Microstrip filter

Abstract

The utility model discloses a microstrip filter. The microstrip filter comprises a dielectric substrate which comprises a first surface and a second surface which are opposite and perpendicular to the thickness direction of the dielectric substrate; the microstrip transmission line is formed on the first surface; the reference ground is formed on the second surface; the at least one via hole is formed in the first surface and extends towards the second surface, and the depth of the at least one via hole is smaller than the thickness of the dielectric substrate; and the metal layer is filled in the at least one via hole, and the orthographic projection of the metal layer on the first surface is overlapped with the orthographic projection of the microstrip transmission line on the first surface. According to the microstrip filter, the metal layers are arranged in the through holes to serve as resonance branches, the three-dimensional space of the dielectric substrate can be fully utilized, product miniaturization is achieved, and meanwhile the large-bandwidth suppression effect is achieved.

Description

Technical Field

[0001] This application relates to the field of communication technology, and in particular to a microstrip filter. Background Technology

[0002] Rayvision integrated machines are widely used in scenarios such as digital roads, smart intersections, holographic tunnels, blind spot warnings, and speeding alerts to achieve digital transformation of transportation. However, most Rayvision integrated machines currently operate in the millimeter-wave band, and signals in this band may interfere with communication, thus requiring the use of microstrip filters. To achieve better filtering of the millimeter-wave band, wireless design needs to be implemented on the PCB motherboard of the microstrip filter. Currently, filtering is mostly achieved through methods such as folded resonant spurs and placing resonators on multi-layer PCB motherboards. However, the space available for wireless design on the PCB motherboard is limited, and the above methods occupy a large area of ​​the PCB motherboard, which cannot meet the current requirements for product miniaturization and high bandwidth suppression. Utility Model Content

[0003] This application discloses a microstrip filter that, by setting a metal layer in the via as a resonant spur, can make full use of the three-dimensional space of the dielectric substrate, achieve product miniaturization, and at the same time achieve a large bandwidth suppression effect.

[0004] To achieve the above objectives, this application provides the following technical solution:

[0005] This application provides a microstrip filter, including:

[0006] A dielectric substrate includes a first surface and a second surface that are perpendicular to and opposite to each other in its thickness direction;

[0007] Microstrip transmission lines formed on the first surface;

[0008] A reference ground formed on the second surface;

[0009] At least one via formed on the first surface and extending toward the second surface, wherein the depth of the at least one via is less than the thickness of the dielectric substrate;

[0010] A metal layer filling the at least one via, wherein the orthographic projection of the metal layer on the first surface overlaps with the orthographic projection of the microstrip transmission line on the first surface.

[0011] The aforementioned microstrip filter, by incorporating a metal layer within a via as a resonant stub, fully utilizes the three-dimensional space of the dielectric substrate, facilitating product miniaturization while achieving excellent filtering performance. Specifically, the microstrip filter of this application includes a dielectric substrate with opposing first and second surfaces, perpendicular to the thickness direction of the substrate. A microstrip transmission line is formed on the first surface, and a reference ground is formed on the second surface. At least one via is also formed on the first surface, extending from the first surface to the second surface, with each via having a depth less than the thickness of the substrate. Each via is filled with a metal layer, the length of which is the same as the depth of the via. The orthographic projection of the metal layer onto the first surface overlaps with the orthographic projection of the microstrip transmission line onto the first surface. In other words, one end of each metal layer is electrically connected to the microstrip transmission line, while the other end is spaced from the reference ground, remaining open-circuit, thus serving as an open-circuit stub for filtering.

[0012] The metal layer of the microstrip filter in this application is located in the three-dimensional space of the vias, without occupying planar area. The length of the metal layer can be adjusted by controlling the length of the vias, thereby achieving filtering. When multiple vias are formed on the first surface, the microstrip filter includes multiple metal layers, i.e., multiple open-circuit stubs. The notch characteristics can be achieved by superimposing the resonant characteristics of multiple open-circuit stubs. Through the combined action of the microstrip transmission line and multiple open-circuit stubs, a band-stop filtering effect in the millimeter-wave band can be achieved, realizing large bandwidth suppression. At the same time, the three-dimensional space of the vias facilitates the miniaturization and integration design of the product. The microstrip filter structure of this application has a simple design and is easy to apply in product engineering.

[0013] In some embodiments, the depth direction of the at least one via is parallel to the normal direction of the first surface.

[0014] In some embodiments, the at least one via includes a first via with a depth of c / (4f0), where c is the speed of light and f0 is the filtering frequency.

[0015] In some embodiments, along the transmission direction of the microstrip transmission line, the at least one via includes a first via, a second via, ..., an nth via arranged side by side, where n is a positive integer greater than or equal to 2;

[0016] The depth of the nth via is c / (4f) n-1 ), where c is the speed of light, f0 is the filter frequency, and f n-1 f n-2 The nearest frequency.

[0017] In some embodiments, the spacing between any two adjacent vias is λ / 4, where λ is the wavelength corresponding to the operating frequency of the microstrip filter.

[0018] In some embodiments, the depth of the at least one via increases sequentially; or, the depth of the at least one via decreases sequentially.

[0019] In some embodiments, the at least one via is arranged in multiple rows, and the microstrip transmission line includes multiple sub-microstrip lines, each of which is electrically connected to only one row of the vias.

[0020] In some embodiments, the length of the microstrip transmission line is (n-1)λ / 4.

[0021] In some embodiments, the width of the microstrip transmission line is 1.9mm-2.5mm.

[0022] In some embodiments, the resistance of the microstrip transmission line is 10 ohms to 100 ohms. Attached Figure Description

[0023] Figure 1 A three-dimensional structural diagram of a microstrip filter provided in an embodiment of this application;

[0024] Figure 2 This is a top view of a microstrip filter provided in an embodiment of this application;

[0025] Figure 3 A bottom view of the structure of a microstrip filter provided in an embodiment of this application;

[0026] Figure 4 This is a front view schematic diagram of a microstrip filter provided in an embodiment of this application;

[0027] Figure 5 This is a schematic diagram illustrating the filtering effect of a microstrip filter provided in an embodiment of this application;

[0028] Figure 6 A top view of another microstrip filter provided in an embodiment of this application;

[0029] Icons: 1. Dielectric substrate; 11. First surface; 12. Second surface; 2. Microstrip transmission line; 21. Input port; 22. Output port; 23. Output port; 3. Reference ground; 4. Via; 5. Metal layer. Detailed Implementation

[0030] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application. In the description of the embodiments of this application, unless otherwise stated, " / " means "or", for example, A / B can mean A or B; "and / or" in the text is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A alone, A and B simultaneously, and B alone.

[0031] The terms "first" and "second" are used for descriptive purposes only and should not be construed as implying relative importance or implicitly indicating the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of the embodiments of this application, unless otherwise stated, "multiple" means two or more.

[0032] like Figures 1-6 As shown, this application embodiment provides a microstrip filter, including:

[0033] The dielectric substrate 1 includes a first surface 11 and a second surface 12 that are perpendicular to its thickness direction;

[0034] Microstrip transmission line 2 formed on the first surface 11;

[0035] Reference ground 3 formed on the second surface 12;

[0036] At least one via 4 is formed on the first surface 11 and extends toward the second surface 12, wherein the depth of the at least one via 4 is less than the thickness of the dielectric substrate 1.

[0037] A metal layer 5 is filled in at least one via 4, and the orthographic projection of the metal layer 5 on the first surface 11 overlaps with the orthographic projection of the microstrip transmission line 2 on the first surface 11.

[0038] The aforementioned microstrip filter, by setting a metal layer in the via 4 as a resonant spur, fully utilizes the three-dimensional space of the dielectric substrate 1, which is beneficial for product miniaturization and achieves good filtering effect. Specifically, the microstrip filter of this embodiment includes a dielectric substrate 1, which has a first surface 11 and a second surface 12 opposite to each other, and the first surface 11 and the second surface 12 are perpendicular to the thickness direction of the dielectric substrate 1. A microstrip transmission line 2 is formed on the first surface 11 of the dielectric substrate 1, and a reference ground 3 is formed on the second surface 12 of the dielectric substrate 1. At least one via 4 is also formed on the first surface 11 of the dielectric substrate 1, each via 4 extending from the first surface 11 to the second surface 12, and the depth of each via 4 is less than the thickness of the dielectric substrate 1. A metal layer 5 is filled in each via 4, the length of the metal layer 5 is the same as the depth of the via 4, and the orthographic projection of the metal layer 5 on the first surface 11 overlaps with the orthographic projection of the microstrip transmission line 2 on the first surface 11. In other words, one end of each metal layer 5 is electrically connected to the microstrip transmission line 2, and the other end is spaced apart from the reference ground 3, forming an open circuit, thus achieving a filtering effect as an open-circuit stub. It should be noted that, in this embodiment, the reference ground 3 uses copper as the ground surface.

[0039] The metal layer 5 of the microstrip filter in this application is located in the three-dimensional space of the vias, without occupying planar area. The length of the metal layer 5 can be adjusted by controlling the length of the vias 4, thereby achieving filtering. When multiple vias 4 are formed on the first surface 11, the microstrip filter includes multiple metal layers 5, that is, multiple open-circuit stubs. The notch characteristics can be achieved by superimposing the resonant characteristics of multiple open-circuit stubs. Through the combined action of the microstrip transmission line 2 and multiple open-circuit stubs, a band-stop filtering effect in the millimeter-wave band (30GHz~300GHz) can be achieved, realizing large bandwidth suppression. At the same time, the three-dimensional space of the vias 4 is conducive to realizing miniaturized integrated design of the product. The microstrip filter structure of this application is simple and easy to apply in product engineering. The microstrip filter of this application embodiment can be applied to a 96GHz millimeter-wave band traffic road monitoring integrated camera, which can effectively suppress millimeter-wave radar signal interference.

[0040] In some embodiments, the depth direction of at least one via 4 is parallel to the normal direction of the first surface 11.

[0041] One possible way to achieve this is, such as Figure 1 As shown, three vias 4 are formed on the first surface 11 of the dielectric substrate 1, extending towards the second surface 12. The depth direction of each via 4 is parallel to the normal direction of the first surface 11. This arrangement makes it easier to control the depth of each via 4 and achieve a better filtering effect. It can be understood that the depth direction of the via 4 can also form a certain angle with the normal direction of the first surface 11; the specific setting method is not limited.

[0042] In some embodiments, at least one via includes a first via with a depth of c / (4f0), where c is the speed of light and f0 is the filtering frequency.

[0043] In one possible implementation, the first surface 11 of the dielectric substrate 1 may have only one first via, the depth of which is c / (4f0). Since the metal layer 5 fills the first via, and the length of the metal layer 5 is the same as the depth of the first via, the length of the metal layer 5 is also c / (4f0), where c is the speed of light and f0 is the filtering frequency. That is, the length of the metal layer 5 is 1 / 4 wavelength of the required filtering frequency, equivalent to a 1 / 4 wavelength open-circuit stub for filtering. The required filtering frequency can be a millimeter-wave frequency or a frequency in other frequency bands, indicating that the microstrip filter of this embodiment can achieve filtering effects in both millimeter-wave and other frequency bands, and has a wide range of applications. It should be noted that the metal layer 5 can be a metal pillar.

[0044] In some embodiments, along the transmission direction of the microstrip transmission line 2, at least one via 4 includes a first via, a second via, ..., an nth via arranged side by side, where n is a positive integer greater than or equal to 2; the depth of the nth via is c / (4f n-1 ), where c is the speed of light, f0 is the filter frequency, and f n-1 f n-2 The adjacent frequency points. It should be noted that f0, f n-1 f n-2 The size relationship is not specifically limited.

[0045] One possible way to achieve this is, such as Figures 1-4 As shown, along the transmission direction of the microstrip transmission line 2, the first surface 11 of the dielectric substrate 1 is provided with three vias 4, namely a first via, a second via, and a third via. The first via is located on the side near the input port 21 of the microstrip transmission line 2, and the third via is located on the side near the output port 22 of the microstrip transmission line 2. The first via, the second via, and the third via are arranged side by side, and their arrangement direction is parallel to the transmission direction of the microstrip transmission line 2.

[0046] The depth of the first via is c / (4f0), the depth of the second via is c / (4f1), and the depth of the third via is c / (4f2), where c is the speed of light, f0 is the filtering frequency, f1 is the nearest frequency to f0, and f2 is the nearest frequency to f1. Since the first via, the second via, and the third via are filled with the first metal layer, the second metal layer, and the third metal layer, respectively, the length of the first metal layer is c / (4f0), which is equivalent to a 1 / 4 wavelength open-circuit stub A, achieving a band-stop effect in the f0 frequency band; the length of the second metal layer is c / (4f1), where f1 is the nearest frequency point to f0, effectively providing the first transmission zero, and the second metal layer is equivalent to a 1 / 4 wavelength open-circuit stub B, achieving a band-stop effect in the f1 frequency band; the length of the third metal layer is c / (4f2), where f2 is the nearest frequency point to f1, effectively providing the second transmission zero, and the third metal layer is equivalent to a 1 / 4 wavelength open-circuit stub C, achieving a band-stop effect in the f2 frequency band.

[0047] In other words, the first, second, and third metal layers are arranged side-by-side as the resonant stubs of the microstrip filter, with one end connected to microstrip transmission line 2 and the other end open-circuited. The lengths of the first, second, and third metal layers are respectively 1 / 4 wavelength of the desired filtering frequency f0 and the adjacent frequencies f1 and f2, with equivalent 1 / 4 wavelength open-circuit stubs A, B, and C, as shown. Figure 5 As shown, by utilizing the resonant characteristics of multiple 1 / 4 wavelength open-circuit stubs, multiple zeros can be superimposed to achieve notch characteristics, thus realizing a large bandwidth and high band-stop suppression effect.

[0048] This application embodiment achieves a band-stop filtering effect in the millimeter-wave band through the combined action of a microstrip transmission line 2 and multiple single-ended, ungrounded, quarter-wavelength open-circuit stubs with different resistance values, thus achieving wide bandwidth suppression. Simultaneously, utilizing the three-dimensional space of the via 4 facilitates miniaturized integrated design. The microstrip filter structure of this application is simple in design and easy to apply in product engineering. The microstrip filter of this application embodiment can be applied to a 96GHz millimeter-wave band traffic roadside radar-visual integrated camera, effectively suppressing millimeter-wave radar signal interference.

[0049] It should be noted that the first surface 11 of the dielectric substrate 1 of this application may also be provided with other numbers of vias 4, such as 2, 4, 6, 7, etc., depending on the actual situation. By controlling the length of the vias 4 to adjust the length of the metal layer 5, the transmission zero point can be adjusted, thereby adjusting the filtering effect. By adjusting the number of metal layers 5, the required filtering bandwidth can be adjusted.

[0050] In some embodiments, the spacing between any two adjacent vias 4 is λ / 4, where λ is the wavelength corresponding to the operating frequency of the microstrip filter.

[0051] One possible way to achieve this is, such as Figures 1-4As shown, along the transmission direction of the microstrip transmission line 2, the first surface 11 of the dielectric substrate 1 is provided with three vias 4, namely the first via, the second via, and the third via. The spacing between the first via and the second via, and between the second via and the third via, is 1 / 4 of the wavelength corresponding to the operating frequency of the microstrip filter, which is beneficial to achieving the filtering effect in the millimeter-wave band.

[0052] In some embodiments, the depth of at least one via 4 increases sequentially; or, the depth of at least one via 4 decreases sequentially.

[0053] One possible way to achieve this is, such as Figure 1 As shown, the depths of the first, second, and third vias decrease sequentially. Of course, the depths of the first, second, and third vias can also increase sequentially. By regularly setting the depth of via 4, and thus regularly controlling the length of the metal layer 5, it is beneficial to achieve better filtering effects in the millimeter-wave frequency band.

[0054] In some embodiments, at least one via 4 is arranged in multiple rows, and the microstrip transmission line 2 includes multiple sub-microstrip lines 23, each sub-microstrip line 23 being electrically connected to only one row of via 4.

[0055] One possible way to achieve this is, such as Figure 6 As shown, the vias 4 on the first surface 11 of the dielectric substrate 1 are distributed in two rows, with each row including three vias 4 side by side. Correspondingly, each row of vias corresponds to a sub-microstrip line 23 to realize the electrical connection between the metal layer 5 in each row of vias 4 and the sub-microstrip line 23.

[0056] In some embodiments, the length of the microstrip transmission line 2 is (n-1)λ / 4.

[0057] One possible way to achieve this is, such as Figure 1 , Figure 2 , Figure 4 As shown, when a plurality of vias 4 are provided on the first surface 11 of the dielectric substrate 1, the length of the microstrip transmission line 2 is (n-1)λ / 4. For example, when the number of vias 4 is 3, the length of the microstrip transmission line 2 is 2λ / 4.

[0058] In some embodiments, the width of the microstrip transmission line 2 is 1.9mm-2.5mm. For example, the width of the microstrip transmission line 2 is 1.9mm, 2.0mm, 2.1mm, 2.2mm, 2.3mm, 2.4mm, 2.5mm, etc., depending on the situation.

[0059] In some embodiments, the resistance of the microstrip transmission line 2 is between 10 ohms and 100 ohms. For example, the resistance of the microstrip transmission line 2 can be 10 ohms, 15 ohms, 20 ohms, 25 ohms, 30 ohms, 40 ohms, 50 ohms, 60 ohms, 70 ohms, 80 ohms, 90 ohms, 100 ohms, etc., and the specific resistance value is not limited. In the embodiments of this application, the resistance of the microstrip transmission line 2 is 50 ohms.

[0060] Obviously, those skilled in the art can make various modifications and variations to this application without departing from the spirit and scope of this application. Therefore, if such modifications and variations fall within the scope of the claims of this application and their equivalents, this application also intends to include such modifications and variations.

Claims

1. A microstrip filter, characterized in that, include: A dielectric substrate includes a first surface and a second surface that are perpendicular to and opposite to each other in its thickness direction; Microstrip transmission lines formed on the first surface; A reference ground formed on the second surface; At least one via formed on the first surface and extending toward the second surface, wherein the depth of the at least one via is less than the thickness of the dielectric substrate; A metal layer filling the at least one via, wherein the orthographic projection of the metal layer on the first surface overlaps with the orthographic projection of the microstrip transmission line on the first surface.

2. The microstrip filter according to claim 1, characterized in that, The depth direction of the at least one via is parallel to the normal direction of the first surface.

3. The microstrip filter according to claim 2, characterized in that, The at least one via includes a first via with a depth of c / (4f0), where c is the speed of light and f0 is the filtering frequency.

4. The microstrip filter according to claim 2, characterized in that, Along the transmission direction of the microstrip transmission line, the at least one via includes a first via, a second via, ..., an nth via arranged side by side, where n is a positive integer greater than or equal to 2; The depth of the nth via is c / (4f) n-1 ), where c is the speed of light, f0 is the filter frequency, and f n-1 f n-2 The nearest frequency.

5. The microstrip filter according to claim 4, characterized in that, The spacing between any two adjacent vias is λ / 4, where λ is the wavelength corresponding to the operating frequency of the microstrip filter.

6. The microstrip filter according to claim 4, characterized in that, The depth of the at least one via increases sequentially; or, the depth of the at least one via decreases sequentially.

7. The microstrip filter according to claim 1, characterized in that, The at least one via is arranged in multiple rows, and the microstrip transmission line includes multiple sub-microstrip lines, each of which is electrically connected to only one row of the vias.

8. The microstrip filter according to claim 4, characterized in that, The length of the microstrip transmission line is (n-1)λ / 4.

9. The microstrip filter according to claim 3, characterized in that, The width of the microstrip transmission line is 1.9mm-2.5mm.

10. The microstrip filter according to claim 3, characterized in that, The resistance of the microstrip transmission line is 10 ohms to 100 ohms.

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