An energy selective surface with high shielding effectiveness

Abstract

The present invention provides an energy selective surface with high shielding effectiveness. The energy selective surface unit comprises, from top to bottom, a first energy selective structure 1, a first dielectric substrate layer 2, a second energy selective structure 3, an air layer 4, a frequency selective structure 5, and a second dielectric substrate layer 6; the first energy selective structure 1 is located on the upper surface of the first dielectric substrate layer 2; the second energy selective structure 3 is located on the lower surface of the first dielectric substrate layer 2; the frequency selective structure 5 is located on the upper surface of the second dielectric substrate layer 6; the present invention designs an energy selective surface by using a cascade method of an energy selective surface and a frequency selective surface; compared with a traditional energy selective surface, the present invention has a fast roll-off characteristic in a transmission state; and has a very high shielding effectiveness and a wide protection bandwidth in a protection state.

Description

Technical Field

[0001] The invention belongs to the technical field of electromagnetic protection, and in particular relates to an energy selective surface with high shielding effectiveness. Background Art

[0002] With the rapid development of electronic technology, the number of TTL, CMOS, transistors and other devices used in highly integrated chips has increased significantly. The increased density has made the pulse voltage they can withstand smaller and smaller, and the harm of electromagnetic pulses to electronic communication equipment has become increasingly prominent. In the increasingly complex high-power battlefield electromagnetic environment, high-power electromagnetic pulse weapons are particularly harmful to communication equipment. The interference and damage to communication electronic equipment is mainly caused by the coupling of electromagnetic fields and electronic systems. It can attack and interfere with any communication electronic equipment within the attack range, which can break down and burn electronic devices at the least, or destroy the entire communication system at the most.

[0003] The coupling modes of electromagnetic pulses and communication electronic equipment can be divided into "front door coupling" and "back door coupling". "Back door coupling" refers to the coupling formed by electromagnetic energy through holes, seams, cable connectors, etc. on the target metal shell. It mainly adopts traditional shielding, grounding, filtering and other technologies for protection, and the technology is relatively mature. "Front door coupling" refers to the direct coupling between electromagnetic pulses and the target's antenna, transmission line and other media. The radiated energy of the external electromagnetic field can be directly transmitted to the system through the system's antenna. At present, the technical means for "front door coupling" are mainly limiters and frequency selective surfaces, and each has its own shortcomings. Limiters will affect the passage of normal signals; frequency selective surfaces cannot work against strong electromagnetic threats within the band.

[0004] Energy selective surface is a new type of electromagnetic surface proposed in recent years. It is a typical adaptive strong electromagnetic protection device. Today's dual-resonance energy selective surface (reference [1][2]) can have a large shielding effectiveness at the center frequency, but once it deviates from the center frequency, the shielding effectiveness will drop sharply. In general, the shielding effectiveness of the dual-resonance energy selective surface in the passband is not high. If the attack frequency of a high-power microwave weapon deviates from the center frequency, it may break through the protection of the energy selective surface and cause damage to the electronic equipment through the antenna. Therefore, the energy selective surface needs to have a high shielding effectiveness in the entire passband. From this perspective, no scholar has proposed a method to improve the shielding effectiveness of the energy selective surface in the public literature.

[0005] References [1] N. Hu et al., "Design of Ultrawideband Energy-Selective Surface for High-Power Microwave Protection," in IEEE Antennas and Wireless Propagation Letters, vol. 18, no. 4, pp. 669-673, April 2019, doi: 10.1109 / LAWP.2019.2900760.

[0006] References [2] L. Zhou, L. Liu and Z. Shen, "High-Performance Energy Selective Surface Based on the Double-Resonance Concept," in IEEE Transactions on Antennas and Propagation, vol. 69, no. 11, pp. 7658-7666, Nov. 2021, doi: 10.1109 / TAP.2021.3075548. Summary of the invention

[0007] The purpose of the present invention is to address the above-mentioned electromagnetic protection problems and to provide an energy selective surface with high shielding effectiveness.

[0008] To achieve the above-mentioned purpose of the invention, the technical solution of the present invention is as follows:

[0009] An energy selective surface with high shielding effectiveness, characterized in that it comprises, from top to bottom, a first energy selective structure 1, a first dielectric substrate layer 2, a second energy selective structure 3, an air layer 4, a frequency selective structure 5, and a second dielectric substrate layer 6

[0010] The first energy selection structure 1 is located on the upper surface of the first dielectric substrate layer 2. The first energy selection structure 1 is composed of periodically arranged energy selection structure units. The first energy selection structure unit includes two upper and lower first gap structures 11, and a first "I"-shaped structure 12. The vertical center position of the first "I"-shaped structure 12 has a gap for installing a PIN diode 13; the second energy selection structure 3 is located on the lower surface of the first dielectric substrate layer 2. The second energy selection structure 3 is composed of periodically arranged energy selection structure units. The second energy selection structure unit is obtained by rotating the first energy selection structure unit 90 degrees around the center; the air layer 4 is located between the second energy selection structure 3 and the frequency selection structure 5; the frequency selection structure 5 is located on the upper surface of the second dielectric substrate layer 6. The frequency selection structure 5 is composed of periodically arranged frequency selection structure units. The frequency selection structure unit includes two upper and lower second gap structures 51, two left and right third gap structures 52, and a metal frame 53. The metal frame has a second "I"-shaped structure.

[0011] As a preferred solution, the periods of the first energy selection structure unit, the second energy selection structure unit and the frequency selection structure unit are all P.

[0012] As a preferred solution, the width of the first gap structure 11 is ge.

[0013] As a preferred solution, the transverse metal line width of the first I-shaped structure 12 is we1, and the vertical metal line width is we2.

[0014] As a preferred solution, the second gap structure 51 is bent, and the gap width is gf1.

[0015] As a preferred solution, the third gap structure 52 is bent and has a gap width of gf2.

[0016] As a preferred solution, the width of the metal strip in the metal frame 53 is wf1.

[0017] As a preferred solution, the second "I"-shaped structure 54 is composed of two "I"-shaped structures placed horizontally and vertically, the width of the middle vertical line of the "I"-shaped structure is wf2, the width of the upper and lower horizontal lines is wf3, and the length is lf.

[0018] As a preferred solution, the gap width between the transverse metal wire and the metal frame 53 in the second I-shaped structure 54 is gf3.

[0019] As a preferred solution, the PIN diode model is BAP-70-03 produced by NXP.

[0020] In terms of working principle:

[0021] The energy selective surface is realized by loading a PIN diode on a metal structure. When the power density is low, the diode is in the cut-off state, which can be approximately equivalent to a small capacitor. When the power density is high, the diode is in the on state, which can be approximately equivalent to a small inductor connected in series with a small resistor. When the working state of the diode changes, it will cause a huge difference in the surface impedance of the ESS, thereby realizing two working states of the ESS: transmission and shielding.

[0022] In order to further explain the principle, an equivalent circuit is established to analyze the energy selective surface. Figure 1 The equivalent circuit diagram of the cascade connection of the energy selective surface and the frequency selective surface is given. The air layer between the two surfaces is regarded as a transmission line, that is, a series inductor and a parallel capacitor are added between the energy selective surface and the frequency selective surface. And the equivalent parallel capacitance value is very small and can be ignored. So if Figure 1 As shown, the two surfaces are coupled through a series inductor L0. The thicker the air layer between the two surfaces, the larger the inductor L0 value, and the smaller the coupling between the energy selective surface and the frequency selective surface. Therefore, when the thickness of the air layer is certain, the energy selective structure and the frequency selective structure are weakly coupled, that is, the two-layer structure can maintain independence. According to the above analysis, the energy selective structure and the frequency selective structure can be designed separately.

[0023] The energy selection structure is a dual-resonance energy selection surface, which has low insertion loss at the center frequency in the transmission state; and high shielding effectiveness at the center frequency in the shielding state. However, the energy selection structure in the present invention is different from the traditional dual-resonance energy selection surface in that the energy selection structure in the present invention separates vertical polarization and horizontal polarization, and prints the first energy selection structure 1 and the second energy selection structure 3 on the upper and lower layers of the dielectric substrate respectively, reducing the number of diodes used. The second energy selection structure 3 is obtained by rotating the first energy selection structure 1 90 degrees around the center, and because the thickness of the first dielectric substrate layer 2 is very small, the performance of the two polarizations is almost completely consistent. Figure 2 The equivalent circuit diagrams of the energy selective structure in the transmission state and the shielding state in the present invention are given. After the energy selective surface and the frequency selective structure are cascaded, in the shielding state, in order to achieve high shielding effectiveness in the passband, the frequency selective surface needs to form a transmission zero point at the high frequency and low frequency of the passband. To achieve this purpose, the present invention designs an equivalent circuit of the frequency selective surface, such as Figure 3 shown.

[0024] In the transmission state, since both the energy selection structure and the frequency selection structure will form a reflection zero point at the center frequency, it can be predicted that after cascading, the present invention will form a second-order resonance. And after cascading, the transmission zero points formed by the frequency selection structure at the low frequency and high frequency of the center frequency will be retained, so that the present invention has a fast roll-off characteristic. In the shielding state, the reflection zero point of the energy selection structure at the original passband position becomes a transmission zero point. After cascading, overall, the present invention has a transmission zero point at the center frequency point, and the second-order resonance point disappears. Similarly, the transmission zero points formed by the frequency selection structure at the low frequency band and high frequency band of the center frequency will be retained. The three transmission zero points work together to form a high shielding efficiency stopband covering the entire passband.

[0025] The beneficial effects of the present invention are:

[0026] The present invention designs the equivalent circuits of the energy selection structure and the frequency selection structure respectively, and designs the specific structure according to the equivalent circuits. The present invention realizes by cascading the energy selection structure and the frequency selection structure: when low power density is incident, the energy selection surface designed by the present invention generates a passband in the C band, ensuring that the protected antenna receives and transmits signals normally, and has a fast roll-off characteristic; when high power density is incident, the energy selection surface designed by the present invention can form a high shielding effectiveness in the entire C band. And due to the rotational symmetry designed by the present invention, it is polarization insensitive. Compared with the existing energy selection surface, the energy selection surface designed by the present invention has a fast roll-off characteristic in the transmission state, a wider shielding bandwidth and a higher shielding effectiveness in the shielding state. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 An equivalent circuit diagram of the energy selective surface and the frequency selective surface cascaded in the present invention;

[0028] Figure 2 The equivalent circuit diagram of the energy selection structure provided by the present invention in the transmission state and the shielding state;

[0029] Figure 3 An equivalent circuit diagram of the frequency selection structure provided by the present invention;

[0030] Figure 4 A side view of an energy selective surface with high shielding effectiveness provided by the present invention;

[0031] Figure 5 This is a schematic diagram of the unit structure of the first energy selection structure 1 provided by the present invention;

[0032] Figure 6 This is a schematic diagram of the unit structure of the second energy selection structure 3 provided by the present invention;

[0033] Figure 7 A schematic diagram of a unit structure of a frequency selection structure provided by the present invention;

[0034] Figure 8 The frequency response of the energy selection structure provided by the present invention in the shielding state and the transmission state;

[0035] Fig. 9 The frequency response of the frequency selection structure provided by the present invention;

[0036] Fig.10 Frequency response in shielding state and transmission state for energy selection surface of high shielding effectiveness provided by the present invention;

[0037] 1 is the first energy selection structure, 2 is the first dielectric substrate layer, 3 is the second energy selection structure, 4 is the air layer, 5 is the frequency selection structure, 6 is the second dielectric substrate layer, 11 is the first gap structure, 12 is the first "I" shaped structure, 13 is a PIN diode, 51 is the second gap structure, 52 is the third gap structure, 53 is a metal frame, and 54 is the second "I" shaped structure. DETAILED DESCRIPTION

[0038] The following describes the embodiments of the present invention through specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention.

[0039] This embodiment provides an energy selective surface with high shielding effectiveness. The energy selective surface includes, from top to bottom, a first energy selective structure 1, a first dielectric substrate layer 2, a second energy selective structure 3, an air layer 4, a frequency selective structure 5, and a second dielectric substrate layer 6.

[0040] The first energy selection structure 1 is located on the upper surface of the first dielectric substrate layer 2. The first energy selection structure 1 is composed of periodic arrangement of energy selection structure units. The first energy selection structure unit includes two upper and lower first gap structures 11 and a first "I"-shaped structure 12. The vertical center position of the first "I"-shaped structure 12 has a gap for installing a PIN diode 13. The second energy selection structure 3 is located on the lower surface of the first dielectric substrate layer 2. The second energy selection structure 3 is composed of periodic arrangement of energy selection structure units. The second energy selection structure unit is obtained by rotating the first energy selection structure unit around the center by 90 degrees. The air layer 4 is located between the second energy selection structure 3 and the frequency selection structure 5. The frequency selection structure 5 is located on the upper surface of the second dielectric substrate layer 6. The frequency selection structure 5 is composed of periodic arrangement of frequency selection structure units. The frequency selection structure unit includes two upper and lower second gap structures 51, two left and right third gap structures 52, and a metal frame 53. The metal frame has a second "I"-shaped structure. The periods of the first energy selection structure unit, the second energy selection structure unit and the frequency selection structure unit are all P. The width of the first gap structure 11 is ge. The width of the horizontal metal line of the first "I"-shaped structure 12 is we1, and the width of the vertical metal line is we2. The second gap structure 51 is bent, and the gap width is gf1. The third gap structure 52 is bent, and the gap width is gf2. The width of the metal strip in the metal frame 53 is wf1. The second "I"-shaped structure 54 is composed of two "I"-shaped structures placed horizontally and vertically. The width of the vertical line in the middle of the "I"-shaped structure is wf2, and the width of the upper and lower horizontal lines is wf3, and the length is lf. The width of the gap between the horizontal metal line and the metal frame 53 in the second "I"-shaped structure 54 is gf3. The PIN diode model is BAP-70-03 of NXP.

[0041] Figure 1 This is an equivalent circuit diagram of the cascaded energy selective surface and the frequency selective surface provided by the present invention. According to analysis, in order to ensure that the performance after cascading meets the requirements, the energy selective surface and the frequency selective surface need to maintain a certain distance.

[0042] Figure 2 The equivalent circuit diagram of the energy selection structure provided by the present invention in the transmission state and the shielding state, the capacitor C1 is equivalently provided by the first gap structure 11, the inductor L1 is equivalently provided by the vertical line of the "I"-shaped structure, and the inductor L2 is equivalently provided by the horizontal line of the rotated "I"-shaped structure. In the transmission state, C1, L1, L2 and Cdiode form a reflection zero point at the center frequency; in the shielding state, C1, L1 and Ldiode form a transmission zero point at the center frequency.

[0043] Figure 3This is an equivalent circuit diagram of the frequency selection structure provided by the present invention. Capacitor Cf1 is equivalent to the second slot structure 51 or the third slot structure 52; Lf1 is equivalent to the metal frame; Cf2 is equivalent to the slot between the second "I"-shaped structure and the metal frame; Lf2 is equivalent to the vertical metal line in the middle of the second "I"-shaped structure. This structure forms a reflection zero point at the center frequency and a transmission zero point at the high frequency and low frequency of the center frequency.

[0044] according to Figure 1 , Figure 2 and Figure 3 The principles and equivalent circuits shown are used to build implementation models such as Figure 4 , 5 , as shown in Figure 6. Figure 4 This is a side view of this embodiment, which includes, from top to bottom, a first energy selection structure, a first dielectric substrate layer, a second energy selection structure, an air layer, a frequency selection structure, and a second dielectric substrate layer. The first energy selection structure is located on the upper surface of the first dielectric substrate layer, the second energy selection structure is located on the lower surface of the first dielectric substrate layer, and the frequency selection structure is located on the upper surface of the second dielectric substrate layer. Both the first dielectric substrate layer and the second dielectric substrate layer use F4B plates with a dielectric constant of 2.65, and have the same thickness of 0.5 mm. The thickness of the air layer is 7 mm.

[0045] Figure 5 This is a schematic diagram of the first energy selection structural unit structure. The size of the unit structure is p*p, and the value of p is 12 mm. The width of the first gap structure is ge=0.2 mm, which controls the size of the C1 value. The width of the horizontal metal wire of the first "I" shaped structure is we1=0.4 mm, which controls the size of the L2 value. The vertical metal wire width is we2=2.5 mm, which controls the size of the L1 value. Figure 6 Schematic diagram of the structure of the second energy selection structural unit. The second energy selection structural unit is obtained by rotating the first energy selection structural unit 90 degrees around the center.

[0046] Figure 7The schematic diagram of the frequency selective structure shows that the size of the unit structure is p*p, and the value of p is 12mm; the second gap structure is bent, and the gap width is gf1=0.16mm, which controls the value of Cf1; the third gap structure is bent, and the gap width is gf2=0.16mm; the width of the metal strip in the metal frame is wf1=1.23mm, which controls the value of Lf1; the second "I"-shaped structure is composed of two "I"-shaped structures placed horizontally and vertically, and the width of the vertical line in the middle of the "I"-shaped structure is wf2=0.3mm, which controls the value of Lf2, and the width of the upper and lower horizontal lines is wf3=0.5mm, and the length is lf=5mm; the gap width between the horizontal metal line and the metal frame in the second "I"-shaped structure is gf3=0.2mm. The value of Cf2 is controlled by lf and gf3.

[0047] Figure 8 The frequency response of the energy selective structure in shielding and transmission states is shown. Under low power density electromagnetic wave incident conditions, the insertion loss is less than 1dB from 4GHz to 5GHz, and the resonance point is at 4.6GHz; under high power density electromagnetic wave incident conditions, the shielding effectiveness is greater than 10dB from 3.34GHz to 8.19GHz, and the resonance point is also at 4.6GHz. Fig. 9 The frequency response of the frequency selective structure is demonstrated, forming a reflection zero at 4.8 GHz and transmission zeros at 3.3 GHz and 7.4 GHz, which is consistent with the results of theoretical analysis.

[0048] Fig.10 The frequency response of the energy selective surface shielding state and the transmission state with high shielding effectiveness is demonstrated. Under the low power density electromagnetic wave incident state, the insertion loss is less than 1.5dB from 4.47GHz to 5.54GHz, and transmission zero points are formed at 3.2GHz and 7.4GHz, with fast roll-off characteristics; under the high power density electromagnetic wave incident state, the three transmission zero points formed by the energy selective structure and the frequency selective structure are connected together, thus achieving a shielding effectiveness greater than 25dB from 3.15GHz to 9.52GHz.

[0049] In order to further compare the advantages of this solution, the performance parameters of references [1] and [2] are summarized as shown in Table 1.

[0050] Protection band Shielding effectiveness Transmittance band Insertion loss References[1] 2.28-3.25GHz >20dB 2.28-3.81GHz <1dB References[2] 2.4-3.44GHz >20dB 2.6-3.52GHz <1dB

[0051] Compared with references [1] and [2], the advantages of the present invention are as follows: in the transmission state, it has the characteristic of rapid roll-off; in the shielding state, the protection frequency band is significantly expanded, and the shielding effectiveness is further improved, which can provide a shielding effectiveness of more than 25dB in the range of 3.15GHz to 9.52GHz.

[0052] References [1] N. Hu et al., "Design of Ultrawideband Energy-Selective Surface for High-Power Microwave Protection," in IEEE Antennas and Wireless Propagation Letters, vol. 18, no. 4, pp. 669-673, April 2019, doi: 10.1109 / LAWP.2019.2900760.

[0053] References [2] L. Zhou, L. Liu and Z. Shen, "High-Performance Energy Selective Surface Based on the Double-Resonance Concept," in IEEE Transactions on Antennas and Propagation, vol. 69, no. 11, pp. 7658-7666, Nov. 2021, doi: 10.1109 / TAP.2021.3075548.

[0054] The above embodiments are merely illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Anyone familiar with the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by a person of ordinary skill in the art without departing from the spirit and technical ideas disclosed by the present invention shall still be covered by the claims of the present invention.

Claims

1. An energy selective surface with high shielding effectiveness, characterized in that: The structure comprises, from top to bottom, a first energy selection structure (1), a first dielectric substrate layer (2), a second energy selection structure (3), an air layer (4), a frequency selection structure (5), and a second dielectric substrate layer (6); The first energy selection structure (1) is located on the upper surface of the first dielectric substrate layer (2), the first energy selection structure (1) is composed of energy selection structure units arranged periodically, the first energy selection structure unit comprises two upper and lower first slit structures (11), and a first "I"-shaped structure (12), the first "I"-shaped structure (12) has a slit at the center of the vertical line for installing a PIN diode (13); the second energy selection structure (3) is located on the lower surface of the first dielectric substrate layer (2), the second energy selection structure (3) is composed of second energy selection structure units arranged periodically, the second energy selection structure unit is composed of the first energy selection structure unit surrounding the center Rotated 90 degrees, the air layer (4) is located between the second energy selection structure (3) and the frequency selection structure (5); the frequency selection structure (5) is located on the upper surface of the second dielectric substrate layer (6); the frequency selection structure (5) is composed of periodically arranged frequency selection structure units, the frequency selection structure units include two upper and lower second slot structures (51), two left and right third slot structures (52), and a metal square frame (53); a second "I"-shaped structure (54) is located in the metal square frame; the second "I"-shaped structure (54) is composed of two "I"-shaped structures placed horizontally and vertically, the two "I"-shaped structures are of the same size, perpendicular to each other and symmetrical about the center.

2. The energy selective surface with high shielding effectiveness according to claim 1, characterized in that: The periods of the first energy selection structure (1) unit, the second energy selection structure (3) unit and the frequency selection structure (5) unit are all P.

3. The energy selective surface with high shielding effectiveness according to claim 1, characterized in that: The width of the first gap structure (11) is ge.

4. The energy selective surface with high shielding effectiveness according to claim 1, characterized in that: The width of the transverse metal line of the first I-shaped structure (12) is we1, and the width of the vertical metal line is we2.

5. The energy selective surface with high shielding effectiveness according to claim 1, characterized in that: The second gap structure (51) is bent and has a gap width of gf1.

6. The energy selective surface with high shielding effectiveness according to claim 1, characterized in that: The third gap structure (52) is bent and has a gap width of gf2.

7. The energy selective surface with high shielding effectiveness according to claim 1, characterized in that: The width of the metal strip in the metal frame (53) is wf1.

8. The energy selective surface with high shielding effectiveness according to claim 1, characterized in that: The width of the middle vertical line of the second "I"-shaped structure (54) is wf2, the width of the upper and lower horizontal lines is wf3, and the length is lf; the width of the gap between the horizontal metal line and the metal frame (53) in the second "I"-shaped structure (54) is gf3.

9. The energy selective surface with high shielding effectiveness according to claim 1, characterized in that: The PIN diode model is BAP-70-03 from NXP.

Images