A three-frequency directional antenna, terminal and unmanned device

Abstract

The application provides a three-frequency directional antenna, a terminal and an unmanned device, which comprise a dielectric substrate, a three-frequency dipole radiation unit configured to emit electromagnetic waves of three different working frequency bands, and a reflector array configured to perform hierarchical reflection on the electromagnetic waves of the three different working frequency bands. The three-frequency dipole radiation unit comprises two symmetrical dipole units, each of the dipole units comprises an upper-layer dipole arm and a lower-layer dipole arm, the upper-layer dipole arm is close to the reflector array, the lower-layer dipole arm comprises a first radiation arm and a second radiation arm, and the second radiation arm partially or completely surrounds the periphery of the first radiation arm. The reflector array comprises a first reflection strip, a second reflection strip and a third reflection strip which are printed at intervals along the length direction of the dielectric substrate, and the center points of the first reflection strip, the second reflection strip and the third reflection strip are located on the symmetry axis of the two dipole units. The application realizes the effects of low profile, small size, high gain and three-frequency end-fire directional radiation on a single-sided PCB.

Description

Technical Field

[0001] This application relates to the field of antenna technology, specifically to a tri-band directional antenna, a terminal, and an unmanned device. Background Technology

[0002] With the widespread application of drones in surveying, inspection, logistics, and emergency rescue, the demand for stable long-range communication capabilities is becoming increasingly urgent. One of the keys to achieving this goal lies in the performance of the airborne antenna. However, drone platforms impose extremely stringent limitations on antenna installation space, which presents a significant challenge to antenna design.

[0003] Currently, for multi-band wireless communication needs, the common multi-band antenna design schemes mainly include the following: 1) Microstrip antennas employing multi-stub loading or stacked patch structures. While these antennas can achieve impedance matching across multiple frequency bands, they are limited by the resonant characteristics of the microstrip patch itself. When covering lower frequency bands such as 1.4 GHz, the patch size is often large. Furthermore, to accommodate both 2.45 GHz and 5.5 GHz, complex multi-resonant structures are typically required, which not only occupy a large area but also exhibit weak directional radiation capability in low-frequency bands, making it difficult to achieve stable high gain.

[0004] 2) Traditional directional antenna structures such as Yagi antennas and log-periodic antennas are used. These antennas can provide good directional radiation and high gain, but their size is determined by the operating wavelength. In the 1.4GHz band, the size of the active element, director, and reflector of the Yagi antenna increases significantly, and the overall length usually exceeds half the wavelength, making it difficult to meet the miniaturization requirements. If it is simply combined with 2.45GHz and 5.5GHz antenna elements, the overall structure becomes even more bloated, which is not conducive to internal integration of the device.

[0005] 3) Miniaturized antennas achieved through methods such as zigzag lines and high dielectric constant substrates. While this type of design significantly reduces the antenna size, it usually comes at the cost of reduced gain and radiation efficiency, especially in the low-frequency band where the gain often drops below 0 dBi and the directivity is poor, making it difficult to meet the requirements of long-distance directional communication.

[0006] Therefore, there is an urgent need for an innovative antenna solution that can cover the 1.4GHz, 2.45GHz and 5.5GHz frequency bands in an extremely compact physical size, and achieve directional radiation and high gain to meet the long-distance communication needs of UAVs. Summary of the Invention

[0007] To address the aforementioned technical problems, this application provides a tri-band directional antenna, a terminal, and an unmanned device.

[0008] According to a first aspect of this application, a tri-band directional antenna is proposed, comprising: Dielectric substrate; A three-frequency dipole radiating unit, printed on one side of the surface of the dielectric substrate, is configured to emit electromagnetic waves in three different operating frequency bands; and A reflector array printed on the other side of the same surface of the dielectric substrate, the reflector array being configured to perform graded reflection of electromagnetic waves in three different operating frequency bands; The tri-frequency dipole radiation unit includes two symmetrical dipole units. Each dipole unit includes an upper dipole arm and a lower dipole arm. The upper dipole arm is close to the reflector array. The lower dipole arm includes a first radiation arm and a second radiation arm. The second radiation arm partially or completely surrounds the periphery of the first radiation arm. The reflector array includes a first reflective strip, a second reflective strip, and a third reflective strip printed at intervals along the length of the dielectric substrate, wherein the center points of the first reflective strip, the second reflective strip, and the third reflective strip are located on the axis of symmetry of the two dipole units.

[0009] Preferably, the dipole unit further includes a signal transmission arm connecting the upper dipole arm and the lower dipole arm, the signal transmission arm having a power supply point and a pad at the power supply point.

[0010] Preferably, the upper dipole arm extends obliquely upward along the length of the dielectric substrate from a position near the feed point, and its end bends downward and converges near the reflector array.

[0011] Preferably, the first radiating arm extends horizontally along the length direction of the dielectric substrate from one side of the signal transmission arm. The first radiating arm includes a first radiating stub and a second radiating stub. The first radiating stub and the second radiating stub have a two-stage stepped structure, and the length ratio of the first radiating stub to the second radiating stub is 1:10. The second radiating arm extends horizontally along the length of the dielectric substrate from one side of the signal transmission arm at intervals, and wraps around the periphery of the second radiating branch in a bent manner to form a U-shaped surrounding structure.

[0012] Preferably, the first reflective strip, the second reflective strip, and the third reflective strip are all straight microstrip lines, and their lengths correspond to half the wavelength of the electromagnetic waves in their reflected operating frequency band. The third reflective strip bends downwards at both ends.

[0013] Preferably, the upper dipole arm is configured to operate in a first frequency band, the first radiating arm is configured to operate in a second frequency band, the second radiating arm is configured to operate in a third frequency band, and the third frequency band is lower than the second frequency band.

[0014] Preferably, the center frequency of the first frequency band is 5.5 GHz, the center frequency of the second frequency band is 2.4 GHz, and the center frequency of the third frequency band is 1.4 GHz; The total length of the upper dipole arm and the first radiating arm is one-quarter wavelength of the center frequency of their respective operating frequency bands, and the total length of the second radiating arm is half wavelength of the center frequency of its operating frequency band.

[0015] Preferably, it also includes a coaxial feed line, wherein the inner and outer conductors at one end of the coaxial feed line are electrically connected to the pads of the two dipole units respectively, and the other end of the coaxial feed line is connected to an SMA female connector, thereby forming the antenna output.

[0016] According to a second aspect of this application, a terminal is proposed, comprising a tri-band directional antenna as described above.

[0017] According to a third aspect of this application, an unmanned device is proposed, comprising a tri-band directional antenna as described above.

[0018] This application proposes a tri-band directional antenna. When a radio frequency signal is sent to the feed point via a coaxial feed line, the tri-band dipole radiating element is excited, simultaneously generating radiated currents of 1.4 GHz, 2.4 GHz, and 5.5 GHz. The radiated electromagnetic waves in each frequency band propagate in all directions. The electromagnetic waves propagating towards the reflector array are reflected and superimposed into the forward radiation field upon encountering the corresponding frequency band's reflector strip. Since the length of the reflector strip is precisely designed to be half the wavelength of the corresponding frequency band, the reflector strip exhibits a high impedance state, thus efficiently reflecting energy back towards the dipole. Simultaneously, the reflection phase of the three reflector strips is independently controlled for different frequency bands, ensuring that the reflected waves of the three frequency bands are superimposed in phase, ultimately forming an end-fire directional beam pointing from the dipole towards the opposite direction of the reflector array. Because all reflector strips are located on the same side of the dipole, the antenna exhibits unidirectional end-fire characteristics, and the main lobe directions of the three frequency bands are highly consistent. Therefore, the antenna of this application achieves low profile, small size, high gain, and tri-band end-fire directional radiation on a single-sided PCB. Attached Figure Description

[0019] The accompanying drawings are included to provide a further understanding of the embodiments and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments and, together with the description, serve to explain the principles of this application. Other embodiments and many anticipated advantages of these embodiments will be readily recognized as they become better understood through reference to the following detailed description. Elements in the drawings are not necessarily to scale. The same reference numerals refer to corresponding similar parts.

[0020] Figure 1 This is a schematic diagram of the overall assembly structure of a tri-band directional antenna according to an embodiment of this application; Figure 2 This is a schematic diagram illustrating the assembly structure of the tri-band directional antenna according to an embodiment of this application; Figure 3 This is a schematic diagram of the structure of a three-band directional antenna according to an embodiment of this application; Figure 4 This is a diagram showing the return loss performance parameters of a three-band directional antenna according to an embodiment of this application; Figure 5 This is an efficiency diagram of a three-band directional antenna according to an embodiment of this application; Figure 6 This is the vertical plane radiation pattern of the tri-band directional antenna in the 1.43GHz~1.49GHz range according to an embodiment of this application; Figure 7 This is the horizontal radiation pattern of the tri-band directional antenna in the 1.43GHz~1.49GHz range according to an embodiment of this application; Figure 8 This is the vertical plane radiation pattern of the tri-band directional antenna in the 2.4GHz~2.5GHz range according to an embodiment of this application; Figure 9 This is the horizontal radiation pattern of the tri-band directional antenna in the 2.4GHz~2.5GHz range according to an embodiment of this application; Figure 10 This is the vertical plane radiation pattern of the tri-band directional antenna in the 5.15GHz~5.85GHz range according to an embodiment of this application; Figure 11 This is the horizontal radiation pattern of the tri-band directional antenna in the 5.15GHz~5.85GHz range according to an embodiment of this application.

[0021] The meaning of each number in the diagram: 10. Dielectric substrate; 20. Tri-frequency dipole radiating unit; 21. Dipole unit; 211. Upper dipole arm; 212. Lower dipole arm; 2121. First radiating arm; 21211. First radiating stub; 21212. Second radiating stub; 2122. Second radiating arm; 213. Signal transmission arm; 2131. Pad; 30. Reflector array; 31. First reflective strip; 32. Second reflective strip; 33. Third reflective strip; 40. Coaxial feeder; 41. SMA female connector; 50. Outer shell. Detailed Implementation

[0022] In the following detailed description, reference is made to the accompanying drawings, which form part of the detailed description and illustrate illustrative specific embodiments in which the present application may be practiced. In this regard, directional terms such as “top,” “bottom,” “left,” “right,” “up,” “down,” etc., are used with reference to the orientation of the described figures. Because components of the embodiments can be positioned in several different orientations, directional terms are used for illustrative purposes and are by no means limiting. It should be understood that other embodiments may be utilized or logical changes may be made without departing from the scope of the present application. Therefore, the following detailed description should not be taken in a limiting sense, and the scope of the present application is defined by the appended claims.

[0023] With the widespread application of drones in various fields, drones have extremely stringent requirements for antenna performance and size. They not only require the antenna to be able to operate in multiple frequency bands, but also to have high-gain end-fire directional radiation and meet the requirements of low profile and small size for multiple targets.

[0024] The existing antenna design schemes mainly include the following: 1. Conventional Yagi Antenna Design: The Yagi antenna (also known as the Yagi-Uda antenna) is the most classic end-fire directional antenna. It consists of an active element and multiple passive elements (reflectors and directors) arranged along the antenna axis. It features simple structure, strong directivity, and high gain, and is widely used in various wireless communication systems. However, this type of antenna has disadvantages such as large size, high profile, and narrow operating bandwidth. Within the traditional Yagi antenna framework, there is an irreconcilable contradiction between miniaturization and high gain and wide bandwidth.

[0025] 2. PCB Printed Antenna Design Scheme: A PCB antenna (printed circuit board antenna) is an antenna directly integrated onto a printed circuit board. Specific shapes and patterns (such as serpentine lines, inverted F-shapes, patches, etc.) are etched onto the copper layer of the PCB itself to enable it to effectively transmit or receive radio waves. Due to its low cost, small size, and high integration, PCB antennas have become the mainstream antenna solution for modern compact wireless electronic devices. However, due to the limitations of the PCB board, these antennas have lower gain and efficiency, narrower bandwidth, higher environmental sensitivity, and higher design complexity, making them difficult to meet the complex application scenarios of drones.

[0026] 3. Microstrip Antenna Design Scheme: Microstrip patch antennas are a widely used planar antenna structure, consisting of a three-layer structure of a radiating patch, a dielectric substrate, and a ground plane. They offer advantages such as low profile, small size, light weight, and ease of circuit integration. However, this type of antenna suffers from the most significant drawback of narrow bandwidth, and also exhibits low efficiency and gain, with performance heavily influenced by the substrate material, making it difficult to meet the communication requirements of unmanned aerial vehicles (UAVs).

[0027] 4. Omnidirectional Antenna Design: Omnidirectional antennas radiate or receive electromagnetic waves uniformly in a 360-degree horizontal direction. They offer advantages such as simple installation and wide coverage, and are widely used in Wi-Fi routers, mobile base stations, and IoT devices. However, compared to directional antennas, omnidirectional antennas have relatively low gain, are susceptible to interference from co-channel signals from various directions, and are prone to multipath interference in multi-reflection environments. Furthermore, the vertical beam of an omnidirectional antenna is narrow; higher gain results in narrower vertical coverage, and the coverage area below the antenna is smaller. Therefore, it is difficult to meet the long-distance communication needs of drones.

[0028] 5. Monopole Antenna Design: A monopole antenna relies on the ground or a conductive plane as its mirror image, effectively functioning as half of a dipole antenna through the mirror principle. However, in practical applications, insufficient ground plane size, discontinuities, or the presence of metallic interference can lead to abnormal mirror current distribution, causing impedance mismatch, pattern distortion, or efficiency degradation. The electrical performance of a monopole antenna is highly dependent on the size, conductivity, and orientation of the ground plane. Its radiation efficiency is generally between 40% and 60%, signal coverage is hemispherical, and its anti-interference capability is relatively weak. In applications with limited space or unsatisfactory grounding conditions, the performance of a monopole antenna is difficult to guarantee.

[0029] 6. Dipole Antenna Design: A dipole antenna consists of two radiating elements of equal length. It can operate normally without relying on a ground plane and has high radiation efficiency (60%~80%). However, its large structural size is not conducive to miniaturization. The gain of a dipole antenna is usually not high, making it difficult to meet the requirements of high-power or long-distance communication. The presence of surrounding metal objects or other reflective surfaces may affect its radiation mode and overall performance. The physical size of a dipole antenna is often large, which is not conducive to miniaturization applications.

[0030] In summary, existing antenna designs struggle to simultaneously cover three frequency bands (1.4 GHz, 2.4 GHz, and 5.5 GHz), provide high-gain end-fire directional radiation, and meet the requirements of low profile and small size for multiple targets within a single structure. These shortcomings of existing technologies are precisely the technical problems that this application aims to solve.

[0031] According to a first aspect of this application, a tri-band directional antenna is proposed. The specific structure of the tri-band directional antenna according to an embodiment of this application will be described below with reference to the accompanying drawings.

[0032] Reference Figures 1 to 3 The tri-band directional antenna of this application includes a dielectric substrate 10. Tri-band dipole radiating elements 20 and reflector arrays 30 are respectively printed on both sides of the same surface of the dielectric substrate 10 in patch form. The tri-band dipole radiating elements 20 are used to emit electromagnetic waves in three different operating frequency bands, and the reflector array 30 is used to perform graded reflection of the electromagnetic waves in the three different operating frequency bands. It also includes a coaxial feed line 40. The inner conductor (core) and outer conductor (shielding layer) of one end of the coaxial feed line 40 are electrically connected to the feed point of the tri-band dipole radiating elements 20. The other end of the coaxial feed line 40 is connected to an SMA female connector 41 for connection to the radio frequency port of an external device, thereby forming the antenna output.

[0033] In this embodiment, the dielectric substrate 10 is a single-sided copper-clad FR-4 standard PCB board with an overall arc shape, a length L=88mm, a width W=15mm, and a thickness of 1.0mm (typical value). The copper layer is only located on the front (top surface) of the substrate, with no copper layer on the back. All antenna patterns are formed on this copper layer in one step using a standard photolithography etching process. It is understood that in other embodiments, the dielectric substrate can also be replaced by CEM-1, Rogers, etc., and this is not a limitation.

[0034] In some embodiments, the tri-band directional antenna also includes a housing 50. The housing 50 is injection molded from plastic (PC or ABS), approximately 95 mm in length and 16 mm in outer diameter. The entire antenna is assembled within the housing 50, which has an opening at one end. One end of the coaxial feed cable 40, connected to an SMA female connector 41, passes through this opening and is threaded onto the housing 50. The housing 50 serves to protect the antenna, enhance its appearance, and provide an installation interface. The antenna does not require additional grounding within the housing 50.

[0035] The tri-band directional antenna of this application, through the structural and arrangement design of the tri-band dipole radiating element 20 and the reflector array 30, simultaneously achieves coverage of three frequency bands (1.4 GHz, 2.4 GHz, and 5.5 GHz), possesses high-gain end-fire directional radiation, and meets the requirements of low profile and small size for multiple targets. The structural and arrangement design of the tri-band dipole radiating element 20 and the reflector array 30 will be described in detail below.

[0036] In some embodiments, the tri-frequency dipole radiating unit 20 includes two symmetrical dipole units 21, hereinafter referred to as the "left arm" and "right arm" based on their location. Both the left and right arms include an upper dipole arm 211, a lower dipole arm 212, and a signal transmission arm 213 connecting them. The upper dipole arm 211 is located near the reflector array 30 and is used to emit electromagnetic waves in a first frequency band. The lower dipole arm 212 includes a first radiating arm 2121 and a second radiating arm 2122. The second radiating arm 2122 partially or completely surrounds the periphery of the first radiating arm 2121. The first radiating arm 2121 is used to emit electromagnetic waves in a second frequency band, and the second radiating arm 2122 is used to emit electromagnetic waves in a third frequency band. The signal transmission arm 213 is used to radiate radio frequency signals of different frequency bands onto corresponding radiators to achieve signal transmission.

[0037] Specifically, a power supply point is formed near the upper end of the signal transmission arm 213, and a pad 2131 is provided at the power supply point. The inner conductor of one end of the coaxial feed line 40 is connected to the pad 2131 (signal end) of the left arm, and the outer conductor is connected to the pad 2131 (ground end) of the right arm.

[0038] The upper dipole arm 211 extends obliquely upward along the length of the dielectric substrate 10 from a position near the feed point, and its end bends downward and converges near the reflector array 30. This structural design reduces signal divergence radiated by the upper dipole arm 211 and avoids interference with the reflector array 30.

[0039] The first radiating arm 2121 extends horizontally along the length of the dielectric substrate 10 from the side of the signal transmission arm 213 near the lower end. The first radiating arm 2121 includes a first radiating stub 21211 and a second radiating stub 21212. The first radiating stub 21211 and the second radiating stub 21212 are a two-stage stepped structure. The two-stage stepped structure can optimize the impedance matching of the second frequency band from the feed point to the end of the radiating arm.

[0040] In this embodiment, the length ratio of the first radiating branch 21211 to the second radiating branch 21212 is 1:10.

[0041] The second radiating arm 2122 extends horizontally along the length of the dielectric substrate 10 from one side of the signal transmission arm 213 at intervals, and wraps around the periphery of the second radiating branch 21212 in a bent form, forming a U-shaped surrounding structure.

[0042] In this embodiment, in order to accommodate the second radiating arm 2122 within the limited length of the dielectric substrate 10, the second radiating arm 2122 extends horizontally to the end of the first radiating arm 2121, then bends upwards and then horizontally back, ultimately forming a U-shaped wraparound structure through two bending structures. It is understood that in other embodiments, the number of bends in the second radiating arm can be increased to accommodate the second radiating arm within an even more limited length.

[0043] It should be noted that the structural design of the second radiating arm 2122 surrounding the first radiating arm 2121 in this embodiment is based on the design concept of "low frequency surrounding high frequency", that is, the third frequency band is lower than the second frequency band, thereby solving the technical problem of "how to accommodate the long low frequency radiating arm within a limited length".

[0044] Therefore, in this embodiment, the center frequency of the operating frequency band of the first radiating arm 2121 is preferably 2.4 GHz, the center frequency of the operating frequency band of the second radiating arm 2122 is preferably 1.4 GHz, and the center frequency of the operating frequency band of the upper dipole arm 211 is preferably 5.5 GHz. It is understood that in other embodiments, the center frequencies of the operating frequency bands of the first radiating arm 2121, the second radiating arm 2122, and the upper dipole arm 211 can also be 5.5 GHz, 1.4 GHz, and 2.4 GHz, or 5.5 GHz, 2.4 GHz, and 1.4 GHz, respectively. As long as the design concept of "low frequency surrounding high frequency" is followed, it is considered one of the inventive concepts of this application.

[0045] In this embodiment, the total length of the upper dipole arm 211 is about 1 / 4 (about 15 mm) of the wavelength corresponding to the 5.5 GHz band, and it adopts a straight microstrip line with a linewidth of 1.5 mm.

[0046] In this embodiment, the total length of the first radiating arm 2121 is approximately 1 / 4 of the wavelength corresponding to the 2.4 GHz band (approximately 18.7 mm), and it adopts a straight microstrip line with a linewidth of 0.75 mm.

[0047] In this embodiment, the total length of the second radiating arm 2122 is approximately half the wavelength corresponding to the 1.4 GHz band (approximately 80 mm), and it adopts a straight microstrip line with a linewidth of 0.75 mm.

[0048] Furthermore, the reflector array 30 includes a first reflective strip 31, a second reflective strip 32, and a third reflective strip 33 printed at intervals along the length direction of the dielectric substrate 10, wherein the center points of the first reflective strip 31, the second reflective strip 32, and the third reflective strip 33 are located on the axis of symmetry of the left and right arms.

[0049] Specifically, the first reflector strip 31, the second reflector strip 32, and the third reflector strip 33 are used to reflect electromagnetic waves in the 5.5GHz, 2.4GHz, and 1.4GHz frequency bands, respectively, and their lengths correspond to half the wavelength of their operating frequency band in free space (after considering the shortening effect of the dielectric constant of the substrate, the actual physical length is calculated according to the conventional microstrip antenna design formula).

[0050] In this embodiment, the total length of the first reflective strip 31 is approximately half the wavelength of the 5.5 GHz band in free space (approximately 27 mm), and it adopts a straight microstrip line with a line width of 0.5 mm.

[0051] In this embodiment, the total length of the second reflective strip 32 is approximately half the wavelength of the 2.4 GHz band in free space (approximately 45 mm), and it adopts a straight microstrip line with a line width of 0.5 mm.

[0052] In this embodiment, the total length of the third reflective strip 33 is approximately half the wavelength of the 1.4 GHz band in free space (approximately 86 mm), and it adopts a straight microstrip line with a line width of 0.5 mm.

[0053] In some embodiments, the third reflective strip 33 bends downward at both ends. This structural design allows for better reflection of 1.4 GHz band signals and enables the longest possible length of the third reflective strip 33 to be accommodated within the limited length of the dielectric substrate 10.

[0054] In some embodiments, the first reflective strip 31 is arranged at a strictly equal interval with respect to the end of the upper dipole arm 211, and among the reflective strips themselves, with a preferred interval of 0.4 mm. In this way, the center points of the three reflective strips are all located on the axes of symmetry of the left and right arms, and the distance between each reflective strip and the dipole remains equal. This "hierarchical reflection" arrangement allows electromagnetic waves of different frequency bands to be independently reflected by reflective strips of corresponding lengths, forming an end-fire directional beam perpendicular to the direction of the reflective strip arrangement.

[0055] Therefore, the working principle of the tri-band directional antenna of this application is as follows: When the radio frequency signal is sent to the feed point through the coaxial feed line 40, the tri-frequency dipole radiating element 20 is excited, simultaneously generating radiated currents of 1.4 GHz, 2.4 GHz, and 5.5 GHz, with electromagnetic waves radiated in each frequency band propagating in all directions. Among these, the electromagnetic waves propagating towards the reflector array 30 are reflected and superimposed into the forward radiation field after encountering the corresponding frequency band's reflective strip. Since the length of the reflective strip is precisely designed to be half the wavelength of the corresponding frequency band in free space, the reflective strip exhibits a high impedance state, thus efficiently reflecting energy back towards the dipole. Simultaneously, the three reflective strips independently adjust the reflection phase of different frequency bands, causing the reflected waves of the three frequency bands to superimpose in phase, ultimately forming an end-fire directional beam pointing from the dipole towards the opposite direction of the reflector array 30. Because all reflective strips are located on the same side of the dipole, the antenna exhibits unidirectional end-fire characteristics, and the main lobe directions of the three frequency bands are highly consistent.

[0056] The overall performance of the tri-band directional antenna of the present application embodiment will be analyzed and explained below with reference to the accompanying drawings.

[0057] Reference Figure 4 The return loss performance parameter diagram of the tri-band directional antenna shows that the resonant frequencies of the tri-band directional antenna in this embodiment are 1.4GHz (1.43GHz~1.49GHz), 2.4GHz (2.4GHz~2.5GHz), and 5.5GHz (5.15GHz~5.85GHz), and the return loss is less than -10dB, indicating good performance.

[0058] Reference Figure 5 The efficiency diagram of the tri-band directional antenna shows that the resonant frequencies of the tri-band directional antenna in this embodiment are 1.4GHz (1.43GHz~1.49GHz), 2.4GHz (2.4GHz~2.5GHz), and 5.5GHz (5.15GHz~5.85GHz), and the efficiency is greater than 70% in all cases. The high transmission efficiency meets the transmission performance requirements of communication equipment.

[0059] Reference Figure 6 and Figure 7 The tri-band directional antenna has a 2D radiation pattern of 1.43GHz~1.49GHz. Taking the center frequency point, the maximum gain is greater than 3dBi, which meets the requirements for long-distance transmission performance.

[0060] Reference Figure 8 and Figure 9 The tri-band directional antenna has a 2D radiation pattern in the 2.4GHz~2.5GHz range. Taking the center frequency point, the maximum gain is greater than 5dBi, which meets the requirements for long-distance transmission performance.

[0061] Reference Figure 10 and Figure 11The tri-band directional antenna has a 2D radiation pattern of 5.15GHz to 5.85GHz. Taking the center frequency point, the maximum gain is greater than 5.2dBi, which meets the requirements for long-distance transmission performance.

[0062] In summary, the tri-band directional antenna of this application achieves the following beneficial effects: By integrating the compact layout of the low-frequency-surround-high-frequency tri-band dipole radiating element 20 and the multi-band distributed reflector array 30 onto the same surface of the dielectric substrate 10, the antenna can simultaneously cover three frequency bands—1.4 GHz, 2.4 GHz, and 5.5 GHz—within a small space of only 88 mm in length, 15 mm in width, and 1 mm in thickness. It achieves end-fire directional radiation in each band (3 dBi gain at 1.4 GHz, 5 dBi gain at 2.4 GHz, and 5.2 dBi gain at 5.5 GHz), while maintaining the advantages of low profile, low cost, and ease of mass production. This solution completely solves the technical problems of large antenna size, high profile, low gain, and difficulty in simultaneously covering multiple frequency bands in existing technologies.

[0063] According to a second aspect of this application, a terminal is also proposed, comprising a tri-band directional antenna as described in the first aspect above.

[0064] In this embodiment, the terminal is a drone remote controller. In other embodiments, the terminal can also be other remote controllers (such as TV remote controllers), CPEs, routers, IoT gateway devices, or other electronic devices; there are no restrictions here.

[0065] According to a third aspect of this application, an unmanned device is also proposed, comprising a tri-band directional antenna as described in the first aspect above.

[0066] In this embodiment, the unmanned device is a drone. In other embodiments, the unmanned device may also be an unmanned vehicle, an unmanned boat, etc., and there is no limitation here.

[0067] It is obvious that those skilled in the art can make various modifications and alterations to the embodiments of this application without departing from the spirit and scope of this application. In this way, this application also aims to cover such modifications and alterations if they fall within the scope of the claims and their equivalents. The word "comprising" does not exclude the presence of other elements or steps not listed in the claims. The simple fact that certain measures are described in mutually different dependent claims does not indicate that a combination of these measures cannot be used for profit. Any reference numerals in the claims should not be considered limiting in scope.

Claims

1. A tri-band directional antenna, characterized in that, include: Dielectric substrate; The tri-frequency dipole radiating unit is printed on one side of the surface of the dielectric substrate and is configured to emit electromagnetic waves in three different operating frequency bands. as well as A reflector array printed on the other side of the same surface of the dielectric substrate, the reflector array being configured to perform graded reflection of electromagnetic waves in three different operating frequency bands; The tri-frequency dipole radiation unit includes two symmetrical dipole units. Each dipole unit includes an upper dipole arm and a lower dipole arm. The upper dipole arm is close to the reflector array. The lower dipole arm includes a first radiation arm and a second radiation arm. The second radiation arm partially or completely surrounds the periphery of the first radiation arm. The reflector array includes a first reflective strip, a second reflective strip, and a third reflective strip printed along the length of the dielectric substrate and spaced apart vertically from each other. The center points of the first reflective strip, the second reflective strip, and the third reflective strip are located on the axis of symmetry of the two dipole units. The dipole unit further includes a signal transmission arm that connects the upper dipole arm and the lower dipole arm. The signal transmission arm is provided with a power supply point and a pad is provided at the power supply point. The upper dipole arm extends obliquely upward along the length of the dielectric substrate from a position above the feed point, and its end bends downward and converges near the reflector array. The first radiating arm extends horizontally along the length of the dielectric substrate from a position below the feed point. The first radiating arm includes a first radiating stub and a second radiating stub. The first radiating stub connects to the signal transmission arm. The first radiating stub and the second radiating stub form a two-stage lower stepped structure. The second radiating arm is spaced apart from the first radiating arm and extends horizontally along the length of the dielectric substrate. The second radiating arm is bent around the periphery of the second radiating branch to form a U-shaped surrounding structure.

2. The tri-band directional antenna according to claim 1, characterized in that, The first reflective strip, the second reflective strip, and the third reflective strip are all straight microstrip lines, and their lengths correspond to half the wavelength of the electromagnetic waves in their reflected operating frequency band. The third reflective strip bends downwards at both ends.

3. The tri-band directional antenna according to claim 1, characterized in that: The upper dipole arm is configured to operate in a first frequency band, the first radiating arm is configured to operate in a second frequency band, and the second radiating arm is configured to operate in a third frequency band. The third frequency band is lower than the second frequency band.

4. The tri-band directional antenna according to claim 3, characterized in that, The center frequency of the first frequency band is 5.5 GHz, the center frequency of the second frequency band is 2.4 GHz, and the center frequency of the third frequency band is 1.4 GHz; The total length of the upper dipole arm and the first radiating arm is one-quarter wavelength of the center frequency of their respective operating frequency bands, and the total length of the second radiating arm is half wavelength of the center frequency of its operating frequency band.

5. The tri-band directional antenna according to claim 1, characterized in that, It also includes a coaxial feed line, one end of which has an inner conductor and an outer conductor electrically connected to the pads of the two dipole units, and the other end of which is connected to an SMA female connector, thereby forming the antenna output.

6. A terminal, characterized in that, Includes the tri-band directional antenna as described in any one of claims 1-5.

7. An unmanned device, characterized in that, Includes the tri-band directional antenna as described in any one of claims 1-5.

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