Low-profile single-station direction-finding antenna array of small mobile equipment

Abstract

The utility model relates to the technical field of antennas, in particular to a low-profile single-station direction-finding antenna array of small mobile equipment. According to the technical scheme, a low-profile capacitor loading monopole antenna with a short-circuit probe is designed, and a three-unit array is formed. The array can be directly printed and manufactured on a common circuit board, and the integration level of a direction finding system is improved. The source direction of the signals is calculated by comparing the phase differences of the signals received by the units of the array, so that the direction finding function is completed. Besides, the antenna is connected with the computing chip through the coplanar waveguide printed on the circuit board, and the high-precision circuit board printing ensures the consistency of the sizes of the three units of the direction-finding array, so that the phase error of the circuit between the antenna units and the chip is eliminated.

Description

Technical Field

[0001] This utility model relates to the field of antenna technology, specifically to a low-profile monostation direction-finding antenna array for small mobile devices. Background Technology

[0002] Currently, with the popularization of 5G and the Internet of Things, all industries are developing towards informatization and intelligence, and location-based services are becoming increasingly common, bringing huge demand for positioning. On the other hand, the application of miniaturized mobile devices such as drones is becoming more mature and widespread, and the need for precise control of these mobile devices has placed higher demands on their location information, which requires high-precision positioning systems that can be used on small frequency stations.

[0003] Currently, commonly used positioning technologies include WiFi, Bluetooth, and Ultra-Wideband (UWB), but each has its own limitations. For example, WiFi and Bluetooth are mature and low-cost, but their positioning accuracy is only 3m-10m, which cannot meet the needs of high-precision positioning. UWB technology has strong multipath resolution and high positioning accuracy, with theoretical ranging accuracy reaching centimeter or even sub-centimeter levels, meeting the needs of high-precision indoor positioning. However, a single UWB station can only achieve one-dimensional high-precision ranging, requiring the support of more than three base stations for UWB positioning, resulting in high costs. When the number of rooms is large, the number of base stations required increases exponentially. Furthermore, multi-base station positioning systems require high-precision clock synchronization. To ensure accurate clock synchronization between base stations, the current main method is wired connection, which presents significant difficulties for system installation and deployment.

[0004] Interferometer-based direction-finding array antennas require only a single device for direction finding, reducing dependence on the installation environment and lowering deployment costs. Currently, interferometer direction-finding antenna arrays mainly employ basic antenna forms such as monopole antennas and patch antennas, and in terms of array configuration, they include linear arrays and circular arrays.

[0005] The accuracy of interferometric direction finding primarily depends on its phase detection accuracy. To improve its performance, current research mainly focuses on the algorithm level, proposing methods such as phase difference ambiguity resolution, channel amplitude and phase correction, and data processing. However, improvements in direction finding accuracy from the algorithm and software levels are limited; the maximum improvement is determined by the accuracy level achievable by the positioning antenna hardware. To complement the performance improvement of deambiguity algorithms, some research has been conducted on antenna array layout, mainly using correlation coefficients to optimize the antenna array spacing to enhance the deambiguity resolution capability of the interferometric direction finding antenna array. However, existing research has not fundamentally solved the problem of single-valued phase difference in interferometric direction finding antenna arrays. Multiple phase values ​​during measurement will cause direction finding ambiguity.

[0006] Based on the above situation, currently used positioning antennas are unable to meet the market demand for high-tech maturity and low cost in terms of both accuracy and cost.

[0007] Therefore, it is necessary to provide a new antenna array to solve the technical problem that the aforementioned positioning system antennas are large in size, have low integration, and are difficult to use on miniaturized mobile devices. Utility Model Content

[0008] This utility model provides a low-profile monostation direction-finding antenna array for a small mobile device. The array is characterized by a capacitively loaded monopole antenna with a short-circuit probe forming a three-element array, comprising a metal base plate, a dielectric substrate, a dielectric base plate, a capacitive loading element, a short-circuit metal pillar, a low-profile monopole, a feed line, a metal grounding pillar, and a direction-finding chip interface. The dielectric substrate is circular, and the metal base plate is sandwiched between the dielectric substrate and the dielectric base plate. The metal base plate has three or more vertices and forms an axisymmetric array about the center of the dielectric substrate. The dielectric base plate has the same radius as the dielectric substrate. The capacitive loading element is an etched pattern on the side of the dielectric substrate away from the dielectric base plate, and the pattern is an annular pattern. The short-circuit metal pillar is a cylinder, with its axial direction parallel to the axial direction of the dielectric substrate. In the dielectric substrate; one end of the short-circuited metal post is connected to the capacitor load, and the other end is connected to the metal base plate; the short-circuited metal post is located at the center of the array and on the extension line of the capacitor load; the low-profile monopole is a through-hole in the dielectric substrate, its central axis coincides with the centroidal axis of the capacitor load, the upper end of the low-profile monopole is connected to the capacitor load, and the lower end of the low-profile monopole is provided with a grounded coplanar waveguide; the feed line is the feed line of the grounded coplanar waveguide, one end of the feed line is connected to the grounded coplanar waveguide at the lower end of the low-profile monopole, and the other end is connected to the direction-finding chip interface; the metal grounding post is the metal grounding post of the grounded coplanar waveguide, and the metal grounding post is a through-hole provided on the dielectric substrate, and the through-hole is arranged non-contactly along both sides of the grounded coplanar waveguide.

[0009] Furthermore, the thickness of the metal substrate is between 8μm and 30μm; the metal substrate includes three vertices, the distances of the three vertices from the center from farthest to nearest are 0.8λ0 to 0.85λ0, which is equal to the radius of the dielectric substrate; 0.75λ0 to 0.8λ0, which is less than the radius of the dielectric substrate; and the nearest point is 0.65λ0 to 0.7λ0 (less than the distance of the previous point).

[0010] Furthermore, the distance between the capacitor loading and the center of the array is 0.2λ0 to 0.25λ0, and the radius of the circular pattern is 0.08λ0 to 0.1λ0; the distance between the center of the array and the center of the capacitor loading circle is 0.1λ0 to 0.12λ0; and the radius of the short-circuit metal pillar is 0.032λ0 to 0.032λ0.

[0011] Furthermore, the radius of the annular pattern is 0.08λ0 to 0.1λ0.

[0012] Furthermore, the low-profile monopole has a radius of 0.025λ0 to 0.027λ0.

[0013] Furthermore, the dielectric substrate is a Teflon dielectric substrate with a dielectric constant of 2.1, with a thickness of 0.1λ0 to 0.12λ0, equal to the height of the short-circuit metal pillar, and a radius of 0.8λ0 to 0.85λ0; the dielectric substrate is an FR4 dielectric substrate with a dielectric constant of 4.4, with a thickness of approximately 0.02λ0 to 0.025λ0 and a radius of approximately 0.8λ0 to 0.85λ0.

[0014] Furthermore, the grounded coplanar waveguide impedance is 50Ω, and the width of the feed line in the middle section and the width of the gaps on both sides are adjusted by the 50Ω impedance.

[0015] Furthermore, the metal grounding posts are arranged along both sides of the coplanar waveguide, and the distance from the coplanar waveguide is much less than λ0.

[0016] This technical solution designs a low-profile, capacitively loaded monopole antenna with a short-circuit probe, forming a three-element array. This array can be directly printed on a general circuit board, improving the integration of the direction-finding system. By comparing the phase difference of the received signals in each element of the array, the direction of signal origin is calculated, thus completing the direction-finding function.

[0017] In addition, the antenna is connected to the computing chip through a coplanar waveguide printed on the circuit board. The high-precision circuit board printing ensures the consistency of the dimensions of the three units of the direction finding array, thereby eliminating the phase error of the circuit between the antenna unit and the chip.

[0018] The method used in this patent has the following advantages compared to traditional methods:

[0019] This significantly reduces the height of the UBW direction-finding antenna to 0.1λ0. Typical UWB monostation direction-finding antenna arrays use monopole antennas as array elements, with a height generally one-quarter of the wavelength corresponding to the center frequency (0.25λ0), making this a reduction of 0.15λ0.

[0020] The capacitor-loaded monopole antenna with a short-circuit probe can be directly fabricated by etching and drilling holes on the dielectric substrate, increasing integration with back-end chips and other devices, and eliminating the need for a coaxial transmission line antenna wrapped around the dielectric substrate. This patent uses a grounded coplanar waveguide to connect the chip and the antenna, improving fabrication consistency and further reducing phase error. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the three-dimensional structure of a monostation direction-finding antenna array;

[0022] Figure 2 This is a front view of a single-station direction-finding antenna array;

[0023] Figure 3 This is a side view of a monostation direction-finding antenna array;

[0024] Figure 4 This is a rear view of a monostation direction-finding antenna array.

[0025] Figure 5 A simulated monopole standing wave ratio diagram for a capacitor with a short-circuit probe;

[0026] Figure 6 Phase pattern of a capacitively loaded monopole with a short-circuit probe;

[0027] Figure reference numerals: 1. Array metal base plate, 2. Capacitor loading, 3. Short-circuit metal pillar, 4. Low-profile monopole, 5. Dielectric board, 6. Dielectric substrate, 7. Feed line, 8. Metal grounding post, 9. Direction finding chip interface. Detailed Implementation

[0028] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0029] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. In the description of the present invention, it should be understood that the terms "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention.

[0030] Furthermore, the terms "first," "second," a, b, c, d, e, f, etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0031] λ0 is the wavelength to be measured.

[0032] Example 1

[0033] refer to Figures 1 to 4This embodiment discloses a low-profile monostation direction-finding antenna array for a small mobile device, comprising a capacitor-loaded monopole antenna with a short-circuit probe arranged in a three-element array. The array includes a metal base plate 1, a dielectric substrate 5, a dielectric substrate 6, a capacitor load 2, a short-circuit metal pillar 3, a low-profile monopole 4, a feed line 7, a metal grounding pillar 8, and a direction-finding chip interface 9. The dielectric substrate 5 is circular, and the metal base plate 1 is sandwiched between the dielectric substrate 5 and the dielectric substrate 6. The metal base plate 1 has three or more vertices and is arranged in an axisymmetric array with the center of the dielectric substrate 5 as the axis. The dielectric substrate 6 has the same radius as the dielectric substrate 5. The capacitor load 2 is a pattern etched on the side of the dielectric substrate 5 away from the dielectric substrate 6; the pattern is an annular pattern. The short-circuit metal pillar 3 is a cylinder, and its axial direction is perpendicular to the dielectric substrate. The plate 5 is embedded in the dielectric substrate 5 parallel to the axial direction; one end of the short-circuit metal post 3 is connected to the capacitor load 2, and the other end is connected to the metal base plate 1; the short-circuit metal post 3 is located at the center of the array and on the extension line of the capacitor load 2; the low-profile monopole 4 is a through hole in the dielectric substrate 5, the central axis of which coincides with the centroidal axis of the capacitor load 2, the upper end of the low-profile monopole 4 is connected to the capacitor load 2, and the lower end of the low-profile monopole 4 is provided with a grounded coplanar waveguide; the feed line 7 is the feed line 7 of the grounded coplanar waveguide, one end of the feed line 7 is connected to the grounded coplanar waveguide at the lower end of the low-profile monopole 4, and the other end is connected to the direction finding chip interface 9; the metal ground post 8 is the metal ground post 8 of the grounded coplanar waveguide, and the metal ground post 8 is a through hole on the dielectric substrate 6, and the through hole is arranged non-contactly along both sides of the grounded coplanar waveguide.

[0034] The thickness of the metal substrate 1 is between 8 μm and 30 μm. The metal substrate 1 includes three vertices, with the distances from the center from the farthest point to the nearest point being 0.8λ0 to 0.85λ0, equal to the radius of the dielectric substrate; 0.75λ0 to 0.8λ0, less than the radius of the dielectric substrate; and the nearest point being 0.65λ0 to 0.7λ0 (less than the distance from the previous point). The distance from the center of the three vertices is the axis of symmetry.

[0035] The distance between the capacitor load 2 and the center of the array is 0.2λ0 to 0.25λ0, and the radius of the circular pattern is 0.08λ0 to 0.1λ0; the distance between the center of the array and the center of the capacitor load 2 is 0.1λ0 to 0.12λ0; the radius of the short-circuit metal pillar 3 is 0.032λ0 to 0.032λ0.

[0036] The radius of the annular pattern is 0.08λ0 to 0.1λ0.

[0037] The low-profile monopole 4 has a radius of 0.025λ0 to 0.027λ0.

[0038] Dielectric substrate 5 is a Teflon dielectric substrate with a dielectric constant of 2.1 and a thickness of 0.1λ0 to 0.12λ0. It has the same height as the short-circuit metal pillar 3 and a radius of 0.8λ0 to 0.85λ0. Dielectric substrate 6 is an FR4 dielectric substrate with a dielectric constant of 4.4 and a thickness of approximately 0.02λ0 to 0.025λ0 and a radius of approximately 0.8λ0 to 0.85λ0.

[0039] The grounded coplanar waveguide impedance is 50Ω, and the width of the middle section feeder 7 and the width of the gaps on both sides are adjusted by the 50Ω impedance. The calculation method is a common industry method, usually calculated by software.

[0040] Metal grounding posts 8 are arranged along both sides of the coplanar waveguide, and the distance from the coplanar waveguide is much less than λ0.

[0041] This embodiment designs a low-profile, capacitively loaded monopole antenna with a short-circuit probe, forming a three-element array. This array can be directly printed on a general circuit board, improving the integration of the direction-finding system. By comparing the phase difference of the signals received by each element of the array, the direction of signal origin is calculated, thereby completing the direction-finding function.

[0042] Meanwhile, the antenna is connected to the computing chip through a coplanar waveguide printed on the circuit board. The high-precision circuit board printing ensures the consistency of the dimensions of the three units of the direction finding array, thereby eliminating the phase error of the circuit between the antenna unit and the chip.

[0043] On the one hand, the need for a low profile and miniaturization in the antenna must be considered, requiring a dielectric constant as high as possible; on the other hand, excessively high dielectric constants can worsen the antenna's input impedance. Therefore, the following formula is typically used when selecting the dielectric constant:

[0044]

[0045] In the formula, ε r Let be the dielectric constant of the dielectric substrate. Substituting the following formula into the above formula yields the approximate range of the required dielectric constant. One end of the feed line connects to the grounded coplanar waveguide at the lower end of the low-profile monopole, and the other end connects to the direction-finding chip interface; the metal grounding post is the metal grounding post of the grounded coplanar waveguide, and the metal grounding post is a through-hole provided on the dielectric substrate 6, with the through-hole arranged non-contactly along both sides of the grounded coplanar waveguide. That is, when the component is placed horizontally, the through-hole and the grounded coplanar waveguide do not intersect in the direction of gravity.

[0046] Example 2

[0047] This embodiment further elaborates on the effect of distance. In order to facilitate understanding of this technology, it is described in detail below. The scheme designs a low-profile UBW monostation direction-finding antenna array with an operating frequency of 7.7GHz to 8.3GHz and a center frequency of 8GHz.

[0048] The array employs capacitively loaded monopoles with short-circuit probes. On one hand, the metallic capacitively loaded disk can accumulate more charge, increasing the current intensity flowing through the monopole surface. On the other hand, the use of short-circuit probes extends the current path across the monopole surface. These structural features together improve the resonant frequency of the low-profile monopole, enabling it to achieve a higher operating frequency with a shorter height. In this example, the low-profile monopole has a radius of 1 mm and a height of 4 mm, only 0.1λ0 of the operating wavelength. The radius of the loaded metal disk is 3 mm, the radius of the short-circuit probe is 1.2 mm, and the distance between the short-circuit probe and the monopole is 3.78 mm. The radius of the capacitively loaded disk, the radius of the short-circuit probe, and their distance from the monopole are related not only to the resonant frequency but also to the antenna's input impedance. Generally, a larger radius of the capacitively loaded disk results in a higher resonant frequency, and a greater distance between the short-circuit probe and the monopole also results in a higher resonant frequency. Furthermore, to achieve impedance matching with a 50Ω transmission line, these parameters need to be optimized to obtain the aforementioned dimensional parameters. The standing wave ratio (SWR) parameters of a capacitively loaded monopole with a short-circuit probe are as follows: Figure 5 As shown.

[0049] To achieve direction finding by comparing the phase difference of signals arriving at each element of the array, the three elements of the array need to be rotated around the array center at 120° intervals. Simultaneously, for rapid positioning, the far-field phase pattern of each element needs to be adjusted to approximate a sine function, allowing for quick lookup of tables after signal reception to determine the azimuth angle φ and elevation angle θ of the received signal source. In this example, due to coupling and reflection between the three elements causing distortion in the element phase pattern, a polygonal metal ground plane is used to adjust the element phase pattern to fit the sine function as closely as possible. The shape of the ground plane should ideally make the distance from each element to the edge of the ground plane as equal as possible. The shape of the ground plane can be determined by the positions of the three vertices. The distances of the three vertices from the array center, from farthest to nearest, are 32.5 mm, 29.5 mm, and 25.3 mm, respectively. The resulting phase pattern is shown below. Figure 6 As shown.

[0050] The specific steps for eliminating phase errors introduced by connection circuits are as follows:

[0051] Step 1: Determine the size of the ground plane for the array antenna based on the center frequency of the operating frequency band of the positioning system. The ground plane is circular, with a radius approximately 0.85 times the wavelength corresponding to the center frequency (hereinafter referred to as λ0).

[0052] Step 2: Use a double-layer dielectric substrate as the basic structure of the antenna. The upper layer is etched with a metal antenna pattern, the middle layer is etched with a metal antenna ground plane, and the bottom layer is etched with the feed circuit.

[0053] Step 3: Optimize the metal ground plane of the antenna. Based on the different propagation phases of electromagnetic waves on the metal surface and in free space, adjust the far-field phase of the antenna at each angle so that its distribution fits the sin function.

[0054] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A low-profile monostatic direction-finding antenna array for a small mobile device, characterized in that: The capacitively loaded monopole antenna of the short-circuit probe forms a three-unit array, which includes a metal bottom plate, a dielectric plate, a dielectric substrate, a capacitive loading, a short-circuit metal column, a low-profile monopole, a feeder, a metal grounding column and a direction-finding chip interface; the dielectric plate is circular, the metal bottom plate is sandwiched between the dielectric plate and the dielectric substrate, the metal bottom plate is provided with three or more vertices, and forms an axisymmetric array with the center of the dielectric plate as the axis, and the dielectric substrate and the dielectric plate have the same radius; the capacitive loading is a pattern etched on the side of the dielectric plate away from the dielectric substrate, and the pattern is a ring pattern; the short-circuit metal column is a cylinder, and its axial direction is parallel to the axial direction of the dielectric plate and is embedded in the dielectric plate; one end of the short-circuit metal column The low-profile monopole is a through hole provided in the dielectric plate, and its central axis coincides with the centroid axis of the capacitor loading. The upper end of the low-profile monopole is connected to the capacitor loading, and a grounded coplanar waveguide is provided at the lower end of the low-profile monopole. The feeder is a feeder of the grounded coplanar waveguide, one end of the feeder is connected to the grounded coplanar waveguide at the lower end of the low-profile monopole, and the other end is connected to the direction finding chip interface. The metal grounding column is a metal grounding column of the grounded coplanar waveguide, and the metal grounding column is a through hole provided on the dielectric substrate, and the through hole is non-contactly arranged along both sides of the grounded coplanar waveguide.

2. The low-profile monostatic direction-finding antenna array for a small mobile device according to claim 1, characterized in that: The thickness of the metal bottom plate is between 8 μm and 30 μm. The metal bottom plate includes three vertices, and the distances of the three vertices from the center from far to near are respectively is equal to the radius of the dielectric substrate; smaller than the radius of the dielectric substrate; and the closest point 3. The low-profile monostatic direction-finding antenna array for a small mobile device according to claim 1, characterized in that: The distance between the capacitor loading and the center of the array is The radius of the circular pattern is The distance between the center of the array and the center of the capacitor loading circle is The radius of the short-circuit metal column is 4. The low-profile monostatic direction-finding antenna array for a small mobile device according to claim 1, characterized in that: The radius of the annular pattern is 5. The low-profile monostatic direction-finding antenna array for a small mobile device according to claim 1, characterized in that: The radius of the low-profile monopole is 6. The low-profile monostatic direction-finding antenna array for a small mobile device according to claim 1, characterized in that: The dielectric plate has a dielectric constant of 2.1 and a thickness of The height is equal to that of the short-circuit metal column, and the radius is The dielectric substrate is an FR4 dielectric board with a dielectric constant of 4.4, and its thickness is about The radius is approximately 7. The low-profile monostatic direction-finding antenna array for a small mobile device according to claim 1, characterized in that: The grounded coplanar waveguide impedance is 50Ω, and the width of the feeder in the middle section and the width of the gaps on both sides are adjusted by the 50Ω impedance.

8. The low-profile monostatic direction-finding antenna array for a small mobile device according to claim 1, characterized in that: The metal grounding posts are arranged along both sides of the coplanar waveguide, and the distance between the metal grounding posts and the coplanar waveguide is much smaller than λ0.

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