A metallic cavity antenna for foreign object detection (FOD) on airport runways

Abstract

This application belongs to the field of communication equipment manufacturing technology, specifically relating to a metal cavity antenna for foreign object detection (FOD) on airport runways. It includes a radiating cavity layer, a metal waveguide feed layer, and a feed circuit transmitting / receiving layer. The radiating cavity layer is located at the top of the antenna structure and includes multiple independent radiating cavity units. Each unit is formed by a front-end, rear-end, and middle radiating cavity plate enclosing a resonant cavity structure, with a radiating channel, radiating cavity, and feed slot on its side. The metal waveguide feed layer is located below and has multiple electromagnetic coupling ports corresponding to the feed slots. The feed circuit transmitting / receiving layer has multiple radio frequency modules, with corresponding coupling ports used for radio frequency signal transmission and reception. This application solves the technical problems of insufficient detection efficiency and stability caused by the non-modularity, directional deviation, complex assembly, and poor heat dissipation of existing FOD metal cavity antenna structures. It possesses independent processing capabilities, improving assembly efficiency, heat dissipation, and detection range.

Description

Technical Field

[0001] This utility model belongs to the field of communication equipment manufacturing technology, and specifically relates to a metal cavity antenna for foreign object detection (FOD) on airport runways. Background Technology

[0002] In high-frequency communications, radar detection, and aerospace fields, metallic cavity antennas play a crucial role in the transmission and reception of millimeter-wave signals due to their excellent directivity, high gain, and low loss characteristics. Particularly in airport runway foreign object detection (FOD) systems, these antennas are widely used to construct high-resolution radar systems to achieve rapid identification and location of foreign objects (such as stones, metal fragments, bird remains, etc.), ensuring flight safety.

[0003] Traditional metal cavity antenna structures typically employ a single, integrated metal cavity, with a highly integrated radiating cavity, feeding structure, and connecting components. While this type of structure possesses a certain level of strength and enclosure, it still suffers from numerous structural defects in practical applications of FOD detection systems, limiting its system performance and engineering deployment efficiency. These defects are mainly reflected in the following aspects:

[0004] 1. Non-modular structure leads to inconvenient maintenance and poor scalability: Most existing antennas are integrally manufactured, with fixed and non-disassembleable radiating cavity structures, lacking modular design. When replacement, repair, or upgrades are needed, the entire antenna unit often requires replacement, resulting in high maintenance costs and low efficiency. Furthermore, the lack of assemblable sub-modules makes array-based expansion difficult, failing to flexibly adapt to the deployment requirements of different airport runway widths and detection areas, thus limiting the system's deployment flexibility and scalability.

[0005] 2. Insufficient structural symmetry leads to mechanical imbalance and electromagnetic directivity shift: Traditional antennas often exhibit asymmetry in their internal cavity layout, resulting in uneven structural mass distribution. This causes stress concentration and deformation in operating or vibrating environments, affecting the consistency of electromagnetic radiation directionality. For FOD systems, this directional shift reduces the accuracy and reliability of target identification, especially during wide-field-of-view runway scanning.

[0006] 3. Low integration and complex assembly affect production efficiency and consistency: In a monolithic structure, each layer of components (radiating cavity, feed layer, signal processing module) is often processed and then assembled in segments. This not only increases assembly complexity but also introduces problems such as registration errors and feed mismatches, leading to significant performance differences between different units. Furthermore, the complex assembly process restricts the rapid manufacturing and deployment capabilities of large-scale antenna systems, hindering the ability to meet the rapid deployment and operational support requirements of airport systems.

[0007] 4. Heavy weight and poor heat dissipation restrict mobile platform deployment and high-power applications: Traditional cavity structures mostly use solid metal materials, resulting in heavy weight after processing and a lack of effective lightweight structural design. This not only increases the load burden on FOD detection vehicles or track platforms but also increases operating energy consumption. Furthermore, the sealed structure is prone to localized heat accumulation, which can easily cause antenna performance degradation or signal drift in scenarios where high-power radar operates continuously, affecting system stability.

[0008] 5. Limited structural form, making it difficult to achieve precise control over electromagnetic modes and radiation patterns: Traditional radiation cavities mostly adopt regular rectangular cavity structures, which limit the distribution of standing wave fields and cause prominent near-field interference and current accumulation problems, especially in high-frequency arrays, resulting in high sidelobes, beam instability, and low coupling efficiency. This cavity structure limits the radar system's ability to distinguish targets and control radiation patterns in complex environments.

[0009] In summary, the application of existing metal cavity antenna structures in FOD detection systems is limited by a series of structural problems, such as their closed and non-removable structure, unstable directivity, and insufficient modularity and lightweight design. These limitations make it difficult to meet the comprehensive requirements of modern airports for detection accuracy, coverage, system response speed, and environmental adaptability. Therefore, there is an urgent need for a novel structural design for metal cavity antennas to achieve a modular, highly integrated, lightweight, and highly directive integrated antenna system, thereby improving the detection capability, deployment efficiency, and operational flexibility of FOD detection systems. Utility Model Content

[0010] To address the aforementioned problems, this utility model provides a metal cavity antenna for foreign object detection (FOD) on airport runways. Through a modular, lightweight, and highly integrated multi-layer structure design, it solves the problems of existing metal cavity antennas, such as difficulty in ensuring processing accuracy, inconvenient structural maintenance, poor directivity control, low material utilization, and poor system scalability.

[0011] This utility model provides a metal cavity antenna for foreign object detection (FOD) on airport runways, comprising a radiating cavity layer, a metal waveguide feed layer, and a feed circuit transmitting and receiving layer. The radiating cavity layer is located at the top of the antenna structure and includes multiple independent radiating cavity units segmented along the main electromagnetic wave beam direction. Each radiating cavity unit includes a front radiating cavity plate, a rear radiating cavity plate, and multiple middle radiating cavity plates disposed between the front and rear radiating cavity plates, which together form a closed resonant cavity structure.

[0012] One side of the radiation cavity unit is provided with multiple radiation channels, radiation cavities and feeding slots in sequence from top to bottom. The radiation channels extend downward from the top to a preset depth and have the main beam direction as the exit direction. The radiation channels are connected to the radiation cavities below them. The feeding slots are located at the bottom of the radiation cavity unit and are connected to the radiation cavities.

[0013] The metal waveguide feed layer is disposed below the radiation cavity layer, and has multiple electromagnetic coupling ports on it, each corresponding to a feed gap above it; the feed circuit transmitter-receiver layer is disposed below the metal waveguide feed layer, and has at least one radio frequency circuit device. The radio frequency circuit device has multiple radio frequency transmitter modules and / or receiver modules inside, each module corresponding to an electromagnetic coupling port in the metal waveguide feed layer, for realizing the transmission and reception of radio frequency signals.

[0014] In a preferred embodiment, one side of the rear-end radiating cavity plate and each middle radiating cavity plate is a planar structure, and the other side is provided with multiple radiating channels, radiating cavities and power feeding gap radiating structures. The radiating structures of each cavity plate are stacked in a uniform direction. Both sides of the front-end radiating cavity plate are planar structures, wherein the side facing the adjacent middle radiating cavity plate covers and closes the radiating channels, radiating cavities and power feeding gaps on the middle radiating cavity plate.

[0015] In a preferred implementation, the rear-end radiating cavity plate and the multiple middle radiating cavity plates are symmetrically arranged with two radiating cavity sub-units around their respective structural centerlines. The two radiating cavity sub-units in each cavity plate form two sets of radiating cavity sub-arrays of the radiating cavity layer after assembly.

[0016] In a preferred implementation, the rear-end radiation cavity plate, the middle radiation cavity plate, and the front-end radiation cavity plate are further provided with through-holes for weight reduction, and the weight reduction holes are located in the structural non-functional area between the two sets of radiation cavity sub-arrays.

[0017] In a preferred embodiment, the number of weight reduction holes is at least three, with one weight reduction hole located on the structural centerline of the metal cavity antenna, and the other two weight reduction holes symmetrically distributed on both sides of the structural centerline, arranged at equal intervals along the horizontal direction.

[0018] In a preferred embodiment, the three weight-reducing holes are further provided at the same positions on the rear-end radiating cavity plate, each of the middle radiating cavity plates, and the front-end radiating cavity plate, with the weight-reducing holes on each cavity plate being aligned and interconnected.

[0019] In a preferred embodiment, one side of the rear-end radiation cavity plate and the middle radiation cavity plate is provided with a concave plane region with a recessed structure, the concave plane region being used to set up the radiation channel, the radiation cavity and the power supply gap.

[0020] In a preferred embodiment, further, within the concave plane region, multiple baffles are arranged sequentially at intervals along the width direction of the plate, and the gap formed between two adjacent baffles constitutes the radiation channel.

[0021] In a preferred embodiment, the upper part of the plurality of baffles is flush with the top of the cavity plate, and the lower part of the plurality of baffles gradually decreases in length from both ends of the concave plane region toward the center, and is arranged in a symmetrical decreasing pattern.

[0022] In a preferred embodiment, the radiation cavity is located at the bottom of each baffle and has a rhomboid structure. The four sides of the rhomboid structure are formed by the bottom of multiple baffles and the two side walls of the concave plane area.

[0023] The beneficial effects of this utility model are:

[0024] First, the airport runway FOD detection metal cavity antenna of this utility model achieves a modular and hierarchical structural layout by refining the radiating cavity layer into multiple independent radiating cavity units and sequentially designing radiating channels, radiating cavities, and feed slots on its sides. Compared with the traditional integrated structure, this solution adopts segmented independent radiating cavity units, which are easy to disassemble, maintain, and replace. Different numbers and types of units can be flexibly assembled, supporting array expansion for different runway widths and detection requirements, greatly improving the flexibility and scalability of system deployment. The regularly arranged multi-unit cavity structure results in a more balanced mass and electromagnetic layout, effectively avoiding stress concentration and directional deviation problems caused by structural asymmetry, improving radar beam directivity consistency, and enhancing FOD detection accuracy and reliability. In the multi-layer structure design, the radiating layer, waveguide layer, and feed circuit layer are efficiently coupled through standard interfaces, reducing assembly errors and complexity. The radiating cavity adopts a multi-plate enclosure structure, reducing the amount of solid metal used and achieving overall weight reduction. Each independent radiating cavity unit has a directional resonant cavity design, with the radiating channel aligned with the main beam direction, enhancing the control of electromagnetic wave output.

[0025] Secondly, in the preferred implementation, the rear and middle radiating cavity plates of this utility model adopt a multi-level radiating channel, radiating cavity and feeding gap on one side, while the other side remains flat. This helps to ensure good fit and mechanical stability between the plates while maintaining the integration of electromagnetic functions. The front radiating cavity plate adopts a double-sided planar structure, and its inner side covers and seals the radiating structure of the adjacent middle cavity plate to form a complete closed cavity resonant system. This closed stacked arrangement not only improves the overall sealing and protection performance of the antenna structure and effectively prevents external interference and clutter leakage, but also enhances the resonance effect and directional control capability of the cavity. At the same time, the uniform directional sequence arrangement facilitates modular assembly and improves the structural consistency and uniformity of the radiating array.

[0026] Third, in the preferred implementation, this invention symmetrically arranges two radiating cavity sub-units around their respective structural centerlines on the rear radiating cavity plate and multiple middle radiating cavity plates, so that after assembly, each cavity plate forms two sets of sub-array layouts of the radiating cavity layer. On the one hand, this enhances the symmetry and electromagnetic consistency of the overall antenna structure, effectively reducing pattern distortion and beam offset caused by structural deviations; on the other hand, the dual-sub-array configuration improves space utilization and radiating element density, enhances the focusing capability and radiation gain of the radar beam, and helps to achieve FOD target identification with higher resolution and longer detection range.

[0027] Fourth, in the preferred implementation, this utility model provides through-holes on the rear radiation cavity plate, the middle radiation cavity plate, and the front radiation cavity plate, and arranges them in the non-functional area between the two sets of radiation cavity sub-arrays. This not only effectively reduces the weight of the overall structure and improves the lightweight level of the components, but also avoids the impact on the functional area.

[0028] Fifth, in the preferred implementation, this utility model, by setting at least three weight-reducing holes and adopting a symmetrical distribution and equidistant arrangement design, can maintain the mechanical symmetry and stability of the cavity structure and avoid deformation or performance degradation caused by uneven stress.

[0029] Sixth, in the preferred implementation, the present invention provides a concave plane area with a recessed structure on one side of the rear radiating cavity plate and the middle radiating cavity plate, which facilitates the reasonable layout of the radiation channel, radiation cavity and feed gap in the area, thereby effectively saving the overall space of the antenna structure and improving the integration between the components.

[0030] Seventh, in the preferred implementation, this utility model, by arranging multiple baffles at intervals along the width direction of the plate in the concave plane area and forming a radiation channel between adjacent baffles, can effectively guide airflow or heat radiation to be distributed in an orderly manner in the area, thereby improving ventilation or heat dissipation efficiency. The upper part of the baffles is flush with the top of the cavity plate, which is conducive to forming a uniform upper surface and enhancing the overall flatness and sealing of the structure. The design of the lower part with symmetrically decreasing length from both ends to the center helps to form a gradual channel structure and reduce flow resistance.

[0031] Eighth, in the preferred embodiment, the present invention sets the radiation cavity as a rhomboid structure located at the bottom of the baffle, and the four sides of the rhomboid structure are jointly enclosed by the bottom of all the baffles and the two side walls of the concave plane area, which can effectively form a stable and uniform radiation space. This structural design not only enhances the structural strength and airtightness of the cavity, but also helps to improve the concentration and conduction efficiency of radiation energy. Attached Figure Description

[0032] Figure 1 This is a three-dimensional structural diagram of a foreign object detection (FOD) metal cavity antenna for airport runways, according to an embodiment of the present invention.

[0033] Figure 2 This is a front view of an airport runway foreign object detection (FOD) metal cavity antenna according to an embodiment of the present invention.

[0034] Figure 3 This is a top view of an airport runway foreign object detection (FOD) metal cavity antenna according to an embodiment of the present invention.

[0035] Figure 4 An exploded view of an airport runway foreign object detection (FOD) metal cavity antenna according to an embodiment of this utility model;

[0036] Figure 5 This is a sheet structure diagram of the radiating layer structure of the airport runway foreign object detection (FOD) metal cavity antenna according to an embodiment of the present invention.

[0037] Among them, 1-radiating cavity layer; 10-rear radiating cavity plate; 11-middle radiating cavity plate; 111-feed gap; 112-bar; 113-radiation channel; 114-radiating cavity; 12-front radiating cavity plate; 13-first mounting hole; 14-weight reduction hole; 15-second mounting hole; 2-metal waveguide feed layer; 20-electromagnetic coupling port; 3-feed circuit transmit and receive layer; 30-RF circuit device. Detailed Implementation

[0038] To enable those skilled in the art to better understand the technical solutions of this application, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0039] The directional terms such as above, below, left, right, front, and back used in this application are based on the positional relationships shown in the attached drawings. Different attached drawings may result in different positional relationships, therefore they should not be interpreted as limitations on the scope of protection.

[0040] In this application, the terms "installation," "connection," "interlocking," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, an integral connection, a mechanical connection, an electrical connection, or a connection that allows communication between components. They can also refer to a direct connection or an indirect connection through an intermediate medium. They can refer to the internal connection of two components or the interaction between two components. For those skilled in the art, the specific meaning of the above terms in this application can be understood according to the specific circumstances.

[0041] This invention provides a metallic cavity antenna for foreign object detection (FOD) on airport runways. It employs a multi-layer integrated structure and a modular design, consisting of a radiating cavity layer, a metallic waveguide feed layer, and a feed circuit transmitting / receiving layer stacked sequentially from top to bottom. The radiating cavity layer comprises multiple standardized and functionally independent radiating cavity units. Each unit is assembled into a closed resonant structure via front, middle, and rear cavity boards, enabling independent fabrication, replacement, and maintenance, thus improving system assembly efficiency, reliability, and scalability. Through an arrayed arrangement of radiating units and a bidirectional electromagnetic coupling path design, the antenna achieves high directivity, high gain, and array-based transceiver functionality, supporting precise radio frequency signal input and efficient radiation, thereby enhancing the detection range, identification accuracy, and response speed of FOD targets. Combined with a robust and durable mechanical structure and lightweight optimized design, this antenna is suitable for continuous all-weather operation in the complex environment of airports, providing a high-performance, highly adaptable, easily deployable, and scalable key antenna solution for FOD detection systems.

[0042] Example 1

[0043] As per the instruction manual Figure 1-5 A metallic cavity antenna for foreign object detection (FOD) on airport runways comprises a three-layer structure stacked from top to bottom: a radiating cavity layer 1, a metallic waveguide feed layer 2, and a feed circuit transmitting / receiving layer 3. These three layers are mechanically connected to form a robust and functionally integrated antenna module.

[0044] The radiating cavity layer 1, located at the top of the antenna structure, is used to realize the spatial radiation and reception functions of electromagnetic waves. This radiating cavity layer 1 is divided into multiple independent radiating cavity units along a direction perpendicular to the main electromagnetic wave beam (i.e., perpendicular to the front and rear end faces of the radiating cavity layer 1). Each radiating cavity unit adopts a modular structure, facilitating array assembly and performance tuning.

[0045] Each radiating cavity unit includes a front-end radiating cavity plate 12 and a rear-end radiating cavity plate 10, as well as multiple structurally identical middle radiating cavity plates 11 disposed between the front-end radiating cavity plate 12 and the rear-end radiating cavity plate 10, to form a closed cavity structure with good resonance characteristics. On one side of each radiating cavity unit (i.e., the side in the direction of the main beam), three functional structures are arranged sequentially from top to bottom: multiple radiation channels 113, a radiation cavity 114, and a feed slot 111.

[0046] Multiple radiation channels 113 extend downwards from the top of one side of the radiation cavity unit to a predetermined design depth, with the main beam direction as the exit direction. The exits of the multiple radiation channels 113 together form the radiation array of the antenna, used to achieve directional electromagnetic beam transmission and reception. The radiation channels 113 are electromagnetically connected to the radiation cavity 114 below them, used to effectively couple the electromagnetic energy excited in the radiation cavity to the external space, or to guide external incident waves into the cavity, thereby supporting bidirectional transmission and reception. The radiation cavity 114 constitutes a local electromagnetic resonant unit, which enhances the local coupling efficiency, resonance intensity, and radiation directivity of electromagnetic energy in this region.

[0047] The feed slot 111 is an opening located at the bottom of the radiating cavity unit and communicates with the radiating cavity 114. It receives high-frequency electromagnetic energy introduced from the metal waveguide feed layer 2, and electromagnetically excites the radiating cavity 114 through the opening coupling. It can also receive external signals in the reverse direction. The metal waveguide feed layer 2 is located below the radiating cavity layer 1 and is used for the introduction, transmission, and power distribution of radio frequency signals. Multiple electromagnetic coupling ports 20 are provided on it, each corresponding to the feed slot 111 above it. The electromagnetic coupling ports 20 are used to inject radio frequency signals from the lower layer into the radiating cavity unit through the opening coupling and support the reverse reception of electromagnetic energy. The radiating cavity unit 1, the metal waveguide feed layer 2, and the electromagnetic coupling ports 20 together constitute a shared transmit / receive channel structure, supporting bidirectional propagation of radio frequency signals within the same channel. This allows the transmitted signal from the feed circuit to be radiated outwards, and external space signals to be introduced into the receiving module via the radiation channel, achieving integrated transmit and receive of the antenna system.

[0048] The feed circuit transmitter-receiver layer 3 is equipped with at least one radio frequency (RF) circuit device 30 for transmitting and receiving RF signals. The RF circuit device 30 is a multi-channel integrated module, internally integrating multiple independent RF transmitter and / or receiver modules. Each module corresponds to an electromagnetic coupling port 20 in the metal waveguide feed layer 2, establishing a one-to-one energy path with each radiating cavity unit. The RF circuit device 30 may also include a power supply unit, a phase-shifting modulation unit, and control circuitry for dynamic control of beam direction, power amplitude, and communication parameters.

[0049] This embodiment employs a modular radiating cavity structure and a multi-layer integrated feeding scheme. The overall structure consists of a radiating cavity layer, a metal waveguide feeding layer, and a feed circuit transmitting / receiving layer, arranged sequentially from top to bottom. Unlike the monolithic metal cavity structure in existing technologies, the radiating cavity layer is composed of multiple independently fabricated, assembled, and replaceable radiating cavity units. Each unit is assembled from a central cavity board and front and rear end boards. Efficient assembly is achieved through standardized design and array arrangement, offering advantages such as high fabrication precision, convenient maintenance, and system scalability. This antenna structure achieves precise radio frequency signal input and radiation control through the metal waveguide layer and electromagnetic coupling port, constructing a complete electromagnetic link from signal transmission, waveguide, radiation to signal reception. It also enables array-type bidirectional transmit / receive capability, making it suitable for multi-channel, high-beam-consistency millimeter-wave signal control systems. Specifically, this antenna offers the following advantages in airport runway FOD detection scenarios: its high directivity and high gain enable long-range, accurate detection of runway surface targets (such as stones, metal fragments, and animal remains); its modular array structure supports wide field-of-view coverage and zoned deployment, adapting to the deployment requirements of wide areas of airport runways; its bidirectional transceiver channels support rapid scanning and target echo reception, improving real-time detection and target recognition rates; and its robust structure and high maintainability allow for continuous all-weather operation in complex airport environments. In summary, this metal cavity antenna structure not only improves detection accuracy and efficiency but also provides a highly reliable, easily deployable, and scalable key antenna technology solution for airport FOD detection systems.

[0050] Example 2

[0051] This embodiment includes all the structures of Embodiment 1, as detailed in the appendix to the specification. Figure 1 and Figure 3 In this embodiment, one side of the rear radiation cavity plate 10 and each middle radiation cavity plate 11 is a planar structure, and the other side is provided with multiple radiation channels 113, radiation cavities 114 and power feeding gaps 111. These structures with radiation functions are stacked in a unified direction to form consistent radiation directionality and structural integrity.

[0052] Both sides of the front-end radiating cavity plate 12 are planar structures, with the side facing the central radiating cavity plate 11 covering and sealing the radiating channel 113, radiating cavity 114, and power supply gap 111 thereon. This structural design ensures that each radiating unit forms a closed and independent radiating cavity, effectively improving electromagnetic radiation efficiency and shielding characteristics.

[0053] The rear-end radiating cavity plate 10 and multiple middle radiating cavity plates 11 are symmetrically arranged with two radiating cavity sub-units around their respective structural centerlines a. A complete radiating cavity structure is formed by sequentially stacking and assembling the rear-end radiating cavity plate 10, middle radiating cavity plate 11, and front-end radiating cavity plate 12 along a unified direction. The two radiating cavity sub-units in each cavity plate, after assembly, together constitute two sets of radiating cavity sub-arrays of radiating cavity unit 1, achieving a symmetrical distribution of the array structure. This effectively improves the overall structural symmetry and mechanical balance of the system, and ensures the consistency and stability of the radiation performance.

[0054] The radiating cavity unit 1 further includes a first mounting hole 13 and a second mounting hole 15 for structural installation and positioning. The first mounting hole 13 is symmetrically arranged on both sides of the two radiating cavity sub-units of each cavity plate, penetrating the rear radiating cavity plate 10, the middle radiating cavity plate 11, and the front radiating cavity plate 12. The multi-layer structure is reliably assembled using bolts or other fastening methods, ensuring a high degree of consistency in structure and electromagnetic performance among the sub-units. The second mounting hole 15 is located at the bottom of each cavity plate and mates with the corresponding mounting hole on the metal waveguide feed layer 2. Through fitting and positioning, a stable connection is achieved between the cavity structure and the feed structure, further improving the assembly accuracy and electromagnetic coupling performance of the overall structure.

[0055] This embodiment features multiple radiation channels, radiation cavities, and feed slots arranged on the same side of the rear, middle, and front radiation cavity plates, stacked sequentially in a unified direction. Two sets of radiation cavity sub-units are symmetrically arranged around the structural centerline within each cavity plate, forming a closed, symmetrical dual-sub-array structure. This structure achieves consistency in radiation directivity and stability in radiation performance. Furthermore, the symmetrical arrangement enhances the overall mechanical balance and stability, preventing uneven stress and assembly errors caused by structural offset, and strengthening anti-interference capabilities. The two sets of radiation cavity sub-arrays enable paired collaborative operation of the radiation units, achieving wide beamwidth, high gain, and low sidelobe spatial radiation characteristics, improving the antenna system's radiation efficiency, pattern symmetry, and system performance consistency. Simultaneously, the first and second mounting holes are used for through-hole fixation of the multi-plate structure and precise alignment of the feed structure, enhancing overall assembly accuracy, electromagnetic coupling performance, and shielding effectiveness.

[0056] Example 3

[0057] In this embodiment, based on Embodiment 2, the rear radiating cavity plate 10, the middle radiating cavity plate 11, and the front radiating cavity plate 12 are provided with through-hole weight reduction holes 14. These weight reduction holes 14 are located in the non-functional area between the two sets of radiating cavity subarrays and are situated within the non-electromagnetically sensitive area of ​​the metal cavity antenna. This effectively avoids the radiating cavity elements, ensuring that the main function of the antenna is not affected while reducing the overall structural weight and improving lightweight performance.

[0058] The number of weight reduction holes 14 is at least three, one of which is located on the symmetrical center line a of the metal cavity antenna, and the other two are symmetrically distributed on both sides of the center line, and are arranged at equal distances along the horizontal direction. The overall distribution is in the shape of a triangle or equilateral triangle, so as to maintain the structural symmetry and the balance of mass distribution, while also helping to release internal stress evenly and improve mechanical stability.

[0059] Specifically, three symmetrically arranged weight-reduction holes 14 are provided at the same positions on the rear radiating cavity plate 10, each of the middle radiating cavity plates 11, and the front radiating cavity plate 12. Each hole is symmetrically arranged around the left and right symmetrical center line a of the plate. By sequentially stacking and assembling the cavity plates, the weight-reduction holes 14 on each plate form a set of longitudinally continuous weight-reduction hole channels, forming a longitudinal lightweight structure that runs through the entire radiating cavity unit 1. This reduces the overall weight of the antenna while maintaining structural strength and electrical performance stability.

[0060] The weight-reduction hole 14 structure in this embodiment effectively reduces the overall weight without weakening the structural strength by eliminating non-critical solid areas. This improves the movement efficiency of the antenna carrier (such as FOD detection vehicles / track systems), reduces installation load and energy consumption, and meets the high requirements for lightweight structures in aviation, automotive, and other applications. The weight-reduction hole penetrates the middle section, forming a heat flow channel, which helps improve air convection efficiency and reduce local temperature rise in the cavity, especially for the rapid release of heat inside the cavity under high-power operating scenarios.

[0061] Example 4

[0062] In this embodiment, based on Embodiment 2, a concave plane region with a recessed structure is provided on one side of the rear radiation cavity plate 10 and the middle radiation cavity plate 11. This concave plane region is used to set up radiation functional structures such as radiation channels 113, radiation cavities 114, and power feeding gaps 111, thereby improving structural integration and manufacturing consistency. Within the concave plane, multiple baffles 112 are arranged sequentially at intervals along the width direction of the plate. The gap between two adjacent baffles 112 forms a radiation channel 113, forming an array radiation window for effective electromagnetic wave radiation output.

[0063] The upper parts of the multiple baffles 112 are flush with the top of the cavity plate, maintaining a consistent plate height and forming a regular top plane reference, which facilitates subsequent stacking and assembly. Notably, the length of the baffles 112 gradually decreases from both ends of the concave plane region towards the center, exhibiting a symmetrical decreasing arrangement. The bottom region of the multiple baffles 112 forms a radiating cavity 114, which is a rhomboid structure. Its four sides are enclosed by the bottom of the multiple baffles 112 and the two side walls of the concave plane region. The rhomboid radiating cavity 114 is a non-rectangular, centrally symmetrical polygonal cavity in electromagnetic resonant cavities. Compared to conventional rectangular cavities, its internal boundary conditions change, resulting in a more uniform and dispersed distribution of electric and magnetic standing waves. Especially in the diagonal direction, it can form symmetrical and gradually changing electromagnetic modes, achieving better mode field distribution and coupling efficiency, and improving overall radiation efficiency. Its edge direction extends diagonally, causing the coupling path to be extended obliquely, reducing near-field coupling interference and surface current accumulation.

[0064] Each radiating cavity 114 has a feeding slot 111 directly below it, and the feeding slot 111 penetrates the bottom of the cavity plate to correspond one-to-one with the electromagnetic coupling port 20 on the metal waveguide feeding layer 2. The feeding slot 111 is used to couple and inject the electromagnetic energy in the feeding structure into the interior of the rhomboid radiating cavity to form good electromagnetic coupling.

[0065] The acute angle of the rhomboid structure of the radiation cavity 114 ranges from 45° to 65°, while the corresponding obtuse angle ranges from 115° to 135°. This angle setting facilitates the formation of an electromagnetic mode field that gradually varies along the diagonal direction, extending the coupling path and making the standing wave distribution more uniform, further optimizing the mode field characteristics and overall radiation efficiency. The radiation channel 113 between two adjacent baffles 112 serves as an electromagnetic wave radiation window, with a channel width ranging from 0.5mm to 1.2mm. This width is determined comprehensively based on the target operating frequency band, electromagnetic discharge efficiency, and array spacing. For high-frequency microwave bands (>20GHz), the lower limit width is recommended. For mid-to-low frequency bands (6-18GHz), a mid-to-high range can be used to ensure width accuracy and array period consistency, which can improve directional stability. Figure 1 Consistency and main lobe gain. The opening width (short side) of the feed slot 111 ranges from 0.2mm to 0.6mm, and the length direction is adjusted according to the cavity size. The smaller the opening width, the more concentrated the coupling efficiency, which is suitable for bandpass control. A larger opening width is easier to match the wideband coupling requirements.

[0066] In this embodiment, multiple baffles 112 construct a series of rhomboid radiating cavity structures arranged in a symmetrical gradient manner, forming a radiating array unit with consistent electromagnetic characteristics, stable mechanical structure, and simple assembly. It is suitable for high-gain, low-profile, and high-density integrated array antenna systems, and has good engineering practical value and application promotion prospects.

[0067] Example 5

[0068] Based on Example 1, this example combines high-precision processing and assembly of multi-layer metal sheets to realize the overall construction of a metal cavity antenna with a complex three-dimensional electromagnetic functional structure.

[0069] First, based on the three-dimensional electromagnetic model of the radiating cavity unit in the metal cavity antenna, its internal structure is designed in layers. Aluminum alloy, copper alloy, or other highly conductive metal materials are selected as raw materials according to the structural characteristics and electromagnetic functional requirements of each layer. The metal sheets can be prepared by integral casting followed by cutting or by laser precision machining of sheet metal to obtain functional layer metal sheets with precise shapes and consistent dimensions.

[0070] Subsequently, each prefabricated metal sheet is placed sequentially on a processing platform with positioning functions. Precise alignment and fixation are achieved using laser positioning and vacuum adsorption devices to ensure spatial consistency of each layer. CNC milling and laser engraving techniques are then used to precisely machine localized areas of the sheets, forming electromagnetic functional structures such as radiation channels, radiation cavities (resonant cavities), and feeding gaps. Edges and connecting areas are chamfered and deburred to ensure the microstructure meets micron-level dimensional accuracy.

[0071] After processing, the metal sheets are stacked and assembled in numerical order, and mechanically connected through pre-set mounting holes and bolt fastening structures to ensure the consistency and rigidity of the overall structure. Conductive adhesive layers or conductive gaskets can be added at the connection interfaces to improve the electromagnetic continuity and shielding performance between layers.

[0072] After the radiating cavity unit structure is constructed, a metal waveguide feed layer 2 and a feed circuit transmit / receive layer 3, matching its electromagnetic function, are further fabricated and integrated. The metal waveguide feed layer 2 forms several waveguide channels and feed ports according to the feed path design, and is processed using high-precision milling or mold forming processes. The channel structure corresponds one-to-one with the feed gaps at the bottom of the radiating cavity, ensuring efficient energy coupling. The feed circuit transmit / receive layer 3 includes a printed circuit board (PCB) or other RF circuit modules, used to excite and receive front-end signals, and can be installed using surface mount soldering, module integration, or other methods. Structural and signal connections between the feed layer, radiating cavity layer, and circuit layer are completed through mechanical connections, shielded frame mating, and flexible RF connectors (such as springs / probes). Finally, the constructed metal cavity antenna body structure has advantages such as stable interlayer structure, highly consistent electromagnetic performance, strong thermal / mechanical reliability, and a clear and controllable process path, making it suitable for the high-sensitivity, high-gain, and high-reliability array antenna application requirements in airport FOD monitoring systems.

[0073] This utility model discloses an airport runway foreign object detection (FOD) metallic cavity antenna, which adopts a three-layer structure stacked sequentially from top to bottom, including a radiating cavity layer, a metallic waveguide feed layer, and a feed circuit transmitting and receiving layer. The three layers are integrated into a single unit through standardized mechanical connections. In the radiating cavity layer, multiple independent modular radiating cavity units are used, with each unit featuring a three-section structure of a front-end board, a middle board, and a rear-end board, forming a closed resonant cavity. It connects to the lower metallic waveguide feed layer via an electromagnetic coupling port, achieving efficient RF energy injection and signal reverse reception. While ensuring consistent radiation directivity, this antenna structure effectively reduces structural weight and improves overall mechanical balance and electromagnetic consistency through symmetrical arrangement, array design, and lightweight optimization schemes such as weight-reducing holes and baffle structures. It also supports efficient transmission and reception of multi-channel signals, meeting the stringent requirements of millimeter-wave radar systems for high gain, high precision, and high bandwidth, making it particularly suitable for complex scenarios such as wide-area coverage, rapid scanning, and foreign object echo identification on airport runways.

[0074] The above description is merely an embodiment of this utility model, and common knowledge regarding specific structures and characteristics is not described in detail here. It will be apparent to those skilled in the art that this utility model is not limited to the details of the above exemplary embodiments, and that it can be implemented in other specific forms without departing from the spirit or essential characteristics of this utility model. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of this utility model is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within this utility model. No reference numerals in the claims should be construed as limiting the scope of the claims.

Claims

1. A metallic cavity antenna for foreign object detection (FOD) on airport runways, comprising a radiating cavity layer (1), a metallic waveguide feed layer (2), and a feed circuit transmitting and receiving layer (3), characterized in that, The radiation cavity layer (1) is located at the top of the antenna structure and includes multiple independent radiation cavity units segmented along the main electromagnetic beam direction. Each radiation cavity unit includes a front radiation cavity plate (12), a rear radiation cavity plate (10), and multiple middle radiation cavity plates (11) disposed between the front and rear radiation cavity plates, which together form a closed resonant cavity structure. The radiation cavity unit has multiple radiation channels (113), a radiation cavity (114) and a feed slot (111) arranged sequentially from top to bottom on one side. The radiation channel (113) extends downward from the top to a preset depth and takes the main beam direction as the exit direction. The radiation channel (113) is connected to the radiation cavity (114) below it. The feed slot (111) is located at the bottom of the radiation cavity unit and is connected to the radiation cavity (114). The metal waveguide feed layer (2) is located below the radiation cavity layer (1) and has multiple electromagnetic coupling ports (20) on it. Each electromagnetic coupling port (20) corresponds to the feed gap (111) above it. The feed circuit transmit and receive layer (3) is located below the metal waveguide feed layer (2) and has at least one radio frequency circuit device (30). The radio frequency circuit device (30) has multiple radio frequency transmit modules and / or receive modules inside it. Each module corresponds one-to-one with the electromagnetic coupling port (20) in the metal waveguide feed layer (2) to realize the transmission and reception of radio frequency signals.

2. The airport runway foreign object detection (FOD) metallic cavity antenna according to claim 1, characterized in that, The rear-end radiation cavity plate (10) and each of the middle radiation cavity plates (11) have a planar structure on one side and multiple radiation channels (113), radiation cavities (114) and power supply gaps (111) on the other side. The radiation structures of each cavity plate are stacked in a uniform direction. The front-end radiation cavity plate (12) has a planar structure on both sides. The side facing the adjacent middle radiation cavity plate (11) covers and closes the radiation channels (113), radiation cavities (114) and power supply gaps (111) on the middle radiation cavity plate (11).

3. The airport runway foreign object detection (FOD) metallic cavity antenna according to claim 2, characterized in that, The rear-end radiation cavity plate (10) and multiple middle radiation cavity plates (11) are respectively symmetrically arranged with two radiation cavity sub-units around their respective structural centerlines. After assembly, the two radiation cavity sub-units in each cavity plate form two sets of radiation cavity sub-arrays of the radiation cavity layer (1).

4. The airport runway foreign object detection (FOD) metallic cavity antenna according to claim 3, characterized in that, The rear radiation cavity plate (10), the middle radiation cavity plate (11) and the front radiation cavity plate (12) are provided with through-type weight reduction holes (14), which are located in the structural non-functional area between the two sets of radiation cavity sub-arrays.

5. The airport runway foreign object detection (FOD) metallic cavity antenna according to claim 4, characterized in that, The number of weight reduction holes (14) is at least three, one of which is located on the center line of the structure of the metal cavity antenna, and the other two weight reduction holes are symmetrically distributed on both sides of the center line of the structure and are arranged at equal offsets along the horizontal direction.

6. The airport runway foreign object detection (FOD) metallic cavity antenna according to claim 5, characterized in that, Three weight-reducing holes (14) are opened at the same position on the rear radiation cavity plate (10), each middle radiation cavity plate (11) and the front radiation cavity plate (12), and the weight-reducing holes (14) on each cavity plate are aligned and interconnected.

7. The airport runway foreign object detection (FOD) metallic cavity antenna according to claim 1, characterized in that, The rear radiation cavity plate (10) and the middle radiation cavity plate (11) have a concave plane area with a recessed structure on one side. The concave plane area is used to set up the radiation channel (113), the radiation cavity (114) and the power supply gap (111).

8. The airport runway foreign object detection (FOD) metallic cavity antenna according to claim 7, characterized in that, Within the concave plane region, multiple baffles (112) are arranged sequentially at intervals along the width direction of the plate, and the gap formed between two adjacent baffles (112) constitutes the radiation channel (113).

9. The airport runway foreign object detection (FOD) metallic cavity antenna according to claim 8, characterized in that, The upper part of the plurality of baffles (112) is flush with the top of the cavity plate, and the lower part of the plurality of baffles (112) gradually decreases in length from both ends of the concave plane region toward the center, and is arranged in a symmetrical decreasing pattern.

10. The airport runway foreign object detection (FOD) metallic cavity antenna according to claim 7, characterized in that, The radiation cavity (114) is located at the bottom of each baffle (112) and has a rhomboid structure. The four sides of the rhomboid structure are formed by the bottom of multiple baffles (112) and the two side walls of the concave plane area.

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