Omnidirectional antenna
By setting up upper and lower symmetric oscillator arms and coaxial cables in the omnidirectional antenna, the integrated introduction of dual-ports is solved, and the complexity and high cost of design of wide-band miniaturized omnidirectional antennas in the prior art is achieved, and the wideband impedance matching and omnidirectionality of the antenna plane are achieved.
Patent Information
- Application Number
- CN202421815048.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-07-30
- Publication Date
- 2025-05-09
- Estimated Expiration
- 2034-07-30
AI Technical Summary
The existing broadband miniaturized omnidirectional antennas have complexity and high costs in the design and manufacturing process, and the feeder travel has an adverse impact on the antenna performance, making it difficult to balance performance, cost, size and installation convenience.
By setting up two symmetrical oscillator arms and coaxial cables in the omnidirectional antenna, the coaxial cable of the first antenna body passes through the second antenna body, realizing the integrated lead-out of the dual-port, reducing the structural complexity and manufacturing cost, and solving the adverse impact of feeder passing on the antenna.
The wide band impedance matching and the omnidirectionality of the antenna plane pattern are achieved, reducing the difficulty of coaxial installation of antenna products, and improving the gain and polarization purity of the antenna.
Smart Images
Figure CN222851661U_ABST
Abstract
Description
Technical Field
[0001] The present application relates to the field of antenna technology, and in particular to an omnidirectional antenna. Background Art
[0002] Omnidirectional antennas, as a type of antenna that can radiate and receive electromagnetic waves evenly in the surrounding space, are widely used in wireless communication systems, especially in situations where non-directional coverage is required. It can provide 360-degree uniform radiation characteristics on the horizontal plane, ensuring consistent signal transmission efficiency in any direction, and is therefore particularly suitable for building base stations, wireless local area networks (WLANs), Internet of Things (IoT) devices, and emergency communication systems, achieving wide signal coverage and efficient data transmission.
[0003] However, with the rapid development of communication technology, the requirements for antenna performance are also increasing, especially broadband miniaturized omnidirectional antennas have become the new favorite of the market. This type of antenna needs to cover a wider frequency range to meet the needs of multi-band communications, and strive to achieve a smaller size while maintaining high performance. Traditionally, broadband miniaturized omnidirectional antennas are mostly single-port forms, and antennas with multiple ports usually need to adopt a design that includes complex frequency division and combining structures and sectors. This processing method is difficult to design and costly.
[0004] In addition, if one attempts to directly integrate multiple ports into one antenna structure to support multi-band or multi-system applications, not only will the antenna design and manufacturing process become more complicated, but it may also cause mutual interference due to the serial arrangement of the feeder (i.e., the signal line connecting the antenna to the transceiver), thereby affecting the antenna's radiation performance, receiving sensitivity and other performance.
[0005] Therefore, in the process of pursuing broadband miniaturized omnidirectional antennas, how to balance performance, cost, size and ease of installation has become an important challenge in the current technological development.
[0006] There is currently no effective technical solution to the above problems. Utility Model Content
[0007] The purpose of the present application is to provide an omnidirectional antenna to achieve dual-port integrated lead-out without the need to adopt a frequency division and combination method for layout design, and to solve the adverse effects of a feeder line passing near the antenna on the antenna.
[0008] The present application provides an omnidirectional antenna, which includes a first antenna body and a second antenna body arranged vertically, wherein the first antenna body and the second antenna body each include two dipole arms symmetrically arranged vertically and a coaxial cable connected to the two dipole arms, and the coaxial cable of the first antenna body passes through the inside of the second antenna body.
[0009] The omnidirectional antenna of the present application is based on a first antenna body and a second antenna body arranged up and down, and realizes the dual-port lead-out of the omnidirectional antenna without adopting the layout design in a frequency division and combination manner, which can effectively reduce the manufacturing cost of the antenna and reduce the structural complexity. At the same time, the coaxial cable of the first antenna body is designed to pass through the second antenna body for arrangement, and the dual-port integrated lead-out is realized to reduce the difficulty of coaxial installation of the antenna product, and solves the adverse effect of the feed line passing near the antenna on the antenna, thereby realizing wide-band impedance matching and the omnidirectionality of the antenna azimuth plane radiation pattern.
[0010] In the omnidirectional antenna, the two dipole arms are columnar, and adjacent ends have contraction portions contracting toward the center.
[0011] In this example, the gradually shrinking portion can compress the beam width of the omnidirectional antenna in the vertical plane, thereby improving the gain of the antenna. Secondly, the waves emitted by the first antenna body or the second antenna body are reflected by the corresponding two shrinking portions and become plane radiation to the free space, which facilitates improving the polarization purity of the antenna.
[0012] The omnidirectional antenna, wherein the contraction portion is a conical contraction structure.
[0013] In this example, the tapered portion has a uniform curved surface to further improve the gain and corresponding reflection effect of the antenna.
[0014] The omnidirectional antenna, wherein at least one dipole arm in the first antenna body and / or at least one dipole arm in the second antenna body is provided with an adjustment sheet for adjusting the working frequency band.
[0015] The omnidirectional antenna, wherein the two dipole arms are respectively connected to the outer conductor and the inner conductor of the coaxial cable.
[0016] The omnidirectional antenna, wherein the distance between the first antenna body and the second antenna body is 0.8-1.2 times the length of the dipole arm.
[0017] The omnidirectional antenna, wherein the coaxial cable of the first antenna body passes through the contraction parts of the two dipole arms of the second antenna body.
[0018] The omnidirectional antenna, wherein the positions of the contraction parts of the two dipole arms through which the coaxial cable of the first antenna body passes are symmetrical.
[0019] The omnidirectional antenna, wherein the exposed portion of the coaxial cable of the first antenna body located between the two dipole arms of the second antenna body is in a spiral shape.
[0020] In the omnidirectional antenna, the axial length of the spiral portion of the coaxial cable is less than 1 / 5 of the total length of the two dipole arms.
[0021] As can be seen from the above, the omnidirectional antenna of the present application is composed of a first antenna body and a second antenna body arranged upper and lower, and realizes the dual-port lead-out of the omnidirectional antenna without adopting the layout design in a frequency division and combination manner, which can effectively reduce the manufacturing cost of the antenna and reduce the structural complexity. At the same time, the coaxial cable of the first antenna body is designed to pass through the second antenna body for arrangement, and the dual-port integrated lead-out is realized to reduce the difficulty of coaxial installation of the antenna product, and solves the adverse effects of the feed line passing near the antenna on the antenna, thereby realizing wide-band impedance matching and the omnidirectionality of the antenna azimuth plane radiation pattern. BRIEF DESCRIPTION OF THE DRAWINGS
[0022] Figure 1 A schematic diagram of a front cross-sectional structure of an omnidirectional antenna provided in some embodiments of the present application.
[0023] Figure 2 A schematic diagram of a front cross-sectional structure of an omnidirectional antenna provided in some other embodiments of the present application.
[0024] Figure 3 It is a structural schematic diagram of a comparative example when the coaxial cable of the first antenna body does not pass through the second antenna body.
[0025] Figure 4 for Figure 1 The standing wave ratio diagram of the second antenna body of the omnidirectional antenna shown.
[0026] Figure 5 for Figure 2 The standing wave ratio diagram of the second antenna body of the omnidirectional antenna shown.
[0027] Figure 6 for Figure 3 The standing wave ratio diagram of the second antenna body of the omnidirectional antenna shown.
[0028] Figure 7 for Figure 1 The azimuth plane radiation pattern of the second antenna body of the omnidirectional antenna shown.
[0029] Figure numerals: 1. first antenna body; 2. second antenna body; 3. dipole arm; 4. coaxial cable; 5. contraction part; 6. adjustment sheet; 7. exposed part. DETAILED DESCRIPTION
[0030] The embodiments of the present invention are described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and cannot be understood as limiting the present invention.
[0031] In the description of the present utility model, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present utility model and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present utility model. In addition, the terms "first" and "second" are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present utility model, the meaning of "multiple" is two or more, unless otherwise clearly and specifically defined.
[0032] In the description of the present utility model, it should be noted that, unless otherwise clearly specified and limited, the terms "installation", "connection" and "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection, an electrical connection, or mutual communication; it can be a direct connection, or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present utility model can be understood according to specific circumstances.
[0033] In the present utility model, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may include that the first and second features are in direct contact, or may include that the first and second features are not in direct contact but are in contact through another feature between them. Moreover, a first feature being "above", "above" and "above" a second feature includes that the first feature is directly above and obliquely above the second feature, or simply indicates that the first feature is higher in level than the second feature. A first feature being "below", "below" and "below" a second feature includes that the first feature is directly below and obliquely below the second feature, or simply indicates that the first feature is lower in level than the second feature.
[0034] The disclosure below provides many different embodiments or examples for realizing different structures of the utility model. In order to simplify the disclosure of the utility model, the components and settings of specific examples are described below. Of course, they are merely examples, and the purpose is not to limit the utility model. In addition, the utility model may repeat reference numbers and / or reference letters in different examples, and such repetition is for the purpose of simplification and clarity, and does not itself indicate the relationship between the various embodiments and / or settings discussed. In addition, the utility model provides various specific examples of processes and materials, but those of ordinary skill in the art may be aware of the application of other processes and / or the use of other materials.
[0035] Please refer to Figure 1 and Figure 2 Some embodiments of the present application provide an omnidirectional antenna, which includes a first antenna body 1 and a second antenna body 2 arranged vertically, and the first antenna body 1 and the second antenna body 2 each include two dipole arms 3 symmetrically arranged vertically and a coaxial cable 4 connected to the two dipole arms 3, and the coaxial cable 4 of the first antenna body 1 passes through the inside of the second antenna body 2.
[0036] Specifically, the first antenna body 1 and the second antenna body 2 are both radiating units of the antenna, and the coaxial cable 4 is used to connect the corresponding antenna bodies and feeding components (not shown in the figure), that is, the two dipole arms 3 of the first antenna body 1 are directly fed through the corresponding coaxial cables 4, and the two dipole arms 3 of the second antenna body 2 are directly fed through the corresponding coaxial cables 4; wherein the coaxial cable 4 has the advantages of low loss, strong anti-interference ability, easy installation and uniform impedance. It is used as a feeder in the present application and can meet the requirements of the antenna system for signal transmission efficiency and stability.
[0037] More specifically, if Figure 1 and Figure 2 As shown, the coaxial cable 4 of the second antenna body 2 is led out from the bottom thereof, and the coaxial cable 4 connected to the two dipole arms 3 of the first antenna body 1 passes through the two dipole arms 3 in the second antenna body 2 and is led out from the bottom of the second antenna body 2, so that the ports of the two antenna bodies can be led out from adjacent positions, realizing the integrated lead-out of the dual ports and effectively reducing the difficulty of coaxial installation of the antenna product.
[0038] More specifically, the first antenna body 1 and the second antenna body 2 constituting the omnidirectional antenna both operate in two operating frequency bands and are broadband antennas. In the embodiment of the present application, they preferably operate in low frequency bands and medium frequency bands, such as 703-960MHz and 1710-2690MHz bands.
[0039] More specifically, when the coaxial cable 4 is used as a feeder, if it passes near the outside of the antenna body, it will have an adverse effect on the antenna body. If the coaxial cable 4 of the first antenna body 1 is set as follows Figure 3 The method shown in FIG. 1 is to pass through the outside of the second antenna body 2, and the standing wave ratio diagram obtained is as follows: Figure 6 As shown in the figure, it can be seen that the standing wave ratio of the corresponding low-frequency band of the second antenna body 2 is greater than 2. It can be seen that the coaxial cable 4 of the first antenna body 1 under this structure deteriorates the impedance matching in the low-frequency band. On the contrary, the omnidirectional antenna of the embodiment of the present application sets the coaxial cable 4 of the first antenna body 1 to pass through the two dipole arms 3 of the second antenna body 2, which can effectively solve the adverse effects of the feed line passing near the antenna on the antenna, thereby achieving wide-band impedance matching and the omnidirectionality of the antenna azimuth plane radiation pattern.
[0040] It should be noted that the two dipole arms 3 in the first antenna body 1 and the two dipole arms 3 in the second antenna body 2 are both separately arranged, and the corresponding separation distance can be adjusted according to the working frequency band covered by the corresponding antenna body.
[0041] It should be noted that both the first antenna body 1 and the second antenna body 2 are omnidirectional antennas, that is, they can transmit and receive signals uniformly in all directions without a specific radiation direction.
[0042] More specifically, the coaxial cable 4 of the first antenna body 1 passes through the dipole arm 3 located at the bottom of the first antenna body 1 from the center and is connected to the middle of the dipole arm 3 located at the top, and the coaxial cable 4 of the second antenna body 2 passes through the dipole arm 3 located at the bottom of the second antenna body 2 from the center and is connected to the middle of the dipole arm 3 located at the top.
[0043] The omnidirectional antenna of the embodiment of the present application is composed of a first antenna body 1 and a second antenna body 2 arranged up and down, and realizes the dual-port lead-out of the omnidirectional antenna without adopting the layout design in a frequency division and combination manner, which can effectively reduce the manufacturing cost of the antenna and reduce the structural complexity. At the same time, the coaxial cable 4 of the first antenna body 1 is designed to pass through the second antenna body 2 for arrangement, and realizes the integrated lead-out of the dual ports to reduce the difficulty of coaxial installation of the antenna product, and solves the adverse effect of the feed line passing near the antenna on the antenna, thereby realizing wide-band impedance matching and the omnidirectionality of the antenna azimuth plane radiation pattern.
[0044] In some preferred embodiments, the two vibrator arms 3 are columnar, and adjacent ends have contraction portions 5 contracting toward the center.
[0045] Specifically, the dipole arm 3 is an important component of the antenna, which has the function of guiding and amplifying electromagnetic waves so that the electromagnetic signal received by the antenna is stronger.
[0046] More specifically, in the embodiment of the present application, the vibrator arm 3 preferably includes a cylindrical portion and a contraction portion 5 that gradually contracts toward the axis based on the outer contour of the cylindrical portion.
[0047] More specifically, the cylindrical parts of the two vibrator arms 3 are preferably coaxially arranged.
[0048] More specifically, the gradually shrinking contraction portion 5 can compress the beam width in the vertical plane of the omnidirectional antenna, thereby improving the gain of the antenna. Secondly, the waves emitted by the first antenna body 1 or the second antenna body 2 are reflected by the corresponding two contraction portions 5 and become plane radiation to the free space, which is convenient for improving the polarization purity of the antenna.
[0049] In some preferred embodiments, the contraction portion 5 may be a conical contraction structure or a spherical contraction structure or other types of contraction structures. In the embodiment of the present application, a conical contraction structure is preferred.
[0050] Specifically, in the embodiment of the present application, the conically contracted contraction portion 5 has a uniform curved surface to further improve the gain of the antenna and the corresponding reflection effect.
[0051] More specifically, the constricted portion 5 is preferably truncated cone-shaped and has broadband characteristics.
[0052] More specifically, the taper of the contraction portion 5 is 1:1-3:1, and in the embodiment of the present application, preferably 2:1.
[0053] In some preferred embodiments, at least one dipole arm 3 in the first antenna body 1 and / or at least one dipole arm 3 in the second antenna body 2 is provided with an adjustment sheet 6 for adjusting the working frequency band.
[0054] It should be noted that the omnidirectional antenna of the embodiment of the present application further includes a housing (not shown in the figure) for mounting the first antenna body 1 and the second antenna body 2 .
[0055] Specifically, the adjustment plate 6 is used to adjust the position of the corresponding dipole arm 3 on the outer shell to change the distance between the two dipole arms 3 in the first antenna body 1 and / or change the distance between the two dipole arms 3 in the second antenna body 2 and / or change the distance between the first antenna body 1 and the second antenna body 2, thereby realizing the adjustment of the working frequency band of the omnidirectional antenna so that the working frequency range covered by the omnidirectional antenna meets expectations.
[0056] More specifically, the adjustment plate 6 can be fixedly connected to the corresponding dipole arm 3 and its position on the outer shell can be adjusted so as to change the distance between the two dipole arms 3 in the corresponding antenna body by sliding adjustment. It can also be threadedly connected to the corresponding dipole arm 3 and rotatably connected to the outer shell so as to change the distance between the two dipole arms 3 in the corresponding antenna body by rotational adjustment.
[0057] In some preferred embodiments, the two dipole arms 3 are respectively connected to the outer conductor and the inner conductor of the coaxial cable 4 .
[0058] Specifically, the coaxial cable 4 is connected to the two dipole arms 3 in the first antenna body 1 or the second antenna body 2 through its outer conductor and inner conductor, respectively, so that the single-end lead-out of the feeder can be realized, thereby realizing the integration and miniaturization of the line.
[0059] In some preferred embodiments, the distance between the first antenna body 1 and the second antenna body 2 is 0.8-1.2 times the length of the dipole arm 3 .
[0060] Specifically, the two dipole arms 3 of the first antenna body 1 and the two dipole arms 3 of the second antenna body 2 are the same in length.
[0061] More specifically, in the embodiment of the present application, the distance between the first antenna body 1 and the second antenna body 2 is preferably the same as the length of the dipole arm 3, so that the first antenna body 1 and the second antenna body 2 have sufficient isolation and avoid the overall volume of the omnidirectional antenna being too large.
[0062] In some preferred embodiments, the coaxial cable 4 of the first antenna body 1 passes through the contraction portions 5 of the two dipole arms 3 of the second antenna body 2 .
[0063] Specifically, the coaxial cable 4 of the first antenna body 1 passes through the side of the contraction portion 5 of the two dipole arms 3 of the second antenna body 2, such as the coaxial cable 4 passes through the curved surfaces of the truncated cone-shaped contraction portions 5 of the two dipole arms 3 in sequence to generate an exposed portion 7 located outside the second antenna body 2 between the two dipole arms 3; in this embodiment, the position of the exposed portion 7 of the coaxial cable 4 of the first antenna body 1 is staggered and isolated from the coaxial cable 4 of the second antenna body 2, which can effectively avoid electrical connection between the two coaxial cables 4, so that the coaxial cable 4 of the second antenna body 2 can smoothly connect the two dipole arms 3 in the second antenna body 2 without interference.
[0064] More specifically, the coaxial cable 4 of the first antenna body 1 can be integrated or divided into cables that pass through the two dipole arms 3 of the second antenna body 2 respectively, and then connected based on the exposed ends of the two cables passing through the corresponding contraction parts 5. The latter method facilitates the split assembly of the omnidirectional antenna.
[0065] In some preferred embodiments, the positions of the contraction parts 5 of the two dipole arms 3 through which the coaxial cable 4 of the first antenna body 1 passes are symmetrical.
[0066] Specifically, this arrangement allows the two dipole arms 3 of the second antenna body 2 to still retain the characteristics of a symmetrical structure. For example, in an embodiment where the contraction portion 5 is truncated cone-shaped, the position points of the curved surface of the contraction portion 5 of the two dipole arms 3 of the second antenna body 2 through which the coaxial cable 4 of the first antenna body 1 passes respectively belong to axial sections of the same size on the two contraction portions 5, and at the same time, the exposed portion 7 of the aforementioned coaxial cable 4 also has a symmetrical characteristic.
[0067] In some embodiments, Figure 2 As shown, the exposed portion 7 of the coaxial cable 4 of the first antenna body 1 between the two dipole arms 3 of the second antenna body 2 is in a vertical straight line shape.
[0068] In some preferred embodiments, Figure 1 As shown, the exposed portion 7 of the coaxial cable 4 of the first antenna body 1 located between the two dipole arms 3 of the second antenna body 2 is in a spiral shape.
[0069] Specifically, the spiral exposed portion 7 constitutes a spiral cable, which is equivalent to a parasitic unit of the second antenna 2 and can generate parasitic capacitance to optimize the impedance matching effect of the second antenna 2 .
[0070] More specifically, the distributed parameters of the spiral cable (capacitance or inductance, which may vary according to the number of spiral turns, diameter, etc.) are determined according to the impedance matching effect of the second antenna 2 .
[0071] In some preferred embodiments, the axial length of the spiral portion of the coaxial cable 4 is less than 1 / 5 of the total length of the two dipole arms 3 .
[0072] Specifically, in order to prevent the spiral cable (ie, the spiral portion) from affecting the circularity of the directional pattern of the second antenna body 2 , the omnidirectional antenna of the embodiment of the present application designs the axial length of the spiral portion of the coaxial cable 4 to be less than 1 / 5 of the total length of the two dipole arms 3 .
[0073] In order to more clearly illustrate the characteristics of the omnidirectional antenna of the embodiment of the present application, the present application also introduces the following Figure 3 A comparative example is shown for comparison and analysis. In this comparative example, the coaxial cable 4 in the first antenna body 1 does not pass through the second antenna body 2, but passes through the second antenna body 2 from the outside.
[0074] analyze Figure 4 , Figure 5 and Figure 6 It can be seen that Figure 1 The standing wave ratio outputted from the coaxial circuit port of the second antenna body 2 of the omnidirectional antenna shown is also basically stable below 1.5 in the operating frequency bands of 703-960 and 1710-2690 MHz, which can meet the use requirements; Figure 2 The standing wave ratio outputted by the coaxial circuit port of the second antenna body 2 of the omnidirectional antenna shown in the figure exceeds 2 in the lowest frequency part of the 703-960 working frequency band, that is, the impedance matching of the second antenna body 2 deteriorates in the low frequency band. The introduction of the spiral cable on the lateral surface can effectively avoid the deterioration of the impedance matching of the second antenna body 2 in the low frequency band. Figure 3The standing wave ratio output by the coaxial circuit port of the second antenna body 2 of the comparative omnidirectional antenna shown exceeds 2 in most of the 703-960 operating frequency band, which illustrates that arranging the coaxial cable 4 of the first antenna body 1 in the two dipole arms 3 of the second antenna body 2 can effectively solve the adverse effect of the feed line passing near the antenna on the antenna, thereby achieving wide-band impedance matching and omnidirectionality of the antenna azimuth plane radiation pattern.
[0075] analyze Figure 7 It can be seen that the non-circularity of the azimuth plane pattern of the second antenna body 2 in the omnidirectional antenna of the embodiment of the present application in the 703-960 and 1710-2690 MHz operating frequency bands is less than 2, and has a uniform radiation characteristic with omnidirectional beam coverage in the azimuth plane.
[0076] In the description of this specification, the description with reference to the terms "one embodiment", "certain embodiments", "illustrative embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials, or characteristics described in conjunction with the embodiments or examples are included in at least one embodiment or example of the utility model. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.
[0077] The above are only some embodiments of the present invention. For those skilled in the art, several modifications and improvements can be made without departing from the inventive concept of the present invention, which all belong to the protection scope of the present invention.
Claims
1. An omnidirectional antenna, characterized in that: The omnidirectional antenna includes a first antenna body and a second antenna body arranged vertically. The first antenna body and the second antenna body each include two dipole arms symmetrically arranged vertically and a coaxial cable connected to the two dipole arms. The coaxial cable of the first antenna body passes through the inside of the second antenna body.
2. The omnidirectional antenna according to claim 1, characterized in that: The two vibrator arms are columnar, and adjacent ends have contraction portions contracting toward the center.
3. The omnidirectional antenna according to claim 2, characterized in that: The contraction portion is a conical contraction structure.
4. The omnidirectional antenna according to claim 1, characterized in that: At least one dipole arm in the first antenna body and / or at least one dipole arm in the second antenna body is provided with an adjustment sheet for adjusting the working frequency band.
5. The omnidirectional antenna according to claim 1, characterized in that: The two dipole arms are respectively connected to the outer conductor and the inner conductor of the coaxial cable.
6. The omnidirectional antenna according to claim 1, characterized in that: The distance between the first antenna body and the second antenna body is 0.8-1.2 times the length of the dipole arm.
7. The omnidirectional antenna according to claim 1, characterized in that: The coaxial cable of the first antenna body passes through the contraction parts of the two dipole arms of the second antenna body.
8. The omnidirectional antenna according to claim 7, characterized in that: The positions of the contraction parts of the two dipole arms through which the coaxial cable of the first antenna body passes are symmetrical.
9. The omnidirectional antenna according to claim 7, characterized in that: The exposed portion of the coaxial cable of the first antenna body located between the two dipole arms of the second antenna body is in a spiral shape.
10. The omnidirectional antenna according to claim 9, characterized in that: The axial length of the spiral portion of the coaxial cable is less than 1 / 5 of the total length of the two dipole arms.