Wireless communication transmitter and method based on transmission-type space-time joint coding metasurface

Abstract

The invention discloses a wireless communication transmitter and method based on a transmission-type space-time joint coding metasurface, and belongs to the technical field of high-frequency-band wireless communication. The transmitter comprises a 10 * 10 transmission type intelligent metasurface array, a four-way space-time joint encoder and a control system, 0-degree, 90-degree, 180-degree and 270-degree four-phase compensation of + 1-order harmonic waves is generated by applying four-way control signals with different time delays (0, 0.25 T, 0.5 T and 0.75 T), baseband signal modulation is completed by combining QPSK mapping, and dynamic beam forming is achieved through spatial domain phase gradient compensation. The time delay configuration of the difference 90-degree phase of the four paths of signals enables each column unit of the metasurface to synchronously complete information modulation and beam pointing control under time domain and space domain joint coding. According to the invention,-30-30-degree beam scanning is realized in the 6.6 GHz frequency band, the main lobe gain reaches 17.8 dBi, the orientation error is less than 2 degrees, and the constellation diagram EVM is superior to 8%. The method has the advantages of low loss, high orientation precision and confidentiality, and is suitable for a 6G communication system and a dynamic reconfigurable network.

Description

Technical Field

[0001] The present invention relates to the field of wireless communication technologies, and particularly to a wireless communication transmitter and method based on a transmissive spatio-temporal joint coding metasurface, which is applicable to low-power signal modulation and dynamic beamforming in 6G high-frequency band communications. Background Art

[0002] In the information age, wireless communication technologies have become the core driving force for the development of modern society. With the large-scale deployment of 5G networks and the accelerated exploration of 6G technologies, the requirements of communication systems for transmission rate, latency, energy efficiency, and environmental adaptability have increased exponentially. Traditional wireless transmitters rely on complex radio frequency links, mixers, and multi-stage power amplifiers to achieve signal modulation and radiation, resulting in a sharp increase in hardware complexity and cost. Especially in the millimeter-wave band, the coupling effect of antenna arrays, the nonlinear distortion of power amplifiers, and electromagnetic compatibility problems severely restrict the further improvement of system performance. Taking 5G base stations as an example, the power consumption of their radio frequency front-ends accounts for more than 60%, and the large-scale deployment of the multiple-input multiple-output (MIMO) architecture faces high hardware costs. Therefore, exploring new types of high-efficiency and low-cost wireless communication architectures has become a common goal in academia and industry.

[0003] In the field of wireless communication, metasurface technologies have shown significant potential. Some literature has realized QPSK, 8PSK, and 16QAM modulations based on time-domain coding reflective metasurfaces, verifying the feasibility of passive modulators; some literature has completed 10Gbps high-speed data transmission using reflective metasurfaces in the millimeter-wave band, breaking through the bandwidth limitations of traditional radio frequency links; recently, optically controlled time-domain coding metasurfaces have achieved non-contact dynamic regulation through photosensitive materials, providing a new solution for the integration of intelligent metasurfaces. However, existing research has mostly focused on reflective metasurfaces, whose inherent limitations are that the signal radiation direction is limited, and it is difficult to simultaneously achieve spatio-temporal joint coding. Although transmissive intelligent metasurfaces can achieve forward beamforming, existing solutions generally face challenges such as high insertion loss and spatio-temporal modulation coupling, which restrict their applications in directional communications.

[0004] In summary, traditional wireless transmitters rely on complex radio frequency links, with high hardware costs and low energy efficiency. Existing reflective metasurface solutions have problems such as limited radiation direction and large insertion loss. Although transmissive metasurfaces can radiate forward, the problem of spatio-temporal modulation coupling is prominent. The present invention synchronously completes baseband modulation and beam control in a single array through spatio-temporal joint coding, solving the above technical bottlenecks. Summary of the Invention

[0005] Object of the Invention: To provide a wireless communication transmitter with low complexity and high energy efficiency, which directly realizes signal modulation and beamforming through a transmissive spatio-temporal coding metasurface, improving the accuracy and confidentiality of directional communications.

[0006] Technical solution:

[0007] A wireless communication transmitter based on a transmissive spatio-temporal joint coding metasurface, comprising:

[0008] A transmitting end, configured to convert the information to be transmitted into a binary data stream, and map it into four path delay control signals according to QPSK modulation, with delays of 0, 0.25T, 0.5T, and 0.75T respectively, where T is the symbol period;

[0009] A metasurface modulation end, including:

[0010] A 10×10 transmissive metasurface array, the unit of which is composed of a receiving layer, a feeding layer, a transmitting layer, and a dielectric layer. The receiving layer integrates two PIN diodes connected in reverse, and realizes a 180° transmission phase difference through the ON-OFF state switching;

[0011] A four-path spatio-temporal joint encoder, configured to load the delay control signals to each column of the metasurface to generate a transmitted wave with a spatial phase gradient;

[0012] A receiving end, demodulates the phase information of the received metasurface transmitted wave, looks up the table to obtain the transmitted bits corresponding to the constellation points under this modulation system, and restores the transmitted media information according to the bit information stream.

[0013] Preferably, the working frequency band of the transmissive intelligent metasurface unit is 6.0 GHz - 7.23 GHz, the transmission coefficient is greater than -3 dB, the amplitude of the reflection coefficient is averaged and suppressed below -5 dB, the phase difference between the two working modes is 180° ± 5°, the unit size is 27 mm × 27 mm × 5.632 mm, and it has a 1Bit phase resolution within the error range.

[0014] Preferably, the coding method adopted by the four-path spatio-temporal joint encoder includes:

[0015] Map every two bits of the QPSK modulation into four path delay control signals (0, 0.25T, 0.5T, 0.75T);

[0016] According to the spatial beam pointing requirement, dynamically select and gate the four path signals and load them to each column of the metasurface to generate 0°, 90°, 180°, and 270° phase compensations of the +1st harmonic;

[0017] Realize beamforming through the superposition of phase gradients.

[0018] Preferably, the QPSK modulation method includes:

[0019] Map the information bit stream into four path delay control signals according to the constellation points 00, 01, 10, 11;

[0020] The time-delay signal is loaded onto the metasurface through a time-domain encoder, so that the +1st order harmonic forms an orthogonal phase distribution in the target direction;

[0021] At the receiving end, a clear QPSK constellation diagram is demodulated only at the preset beam angle, and the signals at non-preset angles are scattered.

[0022] Preferably, the spatial beamforming calculates the phase compensation through the following formula:

[0023]

[0024] where θ and are the azimuth angle and elevation angle of the main lobe respectively, d x and d y are the unit periods in the x-direction and y-direction of the metasurface unit respectively, k c is the wave number in free space under the working state of the center frequency, is that the initial phase corresponding to the (m,n)th meta-element is affected by the distance between the meta-element and the phase center of the feed source, and it is expressed as: where λ c is the working wavelength in free space, and r represents the path length from the feed source to the (m,n)th metasurface unit.

[0025] Preferably, the metasurface array realizes -30° dynamic beam scanning in the 6.6 GHz band, the main lobe gain ≥ 15.9 dBi, and the 3dB beam width ≤ 13.3°.

[0026] The present invention also provides a wireless communication method based on the transmitter, including the following steps:

[0027] (1) Encode the information to be transmitted into a binary bit stream, and map every two bits into four time-delay control signals according to the QPSK modulation rule. The time-delay values of the time-delay control signals are 0, 0.25T, 0.5T, and 0.75T respectively, and the duty cycle is 0.5, where T is the symbol period;

[0028] (2) Load the corresponding time-delay control signals onto each column of the 10×10 transmissive metasurface array through a four-way space-time joint encoder. Among them, each column of units realizes a 180° transmission phase difference through the ON-OFF state switching of PIN diodes, and generates a transmission wave with a spatial phase gradient;

[0029] (3) Utilize the phase distribution of the +1st order harmonic to synchronously realize the QPSK modulation of the baseband signal and the dynamic beamforming in the 6.6 GHz band, so that the main lobe scans within the range of -30° to 30°, and the main lobe gain ≥ 15.9 dBi;

[0030] (4) The receiving end restores the original data by demodulating the phase information of the transmission wave, where:

[0031] When the receiving antenna is at the preset beam pointing angle, the error vector magnitude (EVM) of the demodulated QPSK constellation diagram is better than 8%;

[0032] When the receiving antenna is at a non-preset angle, the constellation diagram is scattered and no valid information can be demodulated.

[0033] Beneficial effects:

[0034] The present invention proposes a wireless communication transmitter and method based on a transmissive spatio-temporal joint coding metasurface. By designing the periodic time-varying transmission coefficient and the spatial phase gradient, the system can synchronously complete baseband signal modulation and beamforming in a single array. Specifically, by adjusting the time delay (0, 0.25T, 0.5T, 0.75T) of the control signal, four groups of orthogonal phase states are generated, which are respectively mapped to the four symbols of QPSK modulation; at the same time, spatial domain coding realizes beam pointing control through time delay gradient compensation, so that the +1st harmonic energy is focused on the target direction. This scheme abandons traditional mixers, power amplifiers and multi-channel radio frequency links, significantly reducing the hardware complexity. Experiments show that the designed 10×10 transmissive metasurface array can achieve beam scanning from -30° to 30° at the 6.6 GHz frequency band, the main lobe gain reaches 17.8 dBi, the directional error is less than 2°, and the error vector magnitude (EVM) of the constellation diagram is better than 8%. Compared with the reflective scheme, the transmissive design has the advantages of forward radiation and low profile, providing a new paradigm for high-security directional communication, dynamically reconfigurable networks and terahertz communication systems. Description of the drawings

[0035] Figure 1 are the design indexes of the transmissive metasurface unit, where (a) 3D schematic diagram of the 1Bit transmissive metasurface unit; (b) receiving patch layer of the 1Bit transmissive metasurface unit; (c) receiving transmission patch layer of the 1Bit transmissive metasurface unit; (d) surface current distribution when the 1Bit transmissive metasurface unit is in the digital coding state '1'; (e) surface current distribution when the 1Bit transmissive metasurface unit is in the digital coding state '0'; (f) magnitude response of the S parameters of the 1Bit transmissive metasurface unit; (g) phase response of the transmission coefficient of the 1Bit transmissive metasurface unit.

[0036] Figure 2 are the beam focusing, gain calculation and simulation results of the transmissive metasurface array, where (a) phase coding distributions corresponding to the main lobes generated by the 1Bi transmissive metasurface array pointing to θ = -30°, -20°, -10°, 0°, 10°, 20°, 30° (blue blocks indicate the digital coding state '1', and yellow blocks indicate the digital coding state '0'); (b) schematic diagram of spatial beam scanning realized according to the calculated coding and data analysis summary of the direction diagram.

[0037] Figure 3 It is a wireless communication system architecture based on a transmissive intelligent metasurface, where (a) is the transmitter architecture based on the transmissive intelligent metasurface; (b) is the wireless communication system; (c) are the constellation diagram and transmission photo screenshots of the receiver assisted by the beamforming system. In the group of figures title (θ1, θ2), θ1 represents the pointing direction of the harmonic beam, and θ2 represents the position of the receiving antenna. Detailed implementation manners

[0038] Example 1: Design of a 1Bit transmissive intelligent metasurface

[0039] According to the harmonic modulation coding principle, a transmissive intelligent metasurface unit that satisfies positive first-order harmonic QPSK modulation and performs spatial domain beamforming only needs to have a phase resolution of 1Bit. By controlling the output of positive and negative digital levels of the control circuit, the phase of the transmissivity of the intelligent metasurface presents a 180° change.

[0040] The three-dimensional schematic diagram of the 1Bit transmissive intelligent metasurface unit is as shown in Figure 1 (a) therein. The unit consists of a receiving layer, a feeding layer, and a transmitting layer. The receiving layer includes a receiving medium and receiving metal patches, as shown in Figure 1 (b) therein: The receiving metal patch is printed with a hollowed-out "H"-shaped metal patch on the outside and a rectangular metal patch on the inside. The transmitting layer includes a transmitting medium and transmitting metal patches, as shown in Figure 1 (c) therein: The transmitting metal patch uses a hollowed-out "Π"-shaped metal patch to radiate electromagnetic wave energy outward. The central positions of the receiving patch and the transmitting patch are connected by a feeding copper column with a diameter of 0.75mm and a length of 5.56mm. The feeding layer and the receiving patch are connected by a feeding copper column with a diameter of 0.31mm and a length of 2.86mm. The electromagnetic wave energy is transmitted from the receiving layer to the transmitting layer along the feeding copper column.

[0041] The feeding layer has three layers: a ground layer, a feeding line layer, and a ground layer. Each layer contains a layer of medium and a layer of metal wiring. The feeding line layer is connected to the rectangular metal patch inside the receiving layer, and the ground layer is connected to the hollowed-out "H"-shaped metal patch outside the receiving layer. The feeding line layer is printed with fan-shaped capacitive feeding patches to effectively isolate direct current.

[0042] Two anti-connected switching diodes, with the same model MADP-000907-14020 produced by MACOM Company, are embedded between the hollowed-out "H"-shaped metal patch and the rectangular patch in the receiving layer. For the convenience of description, the switching diode located above the rectangular patch is defined as "PIN1", and the switching diode located below the rectangular patch is defined as "PIN2". The negative electrode of PIN1 is connected to the rectangular patch, and the positive electrode is connected to the "H"-shaped patch; the positive electrode of PIN2 is connected to the rectangular patch, and the negative electrode is connected to the "H"-shaped patch. When a positive level is applied to the feeding layer, the PIN2 tube conducts, and the current is as shown in Figure 1As shown in Fig. (d): The current flows from the rectangular patch to the "H"-shaped patch, mapping the digital coding state "1"; when a negative level is applied to the feeder layer, PIN1 is turned on, and the current is as Figure 1 As shown in Fig. (e): The current flows from the "H"-shaped patch to the rectangular patch, mapping the digital coding state "0". The mapping relationship between the digital coding states of the intelligent metasurface and the on / off states of the two switching diodes is shown in Table 1.

[0043] Table 1 Mapping relationship between digital coding states of intelligent metasurface and on / off states of two switching diodes

[0044]

[0045] The thicknesses of the 4 metal layers and 1 metal feeder layer of the transmissive intelligent metasurface are all 0.018 mm ( Figure 1 the yellow material in Fig. (a)). The dielectric layer under the receiving patch and above the transmitting patch uses F4B material with a dielectric constant of 2.65, a loss tangent of 0.0015, and a thickness of 2.50 mm ( Figure 1 the gray material in Fig. (a)). Under the first ground layer and above the second ground layer, Rogers RO4450F material with a dielectric constant of 3.7, a loss tangent of 0.004, and a thickness of 0.16 mm is used ( Figure 1 the green material in Fig. (a)). Under the first layer of Rogers RO4450F material, Rogers RO4350B material with a dielectric constant of 3.66, a loss tangent of 0.0037, and a thickness of 0.17 mm is used to bond another layer of Rogers RO4450F material ( Figure 1 the blue material in Fig. (a)).

[0046] The optimized results of the above various structural shapes and dimensions through CST Microwave Studio are shown in Table 2. It should be noted that the intelligent metasurface unit adopts a 45° oblique polarization design method.

[0047] Table 2 Structural parameter table of intelligent metasurface unit

[0048]

[0049] The transmission metasurface unit was simulated and analyzed by the commercial electromagnetic simulation software CST Microwave Studio. In the frequency-domain simulation of the S parameters of the intelligent metasurface unit, a 45° polarized plane wave excitation was set, and the boundary was set using Unit Cell. Figure 1Figure (f) shows the S-parameter amplitude response of the intelligent metasurface unit. It can be seen that within the operating frequency band from 5.8 GHz to 7.2 GHz, the amplitude of the transmission coefficient of the two operating states of the metasurface unit is greater than -3 dB, and the amplitude of the reflection coefficient is averaged to be suppressed below -5 dB. This indicates that the intelligent metasurface has excellent transmission characteristics and can effectively suppress reflection, meeting the amplitude design requirements of the transmissive intelligent metasurface. Figure 1 Figure (g) shows the phase response of the transmission coefficient of the intelligent metasurface. The phase difference within the operating frequency band is 180 ± 5°, and it has 1-bit phase resolution within the error range, meeting the phase design requirements of the 1-bit transmissive intelligent metasurface.

[0050] The transmissive intelligent metasurface composed of periodically arranged transmissive metasurface units is usually excited by a feed antenna in space wave. The metasurface unit adjusts the phase and amplitude of the incident electromagnetic wave to form a specific radiation beam in the target area and achieve the expected electromagnetic function. Considering that the electromagnetic wave emitted by the feed antenna is not a plane wave, the phase distribution at the metasurface will show non-uniformity. Therefore, in order to achieve precise control of the electromagnetic beam, the transmissive metasurface needs to perform phase compensation. Suppose the metasurface array contains M×N encodings. According to classical antenna theory, once the far-field scattering function and the main lobe direction of the metasurface are calculated, a fixed encoding sequence can be obtained, and the phase distribution of the super-elements in the metasurface array corresponding to the main lobe direction angle can be expressed as:

[0051]

[0052] where θ and are the azimuth angle and elevation angle of the main lobe respectively, d x and d y are the unit periods of the metasurface unit in the x-direction and y-direction respectively, and k c is the wave number in free space under the operating state of the center frequency. is the initial phase corresponding to the (m,n)th super-element and is affected by the distance between the super-element and the phase center of the feed, which is expressed as: where λ c is the operating wavelength in free space. r represents the path length from the feed to the (m,n)th metasurface unit.

[0053] To evaluate the beam focusing function of the transmissive intelligent metasurface in free space and its gain improvement and beam shaping ability for the feed antenna, we designed a 10×10 1-bit transmissive intelligent metasurface array and placed it 247.95 mm in front of a feed horn antenna operating in the 5 GHz - 8 GHz frequency band with a maximum gain of 15.8 dB. The compensation phases required for the transmissive intelligent metasurface to form beams with main lobes pointing to θ = -30°, -20°, -10°, 0°, 10°, 20°, 30° were calculated according to Equation (2.1), and the coding distribution is as shown in Figure 2 (a), and the operating states of each unit in the intelligent metasurface array were set according to the coding distribution. The CST Microwave Studio was used to perform additional simulations of the far-field patterns for these calculated coding sequences. Figure 2 (b) shows the far-field pattern of the beam shaping system, and the gain, main lobe pointing, and its 3 dB beam width data are summarized in the table shown in Figure 2 (b). The simulation results show that the transmissive intelligent metasurface has beam scanning ability in the range of -30° to 30°. There are differences between the simulation and calculation results, mainly because the calculation provides an idealized solution. Nevertheless, the deviation between the simulation and calculation angles of the main lobe direction remains within ±2°, and the 3 dB beam width is on average controlled below 11.3°, verifying the beam scanning performance of the system. The main lobe gain remains above 15.9 dBi, and compared with the original feed horn antenna, the maximum gain is increased by more than 2 dBi, verifying the beam focusing performance of the system and its gain improvement for the feed antenna.

[0054] Example 2: Wireless communication transmitter based on transmissive spatio-temporal joint coding metasurface

[0055] To perform beam shaping on harmonics, it is necessary to design the spatial phase distribution of the transmissive intelligent metasurface. By constructing a corresponding time delay gradient function on the transmission coefficients of different metasurface units, the necessary phase gradient is provided to deflect the harmonics to any direction. The harmonic phase distribution generated by the time delay gradient function t g (x) causes the k-th order harmonic beam to be deflected to the angle θ in the xoz plane:

[0056]

[0057] In the above formula, λ k is the wavelength of the k-th order harmonic, and the time delay gradient function t g (x) = -kω0t s .

[0058] Since the positive and negative first-order harmonics have a higher energy conversion efficiency than other harmonics, the positive first-order harmonic is selected to implement the information modulation process. First, the control signal is time-delayed by t t to 0, The periodic cycle generates four digital coding sequences, corresponding to the additional phase shifts of the positive first-order harmonics of 0°, 90°, 180°, and 270°. In the I / Q plane, when the azimuth angle of the constellation points rotates by 90°, the points in each quadrant coincide with the constellation points in the adjacent quadrants. According to the relationship between the coding sequence time delay and the harmonic phase, the 90° rotation of the azimuth angle in the constellation diagram actually corresponds to a 0.25T0 change in the coding sequence time delay. Table 4 shows the mapping relationship between the transmitted bits, information symbols, and digital coding sequences in QPSK modulation.

[0059] Table 4 Mapping Relationship between Transmitted Bits, Information Symbols, and Digital Coding Sequences in QPSK Modulation

[0060]

[0061] The time-domain waveform of the transmission coefficient mapped with the message symbol is the digital drive voltage for controlling the metasurface. According to the metasurface unit design, the two states of the transmission coefficient can be mapped to the logic high level and logic low level of the digital drive voltage. Perform t on the time-domain waveform of the transmission coefficient s are 0 and time delays of to obtain four control signals. The spatio-temporal joint encoder selects one of the four control signals according to the time delay gradient required for spatial beamforming. The above is the realization of the harmonic regulation by the transmissive metasurface using spatio-temporal joint coding, which can perform information modulation transmission of media information in the time domain and achieve precise beamforming in the spatial domain.

[0062] The wireless communication transmitter based on the transmissive intelligent metasurface is as Figure 3 shown in (a) below. It consists of a transmissive intelligent metasurface, a NI control platform, and an FPGA control module. At the transmitter, the National Instruments control platform NIPXIe-1092 integrated with an FPGA module (model NIPXIe-7976R), a DIO module (model NIPXIe-5783), and a synchronous clock module (model NIPXIe-6674T) first converts the data to be transmitted, such as a picture, into a binary data stream (01101011100010...), and maps the obtained data bit stream to a digital coding sequence according to the constellation point set under the used modulation system The time-domain waveform of the digital coding sequence generates the corresponding control signal and loads it onto the transmissive intelligent metasurface. Subsequently, according to the spatial coding information transmitted by the host computer, the spatio-temporal joint encoder loads the high and low digital voltage signals corresponding to the coding sequence onto the transmissive intelligent metasurface through the connection interface, generating a phase gradient to perform harmonic beamforming.

[0063] Figure 3Figure (b) shows a wireless communication laboratory scenario: A microwave signal source (model BF-M2015-AP) generates a carrier signal with a frequency of 6.6 GHz and radiates electromagnetic waves to the metasurface through a connected feed horn. The transmissive intelligent metasurface switches between different operating states according to the level of the control signal, continuously radiating electromagnetic waves with different phase information, completing baseband information modulation while directing the main lobe of the transmitted electromagnetic wave to a specific angle. At the receiving end, an external differential receiver architecture is used. The received signal is first down-converted to a 5 GHz band signal by a radio frequency front-end with an operating frequency of 6.6 GHz and a local oscillator frequency of 9.6 GHz and then connected to a commercial software-defined radio platform (model NI USRP-2974) for processing. The phase information of the metasurface transmitted wave received is demodulated, the transmission bits corresponding to the constellation points under this modulation system are obtained by looking up a table, and the transmitted media information is recovered according to the bit information stream.

[0064] To verify the ability of the transmitter to control the direction of the electromagnetic wave beam and the quality of the communication channel with the assistance of the beamforming system, a simple experimental verification was carried out in an indoor anechoic chamber environment: The test system consists of three main parts: a transmitter, an upper computer beamforming assistance system, and a receiver. At the transmitting end, we configured the metasurface for baseband information modulation and the corresponding feed, and the distance between the two is strictly equal to the preset focal length of 247 mm. The upper computer beamforming assistance system loads the control signal time delay gradients of each column of the 10-column transmissive metasurface as

[0065] corresponding to the positive first harmonic with azimuth deflections of θ = -30°, -20°, -10°, 0°, 10°, 20°, 30° respectively. At the receiving end, the received photo and constellation diagram IQ data are measured in turn at azimuth angles of -30°, -20°, -10°, 0°, +20°, +30°. Figure 3 Figure (c) shows some experimental results. When the receiving antenna is located at the specified angle where the beam is deflected as preset, a perfect QPSK constellation diagram is demodulated, and the star clusters are stable, dense, and concentrated in four orthogonal phases, and the transmitted picture is clear and stable. The constellation diagrams at non-preset deflection angles are scattered, and the received photos are garbled. This result is consistent with the far-field radiation pattern experiment. Only when the system forms a main beam pointing to the user can a clear constellation diagram and smooth and uninterrupted photo transmission be obtained, which verifies that the proposed system has excellent beamforming ability. The above experimental results show that the harmonic information coding mechanism we proposed has the characteristics of direction modulation, can be used as a good communication auxiliary guarantee device, and can also be equipped with a modal perception module to track the user in real time for communication guarantee.

Claims

1. A wireless communication transmitter based on a transmissive spatio-temporal joint coding metasurface, characterized in that Comprising: A transmitting end, configured to convert the information to be transmitted into a binary data stream, and map it into four delay control signals according to QPSK modulation, with delays of 0, 0.25T, 0.5T, and 0.75T respectively, where T is the symbol period; A metasurface modulation end, including: A 10×10 transmissive metasurface array, the unit of which consists of a receiving layer, a feeding layer, a transmitting layer, and a dielectric layer. The receiving layer integrates two PIN diodes connected in reverse, and realizes a 180° transmission phase difference through the ON-OFF state switching; A four-way spatio-temporal joint encoder, configured to load the delay control signals to each column of the metasurface to generate a transmitted wave with a spatial phase gradient; A receiving end, demodulating the phase information of the received metasurface transmitted wave, looking up the table to obtain the transmission bits corresponding to the constellation points under this modulation system, and restoring the transmitted media information according to the bit information stream.

2. The transmitter according to claim 1, characterized in that, The operating frequency band of the transmissive intelligent metasurface unit is 6.0GHz - 7.23GHz, the transmission coefficient is greater than -3dB, the amplitude of the reflection coefficient is averaged and suppressed below -5dB, the phase difference between the two operating modes is 180° ± 5°, the unit size is 27mm × 27mm × 5.632mm, and it has a 1Bit phase resolution within the error range.

3. The transmitter according to claim 1, characterized in that, The encoding method adopted by the four-way spatio-temporal joint encoder includes: Mapping every two bits of the QPSK modulation into four delay control signals (0, 0.25T, 0.5T, 0.75T); According to the spatial beam pointing requirement, dynamically selecting and gating the four-way signals and loading them to each column of the metasurface to generate 0°, 90°, 180°, and 270° phase compensations of the +1st harmonic; Realizing beamforming through the superposition of phase gradients.

4. The transmitter according to claim 1, wherein The QPSK modulation method includes: Mapping the information bit stream into four delay control signals according to the constellation points 00, 01, 10, and 11; Loading the delay signals to the metasurface through a time-domain encoder, so that the +1st harmonic forms an orthogonal phase distribution in the target direction; The receiving end only demodulates a clear QPSK constellation diagram at a preset beam angle, and the signals at non-preset angles are scattered.

5. The transmitter according to claim 1, wherein The spatial beamforming calculates the phase compensation through the following formula: where θ and are the azimuth angle and elevation angle of the main lobe respectively, d x and d y are the unit periods of the metasurface unit in the x - direction and y - direction respectively, k c is the wavenumber in free space at the operating state of the center frequency, is the initial phase corresponding to the (m,n) - th meta - element, which is affected by the distance between the meta - element and the phase center of the feed source, and is expressed as: where λ c is the operating wavelength in free space, and r represents the path length from the feed source to the (m,n) - th metasurface unit.

6. The transmitter according to claim 1, characterized in that, The metasurface array realizes a -30° dynamic beam scan in the 6.6GHz frequency band, the main lobe gain ≥ 15.9dBi, and the 3dB beam width ≤ 13.3°.

7. A wireless communication method based on the transmitter according to any one of claims 1-6, characterized in that, Including the following steps: (1) Encoding the information to be transmitted into a binary bit stream, mapping every two bits into four delay control signals according to the QPSK modulation rule, the delay values of the delay control signals are 0, 0.25T, 0.5T, and 0.75T respectively, and the duty cycle is 0.5, where T is the symbol period; (2) Loading the corresponding delay control signals to each column of the 10×10 transmissive metasurface array through a four-way spatio-temporal joint encoder, where each column unit realizes a 180° transmission phase difference through the ON-OFF state switching of the PIN diode, and generates a transmitted wave with a spatial phase gradient; (3) Utilize the phase distribution of the +1st harmonic to synchronously implement baseband signal QPSK modulation and dynamic beamforming in the 6.6 GHz frequency band, enabling the main lobe to scan within the range of -30° to 30°, with the main lobe gain ≥ 15.9 dBi; (4) The receiving end restores the original data by demodulating the phase information of the transmitted wave, where: When the receiving antenna is located at the preset beam pointing angle, the error vector magnitude (EVM) of the demodulated QPSK constellation diagram is better than 8%; When the receiving antenna is located at a non-preset angle, the constellation diagram is scattered and no valid information can be demodulated.

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