CN111029691A - Surface plasmon band elimination filter with tunable center frequency - Google Patents
Surface plasmon band elimination filter with tunable center frequency Download PDFInfo
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- CN111029691A CN111029691A CN201911387091.8A CN201911387091A CN111029691A CN 111029691 A CN111029691 A CN 111029691A CN 201911387091 A CN201911387091 A CN 201911387091A CN 111029691 A CN111029691 A CN 111029691A
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01P—WAVEGUIDES; RESONATORS, LINES, OR OTHER DEVICES OF THE WAVEGUIDE TYPE
- H01P1/00—Auxiliary devices
- H01P1/20—Frequency-selective devices, e.g. filters
Abstract
The invention discloses a surface plasmon band elimination filter with tunable center frequency, which comprises a coplanar waveguide, an electromagnetic wave mode converter, an SPP transmission line and a high dielectric constant dielectric block. The invention adopts a BST medium block with high dielectric constant which is sensitive to temperature change and external electric field change to be embedded into the gap of the SPP transmission line for the first time, and flexibly realizes the purpose of tunable center frequency of the SPP band-stop filter; the SPP band elimination filter provided by the invention has the advantages of simple and compact structure, convenience in processing and manufacturing, novelty and excellent scientific application value in the field of radio frequency microwaves.
Description
Technical Field
The invention belongs to the technical field of radio frequency microwave, and particularly relates to a surface plasmon band elimination filter with tunable center frequency.
Background
Surface Plasmon Polaritons (SPP) refer to a surface wave (generally, TM mode propagation) that propagates along the interface between a metal and a medium, and has the excellent characteristics of slow wave, field confinement effect, and diffraction limit breakthrough. Since the electromagnetic wave can be restricted in the sub-wavelength range with high intensity, the electronic component can be miniaturized by using the SPP, SPP devices with different functions can be realized, and circuits and systems with high integration level can be constructed.
The filter plays an important role as a key component in a circuit system, and is mainly used for filtering interference signals, so that the frequency spectrum of a useful signal is purer, and therefore, more excellent communication quality is obtained. At present, there are few reports about SPP band-stop filters, and the implementation manner of the SPP band-stop filter that has been reported is to use a comb-shaped cell structure, and every two new cells include a specific gap therebetween, so as to introduce a series-connected coupling capacitor between two comb-shaped cells. Under certain working frequency, the surface impedance matching can be interfered by introduced coupling capacitance, so that the SPP wave has a trap characteristic in the transmission process, and in addition, the multi-stop-band filter can be realized by changing the number of the comb-shaped cells and the size of the gaps. Although the mode can obtain better stop band characteristics, the stop band working frequency is fixed, cannot be tuned, and has larger size, thereby greatly limiting the application range of the stop band stop circuit.
Disclosure of Invention
The invention aims to provide a surface plasmon band elimination filter with tunable center frequency, and solves the problems of narrow working frequency band and limited center frequency tuning of the conventional SPP band elimination filter.
The technical solution for realizing the purpose of the invention is as follows: a surface plasmon band elimination filter with tunable center frequency comprises a coplanar waveguide, an electromagnetic wave mode converter, an SPP transmission line and a high dielectric constant dielectric block;
the coplanar waveguide is composed of a central conductor strip and rectangular ground planes which are close to two sides of the central conductor strip;
the electromagnetic wave mode converter comprises an H-shaped metal unit with gradually increasing depth of a groove etched on a central conductor strip in sequence, and two arc-shaped ground planes etched in an exponential mode on the ground planes adjacent to two sides of the central conductor strip;
the SPP transmission line is composed of a series of H-shaped metal units with the same groove depth, a rectangular groove is etched in the middle of the SPP transmission line, the central conductor strip at the position is disconnected, direct electrical connection does not exist, a high-dielectric-constant dielectric block is embedded into the etched rectangular groove on the SPP transmission line and is in direct contact with metal on two sides of the SPP transmission line, and electrical connection exists.
Compared with the prior art, the invention has the following remarkable advantages: (1) the SPP band-stop filter provided by the invention is of a planar structure, is simple and novel in structure, can realize tunable working frequency of the center of a stop band in a wide working frequency range, and has good flexibility; compared with the traditional SPP band elimination filter with only fixed working frequency or narrow band, the application range of the filter is greatly expanded; (2) the SPP band elimination filter provided by the invention has a very compact integral structure, greatly reduces the circuit area, is low in manufacturing cost, provides a more compact low-cost solution for the integration of a multi-array wireless communication system, and has good advantages and scientific application value in a microwave millimeter wave wireless communication system.
Drawings
FIG. 1 is a schematic diagram of an SPP band-stop filter according to an embodiment of the present invention.
Fig. 2 is a schematic diagram of the position of a BST dielectric block in an SPP band reject filter in an embodiment of the present invention.
Fig. 3 is a diagram of simulation results of variation of the stopband center operating frequency of the SPP band-stop filter according to the dielectric constant of the BST dielectric block in accordance with an embodiment of the present invention.
Detailed Description
As shown in fig. 1, a surface plasmon band reject filter with tunable center frequency includes a coplanar waveguide, an electromagnetic wave mode converter, an SPP transmission line, and a high dielectric constant dielectric block;
the coplanar waveguide is composed of a central conductor strip and rectangular ground planes which are close to two sides of the central conductor strip; the distance between the central conductor strip and the rectangular ground plane is 1-2 mm;
the electromagnetic wave mode converter is characterized in that H-shaped metal units with gradually increasing groove depths are sequentially etched on a central conductor strip, and ground planes adjacent to two sides are etched into two arc-shaped ground planes in an exponential mode;
the SPP transmission line is composed of a series of H-shaped metal units with the same groove depth, a rectangular groove is etched in the middle of the SPP transmission line, a metal conductor strip at the position is disconnected, direct electrical connection does not exist, a high-dielectric-constant dielectric block is directly embedded into the etched rectangular groove on the SPP transmission line and is in direct contact with metal on two sides of the SPP transmission line, and electrical connection exists.
Further, the dielectric constant of the high dielectric constant dielectric block is larger than 100.
Further, the high dielectric constant dielectric block is a perovskite series dielectric block.
Preferably, the high dielectric constant dielectric block is a barium strontium titanate dielectric block, a barium titanate dielectric block or a calcium titanate dielectric block.
Further, the mathematic of the metal structure material is aluminum, copper, silver or gold, and the metal structure comprises the coplanar waveguide, the electromagnetic wave mode converter and the SPP transmission line.
The dielectric substrate base plate material is Rogers PCB, quartz plate or semiconductor material, and the semiconductor material is Si, SiGe, GaAs, GaN, InP and the like.
The surface plasmon band elimination filter is a two-port network, one end of the two-port network is used as an input end, and the other end of the two-port network is used as an output end. The high dielectric constant dielectric block is arranged at the central position of the surface plasmon band elimination filter, and the band elimination filter is of a vertically and horizontally symmetrical structure.
The electromagnetic wave mode converter etches H-shaped grooves on the central metal strip, and the depth of the H-shaped grooves is sequentially increased to be consistent with the depth of the grooves of the SPP transmission line; the grooves on the SPP transmission line are arranged periodically.
The GND planes adjacent to the two sides of the central metal belt are gradually changed into an arc-shaped GND plane according to the size of an index; the electromagnetic wave mode converter is used for realizing the transition of electromagnetic wave energy from the coplanar waveguide to the SPP transmission line for propagation, namely completing the conversion from TEM wave to TM wave.
The invention adopts a BST medium block with high dielectric constant which is sensitive to temperature change and external electric field change to be embedded into the gap of the SPP transmission line for the first time, and flexibly realizes the purpose of tunable center frequency of the SPP band-stop filter. The SPP band elimination filter provided by the invention has the advantages of simple and compact structure, convenience in processing and manufacturing, novelty and excellent scientific application value in the field of radio frequency microwaves.
The present invention is further illustrated by the following examples, which are to be construed as merely illustrative and not limitative of the remainder of the disclosure, and all changes and modifications that fall within the meaning and range of equivalency of the appended claims are intended to be embraced therein.
Examples
This embodiment provides an SPP band-stop filter with tunable center frequency, as shown in fig. 1, including a coplanar waveguide I, an electromagnetic wave mode converter II, an SPP transmission line III, and barium strontium titanate ((Ba) with high dielectric constantxSr1-x)TiO3BST for short) dielectric block IV.
The SPP band elimination filter is a two-port network, one end of the SPP band elimination filter serves as an input end, and the other end of the SPP band elimination filter serves as an output end, so that the SPP band elimination filter can be used reciprocally.
The coplanar waveguide I comprises a central metal strip on one and the same plane, and two ground planes, briefly referred to as GND, are symmetrically constructed on both sides of the central metal strip. An electromagnetic wave propagating in a coplanar waveguide is a TEM wave whose electric and magnetic field components are perpendicular to the direction of propagation. And the proper size is selected, so that the coplanar waveguide can be well matched with the broadband impedance of other 50-ohm circuit ports.
The electromagnetic wave mode converter II is implemented as follows: etching an H-shaped groove on the central metal strip, wherein the depth of the H-shaped groove is sequentially increased to be consistent with the depth of the groove of the SPP transmission line; the GND planes immediately adjacent to the two sides of the central metal strip are gradually changed into an arc-shaped GND plane according to the exponential size. Because the electromagnetic wave transmitted by the SPP transmission line is TM wave without magnetic field component and only with electric field component in the transmission direction, the electromagnetic wave mode converter is mainly used for realizing the high-efficiency transition of electromagnetic wave energy from the coplanar waveguide to the SPP transmission line, namely completing the conversion from TEM wave to TM wave.
The SPP transmission line III is implemented by periodically etching H-grooves of the same size in the central metal strip, wherein the depth of the H-grooves is directly related to the operating frequency of the SPP transmission line, and the operating frequency tends to decrease as the depth of the grooves increases. The electromagnetic wave propagating on the SPP transmission line is a TM wave having no magnetic field component but only an electric field component in the propagation direction.
The depth and the width of the H-shaped groove are changed, the working frequency of the SPP transmission line can be changed, input and output matching is improved, and extra design freedom is obtained to adjust the overall frequency response of the SPP transmission line.
The BST dielectric block IV is a ferroelectric material, and can reach a very high dielectric constant due to spontaneous polarization, ferroelectric paraelectric phase change can be caused by temperature change, and the applied electric field can cause redirection of dipole moment, so that the purpose of changing the dielectric constant of the BST dielectric block can be achieved by changing the temperature or the intensity of the applied electric field, and the adjustment of trap wave working frequency is realized.
As shown in fig. 2, in order to embed the BST dielectric block on the SPP transmission line, a rectangular groove is etched on the SPP transmission line, the BST dielectric block is embedded into the etched groove, and the BST dielectric block is in direct contact with both sides of the SPP transmission line and has electrical connection. Under a certain working frequency, due to the existence of the BST medium block, a Fabry-Perot interference phenomenon is caused, so that a required transmission signal and a multipath reflection signal mutually cancel and interfere, a trapped wave is generated, and the frequency response presented at the moment shows a band elimination characteristic.
The dielectric constant of the BST dielectric block can be changed by changing the temperature or applying an external electric field with different strength, and at this time, the change of the dielectric constant of the BST dielectric block can cause the change of the notch frequency of the SPP filter, and the larger the dielectric constant of the BST dielectric block is, the smaller the notch frequency tends to be. Therefore, by setting a suitable operating temperature or applying a suitable applied electric field strength, the BST dielectric block can obtain a desired dielectric constant, thereby allowing the SPP filter to operate at a desired notch frequency.
The dielectric substrate material of this embodiment is Rogers-4003 and the metal structure material is copper.
The SPP band-stop filter with the tunable stop band center frequency and the low loss, the wide band and the small size is realized by adopting the high dielectric constant dielectric block which is sensitive to the temperature change and the external electric field intensity to be embedded into the SPP transmission line and changing the dielectric constant of the dielectric block through changing the temperature and the external electric field intensity. As shown in fig. 3, when the dielectric constant of the BST dielectric block is increased from 375 to 475 by 25, the center operating frequency of the stop band is decreased from 8.7GHz to 7.6GHz, wherein dielectric constants 375, 400, 425, 450, 475 correspond to the center operating frequencies of the stop band, respectively, 8.7GHz, 8.3GHz, 8.12GHz, 7.9GHz, and 7.6 GHz.
Although specific embodiments of the present invention have been described above with reference to the accompanying drawings, it will be appreciated by those skilled in the art that these are merely illustrative and that various changes or modifications may be made to these embodiments without departing from the principles and spirit of the invention. The scope of the invention is only limited by the appended claims.
In the description of the present invention, it should be noted that, unless otherwise specified and limited, the terms "connected" and "connected" should be interpreted broadly, and may be, for example, a mechanical connection or an electrical connection, a communication between two elements, a direct connection, or an indirect connection via an intermediate medium, and the specific meaning of the terms may be understood by those skilled in the relevant art according to specific situations. Further, the present invention provides examples of certain specific processes and materials, but one of ordinary skill in the art may recognize the applicability of other processes and/or the use of other materials.
Claims (10)
1. A surface plasmon band elimination filter with tunable center frequency is characterized by comprising a coplanar waveguide, an electromagnetic wave mode converter, an SPP transmission line and a high dielectric constant dielectric block;
the coplanar waveguide is composed of a central conductor strip and rectangular ground planes which are close to two sides of the central conductor strip;
the electromagnetic wave mode converter comprises an H-shaped metal unit with gradually increasing depth of a groove etched on a central conductor strip in sequence, and two arc-shaped ground planes etched in an exponential mode on the ground planes adjacent to two sides of the central conductor strip;
the SPP transmission line is composed of a series of H-shaped metal units with the same groove depth, a rectangular groove is etched in the middle of the SPP transmission line, the central conductor strip at the position is disconnected, direct electrical connection does not exist, a high-dielectric-constant dielectric block is embedded into the etched rectangular groove on the SPP transmission line and is in direct contact with metal on two sides of the SPP transmission line, and electrical connection exists.
2. The center-frequency tunable surface plasmon band stop filter of claim 1 wherein said high dielectric constant dielectric block has a dielectric constant greater than 100.
3. A center frequency tunable surface plasmon band reject filter according to claim 1 or 2 wherein said high dielectric constant dielectric block is a perovskite series dielectric block.
4. The surface plasmon band stop filter with tunable center frequency according to claim 3, wherein said high dielectric constant dielectric block is a barium strontium titanate dielectric block, a barium titanate dielectric block or a calcium titanate dielectric block.
5. The center-frequency tunable surface plasmon band stop filter of claim 1 wherein the metal structure material properties of the coplanar waveguide, the electromagnetic wave mode converter, the SPP transmission line are aluminum, copper, silver or gold.
6. The surface plasmon band reject filter with tunable center frequency according to claim 1, wherein the dielectric substrate material of the surface plasmon band reject filter is Rogers PCB, quartz plate or semiconductor material.
7. The surface plasmon band reject filter with tunable center frequency of claim 1, wherein said surface plasmon band reject filter is a two-port network with one end as input and the other end as output.
8. The center-frequency tunable surface plasmon band stop filter of claim 7 wherein said surface plasmon band stop filter is side-to-side symmetric about a center line.
9. The surface plasmon band reject filter with tunable center frequency of claim 1 wherein said electromagnetic wave mode converter has H-shaped grooves etched in the center conductor strip, the depth of the H-shaped grooves increasing sequentially to be the same as the groove depth of the SPP transmission line.
10. The center-frequency tunable surface plasmon band reject filter of claim 1 wherein said grooves on said SPP transmission line are periodically arranged.
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| CN201911387091.8A CN111029691A (en) | 2019-12-30 | 2019-12-30 | Surface plasmon band elimination filter with tunable center frequency |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114914652A (en) * | 2022-05-30 | 2022-08-16 | 西安工业大学 | SSPPs transmission line and filter for central metal strip sputtering ITO film equalization filtering |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114914652A (en) * | 2022-05-30 | 2022-08-16 | 西安工业大学 | SSPPs transmission line and filter for central metal strip sputtering ITO film equalization filtering |
| CN114914652B (en) * | 2022-05-30 | 2024-03-29 | 西安工业大学 | Balanced filtering SSPPs transmission line and filter with sputtered ITO (indium tin oxide) film on central metal strip |
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