Tree antenna and self-adaptive frequency sweeping method thereof

Abstract

The invention discloses a tree antenna and a self-adaptive frequency sweeping method thereof, the tree antenna comprises a tree loading body and bent conformal Vivaldi radiators, one or more conformal Vivaldi radiators are attached to any position of the surface of the tree loading body and are in contact connection with the tree loading body, and the surface of each conformal Vivaldi radiator is covered with a shell with the same color as the tree loading body. According to the tree antenna provided by the invention, radiation and gain of an electromagnetic field are improved by using trees according to a dielectric rod antenna principle, the transmitting frequency bands of electromagnetic signals are adaptively regulated and controlled for different trees in combination with an adaptive frequency sweeping technology, efficient electromagnetic signal transmitting and receiving are realized, and the tree antenna is simple in structure, economical, environment-friendly and high in practicability. The method has application value in the fields of agriculture, forestry and the like.

Description

Technical Field

[0001] The invention relates to the field of electronic technology, and in particular to a tree antenna and an adaptive frequency scanning method thereof. Background Art

[0002] Electronic communications and monitoring in the jungle are often blocked by trees, which can lead to failure. Consider using trees as antennas to send and receive signals directly to avoid the blockage problem.

[0003] In the current research on tree antennas, existing solutions often require damage to the trees, such as inserting conductors, changing their growth conditions, etc. On the other hand, due to the uncertainty of plant size and material, it is difficult to use them for wireless communications that require precise frequencies. Therefore, the electromagnetic radiation characteristics of plants have not been effectively utilized until now.

[0004] Patent application specification CN107248536A discloses a plant antenna, including a carrier plant, the carrier plant has two cavities arranged at intervals, the two cavities are filled with liquid metal that remains liquid at room temperature, and also includes a connecting wire; the connecting wire is a radio frequency wire, one end of the radio frequency wire is provided with two connectors, the two connectors are respectively connected to the liquid metal in the two cavities; the connecting wire is a wire, the two ends of the wire are respectively connected to the liquid metal in the two cavities, and a balancer is provided on the wire; the connecting wire is a wire, the two ends of the wire are respectively connected to the liquid metal in the two cavities. For this invention, firstly, the liquid metal used is expensive and not suitable for large-scale application; secondly, injecting liquid metal into the plant body is not conducive to the protection of the ecological environment, and may cause water and soil pollution; furthermore, if the liquid metal is absorbed by the plant and gradually enriched in the food chain, it may eventually affect the health of animals and humans.

[0005] Patent application specification CN85103804A discloses an antenna device for receiving or transmitting electromagnetic waves, the essential feature of which is to plant a plant in the center of a conductive layer container, and to install a magnetic ring induction coil under the plant crown. The radio frequency energy in the plant is obtained by using the conductive layer and the magnetic ring induction coil. This antenna design requires the installation of an arc-shaped metal layer at the root of the plant, which is only suitable for small potted plants, but not for large trees in the jungle. Summary of the invention

[0006] In view of the deficiencies in the prior art, the present invention provides a tree antenna based on a conformal Vivaldi radiator.

[0007] The technical solution adopted by the present invention is as follows:

[0008] The present invention comprises a tree carrier and a curved conformal Vivaldi radiator. One or more conformal Vivaldi radiators are attached to any position of the surface of the tree carrier and are in contact with and connected to the tree carrier.

[0009] Also included is a housing, wherein the conformal Vivaldi radiator surface is covered with a housing of the same color as the tree loader.

[0010] The working mode of the tree antenna is determined by the tree loading body. The relationship between the working mode of the tree antenna and the tree loading body is set according to the following formula:

[0011]

[0012] Among them, ζ and ξ are real numbers, representing the propagation constants β and z , and the product of the tree load diameter b, β z and β d are the propagation constants inside the tree loader, represents the propagation constant of the tree load outside the body, β ρ and β z Respectively represent β d The tangential ρ component and longitudinal z component of the load on the tree, ε d and ε c represent the relative dielectric constants inside and outside the tree carrier, μ d and μ c They respectively represent the relative magnetic permeabilities inside and outside the tree loading body, and the eigenvalue χ represents the electromagnetic wave transmission mode of the tree loading body.

[0013] When the tree antenna transmits only the main mode, the diameter of the tree carrier is set according to the following formula:

[0014]

[0015] Where b is the diameter of the tree carrier, χ 01 represents the eigenvalue of the main mode, λ0 is the working wavelength in the main mode state, ε d and ε c represent the relative dielectric constants inside and outside the tree carrier, μ d and μ c Respectively represent the relative magnetic permeability inside and outside of the tree loading body.

[0016] The conformal Vivaldi radiator includes a dielectric substrate, a metal ground plate, a slot, a circular resonant cavity and a metal microstrip line. One side of the dielectric substrate is attached to a tree carrier and is provided with a metal microstrip line, and the other side is attached to a metal ground plate. The metal ground plate is provided with a slot and a circular hole serving as a circular resonant cavity. The slot is arranged along the radiation direction, and the slot is arranged in a trumpet-shaped opening shape, and the circular hole is opened at the end of the narrow end of the trumpet-shaped opening.

[0017] The groove lines of the groove walls on both sides of the slot groove are arranged symmetrically with respect to the middle symmetry axis. The groove lines of the groove walls on each side are mainly composed of parallel groove lines and gradient groove lines. The parallel groove line is a line segment parallel to the symmetry axis, and the gradient groove line is a curve. One end of the parallel groove line is connected to the gradient groove line, and the other end of the parallel groove line extends to the circular resonant cavity.

[0018] The metal microstrip line is mainly composed of a vertical microstrip line, a horizontal microstrip line and a fan-shaped microstrip line. One end of the vertical microstrip line extends away from the radiation direction to the edge of the dielectric substrate, and the other end of the vertical microstrip line is connected to one end of the horizontal microstrip line. The horizontal microstrip line is arranged perpendicular to the radiation direction, and one end of the horizontal microstrip line away from the vertical microstrip line is connected to the fan-shaped microstrip line.

[0019] The dielectric substrate is made of PET dielectric material.

[0020] An adaptive frequency scanning method for a tree antenna comprises the following steps:

[0021] S1. Setting a signal in a preset frequency range as an excitation signal, performing ultra-wideband frequency sweep on the excitation signal, and dividing the excitation signal into excitation signals of multiple different frequency bands;

[0022] S2, inputting the excitation signals of different frequency bands into the metal microstrip line of the tree antenna in sequence, wherein the excitation signal reflected back to the transmission direction is used as the reflection signal, and the reflection coefficient of the tree antenna under different frequency bands is obtained according to the processing of the excitation signal and the reflection signal, and the frequency band with the lowest reflection coefficient is extracted as the optimal frequency band;

[0023] S3, setting a fixed time, during which the tree antenna uses the best frequency band to transmit and receive signals;

[0024] S4: After the fixed time is over, return to S1 and repeat the cycle.

[0025] The beneficial effects of the present invention are as follows:

[0026] (1) The present invention loads a conformal Vivaldi radiator onto a tree. According to the dielectric rod theory, the tree is used to guide electromagnetic radiation, and the propagating surface wave is intercepted by the structural changes of the tree loading body, so that power radiation is generated at the discontinuous part of the tree loading body, realizing the function of the tree antenna, and achieving the effects of radiation enhancement and far-field gain adjustment. The tree antenna proposed by the present invention has good concealment, ecological adaptability, simple structure, economy and environmental protection, and has application value in agriculture, forestry and other fields.

[0027] (2) The tree antenna proposed in the present invention can realize omnidirectional electromagnetic radiation above the ground. A terminal network is formed by multiple tree antennas, which helps to cover dense electromagnetic fields in complex jungle environments, thereby realizing electromagnetic dynamic monitoring and data communication between terminals.

[0028] (3) The present invention proposes an adaptive frequency scanning technology suitable for tree antennas, that is, an adaptive frequency scanning electromagnetic signal transceiver architecture is proposed. By utilizing the reflection characteristics of radio frequency signals and the transmission characteristics of electromagnetic signals between trees, the problems of impedance matching and operating frequency uncertainty are solved, and the operating frequency uncertainty caused by the size and material differences between plants is avoided. At the same time, the system can work effectively in different weather environments.

[0029] At the same time, the present invention also proposes an adaptive frequency scanning technology suitable for tree antennas to solve the problems of difficult impedance matching and uncertain operating frequency. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is a schematic diagram of a tree antenna;

[0031] Figure 2 The single conformal Vivaldi radiator structure in Example 1;

[0032] Figure 2 (a) is a front view of a single conformal Vivaldi radiator;

[0033] Figure 2 (b) Schematic diagram of the metal microstrip line of a single conformal Vivaldi radiator;

[0034] Figure 3 Schematic diagram of antenna for tree loading based on conformal Vivaldi radiator;

[0035] Figure 3 (a) A conventional uniform continuous dielectric rod is used as a theoretical derivation model for surface waves.

[0036] Figure 3 (b) The gradient dielectric rod simulates the trunk structure of the tree load;

[0037] Figure 4 It is a schematic diagram of a planar expansion of a single conformal Vivaldi radiator in Example 1;

[0038] Figure 4 (a) is the metal ground plate and slot line of the Vivaldi radiator;

[0039] Figure 4 (b) is the metal microstrip line of the Vivaldi radiator;

[0040] Figure 5 The reflection coefficient S obtained by attaching a single conformal Vivaldi radiator to a tree carrier in Example 1 is 11 Simulation result diagram;

[0041] Figure 6 A diagram showing the far-field gain simulation results obtained by loading trees on a single conformal Vivaldi radiator in Example 1;

[0042] Figure 7 The annular Vivaldi radiator in Example 2 is composed of four conformal Vivaldi radiators.

[0043] Figure 8 This is a simulation result diagram of the far-field radiation gain of the annular Vivaldi radiator and the annular Vivaldi radiator loaded with trees in Example 2;

[0044] Figure 8 (a) is the far-field radiation gain using only the ring Vivaldi radiator;

[0045] Figure 8 (b) Far-field radiation gain of the ring-shaped Vivaldi radiator attached to the tree load;

[0046] Fig. 9 This is a flow chart of the adaptive frequency scanning technology applicable to the tree antenna working mode in the present invention.

[0047] Among them, 1. tree load; 2. conformal Vivaldi radiator; 3. dielectric substrate; 4. metal ground plate; 5. slot; 6. circular resonant cavity; 7. metal microstrip line. DETAILED DESCRIPTION

[0048] The exemplary embodiments disclosed in the present invention will be described in more detail below with reference to the accompanying drawings. Although the exemplary embodiments disclosed in the present invention are shown in the accompanying drawings, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments described herein. On the contrary, these embodiments are provided to enable a more thorough understanding of the present invention and to fully convey the scope of the present invention to those skilled in the art.

[0049] Tree antennas such as Figure 1 As shown, it includes a tree carrier 1 and a curved conformal Vivaldi radiator 2 , and one or more conformal Vivaldi radiators 2 are attached to any position of the surface of the tree carrier 1 and are in contact with and connected to the tree carrier 1 .

[0050] The tree loading body is the trunk of the tree, that is, the trunk part above the ground and below the branches.

[0051] The curvature of the conformal Vivaldi radiator 2 is mainly determined by the curvature of the epidermis of the tree carrier 1. The conformal Vivaldi radiator 2 is consistent with the arc shape of the epidermis of the trunk of the tree carrier 1 and is integrated with the trunk of the tree carrier 1, that is, the conformal Vivaldi radiator 2 has a curvature radius consistent with the trunk of the tree carrier 1. The conformal Vivaldi radiator 2 is attached to the epidermis of the trunk of the tree carrier 1 above the ground, and is bound around the trunk of the tree carrier 1 with a cable tie.

[0052] The tree antenna also includes a shell, and the surface of the conformal Vivaldi radiator 2 is covered with a shell having the same concealed color as the tree loading body (1), which has good concealment and ecological adaptability.

[0053] The tree load can be regarded as a combination of many dielectrics, and the radiation of the tree antenna can be explained by the dielectric rod antenna theory; the dielectric rod antenna uses structural changes to intercept the propagating surface waves, so that it produces power radiation in the discontinuous part of the dielectric rod, so it is also called a surface wave antenna. The dielectric rod antenna is a special case of the dielectric rod waveguide; the dielectric rod waveguide is a low-loss waveguide made of one or more layers of dielectric materials. When the structure of the dielectric rod waveguide has discontinuities (that is, there are bends, steps and tapers), the dielectric rod waveguide will generate radiation; due to the growth conditions, the tree load naturally has structural discontinuities, which is suitable for surface wave propagation and acts as an antenna for electromagnetic radiation.

[0054] The conformal Vivaldi radiator 2 generates electromagnetic radiation after receiving an excitation signal, which stimulates the formation of a HEM field in the tree loading body 1 and performs conduction radiation along the trunk of the tree loading body 1 .

[0055] like Figure 3 As shown, Figure 3 (a) is a theoretical derivation model of a conventional uniform continuous dielectric rod used as a surface wave. Figure 3 (b) shows the main structure of the gradient dielectric rod simulating the tree load. Taking the uniform continuous dielectric rod as an example, its waveguide has three layers: the core (μ i ,ε i ), outer dielectric (μ d ,ε d ) and outer cladding (μc ,ε c ).

[0056] When the tree loading body is regarded as a dielectric waveguide, according to Maxwell's equations and the boundary conditions of the dielectric waveguide, the HEM field expression in the tree loading body 1 can be expressed as follows:

[0057]

[0058] in, and denote the propagation constants inside and outside the dielectric waveguide, ε d and ε c represent the relative dielectric constants inside and outside the dielectric waveguide, μ d and μ c represents the relative magnetic permeability inside and outside the dielectric waveguide, m represents the mode order, ω represents the frequency, and b represents the diameter of the dielectric rod. m and K m are the m-order Bessel functions of the first and second kind.

[0059] To evaluate the dielectric rod in an air environment, use μ c =μ0 and ε c =ε0, the relationship between the propagation constants is obtained according to the boundary conditions:

[0060]

[0061] ζ=β z b

[0062]

[0063] When the tree load is in the air environment, according to the boundary conditions of the tree load and the relationship between the propagation constant, the HEM field expression is solved to obtain its distribution characteristics, that is, the electrical radiation characteristics and working mode of the tree antenna are determined by the tree load 1. The relationship between the electrical radiation characteristics and working mode of the tree antenna and the tree load 1 is set according to the following formula:

[0064]

[0065] Among them, ζ and ξ are real numbers, representing the propagation constants β and z , and the product of the tree load diameter b, are used to solve the first-kind m-order Bessel function J m and the second kind m-order Bessel function K m , β z and β d are the propagation constants inside the tree loader, represents the propagation constant of the tree load outside the body, β ρ and β z Respectively represent β d The tangential ρ component and longitudinal z component of the load on the tree, ε d and ε c represent the relative dielectric constants inside and outside the tree carrier (1), μ d and μ c represent the relative magnetic permeability inside and outside the tree loading body (1), the eigenvalue χ, Represents the electromagnetic wave transmission mode of the tree load.

[0066] The working mode refers to the main mode and m-order higher-order mode in the electromagnetic wave transmission mode of the tree load. The main mode has low transmission loss; different modes correspond to different working frequencies. The transmission mode refers to the shape and characteristics of the electromagnetic wave propagating in the waveguide. It defines the distribution of the electric and magnetic fields when the signal propagates inside the tree load. Different modes are often represented by different numbers, such as TE 01 Indicates the fundamental mode, TE mn (m>1, n>1) is a high-order mode; the transmission mode is affected by the size and material (specifically the dielectric constant and magnetic permeability) of the tree load; different transmission modes correspond to different frequencies, and selecting a given working frequency means that a specific mode is used to transmit electromagnetic waves.

[0067] The above formula only has practical significance when ξ remains a real number. The field outside the tree load will decay exponentially in the transverse direction, which is a necessary condition for the transmission of surface waves along the tree load.

[0068] For each value of m, there are a finite number of eigenvalues ​​χ mn This generates surface waves that propagate along the dielectric rod. For example, HEM 11 (HE 11 ) mode has an eigenvalue of χ 10 = 0, representing the main mode. In order to maintain low-loss main mode transmission, χ 2 +ξ 2 Should be less than the square of the eigenvalue of the second mode:

[0069] χ 2 +ξ 2 < 01 2

[0070] Therefore, the maximum diameter of the cylindrical dielectric rod under the main mode transmission condition can be given, that is, when the tree antenna only transmits the main mode, the diameter of the tree load 1 is set according to the following formula:

[0071]

[0072] Wherein, b represents the diameter of the tree carrier 1, and x 01 represents the eigenvalue of the main mode, and λ0 is the operating wavelength in the main mode state.

[0073] The main mode is the mode with the lowest operating frequency.

[0074] These equations show that the diameter of the dielectric rod affects the electromagnetic radiation characteristics and operating mode of the dielectric rod antenna.

[0075] The conformal Vivaldi radiator 2 includes a dielectric substrate 3, a metal ground plate 4, a slot 5, a circular resonant cavity 6 and a metal microstrip line 7. One side of the dielectric substrate 3 is attached to the tree support 1 and the metal microstrip line 7 is arranged on the surface, and the other side is attached to the metal ground plate 4. The metal ground plate 4 is provided with a slot 5 and a circular hole serving as the circular resonant cavity 6. The slot 5 is arranged along the radiation direction. The slot 5 is arranged in a trumpet-shaped opening shape. The circular hole is opened at the end of the narrow end of the trumpet-shaped opening, and the narrow end of the trumpet-shaped opening is connected to the circular hole.

[0076] The groove lines of the groove walls on both sides of the slot groove 5 are arranged symmetrically about the middle symmetry axis, and the groove lines of the groove walls on each side are mainly composed of parallel groove lines and gradient groove lines. The parallel groove line is a line segment parallel to the symmetry axis, and the gradient groove line is a curve. One end of the parallel groove line is connected to the gradient groove line, and the gradient groove line gradually bends away from the parallel groove line and away from the symmetry axis and extends to one end of the metal grounding plate 4, and the other end of the parallel groove line extends to the circular resonant cavity 6.

[0077] The direction of the symmetry axis is the same as the radiation direction; the gradient slot line is responsible for guiding the electromagnetic waves radiated by the antenna, the parallel slot line and the metal microstrip line 7 are coupled with each other and transmit electromagnetic waves, and the circular resonant cavity 6 is used to achieve impedance matching of the metal microstrip line 7.

[0078] The metal microstrip line 7 is mainly composed of a vertical microstrip line, a horizontal microstrip line and a fan-shaped microstrip line. The vertical microstrip line is arranged vertically and one end of the vertical microstrip line extends away from the radiation direction to the edge of the dielectric substrate 3. The other end of the vertical microstrip line is connected to one end of the horizontal microstrip line. The horizontal microstrip line is arranged perpendicular to the radiation direction and pointing to the direction of the circular resonant cavity 6. One end of the horizontal microstrip line away from the vertical microstrip line is connected to the fan-shaped microstrip line, and the fan-shaped microstrip line is arranged near the circular resonant cavity 6.

[0079] The end of the metal microstrip line 7 is in a fan-shaped structure, which is mainly used to achieve impedance matching; at the same time, the metal microstrip line 7 couples and feeds the slot line 5 through the dielectric substrate 3 .

[0080] The dielectric substrate 3 is made of flexible PET dielectric material with a dielectric constant of 2.9.

[0081] Tree loaders in different growth states have different diameters and dielectric parameters, and their working modes and frequencies are difficult to determine. To address this problem, the present invention proposes an adaptive frequency sweeping technology suitable for tree antennas. The key point of the adaptive frequency sweeping technology is that it can automatically analyze the spectrum of interference signals and automatically select the frequency band with the strongest radiation capacity to transmit signals in complex situations.

[0082] Through the reflection characteristics of radio frequency signals and the transmission characteristics of electromagnetic signals between tree antennas, ultra-wideband frequency sweeping is used to obtain the best operating frequency band of tree antennas in the short term, and the transmission frequency band of electromagnetic signals is adaptively adjusted for different tree antennas to achieve efficient electromagnetic signal transmission and reception. The adaptive frequency sweeping method can overcome the problem that tree antennas are easily affected by tree growth conditions and weather changes, resulting in impedance matching difficulties and uncertain operating frequencies;

[0083] The method comprises the following steps:

[0084] S1. Set a signal in a certain frequency range as an excitation signal, perform ultra-wideband frequency sweep on the excitation signal, and divide the excitation signal into excitation signals in multiple different narrowband frequency bands;

[0085] S2, inputting the excitation signals of different narrowband frequency bands into the metal microstrip line 7 of the tree antenna in sequence, a part of the excitation signal is radiated by the antenna, and the other part is not effectively radiated due to the impedance characteristics of the antenna and is reflected back to the transmission direction of the excitation signal as a reflection signal, and the radiation efficiency and reflection coefficient of the tree antenna under different narrowband frequency bands are obtained according to the processing of the excitation signal and the reflection signal, and the narrowband frequency band with the highest radiation efficiency and the lowest reflection coefficient is extracted as the optimal frequency band;

[0086] S3, setting a fixed time, during which the tree antenna uses the best frequency band to transmit and receive signals;

[0087] S4: After the fixed time is over, return to S1 and repeat the cycle.

[0088] The radiation efficiency indicates the ability of the antenna to effectively convert input power into electromagnetic waves and radiate outward. It is the ratio of the radiation power to the input power. The reflection coefficient indicates the impedance matching of the signal at the antenna input end, and measures how much of the input power is reflected back to the signal source. It is the ratio of the reflected power to the input power.

[0089] Specific embodiments 1 and 2 of the present invention are as follows:

[0090] Example 1

[0091] like Figure 4As shown, the length of the metal ground plate of a single conformal Vivaldi radiator 2 is H and the width is W; the width of the rectangular part of the slot 5 is GW, that is, the distance between the two parallel slot lines is GW, and the gradient slot line part changes in the form of a natural exponential: 0.5GW×e rx , r is the gradient rate, x is the extension direction;

[0092] The radius of the circular resonant cavity 6 is R1; the line width of the metal microstrip line 7 is MW, the line lengths are L1 and L2, and the end fan radius is R2;

[0093] A single conformal Vivaldi radiator 2 is bent 180° to form an arch shape, and is covered on the branch surface of the tree loading body 1 at a distance of 15 mm, and an electromagnetic simulation is performed. The tree loading body 1 is a traditional tree structure, and the dielectric constant adopts the dielectric constant (ε=60, μ=1) and conductivity (10S / m) of salt water. The specific dimensions of a single conformal Vivaldi radiator 2 are shown in the following table:

[0094]

[0095] The simulation results are plotted in the form of a spectrum curve. Analyze the reflection coefficient S 11 Simulation results, such as Figure 5 As shown, the S of a single conformal Vivaldi radiator 2 after loading trees 11 The reflection coefficient is significantly reduced, and the reflection coefficient is lower than -10dB in the frequency band below 2000MHz. At the same time, more significant resonance (valley value) is produced after loading the trees. The far-field gain simulation results are as follows: Figure 6 As shown in the figure, in the 1500-2000MHz frequency band, compared with the unloaded case, the far-field gain of a single conformal Vivaldi radiator 2 is greatly enhanced after loading with trees, and the reflection coefficient S 11 There is a significant improvement; in addition, the gain at multiple resonant frequency points (peak values) after loading the trees is significantly enhanced.

[0096] In this embodiment, after the conformal Vivaldi radiator 2 is loaded with trees, the electromagnetic radiation is guided by the trees, thereby generating a radiation enhancement effect, especially having a better enhancement effect on radiators of electrically small size.

[0097] Example 2

[0098] like Figure 7As shown, the conformal Vivaldi radiator 2 is bent 90 degrees to form an arch shape, and four conformal Vivaldi radiators 2 are connected to each other to form a ring Vivaldi radiator, and surround the trunk of the tree. The ring Vivaldi radiator surrounds the trunk of the tree load 1, and the four conformal Vivaldi radiators are excited at the same time to form a high-breadth electromagnetic radiation range. The simultaneous action of the four conformal Vivaldi radiators obtains omnidirectional radiation characteristics at the expense of maximum gain.

[0099] Electromagnetic simulation was performed according to the structural parameters in Example 1, and four conformal Vivaldi radiators 2 were excited at the same time. The far-field gain patterns under and without trees were compared. The simulation results are as follows: Figure 8 shown. Figure 8 (a) is the far-field radiation gain of the ring Vivaldi radiator (752MHz operating frequency), where Phi = 0° and Phi = 90° represent the radiation patterns of two different vertical sections respectively; Figure 8 (b) is the far-field radiation gain of the annular Vivaldi radiator after loading trees (800MHz operating frequency), where Phi=48°, Phi=78°, and Phi=189° represent the radiation patterns of three different vertical sections, respectively.

[0100] After the annular Vivaldi radiator was loaded with trees, the maximum gain dropped from 20dBi to 6.05dBi. The main reason is that the trees also guided the electromagnetic radiation in the horizontal direction, and the simultaneous action of the four radiators formed omnidirectional radiation in the vertical positive direction, which looked like a conical three-dimensional far-field gain diagram. After the energy was omnidirectionally radiated, the maximum gain was inevitably reduced.

[0101] Furthermore, the omnidirectional radiation gain of multiple tree antennas helps to form a dense electromagnetic field in the jungle area, which has a better effect on communication in complex jungle environments. Furthermore, each tree antenna can be used as a transceiver terminal, and multiple terminals form a sensor network, thereby realizing electromagnetic dynamic monitoring in the jungle environment.

[0102] The above are only embodiments of the present application and are not intended to limit the present application. For those skilled in the art, the present application may have various changes and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included within the scope of the claims of the present application.

Claims

1. A tree antenna, characterized in that: It comprises a tree carrier (1) and a curved conformal Vivaldi radiator (2), wherein one or more conformal Vivaldi radiators (2) are attached to any position of the surface of the tree carrier (1) and are in contact and connection with the tree carrier (1).

2. A tree antenna according to claim 1, characterized in that: It also includes a shell, wherein the surface of the conformal Vivaldi radiator (2) is covered with a shell having the same color as the tree loading body (1).

3. The tree antenna according to claim 1, characterized in that: The working mode of the tree antenna is determined by the tree loading body (1). The relationship between the working mode of the tree antenna and the tree loading body (1) is set according to the following formula: Among them, ζ and ξ are real numbers, representing the propagation constants β and z , and the product of the tree load diameter b, β z and β d are the propagation constants inside the tree loader, represents the propagation constant of the tree load outside the body, β ρ and β z Respectively represent β d The tangential ρ component and longitudinal z component of the load on the tree, ε d and ε c represent the relative dielectric constants inside and outside the tree carrier (1), μ d and μ c They respectively represent the relative magnetic permeabilities inside and outside the tree loading body (1), and the eigenvalue χ represents the electromagnetic wave transmission mode of the tree loading body.

4. A tree antenna according to claim 2, characterized in that: When the tree antenna transmits only the main mode, the diameter of the tree loading body (1) is set according to the following formula: Where b represents the diameter of the tree carrier (1), 01 represents the eigenvalue of the main mode, λ0 is the working wavelength in the main mode state, ε d and ε c represent the relative dielectric constants inside and outside the tree carrier (1), μ d and μ c Respectively represent the relative magnetic permeability inside and outside the tree loading body (1).

5. The tree antenna according to claim 1, characterized in that: The conformal Vivaldi radiator (2) comprises a dielectric substrate (3), a metal ground plate (4), a slot (5), a circular resonant cavity (6) and a metal microstrip line (7). One side of the dielectric substrate (3) is attached to the tree loading body (1) and is provided with a metal microstrip line (7), and the other side is attached to a metal ground plate (4). The metal ground plate (4) is provided with a slot (5) and a circular hole serving as a circular resonant cavity (6). The slot (5) is arranged along the radiation direction. The slot (5) is arranged in a trumpet-shaped opening shape, and the circular hole is opened at the end of the narrow end of the trumpet-shaped opening.

6. A tree antenna according to claim 5, characterized in that: The groove lines of the groove walls on both sides of the slot groove (5) are arranged symmetrically about the middle symmetry axis. The groove lines of the groove walls on each side are mainly composed of parallel groove lines and gradient groove lines. The parallel groove line is a line segment parallel to the symmetry axis, and the gradient groove line is a curve. One end of the parallel groove line is connected to the gradient groove line, and the other end of the parallel groove line extends to the circular resonance cavity (6).

7. The tree antenna according to claim 5, characterized in that: The metal microstrip line (7) is mainly composed of a vertical microstrip line, a horizontal microstrip line and a fan-shaped microstrip line. One end of the vertical microstrip line extends away from the radiation direction to the edge of the dielectric substrate (3). The other end of the vertical microstrip line is connected to one end of the horizontal microstrip line. The horizontal microstrip line is arranged perpendicular to the radiation direction. One end of the horizontal microstrip line away from the vertical microstrip line is connected to the fan-shaped microstrip line.

8. The tree antenna according to claim 1, characterized in that: The dielectric substrate (3) is made of PET dielectric material.

9. The adaptive frequency scanning method for a tree antenna according to any one of claims 1 to 8, characterized in that: The method comprises the following steps: S1. Setting a signal in a preset frequency range as an excitation signal, performing ultra-wideband frequency sweep on the excitation signal, and dividing the excitation signal into excitation signals of multiple different frequency bands; S2, inputting the excitation signals of different frequency bands into the metal microstrip line (7) of the tree antenna in sequence, wherein the excitation signal reflected back to the transmission direction is used as the reflection signal, and the reflection coefficient of the tree antenna under different frequency bands is obtained according to the processing of the excitation signal and the reflection signal, and the frequency band with the lowest reflection coefficient is extracted as the optimal frequency band; S3, setting a fixed time, during which the tree antenna uses the best frequency band to transmit and receive signals; S4: After the fixed time is over, return to S1 and repeat the cycle.

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