Broadband wave-selective surface with absorbing bands

Abstract

The present invention provides a broadband waveform selection surface with an absorbing band, wherein the waveform selection surface unit comprises, from top to bottom, an absorbing and penetrating integrated frequency selection surface 1, a first dielectric layer 2, an air layer 3, a waveform selection surface 4, a second dielectric layer 5, and a bottom metal groove line 6; the absorbing and penetrating integrated frequency selection surface structure 1 is located on the upper surface of the first dielectric substrate 2; the air layer 3 is below the first dielectric substrate 2; the waveform selection surface 4 is located on the upper surface of the second dielectric substrate 5, and the bottom metal groove line 6 is located on the lower surface of the second dielectric substrate 5; the present invention realizes a multifunctional energy selection surface by cascading the absorbing and penetrating integrated frequency selection surface and the waveform selection surface, which can not only screen the incident wave in the energy domain, but also screen the incident wave in the time domain; when the incoming wave is a continuous wave, the present invention will maintain a transmission state, and when the incoming wave is a high-energy pulse wave, the present invention will be in a protection state and have high shielding effectiveness.

Description

Technical Field

[0001] The invention belongs to the technical field of electromagnetic protection, and in particular relates to a broadband waveform selective surface with an absorbing band. Background Art

[0002] Entering the 21st century, electronic technology continues to develop, and the trend of informatization, intelligence, integration and unmanned operation is irreversible. Electronic equipment with digital devices and radio frequency devices are widely used in various military fields, becoming the "eyes" and "brains" of military equipment.

[0003] There are two major types of electromagnetic protection: backdoor protection and frontdoor protection. Backdoor protection refers to the use of shielding, grounding, filtering and other technologies to protect holes, gaps, cables, etc. in the housing of electronic equipment; while frontdoor protection refers to electromagnetic protection from the antenna and sensors of the system. At present, most of the protection measures against strong electromagnetic threats are based on "backdoor" protection measures such as filtering, shielding and grounding, and the research is relatively in-depth, while the research on frontdoor protection measures is not sufficient. [1] . The mainstream front-door protection method is to add a limiter to the RF front-end circuit and load a frequency selective surface (FSS) at the front end of the antenna. Although the limiter can greatly attenuate the current flowing into the circuit, it will affect the passage of normal signals while satisfying the requirement of greatly attenuating the signal, thus affecting the signal quality. In terms of reducing the probability of detection, the FSS can only achieve a low radar cross-section (RCS) in the case of a single-station radar. The frequency selective surface (FSR) with absorption can absorb electromagnetic waves with an operating frequency in the absorbing frequency band, thereby achieving a low RCS in the case of multi-station radars, and in terms of stealth.

[0004] On the other hand, FSR dissipates the absorbed electromagnetic waves by heat, and its power handling capacity is limited. It is unable to handle the situation of high-power electromagnetic wave incident, while FSS cannot handle high-power electromagnetic waves within the band. Energy selective surface is a typical adaptive strong electromagnetic protection device. At present, most energy selective surfaces can provide protection against high-power electromagnetic pulses within the working frequency band. However, the energy selective surface will completely reflect the high-energy electromagnetic waves, resulting in a significant increase in RCS. Therefore, how to achieve both the reduction of the RCS of the sensitive body itself to achieve the stealth effect and the protection against high-power electromagnetic weapons is an unresolved problem. Summary of the invention

[0005] The purpose of the present invention is to address the above-mentioned electromagnetic protection problem and to propose a broadband waveform selective surface with an absorbing band.

[0006] To achieve the above-mentioned purpose of the invention, the technical solution of the present invention is as follows:

[0007] A waveform selection surface unit includes, from top to bottom in sequence: a through-and-absorb frequency selection surface, a first dielectric layer, an air layer, a waveform selection surface, a second dielectric layer, and a bottom metal slot line;

[0008] The through-and-absorb frequency selection surface structure is located on the upper surface of the first dielectric substrate. The through-and-absorb frequency selection surface unit structure includes a bowtie-shaped metal patch, a thin-film resistor located at the center of the bowtie metal patch for connecting the bowtie, a pair of open-loop-shaped metal patches, and two thin-film resistors located at the centers of the open loops; below the first dielectric substrate is an air layer; the waveform selection surface is located on the upper surface of the second dielectric substrate; the waveform selection surface unit structure is evolved from an "I"-shaped metal patch. On the basis of the "I"-shaped metal patch, a rectangular slot is opened at each of the four corners of the "I", a slot line and a rectangular slot are opened in the center of the "I", and two rectangular metal patches are provided in the center of this rectangular slot; the two central metal patches are connected by a lumped capacitor, and the two metal patches are connected to the "I"-shaped patch by 4 PIN diodes; below the second dielectric substrate is the bottom metal slot line.

[0009] As a preferred solution, the periods of the through-and-absorb frequency selection surface unit, the waveform selection surface unit, and the bottom metal slot line are all p .

[0010] As a preferred solution, the width of the bowtie of the bowtie-shaped metal patch structure in the through-and-absorb frequency selection surface unit is d 1 , and the length is d 2 ; the resistance value of the thin-film resistor used to connect the bowtie metal patch in the unit is Z0.

[0011] As a preferred solution, the line width of the open-loop-shaped metal patch in the through-and-absorb frequency selection surface unit is wg , and the line lengths are respectively d 3 , d 4 . The resistance value of the thin-film resistor used to connect the open loop is Z1.

[0012] As a preferred solution, for the "I"-shaped metal patch in the waveform selection surface unit structure, the length and width of the "I" are respectively w 1 , w 3 ; the length and width of the rectangular slots opened at the four corners of the "I" are respectively w 5 , w 6 , and the distance between adjacent two rectangular slots is w 2 .

[0013] As a preferred solution, a groove line with a width of g 1 , the length of the rectangular slot is w 4 .

[0014] As a preferred solution, the two rectangular metal patches in the center of the "I" character in the waveform selection surface unit structure are spaced apart from each other. g 2 The total capacitance value of the lumped capacitor connected between them is C1.

[0015] As a preferred solution, the line width of the bottom metal groove line is l 2 , the arch height is l 1 .

[0016] As a preferred solution, the thickness of the first dielectric substrate is h 1 , the thickness of the second dielectric substrate is h 2 The thickness of the air layer is h 3 The first dielectric substrate and the second dielectric substrate use the same plate material.

[0017] As a preferred solution, the PIN diode model used in the waveform selection surface unit structure is HSMS 2864 from Agilent.

[0018] In terms of working principle:

[0019] The frequency selective surface (FSR) with absorption and penetration is achieved by adding materials with electromagnetic loss characteristics or lumped loss devices on the basis of the frequency selective surface, which can achieve in-band transmission and out-band absorption. When electromagnetic waves outside the operating frequency are incident, the electromagnetic waves are received by the antenna and then dissipated as heat at the matching load, thereby achieving the absorption effect. When electromagnetic waves within the operating frequency are incident, the electromagnetic waves will be directly transmitted and FSR will not have any effect on them.

[0020] The energy selective surface (ESS) 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 ESS transmission and shielding. In order to facilitate further explanation of the principle, the energy selective surface is analyzed by establishing an equivalent circuit. The waveform selective surface is based on the energy selective surface and uses a diode to design a rectifier circuit to achieve the screening of different waveforms.

[0021] Figure 1 The unit structure diagram of the integrated absorption and penetration frequency selective surface is given. The integrated absorption and penetration frequency selective surface consists of a bowtie-shaped metal patch and a pair of open ring metal patches. There are matching loads in the center of the two sets of metal patches. The open ring structure has a single absorption band. The bowtie antenna itself is a broadband antenna. When the bowtie antenna is used as a receiving antenna, if the receiving port is connected to the absorbing element and good impedance matching is maintained, good absorption performance can be achieved outside the frequency band. The combination of the ring structure and the bowtie structure allows the ring structure to work at high frequencies and the bowtie structure to work at low frequencies, thereby greatly expanding the absorption band.

[0022] Figure 2 The equivalent circuit diagram of the waveform selection surface is given. The main part of the waveform selection circuit is on the left side of the circuit. Only when the voltage across the diode reaches a sufficient value can it start to work normally and show switching characteristics. The lumped circuit including the rectifier circuit and the RC circuit can work normally. This is the reason why the waveform selection surface has energy selection characteristics. Before the voltage across the diode reaches a certain value, the diode is in a non-working state. In this state, the diode can be equivalent to a small capacitor. The capacitors formed by these diodes and the gap structure are in parallel, which can reduce the resonant frequency of the passband and stopband. Figure 2 As shown, R1 and C l are the lumped capacitance and resistance,

[0023] D1, D2, D3 and D4 are four diodes. The diodes can work normally for electromagnetic waves incident with high power density. The rectifier circuit will convert the AC signal into a DC signal and then add it to both ends of the RC circuit. If the incident wave is a high-energy pulse wave, most of the energy will be concentrated on the lumped capacitor C1, and then dissipated in the form of heat on the lumped resistor R1. This will protect the back-end electronic equipment. If the incident wave is a high-energy continuous wave, it will be stored in C lThe internal energy can be ignored compared with the total incident energy, and the impact on the incident signal can be ignored. This achieves the screening effect of different waveforms. C1 and L1 in the figure are the equivalent capacitance and equivalent inductance of the "I"-shaped metal patch on the same layer, and L2 is the equivalent inductance of the bottom metal slot line.

[0024] The beneficial effects of the present invention are:

[0025] The frequency selective surface with absorption and penetration is cascaded with the energy selective surface, and on this basis, a rectifier circuit is added to the energy selective surface to achieve the function of waveform selection.

[0026] The present invention cascades an absorptive and penetrating frequency selective surface with an energy selective surface to form a surface that has both an absorbing band and a broadband waveform selection function. This structure can reflect low-frequency signals outside the passband, absorb high-frequency signals, and only intercept high-power electromagnetic pulses within the passband, while low-power electromagnetic pulse signals and continuous wave signals within the passband can freely pass through the surface to be received or transmitted by the antenna. Therefore, the structure designed in this chapter can select incident electromagnetic waves from four aspects: spatial domain, frequency domain, energy domain, and time domain, to achieve precise interception, and has extremely high military application value. In addition, the out-of-band absorption band can not only achieve out-of-band protection, but also help to achieve the stealth performance of the structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 A top view of the unit structure of the absorption-through integrated frequency selective surface provided by the present invention;

[0028] Figure 2 An equivalent circuit diagram of a waveform selection surface unit provided by the present invention;

[0029] Figure 3 A top view of the structure of a waveform selection surface unit provided by the present invention;

[0030] Figure 4 A top view of the structure of a back metal unit of a waveform selection surface unit provided by the present invention;

[0031] Figure 5 A side view of a unit of a broadband waveform selective surface with an absorbing band provided by the present invention;

[0032] Figure 6 The figure is a frequency response diagram of the broadband waveform selective surface with an absorbing band provided by the present invention when a low-power continuous wave is incident.

[0033] Figure 7 This is a frequency response diagram of the broadband waveform selective surface with an absorbing band provided by the present invention when a low-power pulse wave is incident.

[0034] Figure 8 The figure is a frequency response diagram of the broadband waveform selective surface with an absorbing band provided by the present invention when a high-power continuous wave is incident.

[0035] Fig. 9 This is a frequency response diagram of the broadband waveform selective surface with an absorbing band provided by the present invention when a high-power pulse wave is incident.

[0036] 1 is the frequency selective surface with absorption and penetration, 2 is the first dielectric layer, 3 is the air layer, 4 is the waveform selective surface, 5 is the second dielectric layer, and 6 is the bottom metal slot line. DETAILED DESCRIPTION

[0037] 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.

[0038] This embodiment provides a broadband waveform selection surface with an absorbing band. The waveform selection surface unit includes, from top to bottom, an absorption-transmitting integrated frequency selection surface 1, a first dielectric layer 2, an air layer 3, a waveform selection surface 4, a second dielectric layer 5, and a bottom metal groove line 6.

[0039] The absorbent-through integrated frequency selective surface structure 1 is located on the upper surface of the first dielectric substrate 2, and the absorbent-through integrated frequency selective surface unit structure includes a bow tie-shaped metal patch, a thin film resistor 12 located at the center of the bow tie metal patch for connecting the bow tie, a pair of open ring metal patches 11, and two thin film resistors 13 located at the center of the open ring; below the first dielectric substrate 2 is an air layer 3; the waveform selection surface 4 is located on the upper surface of the second dielectric substrate 5; the waveform selection surface unit structure is changed from an "I"-shaped metal patch, and on the basis of the "I"-shaped metal patch, a rectangular groove 51 is opened at each of the four corners of the "I" character, a groove line 52 and a rectangular groove are opened in the center of the "I" character, and two rectangular metal patches 41 are opened in the center of the rectangular groove; the two central metal patches are connected by a lumped capacitor 43, and the two metal patches are connected to the "I"-shaped patch by four PIN diodes 42; below the second dielectric substrate 5 is a bottom metal groove line 6;

[0040] Figure 1This is the top view structure diagram of the unit of the integrated absorption and penetration frequency selective surface provided by the present invention. According to the analysis, it can be known that the bowtie antenna and the split ring antenna capture the incident waves outside the working frequency band. By connecting the two antennas to the matching load, good wave absorption performance can be achieved outside the frequency band. Combining the ring structure and the bowtie structure enables the ring structure to work at high frequencies and the bowtie structure to work at low frequencies, thus greatly expanding the wave absorption frequency band.

[0041] Figure 2 This is the equivalent circuit diagram of the waveform selective surface unit provided by the present invention, as Figure 2 shown, where R1 and Cl are lumped capacitors and lumped resistors, and D1, D2, D3, and D4 are four diodes. For electromagnetic waves incident with a high power density, the diodes can work normally. The rectifier circuit will convert the AC signal into a DC signal and then apply it across the RC circuit. When the incident wave is a high-energy pulse wave, most of the energy will be concentrated on the lumped capacitor C1 and then dissipated in the lumped resistor R1 in the form of heat. Thus, the protection of the backend electronic device is achieved. If the incident wave is a high-energy continuous wave, the energy stored in Cl can be ignored compared with the total incident energy, and the influence on the incident signal can be ignored. Thus, the screening effect for different waveforms is achieved. C1 and L1 in the figure are the equivalent capacitance and equivalent inductance of the "I"-shaped metal patch on the same layer, and L2 is the equivalent inductance of the metal slot line at the bottom layer.

[0042] Figure 3 This is the top view structure diagram of the unit of the waveform selective surface unit provided by the present invention. The unit size is p * p , where p is 20 mm; the length and width of the "I" are w 1 , w 3 respectively; the length and width of the rectangular slots opened at the four corners of the "I" are w 5 , w 6 respectively, the distance between adjacent two rectangular slots is w 2 , the width of the slot line opened at the center of the "I" is g 1 , the length of the rectangular slot is w 4 . Among them, w 1 = is 2 mm; w 2 = is 2.35 mm; w 3 = is 10 mm;w 4 = 6mm; w 5 = 2mm; w 5 = 3.5mm; g 1 =1mm.

[0043] Figure 4 This is a top view of the back metal unit structure of the waveform selection surface unit provided by the present invention. According to the analysis, the line width of the bottom metal groove line is l 2 , the arch height is l 1 Such a shape can achieve an equivalent inductance of L2. l 1 =1mm; l 2 =0.5mm.

[0044] Figure 5 This is a side view of a unit of a broadband waveform selective surface with an absorbing band provided by the present invention. According to analysis, in order to ensure that the performance after cascading meets the requirements, a certain distance needs to be maintained between the integrated frequency selective surface and the waveform selective surface.

[0045] Figure 6 The frequency response diagram of the broadband waveform selective surface with an absorbing band provided by the present invention when a low-power continuous wave is incident, Figure 7 The frequency response diagram of the broadband waveform selective surface with an absorption band provided by the present invention when a low-power pulse wave is incident can be analyzed based on this. Under the low-power incident state, the diode does not start working, so there is no waveform selection characteristic at this time. At this time, both pulse waves and continuous waves can be reflected on the surface in the working frequency band in the low frequency band of the working frequency band and absorbed in the high frequency band of the working frequency band. The reflectivity is greater than 90% in 0-0.75GHz; the transmittance to low-power pulse waves and continuous waves in 1.51-2.28GHz is greater than 0.7, and the relative bandwidth is 40.6%; in 5.93-14.12GHz, the absorption rate of the incident wave is greater than 90%.

[0046] Figure 8 The frequency response diagram of the broadband waveform selective surface with an absorbing band provided by the present invention when a high-power continuous wave is incident, Fig. 9This is a frequency response diagram of the broadband waveform selection surface with an absorption band provided by the present invention when a high-power pulse wave is incident. Based on this, it can be analyzed that under the high-power incident state, the diode starts to work. As can be seen from the figure, at this time, the continuous wave can still pass through the surface. Since the change in the working state of the diode will also affect the performance of the frequency selection, the transmission performance will be slightly worse. At this time, the pulse wave is intercepted by the surface. In the entire 0-15GHz frequency band, the high-power pulse wave transmittance is less than 0.3.

[0047] 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.

[0048]

[0049] Compared with references [1] and [2], the advantages of the present invention are as follows: the cross-section has been significantly reduced to less than one twentieth of the center frequency wavelength; the passband bandwidth has been significantly improved, and in the transmission state, it has a wide passband bandwidth; the protection band has been significantly expanded, and protection can be provided within 0-15GHz; the functions are further integrated, realizing the four functions of frequency selection, energy selection, waveform selection and wave absorption.

[0050] References [1] G. Qian, J. Zhao, X. Ren, et al. Switchable broadband dual-polarized frequency-selective rasorber / absorber[J]. IEEE Antennas and Wireless Propagation Letters, 2019, 18(12): 2508-2512.

[0051] References [2] W. Gong, W. Zhang, X. Chen, et al. A low-profile energyselective surface with ultra-wide absorption band[J]. IEEE Transactions on Microwave Theory and Techniques, 2023, 71(3): 1348-1355 (A low-profile energy selective surface with ultra-wide absorption band, IEEE Transactions on Microwave Theory and Techniques)

[0052] 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. A broadband waveform selective surface with an absorbing band, characterized in that: The components include, from top to bottom, an absorbent and penetrating frequency selective surface (1), a first dielectric substrate (2), an air layer (3), a waveform selective surface (4), a second dielectric substrate (5), and a bottom metal slot line (6); The absorbent-through integrated frequency selective surface (1) is located on the upper surface of the first dielectric substrate (2), and the absorbent-through integrated frequency selective surface unit comprises a bow tie-shaped metal patch, a thin film resistor (12) located at the center of the bow tie metal patch for connecting the bow tie, a pair of open ring metal patches (11), and two thin film resistors (13) located at the center of the open rings; an air layer (3) is located below the first dielectric substrate (2); the waveform selective surface (4) is located on the upper surface of the second dielectric substrate (5); the waveform selective surface unit is derived from an "I"-shaped metal patch, and based on the "I"-shaped metal patch, a rectangular groove (51) is opened at each of the four corners of the "I" character, a groove line (52) and a rectangular groove are opened at the center of the "I" character, and two rectangular metal patches (41) are opened in the center of the rectangular groove; the two central metal patches are connected by a lumped capacitor (43), and the two metal patches are connected to the "I"-shaped patch by four PIN diodes (42); and a bottom metal groove line (6) is located below the second dielectric substrate (5).

2. The broadband waveform selective surface with an absorbing band according to claim 1, characterized in that: The periods of the absorption-through integrated frequency selective surface unit, the waveform selective surface unit and the bottom metal slot line (6) are p .

3. The broadband waveform selective surface with an absorbing band according to claim 1, characterized in that: The PIN diode (42) used in the waveform selection surface unit is HSMS 2864 from Agilent Technologies.

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