A novel Vivaldi antenna

Abstract

The present invention discloses a novel Vivaldi antenna, belonging to the technical field of antennas. By means of a substrate tapered slot structure and loading 3DGP, the present invention solves the problems of low gain and poor directivity of two-dimensional structure antennas. Compared with traditional Vivaldi antennas, the gain is increased by 1.28 dB. Compared with existing gain improvement technologies, the present invention cuts the dielectric substrate and sets directors, without involving complex preparation processes, without adding extra large-sized components, and without increasing the size of the Vivaldi antenna. Therefore, the present invention can effectively improve the gain while not increasing the antenna size and reducing the preparation complexity, and can be widely applied to the application scenarios of small household appliances.

Description

Technical Field

[0001] The present invention relates to a novel Vivaldi antenna, belonging to the technical field of antennas. Background Art

[0002] The Vivaldi antenna is an end-fire traveling wave antenna, which has the advantages of high gain, small size, strong directivity, etc., and is suitable for wireless energy transmission over medium and long distances and scenarios with small antenna installation spaces. Its principle is to couple energy to the slot line through a microstrip transmission line, and radiate or receive electromagnetic waves through the radiation arms of the slot line.

[0003] In scenarios such as wireless charging of small household appliances and wireless power supply of Internet of Things sensors, the Vivaldi antenna has many problems. For example, 1. The loss is relatively large, such as air loss, dielectric loss, etc. 2. The gain is not large enough, resulting in low energy transmission efficiency between antennas and making it difficult to drive small household appliances. 3. The size of the Vivaldi antenna is relatively large, resulting in difficult antenna installation.

[0004] To solve the problem of low gain, Cheng H et al. proposed a compound optical lens excited by metamaterials, whose unit is a closed symmetric S-shaped resonator, so as to enhance the gain and directivity of the antipodal Vivaldi antenna. The simulation results show that its gain is increased by 1.35 dB at a frequency of 5.8 GHz, and the maximum gain is 9.66 dB (Cheng H, Hua L, Wang Y, et al. Design of high gain Vivaldi antenna with a compound optical lens inspired by metamaterials[J]. International Journal of RF and Microwave Computer-Aided Engineering.). Although this scheme can improve the gain, its size is too large, the processing is complex, and the error is relatively large.

[0005] Sun H H et al. designed an antenna with a three-dimensional structure formed by four Vivaldi antennas. The directivity of the antenna was enhanced by adjusting the tilt angle of the radiator and the position of the reflector (Sun H H, Lee Y H, Luo W, et al. Compact Dual-Polarized Vivaldi Antenna with High Gain and High Polarization Purity for GPR Applications[J]. Sensors, 2021, 21(2):503.). Its maximum gain reached 12 dB. However, due to its three-dimensional structure, it was very difficult to install and had large machining errors.

[0006] Lv H et al. designed an antenna based on the traditional Vivaldi antenna, which proposed an antenna composed of two Vivaldi antenna elements and adopted a double-slot structure to improve the gain (Lv H, Huang Q, Hou J, et al. Wideband dual-polarized vivaldi antenna with gain enhancement[J]. Applied Computational Electromagnetics Society Journal, 2018, 33(09):990-996.). Its size was 145mm×58mm×0.5mm, which was small and easy to install. However, its gain at 5.8 GHz was only 9.05 dB, making it difficult to meet the application scenarios such as wireless charging of small household appliances and wireless power supply of Internet of Things sensors. Summary of the Invention

[0007] To solve the problems of low antenna gain and large volume and inconvenient installation in current small household appliances, the present invention provides a Vivaldi antenna, including: radiation arms, a dielectric substrate, and microstrip lines. The radiation arms are arranged on the top layer of the dielectric substrate, and the microstrip lines are arranged on the bottom layer of the dielectric substrate. The Vivaldi antenna is provided with a substrate tapered slot on the dielectric substrate;

[0008] The substrate tapered slot is obtained by numerically controlled cutting of the substrate at the middle position of the slot line of the Vivaldi antenna, and has the same shape and the same axis of symmetry as the tapered slot line of the radiation arm; a director is provided inside the substrate tapered slot.

[0009] Optionally, the distance between the tapered slot line of the radiation arm and the slot line of the substrate tapered slot is:

[0010]

[0011] Among them, L A and Q A are the length and width of the antenna, f is the resonant frequency, and ε r is the relative dielectric constant of the dielectric substrate, L R is the length of the radiation arm, and c is the speed of light.

[0012] Optionally, the director is a three-dimensional tapered director, which is installed inside the tapered slot of the substrate and is perpendicular to the slot line and the microstrip line.

[0013] Optionally, the vertical height of the three-dimensional tapered director is the same as the thickness of the dielectric substrate.

[0014] Optionally, the tapered slot line of the radiation arm is an exponential tapered slot line.

[0015] Optionally, the expression of the exponential tapered slot is:

[0016] y = s * (e c*x + C1)

[0017] where c is the slope of the curve, s is the magnification factor of the exponential slot line on the y-axis, and s * C1 is the distance that the exponential slot line moves on the y-axis.

[0018] Optionally, the Vivaldi antenna further includes: a circular slot line, and there is a rectangular slot line between the tapered slot line of the radiation arm and the circular slot line.

[0019] Optionally, the dielectric constant ε r of the dielectric substrate is 2.55, and the tangent of the dielectric loss angle tanδ = 0.009.

[0020] Optionally, the length of the dielectric substrate is 114 mm, the width is 60 mm, and the thickness is 1 mm.

[0021] Optionally, the fan-shaped microstrip line and the circular slot line form a balun structure.

[0022] The beneficial effects of the present invention are:

[0023] The present invention solves the problems of low gain and poor directivity of two-dimensional structure antennas by means of a substrate gradient groove structure and loading 3DGP. Compared with traditional Vivaldi antennas, the gain is increased by 1.28 dB. Compared with existing gain improvement techniques, such as loading composite optical lenses excited by metamaterials, loading additional media on the substrate, and loading multiple curved branches on the antenna radiation arms, etc., the present invention cuts the dielectric substrate and sets directors, without involving complex preparation processes, and without adding large-sized components additionally, and will not increase the size of the Vivaldi antenna. Therefore, the present invention can effectively improve the gain while not increasing the antenna size and reducing the preparation complexity, and can be widely applied to application scenarios such as wireless charging of small household appliances and wireless power consumption of Internet of Things sensors. Brief Description of the Drawings

[0024] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the drawings required for description in the embodiments. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0025] Figure 1 It is a structural diagram of a Vivaldi antenna, where (a) is a front photo of a traditional Vivaldi antenna, (b) is a back photo of a traditional Vivaldi antenna, and (c) is a structural diagram of the substrate gradient groove of the Vivaldi antenna of the present invention.

[0026] Figure 2 It is an overall structural diagram of the Vivaldi antenna of the present invention.

[0027] Figure 3 It is a radiation pattern of the end-fire direction of a traditional Vivaldi antenna, a Vivaldi antenna with a gradient groove substrate, and a Vivaldi antenna loaded with 3DGP in the second embodiment of the present invention.

[0028] Figure 4 It is a simulation schematic diagram of the return loss of a traditional Vivaldi antenna, a Vivaldi antenna with a gradient groove substrate, and a Vivaldi antenna loaded with 3DGP at 4 - 6 GHz in the second embodiment of the present invention.

[0029] Figure 5 It is a relationship diagram between the gain per unit area and frequency of a traditional Vivaldi antenna, a Vivaldi antenna with a gradient groove substrate, and a Vivaldi antenna loaded with 3DGP in the second embodiment of the present invention. Detailed Description of the Embodiments

[0030] To make the objectives, technical solutions and advantages of the present invention clearer, the embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.

[0031] Embodiment 1:

[0032] This embodiment provides a Vivaldi antenna, including: a radiation arm, a dielectric substrate and a microstrip line. The radiation arm is disposed on the top layer of the dielectric substrate, and the microstrip line is disposed on the bottom layer of the dielectric substrate. The Vivaldi antenna of this embodiment is provided with a substrate tapered slot on the dielectric substrate;

[0033] The substrate tapered slot is obtained by numerically controlled cutting of the substrate at the middle position of the slot line of the Vivaldi antenna, having the same shape and the same axis of symmetry as the tapered slot line of the radiation arm; a director is provided inside the substrate tapered slot.

[0034] Embodiment 2:

[0035] This embodiment provides a Vivaldi antenna, as Figure 1 and Figure 2 shown, including: a tapered slot substrate, an exponential tapered slot line, a rectangular slot line, a circular slot line, a microstrip balun, and a three-dimensional gradient patch (3DGP).

[0036] The dielectric constant ε r of the substrate used in this example is 2.55, the tangent of the dielectric loss angle tanδ is 0.009, the length is 114 mm, the width is 60 mm, and the thickness is 1 mm.

[0037] The expression of the exponential tapered slot in this embodiment is:

[0038] y = s*(e c*x + C1)

[0039] where c is the slope of the curve, s is the magnification factor of the exponential slot line on the y-axis, and s*C1 is the distance that the exponential slot line moves on the y-axis. When x = 0, it is the end of the exponential slot line, and its width is determined by s and C1. When x is equal to the maximum value, it is the opening of the slot line, and its width is determined by s, C1, and c.

[0040] The radius of the circular slot line is r, and there is also a rectangular slot line between the end of the exponential slot line and the circular slot line for the transition between the two.

[0041] The microstrip balun is composed of a fan-shaped microstrip line and two rectangular microstrip lines, where the radius of the fan-shaped microstrip line is the same as the radius of the circular slot line.

[0042] The slot line on the front of the traditional Vivaldi antenna is exponentially opened to form a trumpet-like shape. The extended branch part at the end of the slot line is a circular resonant cavity, which can ensure that the end of the slot line remains short-circuited at the operating frequency; the back is a microstrip transmission line, and the end of the microstrip line is a fan-shaped short-circuit structure, which can ensure that the microstrip line remains open at the operating frequency. At the same time, the radius of the fan and the diameter of the circular resonant cavity are both one-quarter wavelength, forming a balun structure, ensuring that more energy can be coupled from the microstrip line to the slot line and radiated through the radiation arm.

[0043] The Vivaldi antenna of this embodiment has a substrate tapered slot with the same shape as the exponential tapered slot radiation arm dug on the substrate at the opening of the slot line. Since the radiation arm and the substrate tapered slot have the same shape, the electromagnetic waves radiated from the edge of the radiation arm in the end-fire direction reach the edge of the substrate after the same distance, that is, the phase of the electromagnetic waves changes in the same way, and the electromagnetic waves reaching the edge of the substrate are the same as those of the radiation arm, thereby effectively improving the gain. The tapered slot is formed by the x-axis (end-fire direction, Figure 1 The moving distance d is relative to the radiating arm in the up and down directions of the antenna, thereby improving the phase difference at the antenna aperture and converting the non-uniform wavefront into a plane wavefront. The moving distance satisfies the following formula:

[0044]

[0045] Among them, L A , W A is the length and width of the antenna, f is the resonant frequency, ε r is the relative dielectric constant of the dielectric substrate, L R is the length of the radiation arm and c is the speed of light.

[0046] At the same time, since the edges of the substrate gradient grooves are smooth, the loss caused by the dielectric-air interface mismatch is reduced; the loss of the antenna includes dielectric loss, and the grooves of the substrate can shorten the radiation distance of the electromagnetic wave in the medium, thereby reducing the dielectric loss.

[0047] The three-dimensional gradient director 3DGP of this embodiment is defined as a three-dimensional curved surface formed by a two-dimensional rectangular director on a plane bending along a nonlinear function. The nonlinear function in this embodiment is the e index. The specific design is as follows: Figure 2 As shown, Figure 2 The two dark three-dimensional curved surfaces on the inner side of the gradient groove of the middle substrate are directors, which are perpendicular to the groove line and microstrip line, that is, the groove line and microstrip line are parallel to the xy plane, while the director is parallel to the z axis, which is equivalent to magnetic flux, so it is also a magnetic dipole director. The vertical height of the director is the same as the thickness of the substrate, and the distance between its starting end and the end and the end of the gradient groove of the substrate is P begin ,P end .

[0048] By loading the 3DGP, the surface electric field in the horizontal and vertical planes of the antenna becomes more uniform, improving the antenna impedance matching and effectively increasing the antenna gain.

[0049] The specific parameters of the Vivaldi antenna in this embodiment are shown in Table 1:

[0050] Table 1: Specific parameters of the Vivaldi antenna in this embodiment

[0051] Parameter Value / mm Parameter Value / mm s 1 <![CDATA[L1]]> 15.5 c 0.06 <![CDATA[L2]]> 18 <![CDATA[C1]]> 0 r 2 <![CDATA[W1]]> 3 <![CDATA[P begin > 11.5 <![CDATA[W2]]> 1 <![CDATA[P end > 46.5 L 100 d 32.5

[0052] This embodiment conducts modeling and simulation in the electromagnetic simulation software HFSS. At a frequency of 5.8 GHz, the radiation patterns in the end-fire direction of the traditional Vivaldi antenna, the tapered slot substrate Vivaldi antenna, and the Vivaldi antenna loaded with 3DGP are as Figure 3 shown. The maximum gain of the traditional Vivaldi antenna in the end-fire direction is 8.64 dB, while the maximum gains of the tapered slot substrate Vivaldi antenna and the Vivaldi antenna loaded with 3DGP in this direction are increased by 0.03 dB and 1.28 dB respectively.

[0053] As Figure 4 is the simulation schematic diagram of the return loss of the traditional Vivaldi antenna, the tapered slot substrate Vivaldi antenna, and the Vivaldi antenna loaded with 3DGP in the range of 4 - 6 GHz. When S 11 <-10 dB, the operating frequency bands of all three antennas cover 4.14 - 5.86 GHz. Near 5.8 GHz, compared with the traditional Vivaldi antenna, the return losses of the tapered slot substrate Vivaldi antenna and the Vivaldi antenna loaded with 3DGP are significantly improved.

[0054] Therefore, the Vivaldi antenna in this embodiment can effectively increase the gain. In this embodiment, the gain is increased by cutting the dielectric substrate and setting the director, without involving complex preparation processes and without increasing the size of the antenna, effectively reducing the processing difficulty and installation difficulty, and can be widely applied to the application scenarios of small household appliances.

[0055] In addition, there is a close relationship between the gain of the antenna and its size, that is, when the gain increases by 3 dB, its volume approximately doubles. In scenarios such as small household appliances or drones, when designing an energy receiving antenna, a trade-off needs to be made between the size and gain of the antenna. To better describe the balance relationship between the size and gain of the Vivaldi antenna, this embodiment proposes the gain per unit area (R GS ) to normalize the Vivaldi antenna, and the formula is as follows:

[0056]

[0057] where S is the bottom area of the dielectric substrate of the microstrip antenna, with the unit of cm 2 .

[0058] The relationship between the gain per unit area and frequency of the existing dual-slot Vivaldi antenna, the Vivaldi antenna loaded with a composite optical lens, the traditional Vivaldi antenna, and the Vivaldi antenna loaded with 3DGP proposed in this embodiment is as Figure 5 shown. It can be found that in the frequency range of 3 GHz - 11 GHz, the Vivaldi antenna proposed in this embodiment has a significant improvement in the gain per unit area compared with the other three antennas. Among them, at the frequency point of 5.8 GHz, the gain per unit area of the Vivaldi antenna in this embodiment has increased by 19%, 79%, and 503% respectively compared with the dual-slot Vivaldi antenna, the Vivaldi antenna loaded with a composite optical lens, and the traditional Vivaldi antenna.

[0059] Therefore, compared with other existing antennas, the Vivaldi antenna in this embodiment can maintain a smaller size while obtaining a higher gain.

[0060] Some steps in the embodiments of the present invention can be implemented by software, and the corresponding software program can be stored in a readable storage medium, such as an optical disc or a hard disk, etc.

[0061] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A Vivaldi antenna, comprising: Radiating arm, dielectric substrate and microstrip line, the radiating arm is arranged on the top layer of the dielectric substrate, and the microstrip line is arranged on the bottom layer of the dielectric substrate. It is characterized in that a substrate tapered slot is provided on the dielectric substrate; The substrate tapered slot is obtained by numerically controlled cutting of the substrate at the middle position of the Vivaldi antenna slot line, and has the same shape and the same axis of symmetry as the tapered slot line of the radiating arm; a director is provided inside the substrate tapered slot; The distance between the tapered slot line of the radiating arm and the slot line of the substrate tapered slot is: Among them, and are the length and width of the antenna, is the resonant frequency, is the relative dielectric constant of the dielectric substrate, is the radiation arm length, c is the speed of light; The tapered slot line of the radiating arm is an exponential tapered slot line; The expression of the exponential tapered slot is: wherein c is the slope of the curve, s is the magnification factor of the exponential slot line on the y-axis, is the distance that the exponential slot line moves on the y-axis; The director is a three-dimensional tapered director, which is installed inside the substrate tapered slot and is perpendicular to the slot line and the microstrip line; The vertical height of the three-dimensional tapered director is the same as the thickness of the dielectric substrate.

2. The Vivaldi antenna according to claim 1, characterized in that, The Vivaldi antenna further includes: a circular slot line, and a rectangular slot line is provided between the tapered slot line of the radiating arm and the circular slot line.

3. The Vivaldi antenna according to claim 1, characterized in that, The dielectric constant of the dielectric substrate .

4. The Vivaldi antenna according to claim 1, characterized in that, The dielectric substrate has a length of 114 mm, a width of 60 mm, and a thickness of 1 mm.

5. The Vivaldi antenna according to claim 2, wherein The fan-shaped microstrip line and the circular slot line form a balun structure.

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