CN107576953B - Coherent and incoherent mixed target DOA estimation method based on co-prime MIMO array - Google Patents
Coherent and incoherent mixed target DOA estimation method based on co-prime MIMO array Download PDFInfo
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Abstract
The invention discloses a coherent and incoherent mixed target DOA estimation method based on a co-prime MIMO array, which constructs a uniformly and densely distributed virtual MIMO array comprising a greater number of transmitting array elements and receiving array elements compared with an actual sparse co-prime MIMO array, and utilizes the obtained equivalent multi-snapshot data of the virtual MIMO array to perform DOA estimation, thereby solving the problem of coherent and incoherent mixed target DOA estimation and breaking through the limitation of the actual array element number of the co-prime MIMO array on the maximum distinguishable target number. The invention can also obtain the virtual MIMO array with different numbers of transmitting and receiving array elements, corresponding to different maximum distinguishable coherent target numbers and maximum distinguishable coherent and incoherent target total numbers, and meets the requirements of different scenes on coherent and incoherent target DOA estimation by flexibly selecting the number of the transmitting and receiving array elements of the virtual MIMO array, thereby improving the DOA estimation flexibility.
Description
Technical Field
The invention relates to a signal processing method, in particular to a coherent and incoherent mixed object DOA estimation method based on a co-prime MIMO array.
Background
Based on space-time sampling of a sensor array, azimuth position information of a plurality of space targets can be determined by direction of arrival (DOA) estimation, the method has high resolution, and is widely applied to the fields of communication, radar, sonar, seismic sensing and the like. For a fully-received array with adjacent array elements evenly spaced at half-wavelength intervals, the maximum resolvable number of incoherent objects is limited by the number of actual array elements. In order to break through the limitation of resolution number, a sparse receiving array with the adjacent array element spacing larger than half wavelength is used for designing a non-coherent target DOA estimation method, and commonly used sparse receiving arrays comprise a minimum redundant array, a minimum hole array, a nested array and a co-prime array, wherein the co-prime array proposed in recent years has outstanding advantages in the aspects of array element position determination, adjacent array element coupling mutual interference and the like, and gradually becomes a focus. At present, a mutual-prime receiving array-based incoherent target DOA estimation method mainly utilizes the characteristic that corresponding 'difference synergistic array' virtual array elements are uniformly distributed at a half-wavelength interval, and related elements are rearranged to construct 'difference synergistic array' equivalent single snapshot data, so that the DOA estimation of an incoherent target is realized. Because the number of the virtual array elements of the 'difference cooperative array' is greater than the number of the actual array elements of the co-prime array, the DOA estimation of the incoherent target with more than the actual array elements can be realized by using the 'difference cooperative array'.
However, in the above DOA estimation method based on the "difference synergistic array", the equivalent single snapshot signal used is derived from the relevant elements obtained after the actual multi-snapshot signal is correlated, and if there are multiple coherent targets, cross terms between the targets will be generated when the correlation is solved, so that a false target exists in the DOA estimation result, and therefore, the above method is not suitable for the case where coherent targets exist, that is, the DOA estimation of the coherent targets cannot be realized. Considering a multiple-input multiple-output (MIMO) array, the DOA estimation of coherent and incoherent mixed targets is easy to implement, and the traditional method requires that a transmitting array and a receiving array are generally uniformly and densely distributed arrays, and the interval between adjacent array elements is half wavelength. At this time, the total number of the maximum resolvable coherent and incoherent objects is limited by the number of the receiving array elements, which is equal to the number of the receiving array elements minus 1, and the number of the coherent objects is limited by the number of the transmitting array elements, which is equal to the number of the transmitting array elements. The invention introduces sparse co-prime layout into the MIMO array, on one hand, the DOA estimation of coherent and non-coherent mixed targets is realized by utilizing the characteristics of the MIMO array, on the other hand, the maximum distinguishable target number is increased by utilizing the sparse transmitting and receiving array layout, and the limitation of the receiving array element number and the transmitting array element number to the maximum distinguishable target total number and the maximum distinguishable coherent target number is broken through. The invention has important value for improving the target capturing capability of radar and sonar and improving the capacity of a communication channel.
Disclosure of Invention
The invention aims to provide a coherent and incoherent mixed target DOA estimation method based on a co-prime MIMO array, which solves the problem of coherent and incoherent mixed target DOA estimation on the one hand, and breaks through the limitation of the actual array element number of the MIMO array to the maximum distinguishable target number by utilizing the sparse characteristic of the co-prime layout and the uniform dense distribution characteristic of the 'and cooperative array' on the other hand.
In order to achieve the purpose, the technical scheme adopted by the invention is as follows: a coherent and incoherent mixed object DOA estimation method based on a co-prime MIMO array comprises the following steps:
(1) selecting an area, and arranging N transmitting array elements and 2M-1 receiving array elements according to a mutual-prime layout to form a mutual-prime MIMO array, wherein M is less than N, the transmitting array elements and the receiving array elements are positioned on the same straight line, and the positions of the N transmitting array elements are Pt{ Mnd; n is 0,1, …, N-1, and the positions of 2M-1 receiving antennas are Pr-Nmd; m is 1,2, …,2M-1, d is the basic spacing of half wavelength;
(2) n transmitting array elements sequentially transmit electromagnetic wave signals with the frequency of c/2d to carry out far-field target detection, wherein c is the light speed, if a target is detected, the electromagnetic wave signals are scattered and then returned, the returned echo signals are simultaneously received by 2M-1 receiving array elements to obtain echo signals of (2M-1) multiplied by N receiving and transmitting channels, and the echo signals of each channel are respectively subjected to K times of sampling to generate K times of snapshot data;
(3) adding the positions of N transmitting array elements and the positions of 2M-1 receiving array elements in sequence, obtaining a virtual array element once every addition, forming a virtual array formed by the virtual array elements, and recording the virtual array element as a co-prime MIMO array and a co-pilot array, wherein the positions of the virtual array elements are as follows:
S＝{Mnd+Nmd；n＝0,1,…,N-1；m＝1,2,…,2M-1} (1)
(4) extracting middle uniformly distributed virtual array elements from the sum cooperative array to form a reference sum cooperative array, wherein the uniformly distributed virtual array elements are MN + M-1 virtual array elements which are uniformly distributed in the interval from (MN-M +1) d to (2MN-1) d at an interval d;
(5) constructing a uniformly-densely distributed virtual MIMO array comprising A virtual transmitting array elements and B virtual receiving array elements based on the reference and cooperative arrays,the positions of A virtual transmitting array elements are Pv,t＝{(xt+ i) d; i is 1,2, …, A, and the positions of B virtual receiving array elements are Pv,r＝{(xr+ j) d; j ═ 1,2, …, B }, while satisfying:
wherein xtAnd xrIs an arbitrary real number, and xt-xr＝MN-M-1；
(6) Sequentially forming a virtual transceiving channel by the ith virtual transmitting array element and the jth virtual receiving array element to obtain (x)t+i)+(xr+ j) using the position and value as reference, searching a virtual array element corresponding to the value from the reference and cooperative array, searching a transceiving channel for generating the virtual array element from the co-prime MIMO array, and using K pieces of snapshot data of the transceiving channel as equivalent snapshot data of the virtual transceiving channel; finally forming a B multiplied by A multiplied by K three-dimensional data matrix XV;
(7) obtaining a two-dimensional correlation matrix Rv with dimension B multiplied by B by solving a time average mode for the K snapshot data for the XV, namely:
wherein the superscript H represents the pair matrix XvTranspose conjugate operation of (k);
(8) and aiming at a correlation matrix Rv with dimension B multiplied by B, calculating a spatial spectrum containing a target DOA estimated value according to a MUSIC subspace DOA estimation algorithm.
Preferably, the method comprises the following steps: in the step (5), the number and the position of the virtual transceiving array elements can be determined by the following formula (4),
wherein, b is any real number, and the position of the virtual transceiving array element can be represented as:
preferably, the method comprises the following steps: in the step (5), A is less than B.
In the invention, N transmitting array elements and 2M-1 receiving array elements of the co-prime MIMO array in the first step are all sparsely arranged at a distance exceeding a half wavelength (basic distance d), while A transmitting array elements and B receiving array elements of the virtual MIMO array in the fifth step are all densely arranged at a distance equal to the half wavelength, and under the premise of 'being equivalent to a cooperative array', the total number of the virtual array elements is greater than the total number of the actual array elements, namely (A + B) > (N + 2M-1). Therefore, it is easy to obtain A > N and B > 2M-1 simultaneously, i.e. the number of virtual transmitting array elements is larger than the number of actual transmitting array elements, while the number of virtual receiving array elements is larger than the number of actual receiving array elements. Since the number of virtual array elements determines the maximum number of resolvable targets, the use of virtual array elements more than the actual number of array elements can achieve the limitation that the total number of maximum resolvable coherent and incoherent targets exceeds the number of receiving array elements, wherein the maximum resolvable coherent target number breaks through the limitation of the actual number of transmitting array elements of the co-prime MIMO array.
The 'and cooperative array' corresponding to the co-prime MIMO array in the third step can be divided into three parts, wherein the middle uniform part comprises MN + M-1 virtual array elements which are uniformly distributed in the interval from (MN-M +1) d to (2MN-1) d at the interval d, and the two end non-uniform parts comprise relatively less MN-M-N +1 virtual array elements which are non-uniformly distributed in the interval from Nd to (MN-M-1) d and from (2MN +1) d to (3 MN-M-N) d. In order to construct the virtual MIMO array in the step five, only MN + M-1 virtual array elements in the middle uniform part are selected as a reference and cooperative array in the step four.
Based on the virtual MIMO array constructed in the fifth step, the maximum resolvable target number is limited by the virtual receiving array element number, namely the maximum resolvable B-1 coherent and incoherent mixed targets are resolved; of the B-1 targets, the maximum resolvable coherent target number is limited by the virtual transmit array element number, i.e., at most A coherent targets are resolvable. In order to ensure that the degrees of freedom provided by the virtual MIMO array can be fully used for DOA estimation of coherent and incoherent mixed targets, A < B is required to be satisfied.
And: in the fifth step, the number a of virtual transmitting array elements and the number B of virtual receiving array elements of the virtual MIMO array are any two positive integers satisfying a + B ═ MN + M, and there are various different combinations of values, that is, the virtual MIMO array with different numbers of transmitting and receiving array elements can be obtained, and the number of the maximum resolvable coherent targets and the total number of the maximum resolvable coherent and incoherent targets correspond to the different numbers of the maximum resolvable coherent targets and the total number of the maximum resolvable coherent and incoherent targets, where the larger the number B of the virtual receiving array elements is, the smaller the number a of the virtual transmitting array elements is, the larger the total number of the resolvable coherent and incoherent targets is, but the smaller the number B of the resolvable coherent and incoherent targets is, the larger the smaller the total number of the resolvable coherent and incoherent targets is, but the larger the. Therefore, the number of the transmitting and receiving array elements of the virtual MIMO array can be flexibly selected to meet the requirements of different scenes on the DOA estimation of coherent and incoherent mixed targets.
On one hand, when the number a of the virtual transmitting array elements is 1, the number of the virtual receiving array elements reaches the maximum value B, MN + M-1, at this time, the DOA of the coherent target cannot be estimated, but the DOA estimation capability of the incoherent target reaches the maximum value, and at most MN + M-2 incoherent targets can be estimated (resolved); on the other hand, when the number of virtual array elements MN + M-1 of the "reference and cooperative array" in step four is an even number and B is a +1, i.e., a is (MN + M-1)/2 and B is (MN + M +1)/2, the DOA estimation capability for coherent targets reaches the maximum value, but the total number of resolvable targets reaches the minimum value, i.e., the maximum number of resolvable targets is B-1, and the maximum number is B-1 coherent targets.
Compared with the prior art, the invention has the advantages that: the invention introduces the co-prime layout into the MIMO array, utilizes the sparse characteristic of the co-prime layout and the uniform dense distribution characteristic of the 'and cooperative array' and is based on the basic idea of the 'and cooperative array' equivalence to construct the uniformly dense virtual MIMO array which has the same 'and cooperative array' with the sparse co-prime MIMO array, compared with the actual co-prime MIMO array, the virtual MIMO array has more transmitting array elements and receiving array elements, therefore, the invention obtains the equivalent multi-snapshot data of the virtual MIMO array and then carries out DOA estimation, can solve the problem of coherent and incoherent mixed target DOA estimation, can break through the limitation of the actual array element number of the co-prime MIMO array to the maximum distinguishable target number, since the number of receiving array elements limits the total number of maximum resolvable coherent and incoherent objects, the number of transmitting array elements limits the maximum resolvable number of coherent objects therein. In addition, the invention can obtain the virtual MIMO array with different numbers of transmitting and receiving array elements, and the virtual MIMO array corresponds to different maximum distinguishable coherent target numbers and maximum distinguishable coherent and incoherent target total numbers, therefore, the invention improves the DOA estimation flexibility, and can meet the requirements of different scenes on coherent and incoherent mixed target DOA estimation by flexibly selecting the number of the transmitting and receiving array elements of the virtual MIMO array.
Drawings
FIG. 1 is a schematic diagram of the test of the present invention;
fig. 2 is a schematic diagram of a co-prime MIMO array, a "sum cooperative array" and a corresponding virtual MIMO array of M-3 and N-4;
FIG. 3 is a DOA estimation result when the number of spatial objects is 9 and 5 coherent objects are included;
fig. 4 shows the DOA estimation results when the number of spatial objects is 8 and 6 coherent objects are included.
Detailed Description
The invention will be further explained with reference to the drawings.
Example 1:
referring to fig. 1, a coherent and incoherent mixed target DOA estimation method based on a co-prime MIMO array includes the following steps:
(1) selecting an area, and arranging N transmitting array elements and 2M-1 receiving array elements according to a mutual-prime layout to form a mutual-prime MIMO array, wherein M is less than N, the transmitting array elements and the receiving array elements are positioned on the same straight line, and the positions of the N transmitting array elements are Pt{ Mnd; n is 0,1, …, N-1, and the positions of 2M-1 receiving antennas are Pr-Nmd; m is 1,2, …,2M-1, d is the basic spacing of half wavelength;
(2) n transmitting array elements sequentially transmit electromagnetic wave signals with the frequency of c/2d to detect a target, if the target is detected, the electromagnetic wave signals are scattered and returned, returned echo signals are simultaneously received by 2M-1 receiving array elements to obtain echo signals of (2M-1) multiplied by N receiving and transmitting channels, and the echo signals of each channel are respectively subjected to K-time sampling to generate K pieces of snapshot data;
(3) adding the positions of N transmitting array elements and the positions of 2M-1 receiving array elements in sequence, obtaining a virtual array element once every addition to form a virtual array consisting of the virtual array elements, and recording the virtual array elements as a sum cooperative array of a co-prime MIMO array, wherein the positions of the virtual array elements are recorded as:
S＝{Mnd+Nmd；n＝0,1,…,N-1；m＝1,2,…,2M-1} (1)
(4) extracting middle uniformly distributed virtual array elements from the sum cooperative array to form a reference sum cooperative array, wherein the uniformly distributed virtual array elements are MN + M-1 virtual array elements which are uniformly distributed in the interval from (MN-M +1) d to (2MN-1) d at an interval d;
(5) constructing a uniformly-densely distributed virtual MIMO array comprising A virtual transmitting array elements and B virtual receiving array elements based on a reference and cooperative array, wherein the positions of the A virtual transmitting array elements are Pv,t＝{(xt+ i) d; i is 1,2, …, A, and the positions of B virtual receiving array elements are Pv,r＝{(xr+ j) d; j ═ 1,2, …, B }, while satisfying:
wherein xtAnd xrIs an arbitrary real number, and xt-xr＝MN-M-1；
(6) Sequentially forming a virtual transceiving channel by the ith virtual transmitting array element and the jth virtual receiving array element to obtain (x)t+i)+(xr+ j) using the position and value as reference, searching a virtual array element corresponding to the value from the reference and cooperative array, searching a transceiving channel for generating the virtual array element from the co-prime MIMO array, and using K pieces of snapshot data of the transceiving channel as equivalent snapshot data of the virtual transceiving channel; finally forming a B multiplied by A multiplied by K three-dimensional data matrix XV;
(7) obtaining a two-dimensional correlation matrix Rv with dimension B multiplied by B by solving a time average mode for the K snapshot data for the XV, namely:
wherein the superscript H represents the pair matrix XvTranspose conjugate operation of (k);
(8) and aiming at a correlation matrix Rv with dimension B multiplied by B, calculating a spatial spectrum containing a target DOA estimated value according to a MUSIC subspace DOA estimation algorithm. .
Wherein: in the step (5), the number and the position of the virtual transceiving array elements can be determined by the following formula (4),
wherein, b is any real number, and the position of the virtual transceiving array element can be represented as:
and in the step (5), A is less than B.
Example 2:
see fig. 2-4; in this embodiment, MATLAB simulation software is used to perform simulation, a coherent and incoherent mixed target to be measured is set in a far field, a co-prime MIMO array with M3 and N4 is used, the number of snapshots is set to 2000, the signal-to-noise ratio is set to 10dB, and the basic spacing d of half wavelengths is set to 1.
(1) Arranging 4 transmitting array elements and 5 receiving array elements according to a mutual-prime layout to form a mutual-prime MIMO array, wherein the positions of the 4 transmitting array elements are PtWhere the positions of the 5 receiving antennas are P, {0,3,6,9}, respectivelyr4,8,12,16,20, as shown in fig. 2.
(2)4 transmission array elements transmit electromagnetic wave signals with the frequency c/2d being 150MHz in sequence, echo signals after reaching a target and being scattered are received by 5 receiving array elements at the same time, so that echo signals of 5 multiplied by 4 receiving and transmitting channels are obtained, and the echo signals of each channel are respectively subjected to 2000 times of sampling to generate 2000 snapshot data.
(3) Adding the positions of 4 transmitting array elements and the positions of 5 receiving array elements in sequence to obtain the positions of virtual array elements in a 'co-array' corresponding to the co-prime MIMO array, and recording as:
S＝{3n+4m；n＝0,1,…,3；m＝1,2,…,5}
as shown in fig. 1, the "sum cooperative array" of the co-prime MIMO array may be divided into three parts, where the middle uniform part includes 14 virtual array elements (MN + M-1) uniformly distributed in an interval from (MN-M +1) to (2MN-1) 23 with a distance d equal to 1, and the two end non-uniform parts include 6 virtual array elements (MN-M-N +1) relatively less non-uniformly distributed in two intervals from N equal to 4 to (MN-M-1) equal to 8 and from (2MN +1) equal to 25 to (3 MN-M-N) equal to 29.
(4) And (MN + M-1) ═ 14 virtual array elements which are uniformly distributed in the interval of (MN-M +1) ═ 10 to (2MN-1) ═ 23 are uniformly distributed at the interval of d ═ 1, and the whole array is taken as the 'reference and cooperative array'.
(5) Based on this "reference and cooperative array", a plurality of virtual MIMO arrays with different numbers of combinations of a and B may be constructed on the condition that the sum of the numbers of virtual transmit and receive array elements, a + B, satisfies a + B ═ MN + M. According to the method for determining the number and the positions of the virtual MIMO array elements given by the formula (5), if x is settB is 4 and a is 5, then B is 10, and a is 5 virtual transmit elements are located at Pv,tThe positions of 10 virtual receiving array elements are P, 5,6,7,8,9, B v,r5,6,7,8,9,10,11,12,13,14}, as in the virtual MIMO array 1 of fig. 2. If x is settIf B is 4 and a is 6, then a virtual MIMO array 2 containing a 6 virtual transmit elements and B9 virtual receive elements as shown in fig. 2 can be obtained according to equation (5), where the positions of the 6 virtual transmit elements are Pv,tThe positions of 10 virtual receiving array elements are P, B ═ 5,6,7,8,9,10}, and B ═ 10v,r1, {5,6,7,8,9,10,11,12,13 }. Obviously, the sum cooperative array of the two virtual MIMO arrays is the same as the reference sum cooperative array of the co-prime MIMO array, and the three are considered to be equivalent.
(6) Taking the virtual MIMO array 1 as an example, regarding a virtual transceiving channel composed of the ith virtual transmitting array element and the jth virtual receiving array element, with the value of the sum of the positions of the transceiving virtual array elements (4+ i) + (4+ j) as a reference, the virtual array element at the reference position in the "reference and cooperative array" is identified, and 2000 pieces of snapshot data of the corresponding transceiving channel in the co-prime MIMO array of the virtual array element are generated as equivalent snapshot data of the virtual transceiving channel. For example, for the 2 nd virtual transmitting array element at position 6 and the 3 rd virtual receiving array element at position 7, the sum of the positions of the virtual transmitting and receiving array elements is 13, and the sum of the positions of the actual transmitting array element at position 9 and the actual receiving array element at position 4 in the co-prime MIMO array is also 13, then the actual transmitting and receiving array elements at position 4 and position 9 and the virtual transmitting and receiving array elements at position 7 and position 6 are considered to be equivalent to the "sum co-array" array element position 13, so that 2000 pieces of snapshot data corresponding to the actual transmitting and receiving channels are taken as 2000 pieces of equivalent snapshot data of the virtual transmitting and receiving channels equivalent to the "sum co-array".
The equivalent snapshot data of all the virtual transceiving channels are determined in sequence, and the equivalent snapshot data are arranged in sequence according to the numbers of the virtual transceiving array elements to form a three-dimensional data matrix Xv with the dimension of 10 multiplied by 5 multiplied by 2000, namely the line number sequentially corresponds to the 1 st to 10 th virtual receiving array elements, the column number sequentially corresponds to the 1 st to 5 th virtual transmitting units, and the page number sequentially corresponds to the 1 st to 2000 th snapshot data.
(7) For an equivalent three-dimensional data matrix of 10 × 5 × 2000 of the virtual MIMO array 1, a two-dimensional correlation matrix Rv with dimensions of 10 × 10 is obtained by averaging 2000 snapshot data over time, that is:
wherein the superscript H represents the pair matrix XvTranspose conjugate operation of (:, k).
Step eight: according to the MUSIC subspace DOA estimation algorithm, carrying out eigenvalue decomposition on the correlation matrix Rv with dimension of 10 multiplied by 10 obtained in the seventh step, and extracting a noise subspace matrix UNFrom this, the spatial spectrum function is calculated:
and changing theta of the spatial spectrum function to discretely take 1000 values between minus 90 degrees and 90 degrees, and searching an angle corresponding to a peak value of the spectrum function to be used as an estimated value of the target DOA. Wherein the content of the first and second substances,
for the steering matrix of the virtual receive array, the superscript T represents the transpose operation on the steering matrix.
For a virtual MIMO array 1 comprising 5 virtual transmit elements and 10 virtual receive elements, the total number of maximum resolvable coherent and incoherent targets is theoretically 9 (the number of virtual receive elements minus 1), where the maximum resolvable coherent target number is 5 (the number of virtual transmit elements), which exceeds the number of actual receive elements minus 1 (i.e. 4) and the number of actual transmit elements (i.e. 4) of the co-prime MIMO array, respectively. To verify the conclusion, 9 spatial targets are set in the simulation, sine values sin θ of the actual directions θ are sequentially-0.8, -0.6, -0.4, -0.2, 0, 0.2, 0.4, 0.6, and 0.8, the first 5 targets are coherent targets, the last 4 targets are incoherent targets, and the DOA estimation result is shown in fig. 3, which confirms the feasibility of implementing DOA estimation of 5 coherent targets and 4 incoherent targets by using the virtual MIMO array 1.
For the virtual MIMO array 2 comprising 6 virtual transmit elements and 9 virtual receive elements, the total number of maximum resolvable coherent and incoherent objects is theoretically 8, wherein the number of maximum resolvable coherent objects is 6, which also exceeds the number of actual receive elements of the co-prime MIMO array minus 1 (i.e. 4) and the number of actual transmit elements 4 (i.e. 4), respectively. To verify the conclusion, 8 spatial targets are set in the simulation, the sine values sin θ of the actual directions θ are sequentially-0.8, -0.6, -0.4, -0.2, 0, 0.2, 0.4, 0.6, and 0.8, the first 6 targets are coherent targets, the last 2 targets are incoherent targets, and the DOA estimation result is shown in fig. 4, which confirms the feasibility of implementing DOA estimation of 6 coherent targets and 2 incoherent targets by using the virtual MIMO array 1.
The simulation results shown in fig. 3 and 4 demonstrate three advantages of the present invention, one is that DOA estimation for a mixed coherent and non-coherent target is achieved; the total number of coherent and incoherent targets breaks through the limit that the number of actual receiving array elements of the co-prime MIMO array is reduced by 1, wherein the number of coherent targets breaks through the limit of the number of actual transmitting array elements of the co-prime MIMO array; and thirdly, the virtual MIMO array with different virtual array element numbers can be obtained, DOA estimation of different numbers of targets can be realized, DOA estimation flexibility is improved, and the requirements of different scenes on coherent and incoherent mixed target DOA estimation can be met.
Claims (3)
1. A coherent and incoherent mixed object DOA estimation method based on a co-prime MIMO array is characterized in that: the method comprises the following steps:
(1) selecting an area, and arranging N transmitting array elements and 2M-1 receiving array elements according to a mutual-prime layout to form a mutual-prime MIMO array, wherein M is less than N, the transmitting array elements and the receiving array elements are positioned on the same straight line, and the positions of the N transmitting array elements are Pt{ Mnd; n is 0,1, …, N-1, and the positions of 2M-1 receiving antennas are Pr-Nmd; m is 1,2, …,2M-1, d is the basic spacing of half wavelength;
(2) n transmitting array elements sequentially transmit electromagnetic wave signals with the frequency of c/2d to carry out far-field target detection, wherein c is the light speed, if a target is detected, the electromagnetic wave signals are scattered and then returned, the returned echo signals are simultaneously received by 2M-1 receiving array elements to obtain echo signals of (2M-1) multiplied by N receiving and transmitting channels, and the echo signals of each channel are respectively subjected to K times of sampling to generate K times of snapshot data;
(3) adding the positions of N transmitting array elements and the positions of 2M-1 receiving array elements in sequence, obtaining a virtual array element once every addition, forming a virtual array formed by the virtual array elements, and recording the virtual array element as a co-prime MIMO array and a co-pilot array, wherein the positions of the virtual array elements are as follows:
S＝{Mnd+Nmd；n＝0，1，…，N-1；m＝1，2，…，2M-1} (1)
(4) extracting middle uniformly distributed virtual array elements from the sum cooperative array to form a reference sum cooperative array, wherein the uniformly distributed virtual array elements are MN + M-1 virtual array elements which are uniformly distributed in the interval from (MN-M +1) d to (2MN-1) d at an interval d;
(5) constructing a uniformly-densely distributed virtual MIMO array comprising A virtual transmitting array elements and B virtual receiving array elements based on a reference and cooperative array, wherein A, B are any two positive integers meeting the requirement that A + B is MN + M, A is not equal to 1, and the positions of the A virtual transmitting array elements are Pv，t＝{(xt+ i) d; i is 1,2, …, A, and the positions of B virtual receiving array elements are Pv，r＝{(xr+ j) d; j ═ 1,2, …, B }, while satisfying:
wherein xtAnd xrIs an arbitrary real number, and xt-xr＝MN-M-1；
(6) Sequentially forming a virtual transceiving channel by the ith virtual transmitting array element and the jth virtual receiving array element to obtain (x)t+i)+(xr+ j) using the position and value as reference, searching a virtual array element corresponding to the value from the reference and cooperative array, searching a transceiving channel for generating the virtual array element from the co-prime MIMO array, and using K pieces of snapshot data of the transceiving channel as equivalent snapshot data of the virtual transceiving channel; finally forming a B multiplied by A multiplied by K three-dimensional data matrix XV;
(7) obtaining a two-dimensional correlation matrix Rv with dimension B multiplied by B by solving a time average mode for the K snapshot data for the XV, namely:
wherein the superscript H represents the pair matrix xvTranspose conjugate operation of (k);
(8) and aiming at a correlation matrix Rv with dimension B multiplied by B, calculating a spatial spectrum containing a target DOA estimated value according to a MUSIC subspace DOA estimation algorithm.
2. The coherent and non-coherent mixed target DOA estimation method based on the co-prime MIMO array according to claim 1, characterized in that: in the step (5), the number and the position of the virtual transceiving array elements can be determined by the following formula (4),
wherein, b is any real number, and the position of the virtual transceiving array element can be represented as:
Pv，t＝{(b+i)d；i＝1，2，…，MN+M-B}
Pv，r＝{(MN-M-b-1+j)d；j＝1，2，…，B} (5)。
3. the coherent and non-coherent mixed target DOA estimation method based on the co-prime MIMO array according to claim 1, characterized in that: in the step (5), A is less than B.
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| EP3961241B1 (en) * | 2019-05-17 | 2023-06-07 | Mitsubishi Electric Corporation | Antenna device and radar device |
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| CN110376557B (en) * | 2019-06-03 | 2021-08-13 | 西安电子科技大学 | Grating lobe suppression method based on non-uniform nested MIMO radar |
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