CN119324301A

CN119324301A - Miniaturized band-pass filter based on LTCC

Info

Publication number: CN119324301A
Application number: CN202411874672.5A
Authority: CN
Inventors: 梁毅庆; 吴森炜; 郭新华; 王荣坤; 周思齐; 李秀万; 郭鹏乾
Original assignee: Huaqiao University
Current assignee: Huaqiao University
Priority date: 2024-12-19
Filing date: 2024-12-19
Publication date: 2025-01-17

Abstract

The invention provides a miniaturized band-pass filter based on LTCC, and relates to the technical field of microwave millimeter wave circuits. The design focuses on stabilizing the frequency response, reducing the influence of material errors, and the manufacturing process of the whole filter comprises accurate screen printing and sintering processes, ensures the accurate integration of elements, has low insertion loss and high Q value, is suitable for 5G communication and satellite communication application, improves the high-frequency signal processing performance, and reduces the size of the filter.

Description

Miniaturized band-pass filter based on LTCC

Technical Field

The invention relates to the technical field of microwave millimeter wave circuits, in particular to a miniaturized band-pass filter based on an LTCC.

Background

In modern wireless communication systems, advances in signal processing technology play a vital role in improving communication quality, increasing frequency band utilization, and improving overall system performance. As one of the core components in signal processing, the accuracy of its design and manufacture directly affects the performance of the communication device. With the increasing demand for high performance filters in the fields of 5G communication, radar and satellite communication, higher requirements are placed on the size of the filter, the stability of the frequency response and the insertion loss.

Conventional filter designs often suffer from large size, difficulty in integration, sensitivity to manufacturing errors, and the like. To overcome these limitations, low temperature co-fired ceramic (LTCC) technology has become an ideal choice for achieving miniaturized, high performance filters because of its ability to achieve co-firing of multiple layers of ceramic materials at lower temperatures, and high dielectric constants and good thermal matching characteristics. LTCC technology enables passive components such as inductors, capacitors, etc. to be highly integrated in a compact three-dimensional structure, thereby achieving miniaturization and high performance of the filter.

However, the design and manufacturing processes of LTCC filters currently on the market are complex, involving precise multi-layer material stacking, screen printing, precise dimensional control, and a strict sintering process. During this process, small variations in material, such as thickness, dielectric constant and geometric variations, can lead to significant degradation of the filter performance. In addition, filters in high frequency applications require extremely high signal transmission characteristics, and any non-ideal coupling or reflection can severely impact system performance.

In view of this, the present application has been proposed.

Disclosure of Invention

The present invention provides a miniaturized bandpass filter based on LTCC that at least partially ameliorates the above-described problems.

In order to achieve the above purpose, the present invention adopts the following technical scheme:

A miniaturized band-pass filter based on LTCC comprises an LTCC substrate, a first capacitor C1, a second capacitor C2, a third capacitor C3, a fourth capacitor C4, an inductor L1, an input coupling feeder line Lin, an output coupling feeder line Lout, a first input port P1, a second output port P2, a first metal grounding plate GND1 and a second metal grounding plate GND2, wherein the first capacitor C1, the second capacitor C2, the third capacitor C3, the fourth capacitor C4, the inductor L1, the input coupling feeder line Lin and the output coupling feeder line Lout are integrated inside the LTCC substrate through screen printing;

The input coupling feeder line Lin and the output coupling feeder line Lout are respectively configured at two sides of the LTCC substrate, the sizes of the input coupling feeder line Lin and the output coupling feeder line Lout are consistent, one end of the input coupling feeder line Lin and one end of the output coupling feeder line Lout are respectively connected with the first input port P1 and the second output port P2, the other end of the input coupling feeder line Lin is connected with the first capacitor C1, the other end of the output coupling feeder line Lout is connected with the second capacitor C2, the first input port P1 is connected with the first capacitor C1, the second output port P2 is connected with the second capacitor C2, the first metal grounding plate GND1 is connected with the inductor L1, and the second metal grounding plate GND2 is connected with the third capacitor C3 and the fourth capacitor C4;

The first capacitor C1, the second capacitor C2, the third capacitor C3, and the fourth capacitor C4 are mirror symmetrical, and the third capacitor C3 and the fourth capacitor C4 are perpendicular to the first capacitor C1 and the second capacitor C2.

In summary, the miniaturized band-pass filter based on the LTCC adopts the LTCC multilayer structure, and integrates a plurality of passive elements such as 4 VIC capacitors, 1 spiral inductor and the like on the multilayer structure, so that the design of the miniaturized band-pass filter with the multilayer structure is realized by compact layout, the stability of the filtering function of the filter is improved, and the generation of parasitic modes is reduced.

Drawings

Fig. 1 is a schematic diagram of the overall structure of a LTCC-based miniaturized bandpass filter according to an embodiment of the invention;

Fig. 2 is a front view of an internal integrated passive device structure of an LTCC substrate provided in accordance with a first embodiment of the invention;

Fig. 3 is a top view of an internally integrated passive device structure of an LTCC substrate provided in accordance with a first embodiment of the invention;

fig. 4 is a front view of the overall structure of an internally integrated passive device of an LTCC substrate provided in accordance with a first embodiment of the present invention;

FIG. 5 is a graph of S parameter for LTCC media with dielectric constant of 9.1 and Lc1 length of 0.9mm according to the embodiment of the present invention;

FIG. 6 is a graph S11 of the LTCC dielectric with a dielectric constant of 9.1 and a length of Lc1 according to the embodiment of the present invention;

FIG. 7 is a graph S21 of the LTCC medium provided by the embodiment of the invention with a dielectric constant of 9.1 and a length of Lc 1;

FIG. 8 is a graph of S parameter when the dielectric constant of the LTCC medium provided by the embodiment of the invention is 9.1 and the length of Lc1 is changed;

FIG. 9 is a graph S11 of the LTCC dielectric with a dielectric constant of 9.0 and a length of Lc1 according to the embodiment of the present invention;

FIG. 10 is a graph S21 of the LTCC medium provided by the embodiment of the invention with a dielectric constant of 9.0 and a length of Lc 1;

FIG. 11 is a graph showing the S-parameters of LTCC media with dielectric constants of 9.0 and Lc1 when the length of the LTCC media is changed.

Detailed Description

The present invention will be described in further detail with reference to the following examples in order to make the objects, technical solutions and advantages of the present invention more apparent. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the invention.

Referring to fig. 1 to 11, a miniaturized band-pass filter based on LTCC according to a first embodiment of the present invention includes an LTCC substrate, a first capacitor C1, a second capacitor C2, a third capacitor C3, a fourth capacitor C4, an inductor L1, an input coupling feeder line Lin and an output coupling feeder line Lout integrated inside the LTCC substrate by screen printing, and a first input port P1, a second output port P2, a first metal ground plate GND1, a second metal ground plate GND2 attached to an outer surface of the LTCC substrate;

Specifically, in the present embodiment, in the high dielectric constantAnd r=11.8, wherein the sizes of the integrated first capacitor C1, second capacitor C2, third capacitor C3, fourth capacitor C4 and inductor L1 are small, so that the capacity of the filter for realizing high-frequency operation under the small size is greatly improved, and stable filtering within the passband range of the filter can be ensured when the process or external environment changes.

The input coupling feeder line Lin and the output coupling feeder line Lout in the miniaturized band-pass filter based on the LTCC are all 50 omega-impedance line widths, and impedance matching of a feed port is guaranteed. The input coupling feeder LINE Lin and the output coupling feeder LINE Lout are respectively provided with a length of a preset constant L_LINE, a width of a preset constant W_LINE and a thickness of a preset constant H_L, and are positioned on the 14 th layer of the LTCC substrate.

In short, the miniaturized band-pass filter based on the LTCC realizes miniaturization of the filter, maintains the due high performance of the filter, simplifies the production flow through multilayer integration and surface mounting ports and a grounding plate, and reduces the production cost.

Preferably, the LTCC substrate is a low-temperature co-fired ceramic dielectric substrate, the relative dielectric constant of the LTCC substrate is 9.1, the total thickness of the substrate is 2.34mm, the number of process layers is 22, and the thickness of each process layer substrate is a preset constant h_ltcc.

In the present embodiment, the LTCC substrate has a relative dielectric constant of 9.1, which contributes to achieving high-frequency operation capability in a smaller size while reducing the generation of parasitic modes. And the high dielectric constant material can enhance the electric field strength of the capacitor, thereby realizing the required capacitance value in a smaller volume.

Preferably, the first capacitor C1, the second capacitor C2, the third capacitor C3, and the fourth capacitor C4 are VIC capacitors formed by five layers of capacitor plates, the inductor L1 is a spiral inductor, the first input port P1 and the second output port P2 adopt a U-shaped structure, and the first metal ground plate GND1 and the second metal ground plate GND2 adopt a groove structure.

In this embodiment, according to design requirements, such as passband frequency, design volume, etc., the sizes and structures of the first capacitor C1, the second capacitor C2, the third capacitor C3, the fourth capacitor C4, and the inductor L1 integrated in the LTCC are confirmed, and the spatial distance between each capacitor and each inductor is confirmed to avoid electromagnetic coupling from affecting the implementation effect of the filter. In the manufacturing process of the miniaturized band-pass filter based on the LTCC, the passband range and the filtering effect of the filter can be kept basically unchanged without being influenced by tiny errors of materials, such as thickness, dielectric constant, deviation of geometric dimensions and the like.

Preferably, the first capacitor C1 includes a first layer plate C11, a second layer plate C12, a third layer plate C13, a fourth layer plate C14, a fifth layer plate C15, a first through hole c1_tk1, a second through hole c1_tk2, and five lead-out strip structures corresponding to the first layer plate C11, the second layer plate C12, the third layer plate C13, the fourth layer plate C14, and the fifth layer plate C15, respectively;

The first layer of polar plate C11 is connected with the first input port P1 through the input coupling feeder line Lin, the first layer of polar plate C11, the third layer of polar plate C13 and the fifth layer of polar plate C15 are combined with the first through hole c1_tk1 through corresponding lead-out belt structures to form a first pole of the first capacitor C1, and the second layer of polar plate C12 and the fourth layer of polar plate C14 are combined with the second through hole c1_tk2 through corresponding lead-out belt structures to form a second pole of the first capacitor C1.

Preferably, the second capacitor C2 includes a sixth layer plate C21, a seventh layer plate C22, an eighth layer plate C23, a ninth layer plate C24, a tenth layer plate C25, a third through hole c2_tk1, a fourth through hole c2_tk2, and five feed-strip lines corresponding to the sixth layer plate C21, the seventh layer plate C22, the eighth layer plate C23, the ninth layer plate C24, and the tenth layer plate C25, respectively;

The sixth-layer polar plate C21 is connected with the second output port P2 through an output coupling feeder line Lout, the sixth-layer polar plate C21, the eighth-layer polar plate C23 and the tenth-layer polar plate C25 are combined with the third through hole C2_TK1 through corresponding lead-out belt structures to form a first pole of the second capacitor C2, and the seventh-layer polar plate C22 and the ninth-layer polar plate C24 are combined with the fourth through hole C2_TK2 through corresponding lead-out belt structures to form a second pole of the second capacitor C2;

The first feedback line c1_line led out from the fourth layer of polar plate C14 of the first capacitor C1 is connected to the second feedback line c2_line led out from the ninth layer of polar plate C24 of the second capacitor C2, so as to realize the series connection of the first capacitor C1 and the second capacitor C2.

Preferably, each plate of the first capacitor C1 and the second capacitor C2 has the same size, a length of a preset constant Lc1, a width of a preset constant Wc1, and a thickness of a preset constant h_c.

In the embodiment, the first capacitor C1 and the second capacitor C2 have the same structure and size and are composed of 5 polar plates, the capacitive polar plates are made of silver in the LTCC substrate by a screen printing technology, and the polar plates are connected through silver through holes.

Specifically, the first layer of polar plate C11 of the first capacitor C1 has a length Lc1, a width Wc1, and a thickness h_c, and is located at the 14 th layer of the LTCC substrate, and a first feed line led out from the first layer of polar plate C11 is connected to the input coupling feed line Lin, and is connected to the third layer of polar plate C13 and the fifth layer of polar plate C15 through a first through hole c1_tk1. The second layer polar plate C12 of the first capacitor C1 is long Lc1, wide Wc1 and thick H_c, is positioned on the 13 th layer of the LTCC substrate, is staggered by 0.1mm from C11 in the Y-axis direction, and is led out to be connected with the fourth layer polar plate C14 through a second through hole C1_TK2. The third layer polar plate C13 of the first capacitor C1 is long Lc1, wide Wc1 and thick H_c, is positioned on the 12 th layer of the LTCC substrate, the fourth layer polar plate C14 of the first capacitor C1 is long Lc1, wide Wc1 and thick H_c, is positioned on the 11 th layer of the LTCC substrate, the fifth layer polar plate C15 of the first capacitor C1 is long Lc1, wide Wc1 and thick H_c and is positioned on the 10 th layer of the LTCC substrate, the first feed-through strip line C1_line led out by the fourth layer polar plate C14 of the first capacitor C1 is connected with the second feed-through strip line C2_line led out by the ninth layer polar plate C24 of the second capacitor C2, the series connection of the first capacitor C1 and the second capacitor C2 is realized, and the electric connection of the first capacitor C1, the second capacitor C2, the third capacitor C3, the fourth capacitor C4 and the inductor L1 is realized on the long two feed-through strips.

In this embodiment, the structure and the working principle of the second capacitor C2 are identical to those of the first capacitor C1, so that redundant description is omitted.

Preferably, the third capacitor C3 includes an eleventh-layer plate C31, a twelfth-layer plate C32, a thirteenth-layer plate C33, a fourteenth-layer plate C34, a fifteenth-layer plate C35, a fifth through hole c3_tk1, a sixth through hole c3_tk2, and five lead-out band structures corresponding to the eleventh-layer plate C31, the twelfth-layer plate C32, the thirteenth-layer plate C33, the fourteenth-layer plate C34, and the fifteenth-layer plate C35, respectively;

The eleventh layer of electrode plate C31, the thirteenth layer of electrode plate C33 and the fifteenth layer of electrode plate C35 are combined with the fifth through hole c3_tk1 through corresponding lead-out belt structures to form a first electrode of the third capacitor C3, the twelfth layer of electrode plate C32 and the fourteenth layer of electrode plate C34 are combined with the sixth through hole c3_tk2 through corresponding lead-out belt structures to form a second electrode of the third capacitor C3, a third input coupling feeder line c3_lin led out by the third capacitor C3 through the eleventh layer of electrode plate C31 is connected with the first feed-out belt line c1_line, and a third output coupling feeder line c3_out led out by the third capacitor C3 through the fourteenth layer of electrode plate C34 is connected with the second metal grounding plate GND 2.

Preferably, the fourth capacitor C4 includes a sixteenth layer plate C41, a seventeenth layer plate C42, an eighteenth layer plate C43, a nineteenth layer plate C44, a twentieth layer plate C45, a seventh through hole c4_tk1, an eighth through hole c4_tk2, and five lead-out band structures corresponding to the sixteenth layer plate C41, the seventeenth layer plate C42, the eighteenth layer plate C43, the nineteenth layer plate C44, and the twentieth layer plate C45, respectively;

The sixteenth layer of electrode plate C41, the eighteenth layer of electrode plate C43 and the twentieth layer of electrode plate C45 are combined with the seventh through hole c4_tk1 through corresponding lead-out band structures to form a first electrode of a fourth capacitor C4, the seventeenth layer of electrode plate C42 and the nineteenth layer of electrode plate C44 are combined with the eighth through hole c4_tk2 through corresponding lead-out band structures to form a second electrode of the fourth capacitor C4, a fourth input coupling feeder c4_lin led out by the fourth capacitor C4 through the sixteenth layer of electrode plate C41 is connected with the first feed-out band c1_line, a fourth output coupling feeder c4_out led out by the fourth capacitor C4 through the nineteenth layer of electrode plate C44 is connected with the second metal grounding plate GND2, and the third capacitor C3 and the fourth capacitor C4 are perpendicular to the first feed-out band line c1_line and the second feed-out band c2_line.

Preferably, the third capacitor C3 and each plate of the fourth capacitor C4 have the same size, the length is a preset constant Lc2, the width is a preset constant Wc2, and the thickness is a preset constant h_c.

In this embodiment, the third capacitor C3 and the fourth capacitor C4 have the same structure and the same structure, and each capacitor plate is formed by 5 electrode plates, and the capacitor electrode plates are made of silver inside the LTCC substrate by using a screen printing technology, and the electrode plates are connected through silver through holes.

Specifically, the eleventh-layer plate C31 has a length Lc2, a width Wc2, and a thickness h_c, is located at the 9 th layer of the LTCC substrate, and the third capacitor C3 is connected to the first feed-line c1_line through a third lead-out input coupling feed line c3_lin led out from the eleventh-layer plate C31 and is connected to the thirteenth-layer plate C33 and the fifteenth-layer plate C35 through a fifth through hole c3_tk1. The twelfth electrode plate C32 is long Lc2, wide Wc2 and thick H_c, is positioned on the 8 th layer of the LTCC substrate, is staggered by 0.1mm from C31 in the Y-axis direction, and is led out to be connected with the fourteenth electrode plate C34 through a sixth through hole C3_TK2. The thirteenth-layer polar plate C33 is long Lc2, wide Wc2 and thick H_c, is positioned on the 7 th layer of the LTCC substrate, the fourteenth-layer polar plate C34 is long Lc2, wide Wc2 and thick H_c, is positioned on the 6 th layer of the LTCC substrate, the fifteenth-layer polar plate C35 is long Lc2, wide Wc2 and thick H_c, is positioned on the 5 th layer of the LTCC substrate, the third capacitor C3 is connected to the first feed-in strip line C1_line through a third lead-out input coupling feeder C3_Lin led out by the eleventh-layer polar plate C31, the third capacitor C3 is connected to the second metal grounding plate GND2 on the surface of the LTCC substrate through a third output coupling feeder C3_out led out by the fourteenth-layer polar plate C34, and the grounding of the third capacitor C3 and the fourth capacitor C4 are perpendicular to the first feed-in strip line C1_line and the second feed-in line C2_line.

In the present embodiment, the structure and the working principle of the fourth capacitor C4 are identical to those of the third capacitor C3, so that redundant description is omitted.

In this embodiment, the first layer of electrode plate C11, the second layer of electrode plate C12, the third layer of electrode plate C13, the fourth layer of electrode plate C14 and the fifth layer of electrode plate C15 are spaced by h_ltcc+h_c in the Z-axis direction of the space, and the first layer of electrode plate C11, the third layer of electrode plate C13 and the fifth layer of electrode plate C15 are offset by 0.1mm in the Y-axis direction of the space of the second layer of electrode plate C12 and the fourth layer of electrode plate C14. Because the intervals and the dislocation between the five layer polar plates of the second capacitor C2, the third capacitor C3 and the fourth capacitor C4 are the same as those of the first capacitor C1, the description thereof will not be repeated.

Preferably, the inductor L1 includes a plurality of microstrip lines, a ninth through hole l1_tk1, a tenth through hole l1_tk2, and an eleventh through hole l1_tk3, the inductor L1 is connected to the first feed-through line c1_line through the ninth through hole l1_tk1, and the inductor L1 is connected to the first metal ground plane GND1 through the microstrip lines.

In this embodiment, the miniaturized band-pass filter based on LTCC integrates an inductor L1 by using a multi-section microstrip line (L11, L12, L13, L14, L15, L16, L17, L18, L19) and a silver via hole (l1_tk1, l1_tk2, l1_tk3) between microstrip lines in the LTCC substrate through a screen printing technology, wherein the microstrip lines are connected by the silver via hole to realize a spiral structure of the inductor L1. In electrical configuration, the inductance L1 is located between the third capacitance C3 and the fourth capacitance C4.

Specifically, the inductor L1 is spatially perpendicular to the microstrip line L11, and the inductor L1 is connected to the first feed-through line c1_line through the ninth through hole l1_tk1, so that the inductor L1 is electrically connected to the first capacitor C1, the second capacitor C2, the third capacitor C3, and the fourth capacitor C4. The inductor L1 realizes a spiral structure of the inductor L1 through tenth through holes L1_TK2 and eleventh L1_TK3, namely interlayer electrical connection of the inductor L1. The inductor L1 is connected to the first metal ground plane GND1 through a microstrip line L19, and the ground of the inductor L1 is realized. The miniaturized band-pass filter based on LTCC can extend the microstrip line L11 according to requirements so as to ensure that the inductor L1 is connected to the first feed-through line C1_line through a ninth through hole L1_TK1, and the extended microstrip line L19 ensures that one end of the inductor L1 is grounded.

Specifically, in this embodiment, the microstrip line L11 has a length l_l1+0.25mm, a width w_l1, and a thickness h_l, that is, the microstrip line L11 has a length l_l1+a, a width w_l1, and a thickness h_l, the microstrip lines L11, L12, and L13 are located at the 15 th layer of the LTCC substrate, the microstrip lines L14, L15, and L16 are located at the 16 th layer of the LTCC substrate, the microstrip lines L17, L18, and L19 are located at the 17 th layer of the LTCC substrate, the silver via l1_tk1 penetrates the substrate and is connected to the 11 th layer of the first feed-line c1_line from the 15 th layer of the microstrip line L11, the silver via l1_tk2 is connected to the microstrip lines L13 and L14, and the silver via l1_tk3 is connected to the microstrip lines L16 and L17.

In the present embodiment, as can be seen from the above description, the electrical topology of the miniaturized band-pass filter based on LTCC is in a symmetrical structure, and this symmetrical layout helps to reduce electromagnetic coupling effects, thereby improving the performance of the filter. Symmetrical structures can generally provide better impedance matching and lower return loss.

In summary, the LTCC-based miniaturized bandpass filter exhibits excellent electromagnetic performance by designing specific VIC capacitance and spiral inductance structures, effectively improving the performance of the filter in high frequency applications, particularly stabilizing the frequency response, and reducing the effects due to small errors in materials. The capacitor and the inductor of the filter are connected through the silver through hole, so that the insertion loss is further reduced, the Q value is improved, and the signal processing capacity and the overall performance of the system are improved.

In short, the miniaturized band-pass filter based on LTCC realizes a compact electrical structure through the microstrip line design of the spiral inductor and the multi-layer polar plate configuration of the VIC capacitor. The filter effectively solves the problem of frequency response deviation caused by tiny errors of materials in the LTCC multilayer structure, realizes miniaturization and high integration level of the filter on the basis of keeping high-frequency performance and low insertion loss, and simultaneously enhances electromagnetic compatibility and anti-interference capability. The structure not only saves space, but also improves the overall integration level of the filter, and is suitable for 5G communication, radar and satellite communication equipment which need miniaturization and high performance.

While the foregoing is directed to the preferred embodiments of the present invention, it will be appreciated by those skilled in the art that changes and modifications may be made without departing from the principles of the invention, such changes and modifications are also intended to be within the scope of the invention.

Claims

1. A miniaturized bandpass filter based on LTCC, characterized in that it comprises: an LTCC substrate, a first capacitor (C1), a second capacitor (C2), a third capacitor (C3), a fourth capacitor (C4), an inductor (L1), an input coupling feed line (Lin) and an output coupling feed line (Lout) integrated inside the LTCC substrate by screen printing, and a first input port (P1), a second output port (P2), a first metal ground plate (GND1), and a second metal ground plate (GND2) mounted on the outer surface of the LTCC substrate;

The input coupling feed line (Lin) and the output coupling feed line (Lout) are respectively arranged on both sides of the LTCC substrate, and the input coupling feed line (Lin) and the output coupling feed line (Lout) have the same size, one end of the input coupling feed line (Lin) and one end of the output coupling feed line (Lout) are respectively connected to the first input port (P1) and the second output port (P2), the other end of the input coupling feed line (Lin) is connected to the first capacitor (C1), the other end of the output coupling feed line (Lout) is connected to the second capacitor (C2), the first input port (P1) is connected to the first capacitor (C1), the second output port (P2) is connected to the second capacitor (C2), the first metal ground plate (GND1) is connected to the inductor (L1), and the second metal ground plate (GND2) is connected to the third capacitor (C3) and the fourth capacitor (C4);

The first capacitor (C1), the second capacitor (C2), the third capacitor (C3), and the fourth capacitor (C4) are mirror-symmetrical, and the third capacitor (C3) and the fourth capacitor (C4) are perpendicular to the first capacitor (C1) and the second capacitor (C2).

2. The miniaturized bandpass filter based on LTCC according to claim 1 is characterized in that the LTCC substrate is a low-temperature co-fired ceramic dielectric substrate, whose relative dielectric constant is 9.1, the total thickness of the substrate is 2.34 mm, the number of process layers is 22 layers, and the thickness of each process layer substrate is a preset constant H_LTCC.

3. The miniaturized bandpass filter based on LTCC according to claim 1 is characterized in that the first capacitor (C1), the second capacitor (C2), the third capacitor (C3), and the fourth capacitor (C4) are all VIC capacitors composed of five layers of capacitor plates, the inductor (L1) is a spiral inductor, the first input port (P1) and the second output port (P2) adopt a U-shaped structure, and the first metal ground plate (GND1) and the second metal ground plate (GND2) adopt a groove type.

4. The miniaturized bandpass filter based on LTCC according to claim 1, characterized in that the first capacitor (C1) comprises a first layer of plates (C11), a second layer of plates (C12), a third layer of plates (C13), a fourth layer of plates (C14), a fifth layer of plates (C15), a first through hole (C1_TK1), a second through hole (C1_TK2), and five lead-out strip structures corresponding to the first layer of plates (C11), the second layer of plates (C12), the third layer of plates (C13), the fourth layer of plates (C14), and the fifth layer of plates (C15);

The first layer of plates (C11) is connected to the first input port (P1) through an input coupling feed line (Lin); the first layer of plates (C11), the third layer of plates (C13) and the fifth layer of plates (C15) are combined with the first through hole (C1_TK1) through corresponding lead-out band structures to form the first pole of the first capacitor (C1); the second layer of plates (C12) and the fourth layer of plates (C14) are combined with the second through hole (C1_TK2) through corresponding lead-out band structures to form the second pole of the first capacitor (C1).

5. The miniaturized bandpass filter based on LTCC according to claim 4, characterized in that the second capacitor (C2) comprises a sixth layer of plates (C21), a seventh layer of plates (C22), an eighth layer of plates (C23), a ninth layer of plates (C24), a tenth layer of plates (C25), a third through hole (C2_TK1), a fourth through hole (C2_TK2), and five feed strip lines corresponding to the sixth layer of plates (C21), the seventh layer of plates (C22), the eighth layer of plates (C23), the ninth layer of plates (C24), and the tenth layer of plates (C25);

The sixth electrode plate (C21) is connected to the second output port (P2) through an output coupling feed line (Lout); the sixth electrode plate (C21), the eighth electrode plate (C23) and the tenth electrode plate (C25) are combined with the third through hole (C2_TK1) through corresponding lead-out strip structures to form the first electrode of the second capacitor (C2); the seventh electrode plate (C22) and the ninth electrode plate (C24) are combined with the fourth through hole (C2_TK2) through corresponding lead-out strip structures to form the second electrode of the second capacitor (C2);

The first capacitor (C1) is connected to a second feeder line (C2_line) derived from a ninth layer of the electrode plate (C24) of the second capacitor (C2) through a first feeder line (C1_line) derived from a fourth layer of the electrode plate (C14), so as to realize the series connection of the first capacitor (C1) and the second capacitor (C2).

6. The miniaturized bandpass filter based on LTCC according to claim 1, characterized in that each plate of the first capacitor (C1) and the second capacitor (C2) has the same size, a length of a preset constant Lc1, a width of a preset constant Wc1, and a thickness of a preset constant H_c.

7. The miniaturized bandpass filter based on LTCC according to claim 5, characterized in that the third capacitor (C3) comprises an eleventh layer of plates (C31), a twelfth layer of plates (C32), a thirteenth layer of plates (C33), a fourteenth layer of plates (C34), a fifteenth layer of plates (C35), a fifth through hole (C3_TK1), a sixth through hole (C3_TK2), and five lead-out strip structures corresponding to the eleventh layer of plates (C31), the twelfth layer of plates (C32), the thirteenth layer of plates (C33), the fourteenth layer of plates (C34), and the fifteenth layer of plates (C35);

The eleventh layer of plates (C31), the thirteenth layer of plates (C33) and the fifteenth layer of plates (C35) are combined with the fifth through hole (C3_TK1) through the corresponding lead-out strip structure to form the first pole of the third capacitor (C3); the twelfth layer of plates (C32) and the fourteenth layer of plates (C34) are combined with the sixth through hole (C3_TK2) through the corresponding lead-out strip structure to form the second pole of the third capacitor (C3); the third capacitor (C3) is connected to the first feed strip line (C1_line) through the third input coupling feed line (C3_Lin) derived from the eleventh layer of plates (C31); and the third capacitor (C3) is connected to the second metal ground plate (GND2) through the third output coupling feed line (C3_out) derived from the fourteenth layer of plates (C34).

8. The miniaturized bandpass filter based on LTCC according to claim 7, characterized in that the fourth capacitor (C4) comprises a sixteenth layer of plates (C41), a seventeenth layer of plates (C42), an eighteenth layer of plates (C43), a nineteenth layer of plates (C44), a twentieth layer of plates (C45), a seventh through hole (C4_TK1), an eighth through hole (C4_TK2), and five lead-out strip structures corresponding to the sixteenth layer of plates (C41), the seventeenth layer of plates (C42), the eighteenth layer of plates (C43), the nineteenth layer of plates (C44), and the twentieth layer of plates (C45);

The sixteenth layer of plates (C41), the eighteenth layer of plates (C43) and the twentieth layer of plates (C45) are combined with the seventh through hole (C4_TK1) through the corresponding lead-out strip structure to form the first pole of the fourth capacitor (C4); the seventeenth layer of plates (C42) and the nineteenth layer of plates (C44) are combined with the eighth through hole (C4_TK2) through the corresponding lead-out strip structure to form the second pole of the fourth capacitor (C4); the fourth capacitor (C4) is connected to the first feed strip line (C1_line) through the fourth input coupling feed line (C4_Lin) led out from the sixteenth layer of plates (C41); the fourth capacitor (C4) is connected to the second metal ground plane (GND2) through the fourth output coupling feed line (C4_out) led out from the nineteenth layer of plates (C44); and the third capacitor (C3) and the fourth capacitor (C4) are perpendicular to the first feed strip line (C1_line) and the second feed strip line (C2_line).

9. The miniaturized bandpass filter based on LTCC according to claim 8, characterized in that each plate of the third capacitor (C3) and the fourth capacitor (C4) has the same size, a length of a preset constant Lc2, a width of a preset constant Wc2, and a thickness of a preset constant H_c.

10. The miniaturized bandpass filter based on LTCC according to claim 5, characterized in that the inductor (L1) comprises a plurality of microstrip lines, a ninth through hole (L1_TK1), a tenth through hole (L1_TK2), and an eleventh through hole (L1_TK3), the inductor (L1) is connected to the first feeding strip line (C1_line) through the ninth through hole (L1_TK1), and the inductor (L1) is connected to the first metal ground plate (GND1) through the microstrip line.