Electric tuning frequency hopping filter and communication equipment

Abstract

The utility model provides an electric tuning frequency hopping filter and communication equipment. The electric tuning frequency hopping filter comprises a left variable capacitor, a right variable capacitor, and an input end, an input inductor, a first coupling structure, a second coupling structure, an output inductor, a first grounding pad, a second grounding pad and an output end which are arranged on a printed circuit board, wherein the first coupling structure is provided with a first part and a second part, and the second coupling structure is provided with a first part and a second part; a left notch is formed between the first part of the first coupling structure and the first grounding bonding pad, and the first part and the first grounding bonding pad are connected through a left variable capacitor; a right notch is formed between the first part of the second coupling structure and the second grounding bonding pad, and the first part and the second grounding bonding pad are connected through a right variable capacitor; the distance between the first portion of the first coupling structure and the first portion of the second coupling structure is greater than the distance between the second portion of the first coupling structure and the second portion of the second coupling structure.

Description

Technical Field

[0001] The utility model relates to a filter and a communication device, in particular to an electrically tuned frequency hopping filter and a communication device. Background Art

[0002] An electrically tuned frequency hopping filter is a filter that can quickly change its center frequency within a wide frequency range and is mainly used in frequency hopping communication systems. Frequency hopping communication is an anti-interference and confidentiality communication technology that transmits signals by rapidly and randomly hopping the carrier frequency over multiple preset frequencies to combat interference and eavesdropping. An electrically tuned frequency hopping filter is one of the key components to achieve this technology. It can automatically adjust its passband center frequency according to the frequency hopping pattern to match the currently used carrier frequency.

[0003] Existing electrically tuned filters are usually implemented using varactor diodes and hand-wound inductors. Harmonic signals are filtered out through capacitors, inductors and other components, and the required fundamental signals are transmitted, thereby ensuring the normal operation of the circuit and helping the radio communication system to improve its anti-interference ability. This type of filter requires manual debugging, has poor reliability consistency, and has a fixed structure, so it cannot meet some specific needs. Utility Model Content

[0004] In view of the defects of the prior art, the utility model successfully develops an electrically tuned frequency hopping filter.

[0005] On one hand, the utility model provides an electrically tuned frequency hopping filter comprising: a left variable capacitor, a right variable capacitor, and an input terminal, an input inductor, a first coupling structure, a second coupling structure, an output inductor, a first grounding pad, a second grounding pad, and an output terminal arranged on a printed circuit board; wherein the first coupling structure has a first part and a second part, and the second coupling structure has a first part and a second part; a left notch is provided between the first part of the first coupling structure and the first grounding pad, and the two are connected through the left variable capacitor; a right notch is provided between the first part of the second coupling structure and the second grounding pad, and the two are connected through the right variable capacitor; and a distance between the first part of the first coupling structure and the first part of the second coupling structure is greater than a distance between the second part of the first coupling structure and the second part of the second coupling structure.

[0006] Furthermore, the input inductor is physically connected to the first coupling structure; the second coupling structure is physically connected to the output inductor, and the first coupling structure is symmetrically arranged with the second coupling structure on the printed circuit board.

[0007] Furthermore, the left variable capacitor or the right variable capacitor is a chip variable capacitor.

[0008] Furthermore, the left variable capacitor or the right variable capacitor is a controlled varactor diode.

[0009] Further, the first part of the first coupling structure includes a left first microstrip line, the second part of the first coupling structure includes a left second microstrip line, a left third microstrip line and a left fourth microstrip line, the first ground pad is connected to the first upper ground via, and a first lower ground via connected to the ground of the first coupling structure is formed on the left fourth microstrip line; the first part of the second coupling structure includes a right first microstrip line, the second part of the second coupling structure includes a right second microstrip line, a right third microstrip line and a right fourth microstrip line, the second ground pad is connected to the second upper ground via, and a second lower ground via connected to the ground of the second coupling structure is formed on the right fourth microstrip line.

[0010] Further, the left first microstrip line, the left second microstrip line, the left third microstrip line and the left fourth microstrip line are connected in sequence, the left first microstrip line, the left second microstrip line and the left fourth microstrip line extend in the vertical direction, and the left fourth microstrip line is closer to the second coupling structure than the left first microstrip line, and the left third microstrip line extends in the horizontal direction; the right first microstrip line, the right second microstrip line, the right third microstrip line and the right fourth microstrip line are connected in sequence, the right first microstrip line, the right second microstrip line and the right fourth microstrip line extend in the vertical direction, and the right fourth microstrip line is closer to the first coupling structure than the right first microstrip line, and the right third microstrip line extends in the horizontal direction.

[0011] Further, a first spacing is formed between the left first microstrip line and the right first microstrip line, and a second spacing is formed between the left fourth microstrip line and the right fourth microstrip line, and the first spacing is greater than the second spacing.

[0012] Furthermore, the first part of the first coupling structure includes a left first microstrip line, the second part of the first coupling structure includes a left second microstrip line, the first ground pad is connected to the first upper ground via, and the second end of the left second microstrip line is connected to the ground; the first part of the second coupling structure includes a right first microstrip line, the second part of the second coupling structure includes a right second microstrip line, the second ground pad is connected to the second upper ground via, and the second end of the right second microstrip line is connected to the ground; the first coupling structure and the second coupling structure form an inverted figure eight shape.

[0013] Further, the second end of the left second microstrip line and the second end of the right second microstrip line are connected to the same ground.

[0014] Another aspect of the utility model provides a communication device, characterized by comprising any one of the aforementioned filters.

[0015] The beneficial effects of the utility model are as follows: the filter of the utility model adopts microstrip line technology, which greatly improves the reliability and consistency of the product, has high production efficiency, and has a fixed structure; the filter of the utility model can achieve that the relative bandwidth increases with the increase of the center frequency within different frequency ranges. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The specific contents of the utility model are described below with reference to the accompanying drawings, which will help to more easily understand the above and other purposes, features and advantages of the utility model. The accompanying drawings are only for illustrating the principles of the utility model. The sizes and relative positions of the units in the accompanying drawings do not need to be drawn in proportion.

[0017] Figure 1 is a schematic diagram of the structure of the electrically tuned frequency modulated filter in Example 1;

[0018] Figure 2A is a bandwidth diagram of the electrically tuned frequency-modulated filter at 1 GHz in Example 1;

[0019] Figure 2B is a bandwidth diagram of the electrically tuned frequency modulation filter at 1.5 GHz in Example 1;

[0020] Figure 2C is a bandwidth diagram of the electrically tuned frequency modulation filter at 2 GHz in Example 1;

[0021] Figure 3 It is a schematic diagram of the structure of the electrically tuned frequency-modulated filter in Example 2. DETAILED DESCRIPTION

[0022] In order to make the above-mentioned purpose, features and advantages of the utility model more obvious and easy to understand, the specific implementation of the utility model is described in detail below in conjunction with the accompanying drawings, so that the above-mentioned and other purposes, features and advantages of the utility model will be clearer. The same reference numerals in all the drawings indicate the same parts. The drawings are not deliberately drawn to scale, and the focus is on illustrating the main purpose of the utility model.

[0023] The terms and words used in the following description and claims are not limited to the written meanings, but are only used by the inventor so that the present invention can be clearly and consistently understood. Therefore, it is obvious to those skilled in the art that the following description of various embodiments of the present invention is provided for the purpose of illustration only, and not for the purpose of limiting the present invention as defined by the attached claims and their equivalents.

[0024] It should be understood that the singular forms of "a", "an", and "the" include plural objects unless the context clearly indicates otherwise. Thus, for example, reference to a "module" includes reference to one or more such modules. The advantages and features of the present invention and methods of implementing the present invention can be more easily understood by reference to the detailed description and drawings of the embodiments below. However, the present invention can be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; on the contrary, these embodiments are provided so that the present invention will be thorough and complete and will fully convey the concepts of the present invention to those skilled in the art.

[0025] Example 1

[0026] See also Figure 1 , Figure 1 A specific embodiment of the electrically tuned frequency hopping filter of the utility model is shown. The electrically tuned frequency hopping filter of this embodiment includes an input terminal 5, an input inductor 3, a first coupling structure 1, a first grounding pad 12, a second coupling structure 2, an output inductor 4, a second grounding pad 22 and an output terminal 6, which are arranged compatible with a printed circuit board (PCB board); Figure 1 In the figure, there is a first coupling structure 1 arranged on the left and a second coupling structure 2 arranged on the right, and the first coupling structure 1 and the second coupling structure 2 are symmetrically arranged on the printed circuit board. The input end 5 of the filter is connected to the first coupling structure 1 through the input inductor 3, and the output end 6 of the filter is connected to the second coupling structure 2 through the output inductor 4.

[0027] Exemplarily, the printed circuit board in the present invention may use Rogers 4350B board material with a thickness of about 0.2-1.2 mm.

[0028] Furthermore, the inductance of the input inductor 3 and the output inductor 4 is 0.5-100nH, and the wiring width on the printed circuit board is 0.05-0.6mm, and the length is 0.5-10mm. It is understandable that the input inductor 3 and the output inductor 4 can also be arranged on the printed circuit board in the form of chip inductors.

[0029] The first coupling structure 1 and the second coupling structure 2 can use microstrip lines or strip lines. The specific selection of microstrip lines and strip lines depends on the needs of specific applications, including operating frequency, cost budget, space constraints, signal integrity and shielding requirements. Based on the structural characteristics of microstrip lines and strip lines, they can be well compatible with printed circuit boards (PCB boards). Microstrip lines or strip lines are preferably gold wires, silver wires or copper wires. This method greatly shortens working hours, improves production efficiency, and improves product consistency and reliability.

[0030] Specifically, the first coupling structure 1 has a first part and a second part, wherein the first part of the first coupling structure 1 includes a left first microstrip line 14. The second part of the first coupling structure 1 includes a left second microstrip line 15, a left third microstrip line 16 and a left fourth microstrip line 17, and the first part and the second part of the first coupling structure 1 are separated by the connection between the second coupler 1 and the input inductor 3. The first grounding pad 12 is connected to the first upper grounding via 11, the first end of the left fourth microstrip line 17 is connected to the left third microstrip line 16, and the second end of the left fourth microstrip line 17 is formed with a lower grounding via 18 connected to the ground of the first coupling structure 1. A left notch is formed between the first grounding pad 12 and the left first microstrip line 14, and a left variable capacitor 13 is connected to the left notch. The left variable capacitor 13 can be a patch capacitor in any form, such as a varactor diode, a varactor transistor, etc. The left first microstrip line 14, the left second microstrip line 15, the left third microstrip line 16 and the left fourth microstrip line 17 are connected in sequence. In this embodiment, the left first microstrip line 14 , the left second microstrip line 15 and the left fourth microstrip line 16 extend in the vertical direction, and the left fourth microstrip line 17 is closer to the second coupling structure 2 than the left first microstrip line 14 , while the left third microstrip line 16 extends in the horizontal direction.

[0031] The second coupling structure 2 has a first part and a second part, wherein the first part of the second coupling structure 2 includes a right first microstrip line 24. The second part of the second coupling structure 2 includes a right second microstrip line 25, a right third microstrip line 26 and a right fourth microstrip line 27. The first part and the second part of the second coupling structure 2 are separated by the connection between the second coupler 2 and the output inductor 6. The second grounding pad 12 is connected to the second upper grounding via 21, the first end of the right fourth microstrip line 27 is connected to the right third microstrip line 26, and the second end of the left fourth microstrip line 27 is formed with a lower grounding via 28 connected to the second coupling structure 2. A right notch is formed between the second grounding pad 12 and the right first microstrip line 24, and a right variable capacitor 23 is connected to the right notch. The right variable capacitor 23 can be a variable capacitor in any form, such as a varactor diode, a varactor transistor, etc. The right first microstrip line 24, the right second microstrip line 25, the right third microstrip line 26 and the right fourth microstrip line 27 are connected in sequence. In this embodiment, the right first microstrip line 24, the right second microstrip line 25 and the right fourth microstrip line 27 extend in the vertical direction, and the right fourth microstrip line 27 is closer to the first coupling structure 1 than the right first microstrip line 24, while the right third microstrip line 26 extends in the horizontal direction.

[0032] Through the above layout, a first opening P1 is formed between the left first microstrip line 14 and the right second microstrip line 24, and a second opening P2 is formed between the left fourth microstrip line 16 and the right fourth microstrip line 26, wherein the opening width of the first opening P1 is greater than the opening width of the second opening P2.

[0033] It should be understood that although the first coupler and the second coupler are implemented in the present specific embodiment in the form of an inductor through a metal fold line pattern, it is sufficient that a coupling function can be generated between the first coupler and the second coupler. Therefore, the first coupler and the second coupler can also be other structures besides being presented in the form of an inductor, such as a resonator.

[0034] In the utility model, the signal enters from the input terminal 5 (RFin terminal) of the filter, passes through the input inductor 3, and is then transmitted to the first coupling structure 1. Then the signal is coupled to the second coupling structure 2 through the first coupling structure 1, and then output from the output terminal 6 (RFout terminal) through the output inductor 4. Among them, the first part of the first coupling structure 1 is connected to the first grounding pad 12 through the left variable capacitor 13, and is grounded through the first upper grounding through hole 11, and the left fourth microstrip line 17 of the first coupling structure 1 is grounded through the first lower grounding through hole 18. The first part of the second coupling structure 1 is connected to the second grounding pad 22 through the right variable capacitor 23, and is grounded through the second upper grounding through hole 21, and the right fourth microstrip line 27 of the second coupling structure 2 is grounded through the second lower grounding through hole 28. The left variable capacitor 13 and the right variable capacitor 23 are, for example, varactor diodes. Further, the varactor diode is a controllable varactor diode, and the capacitance value of the controllable varactor diode can be changed by the control circuit. The specific structure of the control circuit can be any structure that can realize the above-mentioned specific control function, and there is no specific limitation on it. The control circuit can also be set on the PCB board, and the part that originally requires manual debugging can be directly integrated into the inside or surface of the printed circuit board.

[0035] By adjusting the capacitance value of the left variable capacitor 13 and / or the right variable capacitor 23, the bandwidth of the filter can be adjusted, for example, by selecting different types of varactor diodes, thereby having different capacitance variation ranges, or by adjusting the capacitance value of the varactor diode. In addition to adjusting the capacitance value, the input inductor 3 and the output inductor 4 also have a significant impact on the signal, so that by adjusting the input inductor 3 and the output inductor 4, more flexible and wider signal processing can be achieved.

[0036] In addition, in the present invention, the first part of the first coupler and the first part of the second coupler can be regarded as electrical parts, and the second part of the first coupler and the second part of the second coupler can be regarded as magnetic parts. The smaller the spacing of the magnetic parts, the larger the relative bandwidth, and the larger the spacing of the magnetic parts, the smaller the relative bandwidth. Therefore, the bandwidth can be adjusted by adjusting the relative distance between the microstrip lines or strip lines.

[0037] The above structure can realize a frequency hopping filter whose relative bandwidth (for example, from 5% to 6%, or from 10% to 15%) increases as the center frequency increases in different frequency ranges (for example, within 500-1500MHz, 1000-2000MHz, etc.).

[0038] The filter of the utility model is tested, such as Figure 2A As shown, at 1GHz, the 3dB bandwidth is about 136MHz, and the relative bandwidth is 13.6%; at 1.5GHz, as shown Figure 2B As shown, the 3dB bandwidth is about 224MHz, and the relative bandwidth is 14.9%; Figure 2C As shown, at 2 GHz, the 3 dB bandwidth is about 332 MHz, and the relative bandwidth is 16.6%.

[0039] It can be seen that, for the electrically tuned frequency hopping filter of the present invention, within the frequency hopping range covered by the filter, as the center frequency changes from 1 GHz to 2 GHz, the relative bandwidth increases from 13.6% to 16.6%.

[0040] Example 2

[0041] See also Figure 3 , Figure 3 Another specific embodiment of the electrically tuned frequency hopping filter of the utility model is shown.

[0042] The electrically tuned frequency hopping filter of this embodiment includes an input terminal 5, an input inductor 3, a first coupling structure 1, a first ground pad 12, a second coupling structure 2, an output inductor 4, a second ground pad 22 and an output terminal 6 arranged compatible with a printed circuit board (PCB board).

[0043] exist Figure 3 The first coupling structure 1 arranged on the left and the second coupling structure 2 arranged on the right are arranged symmetrically relative to the central axis of the filter. The input end 5 of the filter is connected to the first coupling structure 1 through the input inductor 3, and the output end 6 of the filter is connected to the second coupling structure 2 through the output inductor 4.

[0044] Exemplarily, the printed circuit board in the present invention may use Rogers 4350B board material with a thickness of about 0.2-1.2 mm.

[0045] Furthermore, the inductance of the input inductor 3 and the output inductor 4 is 0.5-100nH, and the wiring width on the printed circuit board is 0.05-0.6mm, and the length is 0.5-10mm. It is understandable that the input inductor 3 and the output inductor 4 can also be arranged on the printed circuit board in the form of chip inductors.

[0046] The first coupling structure 1 and the second coupling structure 2 can use microstrip lines or strip lines. The specific selection of microstrip lines and strip lines depends on the needs of specific applications, including operating frequency, cost budget, space constraints, signal integrity and shielding requirements. Based on the structural characteristics of microstrip lines and strip lines, they can be well compatible with PCB boards. Microstrip lines or strip lines are preferably gold wires, silver wires or copper wires. This method greatly shortens working hours, improves production efficiency, and improves product consistency and reliability.

[0047] Specifically, the first coupling structure 1 has a first part and a second part. The first part of the first coupling structure 1 includes a left first microstrip line 14', the second part of the first coupling structure 1 includes a left second microstrip line 15', and the first part and the second part of the first coupling structure 1 are separated by the connection between the first coupler 1 and the input inductor 3. The first grounding pad 12 is connected to the first upper grounding via 11, the first end of the left second microstrip line 15' is connected to the left first microstrip line 14, and the second end of the left second microstrip line 15' is connected to the ground 7. A left notch is formed between the first grounding pad 12 and the left first microstrip line 14', and a left variable capacitor (not shown in the figure) can be connected to the left notch. The left variable capacitor can be a variable capacitor in any form, such as a varactor diode, a varactor transistor, etc.

[0048] The second coupling structure 2 has a first part and a second part, wherein the first part of the second coupling structure 2 includes a right first microstrip line 24', the second part of the second coupling structure 2 includes a right second microstrip line 25', and the first part and the second part of the second coupling structure 2 are separated by the connection between the second coupling structure 2 and the output inductor 4. The second grounding pad 12 is connected to the second upper grounding via 21, the first end of the right second microstrip line 25' is connected to the right first microstrip line 24', and the second end of the right second microstrip line 25' is connected to the ground 7. A right notch is formed between the second grounding pad 12 and the right first microstrip line 24', and a right variable capacitor (not shown in the figure) is connected to the right notch. The right variable capacitor can be any form of variable capacitor, such as a varactor diode, a varactor transistor, etc.

[0049] The first coupling structure 1 and the second coupling structure 2 form an inverted figure eight shape as a whole, that is, the distance between the two gradually narrows from top to bottom. That is, through the overall layout of the first coupling structure 1 and the second coupling structure 2, the uppermost ends of the left first microstrip line 14' and the right first microstrip line 24' have a first opening P1, and the lowermost ends of the left second microstrip line 15' and the right second microstrip line 25' have a second opening P2, wherein the spacing of the first openings P1 is greater than the spacing of the second openings P2.

[0050] It should be understood that although the first coupler and the second coupler are implemented in the present embodiment in the form of an inductor through a metal strip pattern, it is sufficient for the first coupler and the second coupler to generate a coupling function. Therefore, the first coupler and the second coupler may also be other structures besides being in the form of an inductor, such as a resonator.

[0051] In this embodiment, the signal is transmitted from the input end 5 (RFin end) of the filter through the input inductor 3, and then transmitted to the first coupling structure 1, and then the signal is coupled to the second coupling structure 2 through the first coupling structure 1, and then output from the output end 6 (RFout end) through the output inductor 4. Among them, the first part of the first coupling structure 1 is connected to the first grounding pad 12 through the left variable capacitor, and is grounded through the first upper grounding through hole 11, and the left second microstrip line 15' of the first coupling structure 1 is connected to the ground 7. The first part of the second coupling structure 1 is connected to the second grounding pad 22 through the right variable capacitor, and is grounded through the second upper grounding through hole 21, and the second microstrip line 25' of the second coupling structure 2 is connected to the ground 7. The left variable capacitor and the right variable capacitor can be, for example, varactor diodes. Further, the varactor diode is a controllable varactor diode, and the capacitance value of the varactor diode can be changed by the control circuit. The specific structure of the control circuit can be any structure that can realize the above-mentioned specific control function, and it is not specifically limited. The control circuit can also be arranged on the PCB board, so that the part that originally needs manual debugging can be directly integrated into the inside or surface of the PCB.

[0052] By adjusting the capacitance value of the left variable capacitor and / or the right variable capacitor, the bandwidth of the filter can be adjusted, for example, by selecting different types of varactor diodes to have different capacitance variation ranges, or by adjusting the capacitance value of the varactor diode. In addition to adjusting the capacitance value, the input inductor 3 and the output inductor 4 also have a significant impact on the signal, so that by adjusting the input inductor 3 and the output inductor 4, more flexible and wider signal processing can be achieved.

[0053] In addition, in the present invention, the first part of the first coupling structure 1 and the first part of the second coupling structure 2 can be regarded as electrical parts; the first part of the first coupling structure 1 and the second part of the second coupling structure 2 can be regarded as magnetic parts, and the smaller the spacing of the magnetic parts, the larger the relative bandwidth, and the larger the spacing of the magnetic parts, the smaller the relative bandwidth. Therefore, the bandwidth can be adjusted by adjusting the relative distance between the microstrip lines or strip lines.

[0054] The above structure can also realize a frequency hopping filter whose relative bandwidth increases (for example, from 5% to 6%, or from 10% to 15%) as the center frequency increases in different frequency ranges (for example, within 500-1500MHz, 1000-2000MHz, etc.).

[0055] Furthermore, in this embodiment, the microstrip line or stripline has a simpler pattern, and the second end of the left second microstrip line 15' and the second end of the right second microstrip line 25' share a common ground, which is more convenient to design on the same layer of the PCB board and improve production efficiency.

[0056] Furthermore, the electrically tuned FM filter disclosed herein can be used in electronic devices, such as desktop computers, notebooks, smart phones, smart watches, wearable devices, Internet server intelligent voice systems, routers, automotive electronic devices, Internet of Things (IoT) devices, medical devices, etc.

[0057] Although the technology has been illustrated and described with respect to one or more embodiments, changes and / or modifications may be made to the illustrated examples without departing from the spirit and scope of the appended claims. In particular, with respect to the various functions performed by the above-described components or structures (assemblies, devices, circuits, systems, etc.), the terms used to describe such components (including references to "means") are intended to correspond to any component or structure (e.g., functionally equivalent) that performs the specified function of the described component, even if not structurally equivalent to the disclosed structure that performs the function in the example embodiments described herein, unless otherwise specified. In addition, although a particular feature may have been disclosed with respect to one of several embodiments, such a feature may be combined with one or more other features in other embodiments as may be desired and advantageous for any given or particular application. In addition, to the extent that the terms "comprising," "including," "having," "having," "containing," or variations thereof are used in the detailed description or claims, such terms are intended to be inclusive in a manner similar to the term "comprising."

[0058] In the above description, many specific details are described to facilitate a full understanding of the present invention. However, the above description is only a preferred embodiment of the present invention. The present invention can be implemented in many other ways different from those described herein, so the present invention is not limited by the specific implementation disclosed above. At the same time, any person familiar with the technical field can make many possible changes and modifications to the technical solution of the present invention by using the methods and technical contents disclosed above without departing from the scope of the technical solution of the present invention, or modify it into an equivalent embodiment of equivalent changes. Any simple modification, equivalent change and modification made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention still falls within the scope of protection of the technical solution of the present invention.

Claims

1. An electrically tuned frequency hopping filter, characterized in that: include: A left variable capacitor, a right variable capacitor, and an input terminal, an input inductor, a first coupling structure, a second coupling structure, an output inductor, a first ground pad, a second ground pad, and an output terminal arranged on a printed circuit board; wherein the first coupling structure has a first portion and a second portion, and the second coupling structure has a first portion and a second portion; A left notch is provided between the first portion of the first coupling structure and the first ground pad and is connected via a left variable capacitor; A right notch is formed between the first portion of the second coupling structure and the second ground pad and is connected via a right variable capacitor; A distance between a first portion of the first coupling structure and a first portion of the second coupling structure is greater than a distance between a second portion of the first coupling structure and a second portion of the second coupling structure.

2. The filter according to claim 1, characterized in that: The input inductor is physically connected to the first coupling structure; the second coupling structure is physically connected to the output inductor, and the first coupling structure is symmetrically arranged with the second coupling structure on the printed circuit board.

3. The filter according to claim 2, characterized in that: The left variable capacitor or the right variable capacitor is a chip variable capacitor.

4. The filter according to claim 3, characterized in that: The left variable capacitor or the right variable capacitor is a controlled varactor diode.

5. The filter according to any one of claims 1 to 4, characterized in that: The first part of the first coupling structure includes a left first microstrip line, the second part of the first coupling structure includes a left second microstrip line, a left third microstrip line and a left fourth microstrip line, the first ground pad is connected to the first upper ground via, and a first lower ground via connected to the ground of the first coupling structure is formed on the left fourth microstrip line; The first part of the second coupling structure includes a right first microstrip line, the second part of the second coupling structure includes a right second microstrip line, a right third microstrip line and a right fourth microstrip line, the second ground pad is connected to the second upper ground via, and a second lower ground via connected to the ground of the second coupling structure is formed on the right fourth microstrip line.

6. The filter according to claim 5, characterized in that: The first left microstrip line, the second left microstrip line, the third left microstrip line and the fourth left microstrip line are connected in sequence, the first left microstrip line, the second left microstrip line and the fourth left microstrip line extend in a vertical direction, and the fourth left microstrip line is closer to the second coupling structure than the first left microstrip line, and the third left microstrip line extends in a horizontal direction; The right first microstrip line, the right second microstrip line, the right third microstrip line and the right fourth microstrip line are connected in sequence, the right first microstrip line, the right second microstrip line and the right fourth microstrip line extend in the vertical direction, and the right fourth microstrip line is closer to the first coupling structure than the right first microstrip line, and the right third microstrip line extends in the horizontal direction.

7. The filter according to claim 6, characterized in that: A first distance is formed between the left first microstrip line and the right first microstrip line, and a second distance is formed between the left fourth microstrip line and the right fourth microstrip line, and the first distance is greater than the second distance.

8. The filter according to any one of claims 1 to 4, characterized in that: The first part of the first coupling structure includes a left first microstrip line, the second part of the first coupling structure includes a left second microstrip line, the first ground pad is connected to the first upper ground through hole, and the second end of the left second microstrip line is connected to the ground; the first part of the second coupling structure includes a right first microstrip line, the second part of the second coupling structure includes a right second microstrip line, the second ground pad is connected to the second upper ground through hole, and the second end of the right second microstrip line is connected to the ground; the first coupling structure and the second coupling structure form an inverted figure eight shape.

9. The filter according to claim 8, characterized in that: A second end of the left second microstrip line and a second end of the right second microstrip line are connected to the same ground.

10. A communication device, characterized in that: A filter comprising any one of claims 1-9.

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