Low pass filter based on LTCC

Abstract

The utility model provides a low-pass filter based on LTCC (Low Temperature Co-Fired Ceramic), which is characterized by comprising an LTCC substrate, and three capacitors and four inductors which are embedded in the LTCC substrate, the three capacitors are a first capacitor, a second capacitor and a third capacitor; the four inductors are a first inductor, a second inductor, a third inductor and a fourth inductor; the four inductors are connected in sequence and are configured to be correspondingly arranged above the three capacitors. The three capacitors are configured into a parallel plate structure. And the conductor coils of the four inductors are constructed into a spatial spiral structure.

Description

Technical Field

[0001] At least one embodiment of the utility model relates to the technical field of filters, and in particular to a low-pass filter based on LTCC (Low Temperature Co-fired Ce-ramic). Background Art

[0002] As an important component of radio frequency circuits, filters are often used to select signals within a specific frequency band, and at the same time have a certain inhibitory effect on out-of-band clutter and harmonic signals. The LC filter in the form of lumped parameters is a more common type of filter. LC filters are mostly arranged by capacitors and inductors according to the design method, making them frequency selective for signals. However, the development of LC filters is limited by their composition structure and connection method: the chip components that make up the filter have a large package size and are not easy to reduce; the actual working value of a single component deviates from the theoretical value; the chip device connection solder joints and the wiring between devices further reduce the filter's resistance and stability to moisture, oxidation, vibration and other environments. Utility Model Content

[0003] Based on the above problems, the utility model provides a low-pass filter based on LTCC, characterized in that it includes an LTCC substrate, and three capacitors and four inductors buried in the LTCC substrate; the three capacitors are a first capacitor, a second capacitor, and a third capacitor; the four inductors are a first inductor, a second inductor, a third inductor, and a fourth inductor; the four inductors are connected in sequence and are constructed to be correspondingly arranged above the three capacitors.

[0004] According to an embodiment of the present invention, the three capacitors are constructed into a parallel plate structure.

[0005] According to an embodiment of the present invention, the conductor coils of the four inductors are constructed into a spatial spiral structure.

[0006] According to an embodiment of the utility model, the first inductor is correspondingly arranged above the first capacitor, and the conductor coil is constructed into a spatial spiral structure, and the initial end and the terminal end of the spiral structure are respectively located in two high and low planes.

[0007] According to an embodiment of the utility model, the second inductor is correspondingly arranged above the second capacitor, and is constructed to include two spatial spiral structures.

[0008] According to the embodiment of the utility model, one of the two spatial spiral structures is constructed to rotate from the lower initial end to the upper side, extend to the side, and then rotate from the upper side to the lower side, forming two adjacent spatial spiral structures.

[0009] According to an embodiment of the utility model, the third inductor and the fourth inductor are correspondingly arranged above the third capacitor and are constructed into a spatial spiral structure.

[0010] According to the embodiment of the utility model, the three capacitors and the four inductors are connected through transmission lines and / or metallized vias.

[0011] According to an embodiment of the present invention, the conductor line bodies of the four inductors are constructed into a flat structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 This is a schematic diagram of the circuit principle of a low-pass filter.

[0013] Figure 2 It is a schematic diagram of a three-dimensional structure of a low-pass filter based on LTCC according to an embodiment of the utility model.

[0014] Figure 3 It is a schematic diagram of the main internal structure of the LTCC-based low-pass filter according to an embodiment of the utility model.

[0015] Figure 4 It is a schematic diagram of simulation results of a low-pass filter based on LTCC according to an embodiment of the utility model.

[0016] [Description of the main components of the embodiment of the utility model in the accompanying drawings]

[0017] C1-first capacitor; C2-second capacitor; C3-third capacitor; L1-first inductor;

[0018] L2-second inductor; L3-third inductor; L4-fourth inductor;

[0019] It should be noted that, for the sake of clarity, in the drawings used to describe the embodiments of the present invention, the sizes of structures or regions may be enlarged or reduced, that is, these drawings are not drawn according to the actual scale. DETAILED DESCRIPTION

[0020] In order to solve the problem of large size and heavy weight of the current LC low-pass filter, the present invention proposes a low-pass filter based on LTCC technology, remodels the traditional LC low-pass filter circuit, applies a three-dimensional layout architecture based on LTCC, adopts a spiral layout for the inductor in the prototype circuit, and adopts a parallel plate layout for the capacitor in the prototype circuit, so as to achieve miniaturization and lightweight of the low-pass filter.

[0021] Low temperature co-fired ceramic technology is a multilayer ceramic technology with the characteristics of three-dimensional wiring. At the same time, passive components can be embedded in the interior of multilayer ceramics, thereby realizing the miniaturization and integration of passive devices and circuits. In the process of realizing the present disclosure, the inventor found that by utilizing the advantages of LTCC technology in a three-dimensional structure and adopting a stacking method to realize lumped capacitance and inductance in the Z direction, the volume of the microwave filter can be effectively reduced and the integration and reliability of the LC filter can be improved. Miniaturized LTCC technology LC filters have promoted the rapid development of civilian and military electronic products in the direction of high reliability, miniaturization, high performance and low cost.

[0022] The production process of LTCC is extremely complicated, mainly including multiple processes such as punching, filling holes, conductor printing, lamination, hot cutting, sintering, dicing and post-firing. After these processes, the production and processing of LTCC low-pass filter is completed, and the final product size is only 3.7mm×3mm×0.6mm. In terms of miniaturization of filters, LTCC technology has a strong advantage. Compared with traditional crystal and SAW filters, the volume is reduced by at least 5 times. The design method disclosed in this disclosure provides a better idea for low-pass filter design.

[0023] In order to make the purpose, technical solution and advantages of the utility model more clear, the utility model is further described in detail below in combination with specific embodiments and with reference to the accompanying drawings. The following description of at least one exemplary embodiment is actually only illustrative and is by no means a limitation on the utility model and its application or use. Based on the embodiments of the utility model, all other embodiments obtained by ordinary technicians in this field without carrying out creative work are within the scope of protection of the utility model.

[0024] The utility model provides a low-pass filter based on LTCC, combined with Figure 2 and Figure 3 As shown, the low-pass filter includes an LTCC substrate, and three capacitors and four inductors buried in the LTCC substrate; the three capacitors are a first capacitor C1, a second capacitor C2, and a third capacitor C3; the four inductors are a first inductor L1, a second inductor L2, a third inductor L3, and a fourth inductor L4; the four inductors are connected in sequence and are constructed to be correspondingly arranged above the three capacitors.

[0025] According to an embodiment of the present invention, the three capacitors are constructed into a parallel plate structure.

[0026] According to an embodiment of the present invention, the conductor coils of the four inductors are constructed into a spatial spiral structure.

[0027] According to the embodiment of the utility model, the first inductor L1 is correspondingly arranged above the first capacitor C1, and the conductor coil is constructed into a spatial spiral structure, and the initial end and the terminal end of the spiral structure are respectively located in two high and low planes.

[0028] According to the embodiment of the utility model, the second inductor L2 is correspondingly arranged above the second capacitor C2 and is constructed to include two spatial spiral structures. One of the two spatial spiral structures is constructed to spiral from the initial end at the bottom to the top, extend to the side, and then spiral from the top to the bottom, forming two adjacent spatial spiral structures.

[0029] According to the embodiment of the utility model, the third inductor L3 and the fourth inductor L4 are correspondingly arranged above the third capacitor C3 and are constructed into a spatial spiral structure.

[0030] According to the embodiment of the utility model, the three capacitors and the four inductors are connected through transmission lines and / or metallized vias.

[0031] According to an embodiment of the present invention, the conductor line bodies of the four inductors are constructed into a flat structure.

[0032] The present invention adopts 6 layers of LTCC material (Dupont 951), builds models based on spiral inductors and planar capacitors, and then performs three-dimensional modeling and simulation optimization on all components in the filter. Figure 1 As can be seen from the circuit schematic diagram, there are a total of 4 inductors and 3 capacitors, and the inductance and capacitance values ​​are different. In particular, the inductance value of inductor L2 is relatively large. Inductor L2 uses the upper spiral and lower spiral scheme of the inductor coil to form a high inductance value, which is conducive to signal line connection. Due to the existence of many coupling effects, inductance effects and capacitance effects in the three-dimensional LTCC low-pass filter model, the filter simulation is difficult. By analyzing the simulation results of the flexible layout of inductors and capacitors in space, the model is continuously optimized and adjusted to obtain the optimal simulation results as shown in the figure. Figure 4 As shown, from the simulation results, it can be seen that the low-pass filter has good in-band characteristics and out-of-band suppression characteristics, low in-band loss, good out-of-band suppression effect, and low reflection loss.

[0033] So far, the embodiments of the utility model have been described in detail in conjunction with the accompanying drawings. It should be noted that the implementation methods not shown or described in the drawings or the body of the specification are all forms known to ordinary technicians in the relevant technical field and are not described in detail. In addition, the above definitions of each element and method are not limited to the various specific structures, shapes or methods mentioned in the embodiments, and ordinary technicians in the field can simply change or replace them.

[0034] According to the above description, those skilled in the art should have a clear understanding of the low-pass filter of the present invention.

[0035] In summary, the utility model provides a low-pass filter based on LTCC, which makes the original plane structure of the filter three-dimensional. Based on the technical characteristics of LTCC multilayer technology, the capacitor is realized by stacking structure, the inductor is realized by spiral coupling line form, and the vertical interconnectivity of LTCC wiring is used to complete the design of the filter. LTCC technology makes the filter design more compact, while reducing the influence of the performance difference of the original LC filter single component and the influence of the connection between the components, improving the stability of the filter, and greatly reducing the volume of the filter.

[0036] It should also be noted that the directional terms mentioned in the embodiments, such as "upper", "lower", "front", "back", "left", "right", etc., are only reference directions of the drawings and are not intended to limit the scope of protection of the present invention. Throughout the drawings, the same elements are represented by the same or similar reference numerals. Conventional structures or constructions will be omitted when they may cause confusion in the understanding of the present invention. In addition, the shapes and sizes of the components in the drawings do not reflect the actual size and proportion, but only illustrate the contents of the embodiments of the present invention.

[0037] The ordinal numbers used in the specification and claims, such as "first", "second", "third", etc., to modify the corresponding elements, do not themselves mean that the elements have any ordinal numbers, nor do they represent the order of one element and another element, or the order in the manufacturing method. The use of these ordinal numbers is only used to clearly distinguish a component with a certain name from another component with the same name.

[0038] In addition, unless the steps are specifically described or must occur in sequence, the order of the above steps is not limited to the above list, and can be changed or rearranged according to the required design. And the above embodiments can be mixed and matched with each other or with other embodiments based on design and reliability considerations, that is, the technical features in different embodiments can be freely combined to form more embodiments.

[0039] Those skilled in the art can understand that the embodiments described above are exemplary and can be improved by those skilled in the art. The structures described in various embodiments can be freely combined without causing conflicts in structure or principle.

[0040] The specific embodiments described above further illustrate the purpose, technical solutions and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A low-pass filter based on LTCC, characterized in that: It includes a LTCC substrate, and three capacitors and four inductors embedded in the LTCC substrate; The three capacitors are a first capacitor, a second capacitor, and a third capacitor; The four inductors are a first inductor, a second inductor, a third inductor, and a fourth inductor; The four inductors are connected in sequence and are configured to be arranged correspondingly above the three capacitors.

2. The low-pass filter according to claim 1, characterized in that The three capacitors are constructed as a parallel plate structure.

3. The low-pass filter according to claim 1, characterized in that The conductor coils of the four inductors are constructed as a spatial spiral structure.

4. The low-pass filter according to claim 1, characterized in that The first inductor is correspondingly arranged above the first capacitor, and the conductor coil is constructed into a spatial spiral structure, wherein an initial end and an end of the spiral structure are respectively located in two upper and lower planes.

5. The low-pass filter according to claim 1, characterized in that The second inductor is correspondingly arranged above the second capacitor and is constructed to include two spatial spiral structures.

6. The low-pass filter according to claim 5, wherein one of the two spatial spiral structures is constructed to rotate from a lower initial end to an upper end, extend to the side, and then rotate from an upper end to a lower end, thereby forming two adjacent spatial spiral structures.

7. The low-pass filter according to claim 1, characterized in that The third inductor and the fourth inductor are correspondingly arranged above the third capacitor and are constructed into a spatial spiral structure.

8. The low-pass filter according to any one of claims 1 to 7, characterized in that: The three capacitors and the four inductors are connected through transmission lines and / or metalized vias.

9. The low-pass filter according to any one of claims 1 to 7, characterized in that: The conductor line bodies of the four inductors are configured as flat structures.

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