A low, slow and small target high-precision interferometric measurement method based on a distributed phased array

Abstract

The application discloses a low, slow and small target high-precision interferometric measurement method based on distributed phased arrays, and belongs to the technical field of radar measurement. The method comprises the following steps: determining basic parameters of a system; calculating the angle measurement accuracy of each phased array antenna; calculating the baseline phase difference caused by the angle measurement error of a single phased array; determining the unambiguous baseline length; processing the received target signals by using two distributed phased arrays respectively to obtain target angle measurement results and phase information; calculating the phase difference of the two distributed phased arrays; calculating the carrier phase difference; and calculating the target angle according to the carrier phase difference. The method can realize unambiguous high-precision interferometric measurement only by using a single frequency point and a single baseline, and can be used for high-precision measurement of low, slow and small targets under the condition that the frequency point and the array size are limited.

Description

Technical Field

[0001] This invention relates to the field of radar measurement technology, specifically to a high-precision interferometric measurement method for low-speed, small targets based on a distributed phased array. Background Technology

[0002] With the rapid development and widespread application of UAV technology, the demand for high-precision measurement of low-altitude, slow-moving, and small targets such as UAVs is gradually increasing. Carrier phase interferometry, characterized by high angular accuracy and simple structure, has been widely used in radar detection and high-precision measurement fields. Its angular accuracy is proportional to the baseline length. Constructing an interferometric baseline based on a distributed phased array can effectively improve the measurement accuracy of low-altitude, slow-moving, and small targets. However, an excessively long baseline can lead to phase ambiguity, causing angular measurement errors. Therefore, it is necessary to rationally plan the baseline length and carrier frequency to achieve unambiguous, high-precision measurement.

[0003] Current research on high-precision interferometric measurement methods mainly includes two types: multi-frequency point deambiguity and staggered baseline deambiguity. Chinese Patent CN120314881A discloses a sparsely distributed dual-element multi-frequency deambiguity interferometric angle measurement method and system. This method first uses the Chinese remainder theorem to deduce the selection value of the unambiguous frequency, and then performs dual-frequency deambiguity angle measurement under the premise of unambiguity. This method requires the system to have the ability to transmit at multiple frequencies simultaneously and has high requirements for phase consistency between different frequency channels, making system implementation very difficult. Chinese Patent CN115598593A discloses a high-precision lateral positioning method, system, device, and terminal with equal-length short baselines. It forms staggered baselines of varying lengths by setting multiple receiving antennas at equal intervals, and then uses the proportional relationship between the phase differences of the received signals from multiple baselines to achieve deambiguity angle measurement. This method has high requirements for layout space and is not suitable for scenarios with limited array size and dimensions. Therefore, the existing technology lacks a low-speed, small target measurement technique suitable for scenarios with limited array size and requiring only a single-frequency channel. Summary of the Invention

[0004] The purpose of this invention is to address the aforementioned problems by providing a high-precision interferometric measurement method for low-speed, small targets based on a distributed phased array. This invention presents a method for calculating the unambiguous baseline length under the premise of determining the carrier frequency and the size of the distributed phased array. An initial angle is obtained through phased array angle measurement, and then unambiguous carrier phase interferometric angle measurement is performed on a single baseline and single frequency point.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] A high-precision interferometric measurement method for small, slow targets based on a distributed phased array includes the following steps:

[0007] Step 1: Determine the basic system parameters, including the carrier frequency f. c The range of values ​​for phased array antenna aperture L and baseline length of distributed phased array is Dmin~Dmax;

[0008] Step 2: Calculate the angular measurement accuracy of each phased array antenna;

[0009] Step 3: Calculate the baseline phase difference dΦ caused by the angle measurement error of a single phased array;

[0010] Step 4: Use dΦ_max-dΦ_min<2π as the criterion for determining that no phase blurring has occurred, and determine the length D of the unblurred baseline, where dΦ_max and dΦ_min represent the maximum and minimum values ​​of the baseline phase difference under the same baseline length, respectively.

[0011] Step 5: The received target signal is processed by two distributed phased arrays to obtain the target angle measurement result θ. m And phase information Φ1, Φ2, where θ m Φ1 and Φ2 are the average values ​​of the angle measurement results of the two distributed phased arrays, respectively, and are the target phase information of the two distributed phased arrays.

[0012] Step 6, based on θ m Calculate the phase difference dΦ_m between two distributed phased arrays:

[0013] dΦ_m = 2π•f c •D•sin(θ m ) / c = 2πk+dφ_m

[0014] Where c is the speed of light, k is the number of integer phase cycles, and dφ_m is the measured phase difference after removing integer cycles;

[0015] Step 7: Using the target phase information Φ1, Φ2 of the two distributed phased arrays and the number of unambiguous phase integer cycles k, calculate the carrier phase difference dΦ_g:

[0016] dΦ_g = 2πk+Φ1-Φ2;

[0017] Step 8: Calculate the target angle θ based on the carrier phase difference dΦ_g. g :

[0018] θ g = asin(dΦ_g•c / 2πf c D).

[0019] Furthermore, in step 2, the sum-difference beam angular measurement method is used for a single phased array antenna, and the formula for calculating the angular measurement accuracy is:

[0020] σ = θ3dB / 10

[0021] Where σ represents the angle measurement accuracy, θ 3dB This indicates the 3dB beamwidth of the array antenna.

[0022] Compared with the prior art, the present invention has the following advantages:

[0023] 1. Compared with existing high-precision interferometric measurement methods for low-speed, small targets, this invention does not require the system to have the ability to transmit and receive at multiple frequencies simultaneously. In one-dimensional measurement, only two distributed phased arrays are set up, and multiple interferometric measurement baselines do not need to be constructed.

[0024] 2. This invention only requires a single frequency point and a single baseline to achieve unambiguous high-precision interferometric measurement, and can be used for high-precision measurement of low, slow and small targets under conditions where frequency point and array size are limited. Attached Figure Description

[0025] Figure 1 This is the root mean square error diagram of the angle measurement simulation results in this embodiment of the invention. Detailed Implementation

[0026] The specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0027] A high-precision interferometric measurement method for small, slow targets based on a distributed phased array includes the following steps:

[0028] Step 1: Determine the basic system parameters, including the carrier frequency f. c The selectable range of phased array antenna aperture L and distributed phased array center spacing (i.e., baseline length D) is Dmin to Dmax.

[0029] In the embodiment, the system carrier frequency is determined to be 16.5 GHz; the system baseline length is determined to be selectable within the range of 1~2 m; each distributed phased array is determined to have 2304 array elements, the azimuth and elevation spacing of the array elements is 9.2 mm, the array elements are arranged in a 48*48 pattern, and the array antenna aperture L=432.4 mm.

[0030] Step 2: Calculate the angle measurement accuracy of each phased array antenna. A typical sum-difference beamforming method is used for the angle measurement accuracy of a single phased array antenna. The commonly used empirical formula for its angle measurement accuracy is:

[0031] σ = θ 3dB / 10,

[0032] Where σ represents the angle measurement accuracy, θ 3dB This indicates the 3dB beamwidth of the array antenna.

[0033] In this embodiment, the 3dB beamwidth of each distributed phased array is measured as follows:

[0034] θ 3dB = 2.1173°

[0035] The angular measurement accuracy of a distributed phased array is calculated as follows:

[0036] σ = θ 3dB / 10 = 0.21173°.

[0037] Step 3: Calculate the phase difference caused by the angle measurement error of a single phased array. Assuming the target is located at angle θ0, the measurement result range caused by the measurement error of a single array is [θ0-σ / 2, θ0+σ / 2]. Calculate the baseline phase difference dΦ when the measurement result is within this range and the baseline length is between Dmin and Dmax.

[0038] In this embodiment, it is assumed that the target is located at an angle of 60°, and the measurement result range due to the measurement error of a single array is [60-0.1059, 60+0.1059].

[0039] Set the baseline length in the range of 1~2m with a step value of 0.1m, and set the angle in the range of [60-0.1059, 60+0.1059] with a step value of 0.0001°.

[0040] Calculate the baseline phase difference for each baseline length in the range [60-0.1059, 60+0.1059], where the nth baseline length D is... n At the m-th angle θ m Baseline phase difference dΦ_D nm The calculation formula is:

[0041] dΦ_D nm = 2πf c D n sin(θ m ) / c

[0042] Step 4: Calculate the unambiguous baseline length. Use dΦ_max - dΦ_min < 2π as the criterion to determine whether phase ambiguity has occurred. Here, dΦ_max and dΦ_min represent the maximum and minimum values ​​of the baseline phase difference for the same baseline length, respectively.

[0043] In the embodiment, it was calculated that when the baseline length is 1.3m, the difference between the maximum and minimum phase difference within the angle variation range of [60-0.1059, 60+0.1059] is 0.8278, which satisfies the criterion of dΦ_max-dΦ_min<2π, and the baseline length is determined to be 1.3m.

[0044] Step 5: Dual-array target measurement. After determining the unambiguous baseline length D, the two distributed phased arrays process the received target signals to obtain the target angle measurement result θ. m And phase information Φ1, Φ2, where θ m Φ1 and Φ2 represent the average angle measurement results of the two distributed phased arrays, respectively, and are the target phase information of the two distributed phased arrays.

[0045] Step 6: Calculate the phase difference. Given the measurement result θ... m According to the measurement result θ m The phase difference between the two distributed phased arrays is calculated as follows:

[0046] dΦ_m = 2πf c Dsin(θ m ) / c = 2πk+dφ_m,

[0047] Where c is the speed of light, k is the number of integer phase cycles, and dφ_m is the measured phase difference after removing integer cycles.

[0048] Step 7: Solve for the high-precision, unambiguous phase difference. Using the target phase information Φ1, Φ2 of each distributed phased array and the number of unambiguous phase integer cycles k, calculate the carrier phase difference:

[0049] dΦ_g = 2πk+dφ_g,

[0050] Where dφ_g = Φ1-Φ2.

[0051] Step 8: Calculate the target angle. Calculate the target angle based on the carrier phase difference dΦ_g:

[0052] θ g = asin(dΦ_g*c / 2πf c D).

[0053] Thus, high-precision interferometry for low-speed, small targets based on distributed phased arrays was completed.

[0054] Multiple simulation experiments were conducted under different signal-to-noise ratios, and the angle measurement error of this method was statistically obtained as follows: Figure 1 As shown. From Figure 1 It can be seen that this method has high accuracy.

[0055] This method only requires a single frequency point and a single baseline to achieve unambiguous high-precision interferometric measurement, and can be used for high-precision measurement of low, slow and small targets under conditions where frequency point and array size are limited.

Claims

1. A high-precision interferometric measurement method for low-speed, small targets based on a distributed phased array, characterized in that, Includes the following steps: Step 1: Determine the basic system parameters, including the carrier frequency. f c Phased array antenna aperture L The range of values ​​for the baseline length of a distributed phased array Dmin ~ Dmax ; Step 2: Calculate the angle measurement accuracy of each phased array antenna; Step 3: Calculate the baseline phase difference caused by the angle measurement error of a single phased array. dΦ The specific method is as follows: Determine the range of measurement results [θ0-σ / 2, θ0+σ / 2] caused by the angle measurement error of a single phased array, where θ0 is the assumed angle of the target and σ is the angle measurement accuracy; Calculate the baseline phase difference for each baseline length within the range [θ0-σ / 2, θ0+σ / 2], and the nth baseline length. D n At the m-th angle θ m Baseline phase difference dΦ_D nm The calculation formula is: dΦ_D nm = 2π f c D n sin ( θ m ) / c ； Step 4, dΦ_max - dΦ_min <2 π As a criterion for determining the absence of phase ambiguity, the length of the unambiguous baseline is determined. D ,in, dΦ_max and dΦ_min These represent the maximum and minimum values ​​of the baseline phase difference for the same baseline length, respectively. Step 5: The received target signal is processed by two distributed phased arrays to obtain the target angle measurement result. θ m and phase information Φ 1. Φ 2, of which, θ m This is the average of the angle measurement results from two distributed phased arrays. Φ 1. Φ 2 represents the target phase information of two distributed phased arrays; Step 6, according to θ m Calculate the phase difference between two distributed phased arrays dΦ_m : dΦ_m = 2 π • f c • D • sin ( θ m ) / c = 2 πk + dφ_m in, c At the speed of light, k The number of integer cycles in the phase. dφ_m To remove the measurement phase difference after integer cycles; Step 7: Utilize the target phase information from the two distributed phased arrays Φ 1. Φ 2 and unambiguous phase integer number of cycles k Calculate carrier phase difference dΦ_g : dΦ_g = 2 πk + Φ 1- Φ 2； Step 8, based on carrier phase difference dΦ_g Calculate the target angle θ g : θ g = asin ( dΦ_g • c / 2 πf c D )。 2. The high-precision interferometric measurement method for low-speed, small targets based on a distributed phased array according to claim 1, characterized in that, In step 2, the sum-difference beam angular measurement method is used for a single phased array antenna. The formula for calculating the angular measurement accuracy is: σ = θ 3dB / 10 in, σ Indicates the accuracy of angle measurement. θ 3dB This indicates the 3dB beamwidth of the array antenna.

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