A Radar-Assisted Altitude Estimation Method under Multipath Effects

Abstract

The present invention relates to the field of radar signal processing, and particularly to a radar-assisted height estimation method under multipath effects. The present invention includes 5 main steps. Step 1: Calculate the path difference between the multipath echo and the direct wave at different heights of each row line source. Step 2: Calculate the theoretical echo amplitude of each row line source. Step 3: Calculate the actual echo amplitude at the target range cell of each row line source. Step 4: Calculate the correlation between the theoretical echo amplitude and the actual echo amplitude and normalize it. Step 5: Determine the accurate height estimation result of the target by combining the normalized correlation result and the traditional specific comparison height estimation result. The present invention makes the target height estimation result under multipath effects more accurate.

Description

Technical Field

[0001] The present invention relates to the field of radar signal processing, and particularly to a radar-assisted height estimation method under multipath effects. Background Art

[0002] In the practical application of radar height measurement algorithms, when the radar detects low-altitude targets, it is sometimes affected by multipath effects. The receiver not only receives the direct-path signal reflected from the target, but also receives the reflected signal from the ground, thus forming a multipath composite signal, resulting in large fluctuations and instability in the height measurement results of traditional amplitude comparison height measurement methods, and multiple height results may be measured.

[0003] Therefore, a radar-assisted height estimation method under multipath effects is needed. By combining the height measurement results of the traditional amplitude comparison height measurement method and analyzing the target height value closest between the two height measurement results, accurate height information of the target under multipath effects can be obtained. Summary of the Invention

[0004] Aiming at the deficiencies of the traditional amplitude comparison height measurement method under multipath effects, the present invention provides a radar-assisted height estimation method under multipath effects. By using this algorithm in combination with the height measurement results of the traditional amplitude comparison height measurement method under multipath effects, accurate height information of the target under multipath effects can be obtained.

[0005] The technical solution of the present invention is: a radar-assisted height estimation method under multipath effects, characterized by including the following steps:

[0006] Step 1: According to the formula calculate the path difference between the multipath echo and the direct wave at different heights of each row line source;

[0007] where R is the target distance detected by the radar; h r is the vertical height of each row line source of the radar; h t is the predicted target height.

[0008] Step 2: According to the formula A 理论 =(cos(2π(mod(δ 0 ,λ) / λ))+1) / 2, calculate the theoretical echo amplitude A 理论 of each row line source; where the operator mod(δ 0 ,λ) returns the remainder of δ 0 divided by λ, and λ is the radar wavelength.

[0009] The beneficial effects of Step 1 and Step 2 are: considering the influence of the path difference between the direct wave and the reflected wave received by the radar caused by multipath effects on target height measurement.

[0010] Step 3: Record the complex echo point values at the target distance units of each row line source as sig, and calculate the actual echo amplitude at the target distance units of each row line source according to the formula sig 归一化 = abs(sig) / max(abs(sig)).

[0011] Step 4: Calculate the correlation between the theoretical echo amplitude and the actual echo amplitude and normalize it;

[0012] Expand sig 归一化 to an N-row x-column matrix, where N is the number of radar row line sources and x is the number of columns of A 理论 . The data in each column is the same as that in the first column, and the expanded matrix is denoted as A 实际 .

[0013] Calculate the correlation between the theoretical echo amplitude and the actual echo amplitude through the formula aa = 1 / sum(abs(A 实际 - A 理论 ))), where the operator sum(x) means to sum the matrix x in the row direction, and the operation result is a 1-row vector. The division in aa = 1 / sum(abs(A 实际 - A 理论 )) is element-wise division, that is, to find the reciprocal of each element in the result of sum(abs(A 实际 - A 理论 ))).

[0014] For the convenience of subsequent judgment, we normalize the correlation result aa, that is, aa 归一化 = aa / max(ab).

[0015] Step 5: Determine the accurate height measurement result of the target by combining the normalized amplitude correlation and the traditional amplitude comparison height measurement result.

[0016] The column in aa 归一化 with the correlation closest to 1 (the highest correlation), and the corresponding predicted target height h t value is the target height measured by this algorithm.

[0017] The beneficial effect of Step 5 is: By comparing the correlation between the theoretical amplitude value and the actual amplitude value, search for the theoretical echo amplitude values corresponding to different target heights, and find the theoretical echo amplitude value closest to the actual echo signal amplitude value (that is, the strongest correlation), and its corresponding predicted target height value is the measured target height value.

[0018] This algorithm will have height measurement ambiguity in some cases, that is, there will be multiple columns with a correlation of 1 in aa 归一化 . At this time, it is necessary to combine the traditional amplitude comparison height measurement method and select the result similar to the height measurement of the traditional height measurement method.

[0019] The beneficial effect of this step is that by combining the height estimation method described in this patent with the result of the amplitude comparison height measurement method under the influence of multipath effect, not only can the incorrect height estimation result generated by the amplitude comparison height measurement method under the multipath effect be removed, but also the height measurement ambiguity that may occur in certain cases of the algorithm described in this patent can be removed. That is, by comprehensively making decisions by combining the two height measurement methods, a more accurate and reliable height measurement result can be obtained.

[0020] The beneficial effects of the present invention are as follows: 1. Considering the influence of the wave path difference of the multipath effect on the height measurement result, the target height measurement result under the multipath effect is more accurate. 2. By combining and considering the height measurement result of the traditional amplitude comparison, the height measurement ambiguity that may be caused by this algorithm is screened. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a schematic diagram of the physical meanings of the variable symbols used in the description of the present invention.

[0022] Figure 2 It is a schematic diagram of the implementation process of a radar-assisted height estimation method under multipath effect. DETAILED DESCRIPTION OF THE INVENTION

[0023] The following will elaborate on the embodiments of the present invention in conjunction with the drawings, so that the advantages and features of the present invention can be more easily understood by those skilled in the art, thereby making a clearer and more definite definition of the protection scope of the present invention.

[0024] The embodiment of the present invention provides a radar-assisted height estimation method under multipath effect, which can be applied to the field of target height measurement in radar signal processing.

[0025] Please refer to Figure 2 , a method for interference direction finding of a phased array radar includes the following steps:

[0026] Step 1: Calculate the wave path difference between the multipath echo and the direct wave at different heights of each row line source according to the formula where R is the target distance detected by the radar; h

[0027] r is the vertical height of each row line source of the radar. In this embodiment, the number of row line sources used is 30, so h r has 1 column and 30 rows; h t is the predicted target height.

[0028] The target distance and the radar antenna height are actual measured values. The predicted target height can take a predicted height every 100 m within the range of 0 to the maximum value of the height measurement index. In this example, the values are taken every 100 m from 1 to 12000, and h t has a total of 120 numbers and is a row vector.

[0029] ​Therefore, the calculated wave path difference δ 0 is a 30-row and 120-column matrix.

[0030] Step 2: Calculate the theoretical echo amplitude A of each row line source 理论 .

[0031] A 理论 =(cos(2π(mod(δ 0 ,λ) / λ)) + 1) / 2, where A 理论 is a 30-row and 120-column matrix, and the operator mod(δ 0 ,λ) returns the remainder of δ 0 divided by λ, and λ is the radar wavelength.

[0032] Step 3: Calculate the actual echo amplitude at the target distance cell of each row line source.

[0033] Take the complex value of the echo point at the target distance cell of each row line source and denote it as sig, which is a vector containing 30 complex values. Normalize the amplitude of sig: sig 归一化 = abs(sig) / max(abs(sig)), where sig 归一化 is a 30-row and 1-column vector, and the operator abs(x) means taking the modulus value of x.

[0034] Step 4: Calculate and normalize the correlation between the theoretical echo amplitude and the actual echo amplitude.

[0035] To perform a correlation analysis between the theoretical echo amplitudes and the actual echo amplitudes at different predicted heights, expand sig 归一化 to a 30-row and 120-column matrix, where each column has the same data as the first column. Denote the expanded matrix as A 实际 .

[0036] Calculate the correlation between the theoretical echo amplitude and the actual echo amplitude through the formula aa = 1 / sum(abs(A 实际 - A 理论 ), where the operator sum(x) means summing up the matrix x in the row direction, and the operation result is a 1-row vector. The division in aa = 1 / sum(abs(A 实际 - A 理论 )) is a dot division, that is, finding the reciprocal of each element in the result of sum(abs(A 实际 - A 理论 ).

[0037] To facilitate subsequent judgment, normalize the correlation result aa, that is, aa 归一化= aa / max(abs(aa)), where the operator max(x) means to take the maximum element value in the vector x, aa 归一化 The result of is a 1-row and 120-column vector.

[0038] Step 5, Combine the correlation aa 归一化 and the traditional amplitude comparison height measurement result to determine the accurate height measurement result of the target.

[0039] aa 归一化 The column in which the correlation is closest to 1 (the highest correlation), and the value of the element corresponding to its column number h t in is the height of the target measured by this algorithm.

[0040] This algorithm may have height measurement ambiguity in some cases, that is, aa 归一化 There will be multiple columns with a correlation of 1 in it. At this time, it is necessary to combine the traditional amplitude comparison height measurement method and select the result close to the height measurement of the traditional height measurement method.

[0041] For example: The height values with a correlation of 1 measured by this method are 6000m and 4500m; the height values measured by the traditional amplitude comparison height measurement method are 5500m, 6100m, and 6700m, then the selected height measurement result is 6000m.

[0042] The above are only the embodiments of the present invention, and do not limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made by using the content of the specification and drawings of the present invention, or directly or indirectly applied in other related technologies.

Claims

1. A radar-assisted height estimation method under multipath effects, characterized in that: It includes the following steps: Step 1. According to the formula calculate the path difference between the multipath echoes at different heights of each row line source and the direct wave; where R is the target distance detected by the radar; h r is the vertical height of each row line source of the radar; h t is the predicted target height; Step 2: According to formula A 理论 =(cos(2π(mod(δ 0 , λ) / λ)) + 1) / 2, calculate the theoretical echo amplitude A of each row line source 理论 ; where the operator mod(δ 0 , λ) returns the remainder after δ 0 is divided by λ, and λ is the radar wavelength; Step 3: Record the complex value of the echo point at each line source target distance unit as sig, and calculate the actual echo amplitude at the target distance unit of each line source according to the formula sig 归一化 = abs(sig) / max(abs(sig)), Step 4: Calculate the correlation between the theoretical echo amplitude and the actual echo amplitude and normalize it; Expand sig 归一化 to an N-row by x-column matrix, where N is the number of radar row sources and x is the number of columns of A 理论 . The data in each column is the same as that in the first column. The expanded matrix is denoted as A 实际 ; Calculate the correlation between the theoretical echo amplitude and the actual echo amplitude through the formula aa = 1 / sum(abs(A 实际 -A 理论 )) where the operator sum(x) means to sum the matrix x in the row direction and the operation result is a 1-row vector; the division in aa = 1 / sum(abs(A 实际 -A 理论 )) is dot division; normalize the correlation result aa, that is, aa 归一化 = aa / max(abs(aa)); Step 5. Determine the accurate height measurement result of the target by combining the normalized amplitude correlation and the traditional amplitude comparison height measurement result; aa 归一化 The height h of the predicted target corresponding to the column with the correlation closest to 1 t The value of which is the target height measured by this algorithm; aa 归一化 When there are multiple columns with a correlation of 1, combine the traditional amplitude comparison height measurement method and select the result close to the height measurement by the traditional height measurement method.

2. The radar-assisted height estimation method under multipath effects according to claim 1, characterized in that: The number of row line sources in step 1 is 30.

3. The radar-assisted height estimation method under multipath effects according to claim 1, characterized in that: In step 1, the predicted target height is taken at every 100 m within the range from 0 to the maximum value of the height measurement index.

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