A wave-transparent window movable switchable absorption-transmission integrated metamaterial structure

Abstract

The application provides a wave-absorbing and wave-transmitting integrated metamaterial structure with a dynamic switchable wave-transmitting window, and belongs to the technical field of novel artificial electromagnetic materials. The metamaterial structure is composed of metamaterial structure units arranged periodically. The unit period of the metamaterial structure unit is 15.0 mm. The metamaterial structure unit comprises a double-layer spiral chiral superunit, a patch mesh complementary structure, a dielectric substrate layer, a carbon-based resistance film and a PIN diode. The metal structure layer comprises a chiral wave-absorbing layer and an active wave-transmitting layer. The dielectric substrate layer is provided with multiple dielectric substrate layers. The chiral wave-absorbing layer and the active wave-transmitting layer are arranged on different dielectric substrate layers from top to bottom. The carbon-based resistance film is printed in the gap of the chiral wave-absorbing layer. The PIN diode is printed in the gap of the active wave-transmitting layer. The application can realize dynamic switching of the wave-transmitting window in the 7-9.6 GHz wave band and realize efficient absorption in the out-of-band frequency bands of 3-6 GHz and 11-21 GHz. The application effectively solves the problems of wave-absorbing, wave-transmitting compatible design, wideband wave-transmitting window dynamic switching and the like. The application is compatible with electromagnetic and mechanical bearing functions and can be applied to a multifunctional electromagnetic integrated system and an intelligent antenna cover system.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of novel artificial electromagnetic materials, and particularly relates to a kind of absorbing and transmitting integrated metamaterial structure with dynamically switchable wave-transparent window. BACKGROUND

[0002] In the past decade, metasurfaces have attracted great interest due to their flexible manipulation of electromagnetic wavefronts. Metasurfaces are artificial electromagnetic surfaces designed by periodically or quasi-periodically arranging subwavelength units. As a two-dimensional form of metamaterials, metasurfaces not only inherit the unique electromagnetic properties of metamaterials, but also have the advantages of low loss, simple manufacturing, light weight, and high integration. In particular, metamaterial absorbers have wide application prospects in microwave and terahertz engineering, and have developed rapidly in the past decade. Compared with traditional electromagnetic absorbers, metamaterial absorbers have the following advantages. First, metamaterial absorbers can arbitrarily control the permittivity and permeability, and thus absorb electromagnetic wave energy by achieving impedance matching in free space. Therefore, perfect absorption can be achieved even on a very thin substrate. Second, metamaterial absorbers can be manufactured using traditional printed circuit board (PCB) technology. Therefore, compared with traditional ferrite-based electromagnetic absorbers, the total cost is relatively low.

[0003] However, most passive metamaterial absorbers have fixed and single functions in a specific frequency band, and cannot be dynamically controlled, making it difficult to meet the demand for multifunctional and intelligent devices. With the development of reconfigurable mechanisms, active metamaterial absorbers that can dynamically modulate functions have also developed rapidly. In particular, absorbing and transmitting integrated active metamaterial absorbers can respond differently according to changes in external conditions, enabling functional reconfiguration and reuse, which is of great significance in electromagnetic aperture stealth and intelligent antenna cover design. However, existing absorbing and transmitting integrated reconfigurable metasurfaces still have many defects. For example, most current active metamaterial absorbers cannot achieve compatible design of high-efficiency absorption and transparent window design, the transparent window bandwidth is generally narrow, the transparent window loss is large, and the wide-angle adaptability is poor, making it difficult to meet the application requirements of electromagnetic aperture broadband, high-efficiency, and omnidirectional stealth design. SUMMARY

[0004] The application proposes a kind of absorbing and transmitting integrated metamaterial structure with dynamically switchable wave-transparent window, which breaks through the technology of antenna cover wave-transparent window dynamic switching and the compatible design technology of in-band wave transmission and out-of-band absorption, solves the bottleneck problems such as difficulty in expanding the wave-transparent bandwidth, large loss of wave-transparent window, and poor wide-angle adaptability, has the characteristics of high integration and batch production, is compatible with electromagnetic and mechanical bearing functions, and can be used in multifunctional electromagnetic integrated systems and antenna cover systems.

[0005] The technical scheme adopted by the application is:

[0006] In a first aspect, the present invention provides a metamaterial structure with a wave-transmitting window that can be dynamically switched. The metamaterial structure is composed of a periodically arranged metamaterial structure unit, and the metamaterial structure unit is prepared by the following steps:

[0007] Step 1: Design the absorbing part of the metamaterial structure unit. The absorbing part includes a double-layer helical chiral metastructure unit. The double-layer helical chiral metastructure unit has the same structural shape and is composed of four helices rotated 90° about the center origin. The mathematical expression of the helices in the polar coordinate system is:

[0008]

[0009] The parameters g 0 =0.2, g 1 =0.035, g 2 =0.15, t The value range of is (0, 5π / 2);

[0010] Step 2: Design the active frequency selection part of the metamaterial structural unit, which includes a patch grid complementary structure, and the patch grid complementary structure includes a first square structure metal patch layer, a second square structure metal patch layer, and a metal grid strip structure;

[0011] Step 3: Design the dielectric substrate layer. The dielectric substrate layer includes the first substrate layer, the second substrate layer, the third substrate layer, and the fourth substrate layer from top to bottom. The thickness of the first substrate layer and the second substrate layer is 0.1375 mm, and the thickness of the air layer between them is 5 mm. The thickness of the second substrate layer and the third substrate layer is 1.575 mm, and the thickness of the air layer between them is 8 mm. The third substrate layer and the fourth substrate layer are pressed together.

[0012] Step 4: Print the double-layer helical chiral metastructure unit on the front of the first substrate layer and the second substrate layer respectively; print the first square structure metal patch layer and the second square structure metal patch layer on the front of the third substrate layer and the fourth substrate layer respectively, and print the metal grid strip structure on the back of the third substrate layer.

[0013] In some embodiments, in step 1, the width of the spiral line is 0.15 mm.

[0014] In some embodiments, the tail of the spiral line is connected to a vertical metal line or a horizontal metal line. The vertical metal line and the horizontal metal line are loaded with a carbon-based resistor film. The carbon-based resistor film has a length of 1.1 mm and a width of 0.2 mm.

[0015] In some embodiments, the sheet resistance of the carbon-based resistor film on the first substrate layer is 150Ω / m^2, and the sheet resistance of the carbon-based resistor film on the second substrate layer is 90Ω / m^2.

[0016] In some embodiments, the first square structure metal patch layer and the second square structure metal patch layer are both composed of multiple square metal patch units, the width of the square metal patch unit is 6.5 mm, a vertical metal feed line is arranged between two adjacent square metal patch units on the third substrate layer, and a horizontal metal feed line is arranged between two adjacent square metal patch units on the fourth substrate layer. Notches are arranged on the vertical metal feed line and the horizontal metal feed line, and PIN diodes are loaded at the notches to realize dynamic switching of the switch state of the wave-transmitting window.

[0017] In some embodiments, the line width of the vertical metal feed line and the horizontal metal feed line are both 0.35 mm, and the gap length is 0.3 mm.

[0018] In some embodiments, the line width of the metal mesh structure is 2.5 mm, and the distance between two mesh bars in the metal mesh structure is 5 mm.

[0019] In some embodiments, the metamaterial structure realizes dynamic switching of the wave-transmitting window in the 7-9.6 GHz band and achieves efficient absorption in the out-of-band frequency bands of 3-6 GHz and 11-21 GHz.

[0020] In a second aspect, the present invention provides an application of the absorbent-transmitter metamaterial structure with a wave-transmitting window that can be dynamically switched in a multifunctional electromagnetic integrated system or a smart antenna cover system.

[0021] Beneficial effects of the present invention:

[0022] 1. The present invention provides a metamaterial structure with a dynamically switchable absorbent window. By loading a resistive film structure into a double-layer chiral absorber structure, efficient and selective absorbers are achieved. In addition, a parallel resonant branch is combined to achieve broadband windowing of the absorber.

[0023] 2. The absorbent-transmitting metamaterial structure with a wave-transmitting window that can be dynamically switched provided by the present invention realizes dynamic switching of the wave-transmitting window by integrating a PIN diode. The control method is simple and can be used for the integration of other functions.

[0024] 3. The present invention significantly reduces active components, lowers power consumption, and improves passband wave transmission efficiency by optimizing the unit structure and feeding network.

[0025] 4. The present invention adopts a resistor film to replace the traditional chip resistor to achieve wave absorption, which improves the composite molding ability of the material and facilitates integration and mass production.

[0026] 5. The embodiment of the present invention provides a metamaterial structure with a wave-transmitting window that can be dynamically switched. The structure can achieve dynamic switching of the wave-transmitting window in the 7-9.6 GHz band and achieve efficient absorption in the out-of-band frequency bands of 3-6 GHz and 11-21 GHz.

[0027] 6. The present invention effectively solves the problems of compatible design of wave absorption and wave transmission, dynamic switching of broadband wave-transparent windows, etc., is compatible with electromagnetic and mechanical bearing functions, and can be applied to multifunctional electromagnetic integrated systems and intelligent antenna cover systems. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0029] Figure 1 It is an overall diagram of the present invention;

[0030] Figure 2 It is a split diagram of the present invention;

[0031] Figure 3 This is a simulated transmission coefficient diagram of the bottom wave-transmitting metamaterial structure in the present invention;

[0032] Figure 4 is an equivalent circuit model diagram of the present invention;

[0033] Figure 5 is a diode equivalent circuit diagram of the present invention;

[0034] Figure 6 Graph showing the simulated reflection coefficient and absorption results of a single-layer chiral absorbing layer in the present invention;

[0035] Figure 7 Graph showing the simulated reflection coefficient and absorption results of the double-layer chiral absorbing layer of the present invention;

[0036] Figure 8 is a simulated transmission coefficient diagram of the present invention;

[0037] Figure 9 This is a diagram of the simulated wave absorption results of the present invention.

[0038] Among them, 1. First substrate layer; 2. Second substrate layer; 3. Third substrate layer; 4. Fourth substrate layer; 5. Spiral line; 6. Vertical metal line; 7. Horizontal metal line; 8. Carbon-based resistor film; 9. Square metal patch unit; 10. Metal grid structure; 11. PIN diode; 12. Vertical metal feed line; 13. Horizontal metal feed line. DETAILED DESCRIPTION

[0039] In order to make the purposes, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application.

[0040] When the incident wave irradiates the absorption-transmission integrated metamaterial structure, the ideal transmission window needs that the incident wave in the frequency band can be transmitted through the high-frequency absorption surface and the low-frequency absorption completely. In order to ensure the performance of the transmission, the designed absorption structure should basically ensure that the transmission loss of the incident wave in the transmission window is zero; at the same time, the performance of the bottom band-pass FSS transmission window should also make the incident wave in the transmission frequency band pass completely without obstacles. At the same time, the band-pass FSS completely reflects the incident wave outside the passband to ensure good absorption of the absorption surface. Considering the partial influence of multi-layer surface coupling, after the upper and lower surfaces that meet the requirements of the transmission window are designed, the electromagnetic properties of the overall structure should be optimized to achieve the design goal of the transmission.

[0041] The embodiment provides an absorption-transmission integrated metamaterial structure with a dynamically switchable transmission window, wherein the metamaterial structure is composed of periodic arrangement of metamaterial structure units, and the period of the metamaterial structure unit is 15.0 mm.

[0042] The metamaterial structure unit is prepared through the following steps:

[0043] Firstly, the absorption part of the metamaterial structure unit is designed, and the absorption part comprises double-layer spiral line 5 chiral super unit, the double-layer spiral line 5 chiral super unit has the same structure shape and is composed of four spiral lines 5 rotating at 90° along the center origin, and the mathematical expression of the spiral line 5 in the polar coordinate system is as follows:

[0044]

[0045] wherein the parameter g 0 = 0.2, g 1 = 0.035, g 2 = 0.15, t the value range of the parameter is (0, 5pi / 2), and the width of the spiral line 5 is 0.15 mm.

[0046] The tail of the spiral line 5 is connected with the vertical metal line 6 or the horizontal metal line 7, the vertical metal line 6 and the horizontal metal line 7 are loaded with a carbon-based resistance film 8, the length of the carbon-based resistance film 8 is 1.1 mm, and the width of the carbon-based resistance film 8 is 0.2 mm. The sheet resistance of the carbon-based resistance film 8 on the first substrate layer 1 is 150 ohm / m^2, and the sheet resistance of the carbon-based resistance film 8 on the second substrate layer 2 is 90 ohm / m^2.

[0047] The single-layer helical 5-chiral meta-unit is simulated, and the performance is as follows Figure 6 As shown in the simulation results, the reflectivity is less than -10dB in the range of 16-21GHz, and the absorption rate is higher than 80%, which indicates that the electromagnetic wave is almost completely reflected, achieving efficient absorption. The double-layer chiral absorption layer is simulated, and the performance is shown in Figure 7 The simulation results show that the reflectivity is less than -10dB in the 4-6GHz and 11-18GHz bands, and the absorption rate is higher than 80%, indicating that the electromagnetic waves are almost completely reflected, achieving efficient absorption.

[0048] Next, the active frequency selection part of the metamaterial structure unit is designed. The active frequency selection part includes a patch grid complementary structure. The patch grid complementary structure includes a first square structure metal patch layer, a second square structure metal patch layer and a metal grid strip structure 10. The metal grid strip structure 10 is added between the first square structure metal patch layer and the second square structure metal patch layer.

[0049] The first square structure metal patch layer and the second square structure metal patch layer are both composed of a plurality of square metal patch units 9, and the width of the square metal patch unit 9 is 6.5 mm. Vertical metal feed lines 12 are loaded between the square metal patch units 9 in the first square structure metal patch layer, and horizontal metal feed lines 13 are loaded between the square metal patch units 9 in the second square structure metal patch layer. Both the vertical metal feed lines 12 and the horizontal metal feed lines 13 are provided with gaps, and PIN diodes 11 are loaded at the gaps, that is, the PIN diodes 11 are placed in the x-direction and y-direction of the square gap patch respectively, to realize dynamic switching of the wave-transmitting window switch state. When the diodes in both directions are in conduction, that is, in the "ON" state, the wave-transmitting metamaterial fully reflects the incident electromagnetic wave; when both diodes are in the off state, that is, in the "OFF" state, the wave-transmitting metamaterial fully transmits the incident electromagnetic wave at 7-10 GHz, such as Figure 3 As shown, since all PIN diodes 11 are arranged in series, power feeding is simple and easy to implement.

[0050] The vertical metal feed line 12 and the horizontal metal feed line 13 have a line width of 0.35 mm and a gap length of 0.3 mm. The metal mesh bar structure 10 has a line width of 2.5 mm and a spacing of 5 mm between two bars in the metal mesh bar structure 10.

[0051] The equivalent circuit model helps to understand the working principle of AFSS. The equivalent circuit of the upper and lower square metal patch layers is similar to that of ordinary patches, which is equivalent to L a and C a series resonant circuit. L ais the equivalent inductance of the square patch, C a Represents the gap capacitance between the two patches. The two dielectric layers are represented by two short transmission lines, which can be represented by an LC resonant circuit ( L t , C t ) instead. The middle grid can be equivalent to a parallel inductor L m . Figure 4 The equivalent circuit model of the integrated metamaterial structure is shown. When the PIN diode 11 is on, it is equivalent to a series circuit of L and R. When it is off, the PIN diode 11 is equivalent to a series circuit of L and C. In this design, the PIN diode 11 type is MADP-000907-14020. According to the PIN diode 11 data sheet, the equivalent parameters of the PIN diode 11 are L s =30 pH, R on =7.8Ω, C off =0.025 pF, e.g. Figure 5 shown.

[0052] For the upper impedance absorption surface, the electromagnetic wave loss of the absorber mainly has three mechanisms: resistance loss, dielectric loss, and magnetic loss. Resistance loss is caused by the loading of lossy components such as lumped resistors or high-resistance surfaces. The electric field induces a macroscopic current. The current passes through the resistor, and the electrical energy is converted into heat energy by the resistor and consumed. Dielectric loss is caused by the absorption and consumption of the incident wave energy penetrating the dielectric substrate. The dielectric loss capacity is positively correlated with its electric loss tangent. The magnetic loss capacity is also positively correlated with the magnetic loss tangent. This design uses the method of loading a resistive film on the chiral structure to achieve low-frequency and high-frequency wave absorption respectively. At the same time, the structure has good selective wave absorption performance and does not affect the transmission of the wave transmission frequency band.

[0053] In addition, the dielectric substrate layer is designed, and the dielectric substrate selected for the optimized absorbing part is Rogers RT5880, with a dielectric constant of εr=2.2.

[0054] The dielectric substrate layers include, from top to bottom, a first substrate layer 1, a second substrate layer 2, a third substrate layer 3 and a fourth substrate layer 4. The thickness of the first substrate layer 1 and the second substrate layer 2 is 0.1375 mm, and the thickness of the air layer between them is 5 mm. The thickness of the second substrate layer 2 and the third substrate layer 3 is 1.575 mm, and the thickness of the air layer between them is 8 mm. The third substrate layer 3 and the fourth substrate layer 4 are pressed together.

[0055] The double-layer helical line 5 chiral superstructure units are printed on the front surface of the first substrate layer 1 and the second substrate layer 2 respectively; the first square structure metal patch layer and the second square structure metal patch layer are printed on the front surface of the third substrate layer 3 and the fourth substrate layer 4 respectively, and the metal mesh strip structure 10 is printed on the back surface of the third substrate layer 3.

[0056] The material of the wave absorbing part and the active frequency selection part is copper, and the conductivity of the copper is 5.8*10 7 S / m.

[0057] The composite structure is shown in Figure 1 , from top to bottom, the wave absorbing part and the active frequency selection part are arranged in sequence. The transmittance is shown in Figure 8 , when the diode is in the off state, the transmittance is greater than 90% in the frequency range of 7.4-9.3 GHz; when the diode is in the on state, the transmittance is less than 15% in the frequency range of 7.4-9.3 GHz, realizing the switching between the transmission and the reflection. At the same time, the performance of the active wave-transparent metamaterial structure before and after the composition changes little, indicating that the upper impedance absorbing surface does not affect the transmission of electromagnetic waves in the wave-transparent frequency band. The wave absorption rate is shown in Figure 9 , the absorption in the frequency range of 3-6 GHz is greater than 80% in both states, and the average absorption in the frequency range of 11-21 GHz is also greater than 80%.

[0058] The above-described embodiments are only the preferred specific implementation of the present application, the protection scope of the present application is not limited thereto, any skilled person in the art can obtain the simple changes or equivalent replacements of the technical solutions within the technical range disclosed by the present application, which all belong to the protection scope of the present application.

Claims

1. A metamaterial structure with a wave-transmitting window that can be dynamically switched, characterized in that: The metamaterial structure is composed of periodically arranged metamaterial structural units, which are prepared by the following steps: Step 1: Design the absorbing part of the metamaterial structure unit. The absorbing part includes a double-layer helical chiral metastructure unit. The double-layer helical chiral metastructure unit has the same structural shape and is composed of four helices rotated 90° about the center origin. The mathematical expression of the helices in the polar coordinate system is: The parameters g 0 =0.2, g 1 =0.035, g 2 =0.15, t The value range of is (0, 5π / 2); Step 2: Design the active frequency selection part of the metamaterial structural unit, which includes a patch grid complementary structure, and the patch grid complementary structure includes a first square structure metal patch layer, a second square structure metal patch layer, and a metal grid strip structure; Step 3: Design the dielectric substrate layer. The dielectric substrate layer includes the first substrate layer, the second substrate layer, the third substrate layer, and the fourth substrate layer from top to bottom. The thickness of the first substrate layer and the second substrate layer is 0.1375 mm, and the thickness of the air layer between them is 5 mm. The thickness of the second substrate layer and the third substrate layer is 1.575 mm, and the thickness of the air layer between them is 8 mm. The third substrate layer and the fourth substrate layer are pressed together. Step 4: Print the double-layer helical chiral meta-unit on the front of the first substrate layer and the second substrate layer respectively; print the first square structure metal patch layer and the second square structure metal patch layer on the front of the third substrate layer and the fourth substrate layer respectively; and print the metal grid strip structure on the back of the third substrate layer; The first square structure metal patch layer and the second square structure metal patch layer are both composed of multiple square metal patch units. The width of the square metal patch unit is 6.5 mm. A vertical metal feed line is set between two adjacent square metal patch units on the third substrate layer. A horizontal metal feed line is set between two adjacent square metal patch units on the fourth substrate layer. Notches are set on the vertical metal feed line and the horizontal metal feed line. PIN diodes are loaded at the notches to realize dynamic switching of the wave-transmitting window switch state.

2. The absorbent and permeable metamaterial structure with a wave-transmitting window that can be dynamically switched according to claim 1, characterized in that: In step 1, the width of the spiral is 0.15 mm.

3. The absorbent and permeable metamaterial structure with a wave-transmitting window that can be dynamically switched according to claim 2, characterized in that: The tail of the spiral line is connected to a vertical metal line or a horizontal metal line. The vertical metal line and the horizontal metal line are loaded with a carbon-based resistor film. The length of the carbon-based resistor film is 1.1 mm and the width is 0.2 mm.

4. The absorbent and permeable metamaterial structure with a wave-transmitting window that can be dynamically switched according to claim 3, characterized in that: The sheet resistance of the carbon-based resistor film on the first substrate layer is 150Ω / m^2, and the sheet resistance of the carbon-based resistor film on the second substrate layer is 90Ω / m^2.

5. The absorbent and permeable metamaterial structure with a wave-transmitting window that can be dynamically switched according to claim 4, characterized in that: The line width of the vertical metal feed line and the horizontal metal feed line are both 0.35 mm, and the gap length is 0.3 mm.

6. The absorbent and permeable metamaterial structure with a wave-transmitting window that can be dynamically switched according to claim 4, characterized in that: The line width of the metal mesh bar structure is 2.5 mm, and the distance between two bars in the metal mesh bar structure is 5 mm.

7. The absorbent and permeable metamaterial structure with a wave-transmitting window that can be dynamically switched according to claim 1, characterized in that: The metamaterial structure realizes dynamic switching of the wave-transmitting window in the 7-9.6 GHz band and realizes efficient absorption in the out-of-band frequency bands of 3-6 GHz and 11-21 GHz.

8. Application of the absorbent-transmitter metamaterial structure with a dynamically switchable wave-transmitting window according to any one of claims 1 to 7 in a multifunctional electromagnetic integrated system or a smart antenna cover system.

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