Channel error estimation method and device for space-borne synthetic aperture radar

Abstract

The application relates to the technical field of satellite remote sensing imaging, in particular to a channel error estimation method and device of a satellite-borne synthetic aperture radar. The method comprises the following steps: obtaining a measurement matrix of a plurality of calibrators under full polarization channels of the satellite-borne synthetic aperture radar and a feature matrix of each calibrator; determining an estimated value of a Faraday rotation angle based on a double-angle formula, the measurement matrix and the feature matrix corresponding to each calibrator; determining an initial estimated value of a channel error based on the estimated value of the Faraday rotation angle; and determining a target estimated value of the channel error under consideration of calibrator errors and system thermal noise based on the estimated value of the Faraday rotation angle, the initial estimated value of the channel error, a least square method and the measurement matrix and the feature matrix corresponding to each calibrator. The scheme considers the system thermal noise and the calibrator errors, and can improve the precision of the target estimated value of the channel error.

Description

Technical Field

[0001] This invention relates to the field of satellite remote sensing imaging technology, and in particular to a method and apparatus for estimating channel errors in a spaceborne synthetic aperture radar. Background Technology

[0002] Spaceborne synthetic aperture radar (SAR) is an active microwave imaging radar that transmits linear frequency modulated signals in pulse form and receives the scattered echo signals from ground targets. It then processes these echoes to obtain radar images with the required resolution and swath width. Due to its all-weather, all-day operation and high resolution, along with its certain penetration capability, it is widely used in military reconnaissance, topographic mapping, marine observation, ecological monitoring, and natural disaster monitoring.

[0003] When using spaceborne synthetic aperture radar (SAR) to detect targets, channel errors, system thermal noise, and Faraday rotation angle all affect the accuracy of the target backscattering coefficient measurement. Therefore, accurate estimation of the channel errors of spaceborne SAR is necessary. However, existing methods for estimating the channel errors of spaceborne SAR do not consider the radar's system thermal noise and calibrator errors, which inevitably affects the estimation accuracy of the channel errors.

[0004] Therefore, a new method for estimating channel errors in spaceborne synthetic aperture radar is urgently needed. Summary of the Invention

[0005] To address the problem that existing methods for estimating channel errors in spaceborne synthetic aperture radar (SAR) are difficult to guarantee in terms of estimation accuracy, this invention provides a method and apparatus for estimating channel errors in spaceborne SAR.

[0006] In a first aspect, embodiments of the present invention provide a method for estimating channel errors in a spaceborne synthetic aperture radar, comprising:

[0007] The measurement matrices of multiple calibrators under the full polarization channel of the spaceborne synthetic aperture radar and the characteristic matrix of each calibrator were obtained respectively.

[0008] Based on the double-angle formula, the measurement matrix corresponding to each calibrator, and the characteristic matrix, the estimated value of the Faraday rotation angle is determined;

[0009] Based on the estimated value of the Faraday rotation angle, an initial estimate of the channel error is determined;

[0010] Based on the estimated value of the Faraday rotation angle, the initial estimated value of the channel error, the least squares method, the measurement matrix corresponding to each calibrator, and the characteristic matrix, the target estimated value of the channel error considering the calibrator error and the system thermal noise is determined.

[0011] Secondly, embodiments of the present invention also provide a channel error estimation device for a spaceborne synthetic aperture radar, comprising:

[0012] The acquisition unit is used to acquire the measurement matrices of multiple calibrators in the fully polarized channel of the spaceborne synthetic aperture radar and the feature matrix of each calibrator.

[0013] The first estimation unit is used to determine the estimated value of the Faraday rotation angle based on the double-angle formula, the measurement matrix corresponding to each calibrator, and the characteristic matrix.

[0014] The second estimation unit is used to determine the initial estimate of the channel error based on the estimated value of the Faraday rotation angle;

[0015] An iterative unit is used to determine a target estimate of the channel error, taking into account the calibrator error and system thermal noise, based on the estimated value of the Faraday rotation angle, the initial estimate of the channel error, the least squares method, the measurement matrix corresponding to each calibrator, and the characteristic matrix.

[0016] Thirdly, embodiments of the present invention also provide a computing device, including a memory and a processor, wherein the memory stores a computer program, and when the processor executes the computer program, it implements the method described in any embodiment of this specification.

[0017] Fourthly, embodiments of the present invention also provide a computer-readable storage medium having a computer program stored thereon, which, when executed in a computer, causes the computer to perform the methods described in any embodiment of this specification.

[0018] This invention provides a method, apparatus, computing device, and storage medium for estimating channel errors in a spaceborne synthetic aperture radar. First, the measurement matrices of multiple calibrators under the fully polarized channel of the spaceborne synthetic aperture radar, as well as the characteristic matrix of each calibrator, are acquired. Then, based on the double-angle formula, the measurement matrix and characteristic matrix corresponding to each calibrator, an estimated value of the Faraday rotation angle is determined. Next, based on the estimated value of the Faraday rotation angle, an initial estimated value of the channel error can be determined. Finally, based on the estimated value of the Faraday rotation angle, the initial estimated value of the channel error, the least squares method, and the measurement matrix and characteristic matrix corresponding to each calibrator, a target estimated value of the channel error considering calibrator errors and system thermal noise is determined. In this scheme, since the measurement matrix is ​​obtained by the actual measurement of the calibrator by the spaceborne synthetic aperture radar, the measurement matrix itself is measured under the condition that calibrator error and system thermal noise exist simultaneously. Therefore, based on the estimated value of Faraday rotation angle, the initial estimated value of channel error, the least squares method, the measurement matrix and characteristic matrix corresponding to each calibrator, the target estimated value of channel error under the consideration of calibrator error and system thermal noise can be obtained, thereby improving the accuracy of the target estimated value of channel error. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a flowchart of a channel error estimation method for a spaceborne synthetic aperture radar according to an embodiment of the present invention;

[0021] Figure 2 This is a hardware architecture diagram of a computing device provided in an embodiment of the present invention;

[0022] Figure 3 This is a structural diagram of a channel error estimation device for a spaceborne synthetic aperture radar provided in an embodiment of the present invention. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0024] As mentioned earlier, existing methods for estimating channel errors in spaceborne synthetic aperture radar do not consider the radar's system thermal noise and calibrator errors, which inevitably affects the accuracy of channel error estimation for spaceborne synthetic aperture radar.

[0025] To address the aforementioned technical problems, the inventors could consider using a spaceborne synthetic aperture radar to actually measure each calibrator in a fully polarized channel, thus obtaining a measurement matrix when both calibrator error and system thermal noise are present. Then, based on the measurement matrix corresponding to each calibrator, an estimated value of the Faraday rotation angle is determined to further determine the initial estimate of the channel error. Finally, based on the estimated value of the Faraday rotation angle, the initial estimate of the channel error, the least squares method, the measurement matrix corresponding to each calibrator, and the characteristic matrix, a higher-precision target estimate of the channel error can be obtained, taking into account both calibrator error and system thermal noise.

[0026] The following describes the specific implementation of the above concept.

[0027] Please refer to Figure 1 This invention provides a method for estimating channel errors in a spaceborne synthetic aperture radar, the method comprising:

[0028] Step 100: Obtain the measurement matrices of multiple calibrators in the fully polarized channel of the spaceborne synthetic aperture radar and the feature matrix of each calibrator.

[0029] Step 102: Based on the double-angle formula, the measurement matrix and characteristic matrix corresponding to each calibrator, determine the estimated value of the Faraday rotation angle;

[0030] Step 104: Determine the initial estimate of the channel error based on the estimated value of the Faraday rotation angle;

[0031] Step 106: Based on the estimated value of the Faraday rotation angle, the initial estimated value of the channel error, the least squares method, the measurement matrix and characteristic matrix corresponding to each calibrator, determine the target estimated value of the channel error considering the calibrator error and the system thermal noise.

[0032] In this embodiment of the invention, since the measurement matrix is ​​obtained by the actual measurement of the calibrator by the spaceborne synthetic aperture radar, the measurement matrix itself is measured under the condition that the calibrator error and the system thermal noise exist simultaneously. Therefore, based on the estimated value of the Faraday rotation angle, the initial estimated value of the channel error, the least squares method, the measurement matrix and the characteristic matrix corresponding to each calibrator, the target estimated value of the channel error under the consideration of the calibrator error and the system thermal noise can be obtained, thereby improving the accuracy of the target estimated value of the channel error.

[0033] For step 100:

[0034] In polarimetric calibration, point targets with known polarimetric characteristics are typically used as calibration points to intuitively assess the polarimetric calibration accuracy of the scene, usually described by polarimetric characteristic responses. In engineering polarimetric calibration, multiple artificial, high-precision calibrators are typically deployed in the scene. Their responses are usually strong scattering points in amplitude and typically have a fixed polarimetric characteristic matrix. These are categorized as passive calibrators and active calibrators (PARCs). Passive calibrators generally refer to reflectors with specific geometries, primarily metal spheres and corner reflectors. Active calibrators, deployed within the polarimetric synthetic aperture radar (PSA) imaging scene, offer higher signal-to-noise ratios and calibration device accuracy than passive calibrators. Furthermore, they not only have wider beamwidths in both azimuth and range directions but are also small, lightweight, easy to place in the field, convenient to control the absolute scattering coefficient, and flexible in use.

[0035] In this embodiment, in order to determine the first formula by combining the two systems, at least four scalers are required, and the cross-polarization channel can ensure a high channel isolation, thereby ensuring high calibration of polarization information. In this embodiment, the characteristic matrices of polarization of each scaler are different, and the two active scalers are cross-polarized, as are the two passive scalers.

[0036] Therefore, in some implementations, the scaler includes two active scalers and two passive scalers; wherein the feature matrix of each scaler is different.

[0037] Specifically, two active scalers, PARC, are selected. X and PARC Y Their feature matrices are as follows:

[0038]

[0039]

[0040] Simultaneously, two other passive scalers (which can use a meshed trihedral shape) are selected, with the following feature matrices:

[0041]

[0042]

[0043] Next, the selected calibrators are placed in the scene, and the spaceborne synthetic aperture radar is used to measure each selected calibrator in each fully polarized channel. The measurement values ​​of each calibrator under HH polarization, VH polarization, HV polarization and VV polarization can be obtained, and the measurement matrix of the calibrator can be constructed.

[0044] For example, for the active scaler PARC X The active scaler PARC was trained using a spaceborne synthetic aperture radar under HH, VH, HV, and VV polarizations. X Measurements can be performed to obtain the active calibrator PARC. X The measured values ​​under each fully polarized channel, i.e. and So, active scaler PARC X The measurement matrix can be represented as:

[0045]

[0046] Similarly, the active scaler PARC can be obtained separately. Y The measurements of the two passive calibrators in each fully polarized channel, and the measurement matrix composed of the measurements, are shown below:

[0047]

[0048]

[0049]

[0050] Regarding step 102:

[0051] In some implementations, step 102 may include the following steps S1-S3:

[0052] Step S1: Substitute the measurement matrix and characteristic matrix corresponding to each calibrator into the target relation to determine the first formula by combining the equations. The target relation is the expression for the relationship between the measurement matrix and the characteristic matrix of the spaceborne synthetic aperture radar in the fully polarized channel.

[0053] In step S1, in the fully polarized system of a spaceborne synthetic aperture radar, the relationship between the scattering measurement matrix M and the characteristic matrix S of ground objects can be expressed as:

[0054]

[0055] Where A(r,θ) is the amplitude gain factor, representing the amplitude gain of the radar system; φ is the phase factor, representing the overall system phase shift caused by delays due to ground targets and aircraft passing by; M, S, and N are the measurement matrix, characteristic matrix, and noise matrix, respectively; the subscripts indicate the H or V channel; the noise of each channel can be considered as independent additive noise; and Ω is the Faraday rotation angle.

[0056] f and δ are channel errors, where f is channel inconsistency and δ is crosstalk between channels.

[0057] δ1 represents the ratio of crosstalk signal introduced into the V-polarized channel by the received H-polarized channel signal;

[0058] δ2 represents the ratio of crosstalk signal introduced into the H-polarized channel by the received V-polarized channel signal;

[0059] δ3 represents the ratio of crosstalk signal introduced into the H-polarized channel by the transmitted V-polarized channel signal;

[0060] δ4 represents the ratio of crosstalk signal introduced into the V-polarized channel by the transmitted H-polarized channel signal;

[0061] f1 represents the amplitude-phase imbalance ratio of the V-polarized channel relative to the H-polarized channel at the receiving end;

[0062] f2 represents the amplitude-phase imbalance ratio of the V-polarized channel to the H-polarized channel at the transmitter.

[0063] By measuring the echo gain and self-gain of the calibrator, the amplitude gain factor A(r,θ) and phase factor φ can be eliminated. When the noise matrix is ​​ignored, equation (1) can be expressed as:

[0064]

[0065] It should be noted that formula (2) is the target relation.

[0066] Substitute the measurement matrix and feature matrix corresponding to each calibrator obtained in step 100 into the target relation, that is, substitute each element value in the measurement matrix and feature matrix into formula (2), and combine the formulas obtained by substituting the measurement matrix and feature matrix corresponding to the four calibrators into the target relation to obtain the first formula as shown below:

[0067] d1sin2Ω+e1cos2Ω=a1

[0068] in:

[0069]

[0070] In the formula, a1, d1, and e1 are symbols used to simplify the first formula and have no actual meaning, and Ω is the Faraday rotation angle.

[0071] Step S2: Based on the double-angle formula and the first formula, determine the second formula.

[0072] In this embodiment of the invention, step S2 may include:

[0073] Squaring both sides of the first equation;

[0074] Based on the double-angle formula, the first formula after squaring is simplified to determine the second formula.

[0075] Specifically, squaring both sides of the first equation, we get:

[0076]

[0077] In equation (3),

[0078] Therefore, based on the following double-angle formula:

[0079]

[0080] Formula (3) can be simplified to:

[0081] Rcos(4Ω-φ)=X (4)

[0082] in:

[0083]

[0084] In the formula, R, φ, and X are all symbols used to simplify formula (4) and have no actual meaning.

[0085] Therefore, based on the above formula (4), the second formula can be determined as follows:

[0086]

[0087] in, is an estimated value of the Faraday rotation angle, where k is an integer.

[0088] Step S3: Based on the second formula, determine the estimated value of the Faraday rotation angle.

[0089] In this embodiment of the invention, step S3 may include:

[0090] Based on the second formula, the initial value of the Faraday rotation angle is determined; wherein, the initial value of the Faraday rotation angle is within the target interval;

[0091] Based on the initial value of the Faraday rotation angle, determine the estimated value of the Faraday rotation angle.

[0092] In this embodiment, the target interval is By adjusting the value of the integer k in the second formula, we can obtain the solution. when The value in At that time, The value is determined as the initial value of the Faraday rotation angle.

[0093] Then, substitute the initial values ​​of the Faraday rotation angles into the following formulas:

[0094]

[0095] The initial value of the Faraday rotation angle that minimizes the magnitude of the error is selected as the estimated value of the Faraday rotation angle.

[0096] In this embodiment, the first formula is simplified using the double-angle formula to eliminate the quadratic term, thereby obtaining an estimated value of the Faraday rotation angle. This reduces the complexity of the solution and increases the calculation speed of the estimated value of the Faraday rotation angle.

[0097] Regarding step 104:

[0098] Substituting the estimated Faraday rotation angle obtained in step 102, and the measurement matrix and characteristic matrix corresponding to each calibrator obtained in step 100 into the target relation, i.e., formula (2), by combining them, we can obtain the expression for the initial estimate of the channel error as shown below:

[0099]

[0100]

[0101]

[0102]

[0103]

[0104]

[0105] in:

[0106]

[0107]

[0108]

[0109]

[0110]

[0111] In the formula, δ1, δ2, δ3, δ4, f1, and f2 represent channel errors. δ1 represents the ratio of crosstalk signal introduced into the V-polarized channel by the received H-polarized channel signal; δ2 represents the ratio of crosstalk signal introduced into the H-polarized channel by the received V-polarized channel signal; δ3 represents the ratio of crosstalk signal introduced into the H-polarized channel by the transmitted V-polarized channel signal; δ4 represents the ratio of crosstalk signal introduced into the V-polarized channel by the transmitted H-polarized channel signal; f1 represents the amplitude and phase imbalance ratio of the received V-polarized channel relative to the H-polarized channel; f2 represents the amplitude and phase imbalance ratio of the transmitted V-polarized channel relative to the H-polarized channel; b1 b2, b3 a2

[0112] , , and a3 are all symbols used to simplify the expression for channel error calculation; they have no actual meaning. M is the estimated value of the Faraday rotation angle, and M is the measurement value of each calibrator in each fully polarized channel.

[0113] Regarding step 106:

[0114] In some implementations, step 106 may include:

[0115] Based on the estimated value of the Faraday rotation angle, the initial estimated value of the channel error, and the characteristic matrix corresponding to each scaler, the estimated value of each scaler under each fully polarized channel is determined.

[0116] The calculation result of the cost function is determined based on the least squares method, the measured and estimated values ​​of each scaler in each fully polarized channel;

[0117] Determine if the cost function calculation result is less than or equal to the set threshold; if yes, use the initial estimate of the current channel error as the target estimate of the channel error; if no, adjust the estimate of the Faraday rotation angle and the initial estimate of the channel error, and jump to execute the estimate of each scaler under each fully polarized channel based on the estimate of the Faraday rotation angle, the initial estimate of the channel error, and the characteristic matrix corresponding to each scaler.

[0118] In this embodiment, the estimated value of the Faraday rotation angle calculated in step 102 is used. The initial estimate of the channel error obtained in step 104 Substituting the feature matrix corresponding to each calibrator obtained in step 100 into the target relation (Formula 2), we can obtain the estimated value of each calibrator in each fully polarized channel.

[0119] Based on the least squares method, the measured and estimated values ​​of each scaler in each fully polarized channel, the calculation result of the cost function is determined according to the following formula:

[0120]

[0121] In the formula, M i,j For each calibrator, the measurement value is given in each fully polarized channel, where i represents the calibrator number and j represents the fully polarized channel. This is the estimate for each scaler in each fully polarized channel.

[0122] A threshold value is set for the calculation result of the cost function. The estimated value of the Faraday rotation angle and the initial estimated value of the channel error are continuously adjusted iteratively (the specific adjustment method can be set according to the actual situation). After each adjustment, the estimated value of each calibrator under each fully polarized channel is calculated, and the value of F(M) is calculated in this way. If F(M) is greater than the set threshold, the adjustment continues until F(M) is less than or equal to the set threshold, and then the target estimated value of the channel error can be obtained.

[0123] It should be noted that since the measurement matrix is ​​obtained by the spaceborne synthetic aperture radar through actual measurements of the calibrators, and the measurement matrix itself is obtained under the condition that calibrator error and system thermal noise coexist, the target estimate of the channel error can be obtained by considering the calibrator error and system thermal noise based on the estimated value of the Faraday rotation angle, the initial estimate of the channel error, the least squares method, the measurement matrix and characteristic matrix corresponding to each calibrator, thereby improving the accuracy of the target estimate of the channel error. Furthermore, in this embodiment, the optimization solution method based on the least squares criterion can iteratively solve the problem while considering system thermal noise and calibrator error, thereby improving the estimation accuracy of the channel error.

[0124] To demonstrate the effectiveness of this method, the following MATLAB simulation experiment was conducted. The simulation parameters, added system thermal noise, and scaler error were all derived according to the ESA BIOMASS program reference values. The simulation parameter settings, including channel error, are shown in Table 1 below:

[0125] Table 1

[0126] Simulation parameters Selected parameter value Ω 48.81° <![CDATA[f1]]> 0.989518320664610-0.006869874578892i <![CDATA[f2]]> 1.000218460599857-0.002087554712170i <![CDATA[δ1]]> 0.008494496045550-0.031667414741174i <![CDATA[δ2]]> 0.011996324589392-0.022099558817945i <![CDATA[δ3]]> 0.010530272294251+0.021556515464907i <![CDATA[δ4]]> -0.001573408145126+0.044661795040908i

[0127] In the simulation, during the least squares solution process, the estimated values ​​of the Faraday rotation angle and the initial estimates of the channel error are adjusted using the MATLAB function fminunc, with the following options set:

[0128] Table 2

[0129] parameter value MaxFunctionEvaluations 100000 StepTolerance 1e-40 OptimalityTolerance 1e-40 FiniteDifferenceType central MaxIterations 10000 Display none

[0130] The target estimates of the channel error obtained using this method are shown in Table 3:

[0131] Table 3

[0132] Channel error Target estimate of channel error <![CDATA[f1]]> 0.989460139996617-0.008464481046585i <![CDATA[f2]]> 1.000486391358069-0.000789285430352i <![CDATA[δ1]]> 0.004722016724272-0.031850035687894i <![CDATA[δ2]]> 0.016552228707427-0.022044793272898i <![CDATA[δ3]]> 0.014940291270642+0.021787011091612i <![CDATA[δ4]]> -0.006002338877522+0.044681018891032i

[0133] The amplitudes of the estimated and measured values ​​were taken and the difference was calculated, resulting in the channel error estimation analysis shown in Table 4:

[0134] Table 4

[0135] Channel error Channel error estimation error (amplitude) <![CDATA[f1]]> 0.001595667501999 <![CDATA[f2]]> 0.001325628160273 <![CDATA[δ1]]> 0.003776896959099 <![CDATA[δ2]]> 0.004556233268573 <![CDATA[δ3]]> 0.004416038451606 <![CDATA[δ4]]> 0.004428972452927

[0136] As can be seen from the comparison, in the presence of system thermal noise and scaler error, the method of this application can fit the order of magnitude of the real and imaginary parts of the channel error, and obtain a higher accuracy estimate of the channel error.

[0137] like Figure 2 , Figure 3 As shown, this embodiment of the invention provides a channel error estimation device for a spaceborne synthetic aperture radar. The device embodiment can be implemented through software, hardware, or a combination of both. From a hardware perspective, such as... Figure 2 The diagram shown is a hardware architecture diagram of a computing device housing a channel error estimation device for a spaceborne synthetic aperture radar according to an embodiment of the present invention. Except for... Figure 2 In addition to the processor, memory, network interface, and non-volatile memory shown, the computing device in the embodiment may also include other hardware, such as a forwarding chip responsible for processing packets. Taking software implementation as an example, such as... Figure 3 As shown, as a logical device, it is formed by the CPU of its computing device reading the corresponding computer program from the non-volatile memory into the main memory and running it. This embodiment provides a channel error estimation device for a spaceborne synthetic aperture radar, comprising:

[0138] The acquisition unit 301 is used to acquire the measurement matrix of multiple calibrators in the fully polarized channel of the spaceborne synthetic aperture radar and the feature matrix of each calibrator.

[0139] The first estimation unit 302 is used to determine the estimated value of the Faraday rotation angle based on the double-angle formula, the measurement matrix and characteristic matrix corresponding to each calibrator;

[0140] The second estimation unit 303 is used to determine the initial estimate of the channel error based on the estimated value of the Faraday rotation angle;

[0141] Iteration unit 304 is used to determine the target estimate of the channel error considering the calibrator error and system thermal noise based on the estimated value of the Faraday rotation angle, the initial estimate of the channel error, the least squares method, the measurement matrix and characteristic matrix corresponding to each calibrator.

[0142] In one embodiment of the present invention, the scaler in the acquisition unit 301 includes two active scalers and two passive scalers; wherein the feature matrix of each scaler is different.

[0143] In one embodiment of the present invention, the first estimation unit 302 is specifically used to perform:

[0144] Substitute the measurement matrix and characteristic matrix corresponding to each calibrator into the target relation to determine the first formula by combining the equations; where the target relation is the relationship expression between the measurement matrix and the characteristic matrix of the spaceborne synthetic aperture radar in the fully polarized channel.

[0145] Based on the double-angle formula and the first formula, the second formula is determined;

[0146] Based on the second formula, the estimated value of the Faraday rotation angle is determined.

[0147] In one embodiment of the present invention, when the first estimation unit 302 performs the determination of the second formula based on the double-angle formula and the first formula, it is specifically used for:

[0148] Squaring both sides of the first equation;

[0149] Based on the double-angle formula, the first formula after squaring is simplified to determine the second formula.

[0150] In one embodiment of the present invention, when the first estimation unit 302 performs the task of determining the estimated value of the Faraday rotation angle based on the second formula, it is specifically used for:

[0151] Based on the second formula, the initial value of the Faraday rotation angle is determined; wherein, the initial value of the Faraday rotation angle is within the target interval;

[0152] Based on the initial value of the Faraday rotation angle, determine the estimated value of the Faraday rotation angle.

[0153] In one embodiment of the present invention, the measurement matrix in the acquisition unit 301 includes the measurement values ​​of the calibrator under HH polarization, VH polarization, HV polarization and VV polarization respectively;

[0154] In one embodiment of the present invention, the iteration unit 304 is specifically used for:

[0155] Based on the estimated value of the Faraday rotation angle, the initial estimated value of the channel error, and the characteristic matrix corresponding to each scaler, the estimated value of each scaler under each fully polarized channel is determined.

[0156] The calculation result of the cost function is determined based on the least squares method, the measured and estimated values ​​of each scaler in each fully polarized channel;

[0157] Determine if the cost function calculation result is less than or equal to the set threshold; if yes, use the initial estimate of the current channel error as the target estimate of the channel error; if no, adjust the estimate of the Faraday rotation angle and the initial estimate of the channel error, and jump to execute the estimate of each scaler under each fully polarized channel based on the estimate of the Faraday rotation angle, the initial estimate of the channel error, and the characteristic matrix corresponding to each scaler.

[0158] In one embodiment of the present invention, the calculation result of the cost function in the iteration unit 304 is calculated according to the following formula:

[0159]

[0160] In the formula, M i,j For each calibrator, the measurement value is given in each fully polarized channel, where i represents the calibrator number and j represents the fully polarized channel. This is the estimate for each scaler in each fully polarized channel.

[0161] It is understood that the structures illustrated in the embodiments of the present invention do not constitute a specific limitation on a channel error estimation device for a spaceborne synthetic aperture radar. In other embodiments of the present invention, a channel error estimation device for a spaceborne synthetic aperture radar may include more or fewer components than illustrated, or combine some components, split some components, or arrange different components. The illustrated components may be implemented in hardware, software, or a combination of software and hardware.

[0162] The information interaction and execution process between the modules in the above-mentioned device are based on the same concept as the method embodiment of the present invention, and the specific details can be found in the description of the method embodiment of the present invention, and will not be repeated here.

[0163] This invention also provides a computing device, including a memory and a processor. The memory stores a computer program, and when the processor executes the computer program, it implements a channel error estimation method for a spaceborne synthetic aperture radar according to any embodiment of this invention.

[0164] This invention also provides a computer-readable storage medium storing a computer program, which, when executed by a processor, causes the processor to perform a channel error estimation method for a spaceborne synthetic aperture radar according to any embodiment of this invention.

[0165] Specifically, a system or apparatus equipped with a storage medium may be provided, on which software program code implementing the functions of any of the embodiments described above is stored, and the computer (or CPU or MPU) of the system or apparatus may read and execute the program code stored in the storage medium.

[0166] In this case, the program code read from the storage medium can itself implement the function of any of the above embodiments, and therefore the program code and the storage medium storing the program code constitute part of the present invention.

[0167] Examples of storage media used to provide program code include floppy disks, hard disks, magneto-optical disks, optical disks (such as CD-ROM, CD-R, CD-RW, DVD-ROM, DVD-RAM, DVD-RW, DVD+RW), magnetic tapes, non-volatile memory cards, and ROMs. Alternatively, program code can be downloaded from a server computer via a communication network.

[0168] Furthermore, it should be clear that not only can the program code read by the computer be executed, but also the operating system or other components operating on the computer can be instructed based on the program code to perform some or all of the actual operations, thereby realizing the function of any of the embodiments described above.

[0169] Furthermore, it is understood that the program code read from the storage medium is written to the memory set in the expansion board inserted into the computer or to the memory set in the expansion module connected to the computer. Then, based on the instructions of the program code, the CPU or other components installed on the expansion board or expansion module execute some and all of the actual operations, thereby realizing the function of any of the above embodiments.

[0170] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus.

[0171] Those skilled in the art will understand that all or part of the steps of the above method embodiments can be implemented by hardware related to program instructions. The aforementioned program can be stored in a computer-readable storage medium. When the program is executed, it performs the steps of the above method embodiments. The aforementioned storage medium includes various media that can store program code, such as ROM, RAM, magnetic disk, or optical disk.

[0172] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for estimating channel errors in a spaceborne synthetic aperture radar, characterized in that, include: The measurement matrices of multiple calibrators under the full polarization channel of the spaceborne synthetic aperture radar and the characteristic matrix of each calibrator were obtained respectively. Based on the double-angle formula, the measurement matrix corresponding to each calibrator, and the characteristic matrix, the estimated value of the Faraday rotation angle is determined; Based on the estimated value of the Faraday rotation angle, an initial estimate of the channel error is determined; Based on the estimated value of the Faraday rotation angle, the initial estimated value of the channel error, the least squares method, the measurement matrix corresponding to each calibrator, and the characteristic matrix, the target estimated value of the channel error considering the calibrator error and the system thermal noise is determined.

2. The method according to claim 1, characterized in that, The scaler includes two active scalers and two passive scalers; wherein the feature matrix of each scaler is different.

3. The method according to claim 2, characterized in that, The process of determining the estimated value of the Faraday rotation angle based on the double-angle formula, the measurement matrix corresponding to each calibrator, and the characteristic matrix includes: Substitute the measurement matrix and the feature matrix corresponding to each calibrator into the target relation to determine the first formula by combining the equations; wherein, the target relation is the relationship expression between the measurement matrix and the feature matrix of the spaceborne synthetic aperture radar in the fully polarized channel. Based on the double-angle formula and the first formula, the second formula is determined; Based on the second formula, the estimated value of the Faraday rotation angle is determined.

4. The method according to claim 3, characterized in that, The determination of the second formula based on the double-angle formula and the first formula includes: Squaring both sides of the first formula; Based on the double-angle formula, the first formula after squaring is simplified to determine the second formula.

5. The method according to claim 3, characterized in that, The step of determining the estimated value of the Faraday rotation angle based on the second formula includes: Based on the second formula, the initial value of the Faraday rotation angle is determined; wherein, the initial value of the Faraday rotation angle is within the target interval; Based on the initial value of the Faraday rotation angle, an estimated value of the Faraday rotation angle is determined.

6. The method according to claim 1, characterized in that, The measurement matrix includes the calibrator measurements under HH polarization, VH polarization, HV polarization, and VV polarization, respectively; The determination of the target estimate of the channel error, considering both calibrator error and system thermal noise, based on the estimated value of the Faraday rotation angle, the initial estimate of the channel error, the least squares method, the measurement matrix corresponding to each calibrator, and the characteristic matrix, includes: Based on the estimated value of the Faraday rotation angle, the initial estimated value of the channel error, and the characteristic matrix corresponding to each scaler, the estimated value of each scaler in each fully polarized channel is determined. The calculation result of the cost function is determined based on the least squares method, the measured and estimated values ​​of each scaler in each fully polarized channel; Determine whether the cost function calculation result is less than or equal to a set threshold; if yes, use the initial estimate of the current channel error as the target estimate of the channel error; if no, adjust the estimate of the Faraday rotation angle and the initial estimate of the channel error, and jump to execute the estimation based on the estimate of the Faraday rotation angle, the initial estimate of the channel error, and the characteristic matrix corresponding to each calibrator to determine the estimate of each calibrator under each fully polarized channel.

7. The method according to claim 6, characterized in that, The cost function is calculated according to the following formula: In the formula, M i,j For each calibrator, the measurement value is given in each fully polarized channel, where i represents the calibrator number and j represents the fully polarized channel. This is the estimate for each scaler in each fully polarized channel.

8. A channel error estimation device for a spaceborne synthetic aperture radar, characterized in that, include: The acquisition unit is used to acquire the measurement matrices of multiple calibrators in the fully polarized channel of the spaceborne synthetic aperture radar and the feature matrix of each calibrator. The first estimation unit is used to determine the estimated value of the Faraday rotation angle based on the double-angle formula, the measurement matrix corresponding to each calibrator, and the characteristic matrix. The second estimation unit is used to determine the initial estimate of the channel error based on the estimated value of the Faraday rotation angle; An iterative unit is used to determine a target estimate of the channel error, taking into account the calibrator error and system thermal noise, based on the estimated value of the Faraday rotation angle, the initial estimate of the channel error, the least squares method, the measurement matrix corresponding to each calibrator, and the characteristic matrix.

9. A computing device comprising a memory and a processor, wherein the memory stores a computer program, and the processor, when executing the computer program, implements the method as described in any one of claims 1-7.

10. A computer-readable storage medium having a computer program stored thereon, which, when executed in a computer, causes the computer to perform the method of any one of claims 1-7.

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