A Real-Time Angle Measurement Method for Eight-Element Uniform Circular Array Stereobaseline Screening Based on FPGA

Abstract

This invention provides a real-time angle measurement method for an eight-element uniform circular array with a three-dimensional baseline screening based on FPGA, belonging to the field of radar signal processing technology. The method includes: calculating the phase difference between any two adjacent antennas; dividing the eight-element uniform circular array into four antenna combinations, processing these four combinations in parallel, calculating ambiguity numbers for each combination to obtain four corresponding first-order angle sets; dividing the four antenna combinations into two large groups of two pairs, processing these two groups in parallel to obtain all effective angle pairs for each antenna combination; pairwise combining the effective angle pairs of the four antenna combinations, evaluating the error of each pairwise combination, and selecting the pairwise combination with the smallest average error to obtain two final angle pair sets; and obtaining the calculated azimuth and elevation angles based on these two final angle pair sets. This invention enables real-time calculation of the direction of arrival of a target, improving angle measurement accuracy.

Description

Technical Field

[0001] This invention belongs to the field of radar signal processing technology in high-speed rendezvous target measurement scenarios, specifically involving a real-time angle measurement method for an eight-element uniform circular array three-dimensional baseline sieving based on FPGA. Background Technology

[0002] Phase interferometry direction finding is a high-precision direction estimation method based on the phase difference principle during electromagnetic wave propagation. Its basic principle involves using multiple spatially distributed receiving antennas to receive the same incident signal and measuring the phase difference between channels in the antenna array to calculate the direction of arrival (DOA). This method offers advantages such as high measurement accuracy and fast response speed, and is widely used in passive receiving systems, especially in electronic reconnaissance and radio surveillance. It allows for target location measurement by receiving externally radiated signals without the need for active signal transmission, providing excellent concealment and practical application value.

[0003] With the continuous evolution of radar technology, especially the development of array antenna technology and digital signal processing technology, phase interferometer technology has been gradually applied to active radar systems. In active radar, the radar system first transmits a detection signal to the target, and after receiving the target echo, it performs frequency detection and multi-channel signal processing to extract the phase difference information between each receiving channel. Because phase measurement has a 2π periodicity, phase ambiguity may occur under long baseline or high-frequency signal conditions. Therefore, a three-dimensional baseline screening direction finding technique is introduced to achieve accurate estimation of the target's incident direction. Simultaneously, to achieve real-time and efficient operation of the direction finding algorithm, it is necessary to design a suitable FPGA real-time processing solution. Summary of the Invention

[0004] The purpose of this invention is to propose a real-time angle measurement method for an eight-element uniform circular array three-dimensional baseline sieve based on FPGA, which can realize real-time calculation of the direction of incoming wave from the target, avoid phase ambiguity problems, and improve the accuracy of angle measurement.

[0005] This invention is achieved through the following technical solution:

[0006] A real-time angle measurement method for FPGA-based eight-element uniform circular array three-dimensional baseline screening includes the following steps:

[0007] Step S1: Calculate the phase difference between each pair of adjacent antennas based on the intermediate frequency echo signal received by the eight-element uniform circular array antenna.

[0008] Step S2: Divide the eight-element uniform circular array antenna into four antenna combinations. Each antenna combination contains three antennas that are adjacent to each other. Process the four antenna combinations in parallel and calculate the ambiguity number to obtain the corresponding four first-level angle sets. Each first-level angle set is stored in the FPGA on-chip RAM unit. 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 large groups of two pairs. Process the two large groups in parallel. Within each large group, perform spatial distance error filtering on all angle pairs to obtain the set of all effective angle pairs of each antenna combination. Store the angle of arrival and elevation angle in the effective angle pairs in two RAM units respectively.

[0010] Step S4: Combine the effective angle pairs of the four antenna combinations in pairs, evaluate the error of each pair of angle pairs, and select the pair of combinations with the smallest average error to obtain two final angle pairs. Based on the two final angle pairs, obtain the calculated azimuth and elevation angles.

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

[0012] Step S11: Synchronously sample 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 elements of the eight antennas respectively.

[0013] Step S12: Perform FFT column-wise on the eight-channel two-dimensional echo matrix 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 With the imaginary part Im i Using the CORDIC IP core of the FPGA 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 ​​of each pair of adjacent antennas to obtain the phase difference between each pair of adjacent antennas.

[0015] Furthermore, in step S11, the eight-channel two-dimensional echo matrix is ​​stored in the RAM cell 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. Based on the baseline length and the wavelength of the intermediate frequency echo signal, obtain the maximum ambiguity numbers K1 and K2 of the two baselines, and thus obtain the ambiguity number ranges of the two baselines [-K1,K1] and [-K2,K2], where 1≤i'≤4;

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

[0019] Step S23: For the j-th sub-unit, its corresponding fuzzy number is taken as... When the ambiguity number of baseline i2′ is taken as , According to the formula Solve for p = sinβ j′ sinα j′ and q = sinβ j′ cosα j′ The closed-form solution is obtained, and the j-th sub-unit is obtained based on p and q, and the fuzzy number of baseline i2′ is taken as follows. The corresponding angle pair (α) j′ ,β j′ ),in, and Let x be the phase difference between two adjacent baselines, and λ be the wavelength of the intermediate frequency echo signal. A ,y A ,z A ), (x B ,y B ,z B ) and (x C ,y C ,z C ) represent the spatial coordinates of the three antennas in the i'th antenna group, and α represents the spatial coordinates of the three antennas. j When the j-th sub-unit and the baseline i2′ takes the value of , The corresponding azimuth angle, β j When the j-th sub-unit and the baseline i2′ takes the value of , The corresponding pitch angle,

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

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

[0022] Furthermore, in step S3, for any large group, let an angle pair in the first-order angle set of an antenna combination in that large group be (α). i ,β i ), and one angle in the first-order angle set of another antenna combination is (α) j ,β j Then, the spatial distance error between the two angle pairs can be calculated using the formula. If the spatial distance error Δ ij If the distance is less than the preset distance threshold, the angle is considered correct (α). i ,β i ) and angle pair (α) j ,β j If x is a valid angle pair, then the two angle pairs are discarded. 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 These represent the spatial points (x, y) calculated based on the measured angles. i ,y i ,z i ) and (x j ,y j ,z j The radial distance of ).

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

[0024] Step S41: From the effective angles of the four antenna combinations, arbitrarily select two sets from the set to form a combination, resulting in a total of Various combination methods;

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

[0026] Step S43: Quantize both the final azimuth and final elevation angle sets using 13 decimal places and output them in radians, and then apply the formula... and The calculated azimuth and elevation angles are obtained, where N is the number of elements in the final azimuth and elevation angle sets, and α... n β is the nth element in the final azimuth set. n It is the nth element in the final pitch angle set.

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

[0028] Furthermore, in step S2, the eight-element 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 consists of antenna A and antenna B, and antenna B and antenna C. The second group of antenna combinations consists of antenna B and antenna C, and antenna C and antenna D. The third group consists of antenna D and antenna E, and antenna E and antenna F. The fourth group consists of antenna F and antenna G, and antenna G and antenna H.

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

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

[0031] 1. This invention first calculates the phase difference between two adjacent antennas. Then, it divides the eight-element uniform circular array antenna into four antenna combinations, each containing three sequentially adjacent antennas. The four antenna combinations are processed in parallel, and the ambiguity number is calculated for each combination to obtain four corresponding first-level angle sets. Each first-level angle set is stored in the on-chip RAM of the FPGA. Then, the four antenna combinations are divided into two large groups of two pairs, which are processed in parallel. Within each large group, all angle pairs are filtered for spatial distance error to obtain the set of all effective angle pairs for each antenna combination. The angle of arrival and elevation angle of the effective angle pairs are stored in two RAM units respectively. Finally, the effective angle pairs of the four antenna combinations are combined in pairs, and the error of each pair of angle pairs is evaluated. The pair of pairs with the smallest average error is selected to obtain two final angle pair sets. The calculated azimuth and elevation angles are obtained from the two final angle pair sets. This parallel calculation process adapted to FPGA hardware and using a spatial distance filtering mechanism can effectively realize real-time calculation of the direction of arrival of the target wave, avoid phase ambiguity problems, and improve the accuracy of angle measurement. Attached Figure Description

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

[0033] Figure 1 This is a flowchart of the present invention.

[0034] Figure 2 This is a detailed flowchart of the present invention.

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

[0036] Figure 4 This is a detailed flowchart of step S2 of the present invention.

[0037] Figure 5 This is a detailed flowchart of step S3 of the present invention.

[0038] Figure 6 This is a detailed flowchart of step S4 of the present invention.

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

[0040] Figure 8 This is a comparison curve between the azimuth angle of the present invention and the results of Matlab simulation.

[0041] Figure 9 This is a comparison curve between the pitch angle of the present invention and the results of Matlab simulation.

[0042] Figure 10This is the time required for the present invention to complete one angle measurement at a 200MHz clock. Detailed Implementation

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

[0044] Step S1: Calculate the phase difference between each pair of adjacent antennas based on the intermediate frequency echo signal received by the eight-element uniform circular array antenna.

[0045] Specifically, the steps include the following:

[0046] Step S11: The intermediate frequency echo signals received by the eight antennas of the eight-element uniform circular array antenna are synchronously sampled by a high-speed analog-to-digital converter (ADC) to obtain an eight-channel two-dimensional echo matrix. This ensures the consistency of sampling time and maintains the accuracy of phase information. The acquired eight-channel time-domain data is temporarily stored in the on-chip RAM of the FPGA to provide data support for subsequent parallel processing and fast transformation. The caching mechanism adopts a dual-port RAM structure to improve data access efficiency and parallel processing capability. The eight channels correspond to the receiving units of the eight antennas.

[0047] Step S12: Perform FFT column-wise on the eight-channel two-dimensional echo matrix 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 With the imaginary part Im i Using the CORDIC IP core of the FPGA 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 pair of adjacent antennas to obtain the phase difference between each pair of 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, the phase difference between antenna A and antenna B, the phase difference between antenna B and antenna C, the phase difference between antenna C and antenna D, the phase difference between antenna D and antenna E, the phase difference between antenna E and antenna F, the phase difference between antenna F and antenna G, the phase difference between antenna G and antenna H, and the phase difference between antenna H and antenna A are calculated.

[0049] Step S2: Divide the eight-element uniform circular array antenna into four antenna combinations. Each antenna combination contains three antennas that are adjacent to each other. Process the four antenna combinations in parallel and calculate the ambiguity number to obtain the corresponding four first-level angle sets. Each first-level angle set is stored in the FPGA on-chip RAM unit. 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 the following:

[0051] Step S21: For the i'th antenna combination, obtain the baselines i1′ and i2′ corresponding to two adjacent antennas in the antenna combination. Based on the baseline length and the wavelength of the intermediate frequency echo signal, obtain the maximum ambiguity numbers K1 and K2 of the two baselines, and thus obtain the ambiguity number ranges of the two baselines [-K1,K1] and [-K2,K2], where 1≤i'≤4;

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

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

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

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

[0056] Step S23: For the j-th sub-unit, its corresponding fuzzy number is taken as... When the ambiguity number of baseline i2′ is taken as , According to the formula Solve for p = sinβ j′ sinα j′ and q = sinβ j′ cosα j′ The closed-form solution is obtained, and the j-th sub-unit is obtained based on p and q, and the fuzzy number of baseline i2′ is taken as follows. The corresponding angle pair (α) j′ ,β j′ ),in, and Let x be the phase difference between two adjacent baselines, and λ be the wavelength of the intermediate frequency echo signal. A ,y A ,z A ), (x B ,y B ,z B ) and (x C ,y C ,z C ) represent the spatial coordinates of the three antennas in the i'th antenna group, and α represents the spatial coordinates of the three antennas. j When the j-th sub-unit and the baseline i2′ takes the value of , The corresponding azimuth angle, β j When the j-th sub-unit and the baseline i2′ takes the value of , The corresponding pitch angle,

[0057] When the j-th sub-unit is obtained based on p and q and the fuzzy number of baseline i2′ is taken as , The corresponding angle pair (α) j′ ,β j′ Specifically, the outlier filtering process involves defining a complex number S = q + jp. If |S| > 1, the corresponding angle pair is discarded; otherwise, the formula is used to filter out outliers. and Find the angle pair (α) j′ ,β j′ ).

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

[0059] The above processing is performed simultaneously on four antenna groups to obtain four first-order angle sets.

[0060] If K1 = 3 and K2 = 3, then the range of fuzzy numbers for the two baselines is [-3, 3], with a total of 7 values. Within the range of fuzzy numbers 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 the fuzzy number of the other baseline is traversed in the temporal dimension, thereby covering all parameter combinations.

[0061] Step S3: Divide the four antenna combinations into two large groups of two pairs. Process the two large groups in parallel. Within each large group, perform spatial distance error screening on all angle pairs to obtain the set of all effective angle pairs of each antenna combination after the first-level screening. Store the angle of arrival and elevation angle of the effective angle pairs in two RAM units respectively.

[0062] Specific steps are as follows Figure 5 As shown, to improve screening efficiency and system throughput, this step is also designed with a parallel computing structure. For any large group, let an angle pair in the first-order angle set of an antenna combination in that large group be (α... i ,β i ), and one angle in the first-order angle set of another antenna combination is (α) j ,β j Then, the spatial distance error between the two angle pairs can be calculated using the formula. If the spatial distance error Δ ij If the distance is less than the preset distance threshold, the angle is considered correct (α). i ,β i ) and angle pair (α) j ,β j If two angle pairs are considered valid, they are marked as valid and added to the set of valid angle pairs; 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 These represent the spatial points (x, y) calculated based on the measured angles. i ,y i ,z i ) and (x j ,y j ,z j The radial distance is 1, and the coordinate value is calculated using the CORDIC IP core. The radial distance information is then calculated using a multiplier and an adder. The specific process is the existing technology, and the distance threshold is set to 0.1m.

[0063] Step S4: Combine the effective angle pairs of the four antenna combinations in pairs, evaluate the error of each pair of angle pairs, and select the pair of pairs with the smallest average error to obtain the two final angle pairs after secondary filtering. The azimuth and elevation angles are obtained from the two final angle pairs.

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

[0065] Step S41: From the effective angles of the four antenna combinations, arbitrarily select two sets from the set to form a combination, resulting in a total of Various combination methods;

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

[0067] The process of obtaining the average spatial distance error is as follows: Suppose that a certain combination consists of a set of effective angle pairs A and a set of effective angle pairs B. The set of effective angle pairs A contains N effective angle pairs and the set of effective angle pairs B contains M effective angle pairs. Then, we need to calculate the spatial distance error of N*M pairs of effective angle pairs. 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's CRDIC IP core. Therefore, both the final azimuth and pitch angle sets are quantized using 13 decimal places and output in radian form, according to the formula... and The calculated azimuth and elevation angles are obtained, where N is the number of elements in the final azimuth and elevation angle sets, and α... n β is the nth element in the final azimuth set. n It 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 shown below. Figure 7 As shown in Table 1, the radar system parameters and antenna coordinate information are as follows:

[0070] Table 1

[0071]

[0072]

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

[0074] Table 2

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

[0076] like Figure 8 and Figure 9 The diagram shows a comparison between the present invention and Matlab simulations. The backup method ensures that the estimated errors of the output azimuth and elevation angles are consistently controlled within ±2°. This error primarily stems from the quantization error introduced by the inverse trigonometric function calculations performed by the CORDIC IP core in the hardware implementation, as well as the accuracy loss due to numerical truncation. Figure 10 The time required to complete one angle measurement at a 200MHz clock cycle is demonstrated. With a 200MHz processing clock cycle, the processing time required to complete one full angle measurement process, from receiving the input phase difference signal to outputting the final angle result, is approximately 17µs. This shows that the present invention can efficiently and accurately achieve real-time calculation of the direction of arrival of a target wave.

[0077] The above description is merely a preferred embodiment of the present invention and should not be construed as limiting the scope of the present invention. All equivalent changes and modifications made in accordance with the scope of the patent application and the contents of the specification of the present invention should still fall within the scope of the patent of the present invention.

Claims

1. A real-time angle measurement method for FPGA-based eight-element uniform circular array three-dimensional baseline screening, characterized in that: Includes the following steps: Step S1: Calculate the phase difference between each pair of adjacent antennas based on the intermediate frequency echo signal received by the eight-element uniform circular array antenna. Step S2: Divide the eight-element uniform circular array antenna into four antenna combinations. Each antenna combination contains three antennas that are adjacent to each other. Process the four antenna combinations in parallel and calculate the ambiguity number to obtain the corresponding four first-level angle sets. Each first-level angle set is stored in the FPGA on-chip RAM unit. 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 large groups of two pairs. Process the two large groups in parallel. Within each large group, perform spatial distance error filtering on all angle pairs to obtain the set of all effective angle pairs of each antenna combination. Store the angle of arrival and elevation angle in the effective angle pairs in two RAM units respectively. Step S4: Combine the effective angle pairs of the four antenna combinations in pairs, evaluate the error of each pair of angle pairs, and select the pair of combinations with the smallest average error to obtain two final angle pairs. The azimuth and elevation angles are obtained from the two final angle pairs. Step S2 includes the following steps: Step S21: For the i'th antenna combination, obtain the baselines corresponding to two adjacent antennas in the antenna combination. and The maximum ambiguity numbers K1 and K2 of the two baselines are obtained based on the baseline length and the wavelength of the intermediate frequency echo signal, respectively. Thus, the ambiguity number ranges of the two baselines [-K1,K1] and [-K2,K2] are obtained, where 1≤i'≤4. Step S22: The fuzzy numbers of the two baselines are integers within their respective fuzzy number ranges. According to the baselines... The fuzzy number values ​​divide the defuzzification process into 2K1+1 parallel processing sub-units, each sub-unit corresponding to a unique fuzzy number value; Step S23: For the j-th sub-unit, its corresponding fuzzy number is taken as... When the baseline When the fuzzy number takes the value According to the formula Solve and The closed-form solution is obtained, and the j-th sub-unit and baseline are obtained based on p and q. When the fuzzy number takes the value Corresponding angle pair ( , ),in, and These represent the phase difference between two adjacent baselines. The wavelength of the intermediate frequency echo signal is (x) A ,y A ,z A ), (x B ,y B ,z B ) and (x C ,y C ,z C ) represent the spatial coordinates of the three antennas in the i'th antenna group. For the j-th sub-unit and baseline When the fuzzy number takes the value The corresponding azimuth angle, For the j-th sub-unit and baseline When the fuzzy number takes the value The corresponding pitch angle, , ; Step S24: Repeat step S23 to obtain the j-th sub-unit, then traverse the baseline. The angle pairs obtained by taking the values ​​of each fuzzy number are all placed in the i'th first-level angle set.

2. The real-time angle measurement method for eight-element uniform circular array three-dimensional baseline screening based on FPGA according to claim 1, characterized in that: Step S1 includes the following steps: Step S11: Synchronously sample 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 elements of the eight antennas respectively. Step S12: Perform FFT column-wise on the eight-channel two-dimensional echo matrix 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 of the frequency domain data corresponding to the i-th antenna at the target frequency point. With the imaginary part Using the CORDIC IP core of the FPGA according to the formula Calculate the phase value of the i-th antenna at the target frequency. ; Step S13: Subtract the phase values ​​of each pair of adjacent antennas to obtain the phase difference between each pair of adjacent antennas.

3. The real-time angle measurement method for eight-element uniform circular array three-dimensional baseline screening based on FPGA as described in claim 2, characterized in that: In step S11, the eight-channel two-dimensional echo matrix is ​​stored in the RAM cell of the FPGA.

4. The real-time angle measurement method for eight-element uniform circular array three-dimensional baseline screening based on FPGA according to claim 3, characterized in that: In step S23, complex numbers are defined. ,like Then discard the corresponding angle pair; otherwise, follow the formula. and The angle is correct ( , ).

5. The real-time angle measurement method for eight-element uniform circular array three-dimensional baseline screening based on FPGA according to claim 4, characterized in that: In step S3, for any large group, let an angle pair in the first-order angle set of an antenna combination in that large group be denoted as . One angle in the first-order angle set of another antenna combination is The spatial distance error between the two angle pairs can then be calculated using the formula. If spatial distance error If the distance is less than the preset threshold, the angle is considered correct. relative to angle If a pair of angles is considered a valid angle pair, then both angle pairs are discarded. , , , and These represent the spatial points (x, y) calculated based on the measured angles. i ,y i ,z i ) and (x j ,y j ,z j The radial distance of ).

6. The real-time angle measurement method for eight-element uniform circular array three-dimensional baseline screening based on FPGA according to claim 5, characterized in that: Step S4 includes the following steps: Step S41: From the effective angles of the four antenna combinations, arbitrarily select two sets from the set to form a combination, resulting in a total of Various combinations; Step S42: Calculate the average spatial distance error of all effective angle pairs in each combination, select the combination with the smallest average spatial distance error, and combine all effective angle pairs in the combination to obtain the final azimuth angle set and the final pitch angle set. Step S43: Quantize both the final azimuth and final elevation angle sets using 13 decimal places and output them in radians, and then apply the formula... and The calculated azimuth and elevation angles are obtained, where N is the number of elements in the final azimuth and elevation angle sets. The nth element in the final azimuth set It is the nth element in the final pitch angle set.

7. The real-time angle measurement method for eight-element uniform circular array three-dimensional baseline screening based on FPGA according to claim 4, characterized in that: In step S21, according to the formula Obtain the baseline The maximum blur number, where ceil represents rounding up and d1 represents the baseline. The length.

8. The real-time angle measurement method for eight-element uniform circular array three-dimensional baseline sieve based on FPGA according to claim 1, 2, or 3, characterized in that: In step S2, the eight-element 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. The fourth group is antenna F and antenna G, and antenna G and antenna H.

9. The real-time angle measurement method for eight-element uniform circular array three-dimensional baseline screening based on FPGA according to claim 4, characterized in that: In step S21, the baseline is determined by the spatial coordinates of two adjacent antennas.

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