Ltcc notch high pass filter

Abstract

The application provides an LTCC notch high-pass filter, which comprises a ceramic base, a filter structure, an input electrode, an output electrode and a grounding electrode. The filter structure is embedded in the ceramic base by a low-temperature co-firing process; one end of the input electrode is electrically connected with an input end of the filter structure, and the other end extends to the outer surface of the ceramic base to form an external solderable end; one end of the output electrode is electrically connected with an output end of the filter structure, and the other end also extends to the outer surface of the ceramic base; one end of the grounding electrode is connected with a grounding end of the filter structure, and the other end extends to the outer surface of the ceramic base to form a common grounding connection end. The filter structure comprises three capacitive elements, i.e., a first capacitor, a second capacitor and a third capacitor, which are connected in series to form a main signal path; a first series resonance unit is connected between the input end and the first capacitor and between the third capacitor and the output end; and a second series resonance unit is connected between the first capacitor and the second capacitor and between the second capacitor and the third capacitor.

Description

Technical Field

[0001] This application belongs to the field of filter technology, and more specifically, relates to an LTCC notch high-pass filter. Background Technology

[0002] In modern electronic systems, filters are key components for signal processing and are widely used in wireless communication, audio processing, and sensor interfaces. However, traditional filters are typically implemented using discrete components (such as inductors, capacitors, and resistors) or a distributed structure based on a PCB, resulting in large device sizes that are difficult to meet the miniaturization and integration requirements of modern electronic devices. Utility Model Content

[0003] The purpose of this application is to provide an LTCC notch high-pass filter to solve the technical problems of low filter integration and large size in the prior art.

[0004] To achieve the above objectives, the technical solution adopted in this application is as follows:

[0005] An LTCC notch high-pass filter is provided, comprising:

[0006] Ceramic matrix;

[0007] The filter structure is encapsulated within the ceramic substrate.

[0008] The input electrode has one end connected to the input terminal of the filter structure and the other end extending to the outside of the ceramic substrate;

[0009] The output electrode has one end connected to the output end of the filter structure and the other end extending to the outside of the ceramic substrate;

[0010] The grounding electrode has one end connected to the grounding terminal of the filter structure and the other end extending to the outside of the ceramic substrate;

[0011] The filtering structure includes a first capacitor, a second capacitor, and a third capacitor connected in series. A first series resonant unit is connected between the input terminal and the first capacitor, and between the third capacitor and the output terminal. A second series resonant unit is connected between the first capacitor and the second capacitor, and between the second capacitor and the third capacitor.

[0012] As a further improvement to the above technical solution:

[0013] Optionally, the first series resonant unit includes a first inductor and a series-parallel module connected in series. The input terminal of the first inductor is connected between the output terminal and the first capacitor or between the third capacitor and the output terminal. The output terminal of the series-parallel module is grounded.

[0014] The series-parallel module includes a second inductor, a third inductor, and a fourth capacitor. The third inductor and the fourth capacitor form a series resonance, and the second inductor is connected in parallel with the series resonance of the third inductor and the fourth capacitor.

[0015] Optionally, the second series resonant unit includes a fourth inductor and a fifth capacitor forming a series resonance, wherein the input terminal of the inductor is connected between the first capacitor and the second capacitor or between the second capacitor and the third capacitor, and the output terminal of the capacitor is grounded.

[0016] Optionally, the first capacitor and the third capacitor are mirror-symmetrical with respect to the central axis of the ceramic substrate, and the first capacitor, the second capacitor and the third capacitor are located in the first layer of the ceramic substrate;

[0017] The first inductor, the second inductor, the third inductor, and the fourth inductor are located in the second layer of the ceramic substrate;

[0018] The first series resonant unit, arranged in pairs, is mirror-symmetrical with respect to the central axis of the ceramic substrate; the second series resonant unit, also arranged in pairs, is mirror-symmetrical with respect to the central axis of the ceramic substrate; the fourth and fifth capacitors are located in the third layer of the ceramic substrate.

[0019] The first, second, and third levels are set sequentially from top to bottom.

[0020] Optionally, the first inductor, the second inductor, the third inductor, and the fourth inductor are all rectangular spiral inductors.

[0021] Optionally, the first inductor, the second inductor, the third inductor, and the fourth inductor are all double-dielectric-layer rectangular spiral inductors.

[0022] Optionally, the first capacitor, the second capacitor, and the third capacitor are all planar MIM capacitors.

[0023] Optionally, it also includes a planar metal plate, which is connected to a ground electrode, and the third capacitor and the fourth capacitor respectively form a planar MIM capacitor with the planar metal plate.

[0024] The beneficial effects of the LTCC notch high-pass filter provided in this application are as follows:

[0025] The LTCC notch high-pass filter of this application includes a ceramic substrate, a filter structure, an input electrode, an output electrode, and a ground electrode. The filter structure is completely embedded within the ceramic substrate using a low-temperature co-firing process, forming a three-dimensional integrated structure. One end of the input electrode is electrically connected to the input end of the filter structure, and the other end extends to the outer surface of the ceramic substrate to form an external solderable terminal. One end of the output electrode is electrically connected to the output end of the filter structure, and the other end also extends to the outer surface of the ceramic substrate. One end of the ground electrode is connected to the ground terminal of the filter structure, and the other end extends to the outer surface of the ceramic substrate to form a common ground connection terminal. The filter structure adopts a multi-stage capacitor-resonant unit composite topology, specifically including three capacitive elements—a first capacitor, a second capacitor, and a third capacitor—connected in series to form the main signal path. First series resonant units are connected between the input end and the first capacitor, and between the third capacitor and the output end, respectively. Second series resonant units are connected between the first capacitor and the second capacitor, and between the second capacitor and the third capacitor, respectively. This specific connection method forms a multi-order filter network with bandpass characteristics. This structural design allows for optimized arrangement of functional components in three-dimensional space, ensuring both good filtering performance and high device integration. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0027] Figure 1 A circuit diagram of the LTCC notch high-pass filter provided in this application;

[0028] Figure 2 A three-dimensional structural schematic diagram of the LTCC notch high-pass filter provided in this application;

[0029] Figure 3 A partial structural diagram of the LTCC notch high-pass filter provided in this application. Figure 1 ;

[0030] Figure 4 A cross-sectional view of the LTCC notch high-pass filter provided in this application;

[0031] Figure 5 A partial structural diagram of the LTCC notch high-pass filter provided in this application. Figure 2 .

[0032] The following are the labeling elements in the figure:

[0033] 1. Ceramic substrate; 2. Filter structure; 21. First capacitor; 22. Second capacitor; 23. Third capacitor; 24. First series resonant unit; 241. First inductor; 242. Series-parallel module; 2421. Second inductor; 2422. Third inductor; 2423. Fourth capacitor; 25. Second series resonant unit; 251. Fourth inductor; 252. Fifth capacitor; 26. Planar metal plate; 3. Input electrode; 4. Output electrode; 5. Ground electrode. Detailed Implementation

[0034] The embodiments of this utility model are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain this utility model, and should not be construed as limiting this utility model.

[0035] In the description of this utility model, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", etc., indicating the orientation or positional relationship are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this utility model and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this utility model.

[0036] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this utility model, "a plurality of" means two or more, unless otherwise explicitly specified.

[0037] In this utility model, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model according to the specific circumstances.

[0038] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0039] Furthermore, the technical solutions of the various embodiments can be combined with each other, but only if they are based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of this utility model.

[0040] In the following description, suffixes such as "module," "part," "component," or "unit" are used only for the purpose of describing this utility model and have no specific meaning in themselves. Therefore, they can be used in combination.

[0041] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0042] like Figures 1 to 5 As shown, this application provides an LTCC notch high-pass filter, including a ceramic substrate 1, a filter structure 2, an input electrode 3, an output electrode 4, and a ground electrode 5.

[0043] The filter structure 2 is fully embedded inside the ceramic substrate 1 through a low-temperature co-firing process, forming a three-dimensional integrated structure. One end of the input electrode 3 is electrically connected to the input end of the filter structure 2, and the other end extends to the outer surface of the ceramic substrate 1 to form an external solderable end. One end of the output electrode 4 is electrically connected to the output end of the filter structure 2, and the other end also extends to the outer surface of the ceramic substrate 1. One end of the ground electrode 5 is connected to the ground end of the filter structure 2, and the other end extends to the outer surface of the ceramic substrate 1 to form a common ground connection end. The filter structure 2 adopts a multi-level capacitor-resonant unit composite topology, specifically including three capacitive elements, a first capacitor 21, a second capacitor 22, and a third capacitor 23, connected in series to form the main signal path. A first series resonant unit 24 is connected between the input end and the first capacitor 21, and between the third capacitor 23 and the output end, respectively. A second series resonant unit 25 is connected between the first capacitor 21 and the second capacitor 22, and between the second capacitor 22 and the third capacitor 23, respectively. Through the above specific connection method, a multi-order filter network with bandpass characteristics is formed. This structural design enables the optimized arrangement of functional components in three-dimensional space, ensuring both good filtering performance and high device integration.

[0044] In one specific embodiment of this application, the first series resonant unit 24 adopts a composite resonant network structure, which is composed of a first inductor 241 and a series-parallel module 242 connected in series. The input terminal of the first inductor 241 is connected to the signal path between the output terminal and the first capacitor 21, or to the signal path between the third capacitor 23 and the output terminal, while the output terminal of the series-parallel module 242 is directly grounded to form a resonant circuit. The series-parallel module 242 includes a second inductor 2421, a third inductor 2422, and a fourth capacitor 2423, wherein the third inductor 2422 and the fourth capacitor 2423 are connected in series to form a basic resonant branch, causing the filter to generate a notch point at the passband frequency, forming a band-stop filter. By adjusting the values ​​of the second inductor 2421, the third inductor 2422, and the fourth capacitor 2423, the notch point frequency can be adjusted. The second inductor 2421 is connected in parallel across the two ends of the resonant branch to form a composite resonant structure with frequency selectivity. This circuit topology effectively extends the stopband rejection range of the filter while maintaining good signal transmission characteristics within the passband. By appropriately setting the parameter values ​​of each inductor and capacitor, key performance indicators such as the filter's center frequency, bandwidth, and out-of-band rejection can be adjusted.

[0045] In one specific embodiment of this application, the second series resonant unit 25 adopts an inductor-capacitor series resonant structure, which consists of a fourth inductor 251 and a fifth capacitor 252 connected in series. This structure generates two zeros in the left stopband of the filter, achieving steep stopband suppression. By adjusting the value of the fifth capacitor 252, the zeros in the left stopband of the high-pass filter can be adjusted. The input terminal of the fourth inductor 251 is connected to the signal path between the first capacitor 21 and the second capacitor 22, or to the signal path between the second capacitor 22 and the third capacitor 23. The output terminal of the fifth capacitor 252 is directly grounded to form a resonant circuit. This series resonant structure, through the synergistic effect of the fourth inductor 251 and the fifth capacitor 252, can generate a resonant effect at a specific frequency point, thereby effectively improving the frequency selectivity of the filter. By adjusting the inductance of the fourth inductor 251 and the capacitance of the fifth capacitor 252, the position of the resonant frequency point can be controlled, thereby optimizing the passband characteristics and stopband suppression performance of the filter.

[0046] The resonant unit works in conjunction with the aforementioned first series resonant unit 24 to form a complete filter network with multi-order filtering characteristics.

[0047] In one specific embodiment of this application, the LTCC notch high-pass filter adopts a multi-layer symmetrical layout structure, with each functional element arranged in layers inside the ceramic substrate 1. The first capacitor 21 and the third capacitor 23 are mirror-symmetrically distributed with respect to the central axis of the ceramic substrate 1, and together with the second capacitor 22, are disposed in the first layer of the ceramic substrate 1, forming the core capacitive network of the filter. The first inductor 241, the second inductor 2421, the third inductor 2422, and the fourth inductor 251 are all arranged in the second layer of the ceramic substrate 1, forming an inductive network layer. The fourth capacitor 2423 and the fifth capacitor 252 are disposed in the third layer of the ceramic substrate 1, forming the lower layer structure of the capacitive network. The first series resonant unit 24 and the second series resonant unit 25 are both arranged in pairs and maintain a mirror-symmetrical relationship with respect to the central axis of the ceramic substrate 1. The first, second, and third layers are stacked sequentially from top to bottom, and reliable positioning between each layer is achieved through a low-temperature co-firing process. This three-dimensional layout not only ensures the symmetry and consistency of filter performance, but also significantly improves space utilization, making the overall structure more compact.

[0048] In one specific embodiment of this application, the first inductor 241, the second inductor 2421, the third inductor 2422, and the fourth inductor 251 all adopt a rectangular spiral structure, which effectively reduces the area occupied by the components in the lateral plane while maintaining the required inductance. This structural choice allows the filter to significantly optimize the overall device size while maintaining performance indicators, meeting the demand of modern electronic devices for miniaturized filters.

[0049] In one specific embodiment of this application, the first inductor 241, the second inductor 2421, the third inductor 2422, and the fourth inductor 251 all employ a double-dielectric-layer rectangular spiral structure. This structure, by placing a spiral conductor between two dielectric layers with different dielectric constants, effectively reduces parasitic coupling effects between inductor components. The double-dielectric-layer configuration optimizes the electromagnetic field distribution, significantly improving the inductor's quality factor (Q), thereby improving the overall performance of the filter, reducing insertion loss during high-frequency signal transmission, and expanding the filter's operating bandwidth. While maintaining a compact layout, the rectangular spiral structure achieves controllability of inductor parameters by controlling the conductor linewidth, spacing, and number of turns. The introduction of the double-dielectric-layer further enhances high-frequency characteristics, enabling the filter to meet the requirements of ultra-wideband applications.

[0050] In one specific embodiment of this application, the first capacitor 21, the second capacitor 22, and the third capacitor 23 all adopt a metal-insulator-metal (MIM) planar structure. This MIM capacitor structure forms a standard sandwich capacitor structure by placing upper and lower metal electrode plates within a single dielectric layer, separated by an insulating dielectric layer in between. This planar design significantly reduces the number of dielectric layers required to achieve the same capacitance value, simplifying the manufacturing process and improving structural reliability. The metal electrode plates of the MIM capacitor can be rectangular, and the capacitance value can be controlled by adjusting the electrode area and spacing. This structure not only saves vertical space but also reduces the complexity of interlayer interconnections, making the overall filter structure more compact. Simultaneously, the planar characteristics of the MIM capacitor allow for good layout matching with the aforementioned rectangular spiral inductor, jointly forming a high-performance integrated filter network.

[0051] In one specific embodiment of this application, the filter structure 2 further includes a planar metal plate 26. This planar metal plate 26 is electrically connected to the ground electrode 5. The third capacitor 23 and the fourth capacitor 2423 respectively form a metal-insulator-metal (MIM) capacitor structure with the planar metal plate 26. The planar metal plate 26 serves as a common ground electrode, forming capacitive coupling with the upper electrode plates of the third capacitor 23 and the fourth capacitor 2423. By sharing the planar metal plate 26, an integrated layout of multiple capacitor elements is achieved, which not only reduces the number of independent ground electrodes but also optimizes the overall space utilization.

[0052] The LTCC notch high-pass filter provided in this application has dimensions of 4.5mm*3.2mm*1.5mm, a relative permittivity of 5.0±0.3, and a dielectric loss of tanα≤0.003. The filter structure 2 is made of silver. The input electrode 3, output electrode 4, and ground electrode 5 are all three-layer structures, specifically consisting of an inner silver layer, a middle nickel layer, and an outermost tin layer. The filter is of order 7. The filter cutoff frequency is 1000MHz, and the passband range is 1000MHz-1780MHz and 2300MHz-5000MHz. The passband insertion loss is low: in-band insertion is less than 1.2dB. The stopband rejection is steep: at 780MHz, out-of-band rejection is better than 35dB. The notch point frequency range is 1970MHz-2030MHz, with notch point rejection better than 18dB. It has advantages such as low passband loss, high out-of-band rejection, high integration, and low cost, meeting the requirements of downstream electronic devices for miniaturization, high performance, high integration, and low cost.

[0053] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. An LTCC notch high-pass filter, characterized in that, include: Ceramic matrix (1); The filter structure (2) is encapsulated within the ceramic substrate (1). The input electrode (3) is connected at one end to the input end of the filter structure (2) and at the other end extends to the outside of the ceramic substrate (1); The output electrode (4) is connected at one end to the output end of the filter structure (2) and at the other end extends to the outside of the ceramic substrate (1); The grounding electrode (5) has one end connected to the grounding terminal of the filter structure (2) and the other end extending to the outside of the ceramic substrate (1); The filter structure (2) includes a first capacitor (21), a second capacitor (22) and a third capacitor (23) connected in series. A first series resonant unit (24) is connected between the input terminal and the first capacitor (21) and between the third capacitor (23) and the output terminal. A second series resonant unit (25) is connected between the first capacitor (21) and the second capacitor (22) and between the second capacitor (22) and the third capacitor (23).

2. The LTCC notch high-pass filter as described in claim 1, characterized in that, The first series resonant unit (24) includes a first inductor (241) and a series-parallel module (242) connected in series. The input terminal of the first inductor (241) is connected between the output terminal and the first capacitor (21) or between the third capacitor (23) and the output terminal. The output terminal of the series-parallel module (242) is grounded. The series-parallel module (242) includes a second inductor (2421), a third inductor (2422), and a fourth capacitor (2423). The third inductor (2422) and the fourth capacitor (2423) form a series resonance, and the second inductor (2421) is connected in parallel with the series resonance of the third inductor (2422) and the fourth capacitor (2423).

3. The LTCC notch high-pass filter as described in claim 2, characterized in that, The second series resonant unit (25) includes a fourth inductor (251) and a fifth capacitor (252) forming a series resonance. The input terminal of the inductor is connected between the first capacitor (21) and the second capacitor (22) or between the second capacitor (22) and the third capacitor (23). The output terminal of the capacitor is grounded.

4. The LTCC notch high-pass filter as described in claim 3, characterized in that, The first capacitor (21) and the third capacitor (23) are mirror-symmetrical with respect to the central axis of the ceramic substrate (1), and the first capacitor (21), the second capacitor (22) and the third capacitor (23) are located in the first layer of the ceramic substrate (1); The first inductor (241), the second inductor (2421), the third inductor (2422), and the fourth inductor (251) are located in the second layer of the ceramic substrate (1); The first series resonant unit (24) arranged in pairs is mirror-symmetrical with respect to the central plane of the ceramic substrate (1), and the second series resonant unit (25) arranged in pairs is mirror-symmetrical with respect to the central plane of the ceramic substrate (1); the fourth capacitor (2423) and the fifth capacitor (252) are located in the third layer of the ceramic substrate (1); The first, second, and third levels are set sequentially from top to bottom.

5. The LTCC notch high-pass filter as described in claim 3, characterized in that, The first inductor (241), the second inductor (2421), the third inductor (2422) and the fourth inductor (251) are all rectangular spiral inductors.

6. The LTCC notch high-pass filter as described in claim 3, characterized in that, The first inductor (241), the second inductor (2421), the third inductor (2422) and the fourth inductor (251) are all double dielectric layer rectangular spiral inductors.

7. The LTCC notch high-pass filter as described in claim 3, characterized in that, The first capacitor (21), the second capacitor (22) and the third capacitor (23) are all planar MIM capacitors.

8. The LTCC notch high-pass filter as described in claim 3, characterized in that, It also includes a planar metal plate (26), which is connected to the ground electrode (5), and the third capacitor (23) and the fourth capacitor (2423) form planar MIM capacitors with the planar metal plate (26) respectively.

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