FPGA-based eight-unit uniform circular array three-dimensional baseline sieve leakage real-time angle measurement method

Abstract

The invention provides an eight-unit uniform circular array three-dimensional baseline screening leakage real-time angle measurement method based on an FPGA, and belongs to the technical field of radar signal processing, and the method comprises the steps: calculating the phase difference between every two adjacent antennas; the method comprises the following steps: dividing an eight-unit uniform circular array antenna array into four antenna combinations, performing parallel processing on the four antenna combinations, and respectively calculating fuzzy numbers to obtain four corresponding first-level angle sets; dividing the four groups of antenna combinations into two large groups which are combined in pairs, and performing parallel processing on the two large groups to obtain all effective angle pair sets of each group of antenna combinations; and combining the effective angle pair sets of the four groups of antenna combinations in pairs, evaluating the error of the angle pair of each pair of combinations, screening out the pair of combinations with the minimum average error to obtain two final angle pair sets, and obtaining the solved azimuth angle and pitch angle according to the two final angle pair sets. The method can achieve the real-time calculation of the target incoming wave direction, and improves the angle measurement accuracy.

Description

Technical Field

[0001] The present invention belongs to the technical field of radar signal processing in high-speed intersection target measurement scenarios, and particularly relates to an eight-unit uniform circular array stereo baseline screening real-time angle measurement method based on FPGA. Background Art

[0002] Phase interferometer direction-finding technology is a high-precision direction estimation method based on the principle of phase differences during electromagnetic wave propagation. Its basic principle is to utilize multiple spatially distributed receiving antennas to receive the same incident signal and measure the phase differences between the channels in the antenna array to infer the signal's direction of arrival (DOA). This method offers advantages such as high measurement accuracy and fast response speed. It is widely used in passive receiving systems, particularly in electronic reconnaissance and radio monitoring. Without the need for active signal transmission, it can measure the target's direction by receiving externally radiated signals, demonstrating excellent concealment and practical application value.

[0003] With the continuous evolution of radar technology, particularly the development of array antennas and digital signal processing, phase interferometer technology has been gradually adopted and applied in active radar systems. In active radar, the radar system first transmits a detection signal to the target. Upon receiving the target echo, it performs frequency detection and multi-channel signal processing to extract the phase difference information between the receiving channels. Due to the 2π periodicity of phase measurement, phase ambiguity may occur under long baseline or high-frequency signal conditions. Therefore, stereo baseline leakage direction finding technology has been introduced to accurately estimate the target's incident direction. At the same time, to ensure the real-time and efficient operation of the direction finding algorithm, it is necessary to design an adaptive FPGA real-time processing solution. Summary of the Invention

[0004] The purpose of the present invention is to propose an eight-unit uniform circular array stereo baseline screening real-time angle measurement method based on FPGA, which can realize real-time solution of the target wave direction, avoid phase ambiguity problem, and improve the angle measurement accuracy.

[0005] The present invention is achieved through the following technical solutions:

[0006] The FPGA-based eight-unit uniform circular array stereo baseline screening real-time angle measurement method includes the following steps:

[0007] Step S1, calculating the phase difference between each two adjacent antennas based on the intermediate frequency echo signal received by the eight-element uniform circular array antenna array;

[0008] Step S2: Divide the eight-element uniform circular array antenna array into four antenna combinations, each antenna combination containing three adjacent antennas. The four antenna combinations are processed in parallel, and the fuzzy numbers are calculated separately to obtain four corresponding first-level angle sets. Each first-level angle set is stored in the FPGA on-chip RAM unit, where the first-level angle level includes multiple angle pairs, and the angle pairs include azimuth and elevation angles.

[0009] Step S3: Divide the four antenna combinations into two groups, each of which is a pair of two. The two groups are processed in parallel. Within each group, all angle pairs are screened for spatial distance errors to obtain a set of all valid angle pairs for each antenna combination. The arrival angle and elevation angle of the valid angle pairs are stored in two RAM units respectively.

[0010] Step S4: Combine the valid angle pair sets of the four antenna combinations into pairs, evaluate the angle pair errors of each pairwise combination, and select the pairwise combination with the smallest average error to obtain two final angle pair sets. The solved azimuth and elevation angles are obtained based on the two final angle pair sets.

[0011] Furthermore, the step S1 includes the following steps:

[0012] Step S11, synchronously sampling the intermediate frequency echo signals received by the eight antennas of the eight-element uniform circular array antenna array to obtain an eight-channel two-dimensional echo matrix, wherein the eight channels correspond to the receiving units of the eight antennas respectively;

[0013] Step S12: Perform FFT on the eight-channel two-dimensional echo matrix column by column to obtain eight-channel frequency domain data. In the eight-channel frequency domain data, search for the frequency point with the largest amplitude as the target frequency point, and extract the real part Re of the frequency domain data corresponding to the i-th antenna at the target frequency point. i and the imaginary part Im i , using the FPGA's CORDIC IP core according to the formula Calculate the phase value θ of the i-th antenna at the target frequency i ;

[0014] Step S13: Subtract the phase values ​​corresponding to each two adjacent antennas to obtain the phase difference between each two adjacent antennas.

[0015] Furthermore, in step S11, the eight-channel two-dimensional echo matrix is ​​stored in a RAM unit of the FPGA.

[0016] Furthermore, step S2 includes the following steps:

[0017] Step S21: For the i'th antenna combination, obtain the baselines i1' and i2' corresponding to two adjacent antennas in the antenna combination, and obtain the maximum fuzzy numbers K1 and K2 of the two baselines based on the baseline length and the wavelength of the intermediate frequency echo signal, respectively. The fuzzy number ranges of the two baselines are obtained as [-K1, K1] and [-K2, K2], where 1 ≤ i' ≤ 4.

[0018] Step S22: The fuzzy number values ​​of the two baselines are integers within their fuzzy number ranges. The defuzzification process is divided into 2K1+1 parallel processing sub-units according to the fuzzy number value of the baseline i1′. Each sub-unit corresponds to a unique fuzzy number value.

[0019] Step S23: For the jth subunit, the corresponding fuzzy number is When the fuzzy number of the baseline i2′ is According to the formula Solve for p = sinβ j′ sinα j′ and q = sinβ j′ cosα j′ The closed-form solution of , and the j-th subunit is obtained according to p and q and the fuzzy number of the baseline i2′ is taken as The corresponding angle pair (α j′ ,β j′ ),in, and are the phase differences of two adjacent baselines, λ is the wavelength of the intermediate frequency echo signal, (x A ,y A ,z A )、(x B ,y B ,z B ) and (x C ,y C ,z C ) are the spatial position coordinates of the three antennas in the i'th antenna combination, α j When the fuzzy number of the baseline i2′ is the jth subunit and the value is The corresponding azimuth, β j When the fuzzy number of the baseline i2′ is the jth subunit and the value is The corresponding pitch angle,

[0020] Step S24: Repeat step S23 to obtain angle pairs obtained by traversing the fuzzy number values ​​of the baseline i2′ under the j-th sub-unit, and each angle pair is placed in the i'-th primary angle set.

[0021] Furthermore, in step S23, the complex number S=q+jp is defined. If |S|>1, the corresponding angle pair is discarded. Otherwise, according to the formula and Obtain the angle pair (α j′ ,β j′ ).

[0022] Furthermore, in step S3, for any large group, an angle pair in the primary angle set of an antenna combination in the large group is set as (α i ,β i ), one of the angles in the primary angle set of the other antenna combination is (α j ,β j ), the spatial distance error between the two angle pairs is calculated by the formula If the spatial distance error Δ ij If the distance is less than the preset threshold, the angle is considered to be i ,β i ) and the angle pair (α j ,β j ) is a valid angle pair, otherwise the two angle pairs are discarded, where x i =r i cos(β i ), x j =r j cos(β j ), y i =r i sin(β i )cos(α i ), y j =r j sin(β j )cos(α j ), z i =r i sin(β i )sin(α i ), z j =r j sin(β j )sin(α j ), r i and r j They represent the spatial points (x i ,y i ,z i ) and (x j ,y j ,z j ) radial distance.

[0023] Furthermore, step S4 includes the following steps:

[0024] Step S41: arbitrarily select two sets from the effective angle pairs of the four antenna combinations to form a combination mode, with a total of Combination methods;

[0025] Step S42: Calculate the average spatial distance error of all valid angle pairs in each combination, select the combination with the smallest average spatial distance error, and combine all valid angle pairs in the combination to obtain a final azimuth angle set and a final pitch angle set;

[0026] Step S43: quantize the final azimuth angle set and the final pitch angle set using 13 decimal places and output them in radians. and Get the solved azimuth and pitch angles, where N is the number of elements in the final azimuth set and the final pitch angle set, α n is the nth element in the final azimuth set, β n is the nth element in the final pitch angle set.

[0027] Furthermore, in step S21, according to the formula The maximum fuzzy number of the baseline i1′ is obtained, where ceil represents rounding up and d1 represents the length of the baseline i1′.

[0028] Furthermore, in step S2, the eight-unit uniform antenna array includes antenna A, antenna B, antenna C, antenna D, antenna E, antenna F, antenna G and antenna H, the first group of antenna combinations is antenna A and antenna B, and antenna B and antenna C, the second group of antenna combinations is antenna B and antenna C, and antenna C and antenna D, the third group is antenna D and antenna E, and antenna E and antenna F, and the fourth group is antenna F and antenna G, and antenna G and antenna H.

[0029] Furthermore, in step S21, the baseline is determined by the spatial position coordinates of two adjacent antennas.

[0030] The present invention has the following beneficial effects:

[0031] 1. The present invention first calculates the phase difference between two adjacent antennas. Then, the eight-element uniform circular array antenna array is divided into four antenna combinations, each containing three sequentially adjacent antennas. The four antenna combinations are processed in parallel, and fuzzy numbers are calculated separately to obtain four corresponding first-level angle sets. Each first-level angle set is stored in a RAM unit on the FPGA chip. The four antenna combinations are then divided into two groups, each of which is processed in parallel. Within each large group, all angle pairs are screened for spatial distance errors to obtain all valid angle pair sets for each antenna combination. The arrival angle and elevation angle of the valid angle pairs are stored in two RAM units. Finally, the valid angle pair sets of the four antenna combinations are combined in pairs, and the angle pair errors of each pair are evaluated. The pairwise combinations with the smallest average error are selected to obtain two final angle pair sets. The resolved azimuth and elevation angles are obtained based on the two final angle pair sets. In this way, a parallel solution process adapted to FPGA hardware is designed. The spatial distance screening mechanism is adopted to effectively achieve real-time solution of the target arrival direction, avoid phase ambiguity, and improve angle measurement accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The present invention will be further described in detail below with reference to the accompanying drawings.

[0033] Figure 1 Flowchart of the present invention.

[0034] Figure 2 Detailed flow chart of the present invention.

[0035] Figure 3 This is the arrangement form of the eight-unit uniform circular array of the present invention.

[0036] Figure 4 Detailed flowchart of step S2 of the present invention.

[0037] Figure 5 Detailed flowchart of step S3 of the present invention.

[0038] Figure 6 Detailed flowchart of step S4 of the present invention.

[0039] Figure 7 This is a connection diagram of the test equipment of the present invention.

[0040] Figure 8 It is a comparison curve of the azimuth angle of the present invention and the Matlab simulation result.

[0041] Figure 9 It is a comparison curve of the pitch angle of the present invention and the Matlab simulation result.

[0042] Figure 10It is the time required for the present invention to complete one angle measurement under a 200 MHz clock. DETAILED DESCRIPTION

[0043] like Figure 1 and Figure 2 As shown, the FPGA-based eight-unit uniform circular array stereo baseline screening real-time angle measurement method includes the following steps:

[0044] Step S1, calculating the phase difference between each two adjacent antennas based on the intermediate frequency echo signal received by the eight-element uniform circular array antenna array;

[0045] The specific steps include:

[0046] Step S11: Synchronously sample the intermediate frequency echo signals received by the eight antennas of the eight-element uniform circular array antenna array through a high-speed analog-to-digital converter (ADC) to obtain an eight-channel two-dimensional echo matrix. This ensures the consistency of the sampling time to maintain the accuracy of the phase information; the collected eight-channel time domain data is temporarily stored in the FPGA on-chip RAM unit to provide data support for subsequent parallel processing and fast conversion. The cache mechanism adopts a dual-port RAM structure to improve data access efficiency and parallel processing capabilities; wherein the eight channels correspond to the receiving units of the eight antennas respectively;

[0047] Step S12: Perform FFT on the eight-channel two-dimensional echo matrix column by column to obtain eight-channel frequency domain data. In the eight-channel frequency domain data, search for the frequency point with the largest amplitude as the target frequency point, and extract the real part Re of the frequency domain data corresponding to the i-th antenna at the target frequency point. i and the imaginary part Im i , using the FPGA's CORDIC IP core according to the formula Calculate the phase value θ of the i-th antenna at the target frequency i ;

[0048] Step S13: Subtract the phase values ​​corresponding to each two adjacent antennas to obtain the phase difference between each two adjacent antennas, such as Figure 3 As shown, the eight-element uniform circular array antenna includes antenna A, antenna B, antenna C, antenna D, antenna E, antenna F, antenna G, and antenna H. In this embodiment, a phase difference is made between antenna A and antenna B, a phase difference is made between antenna B and antenna C, a phase difference is made between antenna C and antenna D, a phase difference is made between antenna D and antenna E, a phase difference is made between antenna E and antenna F, a phase difference is made between antenna F and antenna G, a phase difference is made between antenna G and antenna H, and a phase difference is made between antenna H and antenna A.

[0049] Step S2: Divide the eight-element uniform circular array antenna array into four antenna combinations, each antenna combination containing three adjacent antennas. The four antenna combinations are processed in parallel, and the fuzzy numbers are calculated separately to obtain four corresponding first-level angle sets. Each first-level angle set is stored in the FPGA on-chip RAM unit, where the first-level angle level includes multiple angle pairs, and the angle pairs include azimuth and elevation angles.

[0050] like Figure 4 As shown, the specific steps include:

[0051] Step S21: For the i'th antenna combination, obtain the baselines i1' and i2' corresponding to two adjacent antennas in the antenna combination, and obtain the maximum fuzzy numbers K1 and K2 of the two baselines based on the baseline length and the wavelength of the intermediate frequency echo signal, respectively. The fuzzy number ranges of the two baselines are obtained as [-K1, K1] and [-K2, K2], where 1 ≤ i' ≤ 4.

[0052] More specifically, the first group of antenna combinations is antenna A and antenna B, and antenna B and antenna C, the second group of antenna combinations is antenna B and antenna C, and antenna C and antenna D, the third group is antenna D and antenna E, and antenna E and antenna F, and the fourth group is antenna F and antenna G, and antenna G and antenna H.

[0053] Each baseline is determined by the spatial position coordinates of the corresponding two adjacent antennas. That is, if i1′=1, the baseline i1′ is determined by the coordinates of antenna A and antenna B.

[0054] According to the formula The maximum fuzzy number of the baseline i1′ is obtained, where ceil represents rounding up and d1 represents the length of the baseline i1′.

[0055] Step S22: The fuzzy number values ​​of the two baselines are integers within their fuzzy number ranges. The defuzzification process is divided into 2K1+1 parallel processing sub-units according to the fuzzy number value of the baseline i1′. Each sub-unit corresponds to a unique fuzzy number value.

[0056] Step S23: For the jth subunit, the corresponding fuzzy number is When the fuzzy number of the baseline i2′ is According to the formula Solve for p = sinβ j′ sinα j′ and q = sinβ j′ cosα j′ The closed-form solution of , and the j-th subunit is obtained according to p and q and the fuzzy number of the baseline i2′ is taken as The corresponding angle pair (α j′ ,β j′ ),in, and are the phase differences of two adjacent baselines, λ is the wavelength of the intermediate frequency echo signal, (x A ,y A ,z A )、(x B ,y B ,z B ) and (x C ,y C ,z C ) are the spatial position coordinates of the three antennas in the i'th antenna combination, α j When the fuzzy number of the baseline i2′ is the jth subunit and the value is The corresponding azimuth, β j When the fuzzy number of the baseline i2′ is the jth subunit and the value is The corresponding pitch angle,

[0057] Where "the jth subunit is obtained based on p and q and the fuzzy number of the baseline i2′ is taken as The corresponding angle pair (α j′ ,β j′ )” is specifically the outlier screening process: define the complex number S = q + jp, if |S| > 1, then discard the corresponding angle pair, otherwise according to the formula and Obtain the angle pair (α j′ ,β j′ ).

[0058] Step S24: Repeat step S23 to obtain angle pairs obtained by traversing the fuzzy number values ​​of the baseline i2′ under the j-th subunit, and each angle pair is placed in the i'th first-level angle set;

[0059] The above processing is performed simultaneously on the four antenna combinations to obtain four first-level angle sets.

[0060] If K1=3 and K2=3, the fuzzy number range of the two baselines is [-3,3], with a total of 7 values. Then, within the fuzzy number range corresponding to the two baselines, after fixing the fuzzy number of one of the baselines, the defuzzification process is divided into 7 parallel sub-units. Each sub-unit corresponds to a unique fuzzy number value, and traverses the fuzzy number of the other baseline in the time series dimension, thereby covering all parameter combinations.

[0061] Step S3: Divide the four antenna combinations into two groups, each of which is a combination of two groups. The two groups are processed in parallel. Within each large group, all angle pairs are screened for spatial distance errors to obtain a set of all valid angle pairs for each antenna combination after the first level of screening. The arrival angle and elevation angle of the valid angle pairs are stored in two RAM units respectively.

[0062] Specific steps are as follows Figure 5 As shown, in order to improve the screening efficiency and system processing throughput, this step is also designed as a parallel computing structure. For any large group, let an angle pair in the first-level angle set of an antenna combination in the large group be (α i ,β i ), one of the angles in the primary angle set of the other antenna combination is (α j ,β j ), the spatial distance error between the two angle pairs is calculated by the formula If the spatial distance error Δ ij If the distance is less than the preset threshold, the angle is considered to be i ,β i ) and the angle pair (α j ,β j ) is a valid angle pair, and a valid flag is marked for it and placed in the valid angle pair set, otherwise the two angle pairs are discarded, where x i =r i cos(β i ), x j =r j cos(β j ), y i =r i sin(β i )cos(α i ), y j =r j sin(β j )cos(α j ), z i =r i sin(β i )sin(α i ), z j =r j sin(β j )sin(α j ), r i and r j They represent the spatial points (x i ,y i ,z i ) and (x j ,y j ,z j ), the specific value is 1, the coordinate value is calculated using the CORDIC IP core, and the radial distance information is calculated through the multiplier and adder. The specific process is the existing technology, and the distance threshold is set to 0.1m.

[0063] Step S4: Combine the effective angle pair sets of the four antenna combinations in pairs, evaluate the angle pair errors of each pairwise combination, and select the pairwise combination with the smallest average error to obtain the two final angle pair sets after the second-level screening. The solved azimuth and elevation angles are obtained based on the two final angle pair sets.

[0064] like Figure 6 As shown, the specific steps include:

[0065] Step S41: arbitrarily select two sets from the effective angle pairs of the four antenna combinations to form a combination mode, with a total of Combination methods;

[0066] Step S42: Calculate the average spatial distance error of all valid angle pairs in each combination, select the combination with the smallest average spatial distance error, and combine all valid angle pairs in the combination to obtain a final azimuth angle set and a final pitch angle set;

[0067] The process of obtaining the average spatial distance error is as follows: suppose a certain combination is composed of a valid angle pair set A and a valid angle pair set B. The valid angle pair set A contains N valid angle pairs, and the valid angle pair set B contains M valid angle pairs. Then, the spatial distance errors of N*M pairs of valid angle pairs need to be calculated. The sum of the spatial distance errors is divided by N*M to obtain the average spatial distance error of the combination.

[0068] Step S43, using 13-bit quantization and radian output is the configuration of the FPGA CRDIC IP core, so the final azimuth angle set and the final pitch angle set are both quantized using 13-bit decimals and output in radian form, and according to the formula and Get the solved azimuth and pitch angles, where N is the number of elements in the final azimuth set and the final pitch angle set, α n is the nth element in the final azimuth set, β n is the nth element in the final pitch angle set.

[0069] In this embodiment, a vector radar simulator is used to generate eight intermediate frequency echo signals under specific trajectories. The device connection diagram is as follows: Figure 7 The radar system parameters and antenna coordinate information are shown in Table 1:

[0070] Table 1

[0071]

[0072]

[0073] The intermediate frequency echo signal trajectory parameters are shown in Table 2:

[0074] Table 2

[0075] parameter Numerical Target speed 6000m / s Misalignment Angle 0° Relative velocity azimuth 120° Pitch angle 10° Azimuth 60°

[0076] like Figure 8 and Figure 9 The figure shows a comparison between the present invention and Matlab simulations. The output azimuth and elevation angle estimation errors are consistently controlled within ±2°. This error is primarily due to quantization errors introduced by the inverse trigonometric functions performed by the CORDIC IP core in the hardware implementation, as well as the loss of precision caused by numerical truncation. Figure 10 The time required to complete a single angle measurement at a 200MHz clock is shown. At a 200MHz processing clock cycle, the processing time required to complete a complete angle measurement process, from receiving the input phase difference signal to outputting the final angle result, is approximately 17µs. This demonstrates that the present invention can efficiently and accurately calculate the target's incoming wave direction in real time.

[0077] The above description is merely a preferred embodiment of the present invention and therefore cannot be used to limit the scope of the present invention. In other words, equivalent changes and modifications made according to the scope of the patent application and the contents of the specification should still fall within the scope of the patent of the present invention.

Claims

1. An FPGA-based eight-unit uniform circular array stereo baseline screening real-time angle measurement method, characterized by: The steps include: Step S1, calculating the phase difference between each two adjacent antennas based on the intermediate frequency echo signal received by the eight-element uniform circular array antenna array; Step S2: Divide the eight-element uniform circular array antenna array into four antenna combinations, each antenna combination containing three adjacent antennas. The four antenna combinations are processed in parallel, and the fuzzy numbers are calculated separately to obtain four corresponding first-level angle sets. Each first-level angle set is stored in the FPGA on-chip RAM unit, where the first-level angle level includes multiple angle pairs, and the angle pairs include azimuth and elevation angles. Step S3: Divide the four antenna combinations into two groups, each of which is a pair of two. The two groups are processed in parallel. Within each group, all angle pairs are screened for spatial distance errors to obtain a set of all valid angle pairs for each antenna combination. The arrival angle and elevation angle of the valid angle pairs are stored in two RAM units respectively. Step S4: Combine the valid angle pair sets of the four antenna combinations into pairs, evaluate the angle pair errors of each pairwise combination, and select the pairwise combination with the smallest average error to obtain two final angle pair sets. The solved azimuth and elevation angles are obtained based on the two final angle pair sets.

2. The FPGA-based eight-unit uniform circular array stereo baseline screening real-time angle measurement method according to claim 1, characterized in that: The step S1 comprises the following steps: Step S11, synchronously sampling the intermediate frequency echo signals received by the eight antennas of the eight-element uniform circular array antenna array to obtain an eight-channel two-dimensional echo matrix, wherein the eight channels correspond to the receiving units of the eight antennas respectively; Step S12: Perform FFT on the eight-channel two-dimensional echo matrix column by column to obtain eight-channel frequency domain data. In the eight-channel frequency domain data, search for the frequency point with the largest amplitude as the target frequency point, and extract the real part Re of the frequency domain data corresponding to the i-th antenna at the target frequency point. i and the imaginary part Im i , using the FPGA's CORDIC IP core according to the formula Calculate the phase value θ of the i-th antenna at the target frequency i ; Step S13: Subtract the phase values ​​corresponding to each two adjacent antennas to obtain the phase difference between each two adjacent antennas.

3. The FPGA-based eight-unit uniform circular array stereo baseline screening real-time angle measurement method according to claim 2, characterized in that: In step S11, the eight-channel two-dimensional echo matrix is ​​stored in the RAM unit of the FPGA.

4. The FPGA-based eight-unit uniform circular array stereo baseline screening real-time angle measurement method according to claim 1, 2, or 3, characterized in that: The step S2 comprises the following steps: Step S21: For the i'th antenna combination, obtain the baselines i'1 and i'2 corresponding to the two adjacent antennas in the antenna combination, and obtain the maximum fuzzy numbers K1 and K2 of the two baselines based on the baseline length and the wavelength of the intermediate frequency echo signal, thereby obtaining the fuzzy number ranges of the two baselines [-K1, K1] and [-K2, K2], where 1≤i'≤4; Step S22: The fuzzy number values ​​of the two baselines are integers within their fuzzy number ranges. The defuzzification process is divided into 2K1+1 parallel processing sub-units according to the fuzzy number value of the baseline i′1, and each sub-unit corresponds to a unique fuzzy number value. Step S23: For the jth subunit, the corresponding fuzzy number is When the fuzzy number of the baseline i′2 is , according to the formula Solve for p = sinβ j′ sinα j′ and q = sinβ j′ cosα j′ The closed-form solution of , and the j-th subunit is obtained according to p and q and the fuzzy number of the baseline i′2 is taken as The corresponding angle pair (α j′ ,β j′ ),in, and are the phase differences of two adjacent baselines, λ is the wavelength of the intermediate frequency echo signal, (x A ,y A ,z A )、(x B ,y B ,z B ) and (x C ,y C ,z C ) are the spatial position coordinates of the three antennas in the i'th antenna combination, α j When the fuzzy number of the jth subunit and the baseline i′2 is The corresponding azimuth, β j When the fuzzy number of the jth subunit and the baseline i′2 is The corresponding pitch angle, Step S24: Repeat step S23 to obtain angle pairs obtained by traversing the fuzzy number values ​​of the baseline i′2 under the j-th subunit, and each angle pair is placed in the i′-th primary angle set.

5. The FPGA-based eight-unit uniform circular array stereo baseline screening real-time angle measurement method according to claim 4, characterized in that: In step S23, define the complex number S=q+jp, if |S|>1, then discard the corresponding angle pair, otherwise according to the formula and Obtain the angle pair (α j′ ,β j′ ).

6. The FPGA-based eight-unit uniform circular array stereo baseline screening real-time angle measurement method according to claim 5, characterized in that: In step S3, for any large group, an angle pair in the primary angle set of an antenna combination in the large group is set as (α i ,β i ), one of the angles in the primary angle set of the other antenna combination is (α j ,β j ), the spatial distance error between the two angle pairs is calculated by the formula If the spatial distance error Δ ij If the distance is less than the preset threshold, the angle is considered to be i ,β i ) and the angle pair (α j ,β j ) is a valid angle pair, otherwise the two angle pairs are discarded, where x i =r i cos(β i ), x j =r j cos(β j ), y i =r i sin(β i )cos(α i ), y j =r j sin(β j )cos(α j ), z i =r i sin(β i )sin(α i ), z j =r j sin(β j )sin(α j ), r i and r j They represent the spatial points (x i ,y i ,z i ) and (x j ,y j ,z j ) radial distance.

7. The FPGA-based eight-unit uniform circular array stereo baseline screening real-time angle measurement method according to claim 6, characterized in that: The step S4 includes the following steps: Step S41: arbitrarily select two sets from the effective angle pairs of the four antenna combinations to form a combination mode, with a total of Combination methods; Step S42: Calculate the average spatial distance error of all valid angle pairs in each combination, select the combination with the smallest average spatial distance error, and combine all valid angle pairs in the combination to obtain a final azimuth angle set and a final pitch angle set; Step S43: quantize the final azimuth angle set and the final pitch angle set using 13 decimal places and output them in radians. and Get the solved azimuth and pitch angles, where N is the number of elements in the final azimuth set and the final pitch angle set, α n is the nth element in the final azimuth set, β n is the nth element in the final pitch angle set.

8. The FPGA-based eight-unit uniform circular array stereo baseline screening real-time angle measurement method according to claim 4, characterized in that: In step S21, according to the formula Get the maximum fuzzy number of baseline i′1, where ceil represents rounding up and d1 represents the length of baseline i′1.

9. The FPGA-based eight-unit uniform circular array stereo baseline screening real-time angle measurement method according to claim 1, 2, or 3, characterized in that: In step S2, the eight-unit uniform antenna array includes antenna A, antenna B, antenna C, antenna D, antenna E, antenna F, antenna G, and antenna H. The first antenna combination group is antenna A and antenna B, and antenna B and antenna C. The second antenna combination group is antenna B and antenna C, and antenna C and antenna D. The third group is antenna D and antenna E, and antenna E and antenna F. The fourth group is antenna F and antenna G, and antenna G and antenna H.

10. The FPGA-based eight-unit uniform circular array stereo baseline screening real-time angle measurement method according to claim 4, characterized in that: In step S21, the baseline is determined by the spatial position coordinates of two adjacent antennas.

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