Target low elevation angle estimation method, target height measurement method and system

Abstract

The invention discloses a target low elevation angle estimation method and a target height measurement method and system. The method comprises the following steps: receiving a reflection signal returned after a detection signal sent by a uniform linear array antenna is scattered by a target; calculating an airspace guiding matrix and a noise subspace according to the transmission information corresponding to the reflection signal and the parameter information of the array antenna; and estimating the elevation angle of the direct path of the target according to the noise subspace and the airspace guiding matrix. According to the method and the system, the noise subspace and the airspace guiding matrix are obtained by analyzing the information contained in the reflected signal and the parameter information of the array antenna, and the direct path elevation angle of the target is estimated based on the noise subspace and the airspace guiding matrix with orthogonal characteristics, so that the direct path elevation angle of the target can be estimated under a low signal-to-noise ratio. And the estimation accuracy of the low elevation angle of the target is greatly improved, so that the height of the target is accurately measured, and the target is effectively tracked and positioned.

Description

Technical Field

[0001] The present invention relates to the technical field of array antennas, and in particular to a target low elevation angle estimation method, a target height measurement method and a system. Background Art

[0002] In the field of radar and communications, low elevation angle refers to the situation where the angle between the radar beam or communication signal and the horizontal line is small. Low elevation angle has wide application value in radar detection, aerospace, geographic surveying and mapping and other fields.

[0003] When the target elevation angle is small, the signal reflected from the target can be processed as two equivalent paths, namely the direct wave path and the reflected wave path. When the target elevation angle is smaller, the angle between the direct wave path and the reflected wave path is smaller, that is, the closer the reflected wave path and the direct wave path are, the greater the influence of the reflected wave path signal on the estimation of the direct wave path angle. Due to the small number of antennas in the uniform linear array antenna, the existing signal analysis algorithm is not sufficient to distinguish the reflected wave path and the direct wave path of the target, resulting in low accuracy of the estimated elevation angle of the target direct wave path, making it impossible to accurately locate and track the target.

[0004] Therefore, the prior art needs to be improved. Summary of the invention

[0005] In view of the above-mentioned deficiencies in the prior art, an object of the present invention is to provide users with a target low elevation angle estimation method, a target height measurement method and a system, so as to overcome the defect of low accuracy of low elevation angles obtained by signal processing methods in the prior art.

[0006] The technical solution adopted by the present invention to solve the technical problem is as follows:

[0007] In a first aspect, this embodiment discloses a method for estimating a target at a low elevation angle, which includes:

[0008] Receive the reflected signal of the detection signal sent by the uniform linear array antenna after being scattered by the target;

[0009] Calculating a spatial steering matrix and a noise subspace according to transmission information corresponding to the reflected signal and parameter information of the array antenna;

[0010] The elevation angle of the target direct path is estimated according to the noise subspace and the spatial steering matrix.

[0011] Optionally, the transmission information corresponding to the reflected signal includes: the wavelength of the detection signal, the attenuation coefficient of the reflected path signal contained in the reflected signal relative to the direct path signal, and the Gaussian noise vector at the sampling time; the parameter information of the array antenna includes the distance between two adjacent antennas in the uniform linear array antenna and the number of antennas in the uniform linear array antenna;

[0012] The step of calculating the spatial steering matrix and the noise subspace according to the transmission information of the received reflected signal and the parameter information of the array antenna comprises:

[0013] The wavelength of the detection signal, the elevation angle of the reflected signal and the array antenna parameter information represent the spatial steering vectors of the multiple reflected signals received by each array antenna;

[0014] According to the spatial steering vectors corresponding to the respective reflected signals received at the specified time, a spatial steering matrix of all reflected signals received by the array antenna at the specified time is obtained;

[0015] All reflected signals received at a specified time are characterized according to the spatial steering matrix corresponding to all reflected signals, the reflection coefficient matrix, the signal vector corresponding to each reflected signal at a specified time, and the Gaussian noise matrix at the sampling time;

[0016] A sampling covariance matrix is ​​calculated for the received reflected signal, and a noise subspace is calculated based on the sampling covariance matrix.

[0017] Optionally, the step of calculating a sampling covariance matrix for the received reflected signal and calculating a noise subspace according to the sampling covariance matrix is:

[0018] Calculate the sampling covariance matrix of the received reflected signal, and transform the sampling covariance matrix into a denoised sampling covariance matrix;

[0019] Perform eigenvalue decomposition on the denoised sampling covariance matrix to obtain the noise subspace.

[0020] Optionally, the expression of the reflected signal received at the specified time is:

[0021]

[0022] Where A=[a(θ 1 )a(θ 2 )] represents the spatial steering matrix, represents the reflection coefficient matrix, s n =[s n (1),L,s n (K)] represents the signal vector of the nth reflected signal at the specified time K, represents the signal matrix, W = [w(1), w(2), L, w(N)] represents the Gaussian noise matrix.

[0023] Optionally, the step of estimating the elevation angle of the target direct path according to the noise subspace and the spatial steering matrix includes:

[0024] The elevation angle of the reflected wave path and the elevation angle of the direct wave path are searched when the orthogonality of the noise subspace and the spatial steering matrix is ​​maximized, and the elevation angle of the target direct path is estimated.

[0025] Optionally, the step of searching for the elevation angle of the reflected wave path and the elevation angle of the direct wave path when the orthogonality of the noise subspace and the spatial steering matrix is ​​maximized also includes: searching for the elevation angle of the reflected wave path and the elevation angle of the direct wave path under the condition that the elevation angle of the reflected wave path is less than zero and the elevation angle of the direct wave path is greater than or equal to zero.

[0026] Optionally, the step of searching for the elevation angle of the reflected wave path and the elevation angle of the direct wave path when the orthogonality of the noise subspace and the spatial steering matrix is ​​maximized comprises:

[0027] Calculate the rank between the transposed matrix of the spatial steering matrix, the noise subspace, the transposed matrix of the noise subspace and the spatial steering matrix, and search for an estimated value corresponding to the elevation angle of the direct wave path when the rank between the transposed matrix of the spatial steering matrix, the noise subspace, the transposed matrix of the noise subspace and the spatial steering matrix is ​​at a minimum value;

[0028] The estimated value corresponding to the elevation angle of the direct wave path when the rank is at the minimum value is used as the estimated elevation angle of the target direct path.

[0029] Optionally, the calculation formula of the estimated value corresponding to the direct wave path elevation angle is:

[0030]

[0031] in, It means to find the θ that maximizes · by searching θ, where θ 1 represents the direct wave path elevation angle, θ 2 represents the elevation angle of the reflected wave path, E N represents the noise subspace, and A represents the spatial steering matrix.

[0032] In a second aspect, this embodiment discloses a method for measuring target height, which includes:

[0033] Calculating an estimated value of the elevation angle of the direct wave path based on the target low elevation angle estimation method;

[0034] The target height is calculated based on the estimated value of the elevation angle of the direct wave path.

[0035] In a third aspect, this embodiment discloses a target low elevation angle estimation system, which includes:

[0036] A signal receiving module is used to receive the reflected signal of the detection signal sent by the uniform linear array antenna after being scattered by the target;

[0037] An information processing module, used for calculating a spatial steering matrix and a noise subspace according to transmission information corresponding to the reflected signal and parameter information of the array antenna;

[0038] The angle estimation module is used to estimate the elevation angle of the direct path to the target based on the noise subspace and the spatial steering matrix.

[0039] Beneficial effects:

[0040] The present embodiment discloses a method for estimating a low elevation angle of a target, a method for measuring the height of a target, and a system for receiving a reflected signal of a detection signal sent by a uniform linear array antenna and returned after being scattered by a target; calculating a spatial steering matrix and a noise subspace according to the transmission information corresponding to the reflected signal and the parameter information of the array antenna; estimating the elevation angle of the direct path of the target according to the noise subspace and the spatial steering matrix. The method of the present embodiment obtains the noise subspace and the spatial steering matrix by analyzing the information contained in the reflected signal and the parameter information of the array antenna, and estimates the elevation angle of the direct path of the target based on the noise subspace and the spatial steering matrix with orthogonal characteristics, which can greatly improve the estimation accuracy of the low elevation angle of the target under low signal-to-noise ratio, thereby accurately measuring the height of the target, and further realizing effective tracking and positioning of the target. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 A flowchart of a method for estimating a target at a low elevation angle according to an embodiment of the present invention;

[0042] Figure 2 It is a schematic diagram of a low elevation angle in an embodiment of the present invention;

[0043] Figure 3 A flowchart of the target height measurement method according to an embodiment of the present invention;

[0044] Figure 4 It is a principle structure block diagram of the system in an embodiment of the present invention;

[0045] Figure 5 This is a comparison diagram of the results of low elevation angle estimation performed using a variety of different signal processing methods in an embodiment of the present invention. DETAILED DESCRIPTION

[0046] In order to make the purpose, technical solution and advantages of the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0047] Target positioning and tracking is a challenging task in low-elevation angle scenarios because at low elevation angles, signal transmission is interfered by the ground or sea surface, and signal superposition or loss in the propagation path leads to positioning errors, thus affecting the accuracy of target positioning and tracking.

[0048] In order to achieve accurate prediction of the target position at low elevation angles in the prior art, it is necessary to extract more accurate information features and process the more accurate information features. However, the existing information signal processing algorithms (for example, the FTT algorithm) cannot distinguish the reflected wave path and the direct wave path of the target when the number of antennas of the uniform linear array antenna is small. Therefore, it is impossible to process the elevation angle of the target direct wave path with high accuracy, and therefore it is impossible to achieve accurate prediction of the target position.

[0049] In order to overcome the above problems, the present invention proposes a target low elevation angle estimation method, a target height measurement method and a system. Based on the full use of the characteristics that the elevation angle of the target direct wave path is greater than zero degrees and the elevation angle of the reflected wave path is less than zero degrees, the elevation angle of the target direct path is estimated based on the noise subspace and the spatial domain steering matrix, and the elevation angle of the target direct path is searched to obtain the accurate value of the target low elevation angle under low signal-noise conditions.

[0050] The following is a further and more detailed description of a target low elevation angle estimation method, a target height measurement method and a system disclosed in this embodiment in conjunction with the drawings provided in this embodiment.

[0051] like Figure 1 As shown, this embodiment discloses a method for estimating a target at a low elevation angle, including:

[0052] Step S1, receiving the reflected signal of the detection signal sent by the uniform linear array antenna after being scattered by the target.

[0053] In this step, a uniform linear array antenna is used to send out a detection signal. After the detection signal sent out by the array antenna is received by the target, the target will scatter the received detection signal and return a reflected signal to the array antenna, and the array antenna will receive the reflected signal returned by the target.

[0054] In this embodiment, a uniform linear array antenna is used, which is composed of multiple antenna units, and each antenna unit is arranged in a straight line with equal spacing. The uniform linear array antenna has uniformity and consistency. The uniformity is that the spacing between any two adjacent antenna units is the same, and the consistency is that each antenna unit has the same amplitude pattern and radiation characteristics. The uniform linear antenna can generate a directional beam, and by adjusting the feed current phase of each antenna unit, the beam direction can be precisely controlled.

[0055] The uniform linear array antenna is used as a receiving antenna to receive the transmission signal from the target. The transmission signal is sent after the detection signal is scattered by the target. During the reception process, the array antenna uses the phase difference between each antenna unit to measure the arrival angle or arrival time difference of the reflected signal. The relevant information of the received reflected signal can be used to determine the location, height and other information of the target.

[0056] Combination Figure 2 As shown in the figure, in this step, after the beam emitted by the array antenna is transmitted to the target, the reflected signal returned by the target can be received by the array antenna in two ways, one is the direct path, that is, the reflected signal is directly received by the array antenna, and the other is the reflected path, that is, the reflected signal emitted by the target is first transmitted to the surface of other objects, reflected from the surface of other objects to the array antenna, and then received by the array antenna. These two different paths correspond to the direct wave path elevation angle θ 1 and the reflected wave path elevation angle θ 2 , if the direct wave path elevation angle θ can be accurately estimated 1 , and then calculate the distance between the array antenna and the target, the location of the target can be calculated.

[0057] The reflected signals received by the array antenna may come from different directions and may contain noise, so they can be denoised first, and then the received reflected signals are sampled to obtain the signal value at discrete time. The sampling rate needs to meet certain requirements to obtain the main characteristics of the signal.

[0058] After sampling the reflected signal, the sampled reflected signal values ​​are arranged in a matrix form. Assuming there are M antennas and each sensor collects N sample points, the sampled data matrix X can be expressed as an M×N matrix, where each row represents a sensor data sequence and each column represents a time snapshot of the sensor data.

[0059] In a uniform linear array antenna, the reflected signals of two paths received by M antennas at the kth sampling time can be expressed as:

[0060]

[0061] in, represents the spatial steering vector of the nth reflected signal, the superscript T represents the transposition operation, θ n represents the elevation angle of the nth reflected signal, j is an imaginary unit and d represents the interval between two adjacent antennas, λ represents the wavelength of the detection signal, β represents the attenuation coefficient of the reflected path signal relative to the direct path signal, and s n (k) represents the nth reflected signal at the kth sampling moment, and w(k) represents the Gaussian noise vector at the kth sampling moment.

[0062] Step S2: Calculate a spatial steering matrix and a noise subspace according to the transmission information corresponding to the reflected signal and the parameter information of the array antenna.

[0063] When the uniform linear antenna receives the reflected signal in the above steps, the information related to the received reflected signal is processed to calculate the spatial domain steering matrix and noise subspace of the reflected signal.

[0064] Specifically, the uniform linear array antenna processes all the reflected signals received at a specified time to obtain a corresponding covariance matrix. The transmission information corresponding to the reflected signal includes: the wavelength of the detection signal, the attenuation coefficient of the reflected path signal contained in the reflected signal relative to the direct path signal, and the Gaussian noise vector at the sampling time; the parameter information of the array antenna includes the distance between two adjacent antennas in the uniform linear array antenna and the number of antennas in the uniform linear array antenna;

[0065] The step of calculating the spatial steering matrix and the noise subspace according to the transmission information of the received reflected signal and the parameter information of the array antenna comprises:

[0066] Step S21: The wavelength of the detection signal, the elevation angle of the reflected signal and the array antenna parameter information represent the spatial steering vectors of the multiple reflected signals received by each array antenna.

[0067] The expression of the spatial steering vector is:

[0068]

[0069] Step S22: Obtain a spatial steering matrix of all reflected signals received by the array antenna at the specified time according to the spatial steering vector corresponding to each reflected signal received at the specified time.

[0070] After obtaining the spatial steering vector corresponding to each reflected signal, the spatial steering matrix corresponding to all reflected signals can be obtained. The expression of the spatial steering matrix is:

[0071] A=[a(θ 1 )a(θ 2 )];

[0072] Among them, a(θ 1 ) represents the spatial steering vector of the reflected signal received by the direct path, a(θ 2 ) represents the spatial steering vector of the reflected signal received by the reflection path.

[0073] Step S23, characterize all reflected signals received at a specified time according to the spatial steering matrix corresponding to all reflected signals, the reflection coefficient matrix, the signal vector corresponding to each reflected signal at a specified time, and the Gaussian noise matrix at the sampling time.

[0074] All received reflected signals are represented according to the spatial steering matrix, reflection coefficient matrix, signal vector, Gaussian noise matrix and other information corresponding to all reflected signals.

[0075] Specifically, all reflected signals received at a specified time can be expressed as:

[0076]

[0077] Where A=[a(θ 1 )a(θ 2 )] represents the spatial steering matrix, represents the reflection coefficient matrix, s n =[s n (1),L,s n (K)] represents the signal vector of the nth reflected signal at the specified time K, represents the signal matrix, W = [w(1), w(2), L, w(N)] represents the Gaussian noise matrix.

[0078] Step S24: Calculate a sampling covariance matrix for the received reflection signal, and calculate a noise subspace according to the sampling covariance matrix.

[0079] When all reflected signals are obtained, the sampling covariance matrix is ​​calculated based on all received reflected signals. The sampling covariance matrix reflects the similarity or difference of signals between different antenna units. If the value of the sampling covariance matrix is ​​large, it means that the signals between antenna units have a strong correlation. If the value of the sampling covariance matrix is ​​small, it means that the signal correlation between antenna units is weak or no correlation.

[0080] The steps for calculating the sampling covariance matrix and noise subspace in this step are as follows:

[0081] The sampling covariance matrix of the received reflected signal is calculated, and the sampling covariance matrix is ​​transformed into a denoised sampling covariance matrix; the denoised sampling covariance matrix is ​​subjected to eigenvalue decomposition to obtain a noise subspace.

[0082] The received signal is represented as a matrix, where each column represents the sensor data at a time, and each row represents the data sequence of a sensor. Therefore, for the signal Y received at all K times, its sampling covariance matrix is ​​calculated, that is:

[0083] R=YY H / K;

[0084] The superscript H represents the conjugate transpose operation.

[0085] In order to reduce the impact of noise, the sampling covariance matrix R can be transformed into a denoised sampling covariance matrix by averaging. The element in the i-th row and j-th column is:

[0086]

[0087] Among them, R i,j Represents the element in the i-th row and j-th column of the sampling covariance matrix R.

[0088] The covariance matrix of the noise reduction sample After eigenvalue decomposition, the noise subspace E can be obtained. N .

[0089] Step S3: Estimate the elevation angle of the direct path to the target based on the noise subspace and the spatial steering matrix.

[0090] There is orthogonality between the noise subspace and the signal subspace, and the spatial steering matrix is ​​used to describe the characteristics of the signal subspace, so there is also an orthogonal relationship between the noise subspace and the spatial steering matrix. By processing the noise subspace and the spatial steering matrix, the characteristics can be analyzed, and the precise positioning and tracking of the signal can be achieved to improve the efficiency and accuracy of the reflection signal processing.

[0091] In this step, based on the orthogonality between the spatial steering matrix and the noise subspace, the direct wave path elevation angle θ is searched. 1 and the reflected wave path elevation angle θ 2 , so that A H E N E N H The smaller the rank of A, the closer A is to E. N The more orthogonal they are, the greater the amplitude normalization value of the following formula is, so the elevation angle of the direct path of the target can be estimated.

[0092] Specifically, the step of estimating the elevation angle of the target direct path according to the noise subspace and the spatial steering matrix includes:

[0093] The elevation angle of the reflected wave path and the elevation angle of the direct wave path are searched when the orthogonality of the noise subspace and the spatial steering matrix is ​​maximized, and the elevation angle of the target direct path is estimated.

[0094] Furthermore, the step of searching for the elevation angle of the reflected wave path and the elevation angle of the direct wave path when the orthogonality of the noise subspace and the spatial steering matrix is ​​maximized also includes: searching for the elevation angle of the reflected wave path and the elevation angle of the direct wave path under the condition that the elevation angle of the reflected wave path is less than zero and the elevation angle of the direct wave path is greater than or equal to zero.

[0095] Specifically, the step of searching for the elevation angle of the reflected wave path and the elevation angle of the direct wave path when the orthogonality of the noise subspace and the spatial steering matrix is ​​maximized comprises:

[0096] The rank between the transposed matrix of the spatial steering matrix, the noise subspace, the transposed matrix of the noise subspace and the spatial steering matrix is ​​calculated, and the estimated value corresponding to the elevation angle of the direct wave path is searched when the rank between the transposed matrix of the spatial steering matrix, the noise subspace, the transposed matrix of the noise subspace and the spatial steering matrix is ​​at a minimum.

[0097] The estimated value corresponding to the elevation angle of the direct wave path when the rank is at the minimum value is used as the estimated elevation angle of the target direct path.

[0098] In this embodiment, the calculation formula for the estimated value corresponding to the elevation angle of the direct wave path is:

[0099]

[0100] in, It means to find the θ that maximizes · by searching θ, where θ 1 represents the direct wave path elevation angle, θ 2 represents the elevation angle of the reflected wave path, E N represents the noise subspace, and A represents the spatial steering matrix.

[0101] When searching for angles, since the elevation angle of the target direct wave path is greater than zero degrees and the elevation angle of the reflected wave path is less than zero degrees, θ is limited during the search. 1 ≥0° and θ 2 <0°, which reduces the calculation complexity and the false detection rate, thereby improving the angle estimation accuracy.

[0102] The method of this embodiment obtains the spatial steering matrix and noise subspace of the reflected signal. On the basis that the spatial steering matrix and the noise subspace are orthogonal, it is proposed that the more orthogonal the spatial steering matrix and the noise subspace are, the more accurate the estimated direct path elevation angle is. The noise subspace is obtained by eigenvalue decomposition of the sampling covariance matrix. Based on the calculated spatial steering matrix, the regional orthogonality between the spatial steering matrix and the noise subspace is analyzed to search for an estimated value of the direct path elevation angle, thereby greatly improving the accuracy of low elevation angle estimation of the target under low signal-to-noise ratio, so that the target can be found in a shorter time, and the height of the target can be measured more accurately through the estimated elevation angle and the distance between the target and the uniform linear array antenna, thereby achieving effective tracking of the target.

[0103] In a second aspect, this embodiment discloses a method for measuring target height, such as Figure 3 As shown, including:

[0104] Step H1, calculating an estimated value of the elevation angle of the direct wave path based on the target low elevation angle estimation method.

[0105] In this step, based on the target low elevation angle estimation method disclosed in the above embodiment, an estimated value of the elevation angle of the direct wave path is calculated.

[0106] Step H2: Calculate the target height based on the estimated value of the elevation angle of the direct wave path.

[0107] On the premise of calculating the estimated value of the direct wave path elevation angle, the target height is calculated based on the height of the array antenna, the position of the radar station, and the direct wave path elevation angle.

[0108] If the horizontal distance between the radar and the target is known, the target height can be obtained by:

[0109] h r =h t +dtan(θ 1 );

[0110] Among them, h r is the target height, h t is the array antenna height, θ 1 is the elevation angle of the direct wave path, and d is the horizontal distance between the radar and the target.

[0111] The target height measurement method provided in this embodiment is a non-contact measurement method, which is not limited by geographical, climatic and other conditions, and can perform continuous and efficient data collection on a global scale. Therefore, improving the accuracy of target height measurement is of great significance in fields such as earth science and urban planning. For example, when applied to the ecological environment, by measuring parameters such as ground height, vegetation height, and glacier thickness, it is possible to gain an in-depth understanding of the ecological and environmental changes on the earth's surface, and provide a scientific basis for fields such as climate change research and ecological and environmental protection. When applied to urban planning, detailed data on urban elevation distribution can be provided, which are of great significance for urban planning, design, construction and management.

[0112] In a third aspect, this embodiment discloses a target low elevation angle estimation system, such as Figure 4 As shown, including:

[0113] The signal receiving module 410 is used to receive the reflected signal of the detection signal sent by the uniform linear array antenna and scattered by the target; its function is as described in step S1.

[0114] The information processing module 420 is used to calculate the spatial steering matrix and the noise subspace according to the transmission information corresponding to the reflected signal and the parameter information of the array antenna; its function is as described in step S2.

[0115] The angle estimation module 430 is used to estimate the elevation angle of the target direct path according to the noise subspace and the spatial steering matrix, and its function is as described in step S2.

[0116] It is conceivable that the target low elevation angle estimation method, target height measurement method and system provided by the present embodiment can not only improve the positioning accuracy of satellite navigation, but also introduce low elevation angle into the target position solution, thereby effectively improving the performance of the satellite overall positioning system. Moreover, improving the estimation accuracy of the target low elevation angle can also enhance the reception capability of satellite signals. In densely built areas such as cities, high-rise buildings may block the communication signals between ground communication stations and satellites with low elevation angles. However, through low elevation angle estimation, these low elevation angle satellite signals can be more effectively utilized, thereby enhancing the signal reception capability, which is of great significance for improving the reliability and coverage of satellite communications.

[0117] Figure 5 The figure shows the Root Mean Square Error (RMSE) performance of the FB+MUSIC algorithm, the TP+MUSIC algorithm, the FB+RRMUSIC algorithm and the target low elevation angle estimation method (TP+RRMUSIC algorithm) proposed in this application under different signal-to-noise ratios (SNR). Figure 5It can be seen that the TP+RRMUSIC low elevation angle estimation algorithm proposed in this application has higher angle estimation accuracy under low signal-to-noise ratio.

[0118] The present embodiment discloses a method for estimating a low elevation angle of a target, a method for measuring the height of a target, and a system, which receive a reflected signal sent by a uniform linear array antenna and returned after being scattered by the target; calculate a spatial steering matrix and a noise subspace according to the transmission information corresponding to the reflected signal and the parameter information of the array antenna; and estimate the elevation angle of the direct path of the target according to the noise subspace and the spatial steering matrix. The method of the present embodiment analyzes the information contained in the reflected signal and the parameter information of the array antenna to obtain a noise subspace and a spatial steering matrix, and estimates the elevation angle of the direct path of the target based on the noise subspace and the spatial steering matrix with orthogonal characteristics, which can greatly improve the estimation accuracy of the low elevation angle of the target under low signal-to-noise ratio, thereby accurately measuring the height of the target, and further achieving effective tracking and positioning of the target.

[0119] Those skilled in the art will readily appreciate other embodiments of the invention after considering the specification and practicing the invention disclosed herein. The present invention is intended to cover any variations, uses or adaptations of the present invention that follow the general principles of the present invention and include common knowledge or customary techniques in the art that are not disclosed in this disclosure. The description and examples are to be considered exemplary only, and the true scope and spirit of the present invention are indicated by the following claims.

[0120] The above-mentioned embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application.

Claims

1. A method for estimating a target at a low elevation angle, characterized in that: include: Receive the reflected signal of the detection signal sent by the uniform linear array antenna after being scattered by the target; Calculating a spatial steering matrix and a noise subspace according to transmission information corresponding to the reflected signal and parameter information of the array antenna; The elevation angle of the target direct path is estimated according to the noise subspace and the spatial steering matrix.

2. The target low elevation angle estimation method according to claim 1, characterized in that: The transmission information corresponding to the reflected signal includes: the wavelength of the detection signal, the attenuation coefficient of the reflected path signal contained in the reflected signal relative to the direct path signal, and the Gaussian noise vector at the sampling time; the parameter information of the array antenna includes the distance between two adjacent antennas in the uniform linear array antenna and the number of antennas in the uniform linear array antenna; The step of calculating the spatial steering matrix and the noise subspace according to the transmission information of the received reflected signal and the parameter information of the array antenna comprises: The wavelength of the detection signal, the elevation angle of the reflected signal and the array antenna parameter information represent the spatial steering vectors of the multiple reflected signals received by each array antenna; According to the spatial steering vectors corresponding to the respective reflected signals received at the specified time, a spatial steering matrix of all reflected signals received by the array antenna at the specified time is obtained; All reflected signals received at a specified time are characterized according to the spatial steering matrix corresponding to all reflected signals, the reflection coefficient matrix, the signal vector corresponding to each reflected signal at a specified time, and the Gaussian noise matrix at the sampling time; A sampling covariance matrix is ​​calculated for the received reflected signal, and a noise subspace is calculated based on the sampling covariance matrix.

3. The method for estimating a target low elevation angle according to claim 2, characterized in that: The steps of calculating the sampling covariance matrix of the received reflected signal and calculating the noise subspace according to the sampling covariance matrix are as follows: Calculate the sampling covariance matrix of the received reflected signal, and transform the sampling covariance matrix into a denoised sampling covariance matrix; Perform eigenvalue decomposition on the denoised sampling covariance matrix to obtain the noise subspace.

4. The target low elevation angle estimation method according to claim 2, characterized in that: The expression of the reflected signal received at the specified time is: Where A = [a(θ1)a(θ2)] represents the spatial steering matrix, represents the reflection coefficient matrix, s n =[s n (1),L,s n (K)] represents the signal vector of the nth reflected signal at the specified time K, represents the signal matrix, W = [w(1), w(2), L, w(N)] represents the Gaussian noise matrix.

5. The target low elevation angle estimation method according to claim 1, characterized in that: The step of estimating the elevation angle of the target direct path according to the noise subspace and the spatial steering matrix comprises: The elevation angle of the reflected wave path and the elevation angle of the direct wave path are searched when the orthogonality of the noise subspace and the spatial steering matrix is ​​maximized, and the elevation angle of the target direct path is estimated.

6. The target low elevation angle estimation method according to claim 5, characterized in that: The step of searching for the elevation angle of the reflected wave path and the elevation angle of the direct wave path when the orthogonality of the noise subspace and the spatial steering matrix is ​​maximized also includes: searching for the elevation angle of the reflected wave path and the elevation angle of the direct wave path under the condition that the elevation angle of the reflected wave path is less than zero and the elevation angle of the direct wave path is greater than or equal to zero.

7. The target low elevation angle estimation method according to claim 5 or 6, characterized in that: The step of searching for the elevation angle of the reflected wave path and the elevation angle of the direct wave path when the orthogonality of the noise subspace and the spatial steering matrix is ​​maximized comprises: Calculate the rank between the transposed matrix of the spatial steering matrix, the noise subspace, the transposed matrix of the noise subspace and the spatial steering matrix, and search for an estimated value corresponding to the elevation angle of the direct wave path when the rank between the transposed matrix of the spatial steering matrix, the noise subspace, the transposed matrix of the noise subspace and the spatial steering matrix is ​​at a minimum value; The estimated value corresponding to the elevation angle of the direct wave path when the rank is at the minimum value is used as the estimated elevation angle of the target direct path.

8. The target low elevation angle estimation method according to claim 7, characterized in that: The calculation formula for the estimated value corresponding to the elevation angle of the direct wave path is: in, It means to find the θ that maximizes · by searching θ, where θ1 represents the elevation angle of the direct wave path, θ2 represents the elevation angle of the reflected wave path, and E N represents the noise subspace, and A represents the spatial steering matrix.

9. A method for measuring target height, characterized in that: include: Calculating an estimated value of the elevation angle of the direct wave path based on the target low elevation angle estimation method according to any one of claims 1 to 8; The target height is calculated based on the estimated value of the direct wave path elevation angle.

10. A target low elevation angle estimation system, characterized in that: include: A signal receiving module is used to receive the reflected signal of the detection signal sent by the uniform linear array antenna after being scattered by the target; An information processing module, used for calculating a spatial steering matrix and a noise subspace according to transmission information corresponding to the reflected signal and parameter information of the array antenna; The angle estimation module is used to estimate the elevation angle of the target direct path according to the noise subspace and the spatial steering matrix.

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