2-bit phase tunable active dual-polarized metasurface

Abstract

The application provides a 2-bit phase-controllable active dual-polarized metasurface, aiming at solving the problems of low working efficiency, few control states and polarization sensitivity of the existing active metasurface. The application comprises, from top to bottom, an active layer, a first dielectric layer, a reflection layer, a second dielectric layer and a feeding layer; the active layer is composed of a metal patch, an inductor and a switch diode element, and is welded at a gap of the metal patch; the reflection layer is basically covered by metal. The feeding layer provides two independent feeding circuits, can load a direct current voltage, and controls the working state of the metasurface. The metallized via connects the metal patch of the active layer to the feeding circuit, and corresponding apertures are left in the dielectric layer and the reflection layer. The active metasurface has polarization insensitivity, and exhibits high-efficiency 2-bit phase control characteristics, i.e. the phase difference of electromagnetic responses in each state is 90°. The application takes into account multiple factors such as cost, manufacturing complexity and performance, and has good application prospect.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of artificial electromagnetic metamaterials, and particularly relates to a 2-bit phase-controllable active dual-polarized metasurface. BACKGROUND

[0002] Active metasurfaces can realize dynamic regulation of electromagnetic waves in multiple dimensions, including frequency spectrum, phase, amplitude, polarization, etc. Such powerful regulation of electromagnetic waves has attracted widespread attention in the scientific community and is expected to be applied to new-generation communication systems, radar systems, imaging systems and stealth design.

[0003] For active metasurface design in the microwave band, active devices such as switch diodes, varactor diodes or liquid crystals are usually loaded inside the metasurface to realize the controllable function. Among them, the active metasurface integrated with switch diodes is the most obvious design method, which has the characteristics of high efficiency, high cutoff frequency, ultra-fast response speed, simple control circuit, easy large-scale integration and low cost. However, switch diodes only have two switchable states, which limits the number of switchable dimensions and states of the active metasurface. At present, most active metasurface designs based on switch diodes focus on single-polarized 1-bit phase-controllable design, single-polarized 2-bit phase-controllable design, and dual-polarized 1-bit phase-controllable design. 1-bit means 2 control states, and 2-bit means 4 control states. In specific applications, single-polarized design makes the metasurface polarization-sensitive, which can only effectively regulate single-polarized waves; the limitation of phase control state will cause a large difference between the actual phase compensation and the theoretical value. This makes it difficult to effectively and accurately control the re-radiation field of the metasurface, further reduces the overall efficiency of the system, increases the inherent loss, and is difficult to meet the actual application requirements.

[0004] Therefore, from the application point of view, it is urgent to explore a dual-polarized multi-bit phase-controllable active metasurface design scheme based on switch diodes to improve the performance of active metasurfaces in various application scenarios. SUMMARY

[0005] The purpose of the application is to provide a 2-bit phase-controllable dual-polarized active metasurface to improve the polarization sensitivity and the small number of phase control states in active design.

[0006] Technical scheme: To achieve the above purpose, the 2-bit phase-controllable active dual-polarized metasurface provided by the application is a multi-layer periodic active metasurface structure, which includes an active layer, a first dielectric layer, a reflection layer, a second dielectric layer and a feed layer from top to bottom. The metallized via in the structure sequentially passes through the first dielectric layer, the reflection layer and the second dielectric layer, and connects part of the metal patches of the active layer and the feed layer.

[0007] The unit structure of the active layer is arranged in central axis symmetry, including a central region, an outer ring region, and four connection regions with the same structure, and the four connection regions can completely coincide by rotating 90°, 180°, and 270° around the center of the unit; each connection region includes first to fourth metal patches, which are connected in turn through switch diodes; the first metal patch is connected to the central region through an inductor, the second and fourth metal patches are connected to the outer ring region through inductors, and the third metal patch is connected to the feed layer through a metal strip, an inductor, and a metallized via; the working state of the switch diode is controlled by loading a feed voltage on the feed layer, and the four states of the metasurface are regulated and controlled.

[0008] Specifically, the four-state regulation mode of the metasurface is that the on-off states of the two switch diodes directly connected to the first metal patch are the same, and the on-off state is recorded as A; the on-off states of the two switch diodes directly connected to the third metal patch are the same, and the on-off state is recorded as B; A and B are not affected by each other; A and B are both turned off, one is turned on, and the other is turned off, and the simultaneous turn-on corresponds to the four states of the metasurface.

[0009] As a preferred embodiment, the unit structure of the active layer is square, the central region of the unit structure is a 45°-inclined cross-shaped metal patch with a metallized via in the center, and the four ends are connected to the four connection regions through four inductors; the outer ring region of the unit structure is a square ring connected to the boundary, and is used for the common anode or common cathode of the switch diode feed.

[0010] As a preferred embodiment, the first to fourth metal patches in each connection region are four open square rings, all of which face the inside, and a 45°-inclined dumbbell-shaped metal patch is arranged in the middle; the dumbbell-shaped metal patch is connected to the metallized via on the side close to the center of the unit, and is welded with an inductor, and is connected to the third metal patch through an inductor on the other side.

[0011] As a preferred embodiment, in a unit structure of the reflective layer, the metal is covered, and circular pores with a diameter larger than that of the metallized via are arranged at the positions of the metallized vias.

[0012] As a preferred embodiment, in a unit structure of the feed layer, the central metallized via is connected to the central metal patch; the four metallized vias around the central metal patch are connected to the metal ring outside the central metal patch through metal strips; one unit structure has two feed circuits, and independent feeding of the four states of the unit is realized.

[0013] As a preferred embodiment, the central metal patch is connected to the metal feed line outside through an inductor or a zero-ohm resistor across the metal ring, and any point on the metal patch at the position of the metallized via is connected to the metal feed line; the positions of the metal feed lines are staggered, and independent feeding of each metasurface unit and state is realized.

[0014] Beneficial effects: By regulating the working state of the active layer switch diode, the metasurface unit presents four phase states with a difference of 90° in the design frequency band and the dual-polarization state, thereby realizing dynamic regulation of 2-bit reflective phase. Compared with the prior art, the 2-bit phase controllable dual-polarized active metasurface provided by the application has the following advantages: 1. Through strict symmetry design, the generation of cross-polarization is reduced, and the regulation of arbitrary polarized electromagnetic waves is further effectively realized. 2. The combination of multiple diodes produces four equivalent electromagnetic structures, realizes 2-bit reflective phase, and can satisfy the accurate and high-quality real-time control of the reradiation field of arbitrary incoming waves in various application scenarios, such as single-beam, multi-beam and vortex wave complex regulation. 3. If the application is applied to communication, radar or imaging systems, the signal-to-noise ratio of the system can be effectively improved, and the system loss can be reduced. 4. The application can be processed by conventional printed circuit board and patch technology, and is easy to process and manufacture. 5. The application can be scaled or adjusted according to different working frequency bands, and the key parameters of the structure proposed in the application can be flexibly designed. BRIEF DESCRIPTION OF DRAWINGS

[0015] Figure 1 is a three-dimensional structure schematic diagram of the metasurface unit in the embodiment of the application.

[0016] Figure 2 is a side view structure schematic diagram of the metasurface unit in the embodiment of the application.

[0017] Figure 3 is a planar structure schematic diagram of the active layer in the embodiment of the application.

[0018] Figure 4 is a planar structure schematic diagram of the reflective layer in the embodiment of the application.

[0019] Figure 5 is a planar structure schematic diagram of the feeding layer in the embodiment of the application.

[0020] Figure 6 is a 2-bit phase controllable dual-polarized active metasurface in the embodiment of the application, and the reflection amplitude diagram corresponding to the four states when the TE polarized electromagnetic wave is normally incident.

[0021] Figure 7 is a 2-bit phase controllable dual-polarized active metasurface in the embodiment of the application, and the reflection amplitude diagram corresponding to the four states when the TM polarized electromagnetic wave is normally incident.

[0022] Figure 8 is a 2-bit phase controllable dual-polarized active metasurface in the embodiment of the application, and the reflection phase diagram corresponding to the four states when the TE polarized electromagnetic wave is normally incident.

[0023] Figure 9 is a 2-bit phase controllable dual-polarized active metasurface in the embodiments of the present application, and the reflection phase diagram corresponding to the 4 states when the TM polarized electromagnetic wave is normally incident.

[0024] Icon: 1: active layer; 2: reflection layer; 3: feed layer; 4: first dielectric layer; 5: second dielectric layer; L1~L8: inductor; P1~P4: switch diode; T1, T2: feed line. DETAILED DESCRIPTION

[0025] The technical solutions of the present application will be further described in detail below in combination with the drawings and specific embodiments.

[0026] As shown in Figure 1 and 2 , it is a 2-bit phase controllable dual-polarized active metasurface unit three-dimensional schematic diagram and side view, the present example contains active layer, reflection layer, feed layer, dielectric layer. From top to bottom along the z-axis are active layer, first dielectric layer, reflection layer, second dielectric layer and feed layer. The overall structure takes the unit as the basic element, which is freely copied and extended periodically, and the size of the overall structure is freely selected according to the application scenario.

[0027] In one structural unit of the active layer, metal patches are etched on the upper surface of the first dielectric layer, and inductors and switch diode elements are welded at the gaps of some metal patches; the metal patches and circuit elements of one unit of the active layer can completely coincide by rotating 90°, 180°, 270° around the center of the square substrate unit. Each unit structure of the active layer includes a central region, an outer ring region, and four connection regions with the same structure, each connection region includes first to fourth metal patches, and the first to fourth metal patches are connected in a cycle through the switch diode; the first metal patch is connected to the central region through the inductor, the second and fourth metal patches are connected to the outer ring region through the inductor, the third metal patch is connected to the feed layer through the metal strip, the inductor and the metallized via, and the central region of the unit structure is connected to the feed layer through the metallized via.

[0028] Most of the reflection layer is covered with metal, and part of the aperture is located at the metallized via, which has a larger diameter than the metallized via to prevent short circuit; one unit of the reflection layer can completely coincide by rotating 90°, 180°, 270° around the center.

[0029] The feed layer has a feed circuit, which can control the working state of the switch diode after loading the feed voltage, and realize the regulation and control of the four states of the metasurface.

[0030] The resonant state of the metasurface is changed by the switching state combination of the switching diodes, and the reflection phase of the metasurface is further controlled. The four state control modes of the specific metasurface are as follows: the on-off states of the two switching diodes directly connected to the first metal patch are the same, and the on-off state is denoted as A; the on-off states of the two switching diodes directly connected to the third metal patch are the same, and the on-off state is denoted as B; the on-off states of A and B are independent of each other; A and B are both turned off, and the metasurface shows state 1; A is turned on, and B is turned off, and the metasurface shows state 2; A is turned off, and B is turned on, and the metasurface shows state 3; A is turned on, and B is turned on, and the metasurface shows state 4; by adjusting the size parameters, the phase difference between adjacent states can be nearly 90° in a specific frequency band.

[0031] As shown in Figures 3 to 5 The preferred structure is described by taking a common square basic structural unit as an example. The center area of the active layer unit is a cross-shaped metal patch obliquely arranged at 45°, there is a metallized via in the center, four inductance elements L1, L2, L3 and L4 are welded at four terminals, the unit center is taken as a coordinate origin, and the four connection area structures are the same along the x and y axes. Among them, the first to fourth metal patches in each connection area are four open square rings surrounding a 45°-obliquely-arranged dumbbell-shaped metal patch. The open square rings all open towards the inside, and the open square rings are connected with switching diodes, and there are four P1, P2, P3 and P4 in total. The outer ring area of the unit is a metal square ring, and two inductances L5 and L6 are connected with the gap between the open square ring and the metal square ring. The dumbbell-shaped metal patch close to the center of the unit is connected with a metallized via and welded with an inductance L7, and the other end is connected with an open square ring through an inductance L8.

[0032] The metal patch structure of the feed layer unit can be divided into two parts: the central metallized via connects the square metal patch; the four peripheral metallized vias connect smaller square metal patches and four 45°-obliquely-arranged metal strips, and the other ends of the metal strips are all connected to the same metal square ring in the middle to realize electrical connection. The central square metal patch is connected to the outer metal feed line through an inductance or a zero-ohm resistance cross-linking square ring; any point on the four peripheral metal patches can be connected to the metal feed line; the positions of the feed lines need to be staggered to realize independent feeding of each metasurface unit and state.

[0033] The structures of the first dielectric layer and the second dielectric layer are the same, but the thicknesses are different. The thickness of the first dielectric layer is related to the working frequency, and the thickness is relatively thick. The second dielectric layer is used to isolate the reflection layer and the feed layer, and the thickness is irrelevant to the structure function and can be arbitrarily selected, and is generally thin. The relative permittivity of the dielectric layer ranges from 2 to 5, the relative permeability ranges from 1 to 5, and the dielectric loss tangent tanσ is less than 0.01.

[0034] The detailed design and effects of the embodiment are described below in combination with a specific simulation example. The thickness of the medium substrate of the first medium layer is h1, and the dielectric constant of the first medium layer is j1; the thickness of the medium substrate of the second medium layer is h2, and the dielectric constant of the second medium layer is j2. 2mm≤h1≤10mm, 0.1mm≤h2≤10mm, 2≤j1≤5, and 2≤j2≤5. The tangent of the loss angle of the material is less than 0.005. In this example, h1=6mm, j1=3.5, h2=0.2mm, j2=3.5, and the tangent of the loss angle is 0.001. Reference Figures 3-5 The period length of the metasurface unit is p, and the diameter of the metallized via is o1. 5mm≤p≤50mm, and 0.2mm≤o1≤1.5mm. In this example, p=23mm, and o1=0.6mm.

[0035] Figure 3 is the planar structure of the active layer, located on the upper surface of the first medium layer, etched with metal patches, and welded with inductors L1-L8 and switch diode elements P1-P4 at the gaps of some metal patches. With the center of the unit as the coordinate origin, along the x and y axes, the internal metal patches can be divided into four regions, and the metal patches and circuit elements can be completely overlapped by rotating 90°, 180°, and 270° around the center of the square substrate unit. The parameters of the overlapped metal patches and circuit elements in the four regions are completely the same. The selected inductors exhibit high impedance in the working frequency band and low resistance in the direct current state; the inductors can effectively isolate the influence of the feeding line on the resonant structure without affecting the feeding; the inductance value is L, and 1nH≤L≤100nH. The switch diode can be selected according to the working frequency, equivalent circuit parameters, and cost factors. In this example, the inductance value L is 27nH, and the switch diode SMP1320-079LF is selected. The square ring metal patch connected with the boundary is the negative electrode of the feeding, and the inner diameter length is a. The metal patch in each region is composed of four open square rings and a 45°-inclined dumbbell-shaped metal patch in the middle, and the open square rings are all directed inward. The side length of the open square ring is b, the width is bw, and the opening gap size is e. The distance between adjacent square rings is c, and the switch diode is connected. The distance between adjacent metal patches in the four regions is d. 2mm≤a≤50mm, 1mm≤b≤8mm, 0.2mm≤bw≤4mm, 0.5mm≤e≤3mm, 0.2mm≤c≤1.5mm, and 0.5mm≤d≤5mm. When the size of the structure changes, the mutual overlap of the metal patches should be considered to ensure that the basic shape does not change. In this example, a=19.8mm, b=8.3mm, bw=1.2mm, e=1.7mm, c=0.7mm, and d=2.6mm.

[0036] Figure 4is the planar structure of the reflecting layer, located between the first dielectric layer and the second dielectric layer, except for the vicinity of the through-hole, which leaves a circular aperture, the rest is covered by metal, the diameter of the aperture is o2; the horizontal distance between the center of the circular aperture on the four outer sides and the center of the unit is f. 0.5mm≤o2≤2.5mm, 1mm≤f≤10mm. In this example, o2=1mm, f=4mm.

[0037] Figure 5 is the planar structure of the feeding layer, located on the lower surface of the second dielectric layer, T1 and T2 are two feeding lines respectively. The central through-hole connects the middle square metal patch with a side length of s1. The four outer through-holes connect the smaller square metal patch and the four 45°-inclined metal strips, the other end of the metal strips are connected to the same metal square ring in the middle, the square ring has a side length of s2, realizing electrical connection. T1 is connected to the outer metal feeding line through an inductor or a zero-ohm resistor across the square ring; T2 can be connected to the outer metal feeding line at any point. The design of the feeding line is irrelevant to the electromagnetic characteristics of the unit, so only the connection state of the circuit needs to be considered, this example only provides one of the connection modes, and the positions of the two feeding lines and the metal feeding lines of each unit need to be staggered with each other to realize independent feeding of each metasurface unit and state. 0.5mm≤s1≤3mm, 0.5mm≤s2≤6mm. In this example, s1=1.1mm, s2=1.8mm.

[0038] The 2-bit phase-adjustable dual-polarized active metasurface described in the application works when external electromagnetic waves are incident on the active layer and then reflected to the free space. The working state of the metasurface unit can be changed by feeding, so that the re-radiation field of the external electromagnetic wave can be effectively and accurately controlled.

[0039] Figure 6 and Figure 7 are respectively the metasurfaces of the embodiments of the application, and the reflection amplitude curve diagrams when two orthogonal polarized TE and TM electromagnetic waves are normally incident. The abscissa is the frequency, and the ordinate is the reflection amplitude in decibels. The reflection amplitude of the metasurface for TE or TM waves is greater than -0.85dB in the entire functional frequency band.

[0040] Figure 8 and Figure 9 are respectively the metasurfaces of the embodiments of the application, and the reflection phase curve diagrams when two orthogonal polarized TE and TM electromagnetic waves are normally incident. The abscissa is the frequency, and the ordinate is the reflection phase in angle value. The phase difference of the four working states of the metasurface unit of the metasurface for TE or TM waves is exactly 90° at 5.05GHz. In the range of 4.8-5.2GHz, the reflection phase difference remains good, basically meeting the requirement of 2-bit phase.

[0041] The super surface realizes 2-bit phase control function based on a switching diode, and is polarization-insensitive and high in reflection efficiency.

[0042] The above is only the preferred embodiment of the present application, the active super surface unit can be scaled by equal proportion or change the key size of the structure, change the model of the used circuit element, flexibly design the required working frequency band, and even can be directly extended to millimeter wave band, infrared, terahertz and visible light band. The above description cannot limit the range of the present application, that is, any simple equivalent change and modification made according to the claims and the description of the present application should still belong to the scope covered by the present application.

Claims

1. A 2-bit phase-tunable active dual-polarized metasurface, characterized in that, From top to bottom, the active layer, the first dielectric layer, the reflective layer, the second dielectric layer and the feed layer are included; The unit structure of the active layer is symmetrically distributed along a central axis, including a central region, an outer ring region and four connection regions with the same structure, and the four connection regions can completely coincide by rotating 90°, 180° and 270° around the center of the unit; each connection region includes first to fourth metal patches, which are connected in turn through switch diodes; the first metal patch is connected to the central region through an inductor, the second and fourth metal patches are connected to the outer ring region through inductors, and the third metal patch is connected to the feed layer through a metal strip, an inductor and a metallized via; the central region of the unit structure is connected to the feed layer through a metallized via; the working state of the switch diode is controlled by loading a feed voltage on the feed layer, and the four states of the metasurface are regulated.

2. The 2-bit phase-steerable active dual-polarized metasurface of claim 1, wherein, The on-off states of the two switch diodes directly connected to the first metal patch are the same, and the on-off state is recorded as A; the on-off states of the two switch diodes directly connected to the third metal patch are the same, and the on-off state is recorded as B; A and B do not affect each other; A and B are both turned off, one is turned on and one is turned off, and simultaneous conduction corresponds to four states of the metasurface.

3. The 2-bit phase-steerable active dual-polarized metasurface of claim 1, wherein, The unit structure of the active layer is square, the central region of the unit structure is a 45°-inclined cross-shaped metal patch with a metallized via in the center, and the four ends are connected to the four connection regions through four inductors; the outer ring region of the unit structure is a square ring connected to the boundary, which is used for common anode or common cathode of switch diode feed.

4. The 2-bit phase-steerable active dual-polarized metasurface of claim 3, wherein, The first to fourth metal patches in each connection region are four open square rings, all of which are inward, and a 45°-inclined dumbbell-shaped metal patch is arranged in the middle; the dumbbell-shaped metal patch is connected to the metallized via on the side close to the center of the unit, and an inductor is welded thereon, and the other side is connected to the third metal patch through an inductor.

5. The 2-bit phase-steerable active dual-polarized metasurface of claim 1, wherein, In a unit structure of the reflective layer, the metal is covered, and circular pores are distributed at the positions of the metallized vias, with a diameter larger than that of the metallized vias.

6. The 2-bit phase-steerable active dual-polarized metasurface of claim 1, wherein, In a unit structure of the feed layer, the central metallized via is connected to the central metal patch; the four peripheral metallized vias are connected to the metal ring outside the central metal patch through metal strips; a unit structure has two feed circuits, which realize independent feeding of four states of the unit.

7. The 2-bit phase-steerable active dual-polarized metasurface of claim 6, wherein, The central metal patch is connected to the outer metal feed line through an inductor or a zero-ohm resistor across the metal ring; any point on the metal patch at the position of the peripheral metallized via is connected to the outer metal feed line; the positions of the outer metal feed lines are staggered, realizing independent feeding of each metasurface unit and state.

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