Miniaturized tunable three-dimensional antenna

Abstract

The invention discloses a miniaturized tunable three-dimensional antenna which comprises a distributed large capacitor structure, a magnetic ferrite material loading coil structure and a tunable feed circuit board. The distributed large-capacitance structure comprises multiple layers of metal plates which are embedded and arranged in a laminated manner along the vertical direction; in the magnetic ferrite material loading coil structure, one end of a coil is connected with a top metal plate of the distributed large capacitor structure. The tunable feed circuit board comprises a plurality of microstrip transmission lines, and each microstrip transmission line is provided with a disconnection part used for arranging an adjustable capacitor / inductor or a switching device. The distributed large-capacitance structure is connected with one microstrip transmission line through one metal column; in the magnetic ferrite material loading coil structure, the other end of the coil is connected with the other microstrip transmission line. The antenna provided by the invention can give consideration to a larger bandwidth through the tuning circuit, allows the antenna to adjust the working frequency within a certain frequency range, and has a very strong anti-interference capability.

Description

Technical Field

[0001] The invention relates to a radio frequency antenna, in particular to a three-dimensional radio frequency antenna. Background Art

[0002] With the rapid development of space electronic technology, the number of antennas in communication equipment such as aircraft and ships has continued to increase, leading to serious electromagnetic interference problems. Antennas need to develop in the direction of miniaturization, tunability, and strong anti-interference. For communication equipment such as aircraft and ships, miniaturization of antennas can reduce the number of antennas in the equipment and improve the electromagnetic environment. At the same time, medium and short wave antennas can be used for military communications and navigation over long distances and in complex environments due to their advantages such as long propagation distance, strong anti-interference ability, and stable signal quality. Summary of the invention

[0003] Purpose of the invention: In view of the above-mentioned prior art, a miniaturized and tunable three-dimensional antenna structure is proposed, which has the characteristics of small and compact structure, tunable frequency, strong anti-interference performance and high power.

[0004] Technical solution: A miniaturized tunable three-dimensional antenna, including a distributed large capacitor structure, a magnetic ferrite material loaded coil structure, and a tunable feed circuit board;

[0005] The distributed large capacitor structure includes multiple layers of metal plates arranged in a stacked manner in a vertical direction;

[0006] The magnetic ferrite material is loaded into the coil structure, and one end of the coil is connected to the top metal plate of the distributed large capacitor structure;

[0007] The tunable feed circuit board comprises a dielectric plate, a plurality of microstrip transmission lines on the upper surface of the dielectric plate, and a metal ground on the lower surface of the dielectric plate; each microstrip transmission line is provided with a disconnecting portion for setting an adjustable capacitor / inductor or a switch device;

[0008] The distributed large capacitor structure is connected to a microstrip transmission line through a metal column; in the magnetic ferrite material loaded coil structure, the other end of the coil is connected to another microstrip transmission line, and the microstrip transmission line connecting the coil is also connected to the metal ground through a metallized via.

[0009] Furthermore, in the distributed large capacitor structure, counting from top to bottom, the odd-numbered layers are square metal plates with larger areas, and are connected as a whole through metal strips at the four corners; the even-numbered layers are metal plates with smaller areas, which are connected as an integral structure through a metal cylinder at the center position, and are connected to a microstrip transmission line of the tunable feed circuit board at the bottom.

[0010] Furthermore, a non-metallized via hole 1 is provided in the center of the dielectric plate, and the bottom of the metal cylinder is fixed by embedding in the non-metallized via hole 1.

[0011] Furthermore, it comprises a plurality of magnetic ferrite material loaded coil structures, which are centrally and symmetrically distributed around the distributed large capacitance structure.

[0012] Furthermore, the magnetic ferrite material is loaded into a coil structure, using a single coil or a plurality of coils connected in series.

[0013] Furthermore, in the magnetic ferrite material loaded coil structure, both ends of the coil are connected to the metal plate of the distributed large capacitor structure and the microstrip transmission line of the tunable feeding circuit board through feeding arms respectively; a non-metallized via two corresponding to the feeding arm is provided on the dielectric plate, and the feeding arm at one end of the feeding arm is embedded in the non-metallized via two.

[0014] Furthermore, the magnetic ferrite material is loaded in the coil structure, and a circular hole having a diameter larger than the upper non-metallized via hole is provided on the metal ground at a position directly opposite to each non-metallized via hole.

[0015] Beneficial effects: A miniaturized and tunable three-dimensional antenna structure, the antenna can take into account a large bandwidth through a tuning circuit, allowing the antenna to adjust the operating frequency within a certain frequency range and having strong anti-interference capabilities. Miniaturized and tunable designs are usually accompanied by higher reliability and durability because they reduce the complexity of physical components, thereby reducing failure points. The three-dimensional antenna operates in the medium and short wave frequency bands, has advantages in penetrating buildings and communicating in adverse weather conditions, and is suitable for use in complex electromagnetic environments. The structure has extremely wide potential applications in the fields of airborne communications, marine and aviation navigation.

[0016] Specifically, the antenna mainly includes a distributed large capacitor structure, a magnetic ferrite material loaded coil structure, and a tunable feed circuit board. The distributed large capacitor structure is composed of a multi-layer metal plate structure inlaid in a vertical direction. The inlay method of the multi-layer metal plate can achieve a larger equivalent capacitance in a smaller size, which is used for the miniaturization and high-power design requirements of the antenna. Due to the periodicity of its structure, the antenna can be assembled in the following way: Figure 3The unit module is used for detachable / expandable assembly, which has good flexibility. The coil design with high magnetic permeability ferrite material as the magnetic core can effectively reduce the heat loss of long wires, and can achieve a higher equivalent inductance value under limited size, which is used for the design needs of antenna miniaturization. According to different application scenarios and requirements, the number of coils is not limited to 2, and the coil structure is not limited to a straight cylindrical shape. The coil is connected to the top metal plate of the distributed large capacitor structure, and the inductor coils are generally distributed symmetrically around the distributed capacitor. The tunable feeding circuit board includes multiple feeding ports and tunable devices. The three-dimensional antenna radiation supports a single-port working state. After the middle port is excited, the three-dimensional antenna is equivalent to an LC series resonant circuit. After being excited from the left or right port, the three-dimensional antenna is equivalent to a T-type circuit structure of LCL. And the excitation port routing can be connected in series with adjustable capacitor and inductor devices to realize the tunable working mode function. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a structural schematic diagram of the three-dimensional antenna of the present invention;

[0018] Figure 2 It is a schematic diagram of the overall structure of the expandable distributed large capacitor;

[0019] Figure 3 The schematic diagram and dimensions of the expandable distributed large capacitor unit structure;

[0020] Figure 4 The schematic diagram and dimensions of the coil structure for magnetic ferrite material loading;

[0021] Figure 5 The schematic diagram and dimensions of the dielectric board feeding structure;

[0022] Figure 6 It is a schematic diagram of the tunable performance of the antenna port reflection coefficient;

[0023] Figure 7 This is the E-plane radiation pattern of the antenna, and the operating frequency band is 1.8MHz;

[0024] Figure 8 This is the H-plane radiation pattern of the antenna, and the operating frequency band is 1.8MHz. DETAILED DESCRIPTION

[0025] The present invention will be further explained below in conjunction with the accompanying drawings.

[0026] like Figure 1 As shown, a miniaturized tunable three-dimensional antenna is composed of three parts, namely a distributed large capacitor structure 1, a magnetic ferrite material loaded coil structure 2, and a tunable feeding circuit board 3.

[0027] like Figure 2As shown, the distributed large capacitor structure 1 includes a multilayer metal plate arranged in a vertical direction. In this embodiment, the distributed large capacitor structure 1 is provided with 51 square metal plate structures. From top to bottom, the odd layers (1, 3, 5...) are square metal plates with larger areas, and the horizontally arranged odd layers are connected as a whole through the vertical metal strips in the four corners; the even layers (2, 4, 6...) are metal plates with smaller areas, and the vertically arranged metal cylinders 101 pass through the center of the horizontally arranged even layers of metal plates in turn, and connect the even layers of metal plates into a metal integral structure through the metal cylinders 101. The staggered stacking design of the multilayer metal plates of the distributed large capacitor structure 1 can increase the facing area between the capacitor plates in a small volume size, thereby achieving a large equivalent capacitance value, and then realizing medium wave frequency band resonant radiation.

[0028] Figure 3 The detailed size information of a single unit in the distributed large capacitor structure 1 is shown. In this embodiment, the gray part of the structure is made of aluminum, and the overall structure is divided into 1 top unit and 24 basic units, respectively. Figure 3 The distributed large capacitance structure 1 is fed by a metal cylinder 101 with a diameter of 8 mm and a height of 502 mm as a feeding arm. The center of the feeding arm is set at the center of the antenna, and the bottom is connected to the tunable feeding circuit board. Figure 3 As shown in the figure, the specific parameter values ​​are defined with different digital numbers, namely: 001 = 110mm, 002 = 110mm, 003 = 2mm, 004 = 70mm, 005 = 70mm, 006 = 2mm, 007 = 55mm, 008 = 55mm, 009 = 2mm, 010 = 20mm, 011 = 4mm, 012 = 4mm, 013 = 10mm, 014 = 12mm. The distributed large capacitor structure is periodic and can be regarded as a top unit and 24 periodic units. Therefore, the requirements for antenna frequency, size and other performances in different application scenarios can be flexibly adjusted by increasing or decreasing the unit structure.

[0029] In the magnetic ferrite material loaded coil structure, ferrite is a magnetic material with high magnetic permeability. When the coil structure size and number of turns are constant, when it is used as the magnetic core of the coil, the equivalent inductance value can be significantly increased, thereby achieving the large inductance parameter value and antenna miniaturization design requirements required for the medium and short wave frequency bands. In this embodiment, two magnetic ferrite material loaded coil structures are vertically arranged on both sides of the distributed large capacitor structure. According to the requirements of different application scenarios, different numbers of magnetic ferrite material loaded coil structures can be arranged in different forms, such as horizontal arrangement or arc coil structure arrangement, and the principle is basically the same as that of this embodiment. In a single magnetic ferrite material loaded coil structure, the two ends of the coil are respectively connected to the top metal plate of the distributed large capacitor structure and the tunable feed circuit board at the bottom through two short sections of metal wires. In addition, this embodiment adopts a single longer coil. Based on the superposition characteristics of the coil series, the coil structure can also adopt a design form of multiple shorter coils in series.

[0030] Figure 4 The structure of the magnetic ferrite material loaded coil in this embodiment and its detailed dimensions are shown. The gray part is a toroidal coil made of aluminum, and the rest is a cylindrical ferrite with a magnetic permeability of 3000 and a magnetic loss tangent of 60. Ferrite is a magnetic material. When it is used as a magnetic core, winding a coil on the magnetic ferrite can enhance the magnetic field around the coil, thereby increasing the inductance value of the inductor. The bottom of the coil is fed through a small feeding arm, and the top of the coil is connected to the top metal plate of the distributed large capacitor structure through another small feeding arm. The specific parameter values ​​are defined by different digital numbers, which are: 015=483.7mm, 016=6mm, 017=14.3mm, 018=21.7mm, 019=3mm, 020=1.5mm, 021=2.8mm, 022=118.5mm.

[0031] The tunable feed circuit board is used for antenna feeding and tuning. The antenna uses a planar microstrip line to complete the feeding. In order to facilitate the miniaturization of the antenna, a dielectric plate with a higher relative dielectric constant can be used to reduce the electrical length required for the feed line. This embodiment uses FR4 with a relative dielectric constant of 4.4.

[0032] Figure 5The structure of the tunable feeding circuit board of this embodiment and its detailed dimensions are shown. The yellow part is copper, and the white part is the dielectric board FR4. In the middle, left and right sides of the upper surface of the dielectric board are three microstrip transmission lines with a characteristic impedance of 20 ohms, and the metal ground is located on the lower surface of the dielectric board. The ports of the microstrip transmission lines in the middle, left and right sides of the feeding structure can be respectively connected to an external signal source to excite the antenna. The disconnected part in the middle of the transmission line is used to set an adjustable capacitor / inductor or a switching device to realize the switching and frequency tuning functions of the antenna excitation port. Among them, the resonant frequency of the antenna is changed by adjusting the value of the series capacitor or inductor, that is, Where C0 is the initial distributed capacitance value, L0 is the initial magnetic coil inductance value, L var It is an adjustable lumped inductor device.

[0033] Specifically, the distributed large capacitor structure is connected to the middle microstrip transmission line through the bottom of the feeding arm, and the bottom ends of the coils of the magnetic ferrite material loaded coil structure on both sides are connected to the microstrip transmission lines on the left and right sides through metal feeding arms. In order to fix the antenna without affecting the radiation performance of the antenna, a non-metallized via is opened at the left, middle and right positions of the dielectric plate of the tunable feeding circuit board, respectively. The middle via is co-centrically embedded with the central feeding arm of the distributed large capacitor structure, the left via is co-centrically embedded with the metal wire at one end of the coil in the left magnetic ferrite material loaded coil structure, and the right via is co-centrically embedded with the metal wire at one end of the coil in the right magnetic ferrite material loaded coil structure. In order to avoid the antenna structure being directly connected to the metal floor, a circular hole with a diameter larger than the non-metallized via above is provided on the metal ground opposite to each non-metallized via. In addition, the ends of the microstrip transmission lines on the left and right sides are respectively connected to the metal ground of the bottom layer through metallized vias, so that when the middle port is feeding, the coils on both sides can be connected back to the ground to ensure the antenna radiation mode. Figure 5 As shown, the specific parameter values ​​are defined by different digital numbers, namely: 023=200mm, 024=200mm, 025=3.5mm, 026=108mm, 027=77mm, 028=3.5mm, 029=16.8mm, 030=6.3mm, 031=0.5mm, 032=8mm, 033=3mm, 034=6mm, 035=48.5mm, 036=22mm.

[0034] In this embodiment, the ports of the middle, left and right microstrip transmission lines of the feeding structure can all be used as antenna excitation to connect to the signal source. Here, only the case of feeding by the left transmission line is taken as an example, and the case of feeding by the middle and right transmission lines is not repeated. Figure 6The tunable performance of the antenna port reflection coefficient is shown. It can be seen that the center frequency of the initial structure is located at 1.8MHz. When an adjustable capacitor is connected in series with the source port, the center frequency moves to high frequency. The smaller the capacitor, the higher the center frequency. When an adjustable inductor is connected in series with the source port, the center frequency moves to low frequency. The larger the inductor, the lower the center frequency. Figure 7 is the radiation pattern of the E plane when the antenna works at 1.8MHz, Figure 8 This is the vertically polarized radiation pattern of the H plane when the antenna works at 1.8MHz. It can be seen that the antenna has good omnidirectional radiation characteristics. The length, width and height of the antenna are 0.003λ0×0.001λ0×0.001λ0 respectively. With the extremely miniaturized size design, the maximum actual gain is about -64.7dBi.

[0035] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A miniaturized tunable three-dimensional antenna, characterized in that: It includes a distributed large capacitor structure, a magnetic ferrite material loaded coil structure, and a tunable feed circuit board; The distributed large capacitor structure includes multiple layers of metal plates arranged in a stacked manner in a vertical direction; The magnetic ferrite material is loaded into the coil structure, and one end of the coil is connected to the top metal plate of the distributed large capacitor structure; The tunable feed circuit board comprises a dielectric plate, a plurality of microstrip transmission lines on the upper surface of the dielectric plate, and a metal ground on the lower surface of the dielectric plate; each microstrip transmission line is provided with a disconnecting portion for setting an adjustable capacitor / inductor or a switch device; The distributed large capacitor structure is connected to a microstrip transmission line through a metal column; in the magnetic ferrite material loaded coil structure, the other end of the coil is connected to another microstrip transmission line, and the microstrip transmission line connecting the coil is also connected to the metal ground through a metallized via.

2. The miniaturized tunable three-dimensional antenna according to claim 1, characterized in that: In the distributed large capacitor structure, counting from top to bottom, the odd-numbered layers are square metal plates with larger areas, which are connected as a whole through metal strips at the four corners; the even-numbered layers are metal plates with smaller areas, which are connected as an integral structure through a metal cylinder at the center position and connected to a microstrip transmission line of the tunable feed circuit board at the bottom.

3. The miniaturized tunable three-dimensional antenna according to claim 2, characterized in that: A non-metallized via hole 1 is provided in the center of the dielectric plate, and the bottom of the metal column is fixed by embedding in the non-metallized via hole 1.

4. The miniaturized tunable three-dimensional antenna according to claim 1, characterized in that: It comprises a plurality of magnetic ferrite material loaded coil structures, which are centrally and symmetrically distributed around the distributed large capacitance structure.

5. The miniaturized tunable three-dimensional antenna according to claim 1, characterized in that: The magnetic ferrite material is loaded into the coil structure, using a single coil or multiple coils connected in series.

6. The miniaturized tunable three-dimensional antenna according to claim 3, characterized in that: In the magnetic ferrite material loaded coil structure, two ends of the coil are respectively connected to the metal plate of the distributed large capacitor structure and the microstrip transmission line of the tunable feeding circuit board through feeding arms; a second non-metallized via hole corresponding to the feeding arm is provided on the dielectric plate, and the feeding arm at one end of the feeding arm is embedded in the second non-metallized via hole.

7. The miniaturized tunable three-dimensional antenna according to claim 6, characterized in that: In the magnetic ferrite material loading coil structure, a circular hole having a diameter larger than the upper non-metallized via hole is provided on the metal ground at a position directly opposite to each non-metallized via hole.

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