Antenna unit, antenna array and security inspection equipment for millimeter wave security inspection imaging

Abstract

The invention provides an antenna unit, an antenna array and security inspection equipment for millimeter wave security inspection imaging. The antenna unit is provided with a radiation end. The antenna unit includes: a horn antenna upper portion provided with a first slot thereby forming a first horn structure; the SIW-based ultra-wideband Vivaldi antenna part is arranged below the horn antenna upper part and is provided with a tapered line radiation structure, and the tapered line radiation structure is positioned below the first horn structure; the horn antenna lower part is located below the SIW-based ultra-wideband Vivaldi antenna part and is provided with a second groove and a plurality of metalized through holes formed in the two sides of the second groove; the bonding layer is positioned between the ultra wide band Vivaldi antenna part based on the SIW and the lower part of the horn antenna; and the base is positioned below the lower part of the horn antenna. The antenna unit is an end-fire antenna capable of limiting the transmission direction of millimeter waves.

Description

Technical Field

[0001] The present invention relates to an antenna unit, an antenna array and a security inspection device for millimeter-wave security inspection imaging. Background Art

[0002] In existing antennas for millimeter-wave security inspection imaging, microstrip patch antennas, metal horn antennas or horn antennas using microstrip-waveguide conversion are usually adopted. However, the bandwidth of a conventional microstrip antenna is relatively narrow, which is not conducive to improving the imaging resolution. And adopting special methods (such as opening an air cavity or slot coupling feeding in the inner layer of a multilayer board, etc.) to increase the bandwidth will make the high-frequency board manufacturing process complex and not easy to process and assemble. In addition, the metal horn antenna is heavy and has high precision requirements for high-frequency processing, so the cost is high and it is not convenient for system integration. The antenna radiation direction of the microstrip-waveguide conversion horn antenna is vertical radiation, which is not suitable for a millimeter-wave security inspection imaging system requiring end-fire radiation. Summary of the Invention

[0003] The object of the present invention is to provide an antenna unit, an antenna array and a security inspection device for millimeter-wave security inspection imaging.

[0004] According to one aspect of the present invention, there is provided an antenna unit for millimeter-wave security inspection imaging. The antenna unit has a radiation end at an end in its length direction, and includes: an upper part of a horn antenna, where a first slot extending inward from the radiation end along the length direction is provided in the upper part of the horn antenna, so as to form a first horn structure; a substrate integrated waveguide (SIW)-based ultra-wideband Vivaldi antenna part, where the SIW-based ultra-wideband Vivaldi antenna part is arranged below the upper part of the horn antenna in the height direction of the antenna unit, and is provided with a tapered line radiation structure, and the tapered line radiation structure is located below the first horn structure; a lower part of the horn antenna, where the lower part of the horn antenna is located below the SIW-based ultra-wideband Vivaldi antenna part in the height direction, and is provided with a second slot extending inward from the radiation end along the length direction, and a plurality of metallized vias arranged on both sides of the second slot in the width direction of the antenna unit; an adhesive layer, where the adhesive layer is located between the SIW-based ultra-wideband Vivaldi antenna part and the lower part of the horn antenna; and a base, where the base is located below the lower part of the horn antenna in the height direction; where the second slot and the plurality of metallized vias in the lower part of the horn antenna cooperate with the base to form a second horn structure, and the second horn structure is located below the tapered line radiation structure; where the first horn structure, the tapered line radiation structure, the adhesive layer and the second horn structure cooperate to form a radiator of the antenna unit.

[0005] In an embodiment, the lower part of the horn antenna includes a multi-layer low-frequency circuit layer and low-frequency dielectric plates located between the layers of the multi-layer low-frequency circuit layer; and each layer of the low-frequency circuit layer and each layer of the low-frequency dielectric plate have hollowed-out areas corresponding to each other in shape and position, such that when the multi-layer low-frequency circuit layer and the multi-layer low-frequency dielectric plates form a stack, the hollowed-out areas of each layer together form the second slot.

[0006] In an embodiment, the first slot and the second slot have the same slot width in the width direction at the radiation end, such that the slot width defines the width dimension of the radiator; the first slot has a first slot height in the height direction, the second slot has a second slot height in the height direction, and the first slot height and the second slot height together determine the height dimension of the radiator; and wherein, the width dimension and the height dimension of the radiator are determined according to the half-power beam width of the antenna element.

[0007] In an embodiment, the width dimension of the radiator is calculated according to the following formula: ; wherein, 2θ 0.5E is the half-power beam width of the antenna element in the width direction; λ is the operating wavelength of the millimeter wave; D1 is the width dimension of the radiator; and the height dimension of the radiator is calculated according to the following formula: ; wherein, 2θ 0.5H is the half-power beam width of the antenna element in the height direction; λ is the operating wavelength of the millimeter wave; D2 is the height dimension of the radiator; and the operating wavelength of the millimeter wave is calculated according to the following formula: ; wherein, c is the speed of light, i.e., the propagation speed of the millimeter wave in vacuum; f is the frequency of the millimeter wave.

[0008] In an embodiment, the tapered-line radiation structure includes a tapered-line structure; and the first slot and the second slot have the same slot length in the length direction, wherein the slot length is consistent with the length of the tapered-line structure in the length direction, and the slot length defines the length dimension of the radiator.

[0009] In an embodiment, the SIW-based ultra-wideband Vivaldi antenna part includes two layers of high-frequency circuit layers and a high-frequency dielectric plate located between the two layers of high-frequency circuit layers, and the tapered-line structure is formed on the two layers of high-frequency circuit layers in a symmetric manner, and the size of the tapered-line structure depends on the dielectric wavelength of the high-frequency dielectric plate and the operating frequency of the antenna element.

[0010] In an embodiment, each of the two high-frequency circuit layers further includes an SIW structure adjacent to the tapered line structure; and one of the two high-frequency circuit layers located above the high-frequency dielectric substrate further includes a microstrip line transition structure adjacent to the SIW structure.

[0011] In an embodiment, the plurality of metallized vias include: a first row of metallized vias formed on one side of the second groove; and a second row of metallized vias formed on the other side of the second groove; the first row of metallized vias and the second row of metallized vias are parallel to each other, and each metallized via in the first row of metallized vias is arranged in one-to-one correspondence with each metallized via in the second row of metallized vias.

[0012] In an embodiment, each of the plurality of metallized vias is formed with a predetermined aperture to have a predetermined size; a predetermined interval is provided between two adjacent metallized vias in the plurality of metallized vias; and the predetermined size and the predetermined interval are determined according to the dielectric wavelength of the multi-layer low-frequency dielectric substrate.

[0013] In an embodiment, the following relationship is satisfied among the dielectric wavelength of the multi-layer low-frequency dielectric substrate, the predetermined size, and the predetermined interval: Vs < λg / 10 and Vd < Vs / 2, where Vs is the predetermined interval; Vd is the predetermined aperture of each metallized via; and λg is the dielectric wavelength of the multi-layer low-frequency dielectric substrate.

[0014] In an embodiment, the SIW-based ultra-wideband Vivaldi antenna portion and the adhesive layer further include a plurality of other metallized vias, and the plurality of other metallized vias and the plurality of metallized vias in the lower portion of the horn antenna are formed to correspond to each other.

[0015] In an embodiment, the first groove is a wedge-shaped groove, and the second groove is a rectangular groove.

[0016] In an embodiment, the multi-layer low-frequency circuit layer includes five low-frequency circuit layers.

[0017] According to another aspect of the present invention, there is provided an antenna array for millimeter-wave security inspection imaging, including: a plurality of transmitting antenna units for transmitting millimeter waves; a plurality of receiving antenna units for receiving millimeter waves reflected by an object to be inspected from the plurality of transmitting antenna units; wherein each of the plurality of transmitting antenna units and the plurality of receiving antenna units is an antenna unit according to an embodiment of the present invention.

[0018] According to another aspect of the present invention, there is provided a security inspection device including an antenna unit according to an embodiment of the present invention or an antenna array according to an embodiment of the present invention.

[0019] It should be understood that the content described in this part is not intended to identify the key or important features of the embodiments of the present invention, nor is it used to limit the scope of the present invention. Other features of the present invention will become easily understood through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The drawings are used to better understand the present solution and do not constitute a limitation to the present invention, where:

[0021] Figure 1 FIG. shows a perspective view of an antenna unit for millimeter-wave security inspection imaging according to an embodiment of the present invention.

[0022] Figure 2 FIG. shows a perspective view of the antenna unit with the cover removed according to an embodiment of the present invention.

[0023] Figure 3 FIG. shows a schematic structural diagram of an upper high-frequency circuit layer according to an embodiment of the present invention.

[0024] Figure 4 FIG. shows a schematic structural diagram of a high-frequency dielectric board according to an embodiment of the present invention.

[0025] Figure 5 FIG. shows a schematic structural diagram of a lower high-frequency circuit layer according to an embodiment of the present invention.

[0026] Figure 6 FIG. shows a schematic structural diagram of an adhesive layer according to an embodiment of the present invention.

[0027] Figure 7 FIG. shows a schematic structural diagram of a low-frequency circuit layer according to an embodiment of the present invention.

[0028] Figure 8 FIG. shows a schematic structural diagram of a low-frequency dielectric board according to an embodiment of the present invention.

[0029] Figure 9 FIG. shows a schematic layout diagram of a multi-layer structure included in an antenna unit according to an embodiment of the present invention.

[0030] Figures 10-11 FIG. shows a simulation result of an antenna unit obtained by modeling and simulating optimization in HFSS software according to an embodiment of the present invention.

[0031] Figure 12 FIG. shows a schematic diagram of an antenna array layout according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0032] To more clearly elaborate the purpose, technical solution and advantages of the present invention, the embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be understood that the following description of the embodiments is intended to explain and illustrate the general concept of the present invention, and should not be construed as a limitation to the present invention. In the specification and drawings, the same or similar reference numerals refer to the same or similar components or elements. For clarity, the drawings are not necessarily drawn to scale, and some well-known components and structures may be omitted in the drawings.

[0033] Unless otherwise defined, the technical terms or scientific terms used in the present invention shall have the ordinary meanings understood by those of ordinary skill in the art to which the present invention pertains. The "first", "second" and similar terms used in the present invention do not denote any order, quantity or importance, but are only used to distinguish different components. The term "a" or "an" does not exclude a plurality. The terms such as "comprising" or "including" mean that the elements or items appearing before this word cover the elements or items listed after this word and their equivalents, without excluding other elements or items. The terms such as "connected" or "coupled" do not necessarily refer to physical or mechanical connections, but may include electrical connections, whether direct or indirect. The terms such as "upper", "lower", "left", "right", "top" or "bottom" etc. are only used to represent relative positional relationships, and when the absolute position of the object being described changes, the relative positional relationship may also change accordingly. When an element such as a layer, film, region or substrate is referred to as being "on" or "under" another element, the element can be "directly" on or under the other element, or there may be intermediate elements.

[0034] Figure 1 A perspective view of an antenna unit 100 for millimeter-wave security inspection imaging according to an embodiment of the present invention is shown. Figure 2 A perspective view of the antenna unit 100 with the cover plate 10 removed according to an embodiment of the present invention is shown.

[0035] As Figures 1-2 shown, the antenna unit 100 for millimeter-wave security inspection imaging according to an embodiment of the present invention has a radiation end P. The radiation end P is located at an end of the antenna unit 100 in its length direction L. According to an embodiment of the present invention, when performing millimeter-wave security inspection imaging, the antenna unit 100 is arranged such that the radiation end P faces the object to be inspected (e.g., a human body), so that millimeter waves are radiated outward from the radiation end P of the antenna unit 100. Optionally or additionally, the radiation end P can also be used to receive signals reflected from the inspected object (e.g., a human body).

[0036] According to an embodiment of the present invention, the antenna unit 100 includes a cover plate 10, a substrate integrated waveguide (SIW)-based ultra-wideband Vivaldi antenna part 20, a lower part of a horn antenna 30, an adhesive layer 40, and a base 50.

[0037] As Figures 1-2 shown, the cover plate 10 is provided with a first groove 110 extending inward from the radiation end P along the length direction L. As an example, the first groove 110 is directly formed from the bottom of the cover plate 10 in the height direction H of the antenna unit 100, so that after the first groove 110 is formed, the first groove 110 can be directly viewed from the bottom and the radiation end P of the cover plate 10. In this way, the manufacturing of the first groove 110 can be facilitated, and the size and position of the first groove 110 can be more easily controlled. However, the embodiments of the present invention are not limited thereto. For example, the first groove 110 may not directly communicate with the outside, but may include a part of the bottom of the cover plate 10 as the bottom wall of the first groove 110. This can be selected according to specific actual needs. According to an embodiment of the present invention, the first groove 110 may constitute a first horn structure R1. In addition, the cover plate 10 may also be referred to as an upper part of a horn antenna and may form a horn antenna part together with the lower part of the horn antenna 30.

[0038] According to an embodiment of the present invention, the SIW-based ultra-wideband Vivaldi antenna part 20 may be disposed below the cover plate 10 in the height direction H of the antenna unit 100 and is provided with a tapered line radiation structure R2 located below the first horn structure R1. As an example, the SIW-based ultra-wideband Vivaldi antenna part 20 may include two layers of high-frequency circuit layers. The two layers of high-frequency circuit layers include an upper high-frequency circuit layer 201 located above in the height direction H and a lower high-frequency circuit layer 203 located below. The SIW-based ultra-wideband Vivaldi antenna part 20 further includes a high-frequency dielectric plate 202 located between the upper high-frequency circuit layer 201 and the lower high-frequency circuit layer 203.

[0039] Figure 3 FIG. shows a schematic structural diagram of the upper high-frequency circuit layer 201 according to an embodiment of the present invention. Figure 4 FIG. shows a schematic structural diagram of the high-frequency dielectric plate 202 according to an embodiment of the present invention. Figure 5 FIG. shows a schematic structural diagram of the lower high-frequency circuit layer 203 according to an embodiment of the present invention.

[0040] Combined with Figure 2 and Figures 3-5As shown, a tapered line structure 510 is formed in the upper high-frequency circuit layer 201, and a tapered line structure 520 is formed in the lower high-frequency circuit layer 203. The tapered line structure 520 is arranged in a manner symmetric to the tapered line structure 510 in the upper high-frequency circuit layer 201. As shown, the tapered line structure is generally composed of a slot line that is narrower at one end and transitions to a wider slot line at the other end. The transition of the slot line follows an exponential variation law.

[0041] Furthermore, in the width direction W of the antenna element 100, a plurality of first metallized vias 610 are provided on both sides of the tapered line structures 510 and 520. As an example, these metallized vias are arranged in two rows of metallized vias located on the left and right sides of the tapered line structure respectively. Among them, the upper high-frequency circuit layer 201 and the lower high-frequency circuit layer 203 are respectively a metal plate or a metal sheet or a metal-clad copper layer. Thus, the tapered line structure 510 of the upper metal plate, the tapered line structure 520 of the lower metal plate, and the plurality of first metallized vias 610 can constitute the tapered line radiation structure R2 included in the SIW-based ultra-wideband Vivaldi antenna portion 20. According to an embodiment of the present invention, the tapered line radiation structure R2 can play a role in radiating and guiding millimeter waves.

[0042] As Figures 3-5 shown, the upper high-frequency circuit layer 201 and the lower high-frequency circuit layer 203 are also provided with an SIW structure 2001 adjacent to the tapered line structure. Moreover, the upper high-frequency circuit layer 201 is also provided with a microstrip line transition structure 2002 adjacent to the SIW structure 2001. The lower high-frequency circuit layer 203 includes a ground layer in the corresponding area of the microstrip line transition structure 2002. The SIW structure 2001 and the microstrip line transition structure 2002 can be used to connect the antenna element 100 to the circuit board, thereby feeding the antenna element 100. In this way, by adopting the SIW structure 2001 and the microstrip line transition structure 2002, the driving circuit part can be completely isolated from the antenna element 100, so that the active chip is isolated from the antenna opening, and thus a better protection effect on the chip can be achieved, and it is also convenient for the integration of planar circuits. In addition, the port width of the microstrip line transition structure 2002 can be calculated according to the required impedance value, and the final port width size and the tapered line size can be obtained by simulation using HFSS (High-Frequency Structure Simulator) electromagnetic simulation software.

[0043] The high-frequency dielectric board 202 is arranged between the upper high-frequency circuit layer 201 and the lower high-frequency circuit layer 203, so as to be used for transmitting millimeter waves. As Figure 4As shown, the high-frequency dielectric board 202 can cooperate with two layers of antenna circuit boards to form a plurality of first metallized vias 610. In addition, as an example, the high-frequency dielectric board 202 can be a Rogers board with a thickness of 0.254 mm. Additionally, the upper high-frequency circuit layer 201 and the lower high-frequency circuit layer 203 can be formed of metal, such as formed of copper. Alternatively, it can also be a copper-clad board surface, and the metal copper skin surface can be further surface-treated to prevent copper oxidation, thereby playing a role in protection or facilitating soldering, etc. The surface-treated surface layer can be metals such as tin, gold, and silver. However, the embodiments of the present invention are not limited thereto.

[0044] As Figures 1-2 shown, the upper high-frequency circuit layer 201, the high-frequency dielectric board 202, and the lower high-frequency circuit layer 203 are stacked on top of each other, thereby constituting the SIW-based ultra-wideband Vivaldi antenna part 20. In addition, by providing the tapered line structures 510, 520 and a plurality of first metallized vias 610, a tapered line radiation structure R2 is included in the SIW-based ultra-wideband Vivaldi antenna part 20, so as to be able to achieve end-fire radiation in which the circuit feeder part is parallel to the antenna radiation direction. Generally, the SIW-based ultra-wideband Vivaldi antenna is also a typical end-fire antenna. Therefore, by making the antenna unit 100 include such an SIW-based ultra-wideband Vivaldi antenna part 20 suitable for end-fire, the antenna unit 100 can be more suitable for active high-resolution millimeter-wave security inspection equipment (for example, E-band high-resolution imaging equipment, more specifically, E-band high-resolution human body imaging equipment), thereby meeting the overall body imaging requirements.

[0045] According to an embodiment of the present invention, the lower part 30 of the horn antenna is located below the SIW-based ultra-wideband Vivaldi antenna part 20 in the height direction H, and is provided with a second slot 310 extending inward from the radiation end P along the length direction L, and a plurality of second metallized vias 620 provided on both sides of the second slot 310 in the width direction W of the antenna unit 100. As an example, as Figures 1-2 shown, the second slot 310 can be formed to penetrate the lower part 30 of the horn antenna in the height direction H. That is, the second slot 310 can be directly viewed from above and below the lower part 30 of the horn antenna. In addition, since the second slot 310 also starts from the radiation end P, the second slot 310 can also be directly viewed from the radiation end P.

[0046] The second slot 310 can be formed below the tapered line structures 510, 520, so that the plurality of second metallized vias 620 on both sides of the second slot 310 can correspond to the plurality of first metallized vias 610. For example, as Figure 1 shown, each of the plurality of second metallized vias 620 can correspond to the corresponding via among the plurality of first metallized vias 610.

[0047] Further, the antenna element 100 further includes an adhesive layer 40. Figure 6 FIG. shows a schematic structural view of the adhesive layer 40 according to an embodiment of the present invention. The adhesive layer 40 may be located between the SIW-based ultra-wideband Vivaldi antenna portion 20 and the lower portion 30 of the horn antenna, and as Figure 6 shown, the adhesive layer 40 is correspondingly formed with a plurality of metallized vias. As an example, after the SIW-based ultra-wideband Vivaldi antenna portion 20, the adhesive layer 40, and the lower portion 30 of the horn antenna are stacked on one another to form a stack, these metallized vias may be formed at a predetermined plurality of positions of the formed stack at one time by passing through the stack. Thereby, the plurality of first metallized vias 610 and the plurality of second metallized vias 620 can be made to correspond to each other.

[0048] As an example, the adhesive layer 40 may be formed of an insulating material composed of resin and fiberglass cloth, and its dielectric constant may be close to the dielectric layer in the SIW-based ultra-wideband Vivaldi antenna portion 20 and the lower portion 30 of the horn antenna.

[0049] The plurality of second metallized vias 620 may form two metal sidewalls similar to horn walls in the lower portion 30 of the horn antenna, so as to confine the millimeter wave to be transmitted between two rows of the second metallized vias 620. Thereby, the outward transmission of the millimeter wave can be effectively blocked, that is, the transmission direction of the millimeter wave is constrained. Herein, the "metallized via" may be understood as performing a metallization treatment on the inner wall of the formed via, for example, coating a metal coating, to form a shielding effect.

[0050] Further, the base 50 is located below the lower portion 30 of the horn antenna in the height direction H to form the bottom wall of the horn wall in the lower portion 30 of the horn antenna. As an example, the base 50 may be a metal base and is a simple planar base without special design. Alternatively, the base 50 may also be a printed circuit board (PCB) having a copper-clad surface to form a metal surface without necessarily being formed of a metal material. According to an embodiment of the present invention, the base 50 may be used to form the metal bottom surface of the lower portion 30 of the horn antenna. As described above, two rows of second metallized vias 620 serving as metal sidewalls are provided on both sides of the second groove 310, so that the space of the second groove 310, the two rows of second metallized vias 620, and the base 50 cooperate to form a second horn structure R3 for outputting millimeter waves outward.

[0051] According to an embodiment of the present invention, the second horn structure R3 may be located below the first horn structure R1 and the tapered line radiation structure R2, such that the first horn structure R1, the tapered line radiation structure R2, and the second horn structure R3 may jointly form a radiator RAD at the radiation end P of the antenna unit 100. The antenna unit 100 according to the embodiment of the present invention uses the radiator RAD to radiate millimeter waves outward for security inspection imaging.

[0052] In this way, by using the tapered line radiation structure R2 to achieve the end-fire function and cooperating with the horn structure in the up and down directions to guide and confine the radiation pattern of the antenna, it is possible to effectively increase the isolation between adjacent antenna units 100, that is, reduce the mutual interference between adjacent antenna units 100. Specifically, the first horn structure R1 and the second horn structure R3 may form a function similar to that of a horn antenna, thereby providing horn walls for the radiator RAD of the antenna unit 100, such as the slot walls of the first slot 110, the slot walls of the second slot 310, and the bottom wall provided by the base 50. These horn walls cooperate with a plurality of metallized through holes to play a role in controlling and restricting the transmission direction of millimeter waves, thereby restricting the transmission of millimeter waves within a set radiation range, reducing the mutual interference between adjacent antenna units, and improving the imaging effect.

[0053] As an example, the first slot 110 may be a wedge-shaped slot, that is, formed inward in a tapered manner from the radiation end P, similar to a part of a conventional horn antenna. The second slot 310 may be a rectangular slot to facilitate preparation and processing.

[0054] In one embodiment, the lower part 30 of the horn antenna includes a multi-layer low-frequency circuit layer 301 and low-frequency dielectric plates 302 located between the layers of the multi-layer low-frequency circuit layer 301. As an example, the multi-layer low-frequency circuit layer 301 may include five low-frequency circuit layers 301, and the case of including five low-frequency circuit layers 301 will be described as an example hereinafter. However, the embodiments of the present invention are not limited thereto, and may include other numbers of layers according to actual needs. In addition, for example, the thicknesses of the respective multi-layer low-frequency circuit layers 301 in the height direction H may be equal to each other. Alternatively, for example, the thicknesses of the respective multi-layer low-frequency circuit layers 301 in the height direction H may not be equal to each other, as long as the total thickness of the multi-layer low-frequency circuit layer 301 meets the height dimension requirements of the second slot 310 in the lower part 30 of the horn antenna. The calculation of the height dimension of the second slot 310 will be described hereinafter.

[0055] Figure 7 A schematic structural diagram of a single-layer low-frequency circuit layer 301 according to an embodiment of the present invention is shown. Figure 8 A schematic structural diagram of a single-layer low-frequency dielectric plate 302 according to an embodiment of the present invention is shown. Figure 9The schematic layout diagram of the multilayer structure included in the antenna unit 100 according to an embodiment of the present invention is shown. That is, Figure 9 The schematic layout diagram of the structure of the antenna unit 100 with the cover plate 10 and the base 50 removed is shown. At this time, the antenna unit 100 includes a SIW-based ultra-wideband Vivaldi antenna part 20 composed of two layers of high-frequency circuit layers and a single layer of high-frequency dielectric board, an adhesive layer 40, and a lower part 30 of the horn antenna composed of multiple layers of low-frequency circuit layers 301 (for example, five layers of low-frequency circuit layers 301) and multiple layers of low-frequency dielectric boards 302. Therefore, the antenna unit 100 at this time includes a multilayer structure.

[0056] Although Figure 7 and Figure 8 only a single layer of low-frequency circuit layer 301 and a single layer of low-frequency dielectric board 302 are shown. It should be understood that each layer of low-frequency circuit layer 301 has the same structural layout as each other, and each layer of low-frequency dielectric board 302 also has the same structural layout as each other.

[0057] As Figures 7-8 described, the low-frequency circuit layer 301 may be formed with a first hollowed-out area 710, and the low-frequency dielectric board 302 may be formed with a second hollowed-out area 720. The first hollowed-out area 710 and the second hollowed-out area 720 may correspond to each other in shape and position, so that when the multiple layers of low-frequency circuit layers 301 and the multiple layers of low-frequency dielectric boards 302 form a stack, the alternately stacked first hollowed-out areas 710 and second hollowed-out areas 720 together form a second groove 310. As an example, in some cases, the multiple layers of low-frequency circuit layers 301 and the multiple layers of low-frequency dielectric boards 302 may be alternately stacked first, and then at a predetermined area, for example, starting from the middle of the radiation end P of the lower part 30 of the horn antenna and inward for a certain distance, the multilayer board is hollowed out simultaneously, so that hollowed-out areas are formed in each layer of low-frequency circuit layer 301 and each layer of low-frequency dielectric board 302 respectively, thereby forming the second groove 310 of the lower part 30 of the horn antenna.

[0058] As an example, the low-frequency circuit layer 301 may be formed of metal, for example, formed of copper. For example, the low-frequency dielectric board 302 may be selected as a conventional and low-cost epoxy glass cloth substrate (FR4). However, the embodiments of the present invention are not limited thereto.

[0059] In this way, by forming the lower part 30 of the horn antenna in the form of a multilayer board, it is more convenient to integrate with the backend drive transmission circuit. Since the chip circuit board is usually in a multilayer form, by forming the lower part 30 of the horn antenna as a multilayer board, it is convenient for circuit connection and wiring, so as to improve the integration degree of the antenna system and simplify the installation.

[0060] In one embodiment, the first slot 110 and the second slot 310 have the same slot width D1 in the width direction W at the radiation end P, such that the slot width D1 defines the width dimension of the radiator RAD, even though the radiator RAD has a width dimension D1. As an example, as Figure 1 shown, after forming the radiator RAD according to an embodiment of the present invention, a radiation opening of the radiator RAD may be formed at the radiation end P. Among them, the dimension of the radiation opening in the width direction W is determined by the slot width D1 of the first slot 110 and the second slot 310. As described above, the first slot 110 and the second slot 310 have the same slot width D1.

[0061] Furthermore, the first slot 110 has a first slot height H1 in the height direction H, and the second slot 310 has a second slot height H2 in the height direction H. The first slot height H1 and the second slot height H2 together determine the height dimension D2 of the radiator RAD. As described above, the radiator RAD is jointly formed by the first horn structure R1, the tapered-line radiation structure R2, and the second horn structure R3 in a stacked manner. Therefore, the height dimension D2 of the radiator RAD should include the heights of the first slot 110 and the second slot 310 and the height of the SIW-based ultra-wideband Vivaldi antenna part 20. However, usually, the thicknesses of the layers in the SIW-based ultra-wideband Vivaldi antenna part 20 are relatively thin and relatively fixed. Therefore, the height dimension D2 of the radiator RAD is mainly related to the heights of the first slot 110 and the second slot 310.

[0062] For example, the first slot height H1 and the second slot height H2 can be set to be equal to each other. Therefore, after calculating the required height dimension D2 of the radiator RAD, the first slot height H1 and the second slot height H2 can be calculated as D2 / 2 respectively. For another example, the first slot height H1 and the second slot height H2 can be set to be unequal, but as long as the sum of the first slot height H1 and the second slot height H2 is equal to the calculated height dimension D2 or the calculated height dimension D2 minus a specific value (for example, corresponding to the height of the SIW-based ultra-wideband Vivaldi antenna part 20 and the adhesive layer 40). On the other hand, the thicknesses of the layers of the multi-layer low-frequency dielectric plate 302 can be determined according to the second slot height H2. For example, the thicknesses of the layers of the multi-layer low-frequency dielectric plate 302 can be made equal to each other, so that the second slot height H2 is divided by the number of layers to calculate the thickness of each layer. For another example, the thicknesses of the layers of the multi-layer low-frequency dielectric plate 302 can be unequal, as long as the sum of the thicknesses of the layers combined with the thickness of the multi-layer low-frequency circuit layer 301 (usually relatively thin) is equal to the second slot height H2.

[0063] The width dimension D1 and the height dimension D2 of the radiator RAD can be understood as the opening aperture of the radiator RAD, and this opening aperture is usually determined by the angular spread of the antenna element 100, that is, determined by the half-power beam width of the antenna element 100. That is, the width dimension D1 and the height dimension D2 of the radiator RAD can be calculated by the half-power beam width of the millimeter wave emitted by the antenna element 100.

[0064] As an example, the width dimension D1 of the radiator RAD is calculated according to the following formula:

[0065] ;

[0066] .

[0067] where 2θ 0.5E is the half-power beam width of the antenna element 100 in the width direction W; λ is the operating wavelength of the millimeter wave; c is the speed of light, that is, the propagation speed of the millimeter wave in a vacuum, usually about 3×10 8 m / s; f is the frequency of the millimeter wave.

[0068] In addition, the height dimension D2 of the radiator RAD is calculated according to the following formula:

[0069] ;

[0070] .

[0071] where 2θ 0.5H is the half-power beam width of the antenna element 100 in the height direction H; λ is the operating wavelength of the millimeter wave; c is the speed of light, that is, the propagation speed of the millimeter wave in a vacuum, usually about 3×10 8 m / s; f is the frequency of the millimeter wave.

[0072] In one embodiment, the first slot 110 and the second slot 310 have the same slot length D3 in the length direction L, where the slot length D3 can be related to the antenna gain requirement. The slot length D3 is consistent with the lengths of the tapered line structures 510, 520 in the length direction L, and the depths of the first slot 110 and the second slot 310 formed inward from the radiation end P are determined according to the slot length D3. The slot length D3 can define the length dimension of the radiator RAD, that is, the radiator RAD has a length dimension D3.

[0073] As described above, the tapered line structures 510 and 520 are used to play roles in electromagnetic wave radiation and guiding. The tapered lines follow an exponential change law, and different radiation parts are used to transmit and receive electromagnetic waves of different frequencies. Therefore, the size of the tapered line structure is related to the operating frequency of the millimeter wave and the dielectric wavelength of the high-frequency dielectric plate 202, that is, the size of the tapered line structure (for example, the length of the tapered line structure) is determined according to the operating frequency of the millimeter wave and the dielectric wavelength of the high-frequency dielectric plate 202.

[0074] In one embodiment, as Figures 1-2 and Figures 7-8 shown, the multiple second metallized vias 620 in the lower part 30 of the horn antenna may include a first row of metallized vias 6201 formed on one side of the second groove 310 and a second row of metallized vias 6202 formed on the other side of the second groove 310. As an example, the first row of metallized vias 6201 and the second row of metallized vias 6202 are arranged parallel to each other, and each metallized via in the first row of metallized vias 6201 is arranged in one-to-one correspondence with each metallized via in the second row of metallized vias 6202. In this way, as described above, by arranging two rows of metallized vias at a certain distance, a structure similar to the horn wall can be formed, thereby restricting the transmission direction of the millimeter wave to achieve the guiding and confinement of the antenna pattern.

[0075] In one embodiment, each of the multiple second metallized vias 620 is formed with a predetermined aperture Vd, so as to have a predetermined size. In addition, the adjacent two metallized vias of the multiple second metallized vias 620 are spaced apart by a predetermined interval Vs. In this embodiment, the predetermined interval Vs can be determined according to the dielectric wavelength of the multi-layer low-frequency dielectric plate 302, and the predetermined aperture Vd can be determined, so as to determine the predetermined size.

[0076] As an example, the following relationship needs to be satisfied among the dielectric wavelength of the multi-layer low-frequency dielectric plate 302, the predetermined aperture Vd, and the predetermined interval Vs to provide sufficient shielding performance:

[0077] Vs < λg / 10 and Vd < Vs / 2,

[0078] where λg is the dielectric wavelength of the multi-layer low-frequency dielectric plate.

[0079] In one embodiment, as Figures 1-2As shown, the antenna unit 100 further includes a plurality of mounting holes 80. For example, the cover plate 10, the SIW-based ultra-wideband Vivaldi antenna part 20, the lower part of the horn antenna 30, the adhesive layer 40, and the base 50 can be mounted together by passing a mounting member through the mounting holes 80. In some cases, the SIW-based ultra-wideband Vivaldi antenna part 20, the lower part of the horn antenna 30, and the adhesive layer 40 can be pre-formed into a multi-layer circuit board structure through PCB processing, and then mounted together with the cover plate 10 and the base 50 via a mounting member.

[0080] Figures 10-11 The simulation results of the antenna unit 100 obtained by HFSS software modeling and simulation optimization according to an embodiment of the present invention are shown. Figure 10 The two-dimensional radiation pattern of the antenna center frequency point is shown, where the solid line represents phi = 0°, that is, the 3dB beam width in the height direction H reaches 63°; the dashed line represents phi = 90°, that is, the 3dB beam width in the width direction W reaches 75°. Figure 11 The port reflection coefficient S11 of the antenna is shown. When S11 < -20dB, the absolute frequency band range is 65.1GHz - 81.1GHz, and the relative bandwidth reaches 20.5%. When S11 < -15dB, the absolute frequency band range is 63.3GHz - 83.4GHz, and the relative bandwidth reaches 27.4%.

[0081] It should be noted that the expressions "height direction", "length direction", "width direction", "above", and "below" in this article are descriptions of the state in which the antenna unit 100 is placed during use.

[0082] In addition, it should be noted that the circuit layer can also be called the copper-clad layer, and the dielectric plate can also be called the substrate or the core board.

[0083] The present invention also provides an antenna array for millimeter-wave security inspection imaging, which includes: a plurality of transmitting antenna units for transmitting millimeter waves; and a plurality of receiving antenna units for receiving millimeter waves reflected by an object to be inspected and transmitted by the plurality of transmitting antennas. Each of the plurality of transmitting antenna units and the plurality of receiving antenna units is an antenna unit 100 according to an embodiment of the present invention. Figure 12 The schematic diagram of the antenna array layout according to an embodiment of the present invention is shown.

[0084] The present invention also provides a security inspection device, including the antenna unit according to an embodiment of the present invention or the antenna array according to an embodiment of the present invention.

[0085] Advantageously, the antenna unit 100 according to an embodiment of the present invention integrates the SIW-based Vivaldi antenna function and the horn antenna function. Thus, while being able to implement an end-fire antenna, it also confines the radiation direction of millimeter waves, resulting in good isolation between adjacent antennas, facilitating the implementation of antenna array and system integration for multiple antenna units 100, and enabling the array antenna to have a relatively wide operating bandwidth, thereby being applicable to the field of security inspection imaging. In addition, the lower part of the horn antenna in the antenna unit 100 is prepared by slotting a multilayer hybrid pressure printed circuit board, making it convenient for assembly and integration with the active chip circuit. Additionally, the antenna unit 100 according to an embodiment of the present invention has low processing costs, simple assembly, and a light product weight.

[0086] It should be understood that various forms of the processes shown above can be used, with steps reordered, added, or deleted. For example, the steps recited in the present disclosure can be executed in parallel, sequentially, or in a different order, as long as the desired results of the technical solution disclosed in the present invention can be achieved, and no limitation is made herein.

[0087] The above specific embodiments do not constitute a limitation to the protection scope of the present invention. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. An antenna unit for millimeter wave security inspection imaging, the antenna unit having a radiation end located at an end in its length direction, characterized in that: include: an upper portion of the horn antenna, wherein the upper portion of the horn antenna is provided with a first slot extending inwardly from the radiation end along the length direction, thereby forming a first horn structure; An ultra-wideband Vivaldi antenna portion based on a substrate integrated waveguide, the ultra-wideband Vivaldi antenna portion based on a substrate integrated waveguide is arranged below the upper portion of the horn antenna in the height direction of the antenna unit, and is provided with a gradient line radiation structure, and the gradient line radiation structure is located below the first horn structure; A horn antenna lower portion, the horn antenna lower portion is located below the substrate integrated waveguide based ultra-wideband Vivaldi antenna portion in the height direction, and is provided with a second slot extending inwardly from the radiation end along the length direction, and a plurality of metallized through holes provided on both sides of the second slot in the width direction of the antenna unit; an adhesive layer, the adhesive layer being located between the substrate integrated waveguide based ultra-wideband Vivaldi antenna portion and the lower portion of the horn antenna; and a base, the base being located below the lower portion of the horn antenna in the height direction; The second slot in the lower part of the horn antenna and the plurality of metallized through holes cooperate with the base to form a second horn structure, and the second horn structure is located below the gradient line radiation structure; The first speaker structure, the gradient line radiation structure, the adhesive layer and the second speaker structure cooperate to form the radiator of the antenna unit.

2. The antenna unit according to claim 1, characterized in that The lower portion of the horn antenna includes a plurality of low-frequency circuit layers and a low-frequency dielectric plate located between each layer of the plurality of low-frequency circuit layers; and Each low-frequency circuit layer and each low-frequency dielectric plate has a hollow area corresponding to each other in shape and position, so that when the multiple low-frequency circuit layers and the multiple low-frequency dielectric plates form a stack, the hollow areas of each layer jointly form the second groove.

3. The antenna unit according to claim 2, characterized in that The first slot and the second slot have the same slot width in the width direction at the radiating end, so that the slot width defines the width dimension of the radiator; The first slot has a first slot height in the height direction, the second slot has a second slot height in the height direction, and the first slot height and the second slot height jointly determine the height dimension of the radiator; as well as The width dimension and the height dimension of the radiator are determined according to the half-power beam width of the antenna unit.

4. The antenna unit according to claim 3, characterized in that The width dimension of the radiator is calculated according to the following formula: ; Among them, 2θ 0.5E is the half-power beam width of the antenna unit in the width direction; λ is the operating wavelength of the millimeter wave; D1 is the width dimension of the radiator; and The height dimension of the radiator is calculated according to the following formula: ; Among them, 2θ 0.5H is the half-power beam width of the antenna unit in the height direction; λ is the operating wavelength of the millimeter wave; D2 is the height dimension of the radiator; and The operating wavelength of the millimeter wave is calculated according to the following formula: ; Among them, c is the speed of light, that is, the propagation speed of millimeter waves in a vacuum; f is the frequency of millimeter waves.

5. The antenna unit according to claim 3, characterized in that: The gradient line radiation structure comprises a gradient line structure; and The first slot and the second slot have the same slot length in the length direction, wherein the slot length is consistent with the length of the gradient line structure in the length direction, and the slot length defines the length dimension of the radiator.

6. The antenna unit according to claim 5, characterized in that The ultra-wideband Vivaldi antenna part based on substrate integrated waveguide includes two high-frequency circuit layers and a high-frequency dielectric plate located between the two high-frequency circuit layers, and The gradient line structure is formed on the two high-frequency circuit layers in a symmetrical manner, and the size of the gradient line structure depends on the dielectric wavelength of the high-frequency dielectric board and the operating frequency of the antenna unit.

7. The antenna unit according to claim 6, characterized in that The two high-frequency circuit layers further include substrate integrated waveguide structures adjacent to the gradient line structure respectively; and The high-frequency circuit layer of the two high-frequency circuit layers, which is located above the high-frequency dielectric board, also includes a microstrip line transition structure adjacent to the substrate integrated waveguide structure.

8. The antenna unit according to claim 2, characterized in that: The plurality of metallized through holes include: a first row of metallized through holes formed on one side of the second slot; and a second row of metallized through holes formed on another side of the second groove; The first row of metallized through holes and the second row of metallized through holes are parallel to each other, and each metallized through hole in the first row of metallized through holes is arranged in a one-to-one correspondence with each metallized through hole in the second row of metallized through holes.

9. The antenna unit according to claim 8, characterized in that Each of the plurality of metallized through holes is formed with a predetermined aperture to have a predetermined size; There is a predetermined interval between two adjacent metallized through holes in the plurality of metallized through holes; and The predetermined size and the predetermined interval are determined according to the dielectric wavelength of the multi-layer low-frequency dielectric plate.

10. The antenna unit according to claim 9, characterized in that The dielectric wavelength of the multilayer low-frequency dielectric plate, the predetermined size and the predetermined interval satisfy the following relationship: Vs<λg / 10 and Vd <Vs / 2, Wherein, Vs is the predetermined interval; Vd is the predetermined aperture of each metallized through hole; λg is the dielectric wavelength of the multilayer low-frequency dielectric plate.

11. The antenna unit according to claim 8, characterized in that The substrate integrated waveguide based ultra-wideband Vivaldi antenna portion and the bonding layer further include a plurality of other metallized through holes, and The plurality of other metallized through holes and the plurality of metallized through holes in the horn antenna lower portion are formed to correspond to each other.

12. The antenna unit according to any one of claims 1 to 11, characterized in that: The first groove is a wedge-shaped groove, and the second groove is a rectangular groove.

13. The antenna unit according to any one of claims 2 to 11, characterized in that: The multi-layer low-frequency circuit layer includes five low-frequency circuit layers.

14. An antenna array for millimeter wave security inspection imaging, characterized in that: The antenna array comprises: A plurality of transmitting antenna units, wherein the transmitting antenna units are used to transmit millimeter waves; a plurality of receiving antenna units, the receiving antenna units being used to receive the millimeter waves emitted by the plurality of transmitting antenna units and reflected by the inspected object; Wherein, each of the multiple transmitting antenna units and the multiple receiving antenna units is an antenna unit according to any one of claims 1-13.

15. A security inspection device, characterized in that: The security inspection device comprises the antenna unit according to any one of claims 1 to 13 or the antenna array according to claim 14.

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