A design method of a body adaptive antenna

Abstract

This application proposes a design method for a vehicle-mounted adaptive antenna. This method uses the metal of the vehicle body as the main radiating element of the antenna. Based on the method of moments (MoM), it starts with the magnetic vector potential, calculates the magnetic field, and then uses the magnetic field to calculate the electric field. Finally, it uses Ampere's law from Maxwell's equations to obtain a wave equation based on the magnetic vector potential. The integral relationship between the electric field and the surface current is solved using the wave equation. By observing the surface current distribution and radiation pattern on the vehicle body structure, modes that meet the coverage and feeding requirements are identified, and these modes are excited by feeding. Alternatively, in cases requiring broadband design, excitation can be added to multiple regions with similar surface current distributions to achieve simultaneous excitation of multiple modes, thus realizing a broadband mode antenna design. Since the main radiating element of this antenna is the metal structure of the vehicle body, it has advantages such as ease of implementation, low cost, simple structure, and no space occupation within the vehicle.

Description

Technical Field

[0001] This application belongs to the field of antenna technology, specifically relating to a method for designing an automotive antenna. Background Technology

[0002] Currently, the main types of automotive antennas include 4G / 5G antennas, WiFi, Bluetooth, GNSS, and AM / FM antennas. Most of these are integrated into a single antenna box. These antenna boxes come in various forms, but primarily consist of shark fin antenna boxes mounted on the roof or rectangular antenna boxes placed inside the vehicle. Shark fin antennas, limited by the vehicle's shape, often have very limited size and height, resulting in very limited internal space. Under these circumstances, it's difficult to integrate so many different antenna types into a confined space. Forcing the integration of multiple antenna types into the shark fin for the sake of integration can cause mutual interference between them, especially for GNSS antennas. Besides conventional antenna specifications such as VSWR and gain, GNSS antennas also require a specific axial ratio, a metric for measuring the performance of circularly polarized antennas. When other antennas are near a GNSS antenna, they inevitably have a direct impact on the axial ratio, severely affecting the GNSS antenna's performance.

[0003] For 4 / 5G and WiFi / Bluetooth antennas, interference between antennas can occur within a confined space, leading to performance degradation. For 4 / 5G and WiFi / Bluetooth antennas with MIMO capabilities, the isolation between antennas is crucial. Limited space forces antennas to be crammed together, reducing the isolation between antennas operating at the same frequency and thus affecting the MIMO performance of wireless communication.

[0004] There are generally two layout options for current vehicle antennas: one is a shark fin-shaped layout placed on the roof; the other is an antenna box-shaped layout placed inside the vehicle, such as in the IP or center console.

[0005] As mentioned above, although the shark fin is well-positioned and the antenna has good metal clearance and is unobstructed, the shark fin is limited by size and has limited internal space, which will result in poor antenna performance. The antenna box is placed inside the vehicle and is easily blocked and interfered with by the vehicle body parts, resulting in poor signal reception quality and other problems.

[0006] Existing data contains numerous design analyses based on ships and aircraft, as well as analyses based on vehicle models; however, their current operating bandwidths are very narrow, making them unsuitable for broadband communication. Furthermore, their power supply structures have high requirements and are relatively complex, making them difficult to implement in engineering. Summary of the Invention

[0007] To address the problems identified in the background section, the following technical solution is adopted:

[0008] A design method for a vehicle-mounted adaptive antenna uses the metal of the vehicle body as the main body of the antenna radiation. Based on the solution method of moments, it starts from the magnetic vector potential, calculates the magnetic field, and calculates the electric field through the magnetic field. Finally, it uses Ampere's law in Maxwell's equations to obtain a wave equation based on the magnetic vector potential.

[0009] Solve the integral relationship between the electric field and the surface current using the wave equation;

[0010] By observing the surface current distribution and radiation pattern on the vehicle body structure, the mode that meets the coverage and feeding requirements can be identified, and the mode can be excited by feeding. Alternatively, in the case of broadband design requirements, excitation can be added in multiple areas with similar surface current distributions to achieve simultaneous excitation of multiple modes, thereby realizing broadband mode antenna design.

[0011] Furthermore, in the above technical solution: numerical calculation is used to solve the integral relationship between the electric field and the surface current; the specific steps are: discretizing the required structure into a mesh, selecting a set of basis functions and test functions, and first expanding the surface current according to the basis functions;

[0012] Then, the integral calculation is transformed into a system of algebraic equations according to the mesh.

[0013] In the calculation process, the coefficient matrix of the algebraic equation system is first obtained, and the coefficient matrix is ​​diagonalized to obtain the eigenvalues ​​and eigenvectors corresponding to the algebraic equation system. The eigenvectors obtained by diagonalization correspond to the characteristic mode currents of the metal region of interest in the vehicle body, and the eigenvalues ​​characterize the radiation contribution of the corresponding characteristic currents to the total field strength.

[0014] By observing the distribution and radiation pattern of characteristic mode currents on the vehicle body structure, the modes that meet the coverage and feeding requirements can be identified, and the modes can be excited by feeding. Alternatively, in the case of broadband design requirements, excitation can be added in areas where the distribution of multiple characteristic mode currents is close to achieve simultaneous excitation of multiple modes, thereby realizing broadband mode antenna design.

[0015] In addition to using an extra parasitic feeding structure, the feeding structure can also be achieved by directly creating a gap in the metal structure; for example, an open gap that meets a quarter wavelength of the operating frequency or a closed gap that meets a half wavelength of the operating frequency; the shape of the gap can be a regular rectangle, or other shapes such as circles, stepped shapes, H-shapes, L-shapes, etc.

[0016] Based on the distribution characteristics of the characteristic mode current on the vehicle body, a multi-feed method can be used to realize the combination or shaping design of the radiation pattern, that is, multiple excitation ports satisfying a certain excitation phase relationship, thereby realizing the antenna radiation pattern shaping design; based on this, beam pointing deflection, scanning, tracking, and control of radiation pattern shape, coverage form, etc. can be realized.

[0017] Taking into account antenna engineering implementation, radiation pattern coverage, and EMC issues, from a practical perspective, antenna feed points are generally placed in relatively exposed locations with good metal clearance, such as vehicle windows, roofs, or metal junctions. Because the metal area of ​​the vehicle body is large, the antenna aperture and gain can be increased, and efficiency will be significantly improved. This greatly reduces the communication system's reliance on RF front-end amplifiers; for example, for FM antennas, the front-end amplifier may be eliminated entirely, thereby reducing the overall cost of the antenna. Moreover, due to the elimination of the amplifier, the antenna complexity is significantly reduced, while reliability increases. At the same time, the antenna layout freedom is significantly improved, and the distance between multiple antennas can be increased considerably, achieving a significant improvement in antenna isolation.

[0018] The technical advantages of this application are as follows: radiation is mainly achieved through the metal structure of the vehicle body, enabling large-aperture radiation; the antenna can more easily achieve broadband and high-efficiency operation through the fusion of multiple modes; the flexible combination of multiple modes of the vehicle body can achieve a combination of various radiation patterns, enabling radiation pattern control; thanks to the size of the vehicle body, it is easier to achieve broadband and high-efficiency design of low-frequency antennas; the antenna design does not require an additional large metal structure, and will not have a significant impact on the appearance of the car, improving the performance of the vehicle antenna while also enhancing the aesthetics of the vehicle body; no separate antenna layout and design are required; the high efficiency of the antenna can effectively reduce the dependence of the vehicle antenna on amplifiers, which can not only reduce the noise figure of the received signal but also reduce the cost of the RF system. The antenna design of this application uses the metal structure of the vehicle body as the main radiation source, without an additional antenna structure, only requiring the introduction of a feeding structure at a suitable location on the vehicle body; therefore, it has the advantages of being easy to implement, low-cost, simple in structure, and occupying almost no vehicle space. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of a car model;

[0020] Figure 2 This is a matching diagram for an S11 antenna with a vehicle body adaptable antenna according to an embodiment of this application. Detailed Implementation

[0021] The present application will be further described below with reference to the accompanying drawings and embodiments.

[0022] The above-described solution will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of this application. The implementation conditions used in the embodiments may be further adjusted according to the conditions of specific manufacturers, and the implementation conditions not specified are generally those in routine experiments.

[0023] A design method for a vehicle body-adaptive antenna, wherein the vehicle body's metal is used as the main body for antenna radiation.

[0024] This design method includes a solution method based on the method of moments, starting from the magnetic vector potential and calculating the magnetic field.

[0025] The electric field is calculated using the calculated magnetic field, and a wave equation based on the magnetic vector potential is obtained using Ampere's law in Maxwell's equations.

[0026] By solving the integral relationship between the electric field and the surface current based on the wave equation, the surface current distribution and radiation pattern on the vehicle body structure are obtained.

[0027] By observing the surface current distribution and radiation pattern on the vehicle body structure, the modes that meet the coverage and power supply requirements are identified, and the modes are excited by power supply.

[0028] Alternatively, in cases requiring broadband design, excitation can be added to multiple regions with similar surface current distributions to achieve simultaneous excitation of multiple modes, thus realizing a broadband mode antenna design. This method requires no additional antenna structure; only a feeding structure needs to be introduced at a suitable location on the vehicle body. Therefore, it has advantages such as ease of implementation, low cost, simple structure, and minimal occupation of vehicle space.

[0029] Example 1

[0030] A design method for vehicle body-adaptive antennas.

[0031] like Figure 1 As shown, the antenna feed point is located at the side window of the vehicle body. There are two current modes with relatively similar distributions at this location. A T-shaped feed port 10 is added to the side of the window. By adjusting the size of the T-shape, the two modes can be excited simultaneously, thereby achieving broadband matching and operation of the antenna.

[0032] like Figure 2 As shown, the T-shaped feeding structure enables the simultaneous operation of the two current modes at the point where the two current modes overlap through appropriate excitation, thereby widening the antenna's operating bandwidth by realizing two resonant modes.

[0033] Simulation analysis of the inherent characteristic mode currents of the vehicle body revealed two similarly distributed current modes at the side window locations. This design method allows a small T-shaped structure to achieve an extremely wide operating bandwidth while maintaining high gain and efficiency. This design enables the antenna to efficiently cover the FM broadcast band, thereby reducing or even eliminating the need for amplifiers in traditional vehicle broadcast antennas, achieving the same reception performance as traditional antennas, but with a lower noise figure and higher communication quality.

[0034] Example 2

[0035] A design method for a vehicle-mounted adaptive antenna, for a broadband antenna design requirement, such as FM (76-108MHz), involves selecting several typical frequency points within a given frequency bandwidth, such as 80MHz, 90MHz, and 100MHz.

[0036] The metal body of the vehicle is calculated and analyzed based on these three frequency points;

[0037] The characteristic mode currents of all major participating radiation at these three frequencies were calculated.

[0038] If only narrowband matching is considered, then it is only necessary to select the characteristic mode current of the corresponding frequency and select a suitable feed point according to the coverage requirements of the radiation pattern. At the same time, when adding the feed structure, the matching problem of the antenna port needs to be considered. For example, the feed point generally needs to be selected near the peak of the characteristic mode current, and the imaginary part of the impedance of the antenna input port can be adjusted by adjusting the form of the parasitic feed structure.

[0039] If considering a broadband antenna, it is necessary to examine the characteristic mode currents at multiple frequencies simultaneously, identify areas where their distributions are similar, and achieve simultaneous excitation of multiple frequency modes by adding parasitic feeding structures. In broadband mode, it is necessary to consider matching multiple frequency points, which requires the use of parasitic feeding structures such as T-shaped and L-shaped structures. These structures have the advantage of easy adjustment of the real and imaginary parts of the input impedance. The imaginary part can be adjusted by length, and the real part by height.

[0040] The above embodiments are only for illustrating the technical concept and features of this application, and are intended to enable those skilled in the art to understand the content of this application and implement it accordingly. They should not be used to limit the scope of protection of this application. All equivalent changes or modifications made in accordance with the spirit and essence of this application should be included within the scope of protection of this application.

Claims

1. A design method for a vehicle body-adaptive antenna, wherein the adaptive antenna uses the metal of the vehicle body as the main body for antenna radiation, characterized in that: The design method includes: The solution method based on the method of moments starts by calculating the magnetic field from the magnetic vector potential. The electric field is calculated using the calculated magnetic field. A wave equation based on magnetic vector potential is obtained by using Ampere's law in Maxwell's equations. By solving the integral relationship between the electric field and the surface current based on the wave equation, the surface current distribution and radiation pattern on the vehicle body structure are obtained. By observing the surface feature mode current distribution and radiation pattern on the vehicle body structure, the modes that meet the coverage and feeding requirements are identified, and the modes are excited by feeding; or, in the case of broadband design requirements, excitation is added in the region where the current distribution of multiple surface feature modes is close, so as to achieve simultaneous excitation of multiple modes and realize broadband mode antenna design. The specific steps of solving the integral relationship between the electric field and the surface current based on the wave equation include: The required structure is discretized into a mesh, a set of basis functions and test functions are selected, the surface current is expanded according to the basis functions, and then the integral calculation is transformed into a system of algebraic equations according to the mesh. The coefficient matrix of the algebraic equation system is obtained, and the coefficient matrix is ​​diagonalized to obtain the eigenvalues ​​and eigenvectors corresponding to the algebraic equation system. The eigenvectors obtained by diagonalization correspond to the characteristic mode currents of the metal region of interest in the vehicle body, and the eigenvalues ​​characterize the radiation contribution of the corresponding characteristic currents to the total field strength. Several frequency points are selected within a given frequency bandwidth, and the metal body of the vehicle is calculated and analyzed based on these frequency points; the characteristic mode currents of all major radiation participants at these frequency points are obtained through calculation. If only narrowband matching is considered, it is only necessary to select the characteristic mode current of the corresponding frequency and select the feed point according to the coverage requirements of the radiation pattern. The feed point is selected near the peak of the characteristic mode current, and the imaginary part of the impedance of the antenna input port is adjusted by adjusting the form of the feed structure. The feed structure is set at the feed point to achieve matching under narrowband antenna. If broadband antennas are considered, it is necessary to simultaneously examine the characteristic mode currents at several frequency points, find the regions where they are similarly distributed, and achieve simultaneous excitation of multiple frequency modes by adjusting the feeding structure. By setting the feeding structure at the feeding point, the broadband operation of the antenna can be achieved. The power supply structure includes either an additional parasitic power supply structure or a gap created directly in the metal structure of the vehicle body.

2. The design method of a vehicle body-adaptive antenna according to claim 1, characterized in that: The parasitic power supply structure includes T-shaped or L-shaped structures.

3. The design method of a vehicle body-adaptive antenna according to claim 1, characterized in that: The gap is defined as either an open gap satisfying a quarter wavelength of the operating frequency or a closed gap satisfying a half wavelength of the operating frequency.

4. The design method of a vehicle body-adaptive antenna according to claim 3, characterized in that: The gaps can take the form of rectangles, circles, steps, H-shapes, or L-shapes.

5. The design method of a vehicle body adaptive antenna according to claim 1, characterized in that: Based on the distribution characteristics of the characteristic mode current on the vehicle body, a multi-feeding method is used to combine or shape the radiation pattern in order to achieve beam pointing deflection, scanning, tracking, and control of the radiation pattern shape and coverage form.

6. The design method of a vehicle body-adaptive antenna according to claim 1, characterized in that: The antenna's feed point is located at the junction of the car window, roof, and metal body.

7. The design method of a vehicle body-adaptive antenna according to claim 6, characterized in that: The antenna feed point is located at the side window of the vehicle body. At this location, there are two current modes with relatively similar distributions at two frequencies. A T-shaped feed port is added to the side of the window, and the size of the T-shape is adjusted to form two resonant modes.

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