Wireless holographic imaging method based on polarization and beam multiplexing deantenna

Abstract

The application belongs to the field of communication, and specifically discloses a wireless holographic imaging method based on polarization and beam multiplexing / demultiplexing antennas. The method is aimed at the multi-mode echo phenomenon existing in active wireless detection, and proposes to use polarization and beam multiplexing / demultiplexing antennas to realize multi-mode fusion and achieve far-field three-dimensional holographic imaging from the perspective of communication. Different polarizations and / or different beam forms are mixed under the compact structure of the antenna while maintaining high isolation. Based on the electromagnetic inverse scattering theory, the mode matching of the transmitting end multiplexing antenna, the receiving end demultiplexing antenna and the multi-mode echo is carried out, and the polarization and beam multiplexing / demultiplexing is realized by jointly using the transmitting end and receiving end antennas. The multi-mode echo is interpreted by the metasurface of the receiving end. Scattering models are established for different application scenarios, and the sparse Bayesian learning method and the deep learning method based on multi-mode information fusion are used to realize wireless far-field hologram reconstruction, and high-resolution, high-precision three-dimensional reconstruction images are obtained.

Description

Technical Field

[0001] This invention belongs to the field of communications, and particularly relates to a wireless holographic imaging method based on polarization and beam multiplexing demultiplexing antennas. Background Technology

[0002] In the face of various complex environments and harsh weather conditions, wireless far-field imaging has multiple echo modes due to scattering and various effects. Traditional imaging methods cannot receive complete information, resulting in low imaging resolution, accuracy, or rich details. Holographic imaging is needed.

[0003] In radio holographic imaging, much research focuses on near-field microwave holographic imaging, while far-field microwave holographic imaging is less studied. Far-field radio imaging largely relies on the Doppler effect and primarily targets moving targets for 3D imaging, such as Synthetic Aperture Radar (SAR) and Inverse Synthetic Aperture Radar (ISAR). For far-field imaging of static targets or environments, ultra-wideband antennas are typically used to improve resolution.

[0004] However, achieving high resolution by increasing bandwidth will introduce more noise power and raise the issue of increasing isolation within the broadband bandwidth. Summary of the Invention

[0005] The purpose of this invention is to provide a wireless holographic imaging method based on polarization and beam multiplexing demultiplexing antennas, aiming to solve the technical problems mentioned in the background art.

[0006] To achieve the above objectives, the present invention provides the following technical solution.

[0007] A wireless holographic imaging method based on polarization and beam multiplexing demultiplexing antennas, the wireless holographic imaging method comprising:

[0008] For wireless far-field active imaging, polarization and beam multiplexing and demultiplexing antennas are designed from a communication perspective. The multiplexing antenna serves as the transmitting antenna of the imaging system, and the demultiplexing antenna serves as the receiving antenna.

[0009] Both the transmitting and receiving antennas are metasurface antenna structures with a multi-layer structure design.

[0010] Perform mode matching on the transmitting antenna, receiving antenna, and multi-mode echo;

[0011] Holographic 3D image reconstruction is performed using a two-dimensional reconstruction algorithm based on multi-modal sparse Bayesian learning with multi-modal information fusion and a three-dimensional reconstruction algorithm based on deep learning.

[0012] Furthermore, the demultiplexing and multiplexing antennas used at the transceiver end of the imaging system achieve multi-mode mixing with different polarizations and / or different beamforms within the same frequency band.

[0013] Furthermore, the metasurface antenna comprises a multi-layered folded transmissive metasurface and a feed antenna at the bottom layer, with an air gap layer between them and their geometric centers aligned.

[0014] Furthermore, the pattern matching uses a matching tracking algorithm that combines ray tracing and orthogonal polarization matching to distinguish different echo signals corresponding to the transmitting end at the receiving end based on the orthogonality of the polarization or mode of the electromagnetic waves transmitted by the transmitting antenna.

[0015] Furthermore, the two-dimensional reconstruction algorithm based on multi-mode sparse Bayesian learning processes and reconstructs each echo based on the multi-mode, multi-channel echo and the scattering model.

[0016] Furthermore, the input for the 3D reconstruction is the previously reconstructed multi-channel 2D image. The 3D reconstruction algorithm mainly relies on a multi-stage, multi-level deep network, while maintaining low algorithm complexity and improving the real-time performance and rapid imaging of the reconstruction algorithm.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0018] First, this invention uses a metasurface antenna as both a transmitting multiplexing antenna and a receiving demultiplexing antenna. The antenna features diverse polarization and beamform combinations, making it adaptable to various harsh environments. The antenna can excite and generate orthogonal modes, maintaining high isolation between different modes, and performs mode matching for transmitted and received electromagnetic waves, enabling precise decoding.

[0019] Second, based on the fusion and processing of multi-mode echo information, this invention can achieve higher resolution wireless far-field three-dimensional holographic imaging; based on sparse Bayesian learning and deep learning methods, a balance is achieved between algorithm complexity and imaging accuracy. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention.

[0021] Figure 1 This is a diagram showing the composition and operation of the wireless holographic imaging system based on polarization and beam multiplexing demultiplexing antenna of the present invention.

[0022] Figure 2 This is a flowchart of the multi-mode fusion three-dimensional reconstruction processing of the present invention.

[0023] exist Figures 1-2In the diagram: 1 is a polarization and beam multiplexing metasurface transmitting antenna; 2 is a polarization and beam demultiplexing metasurface receiving antenna; 3 is a metasurface; 4 is a feed antenna; 5 is a receiving channel; 6 is the transmitting wave; 7 is the receiving echo; 8 is the detection target. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0025] Currently, in the face of problems and demands in the wireless field such as scarce spectrum resources, limited channel capacity, miniaturization, and integration, multiplexing and demultiplexing antenna electrical parameters from a communication perspective can help realize far-field holographic imaging under the above constraints.

[0026] Far-field holographic imaging, as an important application of electromagnetic inverse scattering theory, can simultaneously perform high-resolution three-dimensional geometric imaging, physical imaging, and detection of targets, thus having significant applications in geophysical exploration and environmental monitoring. However, due to the complexity of scenes and targets, the large number of unknowns, ill-conditioned inversion processes, and the existence of diffraction limits, problems remain. Many researchers have explored imaging methods and reconstruction algorithms such as high-resolution, high-contrast, and subwavelength imaging. Among these, reconstruction algorithms involve how to obtain reliable information about the same scene from multiple different images, which determines the final image quality.

[0027] In terms of imaging antenna structure design, planar, compact structures for polarization and beam multiplexing / demultiplexing antennas are easily integrated with current systems. However, within a limited volume, there are trade-offs in maintaining high isolation and high performance when mixing two or more electrical parameters. Combining the polarization and beam domains, multiplexing or demultiplexing multiple polarizations and beamforms within a single antenna for multimode fusion imaging to obtain environmentally adaptable microwave holographic imaging has become an option. Various methods exist for this, such as using vortex wave antennas carrying orbital angular momentum (OAM); using reflective metasurfaces, transmissive metasurfaces, folded metasurfaces, etc., to obtain the desired polarization and beamforms. Combining various applications, using metasurface technology for fine information interpretation is a very promising holographic imaging method. This invention will propose a new method in one aspect.

[0028] The specific implementation of the present invention will be described in detail below with reference to specific embodiments.

[0029] Traditional wireless far-field imaging methods typically employ forward-looking imaging using information from multiple spatial locations and angles. However, high-resolution, high-precision far-field holographic imaging requires significantly more information, involving the resolution of electromagnetic inverse scattering problems. Solving these inverses involves high-dimensional matrix operations, leading to increased computational complexity.

[0030] like Figures 1-2 As shown, in this embodiment of the invention, a wireless holographic imaging method based on a polarization and beam multiplexing demultiplexing antenna is provided. The method includes the following steps:

[0031] For wireless far-field active imaging, polarization and beam multiplexing and demultiplexing antennas are designed from a communication perspective. The multiplexing antenna serves as the transmitting antenna of the imaging system, and the demultiplexing antenna serves as the receiving antenna.

[0032] Both the transmitting and receiving antennas are metasurface antenna structures with a multi-layer structure design.

[0033] Perform mode matching on the transmitting antenna, receiving antenna, and multi-mode echo;

[0034] Holographic 3D image reconstruction is performed using a two-dimensional reconstruction algorithm based on multi-modal sparse Bayesian learning with multi-modal information fusion and a three-dimensional reconstruction algorithm based on deep learning.

[0035] Furthermore, in this embodiment of the invention, the demultiplexing and multiplexing antennas used at the transceiver end of the imaging system achieve multi-mode mixing with different polarizations and / or different beamforms within the same frequency band.

[0036] Furthermore, in this embodiment of the invention, the metasurface antenna comprises a multi-layered folded transmissive metasurface and a feed antenna at the bottom layer, with an air gap layer between them and their geometric centers aligned.

[0037] Furthermore, in this embodiment of the invention, the pattern matching uses a matching tracking algorithm that combines ray tracing and orthogonal polarization matching. Based on the orthogonality of the polarization or mode of the electromagnetic waves transmitted by the transmitting antenna, different echo signals corresponding to the transmitting end are distinguished at the receiving end.

[0038] Furthermore, in this embodiment of the invention, the two-dimensional reconstruction algorithm based on multi-mode sparse Bayesian learning processes and reconstructs each echo in combination with a scattering model according to multi-mode and multi-channel echoes.

[0039] Furthermore, in this embodiment of the invention, the input for the three-dimensional reconstruction is the previously reconstructed multi-channel two-dimensional image. The three-dimensional reconstruction algorithm mainly relies on a multi-stage, multi-level deep network, while maintaining low algorithm complexity and improving the real-time performance and rapid imaging of the reconstruction algorithm.

[0040] This invention designs polarization and beam multiplexing and demultiplexing antennas, where the multiplexed antenna serves as the transmitting antenna of an active imaging system, and the demultiplexing antenna serves as the receiving antenna. Both transmitting and receiving antennas are metasurface antenna structures employing a multi-layer design. Ray tracing combined with orthogonal polarization matching is used for transmitting and receiving wave and multi-mode echo matching. A multi-mode information fusion strategy is employed, using a sparse Bayesian learning algorithm for 2D image reconstruction and a deep learning method for 3D reconstruction.

[0041] This invention designs polarization and beam multiplexing / demultiplexing antennas. It performs electromagnetic wave mode matching by combining transmitted wave and received multimode echo characteristics. It also performs two-dimensional and three-dimensional image reconstruction based on sparse Bayesian learning and deep learning methods.

[0042] In this embodiment of the invention, the multiplexing and demultiplexing antenna is a metasurface antenna, and its metasurface is a multi-layered folded transmission metasurface.

[0043] In this embodiment of the invention, based on the orthogonality of the polarization or mode of the electromagnetic waves transmitted by the transmitting antenna and the presence of multi-mode echo characteristics at the receiving end, a matching tracking algorithm combining ray tracing and orthogonal polarization matching is used to distinguish the different mode echo signals corresponding to the transmitting end at the receiving end.

[0044] In this embodiment of the invention, a two-dimensional image reconstruction algorithm based on sparse Bayesian learning is used to reconstruct each echo in two dimensions using a corresponding scattering model. Based on the reconstructed two-dimensional images, a three-dimensional reconstruction is performed using deep learning methods, and then the images are fused and reconstructed to obtain a three-dimensional holographic image. A balance between the complexity of the reconstruction algorithm and the performance achieved is considered.

[0045] The designed imaging system mainly uses a polarization and beam demultiplexing antenna 2 at the receiving end to receive multi-mode echo signals 7 from different directions. By combining the spatial domain, angular domain and polarization domain, and through information fusion, it achieves high-resolution and high-precision far-field holographic imaging.

[0046] The multi-mode fusion far-field holographic imaging method primarily utilizes a polarization and beam multiplexing antenna 1 at the transmitting end and a demultiplexing antenna 2 at the receiving end. Through the superposition and processing of multi-dimensional signals, more information is extracted to achieve high-resolution holographic imaging. It mainly employs a metasurface structure 3 to achieve fine interpretation of multiple modes, performing orthogonal mode matching on electromagnetic waves transmitted 6 and received 7 in different modes. Electromagnetic waves of different polarizations, directions, and modes are captured from the echoes, obtaining information at different levels for fusion imaging. Its system composition and working schematic diagram are shown below. Figure 1 As shown.

[0047] The transmitting antenna 1 uses a metasurface 3 to perform wavefront transformation on the transmitted wave, modulating the wavefront phase, and generating electromagnetic waves 6 with specific wavefront shapes to achieve far-field high-resolution holographic imaging. Special wavefront shapes, such as vortex waves, may carry more detailed feature information about the target when they are scattered after illuminating the target 8, while traditional plane waves do not have this function.

[0048] Holographic information interpretation primarily relies on demultiplexing antenna 2, a multi-port planar antenna structure that achieves holographic imaging by fusing multi-mode information received from multi-port 5. The multi-port antenna is integrated with metasurface 3 to generate a polarization and beam demultiplexing antenna, with a multi-port feed antenna 4 at the bottom and a multi-layered folded transmissive metasurface structure 3 at the top. By combining metasurface technology, multilayer technology, parasitic elements, and ground-radiated modes, the polarization and beam demultiplexing antenna simultaneously possesses characteristics such as high port isolation and a compact structure. An air gap layer exists between the feed antenna 4 and the metasurface 3. The feed antenna 4 can generate beams of different directions with linear or circular polarization to excite the metasurface. Electromagnetic waves are converted by the metasurface to obtain corresponding polarization and beamforms. The feed antenna can be designed as a broadband / multi-band multi-port antenna structure, including broadband linear or circular polarization. Based on the metasurface conversion, the information carried by different polarizations and beamforms is transmitted to different ports 5, and holographic imaging is achieved by fusing the information received from different ports.

[0049] The pattern matching process combines ray tracing methods with the correspondence between pairs of orthogonal vector polarizations. Appropriate mixing of orthogonal vector polarizations can also yield circular polarization, and further multimode formation and synthesis can generate electromagnetic waves in spiral or vortex states, as well as multi-beam and wide-beam configurations. Far-field holographic imaging involves electromagnetic inverse scattering. Based on multimode fusion, how to effectively utilize the information carried by each mode echo in far-field holographic imaging will involve pattern matching between different polarizations, different beam shapes, and multimode echoes of multiplexed / demultiplexed antennas 1 and 2 at the transceiver end. In the pattern matching process, the relationship between "complementarity" and "fusion" will be involved. Different modes are matched with different channels. Based on the scattering field in wireless far-field imaging, corresponding equations can be established to express the obtained beam shape. Corresponding to the imaging receiver, the transverse electromagnetic wave propagating along the z-direction can be represented by the electromagnetic wave model of the received wave by equation (1).

[0050]

[0051] Where F() represents the scattering function, E mode k represents the echo of each mode. x k y This represents the transverse wave vector relative to the propagation direction. For different echo modes and application scenarios, corresponding scattering models or scattering model libraries are established to facilitate 2D image reconstruction and adaptive image reconstruction.

[0052] The flowchart of 3D reconstruction processing is as follows Figure 2 As shown. First, a scattering model corresponding to different modes is established, and two-dimensional images are reconstructed for different channels. The two-dimensional images obtained from multiple channels are further reconstructed and fused to obtain a three-dimensional holographic image. During this process, image registration between different images will be performed. Based on the actual received multi-mode data, the corresponding algorithm is used for reconstruction. The selected algorithm needs to take into account both processing accuracy and computational efficiency. Two-dimensional reconstruction will be performed using the sparse Bayesian learning algorithm, and three-dimensional image reconstruction will be performed based on the deep learning method. The two-dimensional image reconstruction is as shown in Equation (2).

[0053]

[0054] Where S echo (l) represents the echo signal, σ m S is the target scattering coefficient vector. ref Let N be the reference signal matrix for the imaging plane, and N be the noise. Considerations include increasing information acquisition and improving isolation during the imaging process. Wireless far-field holographic image 3D reconstruction algorithms are highly dependent on multi-modal fusion mechanisms and matching mechanisms, which significantly impact the final imaging quality.

[0055] The deep learning-based methods used in 3D reconstruction balance processing performance and computational complexity when selecting network architectures. Supervised learning methods generally offer better results. Suitable network options include Transformers and Generative Adversarial Networks (GANs). The application framework can be TensorFlow, PyTorch, MindSpore, etc. Because training on datasets containing tens of thousands of images is required, the computational demands on the computer's GPU and memory are typically high.

[0056] As a preferred approach, a hybrid method is an option to balance processing accuracy and computational efficiency, and a semi-supervised learning method can be used when necessary.

[0057] In summary, this invention proposes a method for far-field holographic imaging based on polarization and beam multiplexing / demultiplexing antennas. The multiplexed antenna serves as the transmitting antenna in an active imaging system, while the demultiplexed antenna serves as the receiving antenna. From a communication perspective, antenna electrical parameter multiplexing and demultiplexing are proposed, thereby improving integration and channel capacity. A metasurface antenna is used as the structure for both multiplexing and demultiplexing antennas; the metasurface is a folded transmission metasurface. To address the multi-mode echo phenomenon in wireless far-field detection, a ray tracing combined with orthogonal polarization mode matching method is used for multi-mode matching. For the high-resolution holographic imaging problem, this invention proposes a sparse Bayesian learning method based on multi-mode information fusion and a deep learning method to reconstruct two-dimensional and three-dimensional holographic images.

[0058] Although embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. It can be applied to various fields suitable for the present invention. Other modifications can be readily made by those skilled in the art. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details and examples shown and described herein.

Claims

1. A wireless holographic imaging method based on polarization and beam multiplexing and demultiplexing antennas, characterized in that: For wireless far-field active imaging, polarization and beam multiplexing and demultiplexing antennas are designed from the perspective of communication, wherein the multiplexing antenna serves as the transmitting antenna of the imaging system, and the demultiplexing antenna serves as the receiving antenna; The multi-port antenna is a metasurface antenna structure designed with a multi-layer planar structure; The demultiplexing and multiplexing antennas used at the transmitting and receiving ends of the imaging system realize multi-mode mixing of different polarizations and / or different beam shapes in the same frequency band; Mode matching is performed on the transmitting antenna, the receiving antenna, and the multi-channel echo; The mode matching uses a matching pursuit algorithm of ray tracing plus orthogonal polarization matching, and according to the orthogonality of the polarization or mode of the electromagnetic wave transmitted by the transmitting antenna, the corresponding receiving end distinguishes different echo signals corresponding to the transmitting end; A two-dimensional reconstruction algorithm based on multi-mode sparse Bayesian learning and a three-dimensional reconstruction algorithm based on deep learning are used for adaptive reconstruction of holographic three-dimensional images. The formula for two-dimensional image reconstruction is: ； wherein is the echo signal, is the target scattering coefficient vector, is the reference signal matrix of the imaging plane, and N is the noise.

2. The wireless holographic imaging method based on polarization and beam multiplexing demultiplexing antenna according to claim 1, characterized in that, The metasurface antenna includes a multi-layer structure of folded transmission-type metasurfaces and a feed antenna at the bottom layer, with an air gap layer between them and geometric centers aligned.

3. The wireless holographic imaging method based on polarization and beam multiplexing demultiplexing antennas according to claim 2, characterized in that, The two-dimensional reconstruction algorithm based on multi-mode sparse Bayesian learning adaptively processes and three-dimensionally reconstructs each echo in combination with different scattering models based on multi-mode and multi-channel echoes.

4. The wireless holographic imaging method based on polarization and beam multiplexing demultiplexing antenna according to claim 3, characterized in that, The input of the three-dimensional reconstruction is the multi-channel two-dimensional images reconstructed in the foregoing.

5. The wireless holographic imaging method based on polarization and beam multiplexing demultiplexing antenna according to claim 4, characterized in that, Multi-channel information is derived from electromagnetic echoes of different polarizations, different wavefront shapes, and different beam directions.

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