Radio frequency identification correlated imaging positioning system and method based on adjustable reflecting surface

Abstract

The invention discloses a radio frequency identification correlated imaging positioning system based on an adjustable reflecting surface, and belongs to the technical field of radio frequency identification. The system comprises a reader-writer, an antenna, a time-domain transmission-type metasurface array, a PC (Personal Computer) end, two IO (Input / Output) cards, a plurality of tags to be tested and the like. The PC end controls an external instrument through internal software, and the time domain transmission-type metasurface array is formed by continuously arranging metasurface units in an array mode. The invention further discloses a radio frequency identification correlated imaging positioning method based on the adjustable reflecting surface. According to the invention, the correlation imaging algorithm is used to replace the original traditional radar principle and inverse scattering imaging algorithm, the dependence of the imaging resolution on the relative movement of the object is eliminated, and the correlation analysis is carried out on the superposed signal of the modeling imaging area and the received signal to restore the image. And the imaging resolution is further improved by adjusting the algorithm model.

Description

Technical Field

[0001] The invention belongs to the field of radio frequency identification, and in particular relates to a radio frequency identification associated imaging positioning system and method based on an adjustable reflecting surface. Background Art

[0002] In recent years, the development of IoT technology has promoted the "smartness" of people's lives, work and society. Whether it is smart home, smart transportation or smart industry, the realization of these technologies is inseparable from the integration of IoT with the physical world and the information world. The three major characteristics of IoT are comprehensive perception, reliable transmission and intelligent processing. The comprehensiveness of perception data depends on various types of perception devices, including perception devices such as RFID and sensors, as well as artificial information devices such as smartphones. The basis of reliable transmission is a large network composed of various heterogeneous networks, with the Internet as the core and various local area networks and wireless sensor networks at the end. The task of intelligent processing is ultimately completed by cloud computing, big data and artificial intelligence technologies. These technologies have developed rapidly in the past decade, promoting the implementation of many unprecedented intelligent applications and gradually improving people's lives.

[0003] As the Internet architecture becomes more stable and intelligent technology develops rapidly, the key to the further evolution of the Internet of Things is likely to be in comprehensive perception. How to improve the "quality" of perception layer data is one of the urgent issues that need to be solved. The types of perception devices and application scenarios in the perception layer of the Internet of Things are very wide.

[0004] The RFID system uses the spatial coupling of wireless radio frequency signals to achieve contactless tag transmission and automatic identification. Its main purpose is to automatically identify objects. However, by combining traditional signal processing and popular artificial intelligence technologies, researchers have gradually discovered the potential of RFID in intelligent applications. With the help of RFID, physical quantities or characteristics related to objects in the physical world can be sensed, such as: indoor positioning and sorting tracking, motion recognition, activity recognition, vital sign recognition, and new human-computer interaction. RFID can be used for perception because it has its unique advantages and applicable scenarios.

[0005] In short, the rapid development of IoT technology has brought many benefits to people's lives. In the IoT perception layer, the application of perception technologies such as RFID and perception imaging is also crucial. Through in-depth research on these technologies, we can further improve the quality of comprehensive perception data and promote the better integration of IoT technology into people's lives and work. RFID has the following advantages in use: First, its tags have the advantages of small size, light weight, low price, long service life and various packaging forms. They are widely used in automatic identification in industry and commerce, which facilitates RFID-based intelligent applications and is also conducive to the deployment of RFID systems. Second, RFID uses radio frequency signals instead of visible light for data perception, so it can work in dark environments, avoiding problems such as shadows, reflections and color differences related to visible light, and has very practical application scenarios. Third, RFID signals have reflection and penetration capabilities, and can achieve non-line-of-sight (NLOS) transmission. It can not only perceive objects within the line of sight, but also pass through obstacles to detect objects and perceive objects behind them. This feature expands the scope of RFID applications and can be applied to logistics and warehousing management, intelligent transportation systems, intelligent security and other fields.

[0006] In the process of RFID detection imaging, the spatial characteristics of objects, such as position and orientation, are among the most basic and important characteristics. These physical quantities can not only be directly sensed, but also the motion state and higher-order physical quantities of the object can be derived from them. In the field of the Internet of Things, the use of wireless signals to perceive the geometric structure of an object is imaging the target. Imaging is the basis of many applications. For example, the use of automatic drones can scan livestock in large farmlands and farms, waterproof drones can patrol underground sewage systems, and unmanned helicopters can transport supplies for field soldiers. The development of the Internet of Things can realize many beautiful visions: drones delivering mail, parcels and groceries, self-driving cars picking people up from get off work, and robots rescuing victims at disaster sites as soon as possible. Only when smart devices can "see" objects in the surrounding environment can they make the right decisions. Therefore, wireless imaging technology is crucial for the Internet of Things to produce richer applications.

[0007] Traditional radio frequency imaging systems use synthetic aperture radar, which utilizes transmitting and receiving array antennas to send and receive signals, and images objects by processing the collected echo signals. In this process, the imaging resolution depends on the relative motion of the object, and the final imaging resolution is proportional to the size of the array antenna. Large-scale antenna arrays can provide better imaging effects, but the resulting production costs also increase proportionally. Therefore, how to reduce the size of the antenna array without overly affecting the imaging accuracy and design related systems and algorithms has become a direction that needs to be studied urgently. Summary of the invention

[0008] The purpose of the present invention is to reduce the size of the antenna array without excessively affecting the imaging accuracy, and to provide a radio frequency identification associated imaging positioning system and method based on an adjustable reflecting surface.

[0009] The specific technical solutions adopted by the present invention are as follows:

[0010] In the first aspect, the present invention provides a radio frequency identification associated imaging positioning system based on an adjustable reflective surface, comprising a reader / writer, an antenna, a time-domain transmission metasurface array, a PC terminal, two IO cards, and a plurality of tags to be tested;

[0011] The PC controls external instruments through internal software. The control software inside the PC includes Java compiler, MATLAB, and Labview. The imaging algorithm is compiled and associated with MATLAB. The signal output from Labview to the IO card is continuously changed to process the signal received by the Java compiler from the reader / writer to complete the imaging.

[0012] The time-domain transmission metasurface array is formed by continuously arranging metasurface units in an array form; the metasurface units include two PIN diodes, four inductors and a multi-layer composite structure; the multi-layer composite structure is, from top to bottom, a surface metal pattern layer, a first dielectric layer, a first metal ground layer, a feeder layer, a second metal ground layer, a second dielectric layer and a back metal pattern layer; the surface metal pattern layer includes two groups of patterned metal sheets arranged in a mirror-symmetrical manner, and the back metal pattern layer is exactly the same as the surface metal pattern layer;

[0013] Each group of patterned metal sheets includes an E-shaped metal sheet and a connecting metal sheet, and the E-shaped metal sheet and the connecting metal sheet are connected via an inductor; the two E-shaped metal sheets in the two groups of patterned metal sheets are arranged relative to each other and kept at a distance, and the two E-shaped metal sheets are connected to each other through a horizontal bar connecting the same PIN diode; the feed line layer includes two feed lines with through holes connecting the top and bottom layers of the metasurface unit, and the feed line layer is isolated from the first metal ground layer and the second metal ground layer by a copper-plated ground plane, and the first metal ground layer and the second metal ground layer are separated by a dielectric layer; a through hole is provided on the multi-layer composite structure, and the two connecting metal sheets in the surface metal pattern layer are connected to the two connecting metal sheets in the back metal pattern layer respectively through the through holes that penetrate the multi-layer composite structure.

[0014] As a preferred embodiment of the first aspect, a waveguide is provided in the through hole, and an annular dielectric layer is sheathed on the outside of the waveguide to insulate the waveguide from the metal stratum when the waveguide passes through the metal stratum.

[0015] Furthermore, the materials of the first dielectric layer, the second dielectric layer and the annular dielectric layer are all polytetrafluoroethylene glass cloth copper foil F4B, with a dielectric constant of 2.65 and a loss tangent of 0.001.

[0016] As a preference for the first aspect above, the surface metal pattern layer, the first metal ground layer, the second metal ground layer, the feeder layer and the back metal pattern layer are all made of copper.

[0017] As a preferred embodiment of the first aspect above, in the super surface unit, the connecting metal sheet is rectangular.

[0018] As a preferred embodiment of the above-mentioned first aspect, in the time-domain transmission metasurface array, the metasurface units are periodically and continuously arranged in the form of an n*n rectangular array, where n is an integer not less than 8, and n is preferably 8.

[0019] As a preferred embodiment of the first aspect above, two E-shaped metal sheets in the two groups of patterned metal sheets are arranged relative to each other, and the length and width of the E-shaped metal sheets are 30mm and 60mm respectively, the width of the upper and lower horizontal rectangles is 12mm, the spacing between the middle rectangle is 7mm, and the depth is 24mm; the first dielectric layer, the second dielectric layer, the first metal stratum, and the second metal stratum are squares with a side length of 64mm; the top side length and width of the connecting metal sheet of the surface metal pattern layer are both 4mm, and the radius of the through hole is 0.8mm.

[0020] As a preferred embodiment of the first aspect, the antenna is a ceramic antenna; the reader is impinj R700; and the IO card is a 48-port IO serial-to-parallel conversion card.

[0021] In a second aspect, the present invention provides an imaging method using a radio frequency identification associated imaging positioning system based on an adjustable reflective surface as described in any one of the first aspects above, wherein the external antenna sends a signal, which is modulated by a time-domain transmission metasurface array into a set of random signals of whether the phase changes by 180°, and forms a reference signal with a low correlation at different positions of the tag to be tested, and then receives the intensity and phase information as a received signal by the antenna after passing through the time-domain transmission metasurface array;

[0022] By changing the array arrangement of the 180° deflection unit of the meta, multiple groups of reference signals and receiving signals are generated. Finally, the scattering information of different positions of the tag to be tested is obtained by processing these two arrays, thereby imaging the object. The control and reception of the antenna are read by the reader and then transmitted back to the PC end. The control of the random phase deflection of the time-domain transmission metasurface array is also achieved by connecting the PC end to the IO card to realize the feeding control.

[0023] Inside the PC, Java compiler code is used to implement communication with the external reader / writer, initialize control information and continuously receive the intensity, phase and EPC information transmitted back and send it to MATLAB; Labview is used to control the IO card, continuously generate random signals, and return the random array to MATLAB; finally, MATLAB processes this data and obtains the scattering coefficient of the target position, thereby forming an image.

[0024] As a preferred embodiment of the second aspect, the feeding control method is to generate a set of pseudo-random signals through Labview in the PC end, and control the two IO cards to power the time-domain transmission metasurface array, thereby forming a result of random power supply for each unit, and generating a pseudo-random signal again after a certain period of time, and repeating this process, recording each set of pseudo-random arrays and time differences and transmitting them back to MATLAB.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] By using the correlation imaging algorithm to replace the original traditional radar principle and inverse scattering imaging algorithm, the imaging resolution is freed from the dependence on the relative motion of the object. The image is restored by analyzing the correlation between the superimposed signal of the imaging area and the received signal, and the imaging resolution is further improved by adjusting the algorithm model. In the system, the time-space uncorrelated signals are generated in the form of traditional antennas plus intelligent reflective surfaces to replace the expensive large antenna arrays, thereby reducing the system manufacturing cost. Through the control of the intelligent reflective surface, multiple groups of random signals are generated and imaged in the target range to increase the degree of uncorrelation between signals. The entire system adds real-time imaging functions to the original RFID system, improves the flexibility of imaging applications, gets rid of the dependence on the motion of the imaging object, and greatly saves system costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 A structural diagram of the radio frequency identification associated imaging positioning system based on an adjustable reflective surface provided in this embodiment;

[0028] Figure 2 A flowchart of the system imaging provided for this embodiment;

[0029] Figure 3 is a schematic diagram of a multi-layer composite structure;

[0030] Figure 4 is a schematic diagram of pattern distribution of the surface metal pattern layer;

[0031] Figure 5 This is a schematic diagram of the feeder layer;

[0032] Figure 6 It is the S21 phase curve diagram of the metasurface unit under different on and off conditions;

[0033] Figure 7 It is the S21 amplitude curve diagram of the metasurface unit under different on and off conditions;

[0034] Figure 8 This is the near-field phase distribution diagram of the metasurface 8*8 array;

[0035] Fig. 9 This is a schematic diagram of the correlation imaging results of the metasurface RFID system under simulated noise conditions;

[0036] In the figure: surface metal pattern layer 1, first dielectric layer 201, second dielectric layer 202, first metal ground layer 301, second metal ground layer 302, feed line layer 4, back metal pattern layer 5, through hole 6, PIN diode 7, inductor 8, antenna 9, time domain transmission metasurface array 10, tag to be tested 11, reader / writer 12, IO card 13, java compiler 14, MATLAB 15, Labview 16, PC end 17. DETAILED DESCRIPTION

[0037] In order to make the above-mentioned purpose, features and advantages of the present invention more obvious and easy to understand, the specific implementation mode of the present invention is described in detail below in conjunction with the accompanying drawings. In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below. The technical features in each embodiment of the present invention can be combined accordingly without conflicting with each other.

[0038] In the description of the present invention, it should be understood that the terms "first" and "second" are only used for the purpose of distinguishing descriptions, and should not be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features.

[0039] like Figure 1 and Figure 2As shown, in a preferred embodiment of the present invention, a radio frequency identification associated imaging positioning system based on an adjustable reflective surface is provided, comprising a reader 12, an antenna 9, a time-domain transmission metasurface array 10, a PC terminal 17, two IO cards 13, and a plurality of tags 11 to be tested. In this system, an external port of the PC terminal 17 is connected to the reader 12, and the reader 12 is connected to the antenna 9; another port of the PC terminal 17 is connected to two IO cards 13, and the IO card 13 controls the switching of the time-domain transmission metasurface array 10 units. In this embodiment, an imaging method of a radio frequency identification associated imaging positioning system based on an adjustable reflective surface is provided. Outside the PC terminal 17, after the antenna 9 sends a signal, it is modulated by the time-domain transmission metasurface array 10 into a group of random phase changes of 180°, and a reference signal with a low correlation is formed at different positions of the tag 11 to be tested, and then the antenna 9 receives the intensity and phase information as a received signal after transmission through the time-domain transmission metasurface array 10. Then, the array arrangement of the 180° deflection unit of meta is transformed to generate multiple sets of reference signals and receiving signals. Finally, the scattering information of different positions of the tag 11 to be tested is obtained by processing these two arrays, thereby imaging the object. The control and reception of the antenna 9 are read by the reader 12 and then transmitted back to the PC terminal 17. The control of the random phase deflection of the time-domain transmission metasurface array 10 is also achieved by connecting the IO card 13 to the PC terminal 17 to realize the feeding control. Among them, the feeding control method is to generate a set of pseudo-random signals through Labview 16 in the PC terminal 17, and control the two IO cards 13 to power the time-domain transmission metasurface array 10, so as to form a random power supply result for each unit, and generate a pseudo-random signal again after a certain period of time, and so on, and record each set of pseudo-random arrays and time differences and transmit them back to MATLAB 15. The internal software of the PC terminal 17 controls the externally connected devices: the control software inside the PC 17 includes a java compiler 14, MATLAB 15, and Labview 16. The java compiler 14 is used to write codes to realize communication with the external reader 12, initialize control information, and continuously receive the intensity, phase, and EPC information transmitted back, and send them to MATLAB 15; by continuously changing the signal output by Labview 16 to the IO card 13, and returning the random array to MATLAB 15; finally, MATLAB 15 processes these data and obtains the scattering coefficient of the target position, thereby imaging. In the system provided in this embodiment, the antenna 9 adopts a ceramic antenna; the reader 12 adopts impinj R700; and the IO card 13 adopts a 48-port IO serial-to-parallel conversion card.

[0040] In the system provided in this embodiment, the time-domain transmission metasurface array is formed by continuously arranging metasurface units in an array form, such as Figure 3 and Figure 4As shown, the super surface unit includes two PIN tubes 7, four inductors 8 and a multi-layer composite structure. The multi-layer composite structure is, from top to bottom, a surface metal pattern layer 1, a first dielectric layer 201, a first metal ground layer 301, a feeder layer 4, a second metal ground layer 302, a second dielectric layer 202 and a back metal pattern layer 5. The back metal pattern layer 5 is exactly the same as the surface metal pattern layer 1. Taking the structure of the surface metal pattern layer 1 as an example, the surface metal pattern layer 1 includes two groups of patterned metal sheets arranged in a mirror-symmetrical manner. Each group of patterned metal sheets includes an E-shaped metal sheet and a connecting metal sheet. In the system provided in this embodiment, the connecting metal sheet is rectangular. Preferably, the connecting metal sheet on the surface metal pattern layer 1 can be square, and the length and width of the top side of the connecting metal sheet are both 4mm, and the through hole radius is 0.8mm. The E-shaped metal sheet is connected to the connecting metal sheet through an inductor 8; the two E-shaped metal sheets in the two groups of patterned metal sheets are kept at a distance, and the two E-shaped metal surfaces are arranged opposite to each other and connected to the same PIN diode 7 through a middle horizontal bar. The length and width of the E-shaped metal sheet are 30mm and 60mm respectively, the width of the upper and lower horizontal rectangles is 12mm, the distance between the E-shaped metal sheet and the middle rectangle is 7mm, and the depth of the E-shaped metal sheet is 24mm.

[0041] like Figure 3 and Figure 5 As shown, the feeder layer 4 includes two feeders of through holes 6 connecting the top layer and the bottom layer of the super surface unit, and the feeder layer 4 is isolated from the first metal layer 301 and the second metal layer 302 by a copper-plated ground plane, and the first metal layer 301 and the surface metal pattern layer 1, the second metal layer 302 and the back metal pattern layer 5 are separated by the first dielectric layer 201, and the first metal layer 301 and the second metal layer 302 are separated by the second dielectric layer 202. A through hole 6 is provided on the multi-layer composite structure, and a waveguide is provided in the through hole 6, and a circular dielectric layer is covered on the outside of the waveguide to achieve insulation and isolation from the first metal layer 301 and the second metal layer 302. The two connecting metal sheets in the surface metal pattern layer 1 and the two connecting metal sheets in the back metal pattern layer 5 are respectively connected through the waveguide of the through hole 6 that penetrates the multi-layer composite structure. In the system provided in this embodiment, the surface metal pattern layer 1, the first metal ground layer 301, the second metal ground layer 302, the feed line layer 4 and the back metal pattern layer 5 are all made of metal copper, the first dielectric layer 201, the second dielectric layer 202 and the first metal ground layer 301, the second metal ground layer 302 are squares with a side length of 64 mm; the first dielectric layer 201, the second dielectric layer 202 and the annular dielectric layer are all made of polytetrafluoroethylene glass cloth copper foil F4B, with a dielectric constant of 2.65 and a loss tangent of 0.001.

[0042] In the system provided by this embodiment, in the time-domain transmission metasurface array 10, the metasurface units are periodically and continuously arranged in the form of an n*n rectangular array, where n is an integer not less than 8. When n is 8, the production cost is the lowest and the effect is the best. Therefore, in this embodiment, the metasurface units are periodically and continuously arranged in the form of an 8*8 rectangular array. Figure 6 The phase change of the transmitted wave of the metasurface in the two states of 0 and 1 is shown, where 18 is the S21 phase curve when the PIN tube is turned on, and 19 is the S21 phase curve when the PIN tube is turned off. At the 0.92GHz frequency, by turning on or off the different states of the metasurface unit, it can be clearly seen that the phase of the transmitted wave has changed significantly. This phenomenon shows that the metasurface has a very strong phase modulation capability for electromagnetic waves in this frequency band. The realization of this modulation capability mainly depends on the geometric design and material properties of the metasurface structure, as well as the precise control of the power supply state. By controlling the phase change of the S parameter, the metasurface unit can flexibly modulate the phase during the transmission of the electromagnetic wave, thereby achieving efficient manipulation of the electromagnetic wave. Figure 7 The S21 amplitude curves of the metasurface unit under different on-off conditions are shown, where 20 is the S21 amplitude curve when the PIN tube is on, and 21 is the S21 amplitude curve when the PIN tube is off. Figure 8 As shown, the two columns of PIN tubes on the left are enabled, and the six columns on the right are disabled. The different colors represent the phase changes of the near-field transmission wave of the metasurface array at the frequency of 0.92 GHz in the two states of on and off. Further simulation of the near-field phase of the metasurface array is controlled by the arrangement of the metasurface enabling signal. It can be seen that the phase of the near field is basically consistent with the arrangement of the enabling signal (the abnormal phase on the left and right sides is caused by the edge effect), where 22 is the phase 30°-50° area, and 23 is the phase 140°-160° area. Fig. 9 The restoration of the 11 points of the tag to be tested by the correlation imaging algorithm under -80dB noise is demonstrated, and the noise is filtered out by the singular value decomposition method. Singular value decomposition effectively extracts the main signal components from the imaging data and filters out the noise components by screening and truncating the singular values ​​of the matrix. This method utilizes the signal-noise separation capability of singular value decomposition and can effectively remove noise through reasonable parameter selection.

[0043] The above-described embodiment is only a preferred solution of the present invention, but it is not intended to limit the present invention. A person skilled in the relevant technical field may make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, any technical solution obtained by equivalent replacement or equivalent transformation falls within the protection scope of the present invention.

Claims

1. A radio frequency identification associated imaging positioning system based on an adjustable reflective surface, characterized in that: It includes a reader / writer (12), an antenna (9), a time-domain transmission metasurface array (10), a PC terminal (17), two IO cards (13) and a plurality of tags to be tested (11); The PC end (17) controls the external instrument through internal software, and the control software inside the PC end (17) includes a Java compiler (14), MATLAB (15), and Labview (16); the imaging algorithm is compiled and associated by MATLAB (15), and the signal output by Labview (16) to the IO card (13) is continuously changed to process the signal of the reader (12) received by the Java compiler (14), thereby completing the imaging; The time-domain transmission metasurface array (10) is formed by continuously arranging metasurface units in an array form; the metasurface units include two PIN diodes (7), four inductors (8) and a multi-layer composite structure; the multi-layer composite structure is composed of a surface metal pattern layer (1), a first dielectric layer (201), a first metal ground layer (301), a feeder layer (4), a second metal ground layer (302), a second dielectric layer (202) and a back metal pattern layer (5) from top to bottom; the surface metal pattern layer (1) includes two groups of patterned metal sheets arranged in a mirror-symmetrical manner, and the back metal pattern layer (5) is completely the same as the surface metal pattern layer (1); Each group of patterned metal sheets comprises an E-shaped metal sheet and a connecting metal sheet, and the E-shaped metal sheet and the connecting metal sheet are connected via an inductor (8); the two E-shaped metal sheets in the two groups of patterned metal sheets are arranged relative to each other and kept at a distance, and the two E-shaped metal sheets are connected to each other by connecting the same PIN diode (7) via a horizontal bar in the middle; the feed line layer (4) comprises two feed lines with through holes (6) connecting the top layer and the bottom layer of the super surface unit, the feed line layer (4) is isolated from the first metal layer (301) and the second metal layer (302) by a copper-plated ground plane, and the first metal layer (301) and the second metal layer (302) are separated by a dielectric layer; the multi-layer composite structure is provided with a through hole (6), and the two connecting metal sheets in the surface metal pattern layer (1) and the two connecting metal sheets in the back metal pattern layer (5) are respectively connected via the through hole (6) penetrating the multi-layer composite structure.

2. The RFID-associated imaging positioning system based on an adjustable reflective surface according to claim 1, characterized in that: A waveguide is arranged in the through hole (6), and a ring-shaped dielectric layer is sheathed on the outside of the waveguide to ensure insulation between the waveguide and the metal stratum when the waveguide passes through the metal stratum.

3. The RFID-associated imaging positioning system based on an adjustable reflective surface according to claim 2, characterized in that: The materials of the first dielectric layer (201), the second dielectric layer (202) and the annular dielectric layer are all polytetrafluoroethylene glass cloth copper foil F4B, with a dielectric constant of 2.65 and a loss tangent of 0.

001.

4. The RFID-associated imaging positioning system based on an adjustable reflective surface according to claim 1, characterized in that: The surface metal pattern layer (1), the first metal ground layer (301), the second metal ground layer (302), the feeder layer (4) and the back metal pattern layer (5) are all made of metal copper.

5. The RFID-associated imaging positioning system based on an adjustable reflective surface according to claim 1, characterized in that: In the metasurface unit, the connecting metal sheet is rectangular.

6. The RFID-associated imaging positioning system based on an adjustable reflective surface according to claim 1, characterized in that: In the time-domain transmission metasurface array (10), the metasurface units are periodically and continuously arranged in the form of an n*n rectangular array, where n is an integer not less than 8.

7. The RFID-associated imaging positioning system based on an adjustable reflective surface according to claim 1, characterized in that: Two E-shaped metal sheets in the two groups of patterned metal sheets are arranged relative to each other, the length and width of the E-shaped metal sheet are 30 mm and 60 mm respectively, and the width of the upper and lower transverse rectangles is 12 mm; the distance between the E-shaped metal sheet and the middle rectangle is 7 mm, and the depth of the E-shaped metal sheet is 24 mm; the first dielectric layer (201), the second dielectric layer (202) and the first metal stratum (301), and the second metal stratum (302) are squares with a side length of 64 mm; the top side length and width of the connecting metal sheet of the surface metal pattern layer (1) are both 4 mm, and the through hole radius is 0.8 mm.

8. The RFID-associated imaging positioning system based on an adjustable reflective surface according to claim 1, characterized in that: The antenna (9) is a ceramic antenna; the reader / writer (12) is impinj R700; and the IO card (13) is a 48-port IO serial-to-parallel conversion card.

9. A radio frequency identification associated imaging positioning method based on an adjustable reflective surface of the radio frequency identification associated imaging positioning system according to any one of claims 1 to 8, characterized in that: After the external antenna (9) sends out a signal, it is modulated by the time-domain transmission metasurface array (10) into a group of random signals with a phase change of 180°, and a reference signal with a low correlation is formed at different positions of the tag to be tested (11). After passing through the time-domain transmission metasurface array (10), the antenna (9) receives the intensity and phase information as a received signal; By changing the array arrangement of the 180° deflection units of the meta, multiple groups of reference signals and receiving signals are generated, and finally the scattering information of different positions of the tag (11) to be tested is obtained by processing the two arrays, so as to image the object; the control and reception of the antenna (9) are read by the reader (12) and then transmitted back to the PC end (17), and the control of the random phase deflection of the time-domain transmission metasurface array (10) is also realized by connecting the PC end (17) to the IO card (13) to realize the feeding control; Inside the PC, a Java compiler (14) code is used to implement communication with an external reader (12), initialize control information and continuously receive the intensity, phase and EPC information transmitted back, and send it to MATLAB (15); use Labview (16) to control the IO card (13), continuously generate random signals, and return the random array to MATLAB (15); finally, MATLAB (15) processes these data and obtains the scattering coefficient of the target position, thereby imaging.

10. The RFID-associated imaging positioning method based on an adjustable reflective surface according to claim 9, characterized in that: The power feeding control method is to generate a set of pseudo-random signals through Labview (16) in the PC terminal (17), control two IO cards (13) to power the time-domain transmission metasurface array (10), and form a result of random power supply for each unit, and generate pseudo-random signals again after a certain period of time, and repeat this process, and record each set of pseudo-random arrays and time differences and transmit them back to MATLAB (15).

Images