Miniaturized narrowband band-pass filtering transmission line based on artificial surface plasmon

Abstract

The invention provides a miniaturized narrow-band band-pass filtering transmission line based on artificial surface plasmon, which comprises an SSPP band-pass filtering transmission line, a transition structure and a 50-ohm microstrip line, the 50-ohm microstrip line is arranged on the SSPP band-pass filtering transmission line and is connected with the SSPP band-pass filtering transmission line through the transition structure, the SSPP band-pass filtering transmission line is composed of a plurality of SSPP band-pass filtering units, and the SSPP band-pass filtering units are arranged on the SSPP band-pass filtering transmission line. The SSPP band-pass filtering unit comprises a floor layer, a dielectric layer and a transmission layer which are sequentially stacked from bottom to top, the transmission layer comprises a center conduction band, a short-circuit branch knot and a plurality of open-circuit branch knots, the short-circuit branch knot and the open-circuit branch knots are arranged on the center conduction band, the short-circuit branch knot is provided with a metal through hole penetrating through the dielectric layer, and the metal through hole is communicated with the dielectric layer. The metal through holes are directly connected with the floor layer to form an inductance effect to filter low-frequency signals, the short-circuit branches and the floor layer form a capacitance effect to filter high-frequency signals, and meanwhile, the bent open-circuit branches are arranged, so that the regulation and control capability on frequency bands is enhanced, and the transverse size of the transmission layer is smaller.

Description

Technical Field

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

[0002] Narrowband filters are an important frequency-selective device that allows specific frequency components in a signal to pass through while greatly attenuating other frequency components. Narrowband filters are designed to help the system extract useful information within the target frequency range from complex input signals to meet the needs of signal processing precision and accuracy in different applications. Whether in communication systems, radar systems, biomedical instruments or audio equipment, narrowband filters play a key role.

[0003] In recent years, with the rapid development of communication technology, the application scenarios of narrowband filters have become more and more complex, and higher requirements have been placed on the performance, size and flexibility of narrowband filters. Extremely narrow bandwidth can filter out clutter more efficiently, 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, the lateral dimensions of traditional narrowband filters are generally large, and miniaturized filters are difficult to achieve narrower 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, and when faced with different functional requirements, they often need to be redesigned and the design complexity is high.

[0004] Artificial surface plasmon metamaterial is a man-made periodic structure that can achieve unusual material parameters such as negative dielectric constant and negative magnetic permeability in microwave or millimeter wave frequency bands. It can simulate the plasma characteristics of metals in the optical frequency band and use its interaction with the surrounding electromagnetic space to support artificial surface plasmon mode transmission in the low frequency band. Artificial surface plasmon has low-pass filtering characteristics and is a natural low-pass filter. Applying it to the design of filters with complex functions can effectively reduce the complexity of the design. The dispersion characteristics of artificial surface plasmon can be adjusted by changing the structural parameters. The structure is simple and the regulation is flexible.

[0005] The present invention proposes a frequency-adjustable miniaturized narrow-band bandpass filter transmission line based on artificial surface plasmons, which utilizes the specially designed artificial surface plasmon bandpass characteristics 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 passbands are 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 scheme: a miniaturized narrow-band bandpass filter transmission line based on artificial surface plasmon, characterized in that it comprises: 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, and the SSPP bandpass filter unit includes a floor layer, a dielectric layer and a transmission layer stacked in sequence from bottom to top;

[0010] The transmission layer includes: a central conductive strip, a short-circuit branch and a plurality of open-circuit branches, wherein the short-circuit branch and the plurality of open-circuit branches are arranged on the central conductive strip, and 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-circuit branches are divided into two groups with the same number of open-circuit branches, and are axially symmetrically arranged on both sides of the short-circuit branch along the central axis of the short-circuit branch, and the open-circuit branches in each group are axially symmetrically arranged with respect to each other.

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

[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 colinear with adjacent sides of the short-circuit branch and the plurality of open-circuit branches.

[0015] Further, 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 chamfering is performed at the connecting bend.

[0017] Furthermore, the floor layer and the transmission layer are made of metal materials, and the medium 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 effect: 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 as wide as a 50Ω microstrip line while being able to achieve a passbandwidth 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 passbandwidth, and that extremely narrow passbandwidth 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 It is a schematic diagram of the structure of the transmission layer of the present invention.

[0023] Figure 4 It is a structural 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 It is a dispersion curve simulation diagram of the SSPP bandpass filter unit of the present invention.

[0026] Figure 7 It 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 in conjunction with the accompanying drawings.

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

[0030] The 50Ω microstrip line 3 is arranged 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, and 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 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 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 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.

[0034] In this embodiment, the floor layer 11 and the transmission layer 13 are made of metal materials, copper is used in this embodiment, and the dielectric layer 12 is made of micro-glass fiber reinforced PTFE composite material, Rogers RT5880, its dielectric constant is 2.2, loss tangent tanδ=0.0009, when other types of micro-glass fiber reinforced PTFE composite materials are used, its structural parameters need to be changed accordingly, the SSPP bandpass filter transmission line 1 is composed of 6 SSPP bandpass filter units, the 6 SSPP bandpass filter units are periodically arranged and connected in sequence, there are 4 open-circuit branches 133, the transmission layer 13 is axially symmetrically distributed about the central axis of the short-circuit branch length h1 direction (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 to 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, and the two open-circuit branches 133 in the same group are also It is axisymmetric, the direction of the length h2 of the first rectangular segment of the open branch 133 is the positive direction of the Y axis, the direction of the length h3 of the second rectangular segment is the negative direction of the X axis, and the direction of the length h4 of the third rectangular segment is the negative direction of the Y axis. The widths of the three rectangular segment structures of the open branch 133 are all W2, but the extension directions of the widths of the three rectangular segment structures are different. The direction of the width of the first rectangular segment extends from the central axis to the positive and negative directions of the X axis, the direction of the width of the second rectangular segment is the negative direction of the Y axis, and the direction of the width of the third rectangular segment is the positive direction of the X axis. The length of the central conduction band 131 is the period p of the SSPP bandpass filter unit. The length direction of the central conduction band 131 is perpendicular to the length h1 direction of the short-circuited branch 132. The central conduction band 133 is collinear with the adjacent sides of the short-circuited branch 132 and the open branch 133. 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, the transition structure 2 adopts a bent quarter-wavelength microstrip line, which is divided into three sections, and the bends are chamfered, wherein 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 guide strip in the horizontal direction (X-axis direction), and the third connecting section is aligned with the 50Ω microstrip line in the horizontal direction (X-axis direction). The 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 the structural parameters. The length h1 of the short-circuit branch can independently control the lower cutoff frequency of the passband, and the length h2 of the open-circuit branch can shift the spectrum, but the passband width will change. Therefore, by adjusting the lengths h1 and h2 of the short-circuit branch and the open-circuit branch, the passband can be flexibly controlled.

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

[0043] like Figure 7 As shown, the SSPP bandpass filter transmission line is simulated using the time domain solver of CST software, and 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 bandpass filter transmission line based on artificial surface plasmon provided by the present invention achieves an extremely narrow relative bandwidth of 10.812% at a frequency of 8.6828 GHz. The lateral dimension of its transmission layer is as wide as a 50Ω microstrip line, and the frequency band can be controlled by changing the lengths h1 and h2 of the short-circuit branches and the 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 as wide as a 50Ω microstrip line while being able to achieve a passbandwidth 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 narrower passbandwidth, and that extremely narrow passbandwidth 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 principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A miniaturized narrow-band 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) comprises: 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).

2. According to claim 1, the miniaturized narrow-band bandpass filter transmission line based on artificial surface plasmon is characterized in that: The plurality of open-circuit branches (133) are divided into two groups with the same number of open-circuit 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-circuit branches (133) in each group are arranged axially symmetrically with each other.

3. 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.

4. 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.

5. 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 a plurality of open-circuit branches (133).

6. 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 chamfering is performed at the connecting bend.

7. 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 medium layer (12) is made of micro-glass fiber reinforced PTFE composite material.

8. 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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