Hybrid-mode based substrate integrated waveguide dual-band filter

Abstract

The application provides a hybrid mode based substrate integrated waveguide dual-passband filter, belonging to the microwave field, comprising a top metal layer, a middle dielectric layer and a bottom metal layer arranged in sequence from top to bottom; the middle dielectric layer is provided with first to fourth resonant cavities in the form of isosceles right-angled triangles formed by uniformly arranged metal via columns along the diagonal and the parallel direction of the side of the middle dielectric layer; two gaps are respectively reserved on the metal via columns between the first resonant cavity and the second resonant cavity, between the second resonant cavity and the third resonant cavity and between the third resonant cavity and the fourth resonant cavity, one of the gaps is located at the right angle of the triangle, and the other gap is located at the middle of the right angle side of the triangle; two metal tuning columns are respectively arranged in the first resonant cavity and the fourth resonant cavity, and one metal tuning column is respectively arranged in the second resonant cavity and the third resonant cavity; the oblique sides of the first resonant cavity and the fourth resonant cavity are respectively connected with a microstrip line on the top metal layer; and the filter realizes the filtering effect of four-order dual-passband under the condition that the size of the filter is unchanged.

Description

Technical Field

[0001] This invention relates to the field of microwave technology, and more particularly to a substrate integrated waveguide dual-passband filter based on hybrid modes. Background Technology

[0002] Substrate integrated waveguide (SIW) technology, combining the low loss and high Q value of traditional metallic waveguides with the low cost and ease of fabrication of microstrip structures, has been widely used in millimeter-wave and high-frequency communication systems. However, traditional SIW filters often suffer from structural complexity, adjustment difficulties, and high insertion loss in achieving multi-band communication and bandwidth control, increasing the difficulty of design and manufacturing. In recent years, hybrid-mode filter design has begun to attract attention. This design approach utilizes the interaction between different electromagnetic field modes in a resonant cavity to achieve multi-frequency response in a single structure, providing a new development path for the realization of dual-passband filters. By designing the geometry of the resonant cavity, multiple resonant modes can be excited simultaneously, and frequency selectivity and bandwidth control can be achieved using appropriate coupling methods. Due to its unique geometric characteristics, the triangular resonant cavity is easy to form various different layout structures, increasing design flexibility and making it easier to integrate in microwave circuits.

[0003] For example, the Chinese invention patent application CN113300065A, entitled "Hybrid-Mode Bandpass Filter Based on Triangular Substrate Integrated Waveguide," uses the coupling matrix transformation method to convert two resonant cavities with negative coupling coefficients into a single dual-mode resonant cavity, introducing a pair of transmission zeros, improving out-of-band rejection, and making the overall filter smaller. However, it is still a fourth-order single-passband filter. How to design filters that achieve multi-passband filtering effects without changing size, while still possessing high selectivity, low insertion loss, and ease of fabrication, has become a pressing problem in this field. Summary of the Invention

[0004] The technical problem to be solved by this invention is: how to design a filter to achieve the filtering effect of a fourth-order dual-passband filter without changing its size.

[0005] This invention solves the above-mentioned technical problems through the following technical solution: a substrate-integrated waveguide dual-passband filter based on a hybrid mode. The filter includes a top metal layer, an intermediate dielectric layer, and a bottom metal layer stacked sequentially from top to bottom. On the intermediate dielectric layer, uniformly arranged metal vias along its diagonal and parallel directions form first to fourth resonant cavities in the shape of isosceles right triangles. Two gaps are left on the metal vias between the first and second resonant cavities, between the second and third resonant cavities, and between the third and fourth resonant cavities. One gap is located at the right angle of the triangle, and the other gap is located in the middle of the right angle side of the triangle. There are two metal tuning pillars in the first and fourth resonant cavities. One metal tuning pillar is close to the right angle side, and the other metal tuning pillar is close to the other right angle side and located between the two gaps. There is one metal tuning pillar in the second and third resonant cavities. The metal tuning pillar is located on the perpendicular bisector of the hypotenuse of the triangle. On the top metal layer, the hypotenuses of the first and fourth resonant cavities are connected to a microstrip line.

[0006] Beneficial effects: This invention utilizes the characteristics between different modes of an isosceles right-angled triangular resonant cavity to construct two different coupling gaps to control the energy conduction in the TM130 and TM230 modes. The TM130 is mainly coupled through the middle gap, while the TM230 is coupled through both gaps simultaneously. Different numbers of metal tuning pillars are set at different positions to fine-tune the operating frequency of one mode without affecting the other mode. This design does not increase the area and can generate two fourth-order passbands while maintaining high selectivity.

[0007] Preferably, the length of the gap located at the right angle of the triangle is less than the length of the gap located in the middle of the right angle side of the triangle.

[0008] Beneficial effects: This invention controls the energy conduction in two modes, TM130 and TM230, by using coupling gaps of different sizes. TM130 mainly couples through the middle gap, while the gap at the right angle of the triangle hardly couples. TM230 couples through both gaps simultaneously.

[0009] Preferably, in TM130 mode, energy is coupled through the gap in the middle of the right-angled side of the triangle, while in TM230 mode, energy is coupled through two gaps.

[0010] Preferably, changing the spacing between the two metal tuning pillars in the first and fourth resonant cavities can adjust the resonant frequency of the TM230 mode and the coupling between the resonant cavities; changing the diameter of the metal tuning pillars and the distance between the metal tuning pillars in the second and third resonant cavities and the right angle of the triangle can simultaneously fine-tune the frequency, coupling, and filter matching of the TM130 and TM230 modes.

[0011] Beneficial effects: The two metal tuning pillars in the first and fourth resonant cavities of this invention are located at the weakest point of the electric field of the TM130 mode, mainly controlling the resonant frequency of the TM230 mode. By changing the spacing between the two metal tuning pillars in the first and fourth resonant cavities, the resonant frequency of the TM230 mode and the coupling between the resonant cavities can be controlled. The metal tuning pillars in the second and third resonant cavities are located on the perpendicular bisector of the hypotenuse of the resonant cavity, at the weaker point of the electric field of the two modes, and are used to simultaneously fine-tune the frequency of the two modes. By changing the diameter of the metal tuning pillars and the distance between the metal tuning pillars in the second and third resonant cavities and the right angle of the triangle, the frequency, coupling, and filter matching of the TM130 and TM230 modes can be simultaneously fine-tuned.

[0012] Preferably, the area of ​​the top metal layer is larger than the area of ​​the filter resonant cavity and smaller than the area of ​​the intermediate dielectric layer, and the area of ​​the intermediate dielectric layer is equal to the area of ​​the bottom metal layer.

[0013] Preferably, the microstrip line extends to the edge of the intermediate dielectric layer, and no metal via array is provided at the connection between the microstrip line and the first resonant cavity and the fourth resonant cavity.

[0014] Preferably, the microstrip line is located between the midpoint and the apex of the hypotenuse of the first and fourth resonant cavities, and fine grooves extending into the resonant cavity are respectively opened at the connection points between the microstrip line and the first resonant cavity and between the microstrip line and the fourth resonant cavity.

[0015] Beneficial effects: The present invention has a coplanar waveguide transition structure designed between the two microstrip lines and the resonant cavity, which can improve the impedance matching degree and reduce the insertion loss.

[0016] Preferably, the impedance of the microstrip line is 50 ohms.

[0017] Preferably, the material of the intermediate dielectric layer is Rogers RT / duroid 5880 with a dielectric constant of 2.2.

[0018] Preferably, the filter has an axisymmetric structure.

[0019] The advantages of this invention are as follows: the dual-passband filter is designed with a closed structure, which has strong anti-electromagnetic interference capability; the dual-passband filter is an axisymmetric structure, and without increasing the size, it achieves high selectivity and low insertion loss fourth-order dual-passband filtering characteristics by optimizing the resonant cavity structure and coupling mechanism. Compared with the same type of single-passband filter, it does not increase the structural complexity, and the overall design is compact and concise, meeting the characteristics of miniaturization, easy processing and low cost of microwave devices, and has good application prospects in weather radar, satellite communication and other fields. Attached Figure Description

[0020] Figure 1A three-dimensional view of a substrate-integrated waveguide dual-passband filter based on a hybrid mode, provided in an embodiment of the present invention;

[0021] Figure 2 An exploded view of a substrate-integrated waveguide dual-passband filter based on a hybrid mode, provided in an embodiment of the present invention;

[0022] Figure 3 A top view of a substrate-integrated waveguide dual-passband filter based on hybrid mode provided in an embodiment of the present invention;

[0023] Figure 4 A schematic diagram of the electric field distribution and coupling of a substrate integrated waveguide dual-passband filter based on hybrid mode in TM130 mode, provided for an embodiment of the present invention;

[0024] Figure 5 A schematic diagram of the electric field distribution and coupling of a substrate integrated waveguide dual-passband filter based on hybrid mode in TM230 mode, provided for an embodiment of the present invention;

[0025] Figure 6 The simulation waveform of the S-parameters of the substrate integrated waveguide dual-passband filter based on hybrid mode provided in the embodiments of the present invention;

[0026] In the diagram: 1 top metal layer, 11 microstrip line, 111 fine trench, 2 intermediate dielectric layer, 3 bottom metal layer, 4 metal via array, 5 metal tuning pillar. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to specific embodiments and accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0028] See Figure 1This embodiment provides a substrate-integrated waveguide dual-passband filter based on a hybrid mode, comprising a top metal layer 1, an intermediate dielectric layer 2, and a bottom metal layer 3 stacked sequentially from top to bottom. On the intermediate dielectric layer 2, uniformly arranged metal vias 4 along its diagonals and parallel to its sides constitute a first resonant cavity 21, a second resonant cavity 22, a third resonant cavity 23, and a fourth resonant cavity 24. The first resonant cavity 21 to the fourth resonant cavity 24 are all isosceles right-angled triangular resonant cavities. Metal vias are arranged between the first resonant cavity 21 and the second resonant cavity 22, between the second resonant cavity 22 and the third resonant cavity 23, and between the third resonant cavity 23 and the fourth resonant cavity 24. Two gaps, serving as coupling windows, are left on the aperture array 4. One gap is located at the right angle of the triangle, and the other gap is located in the middle of the right angle side of the triangle. The first resonant cavity 21 and the fourth resonant cavity 24 each have two metal tuning pillars 5. One metal tuning pillar 5 is close to the right angle side of the triangle, and the other metal tuning pillar 5 is close to the other right angle side of the triangle and is located between the two gaps. The second resonant cavity 22 and the third resonant cavity 23 each have one metal tuning pillar 5. The metal tuning pillar 5 is located on the perpendicular bisector of the hypotenuse of the triangle. On the top metal layer 1, the hypotenuses of the first resonant cavity 21 and the fourth resonant cavity 24 are respectively connected to a microstrip line 11.

[0029] This invention utilizes the characteristics between different modes of an isosceles right-angled triangular resonant cavity to construct two different coupling gaps to control energy conduction in two modes: TM130 and TM230. TM130 is mainly coupled through the middle gap, while TM230 is coupled through both gaps simultaneously. Different numbers of metal tuning pillars are placed at different positions to fine-tune the operating frequency of one mode without affecting the other. This design does not increase the area and can generate two fourth-order passbands while maintaining high selectivity.

[0030] This invention controls the energy conduction in two modes, TM130 and TM230, by using coupling gaps of different sizes. TM130 mainly couples through the middle gap, while the gap at the right angle of the triangle hardly couples. TM230 couples through both gaps simultaneously. Changing the spacing of the gaps can control the coupling amount of the two modes at the same time, thereby controlling the bandwidth and matching of the filter. The two metal tuning pillars 5 in the first resonant cavity 21 and the fourth resonant cavity 24 are located at the weakest point of the electric field of the TM130 mode, mainly controlling the resonant frequency of the TM230 mode. By changing the distance S1 between the two metal tuning pillars 5 in the first resonant cavity 21 and the fourth resonant cavity 24, the resonant frequency of the TM230 mode and the coupling between the resonant cavities can be controlled. The metal tuning pillars 5 in the second resonant cavity 22 and the third resonant cavity 23 are located on the perpendicular bisector of the hypotenuse of the resonant cavity, at the weaker point of the electric field of the two modes, and are used to fine-tune the frequency of the two modes simultaneously. By changing the diameter of the metal tuning pillars 5 and the distance S2 between the metal tuning pillars 5 in the second resonant cavity 22 and the right angle of the triangle, the frequency, coupling and filter matching of the TM130 and TM230 modes can be fine-tuned simultaneously.

[0031] The area of ​​the top metal layer 1 is slightly larger than the area of ​​the filter resonant cavity but smaller than the area of ​​the intermediate dielectric layer 2. The size of the top metal layer 1 completely covers the size of the four resonant cavities, and the area of ​​the intermediate dielectric layer 2 is equal to the area of ​​the bottom metal layer 3. Metal vias can be formed on the top metal layer 1 and the bottom metal layer 3, and the positions of these metal vias correspond to the positions of the metal vias 4 on the intermediate dielectric layer 2.

[0032] The microstrip line 11 has an impedance of 50 ohms and extends to the edge of the intermediate dielectric layer 2. No metal vias 4 are provided at the connection points between the microstrip line 11 and the first resonant cavity 21, and between the microstrip line 11 and the fourth resonant cavity 24. The microstrip line 11 is located between the midpoint of the hypotenuse of the first resonant cavity 21 and the 45-degree apex angle of the fourth resonant cavity 24. Fine grooves 111 extending into the resonant cavity are respectively formed at the connection points between the microstrip line 11 and the first resonant cavity 21, and between the microstrip line 11 and the fourth resonant cavity 24. The width of the fine groove 111 is K = 0.4 mm. A coplanar waveguide transition structure is designed between each of the two microstrip lines 11 and the resonant cavity, which can improve impedance matching and reduce insertion loss. One of the two microstrip lines 11 serves as a signal input port, and the other as a signal output port.

[0033] The top metal layer 1 and the bottom metal layer 3 are both made of copper with a thickness of 35 micrometers. The intermediate dielectric layer 2 is made of Rogers RT / duroid 5880 with a dielectric constant of 2.2 and a thickness of 0.508 mm.

[0034] Four isosceles right-angled triangular resonators are combined to form a square fourth-order filter. All four resonators are on the same layer and have the same height. Adjacent resonators share a common metal via array 4. The filter has an axisymmetric structure. The overall dimensions of the dual-band filter are 34mm × 34mm × 0.578mm. (See [reference needed]). Figure 3 The hypotenuse of the isosceles right-angled triangular resonant cavity has a length L = 28.3 mm, the length of the microstrip line 11 is T = 7.87 mm, the distance S1 between the two metal tuning posts 5 in the first resonant cavity 21 and the fourth resonant cavity 24 is 5.6 mm, the distance S2 between the metal tuning posts 5 and the right angle of the triangle in the second resonant cavity 22 and the third resonant cavity 23 is 8.61 mm, and the diameter D of the metal tuning posts 5 is 0.5 mm. The distance between the first resonant cavity 21 and the second resonant cavity 22, and between the third resonant cavity 23 and... On the metal through-hole row 4 between the fourth resonant cavities 24, the length P2 of the gap located at the right angle of the triangle is less than the length P1 of the gap located in the middle of the right angle side of the triangle, where P1=4.6mm and P2=3.78mm. On the metal through-hole row 4 between the second resonant cavity 22 and the third resonant cavity 23, the length P3 of the gap located at the right angle of the triangle is less than the length P4 of the gap located in the middle of the right angle side of the triangle, where P3=2.9mm and P4=4.05mm.

[0035] The dual-passband filter of this invention is designed with a closed structure, which has strong anti-electromagnetic interference capability. The dual-passband filter has an axisymmetric structure. Without increasing the size, it achieves high selectivity and low insertion loss fourth-order dual-passband filtering characteristics by optimizing the resonant cavity structure and coupling mechanism. Compared with the same type of single-passband filter, it does not increase the structural complexity. The overall design is compact and simplified, which meets the characteristics of microwave device miniaturization, easy processing and low cost. It has good application prospects in weather radar, satellite communication and other fields.

[0036] Figure 6 The image shows the S-parameter simulation waveforms of the dual-passband filter of this invention. The horizontal axis represents frequency in GHz, and the vertical axis represents S-parameters in dB. The solid line represents the relationship between the electromagnetic wave reflection coefficient and frequency of the dual-passband filter, and the dashed line represents the relationship between the electromagnetic wave transmission coefficient and frequency. The center frequencies of the two frequency bands are 15.5 GHz and 18.35 GHz, respectively, with operating relative bandwidths of 5% and 3%. The return loss is below -17 dB for both bands, and the in-band insertion loss is greater than -1.5 dB and -2.6 dB, respectively. Out-of-band suppression is good, and the isolation between the two frequency bands is excellent. The operating frequency can be fine-tuned by adjusting the diameter and position of the metal tuning post. Figure 6 This demonstrates that the present invention has good matching characteristics within the operating frequency band.

[0037] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A substrate-integrated waveguide dual-passband filter based on hybrid mode, characterized in that: The filter comprises a top metal layer, an intermediate dielectric layer, and a bottom metal layer stacked sequentially from top to bottom. On the intermediate dielectric layer, uniformly arranged metal vias along its diagonal and parallel sides form first to fourth resonant cavities in the shape of isosceles right triangles. Two gaps are left on the metal vias between the first and second resonant cavities, between the second and third resonant cavities, and between the third and fourth resonant cavities. One gap is located at the right angle of the triangle, and the other gap is located in the middle of the right angle side. The first and fourth resonant cavities each contain two metal tuning pillars: one close to the right angle side, and the other close to the other right angle side and located between the two gaps. The second and third resonant cavities each contain one metal tuning pillar located on the perpendicular bisector of the hypotenuse of the triangle. On the top metal layer, the hypotenuses of the first and fourth resonant cavities are each connected to a microstrip line.

2. The substrate integrated waveguide dual-passband filter based on hybrid mode according to claim 1, characterized in that: The length of the gap located at the right angle of the triangle is less than the length of the gap located in the middle of the right angle side of the triangle.

3. The substrate integrated waveguide dual-passband filter based on hybrid mode according to claim 1, characterized in that: In TM130 mode, energy is coupled through the gap in the middle of the right-angled side of the triangle, while in TM230 mode, energy is coupled through two gaps.

4. The substrate integrated waveguide dual-passband filter based on hybrid mode according to claim 1, characterized in that: Changing the spacing between the two metal tuning pillars in the first and fourth resonant cavities can adjust the resonant frequency of the TM230 mode and the coupling between the resonant cavities; changing the diameter of the metal tuning pillars and the distance between the metal tuning pillars in the second and third resonant cavities and the right angle of the triangle can simultaneously fine-tune the frequency, coupling, and filter matching of the TM130 and TM230 modes.

5. The substrate integrated waveguide dual-passband filter based on hybrid mode according to claim 1, characterized in that: The area of ​​the top metal layer is larger than the area of ​​the filter resonant cavity but smaller than the area of ​​the intermediate dielectric layer, and the area of ​​the intermediate dielectric layer is equal to the area of ​​the bottom metal layer.

6. The substrate integrated waveguide dual-passband filter based on hybrid mode according to claim 1, characterized in that: The microstrip line extends to the edge of the intermediate dielectric layer, and no metal vias are provided at the connection between the microstrip line and the first resonant cavity, or between the microstrip line and the fourth resonant cavity.

7. The substrate integrated waveguide dual-passband filter based on hybrid mode according to claim 1, characterized in that: The microstrip line is located between the midpoint and the apex of the hypotenuse of the first and fourth resonant cavities. At the connection points between the microstrip line and the first resonant cavity and the microstrip line and the fourth resonant cavity, there are fine slots extending into the resonant cavity.

8. The substrate integrated waveguide dual-passband filter based on hybrid mode according to claim 1, characterized in that: The impedance of the microstrip line is 50 ohms.

9. The substrate integrated waveguide dual-passband filter based on hybrid mode according to claim 1, characterized in that: The intermediate dielectric layer is made of Rogers RT / duroid 5880 with a dielectric constant of 2.

2.

10. The substrate integrated waveguide dual-passband filter based on hybrid mode according to claim 1, characterized in that: The filter has an axisymmetric structure.

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