An integrated adjustable filter

Abstract

The present invention relates to the field of radio frequency and microwave technologies, and particularly relates to an integrated tunable filter, which includes a tunable filter body. An input strip line, an output strip line, a coupling strip line group, and a YIG thin film structure group are arranged in the tunable filter body. The input strip line can transmit signals to the output strip line through the coupling strip line group and the YIG thin film structure group. Among them, multiple green ceramic sheets are also arranged in the tunable filter body, and the multiple green ceramic sheets are laminated and sintered into a coupling cavity of the tunable filter body. Metal circuit images can be printed on the green ceramic sheets, and resonant cavities for placing the YIG thin film structure group can be dug out on the green ceramic sheets. By arranging each functional component on the green ceramic sheets and then using the LTCC process, the filter can be made into an integrated form, and the assembly is also simpler. There is no need for additional processing of strip lines, etc. Slots can be directly opened on the green ceramic sheets, and the fixation and position control of the YIG thin film structure are more precise, without subsequent adjustment.

Description

Technical Field

[0001] The present invention relates to the field of radio frequency and microwave technologies, and particularly to an integrated tunable filter. Background Art

[0002] Yttrium iron garnet (YIG) is a microwave gyromagnetic material with both insulating and gyromagnetic properties. By changing the bias magnetic field applied to the YIG material, the gyromagnetic tensor in the YIG material can be changed within an ultra-wideband frequency range, thereby affecting the electromagnetic field characteristics in the thin film. Therefore, the YIG material has ultra-wideband magnetic tuning characteristics. A resonator made of the YIG material can change its resonant frequency by adjusting the bias magnetic field on the YIG material. A filter based on the resonator can also be designed and fabricated into a device with tunable center frequency using the characteristics of the YIG material.

[0003] The YIG tunable filter (YTF) is a tunable device based on the YIG gyromagnetic material, consisting of a YIG resonant circuit and a magnetic circuit. It features a narrow bandwidth, high out-of-band rejection, and electrical tunability. Its working principle is that the resonant circuit composed of the YIG material generates a resonant frequency under the excitation of an external magnetic field, thereby realizing the filtering function at this frequency point. By changing the magnetic field strength, the resonant frequency of the resonator can be changed to achieve the tuning function.

[0004] After a large amount of research work abroad, a series of products have been formed and widely used in systems such as military electronic equipment (electronic warfare reconnaissance and reception, electronic countermeasures, and electronic counter-countermeasures), and their YTF technology has reached a quite high level.

[0005] Currently, the resonant circuit structure of YTF mainly uses YIG sphere resonators. For example, the Chinese patent with the publication number CN108767412B discloses a coupling resonant structure of an ultra-wideband YIG electrically tunable filter based on LTCC. The coupling between its resonant structures is realized through a precisely machined coupling ring structure, which requires high machining accuracy. After assembly, the position and crystal orientation of the YIG sphere need to be further adjusted, and the manufacturing is complex. Summary of the Invention

[0006] In view of the above problems, the present invention provides an integrated tunable filter.

[0007] The technical solution adopted is an integrated tunable filter, which includes a tunable filter body. An input strip line, an output strip line, a coupling strip line group, and a YIG thin film structure group are arranged in the tunable filter body. The input strip line can transmit signals to the output strip line through the coupling strip line group and the YIG thin film structure group. Among them, a multi-layer green ceramic dielectric is also arranged in the tunable filter body, and the multi-layer green ceramic dielectrics are stacked and sintered into a coupling cavity of the tunable filter body. A metal circuit pattern can be printed on the green ceramic dielectric, and a resonant cavity for placing the YIG thin film structure group can be dug out on the green ceramic dielectric.

[0008] Optionally, five layers of green ceramic dielectrics are arranged in the tunable filter body, and the five layers of green ceramic dielectrics are, from top to bottom, the first layer of green ceramic dielectric, the second layer of green ceramic dielectric, the third layer of green ceramic dielectric, the fourth layer of green ceramic dielectric, and the fifth layer of green ceramic dielectric;

[0009] The first layer of green ceramic dielectric and the fourth layer of green ceramic dielectric are green ceramic dielectrics without metal circuit patterns;

[0010] The second layer of green ceramic dielectric and the fifth layer of green ceramic dielectric are green ceramic dielectrics printed with metal circuit patterns;

[0011] The third layer of green ceramic dielectric is a green ceramic dielectric with perforations dug out, and the perforations are used to place the YIG thin film structure group.

[0012] Optionally, an input port and an output port are arranged on the first layer of green ceramic dielectric, and the input port and the output port are respectively located on both sides of the first layer of green ceramic dielectric;

[0013] The metal circuit patterns printed on the second layer of green ceramic dielectric are an input strip line, an output strip line, and a first coupling strip line group. One end of the input strip line is connected to the input port through a metal through hole arranged between the five layers of green ceramic dielectrics. One end of the output strip line is connected to the output port through a metal through hole arranged between the five layers of green ceramic dielectrics. The first coupling strip line group is located between the input strip line and the output strip line;

[0014] The metal circuit pattern printed on the fifth layer of green ceramic dielectric is a second coupling strip line group.

[0015] Optionally, the input port and the output port are located on the upper surface of the first layer of green ceramic dielectric;

[0016] The input strip line, the output strip line, and the first coupling strip line group are located on the upper surface of the second layer of green ceramic dielectric;

[0017] The second coupling strip line group is located on the upper surface of the fifth layer of green ceramic dielectric.

[0018] Optionally, four through holes are formed in the third layer of green ceramic sheet medium, and the YIG thin film structure group includes four YIG thin film structures. The four YIG thin film structures are respectively arranged in the four through holes and form an input resonator, a second resonator, a third resonator, and an output resonator in the signal transmission order.

[0019] Optionally, the first coupling strip line group includes a first coupling strip line, and the second coupling strip line group includes a second coupling strip line and a third coupling strip line.

[0020] Optionally, the input strip line is located above the input resonator and grounded at the terminal, and the downward projection of the input strip line can fall on the input resonator;

[0021] The output strip line is located above the output resonator and grounded at the terminal, and the downward projection of the output strip line can fall on the output resonator;

[0022] The second coupling strip line is located below the input resonator and the second resonator, and the upward projection of the second coupling strip line can fall on the input resonator and the second resonator;

[0023] The third coupling strip line is located below the third resonator and the output resonator, and the upward projection of the second coupling strip line can fall on the third resonator and the output resonator;

[0024] The first coupling strip line is located above the second resonator and the third resonator, and the downward projection of the first coupling strip line can fall on the second resonator and the third resonator.

[0025] Optionally, the input strip line and the second coupling strip line are arranged crosswise, and the included angle is 45° to 90°;

[0026] The output strip line and the third coupling strip line are arranged crosswise, and the included angle is 45° to 90°;

[0027] Both ends of the first coupling strip line are respectively arranged crosswise with the second coupling strip line and the third coupling strip line, and the included angle is 45° to 90°.

[0028] Optionally, the distances between the input strip line, the output strip line, the first coupling strip line and the four YIG thin film structures are adjusted by the thickness of the second layer of green ceramic sheet medium;

[0029] The distances between the second coupling strip line, the third coupling strip line and the four YIG thin film structures are adjusted by the thickness of the fourth layer of green ceramic sheet medium.

[0030] Optionally, the YIG thin film structure includes a gadolinium gallium garnet substrate and a YIG thin film covering the gadolinium gallium garnet substrate, and the YIG thin film structure is made by liquid phase epitaxy technology and has a cuboid shape.

[0031] The beneficial effects of the present invention at least include one of the following;

[0032] 1. By arranging each functional component on a green ceramic substrate and then using the LTCC process, the filter can be made integrated, and the assembly is also simpler, without the need for additional processing of strip lines, etc.

[0033] 2. Slots can be directly opened on the green ceramic substrate, enabling more precise fixation and position control of the YIG thin film structure, without the need for subsequent adjustment.

[0034] 3. The performance of the filter design has an important correlation with the coupling between resonators and the coupling between the input / output and resonators. Therefore, the distances between the input / output strip lines, coupling strip lines, and YIG resonators need to be precisely controlled. Since the LTCC process has high flexibility in the design of the green tape thickness and there are many optional thicknesses, the thinnest can reach about 5 microns. Therefore, compared with the traditional YIG filter design that requires precision machining and precision assembly to achieve, the required coupling can be achieved more precisely. Description of the Drawings

[0035] Figure 1 is a schematic diagram of the structure of an integrated tunable filter;

[0036] Figure 2 is a schematic diagram of the hierarchical structure of an integrated tunable filter;

[0037] Figure 3 is a schematic diagram of the internal structure of an integrated tunable filter;

[0038] Figure 4 is a schematic diagram of the YIG thin film structure;

[0039] Figure 5 is a schematic diagram of the structure of the input / output ports of the filter;

[0040] Figure 6 is a simulation result diagram of an integrated tunable bandpass filter.

[0041] Among them, the reference numerals:

[0042] 1 is the first layer of green ceramic substrate, 2 is the first additional green ceramic substrate, 3 is the second additional green ceramic substrate, 4 is the second layer of green ceramic substrate, 5 is the third additional green ceramic substrate, 6 is the third layer of green ceramic substrate, 7 is the fourth layer of green ceramic substrate, 8 is the fifth layer of green ceramic substrate, 9 is the fourth additional green ceramic substrate, 11 is the input strip line, 12 is the output strip line, 13 is the first coupling strip line, 14 is the second coupling strip line, 15 is the third coupling strip line, 16 is the YIG thin film structure, 17 is the metal via hole, 18 is the input port, 19 is the output port, 20 is the gadolinium gallium garnet substrate, 21 is the YIG thin film, 23 is the tunable filter body, 24 is the input test end, 25 is the output test end. Detailed implementation manners

[0043] The following uses specific specific examples to illustrate the implementation manners of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific implementation manners. Various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that, without conflict, the following embodiments and the features in the embodiments can be combined with each other.

[0044] It should be noted that the diagrams provided in the following embodiments only illustrate the basic concept of the present invention in a schematic manner. Therefore, only the components related to the present invention are shown in the diagrams, rather than being drawn according to the number, shape, and size of the components in actual implementation. The types, quantities, and proportions of the components in actual implementation can be arbitrarily changed, and the component layout type may also be more complex.

[0045] An integrated tunable filter includes a tunable filter body 23. An input strip line 11, an output strip line 12, a coupling strip line group, and a YIG thin film structure group are arranged in the tunable filter body 23. The input strip line 11 can transmit signals to the output strip line 12 through the coupling strip line group and the YIG thin film structure group. Among them, a multi-layer green ceramic dielectric is also arranged in the tunable filter body 23, and the multi-layer green ceramic dielectrics are stacked and sintered into a coupling cavity of the tunable filter body 23. Metal circuit images can be printed on the green ceramic dielectric, and resonant cavities for placing the YIG thin film structure group can be dug out on the green ceramic dielectric.

[0046] The purpose of such a design is that by arranging each functional component on the green ceramic dielectric and then using the LTCC process, the filter can be made into an integrated one, and the assembly is also simpler, without the need for additional processing of strip lines, etc. Slots can be directly opened on the green ceramic dielectric, and the fixation and position control of the YIG thin film structure are more accurate, without the need for subsequent adjustment.

[0047] This embodiment provides a five-layer green ceramic dielectric structure. Five green ceramic dielectrics are arranged in the tunable filter body 23, and the five green ceramic dielectrics are, from top to bottom, the first-layer green ceramic dielectric 1, the second-layer green ceramic dielectric 4, the third-layer green ceramic dielectric 6, the fourth-layer green ceramic dielectric 7, and the fifth-layer green ceramic dielectric 8;

[0048] The first-layer green ceramic dielectric 1 and the fourth-layer green ceramic dielectric 7 are green ceramic dielectrics without metal circuit patterns;

[0049] The second-layer green ceramic dielectric 4 and the fifth-layer green ceramic dielectric 8 are green ceramic dielectrics printed with metal circuit patterns;

[0050] The third green ceramic chip dielectric 6 is a green ceramic chip dielectric with perforations, and the perforations are used to place the YIG thin film structure group.

[0051] Meanwhile, an input port 18 and an output port 19 are arranged on the first green ceramic chip dielectric 1, and the input port 18 and the output port 19 are respectively located on two sides of the first green ceramic chip dielectric 1;

[0052] The metal circuit images printed on the second green ceramic chip dielectric 4 are an input strip line 11, an output strip line 12 and a first coupling strip line group. One end of the input strip line 11 is communicated with the input port 18 through a metal through hole 17 arranged among the five green ceramic chip dielectrics. One end of the output strip line 12 is communicated with the output port 19 through a metal through hole 17 arranged among the five green ceramic chip dielectrics. The first coupling strip line group is located between the input strip line 11 and the output strip line 12;

[0053] The metal circuit image printed on the fifth green ceramic chip dielectric 8 is a second coupling strip line group.

[0054] As Figure 1 shown, in a specific implementation, in order to control the performance of the entire filter, input test terminals 24 and output test terminals 25 can usually be arranged on both sides of the filter for connection with an external circuit. Meanwhile, the input test terminal 24 is connected to the input port 18, and the output test terminal 25 is connected to the output port 19.

[0055] Furthermore, in this embodiment, as Figure 3 and Figure 5 shown, the input port 18 and the output port 19 are located on the upper surface of the first green ceramic chip dielectric 1;

[0056] The input strip line 11, the output strip line 12 and the first coupling strip line group are located on the upper surface of the second green ceramic chip dielectric 4;

[0057] The second coupling strip line group is located on the upper surface of the fifth green ceramic chip dielectric 8.

[0058] Meanwhile, four perforations are formed on the third green ceramic chip dielectric 6, and the YIG thin film structure group includes four YIG thin film structures 16. The four YIG thin film structures 16 are respectively arranged in the four perforations and form an input resonator, a second resonator, a third resonator and an output resonator in the signal transmission order.

[0059] Furthermore, the first coupling strip line group includes a first coupling strip line 13, and the second coupling strip line group includes a second coupling strip line 14 and a third coupling strip line 15.

[0060] Meanwhile, the input strip line 11 is located above the input resonator and grounded at the terminal, and the downward projection of the input strip line 11 can fall on the input resonator;

[0061] The output strip line 12 is located above the output resonator and grounded at the terminal, and the downward projection of the output strip line 12 can fall on the output resonator;

[0062] The second coupling strip line 14 is located below the input resonator and the second resonator, and the upward projection of the second coupling strip line 14 can fall on the input resonator and the second resonator;

[0063] The third coupling strip line 15 is located below the third resonator and the output resonator, and the upward projection of the second coupling strip line 14 can fall on the third resonator and the output resonator;

[0064] The first coupling strip line 13 is located above the second resonator and the third resonator, and the downward projection of the first coupling strip line 13 can fall on the second resonator and the third resonator.

[0065] It should be noted that the operating principle of the entire tunable filter is that the input signal is input from the input port, transmitted to the input strip line through the metallized vias provided on the metal-ceramic chip medium, then coupled to the input resonator through the input strip line, and then coupled to the second coupling strip line through the input resonator, and transmitted along the second coupling strip line, while being coupled to the second resonator. After being processed by the second resonator, it is coupled to the first coupling strip line, and transmitted along the first coupling strip line and coupled to the third resonator. After being processed by the third resonator, it is coupled to the third coupling strip line, and then coupled to the output resonator through the third coupling strip line, and coupled to the output strip line through the output resonator, and finally transmitted to the output port through the metallized vias provided on the metal-ceramic chip medium.

[0066] It should also be noted that the above principle description is mainly for four resonators and is not a limitation. Those skilled in the art can set more resonators and coupling strip lines according to the actual situation, and the principle remains the same.

[0067] In this embodiment, the input strip line 11 and the second coupling strip line 14 are arranged crosswise, and the included angle is 45° to 90°;

[0068] The output strip line 12 and the third coupling strip line 15 are arranged crosswise, and the included angle is 45° to 90°;

[0069] Both ends of the first coupling strip line 13 are arranged crosswise with the second coupling strip line 14 and the third coupling strip line 15 respectively, and the included angle is 45° to 90°.

[0070] It should be noted that usually, the 90° included angle has the best effect.

[0071] In this embodiment, the thickness of the second green ceramic chip dielectric 4 is used to adjust the distances between the input strip line 11, the output strip line 12, the first coupling strip line 13 and the four YIG thin film structures 16;

[0072] The thickness of the fourth green ceramic chip dielectric 7 is used to adjust the distances between the second coupling strip line 14, the third coupling strip line 15 and the four YIG thin film structures 16.

[0073] The purpose of such design is that the distances between the input strip line, the output strip line and the coupling strip line and the YIG thin film structure can be adjusted by the thickness of the green ceramic strip dielectric; the specific gap size and strip line width are obtained according to the bandwidth design requirements of the filter and simulation; the thicker the thickness, the farther the distance between the strip line and the YIG thin film, the weaker the coupling, and the smaller the bandwidth; the thinner the thickness, the closer the distance between the strip line and the YIG thin film, the stronger the coupling, and the wider the bandwidth.

[0074] Based on this, as Figure 2 shown, an adjustable filter with a nine-layer green ceramic chip dielectric structure is provided. On the basis of the five-layer green ceramic chip dielectric structure, a first additional green ceramic chip dielectric 2 and a second additional green ceramic chip dielectric 3 are additionally provided below the first green ceramic chip dielectric to increase the distance between the first green ceramic chip dielectric and the second green ceramic chip dielectric. At the same time, a third additional green ceramic chip dielectric 5 is added to increase the thickness between the second green ceramic chip dielectric and the third green ceramic chip dielectric. Finally, a fourth additional green ceramic chip dielectric is provided below the fifth green ceramic chip dielectric for protection.

[0075] According to the structure given in this embodiment, taking the nine-layer structure as an example, the stacking sequence according to the LTCC process is as follows: The fifth green ceramic chip dielectric with coupling strip lines is stacked on the fourth additional green ceramic chip dielectric, then the fourth green ceramic chip dielectric is stacked, then the third green ceramic chip dielectric with a square hole is stacked. The YIG thin film structure is placed in the square hole, then the third additional green ceramic chip dielectric is stacked, then the second green ceramic chip dielectric with input / output strip lines and coupling strip lines is stacked, and then the second additional green ceramic chip dielectric, the first additional green ceramic chip dielectric and the first green ceramic chip dielectric are stacked according to the required thickness. The first green ceramic chip dielectric has input / output ports above it.

[0076] Meanwhile, when the input signal is input from the input strip line 11, if the input signal frequency is the same as the YIG thin film ferromagnetic resonance frequency, the input YIG thin film resonator is excited to generate a magnetic field and is coupled with the second coupling strip line 14. The second coupling strip line 14 couples the microwave energy to the second YIG thin film resonator. After the second resonator is excited, it couples the microwave energy to the first coupling strip line 13, and finally transmits the energy through the output strip line 12 in the way of strip line - thin film excitation coupling. When the input signal frequency is different from the YIG thin film ferromagnetic resonance frequency, the YIG thin film is not excited, so there is no energy transfer, realizing filtering.

[0077] And based on the above structure, the filter body is placed in the middle position between the two magnetic pole heads of the electromagnet magnetic field, and the magnetic field size ranges from 3600 Oe to 12000 Oe. As Figure 6 shown, it is the test result of the integrated tunable band - pass filter of this embodiment. When the magnetic field size is 3600 Oe, the corresponding center frequency of the filter is 5 GHz, the 3 dB bandwidth is about 30 MHz, the insertion loss is about 5.5 dB, and the out - of - band rejection is greater than 80 dBc; when the external magnetic field size is 12000 Oe, the corresponding center frequency of the filter is 27 GHz, the 3 dB bandwidth is about 60 MHz, the insertion loss is about 4.5 dB, and the out - of - band rejection is greater than 80 dBc. According to the simulation results, it can be seen that as the magnetic field gradually increases, the center frequency of the filter gradually moves to the high frequency, but the 3 dB bandwidth and out - of - band rejection of the filter can be basically kept unchanged.

[0078] Implementing the integrated tunable band - pass filter of the present invention, the performance of the filter design has an important correlation with the coupling between resonators and the coupling between the input / output and resonators. Therefore, the distances between the input / output strip lines, the coupling strip lines and the YIG resonators need to be precisely controlled. Since the LTCC process has high flexibility in the design of the green tape thickness and there are many optional thicknesses, the thinnest can be about 5 microns. Therefore, compared with the traditional YIG filter design that requires precision machining and precision assembly to achieve, the present invention can more precisely achieve the required coupling. Using the LTCC process, the filter can be made into an integrated one, and the assembly is also simpler, without the need for additional processing of strip lines, etc. The LTCC process can directly cut slots, and the fixation and position control of the YIG thin film structure are more precise, without subsequent adjustment. This filter has no parasitic passband outside the band, and the out - of - band rejection reaches more than 100 dBc. At the same time, the 3 dB bandwidth can be basically kept unchanged within the tuning range, the insertion loss is small, and the in - band standing wave is good.

[0079] As Figure 4As shown, the YIG thin film structure 16 includes a gadolinium gallium garnet substrate 20 and a YIG thin film 21 covering the gadolinium gallium garnet substrate 20, and the YIG thin film structure 16 is made by liquid phase epitaxy technology and is in the shape of a cuboid.

[0080] It should be noted at the same time that the metal through holes additionally provided on the green ceramic dielectric are grounded to play a shielding role.

[0081] Finally, it should be noted that the above are only the preferred embodiments of the present invention and are not used to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements for some of the technical features. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. An integrated tunable filter, comprising a tunable filter body (23), wherein an input stripline (11), an output stripline (12), a coupling stripline group and a YIG thin film structure group are arranged in the tunable filter body (23), wherein the input stripline (11) can transmit signals with the output stripline (12) through the coupling stripline group and the YIG thin film structure group, and wherein: The tunable filter body (23) is also provided with a plurality of layers of raw ceramic medium, and the plurality of layers of raw ceramic medium are stacked and sintered to form a coupling cavity of the tunable filter body (23), a metal circuit image can be printed on the raw ceramic medium, and a resonant cavity for placing a YIG thin film structure group can be dug out on the raw ceramic medium; Five layers of raw ceramic medium are arranged in the tunable filter body (23), and the five layers of raw ceramic medium are, from top to bottom, a first layer of raw ceramic medium (1), a second layer of raw ceramic medium (4), a third layer of raw ceramic medium (6), a fourth layer of raw ceramic medium (7) and a fifth layer of raw ceramic medium (8); The first layer of raw ceramic medium (1) and the fourth layer of raw ceramic medium (7) are raw ceramic mediums without metal circuit patterns; The second layer of raw ceramic medium (4) and the fifth layer of raw ceramic medium (8) are raw ceramic medium printed with metal circuit patterns; The third layer of raw ceramic sheet medium (6) is a raw ceramic sheet medium with holes dug therein, and the holes are used to place the YIG thin film structure group; An input port (18) and an output port (19) are provided on the first layer of raw ceramic sheet medium (1), and the input port (18) and the output port (19) are respectively located on two sides of the first layer of raw ceramic sheet medium (1); The metal circuit image printed on the second layer of raw ceramic sheet medium (4) is an input strip line (11), an output strip line (12) and a first coupling strip line group, and one end of the input strip line (11) is connected to the input port (18) through a metal through hole (17) arranged between the five layers of raw ceramic sheet medium, and one end of the output strip line (12) is connected to the output port (19) through a metal through hole (17) arranged between the five layers of raw ceramic sheet medium, and the first coupling strip line group is located between the input strip line (11) and the output strip line (12); The metal circuit image printed on the fifth layer of raw ceramic sheet medium (8) is a second coupling strip line group.

2. The integrated tunable filter according to claim 1, characterized in that: The input port (18) and the output port (19) are located on the upper surface of the first layer of raw ceramic medium (1); The input strip line (11), the output strip line (12) and the first coupling strip line group are located on the upper surface of the second layer of raw ceramic medium (4); The second coupling strip line group is located on the upper surface of the fifth layer of raw ceramic medium (8).

3. An integrated tunable filter according to claim 1 or 2, characterized in that: The third layer of raw ceramic sheet medium (6) is provided with four through-holes, and the YIG thin film structure group includes four YIG thin film structures (16). The four YIG thin film structures (16) are respectively arranged in the four through-holes to form an input resonator, a second resonator, a third resonator and an output resonator in a signal transmission sequence.

4. The integrated tunable filter according to claim 3, characterized in that: The first coupling strip line group comprises a first coupling strip line (13), and the second coupling strip line group comprises a second coupling strip line (14) and a third coupling strip line (15).

5. The integrated tunable filter according to claim 4, characterized in that: The input strip line (11) is located above the input resonator, and the terminal is grounded, and the downward projection of the input strip line (11) can fall on the input resonator; The output strip line (12) is located above the output resonator, and the terminal is grounded, and the downward projection of the output strip line (12) can fall on the output resonator; The second coupling strip line (14) is located below the input resonator and the second resonator, and the upward projection of the second coupling strip line (14) can fall on the input resonator and the second resonator; The third coupling strip line (15) is located below the third resonator and the output resonator, and the upward projection of the second coupling strip line (14) can fall on the third resonator and the output resonator; The first coupling strip line (13) is located above the second resonator and the third resonator, and a downward projection of the first coupling strip line (13) can fall on the second resonator and the third resonator.

6. The integrated tunable filter according to claim 4, characterized in that: The input strip line (11) and the second coupling strip line (14) are arranged to cross each other, and the included angle is 45° to 90°; The output strip line (12) and the third coupling strip line (15) are arranged to cross each other, and the included angle is 45° to 90°; The two ends of the first coupling strip line (13) are respectively arranged to cross the second coupling strip line (14) and the third coupling strip line (15), and the included angle is 45° to 90°.

7. The integrated tunable filter according to claim 4, characterized in that: The spacing between the input strip line (11), the output strip line (12), the first coupling strip line (13) and the four YIG thin film structures (16) is adjusted by adjusting the thickness of the second layer of raw ceramic medium (4); The spacing between the second coupling strip line (14), the third coupling strip line (15) and the four YIG thin film structures (16) is adjusted by adjusting the thickness of the fourth layer of raw ceramic medium (7).

8. The integrated tunable filter according to claim 3, characterized in that: The YIG thin film structure (16) comprises a gadolinium gallium garnet substrate (20) and a YIG thin film (21) covering the gadolinium gallium garnet substrate (20), and the YIG thin film structure (16) is manufactured using liquid phase epitaxy technology and has a rectangular parallelepiped shape.

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