CN116706480B - A compact, highly selective substrate-integrated waveguide triangular cavity wide stopband filter - Google Patents

Abstract

The present invention belongs to the technical field of microwave filters, and discloses a compact, highly selective substrate integrated waveguide triangular cavity wide stopband filter, which is sequentially provided with an upper metal layer, an intermediate dielectric layer substrate, and a lower metal layer from top to bottom, wherein 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 cavity filled with a dielectric, wherein the shape of the cavity is a triangle and is only composed of an isosceles right-angled triangular cavity and an equilateral triangular cavity, wherein the right-angled side length of the isosceles right-angled triangular cavity is linearly related to the side length of the equilateral triangular cavity, and the cavity of the entire filter is a pentagonal structure. The present invention combines the harmonic interleaving technology with the harmonic coupling technology, and gives the relationship between the right-angled side length of the substrate integrated waveguide isosceles right-angled triangular cavity and the side length of the substrate integrated waveguide equilateral triangular cavity, which is not only compact and simple in structure, but also simplifies the design steps, and has important application prospects.

Description

A compact, highly selective substrate-integrated waveguide triangular cavity wide stopband filter

Technical Field

The invention belongs to the technical field of microwave filters, and in particular relates to a compact high-selectivity substrate integrated waveguide triangular cavity wide stopband filter.

Background technique

Wireless communication and military communication have increasing requirements for filter performance. As an indispensable part of the RF microwave front-end circuit, the parameters of the filter directly affect the performance of the entire front-end circuit. After the introduction of substrate integrated waveguide technology, great progress has been made.

Substrate integrated waveguide technology was proposed by combining the advantages of both microstrip circuits and waveguides. It has the characteristics of high quality factor and high power capacity of waveguides, as well as the characteristics of compact structure and easy integration of planar microstrip circuits, filling the technical gap between planar microstrip/stripline and non-planar waveguide/dielectric resonator.

The principle of harmonic interleaving technology is to make the resonant mode frequencies used to construct the passband the same while other stray resonant frequencies are staggered when designing the filter. When multiple resonators are coupled and cascaded to form a filter, the harmonic level can be suppressed. The advantage is that no additional components are added, and there is no need to consider signal coupling. The disadvantage is that it is only applicable to narrow bandwidth and weak coupling, and the stray level is uncontrollable, and it is impossible to make all harmonic levels lower than the ideal value.

Harmonic coupling control technology can accurately control the coupling strength of harmonic signals by reasonably selecting the coupling positions between resonators or between ports and input resonators, so that the stopband suppression function can be achieved when the harmonic coupling is zero or very weak. The coupling matrix corresponding to the stopband response can also be obtained by using the coupling matrix synthesis technology, and this coupling matrix can be applied to high-order harmonics to achieve the purpose of spurious suppression. Its advantage is that no additional distributed components are added. However, the coupling problem of the fundamental frequency and harmonics needs to be considered at the same time, which increases the difficulty of circuit design.

In cross-coupling technology, if the signals transmitted on two different physical transmission paths have the same amplitude but opposite phases, their energy cancels each other out, thus generating a transmission zero on the imaginary axis. However, positive and negative coupling must be achieved simultaneously to provide opposite phases.

There are many deficiencies in the existing substrate integrated waveguide wide stopband filters: 1. The existing research on substrate integrated waveguide wide stopband filters mostly adopts rectangular cavity and square cavity, and rarely adopts triangular cavity. So far, there is no filter with wide stopband performance that adopts isosceles right-angle triangle cavity and equilateral triangle cavity at the same time. 2. Most of the existing substrate integrated waveguide wide stopband filters introduce special electrical coupling or hybrid coupling structures to achieve the negative coupling required for cross-coupling. More parameters make the process of adjusting the parameters of the filter relatively time-consuming. 3. The common substrate integrated waveguide filter realized by combining rectangular cavity and square cavity has an operating frequency that 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 overall size of the filter.

Summary of the invention

In order to solve the above technical problems, the present invention provides a highly selective substrate integrated waveguide triangular cavity wide stopband filter which is simple and compact in structure and easy to design and process. The present invention is a brand-new substrate integrated waveguide wide stopband filter which uses a triangular cavity structure to simplify the overall size determination of the substrate integrated waveguide wide stopband filter, and combines cross-coupling technology, harmonic interleaving technology and harmonic coupling control technology to simplify the structure of the filter, improve the selectivity of the filter passband, broaden the stopband suppression of the filter, and improve the availability of the compactly structured highly selective substrate integrated waveguide triangular cavity wide stopband filter.

In order to achieve the above object, the present invention is achieved through the following technical solutions:

The invention discloses a compact high-selectivity substrate integrated waveguide triangular cavity wide stopband filter. The high-selectivity substrate integrated waveguide triangular cavity wide stopband filter is sequentially provided with an upper metal layer, an intermediate dielectric layer substrate, a lower metal layer, and an upper metal layer from top to bottom. The geometric centers of the patterns of the intermediate dielectric layer substrate and the lower metal layer are all on the same straight line. The upper metal layer is connected to the lower metal layer through a metallized via hole, and forms a cavity filled with a dielectric together with the intermediate dielectric layer substrate. The contour of each cavity is determined by the metallized via hole. The shape of the cavity is a triangle and is only composed of an isosceles right-angled triangle cavity and an equilateral triangle cavity. The right-angle side length of the isosceles right-angled triangle cavity is linearly related to the side length of the equilateral triangle cavity. The cavity of the entire filter is a pentagonal structure.

A further improvement of the present invention is that the linear relationship between the length of the right angle side of the isosceles right triangle cavity and the length of the side of the equilateral triangle cavity is:

Where: a1eff is the length of the right angle side of the isosceles right triangle cavity, aeff is the length of the side of the equilateral triangle cavity. By determining the length of any side of any cavity, the size of the entire filter can be determined.

A further improvement of the present invention is that: the upper metal layer is also connected to two feed lines, the cavity where the feed lines are located is and is only two adjacent and mutually coupled equilateral triangular cavities, a coupling gap is arranged on both sides of each feed line, the width of the coupling gap is 0.2mm, and the length of the coupling gap is 2.5mm. The entire filter is a single-layer structure, the feeding position is at the center of one side of the equilateral triangular cavity, and all the coupling windows inside are offset from the center of the side length where they are located.

A further improvement of the present invention is that: a coupling window formed by a pair of metallized vias is provided between each two adjacent cavities, and electrical coupling is achieved by coupling between the working modes of the isosceles right-angle triangle cavity and the equilateral triangle cavity.

A further improvement of the present invention is that the diameter of the metallized via is 0.5 mm, the spacing between each two adjacent metallized vias except the coupling window is 1 mm, the width of the coupling window between the equilateral triangle cavity connected to the feeder at the cut corner and the isosceles right triangle cavity is 4.19 mm, the offset of the coupling window from the center position of the side where it is located is 3.7 mm, and in counterclockwise order, the width of the coupling window is 4.03 mm, 3.4 mm and 2.3 mm, respectively, and in counterclockwise order, the offset of the coupling window from the center position of the side where it is located is 3.7 mm, 2 mm and 2 mm, respectively.

A further improvement of the present invention is that the hypotenuse of the isosceles right triangle cavity is slightly smaller than the sum of the side lengths of the two equilateral triangle cavities coupled with it, and the right-angled vertex of the isosceles right triangle cavity faces the vertices of the two equilateral triangle cavities coupled with it.

A further improvement of the present invention is that the filter of the present invention has both electrical coupling and magnetic coupling, and generates a transmission zero point on both sides of the passband, thereby improving the selectivity of the substrate integrated waveguide triangular cavity wide stopband filter.

The beneficial effects of the present invention are:

The present invention fills the patent gap in the triangular cavity of high-selectivity substrate integrated waveguide wide stopband filter. Compared with the traditional high-selectivity substrate integrated waveguide wide stopband filter, the coupling structure of the filter is simpler. By using harmonic interleaving technology and harmonic coupling control technology, the electrical coupling required to generate two transmission zero points to improve selectivity and the suppression of stray harmonics are achieved, achieving the stopband width suppressed by the traditional high-selectivity substrate integrated waveguide wide stopband filter.

The present invention innovatively applies the triangular cavity to the design of the substrate integrated waveguide filter, simplifies the determination of the overall size of the substrate integrated waveguide filter at any operating frequency, reduces the overall size of the substrate integrated waveguide filter, has a smaller size, a simpler structure, and is easier to determine the overall size of the filter, which greatly increases the practicability of the present invention in wireless communication systems.

The present invention combines the harmonic interleaving technology with the harmonic coupling technology, and gives the relationship between the right-angle side length of the substrate integrated waveguide isosceles right-angle triangle cavity and the side length of the substrate integrated waveguide equilateral triangle cavity. Not only is the structure compact and simple, but also the design steps are simplified. The high selectivity and wide stopband suppression make the present invention have important application prospects in filtering out interference signals generated by wireless communication applications and parasitic clutter signals generated inside transceivers.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic structural diagram of the present invention.

FIG. 2 is a top view of the present invention.

FIG. 3 is a bottom view of the present invention.

FIG. 4 is an S parameter diagram of the filter of the present invention.

FIG. 5 is a coupling topology diagram of the present invention.

FIG. 6 is a coupling matrix of the present invention.

Detailed ways

The following will disclose the embodiments of the present invention with drawings. For the purpose of clear description, many practical details will be described together in the following description. However, it should be understood that these practical details should not be used to limit the present invention. That is, in some embodiments of the present invention, these practical details are not necessary. In addition, for the purpose of simplifying the drawings, some conventional structures and components will be depicted in a simple schematic manner in the drawings.

As shown in Figure 1, the present invention is a compact high-selectivity substrate integrated waveguide triangular cavity wide stopband filter, which is mainly composed 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 preferably uses Rogers RT5880 with a thickness of 0.508mm, a dielectric constant of 2.2, a loss tangent of 0.0009, and a side length of not less than 59mm for the square where the outer contour of the filter is located. There is a 60° oblique cut angle at the lower right corner of the top view, and the length of the short side at the cut angle is not more than 15mm, and it does not overlap with the metal patch of the cavity.

The upper metal layer and the lower metal layer are connected through the metallized via 2 and combined with the intermediate dielectric layer substrate to form a cavity. The cut angle is consistent with the outer contour of the intermediate dielectric layer substrate and the lower metal layer. The contour of each cavity is determined by the metallized via with a diameter of 0.5 mm. The shape of the cavity is triangular and only consists of isosceles right-angled triangle cavities and equilateral triangle cavities. The right-angled side length of the isosceles right-angled triangle cavity and the side length of the equilateral triangle cavity are linearly related, specifically:

Where: a1eff is the length of the right angle of the isosceles right triangle cavity, aeff is the length of the side of the equilateral triangle cavity, and the length of the right angle of the substrate integrated waveguide isosceles right triangle cavity is about 1.369 times the length of the substrate integrated waveguide equilateral triangle cavity. By determining the length of any side of any cavity, the size of the entire filter can be determined, which reduces the complexity of the filter design and simplifies the design process of the entire high-selectivity substrate integrated waveguide triangle cavity wide stopband filter.

As shown in Figure 2-3, the upper metal layer has four triangular cavities and is composed of an upper metal layer and a feed line. The cavities where the two feed lines of the upper metal layer are located are and are only two adjacent and mutually coupled equilateral triangular cavities. A coupling gap 5 is arranged on both sides of each feed line. The width of the coupling gap 5 is 0.2 mm, and the length of the coupling gap 5 is 2.5 mm. The upper metal layer of the entire cavity is composed of three equilateral triangles and one isosceles right triangle, presenting a pentagon.

The upper metal layer is a complete plane except for the metallized through holes and the coupling gaps on both sides of the feed line, and there are no other slots or slot structures on it. The coupling of the entire filter is realized by a coupling window formed by a pair of widely spaced metallized through holes, which simplifies the design of the traditional electrical coupling structure.

There is a coupling window 6 formed by a pair of metallized vias 2 between each adjacent two cavities. All couplings are realized by simple coupling windows, without introducing special electrical coupling results or mixed coupling structures. Electrical coupling is only achieved by coupling between the working modes of the substrate integrated waveguide isosceles right triangle cavity and the substrate integrated waveguide equilateral triangle cavity. The design steps of the electrical coupling structure are omitted, simplifying the design of the filter.

The entire filter is a single-layer structure, the feeding position is at the center of one side of the equilateral triangle cavity, and all the coupling windows inside are offset from the center of the side length where they are located. Except for the coupling window, the spacing between each two adjacent metallized vias 2 is 1mm, the width of the coupling window 6 between the equilateral triangle cavity connected to the feeder at the cut corner and the isosceles right-angle triangle cavity is 4.19mm, and the offset of the coupling window 6 from the center position of the side where it is located is 3.7mm. In counterclockwise order, the width of the coupling window 6 is 4.03mm, 3.4mm and 2.3mm, respectively, and in counterclockwise order, the offset of the coupling window 6 from the center position of the side where it is located is 3.7mm, 2mm and 2mm, respectively. While ensuring that the working mode can achieve optimal coupling, several stray modes near the working mode are intrinsically suppressed to form a wide stopband filter. The shape and size of the lower metal layer are the same as the shape and size of the bottom surface of the dielectric plate connected to it.

The hypotenuse of the isosceles right triangle cavity is slightly smaller than the sum of the side lengths of the two equilateral triangle cavities coupled with it, and the right-angle vertex of the isosceles right triangle cavity is directly opposite to the vertex of the two equilateral triangle cavities coupled with it. The filter of the present invention has both electrical coupling and magnetic coupling, and generates a transmission zero point on both sides of the passband, thereby improving the selectivity of the substrate integrated waveguide triangle cavity wide stopband filter.

As shown in Figure 4, the 3dB bandwidth of the filter reaches 1.5%, that is, 9.92GHz-10.07GHz. The return loss within the working bandwidth is lower than -20dB, and the minimum insertion loss is 1.24dB. The zero points on both sides of the passband are located at 9.86GHz and 10.12GHz respectively. Since several spurious modes close to the working mode frequency are suppressed in the upper stopband, the filter 20dB suppression stopband bandwidth reaches 2.01f ₀ .

Node S in Figure 5 represents the source, node L represents the load, and nodes 1, 2, 3, and 4 represent the corresponding four cavities. The coupling mode represented by the solid line connecting the nodes is magnetic coupling, and the coupling mode represented by the dotted line connecting the nodes is electrical coupling. Node 1 to node 2, node 2 to node 3, and node 3 to node 4 are all direct coupling paths. Node 1 to node 4 is a cross-coupling path.

The coupling coefficients in the coupling matrix of Figure 6 can not only correspond to the key dimensions of the proposed filter and the determination of the sizes of these dimensions, but also reflect the coupling mode between the various cavities and the cross-coupling that exists. Generally, the coupling mode corresponding to the positive coupling coefficient is defined as magnetic coupling, and the coupling mode corresponding to the negative coupling coefficient is defined as electrical coupling or coupling opposite to the positive coupling phase response.

The present invention combines the harmonic interleaving technology with the harmonic coupling technology, and gives the relationship between the right angle length of the substrate integrated waveguide isosceles right triangle cavity and the side length of the substrate integrated waveguide equilateral triangle cavity, which not only has a compact and simple structure, but also simplifies the design steps. The high selectivity and wide stopband suppression make the present invention have important application prospects in filtering out interference signals generated by wireless communication applications and parasitic clutter signals generated inside transceivers.

The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims (4)

1. A compact high-selectivity substrate integrated waveguide triangular cavity wide stopband filter, wherein the high-selectivity substrate integrated waveguide triangular cavity wide stopband filter is sequentially provided with an upper metal layer, an intermediate dielectric layer substrate (1), and a lower metal layer from top to bottom, wherein the geometric centers of the upper metal layer, the intermediate dielectric layer substrate (1), and the lower metal layer pattern are on the same straight line, the upper metal layer is connected to the lower metal layer through a metallized via (2), and together with the intermediate dielectric layer substrate (1), forms a cavity filled with a dielectric, and the contour of each cavity is Determined by the metallized via (2), the shape of the cavity is a triangle and is only composed of an isosceles right-angled triangle cavity and an equilateral triangle cavity. The length of the right-angled side of the isosceles right-angled triangle cavity is linearly related to the length of the side of the equilateral triangle cavity. The upper metal layer of the cavity of the entire filter is composed of three equilateral triangles and one isosceles right-angled triangle, presenting a pentagon. The length of the hypotenuse of the isosceles right-angled triangle cavity is slightly smaller than the sum of the side lengths of the two equilateral triangle cavities coupled to it. The right-angled vertex of the isosceles right-angled triangle cavity is opposite to the vertices of the two equilateral triangle cavities coupled to it. 2. A compact high-selectivity substrate integrated waveguide triangular cavity wide stopband filter according to claim 1, characterized in that the linear relationship between the right angle length of the isosceles right triangle cavity and the side length of the equilateral triangle cavity is: , Where: a1eff is the length of the right angle side of the isosceles right triangle cavity, aeff is the length of the side of the equilateral triangle cavity. By determining the length of any side of any cavity, the size of the entire filter can be determined. 3. A compact, highly selective substrate integrated waveguide triangular cavity wide stopband filter according to claim 1, characterized in that: the upper metal layer is connected to two feed lines, the cavity where the feed lines are located is and is only two adjacent and mutually coupled equilateral triangular cavities, a coupling slot (5) is provided on both sides of each feed line, the width of the coupling slot (5) is 0.2 mm, the length of the coupling slot (5) is 2.5 mm, the entire filter is a single-layer structure, and the feeding position is at the center of one side of the equilateral triangular cavity. 4. A compact, highly selective substrate integrated waveguide triangular cavity wide stopband filter according to claim 3, characterized in that: a coupling window (6) formed by a pair of metallized vias (2) is provided between each two adjacent cavities, and electrical coupling is achieved by coupling the isosceles right triangle cavity and the equilateral triangle cavity, and all the coupling windows inside are offset from the center of the side length where they are located.