Radar-communication integration approach based on digitally programmable metasurfaces

Abstract

The present invention discloses a radar communication integration method based on digital programmable metasurfaces. The method establishes a mechanism for realizing efficient radar communication integration based on digital coding metasurfaces, and directly realizes time and space frequency modulation on the metasurface surface, thereby greatly simplifying the architecture and reducing system costs compared with traditional phased array or MIMO antennas. The encryption and decryption, one-dimensional range imaging, and simultaneous realization of radar detection and wireless communication of the wireless security system are well verified through simulation and examples, thus demonstrating the great potential of radar communication integration technology based on digital coding metasurfaces to become a universal and ubiquitous intelligent terminal in the future.

Description

Technical Field

[0001] The present invention relates to the technical field of radar communication integration, and in particular to a radar communication integration method based on a digitally programmable metasurface. Background Art

[0002] As important components of electronic information systems, wireless communication systems and radar communication systems have been developed independently for many years. Generally speaking, radar systems are designed to estimate channel information using known source signals, while communication systems are designed to estimate source signals using known channel information. Driven by new military and civilian needs such as 6G wireless communications, smart cities, and smart cooperation, radar detection and wireless communications have shown a trend of integration. Therefore, radar communication integration technology has been proposed, aiming to realize radar and communication functions simultaneously using the same platform and the same signal. In fact, radar communication integration technology has returned to the essence of electromagnetic waves as information carriers. It is in this essential sense that radar communication integration technology has become an important way to achieve integrated, universal, and intelligent platforms.

[0003] At present, radar communication integrated systems mainly perform signal processing in the time domain and frequency domain. Only radar communication integrated systems equipped with phased array antennas or MIMO antennas can process signals carrying spatial information. However, these antenna architectures are complex and the signal processing complexity is high. The high cost and complex architecture problems of such systems need to be solved.

[0004] Digital programmable metasurfaces have been widely studied due to their ability to dynamically control electromagnetic waves. Their integration with radar communication can provide a direction for realizing general and intelligent electromagnetic systems. Digital programmable metasurfaces can replace phased array antennas or MIMO antennas to improve the flexibility of radar communication integration technology in processing multi-dimensional information. Specifically, the spatial information of signals in radar communication integration can be separated and processed in the metasurface, thereby reducing the complexity of signal processing. At the same time, since digital programmable metasurfaces only require one transceiver as an illumination source, the system cost is reduced and the system architecture is simplified. Therefore, radar communication integration technology based on digital programmable metasurfaces can bring higher flexibility and solve the problems of high cost and complex architecture of the current system. Summary of the invention

[0005] In view of this, the purpose of the present invention is to provide a radar communication integration method based on digital programmable metasurface, in which the information carried by electromagnetic waves is sent and received through the digital programmable metasurface, and then estimated and processed. This brings higher flexibility and solves the problems of high cost and complex architecture of the current system.

[0006] In order to achieve the above object, the present invention adopts the following technical solution:

[0007] A radar communication integration method based on a digital programmable metasurface, the method is based on a radar communication integration system, the system includes a transmitting end and a receiving end, wherein the transmitting end and the receiving end are both provided with a digital programmable metasurface, and the radar communication integration method includes the following steps:

[0008] Step S1, performing communication transmission, and encrypting the transmitted signal and decrypting the received signal, which includes: at the transmitting end, performing phase modulation on the transmitted signal, performing phase demodulation on the received signal at the receiving end, and verifying the consistency of the transmitted signal and the received signal;

[0009] Step S2, performing radar verification, which includes: setting a target in the radar communication integrated system, and then applying a two-phase coded signal based on a digital programmable metasurface to perform one-dimensional range imaging on the target, wherein, at the transmitting end, the source signal is modulated by a 180° phase difference through the digital programmable metasurface to obtain a two-phase coded signal, and the signal is then transmitted to the receiving end after being reflected by the target, and at the receiving end, the received signal is processed by a matched filtering algorithm to achieve one-dimensional range imaging of the target;

[0010] Step S3, executing radar communication integration, realizing both radar detection and wireless communication functions through the radar communication integration system, which includes: enabling the digital programmable metasurface to generate dual channels through coding design, wherein the first channel performs the communication transmission described in step S1, and the other channel performs the radar imaging described in step S2, thereby realizing radar communication integration.

[0011] Furthermore, in step S1, a space-time system function is designed at the transmitting end and the receiving end respectively, and the two space-time system functions correspond to each other, and phase modulation and phase demodulation of the signal are implemented through the space-time system function.

[0012] Furthermore, the step S1 includes:

[0013] Assume that the signal I(t) is a plane wave e with propagation vector k. jωt The signal carried and reaching the metasurface reference unit is s(t)=I(t)e jωt , where t represents time, I(t) represents signal amplitude, and ω represents signal angular frequency. Then the signal reaching the mth unit of the metasurface is expressed as:

[0014]

[0015] In formula (1), Where k0 is the propagation constant, θ and denote the elevation angle and azimuth angle respectively, k is the component of the propagation constant in the xy plane; ρm =[x m ,y m ] T , x m and m Respectively represent the coordinates of the mth unit of the hypersurface on the x-axis and y-axis; ρ m represents the coordinates of the mth unit of the hypersurface;

[0016] For a narrowband signal with bandwidth B, we have:

[0017]

[0018] So we get:

[0019]

[0020] If the reflection or transmission coefficient of the mth element is Γ m , then at a distance r from m The signal observed at the point is:

[0021]

[0022] Considering all M units, the total signal at the observation point is expressed as:

[0023]

[0024] In formula (3), is the set of radiation characteristics of M units in the metasurface taking phase compensation into account; is the set of direction vectors of the M units of the hypersurface;

[0025] The system function of the metasurface is defined as Then the observation point signal is expressed as:

[0026]

[0027] Among them, formula (4) shows that the input signal is modulated by the system function of the metasurface.

[0028] Furthermore, the step S2 comprises:

[0029] Assume that the carrier e jωt After the metasurface modulation including phase modulation by the system function h(t), the transmission signal of the metasurface is written as:

[0030] g t (t) = h(t)e jφ(t) e jωt (5)

[0031] In formula (5), φ(t) is a binary phase modulation term, expressed as:

[0032]

[0033] In formula (6), N and τ0 represent the length and symbol period of the binary code, respectively. k It is a binary code, and its value is 0 or 1;

[0034] Assuming the receiver is placed at the same location as the transmitter, the signal received from a target at distance R is:

[0035]

[0036] In formula (7), c represents the speed of light;

[0037] After processing the received signal, the one-dimensional range imaging characteristics of the target are as follows:

[0038]

[0039] In formula (8), Δt is the imaging range, and it is easy to obtain that the correlation coefficient reaches its maximum value at Δt = 2R / c, and ★ represents the convolution calculation. Indicates the transmitted signal g t The conjugate of (t).

[0040] The beneficial effects of the present invention are:

[0041] The present invention establishes a mechanism for realizing efficient radar communication integration based on digitally coded metasurfaces, and realizes time and space frequency modulation directly on the metasurface aperture, thereby greatly simplifying the architecture and reducing system costs compared with traditional phased array or MIMO antennas. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 A schematic diagram of the radar communication integration method based on a digitally programmable metasurface provided in Example 1;

[0043] Figure 2 The wireless secure communication schematic diagram based on the digital programmable metasurface and its signal schematic diagram provided in Example 1, wherein: Figure 2 (a) is a schematic diagram of wireless secure communication. Figure 2 (b) is a schematic diagram showing the original signal. Figure 2 (c) Schematic diagram of phase modulation of the metasurface. Figure 2 (d) is a schematic diagram showing an encrypted signal. Figure 2 (e) is a schematic diagram showing a decrypted signal;

[0044] Figure 3This is a schematic diagram of one-dimensional range imaging based on a digitally programmable metasurface provided in Example 1, wherein: Figure 3 (a) is a schematic diagram of the imaging process. Figure 3 (b) is a schematic diagram of the received signal. Figure 3 (c) is a schematic diagram of one-dimensional range imaging;

[0045] Figure 4 This is a schematic diagram of an application scenario of radar communication integration based on a digitally programmable metasurface provided in Example 1, wherein: Figure 4 (a) is a schematic diagram of a specific application scenario. Figure 4 (b)- Figure 4 (e) shows the simulation result of dual beams. The phase of the beam pointing to 10° remains unchanged, and the phase of the beam pointing to -30° changes from 0° to 270° in steps of 90°. Figure 4 (b) is 0°, Figure 4 (c) is 90°, Figure 4 (d) is 180°, Figure 4 (e) 270°;

[0046] Figure 5 Schematic diagram of the measurement results of the dual-beam radiation pattern and phase with independent phase control, where: Figure 5 (a) is the amplitude result diagram of the radiation pattern of beam 1 when the radiation phase of beam 2 is fixed at 180°. Figure 5 (b) is the amplitude result diagram of the radiation pattern of beam 1 when the radiation phase of beam 2 is fixed at 90°. Figure 5 (c) is the amplitude result diagram of the radiation pattern of beam 1 when the radiation phase of beam 2 is fixed to 0°. Figure 5 (d) is the amplitude result diagram of the radiation pattern of beam 1 when the radiation phase of beam 2 is fixed at 270°. Figure 5 (e) is the phase result diagram of the radiation pattern of beam 1 when the radiation phase of beam 2 is fixed at 180°. Figure 5 (f) is the phase result diagram of the radiation pattern of beam 1 when the radiation phase of beam 2 is fixed at 90°. Figure 5 (g) is the phase result diagram of the radiation pattern of beam 1 when the radiation phase of beam 2 is fixed to 0°. Figure 5 (h) is the phase result diagram of the radiation pattern of beam one when the radiation phase of beam two is fixed at 270°;

[0047] Figure 6 is a schematic diagram of the test results, where Figure 6 (a) is a schematic diagram of the communication channel sampling signal. Figure 6 (b) is a schematic diagram of the communication signal after matched filtering. Figure 6 (c) is a schematic diagram of the sampling signal of the radar channel. Figure 6 (d) Schematic diagram of one-dimensional correlation range imaging of radar targets. DETAILED DESCRIPTION

[0048] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0049] Example 1

[0050] See also Figure 1-Figure 6 This embodiment provides a radar communication integration method based on a digitally programmable metasurface, characterized in that the method comprises the following steps:

[0051] Step S1, performing encryption and decryption tests on the wireless security system on the digital programmable metasurface aperture, which includes: transmitting a signal from a transmitter, phase modulating the signal through the transmitting metasurface, phase demodulating the signal through the receiving metasurface, and finally verifying the consistency of the signal received by the receiver with the transmitted signal;

[0052] Specifically, in this embodiment, step S1 includes:

[0053] Assume that the signal I(t) is a plane wave e with propagation vector k. jωt The signal carried and reaching the metasurface reference unit is s(t)=I(t)e jωt , where t represents time, I(t) represents signal amplitude, and ω represents signal angular frequency. Then the signal reaching the mth unit of the metasurface can be expressed as:

[0054]

[0055] In formula (1), where k0 is the propagation constant, θ and denote the elevation angle and azimuth angle respectively, k is the component of the propagation constant in the xy plane; ρ m =[x m ,y m ] T , x m and m Respectively represent the coordinates of the mth unit of the hypersurface on the x-axis and y-axis; ρ m represents the coordinates of the mth unit of the metasurface. For a narrowband signal with bandwidth B, we can get:

[0056]

[0057] So we get:

[0058]

[0059] If the reflection or transmission coefficient of the mth element is Γ m , then at a distance r from m The signal observed at the point is:

[0060]

[0061] Considering all M units, the total signal at the observation point can be expressed as:

[0062]

[0063] In formula (3), is the set of radiation characteristics of M units in the metasurface taking phase compensation into account; is the set of direction vectors of the M units of the hypersurface;

[0064] The system function of the metasurface is defined as Then the observation point signal can be expressed as:

[0065]

[0066] Among them, formula (4) shows that the input signal is modulated by the system function of the metasurface.

[0067] The above is an analysis of the signal receiving process. The same is true for the signal transmitting process. From the perspective of wireless communication, the digital programmable metasurface has become part of the communication channel. In particular, the programmable nature of this part makes the digital programmable metasurface an adaptive technology for secure communication.

[0068] More specifically, in this embodiment, if Figure 2 As shown, Figure 2 (a) shows a schematic diagram of wireless secure communication based on digital programmable metasurface. The source signal is modulated in both the time domain and the space domain after passing through the metasurface. In the time domain, the metasurface performs phase modulation on the source signal; in the space domain, the metasurface radiates energy in a specific direction. Therefore, the source signal is modulated in both the time domain and the space domain. For decryption, another system function is The digital programmable metasurface is used to recover the encrypted signal. As an example, the encryption and decryption of phase modulated signals based on the metasurface are simulated. Assuming that the source signal is used to modulate the metasurface, Figure 2(b) shows the source signal with four phase states (0°, 90°, 180° and 270°). The source signal is radiated through the directional beam by encoding the aperture of the metasurface with additional phase shifts (72.64°, -19.75°, 252.7° and 160°), as shown in Figure 2. Figure 2 (c) shows the phase shift. The phase shift is calculated by calculating the value of a point 2m away from the metasurface. The encrypted signal calculated at the same point is as follows: Figure 2 (d) As shown in Figure 2, the phase shift of each symbol is close to 0, so the effective information is hidden. The decoding process is completed by another metasurface with conjugate phase shifts (72.64°, 160°, 252.7°, and -19.75°). Figure 2 (e) The decoded signal shown is consistent with the source signal.

[0069] In the above analysis, each bit of the source signal is encrypted according to a set of surface codes of the digital programmable metasurface. In fact, each bit can be encrypted by a series of surface codes to improve security performance. The encryption process is essentially a code division multiple access technology, which was originally used as a security technology for military communications. This process shows that digital programmable metasurfaces can be used for code division multiple access communications. More importantly, the proposed secure communication based on metasurfaces has a significant advantage, that is, the metasurface, as an independent plug-and-play module, can be arbitrarily modified or updated in different scenarios without changing the original system, thus saving a lot of time and cost.

[0070] Step S2: Perform radar verification and use the metasurface-based two-phase coded signal to perform one-dimensional range imaging of the target. Specifically, the transmitter transmits a two-phase coded signal modulated by the metasurface with a 180° phase difference. The signal is reflected by the target and transmitted to the receiver. The signal is processed by the matched filter algorithm to achieve one-dimensional range imaging of the target.

[0071] Specifically, in this embodiment, step S2 includes:

[0072] Since the digitally programmable metasurface can perform phase modulation on the surface, it can be used to generate a two-phase coded signal for one-dimensional range imaging. Assuming the carrier e jωt After the metasurface modulation including phase modulation by the system function h(t), the transmission signal of the metasurface can be written as:

[0073] g t (t) = h(t)e jφ(t) e jωt (5)

[0074] In formula (5), φ(t) is a binary phase modulation term, expressed as:

[0075]

[0076] In formula (6), N and τ0 represent the length and symbol period of the binary code, respectively. k It is a binary code, and its value is 0 or 1.

[0077] Assuming the receiver is placed at the same location as the transmitter, the signal received from a target at distance R is:

[0078]

[0079] In formula (7), c represents the speed of light.

[0080] After correlation processing of the received signal, the one-dimensional range imaging characteristics of the target are obtained as follows:

[0081]

[0082] In formula (8), Δt is the imaging range, and it is easy to obtain that the correlation coefficient reaches its maximum value at Δt = 2R / c, and ★ represents the convolution calculation. Indicates the transmitted signal g t The conjugate of (t).

[0083] More specifically, in this embodiment, if Figure 3 As shown, the Figure 3 A one-dimensional range imaging example based on a hypersurface is shown. The 255-bit m sequence is used to give c k Assignment, and then correspond to c k Two sets of binary values ​​of the mouth face coding are applied to the metasurface. At a point 2m vertically away from the metasurface, the calculated radiation phases are -19.75° and 160°, corresponding to c k 0 and 1. By switching two sets of interface codes according to the m sequence, the digital programmable metasurface can generate a specific two-phase coded signal. The interface switching rate is set to 10MHz, and the sampling rate of the received signal is set to 20Gsa / s. Assuming that a target is placed 2m away from the transceiver, the echo signal can be obtained by matched filtering, such as Figure 3 (b) as shown. Figure 3 (c) is the calculated range image of the target. A peak is observed at 1.995 m, which is very close to the set distance, thus verifying the effectiveness of the proposed one-dimensional range imaging based on the metasurface.

[0084] Step S3, perform verification of radar communication integration, and use the digital programmable metasurface platform to simultaneously realize the two functions of radar detection and wireless communication, which specifically includes: through coding design, the metasurface generates dual channels, one channel performs the communication transmission described in step 1, and the other channel performs the radar imaging described in step 2, thereby realizing radar communication integration.

[0085] Specifically, in this embodiment, step S3 includes:

[0086] Radar communication integration is an important part of the future information system network. In terms of application, the forms of radar communication integration include time division multiplexing, frequency division multiplexing, code division multiplexing and space division multiplexing. Among these forms, time division multiplexing is easy to implement, but the switching time between radar and communication functions limits the real-time performance. Frequency division multiplexing and code division multiplexing have sufficient time and frequency resources, and radar and communication functions can exist at the same time. Space division multiplexing can use directional beams pointing in different directions to independently perform radar and communication. In practical applications, since communication users and radar targets are generally distributed in different spatial areas, space division multiplexing is often combined with other types of multiplexing forms.

[0087] Given that digitally coded metasurfaces can manipulate electromagnetic waves in the spatial, temporal, and frequency domains, they can be used to implement various forms of multiplexing. Figure 4 (a) shows a schematic diagram of the application of radar communication integration based on digital coding metasurface. In the figure, the metasurface generates dual beams with modulated phase. The two beams generate two independent channels, which are used for communication with cooperative users and detection of non-cooperative targets respectively. The phase modulation signals carried by the two channels can be different signals or signals shared by the radar and communication systems.

[0088] More specifically, in this embodiment, the metasurface is configured to generate dual beams pointing at azimuth angles of 10° and -30°. Based on the previous analysis, dual beams with independent radiation phases can be calculated. The radiation phase of each beam has four states. Therefore, 16 sets of aperture coding are required to perform orthogonal phase modulation on the dual beams.

[0089] Figure 4 (b)- Figure 4 (e) shows the simulation results of the far-field patterns, which keep the phase of the beam pointing at 10° constant and change the phase of the beam pointing at -30° in steps of 90°. Figure 5 The measurement results of the dual-beam radiation pattern and phase with independent phase control are given. It can be seen that phase modulation does not change the pointing direction of the directional beam, and the phase modulation of each directional beam can be independently controlled. Therefore, the metasurface provides a flexible method to implement space division multiplexing, frequency division multiplexing and code division multiplexing technology in a unique or hybrid way. This function lays the foundation for the integrated radar communication technology based on metasurface.

[0090] More specifically, in this embodiment, a radar communication integrated system based on a digitally programmable metasurface is built, and the metasurface is used to generate dual beams with azimuths pointing to 20° and -20°, thereby generating two spatial channels. Channel one is used for radar imaging, detecting a metal sheet placed 2.5m away in the direction of (θ=-20°), and the receiving horn is placed next to the metasurface as a radar receiver. Channel two is used for wireless communication, and another horn is placed 1.42m away in the direction of (θ=20°) as a communication receiver. The signals of the two channels are measured independently by an oscilloscope. In this experiment, the m sequence is applied to the two channels. In addition, the m sequences in the two channels are time-synchronized, so they can be used to obtain the relative time delay of the two channels. This experiment can measure the correlation delay of the two channels, and on the premise of knowing the distance of the communication receiver, the distance of the radar target can be obtained.

[0091] Figure 6 (a) and (c) show the sampled signals of the two channels. Due to the inconsistency of the radiation intensity when switching the aperture coding, the amplitudes of different code elements are not completely consistent, but the envelope of the signal shows that the carrier signal has been modulated according to the m sequence. The fluctuation of the envelope can be eliminated by automatic gain control, which has been widely used in electronic information systems.

[0092] Through the matched filtering technology, the recovery of the m sequence received in the communication channel is as follows: Figure 6 (b) shows that Figure 3 Compared with the ideal m-sequence in (b), there is some amplitude jitter in the recovered signal, which is caused by the noise and frequency shift of the frequency converter. However, these have little effect on symbol estimation. The received signal in the radar channel is also processed by matched filtering, and the correlation coefficient of the received signals of the two channels can be calculated by equation (8).

[0093] According to the relevant delay, Figure 6 The peak of the correlation distance image of (d) appears at 3.51m. Since the actual distance between the communication receiver and the metasurface is 1.42m, the test distance between the metasurface and the metal sheet is 4.93m, which is very close to the actual distance of 5m. The above test results verify the effectiveness of the proposed radar communication integration technology based on digital programmable metasurface.

[0094] In summary, the integration of radar and communication functions is an important trend in the development of the world's information network system in the future. It realizes universal and intelligent perception, expression and cognition through electromagnetic waves. The present invention establishes a mechanism for realizing efficient radar communication integration based on digital coding metasurfaces, and directly realizes time and space frequency modulation on the metasurface surface, thereby greatly simplifying the architecture and reducing system costs compared with traditional phased array or MIMO antennas. The encryption and decryption, one-dimensional range imaging, and simultaneous realization of radar detection and wireless communication of the wireless security system are well verified through simulation and examples, thus demonstrating the great potential of radar communication integration technology based on digital coding metasurfaces to become a universal and ubiquitous intelligent terminal in the future.

[0095] The matters not described in detail in the present invention are all known technologies to those skilled in the art.

[0096] The preferred specific embodiments of the present invention are described in detail above. It should be understood that a person skilled in the art can make many modifications and changes based on the concept of the present invention without creative work. Therefore, any technical solution that can be obtained by a person skilled in the art through logical analysis, reasoning or limited experiments based on the concept of the present invention on the basis of the prior art should be within the scope of protection determined by the claims.

Claims

1. A radar communication integration method based on digitally programmable metasurface, characterized in that: The method is based on a radar communication integrated system, which includes a transmitting end and a receiving end, wherein both the transmitting end and the receiving end are provided with a digital programmable metasurface. The radar communication integrated method includes the following steps: Step S1, performing communication transmission, and encrypting the transmitted signal and decrypting the received signal, which includes: at the transmitting end, performing phase modulation on the transmitted signal, performing phase demodulation on the received signal at the receiving end, and verifying the consistency of the transmitted signal and the received signal; Step S2, performing radar verification, which includes: setting a target in the radar communication integrated system, and then applying a two-phase coded signal based on a digital programmable metasurface to perform one-dimensional range imaging on the target, wherein, at the transmitting end, the source signal is modulated by a 180° phase difference through the digital programmable metasurface to obtain a two-phase coded signal, and the signal is then transmitted to the receiving end after being reflected by the target, and at the receiving end, the received signal is processed by a matched filtering algorithm to achieve one-dimensional range imaging of the target; Step S3, performing radar communication integration, realizing both radar detection and wireless communication functions through the radar communication integration system, which includes: enabling the digital programmable metasurface to generate dual channels through coding design, wherein the first channel performs the communication transmission described in step S1, and the other channel performs the radar imaging of step S2, thereby realizing radar communication integration; In the step S1, a time-space system function is designed at the transmitting end and the receiving end respectively, and the two time-space system functions correspond to each other, and phase modulation and phase demodulation of the signal are realized through the time-space system function; The step S1 comprises: Assume that the signal I(t) is a plane wave e with propagation vector k. jωt The signal carried and reaching the metasurface reference unit is s(t)=I(t)e jωt , where t represents time, I(t) represents signal amplitude, and ω represents signal angular frequency. Then the signal reaching the mth unit of the metasurface is expressed as: In formula (1), Where k0 is the propagation constant, θ and denote the elevation angle and azimuth angle respectively, k is the component of the propagation constant in the xy plane; ρ m =[x m ,y m ] T , x m and m Respectively represent the coordinates of the mth unit of the hypersurface on the x-axis and y-axis; ρ m represents the coordinates of the mth unit of the hypersurface; For a narrowband signal with bandwidth B, we have: So we get: If the reflection or transmission coefficient of the mth element is Γ m , then at a distance r from m The signal observed at the point is: Considering all M units, the total signal at the observation point is expressed as: In formula (3), is the set of radiation characteristics of M units in the metasurface taking phase compensation into account; is the set of direction vectors of the M units of the hypersurface; The system function of the metasurface is defined as Then the observation point signal is expressed as: Among them, formula (4) shows that the input signal is modulated by the system function of the metasurface; The step S2 comprises: Assume that the carrier e jωt After the metasurface modulation including phase modulation by the system function h(t), the transmission signal of the metasurface is written as: g t (t)=h(t)e jφ(t) e jωt (5) In formula (5), φ(t) is a binary phase modulation term, expressed as: In formula (6), N and τ0 represent the length and symbol period of the binary code, respectively. k It is a binary code, and its value is 0 or 1; Assuming the receiver is placed at the same location as the transmitter, the signal received from a target at distance R is: In formula (7), c represents the speed of light; After processing the received signal, the one-dimensional range imaging characteristics of the target are as follows: In formula (8), Δt is the imaging range, and it is easy to obtain that the correlation coefficient reaches its maximum value at Δt = 2R / c, and ★ represents the convolution calculation. Indicates the transmitted signal g t The conjugate of (t).

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