A miniaturized Beidou navigation antenna suitable for concealed installation

Abstract

The present invention provides a miniaturized Beidou navigation antenna suitable for concealed installation in confined spaces. The antenna uses a laser etching process to produce four radiating arms, two main radiating spiral arms and two parasitic radiating spiral arms, on the surface of a truncated copper-clad substrate. The antenna feed matching is tuned by loading discrete components, and the design is made taking into account the installation and use environment of the antenna. The present invention realizes the omnidirectional radiation and miniaturized installation requirements of the Beidou navigation antenna in concealed installation environments such as missile-borne and airborne.

Description

Technical Field

[0001] The invention relates to a miniaturized Beidou navigation antenna, in particular to a miniaturized Beidou navigation antenna suitable for concealed installation. Background Art

[0002] At present, my country's Beidou satellite navigation industry is developing rapidly. By 2020, Beidou II will achieve global navigation service coverage, and Beidou III is also under rapid construction. The military and civilian demand for Beidou satellite navigation antennas is also gradually increasing, and various circularly polarized navigation antennas are widely used in TE satellite navigation systems. The antennas commonly used in satellite navigation systems mainly include microstrip antennas, PIFA antennas, dielectric antennas, and various helical antennas. In navigation terminals, these antennas often have low gain (below 0dB) and narrow working frequency bandwidth (less than 5%). At the same time, it is difficult for the antenna beam to meet the requirements of 360° omnidirectional radiation coverage in the horizontal plane. Jackson, DR et al. have described the microstrip navigation antenna in the literature (Microstrip Patch Antenna Designs That Do Not Excite Surface Waves. [J] IEEE Transactions on Antennas and Propagation, Vol. 41, No. 8, August 1993, pp. 1026-1037). The size of an ordinary microstrip circularly polarized antenna is about one-quarter of the wavelength of the medium, the maximum radiation direction is at the zenith, the horizontal plane radiation capability is poor, and the operating bandwidth of the microstrip antenna is narrow. Another type is a dielectric antenna that combines LTCC technology with PIFA antenna and dielectric antenna, such as the one described by Gousettis et al. in the literature (Gousettis, G., JCVardaxoglou, and APFeresidis. Handset Antenna Performance Using Flexible MEBG Structures. [J] Proceedngs IEEE international Workshop on Antenna Technology: Small Antennas and Metamateterials, 2005, pp. 55-58.). Miniaturized dielectric PIFA navigation antennas have the advantages of ultra-miniaturization and high integration, but this type of antenna also has poor radiation pattern performance and cannot meet the requirements of high-precision navigation.The last type is various spiral navigation antennas. In 1963, CHTANG (CHTANG. A Class of Modified log-spiralantenna. [J] IEEE IEEE Transactions on Antennas and Propagation, Vol. 41, No. 8, July 1963, pp. 422-427) proposed a modified non-frequency-variable logarithmic spiral antenna, which has almost no theoretical limit on the working frequency band, high antenna gain, and can optimize the half-wave power angle to greater than 80°. It also has an ultra-wide bandwidth (> 10%) similar to the planar spiral antenna. However, due to the limitations of the working frequency band and radiation aperture, various spiral antennas generally have large antenna sizes, and it is difficult for the antenna to achieve the design requirements of low profile, small diameter, and miniaturization. At present, various navigation terminal system terminal antennas, especially Beidou satellite navigation antennas, are developing towards miniaturization and compact installation. Especially in the cases of high-speed rolling, high-speed movement and concealed special installations such as missile-mounted, aircraft-mounted and high-speed vehicle-mounted, strict requirements are placed on the installation position, installation space and radiation direction of the antenna. The shape of the radiation pattern requires omnidirectional radiation similar to that of a half-wave dipole antenna, so that the missile can still stably receive satellite navigation signals during rolling and level flight. Summary of the invention

[0003] In order to overcome the problem that the existing technology cannot meet the working requirements of right-hand circular polarization, omnidirectional radiation, miniaturized installation, etc. of Beidou navigation antennas in concealed installation environments such as high-speed missile-mounted, airborne and vehicle-mounted, the present invention provides a miniaturized Beidou navigation antenna suitable for concealed installation. The antenna contains four radiating arms, two main radiating spiral arms and two parasitic radiating spiral arms, and the radiating arms are processed on a copper-clad substrate dielectric material (such as microwave ceramics, polyimide, etc.) through an engineering laser etching process. The antenna fully considers the placement impact of the structure under special circumstances such as missile-mounted roll, and is fed through a 50-ohm RF connector. The feeding balun structure is realized by logarithmic taper processing of the coaxial line. A lumped device is added between the main radiating spiral arm of the antenna and the feeding balun to realize antenna loading tuning and balanced feeding, so that the antenna meets the index requirements of omnidirectional radiation and bandwidth.

[0004] The technical solution adopted by the present invention to solve its technical problems is: including an antenna substrate, an antenna base, an antenna radiation spiral arm, a top feed plate and a feed balun. The antenna substrate is made of a truncated cone with a dielectric constant between 3 and 15 and a conductive metal copper film on the surface. The diameter of the upper surface of the truncated cone is 0.075 times the wavelength of the medium, the diameter of the lower surface is 0.06 times the wavelength of the medium, and the height is 0.11 times the wavelength of the medium. The dielectric constant of the substrate needs to be calculated and optimized according to the design frequency, taking into account the performance and size of the antenna. The axial center position of the antenna substrate contains a mounting through hole with a diameter of 5mm, which meets the installation requirements of the installation environment. In the axial direction, there is a balun mounting through hole with a diameter of 3mm at 6mm from the center mounting through hole. The antenna base is made of metal copper as an adjustment component of the antenna radiation pattern. The size is 2mm larger than the diameter of the lower surface of the antenna substrate. The hole position and size are the same as the antenna opening position, and it is glued and fixed to the lower surface of the antenna substrate truncated cone at the corresponding position. The antenna consists of four spiral arms that rotate clockwise and are evenly distributed along the conical ring. The equation of the spiral arm curve in the cylindrical coordinate system is as follows:

[0005]

[0006] Among them, θ, ρ, H represent the polar angle, polar radius and height in cylindrical coordinates respectively, and the subscripts 1 and 2 represent the two boundary lines that make up the spiral arm respectively. ρ0, θ0, b, δ are the unknown parameters of the antenna spiral arm, and θ0 is the half angle of the cone, which is the same as the half angle of the antenna base.

[0007] The parameters of one spiral arm are determined, and the other spiral arms can be obtained in sequence by rotating the first spiral arm around the height axis by ±90° and 180°. Among the four spiral arms, one pair of mirror-symmetrical radiating arms is the main radiating spiral arm, and the other pair of mirror-symmetrical radiating arms is the parasitic radiating spiral arm. The antenna only feeds the main spiral arm, and the parasitic spiral arm is not fed, which plays the role of adjusting the radiation pattern and widening the working bandwidth.

[0008] The top feed board is a balanced feeding component of the antenna. It is cylindrical in shape and is made of a single FR4 standard PCB panel with a thickness of 0.5 mm and a diameter the same as the diameter of the upper surface of the antenna base truncated cone according to the specified design pattern. It is provided with a through hole with the same position and size as the opening of the antenna base. The surface pattern of the top feed board is divided into two areas, one for connecting with the inner conductor of the balun and the positive radiating arm, and the other for connecting with the outer conductor of the balun and the negative radiating arm. The circuit of the area connected with the outer conductor of the balun and the negative radiating arm consists of a ring circuit in the central part and two groups of fan-shaped area circuits. The end of the fan-shaped circuit is the same length as the top arc of the spiral arm. The outer diameter of the central ring circuit is 0.02 times the design wavelength. A hole is opened on one side of the ring circuit so that the outer conductor of the coaxial feed line is connected to the central ring circuit for feeding. The graphics and size of each area are finally obtained after optimization calculation. A position for soldering discrete tuning devices is reserved in each area, with a spacing of 1.5 mm. The feed balun is the RF energy feeding device of the antenna, which plays the role of energy feeding, current balancing and impedance matching. The length of the feed balun is the total height of the antenna plus 6mm. The 6mm size is the interconnection component with the back-end signal receiving board. The whole adopts the standard 141 type RF coaxial cable, after stripping the outer dielectric sheath layer, the outer shielding layer is processed by mechanical processing technology according to the following exponential parameter curve equation

[0009]

[0010] In formula (2), a1, a2, and a3 are coefficients of the parametric equation, which are 8, 0.05, and 1, respectively. At the top of the balun connected to the antenna, the inner conductor is stripped out by 8 mm, processed into an "L" shape and firmly soldered to one end of the main radiation arm. The middle layer dielectric is stripped out by 1 mm as an isolation component to prevent the inner and outer conductors from short-circuiting. The outer conductor is firmly soldered to the other end of the antenna main radiation arm to fix the entire balun.

[0011] The beneficial effects of the present invention are: the installation environment and position of missile-mounted, airborne-mounted and vehicle-mounted antennas are fully considered, and the omnidirectional radiation of the vertical antenna axis is realized by designing the double-arm loading of the antenna and the parasitic radiation of the other two arms, and the half-wave power angle of the antenna is greater than 60°, and the antenna gain is >0dB. And by adding a conical antenna dielectric matrix, the size of the antenna is effectively reduced, so that the height and caliber of the antenna are reduced by more than 5 times that of the traditional antenna, and the miniaturization and omnidirectional radiation of the Beidou navigation antenna are realized.

[0012] The present invention is further described below in conjunction with the accompanying drawings and embodiments: BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 It is a schematic diagram of a miniaturized Beidou navigation antenna suitable for concealed installation according to the present invention.

[0014] Figure 2 It is an exploded view of a miniaturized Beidou navigation antenna suitable for concealed installation according to the present invention.

[0015] Figure 3 It is a side view of a miniaturized Beidou navigation antenna suitable for concealed installation according to the present invention.

[0016] Figure 4 It is a top view of a miniaturized Beidou navigation antenna suitable for concealed installation according to the present invention.

[0017] Figure 5 It is a schematic diagram of the outer conductor of a miniaturized Beidou navigation antenna feeder balun suitable for concealed installation according to the present invention.

[0018] Figure 6 The present invention discloses a standing wave ratio diagram of a miniaturized Beidou navigation antenna suitable for concealed installation.

[0019] Figure 7 The present invention discloses an E-plane radiation pattern of a miniaturized Beidou navigation antenna suitable for concealed installation.

[0020] Figure 8 The invention discloses an H-plane radiation pattern of a miniaturized Beidou navigation antenna suitable for concealed installation.

[0021] In the figure, 1. Antenna substrate, 2. Antenna base, 3. Antenna radiation spiral arm, 4. Top feeding board, 5. Feed balun, 6. Tuning capacitor. DETAILED DESCRIPTION

[0022] By continuously adjusting the upper and lower cross-section positions of the conical spiral antenna, the half angle of the cone, the rise angle of the exponential spiral arm and other parameters, a miniaturized antenna solution that meets the requirements of standing waves and radiation patterns can be obtained. The specific implementation methods are as follows:

[0023] Figure 1 It is a schematic diagram of a miniaturized Beidou navigation antenna suitable for concealed installation according to the present invention. Figure 2This is an exploded schematic diagram of the antenna components. The conical substrate of the antenna is made of polyimide material with a dielectric constant of 3.4. The upper section radius of the substrate material is 17.1mm, the lower section radius is 13mm, the height of the substrate is 23.5mm, and the substrate contains a through hole with a diameter of 6mm, which is the mounting hole. The antenna base is made of all-metal material. A through hole with a radius of 3.58mm is set 6mm from the center of the antenna substrate, and a 50-ohm feed cable is fed through the hole. The value of ρ0 in the spiral equation (1) of the spiral radiation arm of the antenna is 13, the value of b is 0.172, and the phase difference of the boundary of the spiral arm is δ, which is 33.18°. The side of the antenna substrate is metallized by chemical plating or sputtering, and the spiral arm of the antenna is made by engineering etching or laser engraving on the side coating of the substrate. The antenna feed board is a single-sided copper-clad PCB with an inner diameter of 6mm and an outer diameter of 26mm. There is a through hole with a diameter of 3.54mm at a distance of 6mm from the center of the board. Figure 1 As shown in Figure 6, the circuit consists of a central annular circuit and a side fan-shaped circuit. The inner diameter of the annular circuit is 7mm, the outer diameter is 13mm, the fan-shaped angle of the fan-shaped area is 33.18°, and the two side fans have annular discontinuities at radii from 10mm to 10.71mm. The annular discontinuities are used to weld chip electronic components such as resistors and capacitors. Figure 1 The electronic device of the circuit on the left is a capacitor of C=0.1pF, and the electronic device of the circuit on the right is a capacitor of C=60.76pF. The two capacitor devices are mainly used to adjust the feeding phase balance of the antenna. The sector-shaped circuit on the right is not connected to the central ring circuit, and is connected to the central conductor of the feeder line through a circle with a diameter of 17mm. The sector-shaped circuit on the left is connected to the central ring circuit and connected to the outer conductor of the feeder line. The outer side of the sector-shaped circuit is welded to the top of the spiral arm. The feeder of the antenna is a 50 ohm coaxial feeding cable with a total length of 31mm. It is fed from the top of the antenna through a through hole that passes through the antenna. In order to perform balanced matching feeding of the antenna, the outer conductor of the coaxial line is cut as follows. Figure 5 shown.

[0024] The above contents are further detailed descriptions of the present invention in combination with specific preferred embodiments, and the specific implementation of the present invention cannot be limited to these descriptions. For ordinary technicians in the field to which the present invention belongs, several simple deductions or substitutions can be made without departing from the concept of the present invention, which should be regarded as falling within the scope of protection of the present invention.

Claims

1. A miniaturized Beidou navigation antenna suitable for concealed installation, characterized in that: The invention comprises an antenna substrate, an antenna base, an antenna radiation spiral arm, a top feed plate, a feeding balun and a tuning capacitor; the antenna base is arranged at the bottom of the antenna substrate, the top feed plate is arranged at the top of the antenna substrate, a connected central through hole is arranged at the center of the top feed plate and the antenna substrate, and the central through hole is used for installing and fixing the top feed plate, the antenna substrate and the antenna base; the top feed plate, the antenna substrate and the antenna base are provided with connected feeding holes, and the feeding hole is 0.02-0.03 times the design wavelength distance from the center of the antenna substrate; four antenna radiation spiral arms are processed on the antenna substrate by an engineering laser etching process, a pair of mirror-symmetrical radiation arms are main radiation spiral arms, which are composed of a positive radiation arm and a negative radiation arm, and the other pair of mirror-symmetrical radiation arms are parasitic radiation spiral arms; a feeding balun is arranged in the feeding hole, and the feed line in the feeding balun passes through the antenna substrate. The top feed board is a balanced feeding component of the antenna, which is cylindrical as a whole. The top feed board circuit consists of a central ring circuit and fan-shaped circuits on both sides. The surface pattern is divided into two regional circuits. One regional circuit is a regional circuit connected to the inner conductor of the feeding balun and the positive radiation arm, which consists of a fan-shaped circuit not connected to the central ring circuit; the other regional circuit is a regional circuit connected to the outer conductor of the feeding balun and the negative radiation arm, which consists of a central ring circuit and a fan-shaped circuit connected thereto. The fan-shaped circuits on both sides have ring discontinuities for welding tuning capacitors. The ends of the fan-shaped circuits on both sides are of the same length as the top arc of the antenna radiation spiral arm. The outer diameter of the central ring circuit is 0.02 times the design wavelength. A hole is opened at one side of the central ring circuit to connect the outer conductor of the coaxial feed line to the central ring circuit, so that feeding can be performed.

2. The miniaturized Beidou navigation antenna suitable for concealed installation as claimed in claim 1, characterized in that: The corresponding connection points between the two adjacent antenna radiation spiral arms and the top feed plate are perpendicular to the height axis of the antenna base to form a 90° angle.

3. The miniaturized Beidou navigation antenna suitable for concealed installation as claimed in claim 1, characterized in that: The antenna substrate is a truncated cone with a conductive copper film on the surface. The truncated cone is made by intercepting a cone. The upper interception radius of the cone is 0.05-0.07 times the design wavelength, the lower interception radius is 0.07-0.08 times the design wavelength, and the height is 0.09-0.13 times the design wavelength.

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