A two-dimensional direction finding system and method based on a magnetoelectric dipole antenna array

Abstract

The application belongs to the technical field of direction finding, and particularly relates to a two-dimensional direction finding system and method based on a magnetic electric dipole antenna array. The system comprises a direction finding antenna array; the direction finding antenna array is equally divided into three sectors; one magnetic electric dipole antenna five-element array is arranged in each sector, and the five-element array is arranged in a cross array by five antenna elements A1, A2, A3, A4 and A5 in different baseline lengths. The method of the application comprises collecting signal R arrays of the three sectors, screening out a signal coming wave sector through power comparison, obtaining a phase interferometer direction finding angle, calculating a virtual baseline direction finding angle, and finally, performing deblurring on the phase interferometer direction finding angle through the virtual baseline direction finding angle to obtain a final azimuth angle and a pitch angle. The application determines the approximate direction of a coming wave through power, and then receives and processes the sector signal by using a directional antenna array, so that the anti-interference capability is improved; the phase interferometer direction finding angle is deblurred through the virtual baseline method, so that the direction finding precision is ensured, and two-dimensional direction finding is realized.

Description

Technical Field

[0001] This invention belongs to the field of direction finding technology, specifically relating to a two-dimensional direction finding system and method based on a magnetoelectric dipole antenna array. Background Technology

[0002] Directional information of targets such as radar and radio stations is of great significance for electronic reconnaissance, signal sorting, radiation source detection and identification, modulation parameter estimation, threat determination, guiding electronic jamming and electronic attacks, etc. It is a key information needed for decision-making and deployment in electronic warfare. Therefore, high-precision direction finding of target signals is one of the key problems that must be solved in future electronic warfare.

[0003] With the rapid development of wireless communication knowledge and technology, radar and communication signals are constantly opening up new frequency bands and adopting anti-interference technologies such as spread spectrum, frequency hopping, reducing signal dwell time, and increasing signal bandwidth. Faced with these new radar and communication signals, traditional single-method direction finding techniques such as amplitude comparison, phase comparison, and time comparison are difficult to use for direction finding, and each traditional single-method direction finding method has its own shortcomings. Amplitude comparison direction finding system has a relatively simple structure, small size, and low cost, but its disadvantages are that it is susceptible to factors such as inconsistent channel amplitude characteristics, antenna polarization characteristics, and non-ideal beamwidth, resulting in low direction finding accuracy and sensitivity. Doppler direction finding has no spacing error, can resist wavefront distortion, has high direction finding accuracy, strong site adaptability, simple equipment structure, reliable performance, and simple maintenance, but has poor anti-interference capability. Spatial spectral direction finding has almost no restrictions on the spatial distribution of antenna array elements, can simultaneously find directions of multiple signals and perform super-resolution direction finding, and has very high direction finding accuracy, but the computational load is large, and the number of radiation sources must be known in advance. Phase interferometer direction finding has high accuracy and simple algorithm, but suffers from angular ambiguity. The amplitude-phase combined direction finding method uses the advantage of amplitude comparison method without direction finding ambiguity to make up for the disadvantage of phase comparison method with multi-value ambiguity. However, the higher the frequency, the more antenna array elements are required, and the antenna switching is complicated. Summary of the Invention

[0004] The present invention aims to provide a two-dimensional direction finding method based on a magnetoelectric dipole antenna array. It employs a five-element magnetoelectric dipole antenna array to construct an omnidirectional antenna array covering 360 degrees in three sectors. The power of the five antenna elements in the three sectors is obtained through a five-channel receiver. Then, the sector containing the direction of arrival is determined according to the power distribution law. The phase information of the signal received in that sector is then extracted. Finally, the accurate direction of arrival is obtained through the virtual baseline deambiguation method, thereby ensuring the direction finding accuracy while improving the direction finding anti-interference capability.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is: a two-dimensional direction finding system based on a magnetoelectric dipole antenna array, the system including a direction finding antenna array; the direction finding antenna array is divided into three sectors along the circumferential direction, and each sector is provided with a five-element magnetoelectric dipole antenna array, which consists of five antenna elements A1, A2, A3, A4, and A5 arranged in a cross array with different baseline lengths.

[0006] Preferably, A2, A3, A4 and A5 are arranged around A1 in a clockwise direction; wherein, A2, A5 and A1 form a short baseline; and A3, A4 and A1 form a long baseline.

[0007] Preferably, the direction finding system of the present invention has a maximum direction finding angle of 60 degrees.

[0008] Preferably, the direction finding system of the present invention has a direction finding frequency range of 4-19 GHz.

[0009] The present invention further provides a two-dimensional direction finding method based on a magnetoelectric dipole antenna array, comprising:

[0010] (1) Using the direction finding system, the signal R arrays of the three sectors are collected respectively. By comparing the power, the sector where the antenna with the highest power is located is selected as the signal arrival sector.

[0011] (2) First, extract the phase difference between antenna A3 and antenna A5 in the incoming wave sector. Phase difference between antenna A4 and antenna A2 Based on the direction-finding principle of a phase interferometer, the azimuth angle can be obtained:

[0012]

[0013] Where RS is the short baseline length; RL is the long baseline length; f is the frequency; k1 represents the number of phase difference repetition periods (2π), k1=N1,N1+1,…N2; N1 is the minimum value of k1, and N2 is the maximum value of k1;

[0014]

[0015]

[0016] Pitch angle:

[0017] Where k2 represents the number of phase difference repetition periods (2π), k2 = M1, M1+1, ..., M2, M1 is the minimum value of k2, and M2 is the maximum value of k2;

[0018]

[0019] (3) Extract the phase difference between antennas A2, A3, A4, A5 and antenna A1 in the incoming wave sector. and Then, construct a virtual baseline Rx = RL - RS, corresponding to the azimuth phase difference of the virtual baseline. Pitch phase difference of virtual baseline The virtual baseline orientation azimuth angle is calculated based on the principle of phase interferometer: Virtual baseline orientation and elevation angle: in, f is the phase difference; C is the speed of light; f is the frequency.

[0020] (4) Defuzzify the phase interferometer's direction-finding angle using the virtual baseline direction-finding angle, and calculate the absolute value Diff of the difference between the virtual baseline direction-finding angle and the phase interferometer's direction-finding angle:

[0021] Diff AZI (i)=abs(AZI_θ(i)-AZI_θx),i=1:length(AZI_θ),Diff ELE (i) = abs(ELE_θ(i) - ELE_θx), i = 1: length(ELE_θ); find the index III corresponding to the minimum value in Diff. AZI =min(Diff AZI ), III ELE =min(Diff ELE ), AZI_θ(III AZI ELE_θ(III) is the final azimuth angle after deblurring. ELE ) is the final pitch angle after defuzzification.

[0022] Preferably, virtual baseline Where C is the speed of light, fmax is the maximum frequency of direction finding in Hz, and θmax is the direction finding coverage angle.

[0023] Compared with the prior art, the beneficial effects of the present invention are: (1) By power guidance, the sector (120-degree range) is determined, that is, the approximate direction of the incoming wave, and then the directional antenna array is used to receive and process the signal of the sector, which improves the anti-interference capability. (2) By using the virtual baseline method to resolve the ambiguity of the direction finding angle of the phase interferometer, the direction finding accuracy is guaranteed, and the azimuth and elevation angles are obtained by the cross array to realize two-dimensional direction finding. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the direction-finding system in an embodiment of the present invention;

[0025] Figure 2 This is a schematic diagram of a five-element array of a magnetoelectric dipole antenna. Detailed Implementation

[0026] To facilitate understanding of the present invention, it will be described in more detail below with reference to the accompanying drawings and specific embodiments. However, the present invention can be implemented in many different forms and is not limited to the embodiments described in this specification. Rather, these embodiments are provided to provide a more thorough and complete understanding of the disclosure of the present invention.

[0027] The two-dimensional direction-finding system based on a magnetoelectric dipole antenna array provided by this invention includes a direction-finding antenna array 1 and a five-channel direction-finding receiver 2. The entire antenna array is divided into three equal sectors along the circumference, each sector covering 120 degrees. Figure 1 As shown. Each sector contains a five-electromagnetic dipole antenna array, consisting of five antenna elements: A1, A2, A3, A4, and A5. These elements are arranged in a cross shape with different baseline lengths. A1 is located inside the array, and A2, A3, A4, and A5 are arranged clockwise around A1. Figure 2 As shown, RS represents the short baseline length, RL represents the long baseline length, and Rx represents the virtual baseline length. Rx = RL - RS, and Where C is the speed of light 3 × 10 8 fmax is the maximum frequency for direction finding, in Hz, and θmax is the direction finding coverage angle of each sector, which is 120 degrees.

[0028] Given RS = 0.031m and RL = 0.04m, the virtual baseline Rx = RL - RS = 0.009m. Since one sector covers an angle of 120 degrees, the maximum direction-finding angle is 60 degrees. To ensure unambiguous angle measurements by the virtual baseline phase interferometer, the maximum frequency... That is, the maximum direction finding frequency is 19 GHz.

[0029] Assuming the required direction finding accuracy is Δθ = 2π, and the phase difference error is... According to the formula for calculating the angle measurement error of a phase interferometer available

[0030] Therefore, this direction finding system is suitable for direction finding in the 4-19 GHz frequency range and guarantees a direction finding accuracy of 2 degrees.

[0031] The two-dimensional direction finding method based on a magnetoelectric dipole antenna array provided by this invention employs the aforementioned direction finding system, and the specific steps and processes are as follows:

[0032] (1) Estimation of incoming wave direction

[0033] First, the signal arrays R of the three sectors of the direction finding system are acquired separately. The power AMPij of the received signals from the five antennas in each sector is extracted (i = 1, 2, 3; representing sectors 1, 2, and 3; j = 1, 2, 3, 4, 5; representing antennas A1, A2, A3, A4, and A5). Then, the maximum power Max_AMP = max(AMPij) of the received signals from the five antennas in each sector is found. Finally, the maximum power of the three sectors is compared, and the sector containing the antenna with the highest power is the sector of the incoming signal.

[0034] (2) Direction finding using a phase interferometer

[0035] First, extract the phase difference between antennas A3 and A5 within the incoming wave sector determined in step (1). Phase difference between antenna A4 and antenna A2 Based on the direction-finding principle of a phase interferometer, the azimuth angle can be obtained:

[0036] Where k1 represents the number of phase difference repetition periods (2π), taking an integer value; k1 = N1, N1+1, ..., N2, where N1 is the minimum value of k1 and N2 is the maximum value of k1, calculated according to the following formula:

[0037]

[0038]

[0039] Pitch angle: Where k2 = M1, M1+1, ..., M2; k2 represents the number of phase difference repetition periods (2π), taking an integer value; M1 is the minimum value of k2, and M2 is the maximum value of k2, calculated according to the following formula:

[0040]

[0041]

[0042] (3) Virtual baseline azimuth angle calculation

[0043] First, extract the phase difference between antennas A2, A3, A4, and A5 and antenna A1 within the incoming wave sector. and Then, construct a virtual baseline Rx = RL - RS, corresponding to the azimuth phase difference of the virtual baseline. Pitch phase difference of virtual baseline Based on the principle formula of the phase interferometer: in, The phase difference is 3 × 10⁻⁶; C is the speed of light. 8f is the frequency; D is the phase center distance. The virtual baseline azimuth angle is calculated as follows: Virtual baseline orientation and elevation angle:

[0044] (4) Virtual baseline demodulation

[0045] The direction-finding angle of the phase interferometer is de-ambigued by using the virtual baseline direction-finding angle, and the absolute value of the difference between the virtual baseline direction-finding angle and the phase interferometer direction-finding angle, Diff, is calculated: Diff AZI (n)=abs(AZI_θ(n)-AZI_θx),n=1:length(AZI_θ),Diff ELE (n)=abs(ELE_θ(n)-ELE_θx),n=

[0046] 1: length(ELE_θ), find the index III corresponding to the minimum value in the Diff. AZI =min(Diff AZI ), III ELE =min(Diff ELE ), AZI_θ(III AZI ELE_θ(III) is the final azimuth angle after deblurring. ELE ) is the final pitch angle after defuzzification.

Claims

1. A two-dimensional direction finding method based on a magnetoelectric dipole antenna array, characterized in that, include: (1) Using a direction finding system, the signal R arrays of three sectors are collected respectively. By comparing the power, the sector where the antenna with the highest power is located is selected as the signal arrival sector. The direction finding system includes a direction finding antenna array. The direction finding antenna array is divided into three sectors along the circumference. Each sector is equipped with a five-electromagnetic dipole antenna array, consisting of five antenna elements A1, A2, A3, A4, and A5 arranged in a cross array with different baseline lengths. A2, A3, A4, and A5 are arranged around A1 in a clockwise direction. Among them, the short baseline is between A2, A5 and A1, and the long baseline is between A3, A4, and A1. (2) First, extract the phase difference between antenna A3 and antenna A5 in the incoming wave sector. Phase difference between antenna A4 and antenna A2 Based on the direction-finding principle of a phase interferometer, the azimuth angle can be obtained: ; in, For short baseline length; The length of the long baseline; For frequency; This indicates the number of phase difference repetition periods. ; yes The minimum value, yes The maximum value; ； ； Pitch angle: ; in, This indicates the number of phase difference repetition periods. , yes The minimum value, yes The maximum value; ； ； (3) Extract the phase difference between antennas A2, A3, A4, A5 and antenna A1 in the incoming wave sector. , , and Then, construct a virtual baseline. ; azimuth phase difference corresponding to the virtual baseline Pitch phase difference of virtual baseline ； The virtual baseline orientation azimuth angle is calculated based on the principle of phase interferometer: Virtual baseline orientation and elevation angle: ; in, Phase difference; The speed of light; For frequency; (4) Defuzzify the phase interferometer's direction-finding angle using the virtual baseline direction-finding angle, and calculate the absolute value Diff of the difference between the virtual baseline direction-finding angle and the phase interferometer's direction-finding angle: , ;turn up The index corresponding to the minimum value , , It is the final azimuth angle after deblurring. It is the final pitch angle after defuzzification.

2. The two-dimensional direction finding method based on a magnetoelectric dipole antenna array according to claim 1, characterized in that, Virtual baseline ,in, At the speed of light, It is the maximum frequency for direction finding. It is the direction-finding coverage angle.

3. The two-dimensional direction finding method based on a magnetoelectric dipole antenna array according to claim 1 or 2, characterized in that: The maximum direction finding angle of this system is 60 degrees.

4. The two-dimensional direction finding method based on a magnetoelectric dipole antenna array according to claim 1 or 2, characterized in that: The system's direction finding frequency range is 4-19 GHz.

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