Substrate integrated waveguide dual-passband filter based on mixed mode

Abstract

The invention provides a mixed-mode-based substrate integrated waveguide dual-passband filter, which belongs to the field of microwaves and comprises a top metal layer, a middle dielectric layer and a bottom metal layer which are sequentially stacked from top to bottom, metal through hole columns are uniformly distributed on the middle dielectric layer along the parallel directions of the diagonal lines and the edges of the middle dielectric layer to form first to fourth resonant cavities in the shape of an isosceles right triangle; two gaps are reserved in the metal through hole 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 respectively, one gap is located at the right-angle position of the triangle, and the other gap is located in the middle of the right-angle side of the triangle. The first resonant cavity and the fourth resonant cavity are respectively provided with two metal tuning columns, the second resonant cavity and the third resonant cavity are respectively provided with one metal tuning column, and on the top metal layer, the bevel edges of the first resonant cavity and the fourth resonant cavity are respectively connected with one microstrip line; and a fourth-order dual-passband filtering effect is realized under the condition that the size of the filter is not changed.

Description

Technical Field

[0001] The present invention relates to the field of microwave technology, in particular to a substrate integrated waveguide dual-passband filter based on a hybrid mode. Background Art

[0002] Substrate Integrated Waveguide (SIW) technology has been widely used in millimeter-wave and high-frequency communication systems, combining the low loss and high Q of traditional metal waveguides with the low cost and ease of fabrication of microstrip structures. However, traditional SIW filters often suffer from complex structures, difficult tuning, and high insertion loss when implementing multi-band communications and bandwidth control, complicating their design and fabrication. In recent years, hybrid-mode filter designs have gained attention. This design approach exploits the interaction between different electromagnetic field modes within a resonant cavity to achieve multi-frequency response within a single structure, providing a new approach for the realization of dual-band filters. By designing the cavity geometry, multiple resonant modes can be simultaneously excited, and appropriate coupling methods can be used to achieve frequency selectivity and bandwidth control. The unique geometric properties of triangular resonant cavities facilitate the formation of a variety of different layouts, increasing design flexibility and facilitating integration into microwave circuits.

[0003] For example, Chinese invention patent application CN113300065A, "Mixed-Mode Bandpass Filter Based on Triangular Substrate Integrated Waveguide," utilizes a coupling matrix transformation method to transform two resonant cavities with negative coupling coefficients into a single dual-mode resonant cavity. This introduces a pair of transmission zeros, improving out-of-band rejection and making the filter smaller overall, while still a fourth-order single-passband filter. Designing a filter that maintains multi-passband filtering while maintaining high selectivity, low insertion loss, and ease of fabrication has become a pressing challenge in this field. Summary of the Invention

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

[0005] The present invention solves the above-mentioned technical problems through the following technical solutions: a substrate-integrated waveguide dual-passband filter based on a hybrid mode, comprising a top metal layer, an intermediate dielectric layer, and a bottom metal layer stacked sequentially from top to bottom. On the intermediate dielectric layer, rows of metal through-holes are uniformly arranged along its diagonals and parallel to its sides, forming first to fourth resonant cavities in the shape of an isosceles right triangle. Two gaps are left in the rows of metal through-holes between the first and second resonant cavities, between the second and third resonant cavities, and between the third and fourth resonant cavities, respectively: one gap is located at the right angle of the triangle, and the other gap is located between the right-angled sides of the triangle. Two metal tuning posts are respectively provided in the first and fourth resonant cavities, one metal tuning post is located near the right-angled side, and the other metal tuning post is located near the other right-angled side and between the two gaps. The second and third resonant cavities each have one metal tuning post 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.

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

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

[0008] Beneficial effect: The present invention controls the energy conduction in the TM130 and TM230 modes through coupling gaps of different sizes. TM130 is mainly coupled through the gap in the middle, while the gaps at the right angles of the triangle hardly couple energy. TM230 is coupled through both gaps at the same time.

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

[0010] Preferably, by changing the spacing between the two metal tuning columns in the first resonant cavity and the fourth resonant cavity, the resonant frequency of the TM230 mode and the coupling amount between the resonant cavities can be adjusted; by changing the diameter of the metal tuning column and the distance between the metal tuning column and the right angle of the triangle in the second resonant cavity and the third resonant cavity, the frequency, coupling and filter matching of the TM130 and TM230 modes can be fine-tuned at the same time.

[0011] Beneficial effects: The two metal tuning columns in the first and fourth resonant cavities of the present invention are both located at the weakest point of the TM130 mode electric field, mainly regulating the resonant frequency of the TM230 mode. By changing the spacing between the two metal tuning columns in the first and fourth resonant cavities, the resonant frequency of the TM230 mode and the coupling amount between the resonant cavities can be regulated; the metal tuning columns in the second and third resonant cavities are located on the perpendicular bisectors of the hypotenuse of the resonant cavities, at the weaker point of the electric fields of the two modes, and are used to fine-tune the frequencies of the two modes at the same time. By changing the diameter of the metal tuning columns and the distance between the metal tuning columns and the right angles of the triangle in the second and third resonant cavities, the frequencies, coupling and filter matching of the TM130 and TM230 modes can be fine-tuned at the same time.

[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 middle dielectric layer, and the area of ​​the middle 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 through-hole array is provided at the connection between the microstrip line and the first resonant cavity, or at the connection between the microstrip line and the fourth resonant cavity.

[0014] Preferably, the microstrip line is located between the midpoint and the top angle of the oblique sides of the first and fourth resonant cavities, and thin grooves extending into the resonant cavities are respectively opened at the connection points between the microstrip line and the first resonant cavity and the microstrip line and the fourth resonant cavity.

[0015] Beneficial effects: A coplanar waveguide transition structure is 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 provided by the present invention are: the dual-passband filter of the present invention is designed as a closed structure and has strong anti-electromagnetic interference capability; the dual-passband filter is an axisymmetric structure, and without increasing the size, by optimizing the resonant cavity structure and coupling mechanism, a fourth-order dual-passband filtering characteristic with high selectivity and low insertion loss is achieved. Compared with the same type of single-passband filter, there is no increase in structural complexity, and the overall design is compact and streamlined, meeting the characteristics of miniaturization, easy processing and low cost of microwave devices, and has good application prospects in meteorological radar, satellite communications and other aspects. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1A three-dimensional diagram of a hybrid-mode substrate-integrated waveguide dual-passband filter provided by an embodiment of the present invention; Figure 2 An exploded diagram of a hybrid-mode substrate-integrated waveguide dual-passband filter provided by an embodiment of the present invention; Figure 3 A top view of a hybrid-mode substrate-integrated waveguide dual-passband filter provided in an embodiment of the present invention; Figure 4 A schematic diagram of the electric field distribution and coupling of a hybrid-mode substrate-integrated waveguide dual-passband filter in TM130 mode provided by an embodiment of the present invention; Figure 5 A schematic diagram of the electric field distribution and coupling of a hybrid-mode substrate-integrated waveguide dual-passband filter in TM230 mode provided by an embodiment of the present invention; Figure 6 The S-parameter simulation waveform of the hybrid-mode substrate-integrated waveguide dual-passband filter provided in an embodiment of the present invention; In the figure: 1 top metal layer, 11 microstrip line, 111 fine slot, 2 middle dielectric layer, 3 bottom metal layer, 4 metal through hole array, 5 metal tuning column. DETAILED DESCRIPTION

[0021] To make the objectives, technical solutions, and advantages of the present invention more clearly understood, the following describes the technical solutions of the present invention clearly and completely with reference to specific embodiments and the accompanying drawings. It is obvious that the embodiments described are only part of the embodiments of the present invention, not all of them. All other embodiments obtained by persons of ordinary skill in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0022] See also Figure 1The present 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 in sequence from top to bottom. On the intermediate dielectric layer 2, there are evenly arranged metal through-hole rows 4 along its diagonal lines and parallel directions to form 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 triangle resonant cavities. The metal through-holes 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 are arranged in a uniform manner. Two gaps are left on the hole array 4 as coupling windows, wherein one gap is located at the right angle of the triangle, and the other gap is located in the middle of the right-angled side of the triangle. There are two metal tuning posts 5 in the first resonant cavity 21 and the fourth resonant cavity 24 respectively, one metal tuning post 5 is close to the right-angled side of the triangle, and the other metal tuning post 5 is close to the other right-angled side of the triangle and located between the two gaps. There is a metal tuning post 5 in the second resonant cavity 22 and the third resonant cavity 23 respectively, and the metal tuning post 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 connected to a microstrip line 11 respectively.

[0023] The present invention utilizes the characteristics of different modes in an isosceles right-angled triangle resonant cavity to construct two different coupling gaps to control the conduction of energy in the TM130 and TM230 modes. TM130 is coupled primarily through the middle gap, while TM230 is coupled simultaneously through both gaps. Different numbers of metal tuning posts are arranged at different positions to fine-tune the operating frequency of one mode without affecting the other. This design does not increase additional area, can generate two fourth-order passbands, and maintains high selectivity.

[0024] The present invention controls the energy conduction in the TM130 and TM230 modes through coupling gaps of different sizes. TM130 mainly couples through the gap in the middle, while the gaps at the right angles of the triangle hardly couple energy. TM230 couples through two gaps at the same time. By changing the spacing between the gaps, the coupling amount of the two modes can be simultaneously controlled, thereby controlling the bandwidth and matching of the filter. The two metal tuning posts 5 in the first resonant cavity 21 and the fourth resonant cavity 24 are both located at the weakest point of the TM130 mode electric field, and are mainly used to control the resonant frequency of the TM230 mode. By changing the spacing S1 between the two metal tuning posts 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 posts 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 weakest point of the electric field of the two modes, and are used to fine-tune the frequencies of the two modes simultaneously. By changing the diameter of the metal tuning posts 5 and 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, the frequencies, coupling, and filter matching of the TM130 and TM230 modes can be fine-tuned simultaneously.

[0025] The area of ​​the top metal layer 1 is slightly larger than the area of ​​the filter resonant cavity and smaller than the area of ​​the intermediate dielectric layer 2. The top metal layer 1 is sized to completely cover the four resonant cavities, and the area of ​​the intermediate dielectric layer 2 is equal to that of the bottom metal layer 3. Metal via arrays can be provided on each of the top metal layer 1 and the bottom metal layer 3. These metal via arrays correspond to the positions of the metal via array 4 on the intermediate dielectric layer 2.

[0026] The impedance of the microstrip line 11 is 50 ohms. The microstrip line 11 extends to the edge of the intermediate dielectric layer 2. No metal through-hole array 4 is provided at the connection between the microstrip line 11 and the first resonant cavity 21 or the connection 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 fourth resonant cavity 24 and the 45-degree vertex angle. A fine groove 111 extending into the resonant cavity is provided at the connection between the microstrip line 11 and the first resonant cavity 21 or the connection 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 the two microstrip lines 11 and the resonant cavity of the present invention, which can improve the impedance matching and reduce the insertion loss. One of the two microstrip lines 11 serves as a signal input port, and the other serves as a signal output port.

[0027] The top metal layer 1 and bottom metal layer 3 are both made of copper, with a thickness of 35 microns. The middle dielectric layer 2 is made of Rogers RT / duroid 5880, with a dielectric constant of 2.2 and a thickness of 0.508 mm. Four isosceles right-angled triangle resonators are combined into a square fourth-order filter. The four isosceles right-angled triangle resonators are all on the same layer and have equal heights. Two adjacent isosceles right-angled triangle resonators share a metal through-hole row 4. The filter is an axisymmetric structure. The size of the entire dual-band filter is 34mm×34mm×0.578mm. Figure 3 The hypotenuse length L of the isosceles right triangle resonant cavity is 28.3 mm, the length T of the microstrip line 11 is 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, the diameter D of the metal tuning post 5 is 0.5 mm, and 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 array 4 between the fourth resonant cavity 24, the length P2 of the gap at the right angle of the triangle is smaller than the length P1 of the gap located in the middle of the right-angled side of the triangle, where P1 = 4.6 mm and P2 = 3.78 mm. On the metal through-hole array 4 between the second resonant cavity 22 and the third resonant cavity 23, the length P3 of the gap at the right angle of the triangle is smaller than the length P4 of the gap located in the middle of the right-angled side of the triangle, where P3 = 2.9 mm and P4 = 4.05 mm.

[0028] The dual-passband filter of the present invention is designed as a closed structure and has strong anti-electromagnetic interference capability; the dual-passband filter is an axisymmetric structure. Without increasing the size, by optimizing the resonant cavity structure and coupling mechanism, it achieves fourth-order dual-passband filtering characteristics with high selectivity and low insertion loss. Compared with the same type of single-passband filter, it does not increase the structural complexity, and the overall design is compact and streamlined, meeting the characteristics of miniaturization, easy processing and low cost of microwave devices. It has good application prospects in meteorological radar, satellite communications and other aspects.

[0029] Figure 6 This is the S-parameter simulation waveform of the dual-band filter of the present invention. The horizontal axis is frequency in GHz; the vertical axis is S-parameter in dB. The solid line shows the relationship between the electromagnetic wave reflection coefficient and frequency of the dual-band filter, and the dotted line shows the relationship between the electromagnetic wave transmission coefficient and frequency of the dual-band filter. The center frequencies of the two frequency bands are 15.5GHz and 18.35GHz, respectively. The operating relative bandwidths are 5% and 3%, respectively. The return loss is below -17dB, and the in-band insertion loss is greater than -1.5dB and -2.6dB, respectively. The out-of-band suppression is good, and the isolation between the two frequency bands is very good. The operating frequency can be fine-tuned by adjusting the diameter and position of the metal tuning column. Figure 6 It shows that the present invention has good matching characteristics within the working frequency band.

[0030] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A hybrid-mode substrate-integrated waveguide dual-passband filter, characterized by: The filter includes a top metal layer, an intermediate dielectric layer, and a bottom metal layer stacked in sequence from top to bottom. On the intermediate dielectric layer, metal through-hole arrays are evenly arranged along its diagonal lines and parallel to its sides, forming first to fourth resonant cavities in the shape of an isosceles right triangle. Two gaps are left on the metal through-hole arrays between the first and second resonant cavities, between the second and third resonant cavities, and between the third and fourth resonant cavities, respectively. One gap is located at the right angle of the triangle, and the other gap is located in the middle of the right-angled side of the triangle. There are two metal tuning posts in the first and fourth resonant cavities, respectively, one metal tuning post is close to the right-angled side, and the other metal tuning post is close to the other right-angled side and located between the two gaps. There is one metal tuning post in each of the second and third resonant cavities, and the metal tuning post is located on the median perpendicular to 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 hybrid-mode substrate integrated waveguide dual-passband filter according to claim 1, characterized in that: The length of the gap located at the right angle of the triangle is smaller than the length of the gap located in the middle of the right angle side of the triangle.

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

4. The hybrid-mode substrate integrated waveguide dual-passband filter according to claim 1, wherein: By changing the spacing between the two metal tuning posts in the first and fourth resonant cavities, the resonant frequency of the TM230 mode and the coupling between the resonant cavities can be adjusted. By changing the diameter of the metal tuning posts and the distance between the metal tuning posts and the right angle of the triangle in the second and third resonant cavities, the frequency, coupling, and filter matching of the TM130 and TM230 modes can be fine-tuned simultaneously.

5. The hybrid-mode substrate integrated waveguide dual-passband filter according to claim 1, wherein: The area of ​​the top metal layer is larger than the area of ​​the filter resonant cavity and smaller than the area of ​​the middle dielectric layer. The area of ​​the middle dielectric layer is equal to the area of ​​the bottom metal layer.

6. The hybrid-mode substrate integrated waveguide dual-passband filter according to claim 1, wherein: The microstrip line extends to the edge of the middle dielectric layer, and no metal through-hole array is provided at the connection between the microstrip line and the first resonant cavity, or at the connection between the microstrip line and the fourth resonant cavity.

7. The hybrid-mode substrate integrated waveguide dual-passband filter according to claim 1, characterized in that: The microstrip line is located between the midpoint and the top angle of the oblique sides of the first and fourth resonant cavities. Thin grooves extending into the resonant cavities are respectively opened at the connection points between the microstrip line and the first resonant cavity and the microstrip line and the fourth resonant cavity.

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

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

2.

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

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