A method for improving the accuracy of digital array direction finding

Abstract

The application discloses a method for improving the precision of digital array direction finding, which realizes high-precision direction finding of array system through data fusion by guiding interferometer direction finding through multi-beam detection. The steps are as follows: firstly, coarse direction finding results are obtained through amplitude comparison direction finding according to multi-beam formed by full-array digital beam synthesis; then, phase difference measurement is conducted by guiding interferometer through full-array beam detection results, and interferometer direction finding is conducted to solve ambiguity in the coarse azimuth angle range, so that accurate direction finding results are obtained. The application has the advantages of simple principle, small calculation amount, easy engineering implementation, high direction finding precision and the like, and simulation results show that the method is effective and reliable.

Description

Technical Field

[0001] This invention belongs to the field of electronic warfare, specifically relating to a method for improving the direction finding accuracy of digital arrays. Background Technology

[0002] In key areas such as electronic warfare and satellite communications, array direction finding technology serves as a core means of acquiring target location information. Its accuracy directly determines the system's battlefield situational awareness, communication link stability, and electronic warfare effectiveness. Among traditional direction finding methods, multi-beam amplitude comparison direction finding and interferometric direction finding each have their advantages, but they also have limitations.

[0003] Multi-beam amplitude comparison direction finding is a type of amplitude direction finding method. Its principle is to determine the direction of arrival of a signal by comparing the relative amplitudes of signals received by different direction-finding antennas at the same time. Its advantages are simple structure and long detection range. Its disadvantages are that it is difficult to make the transformation ratio of directional information to amplitude information from the antenna amplitude pattern very large, and high-precision signal amplitude measurement is also quite difficult. Therefore, it leads to insufficient direction finding accuracy. In engineering implementation, the direction finding accuracy is generally about 1 / 3 of the beamwidth. ~ .

[0004] Phase interferometers are a typical method of direction finding using the phase comparison method. Their principle is to measure the phase difference between antenna signals located on different wavefronts and then process the data to obtain the signal direction. In the process of generating the phase difference through azimuth conversion, the phase comparison method can easily use the transformation ratio as a large amplification factor, thus converting certain phase difference measurement errors in engineering applications into relatively small direction finding errors. Therefore, the phase comparison method can easily achieve high direction finding accuracy, but its disadvantages include low sensitivity and low detection gain.

[0005] Therefore, finding an algorithm that combines high-gain reconnaissance and high-precision direction finding is an urgent problem to be solved. Summary of the Invention

[0006] This invention proposes a method to improve the direction finding accuracy of digital arrays. By using multi-beam high-gain signal detection to guide the subarray interferometer in direction finding, both high-gain reconnaissance of the system and high-precision direction finding of the digital array are achieved.

[0007] The technical solution for achieving the present invention is as follows: a method for improving the direction-finding accuracy of a digital array, comprising the following steps:

[0008] Step 1: Full-array digital beamforming achieves multi-beam coverage of the required spatial domain through digital signal processing. The received signals of each array unit are weighted and summed to form multiple independent and controllable beam output signals.

[0009] Step 2: Independently detect the output signals of the 8N beams and measure the full array measurement parameters with signal channels, including frequency and amplitude.

[0010] Step 3: By comparing the amplitude values ​​of the 8N beams, the channel with the largest amplitude is selected as the main beam channel. Based on the amplitude of the adjacent beam signals, the theoretical amplitude comparison curve is compared, and the DBF coarse measurement angle is obtained by referring to the table. .

[0011] Step 4: Divide the interferometer into direction-finding subarrays according to the array size. Elements 1-2N form the first subarray, elements 3N-5N-1 form the second subarray, and elements 6N+1-8N form the third subarray. Each subarray is used for coarse angle measurement. The direction forms the direction-finding beam of the interferometer.

[0012] Step 5: Guided by the full array measurement parameters, estimate the phase difference of the output signal of each subarray to obtain the corresponding first phase difference. Second phase difference Third phase difference .

[0013] Step 6: Based on the signal wavelength Angle range Given the array size D, determine the maximum unambiguous value K.

[0014] Step 7: Obtain the fuzzy number Then the second solution is fuzzy phase difference The first unambiguous phase difference is calculated based on the baseline relationship. The fuzzy phase difference with the third solution ; and the measured phase value , , Compare and record all unambiguous phase difference deviations C_signle and the total deviation value c_all.

[0015] Step 8: Repeat steps 6 and 7, iterating through all fuzzy values, and selecting the one with the smallest total deviation c_all as the true fuzzy value. The second true phase difference at this time is .

[0016] Step 9: Calculate the direction finding angle .

[0017] Step 10: If the interferometer fails to resolve ambiguity, report the DBF direction finding results. = If the interferometer successfully resolves the ambiguity, the direction finding of the interferometer is reported. = .

[0018] Compared with the prior art, the significant advantages of this invention are:

[0019] (1) The algorithm is simple in principle, has a small computational load, and is easy to implement in engineering.

[0020] (2) The phase detection results of the full array multi-beam signal guide the sub-array beams for phase detection, and finally the phase detection results are used for interferometer direction finding, which improves the direction finding accuracy of the array system;

[0021] (3) Applicable to digital array detection systems. Attached Figure Description

[0022] Figure 1 This is a flowchart of the signal processing of the present invention.

[0023] Figure 2 This is a schematic diagram of the antenna array.

[0024] Figure 3 This is a schematic diagram of full-array beam coverage (18GHz).

[0025] Figure 4 This is a schematic diagram of the interferometer's direction-finding beam coverage (18GHz).

[0026] Figure 5 This is a comparison curve of the direction finding error of the method of the present invention. Detailed Implementation

[0027] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the 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.

[0028] The technical solutions of the various embodiments of the present invention can be combined with each other, but only if they can be implemented by those skilled in the art. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed by the present invention.

[0029] The following section will further introduce the specific implementation method, as well as the technical difficulties and inventive points of this invention, using this design example as an example.

[0030] Combination Figures 1-5 A method for improving the direction finding accuracy of a digital array includes the following steps:

[0031] Step 1: Full-array digital beamforming achieves multi-beam coverage of the required spatial domain through digital signal processing. The received signals of each array unit are weighted and summed to form multiple independent and controllable beam output signals.

[0032] Assume the system has 8N array elements (N is an integer), the array spacing is d, and the signal wavelength is... For far-field narrowband signals, the signal received by the nth array element is denoted as... The array receives the signal vector. It can be represented as:

[0033] ,

[0034] For the direction of the incoming wave is The plane wave signal, its steering vector for:

[0035] ,

[0036] Where j represents the imaginary part and T represents the transpose.

[0037] By digitally weighting and synthesizing 8N independent beams (with equally spaced beam directions), covering a 90° airspace, the weight vector of the nth beam is... Corresponding pointing angle ,satisfy:

[0038] ,

[0039] Beam output signal for:

[0040] ,

[0041] in, As the conjugate transpose, it completes the in-phase superposition of signals in this direction, thereby maximizing the spatial filtering gain.

[0042] Step 2: Independently detect the output signals of the 8N beams and measure the full array measurement parameters with signal channels, including frequency and amplitude.

[0043] Step 3: By comparing the amplitude values ​​of the 8N beams, select the channel with the largest amplitude as the main beam channel (amplitude A), and compare the amplitudes of the adjacent beam signals (A1, A2) with the theoretical amplitude comparison curve to obtain the DBF coarse angle from the table. .

[0044] Step 4: Divide the interferometer into direction-finding subarrays according to the array size. Elements 1-2N form the first subarray, elements 3N-5N-1 form the second subarray, and elements 6N+1-8N form the third subarray. Each subarray is used for coarse angle measurement. The direction forms the direction-finding beam of the interferometer.

[0045] Step 5: Guided by the full array measurement parameters (frequency, angle), estimate the phase difference of the output signal of each subarray to obtain the corresponding first phase difference. Second phase difference Third phase difference .

[0046] Step 6: Based on the signal wavelength ( ), Angle range ( The maximum unambiguous value K is determined by the array size (D=6Nd) and the array surface size (D=6Nd).

[0047]

[0048] Step 7: Obtain the fuzzy number Then the second solution is fuzzy phase difference The first unambiguous phase difference is calculated based on the baseline relationship. The fuzzy phase difference with the third solution ; and the measured phase value ( , , Compare and record all unambiguous phase difference deviations C_signle and the total deviation value c_all;

[0049] Step 8: Repeat steps 6 and 7, iterating through all fuzzy values, and selecting the one with the smallest total deviation c_all as the true fuzzy value. The second true phase difference at this time is ;

[0050] Step 9: Calculate the direction finding angle according to the following formula. :

[0051]

[0052] in, Represents the speed of light. Indicates signal frequency. This represents the distance between subarray 1 and subarray 3. If... If the fuzzy resolution fails, then the solution will fail. The interferometer's direction-finding angle is .

[0053] Step 10: If the interferometer fails to resolve ambiguity, report the DBF direction finding results. = If the interferometer successfully resolves the ambiguity, the direction finding of the interferometer is reported. = The signal processing flowchart is as follows: Figure 1 As shown.

[0054] To further illustrate the effectiveness of the method of the present invention, a one-dimensional linear array with 16 elements is used as an example to illustrate the effect.

[0055] Antenna array diagram as shown Figure 2 As shown, the array has 16 elements in the azimuth dimension, with an element spacing of 8.5 mm, and operates in the frequency band of 6–18 GHz. The entire array forms 16 beams to cover a 90° azimuth airspace. A schematic diagram of the beam coverage is shown below. Figure 3 As shown, the beam overlap depth is less than 3dB. Based on engineering experience, the accuracy of multi-beam amplitude ratio direction finding is approximately 1 / 6 to 1 / 10 of the beamwidth (the simulation takes the middle value of 1 / 8). Therefore, the accuracy of multi-beam amplitude ratio direction finding is shown in Table 1.

[0056] Select the direction-finding beam of the 1 / 4 subarray synthesizer interferometer, and select the subarray elements as follows: Figure 2 As shown, the interferometer baseline , Then the shortest baseline Baseline length A subarray beam is formed at the target azimuth to cover the 22.5° azimuth airspace. A schematic diagram of the beam coverage is shown below. Figure 4 As shown, according to the formula Calculate the unblurred viewpoint, where The operating wavelength; according to the formula Calculate the direction finding accuracy, where To account for phase detection error, it is usually taken as , To determine the direction finding coverage area, take The direction finding results of this patent are shown in Table 2.

[0057] Comparison of direction finding errors between the method of this invention and the multi-beam amplitude ratio direction finding method Figure 5 As shown in the figure, the comparison results demonstrate that the method of this invention can improve the accuracy of multi-beam amplitude ratio direction finding. This method is effective and feasible, which is of great significance in practical engineering applications.

Claims

1. A method for improving the direction-finding accuracy of a digital array, characterized in that, The steps are as follows: Step 1: Full-array digital beamforming achieves multi-beam coverage of the required spatial area through digital signal processing. The received signals of each array element are weighted and summed to form multiple independent and controllable beam output signals. Step 2: Independently detect the output signals of the 8N beams and measure the full array measurement parameters with signal channels, including frequency and amplitude. Step 3: By comparing the amplitude values ​​of the 8N beams, the channel with the largest amplitude is selected as the main beam channel. Based on the amplitude of the adjacent beam signals, the theoretical amplitude comparison curve is compared, and the DBF coarse measurement angle is obtained by referring to the table. ; Step 4: Divide the interferometer into direction-finding subarrays according to the array size. Elements 1-2N form the first subarray, elements 3N-5N-1 form the second subarray, and elements 6N+1-8N form the third subarray. Each subarray is used for coarse angle measurement. Direction forming interferometer direction finding beam; Step 5: Guided by the full array measurement parameters, estimate the phase difference of the output signal of each subarray to obtain the corresponding first phase difference. Second phase difference Third phase difference ; Step 6: Based on the signal wavelength Angle range Given the array size D, determine the maximum unambiguous value K; Step 7: Obtain the fuzzy number Then the second solution is fuzzy phase difference The first unambiguous phase difference is calculated based on the baseline relationship. The fuzzy phase difference with the third solution ; and the measured phase value , , Compare and record all unambiguous phase difference deviations C_signle and the total deviation value c_all; Step 8: Repeat steps 6 and 7, iterating through all fuzzy values, and selecting the one with the smallest total deviation c_all as the true fuzzy value. The second true phase difference at this time is ; Step 9: Calculate the direction finding angle ; Step 10: If the interferometer fails to resolve ambiguity, report the DBF direction finding results. = If the interferometer successfully resolves the ambiguity, the direction finding of the interferometer is reported. = .

2. The method for improving the direction finding accuracy of a digital array according to claim 1, characterized in that, Step 1 is detailed as follows: Assume the system has 8N array elements, where N is an integer, the array spacing is d, and the signal wavelength is... For far-field narrowband signals, the signal received by the nth array element is denoted as... The array receives the signal vector. Represented as: ， For the direction of the incoming wave is The plane wave signal, its steering vector for: ， Where j represents the imaginary part and T represents the transpose.

3. The method for improving the direction-finding accuracy of a digital array according to claim 2, characterized in that, In step 1, the received signals from each element of the array are weighted and summed to form multiple independent and controllable beam output signals, as detailed below: The beamforming is digitally weighted and synthesized into 8N independently distributed beams at equal intervals, covering a 90° airspace. The weight vector of the nth beam is... Corresponding pointing angle ,satisfy: ， Beam output signal for: ， in, As the conjugate transpose, it completes the in-phase superposition of signals in this direction, thereby maximizing the spatial filtering gain.

4. The method for improving the direction-finding accuracy of a digital array according to claim 1, characterized in that, In step 6, the maximum unfuzzy value K is as follows: ； The array size is D = 6Nd.

5. The method for improving the direction finding accuracy of a digital array according to claim 1, characterized in that, In step 9, the direction finding angle The details are as follows: ； in, Represents the speed of light. Indicates signal frequency. This represents the spacing between subarray 1 and subarray 3; like If the fuzzy resolution fails, then the solution will fail. The interferometer's direction-finding angle is .

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