Dual-band high-gain metasurface antenna for radar imaging

Abstract

The invention provides a dual-band high-gain metasurface antenna for radar imaging, which comprises a metasurface layer, a first dielectric layer, a microstrip patch layer, a second dielectric layer and a grounding layer which are sequentially arranged from top to bottom, a gap which is the same as the diagonal line of the patch group is etched on the rectangular patch on the diagonal line of the patch group; wherein the microstrip patch layer comprises an SIW cavity and a feeder line located at the bottom of the SIW cavity, and a metal surface at the top of the SIW cavity is a top microstrip patch containing a T-shaped power divider; sIW array through holes and a center short-circuit through hole group are formed in the area, corresponding to the microstrip patch layer, of the second dielectric layer, and the antenna has the advantages of wide bandwidth, high gain, low side lobe and good out-of-band rejection effect and is suitable for high-speed communication and target detection of radar imaging.

Description

Technical Field

[0001] The present invention relates to the field of antenna design, and particularly to a dual-band high-gain metasurface antenna for radar imaging. Background Art

[0002] As a key component for transmitting and receiving electromagnetic waves in a radio system, the performance of an antenna plays a decisive role in the overall quality of communication and detection systems. With the development of radar technology towards high resolution and high precision, especially in complex application scenarios such as autonomous driving, security monitoring, and aerospace, higher requirements are put forward for the imaging clarity, target recognition ability, and environmental adaptability of radar imaging systems. However, traditional radar antennas still have obvious deficiencies in terms of working bandwidth, gain, beam control ability, and structural compactness, severely restricting the further improvement of system performance.

[0003] Metasurface (MTS), as a two-dimensional electromagnetic functional material composed of periodic or aperiodic artificially designed microstructural units, has received extensive attention in recent years in the fields of radar imaging, stealth technology, communication systems, etc. due to its high flexibility in regulating the phase, amplitude, polarization, and direction of electromagnetic waves. By precisely designing the metasurface unit structure, functions such as beam scanning, wavefront control, gain enhancement, and bandwidth expansion can be achieved, thus providing a new solution for high-performance radar imaging systems.

[0004] Substrate Integrated Waveguide (SIW) technology, as a feeding structure that combines the advantages of traditional metal waveguides and microstrip circuits, has significant advantages such as low loss, high quality factor, easy integration and manufacturing, and has gradually become an ideal transmission method in the new generation of high-frequency communication and radar systems. Combining SIW technology with the metasurface structure can not only effectively improve the radiation efficiency and frequency band performance of the antenna, but also optimize the compactness and integration of the antenna structure, meeting the requirements of radar imaging for miniaturization and high performance.

[0005] The patent with the publication number "CN118137116A" discloses a substrate integrated cavity metasurface antenna. This antenna combines a substrate integrated cavity and a metasurface structure to achieve multimode resonance and uses SIW as the feeding structure, thereby improving the bandwidth and gain of the antenna. However, the structure of the upper substrate integrated cavity and the lower SIW in this solution increases the complexity of the antenna. The patent with the publication number "CN116365251A" discloses a millimeter-wave dual-band circularly polarized metasurface antenna based on substrate integrated waveguide feeding. This antenna combines a metasurface and a SIW dual-band T-slot antenna. The SIW slot antenna is used as the excitation structure to excite the characteristic modes of the metasurface to achieve the dual-band effect. However, etching slots on the SIW will not introduce new SIW resonance modes, and the resonance points of the SIW are limited by the cavity size, making it difficult to excite the characteristic modes of the metasurface in a wide frequency band, resulting in a narrow bandwidth and low gain of the antenna. Summary of the Invention

[0006] The purpose of the present invention is to provide a dual-band high-gain metasurface antenna for radar imaging, which has a wide bandwidth, high gain, low side lobes, and good out-of-band rejection effect, and is suitable for high-speed communication and target detection in radar imaging.

[0007] To achieve the above objectives, the present technical solution provides a dual-band high-gain metasurface antenna for radar imaging, which includes a metasurface layer, a first dielectric layer, a microstrip patch layer, a second dielectric layer, and a ground layer arranged in sequence from top to bottom. The metasurface layer is a patch group composed of multiple rectangular patches arranged in a rhombus shape, and slots identical to the diagonal of the patch group are etched on the rectangular patches located on the diagonal of the patch group. The microstrip patch layer includes a SIW cavity, a feeder line at the bottom of the SIW cavity, and the metal surface at the top of the SIW cavity is a top microstrip patch containing a T-type power divider. SIW array vias and a central short-circuit via group are provided in the area corresponding to the microstrip patch layer on the second dielectric layer.

[0008] Compared with the prior art, the present technical solution has the following characteristics and beneficial effects: The dual-band high-gain metasurface antenna for radar imaging achieves breakthroughs in wide bandwidth, high gain, compact structure, and anti-interference ability through the innovative integration of metasurface and SIW technologies. It significantly improves the communication efficiency and target detection accuracy of the radar imaging system, and has strong engineering application value. The dual-band high-gain metasurface antenna for radar imaging has wide bandwidth and high gain characteristics, meeting the requirements of complex scenarios: through the collaborative design of the metasurface layer (including rectangular patches of different sizes) and the SIW structure, broadband operation is achieved in two frequency bands of 7.4 - 9.4 GHz and 13.3 - 14.6 GHz, covering the common high and low frequency bands of radar, and is suitable for multi-scenario target detection and communication; the in-band gain reaches 5.4 - 8.2 dBi (low frequency band) and 5.6 - 8.2 dBi (high frequency band), significantly improving the energy radiation efficiency compared with traditional antennas and enhancing the radar's detection ability for long-distance targets. At the same time, it also has the advantages of excellent radiation performance and strong anti-interference ability: the main polarization pattern presents sharp beams at 8.4 GHz and 14.0 GHz, with significant sidelobe suppression effect, reducing environmental clutter interference and improving the radar imaging resolution; the cross-polarization pattern shows low polarization leakage to ensure the purity of signal transmission, suitable for radar communication scenarios sensitive to polarization. Brief Description of the Drawings

[0009] Figure 1 is a schematic structural diagram of a dual-band high-gain metasurface antenna for radar imaging designed by the present invention.

[0010] Figure 2 is a schematic structural diagram of the metasurface layer of a dual-band high-gain metasurface antenna for radar imaging designed by the present invention.

[0011] Figure 3 is a schematic structural diagram of the microstrip patch layer of a dual-band high-gain metasurface antenna for radar imaging designed by the present invention.

[0012] Figure 4 is a side view of a dual-band high-gain metasurface antenna for radar imaging designed by the present invention.

[0013] Figure 5 is a rear view of a dual-band high-gain metasurface antenna for radar imaging designed by the present invention.

[0014] Figure 6 is a top view of a dual-band high-gain metasurface antenna for radar imaging designed by the present invention.

[0015] Figure 7 is a modal significance MS curve graph of the characteristic modes of a dual-band high-gain metasurface antenna for radar imaging designed by the present invention at low and high frequencies.

[0016] Figure 8 These are the surface current distribution diagrams of eight characteristic modes of a dual-band high-gain metasurface antenna for radar imaging designed by the present invention.

[0017] Figure 9 This is the input impedance Z11 of a dual-band high-gain metasurface antenna for radar imaging designed by the present invention.

[0018] Figure 10 This is the SIW resonant electric field without microstrip patches of a dual-band high-gain metasurface antenna for radar imaging designed by the present invention.

[0019] Figure 11 This is the SIW resonant electric field with microstrip patches of a dual-band high-gain metasurface antenna for radar imaging designed by the present invention.

[0020] Figure 12 This is the surface current on the metasurface of resonant modes Z1 and Z2 of a dual-band high-gain metasurface antenna for radar imaging designed by the present invention.

[0021] Figure 13 This is the return loss S11 and gain curve graph of a dual-band high-gain metasurface antenna for radar imaging designed by the present invention.

[0022] Figure 14 This is the co-polarization and cross-polarization radiation patterns of a dual-band high-gain metasurface antenna for radar imaging designed by the present invention at 8.4 GHz and 14.0 GHz.

[0023] In the accompanying drawings: 10 - metasurface layer, 11 - patch group, 111 - rectangular patch, 20 - first dielectric layer, 30 - microstrip patch layer, 31 - feeder line, 32 - top microstrip patch, 33 - SIW cavity, 40 - second dielectric layer, 41 - central shorting via group, 42 - SIW array via, 50 - ground layer. Detailed implementation manners

[0024] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art belong to the scope of protection of the present invention.

[0025] Those skilled in the art should understand that in the disclosure of the present invention, the orientation or positional relationship indicated by the terms "longitudinal", "transverse", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, the above terms should not be construed as limiting the present invention.

[0026] Embodiment 1 This solution provides a dual-band high-gain metasurface antenna for radar imaging, including: A metasurface layer 10, a first dielectric layer 20, a microstrip patch layer 30, a second dielectric layer 40, and a ground layer 50 arranged in sequence from top to bottom. The metasurface layer 10 is a patch group 111 composed of a plurality of rectangular patches 111 arranged in a rhombus shape. Slots identical to the diagonal of the patch group 111 are etched on the rectangular patches 111 located on the diagonal of the patch group 111. The microstrip patch layer 30 includes a SIW cavity 33, a feeder line 31 located at the bottom of the SIW cavity 33, and the metal surface at the top of the SIW cavity 33 is a top microstrip patch 32 including a T-shaped power divider. SIW array vias 42 and a central short-circuit via group 41 are provided in the area of the second dielectric layer 40 corresponding to the microstrip patch layer 30.

[0027] The dual-band high-gain metasurface antenna for radar imaging in this solution combines SIW and MTS technologies, and can achieve a dual-band effect of wide bandwidth and high gain in two frequency bands of 7.4 - 9.4 GHz and 13.3 - 14.6 GHz. The in-band gain is 5.4 - 8.2 dBi and 5.6 - 8.2 dBi, with excellent performance, and is suitable for high-efficiency communication and target detection in radar imaging systems.

[0028] Specifically, as Figure 2 shown, regarding the metasurface layer 10 of the dual-band high-gain metasurface antenna for radar imaging in this solution: The metasurface layer 10 of this solution is located at the center of the first dielectric layer 20, and the metasurface layer 10 is arranged in an interleaved direction with the first dielectric layer 20. In other words, the first dielectric layer 20 is designed in a rectangular shape, the rhombus sides of the patch group 11 of the metasurface layer 10 are set at an inclined angle with the rectangular sides of the first dielectric layer 20, and the center of the patch group 11 overlaps with the center of the first dielectric layer.

[0029] In the metasurface layer 10 of this solution, adjacent rectangular patches 111 are arranged at intervals, and the distance between the rectangular patches 111 in the same row is the same as that between the rectangular patches 111 in adjacent rows, and the distance between the rectangular patches 111 in the same column is the same as that between the rectangular patches 111 in adjacent columns. Thus, vertical and horizontal slits that intersect perpendicularly are formed on the patch group 11. Specifically, the horizontal slits on the patch group 11 are parallel to the horizontal sides of the patch group 11, and the vertical slits on the patch group 11 are parallel to the vertical sides of the patch group 11.

[0030] In some specific embodiments, the widths of the horizontal and vertical slits are the same, both being 0.5 mm.

[0031] Furthermore, the rectangular patches 111 on the patch group 11 of this solution are axisymmetric with respect to the central position of the patch group 11. Specifically, the rectangular patches 111 on the patch group 11 are symmetric both vertically and horizontally with respect to the central position of the patch group 11.

[0032] It should be noted that slits identical to the diagonal of the patch group 111 are etched on the rectangular patches 111 located on the diagonal of the patch group 11. The advantage of this is that it can reduce the interference of the magnetic current caused by the vertically symmetric structure, which helps to adjust the phase control and beamforming characteristics of the antenna and enhance the radiation performance of the antenna.

[0033] In some embodiments, the rectangular patches 111 located on the diagonal of the patch group 11 are at the center of the excitation structure, and the thickness of the etched slits is 0.5 mm, which is used to truncate the magnetic current in order to reduce the interference brought by the vertically symmetric structure, thereby helping to optimize the phase control and beamforming characteristics of the antenna and further enhancing the radiation performance of the antenna.

[0034] In some embodiments, the rectangular patch 111 is rectangular.

[0035] In a specific embodiment, the patch group 11 is composed of 4×4 rectangular patches 111 arranged in a rhombus shape. At this time, each row of the patch group 11 consists of 4 rectangular patches 111, and each column of the patch group 11 also consists of 4 rectangular patches 111.

[0036] In order to ensure that the metasurface layer 10 can excite characteristic modes in two frequency bands, namely low frequency and high frequency, the side length a and the spacing b of the rectangular patches 111 of this solution need to satisfy the following formula: 3*a + 2*b = 1.5λ, where λ is the wavelength corresponding to the operating frequency.

[0037] In addition, the rectangular patches of the patch group 11 of this solution include first rectangular patches, second rectangular patches, and third rectangular patches with unequal sizes, and the sizes of the first rectangular patch P1, the second rectangular patch P2, and the third rectangular patch P3 are different.

[0038] In a specific embodiment of this solution, the first rectangular patch P1 and the third rectangular patch P3 are squares, and the second rectangular patch P2 is a rectangle with a length side equal to the side length of the first rectangular patch P1 and a width side equal to the side length of the third rectangular patch P2.

[0039] In some embodiments, the side length of the first rectangular patch P1 is 5 - 8 mm and is used to excite the characteristic modes in the low-frequency band; the side length of the third rectangular patch P3 is 3 - 4 mm, and the third rectangular patch P3 and the first rectangular patch P1 that is cut together excite the characteristic modes in the high-frequency band; the second rectangular patch P2 can excite a strong surface current in both the low-frequency band and the high-frequency band, and the second rectangular patch P2 plays a role in balancing the low-frequency and high-frequency in the frequency band transition.

[0040] Preferably, the side length of the first rectangular patch P1 is 6 mm, and the side length of the third rectangular patch P3 is 4 mm.

[0041] In some embodiments, multiple third rectangular patches are arranged in the exact center of the patch group 11 to form a small square, four first rectangular patches are arranged at the four corner positions of the patch group 11, and multiple second rectangular patches are arranged between the third rectangular patches and the first rectangular patches. In the structure as Figure 2 shown, four third rectangular patches are arranged in the exact center of the patch group 11 to form a small square, four first rectangular patches are arranged at the four corner positions of the patch group 11, and eight second rectangular patches are arranged between the third rectangular patches and the first rectangular patches.

[0042] In some embodiments, the metasurface layer 10 is made of copper.

[0043] This solution effectively reduces energy loss and simplifies the design and implementation of the antenna by adjusting the placement angle of the metal patches 111 of the metasurface layer 10 and its design structure. In addition, the rotational placement and slotting design of the metasurface layer 10 can effectively adjust the electric and magnetic field distributions, thereby achieving a more uniform radiation performance and lower reflection loss.

[0044] Regarding the first dielectric layer 20 of this solution: The first dielectric layer 20 of this solution is used to physically support the metasurface layer 10. In some embodiments, the first dielectric layer 20 is a dielectric substrate of Rogers RT3003 with low-loss characteristics in high-frequency transmission, and the thickness is 2.28 mm to support the structure of the metasurface layer and ensure the stability and efficient transmission of the antenna.

[0045] A SIW structure is formed among the microstrip patch layer 30, the second dielectric layer 40, and the ground layer 50 of this solution. The SIW structure is used to couple and excite the characteristic modes of the metasurface layer 10 to form the antenna operating frequency band. The SIW structure is a structure that combines traditional metal waveguide technology with integrated circuit technology. It can effectively transmit electromagnetic waves and has the characteristics of smaller size and low loss. Designing the electric field resonance mode of the SIW is to excite specific characteristic modes (ResonantMode) on the metasurface, thereby realizing the control and modulation of electromagnetic waves.

[0046] Regarding the microstrip patch layer 30 of this solution: As Figure 4 and Figure 6 shown, the top microstrip patch 32 is placed at the center position of the patch group 11 of this solution to effectively couple and excite the characteristic modes of the patch group 11, improving the coupling efficiency and radiation performance of the antenna. Specifically, the top microstrip patch 32 is correspondingly arranged at the gap of the diagonal line of the patch group 11, and the symmetry center of the top microstrip patch 32 corresponds to the symmetry center of the patch group 11.

[0047] As Figure 3 shown, a feeding line 31 is loaded at the bottom of the microstrip patch layer 30 of this solution to be able to efficiently transmit signals to the SIW structure. In some specific embodiments, the resistance of the feeding line 31 is 50Ω.

[0048] It should be noted that one end of the feeding line 31 is connected to the SIW cavity 33, and the other end is connected to the side of the second dielectric layer 40 to be used for feeding electrical signals through an externally connected impedance-matched SMA port. In some embodiments, the feeding line 31 is located on the central axis of the second dielectric layer 40, and the microstrip patch layer 10 is an axisymmetric design structure compared to the feeding line 31.

[0049] The top microstrip patch 32 containing a T-shaped power divider is arranged at the top of the SIW cavity 33 to achieve more precise excitation and effectively couple the energy to the metasurface layer 10. At this time, the top microstrip patch 32 containing a T-shaped power divider can be used to excite the characteristic modes of the metasurface layer 10.

[0050] In some embodiments, the SIW cavity 33 is a "concave" shape with a sunken bottom, the top microstrip patch 32 is of T-shaped design, and a T-shaped power divider is provided inside the top microstrip patch 32.

[0051] More specifically, the top microstrip patch 32 is designed in a shape where a horizontal strip patch and a vertical strip patch are arranged in a "T" shape. The horizontal strip patch is designed in a dumbbell shape with a larger width at both ends and a smaller width in the middle, and the two ends of the horizontal strip patch are transitioned to the middle through chamfers, so that the top microstrip patch 32 has a good matching effect. In some specific embodiments, the length of the horizontal strip patch of the top microstrip patch 32 is 28 mm, the width at both ends is 5 mm, and the width in the middle is 1.5 mm.

[0052] Regarding the second dielectric layer 40 of this solution: The second dielectric layer 40 is a dielectric substrate of Rogers RT3003 with a thickness of 1.52 mm. Metal vias 42 and a central shorting via group 41 are inserted on the second dielectric layer 30. The metal vias 42 and the central shorting via group 41 are connected to the ground layer 50 and the microstrip patch layer 30. These vias help optimize the transmission path of electromagnetic waves and control the resonance characteristics of the antenna through electromagnetic coupling, further improving the bandwidth performance of the antenna.

[0053] As Figure 3 and Figure 5 shown, on the second dielectric layer 40 of this solution, an SIW array via 42 and a central shorting via group 41 are provided in the area corresponding to the microstrip patch layer 30. Among them, the SIW array via 42 is arranged corresponding to the side of the SIW cavity 33, and the central shorting via group 41 is arranged corresponding to the central axis of the SIW cavity 33 and is located in the middle area of the SIW cavity 33.

[0054] In some embodiments, the central shorting via group 41 includes two vias arranged at intervals. In a specific embodiment, the radii of the two vias of the central shorting via group 41 are 0.5 mm, and the distance between the vias is 1.5 mm.

[0055] Regarding the ground layer 50 of this solution: The ground layer 50 of this solution is a grounded planar metal copper to ensure a good electromagnetic shielding effect and reduce reflection and radiation losses. It should be noted that, as Figure 4 shown, the ground layer 50 and the second dielectric layer 40 have the same size, and the size of the first dielectric layer 20 is smaller than that of the second dielectric layer 40.

[0056] In some embodiments, the overall size of the dual-band high-gain metasurface antenna for radar imaging is 42.8 mm * 33.7 mm * 3.83 mm, corresponding to the sizes of the ground layer 50 and the second dielectric layer 40. Through experimental verification, the dual-band high-gain metasurface antenna for radar imaging proposed in this solution achieves a dual-band effect of wide bandwidth and high gain in two frequency bands of 7.4 - 9.4 GHz and 13.3 - 14.6 GHz. The in-band gain is 5.4 - 8.2 dBi and 5.6 - 8.2 dBi, with excellent performance, and is suitable for efficient communication and target detection in radar imaging systems.

[0057] Embodiment 2 Performance Test of the Dual-Band High-Gain Metasurface Antenna for Radar Imaging Design the dual-band high-gain metasurface antenna for radar imaging according to Embodiment 1. The structure is as follows: Metasurface layer: The surface is composed of a patch group consisting of 4×4 rectangular patches arranged in a rhombus. The rectangular patches in the patch group are numbered P1, P2, and P3 according to their sizes. Among them, P1 and P3 are square patches with side lengths of 6 mm and 4 mm respectively. The spacing between P1, P2, and P3 is 0.5 mm. The four rectangular patches at the center of the patch group are at the center of excitation and are etched with a slit with a width of 0.5 mm. First dielectric layer: A dielectric substrate of Rogers RT3003 with low-loss characteristics in high-frequency transmission, with a thickness of 2.28 mm. Microstrip patch layer: A 50Ω feeder line is loaded at the bottom. The length of the top microstrip patch is 28 mm, the width at both ends is 5 mm, the width in the middle is 1.5 mm, and the width at both ends with different widths and the width in the middle are transitioned by chamfers.

[0058] Second dielectric layer: A dielectric substrate of Rogers RT3003 with a thickness of 1.52 mm. SIW array vias and a central short-circuit via group are provided in the area corresponding to the microstrip patch layer, and a central short-circuit via group is provided in the middle. The radii of the two vias in the central short-circuit via group are 0.5 mm, and the via spacing is 1.5 mm.

[0059] Ground layer: Copper.

[0060] The modal significance MS curve diagram of the characteristic modes of the dual-band high-gain metasurface antenna for radar imaging placed at low frequency or high frequency is as Figure 7 shown Figure 7Figure (a) shows the modal significance at low frequencies, and figure (b) shows the modal significance at high frequencies. It can be seen that the dual-band high-gain metasurface antenna for radar imaging can excite four characteristic modes at both frequency bands and has high modal significance. Therefore, it is proved that the metasurface layer of the rhombus-shaped patch group enables the dual-band high-gain metasurface antenna for radar imaging to excite characteristic modes with efficient energy coupling and radiation at different frequency bands, thus ensuring the good performance of the dual-band high-gain metasurface antenna for radar imaging within the entire operating frequency band.

[0061] The surface current distribution diagrams of the eight characteristic modes of the dual-band high-gain metasurface antenna for radar imaging are further tested as Figure 8 shown, and the current J 1, J 2, J 3 and J 4 respectively correspond to the surface currents of the four characteristic modes, namely mode 1, mode 2, mode 3, and mode 4, at 8.4 GHz. The current J 5, J 6, J 7 and J 8 respectively correspond to the surface currents of the four characteristic modes, namely mode 5, mode 6, mode 7, and mode 8, at 14.0 GHz. Specifically, the surface current distributions of modes 1 to 4 in the low-frequency band show a relatively uniform radiation pattern, while modes 5 to 8 form a more concentrated current distribution in the high-frequency band. This indicates that the dual-band high-gain metasurface antenna for radar imaging can effectively control the propagation characteristics of electromagnetic waves within different frequency bands. Moreover, the surface current distribution in the low-frequency band is relatively extensive, reflecting the radiation characteristics of the dual-band high-gain metasurface antenna for radar imaging at a larger scale. In the high-frequency band, due to the shorter wavelength, the current distribution becomes more concentrated, showing that the metasurface layer can more precisely control the radiation characteristics in the high-frequency case. Through this optimized design, the dual-band high-gain metasurface antenna for radar imaging can achieve excellent gain and beamforming capabilities in both high-frequency and low-frequency bands, meeting the requirements of the radar imaging system for wide bandwidth, high gain, and low sidelobes.

[0062] To verify the advantages of the structural design of the microstrip patch layer of the dual-band high-gain metasurface antenna for radar imaging, a SIW without a microstrip antenna is designed: the microstrip patch layer of the SIW without a microstrip antenna does not have a microstrip patch designed; a SIW with a microstrip antenna is designed: the SIW with a microstrip antenna has a microstrip patch, but the first dielectric layer and the metasurface layer are not set. The dual-band high-gain metasurface antenna for radar imaging in this solution is defined as the final antenna; the input impedances of the SIW without a microstrip antenna, the SIW with a microstrip antenna, and the final antenna are obtained as Figure 9 shown, Figure 10Electric field distribution inside the cavity of SIW without microstrip patch in four electric field resonance modes. Figure 11 The electric field distribution inside the cavity of SIW with microstrip patch in six electric field resonance modes is given. It can be seen that SIW without microstrip patch excites four electric field resonance modes, namely TE120, hybrid mode, semi-TE310 and TE320 at 8.6, 12.0, 13.2 and 14.9 GHz. Among them, TE120 is introduced by inserting a central shorting via group in the cavity, and the hybrid mode is introduced by the synthesis of TE120 and semi-TE310 electric field resonance modes. SIW with microstrip patch excites new electric field modes at 9.4 GHz and 14.2 GHz, which are introduced by the full-wavelength mode and 1.5-fold wavelength mode of the microstrip patch. The TE120, hybrid mode, semi-TE310 and TE320 excited by the SIW cavity all cause the full-wavelength or 1.5-fold wavelength electric field mode of the top microstrip patch.

[0063] The SIW structure is used to excite the characteristic modes of the metasurface layer to form the antenna operating band. Specifically, the microstrip patch with an electric field mode is used as a radiation element to excite the characteristic modes of the metasurface structure. Therefore, there is a potential operating bandwidth of the antenna between TE120 at 7.9 GHz and the full-wavelength mode at 9.4 GHz, and between semi-TE310 and TE320 at 12.4 GHz. As Figure 9 shown, the complete antenna after loading the metasurface excites two resonance modes, Z1 and Z2, at 8.2 GHz and 13.6 GHz. These two modes are introduced by the characteristic modes excited by the metasurface.

[0064] Figure 12 is the surface current on the metasurface of resonance modes Z1 and Z2. By observing the surface current, it can be seen that Z1 is the superposition of mode 3 and mode 4 in the characteristic modes, and Z2 is the superposition of mode 6 and mode 7. Since the metasurface layer is located at the center of the microstrip patch, but the lower end is affected by the edge electric field of the SIW to a certain extent, the current intensity of the lower part of the metasurface layer is relatively strong.

[0065] Figure 13 is the return loss S of the dual-band high-gain metasurface antenna for radar imaging 11 and gain curve. It can be seen that the operating bandwidth of the dual-band high-gain metasurface antenna for radar imaging is 7.4 - 9.4 GHZ and 13.3 - 14.6 GHz, the in-band gain is 5.4 - 8.2 dBi and 5.6 - 8.2 dBi, and it has the characteristics of wide bandwidth, high gain, low loss and low profile.

[0066] Figure 14The co-polarization and cross-polarization radiation patterns of the dual-band high-gain metasurface antenna for radar imaging at 8.4 GHz and 14.0 GHz are shown, demonstrating the radiation performance of the dual-band high-gain metasurface antenna for radar imaging at these two frequencies. At 8.4 GHz, the co-polarization radiation pattern exhibits obvious directivity, with high gain and low sidelobes; while the cross-polarization radiation pattern indicates good polarization performance of the antenna at this frequency and significant cross-polarization suppression effect. At 14.0 GHz, the co-polarization radiation pattern maintains a relatively consistent radiation pattern and stable gain, while the cross-polarization radiation pattern further verifies that the antenna has a low cross-polarization level.

[0067] Generally speaking, the dual-band high-gain metasurface antenna for radar imaging exhibits good directivity, polarization performance and low cross-polarization characteristics within the said frequency band, and is suitable for efficient wireless communication systems.

[0068] Those skilled in the art should understand that the technical features of the above embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope recorded in this specification.

[0069] The above embodiments only represent several implementation manners of the present application, and the description is relatively specific and detailed, but it should not be understood as a limitation to the scope of the present application. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present application, several modifications and improvements can still be made, and these all belong to the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the appended claims.

Claims

1. A dual-band high-gain metasurface antenna for radar imaging, characterized in that, Including: A metasurface layer (10), a first dielectric layer (20), a microstrip patch layer (30), a second dielectric layer (40), and a ground layer (50) are arranged in sequence from top to bottom. The metasurface layer (10) is a patch group (11) formed by arranging a plurality of rectangular patches (111) in a rhombus shape. A slit identical to the diagonal of the patch group (11) is etched on the rectangular patch (111) located on the diagonal of the patch group (11). The microstrip patch layer (30) includes an SIW cavity (33), a feeder line (31) located at the bottom of the SIW cavity (33), and the metal surface at the top of the SIW cavity (33) is a top microstrip patch (32) including a T-shaped power divider. An SIW array via hole (42) and a central shorting via hole group (41) are provided in the area of the second dielectric layer (40) corresponding to the microstrip patch layer (30).

2. The dual-band high-gain metasurface antenna for radar imaging according to claim 1, characterized in that The first dielectric layer (20) is designed in a rectangular shape, and the rhombus sides of the patch group (11) of the metasurface layer (10) are set at an inclined angle with the rectangular sides of the first dielectric layer (20), and the center of the patch group (11) overlaps with the center of the first dielectric layer.

3. The dual-band high-gain metasurface antenna for radar imaging according to claim 1, characterized in that, The adjacent rectangular patches (111) in the metasurface layer (10) are spaced apart, and the distance between the rectangular patches (111) in the same row is the same as the distance between the rectangular patches (111) in the adjacent row, and the distance between the rectangular patches (111) in the same column is the same as the distance between the rectangular patches (111) in the adjacent column.

4. The dual-band high-gain metasurface antenna for radar imaging according to claim 1, characterized in that The rectangular patches (111) on the patch group (11) are axisymmetric with respect to the center position of the patch group (11).

5. The dual-band high-gain metasurface antenna for radar imaging according to claim 1, wherein The rectangular patches of the patch group (11) include a first rectangular patch, a second rectangular patch, and a third rectangular patch with unequal sizes. The sizes of the first rectangular patch, the second rectangular patch, and the third rectangular patch are different. The first rectangular patch and the third rectangular patch are square, and the second rectangular patch is a rectangle with a length side equal to the side length of the first rectangular patch and a width side equal to the side length of the third rectangular patch.

6. The dual-band high-gain metasurface antenna for radar imaging according to claim 5, wherein The side length of the first rectangular patch is 5 - 8 mm, which is used to excite the characteristic modes in the low-frequency band. The side length of the third rectangular patch is 3 - 4 mm, and the third rectangular patch (P3) and the cut first rectangular patch jointly excite the characteristic modes in the high-frequency band.

7. The dual-band high-gain metasurface antenna for radar imaging according to claim 1, wherein The top microstrip patch (32) is placed at the center position of the patch group (11).

8. The dual-band high-gain metasurface antenna for radar imaging according to claim 1, wherein, The SIW array via holes (42) are arranged corresponding to the side of the SIW cavity (33), and the central shorting via hole group (41) is arranged corresponding to the central axis of the SIW cavity (33) and is located in the middle area of the SIW cavity (33).

9. The dual-band high-gain metasurface antenna for radar imaging according to claim 1, characterized in that The first dielectric layer (20) and the second dielectric layer (40) are Rogers RT3003 dielectric substrates, and the metasurface layer (10) and the ground layer (50) are made of copper.

10. The dual-band high-gain metasurface antenna for radar imaging according to claim 1, characterized in that, It has a dual-band effect in two frequency bands of 7.4 - 9.4 GHz and 13.3 - 14.6 GHz, with in-band gains of 5.4 - 8.2 dBi and 5.6 - 8.2 dBi, and is applied to efficient communication and target detection in a radar imaging system.

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