D8psk modulation method and system based on phase encoding spatiotemporal modulation metasurface

Abstract

The application discloses a D8PSK modulation method and system based on phase coding space-time modulation super surface, specifically: a phase coding unit based on a reflective load phase shifter is constructed, eight discrete phase states are generated by regulating the reflective load impedance so that the phase coding unit generates eight discrete phase states; the phase coding unit is used as a super surface unit, and a phase coding space-time modulation super surface is obtained by arrangement; a D8PSK modulation signal model based on the phase coding space-time modulation super surface is established, information transmission of non-synchronous demodulation is realized while the carrier is space-time modulated; 3-bit information coding and modulation code rate are designed according to the transmission information, different modulation code rates are set as keys to realize encrypted information transmission; a receiving antenna receives a return signal, the return signal is demodulated through the key to realize acquisition of the encrypted information. The application improves the spectrum utilization rate of the space-time modulation super surface, realizes high-speed and stable information transmission, and meets the data security requirements.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of space-time modulation metasurface, and particularly relates to a D8PSK (Differential 8-Phase Shift Keying) modulation method and system based on a phase coding space-time modulation metasurface. BACKGROUND

[0002] In the field of electromagnetic communication, secure communication is a research direction that is continuously closely followed. With the exponential growth of data volume and the increasing complexity of decryption methods, it is essential to ensure the secure transmission of data. Physical layer security provides an innovative approach to protect data transmission from eavesdropping and network threats. Document 1 (A. Mukherjee, S. A. A. Fakoorian, J. Huang, et al., "Principles of physical layer security in multiuser wireless networks: A survey," IEEE Communications Surveys & Tutorials, vol. 16, no. 3, pp. 1550-1573, 2014.) introduces a multi-user wireless network physical layer security that does not rely on high-level encryption in the presence of unauthorized eavesdroppers, exchanges secret information through wireless media, and is mainly achieved by intelligently designing transmission coding strategies. Physical layer security provides strong protection for secure communication. Electromagnetic metasurface as a new type of physical layer security medium has attracted much attention due to its low loss, simple and light physical structure and other characteristics. By loading a series of devices such as varactor tubes and diodes on the electromagnetic metasurface, reconfigurable technology is introduced, enabling the electromagnetic metasurface to realize real-time flexible control and coding capabilities in the time domain and spatial domain.

[0003] Document 2 (Y. Liu et al.,“Ultra‐Wideband Simultaneous Manipulations of Fundamental and Harmonic Waves Based on Space‐Time Coding Metasurface: Basic Principles and mmWave Applications,” Laser&Photonics Review, Jan. 2025.) proposes a millimeter wave wireless communication system, develops an advanced coding strategy, realizes QPSK (Quadrature Phase Shift Keying) modulation on the fundamental and harmonic waves respectively, enables independent and interference-free transmission of data on each frequency channel, and thus improves the communication rate of a single metasurface aperture to the order of Mbps.

[0004] However, PSK (Phase Shift Keying) faces many challenges in practical applications, and synchronization demodulation is one of the key difficulties. The receiving end must accurately capture and lock the carrier phase and clock signal of the sending end. If the synchronization process deviates, the demodulated signal will be distorted, which seriously affects the communication quality and even causes data transmission interruption. In addition, with the increasing demand for communication efficiency in the information age, while ensuring high-speed and stable information transmission rate, the demand for data security is also increasingly prominent. It is necessary to maintain the efficient transmission characteristics of PSK modulation and prevent information from being stolen or tampered with, which puts higher requirements on modulation technology application, and it is urgent to achieve the balance between performance and security through technological innovation. SUMMARY

[0005] The purpose of the present application is to provide a D8PSK modulation method and system based on phase coding space-time modulation metasurface, to improve the spectrum utilization rate of space-time modulation metasurface, and to realize high-speed, stable and secure transmission of data information.

[0006] The technical solution for achieving the purpose of the present application is: a D8PSK modulation method based on phase coding space-time modulation metasurface, comprising the following steps:

[0007] Step 1, construct a phase coding unit based on a reflective load phase shifter, control the reflective load impedance to make the phase coding unit generate eight discrete phase states; the phase coding unit serves as a metasurface unit, and a phase coding space-time modulation metasurface is obtained by arranging the units;

[0008] Step 2, a D8PSK modulation signal model based on phase coding space-time modulation super surface is established, information transmission of non-synchronous demodulation is realized while the carrier is space-time modulated;

[0009] Step 3, 3-bit information coding and modulation code rate are designed according to the transmission information, different modulation code rates are set as keys to realize encrypted information transmission;

[0010] Step 4, the receiving antenna receives the echo signal, and the echo signal is demodulated by the key to realize the acquisition of the encrypted information.

[0011] A D8PSK modulation system based on phase coding space-time modulation super surface, the system is used to realize the D8PSK modulation method based on phase coding space-time modulation super surface, the system comprises first module to fourth module, and the functions of each module are as follows:

[0012] The first module is a phase coding unit based on a reflective load phase shifter, the reflective load impedance is controlled to make the phase coding unit generate eight discrete phase states; the phase coding unit is used as a super surface unit, and a phase coding space-time modulation super surface is obtained by arranging and arranging;

[0013] The second module is a D8PSK modulation signal model based on phase coding space-time modulation super surface, information transmission of non-synchronous demodulation is realized while the carrier is space-time modulated;

[0014] The third module is a 3-bit information coding and modulation code rate designed according to the transmission information, different modulation code rates are set as keys to realize encrypted information transmission;

[0015] The fourth module is a receiving antenna receiving echo signal, and the echo signal is demodulated by the key to realize the acquisition of the encrypted information.

[0016] A mobile terminal comprises a memory, a processor and a computer program stored on the memory and executable on the processor, and the processor realizes the D8PSK modulation method based on phase coding space-time modulation super surface when the program is executed.

[0017] A computer readable storage medium, a computer program is stored on the medium, and the program is executed by the processor to realize the steps in the D8PSK modulation method based on phase coding space-time modulation super surface.

[0018] Compared with the prior art, the present application has the following advantages:

[0019] (1) Constructed the phase encoding array element based on the reflective load phase shifter, and the eight kinds of discrete phase states were generated by regulating the reflective load impedance, and based on the D8PSK modulation signal model of the phase encoding space-time modulation metasurface, the metasurface realized the high-speed information transmission of non-synchronous demodulation while space-time modulating the carrier;

[0020] (2) According to the transmission information, 3-bit information encoding and modulation code rate are designed, different modulation code rates are set as keys, the receiving antenna receives the echo signal, and the echo signal is demodulated by the key to realize the acquisition of encrypted information, realize the encrypted transmission of information, and prevent information from being stolen or tampered with;

[0021] (3) The amplitude information is extracted by space-time modulation, and the phase information is extracted by D8PSK modulation, which can significantly improve the spectrum utilization rate of the space-time modulation metasurface, and realize the high spectrum utilization rate of non-synchronous demodulation encrypted information transmission.

[0022] The application will be described in further detail below with reference to the drawings. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 It is a D8PSK modulation communication system scene diagram based on a phase encoding space-time modulation metasurface.

[0024] Figure 2 It is a top view of a phase encoding unit of a phase encoding space-time modulation metasurface.

[0025] Figure 3 It is a bottom view of a phase encoding unit of a phase encoding space-time modulation metasurface.

[0026] Figure 4 It is a normalized amplitude diagram of eight states of a phase encoding unit of a phase encoding space-time modulation metasurface.

[0027] Figure 5 It is a phase difference diagram of eight states of a phase encoding unit of a phase encoding space-time modulation metasurface.

[0028] Figure 6 It is a D8PSK modulation constellation diagram in the application. DETAILED DESCRIPTION

[0029] In order to improve the spectrum utilization of the space-time modulation super surface, ensure high-speed and stable transmission of information, and ensure data security, the application provides a D8PSK modulation method and system based on a phase encoding space-time modulation super surface, specifically: a phase encoding array element based on a reflective load phase shifter is constructed, and eight discrete phase states are generated by adjusting the reflective load impedance; the D8PSK modulation mechanism is analyzed, and the D8PSK modulation signal model based on the phase encoding space-time modulation super surface is derived, so that the high-speed information transmission of non-synchronous demodulation is realized while the carrier is space-time modulated; according to the transmission information, 3-bit information encoding and modulation code rate are designed, different modulation code rates are set as keys to realize encrypted information transmission; the receiving antenna receives the echo signal, demodulates the echo signal through the key, and realizes the acquisition of the encrypted information. The application can significantly improve the spectrum utilization of the space-time modulation super surface.

[0030] The application will be described in further detail below with reference to the drawings and specific embodiments. It is easily understood that, according to the technical scheme of the application, a person skilled in the art can imagine various embodiments of the application without changing the essential spirit of the application. Therefore, the following specific embodiments and drawings are only exemplary descriptions of the technical scheme of the application, and should not be regarded as the whole or as a limitation or restriction on the technical scheme of the application.

[0031] Various exemplary embodiments of the application will now be described in detail with reference to the accompanying drawings. It should be noted that the relative arrangement, numerical expressions and values of the components and steps set forth in these embodiments do not limit the scope of the application unless otherwise specifically stated.

[0032] The following description of at least one exemplary embodiment is merely exemplary in nature and is in no way intended to limit the application or its application or use.

[0033] Techniques, methods, and equipment known to those of ordinary skill in the relevant art can not be discussed in detail, but should be considered part of the specification where appropriate.

[0034] In all examples shown and discussed herein, any specific values should be interpreted as merely exemplary and not as a limitation. Thus, other examples of the exemplary embodiments can have different values.

[0035] In conjunction with Figure 1 The application provides a D8PSK modulation method based on a phase encoding space-time modulation super surface, as shown in the scene diagram of the D8PSK modulation communication system based on the phase encoding space-time modulation super surface, including the following steps:

[0036] Step 1, constructing a phase encoding unit based on a reflective load phase shifter, regulating the reflective load impedance so that the phase encoding unit generates eight discrete phase states; the phase encoding unit serves as a metasurface unit, and a phase encoding space-time modulation metasurface is obtained by arranging the unit;

[0037] Step 2, establishing a D8PSK modulation signal model based on the phase encoding space-time modulation metasurface, realizing non-synchronous demodulation information transmission while space-time modulating the carrier;

[0038] Step 3, designing a 3-bit information encoding and modulation code rate according to the transmission information, and using different modulation code rates as keys to realize information encryption transmission;

[0039] Step 4, the receiving antenna receives the echo signal, demodulates the echo signal through the key, and realizes the acquisition of the encrypted information.

[0040] As a specific example, in step 1, the phase encoding unit based on the reflective load phase shifter is constructed, and the reflective load impedance is regulated so that the phase encoding unit generates eight discrete phase states; combined with the phase encoding space-time modulation metasurface unit diagram shown in Figure 2 、 Figure 3 , the eight-state reflection coefficient simulation diagram of the phase encoding space-time modulation metasurface unit is shown in Figure 4 、 Figure 5 , and the specific diagram is as follows:

[0041] The reflective load phase shifter includes a directional coupler and a reflective load, and the directional coupler is a 3dB directional coupler.

[0042] The input end of the directional coupler simultaneously serves as the output end, the through end is connected to a reflective load, and the coupling end is connected to another reflective load. The reflective loads connected to the through end and the coupling end are of the same structure, and the isolation end is grounded.

[0043] The reflective load includes a varactor and a microstrip line, the cathode of the varactor is connected to the microstrip line, and the anode is grounded.

[0044] The S parameter of the reflective load phase shifter is , is the reflection coefficient of the reflective load, and is expressed as:

[0045] (1)

[0046] wherein, is the reflective load impedance, is the characteristic impedance, is the reflection coefficient phase, is the imaginary unit;

[0047] Substitute equation (1) into In the middle, get:

[0048] (2)

[0049] That is, the phase shift after the phase shifter is determined by the varactor impedance, the varactor model is MAVR-000120-1411, by adjusting the reverse DC bias voltage at both ends of the varactor, to change the reflection load impedance, so that The change range is , thereby adjusting the DC bias voltage, so that the reflection load phase shifter generates eight discrete phase states.

[0050] As a specific example, the phase encoding unit based on the reflection load phase shifter is constructed in step 1, which is as follows:

[0051] The phase encoding unit is a multi-layer structure, and the side length of the phase encoding unit is , The wavelength of the electromagnetic wave in free space; Taking X-band as an example, the center frequency is selected as , .

[0052] The phase encoding unit includes five layers from top to bottom, wherein:

[0053] The first layer is a patch for receiving and radiating electromagnetic waves, and the patch is composed of a center same inner circle and an outer circle ring metal patch, and the inner circle and the outer circle ring are connected by a rectangular metal patch;

[0054] The second layer is a first dielectric substrate, and the material of the first dielectric substrate adopts F4B plate material, and the thickness is 2 mm;

[0055] The third layer is a metal ground, which is a ground plate of the patch in the first layer and the phase shifter in the fifth layer, and the thickness is 0.035 mm;

[0056] The fourth layer is a second dielectric substrate, and the material of the second dielectric substrate adopts Rogers RO4350B, and the thickness is 0.254 mm, which is a dielectric substrate of the microstrip line structure of the phase shifter in the fifth layer;

[0057] The fifth layer is a phase shifter, and the phase shifter is a microstrip line structure, and the thickness is 0.035 mm, and the port is connected with the patch in the first layer through a coaxial feeder, realizing waveguide transmission.

[0058] As a specific example, the D8PSK modulation signal model based on the phase encoding space-time modulation super surface is established in step 2, which realizes non-synchronous demodulation information transmission while space-time modulating the carrier, combined with Figure 6 The D8PSK modulation constellation diagram is shown, which is as follows:

[0059] The D8PSK modulation mechanism in the phase modulation period of the metasurface unit is analyzed;

[0060] Assume a point frequency signal incident to the phase-coded space-time modulation metasurface, is the amplitude of the point frequency signal, is the carrier frequency of the point frequency signal, represents the time.

[0061] The metasurface unit performs periodic phase modulation on the point frequency signal, the echo signal at time is represented as:

[0062] (3)

[0063] wherein, is the reflection coefficient of the metasurface unit at time is represented as:

[0064] (4)

[0065] wherein, is the relative phase change amount of the reflection load phase shifter at time takes the value of , as shown in the constellation diagram. Figure 6

[0066] Set the first phase modulation period is represented as :

[0067] (5)

[0068] wherein, is the phase modulation period of the metasurface unit, is the time-varying relative phase change amount of the metasurface reflection coefficient in the first phase modulation period, that is, .

[0069] In the second phase modulation period is represented as :

[0070] (6)

[0071] wherein, is the time-varying relative phase change amount of the metasurface reflection coefficient in the second phase modulation period, that is, , and the D8PSK modulation mechanism is obtained​​​ ;

[0072] The Fourier coefficients of the first phase modulation period and the second phase modulation period are made Fourier transform of complex form, The Fourier coefficients are expressed as:

[0073] (7)

[0074] (8)

[0075] Wherein, The Fourier coefficients of the first phase modulation period and the second phase modulation period are respectively, is the phase modulation frequency; is a positive integer, representing the harmonic order.

[0076] From equation (7), equation (8) is obtained , that is, the Fourier coefficients of the first phase modulation period and the second phase modulation period are equal, and there is Phase difference;

[0077] The information transmitted after D8PSK modulation is the phase difference between two adjacent phase modulation periods, taking values as , that is, 3-bit information transmission.

[0078] The D8PSK modulation signal model based on phase coding space-time modulation metasurface is established, and the echo signal of the phase coding space-time modulation metasurface is represented as:

[0079] (9)

[0080] Wherein, is the incident elevation angle, is the radiation elevation angle, is the speed of light, is the unit spacing of the metasurface unit, is the number of metasurface units, is the time-varying reflection coefficient of the th metasurface unit, and there are metasurface units;

[0081] After the Fourier transform of complex form is made on , the following is obtained:

[0082] (10)

[0083] Wherein, is the time-varying reflection coefficient of the one phase modulation period Fourier coefficients of the phase modulation, is a positive integer.

[0084] From equation (10), it can be seen that the code rate of 3-bit information encoding after D8PSK modulation transmission is determined by the phase modulation frequency . Since D8PSK modulation only changes its phase, the information encoding after D8PSK modulation is determined by the phase difference between two adjacent phase modulation periods , that is, the information exists in the phase difference, and the delay does not affect the phase difference, and the modulation code rate can reach the order of 10MHz, and the transmission rate can reach 20Mbps, so that the phase encoding space-time modulation metasurface realizes non-synchronous demodulation information transmission while modulating the carrier in space-time.

[0085] As a specific example, in combination with the D8PSK modulation communication system scene diagram based on the phase encoding space-time modulation metasurface shown in Figure 1 , the 3-bit information encoding described in step 3 is composed of information code and identification code, and the identification code is placed in front of the information code to identify and locate the information code.

[0086] As a specific example, step 3 describes the design of 3-bit information encoding and modulation code rate according to the transmission information, which realizes information encryption transmission by setting different modulation code rates as keys, specifically:

[0087] (3.1) Design the information code according to the known information to determine the information code phase encoding;

[0088] After D8PSK modulation, each information code transmits 3-bit information, and let the information code be , that is, the phase difference between the corresponding two adjacent phase modulation periods is , the information code phase encoding is , and the corresponding phase is ; the information code phase encoding is derived from the information code, assuming that the first information code phase encoding is 0, then the information code corresponding to the phase encoding is ; for information code, the final information code phase encoding is , for example, for 7-bit information code, the final information code phase encoding is 8-bit information code.

[0089] (3.2) Design the identification code phase encoding according to the information code phase encoding to determine the identification code;

[0090] Let the D8PSK phase modulation period be , which contains a plurality of ; for information code, design The bit identification code is placed in front of the information code, for identifying and positioning the information code; the first bit and the last bit of the phase encoding of the information code are respectively and The first bit and the last bit of the phase encoding of the identification code are respectively and Let:

[0091] (11)

[0092] According to formula (11) and bit information code, a bit identification code is designed, and finally a bit identification code phase encoding is obtained, which is determined as a D8PSK phase modulation period , which contains .

[0093] As a specific example, the receiving antenna receives the echo signal in step 4, demodulates the echo signal by the key, and realizes the acquisition of encrypted information, which is specifically:

[0094] For the echo signal of the phase encoding space-time modulated metasurface, according to the change of the time domain signal, the signal in a complete D8PSK phase modulation period is extracted, and are intercepted respectively, that is, the key of the echo signal, only when is known, can bit information encoding be obtained, and then the information code is finally obtained through the identification code, and the required information is extracted;

[0095] Suppose the phase encoding space-time modulated metasurface is single sideband modulated in time and beam controlled in space, then according to formula (10), the amplitude and phase information of the highest harmonic component are set; for space-time modulation, the amplitude information needs to be extracted, and for D8PSK modulation, the phase information needs to be extracted, to realize non-synchronous demodulation of the spectrum and encrypted information transmission.

[0096] In one embodiment, the present application also provides a D8PSK modulation system based on a phase encoding space-time modulated metasurface, which is used to realize the D8PSK modulation method based on the phase encoding space-time modulated metasurface, and the system comprises first to fourth modules, and the functions of each module are as follows:

[0097] ​​The first module is to construct a phase encoding unit based on a reflective load phase shifter, and to regulate the reflective load impedance so that the phase encoding unit generates eight discrete phase states; the phase encoding unit is used as a metasurface unit, and a phase encoding space-time modulation metasurface is obtained by arranging the unit;

[0098] The second module is to establish a D8PSK modulation signal model based on the phase encoding space-time modulation metasurface, to realize non-synchronous demodulation information transmission while modulating the carrier in space-time;

[0099] The third module is to design a 3-bit information encoding and modulation code rate according to the transmission information, to realize information encryption transmission by setting different modulation code rates as keys;

[0100] The fourth module is to receive a back echo signal by an antenna, to demodulate the back echo signal by the key, and to realize encrypted information acquisition.

[0101] In one embodiment, the present application further provides a mobile terminal, which comprises a memory, a processor, and a computer program stored in the memory and executable on the processor, and the processor executes the program to realize the D8PSK modulation method based on the phase encoding space-time modulation metasurface.

[0102] In one embodiment, the present application further provides a computer readable storage medium, which stores a computer program, and the program is executed by a processor to realize the steps in the D8PSK modulation method based on the phase encoding space-time modulation metasurface.

[0103] The above is only the preferred embodiment of the present application, but the protection scope of the present application is not limited to this. Any changes or replacements within the technical scope disclosed by the present application can be easily thought by those skilled in the art, and should be covered within the protection scope of the present application.

Claims

1. A D8PSK modulation method based on phase-coded spatiotemporal modulation metasurface, characterized in that, The method comprises the following steps: Step 1, constructing a phase encoding unit based on a reflective load phase shifter, regulating the reflective load impedance so that the phase encoding unit generates eight discrete phase states; the phase encoding unit serves as a metasurface unit, and a phase encoding space-time modulation metasurface is obtained by arranging the phase encoding unit; Step 2, establishing a D8PSK modulated signal model based on the phase encoding space-time modulation metasurface, realizing non-synchronous demodulation information transmission while space-time modulating the carrier; Step 3, designing a 3-bit information code and a modulation code rate according to the transmission information, setting different modulation code rates as keys to realize encrypted information transmission; Step 4, receiving the echo signal by the receiving antenna, demodulating the echo signal by the key to realize the acquisition of the encrypted information; In step 2, the D8PSK modulated signal model based on the phase encoding space-time modulation metasurface is established to realize non-synchronous demodulation information transmission while space-time modulating the carrier, and specifically comprises: Assume a point frequency signal incident to a phase-coded spatiotemporal modulation metasurface, is the amplitude of the point frequency signal, is the carrier frequency of the point frequency signal, denotes the time instant; The metasurface unit performs periodic phase modulation on the point frequency signal, Time echo signal is expressed as: (3) wherein, is the reflection coefficient of the metasurface unit at the time instant t, is given by (4) wherein, is the relative phase change of the reflective load phase shifter at the moment, taking values from } is set in the first phase modulation period down denoted as : (5) wherein is a phase modulation period of the metasurface unit, is a time-varying relative phase change amount of the metasurface reflection coefficient within the first phase modulation period, i.e. ; In a second phase modulation period Down Indicated as : (6) wherein is the time-varying relative phase change of the reflection coefficient of the metasurface for the second phase modulation period, i.e. , yields ; and ; the first phase modulation period and the second phase modulation period the Fourier transform of the complex form, the Fourier coefficients of the complex form are represented by (7) (8) wherein are the Fourier coefficients of the first and second phase modulation period, respectively are the Fourier coefficients of the first and second phase modulation period, respectively is the phase modulation frequency; is a positive integer representing the harmonic order; (7) and (8) are obtained i.e. the Fourier coefficient amplitudes of the first and second phase modulation periods are equal, there is a phase difference of The information transmitted after D8PSK modulation is the phase difference between two adjacent phase modulation periods , and the value is , that is, 3-bit information transmission; A D8PSK modulation signal model based on phase-coded spatiotemporal modulation metasurface is established, and a return signal of the phase-coded spatiotemporal modulation metasurface is represented as: (9) wherein, is the incident elevation angle, is the radiation elevation angle, is the speed of light, is the unit cell pitch of the metasurface unit, is the number of metasurface units, is the time-varying reflection coefficient of the th metasurface unit, and there are metasurface units in total. right After performing a complex Fourier transform, we obtain: (10) wherein is the Fourier coefficient of the phase modulation period is the Fourier coefficient of the phase modulation period is the Fourier coefficient of the phase modulation period is a positive integer; From formula (10), the code rate of 3-bit information coding after D8PSK modulation transmission is determined by the phase modulation frequency The phase difference between two adjacent phase modulation periods determines the information coding after D8PSK modulation Therefore, when phase coding, the space-time modulation metasurface realizes the information transmission of non-synchronous demodulation while space-time modulating the carrier.

2. The D8PSK modulation method based on phase-coded spatiotemporal metasurface of claim 1, wherein, The reflective load phase shifter in step 1 specifically comprises: The reflective load phase shifter comprises a directional coupler and a reflective load; The input end of the directional coupler simultaneously serves as an output end, a through end is connected to one reflective load, and a coupling end is connected to another reflective load; the reflective loads connected to the through end and the coupling end are of the same structure, and the isolation end is grounded; The reflective load comprises a varactor and a microstrip line, the cathode of the varactor is connected to the microstrip line, and the anode is grounded; The S-parameters of the reflective load phase shifter are , Γ is the reflection coefficient of the reflective load, expressed as: (1) wherein is the reflected load impedance, is the characteristic impedance, is the reflection coefficient phase, is the imaginary unit; Substituting formula (1) into yields: (2) That is, the phase shift after the phase shifter is determined by the varactor impedance, and the reflection load impedance is changed by regulating the reverse DC bias voltage at both ends of the varactor, so that The change range of the reflection load impedance is Thus, the DC bias voltage is regulated, and the reflection load phase shifter generates eight discrete phase states.

3. The D8PSK modulation method based on phase-coded spatiotemporal metasurface of claim 2, wherein, In step 1, the phase encoding unit based on the reflective load phase shifter is constructed, and specifically comprises: The phase encoding unit is a multi-layer structure, and the side length of the phase encoding unit is , is the wavelength of the electromagnetic wave in free space; The phase encoding unit comprises five layers from top to bottom, wherein: The first layer is a patch for receiving and radiating electromagnetic waves, and the patch is composed of a center same inner circle and an outer circle ring metal patch; the inner circle and the outer circle ring are connected by a rectangular metal patch; The second layer is a first dielectric substrate, and the material of the first dielectric substrate is F4B plate with a thickness of 2 mm; The third layer is a metal ground, which serves as a ground plate of the patch in the first layer and the phase shifter in the fifth layer, and has a thickness of 0.035 mm; The fourth layer is a second dielectric substrate, and the material of the second dielectric substrate is Rogers RO4350B with a thickness of 0.254 mm, which serves as a dielectric substrate of the microstrip line structure of the phase shifter in the fifth layer; The fifth layer is a phase shifter, which is a microstrip line structure with a thickness of 0.035 mm, and the port is connected to the patch in the first layer through a coaxial feeder to realize waveguide transmission.

4. The D8PSK modulation method based on phase-coded spatiotemporal metasurface of claim 3, wherein, The 3-bit information code in step 3 is composed of an information code and an identification code, and the identification code is placed in front of the information code to identify and position the information code.

5. The D8PSK modulation method based on phase-coded spatiotemporal metasurface of claim 4, wherein, In step 3, the 3-bit information code and the modulation code rate are designed according to the transmission information, different modulation code rates are set as keys to realize encrypted information transmission, and specifically comprise: (3.1) designing an information code according to known information to determine the phase encoding of the information code; After D8PSK modulation, 3 bits of information are transmitted per information code, assuming the information code is , that is, the phase difference between the corresponding two adjacent phase modulation periods is , the information code phase encoding is , and the corresponding phase is ; the information code phase encoding is derived from the information code, assuming that the first bit of information code phase encoding is 0, the corresponding phase encoding of the information code is ; for bits of information code, the final bits of information code phase encoding are obtained; (3.2) designing the phase encoding of the identification code according to the phase encoding of the information code to determine the identification code; Let the D8PSK phase modulation period be T , which contains several ; for bit information code, design bit identification code to be placed in front of the information code, , used to identify the positioning of the information code; let the first and last bits of the information code phase encoding be and , the first and last bits of the identification code phase encoding be and , let: (11) According to formula (11) and Bit information code, design out Bit identification code, finally get Bit identification code phase encoding, determine a D8PSK phase modulation cycle , including Bit .

6. The D8PSK modulation method based on phase-coded spatiotemporal modulation super-surfaces of claim 5, wherein, In step 4, the receiving antenna receives the echo signal, demodulates the echo signal by the key to realize the acquisition of the encrypted information, and specifically comprises: For the echo signal of phase-coded spatiotemporal modulation metasurface, according to the change of the time domain signal, a complete D8PSK phase modulation period is extracted The signals in the inner are intercepted respectively Fourier transform is performed, That is, the key of the echo signal, only known can be obtained Bit information encoding, and finally get the information code through the identification code, extract the required information;​ Suppose the phase-coded space-time modulation metasurface makes single sideband modulation in time and beam steering in space, then the amplitude and phase information of the highest harmonic component is obtained according to formula (10); the amplitude information needs to be extracted for space-time modulation, and the phase information needs to be extracted for D8PSK modulation, so as to realize non-synchronous demodulation of the spectrum and encrypted information transmission.

7. A D8PSK modulation system based on phase-coded metasurface, characterized in that, The system is used to realize the D8PSK modulation method based on the phase-coded space-time modulation metasurface according to any one of claims 1-6, and the system comprises first to fourth modules, and each module has the following functions: The first module is to construct a phase coding unit based on a reflective load phase shifter, and to control the reflective load impedance so that the phase coding unit generates eight discrete phase states; the phase coding unit serves as a metasurface unit, and a phase-coded space-time modulation metasurface is obtained by arranging the unit; The second module is to establish a D8PSK modulation signal model based on the phase-coded space-time modulation metasurface, to realize non-synchronous demodulation of information transmission while modulating the carrier in time and space; The third module is to design a 3-bit information coding and modulation code rate according to the transmission information, to set different modulation code rates as keys, and to realize encrypted information transmission; The fourth module is to receive a return signal by an antenna, to demodulate the return signal by the key, and to realize acquisition of the encrypted information.

8. A mobile terminal comprising a memory, a processor, and a computer program stored on the memory and executable on the processor, characterized in that, The processor executes the program to realize the D8PSK modulation method based on the phase-coded space-time modulation metasurface according to any one of claims 1-6.

9. A computer-readable storage medium having stored thereon a computer program, characterized in that, The program is executed by the processor to realize the steps in the D8PSK modulation method based on the phase-coded space-time modulation metasurface according to any one of claims 1-6.

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