A broadband antenna for unmanned aerial vehicle image transmission

Abstract

The utility model discloses a kind of broadband antennas for unmanned aerial vehicle image transmission, including semi-flexible line, SMA male connector and the upper five hardware shell fragment antenna array and the lower five hardware shell fragment antenna array located in feed line antenna end. Upper, lower array coaxial superposition form radiation assembly, upper array connects semi-flexible line center conductor, lower array connects outer conductor, both coincide and keep parallel in plan view direction, to generate circular polarization radiation and realize 4.9-7.2GHz wideband operation. Antenna outside is equipped with bottom shell and gum shell, bottom shell has array limiting detent in, gum shell and bottom shell are assembled by circumferential anti-rotation structure cooperation, prevent array displacement in vibration. Semi-flexible line is led out by SMA male connector, and double-layer reinforcing protection is carried out using transparent heat shrink tube and black double-arm heat shrink tube at connecting transition place. The structure design is compact, broadband performance is excellent, assembly is reliable, applicable to high-frequency broadband signal transmission in unmanned aerial vehicle image transmission system.

Description

Technical Field

[0001] This utility model relates to an antenna, specifically a broadband antenna for image transmission in unmanned aerial vehicles (UAVs). Background Technology

[0002] With the widespread application of drones in aerial surveying, emergency rescue, security patrol, and logistics transportation, the requirements for communication distance, stability, and anti-interference capabilities in their image transmission links are constantly increasing. Currently, most mainstream drone image transmission systems operate within the 2.4 GHz, 5.8 GHz, and some higher frequency bands (such as above 6 GHz) spectrum. With the popularization of multi-band parallel communication and high-speed data links, achieving high-gain, low-VSWR, and compact image transmission antennas over a wider bandwidth has become a key factor in optimizing the performance of drone image transmission systems.

[0003] Existing UAV image transmission antennas mainly employ patch antennas, dual-polarized whip antennas, or planar helical antenna structures. While patch antennas offer high gain, they suffer from narrow bandwidth and strong directivity, making it difficult for UAVs to maintain stable communication during attitude changes. Dual-polarized whip antennas are small and simple to manufacture, but their fixed polarization makes them susceptible to multipath reflections. Planar helical antennas can achieve circularly polarized radiation, but they typically require large reflectors and dielectric support structures, increasing overall size and weight, making them unsuitable for lightweight UAV platforms.

[0004] In addition, traditional image transmission antennas generally have the following problems: (1) The operating bandwidth is limited, making it difficult to cover a wide frequency range from 4.9 GHz to 7.2 GHz, which limits the compatibility of multiple systems; (2) The power supply structure is complex, and it is not easy to maintain the coaxiality of the connection point between the center conductor and the outer conductor, which leads to an increase in the standing wave ratio and unstable matching. (3) Poor anti-rotation performance of mechanical structure. Under the vibration of UAV or wind disturbance, the internal array of antenna is prone to relative displacement, which affects the radiation directionality and polarization consistency. (4) The processing and assembly process is complex, and there is no effective limiting structure between the shell and the array, making it difficult to guarantee assembly accuracy and affecting consistency and mass production stability.

[0005] To address the aforementioned issues, the industry has developed some improvement solutions, such as using a double-layer metal array or a broadband design with multi-segment power supply. However, these solutions still suffer from problems such as complex structure, high manufacturing costs, or insufficient control over the radiation direction. Utility Model Content

[0006] To address the aforementioned issues, this invention provides a broadband antenna for UAV image transmission. This antenna features a simple structure, reliable assembly, and stable circular polarization radiation within a wide frequency band of 4.9 GHz to 7.2 GHz, thus meeting the comprehensive requirements of small UAV platforms for broadband, high gain, and lightweight communication systems.

[0007] This utility model is achieved through the following technical solution: a broadband antenna for UAV image transmission, including a semi-flexible cable, an SMA male connector, and an upper metal spring antenna array and a lower metal spring antenna array located at the feeder antenna end; The upper metal spring antenna array and the lower metal spring antenna array are coaxially stacked to form a radiation component. The upper metal spring antenna array is electrically connected to the center conductor of the semi-flexible wire, and the lower metal spring antenna array is electrically connected to the outer conductor of the semi-flexible wire. The upper and lower metal spring antenna arrays overlap and remain parallel in the top view direction to form circularly polarized radiation and extend the operating bandwidth to 4.9–7.2 GHz; The antenna also includes a bottom shell and a plastic shell that cooperate with the radiating components. The bottom shell is provided with an array limiting position. The plastic shell and the bottom shell are assembled with a complementary meshing circumferential anti-rotation structure to limit the rotation and relative displacement of the array during assembly and use, and to ensure the coaxial alignment and stable electrical characteristics of the array. The semi-flexible cable is led out through the SMA male connector and reinforced and protected by transparent heat shrink tubing and black double-arm heat shrink tubing at the transition between the connector and the semi-flexible cable.

[0008] As a preferred technical solution, the upper and lower metal spring antenna arrays are both square spiral four-arm structures, with each arm extending at a 45° angle relative to its base surface to improve the axial ratio and standing wave bandwidth.

[0009] As a preferred technical solution, the central area of ​​the upper metal spring antenna array is provided with a first through hole for the central conductor to pass through and be welded; The central area of ​​the lower metal spring antenna array is provided with a second through hole for the outer conductor to approach and be welded. The diameter of the second through hole is larger than that of the first through hole, so as to achieve separate and firm power / ground connections.

[0010] As a preferred technical solution, the bottom shell is a circular or near-circular structure, with four array slots on the inner wall to limit the lower metal spring antenna array in the radial and circumferential directions. The outer circumference of the bottom shell is provided with threaded edges and several protruding columns. The inner circumference of the plastic shell is provided with matching concave columns, which cooperate with the threaded edges to form a double anti-rotation positioning.

[0011] As a preferred technical solution, the plastic shell has a basic columnar shape. After being assembled with the bottom shell, it presses against and positions the upper and lower metal spring antenna arrays in the axial direction to maintain their parallel relationship and overlap when viewed from above.

[0012] As a preferred technical solution, the semi-flexible cable is a KTRFB-141-50 type low-loss semi-flexible cable with an outer diameter of approximately 4.1mm, and the feeder length can be customized according to application requirements to take into account both the overall wiring and the antenna installation position.

[0013] As a preferred technical solution, the SMA male connector is connected to the semi-flexible wire by a combination of riveting, crimping and welding, and a transparent heat shrink tubing and a black double-arm heat shrink tubing are provided at the transition part between the connector and the semi-flexible wire.

[0014] As a preferred technical solution, the transparent heat shrink tubing has a diameter of approximately 9 mm, a length of 30 mm, a wall thickness of 0.15 mm, and after heat shrinking, it is basically flush with the end face of the SMA male connector. The black double-arm heat shrink tubing has a diameter of 6.4 mm, a length of 18 mm, and a wall thickness of 0.48 mm. After heat shrinking, it is basically flush with the crimping opening of the SMA male connector.

[0015] The beneficial effects of this invention are as follows: By employing a double-layer metal spring array structure at the coaxial feed end, the upper and lower arrays are substantially overlapped and arranged parallel in the top view, forming a compact and radially symmetrical circularly polarized antenna. By welding the upper array to the coaxial center conductor and the lower array to the coaxial outer conductor, not only is the electrical symmetry of the feed path ensured, but the VSWR and input impedance matching are also significantly improved, enabling the antenna to maintain stable radiation performance and broadband response in the 4.9GHz to 7.2GHz frequency band. Compared with traditional single-layer whip or patch antennas, this invention can achieve a wider operating bandwidth and better polarization characteristics in a smaller size, making it particularly suitable for use in UAV image transmission links where pitch and roll angles change.

[0016] Furthermore, by incorporating a limiting and locking structure within the bottom shell and employing a threaded edge and four-post, four-slot anti-rotation engagement design between the rubber shell and the bottom shell, relative rotation of the antenna due to vibration or impact during assembly and use is effectively prevented. This ensures the mechanical stability and consistency of the upper and lower arrays being coaxially aligned, thereby improving the antenna's manufacturing assembly precision and long-term reliability. The collaborative structure of the bottom shell and the rubber shell not only facilitates rapid assembly but also enhances the overall unit's anti-loosening, anti-slip, and resistance to external forces.

[0017] Meanwhile, this utility model uses the KTRFB-141-50 semi-flexible low-loss coaxial feeder, and sets up transparent and black double-layer heat shrink tubing protection at the connection between the SMA male connector and the feeder, which improves the mechanical strength, sealing and moisture protection, and appearance consistency of the connection, ensuring long-term stable use of the antenna in outdoor or flight environments. The transition structure after heat shrink encapsulation can also effectively reduce the bending stress and mechanical torsion risk of the cable. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a schematic diagram of the external structure of this utility model; Figure 2 This is a schematic diagram of the internal structure of the present invention; Figure 3 Design drawing for a metal spring-loaded antenna array; Figure 4 Design diagram of the lower metal spring antenna array; Figure 5 This is an RL free-space test diagram of the novel antenna designed in this paper; Figure 6 This is a VSWR free-space test diagram of the novel antenna designed in this paper; Figure 7 Smith free-space test diagram of the novel antenna designed in this paper; Figure 8 The 3D radiation pattern of the novel antenna at 5500MHz is shown. Figure 9 The 2D radiation pattern of the ZX plane of this novel antenna at 5500MHz is shown. Figure 10 The 2D radiation pattern of the ZY plane of this novel antenna at 5500MHz is shown. Figure 11 This is the 2D radiation pattern of the XY plane of the novel antenna designed in this study at 5500MHz. Detailed Implementation

[0020] All features disclosed in this specification, or all steps in all disclosed methods or processes, may be combined in any way, except for mutually exclusive features and / or steps.

[0021] Any feature disclosed in this specification (including any appended claims, abstract, and drawings) may be replaced by other equivalent or similar features for a similar purpose, unless specifically stated otherwise. That is, unless specifically stated otherwise, each feature is merely one example of a series of equivalent or similar features.

[0022] like Figures 1-11 As shown, this invention proposes a broadband antenna for UAV image transmission. In its implementation, through optimized design of the antenna radiating element, feeding structure, and housing assembly, the antenna achieves stable circular polarization radiation characteristics across a wide frequency range of 4.9 GHz to 7.2 GHz, effectively improving the transmission distance and anti-interference performance of UAV image transmission signals in complex spatial environments. This invention features a compact overall structure and precise component integration, balancing high-frequency broadband characteristics with mechanical reliability. It is suitable for multi-rotor UAVs, fixed-wing UAVs, and other flight platforms requiring lightweight and high-speed data transmission.

[0023] In one specific embodiment, the broadband antenna for UAV image transmission mainly includes a semi-flexible cable 5, an SMA male connector 8, an upper metal spring antenna array 1, a lower metal spring antenna array 2, a bottom shell 3, a plastic shell 4, a transparent heat shrink tubing 6, and a black double-arm heat shrink tubing 7.

[0024] Among them, the semi-flexible cable 5 is a KTRFB-141-50 type low-loss semi-flexible coaxial cable. This cable has good mechanical flexibility and low signal attenuation characteristics. Its outer diameter is about 4.1mm, and it contains a center conductor, an insulating dielectric layer, an outer conductor braided layer, and an outer sheath.

[0025] The center conductor serves as the main signal feed path, while the outer conductor acts as a grounding shield, providing a stable electrical connection for the upper and lower antenna arrays. One end of the semi-flexible wire is fixedly connected to the SMA male connector 8, and the other end extends into the internal area of ​​the antenna radiating element, connecting to the upper metal spring antenna array 1 and the lower metal spring antenna array 2.

[0026] The upper metal spring antenna array 1 and the lower metal spring antenna array 2 are the key radiating units of this utility model. They are coaxially stacked to form a set of parallel metal radiating components. In terms of specific structure, the upper metal spring antenna array 1 is made of a highly conductive copper alloy material with a thickness of about 0.3 mm. The surface is treated with silver or nickel plating to reduce high-frequency loss.

[0027] The upper element has a first through-hole at its center for the center conductor of the semi-flexible wire 5 to pass through and be welded and fixed, thus forming a feed point. The lower element, a metal spring-loaded antenna array 2, is also made of copper, with a slightly greater thickness than the upper element. It has a second through-hole at its center for welding close to and to the outer conductor of the semi-flexible wire 5, thereby achieving a reliable grounding connection. The diameter of the second through-hole is slightly larger than that of the first through-hole, which facilitates ensuring sufficient welding area and electrical contact strength during the welding process.

[0028] The spacing between the upper and lower elements is precisely controlled to achieve optimal electromagnetic coupling conditions, thereby improving the antenna's VSWR and axial ratio performance. The upper and lower elements are almost completely overlapped in the top-view direction, maintaining a strict coaxial relationship, so that they form a stable circularly polarized electric field distribution during transmission, ensuring that the signal can obtain relatively uniform radiation coverage in all angular directions.

[0029] Each metal spring antenna array adopts a square spiral four-arm structure, and its geometry presents a symmetrical shape similar to a spiral unfolding. The four arms extend at a 45° angle relative to the central base plane, so that the current forms a spiral current path on the antenna surface.

[0030] This structure not only significantly improves the purity of circular polarization but also effectively broadens the antenna's operating bandwidth. The length, bending angle, and spacing of the four arms are parametrically designed according to the target frequency band. Electromagnetic simulation verification shows that the antenna maintains a VSWR below 2.0 and an axial ratio of less than 3dB in the 4.9GHz to 7.2GHz range. This design enables the antenna to maintain good signal consistency and directional gain at different attitude angles while providing broadband coverage.

[0031] To ensure the installation accuracy and mechanical stability of the upper and lower antenna elements, this invention features a two-part structure: a base shell 3 and a plastic shell 4. The base shell 3 is circular or nearly circular, manufactured using injection molding or CNC machining, and can be made of lightweight aluminum alloy or high-strength engineering plastic. Inside the base shell 3, four radially arranged element locking positions are used to precisely position the metal spring antenna elements 2 during assembly, preventing slippage and rotation during assembly and use. The outer periphery of the base shell 3 has threaded edges and several protruding pillars. These structures not only prevent rotation but also form a mechanical self-locking connection with the plastic shell 4, improving the overall shock resistance and reliability after assembly.

[0032] The housing 4 is a single cylindrical shape, made of polycarbonate material with good weather resistance and insulation properties. Internally, it has recessed grooves along the circumference that correspond to the protruding columns of the base shell 3. The base shell 3 and housing 4 are assembled by rotational pressing. The interlocking structure between them provides reliable circumferential anti-rotation locking and appropriate axial pressure on the upper and lower elements, ensuring that the parallelism and top-view overlap of the elements are not affected by vibration. After assembly, housing 4 has a smooth and rounded appearance, giving the antenna a compact rod-like structure, facilitating external installation and aerodynamic optimization on the UAV platform.

[0033] To further improve the antenna's environmental adaptability, this invention employs a double-layer heat-shrinkable protection structure in the transition area between the feeder and the connector.

[0034] The transparent heat shrink tubing 6 has a diameter of approximately 9 mm, a length of approximately 30 mm, and a wall thickness of approximately 0.15 mm. After heat shrinking, it tightly wraps around the tail end face of the SMA male connector 8, enabling the connection part to be dustproof and moisture-proof, and providing primary mechanical support.

[0035] A black double-arm heat shrink tubing 7, approximately 6.4mm in diameter, 18mm in length, and 0.48mm in wall thickness, is fitted over the transparent heat shrink tubing 6. After heat shrinking, it fits tightly into the crimping area of ​​the SMA male connector 8. The double-layer heat shrink tubing forms a robust encapsulation structure after cooling and curing, effectively mitigating stress concentration in the feeder under vibration and torsional forces, and further enhancing the overall waterproof performance and long service life of the device.

[0036] The SMA male connector 8 is connected to the semi-flexible wire 5 using a composite process of riveting, crimping, and welding. During the processing, the outer sheath of the semi-flexible wire 5 is first peeled off to expose the braided layer and welded to the grounding terminal of the connector. Then, the center conductor is welded to the inside of the connector pin core and then mechanically fixed by a crimping ring.

[0037] This structure ensures low signal loss and high mechanical strength, enabling it to withstand vibrations, accelerations, and environmental temperature differences generated during drone flight. The SMA male connector 8's shell is made of nickel-plated brass or stainless steel, while the inner pins are gold-plated conductors to ensure reliable contact and oxidation resistance for high-frequency transmission.

[0038] The assembly process of this utility model is as follows: First, the lower metal spring antenna array 2 is placed into the limiting slot of the bottom shell 3, ensuring that its positioning hole is aligned with the center hole; then, the upper metal spring antenna array 1 is coaxially placed above the lower array 2, and fixed by welding the center conductor and outer conductor of the semi-flexible wire 5 to the through holes of the upper and lower arrays respectively; after welding, check whether the upper and lower arrays are parallel and overlapped; then, the bottom shell 3 and the plastic shell 4 are screwed together and locked by their anti-rotation structure to ensure that the antenna assembly is tightly joined; finally, transparent heat shrink tubing 6 and black double-arm heat shrink tubing 7 are inserted at the connection between the SMA male connector 8 and the semi-flexible wire 5, and after heat shrinking, the protective encapsulation is completed. After the above steps, the entire antenna forms an integrated structure that is electrically continuous, mechanically stable, and compact in appearance.

[0039] During use, the antenna is mounted on the UAV image transmission module, and the SMA male connector 8 connects to the image transmission port via a standard RF interface. Due to its dual-array stacked structure, the antenna forms a stable circularly polarized wavefront in space, effectively reducing the impact of UAV attitude changes on the communication link. Even when the UAV pitches, rolls, or yaws during flight, the receiver maintains high signal strength and link stability. Furthermore, its wideband design allows the antenna to be compatible with image transmission systems in different frequency bands, supporting multi-protocol and multi-standard image transmission on the same platform, thus expanding equipment adaptability. Actual test results show that the antenna maintains a gain of approximately 4dBi, a VSWR of less than 2.0, high circular polarization purity, and strong anti-interference performance within the 4.9GHz to 7.2GHz range.

[0040] This invention successfully realizes a broadband antenna with a compact structure, reliable assembly, and wide bandwidth, suitable for UAV image transmission systems, through a coaxial dual-array structure, a limiting and anti-rotation design of the bottom shell 3 and the plastic shell 4, and a double-layer heat-shrink packaging method. This antenna not only maintains stable electrical characteristics and circular polarization radiation effect in complex flight environments, but also exhibits high repeatability and economy in terms of manufacturing process and assembly consistency, demonstrating significant engineering application value and promising prospects for industrial promotion.

[0041] The above description is merely a specific embodiment of this utility model, but the protection scope of this utility model is not limited thereto. Any changes or substitutions conceived without inventive effort should be included within the protection scope of this utility model. Therefore, the protection scope of this utility model should be determined by the scope defined in the claims.

Claims

1. A broadband antenna for image transmission in unmanned aerial vehicles (UAVs), characterized in that: Includes a semi-flexible cable (5), an SMA male connector (8), and an upper metal spring antenna array (1) and a lower metal spring antenna array (2) located at the feed antenna end; The upper metal spring antenna array (1) and the lower metal spring antenna array (2) are coaxially stacked to form a radiation component. The upper metal spring antenna array (1) is electrically connected to the center conductor of the semi-flexible wire (5), and the lower metal spring antenna array (2) is electrically connected to the outer conductor of the semi-flexible wire (5). The upper and lower metal spring antenna arrays overlap and remain parallel in the top view direction to form circularly polarized radiation and extend the operating bandwidth to 4.9–7.2 GHz; The antenna also includes a bottom shell (3) and a plastic shell (4) that cooperate with the radiating components. The bottom shell (3) is provided with a limiting position for the array. The plastic shell (4) and the bottom shell (3) are assembled with a complementary meshing circumferential anti-rotation structure to limit the rotation and relative displacement of the array during assembly and use, and to ensure that the array is coaxial and has stable electrical characteristics. The semi-flexible cable (5) is led out through the SMA male connector (8) and reinforced and protected by transparent heat shrink tubing (6) and black double-arm heat shrink tubing (7) at the transition between the connector (8) and the semi-flexible cable (5).

2. The broadband antenna for UAV image transmission according to claim 1, characterized in that: The upper and lower metal spring antenna arrays (1) and (2) are both square spiral four-arm structures, with each arm extending at a 45° angle relative to its base surface to improve the axial ratio and standing wave bandwidth.

3. The broadband antenna for UAV image transmission according to claim 1, characterized in that: The central region of the upper metal spring antenna array (1) is provided with a first through hole for the central conductor to pass through and be welded; The central area of ​​the lower metal spring antenna array (2) is provided with a second through hole for the outer conductor to approach and be welded. The diameter of the second through hole is larger than that of the first through hole so as to achieve separate and firm power / ground connections.

4. The broadband antenna for UAV image transmission according to claim 1, characterized in that: The bottom shell (3) is a circular or near-circular structure. Four array slots are provided on the inner wall to limit the lower metal spring antenna array (2) in the radial and circumferential directions. The outer circumference of the bottom shell (3) is provided with threaded edges and several protruding columns. The inner circumference of the plastic shell (4) is provided with matching concave columns, which cooperate with the threaded edges to form a double anti-rotation positioning.

5. The broadband antenna for UAV image transmission according to claim 1, characterized in that: The plastic shell (4) has a basic columnar shape. After it is assembled with the bottom shell (3), it presses against and positions the upper and lower metal spring antenna arrays (1) and (2) in the axial direction to maintain their parallel relationship and overlap when viewed from above.

6. The broadband antenna for UAV image transmission according to claim 1, characterized in that: The semi-flexible cable (5) is a KTRFB-141-50 type low-loss semi-flexible cable with an outer diameter of approximately 4.1 mm. The feeder length can be customized according to application requirements to take into account both the overall wiring and the antenna installation position.

7. The broadband antenna for UAV image transmission according to claim 1, characterized in that: The SMA male connector (8) is connected to the semi-flexible wire (5) by a combination of riveting, crimping and welding, and a transparent heat shrink tube (6) and a black double-arm heat shrink tube (7) are provided at the transition part between the connector (8) and the semi-flexible wire (5).

8. The broadband antenna for UAV image transmission according to claim 1, characterized in that: The transparent heat shrink tubing (6) has a diameter of approximately 9 mm, a length of 30 mm, and a wall thickness of 0.15 mm, and after heat shrinking, it is basically flush with the end face of the SMA male connector (8). The black double-arm heat shrink tubing (7) has a diameter of 6.4 mm, a length of 18 mm, and a wall thickness of 0.48 mm. After heat shrinking, it is basically flush with the crimping opening of the SMA male connector (8).

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