Compact substrate integrated waveguide triangular cavity dual-band band-pass filter

Abstract

A compact substrate integrated waveguide triangular cavity dual-band band-pass filter is sequentially provided with an upper metal layer, a dielectric layer substrate clamped between the two metal layers and a lower metal layer from top to bottom, and the upper metal layer is connected with the lower metal layer through a metalized via hole. The middle dielectric layer substrate and the middle dielectric layer substrate form a cavity filled with dielectric, and the shape of the cavity is an isosceles right triangle. The whole filter is composed of four isosceles right-angle triangular cavities, and the whole filter is of a square structure. According to the invention, the passband parallel connection technology and the harmonic coupling control technology are combined, and the mode cross coupling technology is used, so that double passbands are realized, a transmission zero point is generated on a transition band between the two passbands, and the isolation degree between signals passing through the two passbands is improved. In addition, the whole filter is very simple and compact in structure.

Description

Technical Field

[0001] The invention belongs to the technical field of microwave filters, and in particular relates to a compact substrate integrated waveguide triangular cavity dual-band bandpass filter. Background Art

[0002] As an important component in wireless communication and military communication systems, the performance of filters directly affects the front-end performance and application scope of the entire system.

[0003] Triangular substrate integrated waveguides have the advantages of substrate integrated waveguides, and because triangles can be used as basic units to form polygons in mathematics, it is easier to achieve a compact layout when using triangular substrate integrated waveguides to construct microwave devices.

[0004] Harmonic coupling control technology prevents the excitation and propagation of harmonics by properly placing coupling windows and feed lines to make the coupling strength of stray harmonics zero or very weak. The significant advantage of this technology is that it can effectively suppress the propagation of stray harmonics without the use of additional distributed components. But its cost is that designers must fully consider and simultaneously regulate the coupling strength of multiple different modes, which undoubtedly brings challenges to circuit design.

[0005] The passband parallel technology cleverly connects two independent single-band filters in parallel by using an impedance matching network or a shared input and output port, and uses the principle of spectrum superposition to achieve two independent transmission passbands. Its significant advantage is that it can independently design and adjust the performance of the two passbands to meet diverse communication needs. However, a major disadvantage of this technology is that due to the characteristics of the parallel structure, it usually leads to a relatively large circuit size.

[0006] The mode cross-coupling technology controls the generation of transmission zeros by controlling the properties of the mode cross-coupling between two working modes to improve the performance of the filter.

[0007] There are many deficiencies in the existing substrate integrated waveguide dual-band bandpass 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, no isosceles right-angle triangular cavity has been used to realize filters with dual-band bandpass performance. 2. In the absence of physical cross-coupling paths, most of the existing substrate integrated waveguide dual-band bandpass filters introduce some additional structures to generate transmission zeros. Because of the use of additional nearby structures, the structure of the filter is relatively complex. Summary of the invention

[0008] In order to solve the above technical problems, the present invention provides a substrate integrated waveguide triangular cavity dual-band bandpass filter with a simple and compact structure and easy to design and process. It is a brand-new substrate integrated waveguide dual-band bandpass filter. While using a triangular cavity structure to make the entire substrate integrated waveguide dual-band bandpass filter structure more compact, the passband parallel connection technology, harmonic coupling control technology and mode cross-coupling technology are combined to achieve separate control of the internal coupling of the two transmission passbands. In addition, the transmission zero point generated by the mode cross-coupling technology further improves the isolation between the signals passing through the two passbands.

[0009] In order to achieve the above object, the present invention is achieved through the following technical solutions:

[0010] A compact high-selectivity substrate integrated waveguide triangular cavity dual-band bandpass filter comprises an upper metal layer, a dielectric layer substrate and a lower metal layer arranged in sequence from top to bottom, wherein the dielectric layer substrate is clamped between the upper metal layer and the lower metal layer; the geometric centers of the patterns of the upper metal layer, the 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 metallized vias, and together with the dielectric layer substrate located in the middle, forms four isosceles right-angled triangular cavities filled with dielectrics, wherein the contour of each cavity is determined by the metallized vias; and the filter composed of the four cavities presents a square structure.

[0011] Preferably, a filter center line passing through the center of the filter is arranged on the upper metal layer of the present invention, and feed lines are arranged on the left and right sides of the filter center line respectively, and the cavity where the feed lines are located is and is only two non-adjacent isosceles right-angled triangle cavities.

[0012] Preferably, in the present invention, a coupling slot is provided on both sides of each feed line, the width of the coupling slot is 0.4 mm, and the length of the coupling slot is 2.61 mm.

[0013] Preferably, internal coupling windows are respectively arranged on the right-angled sides of each cavity of the present invention, wherein one section of two internal coupling windows is connected to the metallized via hole at the center of the filter, and the other two internal coupling windows are respectively located near the center of the right-angled sides.

[0014] Preferably, the dielectric layer substrate of the present invention adopts Rogers RT5880 with a thickness of 0.508 mm, a dielectric constant of 2.2, and a loss tangent of 0.0009.

[0015] Preferably, the lower metal layer of the present invention has a long side length of greater than or equal to 48 mm and a wide side length of greater than or equal to 40 mm.

[0016] Preferably, the diameter of the metallized via hole of the present invention is 0.5 mm.

[0017] The beneficial effects of the present invention are:

[0018] The present invention fills the patent gap of substrate integrated waveguide dual-band bandpass filter in triangular cavity. Compared with the traditional substrate integrated waveguide dual-band bandpass filter, the proposed filter has a simpler coupling structure, and uses passband parallel technology and harmonic coupling control technology to achieve independent control of the internal coupling of the two working modes, thereby increasing the freedom of filter design. At the same time, due to the use of mode cross-coupling technology, a transmission zero point is generated between the transition bands of the two passbands without adding additional structures, thereby improving the isolation between the signals passing through the two passbands compared with the traditional substrate integrated waveguide dual-band bandpass filter.

[0019] The present invention innovatively applies the triangular cavity to the design of the substrate integrated waveguide filter, which has a simpler and more compact structure, greatly increasing the practicality of the present invention in wireless communication systems. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a structural schematic diagram of the present invention.

[0021] Figure 2 It is a top view of the present invention.

[0022] Figure 3 It is a bottom view of the present invention.

[0023] Figure 4 It is a simplified schematic diagram of the magnetic field vector distribution of the two working modes of the present invention.

[0024] Figure 5 It is a propagation path diagram of the two working modes of the present invention.

[0025] Figure 6 It is the S parameter diagram of the filter of the present invention.

[0026] Figure 7 It is a coupling topology diagram of the present invention.

[0027] Among them, 1. dielectric layer substrate, 2. metallized via, 3. coupling gap, 4. first cavity, 6. second cavity, 8. third cavity, 10. fourth cavity, 5. first internal coupling window, 7. second internal coupling window, 9. third internal coupling window, 11. fourth internal coupling window, 12. second feed line, 13. first feed line, 14. filter center line. DETAILED DESCRIPTION

[0028] 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.

[0029] A compact high-selectivity substrate integrated waveguide triangular cavity dual-band bandpass filter, wherein the substrate integrated waveguide triangular cavity dual-band bandpass filter is sequentially provided with an upper metal layer, a dielectric layer substrate 1 sandwiched between two metal layers, a lower metal layer, an upper metal layer, and the geometric centers of the middle dielectric layer substrate 1 and the lower metal layer pattern are all on the same straight line, the upper metal layer is connected to the lower metal layer through a metallized via 2, and forms a cavity filled with a dielectric together with the middle dielectric layer substrate 1, the contour of each cavity is determined by the metallized via 2, and the shape of the cavity is an isosceles right triangle. The filter composed of these four cavities has a square structure.

[0030] The first cavity 4, the second cavity 6, the third cavity 8 and the fourth cavity 10 constituting the dual-band bandpass filter are all isosceles right-angled triangular cavities.

[0031] The first feed line 13 must be located on the oblique side of the first cavity 4, and the second feed line 12 must be located on the oblique side of the third cavity 8. The first feed line 13 and the second feed line 12 must be located on both sides of the center line 14 of the filter.

[0032] One end of the first internal coupling window 5 and the second internal coupling window 7 must be connected to the metallized via at the right-angle vertex of the second cavity 6 .

[0033] like Figure 1 As shown, the present invention is a compact high-selectivity substrate integrated waveguide triangular cavity dual-band bandpass filter, which is mainly composed of two metal layers and one dielectric layer, and is 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 0.508 mm, a dielectric constant of 2.2, a loss tangent of 0.0009, and the long side length of the rectangle where the filter outer contour is located is not less than 48 mm, and the wide side length is not less than 40 mm.

[0034] The upper metal layer is connected to the lower metal layer 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, and the shape of the cavity is an isosceles right triangle.

[0035] Figure 2-3 As shown, the upper metal layer is composed of an upper metal layer with four triangular cavities and a feed line. The cavities where the two feed lines of the upper metal layer are located are and are only two isosceles right-angled triangular cavities that are not adjacent and physically not coupled to each other. A coupling gap 3 is provided on both sides of each feed line. The width of the coupling gap 3 is 0.4 mm, and the length of the coupling gap 5 is 2.61 mm. The upper metal layer of the entire cavity is composed of four isosceles right-angled triangles and is presented as a square.

[0036] 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 metallized through holes with wide spacing.

[0037] Between each adjacent two cavities, there is a first internal coupling window 5, a second internal coupling window 7, a third internal coupling window 9, and a fourth internal coupling window 11 formed by a pair of metallized vias 2. All couplings are realized by simple coupling windows, without introducing special electrical coupling results or mixed coupling structures. Transmission zeros are generated only by cross-coupling between the working modes of the substrate integrated waveguide isosceles right-angle triangle cavity. The design step of adding additional structures is omitted, simplifying the design of the filter.

[0038] The entire filter is a single-layer structure, and the feeding position is on the left and right sides of the filter center line 14, wherein one end of the first internal coupling window 5 and the second internal coupling window 7 are connected to the metallized via at the center of the filter, and the third internal coupling window 9 and the fourth internal coupling window 11 are located near the center of the two right-angled sides of the fourth cavity 10. The arrangement of these four internal coupling windows enables the working mode coupled into the first passband to be transmitted only through the fourth cavity 10, and the working mode coupled into the second passband to be transmitted only through the second cavity 6, thereby improving the design freedom of the two passbands.

[0039] Figure 4-5 As shown, the two operating modes of the filter are TM 130 Mode and TM 230 mode, where TM 130 mode is transmitted through the fourth cavity 10, TM 230 The mode is transmitted through the second cavity 6. When the feed lines are placed in the four regions A, B, C, and D, the mode cross-coupling relationship between the two feed lines is shown in Table 1. This design places the two feed lines in the A and C regions respectively in order to form a mode cross-coupling with positive coupling properties and generate a transmission zero point in the transition zone of the two passbands. It should be noted that the mode cross-coupling with negative coupling properties cannot generate a transmission zero point in the transition zone of the two passbands.

[0040] Table 1

[0041] A B C D <![CDATA[TM 130 ]]> + － + － <![CDATA[TM 230 ]]> + + + + Coupling relationship just burden just burden

[0042] like Figure 6 As shown in the figure, the 3dB relative bandwidth of the two passbands of the filter reaches 4.4% and 2.8% respectively, and the corresponding absolute bandwidth is 700MHz and 520MHz respectively, and the corresponding passband range is 15.39-16.09GHz and 17.93-18.45GHz. The minimum insertion loss in the passband is -1.08dB and -1.52dB; the return loss in the passband is better than -20dB. The transmission zero point on the transition band between the two passbands is located at 17.32GHz.

[0043] Figure 7 The node S in the figure represents the source, the node L represents the load, and the nodes 1, 2, and 3 represent the three cavities that each working mode passes through. Figure 5 The superscript Ⅰ of the node represents the first passband of the filter, and the superscript Ⅱ represents the second passband of the filter.

[0044] Table 2 and Table 3 show the coupling matrices of the two passbands of the filter. The mutual coupling coefficients in the matrix correspond to all the critical dimensions of the filter. The self-coupling coefficients on the main diagonal of the two matrices are zero, indicating that the cavities that make up the two passbands are synchronously working at the center frequency of their respective passbands.

[0045] Table 2

[0046] S 1 2 3 L S 0 0.0496 0 0 0 1 0.0496 0 0.0472 0 0 2 0 0.0472 0 0.0472 0 3 0 0 0.0472 0 0.0496 L 0 0 0 0.0496 0

[0047] Table 3

[0048] S 1 2 3 L S 0 0.0333 0 0 0 1 0.0333 0 0.317 0 0 2 0 0.317 0 0.317 0 3 0 0 0.317 0 0.0333 L 0 0 0 0.0333 0

[0049] The present invention combines passband parallel connection technology, harmonic coupling control technology and mode cross-coupling technology, and designs a dual-band bandpass filter based on an isosceles right-angle triangle cavity. The filter is not only simple and compact in structure, but also has a relatively high isolation between the signals passing through the two passbands. The high isolation between the signals passing through the two passbands makes the present invention have important application prospects in the multi-band aspect of wireless communication systems.

[0050] 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

1. A compact, highly selective substrate-integrated waveguide triangular cavity dual-band bandpass filter, characterized in that: It comprises an upper metal layer, a dielectric layer substrate (1), and a lower metal layer which are arranged in sequence from top to bottom, and the dielectric layer substrate (1) is clamped between the upper metal layer and the lower metal layer; The geometric centers of the upper metal layer, the dielectric layer substrate (1) and the lower metal layer pattern are all on the same straight line; the upper metal layer is connected to the lower metal layer through a metallized via (2) and forms four isosceles right-angled triangular cavities filled with dielectrics together with the dielectric layer substrate (1) located in the middle, and the outline of each cavity is determined by the metallized via (2); the filter composed of the four cavities has a square structure.

2. A compact high selectivity substrate integrated waveguide triangular cavity dual-band bandpass filter according to claim 1, characterized in that: A filter center line (14) passing through the center of the filter is arranged on the upper metal layer, and feed lines are arranged on the left and right sides of the filter center line (14), respectively. The cavity where the feed lines are located is and only is composed of two non-adjacent isosceles right-angled triangle cavities.

3. A compact high selectivity substrate integrated waveguide triangular cavity dual-band bandpass filter according to claim 2, characterized in that: A coupling slot is provided on both sides of each feed line. The width of the coupling slot is 0.4 mm and the length of the coupling slot is 2.61 mm.

4. A compact high selectivity substrate integrated waveguide triangular cavity dual-band bandpass filter according to claim 3, characterized in that: Internal coupling windows are respectively arranged on the right-angled sides of each cavity, wherein one section of two internal coupling windows is connected to the metallized via hole at the center of the filter, and the other two internal coupling windows are respectively located near the center of the right-angled sides.

5. A compact high selectivity substrate integrated waveguide triangular cavity dual-band bandpass filter according to claim 1, characterized in that: The dielectric layer substrate is Rogers RT5880 with a thickness of 0.508 mm, a dielectric constant of 2.2, and a loss tangent of 0.0009.

6. A compact high selectivity substrate integrated waveguide triangular cavity dual-band bandpass filter according to claim 1, characterized in that: The long side of the lower metal layer is greater than or equal to 48 mm, and the wide side is greater than or equal to 40 mm.

7. A compact high selectivity substrate integrated waveguide triangular cavity dual-band bandpass filter according to claim 1, characterized in that: The diameter of the metallized via is 0.5 mm.

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