A wide stopband substrate integrated waveguide filter with effective suppression of TE201 mode

Abstract

The present invention relates to the field of filters, and specifically to a wide stopband substrate integrated waveguide filter that effectively suppresses the TE201 mode. The present invention is based on a substrate integrated waveguide, and uses 136 metallized through-holes that penetrate a dielectric substrate and upper and lower metal layers to separate and construct five resonant cavities, all of which are square. The cavities are distributed in a right-angled arrangement, and adjacent resonant cavities are coupled in an inductive slot coupling manner, which suppresses the propagation of high-order modes between cavities, effectively suppressing the resonant frequency of high-order modes, especially the resonant frequency of the TE201 mode, thereby improving its wide stopband performance. In addition, the use of the right-angled arrangement of cavities makes the overall filter structure compact, reduces the filter size, and facilitates printing. The present invention also adopts an input structure of a stepped variable impedance feeding structure to suppress the excitation of high-order modes at the input end, especially the excitation of the TE201 mode, thereby improving out-of-band suppression and improving the performance of the filter.

Description

Technical Field

[0001] The present invention relates to the field of filters, and in particular to a substrate integrated waveguide filter with a wide stopband and effective TE201 mode suppression. Background Art

[0002] In recent years, wireless communication technology has developed rapidly, and multi-mode, multi-standard, and multi-band wireless communication services have been widely used. As an important component of the wireless communication system, the performance of the filter will have a direct impact on the signal quality of the entire wireless communication system.

[0003] While traditional filters can meet power handling and quality factor requirements, they are typically bulky and difficult to integrate with other planar structures in the system. Microstrip filters, while addressing these shortcomings, offer suboptimal performance at millimeter-wave frequencies. Substrate-integrated waveguide filters combine the advantages of both traditional and microstrip filters, offering low radiation loss, high quality factor, and ease of planarization.

[0004] However, traditional substrate-integrated waveguide filters require a relatively large area and have poor out-of-band suppression, which limits their practical applications. Summary of the Invention

[0005] In response to the above-mentioned problems or shortcomings, and to address the relatively large area and poor out-of-band suppression effects of existing filters, the present invention provides a substrate-integrated waveguide filter with a wide stopband that effectively suppresses the TE201 mode. The filter effectively suppresses the TE201 mode by adopting a right-angle cavity arrangement and selecting appropriate input / output feeding positions.

[0006] A wide stopband substrate integrated waveguide filter that effectively suppresses TE201 modes comprises a SIW body and a stepped variable impedance feeding structure.

[0007] The SIW body is provided with 136 metallized through holes, all of which penetrate the dielectric substrate and the upper and lower metal layers; the first resonant cavity, the second resonant cavity, the third resonant cavity, the fourth resonant cavity and the fifth resonant cavity, all of which are square, are separated and constructed by the 136 metallized through holes, totaling 5 resonant cavities.

[0008] Among them, the first resonant cavity, the second resonant cavity, the fourth resonant cavity and the fifth resonant cavity are distributed in a field shape, the first resonant cavity is adjacent to the second resonant cavity and the fourth resonant cavity respectively, the fifth resonant cavity is adjacent to the second resonant cavity and the fourth resonant cavity respectively, the first resonant cavity and the fifth resonant cavity have no common edges but a common vertex; the first resonant cavity, the second resonant cavity and the third resonant cavity are arranged in sequence in a straight line, the first resonant cavity is adjacent to the second resonant cavity, and the second resonant cavity is adjacent to the third resonant cavity.

[0009] Two adjacent resonant cavities are coupled in an inductive slot coupling manner, and the inductive slot is centrally arranged on a common side of the adjacent resonant cavities.

[0010] There are two stepped variable impedance feeding structures, which serve as an input end and an output end respectively; based on the direction from the first resonant cavity to the third resonant cavity, the input end is centered on the left side of the first resonant cavity in this direction, and the output end is centered on the right side of the third resonant cavity in this direction.

[0011] The stepped variable impedance feeding structure is divided into two parts: the feeding substrate and the internal feeding structure. The internal feeding structure is adaptively located in the center of the feeding substrate, and the outer edges of the two are hollowed out. From the outside to the inside, the feeding substrate is divided into two rectangular sections that gradually narrow in a step-like manner. From the outside to the inside, the internal feeding structure is divided into three rectangular sections that gradually narrow in a step-like manner.

[0012] Furthermore, the side length of the square resonant cavity is 5.1 mm-5.3 mm.

[0013] Furthermore, the inductive slot (coupling gap) has a width of 0.5 mm to 2.0 mm.

[0014] Furthermore, the thickness of the dielectric substrate is 0.508 mm and the dielectric constant is 2.2.

[0015] Furthermore, the stepped variable impedance feeding structure is a microstrip line.

[0016] In summary, the present invention is based on a substrate integrated waveguide, and uses 136 metallized through-holes that penetrate the dielectric substrate and the upper and lower metal layers to separate and construct the first resonant cavity, the second resonant cavity, the third resonant cavity, the fourth resonant cavity, and the fifth resonant cavity, all of which are square. These five resonant cavities are distributed in a right-angled row of cavities, and adjacent resonant cavities are coupled in an inductive slot coupling manner, which suppresses the propagation of high-order modes between cavities, effectively suppressing the resonant frequency of high-order modes, especially the resonant frequency of the TE201 mode, thereby improving its wide stopband performance. In addition, due to the use of a right-angled row of cavities, the overall filter structure is compact, the filter size is reduced, and printing is simple. The present invention also adopts an input structure of a stepped variable impedance feeding structure to suppress the excitation of high-order modes at the input end, especially the excitation of the TE201 mode, thereby achieving an improvement in out-of-band suppression and improving the performance of the filter. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 is a top view of the present invention;

[0018] Figure 2 It is an enlarged view of the stepped variable impedance feeding structure;

[0019] Figure 3 is the S parameter result of the simulation test of the embodiment sample;

[0020] Figure 4 is the field distribution diagram of the embodiment sample;

[0021] Figure numerals: 1-dielectric substrate, 2-top metal layer, 3-bottom metal layer, 4-input end, 5-output end, 6-metallized through hole, a-first resonant cavity, b-second resonant cavity; c-third resonant cavity, d-fourth resonant cavity, e-fifth resonant cavity. DETAILED DESCRIPTION

[0022] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0023] In this embodiment, a wide stopband substrate integrated waveguide filter that effectively suppresses the TE201 mode has the following specific parameters:

[0024] The relative dielectric constant ε of the dielectric substrate is 2.2, the loss tangent value σ is 0.0009, the thickness of the dielectric substrate is t=0.508 mm, the diameter of the metallized through hole is 0.3 mm, and the center-to-center distance p between adjacent metallized through holes in the same row is 0.47 mm.

[0025] The side length of resonant cavity a (first resonant cavity) is La = 5.25 mm, the side length of resonant cavity b (second resonant cavity) is Lb = 5.15 mm, the side length of resonant cavity c (third resonant cavity) is Lc = 5.28 mm, the side length of resonant cavity d (fourth resonant cavity) is Ld = 5.18 mm, and the side length of resonant cavity e (fifth resonant cavity) is Le = 5.23 mm. The gap width W between resonant cavities a and d is ad =1.9mm, the gap width W between the resonant cavities d and e de =1.55mm, the gap width W between resonant cavities b and e be =1.6mm, the gap width W between resonant cavities a and b ab =0.9mm, the gap width W between resonant cavities b and c bc =1.83mm.

[0026] The center node of the field shape formed by the first, second, fourth and fifth resonant cavities is used as the origin, and the cross in the middle of the field shape is used as the X and Y axes to construct a coordinate system. Starting from the origin, Le is taken in the positive direction of the X and Y axes to construct the fifth resonant cavity; Lb is taken in the positive direction of the X axis and the negative direction of the Y axis to construct the second resonant cavity; Ld is taken in the negative direction of the X axis and the positive direction of the Y axis to construct the fourth resonant cavity; La is taken in the negative direction of the X and Y axes to construct the fifth resonant cavity; then, the position of Le in the positive direction of the X axis is used as the vertex, and Lc is taken in the positive direction of the X axis as one side of the square to construct the third resonant cavity.

[0027] Stepped variable impedance feed structure: A three-stage stepped variable impedance feed is used. The internal feed structure has M1 = 4.27mm, N1 = 1.5mm, M2 = 1.5mm, N2 = 1mm, M3 = 3.4mm, and N3 = 0.6mm from the outside to the inside. The length and width of the feed substrate are M4 = 6.27mm, N4 = 3.25mm, M5 = 2.9mm, and N5 = 1mm from the outside to the inside. The input stepped variable impedance feed structure on the left is 0.025mm higher in the Y-axis direction than the output stepped variable impedance feed structure on the right.

[0028] According to the parameters of this embodiment, a wide stopband substrate integrated waveguide filter model that effectively suppresses TE201 mode is built in HFSS (see the attached figure). Figure 1 、 2 As shown in the figure), the wide stopband effectively suppresses the TE201 mode field distribution and transmission performance of the substrate integrated waveguide filter TE201. The final simulation mode field distribution is shown in the figure. Figure 4 As shown, it basically conforms to the TE101 mode field distribution and has a significant effect on suppressing the TE201 mode. The corresponding S parameter curve of the transmission performance is shown in Figure 3 As shown in the figure, the standing wave in the stop band at 27.5 GHz is 1.4 dB and the insertion loss is -33 dB.

[0029] As can be seen from the above embodiments, the present invention sets five resonant cavities, all of which are square resonant cavities and adopt a right-angled cavity arrangement method, which can effectively reduce the high-order mode resonant frequency inside the resonant cavity, especially in reducing the TE201 mode resonant frequency. This cavity arrangement method can also effectively push the high-order mode resonant frequency away, thereby achieving the wide stopband characteristics of this embodiment. At the same time, the use of a right-angled cavity arrangement method makes the filter structure more compact and achieves miniaturization. In addition, when selecting the feeding structure, this embodiment chooses to use a stepped coupling method for feeding, so that the filter can better suppress the high-order mode on the basis of normal operation, significantly reducing the high-order mode excited, especially reducing the TE201 mode excited, so that the performance of the filter proposed by the present invention in the range of 40-42GHz has been significantly improved.

Claims

1. A substrate integrated waveguide filter with an effectively suppressed TE201 mode in a wide stopband, comprising a SIW body and a stepped variable impedance feeding structure, characterized in that: The SIW body is provided with 136 metallized vias, all of which penetrate through the dielectric substrate and the upper and lower metal layers; the first resonator, the second resonator, the third resonator, the fourth resonator and the fifth resonator, all of which are square, are constructed by separating through 136 metallized vias, with a total of 5 resonators; Among them, the first resonator, the second resonator, the fourth resonator and the fifth resonator are arranged in a cross shape. The first resonator is adjacent to the second resonator and the fourth resonator respectively. The fifth resonator is adjacent to the second resonator and the fourth resonator respectively. The first resonator and the fifth resonator have no common side but a common vertex; the first resonator, the second resonator and the third resonator are arranged in a line in sequence. The first resonator and the second resonator are adjacent. The second resonator and the third resonator are adjacent; Two adjacent resonators are coupled in a manner of inductive slot coupling, and the inductive slot is centrally arranged on the common side of the adjacent resonators; There are two stepped variable impedance feeding structures, which are used as the input end and the output end respectively; based on the direction where the first resonator to the third resonator are located, the input end is centrally arranged on the left side of the first resonator in this direction, and the output end is centrally arranged on the right side of the third resonator in this direction; The stepped variable impedance feeding structure is divided into two parts: a feeding substrate and an internal feeding structure. The internal feeding structure is adaptively centered within the feeding substrate, and there is a hollow between their outer outlines; from the outside to the inside, the feeding substrate is divided into two rectangular segments that gradually narrow in a stepped manner, and from the outside to the inside, the internal feeding structure is divided into three rectangular segments that gradually narrow in a stepped manner.

2. The substrate integrated waveguide filter with a wide stopband and effective TE201 mode suppression according to claim 1, characterized in that: The side lengths of the square first resonator, second resonator, third resonator, fourth resonator and fifth resonator are all 5.1 mm - 5.3 mm.

3. The substrate integrated waveguide filter with a wide stopband and effective TE201 mode suppression according to claim 1, characterized in that: The width of the inductive slot is 0.5 mm - 2.0 mm.

4. The substrate integrated waveguide filter with a wide stopband and effective TE201 mode suppression according to claim 1, characterized in that: The thickness of the dielectric substrate is 0.508 mm, and the dielectric constant is 2.

2.

5. The substrate integrated waveguide filter with a wide stopband and effective TE201 mode suppression according to claim 1, characterized in that: The stepped variable impedance feeding structure is a microstrip line.

6. The substrate integrated waveguide filter with an effectively suppressed TE201 mode in a wide stopband according to claim 1, characterized in that: The side length of the first resonant cavity is La = 5.25mm, the side length of the second resonant cavity is Lb = 5.15mm, the side length of the third resonant cavity is Lc = 5.28mm, the side length of the fourth resonant cavity is Ld = 5.18mm, and the side length of the fifth resonant cavity is Le = 5.23mm; the width of the gap between the first and fourth resonant cavities is W ad =1.9mm, the gap width between the fourth and fifth resonant cavities is W de =1.55mm, the gap width between the fifth and second resonant cavities W be =1.6mm, the gap width between the first and second resonant cavities W ab =0.9mm, the gap width between the second and third resonant cavities is W bc =1.83mm; The thickness t of the dielectric substrate is 0.508 mm, the dielectric constant ε is 2.2, the diameter of the metallized via is 0.3 mm, and the center-to-center distance p of adjacent metallized vias in the same row is 0.47 mm; Taking the central node of the cross shape in the cross formed by the first, second, fourth and fifth resonators as the origin, and the cross in the middle of the cross shape as the X and Y axes to construct a coordinate system. Starting from the origin respectively: taking Le in the positive directions of the X and Y axes respectively to construct the fifth resonator; Taking Lb in the positive direction of the X axis and the negative direction of the Y axis respectively to construct the second resonator; taking Ld in the negative direction of the X axis and the positive direction of the Y axis respectively to construct the fourth resonator; taking La in the negative directions of the X and Y axes respectively to construct the fifth resonator; then, taking the position of Le in the positive direction of the X axis as the vertex, and taking Lc in the positive direction of the X axis again as one side of the square to construct the third resonator; The stepped variable impedance feeding structure: its internal feeding structure has a first section feeding structure length M1 = 4.27mm and a width N1 = 1.5mm from the outside to the inside; a second section feeding structure length M2 = 1.5mm and a width N2 = 1mm; a third section feeding structure length M3 = 3.4mm and a width N3 = 0.6mm; the length and width of the feeding substrate have a first section substrate length M4 = 6.27mm and a width N4 = 3.25mm from the outside to the inside, and a second section substrate length M5 = 2.9mm and a width N5 = 1mm; the input stepped variable impedance feeding structure on the left is 0.025mm higher in the Y-axis direction than the output stepped variable impedance feeding structure on the right.

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