A graphene-based dual-passband tunable filtering attenuator

Abstract

The application belongs to the field of electronic information technology, and discloses a double-passband adjustable filtering attenuator based on graphene, which comprises a lossy dielectric layer, a metal grounding plate arranged on one side of the lossy dielectric layer, an input microstrip line, an output microstrip line, a first three-mode resonator and a second three-mode resonator arranged on the other side of the lossy dielectric layer; an input port is arranged on one end of the input microstrip line, and an output port is arranged on one end of the output microstrip line; the input microstrip line and the output microstrip line are arranged at intervals, a coupling interval is formed between the input microstrip line and the output microstrip line, and the first three-mode resonator and the second three-mode resonator are arranged at intervals in the coupling interval; the first three-mode resonator and the second three-mode resonator each comprise three open-circuit branches and one short-circuit branch, a graphene film resistor is arranged between two adjacent open-circuit branches, and a metal connecting piece connected with the metal grounding plate is arranged on the short-circuit branch. The double-passband adjustable filtering attenuator realizes independent adjustment of two passbands, has a simple structure and is easy to integrate and process.

Description

Technical Field

[0001] This invention belongs to the field of electronic information technology and relates to a graphene-based dual-passband adjustable filter attenuator. Background Technology

[0002] With the development of modern microwave devices, multifunctionality and high integration have attracted increasing attention. The multifunctionality of microwave devices is an effective way to reduce circuit size and enhance versatility. In modern microwave systems, tunable microwave attenuators and bandpass filters are important components in modern communication systems. The former is used to adjust signals to different levels, while the latter is almost the most widely used microwave device in modern systems. In this context, bandpass filters and attenuators are widely combined for specific applications, including automatic level or gain control circuits in communication and radar systems.

[0003] One of the significant characteristics of graphene in the microwave band is that its surface impedance can be electrically adjusted, which provides the possibility for graphene to be applied to tunable microwave devices and circuits. In recent years, many scholars have studied graphene-based filter attenuators and proposed some feasible structures and design methods, realizing the design of single-passband tunable filter attenuators. However, with the increasing demand for high integration in circuit size, circuit designs using multiple single-channel tunable filter attenuators result in larger circuit sizes and more complex structures due to the large number of single-channel tunable filter attenuators, leading to more circuit losses. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art, which is that in circuit designs using multiple single-channel adjustable filter attenuators, the large number of single-channel adjustable filter attenuators leads to a large circuit size and a complex circuit structure, resulting in more circuit losses. This invention provides a graphene-based dual-passband adjustable filter attenuator.

[0005] To achieve the above objectives, the present invention employs the following technical solution:

[0006] A graphene-based dual-passband tunable filter attenuator includes a lossy dielectric layer, a metal ground plane on one side of the lossy dielectric layer, and an input microstrip line, an output microstrip line, a first three-mode resonator, and a second three-mode resonator on the other side.

[0007] An input port is provided at one end of the input microstrip line, and an output port is provided at one end of the output microstrip line. The input microstrip line and the output microstrip line are spaced apart, forming a coupling gap between them. The first three-mode resonator and the second three-mode resonator are spaced apart inside the coupling gap. Both the first three-mode resonator and the second three-mode resonator include three open-circuit stubs and one short-circuit stub. A graphene thin film resistor is provided between two adjacent open-circuit stubs, and the sidewall of the graphene thin film resistor is in close contact with the sidewall of the adjacent open-circuit stub. A metal connector connected to a metal ground plane is provided on the short-circuit stub.

[0008] Optionally, the three open-circuit stubs of the first or second three-mode resonator are all the same length and are all one-quarter of the wavelength of the electromagnetic wave to be filtered; the electrical length of the short-circuit stub is 3° to 5°.

[0009] Optionally, in the three open-circuit stubs of the first or second three-mode resonator, the open-circuit stubs on both sides are symmetrically bent, and the input microstrip line and the output microstrip line are arranged parallel to each other.

[0010] Optionally, the internal components of the first or second three-mode resonator are symmetrically distributed about the short-circuit stubs.

[0011] Optionally, an external voltage source is also included, which is connected to the graphene film resistor to provide a variable external voltage to the graphene film resistor.

[0012] Optionally, it also includes an input SMA port and an output SMA port; the input SMA port is connected to the input port, and the output SMA port is connected to the output port.

[0013] Optionally, the graphene thin film resistor may be square or circular in shape.

[0014] Optionally, the dielectric substrate of the lossy dielectric layer is Rogers RO4003 or Rogers RO5880; the metal ground plane is a metal electroplated film made of silver, copper or aluminum.

[0015] Optionally, the metal connector is a metal through hole or a metal cylinder.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] This invention relates to a graphene-based dual-passband adjustable filter attenuator. It employs a first and a second tri-mode resonator to achieve dual-passband filtering, saving space and reducing size compared to structures with multiple coupled resonant cavities. Furthermore, the filter attenuator is implemented using graphene thin-film resistors, avoiding the welding of lumped resistors and reducing manufacturing costs. Simultaneously, the surface resistance of the graphene thin-film resistors is controllable through an external voltage, thereby enabling adjustable filter attenuation. Additionally, the two passbands of the filter are connected in parallel via input and output microstrip lines, and the spacing between them ensures that the two passbands do not interfere with each other, allowing for independent adjustment of the attenuation of each passband. This graphene-based dual-passband adjustable filter attenuator combines a dual-passband filter and an adjustable attenuator, achieving multifunctionality and high integration in microwave devices. It simplifies circuit structure, reduces circuit size, and is easy to fabricate, showing great potential application in automatic level or gain control circuits in communication and radar systems. Attached Figure Description

[0018] Figure 1 This is a top view schematic diagram of the graphene-based dual-passband adjustable filter attenuator of the present invention.

[0019] Figure 2 This is a side view schematic diagram of the graphene-based dual-passband adjustable filter attenuator of the present invention.

[0020] Figure 3 This is a top view schematic diagram of the first three-mode resonator of the present invention;

[0021] Figure 4 This is a schematic diagram of the equivalent circuit of the graphene-based dual-passband adjustable filter attenuator of the present invention.

[0022] Figure 5 This is a schematic diagram showing the S-parameter results of the graphene-based dual-passband adjustable filter attenuator of the present invention under different resistance values ​​of the graphene thin film.

[0023] Wherein: 11-First open-circuit stub; 12-Second open-circuit stub; 13-Third open-circuit stub; 14-Short-circuit stub; 2-Graphene thin film resistor; 3-Loss dielectric layer; 4-Metal connector; 51-First tri-mode resonator; 52-Second tri-mode resonator; 61-Input port; 62-Output port; 71-Input microstrip line; 72-Output microstrip line; 8-Metal ground plane. Detailed Implementation

[0024] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0025] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0026] The present invention will now be described in further detail with reference to the accompanying drawings:

[0027] See Figures 1 to 3 In one embodiment of the present invention, a graphene-based dual-passband adjustable filter attenuator is provided, which realizes independent adjustment of the two passbands, has a simple structure, is easy to integrate and process, and can be used in the filter design of modern communication systems, enabling the multifunctionality and high integration of microwave devices.

[0028] Specifically, the graphene-based dual-passband tunable filter attenuator includes a lossy dielectric layer 3. A metal ground plane 8 is disposed on one side of the lossy dielectric layer 3, and an input microstrip line 71, an output microstrip line 72, a first tri-mode resonator 51, and a second tri-mode resonator 52 are disposed on the other side. An input port 61 is disposed at one end of the input microstrip line 71, and an output port 62 is disposed at one end of the output microstrip line 72. The input microstrip line 71 and the output microstrip line 72 are spaced apart, forming a coupling gap between them. The first tri-mode resonator 51 and the second tri-mode resonator 52 are spaced apart inside the coupling gap. Both the first tri-mode resonator 51 and the second tri-mode resonator 52 include three open-circuit stubs and one short-circuit stub 14. A graphene thin film resistor 2 is disposed between two adjacent open-circuit stubs, and the sidewall of the graphene thin film resistor 2 is in close contact with the sidewall of the adjacent open-circuit stub. A metal connector 4 connected to the metal ground plane 8 is disposed on the short-circuit stub 14.

[0029] Among them, the graphene film resistor 2 uses graphene, a two-dimensional carbon material with excellent flexibility and conductivity. In the microwave frequency band, its surface reactance can be ignored, and its surface resistance is dominant. The surface resistance can be controlled by applying an external voltage, thereby realizing the adjustable attenuation of the filter.

[0030] Specifically, this invention relates to a graphene-based dual-passband adjustable filter attenuator. It employs a first tri-mode resonator 51 and a second tri-mode resonator 52 to achieve dual-passband filtering, saving space and reducing size compared to structures with multiple coupled resonant cavities. Furthermore, the filter attenuator is implemented using a graphene thin-film resistor 2, avoiding the welding of lumped resistors and reducing manufacturing costs. Simultaneously, the surface resistance of the graphene thin-film resistor 2 is controllable through an external voltage, thereby achieving adjustable filter attenuation. Additionally, the two passbands of the filter are connected in parallel via an input microstrip line 71 and an output microstrip line 72. The spacing between the two passbands ensures they do not interfere with each other, allowing for independent adjustment of the attenuation of each passband. This graphene-based dual-passband adjustable filter attenuator combines a dual-passband filter and an adjustable attenuator, achieving multifunctionality and high integration of microwave devices. It simplifies the circuit structure, reduces circuit size, and is easy to fabricate, showing great potential application in automatic level or gain control circuits in communication and radar systems.

[0031] In one possible implementation, both the first three-mode resonator 51 and the second three-mode resonator 52 consist of four metal stubs, including three quarter-wavelength open-circuit stubs, namely the first open-circuit stub 11, the second open-circuit stub 12, and the third open-circuit stub 13, and a shorter short-circuit stub 14. The length of the short-circuit stub 14 affects the passband bandwidth. In this embodiment, the electrical length of the short-circuit stub 14 is about 3° to 5°, which is used to adjust the bandwidth. The electrical length is the ratio of the physical length of the microstrip transmission line to the wavelength of the transmitted electromagnetic wave. The short-circuit stub 14 is short-circuited through a metal connector 4 that communicates with the bottom metal ground plane 8. Optionally, the metal connector 4 is a metal through hole or a metal cylinder. The short-circuit stub 14 can be selected from metal connectors 4, which are not limited to one, depending on the stub width.

[0032] In one possible implementation, in the three open-circuit stubs of the first tri-mode resonator 51 or the second tri-mode resonator 52, the open-circuit stubs on both sides are symmetrically bent, and the input microstrip line 71 and the output microstrip line 72 are arranged parallel to each other. Specifically, the first tri-mode resonator 51 or the second tri-mode resonator 52 bends two symmetrical open-circuit stubs, namely the first open-circuit stub 11 and the third open-circuit stub 13, so that the first tri-mode resonator 51 and the second tri-mode resonator 52 can be coupled by the same pair of parallel input microstrip lines 71 and output microstrip lines 72, making the external coupling structure very simple; a graphene thin film resistor 2 is added between the bent first open-circuit stub 11 and the third open-circuit stub 13 and the middle second open-circuit stub 12. Changing the external voltage of the graphene thin film resistor 2 causes the resistance value of the graphene thin film resistor 2 to change, thereby realizing the adjustable attenuation of the filter attenuator.

[0033] In this dual-passband adjustable filter attenuator, the two passbands are coupled in two ways through the input microstrip line 71 and the output microstrip line 72, so that the attenuation of the two passbands can be adjusted independently. However, the input microstrip line 71 and the output microstrip line 72 are not limited to being arranged in parallel. Under the condition that the input coupling of the first three-mode resonator 51 and the second three-mode resonator 52 is satisfied, the rest of the input microstrip line 71 and the output microstrip line 72 can be bent.

[0034] In one possible implementation, the internal components of the first tri-mode resonator 51 or the second tri-mode resonator 52 are symmetrically distributed about the short-circuit stub 14. Specifically, the entire first tri-mode resonator 51 or the second tri-mode resonator 52 is symmetrical about the short-circuit stub 14. Through analysis using the odd-even mode method, it can be determined that the first tri-mode resonator 51 or the second tri-mode resonator 52 has three resonant points. Therefore, by changing the length of the stub, different resonant frequencies can be achieved, and the first tri-mode resonator 51 or the second tri-mode resonator 52 can achieve different passbands.

[0035] In one possible implementation, each open-circuit stub of the first trimode resonator 51 and the second trimode resonator 52 can be bent according to actual needs to make the filter structure more compact, and the width of each stub of the first trimode resonator 51 and the second trimode resonator 52 can be changed according to actual needs.

[0036] In one possible implementation, an external voltage source is also included, connected to the graphene film resistor 2, to provide a variable external voltage to the graphene film resistor 2. By providing a variable external voltage to the graphene film resistor 2 through the external voltage source, the resistance value of the graphene film resistor 2 can be changed.

[0037] In one possible implementation, it also includes an input SMA port and an output SMA port; the input SMA port is connected to the input port 61, and the output SMA port is connected to the output port 62. The input port 61 and the output port 62 are located on the side of the lossy dielectric layer 3, and the input SMA port and the input port 61 and the output SMA port and the output port 62 can be soldered together.

[0038] In one possible implementation, the graphene thin film resistor 2 affects the impedance of the microstrip line and attenuates the electromagnetic waves transmitted within the microstrip line. While meeting design requirements, the graphene thin film resistor 2 can be any shape, such as square or circular.

[0039] In one possible implementation, the dielectric substrate of the lossy dielectric layer 3 can be a dielectric with any dielectric constant. Regarding the choice of dielectric, a substrate with a large dielectric constant allows for a smaller model size, while a substrate with a small loss angle results in lower losses but is more expensive. For example, Rogers RO4003 can be used, and Rogers RO5880 can be chosen to reduce losses. The metal microstrip line and metal ground plane 8 can be selected from any metal electroplated film material according to actual needs. Commonly used metal materials include silver, copper, or aluminum, with conductivity and cost decreasing sequentially.

[0040] This invention relates to a graphene-based dual-passband tunable filter attenuator. The equivalent circuit diagram of a single resonator 5 with a graphene thin-film resistor in the example is shown below. Figure 4 As shown, the graphene film resistor 2 is equivalent to a variable resistor connected in parallel across the microstrip line. The smaller the resistance, the less electromagnetic waves are transmitted through the microstrip line, and the greater the signal attenuation. Thus, the change in resistance value controls the change in signal level attenuation.

[0041] The working process of the graphene-based dual-passband tunable filter attenuator of this invention is as follows:

[0042] After the input signal enters the dual-passband adjustable filter attenuator through input port 61, it is coupled to the first tri-mode resonator 51 and the second tri-mode resonator 52 via input microstrip line 71. Due to the filtering characteristics of the tri-mode resonators, only electromagnetic signals with frequencies within two passbands can pass through the dual-passband adjustable filter attenuator, thus achieving dual-passband filtering. When the external voltage is 0V, the resistance of the graphene film resistor 2 is at its maximum. Since the graphene film resistor 2 is connected in parallel to the resonator, the signal can pass through both passbands almost completely with minimal attenuation. When the external voltage is increased, the resistance of the graphene film resistor 2 decreases, and the signal attenuation increases accordingly, thereby achieving adjustable attenuation of the dual-passband filter. Simultaneously, since the two passbands of the dual-passband adjustable filter attenuator have minimal mutual influence, the attenuation of the two passbands of the dual-passband adjustable filter attenuator can be controlled independently by controlling the external voltage of the graphene film resistor 2 on the two tri-mode resonators.

[0043] See Figure 5 This invention illustrates a graphene-based dual-passband tunable filter attenuator, employing... Figure 4 The equivalent circuit shown is simulated and tested, and the S-parameter results of the dual-passband adjustable filter attenuator are obtained. The lines marked with triangles are the S-parameter results of the dual-passband adjustable filter attenuator when the surface resistance of the graphene film resistor 2 is 70Ω and 300Ω (70Ω is the 1.2GHz passband and 300Ω is the 2.1GHz passband). The lines marked with squares are the S-parameter results of the dual-passband adjustable filter attenuator when the surface resistance of the graphene film resistor 2 is 150Ω and 600Ω. The lines marked with circles are the S-parameter results of the dual-passband adjustable filter attenuator when the surface resistance of the graphene film resistor 2 is 300Ω and 1200Ω.

[0044] It can be seen that within the two passbands of 1.2–1.3 GHz and 2–2.2 GHz, the S21 parameter of the dual-passband adjustable filter attenuator continuously increases as the sheet resistance of graphene decreases, achieving an attenuation from -3 dB to -10 dB; the return loss S11 continuously increases with the increase of attenuation, but remains less than -10 dB within the bandwidth, thus realizing the adjustable attenuation of the dual-passband filter.

[0045] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A graphene-based dual-passband tunable filter attenuator, characterized in that, It includes a lossy dielectric layer (3), a metal ground plane (8) is provided on one side of the lossy dielectric layer (3), and an input microstrip line (71), an output microstrip line (72), a first three-mode resonator (51) and a second three-mode resonator (52) are provided on the other side; An input port (61) is provided at one end of the input microstrip line (71), and an output port (62) is provided at one end of the output microstrip line (72). The input microstrip line (71) and the output microstrip line (72) are spaced apart, and a coupling interval is formed between the input microstrip line (71) and the output microstrip line (72). The first three-mode resonator (51) and the second three-mode resonator (52) are spaced apart inside the coupling interval. The first three-mode resonator (51) and the second three-mode resonator (52) each include three open-circuit stubs and one short-circuit stub (14). A graphene thin film resistor (2) is provided between two adjacent open-circuit stubs, and the sidewall of the graphene thin film resistor (2) is in close contact with the sidewall of the adjacent open-circuit stub. A metal connector (4) connected to the metal ground plane (8) is provided on the short-circuit stub (14). The three open-circuit stubs of the first three-mode resonator (51) or the second three-mode resonator (52) have the same length and are all one-quarter of the wavelength of the electromagnetic wave to be filtered; the electrical length of the short-circuit stub (14) is 3° to 5°. In the three open-circuit stubs of the first three-mode resonator (51) or the second three-mode resonator (52), the open-circuit stubs on both sides are symmetrically bent, and the input microstrip line (71) and the output microstrip line (72) are arranged in parallel. The internal components of the first three-mode resonator (51) or the second three-mode resonator (52) are symmetrically distributed about the short-circuit stub (14).

2. The graphene-based dual-passband tunable filter attenuator according to claim 1, characterized in that, It also includes an external voltage source, which is connected to the graphene film resistor (2) to provide a variable external voltage to the graphene film resistor (2).

3. The graphene-based dual-passband tunable filter attenuator according to claim 1, characterized in that, It also includes an input SMA port and an output SMA port; the input SMA port is connected to the input port (61), and the output SMA port is connected to the output port (62).

4. The graphene-based dual-passband tunable filter attenuator according to claim 1, characterized in that, The graphene thin film resistor (2) is square or circular in shape.

5. The graphene-based dual-passband tunable filter attenuator according to claim 1, characterized in that, The dielectric substrate of the lossy dielectric layer (3) is Rogers RO4003 or Rogers RO5880; the metal ground plane (8) is a metal electroplated film made of silver, copper or aluminum.

6. The graphene-based dual-passband tunable filter attenuator according to claim 1, characterized in that, The metal connector (4) is a metal through hole or a metal cylinder.

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