A multifunctional reconfigurable metasurface array and its design method
By designing a multifunctional reconfigurable metasurface with FSR, FSS, absorption and reflection modes, and using PIN diodes to adjust voltage switching, the problems of single metasurface function and reflection risk are solved, and flexible electromagnetic environment adaptation and stealth performance improvement are achieved.
Patent Information
- Application Number
- CN202411133278.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2024-08-19
- Publication Date
- 2025-09-23
- Estimated Expiration
- 2044-08-19
AI Technical Summary
Existing metasurfaces have single functions and are difficult to meet diverse needs in complex electromagnetic environments. In addition, the reflection of fixed metasurfaces outside the passband can easily lead to increased detection risks.
A multifunctional reconfigurable metasurface is designed with four working modes: FSR, FSS, absorption and reflection. Mode switching is achieved by adjusting the bias voltage of the PIN diode. A double-layer unit structure and lumped component distribution are adopted, and a feeding network is integrated to avoid the influence of additional networks.
It enables rapid switching of the metasurface between different modes, enriches its functional applications, adapts to complex electromagnetic environments, reduces the risk of reflection outside the passband, and improves stealth performance and signal transmission capabilities.
Smart Images
Figure CN118889061B_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to a multifunctional reconfigurable electromagnetic metasurface technology, belonging to the technical field of novel artificial electromagnetic metamaterials. Background Art
[0002] In recent decades, the rapid development of metasurfaces has spawned a variety of new devices that not only have the characteristics of low profile, low cost and easy manufacturing, but also have novel and powerful functions. Among them, frequency selective surfaces (FSS) have been widely used in various fields due to their excellent spatial filtering characteristics, including electromagnetic stealth, electromagnetic compatibility, wireless communications, electronic countermeasures, etc. However, frequency selective surfaces usually produce strong reflections outside the passband, which will significantly increase the risk of being detected. In order to solve this problem, researchers proposed the concept of frequency selective rasor (FSR), which allows signals within the passband to propagate in a low-loss manner, while showing strong absorption of signals outside the passband, thereby significantly improving its stealth performance.
[0003] With the increasing complexity of the electromagnetic environment, fixed metasurfaces with a single function are no longer able to meet human needs. Consequently, metasurfaces with reconfigurable properties have attracted widespread attention from researchers. By introducing adjustable technology, reconfigurable metasurfaces with multiple functions can be designed. Specifically, there are currently two main types of reconfigurable FSRs. The first type of reconfigurable FSR has a passband that cannot be closed but can be moved up or down as needed, which is very useful in broadband stealth facilities with frequency-hopping communication capabilities. However, since the passband is always present, the stealth performance of this type of reconfigurable FSR is affected. The second type of reconfigurable FSR has an on / off passband, allowing it to switch between "FSR mode" and "wave-absorbing mode." This allows the metasurface's stealth performance to be improved by closing the passband when filtering is not required.
[0004] This invention proposes a novel reconfigurable metasurface with four operating modes. It can flexibly switch between FSR mode, FSS mode, absorption mode, and reflection mode, further expanding the application prospects of metasurfaces. Compared with existing reconfigurable FSR, the reconfigurable metasurface proposed in this invention also has a highly reflective mode, which facilitates friendly units to detect targets smoothly. Furthermore, the FSS mode adds the ability to transmit specific frequency signals, allowing the target to actively transmit or receive signals. Therefore, this invention has broad potential application prospects in complex electromagnetic environments. Summary of the Invention
[0005] Technical Problem: The purpose of this invention is to propose a multifunctional, reconfigurable metasurface that can be used as a smart radome. This reconfigurable metasurface, composed of a periodic arrangement of basic units, has four operating modes: FSR, FSS, absorption, and reflection. This addresses the limited functionality of existing metasurfaces.
[0006] Technical Solution: This invention discloses a reconfigurable metasurface with four working modes: FSR, FSS, absorption, and reflection. It also proposes a design method for realizing these four functions and switching between them, including the following steps:
[0007] Step 1: Divide the working frequency band of the metasurface into three regions, denoted as f l 、f t and f h , and f l <f t <f h .
[0008] Step 2: Identify the state of the unit in each frequency band in each mode:
[0009] In FSR mode, the low frequency region f l and high frequency region f h are all adjusted to the absorption state, and the middle region f t is adjusted to the transmission state;
[0010] In FSS mode, the middle region f t Maintaining the transmission state, low frequency region f l and high frequency region f h is adjusted to a reflective state;
[0011] In the absorbing mode, the three frequency bands (f l 、f t and f h ) are all adjusted to the absorbing state;
[0012] In reflection mode, the three frequency bands (f l 、f t and f h ) are adjusted to the reflective state.
[0013] In summary, in order to achieve dynamic adjustment of the metasurface between the four modes, the metasurface is required to be in the low frequency region f l and high frequency region f h It is adjustable between the absorption state and the reflection state, and in the intermediate region f t It needs to be adjustable between the absorption state, transmission state and reflection state.
[0014] Step 3: Propose a double-layer unit structure with air between the upper and lower layers. Based on the two-port network model, the impedance requirements of the upper and lower layers of the unit under different conditions are obtained:
[0015] In the absorbing state, the impedance Z t and the impedance Z of the underlying structure b The following formula should be satisfied:
[0016]
[0017] Z b =0, (1b)
[0018] in, Here, f represents the operating frequency; c represents the speed of light in a vacuum; h and ε r They represent the thickness and relative dielectric constant of the air between the upper and lower structures respectively, Z0 represents the wave impedance of vacuum, and j represents the imaginary unit of the complex number.
[0019] In the transmission state, the upper and lower impedances of the unit are Z t and Z b The real part approaches ∞, while the imaginary part passes through 0.
[0020] In the reflection state, the upper impedance of the unit is Z t The real part of the unit tends to 0, and the lower impedance Z b =0 (ie, formula (1b)).
[0021] Combined with the conclusion of step 2, it can be seen that in order to achieve dynamic adjustment of the metasurface between the four modes, the impedance of the upper layer of the unit needs to be in three frequency bands (f l 、f t and f h ) are adjustable, and the impedance of the lower layer of the unit only needs to be in the middle area f t Adjustable, and in the low frequency area f l and high frequency region f h Approaching 0.
[0022] Step 4: Based on the analysis results of the upper and lower layer impedances of the unit in step 3, a preliminary design of the unit structure is performed. In order to achieve the goal of independently adjusting the upper layer impedance of the unit in three frequency bands and adjusting the lower layer impedance in the middle area, the upper / lower layer structure of the unit is designed as follows:
[0023] 1. The upper / lower layer structure of the unit is composed of a metal pattern embedded with a PIN diode, a capacitor tube, and a dielectric substrate from top to bottom.
[0024] 2. The metal pattern of the unit upper structure is 6 metal strips parallel to the y-axis. The distribution of the lumped components is as follows: the PIN diode P1 spans the gap Slot 1 between the first and second metal strips; the PIN diode P2 and two capacitors (C1 and C2) span the gap Slot 2 between the third and fourth metal strips, and the PIN diode is located between the two capacitors; the two PIN diodes P 31 and P 32 Span Slot 3, the gap between the fifth and sixth metal strips.
[0025] 3. The metal pattern of the unit's lower structure consists of two metal strips parallel to the y-axis. The lumped components are distributed as follows: a PIN diode P4 and two capacitors (C3 and C4) span the gap Slot 4 between the two metal strips, and the PIN diode is located between the two capacitors.
[0026] Step 5: Based on the operating frequency band of the multifunctional reconfigurable metasurface, use the simulation software CST STUDIO SUITE2020 to optimize the structural dimensions of the metasurface unit.
[0027] In the FSR mode, the metasurface array is l and high frequency region f h The reflectivity of the metal plate is reduced by more than 10dB compared with the smooth metal plate. t The transmission loss relative to air is less than 3dB;
[0028] In the FSS mode, the metasurface array can be used in the low frequency region f l and high frequency region f h The reflection loss relative to the smooth metal plate is less than 3dB. t The transmission loss relative to air is less than 3dB;
[0029] In the absorbing mode, the metasurface array is made to l 、f t and f h ) has a reflectivity that is reduced by more than 10 dB relative to a smooth metal plate, and a transmittance that is reduced by more than 10 dB relative to air;
[0030] In the reflection mode, the metasurface array is made to l 、f t and f h ) The reflection loss relative to a smooth metal plate is less than 3dB.
[0031] Beneficial effects: The beneficial effects of the present invention are as follows: (1) The modulation method adopted by the present invention is simple. The working mode of the metasurface can be quickly switched by simply changing the magnitude and direction of the bias voltage. (2) The present invention integrates the feed network into the unit pattern, so there is no need to introduce an additional feed network, thus avoiding the impact of the feed network on the performance of the metasurface. (3) Compared with the existing switchable rasor, the present invention has more functions and is expected to be used as a new type of smart antenna cover to cope with the increasingly complex and changing electromagnetic environment. BRIEF DESCRIPTION OF THE DRAWINGS
[0032] Figure 1 Schematic diagram of the double-layer unit structure designed in the present invention, wherein the bottom layer represents the lower structure and the top layer represents the upper structure;
[0033] Figure 2 is a surface schematic diagram of the upper and lower layer structures involved in the present invention, wherein Slot represents a gap, Metal, Dielectric, Capacitor, and PIN diode represent metal, dielectric, capacitor, and PIN diode respectively;
[0034] Figure 3 The simulation results of the impedance of the unit superstructure designed by the present invention in each mode are as follows: Real, Image, Impedance, Frequency, Z t in FSR mode, Z t in FSS mode, Z t inAbsorber mode, Z t In Reflector mode, it represents the real part, imaginary part, impedance, frequency, and Z in FSR mode. t , Z in FSS mode t , Z in absorbing mode t , Z in reflection mode t ;
[0035] Figure 4 The following are the simulation results of the impedance of the unit lower structure designed by the present invention in various modes;
[0036] Figure 5 The frequency response simulation results of the multifunctional reconfigurable metasurface designed by the present invention in various modes are shown in Figure 2, where Frequency Response, Reflectance, and Transmittance represent frequency response, reflectivity, and transmittance, respectively.
[0037] Figure 6This is a sample image of the multifunctional reconfigurable metasurface designed by the present invention, where capacitor, PIN, top, bottom, and side view represent capacitor, diode, upper layer, lower layer, and side view, respectively;
[0038] Figure 7 These are the frequency response test results of the multifunctional reconfigurable metasurface designed by the present invention in various modes, where FrequencyResponse, Reflectance, and Transmittance represent frequency response, reflectivity, and transmittance, respectively. DETAILED DESCRIPTION
[0039] The present invention will be further described below with reference to the accompanying drawings and examples.
[0040] In order to realize a reconfigurable metasurface with four working modes, namely FSR, FSS, absorption and reflection, the present invention designs a metasurface composed of a basic unit arranged in a periodic manner. Figure 1 As shown in , the metasurface unit consists of an upper and lower layer separated by air, and the air thickness is h. Figure 2 As shown in (a), the upper structure of the unit consists of a metal pattern embedded with lumped components and a lower dielectric substrate from top to bottom. The lumped components are distributed as follows: a PIN diode P1 is embedded in the middle of slot 1; a PIN diode P2 is embedded in the middle of slot 2, with capacitors C1 and C2 embedded at both ends; a PIN diode P is embedded at both ends of slot 3. 31 and P 32 .like Figure 2 As shown in (b), the underlying structure of the unit cell consists, from top to bottom, of a metal pattern embedded with lumped components and a lower dielectric substrate. The lumped components are arranged as follows: a PIN diode P4 is embedded in the center of slot Slot4, with capacitors C3 and C4 embedded at either end. Through a periodic arrangement, each column of cells forms a subarray. Within the subarray, the metal strips connecting adjacent cells act as feed lines for the embedded PIN diodes, eliminating the need for an additional feed network. Because capacitors act as open circuits in direct current (DC) circuits and short circuits in alternating current (AC) circuits, PIN diodes P2 and P4 can still be controlled by the DC voltage provided by the metal strips at their ends, unaffected by the capacitors.
[0041] After optimization, the parameters of the metasurface unit are set as follows: g1 = 1.2 mm, g2 = 1 mm, g3 = 0.2 mm, g4 = 0.6 mm, g5 = 0.2 mm, g6 = 1.2 mm, g7 = 1.2 mm, w1 = 1.6 mm, w2 = 1.8 mm, w3 = 1.6 mm, w4 = 1.6 mm, w5 = 2 mm, w6 = 1.8 mm, S1 = 21.4 mm, S2 = 19.44 mm, S3 = 15.4 mm, S4 = 20.44 mm, w7 = w8 = 7.5 mm, g8 = 0.6 mm, P x =16mm, P y = 22mm and h = 10mm. The thickness of the upper and lower metal strips (copper) of the cell structure is 0.035mm, the thickness of the dielectric substrate is 1mm, and the relative dielectric constant is 2.2 (1-0.001j). The PIN diode and capacitor are Skyworks SMP1320-040LF and AccuP_0402 (capacitance = 1pF), respectively.
[0042] The present invention realizes the resonance of the upper structure of the unit in three frequency bands through slots Slot 1, Slot 2 and Slot 3 respectively; and realizes the resonance of the lower structure of the unit in the middle area through slot Slot 4. The resonant frequency and impedance of the slot can be controlled by adjusting the direction and magnitude of the bias voltage at both ends of the corresponding PIN diode. Specifically, when the PIN diodes P1, P 31 and P 32 When a forward bias voltage is applied to both ends, the metal strips on both sides are turned on. At this time, the resonant lengths of slots Slot 1 and Slot 3 are S1 and S3 respectively. On the contrary, when P1, P 31 and P 32 When zero / reverse bias voltage is applied across the two ends, the metal strips on either side are isolated from each other. Therefore, the resonant length between the gaps becomes infinite, and the gap resonance disappears. Slots 2 and 4 control resonance differently because of the capacitor between them. Specifically, when zero / reverse bias voltage is applied across PIN diodes P2 (P4), the resonant length of slot 2 (Slot 4) is the distance between the two capacitors on the y-axis, i.e., S2 (S4). However, when the bias voltage across P2 (P4) is positive, the resonant length of slot 2 (Slot 4) becomes S2 / 2 (S4 / 2). Furthermore, the diode's equivalent resistance can be adjusted by the magnitude of the forward bias current, so this can be used to adjust the equivalent impedance within the resonant frequency band.
[0043] Figure 3 and Figure 4 The impedance simulation results of the upper and lower structures of the unit proposed in the present invention in various modes are shown respectively; Figure 5 The frequency response simulation results of the unit in each mode are shown. In FSR mode, the PIN diodes P1, P 31 and P 32 A forward bias voltage is applied to both ends, and after optimization, the forward currents are adjusted to 20μA, 50μA, and 50μA, respectively. A -5V reverse bias voltage is applied to both ends of PIN diodes P2 and P4. In this case, the resonant lengths of slots Slot 1, Slot 2, Slot 3, and Slot 4 are S1, S2, S3, and S4, respectively. Since S1>S2≈S4>S3, according to the half-wave resonance characteristic, the resonant frequency of slot 1 corresponds to f l ; The resonant frequency of slots Slot 2 and Slot 4 corresponds to f t ; The resonant frequency of slot 3 corresponds to f h .
[0044] like Figure 3 (a) and Figure 4 As shown in (a), in the frequency band f t The impedance of the upper and lower structures of the unit meet the requirements of the transmission state, that is, the real part of the impedance tends to ∞, while the imaginary part exceeds 0. l and f h In the structure, the upper layer behaves as a lossy layer with impedance greater than zero, while the lower layer behaves as a lossless layer with impedance zero, meeting the impedance requirements of the absorption state. In this case, the frequency response simulation results of the unit as a whole are as follows: Figure 5 As shown in (a), within the frequency band of 5.05-5.42 GHz, the transmission loss relative to the air unit structure is less than 3 dB; within the frequency band of 3.85-7.65 GHz, the reflectivity relative to the smooth metal plate unit is reduced by more than 10 dB.
[0045] After optimization, in FSS mode, the bias voltage of all PIN diodes is set to -5V. The impedance of the upper and lower layers of the unit are as follows: Figure 3 (b) and Figure 4 As shown in (a). In the frequency band f t The strong resonance of the upper and lower structures of the unit still exists, and its impedance meets the requirements of the transmission state; in the frequency band f l and f h The resonance of the upper structure of the unit disappears, causing its real part of impedance to approach 0 in these two frequency bands, while the impedance of the lower structure of the unit is the same as that of the FSR mode, which meets the impedance requirements of the reflection state. The frequency response simulation results of the unit as a whole are shown in Figure 2. Figure 5As shown in (b), within the frequency band of 5.06 - 5.82 GHz, the transmission loss relative to the air cell structure is less than 3 dB; within the frequency bands of 3 - 4.95 GHz and 5.96 - 8 GHz, the reflection loss relative to the smooth metal plate cell is less than 3 dB.
[0046] After optimization, in the absorbing mode, the bias voltages at both ends of the PIN diodes P1, P 31 and P 32 are the same as in the FSR mode, that is, they are set to 20 μA, 50 μA, and 50 μA respectively; while the bias currents at both ends of the PIN diodes P2 and P4 are set to 5 μA. In this case, the resonant lengths of the slots Slot 2 and Slot 4 are halved to S2 / 2 and S4 / 2. Since S2 / 2 ≈ S4 / 2 < S3, the resonant frequencies of Slot 2 and Slot 4 are higher than f h , and are outside the operating frequency band. The impedances of the upper and lower layers of the cell are respectively as shown in Figure 3 (c) and Figure 4 (b). Within the frequency bands f l and f h , the impedances of the upper and lower layers are consistent with the FSR mode; within the frequency band f t , the resonances of the upper and lower layers disappear. As shown in Figure 5 (c), in this mode, the reflectivity and transmittance of the cell are both below -10 dB within 3.88 - 7.76 GHz, proving that the cell has strong absorption within this range.
[0047] After optimization, in the reflection mode, the bias voltages of the PIN diodes P1, P 31 and P 32 are set to -5 V; the PIN diodes P2 and P4 are set to the fully - conducting state, and their forward - bias currents are 5 mA. The equivalent resistance of the PIN diode in the fully - conducting state can be ignored. As shown in Figure 3 (d) and Figure 4 (c), in this case, the real part of the impedance of the upper layer of the cell and the impedance of the lower layer tend to 0 throughout the operating frequency band. Therefore, the cell exhibits the reflection mode throughout the operating frequency band. As shown in Figure 5 (d), within 3 - 8 GHz, the reflection loss relative to the smooth metal plate cell is below 3 dB.
[0048] Furthermore, the performance of the multifunctional reconfigurable metasurface proposed in this invention is verified through experiments. A metasurface sample containing 19×14 basic cells is fabricated using printed circuit board (PCB) technology, as shown in Figure 6 . In the FSR mode, the PIN diodes P1, P 31 and P 32The bias voltages of the PIN diodes P2 and P4 are set to 0.56V, 0.63V and 0.63V respectively; the bias voltages of the PIN diodes P2 and P4 are set to -5V. Figure 7 As shown in (a), within the range of 3.78-8 GHz, the reflectivity of the metasurface sample is reduced by more than 10 dB relative to that of the smooth metal plate; within the range of 5.08-5.43 GHz, the transmission loss relative to the air metasurface sample is less than 3 dB.
[0049] In FSS mode, the bias voltage of each PIN diode is set to -5V. The test results are as follows Figure 7 As shown in (b), within 5.11-5.65 GHz, the transmission loss of the metasurface sample relative to the air is less than 3 dB; within 3.5-4.5 GHz and 6.7-7.89 GHz, the reflection loss of the metasurface sample relative to the smooth metal plate is less than 3 dB.
[0050] In the absorption mode, the PIN diodes P1, P 31 and P 32 The bias voltages of the PIN diodes P2 and P4 are set to 0.52V. Figure 7 As shown in (c), in the range of 4.32-8 GHz, the reflectivity and transmittance of the metasurface sample are both lower than -10 dB, showing a strong absorption capability. In the reflection mode, the PIN diodes P1 and P 31 and P 32 The bias voltage of the PIN diodes P2 and P4 is set to 2V. Figure 7 As shown in (d), the reflection loss of the metasurface sample relative to the smooth metal plate is less than 3dB throughout the entire operating frequency band.
[0051] In this embodiment, the metasurface array proposed in the present invention effectively realizes four working modes, and achieves flexible switching between modes by adjusting the working state of each PIN diode.
Claims
1. A multifunctional reconfigurable metasurface, characterized by: The working frequency band of the metasurface is divided into three regions, denoted as f l 、f t and f h , and f l <f t <f h ; The metasurface is at f l and f h Adjustable between absorption and reflection states, at f t Adjustable between absorption, transmission and reflection states; In FSR mode, f l and f h is tuned to the absorbing state, f t is adjusted to the transmission state; in FSS mode, f t Keep the transmission state, f l and f h is adjusted to the reflection state; in the absorption mode, f l 、f t and f h is tuned to the absorption state; in the reflection mode, f l 、f t and f h is adjusted to a reflective state; The metasurface is formed by periodically arranging basic units, which are divided into sub-arrays by columns. Each sub-array is provided with a control signal by an independent control circuit. There are gaps between adjacent sub-arrays, and PIN diodes are embedded in the gaps. By adjusting the bias voltage across the PIN diode, the working mode of the metasurface can be controlled. The working modes include: FSR mode, FSS mode, absorption mode and reflection mode.
2. The multifunctional reconfigurable metasurface according to claim 1, characterized in that: The basic unit comprises an upper and a lower structure separated by air; the upper and lower structures both comprise a metal pattern embedded with a PIN diode and a capacitor and a dielectric substrate arranged in sequence from top to bottom.
3. The multifunctional reconfigurable metasurface according to claim 1, characterized in that: In the absorbing state, the impedance Z t and the impedance Z of the underlying structure b Satisfies the following formula: Z b ＝0， in, f represents the operating frequency; c represents the speed of light in a vacuum; h and ε r Respectively represent the thickness and relative dielectric constant of the air between the upper and lower structures, Z0 represents the wave impedance of vacuum, and j represents the imaginary unit of the complex number; In the transmission state, the upper and lower impedances of the unit are Z t and Z b The real part approaches ∞, while the imaginary part passes through 0; In the reflection state, the upper impedance of the unit is Z t The real part of the unit tends to 0, and the lower impedance Z b =0.
4. The multifunctional reconfigurable metasurface according to claim 1, characterized in that: The metal pattern of the upper structure is 6 metal strips parallel to the y-axis; a PIN diode is embedded in the middle of the gap between the 1st and 2nd metal strips, and its control voltage is provided by the embedded metal strip; a PIN diode is embedded in the middle of the gap between the 3rd and 4th metal strips, and a capacitor is embedded at both ends of the gap, and the control voltage of the PIN diode is provided by the embedded metal strip; two PIN diodes are embedded at both ends of the gap between the 5th and 6th metal strips, and their control voltage is provided by the embedded metal strip; the metal pattern of the lower structure is 2 metal strips parallel to the y-axis, a PIN diode is embedded in the middle of the gap formed by the two metal strips, and a capacitor is embedded at both ends of the gap, and the control voltage of the PIN diode is provided by the embedded metal strip.
5. The design method of the multifunctional reconfigurable metasurface according to claim 4, characterized in that: The steps include: According to the working frequency band of the multifunctional reconfigurable metasurface, the structural dimensions of the metasurface unit are optimized using simulation software: In FSR mode, the metasurface array is l and f h The reflectivity of the smooth metal plate is reduced by more than 10dB. t The transmission loss relative to air is less than 3dB; In FSS mode, the metasurface array is l and f h The reflection loss relative to a smooth metal plate is less than 3dB. t The transmission loss relative to air is less than 3dB; In the absorbing mode, the metasurface array is made to have f l 、f t and f h The reflectivity is reduced by more than 10dB compared with smooth metal plates, and the transmittance is reduced by more than 10dB compared with air; In the reflection mode, the metasurface array is made to have f l 、f t and f h The reflection loss relative to a smooth metal plate is less than 3dB.