CN110022133B - A miniaturized inductively coupled tunable bandpass filter and its preparation method - Google Patents

Abstract

The invention discloses a small-sized inductance coupling type adjustable band-pass filter, and belongs to the technical field of filters. The structure mainly comprises a shell, an input electrode, an output electrode, a grounding electrode, a three-layer grounding plate, inductors among different layers of the grounding plate and capacitors on the surface of the shell, wherein the grounding plate and the inductors are sintered in a ceramic substrate by adopting a low-temperature co-fired ceramic technology, and the capacitors are attached to the upper surface of the shell. The invention has simple structure, low cost, small volume and good batch consistency, and is prepared by using a low-temperature co-fired ceramic technology; meanwhile, the three layers of grounding plates separate different inductors and capacitors, so that parasitic and resonance caused by unnecessary coupling are avoided, and the filtering accuracy and the quality factor are improved.

Description

A miniaturized inductively coupled tunable bandpass filter and its preparation method

technical field

The invention belongs to the technical field of filters, in particular to a miniaturized inductive coupling type adjustable bandpass filter.

Background technique

In recent years, with the rapid development of the miniaturization of mobile communication, satellite communication and defense electronic systems, high performance, low cost and miniaturization have become the development direction of the current microwave/radio frequency field. Both performance and cost put forward higher requirements. The communication countermeasure system needs to realize the signal processing in the complex information environment, and needs the filter to realize the signal selection. Filters are mainly used to separate signals and suppress interference, which is the most extensive and most basic application of filters. In this application, the ESC filter can smoothly pass the signal of the desired frequency and suppress the unwanted frequency. The current communication system requires filters with low insertion loss, low in-band fluctuation, and high signal selectivity, and at the same time, the volume is as small as possible to meet the requirements of sensitivity and dynamic range. The ESC filter has the advantages of small size and wide operating frequency band, which can suppress the second-order combined signal well, and has a broad application prospect.

The operation of the band-pass filter in the ultra-short-wave frequency band requires a large capacitor and a large inductance to form a resonator. In order to meet the miniaturization requirements of devices, the initial method is to use dielectric materials with high dielectric constant, high quality factor, and low loss to reduce the size of the resonator, thereby reducing the volume of the device. However, the traditional process technology has high cost, complicated manufacturing process and poor batch consistency.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a miniaturized inductive coupling type tunable bandpass filter, which solves the problems of high cost, complicated manufacturing process and poor batch consistency under the condition of miniaturization.

The technical scheme adopted in the present invention is as follows:

A miniaturized inductive coupling type adjustable bandpass filter, comprising: a casing, input poles and output poles located at both ends of the casing, grounding poles located on both sides of the casing, and a three-layer grounding plate located inside the casing;

Contact bridges are arranged between the grounding electrodes on both sides of the housing, and the three-layer grounding plates are all in contact with the grounding electrodes; an inductance La, an inductance Lb and an inductance Ld are arranged between the first-layer grounding plate and the second-layer grounding plate. An inductance Lc and an inductance Le are arranged between the second-layer grounding plate and the third-layer grounding plate, and a first welding pad and a second welding pad are arranged on the outer wall surface of the casing close to the third-layer grounding plate;

The input pole, the inductance La, the inductance Lb, the inductance Ld, and the output pole are connected in series in sequence; a first conductive column is arranged between the connection point of the inductance La and the inductance Lb, one end of the inductance Lc, and one end of the first welding pad, and the inductance Lb and the inductance A second conductive column is provided between the connection point of Ld, one end of the inductance Le, and one end of the second soldering pad; the other end of the inductance Lc and the other end of the inductance Le are respectively connected to the ground electrode, and the other end of the first soldering pad Connect the ground electrode after connecting the capacitor Ca, and connect the other end of the second welding pad to the ground electrode after connecting the capacitor Cb;

The second-layer grounding plate and the third-layer grounding plate are provided with holes for passing through the conductive pillars.

Further, the inductance La, the inductance Lb, the inductance Lc, the inductance Ld and the inductance Le are all spiral inductances. Capacitors Cb are adjustable capacitors;

The inductance La and the inductance Ld have the same structure, and the inductance Lc and the inductance Le are completely symmetrical about the Z-axis and are coupled to each other.

Further, the casing is made of low-temperature co-fired ceramics, and the inductor and the ground plate are sintered in the ceramic substrate; the components including the casing, the first welding pad, the second welding pad, the capacitor Ca and the capacitor Cb are all made of FV1206 package, the ground electrode, input electrode and output electrode are exposed.

Further, the casing is in the shape of a rectangular parallelepiped, and the grounding plate of the first layer, the grounding plate of the second layer and the grounding plate of the third layer are all parallel to the bottom surface of the casing; the input pole and the output pole are both 50Ω impedance ports.

A preparation method of a miniaturized inductively coupled tunable bandpass filter, the preparation steps of the filter are as follows:

Ingredients: Select the ceramic raw material formula to configure the ceramic material;

Casting: The prepared ceramic material is made into a casting slurry, and the ceramic substrate is cast out;

Hole punching and hole filling: Punch holes on part of the ceramic substrate to obtain conductive post-avoidance holes and inductance connection holes, and then fill the holes with metal paste;

Conductor printing: Conduct conductor printing with the filled ceramic substrate to prepare a metal conductive tape for forming a spiral inductor. The same spiral inductor and different ceramic substrate layers are connected through the filled inductor connection holes; Conductor printing is performed on the ceramic substrate of the bit hole to form a metal layer of the ground plate that is not in contact with the conductive posts;

Lamination: Laminate the ceramic substrate with printed conductors and the ceramic substrate without printed conductors according to the design structure to form a layered spiral inductor and grounding plate;

Isostatic pressing: Isostatic pressing is performed by placing the laminated modules in water, so that different layers of green ceramic substrates can be tightly pressed to form a complete filter device;

Debinding and sintering: place the isostatically pressed module in a sintering furnace for debinding and sintering;

Connection of surface components: connect the capacitor on the surface layer to the module after debinding and sintering to obtain a low-temperature co-fired ceramic adjustable band-pass filter.

Further, the raw materials of the metal paste and the metal conduction band are silver paste, and the thickness of the printed conductor is 10±1 microns.

Further, in the step of debinding and sintering, when debinding and sintering are performed in the sintering furnace, the temperature of the sintering furnace is 50°C.

To sum up, due to the adoption of the above-mentioned technical solutions, the beneficial effects of the present invention are:

1. The present invention adopts low-temperature co-fired ceramics, and each component is sintered on the ceramic substrate. Due to the low-temperature co-fired ceramic technology, a circuit substrate with a high number of layers can be produced, and a plurality of passive components can be embedded in it, which is beneficial to improve the performance. The assembly density of the circuit reduces the size and weight of the device.

2. The present invention has simple structure, adopts low temperature co-fired ceramic technology, simple manufacturing process, good batch consistency and low cost.

3. Three layers of grounding plates are arranged inside the ceramic shell of the present invention, and the inductive elements and the capacitive elements are placed in layers, which avoids the coupling interference between the inductance of different layers and the inductance, inductance and capacitance of other layers, and reduces the inconsistency between the components. The parasitic and resonance caused by the necessary coupling ensure the accuracy of the filter while reducing the size of the device.

4. Ceramic materials have excellent high frequency, high speed transmission and wide passband characteristics. Depending on the ingredients, the dielectric constant of the ceramic material can vary in a wide range, and the use of high-conductivity metal materials as the conductor material is beneficial to improve the quality factor of the circuit system.

5. Low-temperature co-fired ceramics are sintered at a temperature of about 900 ℃, which can meet the requirements of high current and high temperature resistance, and have better thermal conductivity than ordinary PCB circuit substrates, which greatly optimizes the heat dissipation design of electronic equipment and is reliable. It has high performance and can be used in harsh environments, extending its service life.

6. The present invention adopts FV1206 package, which ensures that the device is easy to be integrated into the system under the condition of small size, and it is convenient for welding.

Description of drawings

In order to illustrate the technical solutions of the embodiments of the present invention more clearly, the following briefly introduces the accompanying drawings used in the embodiments. It should be understood that the following drawings only show some embodiments of the present invention, and therefore do not It should be regarded as a limitation of the scope. For those of ordinary skill in the art, other related drawings can also be obtained from these drawings without creative efforts, wherein:

Fig. 1 is the overall oblique view structural diagram of the present invention;

Fig. 2 is an oblique view of an inductor, a capacitor and a conductive column of the present invention;

Fig. 3 is the front view structure diagram of the inductance capacitor and the conductive column of the present invention;

Fig. 4 is the inductance of the present invention and the slanted structural view of the ground electrode;

FIG. 5 is an oblique structural view of the capacitor and the ground electrode of the present invention;

FIG. 6 is an oblique structural view of the grounding plate and the grounding electrode of the present invention;

7 is a front structural view of an inductor, a conductive column, a ground plate, an input pole, and an output pole of the present invention;

8 is a schematic diagram of an equivalent circuit of the filter of the present invention;

Fig. 9 is the filter preparation flow chart of the present invention;

Fig. 10 is a simulation result diagram of the present invention;

Markings in the figure: 1-inductance La, 2-inductance Lb, 3-inductance Lc, 4-inductance Ld, 5-inductance Le, 6-first soldering pad, 7-second soldering pad, 8-first conductive column, 9-Second conductive column, 10-Grounding pole, 11-Contact bridge, 12-Capacitance Ca, 13-First-layer grounding plate, 14-Second-layer grounding plate, 15-Third-layer grounding plate, 16-Give way Hole, 17-input pole, 18-output pole, 19-shell, 20-capacitor Cb, 21-inductor connection hole.

Detailed ways

In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention, but not to limit the present invention, that is, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. The components of the embodiments of the invention generally described and illustrated in the drawings herein may be arranged and designed in a variety of different configurations.

Thus, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the invention as claimed, but is merely representative of selected embodiments of the invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the present invention.

It should be noted that relational terms such as the terms "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any relationship between these entities or operations. any such actual relationship or sequence exists. Moreover, the terms "comprising", "comprising" or any other variation thereof are intended to encompass a non-exclusive inclusion such that a process, method, article or device that includes a list of elements includes not only those elements, but also includes not explicitly listed or other elements inherent to such a process, method, article or apparatus. Without further limitation, an element qualified by the phrase "comprising a..." does not preclude the presence of additional identical elements in a process, method, article or apparatus that includes the element.

As shown in Figures 1 to 7, wherein Figures 2 to 7 are specific detail views of Figure 1;

A miniaturized inductive coupling type tunable band-pass filter, comprising: a casing 19, an input pole 17 and an output pole 18 located at both ends of the casing 19, a ground pole 10 located on both sides of the casing 19, and inside the casing 19 The three-layer ground plane;

Specifically, the casing 19 is sintered with low-temperature co-fired ceramics, and has the shape of a rectangular parallelepiped as a whole. The input pole 17 and the output pole 18 of the filter are respectively arranged on the two end surfaces of the body 19, and the input pole 17 and the output pole 18 wrap the two end surfaces of the casing 19; The shape of the electrode 10 is a gate-shaped structure, and the inner diameter is consistent with the height of the casing 19. The two grounding electrodes 10 are respectively buckled and embedded in the middle positions on both sides of the casing 19; the three-layer sintered ceramic substrate inside the casing 19 The grounding plates are the first-layer grounding plate 13 , the second-layer grounding plate 14 and the third-layer grounding plate 15 respectively. The three-layered grounding plates are all parallel to the bottom surface of the cuboid shell 19 , and the three-layered grounding plates extend the inner space of the shell 19 . Divided into two parts.

It can be understood that the Low Temperature Co-fired Ceramic (LTCC) technology is to make low temperature sintered ceramic powder into a green ceramic tape with precise and dense thickness, and use laser drilling and microporous grouting on the green ceramic tape. , precision conductor paste printing and other processes to produce the required circuit patterns, and embed multiple passive components (such as low-capacity capacitors, resistors, filters, impedance converters, couplers, etc.) into the multi-layer ceramic substrate, and then Laminated together, the inner and outer electrodes can be made of silver, copper, gold and other metals, respectively, and sintered at 900 ° C to make a high-density circuit that does not interfere with each other in three-dimensional space, or a three-dimensional circuit substrate with built-in passive components. Its surface can mount IC and active devices to make passive/active integrated functional modules, which can further reduce circuit miniaturization and high density.

A contact bridge 11 is provided between the two grounding electrodes 10 on both sides of the housing 19 , and the three-layer grounding plates are all in contact with the grounding electrodes 10 ; There are inductors La 1 , Lb 2 and Ld 4 , and inductors Lc 3 and Le 5 are arranged between the second-layer grounding plate 14 and the third-layer grounding plate 15 , and are close to the outer wall of the casing 19 of the third-layer grounding plate 15 The surface is provided with a first welding pad 6 and a second welding pad 7;

Specifically, the contact bridge 11 is a rectangular metal plate, the width is the same as the width of the door post of the gate-type grounding electrode 10 , and the length is the same as the distance between the gate posts of the two grounding electrodes 10 . Between the door posts of the grounding electrodes 10, two grounding electrodes 10 are connected to form an integral grounding; the three-layer grounding plate is roughly shaped as a rectangular metal plate slightly reduced compared to the bottom surface of the casing 19, which is different from the regular rectangular one. It is that the places on both sides of the grounding plate corresponding to the grounding electrodes 10 protrude, and the protruding parts are in contact with the grounding electrodes 10 on both sides of the housing 19; the inductors are all spiral inductors, sintered in the ceramic substrate, and the spiral inductors are Each layer is a rectangle or 3/4 rectangle made of 0.1mm width metal conductive tape. The structures of the inductor La 7 and the inductor Ld 10 are the same. The inductor Lc 9 and the inductor Le 11 are completely symmetrical about the Z axis and are coupled to each other. ; The capacitor Ca 12 and the capacitor Cb 20 both use adjustable capacitors.

The input pole 17, the inductance La1, the inductance Lb2, the inductance Ld4, and the output pole 18 are connected in series in sequence; A conductive column 8, a second conductive column 9 is provided between the connection point of the inductance Lb 2 and the inductance Ld4, one end of the inductance Le 5, and one end of the second solder pad 7; the other end of the inductance Lc 3 and the other end of the inductance Le 5 One end is respectively contacted and connected to the ground electrode 10, the other end of the first welding pad 6 is connected to the capacitor Ca 12 and then connected to the ground electrode 10, and the other end of the second welding pad 7 is connected to the capacitor Cb 20 and then connected to the ground electrode 10;

Specifically, the filter housing 19 is made of low-temperature co-fired ceramics, the inductor and the grounding plate are both wound on a ceramic substrate with metal conductive tape printed by conductors, the inductor La1, the inductor Lb2 and the inductor Ld4 are When the conductors are printed, they are connected in series in sequence, and the metal conduction strip between the inductors La1 and Lb2 is in contact with the first conductive column 8, and the metal conduction strip between the inductance Lb2 and the inductance Ld4 is in contact with the second conductive column. 9 Contact connection; at the same time, the starting end of the metal conduction band of the inductor La 1 is in contact with the input pole 17, and the terminal of the metal conduction band of the inductor Ld 4 is contacted and connected to the output pole 18; A conductive column 8 is in contact with it, the terminal of the metal conduction band of the inductor Lc 3 is in contact with the ground electrode 10, and the starting end of the metal conduction band of the inductance Le 5 is set as a circular sleeve on the second conductive column 9 to contact and connect with it, The terminal of the metal conduction band of the inductor Le 5 is in contact with the grounding electrode 10; the connecting ends of the first soldering pad 6 and the second soldering pad 7 are the upper end and the lower end respectively, wherein the lower end of the first soldering pad 6 is connected to the first conductive column. 8 connection, the lower end of the second welding pad 7 is connected to the second conductive column 9, the upper end of the first welding pad 6 is welded with capacitor Ca 12, the upper end of the second welding pad 7 is welded with capacitor Cb 20, capacitor Ca 12 and capacitor Cb 20 are separately Both ends are connected to the ground electrode 10 .

Its equivalent circuit is shown in Figure 8, including: input terminal Pin, output terminal Pout, inductor La 1, inductor Lb 2, inductor Lc 3, inductor Ld 4, inductor Le 5, capacitor Ca 12, capacitor Cb 20 and signal ground GND;

The specific connection relationship is as follows:

The input terminal Pin, the inductor La 7, the inductor Lb 8, the inductor Ld 10 and the output terminal Pout are connected in series in sequence, the connection point of the inductor La 7 and the inductor Lb 8 is connected to the signal ground GND through the inductor Lc 9, and the inductor Lb 8 and the inductor Ld 10 are connected through the inductor. Le 11 is connected to the signal ground GND, the capacitor Ca 12 is connected in parallel with the inductor Lc 9, and the capacitor Cb 20 is connected in parallel with the inductor Le 11.

The second-layer grounding plate 14 and the third-layer grounding plate 15 are provided with holes 16 for passing through the conductive columns;

Specifically, the diameter of the conductive column is slightly smaller than the inner diameter of the escape hole 16, and the conductive column penetrates the space separated by the second-layer grounding plate 14 and the third-layer grounding plate 15 through the escape hole 16, so as to facilitate the inductance and capacitance between different layers. connect.

It can be understood that since the shell 19 is made of low-temperature co-fired ceramics, the ground plate, the inductor and the conductive column are all sintered in the ceramic substrate inside the shell 19, the capacitor is mounted on the upper surface of the shell 19, and the three-layer ground plate will Inductors and capacitors are isolated in layers to avoid unnecessary coupling between inductances of different layers and inductances, inductances and capacitors of other layers, resulting in parasitic or resonance interference, and improving the filtering accuracy and Q value of the filter. At the same time, the invention has a simple structure, is mainly composed of an inductor and a capacitor, is sintered by a low-temperature co-fired ceramic technology, is convenient to manufacture, has good batch consistency and low cost.

Ceramic materials have excellent high-frequency, high-speed transmission and wide passband characteristics. According to different ingredients, the dielectric constant of ceramic materials can vary within a wide range. The use of high-conductivity metal materials as conductor materials is beneficial to Improve the quality factor of the circuit system and increase the flexibility of circuit design;

In addition, it can adapt to the requirements of high current and high temperature resistance, and has better thermal conductivity than ordinary PCB circuit substrates, which greatly optimizes the heat dissipation design of electronic equipment, has high reliability, can be used in harsh environments, and prolongs its service life. .

Further, the components including the housing 19, the first solder pad 6, the second solder pad 7, the capacitor Ca 12 and the capacitor Cb 20 all adopt the FV1206 packaging technology, and only the ground electrode 10, the input electrode 17 and the output electrode 18 are exposed. outside;

The specific package size is 3.2*1.6*0.94mm, which ensures the small size and ease of use of the device, and facilitates the welding and integration of the filter into the system; the grounding pole 10, the input pole 17 and the output pole 18 are made of copper. .

The first-layer grounding plate 13 , the second-layer grounding plate 14 and the third-layer grounding plate 15 are all parallel to the bottom surface of the casing 19 to form a multi-layer structure, which is beneficial to the layout of the inductance elements.

The input pole 17 and the output pole 18 are both ports with an impedance of 50Ω, which is convenient for testing.

The preparation process of the filter of the present invention is shown in Figure 9, and the specific preparation method is as follows:

Ingredients: Select the ceramic raw material formula to configure the ceramic material;

Casting: The prepared ceramic material is made into a casting slurry, and the ceramic substrate is cast out;

Hole punching and hole filling: Punch holes on part of the ceramic substrate to obtain conductive post-replacement holes 16 and inductance connection holes 21, and then fill the holes with metal paste;

Conductor printing: Conduct conductor printing with the filled ceramic substrate to prepare a metal conductive tape for forming a spiral inductor. The same spiral inductor and different ceramic substrate layers are connected through the filled inductor connection holes 21; Conduct conductor printing on the ceramic substrate of the hole 16 to form a metal layer of the ground plate that is not in contact with the conductive posts;

Lamination: Laminate the ceramic substrate with printed conductors and the ceramic substrate without printed conductors according to the design structure to form a layered spiral inductor and grounding plate;

Isostatic pressing: Isostatic pressing is performed by placing the laminated modules in water, so that different layers of green ceramic substrates can be tightly pressed to form a complete filter device;

Debinding and sintering: place the isostatically pressed module in a sintering furnace for debinding and sintering;

Connection of surface components: connect the capacitor on the surface layer to the module after debinding and sintering to obtain a low-temperature co-fired ceramic adjustable band-pass filter.

Specifically, conductive pillars are formed after the silver paste is filled in the allowable holes 16, which are used to connect devices between different layers; the metal paste used for hole filling and the raw materials of the metal conduction strip used for conductor printing are all made of silver paste. The thickness of the fabricated metal conduction band is 10±1 microns;

It can be understood that the thickness of the metal conduction band is formed by thinning the pattern of each layer of ceramic substrate corresponding to the printed conductor, that is, the thinned thickness of the ceramic substrate is the printed thickness of the conductor, which corresponds to the thickness of the metal conduction band;

During debinding and sintering, the temperature of the sintering furnace was controlled at 50°C.

The filter housing 19 is formed by stacking multi-layer ceramic substrates, and each layer of ceramic substrates is formed by punching, filling and conductor printing to form a stacked arrangement of spiral inductors, grounding plates and conductive pillars;

For example, the spiral inductor includes a multi-layer structure, each layer of which is a rectangular or 3/4 rectangular shape metal conduction band printed on the ceramic substrate through the conductor, and then the multi-layer ceramic substrate is superimposed, and the rectangular shape between the structures of each layer is printed on the ceramic substrate. The metal conductive strips are connected through the inductance connection holes 21 to form a unified spiral inductance; the conductors of the grounding plate are printed on the entire surface of the ceramic substrate, and where there are conductive pillars and vacant holes 16, the printed conductors are printed along the edge of the vacant holes 16, Not in contact with the conductive posts, but the ground plate printed conductors extend out on both sides of the housing 19 to contact the ground electrodes 10 .

The features and performances of the present invention will be further described in detail below in conjunction with the embodiments.

A miniaturized coupling-type tunable bandpass filter provided by a preferred embodiment of the present invention is shown in FIG. 10 as a simulation result diagram of the present invention. By changing the size of the variable capacitor, the range from 250MHz to Filtering at any point in the 400MHz range. And the filtering accuracy is high and the quality factor is good.

The above are only preferred embodiments of the present invention, and are not intended to limit the protection scope of the present invention. Any modifications, equivalent replacements and improvements made by any person skilled in the art within the spirit and principles of the present invention, etc. , should be included within the protection scope of the present invention.

Claims (6)

1. A miniaturized inductive coupling type tunable bandpass filter, characterized in that it comprises: a casing (19), an input pole (17) and an output pole (18) located at both ends of the casing (19), grounding electrodes (10) on both sides of the body (19) and a three-layer grounding plate inside the casing (19); Contact bridges (11) are provided between the grounding electrodes (10) on both sides of the housing (19), and the three-layer grounding plates are all in contact with the grounding electrodes (10); An inductance La (1), an inductance Lb (2) and an inductance Ld (4) are arranged between the grounding plates (14), and an inductance Lc is arranged between the second-layer grounding plate (14) and the third-layer grounding plate (15). (3) and the inductor Le (5), a first welding pad (6) and a second welding pad (7) are provided on the outer wall surface of the casing (19) close to the third-layer grounding plate (15); The casing (19) is made of low-temperature co-fired ceramics, and the inductor and the grounding plate are sintered in the ceramic substrate; the casing (19), the first welding pad (6), the second welding pad (7), and the capacitor Ca are included. (12) The components including the capacitor Cb (20) are all packaged with FV1206, and the ground electrode (10), the input electrode (17) and the output electrode (18) are exposed to the outside; The input pole (17), the inductance La(1), the inductance Lb(2), the inductance Ld(4), and the output pole (18) are connected in series in sequence; the connection point of the inductance La(1) and the inductance Lb(2), the inductance Lc( A first conductive column (8) is provided between one end of 3) and one end of the first soldering pad (6), the connection point of the inductor Lb (2) and the inductor Ld (4), one end of the inductor Le (5), the first A second conductive column (9) is arranged between one end of the two welding pads (7); the other end of the inductor Lc (3) and the other end of the inductor Le (5) are respectively contacted and connected to the ground electrode (10), and the first welding The other end of the disk (6) is connected to the capacitor Ca (12) and then connected to the ground electrode (10), and the other end of the second welding disk (7) is connected to the capacitor Cb (20) and then connected to the ground electrode (10); The second-layer grounding plate (14) and the third-layer grounding plate (15) are both provided with an escape hole (16) for the conductive column to pass through. 2 . The miniaturized inductive coupling type tunable bandpass filter according to claim 1 , wherein the inductor La ( 1 ), the inductor Lb ( 2 ), the inductor Lc ( 3 ), the inductor Ld ( 4) and the inductor Le(5) are both spiral inductors, each layer of the spiral inductor is a rectangle or 3/4 rectangle made of metal conduction tape, and the capacitor Ca(12) and the capacitor Cb(20) are both acceptable. adjust capacitance; The inductance La(1) and the inductance Ld(4) have the same structure, and the inductance Lc(3) and the inductance Le(5) are completely symmetrical about the Z axis and are coupled to each other. 3. A miniaturized inductively coupled tunable bandpass filter according to claim 1, characterized in that: the casing (19) is in the shape of a rectangular parallelepiped, the first layer of grounding plate (13), the second layer of Both the grounding plate (14) and the third-layer grounding plate (15) are parallel to the bottom surface of the casing (19); Both the input pole (17) and the output pole (18) are ports with an impedance of 50Ω. 4. A preparation method of the miniaturized inductively coupled tunable bandpass filter according to any one of claims 1-3, wherein the preparation step comprises: Ingredients: Select the ceramic raw material formula to configure the ceramic material; Casting: The prepared ceramic material is made into a casting slurry, and the ceramic substrate is cast out; Punching and filling holes: Punch holes on part of the ceramic substrate to obtain the conductive post-avoidance holes (16) and the inductance connection holes (21), and then fill the holes with metal paste; Conductor printing: Conduct conductor printing with the filled ceramic substrate to prepare a metal conductive tape for forming a spiral inductor, and connect different ceramic substrate layers of the same spiral inductor through the filled inductor connection hole (21); Conductor printing is carried out on the ceramic substrate of the conductive post to make way for the hole (16) to form a metal layer of the ground plate that is not in contact with the conductive post; Lamination: Laminate the ceramic substrate with printed conductors and the ceramic substrate without printed conductors according to the design structure to form a layered spiral inductor and grounding plate; Isostatic pressing: Isostatic pressing is performed by placing the laminated modules in water, so that different layers of green ceramic substrates can be tightly pressed to form a complete filter device; Debinding and sintering: place the isostatically pressed module in a sintering furnace for debinding and sintering; Connection of surface components: connect the capacitor on the surface layer to the module after debinding and sintering to obtain a low-temperature co-fired ceramic adjustable band-pass filter. 5 . The method for preparing a miniaturized inductively coupled tunable bandpass filter according to claim 4 , wherein the raw materials of the metal paste and the metal conduction band are silver paste, and the printed The conductor thickness is 10±1 microns. 6 . The method for preparing a miniaturized inductively coupled tunable bandpass filter according to claim 4 , wherein in the debinding and sintering steps, when debinding and sintering are performed in the sintering furnace, the sintering The furnace temperature was 50°C.

Images