Dynamically tunable graphene attenuator based on equivalent surface plasmon

Abstract

The present invention discloses a dynamically adjustable graphene attenuator based on equivalent surface plasmon, which belongs to the field of microwave device technology, including a multi-layer substrate integrated waveguide, a microstrip signal conversion transition part and a microstrip signal transmission part symmetrically arranged on both sides of the waveguide, and the microstrip signal conversion transition part is connected to the integrated waveguide transmission part; metal wires are periodically arranged at the interface of two dielectric substrates with different dielectric constants in the multi-layer substrate, and a graphene sandwich structure is arranged directly above the metal wires and parallel to the interface. The present invention uses electrolyte to regulate the conductivity characteristics of graphene, realizes the dynamic regulation of effective plasma attenuation, is easy to planarly integrate, and can control the attenuation by adjusting the applied voltage of graphene. It has good application prospects in miniaturized, highly integrated and real-time dynamically regulated devices and circuits, and opens up new application prospects for equivalent plasmon devices.

Description

Technical Field

[0001] The invention belongs to the technical field of microwave devices and relates to a dynamically adjustable graphene attenuator based on equivalent surface plasmons. Background Art

[0002] In order to pursue and optimize the small size, multi-scenario application and strong anti-interference functions of communication electronic products, people have conducted in-depth discussions and developments in the miniaturization, high integration and dynamic adjustability of microwave devices in recent years. In order to meet this application demand and engineering technology needs, highly integrated, anti-interference dynamically adjustable microwave devices are of great significance.

[0003] Surface plasmon is a special electromagnetic wave that propagates along the interface between two dielectric substrates with opposite relative dielectric constants. It has significant field localization and field enhancement characteristics. Effective surface plasmon is generated in the waveguide by setting dielectric substrates of appropriate size to produce different effective dielectric constants, and has the characteristics of surface plasmon.

[0004] In electronic communication systems, attenuators have always been an indispensable part, which plays a role in controlling the signal size and impedance changes in buffer circuits to achieve impedance matching. At the same time, in recent years, graphene has received widespread attention due to its special electronic and optical properties, and graphene-based microwave devices have also been reported in some literature, among which graphene-based attenuators account for a large part. Because graphene has the property that its conductivity can be adjusted by voltage, a dynamically adjustable attenuator can be realized based on graphene, and it is conducive to the planar integration of microwave devices. Summary of the invention

[0005] Purpose of the invention: In order to solve the problems existing in the prior art, the present invention provides a dynamically adjustable graphene attenuator based on equivalent surface plasmons, which has the advantages of simple structural design, easy planar integration and miniaturization, and can change the conductivity of graphene by adjusting the external voltage, thereby realizing dynamic regulation of the attenuation of equivalent surface plasmons.

[0006] Technical solution: In order to achieve the above-mentioned invention object, the present invention adopts the following technical solution:

[0007] The invention discloses a dynamically adjustable graphene attenuator based on equivalent surface plasmon, comprising an equivalent surface plasmon waveguide, wherein two sides of the equivalent surface plasmon waveguide are respectively connected to one end of a symmetrically arranged microstrip line signal conversion transition part, and the other end of the microstrip line signal conversion transition part is respectively connected to a symmetrically arranged microstrip line signal transmission part; wherein metal wires and a hollowed-out part of a dielectric substrate arranged in equal periods and having a width equal to that of the waveguide are sequentially arranged from top to bottom in a dielectric layer of the equivalent surface plasmon waveguide for use; wherein a graphene sandwich structure is covered on the metal wires.

[0008] Furthermore, the microstrip line signal transmission part, the microstrip line signal conversion transition part and the equivalent surface plasmon waveguide each include a top metal conduction layer, a dielectric layer and a bottom full-covering metal layer which are stacked in sequence.

[0009] Furthermore, the top metal conduction strip layer includes a rectangular metal conduction strip arranged on the microstrip line signal transmission part, a trapezoidal metal conduction strip arranged on the microstrip line signal conversion transition part, and a full coverage metal ground arranged on the equivalent surface plasmon integrated waveguide.

[0010] Furthermore, the dielectric layer includes a first dielectric substrate, a second dielectric substrate and a dielectric substrate hollowed out in the middle which are stacked in sequence, wherein the hollowed-out portion of the dielectric substrate arranged in the dielectric substrate hollowed out in the middle is located in the equivalent surface plasmon waveguide.

[0011] Furthermore, the metallized vias are arranged equi-periodically on both sides of the dielectric layer and the range covered by the arrangement covers the equivalent surface plasmon waveguide; the graphene sandwich structure is arranged between the first dielectric substrate and the second dielectric substrate; the metal wires are arranged equi-periodically and the width is the waveguide width, the metal wires are arranged between the second dielectric substrate and the dielectric substrate hollowed out in the middle, and the range covered by the metal wire arrangement is the hollowed-out part of the dielectric substrate.

[0012] Furthermore, the graphene sandwich structure includes mutually connected rectangular graphene and L-type graphene for external feeding; the rectangular graphene is arranged in the equivalent surface plasmon waveguide and is located directly above the hollowed-out part of the dielectric substrate; and the L-type graphene is arranged in the microstrip line signal conversion transition part.

[0013] Furthermore, the thickness of the first dielectric substrate, the second dielectric substrate and the dielectric substrate hollowed out in the middle and the width of the hollowed-out portion of the dielectric substrate are calculated by using the effective dielectric constant of the dielectric and Maxwell's electromagnetic equations.

[0014] Furthermore, the designed model was modeled and optimized using the commercial software CST to obtain the period, diameter and height of the metallized vias with equal periods on both sides of the substrate integrated waveguide part; the linear width transformation range and length of the metal conduction band with linearly decreasing width; and the length, width and square resistance of the graphene sandwich.

[0015] Furthermore, the first dielectric substrate, the second dielectric substrate and the hollowed-out dielectric substrate are made of Rogers RO4350B material with a relative dielectric constant of 3.48, and the top metal conduction layer and the bottom full-coverage metal layer are made of copper.

[0016] Furthermore, the graphene sandwich structure includes a layer of diaphragm paper soaked in ionic liquid, polyvinyl chloride layers are symmetrically arranged on the upper and lower surfaces of the diaphragm paper, a single layer of graphene is arranged between the polyvinyl chloride layer and the diaphragm paper, and the single layer of graphene is transferred to the polyvinyl chloride layer.

[0017] Beneficial effects: Compared with the prior art, the dynamically adjustable graphene attenuator based on equivalent surface plasmon of the present invention uses voltage to control the conductivity of graphene, thereby realizing the dynamic adjustable function of equivalent surface plasmon attenuation, and has low return loss. It not only has a simple structural design, but also is easy to be integrated in a planar manner. It is suitable for the miniaturization, high integration and dynamic adjustment requirements of microwave devices and circuits, and has a good engineering application prospect. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a cross-sectional view of a dynamically adjustable graphene attenuator based on equivalent surface plasmons;

[0019] Figure 2 It is a top view of the dynamically adjustable graphene attenuator based on equivalent surface plasmon;

[0020] Figure 3 It is a graphene placement diagram of a dynamically adjustable graphene attenuator based on equivalent surface plasmon;

[0021] Figure 4 It is a diagram of the hollowed-out dielectric substrate and metal wire placement of a dynamically adjustable graphene attenuator based on equivalent surface plasmons;

[0022] Figure 5 is a schematic diagram of the graphene sandwich structure;

[0023] Figure 6 is a curve showing a change in S21 of the attenuation dynamically adjustable transmission device of the embodiment at 5.5 GHz as a function of the graphene square resistance;

[0024] The accompanying drawings are marked as: 1-microstrip line signal transmission part, 2-microstrip line signal conversion transition part, 3-equivalent surface plasmon waveguide, 4-graphene sandwich structure, 5-metallized via, 6-metal wire, 7-hollowed-out part of dielectric substrate, 8-rectangular metal conduction strip, 9-trapezoidal metal conduction strip, 10-full coverage metal ground, 11-second dielectric substrate, 12-L-type graphene, 13-rectangular graphene, 14-single-layer graphene, 15-diaphragm paper, 16-polyvinyl chloride layer, 17-top metal conduction strip layer, 18-first dielectric substrate, 19-middle hollowed-out dielectric substrate, 20-bottom full coverage metal layer. DETAILED DESCRIPTION

[0025] The structure and performance of the present invention are further described below in conjunction with the accompanying drawings. It should be understood that these embodiments are only used to illustrate the present invention and are not used to limit the scope of the present invention. After reading the present invention, the modifications of various equivalent forms of the present invention by those skilled in the art all fall within the scope defined by the claims attached to this application.

[0026] like Figure 1 As shown, the dynamically adjustable graphene attenuator based on equivalent surface plasmon consists of a microstrip line signal transmission part 1, a microstrip line signal conversion transition part 2, an equivalent surface plasmon waveguide 3, a microstrip line signal conversion transition part 2 and a microstrip line signal transmission part 1 from left to right. The microstrip line signal transmission part 1 is located at both ends of the dynamically adjustable graphene attenuator and serves as an input end and an output end respectively. The microstrip line signal transmission part 1 at the input end and the output end is used for signal feeding and extraction. The microstrip line signal conversion transition part 2 is used to realize the mutual conversion between the microstrip line transmission signal and the substrate integrated waveguide signal. The equivalent surface plasmon waveguide 3 is used to transmit the equivalent surface plasmon wave.

[0027] The dynamically adjustable graphene attenuator based on equivalent surface plasmon includes an equivalent surface plasmon waveguide 3, a graphene sandwich structure 4 is inserted in the middle of the equivalent surface plasmon waveguide 3, both sides of the equivalent surface plasmon waveguide 3 are respectively connected to one end of a symmetrically arranged microstrip line signal conversion transition part 2, and the other end of the microstrip line signal conversion transition part 2 is respectively connected to a symmetrically arranged microstrip line signal transmission part 1. In the dielectric layer of the equivalent surface plasmon waveguide 3, metal wires 6 and dielectric substrate hollowing parts 7 arranged in equal periods and having a width of the waveguide are sequentially arranged from top to bottom for use; wherein, the graphene sandwich structure 4 is covered on the metal wires 6.

[0028] The microstrip signal transmission part 1, the microstrip signal conversion transition part 2 and the equivalent surface plasmon waveguide 3 respectively include a top metal conduction layer 17, a dielectric layer and a bottom fully covered metal layer 20 which are stacked in sequence. The top metal conduction layer 17 and the bottom fully covered metal layer 20 form a double-layer metal strip structure. The top metal conduction layer 17 includes a rectangular metal conduction strip 8 arranged on the microstrip signal transmission part 1, a trapezoidal metal conduction strip 9 arranged on the microstrip signal conversion transition part 2 and a fully covered metal ground 10 arranged on the equivalent surface plasmon integrated waveguide.

[0029] The dielectric layer includes a first dielectric substrate 18, a second dielectric substrate 11 and a dielectric substrate 19 which are stacked in sequence, wherein a dielectric substrate hollowed-out portion 7 of the dielectric substrate 19 which is hollowed-out is located in the equivalent surface plasmon waveguide 3. A graphene sandwich structure 4 is arranged in the equivalent surface plasmon waveguide 3 between the first dielectric substrate 18 and the second dielectric substrate 11, and metal wires 6 with a width of the waveguide and arranged in equal periods are arranged between the second dielectric substrate 11 and the dielectric substrate 19 which is hollowed-out in the middle, and the arrangement length covers the dielectric substrate hollowed-out portion 7.

[0030] The microstrip signal transmission part 1 includes a rectangular metal guide strip 8 with a fixed width, a first dielectric substrate 18, a second dielectric substrate 11 and a bottom fully covered metal layer 20 stacked in sequence; the microstrip signal conversion transition part 2 includes a metal guide strip 9 with a linearly reduced width, a first dielectric substrate 18, a second dielectric substrate 11 and a bottom fully covered metal layer 20 stacked in sequence; the equivalent surface plasmon waveguide 3 includes a fully covered metal ground 10 stacked in sequence, a first dielectric substrate 18, a graphene sandwich structure 4, a second dielectric substrate 11, a metal wire 6, a dielectric substrate 19 hollowed out in the middle and a bottom fully covered metal layer 20. Among them, the rectangular metal guide strip 8, the trapezoidal metal guide strip 9 and the fully covered metal ground 10 constitute the top metal guide strip layer 17.

[0031] The metallized vias 5 are arranged equi-periodically on both sides of the dielectric layer and the range covered by the arrangement covers the equivalent surface plasmon waveguide 3; the graphene sandwich structure 4 is arranged between the first dielectric substrate 18 and the second dielectric substrate 11; the metal wires 6 are arranged equi-periodically and the width is the waveguide width, the metal wires 6 are arranged between the second dielectric substrate 11 and the dielectric substrate 19 hollowed out in the middle, and the range covered by the arrangement of the metal wires 6 is the hollowed-out portion 7 of the dielectric substrate.

[0032] The graphene sandwich structure 4 includes interconnected rectangular graphene 13 and L-type graphene 12 for external feeding; the rectangular graphene 13 is arranged in the equivalent surface plasmon waveguide 3 and is located directly above the hollowed-out portion 7 of the dielectric substrate; the L-type graphene 12 is arranged in the microstrip line signal conversion transition portion 2.

[0033] A method for preparing a dynamically adjustable graphene attenuator based on equivalent surface plasmons comprises the following steps:

[0034] 1) The thickness of the first dielectric substrate 18, the second dielectric substrate 11, the thickness of the hollowed-out dielectric substrate 19 and the width of the hollowed-out portion can all be calculated from the effective dielectric constant of the dielectric and Maxwell's electromagnetic equations. The results show that when the thicknesses of the first dielectric substrate 18, the second dielectric substrate 11 and the hollowed-out dielectric substrate 19 are 1.067 mm, 0.203 mm and 0.203 mm respectively, and the width of the hollowed-out portion 7 of the dielectric substrate is 18 mm and the length is 30 mm, the invented device has good transmission function;

[0035] 2) If Figure 1 , Figure 3 As shown, the graphene sandwich structure 4 includes a rectangular graphene 13 and an L-type graphene 12, wherein the rectangular graphene 13 should be arranged directly above the hollowed-out portion 7 of the dielectric substrate to play a role in eliminating effective surface plasmons, and the L-type graphene 12 plays a role in external voltage;

[0036] 3) The designed model is modeled and optimized using the commercial software CST to obtain the period, diameter and height of the metallized vias 5 with equal period on both sides of the substrate integrated waveguide part; the linear width transformation range and length of the metal conduction band 9 with linearly decreasing width; the length, width and square resistance of the graphene sandwich 4. The results show that the period of the metallized vias 5 with equal period on both sides of the substrate integrated waveguide part is 0.2mm, the diameter is 0.1mm, and the height is 1.613mm, which is the sum of the thickness of the five layers of metal and the dielectric substrate; the linear transformation range of the width of the metal conduction band 9 with linearly decreasing width is 3.2mm to 2.2mm, and the length is 20.1mm; the rectangular graphene 13, the width should not be less than the width of the hollowed-out part 7 of the dielectric substrate, which is 18mm, and not greater than the width of the equivalent surface plasmon waveguide 3, which is 22mm, and the length should not be less than the length of the hollowed-out part 7 of the dielectric substrate, which is 30mm, and not greater than the length of the equivalent surface plasmon waveguide 3, which is 40mm; the second is L-type graphene 12, the width is 3mm, and the length should not be less than 10mm.

[0037] 4) The model designed in the above steps is processed and prepared, and its performance is tested. In order to facilitate the placement of the graphene sandwich structure 4 and the metal wire 6, a layered stacking method is adopted, and the first dielectric substrate 18, the second dielectric substrate 11 and the dielectric substrate 19 hollowed out in the middle are made of Rogers RO4350B material with a relative dielectric constant of 3.48, and the metal materials are all copper.

[0038] In step 1), the effective dielectric constant of the dielectric substrate and the air and the Maxwell electromagnetic field equation are used to calculate the dispersion curve equation at the interface between the second dielectric substrate 11 and the hollowed-out dielectric substrate 19. The formula is shown in (Z. Li, L. Liu, H. Sun, Y. Sun, C. Gu, X. Chen, Y. Luo, "Effective surface plasmon polaritons induced by modal dispersion in a waveguide," Physical Review Applied, vol. 7, no. 4, pp. 044028, 2017.). The thickness of the first dielectric substrate 18 and the second dielectric substrate 11 of the attenuator in the designed frequency band and the thickness of the hollowed-out dielectric substrate 19 and the width of the hollowed-out portion thereof can be calculated through the dispersion curve.

[0039] In steps 2) and 3), the time domain simulation method is used to simulate the display, graphene is simulated by a zero-thickness resistor film, and the square resistance of graphene is scanned at intervals of 100Ω / sq in the region of 100Ω / sq to 2500Ω / sq.

[0040] In step 4), if Figure 5 As shown, the graphene sandwich structure includes a layer of diaphragm paper 15 soaked in ionic liquid, the thickness of the diaphragm paper 15 is 0.05 mm, a polyvinyl chloride layer 16 is symmetrically arranged on the upper and lower surfaces of the diaphragm paper 15, the thickness of the polyvinyl chloride layer 16 is 0.075 mm, and a single layer of graphene 14 is arranged between the polyvinyl chloride layer 16 and the diaphragm paper 15, and the single layer of graphene 14 is transferred to the polyvinyl chloride layer 16. A bias voltage is applied between two layers of single-layer graphene, and the change of the square resistance of the graphene sandwich structure 4 can be controlled by adjusting the magnitude of the bias voltage. Different square resistances can produce different dissipations for the transmission power of the effective surface plasmon polaritons. Therefore, by adjusting the bias voltage V of the graphene sandwich structure 4, the change of the square resistance of the graphene sandwich structure 4 can be controlled. b , output signals of different power sizes can be obtained.

[0041] Figure 1 It is a cross-sectional view of a dynamically adjustable graphene attenuator based on equivalent surface plasmons. The first dielectric substrate 18, the second dielectric substrate 11, the dielectric substrate 19 hollowed out in the middle, the top metal conduction layer 17, the bottom metal layer 20, the graphene sandwich structure 4 and the metal wire 6 are closely stacked in sequence.

[0042] Figure 2-5 In order to make it easier to clarify the details of the structure, the top view of the dynamically adjustable graphene attenuator of the equivalent surface plasmon, the graphene placement diagram, and the hollowed-out dielectric substrate and metal wire placement diagram are shown respectively. Figure 4It shows that the period of the metal wires 6 arranged between the third and fourth dielectric substrates is 0.4 mm, the diameter is 0.1 mm, and the length is 22 mm. The width and length of the hollowed-out part 7 of the dielectric substrate are 18 mm and 30 mm.

[0043] Figure 6 It indicates that when the operating frequency is 5.5 GHz, the transmission coefficient of the device in the embodiment changes with the square resistance of the graphene sandwich structure 4. When the square resistance of the graphene sandwich structure 4 is adjusted from 300 ohm / sq to 3000 ohm / sq, the attenuation coefficient of the dynamically adjustable attenuation device can be adjusted from -7 dB to about -15 dB, thereby realizing the dynamic attenuation of the equivalent surface plasmon wave.

Claims

1. A dynamically adjustable graphene attenuator based on equivalent surface plasmon, characterized in that: The invention comprises an equivalent surface plasmon waveguide (3), wherein both sides of the equivalent surface plasmon waveguide (3) are respectively connected to one end of a symmetrically arranged microstrip line signal conversion transition part (2), and the other end of the microstrip line signal conversion transition part (2) is respectively connected to a symmetrically arranged microstrip line signal transmission part (1); wherein metal wires (6) and a dielectric substrate hollowing part (7) arranged in equal periods and having a width equal to the waveguide width are sequentially arranged in the dielectric layer of the equivalent surface plasmon waveguide (3) from top to bottom for use; wherein a graphene sandwich structure (4) is covered on the metal wires (6); and the microstrip line signal transmission part (1) is connected to the microstrip line signal transmission part (2). The part (1), the microstrip line signal conversion transition part (2) and the equivalent surface plasmon waveguide (3) respectively comprise a top metal conduction strip layer (17), a dielectric layer and a bottom fully covered metal layer (20) which are stacked in sequence; the top metal conduction strip layer (17) comprises a rectangular metal conduction strip (8) arranged on the microstrip line signal transmission part (1), a trapezoidal metal conduction strip (9) arranged on the microstrip line signal conversion transition part (2) and a fully covered metal ground (10) arranged on the equivalent surface plasmon integrated waveguide; the dielectric layer comprises a first dielectric substrate (18), a second dielectric substrate (11) and a hollowed-out bottom dielectric substrate (20) which are stacked in sequence. A dielectric substrate (19), wherein a dielectric substrate hollowed-out portion (7) arranged in the dielectric substrate (19) with a hollow middle portion is located in an equivalent surface plasmon waveguide (3); the graphene sandwich structure (4) is arranged between a first dielectric substrate (18) and a second dielectric substrate (11); the metal wires (6) are arranged in an equiperiodic manner and have a width equal to the waveguide width; the metal wires (6) are arranged between the second dielectric substrate (11) and the dielectric substrate (19) with a hollow middle portion, and the arrangement of the metal wires (6) covers the dielectric substrate hollowed-out portion (7); the graphene sandwich structure (4) comprises mutually connected rectangular graphene (13) and an L-shaped graphene (12) for external power feeding; the rectangular graphene (13) is arranged in an equivalent surface plasmon waveguide (3) and is located directly above a hollowed-out portion (7) of a dielectric substrate; the L-shaped graphene (12) is arranged in a microstrip line signal conversion transition portion (2); the graphene sandwich structure (4) comprises a layer of diaphragm paper (15) impregnated with ionic liquid, a polyvinyl chloride layer (16) is symmetrically arranged on the upper and lower surfaces of the diaphragm paper (15), a single layer of graphene (14) is arranged between the polyvinyl chloride layer (16) and the diaphragm paper (15), and the single layer of graphene (14) is transferred to the polyvinyl chloride layer (16).

2. The dynamically adjustable graphene attenuator based on equivalent surface plasmon according to claim 1, characterized in that: The thickness of the first dielectric substrate (18), the second dielectric substrate (11) and the hollowed-out dielectric substrate (19) and the width of the hollowed-out portion (7) of the dielectric substrate are calculated based on the effective dielectric constant of the dielectric and Maxwell's electromagnetic equations.

3. The dynamically adjustable graphene attenuator based on equivalent surface plasmon according to claim 1, characterized in that: The designed model is modeled using commercial software CST to obtain the period, diameter and height of the metallized via (5); the linear transformation range and length of the width of the metal conduction band (9); the length, width and square resistance of the graphene sandwich structure (4); the metallized via (5) is arranged equi-periodically on both sides of the dielectric layer and the range of the arrangement covers the equivalent surface plasmon waveguide (3).

4. The dynamically adjustable graphene attenuator based on equivalent surface plasmon according to claim 1, characterized in that: The first dielectric substrate (18), the second dielectric substrate (11) and the hollowed-out dielectric substrate (19) are made of Rogers RO4350B material with a relative dielectric constant of 3.48, and the top metal conduction layer (17) and the bottom full-covering metal layer (20) are both made of copper.

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