Ultra-wideband polarization reconfigurable metasurface antenna applied to full-polarization ground penetrating radar

Abstract

The invention discloses an ultra-wideband reconfigurable polarization metasurface antenna which is used for acquiring complete polarization information of an underground target. The metasurface can accurately change the polarization mode of receiving and transmitting electromagnetic waves of the fully-polarized ground penetrating radar by adjusting the on-off state of the diodes, and can realize complex antenna configuration of the fully-polarized ground penetrating radar and perform in-situ detection of an underground target under the condition that the number of antennas is not increased or the positions of the antennas are not changed. By performing Fouli polarization synthesis on four different polarization information of a target object, the complete polarization ground penetrating radar has the characteristics of high resolution, accurate positioning and the like on underground target imaging. Based on the characteristics, the full-polarization ground penetrating radar detection system is constructed in combination with the metasurface, rapid and accurate detection in different polarization modes can be carried out, polarization attribute information of a target can be obtained, and the imaging quality is improved. Therefore, in the field of full-polarization ground penetrating radar detection, the metasurface with the characteristics of miniaturization and light weight can provide a solution with low cost, light weight and high degree of freedom.

Description

Technical Field

[0001] The present invention relates to the technical field of ground penetrating radar, and in particular to an ultra-wideband reconfigurable polarization conversion metasurface applied to ground penetrating radar. This metasurface can flexibly convert the polarization state of transmitted / received electromagnetic waves within a wide frequency band range, which is used to improve the imaging quality of ground penetrating radar and is suitable for full-polarization detection of complex underground targets. Background Art

[0002] Ground penetrating radar is a non-destructive testing tool widely used in fields such as geological exploration, engineering inspection, underground pipeline detection, and archaeology. It obtains the characteristics of underground targets by transmitting electromagnetic waves into the ground and receiving the reflected echo signals. Most traditional ground penetrating radar systems use single-polarization antennas for detection and can only obtain reflected signals in a single polarization direction. For underground targets, especially long strip targets such as pipelines, the lack of single-polarization detection information often leads to inaccurate target identification.

[0003] To overcome the limitations of single-polarization ground penetrating radar, researchers have successively proposed a variety of multi-polarization detection methods. The most common scheme is to change the polarization direction by rotating the antenna to obtain data of multiple polarization combinations. However, this method has significant deficiencies.

[0004] Complex and time-consuming measurement: This method requires multiple adjustments of the antenna position to obtain data of different polarization modes, increasing the measurement time and the complexity of the experiment, and requires a large operating space, making it unable to adapt to applications in narrow environments.

[0005] Poor data consistency: During the process of rotating the antenna multiple times, it is difficult to ensure the complete consistency of the antenna position, resulting in poor coherence of the data under different polarization states, thus affecting the analysis of the polarization characteristics of the target and the detection accuracy.

[0006] Another scheme is to obtain multi-polarization information through antennas with different polarization combinations, such as dual-polarization systems and full-polarization systems. The dual-polarization system uses two groups of antennas arranged in different directions to simultaneously obtain data in two polarization directions, while the full-polarization system alternately transmits and receives orthogonally polarized electromagnetic waves through two groups of transmitting and receiving antennas at different time points to obtain the full-polarization information of underground targets. However, these schemes also have many deficiencies.

[0007] System complexity and high cost: The dual-polarization or full-polarization system requires adding multiple sets of antennas and supporting receiving devices, significantly increasing the complexity, cost, and volume of the system, and it is difficult to meet the application requirements of portability and lightweight.

[0008] Data consistency problem: Due to the differences between the positions of multiple antennas, it is difficult to guarantee the coherence of the multi-polarization data obtained, affecting the analysis effect of the polarization characteristics of the target object.

[0009] Therefore, in the prior art, there is still a lack of a ground penetrating radar solution that can achieve full-polarization in-situ detection without increasing the number of antennas, with a compact system structure.

[0010] The present invention provides an ultra-wideband reconfigurable polarization conversion metasurface antenna to solve the above deficiencies of existing ground penetrating radar systems. Compared with existing single-polarization and mechanically rotating antenna solutions, the present invention realizes rapid electrical adjustment of the polarization state by using switching diodes, achieving dynamic reconfiguration of the polarization state. The present invention has the following advantages.

[0011] The system is simpler and more compact: The present invention switches the polarization state electronically, without mechanical rotation or increasing the number of antennas, significantly reducing the structural complexity of the system and facilitating deployment and operation in practical applications.

[0012] High data consistency: Since the polarization conversion of the present invention is achieved through electronic adjustment without physical position changes, consistent data acquisition conditions can be maintained during multiple measurements, improving the coherence of the measurement data and the analysis accuracy of the target polarization characteristics.

[0013] More efficient and convenient operation: By controlling the bias voltage of the switching diode, the present invention can quickly switch the polarization state, significantly reducing the operation time compared to mechanically rotating antennas and improving the overall measurement efficiency.

[0014] Low cost and high adaptability: Compared with full-polarization systems that require multiple sets of antennas, the present invention uses a single metasurface to achieve full-polarization conversion, avoiding the need to add additional antennas and receiving devices, reducing the overall system cost, and being more suitable for lightweight and portable application scenarios.

[0015] The ultra-wideband reconfigurable polarization conversion metasurface antenna of the present invention can achieve efficient polarization conversion in the frequency range of 1.60 GHz to 3.24 GHz, significantly improving the imaging quality and target detection accuracy of the ground penetrating radar, and is particularly suitable for target recognition and positioning in complex underground environments. Summary of the Invention

[0016] The present invention aims to solve problems in traditional ground penetrating radar systems such as single polarization form, polarization switching relying on mechanical rotation structures, high system complexity, slow response speed, and difficulty in achieving real-time dynamic adjustment. It provides an ultra-wideband reconfigurable polarization conversion metasurface antenna for ground penetrating radar, which can flexibly adjust the polarization state of electromagnetic waves in a wide frequency band to improve the detection accuracy and imaging quality of the ground penetrating radar system, and is particularly suitable for multi-polarization detection of complex underground targets.

[0017] The object of the present invention is achieved by the following technical solutions:

[0018] The ultra-wideband reconfigurable polarization conversion metasurface consists of a top-layer metal grating, a middle-layer metasurface integrated with switching diodes, a bottom-layer metal grating, and two polymethyl methacrylate substrates respectively placed between the top layer and the middle layer, and between the bottom layer and the middle layer. The metal gratings of the top layer and the bottom layer are perpendicular to each other, enabling the electromagnetic wave to be selectively adjusted in polarization state when passing through; the middle layer realizes flexible conversion of the polarization state by integrating switching diodes.

[0019] The ultra-wideband reconfigurable polarization conversion metasurface antenna consists of a transmitting antenna, a receiving antenna, and a metasurface. By controlling the bias voltage of the switching diode, the polarization direction of the electromagnetic wave can be adjusted, enabling free switching between four polarization combinations: "horizontal transmission - horizontal reception", "horizontal transmission - vertical reception", "vertical transmission - horizontal reception", and "vertical transmission - vertical reception".

[0020] The ultra-wideband reconfigurable polarization conversion metasurface antenna of the present invention can achieve full-polarization detection of underground targets by integrating it with a ground-penetrating radar system. The built ground-penetrating radar system can ensure that the electromagnetic wave polarization conversion efficiency remains at a high level under the condition of a frequency range from 1.60 GHz to 3.24 GHz. Compared with the existing single-polarization ground-penetrating radar system, the present invention has the following remarkable advantages:

[0021] Reduced number of antennas: The present invention adjusts the polarization state electronically, avoiding mechanical rotation and multiple antenna configurations, realizing dynamic reconfiguration of electromagnetic wave polarization, and significantly reducing the complexity and operation difficulty of the system.

[0022] Improved detection accuracy and efficiency: Through the combination of four polarization modes: "horizontal transmission - horizontal reception", "horizontal transmission - vertical reception", "vertical transmission - horizontal reception", and "vertical transmission - vertical reception", rich target polarization information can be obtained, significantly improving the detection accuracy of the ground-penetrating radar, especially in the identification and positioning of underground targets under complex geological conditions.

[0023] The beneficial effects of the present invention are reflected in the following aspects:

[0024] The present invention provides a novel ultra-wideband reconfigurable polarization conversion metasurface antenna, which has a simple and compact structure and can meet the detection requirements of the ground-penetrating radar for complex underground targets.

[0025] The present invention realizes dynamic reconfiguration of the polarization state through electronic adjustment of the switching diode, and can obtain detection information of multiple polarization modes without mechanical operation, greatly improving the operation convenience.

[0026] Combined with the ground penetrating radar system, the present invention can maintain stable polarization conversion characteristics in a wide frequency band range from 1.60 GHz to 3.24 GHz, so as to obtain high-quality target imaging effects under different environments and conditions. Brief Description of the Drawings

[0027] Figure 1 It is a structural block diagram of the integrated metasurface for the ground penetrating radar system. This figure shows the connection relationship between the metasurface, the transmitting antenna, the receiving antenna and the full-polarization GPR host, and illustrates the signal transmission path and working principle of the system.

[0028] Figure 2 It is a schematic diagram of the composition of the ultra-wideband reconfigurable polarization conversion metasurface structure of the present invention. This figure shows the various components of the metasurface, including the top metal grating, the metasurface integrated with switching diodes in the middle layer, the bottom metal grating and two polymethyl methacrylate substrates.

[0029] Figure 3 It is a top view of the front of each layer of the metasurface unit structure. This figure respectively shows the geometric arrangement of the top and bottom metal gratings, as well as the layout structure of the integrated switching diodes in the middle layer.

[0030] Figure 4 It is a schematic diagram of the polarization conversion principle of the metasurface. This figure shows how to achieve the change of the polarization state of electromagnetic waves by controlling the bias voltage of the switching diode, so as to realize the switching between the polarization modes of "horizontal transmission - horizontal reception", "horizontal transmission - vertical reception", "vertical transmission - horizontal reception" and "vertical transmission - vertical reception".

[0031] Figure 5 It is a comparison diagram of the underground target scanning imaging results in different polarization modes. This figure shows the imaging results in the polarization modes of "horizontal transmission - horizontal reception", "horizontal transmission - vertical reception", "vertical transmission - horizontal reception" and "vertical transmission - vertical reception", and further improves the imaging quality through Pauli polarization decomposition. Detailed Description of the Invention

[0032] The following will make further detailed descriptions in conjunction with the drawings and embodiments.

[0033] Integrate the metasurface of the present invention between the transmitting antenna and the receiving antenna to construct a full-polarization ground penetrating radar system, as Figure 1 shown. The system consists of: a transmitting antenna, a receiving antenna, an ultra-wideband reconfigurable polarization conversion metasurface, a ground penetrating radar host and a polarization control system. The transmitting antenna is used to transmit electromagnetic waves, which are radiated to the underground target after the polarization state is converted by the metasurface, and the receiving antenna is used to receive the echo signals reflected from the target. Figure 3Shows the overall connection relationship between the metasurface and the system, and illustrates the electromagnetic wave transmission path and working principle.

[0034] Figure 2 Shows the structural composition of the metasurface, including the top metal grating, the metasurface integrated with switching diodes in the middle layer, the bottom metal grating, and two polymethyl methacrylate substrates. The metal gratings on the top and bottom are arranged in perpendicular directions to control the polarization states in different directions, while the polarization state is dynamically adjusted through the bias voltage of the switching diodes in the middle layer.

[0035] Figure 3 Is a top view of the front of each layer of the metasurface unit structure, showing the geometric arrangement of the top and bottom metal gratings and the layout structure of the integrated switching diodes in the middle layer. These geometric arrangements are designed to improve the polarization conversion efficiency of the metasurface and ensure efficient polarization control of electromagnetic waves in a wide frequency band. The operating frequency range of the system is from 1.60 GHz to 3.24 GHz. The reflected echo signals are collected by a vector network analyzer, and the computer system performs polarization decomposition and imaging processing on these signals.

[0036] Figure 4 Is a schematic diagram of the polarization conversion principle of the metasurface. This figure shows how to achieve the change of the polarization state of electromagnetic waves by controlling the bias voltage of the switching diodes, so as to achieve " The switching between the polarization modes of "horizontal transmission - horizontal reception", "horizontal transmission - vertical reception", "vertical transmission - horizontal reception", and "vertical transmission - vertical reception". Specifically, when the switching diode is in the "on" state, the metasurface realizes the conversion of the polarization of electromagnetic waves, for example, converting a horizontally polarized wave into a vertically polarized wave; while when the switching diode is in the "off" state, the polarization state of the input wave remains unchanged.

[0037] In this embodiment, an underground target scanning imaging experiment is carried out to verify the detection performance of the metasurface in different polarization modes. Figure 5 Shows the imaging results in " The four polarization modes of "horizontal transmission - horizontal reception", "horizontal transmission - vertical reception", "vertical transmission - horizontal reception", and "vertical transmission - vertical reception". The imaging quality is further improved through Pauli polarization decomposition. The results show that compared with the traditional single - polarization ground - penetrating radar, the ground - penetrating radar system of the present invention can obtain more target information in different polarization modes, improving the imaging quality and target positioning accuracy.

[0038] In this embodiment, the metasurface used adopts an F4B dielectric substrate and polymethyl methacrylate material, with a compact overall structure, low manufacturing cost, and is easy to integrate into the existing ground penetrating radar system. By reducing mechanical rotation and the number of antennas, the present invention significantly reduces the volume and complexity of the detection system, and has good practicability and economy.

[0039] The application of this embodiment shows that the ultra-wideband reconfigurable polarization conversion metasurface can effectively improve the detection accuracy and imaging effect of underground targets through various polarization combinations under complex geological conditions, and is especially suitable for scenarios with complex underground structures or uncertain directions of buried targets, having broad engineering application prospects.

[0040] Although the present invention has been described in detail with general descriptions and specific embodiments above, based on the present invention, some modifications or improvements can be made, which are obvious to those skilled in the art. Therefore, these modifications or improvements made without departing from the spirit of the present invention all fall within the scope of protection required by the present invention.

Claims

1. An ultra-wideband reconfigurable polarization conversion metasurface antenna for fully polarized ground penetrating radar, which is characterized by a simple structure, no need for multiple antennas or complex system design, and a consistent phase center. The antenna can flexibly realize any combination of the four polarization modes of "horizontal transmission-horizontal reception", "horizontal transmission-vertical reception", "vertical transmission-horizontal reception" and "vertical transmission-vertical reception", meeting the detection needs of the fully polarized ground penetrating radar system in a complex underground environment.

2. The ultra-wideband reconfigurable polarization-converting metasurface antenna according to claim 1, comprising: Traditional butterfly antennas as the transmitting and receiving ends respectively, and an ultra-wideband reconfigurable polarization conversion metasurface for achieving polarization conversion or maintenance.

3. The ultra-wideband reconfigurable polarization conversion metasurface according to claim 1, characterized in that: A switching diode is arranged on the metasurface to control its working state, switching between "on" and "off", so as to realize polarization conversion of ultra-wideband incident electromagnetic waves or maintain co-polarization transmission.

4. The ultra-wideband reconfigurable polarization conversion metasurface according to claim 1 is composed of a five-layer structure, wherein: The top layer is a metal grating parallel to the y-axis to filter the cross-polarized waves caused by multiple refractions; The middle layer is a reconfigurable metasurface integrated with a switching diode, which can achieve polarization retention or conversion by changing the switching state of the diode; The bottom layer is a metal grating parallel to the x-axis; Two polymethyl methacrylate substrates are respectively placed between the top layer and the middle layer, and between the bottom layer and the middle layer, to achieve better impedance matching and broaden the working bandwidth.

5. The substrate adopts a hybrid structure of acrylic plate and F4B material, and has a relatively large overall thickness, so as to achieve ultra-wideband electromagnetic response performance, thereby supporting broadband operation in multiple polarization modes.

6. The ultra-wideband reconfigurable polarization conversion metasurface according to claim 1, characterized in that: The metal gratings on the top layer and the bottom layer are parallel to different polarization directions respectively, so as to reduce the cross-polarization electromagnetic waves caused by the target reflection.

7. The fully polarized ground penetrating radar antenna according to claim 4, characterized in that: The metasurface achieves rapid switching of the polarization mode of electromagnetic waves by controlling the working state of the switching diode, and can maintain stable polarization conversion characteristics in the range of 1.60 GHz to 3.24 GHz.

8. The fully polarized ground penetrating radar antenna according to claim 4, characterized in that: The system uses the Pauli polarization decomposition method to process the collected multi-polarization echo signals to improve the imaging quality of underground target detection.

9. A method for using the ultra-wideband reconfigurable polarization conversion metasurface according to claim 1, characterized in that: The method comprises the following steps: controlling the bias voltage of the switching diode to adjust the polarization state of the metasurface; Transmitting horizontally polarized electromagnetic waves; receiving an echo signal; The received signals are subjected to Pauli polarization synthesis to obtain complete polarization information of underground targets.

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