Intelligent metasurface, system and method for measuring two-dimensional direction of arrival angle

Abstract

This invention discloses a smart metasurface, system, and method for measuring two-dimensional direction of arrival (DOA). The metasurface consists of a metal patch layer, an F4B dielectric layer, and a metal backplane layer, comprising n*n basic units. Each unit can be independently controlled by a periodic control voltage. By designing the control voltage signal for each unit, the reflection phase of each unit exhibits a periodic and mutually orthogonal phase change in space. The signal is then received by an auxiliary antenna and processed to obtain the two-dimensional DOA on the smart metasurface. This invention achieves accurate two-dimensional DOA estimation using only a periodic control voltage applied to the metasurface and a single receiving antenna, compared to methods requiring n*n base plates. 2 Compared to a phased array system of the same scale for two-dimensional direction-of-arrival estimation with a single radio frequency front-end, its architecture is simple, significantly reducing hardware costs and facilitating integration. It can be used in multiple fields such as radar, remote sensing, and wireless communication, and has broad application prospects.

Description

Technical Field

[0001] This invention relates to an intelligent metasurface, measurement system, and method for measuring two-dimensional direction of arrival angles, which can be used in fields such as radar, remote sensing, and wireless communication. Background Technology

[0002] Two-dimensional direction of arrival (DOA) measurement technology, as one of the important technologies in radar, remote sensing, and wireless communication, has been widely researched and applied. However, most current DOA estimation methods rely on phased arrays, which require multiple radio frequency front-ends to receive electromagnetic waves. This undoubtedly increases the hardware cost of its system-level applications, resulting in high cost, high power consumption, and high hardware complexity for phased array-based DOA estimation systems, hindering their further popularization. Therefore, it is necessary to develop a low-cost, low-complexity hardware device and related algorithms to meet the needs of the widespread application of DOA technology in radar, remote sensing, and wireless communication systems. Summary of the Invention

[0003] Purpose of the invention: The purpose of this invention is to provide an intelligent metasurface, measurement system, and measurement method for measuring two-dimensional direction of arrival (DOA). By applying mutually orthogonal time-coded sequences to the cells on the metasurface and receiving and demodulating them with an auxiliary receiving antenna, it can measure the two-dimensional incident angle of electromagnetic waves arriving on the intelligent metasurface. It also has a real-time beam control function, which can solve the technical problems of high hardware complexity, high cost, and high power consumption in traditional DOA estimation systems.

[0004] To solve the above-mentioned technical problems, the specific technical solution of the present invention is as follows:

[0005] A smart metasurface for measuring two-dimensional direction of arrival (DOA) includes: n*n basic units, each unit comprising a three-layer structure: the first layer consists of a centrally symmetrical metal patch with a PIN diode soldered on it; the second layer is a dielectric substrate; and the third layer is an unpatterned all-metal layer. The metal patch of the first layer is connected to the all-metal layer of the third layer by metal vias. Control signals are transmitted from the feed line to the metal patch through the metal vias. The switching on and off of the diode is controlled by controlling the voltage between the two metal patches across the diode.

[0006] The control link consists of a field-programmable gate array (FPGA) and digital I / O modules. Each interface of the digital I / O module is connected to the control signal link of a unit, and each unit can be controlled by an independent periodic control signal.

[0007] When the unit control voltage of the smart metasurface switches between 0V and 0.8V, the reflection phase of the unit can generate a phase change of about 180° in the frequency band of 4-5GHz, and the amplitude remains basically unchanged.

[0008] Each metasurface unit is subjected to periodic and orthogonal coded voltage modulation, causing its reflection phase in space to switch periodically and orthogonally continuously, and the time coding of the units does not affect each other.

[0009] Furthermore, the basic unit is made of polytetrafluoroethylene (PTFE) F4BM high-frequency antenna board with copper foil on one side, with a dielectric constant of 2.65 and a loss tangent of 0.001. The metal material is copper, with a thickness of 0.018 mm.

[0010] This invention also provides a two-dimensional direction-of-arrival (AOA) measurement system, including a transmitting antenna, a time modulation module, a receiving antenna, and a data processing module. The time modulation module includes the aforementioned smart metasurface. When the smart metasurface is irradiated by an incident wave, each basic unit on the smart metasurface periodically modulates the incident wave and reflects the modulated electromagnetic wave into free space. The receiving antenna, placed in the far field, receives the reflected signal and transmits it to the data processing module for demodulation. The module then recovers the amplitude and phase distribution excited by the incident wave on the smart metasurface and performs two-dimensional AOA estimation.

[0011] The present invention also provides a two-dimensional direction of arrival (DOA) measurement method, comprising the following steps:

[0012] Step 1: Single tone signal E i =e j2πft With a two-dimensional incident angle θ i and When incident on this intelligent metasurface, where f represents the frequency, the scattering pattern is shown below:

[0013]

[0014] in, The basic unit in row m and column n is in θ and Scattering pattern in the direction, Γ mn (t) is the reflection coefficient of the basic unit in the m-th row and n-th column at time t, and its value corresponds to n. 2 The value of the m*n-th row of a Hadamard matrix of order m;

[0015] Step 2: After time modulation of each basic unit, the amplitude and phase distribution of the incident wave on the metasurface are modulated into an interleaved time-varying signal, which is received by the receiving antenna at the angle of incidence θ and... The signal received at time t is: After n 2 After sampling at intervals of T0, the received signal can be represented in the following matrix form:

[0016]

[0017] Here, matrix A is an n-order square matrix, corresponding to the amplitude and phase information of each fundamental unit on the entire hypersurface. In the above equation, to satisfy matrix operations, it is compressed into a one-dimensional vector. Γ is an n 2 The value is an n-order Hadamard matrix, which corresponds to the time-varying reflection coefficient at the modulation end of the metasurface. Due to the orthogonality of the Hadamard matrix, it is guaranteed that the value of the solvable matrix A can be obtained by using the same Hadamard matrix at the receiving end, thereby reconstructing the amplitude and phase distribution of the incident wave on the metasurface.

[0018] Step 3: The reconstructed amplitude and phase distribution matrix A of the incident wave on the metasurface corresponds to the received signal matrix in the traditional phased matrix angle measurement technique. This allows it to be adapted to traditional wave arrival angle estimation algorithms, such as MUSIC and ESPRIT, to calculate the wave arrival angle value of the metasurface.

[0019] The present invention has the following advantages:

[0020] 1. Low hardware complexity and cost: The intelligent metasurface for measuring two-dimensional angle of arrival proposed in this invention includes n*n basic units, each unit containing a three-layer structure: the first layer is composed of a centrally symmetrical metal patch with a PIN diode soldered on, the second layer is a dielectric substrate, and the third layer is an unetched all-metal layer; the metal patch of the first layer is connected to the all-metal layer of the third layer by metal vias, and the control signal is transmitted from the feed line to the metal patch through the metal vias, and the switching on and off of the diode is controlled by controlling the voltage of the two metal patches across the diode.

[0021] 2. Simple structure, low cost, planar design, and easy integration with other devices: Compared with traditional phased arrays, this invention does not require a large number of electronic phase shifters or T / R components, resulting in low cost, simple structure, and high integration. While meeting the requirements of miniaturization and planar design, it is easy to integrate with other high-frequency / planar circuits.

[0022] In summary, the metasurface designed in this invention can perform real-time measurement of the two-dimensional direction of arrival (DOA) on the metasurface, which can replace the DOA measurement system based on phased array, thereby reducing the hardware complexity and cost of the measurement system. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of two-dimensional direction of arrival angle measurement using the intelligent metasurface in this invention;

[0024] Figure 2 These are schematic diagrams of the overall structure and partial unit structure of the intelligent metasurface in this invention;

[0025] Figure 3The graph shows the reflection amplitude response and reflection phase response curves of the intelligent metasurface in this invention under different operating states of the PIN diode.

[0026] Figure 4 This is a physical image of the intelligent metasurface in this invention and the two-dimensional spatial angle at which the measured two-dimensional wave direction of arrival angle is located;

[0027] Figure 5 This is a physical diagram of the architecture of a two-dimensional direction-of-arrival (DOA) measurement system based on a smart metasurface.

[0028] Figure 6 For the intelligent metasurface in this invention Figure 4 The actual direction of arrival angle of the mid-α angle, the direction of arrival angle measured by the intelligent metasurface, and the angle error curve;

[0029] Figure 7 For the intelligent metasurface in this invention Figure 4 The actual direction of arrival angle of the mid-β angle, the direction of arrival angle measured by the intelligent metasurface, and the angle error curve. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0031] One embodiment of the present invention is as follows: Figure 1 As shown, a smart metasurface for measuring two-dimensional direction of arrival (DOA) is disclosed. The metasurface consists of a metal patch layer, an F4B dielectric layer, and a metal backplane layer, comprising n*n basic units. By carefully designing the control voltage signal for each unit, the reflection phase of each unit exhibits a periodic and mutually orthogonal phase change in space. The signal is received by an auxiliary antenna and processed. The metasurface of this invention can accurately estimate the two-dimensional DOA on the metasurface.

[0032] like Figure 1 As shown, each unit of the smart metasurface in this invention can be independently controlled by a periodic control voltage. Under the control voltage, the unit in the m-th row and n-th column exhibits a time-varying reflection phase Γ. mn (t). When a beam of electromagnetic waves of a single frequency travels at a two-dimensional direction angle θ i and When incident on this smart metasurface, the far-field scattering pattern of the smart metasurface is as follows:

[0033]

[0034] Where θ and It is the angle of the reflected signal after modulation by the intelligent metasurface, d x and d y This indicates the interval between two adjacent units along the x-axis and y-axis. For example... Figure 1 As shown, after time modulation of each element, the amplitude and phase distribution of the incident wave on the metasurface are mapped into an interlaced time-varying signal, which is then modulated at θ and The receiving antenna is positioned at an angular location. The amplitude and phase information of the incident wave on the metasurface unit are compressed into a one-dimensional vector, and the received signal can be expressed as:

[0035]

[0036] in Each row is composed of N 2 The reflection coefficients of each metasurface unit at the same sampling time are used. In this invention, The first row contains all +1s, and the other rows contain the same number of +1s and -1s in a Hadamard matrix. In this case, The rows are orthogonal to each other. The inverse also exists. Therefore, the vector A composed of the amplitude and phase distribution of the incident wave on the metasurface can be reconstructed from the received signal. This distribution can be regarded as the received signal matrix required by the traditional DOA algorithm model, and traditional DOA algorithms, such as the MUSIC algorithm and ESTRPT algorithm, can be directly applied to calculate the two-dimensional angle of arrival on the metasurface.

[0037] The intelligent metasurface structure for measuring two-dimensional wave direction of arrival disclosed in this invention is shown in the figure below. Figure 2 As shown in the diagram, the metasurface consists of a metal patch layer, an F4B dielectric layer, and a metal backplane layer, comprising n*n basic units. Each unit contains a three-layer structure: the top layer consists of two centrally symmetrical reflective patches and a PIN diode (SMP1320-040LF) soldered between the two patches; the layer between the top layer and the metal ground plane is an F4B dielectric substrate (polytetrafluoroethylene) with a dielectric constant of 2.65 and a loss tangent of 0.001. Each metal patch structure in the top layer is connected to a control signal via a metal via. The intelligent metasurface and its unit structure diagram are shown below. Figure 2 As shown, the specific structural parameters are: p = 25mm, h = 4mm, v = 24mm, w = 10.6mm, g = 0.3mm.

[0038] The measured curves of the reflection amplitude response and reflection phase response of the intelligent metasurface in this invention under different operating states of the PIN diode are shown in the figure below. Figure 3 As shown, its operating frequency is 4.3GHz to 4.8GHz, and it has a 180° reflection phase shift in both states, with relatively stable amplitude transformation.

[0039] The physical structure of the intelligent metasurface in this invention is as follows: Figure 4 As shown in the figure. A physical diagram of the architecture of the two-dimensional wave direction angle measurement system utilizing the intelligent metasurface of this invention is shown in the figure. Figure 5 As shown, the entire system consists of a transmitting antenna, a time modulation module, a receiving module, and a data processing module. The time modulation module is located in... Figure 5 On the left side, it consists of the intelligent metasurface and control platform of this invention. The receiving and data processing module is located... Figure 5 On the right side, there is a receiving antenna located in the normal direction of the smart metasurface and connected to a high-performance SDR receiver. When the metasurface is illuminated by an incident wave, each element on the metasurface periodically modulates the incident wave in time, where the modulation code corresponding to the element in the m-th row and n-th column is the corresponding n-th element. 2 The value of the m*n-th row of the Hadamard matrix is ​​given, where a 1 in the Hadamard matrix corresponds to a control voltage of 0.8V, and a 0 in the Hadamard matrix corresponds to a control voltage of 0V. The modulated electromagnetic wave is reflected into free space, where it is received by a receiving antenna placed in the far field. The signal is then transmitted to the signal processing unit for demodulation, recovery of the amplitude and phase distribution excited by the incident wave on the metasurface, and estimation of the two-dimensional angle of arrival.

[0040] Furthermore, utilizing the architecture of the two-dimensional direction-of-arrival (DOA) measurement system based on the intelligent metasurface in this invention, the transmitting antenna scans the α and β angles of a 4.5 GHz single-frequency electromagnetic wave from -75° to +75°, and the intelligent metasurface system estimates the angles accordingly. The actual DOA angle, the DOA angle measured by the intelligent metasurface, and the angle error curve are shown in the figure below. Figure 6 As shown in the figure, the actual direction of arrival angle of angle β, the direction of arrival angle measured by the smart metasurface, and the angle error curve are shown in the figure. Figure 7 As shown, the error between the wave direction of arrival angle measured by the intelligent metasurface and the actual wave direction of arrival angle is small, with the overall error controlled within 4°, demonstrating the application value of this invention.

[0041] In summary, the intelligent metasurface provided by this invention achieves two-dimensional direction of arrival (DOA) measurement simply by controlling the periodic control voltage. Its principle is simple, its hardware architecture is easy to implement, its cost is low, and it is easy to integrate. It has broad application prospects in multiple fields such as radar, remote sensing, and wireless communication.

[0042] The foregoing has shown and described the basic principles and main features of the present invention, as well as its advantages. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. A smart metasurface for measuring the direction of arrival angle, characterized in that: This intelligent metasurface comprises n*n basic units, each containing a three-layer structure: the first layer consists of two centrally symmetrical metal patches with a PIN diode soldered on them; the second layer is a dielectric substrate layer; and the third layer is an unpatterned all-metal layer. The metal patches in the first layer are connected to the all-metal layer in the third layer by metal vias. Each metal patch in the first layer is connected to a control signal link through a metal via. The entire metasurface has a total of 2*n*n control signal links, and each unit is independently controlled by a periodic control voltage. Each basic unit is modulated by a periodic and orthogonal coded voltage, causing its reflection phase in space to switch periodically and orthogonally continuously. The time codes of the units are all different.

2. The intelligent metasurface for measuring the direction of arrival angle according to claim 1, characterized in that: The basic unit of the intelligent metasurface is made of polytetrafluoroethylene F4BM high-frequency antenna board with copper foil on one side, with a dielectric constant of 2.65 and a loss tangent of 0.

001.

3. The intelligent metasurface for measuring the direction of arrival angle according to claim 1, characterized in that: The control link of the intelligent metasurface consists of a field-programmable gate array (FPGA) and digital I / O modules; each interface of the digital I / O module is connected to the control signal link of a basic unit, so that each basic unit is controlled by an independent periodic control signal.

4. The intelligent metasurface for measuring the direction of arrival angle according to claim 1, characterized in that: When the control voltage of the basic unit of the intelligent metasurface switches between 0 V and 0.8 V, the reflection phase of the basic unit undergoes a phase change of about 180° in the frequency band of 4~5 GHz, and the amplitude remains basically unchanged.

5. A two-dimensional direction-of-arrival (DOA) measurement system, characterized in that, It includes a transmitting antenna, a time modulation module, a receiving antenna, and a data processing module; the time modulation module includes the smart metasurface according to any one of claims 1-4; when the smart metasurface is irradiated by an incident wave, each basic unit on the smart metasurface performs periodic time modulation on the incident wave and reflects the modulated electromagnetic wave into free space; The receiving antenna placed in the far field receives the reflected signal and transmits it to the data processing module for demodulation. The module then recovers the amplitude and phase distribution excited by the incident wave on the smart metasurface and performs two-dimensional angle of arrival estimation.

6. A two-dimensional direction-of-arrival (DOA) measurement method based on the system of claim 5, characterized in that, Includes the following steps: Step 1: Single-tone signal With a two-dimensional incident angle θ i and φ i When incident on this intelligent metasurface, where f represents the frequency, the scattering pattern is shown below: ； in, This is the scattering pattern of the basic unit in the m-th row and n-th column in the directions θ and φ. It is the reflection coefficient of the basic unit in the m-th row and n-th column at time t, and its value corresponds to n. 2 The value of the m*n-th row of the Hadamard matrix; Step 2: After time modulation of each basic unit, the amplitude and phase distribution of the incident wave on the metasurface are modulated into an interleaved time-varying signal, which is received by the receiving antenna at incident angles θ and φ. The signal received at time t is... After n 2 After sampling at intervals of T0, the received signal is represented in the following matrix form: ； Here, matrix A is an n-order square matrix, corresponding to the amplitude and phase information of each fundamental unit on the entire hypersurface. In the above equation, to satisfy matrix operations, it is compressed into a one-dimensional vector. ; It is an n 2 The value is an n-order Hadamard matrix, which corresponds to the time-varying reflection coefficient of the metasurface modulation end. Step 3: Calculate the arrival direction angle value of the metasurface using the arrival direction estimation algorithm.

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