CN110988835A - Distributed coherent radar angle measurement method - Google Patents

Distributed coherent radar angle measurement method Download PDF

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CN110988835A
CN110988835A CN201911181172.2A CN201911181172A CN110988835A CN 110988835 A CN110988835 A CN 110988835A CN 201911181172 A CN201911181172 A CN 201911181172A CN 110988835 A CN110988835 A CN 110988835A
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涂刚毅
王雪琦
吴少鹏
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724th Research Institute of CSIC
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
    • G01S7/02—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S13/00
    • G01S7/41—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S13/00 using analysis of echo signal for target characterisation; Target signature; Target cross-section
    • G01S7/411—Identification of targets based on measurements of radar reflectivity

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Abstract

The invention relates to a distributed coherent radar angle measurement method. Aiming at the problem of angle measurement ambiguity caused by grating lobe influence of beams of a distributed array, angle is measured with high precision and ambiguity is resolved by adopting a plurality of array combination methods. The method comprises the following specific steps: 1) forming array element level wave beams; 2) forming a sub-array level beam; 3) estimating a fuzzy angle; 4) a combinatorial array DBF; 5) combining the array angle estimates; 6) and (5) deblurring processing. The method can perform deblurring processing on the monopulse phase comparison measured angle to obtain a high-precision unambiguous angle estimation value.

Description

Distributed coherent radar angle measurement method
Technical Field
The invention relates to the technical field of sparse array angle measurement.
Background
In recent years, with the continuous expansion of application fields and the continuous deepening of application levels, the large-aperture radar is limited by the defects of poor maneuverability, low efficiency-cost ratio and the like, and is difficult to meet the requirements of modern battlefield battle. The lincoln laboratory proposed the concept of distributed coherent radar in 2003 and used it as the direction of the next generation ballistic missile defense system. The core idea of the method is to perform signal coherent fusion by small and distributed radars or array antennas so as to realize the detection performance of a large-aperture radar. Distributed coherent radar is a crystal with the idea of "breaking up the whole into parts". Compared with a large-aperture radar, the distributed coherent radar can realize quick movement, change the position in time and has strong viability. Meanwhile, the distributed coherent radar has the characteristics of easiness in maintenance and expansion, can be deployed at primary site or at front edge, and is flexible and diverse in battle forms.
Target positioning and angle measurement are important research directions as one of the basic functions of radar systems. Due to the dispersed arrangement of the array, the angle measurement of the distributed coherent radar can be regarded as a sparse array angle measurement problem. The distributed coherent radar forms virtual apertures through array sparse distribution, the equivalent aperture is larger than the sum of the radar apertures of all units, the synthetic beam is narrowed, and the angular resolution of the radar can be improved. But simultaneously, because of the sparse distribution, the wave beam can generate a grating lobe phenomenon, so that the problem of angle measurement ambiguity is easy to occur. Therefore, high precision unambiguous angle measurement is an important issue to be solved.
Disclosure of Invention
The invention aims to overcome the defects of fuzzy and low precision of the angle measurement of the one-dimensional distributed coherent array, and the fuzzy high-precision angle estimation value is obtained by carrying out various combinations and divisions on the array and carrying out comprehensive processing on the calculation results of various combination modes.
In order to realize the aim of the invention, the invention provides a distributed coherent radar angle measurement method, which comprises the following steps:
s1 array element level beam forming: taking array elements as units, and performing receiving beam forming processing in each subarray (unit radar);
s2 sub-array level beamforming: dividing the subarray to form two subarray division modes with different forms, and then performing beam forming calculation and beam and difference beam by taking the subarray as a unit;
s3 blur angle estimation: calculating sum-difference beam ratios, and obtaining a plurality of fuzzy angle estimation values according to corresponding numerical relationships;
s4 combined array beamforming: carrying out array element level recombination on the distributed arrays to form two identical sub-arrays, wherein the sub-array distance meets the non-fuzzy angle estimation, and respectively carrying out beam forming on the two sub-arrays;
s5 combined array goniometry: calculating a sum-difference beam ratio, and obtaining an angle estimation value of the combined array according to a corresponding numerical relationship;
s6 deblurring process: and carrying out deblurring processing on the angle values obtained by estimation under the three conditions to obtain the high-precision unambiguous angle estimation value.
The implementation process and the information processing flow of the invention are shown in fig. 2.
By adopting the method, the distributed array is subjected to various combinations to form the subarray, the angle measurement blur caused by sparse distribution can be eliminated, and meanwhile, the high-precision estimation of the angle of the target is realized.
Drawings
FIG. 1: one-dimensional distributed linear array structure chart. Wherein: the distributed linear array structure comprises N subarrays, each array comprises M array elements, the spacing between the array elements is D, and the spacing between the subarrays is D.
FIG. 2: a flow chart for processing high-precision angle measurement information of the distributed coherent radar. Wherein: the S1-S6 in the figure correspond to the S1-S6 processes, respectively, as described in the summary of the invention.
FIG. 3: schematic diagram of the sub-array combination mode. Wherein: in the figure (a), the sub-arrays in the dotted line frame form a combined sub-array 1, and the sub-arrays in the solid line frame form a combined sub-array 2; in the figure (b), the sub-arrays in the dotted line frame form a combined sub-array 3, and the sub-arrays in the solid line frame form a combined sub-array 4; in fig. c, the array elements connected by the dotted lines constitute a combined sub-array 5, and the array elements connected by the solid lines constitute a combined sub-array 6.
Detailed Description
The implementation process and information processing of the present invention are shown in fig. 2, and are specifically described as the following processes:
s1 array element level beam forming: the one-dimensional distributed linear array structure is shown in fig. 1, the number of sub-arrays is N, each sub-array is a uniform linear array composed of M array elements, M and N are even numbers, the array element spacing D in the sub-array is lambda/2, the sub-array spacing is D, and the target incident angle is theta0. In the receiving coherent mode, all transmitting units transmit the same signal and realize in-phase superposition at a target. Assuming that the signal envelope after reflection by the target can be denoted as a (t), let us say the delay τ from the target to the M (M1, 2.., M) th array element in the receiving subarray (unit radar) N (N1, 2.., N)nmCan be expressed as:
Figure BDA0002291300880000021
wherein r is11Representing the first sub-arrayThe element delay, c, represents the electromagnetic wave propagation velocity.
The m-th array element in the subarray n receives a signal a (t-tau)nm)exp(j2πfct-τnm) In the case of narrow band signals, the delays of all array elements in the subarray are approximately equal, so let τ benm＝τnTherefore, the received signal after down-conversion can be expressed as:
snm(t)＝a(t-τn)exp(-j2πfcτnm) (2)；
thus, the subarray n received signal may be expressed as:
Xn＝[xn1xn2…xnm]T＝Asn1+nn(3)；
where a ═ 1exp (j γ) … exp (j (M-1) γ)]T，γ＝2πdsinθ0/λ，nn＝[nn1nn2… nnm]TRepresenting an additive noise signal, sn1(t)＝a(t-τn)exp(-j2πτn1) Representing the received signal of array element 1.
Receiving signals by weight vector W for all array elements of sub-array nn＝[1exp(-jα)…exp(-j(M-1)α)]α ═ 2 π dsin θ/λ, for beamforming:
Xn(t)＝WnXn(4)；
nn(t) represents the noise signal after processing. For all Xn(t) time delay and phase adjustment are carried out, and coherent fusion is carried out to realize N3Signal to noise ratio gain. The method mainly aims at angle measurement and does not excessively express the coherent synthesis part.
S2 sub-array level beamforming: according to the time delay difference estimated in the receiving coherent mode to all Xn(t) performing time compensation processing, namely:
Figure BDA0002291300880000031
assuming that the delay difference estimation is accurate, all the sub-array received signals after the delay compensation can be expressed as:
X＝BX1(t) (6)；
wherein, B ═ 1exp (j β) … exp (j (N-1) β)]T，β＝2πDsinθ0/λ。
The array is divided into two different combinations. Combining one as shown in fig. 3(a), the array is divided into two parts according to geometric shape, sub-array 1-N/2 is marked as combined sub-array 1, sub-array N/2+1-N is marked as combined sub-array 2, and phase center distance d between combined sub-array 1 and combined sub-array 21ND/2. Referring to FIG. 3(b) of the second combination, subarrays 1-N-1 are denoted as combined subarray 3, subarrays 2-N are denoted as combined subarray 4, and the distance between combined subarray 3 and combined subarray 4 is d2D. The sum and difference beams for the two combinations are calculated separately as follows:
FΔ1＝Wco1Xco1-Wco2Xco2(7)；
FΣ1＝Wco1Xco1+Wco2Xco2(8)；
FΔ2＝Wco3Xco3-Wco4Xco4(9)；
FΣ2＝Wco3Xco3+Wco4Xco4(10)；
wherein the content of the first and second substances,
Xco1＝[X1(t) X2(t) … XN/2(t)](11)；
Xco2＝[XN/2+1(t) XN/2+2(t) … XN(t)]T(12)；
Xco3＝[X1(t) X2(t) … XN-1(t)]T(13)；
Xco4＝[X2(t) X3(t) … XN(t)]T(14)；
Wco1＝[1exp(-jκ)…exp(-j(N/2-1)κ)](15)；
Wco2＝[exp(-j(N/2)κ)exp(-j(N/2)κ+1)…exp(-j(N-1)κ)](16)；
Wco3＝[1exp(-jκ)…exp(-j(N-2)κ)](17)；
Wco4＝[exp(-jκ)exp(-j2κ)…exp(-j(N-1)κ)](18)；
s3 blur angle estimation: two combination and difference beam ratios are calculated as follows:
Figure BDA0002291300880000041
Figure BDA0002291300880000042
according to the principle of single-pulse phase comparison angle measurement, the angle estimation value is obtained as follows:
Figure BDA0002291300880000043
Figure BDA0002291300880000044
the phase centers are spaced apart by a large distance, so that highly accurate angle estimation can be obtained, but ambiguity in angle estimation is also brought about.
S4 combined array beamforming: recombining all array elements to obtain the combined subarray 5 shown in fig. 3(c), combining the odd array elements in all the subarrays, using all the even array elements as the combined subarray 6, and making the phase center spacing between the combined subarray 5 and the combined subarray 6 equal to the array element spacing, i.e. d3D. Its sum beam and the above calculated sum beam FΣ1The same, no duplicate calculations are required. Calculating its difference beam:
FΔ3＝Wco5Xco5-Wco6Xco6(23)；
wherein the content of the first and second substances,
Xco5＝[x11(t) x13(t) … xN(M-1)(t)]T(24)；
Xco6＝[x12(t) x14(t) … xNM(t)]T(25)；
Wco5＝{1exp(-j2α)…exp{-j[(N-1)κ+(M-2)α)]} (26)；
Wco6＝{exp(-jα)exp(-j3α)…exp{-j[(N-1)κ+(M-1)α)]} (27)；
s5 combined array goniometry: calculating sum and difference beam ratios:
Figure BDA0002291300880000045
according to the principle of monopulse phase comparison angle measurement, the angle estimation value is obtained as follows
Figure BDA0002291300880000046
Because the distance between the combined subarrays does not exceed half wavelength, angle measurement blurring can not be generated, but the angle measurement angle is low and cannot be directly used as an estimation result.
S6 deblurring process: and integrating the angle estimation values to carry out angle measurement and fuzzy solution processing. According to the principle of single pulse angle measurement, the larger the sub-array distance is, the higher the angle measurement precision is, and the more serious the angle measurement ambiguity problem is, therefore,
Figure BDA0002291300880000051
degree of ambiguity greater than
Figure BDA0002291300880000052
So as to firstly align
Figure BDA0002291300880000053
Carrying out deblurring treatment:
Figure BDA0002291300880000054
then, carrying out deblurring to obtain a non-fuzzy high-precision angle estimation value:
Figure BDA0002291300880000055

Claims (4)

1. a distributed coherent radar angle measurement method is characterized in that:
1) array element level beam forming: taking array elements as units, and performing receiving beam forming processing in each subarray;
2) sub-array level beam forming: dividing the subarray to form two subarray division modes with different forms, and then performing beam forming calculation and beam and difference beam by taking the subarray as a unit;
3) fuzzy angle estimation: calculating sum-difference beam ratios, and obtaining a plurality of fuzzy angle estimation values according to corresponding numerical relationships;
4) combined array beamforming: carrying out array element level recombination on the distributed arrays to form two identical sub-arrays, wherein the sub-array distance meets the non-fuzzy angle estimation, and respectively carrying out beam forming on the two sub-arrays;
5) and (3) combined array angle measurement: calculating a sum-difference beam ratio, and obtaining an angle estimation value of the combined array according to a corresponding numerical relationship;
6) and (3) deblurring processing: and carrying out deblurring processing on the angle values obtained by estimation under the three conditions to obtain the high-precision unambiguous angle estimation value.
2. The distributed coherent radar angle measurement method according to claim 1, wherein: the subarray level beamforming: and performing time delay compensation on the receiving beams of each subarray according to the coherent parameter estimation values, dividing and combining the subarrays to form two subarray division modes with different fuzziness, and respectively calculating sum beams and difference beams of the two combination modes.
3. The distributed coherent radar angle measurement method according to claim 2, wherein: the combined array beamforming is to: and recombining the distributed arrays, dividing and combining all array elements according to odd numbers and even numbers to form two identical sub-arrays, wherein the distance between the combined sub-arrays meets the fuzzy-free angle estimation, and respectively performing beam forming on the two sub-arrays.
4. A distributed coherent radar angle measurement method according to claim 3, characterized in that: the deblurring processing comprises the following steps: firstly, the fuzzy-free angle estimation value is used for carrying out the fuzzy resolving treatment on the angle estimation value with low fuzzy degree, and then the obtained angle estimation value is used for carrying out the fuzzy resolving treatment on the angle estimation value with high fuzzy degree, so that the high-precision fuzzy-free angle estimation is realized.
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CN113917425A (en) * 2021-09-30 2022-01-11 中国船舶重工集团公司第七二四研究所 Cylindrical surface phased array radar angle measurement method

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