Four-arm helical antenna and unmanned equipment

Abstract

The utility model discloses a four-arm helical antenna and unmanned equipment, and relates to the technical field of antennas. The four-arm helical antenna comprises four antenna arm groups which are uniformly arranged on a dielectric cylinder, wherein each antenna arm group comprises a low-frequency antenna arm and a high-frequency antenna arm; the low-frequency antenna arm is inclined upwards from the bottom end of the dielectric cylinder and extends to the top of the dielectric cylinder, and the low-frequency antenna arm is a broken line type spiral arm; the high-frequency antenna arm obliquely extends upwards from the bottom end of the dielectric cylinder, and the high-frequency antenna arm is a linear spiral arm; and the inclination angle of the low-frequency antenna arm is different from that of the high-frequency antenna arm. Through the above technical means, the fold line type low-frequency antenna arm and the linear type high-frequency antenna arm can realize the broadband double-frequency radiation characteristic, the fold line type low-frequency antenna arm does not increase the size of the antenna and can increase the bandwidth of a low-frequency band, and it is ensured that the antenna has enough bandwidth under the small-size design. The problem that an existing antenna design scheme cannot meet the design requirement of miniaturization and wide bandwidth is solved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of antennas, and in particular to a four-arm spiral antenna and an unmanned device. BACKGROUND

[0002] With the rapid development of antenna technology, terminal antennas are gradually becoming small and integrated to adapt to communication devices in various fields. Terminal antennas include microstrip antennas and spiral antennas. Compared with microstrip antennas, spiral antennas, especially four-arm spiral antennas, are more suitable for the small market due to their light weight and small size. At the same time, in order to cover the four global satellite navigation systems and achieve high-precision positioning, especially to realize the PPP (Precise Point Positioning) function of terminal RTK (Real-Time Kinematic), the terminal antenna also needs to have a wide enough bandwidth. This means that the four-arm spiral antenna for navigation terminals needs to be designed to be small and wide.

[0003] In the prior art, the design scheme of the four-arm spiral antenna includes cascading coaxial structures with different frequencies, adopting a tapered structure to achieve wideband, and generating dual frequencies by using different arm lengths. However, the coaxial design scheme and the tapered design scheme will respectively increase the size of the antenna in the axial and radial directions, and the antenna bandwidth of the design scheme of generating dual frequencies by using different arm lengths is relatively narrow. In this regard, the above design schemes cannot meet the design requirements of small size and wide bandwidth. SUMMARY

[0004] The present application provides a four-arm spiral antenna and an unmanned device to realize dual-frequency operation through a low-frequency antenna arm of a broken line type and a high-frequency antenna arm of a straight line type. The low-frequency antenna arm of the broken line type does not increase the size of the antenna and can increase the bandwidth of the low-frequency frequency band, ensuring that the antenna can have a wide enough bandwidth under the design of small size, thereby solving the problem that the existing antenna design scheme cannot meet the design requirements of small size and wide bandwidth.

[0005] In a first aspect, the present application provides a four-arm spiral antenna, an antenna arm group, and a dielectric cylinder, wherein:

[0006] The four antenna arm groups are uniformly arranged on the dielectric cylinder, and each antenna arm group includes a low-frequency antenna arm and a high-frequency antenna arm.

[0007] The low-frequency antenna arm extends upward and obliquely from the bottom end of the dielectric cylinder to the top of the dielectric cylinder, and the low-frequency antenna arm is a broken line type spiral arm.

[0008] The high-frequency antenna arm extends upward and obliquely from the bottom end of the dielectric cylinder, and the high-frequency antenna arm is a straight line type spiral arm.

[0009] The tilt angle of the low-frequency antenna arm is different from the tilt angle of the high-frequency antenna arm.

[0010] In a second aspect, the present application provides an unmanned device comprising the four-arm helical antenna as described in the first aspect.

[0011] In the present application, four antenna arm groups are uniformly arranged on the dielectric cylinder of the four-arm helical antenna, each antenna arm group comprising a low-frequency antenna arm and a high-frequency antenna arm, the low-frequency antenna arm extending upward from the bottom end of the dielectric cylinder to the top of the dielectric cylinder at a tilt angle, and the high-frequency antenna arm extending upward from the bottom end of the dielectric cylinder at a tilt angle different from that of the low-frequency antenna arm, the low-frequency antenna arm being used for receiving and transmitting low-frequency signals, and the high-frequency antenna arm being used for receiving and transmitting high-frequency signals, so as to realize dual-frequency operation and increase the bandwidth of the four-arm helical antenna. The low-frequency antenna arm is a broken-line helical arm, and the high-frequency antenna arm is a straight-line helical arm. The broken-line low-frequency antenna arm does not increase the size of the antenna and can increase the bandwidth of the low-frequency frequency band. The antenna can have a wide enough bandwidth under small size design, realizing miniaturization and wide bandwidth design of the four-arm helical antenna, solving the problem that the existing antenna design scheme cannot meet the design requirements of miniaturization and wide bandwidth, and effectively expanding the application scenarios of the four-arm helical antenna. BRIEF DESCRIPTION OF DRAWINGS

[0012] Figure 1 is a structural schematic diagram of a four-arm helical antenna provided by an embodiment of the present application;

[0013] Figure 2 is one of structural schematic diagrams of an antenna arm group provided by an embodiment of the present application;

[0014] Figure 3 is another of structural schematic diagrams of an antenna arm group provided by an embodiment of the present application;

[0015] In the figure, 10 is a dielectric cylinder; 20 is an antenna arm group; 21 is a low-frequency antenna arm; 211 is a first antenna arm; 212 is a first connecting part; 213 is a second antenna arm; 214 is a second connecting part; 215 is a third antenna arm; 22 is a high-frequency antenna arm; 23 is a first short-circuit port; 24 is a feeding port; and 25 is a second short-circuit port. DETAILED DESCRIPTION

[0016] In order to make the purposes, technical solutions and advantages of the present application clearer, the following further describes the specific embodiments of the present application with reference to the drawings. It should be understood that the specific embodiments described herein are merely intended to explain the present application, but not to limit the present application. In addition, it should be noted that only the parts related to the present application are shown in the drawings for the convenience of description, but not all the parts. Before discussing the example embodiments in more detail, it should be mentioned that some example embodiments are described as processes or methods depicted as flowcharts. Although the flowcharts describe the operations (or steps) as sequential processes, many of the operations can be implemented in parallel, concurrently or simultaneously. In addition, the order of the operations can be rearranged. The process can be terminated when the operations are completed, but can also have additional steps not included in the drawings. The process can correspond to a method, function, procedure, subroutine, subprogram, etc.

[0017] The terms "first", "second", etc. in the specification and claims of the present application are used to distinguish similar objects, and are not intended to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged under appropriate circumstances, so that the embodiments of the present application can be implemented in an order other than that illustrated or described herein, and the objects distinguished by "first", "second", etc. are generally of a kind and do not limit the number of objects, for example, the first object can be one or more. In addition, "and / or" in the specification and claims indicates at least one of the connected objects, and the character " / ", generally indicates that the objects before and after are in a "or" relationship.

[0018] In related implementations, the design scheme of the four-arm spiral antenna uses two structures of different frequencies to cascade coaxially, adopts a taper structure to achieve wideband, and uses different arm lengths to generate dual frequency when implementing dual frequency. Among them, the coaxial design scheme is to stack two spiral antennas up and down, which increases the size of the antenna in the axial direction. The taper design scheme is to set the spiral antenna on a tapered column, which increases the size of the antenna in the radial direction. The design scheme of different arm lengths generating dual frequency is to set spiral antennas of different arm lengths on a cylindrical body at the same time, which causes different spiral antennas to affect each other, resulting in low antenna gain and narrow bandwidth. Therefore, the above design precautions cannot meet the design requirements of miniaturization and wide bandwidth.

[0019] To solve the problems existing in the above implementation, the present embodiment provides a four-arm spiral antenna to achieve wideband dual-frequency radiation characteristics by a low-frequency antenna arm of a broken line type and a high-frequency antenna arm of a straight line type. The low-frequency antenna arm of the broken line type does not increase the size of the antenna and can increase the bandwidth of the low-frequency band, ensuring that the antenna can also have a wide enough bandwidth under the design of small size.

[0020] In an embodiment, Figure 1A structural schematic diagram of a four-arm helical antenna is provided in the embodiments of the present application. Referring to Figure 1 The four-arm helical antenna comprises an antenna arm group 20 and a dielectric cylinder 10, and the four antenna arm groups 20 are uniformly arranged on the dielectric cylinder 10. Each antenna arm group 20 comprises a low-frequency antenna arm 21 and a high-frequency antenna arm 22. The low-frequency antenna arm 21 extends upwardly from the bottom end of the dielectric cylinder 10 to the top of the dielectric cylinder 10, and the low-frequency antenna arm 21 is a broken-line helical arm. The high-frequency antenna arm 22 extends upwardly from the bottom end of the dielectric cylinder 10, and the high-frequency antenna arm 22 is a straight-line helical arm. The inclination angle of the low-frequency antenna arm 21 is different from that of the high-frequency antenna arm 22.

[0021] For example, a flexible dielectric plate is arranged on the dielectric cylinder 10, and the antenna arm group 20 is arranged on the flexible dielectric plate. The four antenna arm groups 20 are uniformly and rotationally distributed on the flexible dielectric plate. The four antenna arm groups 20 extend correspondingly to four directions to form four annular radiators, thereby realizing omnidirectional signal receiving and transmitting.

[0022] At the same time, in the circumferential direction of the dielectric cylinder 10, the low-frequency antenna arm 21 and the high-frequency antenna arm 22 are alternately arranged, thereby receiving and transmitting high-frequency and low-frequency signals in four directions, and realizing omnidirectional high-frequency and low-frequency signal receiving and transmitting.

[0023] Figure 2 FIG. 1 is a structural schematic diagram of an antenna arm group 20 provided in the embodiments of the present application. Figure 2 The antenna arm group 20 shown is in the unfolded state. As shown in FIG. 1, the antenna arm group 20 comprises a low-frequency antenna arm 21 and a high-frequency antenna arm 22. Figure 2As shown, one antenna arm group 20 includes a low-frequency antenna arm 21 and a high-frequency antenna arm 22, the low-frequency antenna arm 21 is used to receive and transmit low-frequency signals, and the high-frequency antenna arm 22 is used to receive and transmit high-frequency signals. Among them, the low-frequency antenna arm 21 extends from the bottom end to the top of the medium cylinder 10, and its length is longer to effectively match the wavelength of the low-frequency signal. The high-frequency antenna arm 22 extends from the bottom end of the medium cylinder 10 but does not extend to the top, and its length is shorter to effectively match the wavelength of the high-frequency signal. The four-arm helical antenna receives or transmits low-frequency signals and high-frequency signals through the low-frequency antenna arm 21 and the high-frequency antenna arm 22 respectively, thereby realizing dual-frequency operation. The dual-frequency operation process includes a signal receiving process and a signal transmitting process. In the signal receiving process, when the low-frequency signal propagates to the low-frequency antenna arm 21, the low-frequency antenna arm 21 generates an induced current, which is transmitted to the receiver through the low-frequency antenna arm 21 and the feed network, and the receiver processes the induced current. When the high-frequency signal propagates to the high-frequency antenna arm 22, the high-frequency antenna arm 22 generates an induced current, which is transmitted to the receiver through the high-frequency antenna arm 22 and the feed network, and the receiver processes the induced current. In the signal transmitting process, the transmitter transmits the low-frequency signal to the low-frequency antenna arm 21 through the feed network, and the low-frequency antenna arm 21 radiates the low-frequency signal; the transmitter transmits the high-frequency signal to the high-frequency antenna arm 22 through the feed network, and the high-frequency antenna arm 22 radiates the high-frequency signal.

[0024] The low-frequency antenna arm 21 is designed as a broken line type spiral arm, that is, the low-frequency antenna arm 21 is connected by a plurality of straight line type antenna arms. The design of the broken line type can increase the length of the low-frequency antenna arm 21 without occupying a large space. The low-frequency antenna arm 21 with increased length can better match the wavelength of the low-frequency signal, thereby widening the low-frequency bandwidth of the low-frequency antenna arm 21. The high-frequency antenna arm 22 is designed as a straight line type spiral arm, which does not increase the length of the high-frequency antenna arm 22, so as to effectively match the wavelength of the high-frequency signal. The straight line type spiral arm has the advantages of simple structure, easy manufacturing and debugging, etc.

[0025] Because the inclination angles of the low-frequency antenna arm 21 and the high-frequency antenna arm 22 are different, the electromagnetic coupling strength between the low-frequency antenna arm 21 and the high-frequency antenna arm 22 is optimized, so that the high-frequency antenna arm 22 can effectively obtain energy from the low-frequency antenna arm 21 within the required frequency range, realize impedance matching of the low-frequency antenna arm 21 and the high-frequency antenna arm 22 with the feedback network, reduce reflection loss, and improve transmission efficiency.

[0026] In this embodiment, the low-frequency antenna arm 21 and the high-frequency antenna arm 22 are alternately arranged on the dielectric cylinder 10 in a spiral manner to form a four-arm spiral antenna, so that the four-arm spiral antenna can receive and transmit low-frequency signals and high-frequency signals through the low-frequency antenna arm 21 and the high-frequency antenna arm 22, and realize dual-frequency operation. The low-frequency antenna arm 21 in the zigzag shape and the high-frequency antenna arm 22 in the straight line shape not only expand the bandwidth of the antenna, but also do not occupy a large space, and realize the miniaturization and wide bandwidth design of the four-arm spiral antenna.

[0027] In an embodiment, the low-frequency antenna arm 21 is a main radiation arm, and the high-frequency antenna arm 22 is a parasitic arm. That is, the low-frequency antenna arm 21 is connected to the feed network, and the high-frequency antenna arm 22 is not connected to the feed network. The induced current is generated by the coupling between the low-frequency antenna arm 21 and the high-frequency antenna arm 22, so that the low-frequency antenna arm 21 and the high-frequency antenna arm 22 realize dual-frequency operation. For example, the dual-frequency operation process is as follows: in the signal receiving process, when the electromagnetic wave signal reaches the antenna, the low-frequency antenna arm 21 captures the electromagnetic wave signal, and the captured electromagnetic wave signal generates an induced current on the low-frequency antenna arm 21, and the induced current is transmitted to the feed network connected to the low-frequency antenna arm 21. At the same time, the high-frequency antenna arm 22 inductively couples the signal current from the low-frequency antenna arm 21 through the electromagnetic field, and indirectly transmits the signal current to the feed network. In the signal transmitting process, the feed network transmits the signal current to the low-frequency antenna arm 21, and the high-frequency antenna arm 22 inductively couples the signal current from the low-frequency antenna arm 21 through the electromagnetic field, and the high-frequency antenna arm 22 and the low-frequency antenna arm 21 convert the signal current into electromagnetic wave signals and radiate them into space.

[0028] The existence of the parasitic arm can expand the operating frequency band of the antenna and improve the gain. The resonant frequency of the parasitic arm is higher than that of the main radiation arm, which can provide additional resonant points for the antenna without increasing the size of the antenna material, which helps to expand the operating frequency band of the antenna and cover a wider frequency range. Therefore, in this embodiment, the low-frequency antenna arm 21 is designed as a main radiation arm and the high-frequency antenna arm 22 is designed as a parasitic arm to expand the operating frequency band of the antenna and improve the gain.

[0029] Reference Figure 1 and Figure 2 The bottom end of the dielectric cylinder 10 is provided with a second short-circuit port 25, and the second short-circuit port 25 forms a second ground point corresponding to the connection of the high-frequency antenna arm 22. For example, the high-frequency antenna arm 22 as a parasitic arm is grounded through the second short-circuit port 25, so that the high-frequency antenna arm 22 forms a good electrical connection with other parts of the antenna system. When the high-frequency antenna arm 22 is grounded, the frequency difference between the resonant point of the low-frequency antenna arm 21 and the resonant point of the high-frequency antenna arm 22 can be effectively reduced, and even merged into the same resonant point, effectively widening the low-frequency bandwidth of the antenna.

[0030] Optionally, the angle between the extending direction of the high-frequency antenna arm 22 and the vertical direction is 24°-36°. The angle between the extending direction of the low-frequency antenna arm 21 and the vertical direction is 21°-29°. Through tests, when the angle between the extending direction of the high-frequency antenna arm 22 and the vertical direction is in the range of 24°-36°, and the angle between the extending direction of the low-frequency antenna arm 21 and the vertical direction is in the range of 21°-29°, the high-frequency antenna arm 22 and the low-frequency antenna arm 21 can achieve a higher impedance matching effect with the feedback network, effectively improving the energy transmission efficiency.

[0031] In an embodiment, the low-frequency antenna arm 21 in the zigzag shape can be connected by two, three or more antenna arms. When the number of antenna arms is large, the occupied space of the low-frequency antenna arm 21 will also increase. Therefore, the low-frequency antenna arm 21 in the zigzag shape can be connected by three antenna arms, which widens the bandwidth of the low-frequency band without occupying too much space.

[0032] Reference Figure 1 and Figure 2 The low-frequency antenna arm 21 includes the first antenna arm 211, the second antenna arm 213, the third antenna arm 215, the first connecting part 212 and the second connecting part 214, which are parallel to each other. The first antenna arm 211 and the second antenna arm 213 extend upwardly from the bottom end of the dielectric cylinder 10 to the top of the dielectric cylinder 10, and the third antenna arm 215 extends upwardly from the bottom end of the dielectric cylinder 10. The first end of the first antenna arm 211 is connected to the first end of the second antenna arm 213 through the first connecting part 212, and the second end of the second antenna arm 213 is connected to the first end of the third antenna arm 215 through the second connecting part 214. The first connecting part 212 and the second connecting part 214 are arranged at the top end and the bottom end of the dielectric cylinder 10, respectively. The first connecting part 212 and the second connecting part 214 are relatively short in length, and are used to connect the first antenna arm 211, the second antenna arm 213 and the third antenna arm 215 to form the low-frequency antenna arm 21 in the zigzag shape. The first antenna arm 211, the second antenna arm 213 and the third antenna arm 215 effectively extend the length of the low-frequency antenna arm 21 with a small space size, achieve better reception and transmission of low-frequency signals by the low-frequency antenna arm 21, and further widen the low-frequency bandwidth of the low-frequency antenna arm 21. Moreover, the first antenna arm 211, the second antenna arm 213 and the third antenna arm 215 can optimize the input impedance of the low-frequency antenna arm 21, so that the low-frequency antenna arm 21 is better matched with the feeding network, thereby reducing the reflection loss and improving the transmission efficiency. The low-frequency antenna arm 21 can achieve resonance, thereby improving the signal gain and further widening the low-frequency bandwidth of the low-frequency antenna arm 21.

[0033] The first antenna arm 211 and the second antenna arm 213 extend from the bottom end to the top of the dielectric cylinder 10, while the third antenna arm 215 extends upward from the bottom of the dielectric cylinder 10, and the length of the third antenna arm 215 is adjustable. In the design process, the length of the third antenna arm 215 can be adjusted to make the low-frequency antenna arm 21 resonate at a low frequency band, thereby expanding the low-frequency bandwidth of the low-frequency antenna arm 21.

[0034] The first connecting part 212 and the second connecting part 214 extend along the horizontal direction. The first connecting part 212 and the second connecting part 214 extending along the horizontal direction can be arranged on the top and bottom of the dielectric cylinder 10 to leave more space for arranging the first antenna arm 211, the second antenna arm 213 and the third antenna arm 215, which is conducive to extending the length of the first antenna arm 211, the second antenna arm 213 and the third antenna arm 215.

[0035] As shown in Figure 2 The low-frequency antenna arm 21 shown in the figure can be understood that the second antenna arm 213 is arranged between the first antenna arm 211 and the third antenna arm 215. In another embodiment, Figure 3 is a second structural diagram of the antenna arm group 20 provided by the present application. As Figure 3 shown, the third antenna arm 215 is arranged between the first antenna arm 211 and the second antenna arm 213, which can optimize the impedance matching of the low-frequency parasitic resonance and improve the gain bandwidth. It can be understood that no matter how the first antenna arm 211, the second antenna arm 213 and the third antenna arm 215 are arranged, the first antenna arm 211, the second antenna arm 213, the third antenna arm 215, the first connecting part 212 and the second connecting part 214 can be connected to form a broken line type antenna arm, which can be used as a low-frequency antenna arm.

[0036] Referring to Figure 1 and Figure 2 , the first short-circuit port 23 is arranged on the second connecting part 214, and the first short-circuit port 23 forms the first ground point corresponding to the connection of the low-frequency antenna arm 21. For example, the low-frequency antenna arm 21 is connected with the first ground point through the first short-circuit port 23 on the second connecting part 214, and the connection of the low-frequency antenna arm 21 with the first ground point can improve the input impedance, improve the problem of mismatching between the antenna impedance and the feeding network impedance caused by too small input impedance, reduce the resonance frequency of the low-frequency antenna arm 21, and increase the radiation efficiency and gain of the low-frequency antenna arm 21.

[0037] Referring to Figure 1 and Figure 2The second end of the first antenna arm 211 is used to connect the feeding port 24, that is, the feeding port 24 is arranged at the bottom of the dielectric cylinder 10, and the end of the first antenna arm 211 arranged at the bottom end of the dielectric cylinder 10 is connected to the feeding port 24. The feeding port 24 is a port of the feeding network. It can be understood that only one feeding port 24 for connecting the low-frequency antenna arm 21 is arranged in the embodiment, so that the low-frequency antenna arm 21 is designed as a main radiation arm and the high-frequency antenna arm 22 is designed as a parasitic arm, and the induced current is generated by the coupling between the low-frequency antenna arm 21 and the high-frequency antenna arm 22, so that the low-frequency antenna arm 21 and the high-frequency antenna arm 22 realize dual-frequency operation.

[0038] In summary, the four-arm spiral antenna provided by the embodiment of the present application is provided with four antenna arm groups 20 uniformly arranged on the dielectric cylinder 10 of the four-arm spiral antenna, each antenna arm group 20 includes a low-frequency antenna arm 21 and a high-frequency antenna arm 22, the low-frequency antenna arm 21 extends upward from the bottom end of the dielectric cylinder 10 to the top of the dielectric cylinder 10, and the high-frequency antenna arm 22 extends upward from the bottom end of the dielectric cylinder 10, the inclination angle of the low-frequency antenna arm 21 is different from the inclination angle of the high-frequency antenna arm 22, the low-frequency antenna arm 21 is used for receiving and transmitting low-frequency signals, and the high-frequency antenna arm 22 is used for receiving and transmitting high-frequency signals, so as to realize dual-frequency operation and increase the bandwidth of the four-arm spiral antenna. The low-frequency antenna arm 21 is a broken-line spiral arm, and the high-frequency antenna arm 22 is a straight-line spiral arm. The broken-line low-frequency antenna arm 21 does not increase the size of the antenna and can increase the bandwidth of the low-frequency frequency band. The antenna can have a wide enough bandwidth under the design of small size, realizes the miniaturization and wide bandwidth design of the four-arm spiral antenna, solves the problem that the existing antenna design scheme cannot meet the design requirement of miniaturization and wide bandwidth, and effectively expands the application scenarios of the four-arm spiral antenna.

[0039] On the basis of the above-mentioned embodiment, the embodiment of the present application further provides an unmanned device, which includes the four-arm spiral antenna as described in the above-mentioned embodiment. Exemplarily, the satellite navigation system of the unmanned device is provided with the four-arm spiral antenna, and the satellite navigation system transmits and receives signals through the four-arm spiral antenna to realize high-precision positioning. Since the four-arm spiral antenna meets the design requirement of miniaturization and wide bandwidth, the satellite navigation system or even the unmanned device can realize miniaturization design and can be applied to specific scenarios, thereby expanding the applicability of the satellite navigation system and the unmanned device.

[0040] The above merely describes the preferred embodiments of the present application and the technical principles applied. The present application is not limited to the specific embodiments herein, and various obvious changes, modifications and replacements made by those skilled in the art without departing from the scope of the present application shall not be excluded. Therefore, although the present application is described in more detail through the above embodiments, the present application is not limited to the above embodiments, and more other equivalent embodiments can be included without departing from the concept of the present application, and the scope of the present application is determined by the scope of the claims.

Claims

1. A four-arm helical antenna, characterized by, The four antenna arm groups are evenly arranged on the dielectric cylinder, and each of the antenna arm groups comprises a low-frequency antenna arm and a high-frequency antenna arm. The low-frequency antenna arm extends upwardly and obliquely from the bottom end of the dielectric cylinder to the top of the dielectric cylinder, and the low-frequency antenna arm is a broken-line spiral arm. The high-frequency antenna arm extends upwardly and obliquely from the bottom end of the dielectric cylinder, and the high-frequency antenna arm is a straight-line spiral arm. The low-frequency antenna arm is a main radiation arm, and the high-frequency antenna arm is a parasitic arm. The low-frequency antenna arm comprises a first antenna arm, a second antenna arm, a third antenna arm, a first connecting part and a second connecting part, the first antenna arm and the second antenna arm extend upwardly and obliquely from the bottom end of the dielectric cylinder to the top of the dielectric cylinder, the third antenna arm extends upwardly and obliquely from the bottom end of the dielectric cylinder, the first end of the first antenna arm is connected to the first end of the second antenna arm through the first connecting part, the second end of the second antenna arm is connected to the first end of the third antenna arm through the second connecting part, and the first connecting part and the second connecting part are arranged at the top end and the bottom end of the dielectric cylinder respectively.

2. The four-arm helical antenna of claim 1, wherein, The third antenna arm is arranged between the first antenna arm and the second antenna arm.

3. The four-arm helical antenna of claim 1, wherein, The second connecting part is provided with a first short-circuit opening, and the first short-circuit opening forms a first ground point corresponding to the connection of the low-frequency antenna arm.

4. The quadrafoil antenna of claim 3, wherein, The second end of the first antenna arm is used for connecting a feeding port.

5. The quadrafoil antenna of claim 3, wherein, The first connecting part and the second connecting part are arranged in the horizontal direction.

6. The quadrafoil antenna of claim 3, wherein, The bottom end of the dielectric cylinder is provided with a second short-circuit opening, and the second short-circuit opening forms a second ground point corresponding to the connection of the high-frequency antenna arm.

7. The quadrafoil antenna of claim 3, wherein, The angle between the extension direction of the high-frequency antenna arm and the vertical direction is 24°-36°; and / or, the angle between the extension direction of the low-frequency antenna arm and the vertical direction is 21°-29°.

8. The quadrafoil antenna of claim 1, wherein, The four-arm spiral antenna comprises the four-arm spiral antenna according to any one of claims 1-9.

9. The quadrafoil antenna of claim 1, wherein, ​ 10. An unmanned device, comprising: ​

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