Electromagnetic sensor array for dual-band direction finding

Abstract

The invention discloses an electromagnetic sensor array for dual-band direction finding. The electromagnetic sensor array comprises three dual-band electric sensors and three dual-band magnetic sensors, the dual-band electric sensors are used for measuring electric field components in the Z-axis direction and are equally distributed according to the radial distance d and the angular spacing of 120 degrees; the dual-band magnetic sensors are used for measuring magnetic field components in the X-axis direction and the Y-axis direction and are equally distributed according to the radial distance of d / 2 and the angular spacing of 120 degrees. The electromagnetic sensor array for dual-band direction finding disclosed by the invention has the beneficial effects that the electromagnetic sensor array is simple in structure and easy to process and manufacture; measurement of a dual-band electric field and a dual-band magnetic field is achieved, and the dual-band electric field and the dual-band magnetic field can be expanded to multiple bands through The spatial diversity of a scalar array and the polarization diversity of a vector array are fused, and the unambiguous accurate estimation of the direction of arrival of an incident electromagnetic signal is realized in the range of an incident pitch angle of 20-85 degrees and an incident azimuth angle of 0-360 degrees by optimizing the array topology.

Description

Technical Field

[0001] This invention belongs to the field of electromagnetic sensors, specifically relating to an electromagnetic sensor array for dual-frequency direction finding. Background Technology

[0002] Direction finding of electromagnetic radiation sources has wide applications in many fields, including communication, navigation, and deep space exploration.

[0003] In existing technologies, direction finding is typically based on array topologies formed by scalar electrical sensors (i.e., conventional antennas), utilizing the spatial diversity of multiple electrical sensors to solve for the angle of arrival (AOA). In recent years, a system using electromagnetic vector sensors for direction finding has been proposed, leveraging the polarization diversity of multiple electromagnetic sensors to solve for the AOA. This system features a compact structure and strong parameter estimation capabilities, but it faces the following challenges when operating across multiple frequency bands:

[0004] 1. There are relatively few magnetic sensors to choose from, and magnetic sensors that can be expanded to operate in multiple frequency bands are even scarcer.

[0005] 2. Multi-band electrical sensors need to be adapted to multi-band magnetic sensors and arrayed together to complete parameter estimation, which presents difficulties in practice.

[0006] 3. Combining spatial diversity and polarization diversity, and designing a suitable array topology based on the response characteristics of electromagnetic sensors, presents practical difficulties. Summary of the Invention

[0007] In view of the current state of the technology and to overcome the above-mentioned defects, the present invention provides an electromagnetic sensor array for dual-band direction finding.

[0008] This invention employs the following technical solution for an electromagnetic sensor array used in dual-band direction finding, comprising three dual-band electrical sensors and three dual-band magnetic sensors, wherein:

[0009] The dual-band electric sensor is used to measure the electric field component along the Z-axis, and is arranged in equal parts according to radial distance d and angular spacing of 120°.

[0010] The dual-band magnetic sensor is used to measure the magnetic field components along the X and Y axes, and is arranged in equal parts with a radial distance of d / 2 and an angular spacing of 120°.

[0011] Where d / λmin≤0.5, and λmin is the wavelength corresponding to the highest operating frequency of the array.

[0012] As the preferred technical solution among the above technical solutions, the dual-band electrical sensor adopts an asymmetric folded dual-band monopole configuration.

[0013] As a preferred technical solution to the above technical solutions, the dual-band electrical sensor includes left and right radiators with different widths to achieve impedance matching.

[0014] As a preferred technical solution to the above technical solutions, the dual-band electrical sensor loads a resonant notch filter between the upper and lower radiators to achieve dual-band operation.

[0015] As a preferred technical solution to the above technical solutions, the dual-band magnetic sensor includes two nested semi-rings, each covering a different frequency band.

[0016] As a preferred technical solution to the above technical solutions, the dual-band magnetic sensor includes an outer ring and an inner ring. The center of symmetry of the inner ring is isolated to apply an equivalent capacitance, which is used to decouple the resonant modes of the outer ring and the inner ring.

[0017] As a preferred technical solution to the above technical solutions, the electromagnetic sensor array used for dual-band direction finding is configured to achieve unambiguous direction finding within the range of incident elevation angles of 20° to 85° and incident azimuth angles of 0° to 360°.

[0018] As a preferred technical solution to the above technical solutions, the electromagnetic sensor array for dual-band direction finding also includes a metal base plate, with the dual-band electrical sensor and the dual-band magnetic sensor mounted on the metal base plate, and a substrate laid between the metal base plate and the radiator.

[0019] As the preferred technical solution for the above technical solutions, the substrate is Roger4003 material.

[0020] The electromagnetic sensor array for dual-band direction finding disclosed in this invention has the following advantages: it has a simple structure and is easy to manufacture; it realizes the measurement of electric and magnetic fields in both bands and can be extended to multiple bands with appropriate improvements; it integrates the spatial diversity of scalar arrays and the polarization diversity of vector arrays, and by optimizing the array topology (such as specific radial distance and angular spacing arrangement), it achieves unambiguous and accurate estimation of the angle of arrival of incident electromagnetic signals in the range of incident elevation angles of 20° to 85° and incident azimuth angles of 0° to 360°. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the composition and topology of the present invention.

[0022] Figure 2 This is a structural dimension diagram of the dual-band electrical sensor of the present invention.

[0023] Figure 3 This is a schematic diagram of the outer ring structure of the dual-band magnetic sensor of the present invention.

[0024] Figure 4A and Figure 4BThese are structural dimension diagrams of the outer ring of the dual-band magnetic sensor of the present invention.

[0025] Figure 5A and Figure 5B These are structural dimension diagrams of the inner ring of the dual-band magnetic sensor of the present invention.

[0026] Figure 6 This is a schematic diagram of the structure of the dual-band magnetic sensor of the present invention.

[0027] Figure 7A , Figure 7B , Figure 7C , Figure 7D , Figure 7E and Figure 7F The figures shown are simulation diagrams of the lower limit of the direction-finding accuracy of the present invention, namely the Cramer-Rao diagram.

[0028] Figure 8A , Figure 8B , Figure 8C , Figure 8D , Figure 8E and Figure 8F These are simulation diagrams of the mutually fuzzy spectrum of the present invention. Detailed Implementation

[0029] This invention discloses an electromagnetic sensor array for dual-band direction finding. The following description, in conjunction with a preferred embodiment (Embodiment 1), is shown in the accompanying drawings. Figures 1 to 8F The specific embodiments of the present invention will be further described below.

[0030] Example 1.

[0031] To facilitate a more detailed understanding of the mechanism of this invention, it is necessary to explain it in conjunction with the operating frequency. This embodiment selects two operating frequency bands for mobile communication: 890MHz to 960MHz (referred to as band A, with a relative bandwidth of approximately 8%) and 1710MHz to 1875MHz (referred to as band B, with a relative bandwidth of approximately 9%) for TM incident waves. The scope of protection of this invention is not limited to the operating frequency bands; the operating frequency bands mentioned are used for better understanding of the implementation process.

[0032] Preferably, the electromagnetic sensor array for dual-band direction finding includes three dual-band electrical sensors and three dual-band magnetic sensors, wherein:

[0033] The dual-band electric sensor is used to measure the electric field component along the Z-axis, and is arranged in equal parts according to radial distance d and angular spacing of 120°.

[0034] The dual-band magnetic sensor is used to measure the magnetic field components along the X and Y axes, and is arranged in equal parts with a radial distance of d / 2 and an angular spacing of 120°.

[0035] Where d / λ min ≤0.5, λmin It is the wavelength corresponding to the array's highest operating frequency.

[0036] Among them, the dual-band electrical sensor adopts an asymmetric folded dual-band monopole configuration.

[0037] The dual-band electrical sensor includes left and right radiators with different widths to achieve impedance matching.

[0038] Among them, the dual-band electrical sensor loads a resonant notch filter between the upper and lower radiators to achieve dual-band operation.

[0039] The dual-band magnetic sensor includes two nested semi-rings, each covering a different frequency band.

[0040] The dual-band magnetic sensor includes an outer ring and an inner ring. The center of symmetry of the inner ring is isolated to apply an equivalent capacitance, which is used to decouple the resonant modes of the outer ring and the inner ring.

[0041] The electromagnetic sensor array used for dual-band direction finding is configured to achieve unambiguous direction finding within the range of incident elevation angles of 20° to 85° and incident azimuth angles of 0° to 360°.

[0042] The electromagnetic sensor array used for dual-band direction finding also includes a metal base plate, with dual-band electrical sensors and dual-band magnetic sensors mounted on the metal base plate, and a substrate laid between the metal base plate and the radiator.

[0043] The substrate is made of Roger4003 material.

[0044] The following describes the working principle of the electromagnetic sensor array for dual-band direction finding disclosed in this embodiment.

[0045] Specifically, the present invention consists of three dual-band electrical sensors and three dual-band magnetic sensors, such as... Figure 1 As shown. Dual-band electrical sensors are used to measure the electric field component along the Z-axis, arranged at equal intervals of radial distance 'd' and angular spacing of 120°. Dual-band magnetic sensors are used to measure the magnetic field components along the X and Y axes, arranged at equal intervals of radial distance 'd / 2' and angular spacing of 120°. A metal base plate is used as the support structure for the sensors, utilizing the mirror principle to reduce the size of each sensor. A substrate made of Roger 4003 is laid between the metal base plate and the radiator.

[0046] The electromagnetic sensor array is broken down into dual-band electrical sensors and dual-band magnetic sensors for detailed explanation.

[0047] The dual-band electrical sensor is an optimized design based on a folded monopole. A folded monopole can be equivalently considered as a combination of two parallel monopoles. This embodiment employs an asymmetric folded dual-band monopole configuration. For example... Figure 2 As shown, the widths w1 and w2 of the left and right radiators are different. By changing these two parameter values, the impedance can be adjusted. Furthermore, the capacitive effect between the radiator and the metal base plate also affects the sensor's impedance; this can be addressed by adjusting... Figure 2 The three parameters (w1, w2, e) are beneficial for implementing optimal impedance matching.

[0048] The resonant frequency is controlled by adjusting the height of the radiator. The total height of the radiator is h, and the resonant frequency in the A-band is strongly correlated with this parameter; the height of the lower half of the radiator is f, and the resonant frequency in the B-band is strongly correlated with this parameter. A resonant notch filter is loaded between the upper and lower radiators, see [link to diagram]. Figure 2 As shown in the dashed box, this notch filter is equivalent to a parallel LC circuit, blocking the induced current in the B band while allowing the induced current in the A band to pass through, thereby achieving decoupling of the two resonant modes.

[0049] The dimensions of the dual-band electrical sensor were determined through electromagnetic simulation, as shown in Table 1. The meanings of the symbols in Table 1 are explained in [reference needed]. Figure 2 .

[0050] Table 1. Specific dimensions of the outer ring

[0051] a 53mm e 8.4mm i 1mm b 60mm f 18.6mm w1 25mm c 1.5mm g 27.2mm w2 1mm d 1mm h 55mm

[0052] Furthermore, the dual-band magnetic sensor is designed with two nested semi-rings, each covering a different frequency band, isolating the coupling between the two rings, and integrating the outer and inner rings.

[0053] The outer ring covers the A-band; see the structural diagram below. Figure 3 The excitations at both ends of the loop are opposite. Performance optimization is achieved by utilizing two types of coupling capacitance effects. Figure 3 In the middle, capacitor (symbol C) c (Referring to) the use of ceramic capacitors, with impedance matching achieved by adjusting the capacitance value. The capacitance generated by the coupling between the radiator and the metal base plate is denoted by the symbol C. a This refers to the fact that adjusting the extension or retraction amount can change the resonant frequency. In practice, this design provides the freedom to adjust the operating frequency.

[0054] The dimensions of the outer ring were determined through electromagnetic simulation, as shown in Table 2. The meanings of the symbols in Table 2 are explained in [reference needed]. Figure 4A and Figure 4B .

[0055] Table 2 Specific Dimensions of the Outer Ring

[0056] a 1.524mm e 3.4mm i 0.5mm b 20mm f 10mm j 0.5mm c 2mm g 0.5mm k 0.5mm d 10.7mm h 21.4mm l 60mm

[0057] The inner ring covers the B-band and its working principle and structure are similar to the outer ring. The dimensions of the inner ring were determined through electromagnetic simulation, as shown in Table 3. The meanings of the symbols in Table 3 are explained in [reference needed]. Figure 5A and Figure 5B The difference lies in the fact that the center of symmetry of the inner ring is interrupted, with the interruption distance denoted by m, equivalent to a capacitor (symbol C). b (Referring to). When the outer ring and inner ring are combined, see... Figure 6 As shown, capacitor C b It can decouple the resonant modes of the inner and outer rings. In addition, fine-tuning the isolation distance (changing the capacitance value) can compensate for the resonant frequency shift caused by electromagnetic coupling.

[0058] Table 3 Specific Dimensions of the Inner Ring

[0059] a 1.524mm e 2mm i 0.5mm b 20mm f 8mm j 0.5mm c 3.7mm g 0.5mm k 0.5mm d 8.5mm h 17mm l 60mm

[0060] Although each sensor can independently measure the components of a dual-band electric field or a dual-band magnetic field, when they are combined for direction finding, a comprehensive evaluation is required, taking into account the array topology and array manifold.

[0061] Considering the array's symmetry, the angular spacing between the elements in the array is not adjusted. Therefore, the key variable in the array topology is d / λ. min , where λ min It is the wavelength corresponding to the highest operating frequency (in this embodiment, the highest operating frequency is 1875MHz).

[0062] The direction finding performance is judged based on two criteria: the Cramer-Rao lower limit, which is used to evaluate the theoretical direction finding accuracy limit that the array can achieve; the smaller the value, the higher the direction finding accuracy. The array mutual ambiguity spectrum is used to evaluate the degree of difference between the steering vectors of incident waves in two different directions; the larger the value, the stronger the anti-ambiguity.

[0063] d / λ mi For values ​​of 0.4, 0.5, and 0.6, simulations of the direction-finding Cramer-Rao lower limit for two frequency bands are given, as follows. Figures 7A to 7F As shown, the angular coordinates represent the true incident azimuth angle, the radial axis represents the true incident elevation angle, and the lower the color temperature value, the higher the accuracy. The following trend can be observed: when the incident elevation angle is around 90°, the direction finding accuracy is relatively poor; as d / λ... m With the increase of values, the direction finding accuracy is improved to some extent; the direction finding accuracy of the B band is higher than that of the A band.

[0064] d / λ mi Simulations of array cross-ambiguity spectra for two frequency bands are given when the values ​​are 0.4, 0.5, and 0.6, respectively. Figures 8A to 8FAs shown, the angular coordinates represent the true incident azimuth angle, the radial axis represents the true incident elevation angle, and the higher the color temperature value, the stronger the anti-blurring capability. The following trend can be observed: when the incident elevation angle is near 0°, the risk of blurring is relatively high; as d / λ... m As the value of d / λ increases, the anti-ambiguity of the B band gradually deteriorates. This is especially true when d / λ... mi When the incident elevation angle is 0.6, a large range of ambiguity occurs in the regions of 30°, 90°, 150°, 210°, 270°, and 330°.

[0065] Taking into account both direction-finding accuracy and anti-ambiguity, the key variable d / λ of the array topology in this embodiment... min It should be close to 0.5, and preferably not exceed 0.5. Under this premise, high-precision unambiguous direction finding can be implemented for electromagnetic waves with incident elevation angles ∈ [20°, 85°] and incident azimuth angles ∈ [0°, 360°].

[0066] It is worth mentioning that the specific structure and other technical features of the metal base plate involved in this patent application should be regarded as prior art. The specific structure, working principle, and possible control methods and spatial arrangement methods of these technical features can be conventionally selected in the field and should not be regarded as the inventive point of this patent. This patent will not be further elaborated in detail.

[0067] For those skilled in the art, modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this invention should be included within the protection scope of this invention.

Claims

1. An electromagnetic sensor array for dual-band direction finding, characterized in that, It includes three dual-band electrical sensors and three dual-band magnetic sensors, wherein: The dual-band electric sensor is used to measure the electric field component along the Z-axis, and is arranged in equal parts according to radial distance d and angular spacing of 120°. The dual-band magnetic sensor is used to measure the magnetic field components along the X and Y axes, and is arranged in equal parts with a radial distance of d / 2 and an angular spacing of 120°. Where d / λ min ≤0.5, λ min It is the wavelength corresponding to the array's highest operating frequency.

2. The electromagnetic sensor array for dual-band direction finding according to claim 1, characterized in that, The dual-band electrical sensor adopts an asymmetric folded dual-band monopole configuration.

3. The electromagnetic sensor array for dual-band direction finding according to claim 2, characterized in that, The dual-band electrical sensor includes left and right radiators with different widths to achieve impedance matching.

4. The electromagnetic sensor array for dual-band direction finding according to claim 2, characterized in that, The dual-band electrical sensor uses a resonant notch filter loaded between the upper and lower radiators to achieve dual-band operation.

5. The electromagnetic sensor array for dual-band direction finding according to claim 1, characterized in that, The dual-band magnetic sensor consists of two nested semi-rings, each covering a different frequency band.

6. The electromagnetic sensor array for dual-band direction finding according to claim 1, characterized in that, The dual-band magnetic sensor consists of an outer ring and an inner ring. The center of symmetry of the inner ring is isolated to apply an equivalent capacitance, which is used to decouple the resonant modes of the outer and inner rings.

7. The electromagnetic sensor array for dual-band direction finding according to claim 1, characterized in that, The electromagnetic sensor array used for dual-band direction finding is configured to achieve unambiguous direction finding within the range of incident elevation angles of 20° to 85° and incident azimuth angles of 0° to 360°.

8. The electromagnetic sensor array for dual-band direction finding according to claim 1, characterized in that, The electromagnetic sensor array used for dual-band direction finding also includes a metal base plate, on which dual-band electrical sensors and dual-band magnetic sensors are mounted, and a substrate is laid between the metal base plate and the radiator.

9. The electromagnetic sensor array for dual-band direction finding according to claim 8, characterized in that, The substrate is Roger4003 material.

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