A compact multistage LC filter

Abstract

The utility model relates to filter technical field, specifically disclose a compact multistage LC filter, the filter includes rectangle insulating substrate, its four corner position is equipped with mounting hole, the filter shell is fixedly installed above the insulating substrate, the both ends of filter shell are equipped with input and output port, in the filter shell, the insulating substrate top is equipped with at least two stages filter unit, and each stage filter unit contains spiral inductance and interdigital capacitance, and they are connected through microstrip line between the filter unit of adjacent stage alternately cascaded. Two insulating shield baffles are arranged between the adjacent filter units, which are connected with the insulating substrate and the filter shell, and the shielding layer formed between the insulating shield baffles is connected with the bottom ground plane through the metallized via on the insulating substrate. The filter realizes compact volume, excellent filtering performance and anti-interference ability through three-dimensional inductance, shielding structure and optimized layout.

Description

Technical Field

[0001] This utility model relates to the field of filter technology, and more specifically, to a compact multi-stage LC filter. Background Technology

[0002] In modern electronic systems such as communications and power management, LC filters serve as critical signal processing components, playing a vital role in suppressing interference signals and extracting useful signals. Traditional LC filters typically employ cascaded discrete inductors and capacitors; however, this structure presents several problems. The relatively large size of the components makes it difficult to reduce the overall size of the filter, failing to meet the space-constrained design requirements of increasingly miniaturized and integrated electronic devices. Furthermore, the connecting leads between discrete components introduce additional parasitic parameters, affecting the filter's frequency response characteristics and filtering performance, resulting in poor filtering performance at high frequencies and difficulty in achieving high selectivity and a steep transition band.

[0003] With the development of emerging technologies such as 5G communication and the Internet of Things, higher demands are placed on the performance of LC filters. They not only need excellent filtering characteristics but also a compact structure and ease of integration. To address the shortcomings of traditional LC filters, some improved solutions have emerged in existing technologies, such as using integrated components like planar spiral inductors and interdigital capacitors to construct the filter. However, these solutions still have limitations in further improving the integration and performance of the filter. Electromagnetic interference between multi-stage filtering units is a prominent issue, leading to reduced filter stability and reliability. Therefore, there is an urgent need to develop a new type of compact multi-stage LC filter to meet the pressing demand of modern electronic systems for high-performance, miniaturized filtering components. Utility Model Content

[0004] To overcome the shortcomings mentioned above, this invention provides a compact multi-stage LC filter. By using interdigitated capacitors and spiral inductors in alternating cascades and setting an insulating shielding baffle to generate a shielding layer, electromagnetic interference is suppressed, stability is improved, and the needs of modern electronic systems for high-performance miniaturized filter components are met.

[0005] To achieve the above objectives, this utility model discloses a compact multi-stage LC filter, comprising:

[0006] An insulating substrate, wherein the insulating substrate is rectangular and has mounting holes at four right-angle positions, and a filter housing is fixedly mounted on the top of the insulating substrate;

[0007] On the insulating substrate, at least two stages of filtering units are provided inside the filter housing, each stage of filtering unit including a spiral inductor and an interdigitated capacitor;

[0008] The spiral inductor and the interdigitated capacitor are cascaded alternately, and the filter units of adjacent stages are connected by microstrip lines;

[0009] The spiral inductor adopts a three-dimensional stacked structure, including a bottom coil and at least one layer of through-holes for jumper connection;

[0010] The input port and output port are respectively located at both ends of the filter housing.

[0011] Preferably, two insulating shielding baffles are provided between adjacent filter units, and the two insulating shielding baffles are fixedly connected to the insulating substrate and the filter housing.

[0012] Preferably, a shielding layer is formed between the two insulating shielding baffles, and a metallized via is provided on the insulating substrate at the bottom of the shielding layer, and the shielding layer is connected to the bottom ground plane of the insulating substrate through the metallized via.

[0013] Preferably, the finger width of the interdigitated capacitor is 0.1-0.5 mm, and the interdigital spacing is less than 0.2 mm.

[0014] Preferably, the spiral inductor has 3–8 turns and a line width of 0.05–0.3 mm.

[0015] Preferably, the insulating substrate is a ceramic material or an FR-4 epoxy resin board.

[0016] Therefore, this utility model is a compact multi-stage LC filter using the above structure, and its beneficial effects are as follows:

[0017] (1) Compact size: Through the spiral inductor design with a three-dimensional stacked structure, the inductance is increased by using the bottom coil and jump layer vias. Compared with traditional discrete components, the area occupied is greatly reduced. Combined with the rectangular insulating substrate and integrated layout, it meets the miniaturization requirements of electronic devices.

[0018] (2) Filtering performance optimization: Interdigitated capacitors and spiral inductors are cascaded alternately and connected by microstrip lines to reduce the influence of interstage parasitic parameters. Combined with the precise design of the finger width and spacing, high-frequency selective filtering and steep transition band characteristics are achieved.

[0019] (3) Enhanced anti-interference capability: The insulating shielding baffle and metallized via grounding shield between adjacent filter units effectively suppress electromagnetic coupling interference between multi-level units, and improve the stability and reliability of the filter in complex electromagnetic environments.

[0020] The technical solution of this utility model will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0021] Figure 1This is a schematic diagram of the overall structure of a compact multi-stage LC filter according to this utility model;

[0022] Figure 2 This is a cross-sectional view of a compact multi-stage LC filter according to the present invention.

[0023] Figure Labels

[0024] 1. Insulating substrate; 2. Mounting hole; 3. Filter housing; 4. Input port; 5. Output port; 6. Spiral inductor; 7. Interdigitated capacitor; 8. Microstrip line; 9. Insulating shield; 10. Metallized via. Detailed Implementation

[0025] The technical solution of this utility model will be further described in detail below with reference to the accompanying drawings and embodiments.

[0026] Unless otherwise defined, the technical or scientific terms used in this utility model shall have the ordinary meaning understood by one of ordinary skill in the art to which this utility model pertains. The terms "first," "second," and similar terms used in this utility model do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Terms such as "comprising" or "including" mean that the element or object preceding the word encompasses the elements or objects listed following the word and their equivalents, without excluding other elements or objects. Terms such as "connected" or "linked" are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. Terms such as "upper," "lower," "left," and "right" are used only to indicate relative positional relationships; when the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0027] like Figure 1-2 As shown, this utility model provides a compact multi-stage LC filter, including an insulating substrate 1, which is made of ceramic material or FR-4 epoxy resin board and is rectangular in shape. Mounting holes 2 are provided at the four right-angle positions to facilitate the fixed installation of the filter. A filter housing 3 is fixedly installed on top of the insulating substrate 1. Input ports 4 and output ports 5 are respectively provided at both ends of the filter housing 3, and the input ports 4 and output ports 5 are used for signal input and output, respectively.

[0028] On the insulating substrate 1, at least two stages of filtering units are arranged inside the filter housing 3. Each stage of filtering unit includes a spiral inductor 6 and an interdigital capacitor 7. The spiral inductor 6 adopts a three-dimensional stacked structure, including a bottom coil and a through-hole connecting at least one jumper layer. The coil has 3-8 turns and a line width of 0.05-0.3mm. Through the spiral inductor design with a three-dimensional stacked structure, the inductance is increased by utilizing the bottom coil and the jumper layer through-hole, which significantly reduces the occupied area compared to traditional discrete components. The finger width of the interdigital capacitor is 0.1-0.5mm, and the finger spacing is less than 0.2mm. The spiral inductor 6 and the interdigital capacitor 7 are cascaded alternately, and the filtering units of adjacent stages are connected by microstrip lines 8, which reduces the influence of interstage parasitic parameters. With the precise design of the finger width and spacing, high-frequency selective filtering and steep transition band characteristics are achieved.

[0029] Two insulating shielding plates 9 are provided between adjacent filter units. The two insulating shielding plates 9 are fixedly connected to the insulating substrate 1 and the filter housing 3. A shielding layer is formed between the two insulating shielding plates 9. A metallized via 10 is provided on the insulating substrate 1 at the bottom of the shielding layer. The shielding layer is connected to the bottom ground plane of the insulating substrate 1 through the metallized via 10, which effectively suppresses electromagnetic coupling interference between multi-level units and improves the stability and reliability of the filter in complex electromagnetic environments.

[0030] In summary, this utility model presents a compact multi-stage LC filter with the above-described structure. It achieves miniaturization by stacking helical inductors in three dimensions and utilizing bottom coils and vias. It reduces parasitic parameters by alternating cascades of interdigitated capacitors and helical inductors and connecting them with microstrip lines. It also suppresses electromagnetic interference by setting insulating shielding baffles and metallized via shielding layers, thus meeting the needs of modern electronic systems for high-performance miniaturized filter components.

[0031] Finally, it should be noted that the above are merely preferred embodiments of this utility model and are not intended to limit the utility model. Although the utility model has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this utility model should be included within the protection scope of this utility model.

Claims

1. A compact multi-stage LC filter, characterized in that, include: An insulating substrate, wherein the insulating substrate is rectangular and has mounting holes at four right-angle positions, and a filter housing is fixedly mounted on the top of the insulating substrate; On the insulating substrate, at least two stages of filtering units are provided inside the filter housing, each stage of filtering unit including a spiral inductor and an interdigitated capacitor; The spiral inductor and the interdigitated capacitor are cascaded alternately, and the filter units of adjacent stages are connected by microstrip lines; The spiral inductor adopts a three-dimensional stacked structure, including a bottom coil and at least one layer of through-holes for jumper connection; The input port and output port are respectively located at both ends of the filter housing.

2. A compact multi-stage LC filter according to claim 1, characterized in that, Two insulating shielding plates are provided between adjacent filter units, and the two insulating shielding plates are fixedly connected to the insulating substrate and the filter housing.

3. A compact multi-stage LC filter according to claim 2, characterized in that, A shielding layer is formed between two insulating shielding plates. A metallized via is provided on the insulating substrate at the bottom of the shielding layer. The shielding layer is connected to the bottom ground plane of the insulating substrate through the metallized via.

4. A compact multi-stage LC filter according to claim 1, characterized in that, The finger width of the interdigitated capacitor is 0.1-0.5mm, and the spacing between the fingers is less than 0.2mm.

5. A compact multi-stage LC filter according to claim 1, characterized in that, The spiral inductor has 3–8 turns and a line width of 0.05–0.3 mm.

6. A compact multi-stage LC filter according to claim 1, characterized in that, The insulating substrate is a ceramic material or an FR-4 epoxy resin board.

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