Circularly polarized high-gain omni-directional / bidirectional reconfigurable leaky-wave antenna

Abstract

The application discloses a circularly-polarized high-gain omnidirectional / bidirectional reconfigurable helical leaky-wave antenna, which comprises a plurality of helical metal conductors, the axes of the plurality of helical metal conductors are collinear, and each helix is uniformly distributed on the whole cylindrical surface, and the helix angle of the helix on the helical metal conductor is 5-60 degrees. The application has the characteristics of high gain, circular polarization, ultra-wideband, omnidirectional conical / pie-shaped beam, reconfigurable bidirectional pie-shaped beam, no stop band, small size, low cost, high mechanical strength, simple structure and easy design.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of antennas, and in particular to a circularly polarized high-gain omnidirectional / bidirectional reconfigurable spiral leaky-wave antenna. BACKGROUND

[0002] The existing antennas capable of realizing omnidirectional high-gain radiation mainly include coaxial collinear antennas, linear antenna arrays, compact circularly polarized antenna arrays, and spiral antennas.

[0003] Specifically:

[0004] (1) Coaxial collinear antenna (COCO antenna)

[0005] The coaxial collinear antenna (COCO antenna) is the most common (even nearly the only) technical solution in the current off-the-shelf products in the submarket of omnidirectional high-gain antennas. It can produce omnidirectional (or conical beam) high-gain radiation, and its basic principle is based on the spatial harmonic method leaky-wave antenna. The COCO antenna radiates vertically polarized linearly polarized waves (the electric field direction is parallel to the antenna axis). In terms of structure, the COCO antenna is composed of a large number of segmented coaxial lines, and the inner core (outer skin) of each segment of coaxial line is welded to the outer skin (inner core) of the adjacent segment. The COCO antenna radiates vertically polarized linearly polarized waves. In the usual application scenarios of omnidirectional high-gain antennas, such as WiFi base station antennas, the antennas of the devices (such as mobile phones) communicating with them are generally linearly polarized. At this time, the use of linearly polarized base station antennas will cause polarization isolation, affecting the stability of communication. Moreover, the COCO antenna has a narrow bandwidth, generally less than 5%. The COCO antenna is relatively difficult to process. Its structure includes a large number of independent metal pipes, metal wires, and corresponding insulating materials. These components need to be assembled and welded in sequence, which requires a high demand for labor and equipment. The mechanical strength of the COCO antenna is low. It is difficult to meet the requirements of mechanical strength, such as being unable to withstand wind, and some even being difficult to support its own weight. Therefore, the outer surface of the commercially available antenna will be additionally sleeved with a dielectric tube (usually glass fiber).

[0006] The COCO antenna is heavy. Its structure contains more bulk metal, which increases the weight.

[0007] (2) Linear antenna array

[0008] Linear antenna arrays can also achieve omni-directional high gain radiation. And can achieve various polarizations, such as vertical polarization, horizontal polarization, and circular polarization. Structurally, linear antenna arrays include multiple antenna elements of consistent shape (or very similar shape), which are excited by a feed network. The feed network can be in parallel or in series. Such antennas are generally not considered leaky-wave antennas because there is a clear separation between the antenna elements and the feed network. That is, the feed network contributes almost no beneficial radiation, and the radiation is almost entirely provided by the antenna elements.

[0009] The radiation and transmission structure of such antennas are relatively independent, and independent transmission structures, such as microstrip lines, introduce additional loss, reducing the efficiency of the antenna. At the same time, its structure is more complex, on the one hand it is more difficult to design, on the other hand it often needs a process that can support more complex structures, such as PCB. When the size is large, the production cost is high.

[0010] (3) Compact circularly polarized antenna array

[0011] Compact circularly polarized antenna array, which can produce omni-directional high gain circularly polarized radiation. Such an antenna structure consists of a series of metal line segments and metal rings, which is much simpler in structure compared to linear antenna arrays. The principle is that the metal line segment acts as an "electric radiation source" to produce omni-directional vertically polarized radiation; the metal ring acts as a "magnetic radiation source" to produce omni-directional horizontally polarized radiation. The two kinds of radiation are superimposed with appropriate phases to produce circularly polarized radiation.

[0012] The bandwidth is relatively narrow, only about 5%. The feeding is relatively difficult. The feeding point is in the middle of the antenna, while in the common application field of high gain omni-directional antennas, it is generally desired that the feeding point be at the end of the antenna. The structure is relatively fragile and difficult to process. One is to solder several metal rings on a PCB, and the other is to use metal 3D printing. Both ways are relatively fragile and difficult to process.

[0013] (4) Helix antenna

[0014] Helix antenna (Helix antenna) is structurally similar to a spring, and is divided into two categories according to the structure and radiation characteristics of the helix: axial mode helix antenna and normal mode helix antenna.

[0015] The circumference of each turn of the axial mode helix antenna is close to a wavelength, it radiates circularly polarized waves, and has the maximum gain along the helix axis. Its electrical size is relatively large, generally several wavelengths. The helix can be a single conductor or multiple conductors. In order to improve its bandwidth, there are also designs that use a conical helix or add a small conical helix at the end of the helix.

[0016] The helix of the normal mode helical antenna is a slow wave structure on which electromagnetic waves propagate with wavelengths significantly smaller than the wavelength in free space, so the size of the antenna is generally small. The normal mode helical antenna can produce radiation close to linear polarization or circular polarization. Generally, a single conductor is used, and there are also designs using multiple conductors.

[0017] Helical antennas in general context, although all contain helical structure, but its characteristics and the application of the occasion has the distinction.

[0018] The axial mode helical antenna is a single-beam directional radiation, and the radiation direction is along the helical axis direction.

[0019] The normal mode helical antenna is small size and low gain. The normal mode helical antenna cannot be made large, otherwise the radiation of each point on it is different, which will cause the pattern to split.

[0020] The existing antenna that can realize omnidirectional high gain radiation has the above problems and cannot meet the needs of the development. SUMMARY

[0021] The present application aims to provide a circularly polarized high gain omnidirectional / bidirectional reconfigurable helical leaky-wave antenna, which solves the above problems and has high gain, circular polarization, ultra-wideband, omnidirectional conical / pie-shaped beam, reconfigurable bidirectional pie-shaped beam, no stop band, small size, low cost, high mechanical strength, simple structure and easy design.

[0022] The technical scheme of the present application is a circularly polarized high gain omnidirectional / bidirectional reconfigurable helical leaky-wave antenna, which comprises a plurality of helical metal conductors, the axes of the plurality of helical metal conductors are collinear, and each helix is uniformly distributed on the entire cylindrical surface, and the helix angle of the helix on the helical metal conductor is 5°-60°.

[0023] Preferably, the helical metal conductor is two, and the diameter and pitch of the helix on the helical metal conductor are the same.

[0024] Further, the helical metal conductor is one of a metal wire, a metal strip or a coaxial line.

[0025] Further, the helical metal conductor is wound on a dielectric support, and the dielectric support is one of a rod, a tube or a fishbone.

[0026] Further, the signal amplitude on each helix of the helical metal conductor is equal, and the phase difference is 360° / N, N being the number of helices.

[0027] Further, the helix angle of the helix on the helical metal conductor is the included angle between the helix tangent and the helix axis, and the ratio of the helix diameter to the guide diameter is between 0.028 and 0.55.

[0028] Further, the line length L of each period of the helix on the helical metal conductor is:

[0029]

[0030] wherein L and H are the line length of one period of the helix and the pitch of the helix respectively, θ is the desired radiation direction, λ0 is the wavelength in free space, and λ is the wavelength on the helix. g

[0031] Further, the number of periods of the helix on the helical metal conductor is greater than 1.

[0032] Further, the feeding structure is a microstrip tapered balun, and the microstrip tapered balun is connected below the helical metal conductor.

[0033] Further, an infinite balun is connected above the helical metal conductor.

[0034] The beneficial effects of the present application are:

[0035] 1) High-gain omnidirectional conical / pie-shaped beam

[0036] When the helical leaky-wave antenna of the present application is connected with the microstrip tapered balun, the beam is omnidirectional along the direction and is a narrow beam along the θ direction, that is, a high-gain omnidirectional conical / pie-shaped beam is obtained.

[0037] 2) Beam reconfigurable to bidirectional pie-shaped beam

[0038] When the helical leaky-wave antenna of the present application is connected with the microstrip tapered balun and the infinite balun, and signals with substantially equal amplitudes are fed from the two baluns, the beam of the present application is a narrow beam along the θ direction and is bidirectional along the direction, that is, a high-gain bidirectional pie-shaped beam.

[0039] 3) Stable circularly polarized radiation

[0040] The present application radiates circularly polarized waves, the main polarization is left-handed circular polarization, the cross-polarization content is small, and the axial ratio is low. If right-handed circular polarization is needed for the main radiation, the helix can be wound in the opposite direction. With the change of the beam direction, the beam shape of the circularly polarized radiation always remains stable, there is no grating lobe, and the axial ratio is always small.

[0041] 4) Ultra-wideband

[0042] ​The present invention has a very large impedance bandwidth. When using a microstrip tapered balun, the return loss (|S 11 |) of the present invention can be always better than -10dB from about 70% of the center frequency, to several times of the center frequency. This is significantly better than all the "omni-directional high gain circularly polarized antennas" found in the search range. When using an infinite balun, the -10dB impedance bandwidth is relatively small, which is limited by the infinite balun, while the antenna itself is still ultra-wideband.

[0043] Meanwhile, the |S 21 | of the present invention is relatively stable, which makes the gain of the present invention vary less with frequency.

[0044] 5) The beam can be scanned from back to front, and there is no open stop band when scanning to the front side (θ = 90°)

[0045] The beam of the present invention is scanned with frequency. When the beam direction is scanned to the range of θ = 45°-135°, a relatively good beam shape and axial ratio can always be maintained. By modifying the parameters of the spiral, the scanning range can be further improved.

[0046] When the beam of the present invention is scanned to the front side (θ = 90°), there is no observable open stop band phenomenon. The open stop band is a common drawback of "spatial harmonic method leaky wave antennas", which is manifested as: when the beam is scanned to the front side of the antenna, the |S 11 | of the antenna suddenly rises significantly, the |S 21 | drops significantly, and the gain drops significantly. For the present invention, when the beam is scanned to the front side, i.e. the frequency is 2.5GHz, the |S 11 | of the antenna does not exceed the normal fluctuation, nor does it have a special gain fluctuation.

[0047] 6) Small size

[0048] The spiral angle of the present invention is small, so the diameter of the antenna is small. When the diameter is 19mm, the frequency of the beam to the front side is about 2.5GHz, at which time the diameter of 19mm corresponds to 0.16 wavelengths.

[0049] In particular, when the spiral angle is 5°, without considering the influence of the antenna support, and when radiating to the front side, the diameter of this antenna only needs about 2.8% of the wavelength. Simulation results show that the present invention can still provide omni-directional circularly polarized radiation with good axial ratio at this time. Among the currently searched range, no design can achieve omni-directional circularly polarized radiation at such a small diameter.

[0050] 7) Only need to wind the metal wire into a spiral shape during processing, without a large amount of welding, easy to process. Only a small amount of metal is needed, light in weight, low in cost. The amount of materials needed during production is small, easy to manage.

[0051] 8) easy to design

[0052] There are only four main parameters that can be adjusted in the present application: the number of turns, the diameter, the pitch, and the total length. Simulations show that the present application can always maintain good circular polarization radiation when these parameters are changed in a large range. In contrast, other omnidirectional high-gain circularly polarized antennas often need to carefully adjust the size of each part to achieve good circular polarization. BRIEF DESCRIPTION OF DRAWINGS

[0053] Figure 1 is a perspective view of the present application;

[0054] Figure 2 is a schematic diagram of the microstrip tapered balun in the present application;

[0055] Figure 3 is the simulated and measured S 11 , simulated and measured S 21 parameters of the spiral leaky-wave antenna using the microstrip tapered balun in the present application;

[0056] Figure 4 is the simulated and measured radiation pattern of the spiral leaky-wave antenna using the microstrip tapered balun in the present application, where the dashed line is the simulated result, the solid line is the measured result, the black line is the left-handed circular polarization, and the gray line is the right-handed circular polarization,

[0057] a) 2.5 GHz, radiation pattern in the ZOY plane (φ = 90°)

[0058] b) 2.5 GHz, radiation pattern in the XOY plane (θ = 90°)

[0059] c) 2.0 GHz, radiation pattern in the ZOY plane (φ = 90°)

[0060] d) 3.0 GHz, radiation pattern in the ZOY plane (φ = 90°)

[0061] e) 5.0 GHz, radiation pattern in the ZOY plane (φ = 90°)

[0062] Figure 5 is a schematic diagram of the infinite balun in the present application;

[0063] Figure 6 is a schematic diagram of the spiral leaky-wave antenna using both the microstrip tapered balun and the infinite balun in the present application;

[0064] Figure 7 is the radiation pattern of the spiral leaky-wave antenna in the present application when the same amplitude and opposite signs are fed from both ends of the antenna, where:

[0065] a) is the radiation pattern in the φ = 63° plane at 2.5 GHz,

[0066] b) is 2.5 GHz, the pattern in XOY plane (θ = 90°);

[0067] Figure 8 S parameters for the spiral leaky-wave antenna in the present application when using the microstrip tapered balun and the infinite balun simultaneously, wherein:

[0068] a) is |S 11 |

[0069] b) is |S 21 |

[0070] c) is |S 22 |

[0071] In the figure, the solid line is the measured result, the dashed line is the simulation result, the 1-port is the microstrip tapered balun in the present application, and the 2-port is the infinite balun in the present application. Figure 2 Figure 5

[0072] Figure: 1, spiral metal conductor; 2, dielectric support; 3, antenna port; 41, microstrip tapered balun coaxial connector; 42, microstrip tapered balun PCB bottom layer; 43, microstrip tapered balun PCB top layer; 44, microstrip tapered balun PCB substrate; 51, infinite balun PCB substrate; 52, infinite balun PCB top layer; 53, infinite balun PCB bottom layer; 54, coaxial line connection; 55, spiral coaxial line. DETAILED DESCRIPTION

[0073] In order to make the purpose, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. The components of the embodiments of the present application described and shown in the drawings herein can be arranged and designed in various different configurations.

[0074] Therefore, the following detailed description of the embodiments of the present application provided in the drawings is not intended to limit the scope of the claimed present application, but only represents selected embodiments of the present application. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present application without making creative efforts fall within the scope of protection of the present application.

[0075] It should be noted that: similar reference numbers and letters represent similar items in the following drawings, and therefore, once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings.

[0076] ​​In the description of the present application, it should be noted that the terms "upper", "lower", "inner", and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship when the product of the application is usually placed, and are only for the convenience of describing the present application and simplifying the description, and therefore cannot be understood as indicating or implying that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the present application.

[0077] In addition, the terms "first", "second", and the like are only used to distinguish the description, and cannot be understood as indicating or implying relative importance.

[0078] In the description of the present application, it should be noted that, unless otherwise explicitly specified and limited, the terms "arrangement", "installation", "connection", "connection" should be broadly understood, for example, it can be fixedly connected, or it can be detachably connected, or integrally connected; it can be mechanically connected, or it can be electrically connected; it can be directly connected, or it can be indirectly connected through an intermediate medium, or it can be connected inside two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0079] As shown in Figures 1-8 The present application discloses a circularly polarized high-gain omnidirectional / bidirectional reconfigurable spiral leaky-wave antenna, which comprises a plurality of spiral metal conductors 1, the axes of the plurality of spiral metal conductors 1 are collinear, and each spiral is uniformly distributed on the entire cylindrical surface. The spiral angle of the spiral on the spiral metal conductor 1 is 5°-60°. It has many advantages, such as: high gain, circular polarization, ultra-wideband, omnidirectional conical / pie-shaped beam, reconfigurable to bidirectional pie-shaped beam, no stopband, small size, low cost, high mechanical strength, simple structure and easy to design, etc.

[0080] Preferably, the spiral metal conductor 1 is two, the diameter and pitch of the spiral on the spiral metal conductor 1 are the same.

[0081] The spiral metal conductor 1 is one of a metal wire such as an enameled wire, a metal strip such as a flexible PCB printed and wound, or a more complex structure such as a coaxial line.

[0082] The spiral metal conductor 1 is wound on a dielectric support 2, which is one of a rod, a tube, or a fishbone. The spiral metal conductor 1 can also not require a dielectric support 2 and be supported by its own strength.

[0083] The signal amplitude of each spiral of the spiral metal conductor 1 is equal, and the phase difference is 360° / N in turn, wherein N is the number of spirals. The antenna can be fed at one end of the spiral, or can be fed at both ends of the spiral. If the antenna is fed at one end of the spiral, the antenna can provide an omnidirectional conical / pie-shaped beam. If the antenna is fed at both ends of the spiral, the antenna can provide a bidirectional pie-shaped beam.

[0084] The spiral angle of each spiral of the spiral metal conductor 1 is the included angle between the tangent of the spiral and the axis of the spiral, and the ratio of the spiral diameter to the pitch is between 0.028 and 0.55. The spiral angle is in the range of 5° to 60°. When the spiral angle is close to 0°, the structure in the application degenerates into a "twisted pair", and the energy radiated is extremely small, which has no practical value as an antenna. When the spiral angle is close to 90°, the structure in the application degenerates into a common axial mode spiral antenna, which mainly produces directional radiation along the axis of the spiral, rather than omnidirectional high-gain radiation.

[0085] The length L of each period of the spiral on the spiral metal conductor 1 is:

[0086]

[0087] wherein L and H are the length of one period of the spiral and the pitch of the spiral respectively, θ is the desired radiation direction, λ0 is the wavelength in free space, and λ is the wavelength on the spiral. g

[0088] The number of periods of the spiral on the spiral metal conductor 1 is greater than 1.

[0089] The antenna further comprises a feed structure, which is a microstrip tapered balun connected below the spiral metal conductor 1. An infinite balun is connected above the spiral metal conductor 1. The microstrip tapered balun and the infinite balun can be connected to the spiral leaky-wave antenna of the application alone, or can be fed from both ends of the antenna at the same time.

[0090] The antenna of the application is mainly different from the common "axial mode spiral antenna" in structure in that the spiral angle of each spiral is relatively small (5° to 60°). The spiral angle of a typical axial mode spiral antenna is generally in the range of 76° to 78°. This makes the radiation of the antenna of the application a conical / pie-shaped beam to the side of the antenna, rather than a single beam along the axis of the antenna.

[0091] The antenna structure of the application is mainly different from the common "normal mode spiral antenna" in structure in that the length of the antenna of the application can be large, and the total length can reach several wavelengths or more, so that high-gain radiation can be achieved. The normal mode spiral antenna cannot be large in size, otherwise the radiation will be out of phase, resulting in a split pattern.​

[0092] The principle of the present application is as follows:

[0093] The principle of realizing high-gain omnidirectional conical / pie-shaped beam is as follows:

[0094] The present application can be considered as a leaky-wave antenna based on the "spatial harmonic method". For the traveling wave current propagating along a long metal wire, the phase of the current will change with the position. If the antenna is a straight line, the radiation of the current at each point will mostly cancel each other out, and the total radiation will be very small. In the present application, the current propagates along a spiral, and the change in the direction of current propagation is used to offset the change in the phase of the current, so that the radiation of the current at each point can be superimposed on the side of the antenna, producing a stronger radiation.

[0095] Because the present antenna can be made very long while keeping the radiation of each period on the entire length in phase, it can produce a large in-phase aperture, and thus produce a narrow-beam-width high-gain radiation along the θ direction. The radiation direction is determined by the size of the spiral and the wavelength, and can be specifically referred to formula (1).

[0096] Because the structure of the present application is rotationally symmetric, the beam produced by it is of equal amplitude along the φ direction, i.e. an omnidirectional beam along the φ direction.

[0097] The principle of realizing high-gain "bidirectional" pie-shaped beam is as follows:

[0098] The above-mentioned "omnidirectional" conical / pie-shaped beam has the following characteristics: the radiation phase along the φ direction is constantly changing. For example, the radiation phase in the φ=0 direction is 0, and as the direction φ changes from 0 to 360°, the radiation phase also changes from 0° to 360°.

[0099] At the same time, when feeding from both ends of the antenna, the change rule of the radiation phase is opposite. For example, when φ changes from 0 to 360°, if feeding from the bottom, the radiation phase changes from 0° to 360°, and if feeding from the top, the radiation phase changes from 0° to -360°. At this time, if feeding from the bottom and the top with equal amplitude at the same time, in the φ=0 (or 180°) direction, the phase of the radiation produced by the bottom feeding and the top feeding is 0° (or ±180° respectively), and the radiation produced by the two feedings superimposes each other to produce maximum radiation. In the φ=90 (or 270°) direction, the phase of the radiation produced by the bottom feeding and the top feeding is ±90° (or ±270° respectively), and the radiation produced by the two feedings cancels each other to produce a radiation null. In other directions, the radiation is superimposed (or cancelled) to produce an amplitude between the maximum radiation and zero, and thus a "bidirectional" pie-shaped beam in the shape of an 8 is produced.

[0100] It is important to note that the aforementioned superposition and cancellation only occur when the antenna radiates to the side (θ = 90°). When the antenna radiates to the upper or lower side, the beam angles fed from below and above will be θ and 180°-θ, respectively. Since the two radiation directions are different, no superposition or cancellation effect can occur.

[0101] Specific implementation examples Figure 1 As shown. There are two spiral metal conductors 1, each with an inner diameter D = 19 mm, a wire diameter of 1 mm, a lead H = 76.5 mm, and a wire length L = 97 mm for one cycle. The dielectric support 2 is a plastic tube with a wall thickness T = 3 mm (relative permittivity ε). r =2.7). There are two spiral metal conductors 1, which are sleeved on the dielectric support 2. The upper and lower ends of the conductors are antenna ports 3. The antenna ports 3 can be connected to a balun or a resistor as a matching load. Where L: the length of one cycle of the spiral, H: the lead of the spiral, T: the thickness of the dielectric support 2, and D: the inner diameter of the spiral.

[0102] Figure 2 and Figure 5 Two applicable Figure 1 The antenna feeding structure in the [structure]. Among them, Figure 2 It is a microstrip tapered balun, which is more suitable for bottom-fed applications, i.e., when the feed and balun are at the same end of the antenna. Figure 5 It is an infinite balun, which is more suitable for top feeding, i.e., when the feed and balun are at opposite ends of the antenna. Figure 2 This is suitable for feeding when the number of helical metal conductors 1 is 2, and is connected to the antenna port 3. A microstrip graded balun PCB substrate 44 contains a microstrip graded balun PCB bottom layer 42 and a microstrip graded balun PCB top layer 43. One end of the microstrip graded balun PCB bottom layer 42 and the microstrip graded balun PCB top layer 43 are respectively connected to the helical metal conductors 1, and the other end of the microstrip graded balun PCB bottom layer 42 and the microstrip graded balun PCB top layer 43 are connected to a coaxial connector. Figure 5 This power supply is suitable for when the number of spirals in this invention is 2, and is connected to antenna port 3. It requires the use of a spiral coaxial line 55, in which case the spiral coaxial line 55 replaces... Figure 1 The spiral metal wire in the spiral coaxial line 55 serves as both a feed line and a radiator. The infinite balun PCB substrate 51 contains an infinite balun PCB top layer and an infinite balun PCB bottom layer 53, which are connected to the spiral coaxial line 55 via a coaxial line connection 54.

[0103] The two types of baluns can be used in combination to simultaneously feed power from both ends of the antenna, thus achieving a dual-beam effect. In this case, the coaxial cable required for the infinite balun can be soldered to the ground plane of the microstrip graded balun, and then connected to a coaxial connector, such as... Figure 6 As shown. This allows signals to be transmitted to the infinite balun without interfering with the normal operation of the microstrip graded balun. The helical coaxial line 55 is positioned along... Figure 2 The microstrip tapered balun is soldered and led out at the bottom layer, which can enable simultaneous feeding from both ends of the antenna, and the two baluns do not interfere with each other.

[0104] Based on actual experiments, the present invention has the following beneficial effects:

[0105] 1) High-gain omnidirectional cone / pancake beam

[0106] Figure 1 The embodiments in the example are connected Figure 2 The simulated and measured radiation patterns of the microstrip graded balun time are as follows: Figure 4 As shown. Test results show that the beam of this invention is omnidirectional along the φ direction and narrow along the θ direction, i.e., a high-gain omnidirectional conical / pancake beam.

[0107] 2) The beam is reconfigurable and can be converted into a two-way pie beam.

[0108] Figure 1 The embodiments in the text are simultaneously connected Figure 2 Microband gradient balun, and Figure 5 The simulation and measured radiation patterns are as follows: [Image of an infinite balun in a given context, with signals of approximately equal amplitude fed from both baluns] Figure 7 As shown. Test results show that the beam of this invention is a narrow beam along the θ direction and bidirectional along the φ direction, i.e., a high-gain bidirectional pie beam.

[0109] 3) Stable circularly polarized radiation

[0110] Figure 4 and Figure 7 This invention radiates circularly polarized waves. The primary polarization is left-handed circular polarization, with low cross-polarization content and a low axial ratio. If right-handed circular polarization is required as the primary radiation, the helix can be wound in the opposite direction. Figure 4 The results show that the beam shape of the circularly polarized radiation remains stable as the beam direction changes, with no grating lobes appearing and the axial ratio remaining consistently low.

[0111] 4) Ultra-broadband

[0112] This invention has an extremely large impedance bandwidth. For example... Figure 3 and Figure 8 As shown in Figure a, when using a microstrip graded balun, the return loss (|S) of this invention is... 11|) from about 70% of the center frequency, to several times the center frequency, can always be better than -10dB. This is significantly better than all the "omni high gain circularly polarized antennas" searched in the range. With an infinite balun, the -10dB impedance bandwidth is relatively small, such as Figure 8 c. This is limited by the infinite balun, the antenna itself is still ultra-wideband.

[0113] At the same time, Figure 3 and Figure 8 b show that the |S 21 of the invention is more stable, which makes the gain of the invention change less with frequency.

[0114] 5) The beam can be scanned from back to front frequency, and there is no open stop band when it passes through the front side (θ=90°)

[0115] As shown in Figure 4 , the beam of the invention is scanned with frequency. Figure 1 As shown in the embodiment, when the beam direction is scanned to the range of θ=45°-135°, the beam shape and axial ratio can always be relatively good. By modifying the parameters of the spiral, the scanning range can be further improved.

[0116] As shown in Figure 3 , Figure 4 a and Figure 8 , the beam of the invention is scanned to the front side (θ=90°), and there is no observable open stop band phenomenon. The open stop band is a common drawback of "spatial harmonic method leaky wave antennas", which is manifested as: when the beam is scanned to the front side of the antenna, the |S 11 of the antenna suddenly rises significantly, and the |S 21 of the antenna drops significantly, and the gain drops significantly. For the invention, Figure 3 , Figure 8 a and c show that when the beam is scanned to the front side, i.e. at a frequency of 2.5GHz, the |S 11 of the antenna does not exceed the normal fluctuation. Figure 4 a and Figure 4 c, d and e, there is also no special gain fluctuation.

[0117] 6) Small size

[0118] The spiral angle of the invention is small, so the diameter of the antenna is small, Figure 1 The diameter of the embodiment in the invention is only 19mm. When the beam is directed to the front side, the frequency is about 2.5GHz, at which time the diameter of 19mm corresponds to 0.16 wavelengths.

[0119] In particular, when the helix angle is 5°, the diameter of the antenna is only about 2.8% of the wavelength, without considering the influence of the antenna support, and the antenna radiates in the positive lateral direction. Simulation results show that the application can still provide omnidirectional circularly polarized radiation with good axial ratio. Within the scope of the search, no design can achieve omnidirectional circularly polarized radiation at such a small diameter.

[0120] 7) Only need to wind the metal wire into a spiral shape during processing, without a large number of welds, easy to process. Only a small amount of metal is needed, the weight is light, and the cost is low. The amount of material needed during production is small, easy to manage.

[0121] 8) Easy to design

[0122] The main adjustable parameters of the application are only four: the number of turns, the diameter, the lead, and the total length. Simulations show that the application can always maintain good circularly polarized radiation when these parameters are changed arbitrarily within a large range. In contrast, other omnidirectional high-gain circularly polarized antennas often need to carefully adjust the size of each part to achieve good circular polarization.

[0123] Of course, the application can have other various embodiments, and those skilled in the art can make various corresponding changes and modifications to the application without departing from the spirit and essence of the application. However, these corresponding changes and modifications should all belong to the protection scope of the claims attached to the application.

Claims

1. A circularly polarized high-gain omnidirectional / bidirectional reconfigurable helical leaky antenna, characterized in that: It includes multiple spiral metal conductors (1), the axes of the multiple spiral metal conductors (1) are collinear, and each spiral is evenly distributed on the entire cylindrical surface. The spiral angle of the spiral on the spiral metal conductor (1) is 5°-60°. It also includes a power supply structure, which is a microstrip tapered balun, and the microstrip tapered balun is connected to the bottom of the spiral metal conductor (1); An infinite balun is connected above the spiral metal conductor (1); Among them, the signal amplitude on each spiral of the spiral metal conductor (1) is equal, and the phases are successively different by 360° / N, where N is the number of spirals; if only one end of the spiral is fed, an omnidirectional conical / pancake beam is provided; if signals of equal amplitude are fed into both ends of the spiral at the same time, a bidirectional pancake beam is provided. The helix angle of the spiral on the spiral metal conductor (1) is the angle between the helix tangent and the helix axis. The ratio of the helix diameter to the conductor diameter is between 0.028 and 0.

55. When the helix angle is close to 0°, the structure degenerates into a twisted pair. When the propeller is close to 90°, the structure degenerates into a common axial mode spiral antenna.

2. The circularly polarized high-gain omnidirectional / bidirectional reconfigurable helical leaky antenna according to claim 1, characterized in that: The spiral metal conductor (1) consists of two strands, and the diameter and lead of the spiral on the spiral metal conductor (1) are the same.

3. The circularly polarized high-gain omnidirectional / bidirectional reconfigurable helical leaky antenna according to claim 1, characterized in that: The spiral metal conductor (1) is one of a metal wire, a metal strip, or a coaxial line.

4. The circularly polarized high-gain omnidirectional / bidirectional reconfigurable helical leaky antenna according to claim 1, characterized in that: The spiral metal conductor (1) is wound around the dielectric support (2), which is one of rod-shaped, tubular, or fishbone-shaped.

5. The circularly polarized high-gain omnidirectional / bidirectional reconfigurable helical leaky antenna according to claim 1, characterized in that: The length L of the spiral in each cycle of the spiral metal conductor (1) is: (1) Where L and H are the linear length of one cycle of the helix and the lead of the helix, respectively, θ is the desired radiation direction, λ0 is the wavelength in free space, and λ g It is the wavelength of the electromagnetic wave on the spiral.

6. The circularly polarized high-gain omnidirectional / bidirectional reconfigurable helical leaky antenna according to claim 1, characterized in that: The spiral period of the spiral metal conductor (1) is greater than 1.

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