Miniaturized narrowband bandpass filter transmission line based on artificial surface plasmons

Abstract

The present invention provides a miniaturized narrowband bandpass filter transmission line based on artificial surface plasmons, comprising: an SSPP bandpass filter transmission line, a transition structure, and a 50Ω microstrip line. The 50Ω microstrip line is arranged on the SSPP bandpass filter transmission line and connected to the 50Ω microstrip line through the transition structure. The SSPP bandpass filter transmission line is composed of multiple SSPP bandpass filter units. The SSPP bandpass filter units include a floor layer, a dielectric layer, and a transmission layer stacked in sequence from bottom to top. The transmission layer includes: a central conductive strip, a short-circuit branch, and multiple open-circuit branches. The short-circuit branch and the multiple open-circuit branches are arranged on the central conductive strip. The short-circuit branch is provided with a metal through-hole that penetrates the dielectric layer. The short-circuit branch is directly connected to the floor layer through the metal through-hole to form an inductive effect to filter out low-frequency signals, and the short-circuit branch and the floor layer form a capacitive effect to filter out high-frequency signals. At the same time, curved open-circuit branches are provided to enhance the ability to regulate the frequency band and make the lateral size of the transmission layer more miniaturized.

Description

Technical Field

[0001] The present invention belongs to the technical field of microwave and millimeter wave device design, and in particular relates to a miniaturized narrowband bandpass filter transmission line based on artificial surface plasmons. Background Art

[0002] Narrowband filters are important frequency-selective components that pass specific frequency components in a signal while significantly attenuating other frequencies. Narrowband filters are designed to help systems extract useful information within a target frequency range from complex input signals, meeting the signal processing precision and accuracy requirements of various applications. Narrowband filters play a key role in communications systems, radar systems, biomedical instruments, and audio equipment.

[0003] In recent years, with the rapid development of communication technology, the application scenarios of narrowband filters have become increasingly complex, placing higher demands on the performance, size, and flexibility of narrowband filters. Extremely narrow bandwidth can more efficiently filter out clutter, improve signal quality and energy utilization; smaller size is conducive to the integration and miniaturization of communication systems; flexible bandwidth regulation can cope with complex and changing application scenarios. At present, traditional narrowband filters generally have large lateral dimensions, while miniaturized filters have difficulty achieving narrow passbands. Extremely narrow passbands are difficult to be compatible with extremely small lateral dimensions; traditional filter design methods have poor flexibility in frequency band regulation. When faced with different functional requirements, they often need to be redesigned and the design complexity is high.

[0004] Artificial surface plasmon metamaterials are artificially designed periodic structures capable of achieving unusual material parameters such as negative dielectric constant and negative magnetic permeability at microwave or millimeter wave frequencies. They can mimic the plasmonic properties of metals at optical frequencies and, by leveraging their interaction with the surrounding electromagnetic space, support artificial surface plasmon mode transmission at low frequencies. Artificial surface plasmons exhibit low-pass filtering properties, acting as natural low-pass filters. Applying them to complex filter designs can effectively reduce design complexity. The dispersion properties of artificial surface plasmons can be adjusted by varying structural parameters, resulting in a simple structure and flexible control.

[0005] The present invention proposes a miniaturized narrowband bandpass filter transmission line with adjustable frequency based on artificial surface plasmons. It utilizes the specially designed bandpass characteristics of artificial surface plasmons to achieve an extremely narrow passband while maintaining a small lateral size and improving the flexibility of frequency band regulation. Summary of the Invention

[0006] The purpose of the present invention is to solve the problem that existing miniaturized filters are difficult to achieve a narrow passband, and that extremely narrow passband is difficult to be compatible with extremely small lateral dimensions, and to provide a miniaturized narrow-band passband filter transmission line based on artificial surface plasmons;

[0007] In order to achieve the above-mentioned object, the present invention adopts the following technical solution: a miniaturized narrowband bandpass filter transmission line based on artificial surface plasmon, characterized by comprising: an SSPP bandpass filter transmission line, a transition structure and a 50Ω microstrip line;

[0008] The 50Ω microstrip line is arranged on both sides of the SSPP bandpass filter transmission line and is connected to the 50Ω microstrip line through a transition structure;

[0009] The SSPP bandpass filter transmission line is composed of a plurality of SSPP bandpass filter units, each of which includes a floor layer, a dielectric layer, and a transmission layer stacked sequentially from bottom to top;

[0010] The transmission layer includes: a central conductive strip, a short-circuit branch and a plurality of open-circuit branches. The short-circuit branch and the plurality of open-circuit branches are arranged on the central conductive strip. The short-circuit branch is provided with a metal through-hole penetrating the dielectric layer and is connected to the floor layer through the metal through-hole penetrating the dielectric layer.

[0011] Furthermore, the plurality of open branches are divided into two groups with the same number of open branches, and are arranged axially symmetrically on both sides of the short-circuit branch along the central axis of the short-circuit branch, and the open branches in each group are arranged axially symmetrically with each other.

[0012] Furthermore, the center of the metal through hole is located on the central axis of the short-circuit branch in the length direction.

[0013] Furthermore, the open branch includes a first rectangular segment, a second rectangular segment and a third rectangular segment, the first rectangular segment and the third rectangular segment are vertically arranged, the second rectangular segment is horizontally arranged, one end of the first rectangular segment is connected to the center guide belt, and the other end of the first rectangular segment is connected to the third rectangular segment through the second rectangular segment.

[0014] Furthermore, the length direction of the central conductive strip is perpendicular to the length direction of the short-circuit branch, and the central conductive strip is collinear with adjacent sides of the short-circuit branch and the plurality of open-circuit branches.

[0015] Furthermore, the transition structure includes a first connecting section, a second connecting section and a third connecting section;

[0016] The first connecting segment is parallel to the third connecting segment, and the first connecting segment and the third connecting segment are perpendicular to the second connecting segment. The first connecting segment is connected to the third connecting segment through the second connecting segment, and a chamfer is performed at the connecting bend.

[0017] Furthermore, the floor layer and the transmission layer are made of metal materials, and the dielectric layer is made of micro-glass fiber reinforced PTFE composite material.

[0018] Furthermore, the lateral dimension of the transmission layer is equal to the width of a 50Ω microstrip line.

[0019] Beneficial effects: The short-circuit branches of the present invention can be directly connected to the floor layer through metal through-holes to form an inductive effect to filter out low-frequency signals, and the short-circuit branches and the floor layer can form a capacitive effect to filter out high-frequency signals. At the same time, curved open-circuit branches are provided to enhance the ability to regulate the frequency band and make the lateral size of the transmission layer more miniaturized, thereby ensuring that the lateral size of the transmission layer is the same width as the 50Ω microstrip line while being able to achieve a passband of less than 12%, and the passband can be regulated by changing the structural parameters of the short-circuit branches and the open-circuit branches to achieve flexible regulation of the passband, thereby solving the problem that existing miniaturized filters are difficult to achieve a narrow passband, and that extremely narrow passband is difficult to be compatible with extremely small lateral sizes. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a front view of the structure of the present invention.

[0021] Figure 2 It is a side view of the structure of the present invention.

[0022] Figure 3 Schematic diagram of the structure of the transmission layer of the present invention.

[0023] Figure 4 Schematic diagram of the transition structure of the present invention.

[0024] Figure 5 This is the effect of the length h1 of the short-circuit branch and the length h2 of the open-circuit branch on the unit dispersion characteristics of the present invention.

[0025] Figure 6 This is a simulation diagram of the dispersion curve of the SSPP bandpass filter unit of the present invention.

[0026] Figure 7 This is the S parameter simulation diagram of the present invention.

[0027] In the figure: 1. SSPP bandpass filter transmission line, 11. floor layer, 12. dielectric layer, 13. transmission layer, 131. center guide strip, 132. short-circuit branch, 133. open-circuit branch, 2. transition structure, 3. 50Ω microstrip line. DETAILED DESCRIPTION

[0028] The present invention will be further explained below with reference to the accompanying drawings.

[0029] like Figure 1-3As shown, the present invention provides a miniaturized narrowband bandpass filter transmission line based on artificial surface plasmon, including: an SSPP bandpass filter transmission line 1, a transition structure 2 and a 50Ω microstrip line 3.

[0030] The 50Ω microstrip line 3 is provided on the SSPP bandpass filter transmission line 1 and is connected to the 50Ω microstrip line 3 through a transition structure 2 .

[0031] The SSPP bandpass filter transmission line 1 is composed of a plurality of SSPP bandpass filter units. The SSPP bandpass filter units include a floor layer 11 , a dielectric layer 12 and a transmission layer 13 stacked in sequence from bottom to top.

[0032] The transmission layer 13 includes: a central conductive strip 131, a short-circuit branch 132 and multiple open-circuit branches 133. The short-circuit branch 132 and multiple open-circuit branches 133 are arranged on the central conductive strip 131. The short-circuit branch 132 is provided with a metal through-hole penetrating the dielectric layer 12 and is connected to the floor layer 11 through the metal through-hole penetrating the dielectric layer 12.

[0033] The open branch 133 includes a first rectangular segment, a second rectangular segment and a third rectangular segment. The first rectangular segment and the third rectangular segment are vertically arranged, and the second rectangular segment is horizontally arranged. One end of the first rectangular segment is connected to the center guide belt 131, and the other end of the first rectangular segment is connected to the third rectangular segment through the second rectangular segment.

[0034] In this embodiment, the floor layer 11 and the transmission layer 13 are made of metal materials, in this embodiment copper is used, and the dielectric layer 12 is made of micro-glass fiber reinforced PTFE composite material, in this embodiment Rogers RT5880 has a dielectric constant of 2.2 and a loss tangent of tanδ = 0.0009. When other types of micro-glass fiber reinforced PTFE composite materials are used, their structural parameters must be changed accordingly. The SSPP bandpass filter transmission line 1 is composed of 6 SSPP bandpass filter units, which are periodically arranged and connected in sequence. There are 4 open-circuit branches 133. The transmission layer 13 is axially symmetrical about the central axis in the direction of the short-circuit branch length h1 (i.e., the positive direction of the Y axis). The center of the metal through hole of the short-circuit branch 132 is also located on the central axis. The direction of the width w1 of the short-circuit branch 132 extends from its central axis in the positive and negative directions of the X axis. The four curved open-circuit branches 133 are exactly the same in size. They are divided into two groups by the central axis of the short-circuit branch 132 in the Y-axis direction. The two open branches 133 in the same group are also The open branch 133 is axisymmetric. The length h2 of the first rectangular segment of the open branch 133 is in the positive direction of the Y axis, the length h3 of the second rectangular segment is in the negative direction of the X axis, and the length h4 of the third rectangular segment is in the negative direction of the Y axis. The width of the three rectangular segments of the open branch 133 is w2, but the widths of the three rectangular segments extend in different directions. The width of the first rectangular segment extends from the central axis in the positive and negative directions of the X axis, the width of the second rectangular segment is in the negative direction of the Y axis, and the width of the third rectangular segment is in the positive direction of the X axis. The length of the central conductive strip 131 is equal to the period p of the SSPP bandpass filter unit. The length direction of the central conductive strip 131 is perpendicular to the length direction h1 of the short-circuited branch 132. The adjacent sides of the central conductive strip 131, the short-circuited branch 132, and the open branch 133 are collinear. The parameter settings of the SSPP bandpass filter unit are shown in Table 1.

[0035] Table 1 SSPP narrowband bandpass filter unit parameter settings

[0036]

[0037] like Figure 4 As shown, the transition structure 2 includes a first connecting segment, a second connecting segment and a third connecting segment. The first connecting segment is parallel to the third connecting segment, and the first connecting segment and the third connecting segment are perpendicular to the second connecting segment. The first connecting segment is connected to the third connecting segment through the second connecting segment, and chamfering is performed at the connecting bend.

[0038] In this embodiment, transition structure 2 uses a bent quarter-wavelength microstrip line, which is divided into three sections with chamfers at the bends. The first connecting section is parallel to the third connecting section, and both are perpendicular to the second connecting section. The first connecting section is aligned with the center of the central guide strip in the horizontal direction (X-axis direction), and the third connecting section is aligned with the center of the 50Ω microstrip line in the horizontal direction (X-axis direction). Specific parameters of the transition structure are shown in Table 2.

[0039] Table 2 Transition structure parameter settings

[0040]

[0041] like Figure 5 As shown in the figure, the SSPP bandpass filter unit can adjust the passband by modifying its structural parameters. The length h1 of the short-circuit branch independently controls the lower cutoff frequency of the passband, while the length h2 of the open-circuit branch shifts the spectrum, but this also changes the passband width. Therefore, by adjusting the lengths h1 and h2 of the short-circuit and open-circuit branches, the passband can be flexibly adjusted.

[0042] like Figure 6 As shown in FIG, the eigenmode solver of CST software is used to simulate the SSPP bandpass filter unit structure in an eigenmode manner, which can quickly and accurately obtain the dispersion curve of the unit structure.

[0043] like Figure 7 As shown in the figure, the SSPP bandpass filter transmission line is simulated using the time domain solver of CST software. The S-parameter curve obtained has a passband range of 8.2134GHz to 9.1522GHz, a center frequency of 8.6828GHz, a -10dB bandwidth of 10.812%, and an IR of 1.482dB.

[0044] In the above simulation, the artificial surface plasmon-based bandpass filter transmission line provided by the present invention achieved an extremely narrow relative bandwidth of 10.812% at a frequency of 8.6828 GHz. The lateral dimensions of its transmission layer were as wide as a 50Ω microstrip line, and the frequency band could be controlled by varying the lengths h1 and h2 of the short-circuit and open-circuit branches.

[0045] The short-circuit branches of the present invention can be directly connected to the floor layer through metal through-holes to form an inductive effect to filter out low-frequency signals, and the short-circuit branches and the floor layer can form a capacitive effect to filter out high-frequency signals. At the same time, curved open-circuit branches are provided to enhance the ability to regulate the frequency band and make the lateral size of the transmission layer 13 more miniaturized, thereby ensuring that the lateral size of the transmission layer is the same width as the 50Ω microstrip line while being able to achieve a passband of less than 12%, and the passband can be regulated by changing the structural parameters of the short-circuit branches and the open-circuit branches, thereby achieving flexible regulation of the passband, thereby solving the problem that existing miniaturized filters are difficult to achieve a narrow passband, and that extremely narrow passband is difficult to be compatible with extremely small lateral sizes.

[0046] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A miniaturized narrowband bandpass filter transmission line based on artificial surface plasmon, characterized in that: include: SSPP bandpass filter transmission line (1), transition structure (2) and 50Ω microstrip line (3); The 50Ω microstrip line (3) is arranged on both sides of the SSPP bandpass filter transmission line (1) and is connected to the 50Ω microstrip line (3) via a transition structure (2); The SSPP bandpass filter transmission line (1) is composed of a plurality of SSPP bandpass filter units, wherein the SSPP bandpass filter units include a floor layer (11), a dielectric layer (12), and a transmission layer (13) stacked in sequence from bottom to top; The transmission layer (13) includes: a central conductive strip (131), a short-circuit branch (132), and a plurality of open-circuit branches (133); the short-circuit branch (132) and the plurality of open-circuit branches (133) are arranged on the central conductive strip (131); the short-circuit branch (132) is provided with a metal through-hole penetrating the dielectric layer (12), and is connected to the floor layer (11) via the metal through-hole penetrating the dielectric layer (12); The plurality of open branches (133) are divided into two groups with the same number of open branches, and are arranged axially symmetrically on both sides of the short-circuit branch (132) along the central axis of the short-circuit branch (132), and the open branches (133) in each group are arranged axially symmetrically with each other.

2. The miniaturized narrow-band bandpass filter transmission line based on artificial surface plasmon according to claim 1, characterized in that: The center of the metal through hole is located on the central axis of the short-circuit branch (132) in the length direction.

3. The miniaturized narrow-band bandpass filter transmission line based on artificial surface plasmon according to claim 1, characterized in that: The open branch (133) comprises a first rectangular segment, a second rectangular segment and a third rectangular segment, wherein the first rectangular segment and the third rectangular segment are arranged vertically, and the second rectangular segment is arranged horizontally, one end of the first rectangular segment is connected to the central guide belt (131), and the other end of the first rectangular segment is connected to the third rectangular segment through the second rectangular segment.

4. The miniaturized narrow-band bandpass filter transmission line based on artificial surface plasmon according to claim 1, characterized in that: The length direction of the central conductive strip (131) is perpendicular to the length direction of the short-circuit branch (132), and the central conductive strip (131) is collinear with adjacent sides of the short-circuit branch (132) and the plurality of open-circuit branches (133).

5. The miniaturized narrow-band bandpass filter transmission line based on artificial surface plasmon according to claim 1, characterized in that: The transition structure (2) comprises a first connecting section, a second connecting section and a third connecting section; The first connecting segment is parallel to the third connecting segment, and the first connecting segment and the third connecting segment are perpendicular to the second connecting segment. The first connecting segment is connected to the third connecting segment through the second connecting segment, and a chamfer is performed at the connecting bend.

6. The miniaturized narrow-band bandpass filter transmission line based on artificial surface plasmon according to claim 1, characterized in that: The floor layer (11) and the transmission layer (13) are made of metal materials, and the dielectric layer (12) is made of micro-glass fiber reinforced PTFE composite material.

7. The miniaturized narrow-band bandpass filter transmission line based on artificial surface plasmon according to claim 1, characterized in that: The lateral dimension of the transmission layer (13) is equal to the width of the 50Ω microstrip line (3).

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