An active multifunctional metamaterial with four operation modes

Abstract

The application belongs to the technical field of multifunctional metamaterials, and provides an active multifunctional metamaterial with four working modes, which comprises an impedance layer, a first frequency selection layer and a second frequency selection layer, and the two frequency selection layers are of the same structure and size; a diode P1 is loaded in the impedance layer, diodes P2 and P3 are loaded in the frequency selection layers, and the diodes serve as switching devices to realize working mode switching of the active multifunctional metamaterial; specifically, a reflection-type linear-to-linear polarization converter (RLTL-PC): P1 is turned on, P2 is turned off, P3 is turned on, and an incident wave is x-polarized or y-polarized; an absorber: P1 is turned off, P2 and P3 are turned on, and an incident wave is u-polarized, v-polarized or x-polarized, y-polarized; a frequency selective surface (FSS): P1 is turned on, P2 and P3 are turned off, and an incident wave is x-polarized or y-polarized; and a transmission-type linear-to-circular polarization converter (TLTC-PC): P1 is turned on, P2 and P3 are turned off, and an incident wave is u-polarized or v-polarized.

Description

Technical Field

[0001] This invention belongs to the field of multifunctional metamaterials technology, specifically providing an active multifunctional metamaterial with four working modes. Background Technology

[0002] To improve the adaptability and integration of traditional metamaterials, active multifunctional metamaterials (AMMs) have been extensively studied in recent years. Metamaterials can be categorized into various types based on their function, such as frequency-selective surfaces (FSS), absorbers, and polarization converters (PCs). Generally, passive metamaterials with fixed unit structures exhibit static responses under electromagnetic wave incidence at a certain angle, while active metamaterials not only exhibit tunable characteristics without altering their basic operating mode but also can switch between multiple functions. Therefore, active metamaterials are the preferred solution for realizing highly complex and highly integrated materials.

[0003] PIN diodes are frequently used in the design of active metamaterials. Because PIN diodes can switch between states, active metamaterials exhibit two or more operating modes. Such active metamaterials, capable of switching between multiple functions, are also called active multifunctional metamaterials (AMMs). For example, Sun et al. (S. Sun, W. Jiang, S. Gong, and T. Hong, “Reconfigurable Linear-to-Linear Polarization Conversion Metasurface Based on PIN Diodes,” IEEE Antennas and Wireless Propagation Letters, vol. 17, no. 9, pp. 1722–1726, 2018.) proposed an AMM based on a double-slotted square ring structure, which has two operating modes: a reflection mode and a reflective linear-to-linear polarization converter (RLTL-PC) mode. PIN diodes are used as RF switches, placed in the gaps of the slotted square rings. When the PIN diodes are off, the symmetry of the cell is broken, achieving an anisotropic response of the RLTL-PC. When the diodes are on, the symmetry is restored, and the cell exhibits reflective characteristics. In addition, Phon et al. (R. Phon, S. Ghosh, and S. Lim, “Active Frequency Selective Surface to Switch Between Absorption and Transmission Band With Additional Frequency Tuning Capability,” IEEE Transactions on Antennas and Propagation, vol. 67, no. 9, pp. Sep. 2019.) proposed an AMM that switches between absorber and FSS modes by controlling the state of a PIN diode. It is worth mentioning that Phon's design also uses a varactor diode to adjust the transmission or absorption frequency.Furthermore, Li et al. (R.Li, J.Tian, ​​B.Jiang, Z.Lin, B.Chen, and H.Hu, “A switchable frequency selective rasorber with wide passband,” IEEE Antennas and Wireless Propagation Letters, vol.20, no.8, pp.1567–1571, 2021.) proposed an active absorber-transmitter integrated material with a switchable transmission window, whose operating mode can switch between absorber-transmitter integrated mode and absorber mode. However, the AMMs mentioned above can only switch between two operating modes.

[0004] To improve integrity and integration, AMMs with more operating modes have been proposed. For example, Liang et al. (J.Liang, Q.Cao, Y.Wang, and Z.Wan, “A Multifunctional and Miniaturized Flexible Active Frequency Selective Surface,” IEEE Antennas and Wireless Propagation Letters, vol.20, no.12, pp.2549–2553, 2021.) proposed an AMM with three modes: a polarization-insensitive FSS, a reflector mode, and a polarization-selective mode in the 8–12 GHz range. For example, Shah et al. (G. Shah, Q. Cao, ZUAbidin, Y. Jing, and M. Azeem, “A4-Bit Multistate Frequency-Selective Surface With Dual-Band Multifunction Response,” IEEE Antennas and Wireless Propagation Letters, vol. 20, no. 10, pp. Oct. 2021.) proposed a dual-band AMM that can switch between FSS, reflector, and polarization-selective modes. Compared to the AMM proposed by Liang, Shah's AMM can exhibit more operating modes by controlling the two frequency bands separately. In fact, since a device in polarization-selective mode can act as both an FSS and a reflector of a specific polarization wave, polarization-selective mode can also be considered a specific state rather than an operating mode. Therefore, it is evident that existing AMMs rarely have more than three operating modes. Summary of the Invention

[0005] The purpose of this invention is to propose an active multifunctional metamaterial with four operating modes, mainly composed of an impedance layer and two frequency selective surfaces. The active multifunctional metamaterial loads PIN diodes in the impedance layer and the frequency selective surfaces, and controls the diodes separately through a DC bias signal, thereby realizing the switching between reflective linear-to-linear polarization converter (RLTL-PC), absorber, frequency selective surface (FSS) and transmission linear-to-circular polarization converter (TLTC-PC) modes.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] An active multifunctional metamaterial with four working modes includes, from top to bottom, a first metal patch layer 1, a first dielectric layer 2, a second metal patch layer 3, a first air layer 4, a third metal patch layer 5, a second dielectric layer 6, a fourth metal patch layer 7, a second air layer 8, a fifth metal patch layer 9, a third dielectric layer 10, and a sixth metal patch layer 11.

[0008] The invention is characterized in that a first metal patch layer and a second metal patch layer are respectively disposed on the upper and lower surfaces of a first dielectric layer, and the three together constitute an impedance layer; a third metal patch layer and a fourth metal patch layer are respectively disposed on the upper and lower surfaces of a second dielectric layer, and the three together constitute a first frequency selective layer; a fifth metal patch layer and a sixth metal patch layer are respectively disposed on the upper and lower surfaces of a third dielectric layer, and the three together constitute a second frequency selective layer; a first air layer is disposed between the impedance layer and the first frequency selective layer, and a second air layer is disposed between the first frequency selective layer and the second frequency selective layer; the second frequency selective layer and the first frequency selective layer have the same structure and size; a first PIN diode is loaded in the impedance layer, and a second PIN diode and a third PIN diode are loaded in the frequency selective layer; the first PIN diode, the second PIN diode, and the third PIN diode serve as switching devices to achieve the switching of the working mode of the active multifunctional metamaterial.

[0009] Furthermore, the first metal patch layer is composed of n×n first metal patch units arranged in an array, and the second metal patch layer is composed of n×n second metal patch units arranged in an array. The first metal patch units and the second metal patch units are arranged facing each other and together with the first dielectric layer, they form an impedance unit.

[0010] The first metal patch unit and the second metal patch unit adopt the same structure and are centrally symmetrical, including: a first rectangular patch and a spiral resonator connected to its two ends. The connection between the first rectangular patch and the spiral resonator adopts a linear gradient transition structure. A first loading gap is opened at each end of the first rectangular patch. The first loading gap is adjacent to the linear gradient transition structure and a loading resistor 12 is loaded therein. A first PIN diode 13 is loaded at the center of the spiral resonator. The spiral resonators of adjacent first metal patch units are connected accordingly.

[0011] Both the first metal patch unit and the second metal patch unit are arranged along the centerline of the first dielectric layer. The first metal patch unit is arranged along the y-axis direction, and the second metal patch unit is arranged along the x-axis direction.

[0012] Furthermore, the third metal patch layer is composed of an array of 2n×2n third metal patch units, and the fourth metal patch layer is composed of an array of 2n×2n fourth metal patch units.

[0013] The third metal patch unit is arranged along the y-axis and includes: a first barbell-shaped patch and two bent inductors 15; the first barbell-shaped patch is located at the quarter-unit position of the third metal patch unit in the x-axis direction. The barbell-shaped patch has a centrally symmetrical structure and is composed of a second rectangular patch and circular patches at both ends. The two ends of the first barbell-shaped patch have second loading gaps, which are located outside the circular patches and loaded with second PIN diodes 14; the two bent inductors 15 have the same structure and are connected in series at the three-quarter-unit position of the third metal patch unit in the x-axis direction; the barbell-shaped patches and bent inductors are connected to each other in adjacent third metal patch units; for each third metal patch unit, every 2×2 subarray corresponds to an impedance unit, and the impedance unit is translated by T1 / 8 along the x-axis and by T1 / 4 along the y-axis, where T1 is the unit period of the impedance unit;

[0014] The fourth metal patch unit is arranged along the x-axis and includes a second barbell-shaped patch and a third barbell-shaped patch. The second barbell-shaped patch is located at the one-quarter unit position along the y-axis of the fourth metal patch unit, and the third barbell-shaped patch is located at the three-quarter unit position along the y-axis of the fourth metal patch unit. A third loading slot is opened at each end of the third barbell-shaped patch. The third loading slot is located outside the circular patch and a third PIN diode 16 is loaded therein. The barbell-shaped patches of adjacent fourth metal patch units are connected accordingly. For each fourth metal patch unit, there is a one-to-one correspondence between the fourth and third metal patch units, and the fourth metal patch unit is translated by T2 / 4 along the x-axis and y-axis relative to the third metal patch unit, respectively. T2 is the unit period of the third and fourth metal patch units.

[0015] Furthermore, the range of values ​​for n is ≥5.

[0016] Furthermore, the first barbell-shaped patch has the same structure and size as the second barbell-shaped patch, and the third barbell-shaped patch has the same structure as the second barbell-shaped patch, but the size of the third barbell-shaped patch is larger than that of the second barbell-shaped patch.

[0017] Furthermore, the active multifunctional metamaterial has four operating modes, namely: a reflective linear-to-linear polarization converter (RLTL-PC), an absorber, a frequency selective surface (FSS), and a transmissive linear-to-circular polarization converter (TLTC-PC).

[0018] Reflective Linear-to-Linear Polarization Converter (RLTL-PC): The first PIN diode is on, the second PIN diode is off, the third PIN diode is on, and the incident wave is either u-polarized or v-polarized;

[0019] Absorber: The first PIN diode is off, the second PIN diode is on, the third PIN diode is on, and the incident wave is u-polarized, v-polarized, or x-polarized, y-polarized;

[0020] Frequency Selective Surface (FSS): The first PIN diode is on, the second PIN diode is off, the third PIN diode is off, and the incident wave is either x-polarized or y-polarized;

[0021] Transmission-type linear-circular polarization converter (TLTC-PC): The first PIN diode is on, the second PIN diode is off, the third PIN diode is off, and the incident wave is u-polarized or v-polarized.

[0022] Based on the above technical solution, the beneficial effects of the present invention are as follows:

[0023] This invention provides an active multifunctional metamaterial with four operating modes: a reflective linear-to-linear polarization converter (RLTL-PC), an absorber, a frequency selective surface (FSS), and a transmissive linear-to-circular polarization converter (TLTC-PC). PIN diodes are loaded in the impedance layer and frequency layer as switching devices to achieve effective switching between the four operating modes. Specifically:

[0024] 1. The present invention loads a switchable LC resonator controlled by a first PIN diode on the impedance layer, which enables it to switch between the absorber and the frequency-selective mode, while also reducing the insertion loss of the impedance layer and ensuring the amplitude and phase conditions of the device in a wide frequency band.

[0025] 2. In this invention, different metal patch units are designed on both sides of the dielectric substrate in the double-layer FSS to introduce anisotropic response. At the same time, a second PIN diode and a third PIN diode are loaded to realize switchable anisotropic second-order frequency selection. When the third PIN diode is in the open or closed state, the matching parameter is optimally valued, introducing a 180° or 90° phase difference between u polarization and v polarization, while ensuring that the reflection (or transmission) amplitudes of the two polarizations are equal, corresponding to the realization of RLTL-PC or TLTC-PC mode.

[0026] 3. The present invention is configured with a dual-layer frequency selective surface (FSS), and the passbands of both polarizations (x-polarization and y-polarization) have high sideband roll-off rates, which can provide excellent out-of-band suppression characteristics; at the same time, the passband of the active multifunctional metamaterial can remain stable under 40° oblique incident angle. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the active multifunctional metamaterial with four working modes in this invention.

[0028] Figure 2 This is a schematic diagram of the impedance layer of the active multifunctional metamaterial with four working modes in this invention.

[0029] Figure 3 This is a schematic diagram of the frequency-selective layer of the active multifunctional metamaterial with four operating modes in this invention.

[0030] Figure 4 This is the equivalent circuit diagram of the active multifunctional metamaterial with four operating modes in this invention.

[0031] Figure 5 The above diagram shows the frequency response simulation results of an active multifunctional metamaterial with four operating modes in an embodiment of the present invention. Detailed Implementation

[0032] To make the objectives, technical solutions, and beneficial effects of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0033] This embodiment provides an active multifunctional metamaterial with four operating modes, the structure of which is as follows: Figure 1As shown, (a) is a three-dimensional structural schematic diagram and (b) is a side view structural schematic diagram. From top to bottom (in the -z axis direction), the layers are: first metal patch layer 1, first dielectric layer 2, second metal patch layer 3, first air layer 4, third metal patch layer 5, second dielectric layer 6, fourth metal patch layer 7, second air layer 8, fifth metal patch layer 9, third dielectric layer 10, and sixth metal patch layer 11. The first metal patch layer 1 and the second metal patch layer 3 are respectively disposed on the upper and lower surfaces of the first dielectric layer 2, and together they form an impedance layer. The third metal patch layer 5 and the fourth metal patch layer 7 are respectively disposed on the upper and lower surfaces of the second dielectric layer 6, and together they form a first frequency selective layer. The fifth metal patch layer 9 and the sixth metal patch layer 11 are respectively disposed on the upper and lower surfaces of the third dielectric layer 10, and together they form a second frequency selective layer. A first air layer 4 is disposed between the impedance layer and the first frequency selective layer, and a second air layer 8 is disposed between the first frequency selective layer and the second frequency selective layer.

[0034] Furthermore, the first metal patch layer is composed of an array of n×n first metal patch units, and the second metal patch layer is composed of an array of n×n second metal patch units. The first and second metal patch units are arranged facing each other and together with the first dielectric layer, they form an impedance unit. Figure 2 As shown, (a) is the first metal patch unit and (b) is the second metal patch unit; the first metal patch unit and the second metal patch unit adopt the same structure and are centrally symmetrical, both of which are arranged along the centerline of the first dielectric layer and are perpendicular to each other;

[0035] like Figure 2 As shown in (a), the first metal patch unit is arranged along the y-axis direction and includes: a first rectangular patch and a spiral resonator connected to its two ends; the connection between the two ends of the first rectangular patch and the spiral resonator adopts a linear gradient transition structure, and the two ends of the first rectangular patch are respectively opened along the x-axis direction with a first loading gap, the first loading gap is adjacent to the linear gradient transition structure, and a loading resistor 12 is loaded therein; a first PIN diode 13 is loaded at the center of the spiral resonator, and the spiral resonators between adjacent first metal patch units are connected accordingly;

[0036] like Figure 2 As shown in (b), the second metal patch unit is arranged along the x-axis direction;

[0037] In this embodiment, the impedance unit has a size of 20mm × 20mm. The first and second metal patch units have the same dimensions except for the spiral resonator. The central portion of the first rectangular patch after the loading slot is opened has a size of 3mm × 6.6mm, the width of the first loading slot is 0.4mm, and the resistance of resistor 12 is 150Ω. In the first metal patch unit, the spiral resonator has a clockwise structure, a linewidth of 0.2mm, a gap in the y-direction of 0.2mm, a gap in the x-direction at the PIN diode loading location of 0.45mm, and gaps in the x-direction at other locations. The linewidth of the spiral resonator is 0.2mm, the total length in the x-direction is 2.3mm, the total length in the y-direction is 3.9mm, and the distance between the spiral resonator and the first PIN diode 13 is 0.2mm. In the second metal patch unit, the spiral resonator has a clockwise structure, the linewidth of the spiral resonator is 0.2mm, the gap in the x-direction is 0.3mm, the gap in the y-direction at the PIN diode loading point is 0.65mm, and the gap in the y-direction at other locations is 0.3mm. The total length in the x-direction is 3.3mm, the total length in the y-direction is 2.7mm, and the distance between the spiral resonator and the first PIN diode 13 is 0.3mm.

[0038] Furthermore, the third metal patch layer is composed of an array of 2n×2n third metal patch units, and the fourth metal patch layer is composed of an array of 2n×2n fourth metal patch units. The structures of the third and fourth metal patch units are as follows: Figure 3 As shown, (a) is the third metal patch unit, (b) is the fourth metal patch unit, and (c) is the positional relationship between the third metal patch unit and the fourth metal patch unit;

[0039] like Figure 3 As shown in (a), the third metal patch unit is arranged along the y-axis and includes: a first barbell-shaped patch and two bent inductors 15; the first barbell-shaped patch is located at the quarter-unit position of the third metal patch unit in the x-axis direction, the barbell-shaped patch has a centrally symmetrical structure, and is composed of a second rectangular patch and circular patches at both ends. The two ends of the first barbell-shaped patch are respectively opened with second loading gaps along the x-axis direction. The second loading gaps are located outside the circular patches and are loaded with second PIN diodes 14; the two bent inductors 15 adopt the same structure, are connected in series and are located at the three-quarter-unit position of the third metal patch unit in the x-axis direction; the barbell-shaped patches and bent inductors are connected to each other in adjacent third metal patch units; for the third metal patch unit, every 2×2 subarray corresponds to an impedance unit, and is translated T1 / 8 relative to the impedance unit along the x-axis and T1 / 4 relative to the y-axis, where T1 is the unit period of the impedance unit;

[0040] like Figure 3As shown in (b), the fourth metal patch unit is arranged along the x-axis and includes: a second barbell-shaped patch and a third barbell-shaped patch; the second barbell-shaped patch is located at the one-quarter unit position along the y-axis of the fourth metal patch unit, and the third barbell-shaped patch is located at the three-quarter unit position along the y-axis of the fourth metal patch unit. A third loading slot is formed at each end of the third barbell-shaped patch along the y-axis. The third loading slot is located outside the circular patch and a third PIN diode 16 is loaded therein. The barbell-shaped patches of adjacent fourth metal patch units are connected accordingly. For each fourth metal patch unit, the fourth metal patch unit corresponds to the third metal patch unit, and is translated by T2 / 4 along the x-axis and y-axis relative to the third metal patch unit, respectively. T2 is the unit period of the third and fourth metal patch units, and T2 = T1 / 2. Figure 3 As shown in (c);

[0041] In this embodiment, the line width of the bent inductor 15 is 0.2 mm, the gap of the bent portion is 0.2 mm, the total length of a single bent inductor in the y direction is 3.4 mm, and the distance between adjacent bent inductors is 1.6 mm; the first barbell-shaped patch and the second barbell-shaped patch have the same dimensions, the radius of the circular patch is 0.9 mm, the distance between the two centers is 5 mm, the size of the rectangular patch is 0.8 mm × 10 mm, and the width of the second loading gap is 0.4 mm; in the third barbell-shaped patch, the radius of the circular patch is 1.35 mm, the distance between the two centers is 5 mm, and the size of the rectangular patch is 2 mm × 10 mm.

[0042] Furthermore, the second frequency selection layer has the same structure and size as the first frequency selection layer. Specifically, the fifth metal patch layer is composed of 2n×2n fifth metal patch units arranged in an array, and the sixth metal patch layer is composed of 2n×2n sixth metal patch units arranged in an array. The fifth metal patch unit has the same structure and size as the third metal patch unit, and the sixth metal patch unit has the same structure and size as the fourth metal patch unit.

[0043] Furthermore, the PIN diode is preferably a Skyworks SMP-1345, with a typical capacitance of 0.118 pF in the off state and a typical resistance of 1 ohm in the on state; all PIN diodes are of the same model; the resistance on the first and second metal layers is R = 150 Ω; the thickness of the first, second, and third dielectric layers is 0.5 mm, the thickness of the first air layer is 15 mm, and the thickness of the second air layer is 10 mm; all dielectric layers (substrates) are F4B, with a relative permittivity of ε. r =3.0, loss tangent is tanδ=0.0015; all metal patch layers are PCB printed circuits.

[0044] In terms of working principle:

[0045] like Figure 4 The diagram shown is the equivalent circuit diagram of the active multifunctional metamaterial of this invention. In this diagram, the series-connected inductor L1 and resistor R1 serve as an impedance layer. A switchable LC resonant circuit containing a PIN diode P1 is introduced into the impedance layer. Two switchable LC resonant circuits containing PIN diodes P2 and P3 are cascaded to form a second-order FSS. Since the double-layer FSS introduces anisotropic response through the inductors printed on both sides of the dielectric substrate and the mutually perpendicular capacitors (the PIN diodes introduce equivalent capacitance), and the transmission line in the equivalent circuit diagram is equivalent to a quarter-wavelength converter to introduce a phase difference, the device can achieve polarization conversion while ensuring that the transmission or reflection amplitudes of the two polarized waves are equal. By controlling the states of PIN diodes P1, P2, and P3, the device can switch between four operating modes. When P2 and P3 are both off, the parasitic capacitance of the frequency selective layer and the parallel inductance form an LC resonator, becoming the frequency selective surface, and the device is in the transmission state. Furthermore, because the dimensions and positional structure of the metal sheets on both sides of the dielectric substrate are not perfectly symmetrical, the double-layer FSS exhibits anisotropic response. When the incident wave is u-polarized or v-polarized, the AMM can achieve TLTC-PC; when the incident wave is x-polarized or y-polarized... The AMM can achieve FSS (Firmware Slip-Slip). When diode P3 is in the open state, the device as a whole is in a reflective state. By controlling P2 individually, the RLTL-PC mode or absorber mode can be selected in the reflective state. When P2 is closed and the incident wave is u-polarized or v-polarized, the AMM can achieve RLTL-PC (when P2 is closed and the incident wave is x-polarized or y-polarized, the device does not work). When P2 is open and the incident wave is u-polarized, v-polarized, or x-polarized, y-polarized, the AMM can achieve absorber mode. When P2 is open and P3 is closed, the device does not work. In RLTL-PC, TLTC-PC, and FSS modes, PIN diode P1 is open. At this time, the resonant frequency of the impedance layer can match the transmission band of the double-layer FSS, significantly reducing the insertion loss of the device. In absorber mode, PIN diode P1 is closed, causing the resonant frequency of the impedance layer resonator to shift out of the matching range, as shown in the table below.

[0046]

[0047] like Figure 5 The figure shows the electromagnetic simulation results of the active multifunctional metamaterial (AMM) with four working modes in this embodiment under periodic boundary conditions and linearly polarized wave incidence in high-frequency electromagnetic simulation software. Among them, (a) is the reflection coefficient in RLTL-PC mode. In the figure, R uu R vv and R uv R vu(a) represents the common and cross components of the reflection coefficient along the u and v directions, respectively. It can be seen that the u-polarized incident wave is successfully converted into the v-polarized incident wave, and vice versa; (b) represents the reflection coefficient R in absorber mode. xx R yy With transmission coefficient T xx T yy The device exhibits low reflection and transmission characteristics (i.e., the amplitudes of both reflection and transmission coefficients are less than -10 dB) in the 2.08–5.69 GHz range, with a relative absorption bandwidth of 92.9%. Verification shows that the electromagnetic wave absorption rate of the AMM exceeds 80% in both x and y polarizations from 2.3 to 6.2 GHz; (c) shows the reflection coefficient R in FSS mode. xx R yy With transmission coefficient T xx T yy The AMM exhibits low insertion loss anisotropic transmission coefficients in x-polarization (3.42–5.33 GHz) and y-polarization (4.61–5.93 GHz), respectively. Furthermore, since the PIN diodes on each layer of the AMM can be independently switched on x-polarization and y-polarization, polarization selectivity is also achieved. For the selected x-polarization or y-polarization, the reflection, absorption, and transmission responses can be switched respectively. (d) shows the phase spectrum of the transmission coefficient in TLTC-PC mode. Since the AMM can switch from FSS mode to TLTC-PC mode by changing the polarization direction of the incident wave from x or y to u or v, the amplitude spectrum of the transmission coefficient in TLTC-PC mode is as follows: Figure 5 As shown in (c), the axial ratio (AR) is less than 3 dB at around 5 GHz.

[0048] The above description is merely a specific embodiment of the present invention. Any feature disclosed in this specification may be replaced by other equivalent or similar features unless otherwise specified. All disclosed features, or steps in all methods or processes, may be combined in any way except for mutually exclusive features and / or steps.

Claims

1. An active multifunctional metamaterial with four operating modes, comprising: From top to bottom, the layers are: first metal patch layer (1), first dielectric layer (2), second metal patch layer (3), first air layer (4), third metal patch layer (5), second dielectric layer (6), fourth metal patch layer (7), second air layer (8), fifth metal patch layer (9), third dielectric layer (10), and sixth metal patch layer (11). The invention is characterized in that a first metal patch layer and a second metal patch layer are respectively disposed on the upper and lower surfaces of a first dielectric layer, and the three together constitute an impedance layer; a third metal patch layer and a fourth metal patch layer are respectively disposed on the upper and lower surfaces of a second dielectric layer, and the three together constitute a first frequency selective layer; a fifth metal patch layer and a sixth metal patch layer are respectively disposed on the upper and lower surfaces of a third dielectric layer, and the three together constitute a second frequency selective layer; a first air layer is disposed between the impedance layer and the first frequency selective layer, and a second air layer is disposed between the first frequency selective layer and the second frequency selective layer; the second frequency selective layer and the first frequency selective layer have the same structure and size; a first PIN diode is loaded in the impedance layer, and a second PIN diode and a third PIN diode are loaded in the frequency selective layer; the first PIN diode, the second PIN diode, and the third PIN diode serve as switching devices to achieve the switching of the working mode of the active multifunctional metamaterial. The active multifunctional metamaterial has four operating modes, namely: a reflective linear-to-linear polarization converter, an absorber, a frequency-selective surface, and a transmissive linear-to-circular polarization converter. Reflective linear-to-linear polarization converter: the first PIN diode is on, the second PIN diode is off, the third PIN diode is on, and the incident wave is either u-polarized or v-polarized; Absorber: The first PIN diode is off, the second PIN diode is on, the third PIN diode is on, and the incident wave is u-polarized, v-polarized, or x-polarized, y-polarized; Frequency selective surface: the first PIN diode is on, the second PIN diode is off, the third PIN diode is off, and the incident wave is either x-polarized or y-polarized; Transmissive linear-circular polarization converter: the first PIN diode is on, the second PIN diode is off, the third PIN diode is off, and the incident wave is u-polarized or v-polarized.

2. The active multifunctional metamaterial with four working modes as described in claim 1, characterized in that, The first metal patch layer is composed of n×n first metal patch units arranged in an array, and the second metal patch layer is composed of n×n second metal patch units arranged in an array. The first metal patch units and the second metal patch units are arranged facing each other and together with the first dielectric layer, they form an impedance unit. The first metal patch unit and the second metal patch unit adopt the same structure and are centrally symmetrical, including: a first rectangular patch and a spiral resonator connected to its two ends. The connection between the first rectangular patch and the spiral resonator adopts a linear gradient transition structure. A first loading gap is opened at both ends of the first rectangular patch. The first loading gap is adjacent to the linear gradient transition structure and a loading resistor (12) is loaded therein. A first PIN diode (13) is loaded at the center of the spiral resonator. The spiral resonators of adjacent first metal patch units are connected accordingly. Both the first metal patch unit and the second metal patch unit are arranged along the centerline of the first dielectric layer. The first metal patch unit is arranged along the y-axis direction, and the second metal patch unit is arranged along the x-axis direction.

3. The active multifunctional metamaterial with four working modes as described in claim 1, characterized in that, The third metal patch layer is composed of an array of 2n×2n third metal patch units, and the fourth metal patch layer is composed of an array of 2n×2n fourth metal patch units. The third metal patch unit is arranged along the y-axis and includes: a first barbell-shaped patch and two bent inductors (15); the first barbell-shaped patch is located at the quarter-unit position of the third metal patch unit in the x-axis direction. The barbell-shaped patch has a centrally symmetrical structure and is composed of a second rectangular patch and circular patches at both ends. The two ends of the first barbell-shaped patch are respectively opened with second loading gaps. The second loading gaps are located outside the circular patches and are loaded with second PIN diodes (14); the two bent inductors (15) adopt the same structure and are arranged in series at the three-quarter-unit position of the third metal patch unit in the x-axis direction; the barbell-shaped patches and bent inductors are connected to each other between adjacent third metal patch units; for the third metal patch unit, each 2×2 subarray corresponds to an impedance unit, and is translated T1 / 8 relative to the impedance unit along the x-axis and T1 / 4 relative to the y-axis. T1 is the unit period of the impedance unit; The fourth metal patch unit is arranged along the x-axis and includes: a second barbell-shaped patch and a third barbell-shaped patch; the second barbell-shaped patch is located at the one-quarter unit position in the y-axis direction of the fourth metal patch unit, and the third barbell-shaped patch is located at the three-quarter unit position in the y-axis direction of the fourth metal patch unit. The third barbell-shaped patch has a third loading gap at each end. The third loading gap is located outside the circular patch and a third PIN diode (16) is loaded therein; the barbell-shaped patches of adjacent fourth metal patch units are connected accordingly; for the fourth metal patch unit, the fourth metal patch unit corresponds one-to-one with the third metal patch unit and is translated by T2 / 4 along the x-axis and y-axis respectively relative to the third metal patch unit, where T2 is the unit period of the third and fourth metal patch units.

4. The active multifunctional metamaterial having four working modes as described in claim 2 or 3, characterized in that, The range of values ​​for n is ≥5.

5. The active multifunctional metamaterial with four working modes as described in claim 3, characterized in that, The first barbell-shaped patch has the same structure and size as the second barbell-shaped patch, and the third barbell-shaped patch has the same structure as the second barbell-shaped patch, but the third barbell-shaped patch is larger than the second barbell-shaped patch.

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