Broadband angle insensitive nonlinear electromagnetic transmission modulation surface and working method

Abstract

The invention discloses a broadband angle insensitive nonlinear electromagnetic transmission modulation surface and a working method. The broadband angle insensitive nonlinear electromagnetic transmission modulation surface comprises a plurality of structural units which are periodically arranged; the structural unit comprises a metal layer and a dielectric substrate, the dielectric substrate is of a square structure, the metal layer is arranged on the dielectric substrate, a sawtooth structure, a square metal ring and a PIN diode are arranged in the metal layer, the square metal ring is arranged along the side length of the dielectric substrate, the sawtooth structure is arranged at one end of the outer side of the square metal ring, and the PIN diode is arranged in the square metal ring. Gaps are arranged between the square metal rings on two adjacent edges of the dielectric substrate, and the PIN diodes are installed in the gaps. By introducing the sawtooth structure, reasonable installation of the PIN diode and miniaturization of the unit size are both considered, adaptive response control over high-power electromagnetic waves and low-power signals can be achieved, transmission of the high-power electromagnetic waves is shielded to prevent the high-power electromagnetic waves from damaging a protected instrument circuit, and normal transmitting and receiving of the signals are guaranteed through transmission of the low-power electromagnetic waves.

Description

Technical Field

[0001] This invention belongs to the field of electromagnetic protection technology and relates to a broadband angle-insensitive nonlinear electromagnetic transmission modulation surface and its working method. Background Technology

[0002] With the rapid development of electronic information technology, modern electronic devices, centered on very large-scale integrated circuits and high-density integrated devices, have become key components of various systems. However, these devices lack the ability to withstand strong electromagnetic fields in high-intensity electromagnetic environments. High-power microwaves, in particular, can induce instantaneous high voltages within nanosecond to microsecond ranges through front-door or back-door coupling, causing internal semiconductor devices to break down, burn out, or malfunction, resulting in permanent or temporary failure of the entire electronic system. In today's complex electromagnetic environment, how to achieve adaptive electromagnetic protection—preventing electronic devices from being damaged by high-power electromagnetic waves without affecting their communication or other functions under normal conditions—has become a core problem urgently needing to be solved in the field of electromagnetic protection.

[0003] Energy-selective metasurfaces are a novel type of intelligent electromagnetic structure. By integrating nonlinear devices such as PIN diodes, energy-selective metasurfaces can adaptively switch their operating states according to the incident field strength: transmitting light at low power to ensure communication, and reflecting light at high power to shield against electromagnetic pulses, thus achieving "transparency-compatibility." However, existing energy-selective metasurfaces face challenges in performance, such as achieving both low insertion loss and wide shielding bandwidth within a small unit size, and improving response stability under large incident angles. Commercially available PIN diodes typically have dimensions of 1.0 mm × 0.6 mm or larger, and their mounting size limits and restricts the selection and miniaturization of structural units. These factors limit the application effectiveness of energy-selective metasurfaces in practical systems.

[0004] Therefore, developing an energy-selective metasurface with a large operating bandwidth and wide incident angle stability is of great significance for improving the reliability and applicability of electronic devices in high-intensity electromagnetic environments. Summary of the Invention

[0005] The purpose of this invention is to provide a broadband angle-insensitive nonlinear electromagnetic transmission modulation surface and its working method, solving the problem in the prior art that it is difficult to achieve both low insertion loss and wide shielding bandwidth under small unit size.

[0006] To achieve the above objectives, the present invention employs the following technical solution: A broadband angle-insensitive nonlinear electromagnetic transmission modulation surface includes several structural units arranged periodically. The structural unit includes a metal layer and a dielectric substrate. The dielectric substrate has a square structure. The metal layer is disposed on the dielectric substrate. The metal layer contains a serrated structure, a square metal ring, and a PIN diode. The square metal ring is disposed along the side length of the dielectric substrate. The serrated structure is disposed at one end of the outer side of the square metal ring. A gap is provided between the square metal rings on two adjacent sides of the dielectric substrate. The PIN diode is installed in the gap.

[0007] Furthermore, a copper film is coated on the dielectric substrate.

[0008] Furthermore, the dielectric substrate has a relative permittivity of 4.4 and a loss tangent of 0.02.

[0009] Furthermore, the serrated structure comprises several layers of metal strips arranged sequentially from the inside out.

[0010] Furthermore, the metal strip on the inner side of the serrated structure is the longest, and the inner metal strip is in close contact with the square metal ring.

[0011] Furthermore, the metal strip on the outer side of the sawtooth structure is the shortest, and the outer metal strip is aligned with the edge of the dielectric substrate.

[0012] Furthermore, one end of the serrated structure is flush with one end of the square metal ring, and the end of the serrated structure that is flush with the square metal ring is connected to one end of the PIN diode, while the other end of the PIN diode is connected to the other end of the square metal ring.

[0013] Furthermore, the PIN diodes are mounted clockwise.

[0014] Furthermore, the PIN diode has a cutoff capacitance of 0.018pF and an on-resistance of 5.2Ω.

[0015] A method for operating the broadband angle-insensitive nonlinear electromagnetic transmission modulation surface includes: Within the frequency band of 3.51~5.02GHz, when the electromagnetic field strength irradiating the surface of the structure is lower than the starting field strength, the PIN diode is in the cutoff state, the structure is not connected, the insertion loss of the signal is less than 1.7dB, and the signal can propagate through the metasurface. When the electromagnetic field strength irradiating the surface of the structure exceeds the starting field strength, a voltage sufficient to conduct is induced across the PIN diode, the structure is connected, and a band-stop shielding effect is generated against the electromagnetic waves, with a shielding effect of more than 15dB, and more than 96.8% of the electromagnetic wave energy is reflected. The starting field strength is 0.9 kV / m.

[0016] Compared with the prior art, the present invention has the following beneficial effects: This invention provides a broadband angle-insensitive nonlinear electromagnetic transmission modulation surface. By periodically arranging several structural units on a square dielectric substrate and placing a metal layer on the substrate, it is beneficial to improve electromagnetic coupling efficiency and energy transmission efficiency. This allows the modulation surface to achieve good performance in a small size, meeting the miniaturization and integration requirements of modern electronic devices. Square metal rings are arranged along the side length of the dielectric substrate, and a serrated structure is located at one end of the outer side of the square metal rings. Gaps are formed between the square metal rings on adjacent sides of the dielectric substrate, and PIN diodes are installed within these gaps. This ensures that the modulation surface achieves a relatively consistent transmission modulation effect for electromagnetic waves with different incident angles. Regardless of the direction of electromagnetic wave incidence, it maintains stable performance over a wide angular range, ensuring effective signal processing and transmission at different angles, thus improving signal coverage and quality. This invention can achieve adaptive response control for high-power electromagnetic waves and low-power signals, shielding high-power electromagnetic wave transmission to prevent damage to protected instrument circuits, and transmitting low-power electromagnetic waves to ensure normal signal transmission and reception. The use of miniaturized structural units facilitates polarization independence and angle-stable frequency response. This invention, by introducing a sawtooth structure, balances the rational mounting of PIN diodes with miniaturization of the unit size. The miniaturized structure also makes it suitable for curved electromagnetic shielding applications to a certain extent. Electromagnetic simulations in the time and frequency domains verified the transmission characteristics of the energy-selective metasurface under low-power electromagnetic wave incidence and its shielding characteristics under high-power electromagnetic wave incidence. The basic unit size of the designed energy-selective metasurface structure is 9.4 mm × 9.4 mm. Within a bandwidth of 3.51–5.02 GHz, the shielding effect against high-power electromagnetic waves reaches 15 dB, with a relative bandwidth of 35.7%. The insertion loss for low-power signal transmission in the 3.51–5.02 GHz range is less than 1.7 dB. The results show that the structure of this invention possesses superior performance characteristics such as polarization independence, angle stability, wide shielding bandwidth, and low insertion loss. It is a miniaturized, polarization-independent energy-selective metasurface with a stable frequency response under oblique incidence, which can effectively enhance the survivability of electronic devices in complex electromagnetic environments and has significant engineering application value. Attached Figure Description

[0017] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a schematic diagram of the broadband angle-insensitive nonlinear electromagnetic transmission modulation surface structure of the present invention.

[0019] Figure 2 This is a top view of the structural unit of the broadband angle-insensitive nonlinear electromagnetic transmission modulation surface of the present invention.

[0020] Figure 3 This is an S-parameter curve of Embodiment 1 of the present invention under low-power signal incidence.

[0021] Figure 4 This is a graph showing the S-parameters of Embodiment 1 of the present invention under high-power electromagnetic wave incidence.

[0022] Figure 5 This is a diagram of the nonlinear response of Embodiment 1 of the present invention under the incidence of a time-varying power signal.

[0023] Figure 6 The above are simulation curves of S21 under different incident angles θ for Embodiment 1 of the present invention.

[0024] Figure 7 The figure shows the S21 simulation curves of Embodiment 1 of the present invention with different polarization angles ψ.

[0025] Wherein: 1-dielectric substrate, 2-serrated structure, 3-square metal ring, 4-PIN diode. Detailed Implementation

[0026] To enable those skilled in the art to understand the features and effects of the present invention, the terms and expressions used in the specification and claims are explained and defined in general below. Unless otherwise specified, all technical and scientific terms used herein have the ordinary meaning understood by those skilled in the art regarding the present invention, and in case of conflict, the definitions in this specification shall prevail.

[0027] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0028] For the sake of brevity, not all possible combinations of the technical features in each implementation scheme or embodiment are described herein. Therefore, as long as there is no contradiction in the combination of these technical features, the technical features in each implementation scheme or embodiment can be combined arbitrarily, and all possible combinations should be considered within the scope of this specification.

[0029] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0030] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0031] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the embodiments of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0032] In the description of the embodiments of the present invention, it should be noted that if terms such as "upper," "lower," "horizontal," or "inner" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of the invention is in use, they are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention. Furthermore, terms such as "first" and "second" are only used to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0033] Furthermore, the use of the term "horizontal" does not imply that the component must be absolutely horizontal, but rather that it can be slightly tilted. For example, "horizontal" simply means that its direction is more horizontal than "vertical," and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0034] In the description of the embodiments of the present invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in the present invention according to the specific circumstances.

[0035] The present invention will now be described in further detail with reference to the accompanying drawings: refer to Figure 1 This invention provides a broadband angle-insensitive nonlinear electromagnetic transmission modulation surface, which is composed of a number of structural units arranged periodically, such as... Figure 2 As shown. The structural unit includes a metal layer and a dielectric substrate 1. The dielectric substrate 1 has a square structure. After copper is deposited on the dielectric substrate 1, an energy selection structure is printed. The metal layer is disposed on the dielectric substrate 1, and a PIN diode 4 of the same type is mounted on the metal layer.

[0036] Preferably, the dielectric substrate 1 is of type FR-4, and its relative permittivity is... The loss tangent is 0.02.

[0037] The metal layer includes a square metal ring 3 and a serrated structure 2. The square metal ring 3 is disposed along the four sides of the dielectric substrate 1, and the serrated structure 2 is disposed on the outer side of one end of the square metal ring 3. The serrated structure 2 is composed of several layers of metal strips arranged sequentially from the inside to the outside. Each metal strip has the same width, and its length increases sequentially from the outside to the inside. The longest metal strip on the inner side of the serrated structure 2 is close to the square metal ring 3, and the shortest outer metal strip is aligned with the edge of the dielectric substrate 1. Its length is shorter than half the length of the square metal ring 3 to avoid direct connection between the serrated structures 2 of adjacent structural units.

[0038] The sawtooth structure 2 is used to increase the equivalent resonant length to reduce the resonant frequency. Under the premise that the total width w1+w2 of the sawtooth structure 2 and the square metal ring 3 meets the installation requirements of the PIN diode 4, the square metal ring 3 is allowed to use a smaller line width, thereby synergistically achieving miniaturization and low frequency reduction of the unit structure.

[0039] On each side of the square structure of the dielectric substrate 1, one end of the serrated structure 2 is flush with one end of the square metal ring 3. A gap is formed between the end of the square metal ring 3 flush with the serrated structure 2 and the end of the adjacent side without the serrated structure 2, for mounting PIN diodes 4. The PIN diodes 4 are all mounted clockwise, and the gap size is designed according to the actual size of the PIN diodes 4. As a nonlinear switch, the PIN diodes 4 can adaptively switch states according to the incident electromagnetic wave field strength.

[0040] Preferably, the PIN diode 4 used has a cutoff capacitance of 0.018pF and an on-resistance of 5.2Ω, and each structural unit is equipped with 4 of this type of PIN diode 4.

[0041] The working method of the broadband angle-insensitive nonlinear electromagnetic transmission modulation surface of the present invention is as follows: Within the frequency band of 3.51~5.02GHz, when the electromagnetic field strength irradiating the surface of the structure is lower than the starting field strength, the PIN diode 4 is in the cut-off state, the structure is not connected, the insertion loss of the signal is less than 1.7dB, and the signal can propagate through the metasurface. When the electromagnetic field strength irradiating the surface of the structure exceeds the starting field strength, a voltage sufficient to conduct is induced across the PIN diode 4, the structure is connected, and a band-stop shielding effect is generated for the electromagnetic waves. The shielding effect reaches more than 15dB, and more than 96.8% of the electromagnetic wave energy is reflected, achieving the effect of energy selection. The starting field strength is 0.9 kV / m.

[0042] The technical solution of the present invention will be further described in detail below through specific embodiments: Example 1: In this embodiment, the broadband angle-insensitive nonlinear electromagnetic transmission modulation surface is composed of several structural units arranged periodically. Each structural unit includes a metal layer and a dielectric substrate 1, with the metal layer disposed on the dielectric substrate 1. The dielectric substrate 1 has a square structure, a side length L = 9.4 mm, and is model FR-4 with a relative permittivity of [missing information]. The loss tangent is 0.02, the thickness h1=0.8mm, and the copper cladding thickness h2=0.018mm.

[0043] The metal layer includes a square metal ring 3 and a serrated structure 2. The square metal ring 3 is disposed along the four sides of the dielectric substrate 1, and the serrated structure 2 is disposed on the outer side of one end of the square metal ring 3. The outer side length of the square metal ring 3 is l1=8.8mm, the inner side length is l2=8.2mm, and the line width is w1=0.3mm.

[0044] The sawtooth structure 2 is composed of 8 layers of metal strips arranged sequentially from the inside out. Each metal strip has a width of t = 0.0375 mm, and the total width is... The length increases by p = 0.15 mm from the outside to the inside. The longest metal strip on the inner side of the sawtooth structure 2 is close to the square metal ring 3; the shortest outer metal strip is aligned with the edge of the dielectric substrate 1, with a length l3 = 4.39 mm, which is 0.01 mm shorter than half of l1, to avoid direct connection between the sawtooth structures 2 of adjacent structural units.

[0045] On each side of the square structure of the dielectric substrate 1, a gap is formed between the end of the square metal ring 3 with the serrated structure 2 and the end of the adjacent side without the serrated structure 2. The gap has a length g = 1.0 mm and a width w1 + w2 = 0.6 mm. The PIN diodes 4 are all mounted clockwise. The cutoff capacitance of the PIN diodes 4 used is 0.018 pF, and the on-resistance is 5.2 Ω. Four of these PIN diodes 4 are mounted in each structural unit.

[0046] Figure 3 The simulation results of S-parameters in the 2–7 GHz frequency domain of Example 1 under periodic boundary conditions are presented when high-power electromagnetic waves are incident perpendicularly onto an energy-selective metasurface. In this case, a voltage sufficient to turn on the PIN diode is induced across it, and the conducting PIN diode is equivalent to a 5.2 Ω resistor. This embodiment achieves a shielding effect of 15 dB within the 3.51–5.02 GHz frequency band, with a relative bandwidth of 35.7%.

[0047] Figure 4 The simulation results of S-parameters in the frequency domain of Example 1, from 2 to 7 GHz, are presented when a low-power electromagnetic signal is incident perpendicularly onto an energy-selective metasurface. The PIN diode is in the off state, equivalent to a capacitance of 0.018 pF. The insertion loss is less than 1.7 dB in the 3.51–5.02 GHz band.

[0048] The Spice model of the PIN diode was imported into electromagnetic simulation software. Using a field-circuit joint electromagnetic simulation method, a time-domain nonlinear simulation of the structure in Example 1 was performed. The applied incident signal was a 4GHz sinusoidal signal with increasing power. The results are as follows: Figure 5As shown, initially, a low-power sinusoidal signal is incident perpendicularly onto the metasurface with a power amplitude of 0.0025W. At this point, the PIN diode is in the off state, and the signal transmits normally through the metasurface with very low loss. Subsequently, the signal energy gradually increases, but the transmitted electromagnetic wave energy stabilizes after a slight increase and no longer increases with the increase of the incident signal energy, thus demonstrating the shielding effect of high-power electromagnetic waves. When a high-power signal is incident, the signal power amplitude is 25W, but only electromagnetic wave energy with an amplitude of about 0.2W passes through. At this point, the PIN diode is in the on state, and most of the energy is reflected by the metasurface, providing high-power microwave protection. Time-domain nonlinear simulation can accurately simulate the nonlinear switching process of the PIN diode from off to on under electromagnetic wave irradiation, thereby comprehensively evaluating its dynamic performance. The simulation results reveal in more detail the selective transmission of electromagnetic waves of different energies in this embodiment.

[0049] The compact, miniaturized structure helps improve angular stability. Figure 6 The S21 curves of Example 1 under different oblique incident angles θ are shown. Within the incident angle range of 0° to 40°, Example 1 exhibits a relatively stable frequency response regardless of whether it is in a band-stop or transparent state, and regardless of whether it is a TE wave or a TM wave incident. This indicates that the performance variation of the energy-selective metasurface designed in this invention meets the design expectations and satisfies the basic requirement of angle insensitivity in practical applications. Furthermore, the proposed structure is a rotationally symmetric structure, which is similar for TE or TM waves of various polarization angles. This design ensures a stable frequency response for electromagnetic waves with different polarization angles. The S21 curves of Example 1 when incident perpendicularly at different polarization angles ψ are shown below. Figure 7 As shown, the obtained frequency response curves highly overlap, which strongly proves that the present invention has successfully achieved polarization-independent characteristics, enabling it to perform stable and reliable energy selection for electromagnetic waves from any polarization direction.

[0050] In summary, this invention provides a miniaturized broadband energy-selective metasurface based on a square resonant ring and a sawtooth structure. Electromagnetic simulations in both the time and frequency domains verify that this structure possesses low-power transmission and high-power shielding characteristics. The designed metasurface unit size is 9.4mm × 9.4mm, with a 15dB shielding bandwidth covering 3.51–5.02 GHz, a relative bandwidth of 35.7%, and an insertion loss for low-power signals better than 1.7dB. Ultimately, a miniaturized, polarization-independent, and angle-stable energy-selective metasurface is obtained. This invention significantly improves the survivability of electronic devices in complex electromagnetic environments, demonstrating significant engineering application value.

[0051] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A broadband angle-insensitive nonlinear electromagnetic transmission modulation surface, characterized in that, It includes several structural units, which are arranged periodically. The structural unit includes a metal layer and a dielectric substrate (1). The dielectric substrate (1) is a square structure. The metal layer is disposed on the dielectric substrate (1). The metal layer is provided with a sawtooth structure (2), a square metal ring (3) and a PIN diode (4). The square metal ring (3) is disposed along the side length of the dielectric substrate (1). The sawtooth structure (2) is disposed at one end of the outer side of the square metal ring (3). A gap is provided between the square metal rings (3) on two adjacent sides of the dielectric substrate (1). The PIN diode (4) is installed in the gap.

2. The broadband angle-insensitive nonlinear electromagnetic transmission modulation surface according to claim 1, characterized in that, A copper film is coated on the dielectric substrate (1).

3. The broadband angle-insensitive nonlinear electromagnetic transmission modulation surface according to claim 1, characterized in that, The dielectric substrate (1) has a relative permittivity of 4.4 and a loss tangent of 0.

02.

4. The broadband angle-insensitive nonlinear electromagnetic transmission modulation surface according to claim 1, characterized in that, The sawtooth structure (2) includes several layers of metal strips arranged sequentially from the inside to the outside.

5. The broadband angle-insensitive nonlinear electromagnetic transmission modulation surface according to claim 4, characterized in that, The metal strip on the inner side of the serrated structure (2) is the longest, and the metal strip on the inner side is in close contact with the square metal ring (3).

6. The broadband angle-insensitive nonlinear electromagnetic transmission modulation surface according to claim 4, characterized in that, The metal strip on the outside of the sawtooth structure (2) is the shortest, and the metal strip on the outside is aligned with the edge of the dielectric substrate (1).

7. The broadband angle-insensitive nonlinear electromagnetic transmission modulation surface according to claim 1, characterized in that, One end of the sawtooth structure (2) is flush with one end of the square metal ring (3). The end of the sawtooth structure (2) that is flush with the square metal ring (3) is connected to one end of the PIN diode (4). The other end of the PIN diode (4) is connected to the other end of the square metal ring (3).

8. The broadband angle-insensitive nonlinear electromagnetic transmission modulation surface according to claim 1, characterized in that, The PIN diode (4) is mounted clockwise.

9. The broadband angle-insensitive nonlinear electromagnetic transmission modulation surface according to claim 1, characterized in that, The cutoff capacitance of the PIN diode (4) is 0.018pF and the on-resistance is 5.2Ω.

10. A method for operating the broadband angle-insensitive nonlinear electromagnetic transmission modulation surface according to any one of claims 1 to 9, characterized in that, include: Within the frequency band of 3.51~5.02GHz, when the electromagnetic field strength irradiating the surface of the structure is lower than the starting field strength, the PIN diode (4) is in the cut-off state, the structure is not connected, the insertion loss of the signal is less than 1.7dB, and the signal can propagate through the metasurface. When the electromagnetic field strength irradiating the surface of the structure exceeds the starting field strength, a voltage sufficient to conduct is induced at both ends of the PIN diode (4), the structure is connected, and a band-stop shielding effect is generated on the electromagnetic wave. The shielding effect reaches more than 15dB, and more than 96.8% of the electromagnetic wave energy is reflected. The starting field strength is 0.9 kV / m.

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