Electromagnetic shielding type low-radar cross section (RCS) metasurface antenna and working method thereof

Abstract

The application belongs to the field of antennas and relates to an electromagnetic protection type low RCS super surface antenna and a working method thereof. The super surface antenna comprises an upper layer dielectric substrate, a slit metal ground, a lower layer dielectric substrate and a feed microstrip line. The upper layer dielectric substrate is etched with polarization conversion super surface units. Between the four polarization conversion super surface units of the slit structure of the slit metal ground, two polarization conversion super surface units on one side of the feed microstrip line are connected through PIN diodes, and two polarization conversion super surface units on the other side of the feed microstrip line are connected through PIN diodes. The application integrates low radar scattering cross section, normal communication and high power microwave self-protection functions, realizes adaptive and reliable switching between normal stealth communication and instantaneous anti-destroying protection through the cooperation of the polarization conversion super surface units and the PIN diodes, and solves the problem that the existing low RCS super surface antenna lacks protection capability under the threat of HPM.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of antennas, and particularly relates to an electromagnetic protection type low RCS metasurface antenna and a working method thereof. BACKGROUND

[0002] With the progress of science and technology, high-power microwaves have posed a serious threat to the safety of electronic information systems. High-power microwaves (HPM) are electromagnetic waves with a frequency of 1-300 GHz and a peak power of more than 100 MW, which can invade systems through "front door" and "back door" coupling and damage sensitive equipment. The existing high-power microwave electromagnetic protection methods are mainly divided into "front door protection" and "back door protection", and the "front door protection" needs to intercept HPM under the premise of ensuring normal signal transmission and reception of equipment, which is the core of the protection system.

[0003] The current mainstream "front door protection" methods include amplitude limiters, frequency domain filters, energy selective surfaces and electromagnetic protection antennas. Among them, the amplitude limiters, energy selective surfaces and other methods need to integrate independent protection devices on the basis of the original electronic information system, which not only significantly increases the redundancy and complexity of the system, but also is not conducive to the miniaturization design of the system, and even difficult to realize integration in some specific scenarios.

[0004] Low radar cross section (RCS) metasurface antenna is a research hotspot in the field of current antennas, which is more easily to realize low RCS performance due to its unique electromagnetic regulation characteristics, and has great application prospect in the field of communication. However, the existing airborne low RCS metasurface antenna only has the functions of conventional communication and low RCS, and has no HPM protection capability. Once the high-value communication platform on board is impacted by HPM, it is easy to cause devastating damage to the electronic information system in the platform, and then cause huge economic losses. Therefore, the existing low RCS metasurface antenna lacks protection capability under the threat of HPM, and it is difficult to meet the electromagnetic safety requirements of high-value platforms, which is a problem to be solved. SUMMARY

[0005] The technical problem to be solved by the present application is to provide an electromagnetic protection type low RCS metasurface antenna and a working method thereof. The metasurface antenna integrating low radar cross section, normal communication and high-power microwave self-protection functions realizes adaptive and reliable switching between normal stealth communication and instantaneous anti-damage protection states through the cooperation of polarization conversion metasurface units and PIN diodes.

[0006] The present application provides an electromagnetic protection type low RCS metasurface antenna, which comprises an upper layer dielectric substrate, a slit metal ground, a lower layer dielectric substrate and a feed microstrip line arranged from top to bottom.

[0007] The upper surface of the upper layer dielectric substrate is etched with polarization conversion metasurface units arranged periodically, and a plurality of polarization conversion metasurface units constitute a metasurface structure.

[0008] Among the four polarization conversion metasurface units above the gap structure of the gap metal ground, the two polarization conversion metasurface units on one side of the feed microstrip line are connected through PIN diodes, and the two polarization conversion metasurface units on the other side of the feed microstrip line are connected through PIN diodes;

[0009] The PIN diode is used to automatically control the state switching of the antenna according to the energy size of the incident electromagnetic wave: when a low-power communication signal is incident, the PIN diode is in a cut-off state, the antenna is in a normal working state, and has a normal signal receiving and transmitting capability; when a high-power microwave is incident, the PIN diode is turned on, so that the polarization conversion metasurface units on both sides of the feed microstrip line are connected, and the metasurface antenna is switched to a protection state of impedance mismatch, loses normal radiation capability and reflects high-power microwave;

[0010] And in the cut-off and on states of the PIN diode, the metasurface antenna has a radar cross section reduction capability.

[0011] Further, the polarization conversion metasurface unit comprises a square dielectric substrate and a metal geometric structure on the upper surface of the square dielectric substrate;

[0012] The metal geometric structure is located in the middle of the square dielectric substrate and comprises a double-arrowhead configuration arranged along the diagonal of the square dielectric substrate, the double-arrowhead configuration is provided with a side slot on both sides of the diagonal, and a strip-shaped slot is arranged in the double-arrowhead configuration along the diagonal direction;

[0013] The side slot and the strip-shaped slot are used to introduce structural asymmetry based on the square dielectric substrate, wherein:

[0014] The side slot is used to control the equivalent LC value in the u direction;

[0015] The strip-shaped slot is used to control the equivalent LC value in the v direction;

[0016] By changing the size parameters of the side slot and the strip-shaped slot, a phase difference is generated in the u direction and the v direction of the incident electromagnetic wave, so that polarization conversion is realized.

[0017] Further, the double-arrowhead configuration is provided with a rounded corner at the sharp corner of the arrow, and a rectangular slot is arranged in the middle of the side slot towards the strip-shaped slot;

[0018] The rounded corner is used to change the equivalent LC value in the v direction;

[0019] The rectangular slot introduces an equivalent capacitor in the u direction;

[0020] By adjusting the size parameters of the rounded corner and the rectangular slot, the adjustment range of the phase difference is expanded and the polarization conversion performance is improved.

[0021] Further, the polarization conversion metasurface units are configured into two types, the two types of structures are consistent, the directions are 90° intersected, and the two types of polarization conversion metasurface units have orthogonal polarization conversion phase responses.

[0022] The plurality of polarization conversion metasurface units are arranged in a two-dimensional periodic array, wherein four adjacent polarization conversion metasurface units are of the same type and constitute a basic array group.

[0023] The plurality of polarization conversion metasurface units are arranged in a two-dimensional periodic array, wherein four adjacent polarization conversion metasurface units are of the same type and constitute a basic array group.

[0024] The plurality of polarization conversion metasurface units are arranged in a two-dimensional periodic array, wherein four adjacent polarization conversion metasurface units are of the same type and constitute a basic array group.

[0025] Further, the slot structure comprises a long vertical groove and short horizontal grooves arranged on both sides of the long vertical groove.

[0026] Further, one end of the feed microstrip line is located at the side edge of the metasurface antenna and is connected with an SMA coaxial interface, and the SMA coaxial interface is used for connecting the metasurface antenna with an external radio frequency device.

[0027] The projection position of the other end of the feed microstrip line passes through the long vertical groove.

[0028] Further, the SMA coaxial interface comprises an interface and a mounting leg, and the mounting leg is fixed to the upper layer dielectric substrate after passing through the lower layer dielectric substrate and the slot metal ground.

[0029] Further, the relative dielectric constant of the lower layer dielectric substrate is 3.66.

[0030] Further, the relative dielectric constant of the upper layer dielectric substrate is 4.4.

[0031] The application also provides a working method of the electromagnetic protection type low RCS metasurface antenna.

[0032] The received incident electromagnetic wave signal is received.

[0033] The energy of the incident electromagnetic wave is induced by the polarization conversion metasurface unit, and an induced voltage is generated at both ends of the PIN diode.

[0034] The size relationship between the induced voltage and the PIN diode conduction threshold value is determined.

[0035] If the induced voltage is less than the conduction threshold value, the PIN diode maintains a cut-off state, at this time, the antenna works in a normal transceiving mode, the feed microstrip line realizes impedance matching through the slot structure and the metasurface structure, and the radiation or reception of communication signals is completed.

[0036] If the induced voltage is greater than or equal to the turn-on threshold, the PIN diode switches to the on state, the control PIN diode switches to the on state, and the antenna switches to the protection state due to impedance mismatch, and high-power microwaves are reflected;

[0037] In the normal transceiving mode and the protection mode, the arrangement of the polarization conversion metasurface unit is controlled by the scattering field of the incident wave, and the radar scattering cross section is reduced.

[0038] The electromagnetic protection type low RCS metasurface antenna has the following beneficial effects:

[0039] 1. The low radar scattering cross section (RCS) characteristic, normal antenna radiation / receiving function and high-power microwave (HPM) protection capability are integrated in a single metasurface antenna structure. The core technical contradiction that the low RCS metasurface antenna does not have the HPM protection capability in the prior art, and the additional protection device increases the system complexity and redundancy is fundamentally solved, and an integrated electromagnetic safety solution is provided for a high-value platform. Specifically, the design discards the independent protection devices such as the limiter and the filter which need to be additionally installed at the front end of the system, and significantly reduces the volume, weight, complexity and cost of the system. This highly integrated scheme avoids the insertion loss, impedance matching and connection reliability problems caused by the cascade of multiple devices, and is beneficial to the miniaturization and high reliability design of the system.

[0040] 2. By introducing the PIN diode as an energy-sensitive switch, automatic sensing and intelligent switching of the antenna working state are realized. The process does not require external instructions, is completely controlled by the incident electromagnetic wave energy, has fast response speed, realizes the leap from passive damage to active protection, and the metasurface antenna can reliably switch between the normal working state (signal transceiving) and the protection state (reflecting HPM), and has the function of reconfiguration.

[0041] 3. Since the PIN diode is precisely loaded at the key position of the polarization conversion metasurface unit, the state change is ingeniously integrated into the overall electromagnetic scattering regulation. Therefore, whether in the cut-off state of normal working or in the on state of protection, the metasurface antenna can effectively offset the scattering field through the periodic arrangement of the metasurface structure, always maintain more than 6dB of RCS reduction performance, realize the effect of stealth in communication and stealth in protection.

[0042] 4. In normal working state, the metasurface antenna exhibits good radiation performance, such as good impedance matching (-10 dB bandwidth) and a gain of up to 5.7 dBi in a specific frequency band. In the protection state, the gain of the antenna in the same frequency band can be sharply reduced to -13.1 dBi, realizing an isolation of more than 18 dB, effectively blocking the invasion of HPM energy, while maintaining the RCS reduction capability.

[0043] In summary, the metasurface antenna is particularly suitable for high-value radio frequency front-end platforms with extreme requirements for stealth, weight, volume, and electromagnetic safety, providing a built-in protection means without sacrificing stealth performance. BRIEF DESCRIPTION OF DRAWINGS

[0044] Figure 1 is a perspective view of the metasurface antenna of the present application;

[0045] Figure 2 is a front view of the metasurface antenna of the present application;

[0046] Figure 3 is a top view of the metasurface antenna of the present application;

[0047] Figure 4 is a structural schematic diagram of one of the embodiments of the polarization conversion metasurface unit in the present application;

[0048] Figure 5 is a structural schematic diagram of another embodiment of the polarization conversion metasurface unit in the present application;

[0049] Figure 6 is a bottom view of the metasurface antenna of the present application;

[0050] Figure 7 is a reflection coefficient schematic diagram of the metasurface structure of the present application;

[0051] Figure 8 is a polarization conversion rate schematic diagram of the metasurface structure of the present application;

[0052] Figure 9 is a reflection coefficient diagram of the metasurface antenna of the present application in different working states;

[0053] Figure 10 is a directional diagram of the metasurface antenna of the present application in different working states;

[0054] Figure 11 is a schematic diagram of the single station RCS of the reference metal plate and the different working states of the metasurface antenna of the present application when the x-polarized wave is vertically incident;

[0055] Figure 12 is a schematic diagram of the single station RCS of the reference metal plate and the different working states of the metasurface antenna of the present application when the y-polarized wave is vertically incident.

[0056] In the figure, 1 - metasurface structure; 11 - polarization conversion metasurface unit; 111 - double arrow configuration; 112 - side groove; 113 - strip-shaped slot; 114 - round corner; 115 - rectangular groove; 12 - PIN diode; 2 - upper layer dielectric substrate; 3 - gap metal ground; 31 - gap structure; 311 - long vertical groove; 312 - short horizontal groove; 4 - lower layer dielectric substrate; 5 - feed microstrip line; 6 - SMA coaxial interface. DETAILED DESCRIPTION

[0057] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the scope of protection of the present application.

[0058] It should be noted that all directionality indications (such as up, down, left, right, front, back, etc.) in the embodiments of the present application are only used to explain the relative positional relationship, motion condition, etc. between components in a certain posture (as shown in the drawings), and if the certain posture changes, the directionality indications also change accordingly.

[0059] In addition, the description such as "first", "second" and the like in the present application is only for the purpose of description, and cannot be understood as indicating or implying the relative importance of the indicated technical features or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first", "second" can explicitly or implicitly include at least one of the features. In the description of the present application, the meaning of "multiple" is at least two, such as two, three, etc., unless otherwise specifically limited.

[0060] In the present application, unless otherwise explicitly specified and limited, the terms "connection", "fixation" and the like should be understood broadly, for example, "fixation" can be fixed connection, or detachable connection, or integral; can be mechanical connection, or electrical connection, or physical connection or wireless communication connection; can be directly connected, or indirectly connected through an intermediate medium, can be the internal communication of two elements or the interaction relationship between two elements, unless otherwise explicitly limited. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0061] In addition, the technical solutions of each embodiment of the present application can be combined with each other, but it must be based on the fact that a person skilled in the art can realize it, when the combination of technical solutions appears contradictory or unachievable, it should be considered that the combination of technical solutions does not exist, nor within the scope of protection required by the present application.

[0062] like Figures 1-6 As shown, the present invention provides an electromagnetically protected low RCS metasurface antenna, comprising, from top to bottom, an upper dielectric substrate 2, a slotted metal ground 3, a lower dielectric substrate 4, and a feed microstrip line 5;

[0063] The upper surface of the upper dielectric substrate 2 is etched with periodically arranged polarization conversion metasurface units 11, and multiple polarization conversion metasurface units 11 constitute metasurface structure 1.

[0064] The upper dielectric substrate 2 is used to support the metasurface structure 1 and to regulate the electromagnetic properties of the metasurface structure 1.

[0065] The slot metal ground 3, the lower dielectric substrate 4, and the feed microstrip line 5 together constitute the slot-coupled feed structure. The slot metal ground 3 is the window for the transfer of electromagnetic energy in the slot-coupled feed structure. The lower dielectric substrate 4 is used to support the slot-coupled feed structure and ensure coupling efficiency. The feed microstrip line 5 is the interface for introducing electromagnetic energy and realizes the adjustment of impedance matching.

[0066] Between the four polarization conversion metasurface units 11 above the slot structure 31 of the slot metal ground 3, two polarization conversion metasurface units 11 located on one side of the feed microstrip line 5 are connected by PIN diodes 12, and two polarization conversion metasurface units 11 located on the other side of the feed microstrip line 5 are connected by PIN diodes 12.

[0067] The PIN diode 12 is used to automatically control the antenna state switching according to the energy of the incident electromagnetic wave: when a low-power communication signal is incident, the PIN diode 12 is in the off state, the antenna is in normal working state, and has the ability to transmit and receive signals normally; when a high-power microwave is incident, the PIN diode 12 is turned on, so that the polarization conversion metasurface unit 11 on both sides of the feed microstrip line 5 is connected, the metasurface antenna switches to the impedance mismatch protection state, loses normal radiation capability and reflects high-power microwave; and in both the off and on states of the PIN diode 12, the metasurface antenna has the ability to reduce radar cross section.

[0068] In one embodiment, the polarization conversion metasurface unit 11 includes a square dielectric substrate and a metal geometry on the upper surface of the square dielectric substrate;

[0069] The metal geometry is located in the middle of the square dielectric substrate, including a double-arrow configuration 111 arranged along the diagonal of the square dielectric substrate. The double-arrow configuration 111 serves as the basic radial structure and the main load-bearing body. The double-arrow configuration 111 has side grooves 112 on both sides of the diagonal, and a strip slit 113 is provided in the middle of the double-arrow configuration 111 along the diagonal direction.

[0070] Side slot 112 and strip slot 113 are used to introduce structural asymmetry based on square dielectric substrate, which is to make the polarization conversion metasurface unit 11 produce different electromagnetic responses to incident waves with different polarization directions, wherein:

[0071] Side slot 112 is used to control the equivalent LC value in the u direction;

[0072] Strip slot 113 is used to control the equivalent LC value in the v direction. As an elongated slot, strip slot 113 mainly introduces equivalent inductance by significantly extending the surface current path in the v direction, which is the dominant factor to control the equivalent LC value in the v direction;

[0073] By changing the size parameters of side slot 112 and strip slot 113, the incident electromagnetic wave produces a phase difference in the u direction and the v direction, so as to realize polarization conversion. That is, the equivalent LC values in the v and u directions can be adjusted, so as to make the incident electromagnetic wave produce a certain phase difference in the two directions, and then the phase difference is adjusted to realize the regulation of the polarization state of the electromagnetic wave.

[0074] The size parameters of side slot 112 and strip slot 113 provide engineers with clear and effective design freedom, which is convenient for accurate regulation of the phase response of the unit to optimize the performance in different frequency bands.

[0075] In addition, the polarization conversion metasurface unit 11 not only undertakes the function of polarization conversion, but also provides an ideal space for the loading of PIN diode 12 at the key position, which ensures that the state switching function can be seamlessly integrated without damaging the inherent polarization conversion and RCS reduction performance.

[0076] In one embodiment, the double-arrow configuration 111 is provided with a rounded corner 114 at the sharp corner of the arrow, and a rectangular slot 115 is arranged in the middle of the side slot 112 towards the strip slot 113;

[0077] The rounded corner 114 is used to change the equivalent LC value in the v direction; specifically, the rounded corner 114 is used to finely regulate the surface current distribution in the v direction. It effectively reduces the equivalent inductance at this point by smoothing the current path, thereby providing a new and sensitive design dimension for the equivalent LC value in the v direction. This enables engineers to fine-tune the phase response in the v direction without significantly changing the core structure (such as strip slot 113).

[0078] The rectangular slot 115 introduces an equivalent capacitance in the u direction; the rectangular slot 115 is introduced in the side slot 112, which is used to introduce a strong and localized equivalent capacitance in the u direction. This additional capacitance is superimposed with the coupling effect generated by the side slot 112 itself, which significantly enhances the electromagnetic response capability of the polarization conversion metasurface unit 11 in the u direction, providing more design space and stronger regulation capability for adjusting the phase in the u direction.

[0079] By adjusting the size parameters of the rounded corners 114 and the rectangular grooves 115, the adjustment range of the phase difference is expanded and the polarization conversion performance is improved. That is, more independent adjustable design parameters are provided for the metasurface unit, making performance optimization more flexible and easier to meet complex multi-index design requirements. The polarization conversion metasurface unit 11 can generate a larger range of phase differences, thereby effectively widening the working bandwidth of polarization conversion. Simulation results confirm that the optimized structure achieves a polarization conversion rate of more than 90% in a wide frequency band of 4.92 GHz-6.27 GHz. In a specific frequency band within the bandwidth (such as 5.34 GHz-5.74 GHz), nearly ideal polarization conversion can be achieved, with a polarization conversion rate of more than 99.9%, greatly improving the RCS reduction effect near the frequency point.

[0080] In one embodiment, the polarization conversion metasurface unit 11 is configured in two types, the two types of structures are consistent, and the directions intersect at 90°. The two types of polarization conversion metasurface units 11 have orthogonal polarization conversion phase responses.

[0081] The plurality of polarization conversion metasurface units 11 are arranged in a two-dimensional periodic array, wherein the four adjacent polarization conversion metasurface units 11 are of the same type and constitute a basic array group.

[0082] The basic array groups are arranged in a chessboard pattern, so that two units in the spatial diagonal direction are of the same type, and two units in another spatial diagonal direction are of another type.

[0083] The arrangement of the basic array groups is used to make the electromagnetic scattering fields from the units cancel each other out, thereby achieving reduction of the radar cross section.

[0084] In this embodiment, since the two types of units have orthogonal (i.e., about 180° different) polarization conversion phase responses, when electromagnetic waves are incident vertically, the cross-polarized wave components reflected by adjacent units cancel each other out coherently due to opposite phases. This efficient scattering cancellation mechanism enables the antenna to achieve an RCS reduction of more than 6 dB within a wide frequency band (e.g., when x-polarized waves are incident, in the frequency band of 4.9 GHz - 7.3 GHz). This arrangement scheme can not only achieve wide-band reduction, but also reach an extreme cancellation effect at specific resonant frequencies through precise phase design. Simulation results show that its peak RCS reduction can be as high as 33.5 dB, greatly reducing the probability of being detected and significantly enhancing the stealth performance of the platform. Since the unit structure is symmetric along the diagonal and the arrangement is also geometrically symmetric, this design is insensitive to the polarization direction of the incident wave. Whether x-polarized or y-polarized plane waves are incident vertically, the antenna can effectively achieve a significant RCS reduction, enhancing the stealth robustness in a complex electromagnetic environment. This arrangement is two-dimensional and is designed entirely based on the electromagnetic characteristics of the metasurface units themselves, without introducing additional three-dimensional structures or absorbing materials. Therefore, while achieving a strong RCS reduction, it perfectly maintains the low-profile and conformal characteristics of the antenna. The RCS reduction mechanism stems from the characteristics of the metasurface units themselves and their arrangement, and is independent of the working state of the PIN diode 12. Therefore, regardless of whether the PIN diode 12 is in the on or off state, that is, regardless of whether the antenna is in the normal working mode or the protection mode, this arrangement can continuously play a role, ensuring full-time stealth.

[0085] In a preferred embodiment, the four polarization conversion metasurface units 11 directly above the slot structure 31 are composed of the four middle polarization conversion metasurface units 11 of four basic array groups, and these four have orthogonal polarization conversion phase responses. With such a setting, the coherence and stability of the RCS performance during state switching are ensured. Since they have orthogonal phase responses, regardless of whether the PIN diode 12 is on or off, the inherent phase difference between them can ensure that the electromagnetic waves they reflect (especially the cross-polarized components) continuously cancel each other out coherently. This means that in the central area that provides radiation energy for the metasurface antenna, during the drastic change process from the communication state to the protection state, its low RCS characteristics always remain unchanged.

[0086] In one of the embodiments, the slot structure 31 includes a long vertical slot 311 and short horizontal slots 312 arranged on both sides of the long vertical slot 311; among them, the long vertical slot 311 and the two short horizontal slots 312 combine to form a "艹"-shaped structure.

[0087] The long vertical slot 311 is perpendicular to the feeding microstrip line 5.

[0088] The long vertical slot 311 dominates a main resonant frequency, responsible for the basic energy transfer with the feed microstrip line 5. The short horizontal slots 312 on both sides are used to adjust the impedance matching. When the HPM attacks, the huge induced energy can act on the PIN diode 12 without delay and with high efficiency, making it be triggered on quickly and reliably, thereby improving the response speed and certainty of the protection state.

[0089] In one embodiment, one end of the feed microstrip line 5 is located at the side of the metasurface antenna and connected with the SMA coaxial interface 6 for connecting external radio frequency equipment.

[0090] The projection position of the other end of the feed microstrip line 5 passes through the long vertical slot 311, so that the projection of the terminal of the feed microstrip line 5 precisely passes through the long vertical slot 311, which means that the strong current area and the radiation field at the end of the feed microstrip line 5 are maximally concentrated below the opening area of the long vertical slot 311. The highest efficiency passes through the gap structure 31, excites the resonance of the metasurface structure 1 above, and is converted into a spatial radiation wave.

[0091] In one embodiment, the SMA coaxial interface 6 includes an interface and a mounting leg which is fixed with the upper dielectric substrate 2 after passing through the lower dielectric substrate 4 and the gap metal ground 3. In this embodiment, the connection strength between the SMA interface and the body of the metasurface antenna is greatly enhanced, which can effectively resist mechanical stress such as plugging, vibration and impact, and prevent system failure caused by loose or falling of the interface.

[0092] In one embodiment, the relative dielectric constant of the lower dielectric substrate 4 is 3.66, and preferably, the material Rogers-4350B is used. Rogers-4350B is a high-frequency special plate material, which has extremely low dielectric loss tangent in the GHz frequency band. This ensures that the high-frequency signal energy transmitted on the feed microstrip line 5 has minimal energy loss, fundamentally ensuring that energy can be efficiently transmitted to the radiation unit and improving the overall radiation efficiency of the antenna.

[0093] In one embodiment, the relative dielectric constant of the upper dielectric substrate 2 is 4.4, and preferably, the material FR-4 is used. FR-4 is a general epoxy glass cloth laminated plate, which has a much lower cost than high-frequency special plate materials such as Rogers-4350B. The upper dielectric substrate 2 mainly serves to support and carry the metasurface structure 1, and the requirement for loss is relatively low. The use of FR-4 can significantly reduce the overall manufacturing cost of the metasurface antenna.

[0094] The application also provides a working method of the above-mentioned electromagnetic protection type low RCS metasurface antenna, comprising the following steps:

[0095] Receiving an incident electromagnetic wave signal;

[0096] The energy of the incident electromagnetic wave is inducted by the polarization conversion metasurface unit 11, and an induced voltage is generated across the PIN diode 12;

[0097] The size relationship between the induced voltage and the conduction threshold of the PIN diode 12 is determined:

[0098] If the induced voltage is less than the conduction threshold, the PIN diode 12 maintains a cut-off state, at which time the antenna operates in a normal transceiving mode, and the feed microstrip line 5 realizes impedance matching with the metasurface structure 1 through the gap structure 31, thereby completing the radiation or reception of communication signals.

[0099] If the induced voltage is greater than or equal to the conduction threshold, the PIN diode 12 switches to a conduction state, and the PIN diode 12 is controlled to switch to a conduction state, at which time the antenna switches to a protection state due to impedance mismatch, and reflects high-power microwaves.

[0100] In the normal transceiving mode and the protection mode, the arrangement of the polarization conversion metasurface unit 11 is controlled by the scattering field of the incident wave, thereby reducing the radar scattering cross section.

[0101] The co-polarization and cross-polarization reflection coefficients of the polarization conversion unit are shown in Figure 7 As shown in the figure, when the incident wave is vertically incident in an x-polarization manner, in the frequency range of 4.9 GHz-6.3 GHz, the co-polarization reflection coefficient is less than -10 dB, and in the frequency range of 5.0 Hz-6.2 GHz, the cross-polarization reflection coefficient is greater than -1 dB. That is, the unit can realize the conversion of the x-polarization incident wave to the y-polarization reflected wave. Since the unit structure is symmetric along the diagonal line, the y-polarization wave incident case is similar.

[0102] PCR (Polarization Conversion Rate) is a physical quantity for measuring the efficiency of the super surface in converting the polarization state of the incident electromagnetic wave to the orthogonal polarization state, which is defined as the ratio of the cross-polarization reflection power to the total reflection power, and is usually expressed in percentage, and the calculation formula is:

[0103]

[0104] In the formula, PCR is the polarization conversion rate, R xx is the co-polarization reflection coefficient, R xy is the cross-polarization reflection coefficient. The polarization conversion rate of the unit calculated by the formula is shown in Figure 8As shown in the figure, the polarization conversion rate is greater than 90% in the frequency range of 4.92GHz-6.27GHz, and the polarization conversion rate is greater than 99.9% in the frequency range of 5.34GHz-5.74GHz

[0105] The S parameter simulation result of the metasurface antenna is as shown in Figure 9 The -10dB impedance bandwidth of the antenna in the normal working state is 4.42GHz-4.78GHz, and the reflection coefficient of the antenna in the protection state increases to above -1dB in the frequency range of 4.42GHz-4.78GHz.

[0106] The directional diagram of the metasurface antenna is as shown in Figure 10 In the figure, 'Phi' represents the plane azimuth angle cut along the main beam direction, wherein 'Phi=0°' corresponds to the E plane, i.e. the electric field vector plane, and Phi='90°' corresponds to the H plane, i.e. the magnetic field vector plane, the maximum gain of the antenna in the normal working state is 5.7dBi, and the gain of the antenna radiation direction in the protection state is reduced to -13.1dBi. Compared with the previous normal working state, it is reduced by 18.8dB.

[0107] The single-RCS comparison result of the antenna in different working states with the single-RCS of the reference metal ground under the condition that the x-polarized and y-polarized plane waves are vertically incident is as shown in Figure 11 , Figure 12 As shown in the figure, when the x-polarized plane wave is vertically incident, in the frequency band of 4.9GHz-7.3GHz, the antenna in the normal working state and the protection state both achieve more than 6dB of RCS reduction, and the peak reduction reaches 33.5dB, when the y-polarized plane wave is vertically incident, in the frequency band of 5.6GHz-7.1GHz, the antenna in the working state and the protection state also has more than 6dB of RCS reduction performance, and the peak reduction reaches 26.1dB.

[0108] As can be seen from the above, the electromagnetic protection type low RCS metasurface antenna provided by the application successfully integrates the three functions of high-efficiency radiation, wideband radar stealth and HPM protection by innovative design of the structure. Experimental data fully prove that it can simultaneously consider excellent communication performance, excellent stealth capability and reliable electromagnetic protection effect in different working states, and provide key technical support for the survival and use ability of high-value platforms in complex electromagnetic battlefield environment.

[0109] The above is only the embodiment of the present application, and does not limit the present application. Any skilled person in the art can make many possible changes, modifications or modifications of the technical solutions of the present application without departing from the scope of the technical solutions of the present application, and equivalent embodiments of equivalent changes. Therefore, any simple modification, equivalent change and modification of the above embodiment according to the technical essence of the present application without departing from the technical solutions of the present application shall fall within the scope of protection of the technical solutions of the present application.

Claims

1. An electromagnetically protected low RCS metasurface antenna, characterized in that, It includes an upper dielectric substrate (2), a gap metal ground (3), a lower dielectric substrate (4), and a feed microstrip line (5) arranged from top to bottom; The upper surface of the upper dielectric substrate (2) is etched with periodically arranged polarization conversion metasurface units (11), and multiple polarization conversion metasurface units (11) constitute a metasurface structure (1). Between the four polarization conversion metasurface units (11) above the slot structure (31) of the slot metal ground (3), two polarization conversion metasurface units (11) located on one side of the feed microstrip line (5) are connected by PIN diodes (12), and two polarization conversion metasurface units (11) located on the other side of the feed microstrip line (5) are connected by PIN diodes (12). The PIN diode (12) is used to automatically control the antenna state switching according to the energy of the incident electromagnetic wave: when a low-power communication signal is incident, the PIN diode (12) is in the cut-off state, the antenna is in normal working state, and has the ability to transmit and receive signals normally; when a high-power microwave is incident, the PIN diode (12) is turned on, so that the polarization conversion metasurface units (11) on both sides of the feed microstrip line (5) are connected, and the metasurface antenna switches to the impedance mismatch protection state, loses normal radiation capability and reflects high-power microwave; Furthermore, the metasurface antenna possesses radar cross-section reduction capability in both the cut-off and conduction states of the PIN diode (12); The polarization conversion metasurface unit (11) includes a square dielectric substrate and a metal geometry on the upper surface of the square dielectric substrate; The metal geometry is located in the middle of the square dielectric substrate, including a double arrow configuration (111) arranged along the diagonal of the square dielectric substrate. The double arrow configuration (111) has side grooves (112) on both sides of the diagonal, and a strip slit (113) is provided in the middle of the double arrow configuration (111) along the diagonal direction. The polarization conversion metasurface unit (11) is configured in two types, both with the same structure and the orientation intersecting at 90°. The two types of polarization conversion metasurface unit (11) have orthogonal polarization conversion phase responses. Multiple polarization conversion metasurface units (11) are arranged in a two-dimensional periodic array, wherein four adjacent polarization conversion metasurface units (11) are of the same type and constitute a basic array group; Several basic array groups are arranged at intervals in a checkerboard pattern, such that two units on the opposite diagonal of the space are of the same type, while two units on the other diagonal of the space are of a different type. The arrangement of the basic array groups is used to cancel out the electromagnetic scattering fields from each element, thereby reducing the radar cross section.

2. The electromagnetically protected low RCS metasurface antenna as described in claim 1, characterized in that, Side slots (112) and strip slots (113) are used to introduce structural asymmetry based on a square dielectric substrate, wherein: The side groove (112) is used to control the equivalent LC value in the u direction; The strip slit (113) is used to control the equivalent LC value in the v direction; By changing the size parameters of the side slot (112) and the strip slit (113), the incident electromagnetic wave can generate a phase difference in the u direction and the v direction, thereby realizing polarization conversion.

3. The electromagnetically protected low RCS metasurface antenna as described in claim 2, characterized in that, The double-arrow configuration (111) has rounded corners (114) at the arrowheads, and a rectangular groove (115) is provided in the middle of the side groove (112) facing the strip slit (113). The fillet (114) is used to change the equivalent LC value in the v direction; The rectangular slot (115) introduces an equivalent capacitance in the u direction; By adjusting the size parameters of the fillet (114) and the rectangular slot (115), the adjustment range of the phase difference is expanded and the polarization conversion performance is improved.

4. The electromagnetically protected low RCS metasurface antenna as described in any one of claims 1-3, characterized in that, The slot structure (31) includes a long vertical slot (311) and short horizontal slots (312) arranged on both sides of the long vertical slot (311). The long vertical slot (311) is perpendicular to the feed microstrip line (5).

5. The electromagnetically protected low RCS metasurface antenna as described in claim 4, characterized in that, One end of the feed microstrip line (5) is located on the side of the metasurface antenna and is connected to an SMA coaxial interface (6). The SMA coaxial interface (6) is used to connect the metasurface antenna to external radio frequency equipment. The projection position of the other end of the feed microstrip line (5) passes through the long vertical slot (311).

6. The electromagnetically protected low RCS metasurface antenna as described in claim 5, characterized in that, The SMA coaxial interface (6) includes an interface and mounting feet. The mounting feet pass through the lower dielectric substrate (4) and the gap metal ground (3) and are then fixed to the upper dielectric substrate (2).

7. The electromagnetically protected low RCS metasurface antenna as described in any one of claims 1-3, characterized in that, The relative permittivity of the lower dielectric substrate (4) is 3.

66.

8. The electromagnetically protected low RCS metasurface antenna as described in any one of claims 1-3, characterized in that, The relative permittivity of the upper dielectric substrate (2) is 4.

4.

9. A method for operating an electromagnetically protected low RCS metasurface antenna as described in any one of claims 1-8, characterized in that, Includes the following steps: Receive incident electromagnetic wave signals; The energy of the incident electromagnetic wave is sensed by the polarization-conversion metasurface unit (11), and an induced voltage is generated across the PIN diode (12); Determine the relationship between the induced voltage and the conduction threshold of the PIN diode (12): If the induced voltage is less than the conduction threshold, the PIN diode (12) remains in the off state. At this time, the antenna works in the normal transmit and receive mode. The feed microstrip line (5) achieves impedance matching with the metasurface structure (1) through the slot structure (31) to complete the radiation or reception of the communication signal. If the induced voltage is greater than or equal to the conduction threshold, the PIN diode (12) switches to the conduction state, and the control PIN diode (12) switches to the conduction state. At this time, the antenna switches to the protection state due to impedance mismatch and reflects high-power microwaves. In both normal transmission and reception mode and protection mode, the arrangement of polarization conversion metasurface units (11) is adjusted by controlling the scattering field of the incident wave to reduce the radar scattering cross section.

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