Sensing and beam manipulation decoupling method based on space-time coding metamaterial

Abstract

The invention discloses a sensing and beam manipulation decoupling method based on a space-time coding metamaterial. By designing a space-time coding matrix and loading the space-time coding matrix to the space-time coding metamaterial through a digital control circuit, the metamaterial can sense incident electromagnetic waves at the same time and control any wave beams. In the aspect of sensing, the amplitude and phase information of each unit can be precisely restored from far-field sampling signals at different time points by distributing linearly independent space codes for the metamaterial at different time slots, so that high-precision sensing of a space electromagnetic field is realized. In the aspect of beam manipulation, independent control is carried out on time-varying period coding signals of all units of the metamaterial, and the reflection coefficient of electromagnetic waves incident to the metamaterial is represented as a complex average value of the amplitude and the phase of a coding sequence, so that specific amplitude and phase distribution is formed in the space, and accurate manipulation of a reflected electromagnetic field is realized. The sensing function and the beam manipulation function can be synchronously realized through a unified space-time coding matrix.

Description

Technical Field

[0001] The present invention relates to the technical field of wireless sensing and novel artificial electromagnetic materials, and more specifically, to a strategy for simultaneously realizing electromagnetic sensing and manipulation based on spatiotemporal coding metamaterials. Background Art

[0002] In recent years, the capabilities of sensing technology in wireless environments have been significantly improved, and its integration with multimodal methods has revolutionized the development of smart spaces. By optimizing the allocation of electromagnetic resources, the performance of radar, integrated sensing and communication (ISAC), and the Internet of Things (IoT) has been significantly improved. Electromagnetic metamaterials have attracted much attention due to their multi-purpose control capabilities of electromagnetic waves. With their planar design, easy integration, and low loss, they are considered to be strong candidates for achieving efficient electromagnetic wave control. This type of material can achieve multi-dimensional electromagnetic response based on a simple architecture, including flexible control of amplitude, phase, polarization, and frequency.

[0003] In practical applications, the most direct and efficient way to integrate sensing technology into electromagnetic metamaterials is to connect additional sensors. Through devices such as receiving arrays, gyroscopes, cameras, brain wave sensors, and eye trackers, the metasurface can obtain feedback information to achieve adaptive electromagnetic wave operations. This deep integration of sensors and metamaterials has overturned the traditional view that the electromagnetic environment is invisible and non-customizable, and promoted the development of adaptive electromagnetic manipulation functions. However, sensor-integrated metasurfaces also bring challenges, such as higher costs and more complex hardware design. In contrast, directional sensing technology based on metasurfaces provides an alternative that does not require additional equipment or redesign of the structure. However, current electromagnetic sensing schemes are usually coupled with electromagnetic manipulation processes and cannot perform both tasks at the same time, which significantly limits the overall efficiency of the adaptive system. Summary of the invention

[0004] Technical problem: In view of the problem of mutual coupling between the perception and electromagnetic manipulation functions based on existing electromagnetic metamaterials, it is difficult to achieve the simultaneous operation of the two by traditional methods. It is usually necessary to integrate external sensor devices or redesign the structure to realize the functions separately, resulting in complex architecture, low efficiency and high hardware cost of electromagnetic adaptive system. The present invention aims to propose a decoupling strategy for perception and beam manipulation based on space-time coding metamaterials. By using a digital control circuit to load the space-time coding matrix onto the space-time coding metamaterial, the metamaterial realizes the simultaneous perception of the incident electromagnetic wave and arbitrary beam manipulation function. In terms of perception, by assigning linearly independent spatial coding to the metamaterial at different time slots, the amplitude and phase information of each unit can be accurately restored from the far-field sampling signals at different time points, thereby realizing high-precision perception of the electromagnetic field in space. In terms of beam manipulation, by independently controlling the time-varying periodic coding signals of each unit of the metamaterial, the reflection coefficient of the electromagnetic wave incident on the metamaterial is expressed as the complex average of the amplitude and phase of the coding sequence, thereby forming a specific amplitude and phase distribution in space, and realizing precise manipulation of the reflected electromagnetic field. This method effectively reduces the hardware complexity and significantly improves the overall efficiency of the adaptive electromagnetic system.

[0005] Technical solution: The present invention discloses a method for decoupling perception and beam manipulation based on space-time coding metamaterials. By independently controlling the time-varying periodic coding signal of each unit of the space-time coding metamaterial, the reflection coefficient of the electromagnetic wave incident on the metamaterial unit can be expressed as the complex average value of the amplitude and phase of the coding sequence. The perception function is realized as follows: by assigning a linearly independent time-varying periodic coding signal to each unit, the amplitude and phase information of the incident electromagnetic wave exciting each unit can be accurately restored from the reflection signals sampled multiple times quickly, thereby realizing the perception of the electromagnetic field in space. At the same time, the time-varying periodic coding signals of different units construct corresponding amplitude and phase distributions in space by forming a specific complex average reflection coefficient, thereby achieving arbitrary manipulation of the reflected electromagnetic field. The specific technical solution of the present invention is as follows:

[0006] The space-time coding metamaterial has M×N units, and each unit has an independent electromagnetic response to electromagnetic waves. Each space-time coding metamaterial unit has four programmable phase states, namely 0°, 90°, 180°, and 270°, which can produce a programmable electromagnetic response to the incident electromagnetic wave. By configuring the coding sequence of each metamaterial unit in time and space through an external programmable digital circuit, it can simultaneously realize the perception and manipulation of the incident electromagnetic wave. Here, the coding state of different units in time and space is represented in the form of a space-time coding matrix (STCM):

[0007]

[0008] Among them, each row of the STCM matrix is ​​the spatial dimension, representing the programmable reflection coefficient state of different units at the same time; each column is the time dimension, representing the programmable reflection coefficient state of the same unit at different times; t0 is the time interval between adjacent codes, and L is the total length of the time code. By designing the coding state of the time and space dimensions of the STCM matrix and configuring it on the space-time coding metamaterial, the metamaterial can realize the perception of the incident electromagnetic wave, beam steering, decoupling and simultaneous implementation of the perception and beam steering functions. The specific steps are as follows:

[0009] Step 1: In terms of electromagnetic sensing function, after the incident electromagnetic wave is modulated in the time and space dimensions by the space-time coding metamaterial configured with STCM, its reflected electromagnetic wave can be received by the probe placed in the normal direction of the far field. The time vector F of its sampling signal can be expressed as

[0010]

[0011] in represents the signal sampled at time t0. Using the sampled signal and STCM, we can obtain the sensory information A generated by the incident electromagnetic wave on the metamaterial. 11 ,a 12 ,...,a mn ] T , where a mn is the electromagnetic wave incident information perceived by the mth row and nth column unit, and its recovery algorithm can be expressed as

[0012] A=STCM -1 F

[0013] The recovered perception information A on the metamaterial array can be combined with existing digital signal processing algorithms to further realize applications such as electromagnetic direction perception and electromagnetic imaging.

[0014] Step 2: In terms of electromagnetic beam steering function, the STCM matrix can be simplified to the spatial dimension and further represented as a space-time-varying coding vector (stcv):

[0015] stcv = [Γ 11 (t) Γ 12 (t)...Γ MN (t)]

[0016] where Γ MN (t) is the time-varying coding sequence function of the Mth row and Nth column in the spatiotemporal coding metamaterial. The average complex reflection coefficient of the time-varying coding sequence in time can be expressed as

[0017]

[0018] in is the average reflection coefficient of the metamaterial unit in the mth row and nth column, Γ mn (lt0) is the reflection coefficient of the lth time slot in the time-varying coding sequence. By designing the length of the corresponding coding sequence and the corresponding coding, any reflection coefficient can be synthesized. The time-varying coding vector stcv can be expressed as a space-coding vector (scv)

[0019]

[0020] By constructing a spatial coding vector scv and realizing adjustable amplitude and phase distribution on the array surface, metamaterials can realize arbitrary manipulation of electromagnetic waves.

[0021] Step 3: To achieve the decoupling of electromagnetic sensing and beam steering, it is necessary to jointly consider the sensing and beam steering functions of STCM and optimize the STCM matrix. In the sensing function, the rows of STCM need to satisfy linear independence to ensure that STCM -1 The existence of beam steering function requires each column of STCM to construct a corresponding coding sequence in the time domain according to its required amplitude and phase distribution.

[0022] According to the constructed STCM and the mapping relationship between reflection coefficient and voltage, the scattering pattern configured to the spatiotemporal coding metamaterial is expressed as:

[0023]

[0024] in is the far-field pattern of the m-th row and n-th column unit at the incident frequency; θ and are elevation and azimuth respectively; d x and d y are the meta-atom periods in the x and y directions, λ c is the wavelength of the incident electromagnetic wave; is the average reflection coefficient of the m-th row and n-th column metamaterial unit, calculated from STCM; by adjusting and optimizing the time-varying coding sequence of each unit, arbitrary amplitude and phase can be formed on the metasurface, thereby manipulating electromagnetic waves.

[0025] Based on the above theory and design, after the STCM matrix is ​​configured on the metamaterial through an external programmable digital circuit, the metamaterial can incident electromagnetic waves to realize any designed electromagnetic wave manipulation function, and at the same time can sense the incident electromagnetic waves to complete electromagnetic direction perception, electromagnetic imaging and other perception functions.

[0026] The present invention also provides a space-time coding metamaterial, which uses the above method to decouple perception and beam steering.

[0027] Beneficial effects:

[0028] Compared with the prior art, the present invention has the following significant beneficial effects: the present invention proposes a decoupling strategy for perception and beam steering based on space-time coding metamaterials, which can simultaneously realize the decoupling of the perception function and beam steering of metamaterials without redesigning the metamaterial structure or integrating additional sensing devices. In the prior art, the realization of perception and beam steering based on metamaterials usually requires redesigning the metamaterial structure, adding receiving units or integrating additional sensing devices, resulting in increased hardware complexity and greater design difficulty. In addition, in the existing perception technology based on coded metamaterials, the perception and electromagnetic manipulation functions are coupled and cannot be performed simultaneously, which reduces the system efficiency. In response to these problems, the decoupling method proposed in the present invention can simultaneously realize the perception of electromagnetic waves and the manipulation of electromagnetic fields, significantly reducing hardware costs and system complexity, while improving the efficiency of wireless systems based on metamaterials. The method has broad application prospects, including but not limited to wireless communications, perception, and new radar systems. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 The schematic diagram of the principle of decoupling the sensing and beam steering of the space-time coding metamaterial in the present invention is shown;

[0030] Figure 2 A space-time coding matrix (STCM) capable of achieving decoupling of perception and beam steering in an embodiment of the present invention;

[0031] Figure 3 It is demonstrated that in an embodiment of the present invention, the absolute error of the incident angle of an incident electromagnetic wave is sensed by configuring a space-time coding metamaterial with different space-time coding matrices (STCM);

[0032] Figure 4 It shows the scattering pattern of the space-time coding metamaterial configured with different space-time coding matrices (STCM) when performing beam scanning in space in an embodiment of the present invention.

[0033] Figure 5 The present invention is a method flow. DETAILED DESCRIPTION

[0034] 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.

[0035] In view of the problem that the existing metamaterials are coupled with the sensing and beam steering functions of electromagnetic waves, which makes it impossible to implement the two at the same time, the present invention proposes a strategy for decoupling the sensing and beam steering functions based on spatiotemporal coding metamaterials. Figure 1 As shown, a 2-bit phase space-time coding metamaterial is used, which has four programmable phase states, causing the incident wave phase to produce phase shifts of 0°, 90°, 180°, and 270° respectively. Figure 2 An implementation case of the STCM matrix that satisfies both sensing and beam manipulation is given, where each column is a spatial dimension, representing the programmable reflection coefficient state of different units at the same time; each row is a temporal dimension, representing the programmable reflection coefficient state of the same unit at different times. By configuring the STCM on the space-time coding metamaterial, when the electromagnetic wave radiates from the source to the space-time coding metamaterial modulated by the space-time coding matrix STCM, the reflected time-varying electromagnetic wave can be expressed as

[0036]

[0037] Among them, Γ mn (t) and are the time-varying reflection coefficient and scattering pattern of the m-th row and n-th column unit, θ and are the elevation angle and azimuth angle of the incident electromagnetic wave, d x and d y are the spacing of the metamaterial units in the two-dimensional plane, λ c is the wavelength of the incident wave. In the perception process, it can be further expressed as

[0038]

[0039] Among them, A is the perception information of the incident wave of each unit on the metamaterial array. By combining the restored perception information with the existing digital signal processing algorithm, electromagnetic direction perception is realized, and its perception accuracy is as follows: Figure 3 As shown, within the range of -60° to 60° incident angle, the absolute error of its angle of arrival estimation (DOA) is less than 1°.

[0040] By designing the time coding of STCM and constructing the average phase gradient, the reflection pattern of the space-time coding metamaterial configured with STCM can be expressed as:

[0041]

[0042] Among them, is the average reflection coefficient of the metamaterial unit in the mth row and nth column. In this case, the reflected electromagnetic wave is control. Figure 4The directional diagram of the controlled electromagnetic beam of the space-time coding metamaterial configured with STCM scanning in the direction of 10° to 60° is given, which confirms that it can achieve arbitrary control of the electromagnetic beam while satisfying the perception.

[0043] In summary, the present invention provides a method for decoupling the perception and beam steering of space-time coded metamaterials. This method can simultaneously realize the perception and beam steering of electromagnetic waves without integrating external sensing devices or redesigning the metamaterial structure, which not only improves the system performance but also significantly reduces the hardware requirements. We believe that this method has broad application prospects, especially in the fields of future communication perception integration and new radar systems.

[0044] The present invention also provides a space-time coding metamaterial, which uses the above method to decouple perception and beam steering.

[0045] The above, in conjunction with the accompanying drawings, has been described in detail a perception and beam steering decoupling strategy based on space-time coding metamaterials provided by the present invention, but the present invention is not limited to the above-mentioned specific implementation manner. The above-mentioned specific implementation manner is illustrative and not restrictive. The embodiments are only for illustrating the technical ideas of the present invention and are not intended to limit the scope of protection of the present invention. Under the enlightenment of the present invention, those of ordinary skill in the art may make changes in the specific implementation manner and scope of application. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for decoupling perception and beam steering based on spatiotemporal coding metamaterials, characterized in that: By designing a space-time coding matrix and loading it onto the space-time coding metamaterial using a digital control circuit, the incident electromagnetic waves can be controlled without the need to integrate additional sensing devices or perform special structural design, thereby achieving simultaneous perception of the incident electromagnetic field and beam manipulation.

2. A method for decoupling perception and beam steering based on spatiotemporal coding metamaterials as claimed in claim 1, characterized in that: The space-time coding metamaterial is a three-layer periodically arranged structure, the top layer of which includes two feed lines connected to each other by irregular hexagonal patches through two PIN diodes; the middle layer is an F4B substrate; and the bottom layer is an unetched metal plane. The hexagonal patch is connected to the bottom layer through holes, serving as analog and digital grounding. By applying voltage to both ends of the two PIN diodes to turn the diodes on or off, the equivalent capacitance, resistance and inductance parameters of the spatiotemporal encoding metamaterial unit can be adjusted, thereby changing the electromagnetic response characteristics of the unit. By independently controlling the on and off of the two PIN diodes, the reflection coefficient of the unit has four states, the reflection amplitudes of the four states are the same, and the phases between adjacent states show a phase difference of 90°.

3. The method for decoupling perception and beam steering based on spatiotemporal coding metamaterials according to claim 1, characterized in that: The space-time coding matrix STCM is expressed as: Where t0 and L represent the time interval and total length of the time-varying coding sequence of each unit, respectively, MN (t0) is the coding reflection coefficient of the M-th row and N-th column unit in the space-time coding metamaterial at time t0; the horizontal axis of STCM is the spatial domain, which represents the distribution of coding states between different metamaterial units in the same time slot; the vertical axis is the time domain, which represents the coding state of each metamaterial unit in different time slots.

4. The method for decoupling perception and beam steering based on spatiotemporal coding metamaterials according to claim 3, characterized in that: The horizontal axis of STCM is the coding sequence of different units on the space-time coding metamaterial in the same time slot. The rows are linearly independent, that is, they are linearly independent spatial codes in different time slots, satisfying the generalized inverse STCM of STCM. -1 Conditions of existence.

5. The method for decoupling perception and beam steering based on spatiotemporal coding metamaterials according to claim 3, characterized in that: The vertical axis of STCM is the time-varying coding sequence of each unit on the spatiotemporal coding metamaterial, which represents the form of the time-varying coding vector stcv: stcv=[Γ 11 (t) Γ 12 (t) ... Γ MN (t)] where Γ MN (t) is the time-varying coding sequence function of the Mth row and Nth column in the spatiotemporal coding metamaterial. The average complex reflection coefficient of the time-varying coding sequence in time is expressed as in is the average reflection coefficient of the metamaterial unit in the mth row and nth column, Γ mn (lt0) is the reflection coefficient of the lth time slot in the time-varying coding sequence. By designing the length of the corresponding coding sequence and the corresponding coding, we can obtain any synthetic reflection coefficient. The time-varying coding vector stcv is expressed as a spatial coding vector scv:

6. The method for decoupling perception and beam steering based on spatiotemporal coding metamaterials according to claim 1, characterized in that: After the incident electromagnetic wave is modulated by different units of the space-time coding metamaterial according to the STCM period, its reflected electromagnetic field is sampled by the far-field antenna according to the modulation interval, and its sampling information is expressed as in It is represented as the information collected by the far-field antenna at time t0, and then its perception information is restored by the following formula: A=SΤCΜ -1 ·F where A=[a 11 ,a 12 ,...,a mn ] T is the perceptual information acquired by the metamaterial, a mn is the perception information of the unit in the mth row and nth column.

7. The method for decoupling perception and beam steering based on spatiotemporal coding metamaterials according to claim 1, characterized in that: The scattering pattern of the space-time coded metamaterial is expressed as: in is the far-field pattern of the m-th row and n-th column unit at the incident frequency; θ and are elevation and azimuth respectively; d x and d y are the meta-atom periods in the x and y directions, λ c is the wavelength of the incident electromagnetic wave; is the average reflection coefficient of the metamaterial unit in the mth row and nth column, calculated from STCM; By adjusting and optimizing the time-varying coding sequence of each unit, arbitrary amplitude and phase can be formed on the metasurface, thereby manipulating electromagnetic waves.

8. A space-time coded metamaterial, characterized in that: The method described in any one of claims 1 to 7 is used to decouple perception and beam steering.

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