Intelligent reflecting surface and covert communication system

Abstract

This application discloses an intelligent reflective surface and a covert communication system, belonging to the field of wireless communication technology. The intelligent reflective surface includes multiple intelligent reflective surface units arranged in an array; each intelligent reflective surface unit includes: a first substrate, a second substrate, and a third substrate; a metal patch and a varactor diode, located on the side of the third substrate opposite to the second substrate; the metal patch includes a first patch and a second patch, and the varactor diode is located between the first patch and the second patch, with its negative and positive terminals electrically connected to the first patch and the second patch, respectively; a metal ground plane, located between the first substrate and the second substrate; a first bias line and a second bias line, located on the side of the first substrate opposite to the second substrate; the first bias line is electrically connected to the metal ground plane and the first patch, respectively, and the second bias line is electrically connected to the second patch. This application can achieve precise control of electromagnetic waves, reduce electromagnetic energy loss, improve energy transmission efficiency, suppress electromagnetic wave leakage, and improve communication covertness.

Description

Technical Field

[0001] This application belongs to the field of wireless communication technology, and in particular relates to an intelligent reflective surface and a covert communication system. Background Technology

[0002] With the rapid development of 5G communication networks, wireless communication technology is increasingly integrated with various industries, and the openness of electromagnetic wave transmission has led to more prominent communication security issues. Conventional encryption technologies can only ensure the security of the information content itself, but cannot reduce the probability of signal interception, making it difficult to meet the comprehensive requirements of special scenarios such as power line inspection for communication concealment, wide coverage, high speed, and low energy consumption. Against this backdrop, covert communication that relies on hidden signals to achieve communication security has become a research hotspot. Intelligent Reflecting Surfaces (IRS), as the core carrier of novel intelligent metasurface technology, can remotely control the propagation path, amplitude, and phase of electromagnetic waves through intelligent reflective surface units, providing a new technical path for the realization of covert communication. Its passive reflection characteristics can minimize the risk of signal leakage, becoming a key technical support for solving the covert communication needs in special scenarios.

[0003] However, the intelligent reflective surface unit in the related technology uses a combination of a single-layer substrate and a single-layer patch, which has a simple structure, cannot achieve precise control of electromagnetic waves, and has a lot of electromagnetic energy loss, low energy transmission efficiency, high risk of electromagnetic wave leakage, and poor communication concealment. Summary of the Invention

[0004] This application aims to address at least one of the technical problems existing in the prior art. To this end, this application proposes an intelligent reflective surface and a concealed communication system, which can achieve precise control of electromagnetic waves, reduce electromagnetic energy loss, improve energy transmission efficiency, suppress electromagnetic wave leakage, and enhance communication concealment.

[0005] In a first aspect, this application provides an intelligent reflective surface, comprising a plurality of intelligent reflective surface units arranged in an array; The intelligent reflective surface unit includes: A first substrate, a second substrate, and a third substrate are stacked sequentially. A metal patch and a varactor diode are located on the side of the third substrate away from the second substrate. The metal patch includes a first patch and a second patch arranged symmetrically to each other. The varactor diode is located between the first patch and the second patch, and the negative terminal of the varactor diode is electrically connected to the first patch, and the positive terminal of the varactor diode is electrically connected to the second patch. A metal ground plane is located between the first substrate and the second substrate; A first bias line and a second bias line are located on the side of the first substrate away from the second substrate. The first bias line is electrically connected to the metal ground plane and the first patch, respectively, and the second bias line is electrically connected to the second patch.

[0006] According to the intelligent reflective surface of this application, by setting up a three-layer substrate, a wide-band varactor diode combined with a metal patch is used on the side of the third substrate away from the second substrate to achieve precise control of wide-band electromagnetic waves, ensure uniform current distribution, reduce energy loss caused by current concentration, and improve energy transmission efficiency. A metal ground plane is set between the first substrate and the second substrate to suppress electromagnetic wave leakage and improve the working efficiency and communication concealment of the intelligent reflective surface.

[0007] According to one embodiment of this application, the smart reflective surface unit further includes: A first metal pillar penetrates the first substrate, the metal ground plane, the second substrate, and the third substrate, and is connected to the first bias line, the metal ground plane, and the first patch, respectively. The second metal pillar penetrates the first substrate, the second substrate, and the third substrate, and is connected to the second bias line and the second patch, respectively.

[0008] According to one embodiment of this application, the first substrate, the second substrate, and the third substrate have different thicknesses; and / or, The first patch and the second patch are respectively T-shaped, circular, or rectangular.

[0009] According to one embodiment of this application, the varactor diode has an operating bandwidth of 10MHz to 70GHz.

[0010] In a second aspect, this application provides a covert communication system, characterized in that it includes a signal transmitting module, a signal receiving module, a control module, and an intelligent reflective surface as described in the first aspect above; The signal transmitting module is electrically connected to the intelligent reflective surface and is used to transmit electromagnetic wave signals to the intelligent reflective surface; The intelligent reflective surface is electrically connected to the signal receiving module and is used to control the reflection of the electromagnetic wave signal according to the reflection coefficient, and reflect the controlled electromagnetic wave signal back to the signal receiving module. The signal receiving module is electrically connected to the control module and is used to receive the modulated electromagnetic wave signal and send a feedback signal to the control module according to the received signal. The control module is electrically connected to the smart reflective surface and is used to adjust the reflection coefficient of the smart reflective surface according to the feedback signal.

[0011] According to one embodiment of this application, the control module is used to apply a bias voltage to the target intelligent reflective surface unit in the intelligent reflective surface according to the feedback signal, and adjust the junction capacitance of the varactor diode in the target intelligent reflective surface unit to adjust the reflection coefficient of the target intelligent reflective surface unit.

[0012] According to one embodiment of this application, the control module is used to apply a bias voltage to the target smart reflective surface unit in the smart reflective surface when the feedback signal is detected to meet a preset condition; Wherein, the feedback signal includes the signal strength of the received signal, the preset condition includes the signal strength of the received signal being lower than the target strength, and / or, the feedback signal includes the signal-to-noise ratio of the received signal, the preset condition includes the signal-to-noise ratio of the received signal being less than the target signal-to-noise ratio.

[0013] According to one embodiment of this application, the control module includes a microprocessor electrically connected to the signal receiving module, a global pointer register electrically connected to the microprocessor, and a plurality of conversion units electrically connected to the global pointer register, wherein the plurality of conversion units are respectively electrically connected to a plurality of smart reflective surface units. The microprocessor is used to generate a control signal based on the feedback signal, the control signal including a data signal and an addressing instruction for the target intelligent reflective surface unit; The global pointer register is electrically connected to the microprocessor and is used to determine the logical address of the target intelligent reflective surface unit according to the addressing instruction, and send the data signal to the conversion unit corresponding to the target intelligent reflective surface unit according to the logical address. The conversion unit corresponding to the target intelligent reflective surface unit is used to convert the data signal into the bias voltage and apply it to the target intelligent reflective surface unit.

[0014] According to one embodiment of this application, the conversion unit includes a data register electrically connected to the global pointer register and a conversion circuit electrically connected to the data register and the corresponding smart reflective surface unit, respectively. The data register corresponding to the target intelligent reflective surface unit is used to convert the data signal into a voltage signal; The conversion circuit corresponding to the target intelligent reflective surface unit is used to perform digital-to-analog conversion on the voltage signal to obtain the bias voltage, and then apply the bias voltage to the target intelligent reflective surface unit.

[0015] According to one embodiment of this application, the conversion circuit includes a digital-to-analog converter circuit and / or an RC filter and integrator circuit.

[0016] The above-described one or more technical solutions in the embodiments of this application have at least one of the following technical effects: By setting up a three-layer substrate, a wide-band varactor diode combined with a metal patch is used on the side of the third substrate away from the second substrate to achieve precise control of wide-band electromagnetic waves, ensure uniform current distribution, reduce energy loss caused by current concentration, and improve energy transmission efficiency. A metal ground plane is set between the first and second substrates to suppress electromagnetic wave leakage and improve the working efficiency and communication concealment of the smart reflective surface. Furthermore, the control module has an independent addressing function. Based on the signal feedback from the signal receiving module, the control module performs precise and independent control of the intelligent reflector unit, with high beam pointing accuracy and fast control response speed.

[0017] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Attached Figure Description

[0018] The above and / or additional aspects and advantages of this application will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which: Figure 1 This is a schematic diagram of the structure of the smart reflective surface provided in the embodiments of this application; Figure 2 This is a cross-sectional schematic diagram of the intelligent reflective surface unit in the intelligent reflective surface provided in the embodiments of this application; Figure 3 This is a top view of the intelligent reflective surface unit in the intelligent reflective surface provided in the embodiments of this application; Figure 4 This is a schematic diagram of the structure of the covert communication system provided in the embodiments of this application; Figure 5 This is a schematic diagram of the structure of the control module in the covert communication system provided in the embodiments of this application. Detailed Implementation

[0019] The embodiments of this application are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this application, and should not be construed as limiting this application.

[0020] The following description, with reference to the accompanying drawings, describes the intelligent reflective surface and covert communication system provided in embodiments of this application. The intelligent reflective surface can be applied to the covert communication system. The covert communication system is suitable for special scenarios with high requirements for communication concealment, transmission rate, and low energy consumption, primarily used in power line inspection, but can also be extended to wireless communication scenarios requiring low probability of interception, such as drone inspection, high-speed rail communication, and communication in complex outdoor environments.

[0021] Figure 1 This is a schematic diagram of the structure of the intelligent reflective surface provided in an embodiment of this application. Figure 2 This is a cross-sectional schematic diagram of the intelligent reflective surface unit provided in the embodiments of this application. Figure 3 This is a top view of the intelligent reflective surface unit provided in an embodiment of this application.

[0022] like Figure 1 As shown, the smart reflective surface 1 provided in this embodiment includes a plurality of smart reflective surface units 10 arranged in an array. The number of smart reflective surface units 10 and the array distribution can be set according to actual needs.

[0023] Combination Figure 2 and Figure 3 As shown, the intelligent reflective surface unit 10 includes a first substrate 11, a second substrate 12, a third substrate 13, a first bias line 14, a second bias line 15, a metal ground plane 16, a metal patch 17, and a varactor diode 18.

[0024] The first substrate 11, the second substrate 12, and the third substrate 13 are stacked sequentially, with the first substrate 11 at the bottom, the third substrate 13 at the top, and the second substrate 12 between the first substrate 11 and the third substrate 13. The thicknesses of the first substrate 11, the second substrate 12, and the third substrate 13 can be set according to actual needs. All three substrates are dielectric substrates. The first substrate 11 uses a high-frequency dielectric material, and its thickness is optimized according to the operating frequency band to ensure efficient electromagnetic wave transmission.

[0025] The metal patch 17 and the varactor diode 18 are located on the side of the third substrate 13 opposite to the second substrate 12, that is, the metal patch 17 and the varactor diode 18 are located on the top of the third substrate 13. The metal patch 17 includes a first patch 171 and a second patch 172 arranged symmetrically to each other. The varactor diode 18 is located between the first patch 171 and the second patch 172, and the negative terminal of the varactor diode 18 is electrically connected to the first patch 171, and the positive terminal of the varactor diode 18 is electrically connected to the second patch 172. The metal patch 17 may include a copper metal patch.

[0026] The varactor diode 18 is used to adjust the current distribution on the surface of the metal patch 17, enabling the intelligent reflective surface unit 10 to be reconfigurable and to flexibly and precisely control the phase and amplitude of electromagnetic waves to meet the needs of different communication scenarios. The metal patch 17 adopts a high-precision manufacturing process to ensure uniform current distribution and reduce energy loss.

[0027] The metal ground plane 16 is located between the first substrate 11 and the second substrate 12. The metal ground plane 16 is precisely designed and calculated to be strictly matched with the distance between the first substrate 11 and the second substrate 12, ensuring effective capture of reflected electromagnetic waves, suppressing electromagnetic wave leakage, and improving the working efficiency and communication concealment of the smart reflective surface. Furthermore, the metal ground plane 16 also enhances the structural stability of the smart reflective surface 1, providing support for its long-term stable operation and adapting to the complex outdoor environment of power line inspection.

[0028] The first bias line 14 and the second bias line 15 are located on the side of the first substrate 11 opposite to the second substrate 12, that is, the first bias line 14 and the second bias line 15 are located at the bottom of the first substrate 11. The first bias line 14 and the second bias line 15 are used to connect the control module in the covert communication system. The first bias line 14 is electrically connected to the metal ground plane 16 and the first patch 171, respectively, and the second bias line 15 is electrically connected to the second patch 172. The cathode of the varactor diode 18 is electrically connected to the metal ground plane 16 and the first bias line 14, respectively, and the anode of the varactor diode 18 is electrically connected to the second bias line 15.

[0029] The first bias line 14 and the second bias line 15 in each intelligent reflective surface unit 10 are electrically connected to the control module of the covert communication system. The control module of the covert communication system applies bias voltages to the positive and negative terminals of the varactor diode 18 through the first bias line 14 and the second bias line 15 to adjust the junction capacitance of the varactor diode 18. By adjusting the magnitude of the bias voltage, the junction capacitance of the varactor diode 18 can be dynamically adjusted, thereby realizing real-time control of the electromagnetic characteristics of the intelligent reflective surface unit 10, and thus enabling the control module to precisely adjust the reflection response of the intelligent reflective surface 1.

[0030] In some embodiments, the smart reflective surface unit 10 further includes a first metal pillar 19 and a second metal pillar 21. The first metal pillar 19 penetrates the first substrate 11, the metal ground plane 16, the second substrate 12, and the third substrate 13, and is connected to the first bias line 14, the metal ground plane 16, and the first patch 171, respectively. The cathode of the varactor diode 18 can be electrically connected to the metal ground plane 16 and the control module in the covert communication system through the first metal pillar 19 and the first bias line 14.

[0031] The second metal pillar 21 penetrates the first substrate 11, the second substrate 12, and the third substrate 13, and is connected to the second bias line 15 and the second patch 172, respectively. The second metal pillar 21 is spaced apart from the metal ground plane 16. The positive terminal of the varactor diode 18 can be electrically connected to the control module in the covert communication system through the second metal pillar 21 and the second bias line 15.

[0032] In practical applications, the distance between the second metal post 21 and the metal ground plane 16 is strictly controlled to avoid electrical contact. At the same time, the connection between the first metal post 19 and the first bias line 14, and between the second metal post 21 and the second bias line 15 are ensured to minimize the possibility of poor contact and ensure the stability and accuracy of the reflection response adjustment of the intelligent reflective surface 1.

[0033] In some embodiments, the first substrate 11, the second substrate 12, and the third substrate 13 have different thicknesses.

[0034] In some embodiments, the first patch 171 and the second patch 172 are T-shaped, circular, or rectangular, respectively. The first patch 171 and the second patch 172 may also be other shapes, which are not specifically limited here. When both the first patch 171 and the second patch 172 are T-shaped, the metal patch 17 and the varactor diode 18 are generally H-shaped.

[0035] In some embodiments, the varactor diode 18 has an operating bandwidth of 10MHz to 70GHz, enabling wide-band electromagnetic wave modulation.

[0036] It should be noted that, depending on the bandwidth requirements of the actual application scenario, the operating frequency band of the varactor diode 18, as well as the shape and size of the first patch 171 and the second patch 172, and the thickness and material of the first substrate 11, the second substrate 12 and the third substrate 13 can be adjusted, but the core structure of the intelligent reflective surface unit 10 remains unchanged to ensure wideband adaptation and precise control.

[0037] Depending on communication distance and coverage, the number and layout of the intelligent reflector units 10 can be adjusted, but the design still follows periodic boundary conditions to ensure that the reflection coefficient phase is linear. The intercept and slope of the linear phase depend on the system's operating frequency band and can be flexibly adjusted according to the transmission requirements of power line inspection. Simultaneously, considering the non-ideal characteristics of the intelligent reflector 1, the overall shape of the intelligent reflector 1 (including the number of intelligent reflector units 10 and their array distribution) is designed based on optimization algorithms, effectively solving the problem of excessive parasitic scattering interference in phase modulation and reducing electromagnetic energy loss.

[0038] In the structural design, the weight and structural durability of the intelligent reflector 1 are considered simultaneously. Lightweight, high-strength substrates and patches are selected to ensure that the intelligent reflector 1 can be quickly deployed (e.g., mounted on a drone) and can operate stably in complex outdoor environments for extended periods. The intelligent reflector 1 can efficiently reflect electromagnetic waves in a wide frequency band of 10MHz to 70GHz, possessing good directionality and gain characteristics to ensure directional signal transmission and further enhance stealth.

[0039] As an example, the smart reflector 1 has an operating bandwidth of 10MHz to 70GHz and comprises 32×32 (arranged in 32 rows and 32 columns) smart reflector units 10. The thicknesses of the first substrate 11, the second substrate 12, and the second substrate 13 are 0.5 to 2mm, respectively, and the thicknesses of the first substrate 11, the second substrate 12, and the second substrate 13 are different. The junction capacitance of the varactor diode 18 is adjustable from 1pF to 10pF. The diameters of the first metal pillar 19 and the second metal pillar 21 are 0.1mm to 0.3mm, respectively. The phase adjustment range of the reflection coefficient of the smart reflector 1 is 0 to 360°, and the reflection efficiency is ≥90%.

[0040] It should be noted that during the design process of the intelligent reflector 1, a three-dimensional model of the intelligent reflector 1 was established using electromagnetic simulation software to ensure that the model is manufacturable. At the same time, the full-wave simulation method was introduced to determine the simulation coefficients of the wireless array, and the unit structure parameters (such as substrate thickness, patch size, varactor diode position, and metal column spacing) were iteratively optimized in multiple rounds to achieve the best electromagnetic reflection performance of the intelligent reflector 1. By simulating the energy loss at different reflection angles, the structure of the intelligent reflector 1 was further optimized to ensure that electromagnetic energy loss is minimized while ensuring communication quality.

[0041] Furthermore, a simplified electromagnetic calculation scheme is adopted, which calculates the reflection coefficient based on the ECM (equivalent circuit model), replaces the varactor diode with the resistance of the transmission line, replaces the metal pillar with the capacitor, and replaces the inductor with the patch, effectively reducing the difficulty of analyzing the electromagnetic characteristics of the unit structure, improving R&D efficiency, and providing convenience for subsequent phase control optimization.

[0042] In summary, the intelligent reflective surface provided in this application adopts a three-layer patch (bias line, metal ground plane, and metal patch) and three-layer substrate structure, combined with a metal ground plane design, which effectively suppresses electromagnetic wave leakage and minimizes the probability of signal interception. A wide-band varactor diode (10MHz~70GHz) combined with the metal patch design enables precise control of electromagnetic waves. Simultaneously, through electromagnetic simulation optimization and unit parameter iteration, bandwidth limitations are overcome, significantly improving the transmission rate. This meets the high-speed transmission requirements of power line inspection data, with a transmission rate more than 30% higher than related technologies, thus achieving a dual improvement in concealment and transmission rate. Furthermore, considering the non-ideal characteristics of the intelligent reflective surface, the reflective surface structure is designed based on an optimized algorithm. Combined with electromagnetic simulation software to simulate energy loss at different reflection angles, the problem of phase modulation due to parasitic scattering interference is effectively solved. At the same time, the use of an ECM equivalent circuit model simplifies electromagnetic calculations and optimizes the unit structure design, resulting in uniform current distribution and reduced energy loss caused by current concentration. Energy transmission efficiency is improved by more than 25% compared to related technologies, and phase modulation accuracy is improved by more than 40%.

[0043] Accordingly, embodiments of this application also provide a covert communication system.

[0044] like Figure 4 As shown, the covert communication system provided in this embodiment includes a signal transmitting module 2, a signal receiving module 3, a control module 4, and a smart reflective surface 1. The smart reflective surface 1 is the same as the smart reflective surface described in the above embodiment, and will not be further elaborated here.

[0045] The signal transmitting module 2 is electrically connected to the smart reflector 1 and is used to transmit electromagnetic wave signals to the smart reflector 1.

[0046] The intelligent reflector 1 is electrically connected to the signal receiving module 3 and is used to control the reflection of electromagnetic wave signals according to the reflection coefficient, and then reflect the controlled electromagnetic wave signals back to the signal receiving module 3. The reflection coefficient may include the reflection phase and amplitude.

[0047] The signal receiving module 3 is electrically connected to the control module 4 and is used to receive the regulated electromagnetic wave signal and send a feedback signal to the control module 4 according to the regulated electromagnetic wave signal.

[0048] The control module 4 is electrically connected to the intelligent reflective surface 1 and is used to adjust the reflection coefficient of the intelligent reflective surface 1 according to the feedback signal.

[0049] The signal transmitting module 2 adopts a low-power, directional transmission design, and its transmission power can be flexibly adjusted according to the communication distance. The signal transmitting module 2 transmits electromagnetic wave signals (i.e., power line inspection data signals, such as fault detection data and inspection image data). The operating frequency band of the signal transmitting module 2 matches the wideband (10MHz~70GHz) of the intelligent reflector 1, ensuring that the signal can be efficiently received and reflected by the intelligent reflector 1. In some embodiments, the signal transmitting module 2 employs an encryption processing unit to perform secondary encryption on the transmitted signal, further enhancing communication security and achieving dual security protection of "covert transmission + content encryption".

[0050] The signal receiving module 3 adopts a high-sensitivity, directional receiving design, enabling it to accurately receive concealed signals (i.e., modulated electromagnetic wave signals) reflected by the intelligent reflector 1. It features signal amplification and filtering functions, effectively suppressing external interference signals and improving signal reception quality. The signal receiving module 3 works in conjunction with the control module 4, providing real-time feedback on parameters such as the signal-to-noise ratio and intensity of the received signal. Based on these feedback parameters, the control module 4 dynamically adjusts the reflection phase and amplitude of the intelligent reflector 1 to ensure stable signal transmission. The signal receiving module 3 also includes a built-in signal analysis unit, which can quickly analyze the received inspection data signals and transmit them to the inspection terminal or backend system for data storage and processing.

[0051] Control module 4 is the core control unit. It adopts a customized design and has independent addressing function, low power consumption, high integration and scalability. It can meet the precise control requirements of intelligent reflective surface 1, and is also suitable for the low energy consumption and complex environment requirements of power line inspection.

[0052] It should be noted that, depending on the needs of different expansion scenarios, parameters such as signal transmission power, transmission rate, and bias voltage adjustment range can be adjusted, and corresponding adaptation modules can be added (such as adding an anti-interference module in military scenarios).

[0053] In this embodiment, the signal transmitting module 2, signal receiving module 3, control module 4, and intelligent reflector 1 work together to achieve concealed and efficient signal transmission. The intelligent reflector 1, as the core component, is responsible for precisely reflecting and controlling the electromagnetic wave signal emitted by the signal transmitting module 2, directing the signal to the signal receiving module 3 and minimizing signal leakage. The control module 4 is responsible for real-time control of the intelligent reflector 1, enabling dynamic adjustment of the reflection phase and amplitude, as well as independent control of the unit. The signal transmitting module 2 is responsible for sending data signals (electromagnetic wave signals) to be transmitted in scenarios such as power line inspection. The signal receiving module 3 is responsible for receiving the concealed signal (controlled electromagnetic wave signal) reflected by the intelligent reflector 1 and performing signal analysis. All modules are connected via dedicated interfaces to ensure stable signal transmission and timely response to control commands. The overall system architecture is simple and highly integrated, allowing for rapid deployment on power line inspection drones or inspection terminals.

[0054] In some embodiments, the control module 4 is used to apply a bias voltage to the target smart reflective surface unit in the smart reflective surface 1 according to the feedback signal, and adjust the junction capacitance of the varactor diode in the target smart reflective surface unit to adjust the reflection coefficient of the target smart reflective surface unit.

[0055] Combination Figures 1 to 3 As shown, the control module 4 is connected to the negative and positive terminals of the varactor diode 18 via the first bias line 14 and the second bias line 15 of each intelligent reflective surface unit 10, respectively. The bias voltage output by the control module 4 is applied to both ends of the varactor diode 18 via the first bias line 14 and the second bias line 15 of the target intelligent reflective surface unit to adjust the junction capacitance of the varactor diode 18, thereby adjusting the reflection coefficient (including reflection phase and amplitude) of the target intelligent reflective surface unit, and further adjusting the reflection coefficient (including reflection phase and amplitude) of the intelligent reflective surface 1. The intelligent reflective surface 1 adjusts the phase and amplitude of the electromagnetic wave signal emitted by the signal transmitting module 2 according to the adjusted reflection coefficient, and reflects the adjusted electromagnetic wave signal to the signal receiving module 3.

[0056] To achieve precise and independent control of each intelligent reflective surface unit 10 of the intelligent reflective surface 1, the control module 4 is designed with an independent addressing function. First, the specific physical location information of each intelligent reflective surface unit 10 is integrated into the control program through a position mapping algorithm to generate a corresponding logical address. Then, all logical addresses are stored. By sending specific addressing commands and combining them with the stored logical addresses, the control module 4 can quickly locate the corresponding intelligent reflective surface unit 10, creating conditions for independent control.

[0057] In some embodiments, the control module 4 is configured to apply a bias voltage to the target smart reflective surface unit in the smart reflective surface when the feedback signal is detected to meet a preset condition. The feedback signal includes the signal strength of the received signal, the preset condition includes the signal strength of the received signal being lower than the target strength, and / or the feedback signal includes the signal-to-noise ratio of the received signal, the preset condition includes the signal-to-noise ratio of the received signal being lower than the target signal-to-noise ratio.

[0058] The signal receiving module 3 monitors parameters such as the signal-to-noise ratio and signal strength of the received signal in real time and feeds these parameters back to the control module 4. Based on the feedback signal, the control module 4 determines the signal transmission quality. If problems such as insufficient signal strength, excessive interference, or phase shift exist, it uses the independent addressing function to locate the corresponding intelligent reflector unit, adjusts the bias voltage of the intelligent reflector unit, changes the junction capacitance of the varactor diode, and thus dynamically adjusts the reflection phase and amplitude of the intelligent reflector unit.

[0059] In this embodiment, the control module 4, based on the signals (including signal-to-noise ratio, signal strength, etc.) fed back by the signal receiving module 3, locates the target intelligent reflective surface unit through independent addressing, dynamically adjusts the bias voltage, reflection phase and amplitude, optimizes the signal transmission quality in real time, and ensures that the system can still communicate stably when the environment changes suddenly, adapting to the application requirements of complex field environments.

[0060] In some embodiments, combined with Figure 5 As shown, the control module 4 includes a microprocessor 41 electrically connected to the signal receiving module, a global pointer register 42 electrically connected to the microprocessor 41, and multiple conversion units 43 electrically connected to the global pointer register. The multiple conversion units 43 are respectively electrically connected to multiple smart reflective surface units 10.

[0061] The microprocessor 41 is used to generate control signals based on feedback signals. The control signals include data signals and addressing instructions for the target intelligent reflective surface unit.

[0062] The global pointer register 42 is electrically connected to the microprocessor 41 and is used to determine the logical address of the target intelligent reflective surface unit according to the addressing instruction, and send the data signal to the corresponding conversion unit of the target intelligent reflective surface unit according to the logical address.

[0063] The conversion unit 43 corresponding to the target intelligent reflective surface unit is used to convert the data signal into a bias voltage and apply it to the target intelligent reflective surface unit.

[0064] The control module 4 meets three core requirements: it can support the long-term stable operation of large-scale control programs, can efficiently execute the independent addressing instructions of the intelligent reflective surface unit 10, and can synchronously perform multi-channel signal conversion and unified output, ensuring accurate and real-time control of the intelligent reflective surface 1.

[0065] For the intelligent reflector 1 with a large number of bit quantizations, its adapted control algorithm is relatively complex, and the optimization process is prone to generating a large amount of temporary data, which places high demands on CPU performance and memory space. Therefore, the control module 4 uses a high-performance microprocessor 41, equipped with a large-capacity memory and a high-speed data cache module to ensure the long-term stable operation of the control program, efficiently process the massive amount of temporary data generated during the optimization process, prevent data loss and processing delays, and ensure that the intelligent reflector 1 can adjust its reflection characteristics in real time and accurately according to communication requirements.

[0066] The control program is initially installed on a PC for system debugging and parameter optimization. In practical engineering applications, the program carrier can be changed to a programmable device (such as a microcontroller) to simplify the control system structure, improve the system's applicability and portability, and adapt to miniaturized deployment requirements such as drone deployment.

[0067] Each intelligent reflective surface unit 10 corresponds to a conversion unit 43. The conversion unit 43 converts the digital signal (i.e., data signal) output by the microprocessor 41 into an analog signal (i.e., bias voltage), reducing the difficulty of controlling the equivalent capacitance.

[0068] To reduce the impact of address conflicts and addressing errors, control module 4 can also be equipped with an error detection and correction function unit to detect errors in the addressing process in real time and automatically complete the correction, ensuring the accuracy and reliability of independent addressing results.

[0069] In some embodiments, the conversion unit 43 includes a data register 431 electrically connected to the global pointer register 42 and a conversion circuit 432 electrically connected to the data register 431 and the corresponding smart reflective surface unit, respectively.

[0070] The data register 431 corresponding to the target intelligent reflective surface unit is used to convert the data signal into a voltage signal.

[0071] The conversion circuit 432 corresponding to the target intelligent reflective surface unit is used to perform digital-to-analog conversion on the voltage signal to obtain a bias voltage, and then apply the bias voltage to the target intelligent reflective surface unit.

[0072] Each conversion circuit 432 is electrically connected to the first bias line 14 and the second bias line 15 of the corresponding smart reflective surface unit, so that the conversion circuit 432 applies the converted bias voltage to the two ends of the varactor diode 18 through the first bias line 14 and the second bias line 15 of the corresponding smart reflective surface unit, adjusts the junction capacitance of the varactor diode 18 of the corresponding smart reflective surface unit, thereby adjusting the reflection coefficient of the corresponding smart reflective surface unit, and thus improving the reflection coefficient of the smart reflective surface 1.

[0073] The conversion circuit 432 employs a high-precision and high-stability design to ensure accurate conversion of digital signals into analog voltage signals (i.e., bias voltage). It also features rapid response capabilities, enabling signal conversion within a short time to meet the need for rapid adjustment of the reflective characteristics of the reflector under real-time communication conditions. The control program accesses the data register 431 to obtain the real-time output of the analog voltage signal, allowing for flexible control of the analog voltage signal output by the conversion circuit 432. This enables precise and dynamic regulation of the reflective characteristics of the intelligent reflector 1, improving the system's response speed and adaptability to environmental changes, ensuring the intelligent reflector 1 functions normally in complex outdoor environments.

[0074] In some embodiments, the conversion circuit 432 includes a digital-to-analog converter circuit and / or an RC filter and integrator circuit.

[0075] To achieve synchronous control of multiple intelligent reflective surface units 10, the control module 4 innovatively introduces a highly integrated DAC (digital-to-analog converter) to enhance the various functions of the register as a memory. The core reason for choosing the DAC is its high degree of integration, which enables multi-channel digital-to-analog conversion within a limited space, simplifies the circuit structure, and improves system reliability and operational stability. At the same time, the DAC has a fast conversion speed, which can fully meet the timeliness requirements of communication systems for data transmission, and its low power consumption can significantly reduce the overall energy consumption of the control module 4 and improve energy utilization efficiency.

[0076] To further reduce hardware costs and circuit complexity, this embodiment can also employ an RC filter integrator circuit. The RC filter integrator circuit is suitable for scenarios with moderate conversion accuracy requirements and strict cost control. It features a simple structure and controllable operating costs. Its design is based on the integration principle of RC circuits, selecting appropriate resistor (R) and capacitor (C) parameters to design a first-order integrator circuit. Combined with an operational amplifier, isolation and buffering are achieved, ensuring the circuit is unaffected by the load. The time constant τ of the RC circuit, τ = RC > input pulse width TK, converts the input rectangular pulse into a sawtooth wave with amplitude linearly varying over time, achieving the conversion from digital signal to analog voltage signal, similar to the effect of a digital-to-analog converter circuit.

[0077] Compared to analog-to-digital converter circuits, using RC filter and integrator circuits can further reduce the number of components used in the circuit, save hardware costs, reduce circuit complexity, enhance system stability and maintainability, simplify the design process of communication systems, accelerate development progress, and further reduce system operating costs.

[0078] In this embodiment, the control module 4 adopts a low-power design scheme, optimizes the circuit structure, and selects low-power components (such as low-power DACs and microprocessors) to reduce operating power consumption and meet the long-endurance requirements of equipment such as power line inspection drones. At the same time, the control module 4 reserves expansion interfaces to improve integration and scalability, which facilitates subsequent system upgrades and the addition of functional modules (such as fault detection modules and data encryption modules) to adapt to the communication needs of different scenarios.

[0079] It should be noted that, depending on the control precision requirements, the conversion accuracy of the DAC and the performance parameters of the microprocessor can be adjusted; the RC filter integration circuit can be replaced with other low-cost digital-to-analog conversion schemes, or both the DAC and RC filter integration schemes can be retained simultaneously to achieve on-demand switching.

[0080] The workflow of the covert communication system provided in this application embodiment is described in detail below. The workflow of the covert communication system is divided into a startup and debugging phase, a normal operation phase, and a dynamic adjustment phase.

[0081] (1) Start-up and debugging phase: After the system starts up, the control module 4 automatically loads the control program and completes the initialization settings (such as the initial value of the bias voltage, addressing logic, DAC conversion parameters, etc.); the signal transmission module 2 and the signal receiving module 3 start up synchronously and complete the self-test; the electromagnetic simulation optimization module (integrated into the control module) calls the preset intelligent reflector model, and combines the current environmental parameters (such as communication distance, interference intensity, etc.) to perform preliminary optimization of the parameters of the intelligent reflector unit 10, determine the initial reflection phase, amplitude and beam direction, and ensure that the system meets the initial communication requirements.

[0082] (2) Normal operation phase: The signal transmitting module 2 sends encrypted power line inspection data signals, which are directionally transmitted to the intelligent reflector 1. Under the control of the control module 4, the intelligent reflector 1 adjusts the current distribution through the varactor diode 18 to regulate the phase and amplitude of the received electromagnetic waves and directionally reflect the signals to the signal receiving module 3. The metal ground plane 16 in the intelligent reflector 1 suppresses electromagnetic wave leakage, reduces the probability of signal interception, and realizes covert communication. The signal receiving module 3 receives the reflected signal, and after amplification, filtering, and analysis, transmits the inspection data to the terminal or back-end system.

[0083] (3) Dynamic adjustment stage: The signal receiving module 3 detects the signal-to-noise ratio, strength and other parameters of the received signal in real time and feeds the parameters back to the control module 4; The control module 4 judges the signal transmission quality according to the feedback parameters. If there are problems such as insufficient signal strength, excessive interference, phase shift, etc., the corresponding intelligent reflector unit 10 is located through the independent addressing function, the bias voltage is adjusted, the junction capacitance of the varactor diode 18 is changed, and the reflection phase and amplitude of the intelligent reflector unit 10 are dynamically adjusted; At the same time, the multi-channel digital-to-analog conversion parameters (or RC filter integral parameters) are optimized to ensure that the signal transmission quality is always in the best state; If there is a sudden change in the environment (such as obstruction, increased interference), the control module 4 quickly adjusts the beam pointing of the intelligent reflector to ensure that the communication is not interrupted.

[0084] It should be noted that during system debugging, the unit parameters and reflection phase should be optimized first using electromagnetic simulation software before actual hardware debugging is performed to ensure that the system performance meets the design requirements; the independent addressing function and dynamic control function should be debugged in particular to avoid addressing errors and control delays.

[0085] During system operation, the power consumption of the control module and the operating status of components need to be checked regularly, and damaged components need to be maintained and replaced in a timely manner. For systems that use RC filter integration schemes, circuit parameters need to be calibrated regularly to ensure conversion accuracy.

[0086] When deployed in outdoor environments (such as power line inspection), the intelligent reflective surface and control module need to be waterproofed, dustproofed, and collision-proofed to ensure long-term stable operation of the module; when carried by drones, the module needs to be securely fixed to prevent it from falling off during flight.

[0087] When adjusting the bias voltage, it is necessary to adjust it gradually according to the actual communication scenario and signal feedback parameters to avoid voltage sudden changes that could damage the varactor diode and ensure stable control of the reflection phase and amplitude.

[0088] When upgrading the system, core functions such as independent addressing, low power consumption, and precise phase modulation must be retained to ensure that the system's covert communication performance is not affected after the upgrade.

[0089] The key parameters of the covert communication system provided in this embodiment can be flexibly adjusted according to the actual application scenario (such as power line inspection distance and data transmission rate requirements). Typical parameter settings are as follows to ensure optimal system performance: (1) Intelligent reflective surface: operating frequency band 10MHz~70GHz, the number of intelligent reflective surface units can be adjusted according to the communication distance (typically 32×32 array), substrate thickness 0.5~2mm (different thicknesses for each layer), junction capacitance of varactor diode adjustable range 1~10pF, metal via diameter 0.1~0.3mm, reflection coefficient phase adjustable range 0~360°, reflection efficiency ≥90%; (2) Control module: microprocessor main frequency ≥1GHz, memory ≥1GB, DAC conversion accuracy ≥12bit, conversion rate ≥1MSps, RC filter integration circuit time constant τ=1~10ms, bias voltage adjustment range 0~5V, operating power consumption ≤5W, addressing response time ≤10μs; (3) Signal transmission module: transmission power 0.1~1W, signal bandwidth 1~100MHz, data transmission rate ≥100Mbps, encryption method AES-256; (4) Signal receiving module: receiving sensitivity ≤ -100dBm, filtering bandwidth 1~100MHz, resolution delay ≤1ms, signal-to-noise ratio ≥20dB.

[0090] It should be noted that the current implementation of covert communication mainly relies on two technical paths: one is traditional encryption technology, which encrypts the transmitted information to ensure that even if the signal is intercepted, the illegal receiver cannot decipher the information content. However, this technology cannot change the transmission characteristics of electromagnetic waves, and the probability of signal interception is relatively high, making it difficult to meet the core requirement of low interception probability in scenarios such as power line inspection. The second is assisted covert communication technology based on intelligent reflective surfaces, which uses the passive reflection characteristics of intelligent reflective surfaces to enhance the link signal-to-noise ratio, reduce the possibility of signal leakage, and improve the covertness of communication. At present, this technology has become a research hotspot in the industry, but there are still many shortcomings in the related designs.

[0091] Existing research on covert communication based on smart reflectors often employs simple patch and substrate combinations for the unit structure of these reflectors. This approach fails to achieve precise electromagnetic wave control, suffers from narrow bandwidth and severely limited transmission rates, falling far short of the performance ceiling of smart reflectors and failing to meet the high-speed data transmission requirements of power line inspection. Furthermore, the smart reflectors do not adequately consider non-ideal characteristics, with parasitic scattering and other factors directly interfering with phase modulation, leading to significant electromagnetic energy loss. Additionally, the unreasonable structural design of the smart reflector units results in a high risk of signal leakage, further reducing communication concealment and energy transmission efficiency. Control modules often employ... The existing control scheme lacks customized design for covert communication scenarios, lacks independent addressing capabilities, has low beam pointing accuracy, and high control algorithm complexity. It cannot achieve precise and independent control of the intelligent reflector unit, and its high power consumption, poor integration, and scalability make it difficult to adapt to the complex and ever-changing field environment of power line inspection, hindering long-term stable operation and future upgrades. Furthermore, the existing design does not fully consider the non-ideal characteristics of the intelligent reflector; parasitic scattering and other factors lead to insufficient phase modulation accuracy, severe electromagnetic energy loss, and significantly bandwidth-limited transmission rates, falling far short of the performance ceiling of the intelligent reflector. In addition, existing technologies mostly use traditional digital-to-analog conversion methods, resulting in high hardware costs, complex circuit structures, and a large number of components, leading to reduced system reliability and increased maintenance difficulty, further limiting the system's engineering applications.

[0092] In power line inspection scenarios, existing technologies either employ conventional wireless communication, which suffers from poor concealment and is easily intercepted; or they utilize simple intelligent reflective surface designs that fail to consider the reflective surface's weight, structural durability, and rapid deployment requirements. Furthermore, they cannot simultaneously meet the comprehensive demands of high speed, low energy consumption, high concealment, and wide coverage, making it difficult to achieve secure and efficient transmission of inspection data and failing to meet the practical application requirements of wide coverage and long endurance in power line inspections. Simultaneously, current UAV-related communication technologies primarily focus on fault location, failing to deeply integrate covert communication with efficient transmission, resulting in insufficient security and reliability in complex terrain inspections.

[0093] Based on this, the covert communication system in this embodiment uses the intelligent reflector 1 as the core carrier, and combines electromagnetic simulation optimization, customized control module design, structural optimization and low-cost hardware design to achieve the comprehensive requirements of covertness, high speed, low energy consumption and high reliability. It is mainly suitable for power line inspection scenarios, and can also be extended to other complex covert communication scenarios. (1) Dual improvement in concealment and transmission rate: The intelligent reflective surface provided in this application adopts a three-layer patch and three-layer substrate structure, combined with a metal ground plane design, which effectively suppresses electromagnetic wave leakage and minimizes the probability of signal interception; the wide-band varactor diode (10MHz~70GHz) combined with the metal patch design realizes precise control of electromagnetic waves, and at the same time, through electromagnetic simulation optimization and unit parameter iteration, it breaks through the bandwidth limitation and significantly improves the transmission rate, which can meet the needs of high-speed transmission of inspection data for power line inspection, and the transmission rate is more than 30% higher than that of the existing technology; (2) High phase control accuracy and low electromagnetic energy loss: This application fully considers the non-ideal characteristics of the intelligent reflector and designs the structure of the intelligent reflector based on the optimization algorithm, which effectively solves the problem of phase control by parasitic scattering interference; at the same time, the ECM equivalent circuit model is used to simplify electromagnetic calculation and optimize the unit structure design, so that the current distribution is uniform and the energy loss caused by current concentration is reduced. The energy transmission efficiency is improved by more than 25% compared with related technologies, and the phase control accuracy is improved by more than 40%. (3) Excellent control performance and adaptability to complex environments: The control module has independent addressing function, which can realize precise and independent control of intelligent reflective surface unit, with high beam pointing accuracy. At the same time, it simplifies the complexity of control algorithm and has fast control response speed. It selects high-performance low-power microprocessor and integrated DAC, optimizes circuit structure, realizes low power consumption and high-speed response control effect, and adapts to the needs of long-endurance equipment such as UAVs. It reserves expansion interface to realize high integration and scalability design, which is convenient for system upgrade and function expansion. It can fully adapt to the complex and ever-changing field environment of power line inspection and solve the problem of poor adaptability of existing control devices. (4) Low hardware cost and low circuit complexity, making it easy to promote in engineering: The introduction of a highly integrated DAC to realize multi-channel digital-to-analog synchronous conversion improves conversion speed and stability; the innovative proposal of using RC filter integration to replace the traditional digital-to-analog conversion option, combined with the application of integrated DAC, simplifies the circuit structure, reduces the number of components, and reduces hardware and operating costs. The hardware cost is reduced by more than 40% compared with the existing technology; at the same time, the circuit complexity is reduced, the system reliability and maintainability are significantly improved, and the problems of high hardware cost and difficult maintenance of related technologies are solved; the RC filter integration circuit combined with operational amplifier realizes isolation buffer, which ensures conversion accuracy and meets system control requirements while reducing cost and circuit complexity; (5) Strong adaptability and wide range of application scenarios: This invention is customized for power line inspection scenarios, taking into account the self-weight of the reflector, structural durability and rapid deployment requirements. It can be mounted on UAVs and is suitable for inspection applications in complex terrains such as mountains and dense forests. At the same time, the system parameters can be flexibly adjusted and can be extended to other covert communication scenarios that require low interception probability, such as UAV inspection, high-speed rail communication, and communication in complex outdoor environments. It has a wider range of adaptability than existing technologies. Combined with UAV inspection technology, it achieves a deep integration of covert communication and efficient inspection, improving the safety and reliability of inspection. (6) High R&D efficiency and strong manufacturability: This invention reduces the analysis difficulty and R&D complexity of the intelligent reflective surface unit by modeling with electromagnetic simulation software, optimizing with full-wave simulation method and simplifying calculation with ECM equivalent circuit, and shortens the R&D cycle; at the same time, the intelligent reflective surface is manufacturable, the processing technology is mature, and it is easy to mass-produce, solving the problems of low R&D efficiency and poor manufacturability of related technologies. (7) Dual security guarantee and high communication reliability: The signal transmission module adds an encryption processing unit to achieve dual security guarantee of "covert transmission + content encryption". Even if the signal is accidentally intercepted, the illegal receiver will not be able to parse the information content, further improving the communication security. At the same time, the modules of the system work together and have dynamic adjustment function. The transmission parameters can be optimized in real time according to environmental changes to ensure stable and uninterrupted communication and solve the problem of insufficient communication reliability of existing technologies.

[0094] This application has both economic and social benefits.

[0095] (1) Economic benefits: This application is mainly adapted to power line inspection scenarios, which can realize the concealed and high-speed transmission of inspection data, improve inspection efficiency, reduce fault finding time and power outage time, and improve power supply reliability. At the same time, the system has low hardware cost and low power consumption, which can reduce inspection cost and communication cost. Combined with UAV inspection technology, it can reduce manual inspection input and further reduce operation and maintenance cost. It is expected to reduce power inspection cost by more than 20%. If applied to distribution network inspection, it can reduce power outages and increase power supply volume every year, generating significant economic benefits. In addition, the system can be mass-produced, and its engineering promotion prospects are broad, which can create certain industrial economic benefits.

[0096] (2) Social benefits: This application improves the security and reliability of covert communication, avoids data leakage in key areas such as power line inspection, and protects public power safety and critical information security; at the same time, it is compatible with efficient inspection methods such as drone inspection, which can reduce the security risks of manual inspection and protect the personal safety of inspection personnel; the system can be extended to military, field exploration and other fields, improve the communication security of related fields, and has important social value; in addition, this invention promotes the integrated development of intelligent reflective surface technology and covert communication technology, and promotes the innovation and upgrading of wireless communication technology.

[0097] This application is mainly applied to special wireless communication scenarios with high requirements for communication concealment, transmission rate, and low energy consumption. The key application scenario is power line inspection. The specific application method is to mount the concealed communication system of this application on a power line inspection drone or inspection terminal to achieve concealed and high-speed transmission of inspection data (such as fault detection data, inspection images, and equipment operating parameters), avoid the interception of inspection data, meet the requirements of long-endurance drones and deployment in complex terrain, improve the safety, efficiency, and reliability of power line inspection, solve the inspection communication problem in areas that are difficult for humans to reach, such as mountains and dense forests, reduce power outage time, and create significant economic benefits.

[0098] Expanded application scenarios include: covert communication for drones, covert communication on high-speed trains, covert communication in field exploration, and covert military communication—scenarios requiring low probability of interception. System parameters (such as the number of intelligent reflector units, transmission power, and operating frequency band) can be flexibly adjusted according to the needs of different scenarios to adapt to varying communication distances and data transmission requirements. Furthermore, this application can be combined with a drone-borne fault diagnosis and location device to achieve an integrated "fault location + covert communication" function, further improving inspection efficiency.

[0099] All technical solutions in this application are based on existing mature electronic technology, electromagnetic simulation technology, and processing technology, and have high feasibility for engineering implementation, as detailed below: (1) Component feasibility: The components used in this application (varactor diodes, DACs, microprocessors, dielectric substrates, metal chips, resistors, capacitors, operational amplifiers, etc.) are all common and mature products on the market, which can be purchased directly and the cost is controllable. There is no need to customize special components. Among them, wide-band varactor diodes and integrated DACs are mass-produced products with stable performance, which can meet the system design requirements. (2) Feasibility of processing technology: The layered structure of the intelligent reflective surface, the surface mount processing, the metal through-hole fabrication and other processes are all existing mature PCB processing technologies. The precision can meet the design requirements and can be mass-produced; the processing technology of the metal ground plane and the offset line is mature and easy to industrialize. (3) Software and algorithm feasibility: The control program, electromagnetic simulation optimization algorithm, position mapping algorithm, addressing algorithm, etc. can all be implemented based on existing programming technology and simulation tools (such as HFSS, CST). The algorithm complexity is moderate and can be run efficiently by microprocessor; the design of RC filter integral circuit can be implemented based on existing RC circuit theory, and the parameter optimization difficulty is low. (4) Testing feasibility: The key performance parameters of the system, such as reflection efficiency, phase modulation accuracy, transmission rate, concealment, and power consumption, can be accurately tested using existing testing equipment (such as spectrum analyzers, network analyzers, and power meters), which facilitates system debugging and performance optimization.

[0100] To further improve the performance of the covert communication system and expand its application scenarios, this application may also: (1) optimize the phase modulation algorithm to further reduce the algorithm complexity, improve the modulation response speed and accuracy, and adapt to the needs of higher-speed communication; (2) develop new lightweight and high-durability substrate materials to further reduce the weight of the intelligent reflective surface module and improve the environmental adaptability and service life of the module; (3) optimize the design of the RC filter integral circuit to improve the conversion accuracy, expand its application range, and achieve seamless switching with the DAC scheme; (4) add multi-scenario adaptive function so that the system can automatically identify the current application scenario and automatically adjust key parameters without manual intervention; (5) combine artificial intelligence technology to realize automatic detection, diagnosis and repair of system faults, and improve the intelligence level and reliability of the system; (6) expand the multi-band adaptability of the system, further expand the working frequency band, and adapt to the needs of more complex covert communication scenarios.

[0101] The terms "first," "second," etc., used in the specification and claims of this application are used to distinguish similar objects and are not used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that embodiments of this application can be implemented in orders other than those illustrated or described herein, and the objects distinguished by "first," "second," etc., are generally of the same class and are not limited in number; for example, a first object can be one or more.

[0102] In the description of this application, "multiple" means two or more.

[0103] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0104] Although embodiments of this application have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of this application, the scope of which is defined by the claims and their equivalents.

Claims

1. A smart reflective surface, characterized in that, It includes multiple intelligent reflective surface units arranged in an array; The intelligent reflective surface unit includes: A first substrate, a second substrate, and a third substrate are stacked sequentially. A metal patch and a varactor diode are located on the side of the third substrate away from the second substrate. The metal patch includes a first patch and a second patch arranged symmetrically to each other. The varactor diode is located between the first patch and the second patch, and the negative terminal of the varactor diode is electrically connected to the first patch, and the positive terminal of the varactor diode is electrically connected to the second patch. A metal ground plane is located between the first substrate and the second substrate; A first bias line and a second bias line are located on the side of the first substrate away from the second substrate. The first bias line is electrically connected to the metal ground plane and the first patch, respectively, and the second bias line is electrically connected to the second patch.

2. The intelligent reflective surface according to claim 1, characterized in that, The intelligent reflective surface unit also includes: A first metal pillar penetrates the first substrate, the metal ground plane, the second substrate, and the third substrate, and is connected to the first bias line, the metal ground plane, and the first patch, respectively. The second metal pillar penetrates the first substrate, the second substrate, and the third substrate, and is connected to the second bias line and the second patch, respectively.

3. The intelligent reflective surface according to claim 1, characterized in that, The first substrate, the second substrate, and the third substrate have different thicknesses; and / or, The first patch and the second patch are respectively T-shaped, circular, or rectangular.

4. The intelligent reflective surface according to any one of claims 1-3, characterized in that, The operating bandwidth of the varactor diode is 10MHz to 70GHz.

5. A covert communication system, characterized in that, It includes a signal transmitting module, a signal receiving module, a control module, and a smart reflective surface as described in any one of claims 1-4; The signal transmitting module is electrically connected to the intelligent reflective surface and is used to transmit electromagnetic wave signals to the intelligent reflective surface; The intelligent reflective surface is electrically connected to the signal receiving module and is used to control the reflection of the electromagnetic wave signal according to the reflection coefficient, and reflect the controlled electromagnetic wave signal back to the signal receiving module. The signal receiving module is electrically connected to the control module and is used to receive the modulated electromagnetic wave signal and send a feedback signal to the control module according to the received signal. The control module is electrically connected to the smart reflective surface and is used to adjust the reflection coefficient of the smart reflective surface according to the feedback signal.

6. The covert communication system according to claim 5, characterized in that, The control module is used to apply a bias voltage to the target intelligent reflective surface unit in the intelligent reflective surface according to the feedback signal, and adjust the junction capacitance of the varactor diode in the target intelligent reflective surface unit to adjust the reflection coefficient of the target intelligent reflective surface unit.

7. The covert communication system according to claim 6, characterized in that, The control module is used to apply a bias voltage to the target smart reflective surface unit in the smart reflective surface when the feedback signal is detected to meet the preset conditions. Wherein, the feedback signal includes the signal strength of the received signal, the preset condition includes the signal strength of the received signal being lower than the target strength, and / or, the feedback signal includes the signal-to-noise ratio of the received signal, the preset condition includes the signal-to-noise ratio of the received signal being less than the target signal-to-noise ratio.

8. The covert communication system according to claim 6, characterized in that, The control module includes a microprocessor electrically connected to the signal receiving module, a global pointer register electrically connected to the microprocessor, and a plurality of conversion units electrically connected to the global pointer register. The plurality of conversion units are respectively electrically connected to the plurality of smart reflective surface units. The microprocessor is used to generate a control signal based on the feedback signal, the control signal including a data signal and an addressing instruction for the target intelligent reflective surface unit; The global pointer register is electrically connected to the microprocessor and is used to determine the logical address of the target intelligent reflective surface unit according to the addressing instruction, and send the data signal to the conversion unit corresponding to the target intelligent reflective surface unit according to the logical address. The conversion unit corresponding to the target intelligent reflective surface unit is used to convert the data signal into the bias voltage and apply it to the target intelligent reflective surface unit.

9. The covert communication system according to claim 8, characterized in that, The conversion unit includes a data register electrically connected to the global pointer register and a conversion circuit electrically connected to the data register and the corresponding smart reflective surface unit, respectively. The data register corresponding to the target intelligent reflective surface unit is used to convert the data signal into a voltage signal; The conversion circuit corresponding to the target intelligent reflective surface unit is used to perform digital-to-analog conversion on the voltage signal to obtain the bias voltage, and then apply the bias voltage to the target intelligent reflective surface unit.

10. The covert communication system according to claim 9, characterized in that, The conversion circuit includes a digital-to-analog converter circuit and / or an RC filter and integrator circuit.

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