Compact and highly selective substrate-integrated waveguide triangular cavity broadband bandstop filters

Abstract

The present invention relates to the field of microwave filters and discloses a compact, highly selective, substrate-integrated waveguide triangular cavity wideband bandstop filter. The filter comprises, from top to bottom, an upper metal layer, an intermediate dielectric layer substrate, and a lower metal layer. The upper metal layer is connected to the lower metal layer through metallized vias and, together with the intermediate dielectric layer substrate, forms a dielectric-filled cavity. The cavities are all triangular in shape and consist of only right-angled isosceles triangular cavities and equilateral triangular cavities. The length of the right-angled isosceles triangular cavities is linearly related to the length of the sides of the equilateral triangular cavities, giving the entire filter a pentagonal structure. The present invention combines harmonic interleaving technology and harmonic coupling technology to propose a relationship between the right-angle side length of a substrate integrated waveguide right-angle isosceles triangular cavity and the side length of a substrate integrated waveguide regular triangular cavity, which not only has a compact and simple structure, but also simplifies the design steps and has important application prospects.

Description

[Technical Field]

[0001] The present invention relates to the field of microwave filters, and more particularly to a compact, highly selective substrate integrated waveguide triangular cavity wideband bandstop filter. [Background technology]

[0002] In wireless and military communications, the requirements for filter performance are constantly increasing. Filters are essential components in RF microwave front-end circuits, and their parameters directly affect the performance of the entire front-end circuit. Substrate Integrated Waveguide (SIW) technology has made great progress since its introduction.

[0003] Substrate integrated waveguide technology combines the advantages of both microstrip circuits and waveguides, combining the high quality factor (Q) and high power capacity of waveguides with the compact size and ease of integration of planar microstrip circuits, thereby bridging the technological gap between planar microstrip / stripline and non-planar waveguides / dielectric resonators.

[0004] The principle of harmonic interleaving technology is to design a filter by using the same resonant mode frequency to construct the passband and interleaving (staggering) other spurious resonant frequencies. When multiple resonators are coupled and cascaded to form a filter, it can achieve suppression of harmonic levels. The advantage is that no additional components are required and signal coupling does not need to be considered. The disadvantage is that it is only applicable to narrow bandwidths and weak coupling cases, spurious levels may not be controlled, and all harmonic levels may not be able to be kept below the ideal value.

[0005] Harmonic coupling control technology precisely controls the coupling strength of harmonic signals by rationally selecting the coupling locations between resonators or between ports and input resonators, making harmonic coupling zero or very weak, thereby achieving stopband suppression. Coupling matrix synthesis technology can also be used to obtain a coupling matrix corresponding to the stopband response, which can then be applied to higher-order harmonics to achieve spurious suppression. The advantage of this approach is that no additional distributed components are required. However, the coupling between the fundamental frequency and the harmonics must be considered simultaneously, which increases the difficulty of circuit design.

[0006] In cross-coupling techniques, if signals transmitted over two different physical transmission paths are equal in amplitude but opposite in phase, their energies can cancel each other out, creating a transmission zero on the imaginary axis. However, to provide opposite phases, positive and negative coupling must be realized simultaneously.

[0007] However, existing substrate integrated waveguide wideband bandstop filters have many drawbacks. 1. Existing research on substrate-integrated waveguide wideband bandstop filters has mostly been realized using rectangular or square cavities, with very few using triangular cavities. To date, there has been no example of a filter with wideband rejection performance that simultaneously employs a right-angle isosceles triangular cavity and a regular triangular cavity.

[0008] 2. Most existing substrate-integrated waveguide wideband bandstop filters introduce dedicated electrical coupling or mixed coupling structures to achieve the negative coupling required for cross-coupling, which increases the number of parameters and makes the filter parameter adjustment process relatively time-consuming.

[0009] 3. In a substrate integrated waveguide filter realized by combining a general rectangular cavity and a square cavity, its operating frequency is related to the side length of the square cavity, the length and width of the rectangular cavity, and the relationship between the side length of the rectangular cavity and the side length of the square cavity is not linear, so it takes more time to adjust the dimensions of the entire filter. Summary of the Invention [Problem to be solved by the invention]

[0010] To solve the above-mentioned technical problems, the present invention aims to provide a substrate-integrated waveguide triangular cavity wideband bandstop filter with high selectivity, simple structure, compact design, and easy processing. This is a brand-new substrate-integrated waveguide wideband bandstop filter that uses a triangular cavity structure to simplify the overall dimensioning of the substrate-integrated waveguide wideband bandstop filter, while combining cross-coupling technology, harmonic interleaving technology, and harmonic coupling control technology to simplify the filter structure, improve the filter's passband selectivity, and widen the filter's stopband suppression, thereby improving the availability of compact, highly selectivity substrate-integrated waveguide triangular cavity wideband bandstop filters. [Means for solving the problem]

[0011] To achieve the above objectives, the present invention is realized by the following technical solutions. The present invention provides a compact, highly selective substrate-integrated waveguide triangular cavity wideband bandstop filter, comprising, from top to bottom, an upper metal layer, an intermediate dielectric layer substrate, and a lower metal layer, wherein the geometric centers of the patterns of the upper metal layer, the intermediate dielectric layer substrate, and the lower metal layer are collinear, the upper metal layer is connected to the lower metal layer through a metallized via, and together with the intermediate dielectric layer substrate, forms a dielectric-filled cavity, the outline of each cavity is determined by the metallized via, the cavities are all triangular in shape and consist only of right-angled isosceles triangular cavities and equilateral triangular cavities, the right-angled side lengths of the right-angled isosceles triangular cavities and the side lengths of the equilateral triangular cavities have a linear relationship, and the cavities of the entire filter exhibit a pentagonal structure.

[0012] In one aspect, the linear relationship between the right-angled side length of the isosceles right triangular cavity and the side length of the equilateral triangular cavity is: JPEG2026507328000002.jpg1222In the formula, a1eff is the right-angled side length of the isosceles right triangular cavity, and aeff is the side length of the equilateral triangular cavity.The dimensions of the entire filter can be determined by determining the side length of any one of the cavities.

[0013] In one embodiment, the upper metal layer is connected to two feed lines, and the cavities in which the feed lines are arranged are two adjacent equilateral triangular cavities that are coupled to each other, and these are the only cavities. Coupling slots are provided on both sides of each feed line, and the coupling slots are 0.2 mm wide and 2.5 mm long. The entire filter has a single-layer structure, the feed position is located at the center of one side of the equilateral triangular cavity, and all internal coupling windows are positioned (offset) from the center of the side on which they exist.

[0014] In one embodiment, between each of the two adjacent cavities there is a coupling window formed by a pair of metallized vias (PTH: Plated Through Hole, which is formed by drilling a hole in a substrate and plating a metal on its inner wall), and electrical coupling is realized by coupling between the operating modes of the right isosceles triangular cavity and the equilateral triangular cavity.

[0015] In one embodiment, the diameter of the metallized via is 0.5 mm, the spacing between two adjacent metallized vias is 1 mm, excluding the coupling window portion, the width of the coupling window between the equilateral triangular cavity connected to the power supply line at the notched corner portion and the right isosceles triangular cavity is 4.19 mm, the offset amount from the center position of the side of the coupling window is 3.7 mm, and in the counterclockwise direction, the widths of the coupling windows are 4.03 mm, 3.4 mm, and 2.3 mm, respectively, and the offset amount from the center position of the side of the coupling window is 3.7 mm, 2 mm, and 2 mm, respectively.

[0016] In one embodiment, the length of the hypotenuse of the right-angled isosceles triangular cavity is slightly smaller than the sum of the side lengths of the two equilateral triangular cavities it joins, and the right-angled vertex of the right-angled isosceles triangular cavity is directly opposite the vertices of the two equilateral triangular cavities it joins.

[0017] In one aspect, the filter of the present invention has both electric and magnetic coupling simultaneously, which generates one transmission zero on each side of the passband, improving the selectivity of the substrate integrated waveguide triangular cavity wideband bandstop filter. [Effects of the Invention]

[0018] This invention fills the patent gap regarding triangular cavities in high-selectivity substrate integrated waveguide wideband bandstop filters. Compared with the conventional filters, the coupling structure of the present filter is simpler, and by using harmonic interleaving and harmonic coupling control techniques, it achieves the electrical coupling necessary to generate two transmission zeros to improve selectivity and suppress spurious harmonics, thereby achieving the stop bandwidth suppressed by the conventional filters.

[0019] The present invention innovatively applies a triangular cavity to the design of a substrate integrated waveguide filter, simplifying the determination of the overall size of the substrate integrated waveguide filter at any operating frequency and reducing the overall size of the substrate integrated waveguide filter. The smaller size, simpler structure, and easier determination of the overall filter size greatly enhance the practical use of the present invention in wireless communication systems.

[0020] The present invention combines harmonic interleaving technology and harmonic coupling technology, and proposes a relationship between the right-angle side length of a substrate integrated waveguide right-angle isosceles triangular cavity and the side length of a substrate integrated waveguide regular triangular cavity, which not only makes the structure compact and simple, but also simplifies the design steps.With high selectivity and wide stopband suppression, the present invention has important potential applications in the fields of eliminating interference signals generated in wireless communication applications and parasitic spurious signals generated inside transceivers. [Brief explanation of the drawings]

[0021] [Figure 1] FIG. 1 is a perspective view showing a structure of the present invention. [Figure 2] FIG. 1 is a plan view of the present invention. [Figure 3] FIG. 2 is a bottom view of the present invention. [Figure 4] FIG. 2 is an S-parameter diagram of the filter of the present invention. [Figure 5] FIG. 1 is a diagram of a connection topology of the present invention. [Figure 6] 1 is a bonding matrix of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0022] Hereinafter, embodiments of the present invention will be described with reference to the drawings. For the sake of clarity, detailed descriptions will be provided in the following description. It should be understood that these detailed descriptions should not be used to limit the present invention. That is, in some embodiments of the present invention, these detailed descriptions are not necessary. In addition, in order to simplify the drawings, some conventional structures and components are shown in a simplified schematic manner in the drawings.

[0023] As shown in Figure 1, the present invention provides a compact, highly selective, substrate-integrated waveguide triangular cavity wideband bandstop filter. It primarily consists of two metal layers and one dielectric layer, divided into an upper metal layer, an intermediate dielectric layer substrate, and a lower metal layer. The intermediate dielectric layer substrate is preferably made of Rogers RT5880 with a thickness of 0.508 mm, a relative permittivity of 2.2, and a dissipation factor of 0.0009. The filter's outline is inscribed in a square with a side length of at least 59 mm. The lower right corner of the plan view has a 60° oblique notch, with the short side of the notch being no longer than 15 mm and not overlapping with the metal patch of the cavity.

[0024] The upper and lower metal layers are connected via metallized vias 2 and bonded to the intermediate dielectric layer substrate to form cavities. The notch angles match the outlines of the intermediate dielectric layer substrate and the lower metal layer. The contours of each cavity are determined by metallized vias with a diameter of 0.5 mm. The cavities are all triangular in shape and consist of only right-angled isosceles triangular cavities and equilateral triangular cavities. There is a linear relationship between the right-angle side length of the right-angled isosceles triangular cavities and the side length of the equilateral triangular cavities, specifically: JPEG2026507328000003.jpg1529, where a1eff is the right-angled side length of the isosceles triangular cavity and aeff is the side length of the equilateral triangular cavity. The right-angled side length of the substrate-integrated waveguide isosceles triangular cavity is approximately 1.369 times the side length of the substrate-integrated waveguide equilateral triangular cavity. Determining the side length of any one cavity determines the overall filter dimensions, reducing the complexity of the filter design and simplifying the overall design process of a high-selectivity substrate-integrated waveguide triangular cavity wideband bandstop filter.

[0025] As shown in Figures 2 and 3, the upper metal layer is formed by coupling the upper metal layer of four triangular cavities with the power supply lines. The cavities in which the two power supply lines of the upper metal layer are arranged are two adjacent equilateral triangular cavities that are coupled to each other, and these are the only cavities. A coupling slot 5 is provided on both sides of each power supply line, and the coupling slot 5 is 0.2 mm wide and 2.5 mm long. The upper metal layer of the entire cavity is composed of three equilateral triangles and one right-angled isosceles triangle, forming a pentagon.

[0026] The upper metal layer is completely flat, with no other grooves or slots on it, except for the metallized vias and the coupling slots on both sides of the feed line. All coupling throughout the filter is achieved through coupling windows formed by pairs of metallized vias with relatively wide spacing, simplifying the design of conventional electrical coupling structures.

[0027] A coupling window 6 formed by a pair of metallized vias 2 is provided between each of two adjacent cavities. All coupling is achieved through simple coupling windows, and no dedicated electrical or hybrid coupling structures are introduced. Electrical coupling is achieved only through coupling between the operating modes of the substrate-integrated waveguide right-angle isosceles triangular cavity and the substrate-integrated waveguide regular triangular cavity. This eliminates the need for designing electrical coupling structures and simplifies filter design.

[0028] The entire filter has a single-layer structure. The feed position is located at the center of one side of the equilateral triangular cavity, and all internal coupling windows are offset from the center of the side on which they reside. The spacing between two adjacent metallized vias 2 is 1 mm, excluding the coupling window portion. The width of the coupling window 6 between the equilateral triangular cavity connected to the feed line at the notched corner and the right-angled isosceles triangular cavity is 4.19 mm, and the offset of the coupling window 6 from the center of that side is 3.7 mm. In the counterclockwise direction, the widths of the coupling windows 6 are 4.03 mm, 3.4 mm, and 2.3 mm, respectively, and the offsets of the coupling windows 6 from the center of that side are 3.7 mm, 2 mm, and 2 mm, respectively. This ensures optimal coupling for the operating mode while essentially suppressing several spurious modes near the operating mode, forming a wideband bandstop filter. The shape and dimensions of the lower metal layer are the same as those of the bottom surface of the dielectric substrate that contacts it.

[0029] The length of the hypotenuse of the right-angled isosceles triangular cavity is slightly smaller than the sum of the side lengths of the two equilateral triangular cavities it couples with, and the right-angled vertex of the right-angled isosceles triangular cavity is directly opposite (located opposite) the vertices of the two equilateral triangular cavities it couples with. The filter of the present invention simultaneously has electric and magnetic coupling, which generates one transmission zero on each side of the passband, thereby improving the selectivity of the substrate integrated waveguide triangular cavity wideband bandstop filter. As shown in Figure 4, the 3 dB bandwidth of the filter is 1.5%, that is, from 9.92 GHz to 10.07 GHz. The return losses within the operating bandwidth are all less than -20 dB, and the minimum insertion loss is 1.24 dB. The zeros on both sides of the passband are located at 9.86 GHz and 10.12 GHz, respectively. In the upper stopband, several spurious modes close to the operating mode frequency are suppressed, so the stopband bandwidth of the filter with 20 dB suppression is JPEG2026507328000004.jpg636

[0030] In Figure 5, node S represents the source, node L represents the load, and nodes 1, 2, 3, and 4 represent the four corresponding cavities. The solid lines connecting the nodes indicate magnetic coupling, while the dashed lines connecting the nodes indicate electrical coupling. Nodes 1 to 2, 2 to 3, and 3 to 4 are all direct coupling paths. Node 1 to 4 is a cross-coupling path.

[0031] The coupling coefficients in the coupling matrix of Figure 6 not only correspond to the critical dimensions of the proposed filter and their magnitude, but also reflect the coupling type between each cavity and any cross-coupling that may exist. Generally, a positive coupling coefficient corresponds to a magnetic coupling, and a negative coupling coefficient corresponds to an electric coupling or a coupling that has the opposite phase response to a positive coupling.

[0032] The present invention combines harmonic interleaving technology and harmonic coupling technology, and proposes a relationship between the right-angle side length of a substrate integrated waveguide right-angle isosceles triangular cavity and the side length of a substrate integrated waveguide regular triangular cavity, which not only achieves a compact and simple structure but also simplifies the design effort.With high selectivity and wide stopband suppression, the present invention has important potential applications in the fields of eliminating interference signals generated in wireless communication applications and parasitic spurious signals generated inside transceivers.

[0033] Although the above describes in more detail the objectives, technical solutions and beneficial effects of the present invention with reference to specific embodiments, it should be understood that the above is only a specific embodiment of the present invention and does not limit the protection scope of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention should all be included in the protection scope of the present invention.

Claims

1. A compact, highly selective substrate integrated waveguide triangular cavity wideband bandstop filter, comprising: From top to bottom, an upper metal layer, an intermediate dielectric layer substrate (1), and a lower metal layer are provided. The geometric centers of the patterns of the upper metal layer, the intermediate dielectric layer substrate (1) and the lower metal layer are on the same straight line; The upper metal layer is connected to the lower metal layer through a metallized via (2) and forms a dielectric-filled cavity with the intermediate dielectric layer substrate (1); The contour of each of the cavities is determined by the metallized vias (2); The cavities are all triangular in shape and are composed of only right-angled isosceles triangular cavities and equilateral triangular cavities; a right-angled side length of the isosceles right triangular cavity and a side length of the equilateral triangular cavity have a linear relationship; The upper metal layer of the cavity of the substrate integrated waveguide triangular cavity wideband bandstop filter as a whole is composed of three equilateral triangles and one right-angled isosceles triangle, forming a pentagon; the length of the hypotenuse of the right-angled isosceles triangular cavity is slightly smaller than the sum of the lengths of the sides of the two equilateral triangular cavities connected to the right-angled isosceles triangular cavity; A compact, highly selective substrate-integrated waveguide triangular cavity wideband bandstop filter, characterized in that the right-angled vertex of the right-angled isosceles triangular cavity is directly opposite the vertices of the two equilateral triangular cavities to which the right-angled isosceles triangular cavity is coupled.

2. The linear relationship between the right-angled side length of the isosceles right triangular cavity and the side length of the equilateral triangular cavity is:

2. The compact, highly selective substrate-integrated waveguide triangular cavity wideband bandstop filter of claim 1, wherein a is the right-angled side length of the isosceles right triangular cavity, and a is the side length of the equilateral triangular cavity, and by determining the side length of any one of the cavities, it is possible to determine the dimensions of the entire filter.

3. the top metal layer is connected to two power supply lines; the cavities in which the feed lines are arranged are only two equilateral triangular cavities that are adjacent to each other and coupled to each other, Each of the feeder lines has a coupling slot (5) on each side thereof; The width of the coupling slot (5) is 0.2 mm and the length is 2.5 mm; The entire filter has a single layer structure.

2. The compact, highly selective substrate integrated waveguide triangular cavity wideband bandstop filter of claim 1, wherein the feed position is at the center of one side of the equilateral triangular cavity.

4. A coupling window (6) formed by a pair of metallized vias (2) is provided between each of two adjacent cavities; Electrical coupling is achieved by coupling a right-angled isosceles triangular cavity with a regular triangular cavity, 4. The compact, highly selective, substrate-integrated, triangular-cavity, broadband bandstop filter of claim 3, wherein all of the internal coupling windows are located off-center on the side on which they reside.

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