Filter and communication device

Abstract

The application provides a filter and a communication device. The filter comprises a substrate and a first filter structure arranged above the substrate. The first filter structure comprises a signal input end arranged at one end of the substrate and a signal output end arranged at the other end of the substrate. The microstrip line is provided between the signal input end and the signal output end, and a gap is provided between the microstrip line and the signal input end and the signal output end. A Z-shaped gap is etched on the microstrip line and penetrates the microstrip line, so that the microstrip line is divided into two stepped impedance lines. In the application, the Z-shaped gap is etched on the microstrip line, so that the microstrip line is divided into two stepped impedance lines which are coupled with each other, a transmission zero point of a high-frequency stop band is coupled out, the working frequency band is improved, and the stop band suppression characteristic is greatly optimized.

Description

Technical Field

[0001] This application relates to the field of filter circuit technology, and in particular to a filter and communication device. Background Technology

[0002] With the development and maturation of communication networks, spectrum resources are becoming increasingly scarce. Filters are common devices for filtering or separating signals, primarily used to reduce or eliminate the impact of harmonics on the system. Below 100MHz, filters can be constructed using resonant circuits designed with three basic components: capacitors, inductors, and resistors. In the 100MHz to 1GHz frequency band, surface acoustic wave (SAW) filters can be used. Under ultra-wideband standards, filters are generally designed with dielectric materials as the substrate for their structure and characteristics. Microstrip filters have advantages such as small size, low cost, flexible structure, and simple manufacturing process, and are widely used in communications, broadcasting, and aerospace fields.

[0003] While existing microstrip filters achieve a relatively wide upper stopband range, most of these microstrip filters operate in the low-frequency range and have a relatively large size and limited application scenarios. Utility Model Content

[0004] Based on this, embodiments of this application provide a filter that improves the operating frequency band of a microstrip filter and optimizes its stopband suppression characteristics.

[0005] In a first aspect, a filter is provided, including a substrate and a first filter structure disposed above the substrate;

[0006] The first filter structure includes a signal input terminal disposed at one end of the substrate and a signal output terminal disposed at the other end of the substrate; a microstrip line is provided between the signal input terminal and the signal output terminal, and there are gaps between the microstrip line and both the signal input terminal and the signal output terminal;

[0007] The microstrip line is etched with a Z-shaped slot that runs through the microstrip line, which divides the microstrip line into two stepped impedance lines.

[0008] In one embodiment, both the signal input terminal and the signal output terminal are provided with taps near the end of the microstrip line;

[0009] There is a strip-shaped gap between the tap line and the microstrip line.

[0010] In one embodiment, the microstrip line is disposed on the central axis between the signal input terminal and the signal output terminal;

[0011] Both the taps connected to the signal input terminal and the taps connected to the signal output terminal are off-center from the central axis; the taps connected to the signal input terminal are located on one side of the microstrip line; and the taps connected to the signal output terminal are located on the other side of the microstrip line.

[0012] In one embodiment, the microstrip line has slot openings on both sides corresponding to the Z-shaped slots; the slot opening near the signal input end is located on the side of the microstrip line away from the tap line connected to the signal input end; the slot opening near the signal output end is located on the side of the microstrip line away from the tap line connected to the signal output end.

[0013] In one embodiment, the width of the slot opening ranges from 0.1mm to 0.7mm; the distance between the slot opening and the end of the microstrip line ranges from 0.5mm to 1.5mm; the width of the gap between the microstrip line and the signal input and signal output ends ranges from 0.1mm to 0.3mm; and the length of the tap line ranges from 2mm to 3mm.

[0014] In one embodiment, both the signal input terminal and the signal output terminal are connected to an open stub line;

[0015] The branch line is an L-shaped line, including vertical and horizontal lines;

[0016] Vertical lines are perpendicular to the corresponding signal input or output terminals; horizontal lines are parallel to the microstrip lines.

[0017] In one embodiment, the horizontal line of the open stub line on the signal input side is located on the side of the microstrip line away from the tap line connected to the signal input side; the horizontal line of the open stub line on the signal output side is located on the side of the microstrip line away from the tap line connected to the signal output side.

[0018] In one embodiment, a second filter structure is further disposed below the substrate;

[0019] The second filter structure is a grounded metal surface; two rectangular holes are etched on the grounded metal surface; the two rectangular holes are parallel to the microstrip line and are located below the microstrip line;

[0020] The two rectangular holes are centrally symmetrical around the center point of the substrate.

[0021] In one embodiment, the first filter structure is centrally symmetrical about the center point of the substrate.

[0022] In a second aspect, a communication device is provided, wherein the communication device includes the filter provided in the first aspect.

[0023] The beneficial effects of the technical solutions provided in this application include at least the following:

[0024] A filter is provided, comprising a substrate and a first filter structure disposed above the substrate. The first filter structure includes a signal input terminal disposed at one end of the substrate and a signal output terminal disposed at the other end of the substrate; a microstrip line is provided between the signal input terminal and the signal output terminal, and a slot is provided between the microstrip line and both the signal input terminal and the signal output terminal. A Z-shaped slot is etched through the microstrip line, dividing the microstrip line into two stepped impedance lines. In this application, by etching a Z-shaped slot on the microstrip line, the microstrip line is divided into two mutually coupled stepped impedance lines, coupling out the transmission zero of the high-frequency stopband, improving the operating frequency band, and significantly optimizing the stopband suppression characteristics. Attached Figure Description

[0025] Figure 1 A schematic diagram illustrating the principle of the first type of filter provided in this application embodiment;

[0026] Figure 2 A schematic diagram illustrating the principle of the second type of filter provided in this application embodiment;

[0027] Figure 3 A schematic diagram illustrating the principle of the third type of filter provided in this application embodiment;

[0028] Figure 4 A schematic diagram illustrating the principle of the fourth type of filter provided in this application embodiment;

[0029] Figure 5 A schematic diagram of the grounding metal surface provided in the embodiments of this application;

[0030] Figure 6 This is a schematic diagram showing the dimensions of the rectangular hole provided in an embodiment of this application;

[0031] Figure 7 The resonance curve of the filter provided in the embodiments of this application;

[0032] Figure 8 The impedance characteristic curve of the filter provided in the embodiment of this application is shown.

[0033] Figure label:

[0034] 1. Substrate; 2. Signal input terminal; 3. Signal output terminal; 4. Microstrip line; 41. Z-shaped slot; 42. Slot opening; 5. Tap line; 6. Open circuit stub line; 61. Horizontal line; 62. Vertical line; 7. Grounding metal surface; 8. Rectangular hole. Detailed Implementation

[0035] To facilitate understanding of this application, a more complete description will be provided below with reference to the accompanying drawings, which illustrate embodiments of the present application. However, the present application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that the disclosure of this application will be thorough and complete.

[0036] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

[0037] It is understood that the terms "first," "second," etc., used herein may be used to describe various elements, but these elements are not limited by these terms. These terms are only used to distinguish one element from another. For example, without departing from the scope of this application, a first resistor may be referred to as a second resistor, and similarly, a second resistor may be referred to as a first resistor. Both the first resistor and the second resistor are resistors, but they are not the same resistor.

[0038] It is understood that the term "connection" in the following embodiments should be understood as "electrical connection," "communication connection," etc., if the connected circuits, modules, units, etc., have electrical signal or data transmission with each other.

[0039] It is understandable that "at least one" refers to one or more, and "multiple" refers to two or more. "At least a part of an element" refers to part or all of an element.

[0040] When used herein, the singular forms of “a,” “an,” and “ / the” may also include the plural forms unless the context clearly indicates otherwise. It should also be understood that the terms “comprising / including” or “having,” etc., specify the presence of the stated features, wholes, steps, operations, components, parts, or combinations thereof, but do not preclude the possibility of the presence or addition of one or more other features, wholes, steps, operations, components, parts, or combinations thereof. Meanwhile, the term “and / or” as used in this specification includes any and all combinations of the associated listed items.

[0041] In one embodiment, to improve the out-of-band rejection of the filter, such as Figure 1As shown, a filter is provided, comprising a substrate 1 and a first filter structure disposed above the substrate 1. The first filter structure includes a signal input terminal 2 disposed at one end of the substrate 1 and a signal output terminal 3 disposed at the other end of the substrate 1; a microstrip line 4 is provided between the signal input terminal 2 and the signal output terminal 3, and a gap is provided between the microstrip line 4 and both the signal input terminal 2 and the signal output terminal 3. A Z-shaped gap 41 penetrating the microstrip line 4 is etched on the microstrip line 4, thereby dividing the microstrip line 4 into two stepped impedance lines.

[0042] Optionally, in this embodiment, substrate 1 is an insulating board. All first filter structures are metallic conductors, preferably copper.

[0043] Optionally, signal input terminal 2 is used to receive communication signals, and signal output terminal 3 is used to output processed communication signals.

[0044] Optionally, in this embodiment, the length of the signal input terminal 2 and the signal output terminal 3 ranges from 3mm to 5mm, and the width ranges from 1mm to 1.4mm. Preferably, as... Figure 2 As shown, the length of signal input terminal 2 and signal output terminal 3 is L0 = 5mm, and the width is W0 = 1.2mm.

[0045] Optionally, in this embodiment, the width of the gap between the microstrip line 4 and the signal input terminal 2 and the signal output terminal 3 ranges from 0.1mm to 0.3mm. Preferably, as... Figure 2 As shown, the width of the gap between the microstrip line 4 and the signal input terminal 2 and the signal output terminal 3 is L4 = 0.2 mm.

[0046] This embodiment provides a filter comprising a substrate 1 and a first filter structure disposed on the substrate 1. The first filter structure includes a signal input terminal 2 disposed at one end of the substrate 1 and a signal output terminal 3 disposed at the other end of the substrate 1; a microstrip line 4 is provided between the signal input terminal 2 and the signal output terminal 3, and a gap is provided between the microstrip line 4 and both the signal input terminal 2 and the signal output terminal 3. A Z-shaped gap 41 is etched through the microstrip line 4, dividing the microstrip line 4 into two stepped impedance lines. In this application, by etching a Z-shaped gap 41 on the microstrip line 4, the microstrip line 4 is divided into two mutually coupled stepped impedance lines, coupling out the transmission zero of the high-frequency stopband, improving the operating frequency band, and significantly optimizing the stopband suppression characteristics.

[0047] In one embodiment, in order to enable the filter of this application to have ultra-wideband characteristics, such as Figure 3 As shown, both signal input terminal 2 and signal output terminal 3 have taps 5 near one end of the microstrip line 4. There is a strip-shaped gap between the taps 5 and the microstrip line 4.

[0048] Optionally, in this embodiment, the length of the tap 5 is in the range of 2mm-3mm. Preferably, as shown below... Figure 2 The length of tap line 5 is L3 = 2.5mm.

[0049] Based on the above embodiments, such as Figure 1 , Figure 3 As shown, the microstrip line 4 is positioned on the central axis between the signal input terminal 2 and the signal output terminal 3, i.e., on the center line. The taps 5 connected to the signal input terminal 2 and the signal output terminal 3 are both off-axis; the tap 5 connected to the signal input terminal 2 is positioned on one side of the microstrip line 4; the tap 5 connected to the signal output terminal 3 is positioned on the other side of the microstrip line 4.

[0050] Based on the above embodiments, such as Figure 1 , Figure 3 As shown, the microstrip line 4 has slot openings 42 on both sides corresponding to the Z-shaped slot 41; the slot opening 42 near the signal input terminal 2 is located on the side of the microstrip line 4 away from the tap line 5 connected to the signal input terminal 2; the slot opening 42 near the signal output terminal 3 is located on the side of the microstrip line 4 away from the tap line 5 connected to the signal output terminal 3. Optionally, in this embodiment, the width of the slot opening 42 of the Z-shaped slot 41 ranges from 0.1mm to 0.7mm; the distance between the slot opening 42 and the end of the microstrip line 4 ranges from 0.5mm to 1.5mm. Preferably, as... Figure 2 As shown, the width of the slot opening 42 is L5 = 0.4 mm. The distance between the slot opening 42 and the end of the microstrip line 4 is L2 = 1 mm.

[0051] In this embodiment, both the signal input terminal 2 and the signal output terminal 3 have taps 5 near the microstrip line 4. A strip-shaped gap exists between the taps 5 and the microstrip line 4. Furthermore, the microstrip line 4 is positioned on the central axis between the signal input terminal 2 and the signal output terminal 3; both the taps 5 connected to the signal input terminal 2 and the signal output terminal 3 are offset from the central axis; the tap 5 connected to the signal input terminal 2 is located on one side of the microstrip line 4; and the tap 5 connected to the signal output terminal 3 is located on the other side of the microstrip line 4. Based on this embodiment, the three-wire coupling structure formed by the taps 5 of the signal input terminal 2, the microstrip line 4, and the taps 5 of the signal output terminal 3 gives the filter ultra-wideband characteristics and a wider application frequency range.

[0052] In one embodiment, to increase the low-frequency band of the filter, the operating frequency band of the filter is further increased, such as... Figure 4As shown, both the signal input terminal 2 and the signal output terminal 3 of the filter are connected to an open-circuit stub line 6. The open-circuit stub line 6 is an L-shaped line, consisting of a vertical line 62 and a horizontal line 61. The vertical line 62 is perpendicularly connected to the corresponding signal input terminal 2 or signal output terminal 3; the horizontal line 61 is parallel to the microstrip line 4.

[0053] Optionally, the width of the vertical line 62 of the L-shaped line ranges from 0.3mm to 1mm. The length of the horizontal line 61 ranges from 3mm to 5mm. Preferably, as... Figure 2 As shown, the width of vertical line 62 is W1 = 0.6 mm. The length of horizontal line 61 is L1 = 4 mm.

[0054] Based on the above embodiment, the horizontal line 61 of the open stub line 6 on the signal input terminal 2 side is located on the side of the microstrip line 4 away from the tap line 5 connected to the signal input terminal 2. The horizontal line 61 of the open stub line 6 on the signal output terminal 3 side is located on the side of the microstrip line 4 away from the tap line 5 connected to the signal output terminal. This results in both ends of the microstrip line 4 having an open stub line 6 on one side and a tap line 5 on the other side.

[0055] Optionally, in some embodiments, the first filter structure is centrally symmetrical about the center point of the substrate 1.

[0056] In this embodiment, both the signal input terminal 2 and the signal output terminal 3 are connected to open stub lines 6. The open stub line 6 is an L-shaped line, including a vertical line 62 and a horizontal line 61. The vertical line 62 is perpendicularly connected to the corresponding signal input terminal 2 or signal output terminal 3; the horizontal line 61 is parallel to the microstrip line 4. Furthermore, the horizontal line 61 of the open stub line 6 on the signal input terminal 2 side is positioned on the side of the microstrip line 4 away from the tap line 5 connected to the signal input terminal 2; the horizontal line 61 of the open stub line 6 on the signal output terminal 3 side is positioned on the side of the microstrip line 4 away from the tap line 5 connected to the signal output terminal. Based on this embodiment, the design of the open stub lines 6 at both ends introduces a transmission zero in the low-frequency stopband of the filter, thereby optimizing the low-frequency sideband roll-off coefficient and stopband suppression characteristics of the filter. Furthermore, to reduce the coupling effect between the open stub line 6 and the tap line 5 at the same end, the open stub line 6 is positioned away from the tap line 5.

[0057] In one embodiment, to optimize the return loss within the passband, such as Figure 5 As shown, the filter also includes a second filter structure disposed below the substrate 1. The second filter structure is a ground metal surface 7. That is, the filter comprises a three-layer structure: the top layer is the first filter structure, the middle layer is the substrate 1, which is essentially an insulating layer, and the bottom layer is the second filter structure, i.e., the ground metal surface 7. Two rectangular holes 8 are etched on the ground metal surface 7, parallel to the microstrip line 4, and positioned below the microstrip line 4. Figure 6As shown, the two rectangular holes 8 are centrally symmetrical about the center point of the substrate 1. Optionally, as... Figure 6 As shown, the horizontal length of rectangular hole 8 is L8 = 0.6 mm. The vertical width of rectangular hole 8 is W3 = 0.7 mm. The distance between the two rectangular holes 8 is S = 2.2 mm.

[0058] In this embodiment, the filter further includes a second filter structure disposed below the substrate 1. The second filter structure is a ground metal surface 7; two rectangular holes 8 are etched on the ground metal surface 7; the two rectangular holes 8 are parallel to the microstrip line 4 and are disposed below the microstrip line 4. The two rectangular holes 8 are centrally symmetrical about the center point of the substrate 1. In this embodiment, a defect ground structure (i.e., two rectangular holes 8) is etched at the position of the ground metal surface 7 perpendicular to the three-wire coupling to enhance coupling and optimize the return loss characteristics in the passband.

[0059] In one embodiment, a filter is provided, such as Figure 4 , Figure 5 As shown, the details are as follows:

[0060] The filter includes a substrate 1 and a first filter structure disposed on the substrate 1. The first filter structure includes a signal input terminal 2 disposed at one end of the substrate 1 and a signal output terminal 3 disposed at the other end of the substrate 1; a microstrip line 4 is provided between the signal input terminal 2 and the signal output terminal 3, and a gap is provided between the microstrip line 4 and both the signal input terminal 2 and the signal output terminal 3. A Z-shaped gap 41 penetrating the microstrip line 4 is etched on the microstrip line 4, so that the microstrip line 4 is divided into two stepped impedance lines. Further, a tap line 5 is provided at the end of the signal input terminal 2 and the signal output terminal 3 adjacent to the microstrip line 4. A strip-shaped gap is provided between the tap line 5 and the microstrip line 4. Further, the microstrip line 4 is disposed on the central axis between the signal input terminal 2 and the signal output terminal 3. The tap line 5 connected to the signal input terminal 2 and the tap line 5 connected to the signal output terminal 3 are both off-axis; the tap line 5 connected to the signal input terminal 2 is disposed on one side of the microstrip line 4; the tap line 5 connected to the signal output terminal 3 is disposed on the other side of the microstrip line 4. Furthermore, the microstrip line 4 has slot openings 42 on both sides corresponding to the Z-shaped slots 41; the slot opening 42 near the signal input terminal 2 is located on the side of the microstrip line 4 away from the tap line 5 connected to the signal input terminal 2; the slot opening 42 near the signal output terminal 3 is located on the side of the microstrip line 4 away from the tap line 5 connected to the signal output terminal 3. Furthermore, both the signal input terminal 2 and the signal output terminal 3 are connected to open stub lines 6. The open stub line 6 is an L-shaped line, including a vertical line 62 and a horizontal line 61. The vertical line 62 is perpendicularly connected to the corresponding signal input terminal 2 or signal output terminal 3; the horizontal line 61 is parallel to the microstrip line 4. Furthermore, the horizontal line 61 of the open stub line 6 on the signal input terminal 2 side is located on the side of the microstrip line 4 away from the tap line 5 connected to the signal input terminal 2; the horizontal line 61 of the open stub line 6 on the signal output terminal 3 side is located on the side of the microstrip line 4 away from the tap line 5 connected to the signal output terminal. Furthermore, it also includes a second filter structure disposed below the substrate 1;

[0061] The second filter structure is a grounded metal surface 7; two rectangular holes 8 are etched on the grounded metal surface 7; the two rectangular holes 8 are parallel to the microstrip line 4 and are located below the microstrip line 4. The two rectangular holes 8 are centrally symmetrical about the center point of the substrate 1.

[0062] The filter provided in this embodiment achieves ultra-wideband characteristics by coupling the input and output taps 5 to the central microstrip line 4. After etching slots on the central microstrip line 4, it is transformed into two symmetrical stepped impedance lines, resulting in optimized double-sided stopbands. Etching a defective ground structure on the ground plane optimizes the return loss in the passband, and loading open-circuit stubs 6 at the input and output terminals introduces low-frequency transmission zeros to optimize sideband roll-off. The filter has an insertion loss of -0.25dB at its center frequency of 17.07GHz, a passband reflection of less than -21.47dB, a -10dB impedance relative bandwidth of 61.8% (11.66~22.21GHz), an absolute bandwidth of 10.55GHz, a low-frequency stopband rejection of -24dB (1~11.05GHz), and a high-frequency stopband rejection of -22dB (22.51~30GHz). It employs a planar microstrip design structure and features a compact structure, wide bandwidth, low insertion loss, and low return loss. This invention can be applied to fields such as ultra-wideband positioning systems, ultra-wideband communication systems, and satellite communications.

[0063] The technical effects of the filter in this embodiment are explained below with reference to its resonance curve. Figure 7 As shown, the filter has an insertion loss of 0.25 dB at its center frequency of 17.07 GHz, a passband reflection of less than -21.47 dB, a -10 dB impedance relative bandwidth of 61.8% (11.66–22.21 GHz), an absolute bandwidth of 10.55 GHz, a low-frequency stopband rejection of 24 dB (1–11.05 GHz), and a high-frequency stopband rejection of 22 dB (22.51–30 GHz). It has four poles in the passband and three transmission zeros out of the passband. A transmission zero at 24 GHz is introduced through the coupling of two stepped impedance microstrips, significantly improving the high-frequency edge roll-off factor. Simultaneously, the high-frequency stopband is suppressed to below 25 dB up to 30 GHz, achieving optimization of the high-frequency stopband harmonic suppression characteristics.

[0064] The technical effects of the filter in this embodiment are explained below with reference to its impedance characteristic curve. Figure 8 As shown, the normalized input impedance of the filter at the center frequency of 17.07 GHz is 0.9042 - i * 0.0604; the normalized input impedance at the low-frequency end of 11.66 GHz is 0.5488 + i * 0.2041; and the normalized input impedance at the high-frequency end of 22.21 GHz is 0.5261 + i * 0.0557. Within this wide bandwidth, the filter impedance is well matched.

[0065] In one embodiment, a communication device is provided, wherein the communication device includes the filter provided in any of the above embodiments.

[0066] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0067] The above embodiments merely illustrate several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A filter, characterized in that, Includes a substrate and a first filter structure disposed above the substrate; The first filter structure includes a signal input terminal disposed at one end of the substrate and a signal output terminal disposed at the other end of the substrate; a microstrip line is provided between the signal input terminal and the signal output terminal, and a gap is provided between the microstrip line and both the signal input terminal and the signal output terminal; The microstrip line is etched with a Z-shaped slot that runs through the microstrip line, thereby dividing the microstrip line into two stepped impedance lines.

2. The filter according to claim 1, characterized in that, Both the signal input terminal and the signal output terminal are provided with taps at the end near the microstrip line; There is a strip-shaped gap between the tap line and the microstrip line.

3. The filter according to claim 2, characterized in that, The microstrip line is disposed on the central axis between the signal input terminal and the signal output terminal; Both the tap line connected to the signal input terminal and the tap line connected to the signal output terminal are offset from the central axis; the tap line connected to the signal input terminal is located on one side of the microstrip line; and the tap line connected to the signal output terminal is located on the other side of the microstrip line.

4. The filter according to claim 3, characterized in that, The microstrip line has slot openings on both sides corresponding to the Z-shaped slot; the slot opening near the signal input terminal is located on the side of the microstrip line away from the tap line connected to the signal input terminal. The slot opening near the signal output terminal is located on the side of the microstrip line away from the tap line connected to the signal output terminal.

5. The filter according to claim 4, characterized in that, The width of the slot opening ranges from 0.1mm to 0.7mm; the distance between the slot opening and the end of the microstrip line ranges from 0.5mm to 1.5mm; the width of the gap between the microstrip line and the signal input terminal and the signal output terminal ranges from 0.1mm to 0.3mm; and the length of the tap line ranges from 2mm to 3mm.

6. The filter according to claim 3, characterized in that, Both the signal input terminal and the signal output terminal are connected to an open-circuit stub wire; The open branch line is an L-shaped line, including vertical and horizontal lines; The vertical line is perpendicularly connected to the corresponding signal input or signal output terminal; the horizontal line is parallel to the microstrip line.

7. The filter according to claim 6, characterized in that, The horizontal line of the open stub line on the signal input side is located on the side of the microstrip line away from the tap line connected to the signal input side; the horizontal line of the open stub line on the signal output side is located on the side of the microstrip line away from the tap line connected to the signal output side.

8. The filter according to claim 1, characterized in that, It also includes a second filter structure disposed below the substrate; The second filter structure is a grounded metal surface; two rectangular holes are etched on the grounded metal surface; the two rectangular holes are parallel to the microstrip line and are located below the microstrip line; The two rectangular holes are centrally symmetrical about the center point of the substrate.

9. The filter according to any one of claims 1-7, characterized in that, The first filter structure is centrally symmetrical about the center point of the substrate.

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

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