Electrically small dual-frequency horizontal polarization omnidirectional antenna

Abstract

The invention discloses an electrically small dual-frequency horizontal polarization omnidirectional antenna, and relates to the technical field of communication, and the antenna is characterized in that an NFRP parasitic layer comprises a plurality of arc-shaped dipole units, and the plurality of arc-shaped dipole units can be sequentially connected end to end to form an annular array; the tail end branches of the adjacent arc-shaped dipole units are connected through an interdigital tight coupling structure; the center of the arc-shaped dipole unit is provided with a feed branch, and the feed branch extends towards the center of circle of the NFRP parasitic layer. Each feed branch knot is provided with a bent branch knot, and the bent branch knots and the NFRP parasitic layer are arranged on the same plane. The top feed layer is provided with a top-layer center bonding pad, the bottom feed layer is provided with a bottom-layer center bonding pad, and the top-layer center bonding pad, the bottom-layer center bonding pad and the feed branches jointly form a balun structure. The antenna provided by the invention is mainly used in the unmanned aerial vehicle, can realize the electrically small size characteristic on the premise of ensuring the dual-frequency radiation performance, and has good out-of-roundness and gain effect.

Description

Technical Field

[0001] This invention relates to the field of communication technology, specifically to an electrically small dual-frequency horizontally polarized omnidirectional antenna. Background Technology

[0002] As the electromagnetic wave transceiver hub for real-time data interaction between UAVs and ground stations, satellites, and other equipment, the performance of antennas is closely related to the communication reliability and mission versatility of UAV systems. With the deepening application of UAVs in logistics inspection, emergency rescue, military reconnaissance, and other fields, higher requirements are placed on the miniaturization, multi-frequency capability, and omnidirectional coverage of antennas.

[0003] Current UAV horizontal omnidirectional antenna design faces three core design challenges: multi-band versus omnidirectional, miniaturization versus multi-band, and miniaturization versus omnidirectional. Traditional dual-band antennas require independent elements / stacked structures, leading to structural redundancy. Although the number of frequency bands can be expanded through stacking, parasitic techniques, miniaturization remains a core challenge. At the same time, electrically small antennas are limited by antenna size, typically resulting in lower gain and poor horizontal omnidirectionality, with non-circularity >3dB, affecting the signal stability of the entire system's communication.

[0004] Current airborne equipment designs increasingly trend towards miniaturization, multi-frequency operation, and good omnidirectional coverage. For the UAV field, which requires multi-frequency horizontally polarized omnidirectional antennas, electrically small antennas (EMS) have significant application potential due to their small size. However, traditional horizontally polarized EMS antennas have limited multi-band designs and typically suffer from low gain and non-circularity exceeding 3dB. Common horizontally polarized omnidirectional antenna designs often employ a ring array of several basic elements to achieve omnidirectional radiation characteristics. To avoid excessive size, the number of ring array elements is generally limited to three, resulting in excessive non-circularity and hindering the introduction of new omnidirectional resonant points, leading to significant non-circularity in the second frequency band. Conversely, antenna designs with more than three array elements often result in excessive size. Therefore, horizontally polarized omnidirectional antennas face three major design contradictions: multi-band operation versus omnidirectionality, miniaturization versus multi-frequency operation, and miniaturization versus omnidirectionality. Simultaneously satisfying miniaturization, multi-frequency operation, and good omnidirectionality presents considerable design challenges. Low-cost design is also a crucial requirement in engineering applications. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention aims to provide an electrically small dual-frequency horizontally polarized omnidirectional antenna, primarily for use in unmanned aerial vehicles (UAVs). This antenna achieves electrically small size characteristics while ensuring dual-frequency radiation performance, and also exhibits good non-circularity and gain.

[0006] This invention is achieved through the following technical solution:

[0007] A electrically small dual-band horizontally polarized omnidirectional antenna includes:

[0008] Top feed layer, bottom feed layer, and NFRP parasitic layer in the middle;

[0009] The NFRP parasitic layer includes several arc-shaped dipole units, which are arranged in a ring array connected end to end in sequence; the terminal branches of adjacent arc-shaped dipole units are connected by an interdigital tight coupling structure; a feeding branch is provided at the center of each arc-shaped dipole unit, and the feeding branch extends toward the center of the NFRP parasitic layer; each feeding branch has a bent branch, and the bent branch is arranged on the same plane as the NFRP parasitic layer;

[0010] The top feed layer has a top center pad, and the bottom feed layer has a bottom center pad. The top center pad, the bottom center pad, and several feed branches together form a balun structure.

[0011] Compared to existing technologies that cannot simultaneously achieve miniaturization, multi-frequency operation, and good omnidirectional design, this invention provides an electrically small dual-frequency horizontally polarized omnidirectional antenna, primarily for use in unmanned aerial vehicles (UAVs). This antenna achieves electrically small size characteristics while maintaining dual-frequency radiation performance, and also exhibits good non-circularity and gain. Its electrical size is only 0.237λ. L (where λ) L(This refers to the lowest operating wavelength). Specifically, the antenna design is based on the Huygens source principle and consists of two dielectric substrates and three metal layers. The top and bottom metal layers are the top and bottom feed layers, respectively. The middle metal layer is a near-field resonant parasitic (NFRP) structure, also known as the NFRP parasitic layer. The top feed layer and the NFRP parasitic layer are the copper-clad surfaces of the first dielectric layer, and the bottom feed layer is the copper-clad surface of the second dielectric layer. Placing the NFRP parasitic layer in copper on the second dielectric layer can achieve a similar effect. The NFRP parasitic layer mainly includes several arc-shaped dipole elements. A large number of arc-shaped dipole elements are arranged in a ring array; the more ring array elements, the lower the non-circularity of the radiation pattern. By feeding several dipole elements with equal amplitude and in-phase power through the feed layer, the horizontal omnidirectional radiation characteristic of the antenna can be achieved. However, without further modifications, the antenna size will increase accordingly. In this scheme, four pairs of curved dipole sub-units are preferably arranged in a ring array to enhance the uniform radiation of the antenna in the horizontal direction. A balun structure is used to feed the four-element NFRP antenna with equal amplitude and in-phase power, thereby achieving good omnidirectional radiation characteristics. Simultaneously, the end stubs of adjacent curved dipole sub-units are connected by an interdigital tight coupling structure, which increases impedance capacitance and enables the antenna to achieve an electrically small size. Furthermore, to achieve dual-band radiation performance, bent stubs are added to the feeding stubs. Utilizing the inner and outer ring radiation modes of the NFRP structure, combined with meandering technology, further miniaturization performance in the high-frequency band is achieved.

[0012] Further optimization, as one implementation of the interdigitated tight coupling structure, includes at least one interdigitated receptive branch disposed on an end branch, and interdigitated slots on adjacent end branches for insertion of the interdigitated receptive branch. In this scheme, the miniaturization degree and low-frequency matching can be adjusted by changing the interdigitation index, the width of the interdigitated branch, and the gap width. Additionally, similar tight-coupled receptive branches can achieve similar effects, such as stacked types and cup-and-spherical types.

[0013] Further optimization, as a specific structure of an arc-shaped dipole unit, the arc-shaped dipole unit includes two arc-shaped radiating arms that are symmetrically distributed radially along the parasitic layer of the NFRP. There is a gap between the two arc-shaped radiating arms, and each of the adjacent ends of the two arc-shaped radiating arms has parallel sub-stubs, and the two sub-stubs together form a feeding stub.

[0014] Further optimization involves a specific structure for a bent stub, comprising U-shaped bends symmetrically distributed on two sub-stubs. The two U-shaped bends have the same axis and diameter, and their openings are opposite each other. The bending position and curvature of the U-shaped bends are used to adjust the high-to-low frequency ratio. In this scheme, the U-shaped bends further achieve miniaturization in the high-frequency band while making the frequency ratio of the high and low frequency bands adjustable, allowing the antenna to generate resonant radiation in the 2.45GHz and 5.8GHz bands respectively. Adjusting the curvature of the U-shaped bends can adjust the frequency ratio of the antenna's high and low resonant points; adjusting the position of the U-shaped bends can adjust the matching of the high-frequency resonant points to a certain extent; and chamfering the outer right angle of the U-shaped bends can further optimize antenna matching.

[0015] Further optimization, to improve the non-circularity performance of the frequency band and make the current radiation more uniform and the non-circularity better, parasitic guiding branches are also arranged at intervals between adjacent bent branches. The parasitic guiding branches are arc-shaped and arranged on the same plane as the sub-branches of the bent branches. In this solution, a metal through hole for metal pins to pass through is provided in the middle of the parasitic guiding branch. The upper and lower layers corresponding to the hole are provided with top peripheral pads and bottom peripheral pads. The top feed layer, NFRP parasitic layer and bottom feed layer are fixed to the peripheral pads by welding metal pins. The antenna can be connected and positioned by welding metal pins to the two dielectric substrates, eliminating the need for multi-layer board lamination and not affecting the electrical performance of the antenna itself, thus possessing low cost and feasibility.

[0016] To further optimize the high-frequency mismatch caused by the addition of the U-shaped bend, the power supply stub is also provided with an arc-shaped matching stub, which is located on the side of the bend stub away from its own axis.

[0017] The matching branches include unit branches symmetrically distributed on two sub-branches. The two unit branches are set on surfaces opposite to the two sub-branches, and their axes and diameters are the same.

[0018] Further optimization, as a specific structure of an electrically small dual-band horizontally polarized omnidirectional antenna, includes a first dielectric layer between the top feed layer and the NFRP parasitic layer, and a second dielectric layer between the bottom feed layer and the NFRP parasitic layer.

[0019] Further optimization involves four groups of feed stubs evenly distributed circumferentially. The top center pad, bottom center pad, and the four groups of feed stubs together form a 1-to-4 balun structure. The top center pad is welded to the coaxial inner conductor, and the bottom center pad is welded to the coaxial outer conductor. In this scheme, the 1-to-4 coaxial balun provides equal-amplitude and in-phase feeding to four pairs of bent dipole units. The 1-to-4 balun pad structure includes four peripheral pads evenly distributed circumferentially, such as four top peripheral pads on the top feed layer and four bottom peripheral pads on the bottom feed layer. Four metal vias are provided circumferentially in the NFRP parasitic layer, located on the parasitic guide stubs. This allows for the connection and positioning of the two dielectric substrates by welding metal pins, eliminating the need for multi-layer board lamination and not affecting the antenna's electrical performance, thus offering low-cost feasibility. The top-layer peripheral pads, the bottom-layer peripheral pads, and four feed lines form a 1-to-4 balun structure, which provides equal-amplitude and in-phase feeding to the dipole unit.

[0020] To further optimize the antenna manufacturing cost, four parasitic guide branches are evenly distributed in the circumferential direction of the NFRP parasitic layer. The parasitic guide branches are provided with metal through holes in the middle for metal pins to pass through. The top feed layer, the NFRP parasitic layer and the bottom feed layer are fixed to the top peripheral pads and the bottom peripheral pads by metal pins.

[0021] To further optimize the high-frequency mismatch caused by the U-shaped bend, both the top and bottom feed layers have cross-shaped stubs on their center pads. Each end of each cross-shaped stub has a feed arc-shaped stub, and each feed arc-shaped stub extends in the same circumferential direction. In this design, matching stubs are set on several feed stubs in the NFRP parasitic layer, and several feed arc-shaped stubs are added to the upper and lower feed layers to further improve the high-frequency mismatch caused by the U-shaped bend. By adjusting the relative lengths between the stubs, the impedance-capacitance is changed, thereby adjusting the high- and low-frequency matching characteristics.

[0022] Further optimization involves using PTFE (polytetrafluoroethylene) glass cloth copper-clad laminate as both the first and second dielectric layers. Specifically, the PTFE glass cloth copper-clad laminate is used as the dielectric substrate material; the substrate type is F4BM, with a relative permittivity of 2.65, a loss tangent of 0.0007, and a thickness of 0.8 mm. The dielectric substrate has a diameter of 29 mm, and its electrical dimension is only 0.237λ. L (where λ) L (The wavelength is 2.45 GHz, which is the lowest resonant center frequency).

[0023] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0024] This invention provides an electrically small dual-frequency horizontally polarized omnidirectional antenna, primarily for use in unmanned aerial vehicles (UAVs). Based on a near-field resonant parasitic (NFRP) antenna design, it combines ring array technology, tight coupling technology, and meandering technology to achieve electrically small characteristics, multi-frequency characteristics, and excellent omnidirectional coverage. The antenna achieves a non-circularity of <0.1dB at low frequencies and <1dB at high frequencies. This antenna solution simultaneously satisfies multi-frequency performance, electrically small size, and excellent omnidirectional coverage, and is low-cost and feasible, possessing very broad application prospects and practical value. Attached Figure Description

[0025] To more clearly illustrate the technical solutions of the exemplary embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of the present invention and should not be considered as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort. In the drawings:

[0026] Figure 1 Exploded view of the omnidirectional antenna provided by this invention;

[0027] Figure 2 Top view of the top feed layer provided by the present invention;

[0028] Figure 3 This is a top view of the NFRP parasitic layer provided by the present invention;

[0029] Figure 4 Top view of the bottom feed layer provided by the present invention;

[0030] Figure 5 The S-parameter simulation diagram of the omnidirectional antenna provided by this invention;

[0031] Figure 6 The horizontal radiation pattern of the 2.45 GHz antenna provided for this invention;

[0032] Figure 7 The horizontal radiation pattern of the 5.8 GHz antenna provided for this invention.

[0033] The attached diagram shows the markings and corresponding component names:

[0034] 1-Top feed layer, 101-Top feed top arc-shaped stub, 102-Top center pad, 103-Top peripheral pad, 2-First dielectric layer, 3-NFRP parasitic layer, 301-Interdigital capacitive stub, 302-Metal via, 303-Parasitic guide stub, 304-Bent stub, 305-Matching stub, 4-Second dielectric layer, 5-Bottom feed layer, 501-Bottom peripheral pad, 502-Bottom center pad, 503-Top feed bottom arc-shaped stub. Detailed Implementation

[0035] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the embodiments and accompanying drawings. The illustrative embodiments and descriptions of the present invention are only used to explain the present invention and are not intended to limit the present invention.

[0036] Example: This example provides an electrically small dual-band horizontally polarized omnidirectional antenna, such as... Figures 1-7 As shown, it includes:

[0037] Top feed layer 1, bottom feed layer 5, and NFRP parasitic layer 3 located in the middle;

[0038] The NFRP parasitic layer 3 includes a plurality of arc-shaped dipole units, which are arranged in a ring array connected end to end in sequence; the end branches of adjacent arc-shaped dipole units are connected by an interdigital tight coupling structure; a feeding branch is provided at the center of each arc-shaped dipole unit, and the feeding branch extends toward the center of the NFRP parasitic layer 3; each feeding branch has a bent branch 304, and the bent branch 304 is arranged on the same side as the NFRP parasitic layer 3;

[0039] The top feed layer 1 has a top center pad 102, and the bottom feed layer 5 has a bottom center pad 502. The top center pad 102, the bottom center pad 502, and several feed branches together form a balun structure.

[0040] Compared to existing technologies that cannot simultaneously achieve miniaturization, multi-frequency operation, and good omnidirectional design, this invention provides an electrically small dual-frequency horizontally polarized omnidirectional antenna, primarily for use in unmanned aerial vehicles (UAVs). This antenna achieves electrically small size characteristics while maintaining dual-frequency radiation performance, and also exhibits good non-circularity and gain. Its electrical size is only 0.237λ. L (where λ) L(This is for the lowest operating wavelength). Specifically, the antenna design is based on the Huygens source principle and consists of two dielectric substrates and three metal layers. The top and bottom metal layers are the top and bottom feed layers, respectively. The middle metal layer is a near-field resonant parasitic (NFRP) structure, specifically NFRP parasitic layer 3. The top feed layer 1 and NFRP parasitic layer 3 are the copper-clad surfaces of the first dielectric layer 2, and the bottom feed layer 5 is the copper-clad surface of the second dielectric layer 4. Copper cladding of NFRP parasitic layer 3 onto the second dielectric layer 4 can achieve a similar effect. NFRP parasitic layer 3 mainly includes several arc-shaped dipole elements. A large number of arc-shaped dipole elements are arranged in a ring array. The more ring array elements, the lower the non-circularity of the radiation pattern. By feeding several dipole elements with equal amplitude and in-phase power through the feed layer, the horizontal omnidirectional radiation characteristic of the antenna can be achieved. However, without modification, the antenna size will also increase. Therefore, in this scheme, the preferred number of arc-shaped dipole sub-units is four pairs. These four pairs of bent arc-shaped dipole sub-units are arranged in a ring array to enhance the antenna's uniform radiation in the horizontal direction. A balun structure is used to feed the four-element NFRP antenna with equal amplitude and in-phase power, thereby achieving good omnidirectional radiation characteristics. Simultaneously, the end stubs of adjacent arc-shaped dipole sub-units are connected by an interdigital tight coupling structure, which increases impedance capacitance and enables the antenna to achieve an electrically small size. Furthermore, to achieve dual-band radiation performance, a bent stub 304 is added to the feeding stub. Utilizing the inner and outer ring radiation modes of the NFRP structure, combined with meandering technology, further miniaturization performance in the high-frequency band is achieved.

[0041] Please see Figure 3 As one implementation of the interdigitated tight coupling structure, the interdigitated tight coupling structure includes at least one interdigitated receptive branch 301 disposed on an end branch, and interdigitated slots that are adapted for insertion into adjacent end branches. In this solution, the miniaturization degree and low-frequency matching can be adjusted by changing the interdigitation index, the width of the interdigitated branches, and the gap width. Furthermore, similar tight coupling receptive branches can achieve similar effects, such as stacked types and cup-and-spherical types.

[0042] Please continue reading. Figure 3 As a specific structure of an arc-shaped dipole unit, the arc-shaped dipole unit includes two arc-shaped radiating arms that are symmetrically distributed radially along the NFRP parasitic layer 3. There is a gap between the two arc-shaped radiating arms, and each of the adjacent ends of the two arc-shaped radiating arms has parallel sub-stubs, and the two sub-stubs together form a feeding stub.

[0043] Please continue reading. Figure 3As a specific structure of the bent stub 304, the bent stub 304 includes U-shaped bends symmetrically distributed on two sub-stubs. The axes and diameters of the two U-shaped bends are the same, and the openings of the two U-shaped bends are arranged opposite each other. The bending position and curvature of the U-shaped bends are used to adjust the high-low frequency ratio. In this scheme, the U-shaped bends further achieve miniaturization performance in the high-frequency band, while making the frequency ratio of the high and low frequency bands adjustable, so that the antenna generates resonant radiation in the 2.45GHz and 5.8GHz frequency bands respectively. Adjusting the curvature of the U-shaped bends can adjust the frequency ratio of the high and low resonant points of the antenna; adjusting the position of the U-shaped bends can adjust the matching of the high-frequency resonant points to a certain extent; and chamfering the outer right angle of the U-shaped bends can further optimize the antenna matching.

[0044] Please continue reading. Figures 2-4 In some possible embodiments, to improve the non-circularity performance of the frequency band and make the current radiation more uniform and the non-circularity better, parasitic guiding branches 303 are also provided at intervals between adjacent bent branches 304. The parasitic guiding branches 303 are arc-shaped and are arranged on the same plane as the sub-branches of the bent branches 304. In this solution, a metal through hole 302 for metal pins to pass through is provided in the middle of the parasitic guiding branch 303. The upper and lower layers corresponding to the hole are provided with a top peripheral pad 103 and a bottom peripheral pad 501. The top feed layer 1, the NFRP parasitic layer 3, and the bottom feed layer 5 are fixed together by welding metal pins to the top peripheral pad 103 and the bottom peripheral pad 501. The antenna can be connected and positioned by welding metal pins to the two dielectric substrates without the need for multi-layer board lamination processing, and without affecting the electrical performance of the antenna itself, which has low cost and feasibility.

[0045] Please continue reading. Figure 3 In some possible embodiments, in order to improve the high-frequency mismatch caused by the addition of the U-shaped bend, the power supply stub is also provided with an arc-shaped matching stub 305, which is located on the side of the bend stub 304 away from its own axis.

[0046] The matching branch 305 includes unit branches symmetrically distributed on two sub-branches. The two unit branches are set on surfaces opposite to the two sub-branches, and their axes and diameters are the same.

[0047] Please see Figure 1 As a specific structure of an electrically small dual-frequency horizontally polarized omnidirectional antenna, a first dielectric layer 2 is also provided between the top feed layer 1 and the NFRP parasitic layer 3, and a second dielectric layer 4 is also provided between the bottom feed layer 5 and the NFRP parasitic layer 3.

[0048] Please see Figures 2-4In some possible embodiments, the feed stubs are four groups evenly distributed in the circumferential direction. The top center pad 102, the bottom center pad 502, and the four groups of feed stubs together form a 1-to-4 balun structure. The top center pad 102 is welded to the coaxial inner conductor, and the bottom center pad 502 is welded to the coaxial outer conductor. In this scheme, the 1-to-4 coaxial balun provides equal amplitude and in-phase feeding to four pairs of bent dipole units. The 1-to-4 balun pad structure includes four peripheral pads evenly distributed in the circumferential direction, such as four top peripheral pads 103 on the top feed layer 1 and four bottom peripheral pads 501 on the bottom feed layer 5. Four metal vias 302 are provided in the circumferential direction of the NFRP parasitic layer 3, and the metal vias 302 are located on the parasitic guide stubs 303. The two dielectric substrates can be connected and positioned by welding metal pins, without the need for multi-layer board lamination, and without affecting the electrical performance of the antenna itself, thus possessing low cost and feasibility. The top peripheral pad 103, the bottom peripheral pad 501, and four feed lines form a one-to-four balun structure, which provides equal amplitude and in-phase power to the dipole unit.

[0049] In some possible embodiments, to reduce antenna manufacturing costs, four parasitic spurs 303 are evenly distributed in the inner circumference of the NFRP parasitic layer 3; the parasitic spurs 303 are provided with metal through holes 302 for metal pins to pass through in the middle; the top feed layer 1, the NFRP parasitic layer 3 and the bottom feed layer 5 are fixed together by metal pins to the top peripheral pad 103 and the bottom peripheral pad 501.

[0050] Please see Figure 2 and Figure 4 In some possible embodiments, to mitigate the high-frequency mismatch caused by the U-shaped bend, both the top feed layer 1 and the bottom feed layer 5 have cross-shaped stubs on their center pads. Each end of the cross-shaped stub has a feed arc-shaped stub, and each feed arc-shaped stub extends in the same circumferential direction. In this solution, matching stubs 305 are provided on several feed stubs of the NFRP parasitic layer 3, and several feed arc-shaped stubs are added to the upper and lower feed layers to further mitigate the high-frequency mismatch caused by the U-shaped bend. By adjusting the relative lengths between the stubs, the impedance-capacitance is changed, thereby adjusting the high- and low-frequency matching characteristics.

[0051] In some possible embodiments, both the first dielectric layer 2 and the second dielectric layer 4 are made of polytetrafluoroethylene (PTFE) glass cloth copper-clad laminate. Specifically, the PTFE glass cloth copper-clad laminate is used as the dielectric substrate material; the board material type is F4BM, with a relative permittivity of 2.65, a loss tangent of 0.0007, and a thickness of 0.8 mm. The dielectric substrate has a diameter of 29 mm, and its electrical dimension is only 0.237λ. L (where λ) L(The wavelength is 2.45 GHz, which is the lowest resonant center frequency).

[0052] This invention provides the above-mentioned solution, based on a near-field resonant parasitic (NFRP) antenna design, combined with ring array technology, tight coupling technology, and meandering technology, to achieve the antenna's electrical smallness, multi-frequency characteristics, and good omnidirectional coverage. The antenna can achieve a non-circularity of <0.1dB at low frequencies and <1dB at high frequencies; Figures 5-7 As shown, Figure 5 The image shows the S-parameter simulation of the antenna of this invention. It can be seen that the antenna achieves dual-frequency performance, with resonant points at 2.45 GHz and 5.8 GHz, respectively. Figure 6 This is the horizontal radiation pattern of the antenna of the present invention at 2.45 GHz. It can be seen that the non-circularity of the horizontal radiation pattern of the antenna at low frequency is <0.1 dB, and the gain can reach 1.21 dB. Figure 7 This is the horizontal radiation pattern of the antenna of the present invention at 5.8 GHz. It can be seen that the non-circularity of the horizontal radiation pattern of the antenna at low frequencies is <1 dB, and the gain can reach 1.75 dB. The antenna of this solution can simultaneously meet the requirements of multi-frequency capability, electrical small size, and excellent omnidirectional coverage, and has low cost and feasibility, with very broad application prospects and practical value.

[0053] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. An electrically small dual-band horizontally polarized omni-directional antenna, characterized in that, The application relates to a top feeding layer (1), a bottom feeding layer (5) and an NFRP parasitic layer (3) arranged in the middle. The NFRP parasitic layer (3) comprises a plurality of arc-shaped dipole units, the arc-shaped dipole units are sequentially connected in a ring shape, the ends of adjacent arc-shaped dipole units are connected through an interdigital tight coupling structure, a feeding branch is arranged at the center of the arc-shaped dipole unit and extends towards the center of the NFRP parasitic layer (3), a bending branch (304) is arranged on each feeding branch, and the bending branch (304) is arranged on the same plane as the NFRP parasitic layer (3). A top center pad (102) is arranged on the top feeding layer (1), a bottom center pad (502) is arranged on the bottom feeding layer (5), and the top center pad (102), the bottom center pad (502) and the feeding branches jointly form a balun structure. The interdigital tight coupling structure comprises at least one interdigital capacitive branch (301) arranged on one end branch and an interdigital slot arranged on the adjacent end branch and matched with the interdigital capacitive branch (301).

2. The electrically small dual-band horizontally polarized omni-directional antenna according to claim 1, wherein, The arc-shaped dipole unit comprises two arc-shaped radiation arms which are radially and symmetrically distributed on the NFRP parasitic layer (3), a gap is arranged between the two arc-shaped radiation arms, parallel sub-branches are arranged on the adjacent ends of the two arc-shaped radiation arms, and the two sub-branches jointly form a feeding branch.

3. The electrically small dual-band horizontally polarized omni-directional antenna according to claim 1, wherein, The bending branch (304) comprises U-shaped bends which are symmetrically arranged on the two sub-branches, the axes and diameters of the two U-shaped bends are the same, and the openings of the two U-shaped bends are oppositely arranged; the bending positions and the radians of the U-shaped bends are used for adjusting the high-low frequency ratio.

4. The electrically small dual-band horizontally polarized omni-directional antenna of claim 3, wherein, A parasitic director branch (303) is arranged between the adjacent bending branches (304), the parasitic director branch (303) is arc-shaped and arranged on the same plane as the bending branch sub-branches.

5. A small electrically double-frequency horizontally polarized omnidirectional antenna according to claim 4, characterized in that, An arc-shaped matching branch (305) is arranged on the feeding branch and arranged on the side of the bending branch (304) away from the axis.

6. The electrically small dual-band horizontally polarized omni-directional antenna according to claim 1, wherein, The matching branch (305) comprises unit branches which are symmetrically arranged on the two sub-branches, the two unit branches are arranged on the surfaces away from each other of the two sub-branches, and the axes and diameters of the two unit branches are the same. First dielectric layers (2) are arranged between the top feeding layer (1) and the NFRP parasitic layer (3), and second dielectric layers (4) are arranged between the bottom feeding layer (5) and the NFRP parasitic layer (3).

7. A small electrically double-frequency horizontally polarized omnidirectional antenna according to any one of claims 1-6, characterized in that, The feeding branches are arranged in four groups in the circumferential direction, the top center pad (102), the bottom center pad (502) and the four groups of feeding branches jointly form a one-to-four balun structure, the top center pad (102) is welded with a coaxial inner conductor, and the bottom center pad (502) is welded with a coaxial outer conductor.

8. A small electrically double-frequency horizontally polarized omnidirectional antenna according to claim 7, characterized in that, ​ 9. A small electrically double-frequency horizontally polarized omnidirectional antenna according to claim 8, characterized in that, The NFRP parasitic layer (3) is uniformly distributed with four parasitic guide branches (303) in the periphery; the parasitic guide branches (303) are provided with metal through holes (302) for the metal needle to pass through, and the top feeding layer (1), the NFRP parasitic layer (3) and the bottom feeding layer (5) are welded and fixed through the metal needle and the top peripheral pad (103) and the bottom peripheral pad (501).

10. The electrically small dual-band horizontally polarized omni-directional antenna of claim 8, wherein, The center pads of the top feeding layer (1) and the bottom feeding layer (5) are provided with cross branches, each end of the cross branch is provided with a feeding arc branch, and each feeding arc branch extends in the same circumferential direction.

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