High-selectivity broadband optical transparent energy selective surface and control method

Abstract

The invention discloses a high-selectivity broadband optical transparent energy selective surface and a control method. The high-selectivity broadband optical transparent energy selective surface comprises a single-layer optical transparent substrate and a parallel circuit structure, the LC series resonance branch is used for forming a fixed stop band in a conventional working state and can form a double-stop-band coupling structure with the field nonlinear device series branch after impedance change under strong electromagnetic attack so as to expand the protection bandwidth, and stable and efficient shielding in the whole target protection frequency band is achieved; and the field-induced nonlinear device series branch is used for performing main shielding and passband adaptive adjustment under strong electromagnetic attack through state switching of the field-induced nonlinear device, that is, the field-induced nonlinear device series branch can change the impedance characteristic under strong electromagnetic field excitation. The LC series branch and the field nonlinear device series branch are integrated on the single-layer light transparent base material, broadband protection performance and low insertion loss which are equivalent to those of a multi-layer or cascade structure are obtained, and meanwhile an extremely small section and a compact structure are achieved.

Description

A highly selective broadband optically transparent energy-selective surface and its control method Technical Field

[0001] This invention relates to the field of strong electromagnetic protection technology, and in particular to a highly selective broadband optically transparent energy selective surface and its control method. Background Technology

[0002] The rapid development of strong electromagnetic attack technologies poses a threat to electronic information systems. Against this backdrop, Energy Selective Surfaces (ESS) have emerged as a radio frequency front-end protection technology, demonstrating broad application prospects. ESSs selectively target the energy of incident electromagnetic waves, ensuring the transmission and reception of normal low-power signals while effectively shielding against strong electromagnetic interference signals. In practical applications, precise frequency control of low-power incident signals and efficient shielding and broadband protection of high-power incident signals are crucial. In existing single-layer ESSs, the shielding effectiveness (SE) of broadband ESSs decreases with increasing frequency under high-power signals. While dual-resonant ESSs offer low insertion loss and high shielding effectiveness at their operating frequency, there is a one-to-one correspondence between their operating bandwidth and resonant frequency; adjusting the operating bandwidth typically causes a shift in the resonant frequency, presenting certain limitations in achieving the aforementioned functions. Multilayer ESS structures or cascaded FSS and ESS structures typically have larger operating bandwidth and better shielding performance and insertion loss, but they also usually have a larger profile, which limits their application scenarios; moreover, most current energy selective surfaces do not have optical transparency properties, so they cannot be used in optical protection windows. Summary of the Invention

[0003] This invention provides a highly selective broadband optically transparent energy-selective surface and a control method thereon to overcome the aforementioned technical problems.

[0004] To achieve the above objectives, the technical solution of the present invention is: a highly selective broadband optically transparent energy selective surface, comprising a single-layer optically transparent substrate and a parallel circuit structure disposed on the single-layer optically transparent substrate; the parallel circuit structure includes an LC series branch and a field-induced nonlinear device series branch; the LC series resonant branch is used to form a fixed stopband under normal operating conditions and can, under strong electromagnetic attacks, form a dual stopband coupling structure with the field-induced nonlinear device series branch after impedance change to expand the protection bandwidth; the field-induced nonlinear device series branch is used to adaptively adjust the main shield and passband under strong electromagnetic attacks through the state switching of the field-induced nonlinear device, that is, it can change its impedance characteristics under strong electromagnetic field excitation.

[0005] Furthermore, the LC series branch includes a first equivalent inductance module, a second equivalent inductance module, and a capacitor module; the first equivalent inductance module and the second equivalent inductance module are connected in series through the capacitor module; the capacitor module includes a first capacitor and a second capacitor connected in parallel.

[0006] Furthermore, both the first and second equivalent inductance modules are formed by multiple straight micro / nano metal wires connected in parallel.

[0007] Furthermore, the series branch of the field-induced nonlinear device includes a third equivalent inductance module, a fourth equivalent inductance module, and a third capacitor; the third equivalent inductance module and the fourth equivalent inductance module are connected in series through the third capacitor; each of the third equivalent inductance module and the fourth equivalent inductance module includes a first arc-shaped inductance structure, a second arc-shaped inductance structure, and a field-induced nonlinear device, wherein the field-induced nonlinear device is a diode; the first arc-shaped inductance structure and the second arc-shaped inductance structure are connected in series through the diode.

[0008] Furthermore, both the first and second arc-shaped inductor structures are formed by multiple arc-shaped micro / nano metal wires connected in parallel.

[0009] A control method for a highly selective broadband optically transparent energy-selective surface includes: controlling the operating state of the energy-selective surface, including: S1, real-time sensing of the field strength of the incident electromagnetic wave; S2, the energy-selective surface adaptively responding within a conduction threshold range based on the sensed field strength, including: S21, if the field strength is lower than a set conduction threshold, controlling the field-induced nonlinear device to be in a cutoff state, so that the energy-selective surface is in a transmission state; at this time, the energy-selective surface has passband characteristics at the center frequency, allowing lossless signal transmission; S22, if the field strength is higher than the set conduction threshold, controlling the field-induced nonlinear device to switch to a conduction state. The energy selection surface is switched to a shielded state with an extended stopband; S3, when the field strength drops back to a safe range, it automatically returns to the transmission state of S21; This also includes: controlling the operating bandwidth of the passband of the energy selection surface in the transmission state, specifically: by controlling the first equivalent inductance module and the second equivalent inductance module to increase the equivalent inductance of the low-frequency stopband resonance by an equal amount while decreasing the equivalent inductance of the high-frequency stopband resonance, the operating bandwidth of the passband in the transmission state is increased; by controlling the first equivalent inductance module and the second equivalent inductance module to increase the equivalent inductance of the high-frequency stopband resonance by an equal amount while decreasing the equivalent inductance of the low-frequency stopband resonance, the operating bandwidth of the passband in the transmission state is decreased.

[0010] Beneficial Effects: This invention constructs a dual-resonance mechanism by introducing a parallel combination of an LC series branch and a field-induced nonlinear device series branch. Under strong electromagnetic attacks, the field-induced nonlinear device causes both branches to resonate within or near the operating frequency band, forming two tightly coupled stopbands. This effectively broadens the frequency range for high shielding effectiveness, overcoming the deficiency of traditional broadband ESS shielding effectiveness degradation at high frequencies and achieving stable and efficient shielding across the entire target protection frequency band. This invention integrates the LC series branch and the field-induced nonlinear device series branch on a single-layer optically transparent substrate, achieving broadband protection performance and low insertion loss comparable to multilayer or cascaded structures while realizing an extremely small profile and compact structure. This allows the ESS to be applied in scenarios with stringent requirements for space, weight, and conformal capability, such as conformal radomes for aircraft and optical windows, greatly expanding its application range. Attached Figure Description

[0011] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0012] Figure 1 is a diagram of the dual-stopband equivalent circuit model in this invention; Figure 2 is a curve of the transmission coefficient of the dual-stopband equivalent circuit model in this invention; Figure 3 is a schematic diagram of the structure of the high-selectivity broadband optically transparent energy selective surface in this invention; Figure 4 is a diagram of the conduction and blocking equivalent circuit model of the high-selectivity broadband optically transparent energy selective surface in an embodiment of this invention; Figure 5 is a schematic diagram of the structure of the LC series branch in an embodiment of this invention; Figure 6 is a schematic diagram of the structure of the series branch of the field-induced nonlinear device in an embodiment of this invention; Figure 7 is a curve of the equivalent circuit model and full-wave electromagnetic simulation results of the high-selectivity broadband optically transparent energy selective surface in an embodiment of this invention. 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, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0013] Figure 1 shows the dual-stopband equivalent circuit model (ECM). As can be seen, the ECM consists of a parallel LC series branch and a series branch of the field-induced nonlinear device. The parallel connection of the LC series branch and the series branch of the field-induced nonlinear device generates parallel resonance at the center frequency of the ESS, forming a passband to allow signal passage. The LC series branch generates LC series resonance at the low-frequency side of the center frequency of the ESS, forming a stopband to shield the signal. When the diode in the series branch of the field-induced nonlinear device is not conducting, LC series resonance is generated at the high-frequency side of the center frequency of the ESS, forming a stopband to shield the signal. Its transmission coefficient curve is shown in Figure 2. At this time, by controlling the resonant frequencies of the LC series branch and the series branch of the field-induced nonlinear device, the passband bandwidth can be adjusted without affecting the resonant frequency of the operating frequency band. When the diode in the series branch of the field-induced nonlinear device is turned on, an LC series resonance is generated at the center frequency of the ESS, forming a stopband to shield the signal. At this time, the LC series stopband and the inductor are close to the series stopband of the field-induced nonlinear device, which will cause resonant coupling. The insertion loss of the passband between the two stopbands increases sharply, the passband narrows or even disappears. Therefore, the protection bandwidth on the operating frequency side can be extended through the resonant frequency of the LC series branch.

[0014] Based on the above principles, this embodiment provides a highly selective broadband optically transparent energy selective surface, as shown in Figure 3. It includes a single-layer optically transparent substrate and a parallel circuit structure disposed on the single-layer optically transparent substrate. The parallel circuit structure includes an LC series branch and a field-induced nonlinear device series branch. The LC series resonant branch forms a fixed stopband under normal operating conditions and, under strong electromagnetic attacks, can form a dual stopband coupling structure with the impedance-changed field-induced nonlinear device series branch to extend the protection bandwidth. The field-induced nonlinear device series branch is used to adaptively adjust the main shielding and passband under strong electromagnetic attacks through the state switching of the field-induced nonlinear device, i.e., it can change its impedance characteristics under strong electromagnetic field excitation.

[0015] In this embodiment, the single-layer optically transparent substrate is made of a thin-layer transparent polyimide material, which makes the energy selective surface optically transparent and has high optical transparency.

[0016] Specifically, this embodiment employs a dual-stopband resonant circuit in a single-layer energy selective surface to achieve frequency control, providing high selectivity and frequency control capability for the signal. Specifically, the physical dimensions of the highly selective broadband optically transparent energy selective surface include the period P, linewidth a, capacitor gap S1, toroidal inductor gap S2, diode gap S3, width d of the arc-shaped and perpendicular parallel conductors, and length L of the perpendicular conductor. The actual equivalent circuit model of this ESS physical structure is shown in Figure 4, including C1 and C... mThe parallel connection of L1 and L2 forms an LC series branch, and the series connection of L3, L4, C2 and two diodes forms a field-induced nonlinear device series branch. The two branches are connected in parallel, and the diode is equivalent to a capacitor C when it is not conducting. diode When conducting, it is equivalent to an inductor Ls and a resistor Rs connected in series.

[0017] Specifically, this embodiment employs a parallel resonant structure in a single-layer surface and utilizes micron-thin copper wires to propose an equivalent optically transparent structure consisting of LC series connection and inductor-diode series connection. This results in the design of a highly selective broadband optically transparent ESS operating at 7.5 GHz, which offers advantages such as high selectivity, bandwidth protection, optical transparency, and low profile.

[0018] Specifically, this embodiment utilizes two independently controllable resonant branches: an LC series branch providing a fixed resonant point, and a resonant point of the field-induced nonlinear device series branch determined by the state of the field-induced nonlinear device (controlled by the incident field strength). Under low-power normal conditions, the passband bandwidth can be flexibly adjusted by separately regulating the resonant frequencies of the two branches. Furthermore, without changing the center operating frequency, the passband width allowing normal signals to pass can be independently adjusted, greatly enhancing design flexibility.

[0019] In a specific embodiment, the LC series branch includes a first equivalent inductance module, a second equivalent inductance module, and a capacitor module; the first equivalent inductance module and the second equivalent inductance module are connected in series through the capacitor module; the capacitor module includes a first capacitor and a second capacitor connected in parallel.

[0020] In a specific embodiment, as shown in Figure 5, both the first equivalent inductance module and the second equivalent inductance module are formed by multiple straight micro-nano metal wires connected in parallel.

[0021] Specifically, both the first and second equivalent inductance modules are formed by multiple straight micro / nano metal wires connected in parallel, and are equivalent to inductors. The gap between the first and second equivalent inductance modules is equivalent to a capacitor C. Compared with traditional single metal wires, the structure formed by multiple straight micro / nano metal wires connected in parallel has a smaller metal duty cycle under the same equivalent inductance. The parallel connection of multiple micro / nano metal wires improves the optical transmittance of the surface structure without affecting the overall equivalent inductance. The equivalent capacitance value of the gap between the first and second equivalent inductance modules is affected by the number of micro / nano metal wires. In this embodiment, the equivalent capacitance value is controlled by loading a capacitor element. In a specific embodiment, the series branch of the field-induced nonlinear device includes a third equivalent inductance module, a fourth equivalent inductance module, and a third capacitor; the third equivalent inductance module and the fourth equivalent inductance module are connected in series through the third capacitor; each of the third equivalent inductance module and the fourth equivalent inductance module includes a first arc-shaped inductance structure, a second arc-shaped inductance structure, and a field-induced nonlinear device, wherein the field-induced nonlinear device is a diode; the first arc-shaped inductance structure and the second arc-shaped inductance structure are connected in series through the diode.

[0022] In a specific embodiment, as shown in FIG6, both the first arc-shaped inductor structure and the second arc-shaped inductor structure are formed by multiple arc-shaped micro-nano metal wires connected in parallel.

[0023] Specifically, both the first and second arc-shaped inductor structures are formed by multiple arc-shaped micro / nano metal wires connected in parallel, and are equivalent to inductors. In this embodiment, a field-induced nonlinear device is set in the gap between the first and second arc-shaped inductor structures to form a series connection between the inductor and the diode, which ensures the smooth conduction of the diode and can reduce the impact of the connection gap capacitance on the parallel connection of the diode.

[0024] Specifically, the highly selective broadband optically transparent energy selective surface designed in this embodiment, which combines the equivalent structure of optically transparent circuits and the equivalent circuit model of dual-stopband, can operate in the 7.5GHz satellite communication frequency band. The thickness of the thin transparent polyimide substrate is h1, the period dimension p = 14.2mm, the width of the metal wire a = 0.05mm, and the capacitor gap S1, the annular inductor gap S2, the diode gap S3, the width d of the arc-shaped and vertical parallel wires, and the length L of the vertical wire can be specifically set according to actual needs. Based on the unit duty cycle equivalent surface transmittance, the transmittance of the energy selective surface given in this embodiment is 94%.

[0025] Specifically, the equivalent circuit model and full-wave electromagnetic simulation results of the energy selective surface given in this embodiment are shown in Figure 7. As can be seen from the figure, under low-power signal conditions, the insertion loss (IL) of this energy selective surface is 0.2 dB at 7.5 GHz. Within the frequency range of 7.2-7.8 GHz, the IL remains below 1 dB, while the insertion loss increases sharply outside the passband, demonstrating excellent frequency selectivity. Under high-power conditions, the shielding effectiveness can reach 50 dB, with an SE greater than 20 dB in the 6.5-8.5 GHz range and a SE greater than 10 dB in the 4-11 GHz range.

[0026] This embodiment also provides a control method for a highly selective broadband optically transparent energy-selective surface, including: controlling the operating state of the energy-selective surface, including: S1, real-time sensing of the field strength of the incident electromagnetic wave; S2, the energy-selective surface adaptively responding within a conduction threshold range based on the sensed field strength, including: S21, if the field strength is lower than a set conduction threshold, controlling the field-induced nonlinear device to be in a cutoff state, so that the energy-selective surface is in a transmission state; at this time, the energy-selective surface has passband characteristics at the center frequency, allowing lossless signal transmission; S22, if the field strength is higher than the set conduction threshold, controlling the field-induced nonlinear device to switch to... In the conduction state, the energy selection surface is switched to a shielded state with an extended stopband; S3, when the field strength drops back to a safe range, it automatically returns to the transmission state of S21; This also includes: controlling the operating bandwidth of the passband of the energy selection surface in the transmission state, specifically: by controlling the first equivalent inductance module and the second equivalent inductance module to increase the equivalent inductance of the low-frequency stopband resonance by an equal amount while decreasing the equivalent inductance of the high-frequency stopband resonance, the operating bandwidth of the passband in the transmission state is increased; by controlling the first equivalent inductance module and the second equivalent inductance module to increase the equivalent inductance of the high-frequency stopband resonance by an equal amount while decreasing the equivalent inductance of the low-frequency stopband resonance, the operating bandwidth of the passband in the transmission state is decreased.

[0027] Specifically, in this embodiment, when it is necessary to generate parallel resonance at the center frequency of the ESS to form a passband to allow signal passage, the diode in the series branch of the field-induced nonlinear device is controlled to be non-conductive; when it is necessary to generate LC series resonance at the center frequency of the ESS to form a stopband for signal shielding, the diode in the series branch of the field-induced nonlinear device is controlled to be conductive. At this time, the equivalent capacitance in the series branch of the field-induced nonlinear device increases, which can shield the signal, ultimately realizing the switching between bandpass and bandstop resonance, and the stopband resonance generated at the center frequency of the ESS has higher shielding efficiency; when it is necessary to control the increase of the passband bandwidth, the total value of the first equivalent inductance module L1 and the second equivalent inductance module L2 remains unchanged, while the inductance value of the first equivalent inductance module L1 is increased and the inductance value of the second equivalent inductance module L2 is decreased; when it is necessary to control the decrease of the passband bandwidth, the total value of the first equivalent inductance module L1 and the second equivalent inductance module L2 remains unchanged, while the inductance value of the second equivalent inductance module L2 is increased and the inductance value of the first equivalent inductance module L1 is decreased.

[0028] Specifically, when the diode is not conducting, the LC series branch will generate stopband resonance on the low-frequency side of the center frequency of the ESS; the field-induced nonlinear device series branch will also generate stopband resonance on the high-frequency side of the center frequency of the ESS. At this time, the passband resonant frequency can be controlled by L1 and L2 together. That is, L1 controls the low-frequency stopband resonant frequency, and L2 controls the high-frequency stopband resonant frequency. When the total value of L1 and L2 remains unchanged, and L1 is increased while L2 is decreased, the passband resonant frequency remains unchanged, the low-frequency stopband resonant frequency shifts to a lower frequency, and the high-frequency stopband resonant frequency shifts to a higher frequency. At this time, the passband bandwidth increases. Conversely, when the total value of L1 and L2 remains unchanged, and L2 is increased while L1 is decreased, the passband resonant frequency remains unchanged, the low-frequency stopband resonant frequency shifts to a higher frequency, and the high-frequency stopband resonant frequency shifts to a lower frequency. At this time, the passband bandwidth decreases, thereby realizing the control of the passband operating bandwidth.

[0029] Specifically, the method for controlling the operating bandwidth of a dual-resonant ESS proposed in this embodiment differs from that of a broadband ESS. The method proposed in this embodiment can achieve bandpass and bandstop resonance switching at the operating frequency, and has higher shielding effectiveness at the operating frequency. Unlike the previous method of directly adjusting the operating bandwidth of a dual-resonant ESS, this method indirectly controls the operating bandwidth by changing the resonant frequencies of the stopbands on both sides of the operating bandwidth, while keeping the resonant frequency of the operating bandwidth constant.

[0030] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A highly selective broadband optically transparent energy-selective surface, characterized in that, The system includes a single-layer optically transparent substrate and a parallel circuit structure disposed on the single-layer optically transparent substrate. The parallel circuit structure includes an LC series branch and a field-induced nonlinear device series branch. The LC series resonant branch is used to form a fixed stopband under normal operating conditions and can form a dual stopband coupling structure with the field-induced nonlinear device series branch after impedance change under strong electromagnetic attacks to expand the protection bandwidth. The field-induced nonlinear device series branch is used to adaptively adjust the main shielding and passband under strong electromagnetic attacks by switching the state of the field-induced nonlinear device, that is, it can change its impedance characteristics under strong electromagnetic field excitation.

2. The highly selective broadband optically transparent energy-selective surface according to claim 1, characterized in that, The LC series branch includes a first equivalent inductance module, a second equivalent inductance module, and a capacitor module; the first equivalent inductance module and the second equivalent inductance module are connected in series through the capacitor module; the capacitor module includes a first capacitor and a second capacitor connected in parallel.

3. The highly selective broadband optically transparent energy-selective surface according to claim 2, characterized in that, Both the first and second equivalent inductance modules are formed by multiple straight micro / nano metal wires connected in parallel.

4. The highly selective broadband optically transparent energy-selective surface according to claim 2, characterized in that, The series branch of the field-induced nonlinear device includes a third equivalent inductance module, a fourth equivalent inductance module, and a third capacitor; the third equivalent inductance module and the fourth equivalent inductance module are connected in series through the third capacitor; each of the third equivalent inductance module and the fourth equivalent inductance module includes a first arc-shaped inductance structure, a second arc-shaped inductance structure, and a field-induced nonlinear device, wherein the field-induced nonlinear device is a diode; the first arc-shaped inductance structure and the second arc-shaped inductance structure are connected in series through the diode.

5. The highly selective broadband optically transparent energy-selective surface according to claim 4, characterized in that, Both the first and second arc-shaped inductor structures are formed by multiple arc-shaped micro / nano metal wires connected in parallel.

6. A method for controlling the highly selective broadband optically transparent energy-selective surface as described in claim 1, characterized in that, include: Controlling the operating state of the energy selective surface includes: S1, real-time sensing of the field strength of the incident electromagnetic wave; S2, the energy selective surface adaptively responds within a conduction threshold range based on the sensed field strength, including: S21, if the field strength is lower than a set conduction threshold, controlling the field-induced nonlinear device to be in the off state, so that the energy selective surface is in the transmission state; at this time, the energy selective surface has passband characteristics at the center frequency, allowing lossless signal transmission; S22, if the field strength is higher than the set conduction threshold, controlling the field-induced nonlinear device to switch to the conduction state, so that the energy selective surface switches to a state with widening... The shielding state of the stopband is extended; S3, when the field strength drops back to the safe range, it automatically returns to the transmission state of S21; wherein, it also includes: controlling the working bandwidth of the passband of the energy selection surface in the transmission state, specifically: by controlling the first equivalent inductance module and the second equivalent inductance module to increase the equivalent inductance of the low-frequency stopband resonance by an equal amount while decreasing the equivalent inductance of the high-frequency stopband resonance, the working bandwidth of the passband in the transmission state is increased; by controlling the first equivalent inductance module and the second equivalent inductance module to increase the equivalent inductance of the high-frequency stopband resonance by an equal amount while decreasing the equivalent inductance of the low-frequency stopband resonance, the working bandwidth of the passband in the transmission state is decreased.

Images