal base plate.

5. A three-band metasurface bandpass filter based on a half-mode slotted gap waveguide according to claim 1, characterized in that, The distance between the periodic metal pin array and the upper metal base plate is less than 1 / 4λ, where λ is the wavelength corresponding to the lowest operating center frequency of the filter.

6. A three-band metasurface bandpass filter based on a half-mode slotted gap waveguide according to claim 1, characterized in that, The periodic metal pin array consists of multiple periodically arranged cuboid metal pins.

7. A three-band metasurface bandpass filter based on a half-mode slotted gap waveguide according to claim 1, characterized in that, The end face of the upper metal base plate that is fastened to the lower metal base plate is the same size as the end face of the lower metal base plate, and the other end face of the upper metal base plate is smaller than the end face of the lower metal base plate.

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