Parameter design method for MIMO ATI SAR two-dimensional ocean current measurement system based on genetic algorithm

Abstract

The application discloses a kind of MIMO ATI SAR two-dimensional ocean current measurement system parameter design methods based on genetic algorithm, comprising: the observation geometry of MIMO ATI SAR system is established, the sea surface flow field measurement system index, interference phase expression and sea surface two-dimensional velocity vector expression are determined;According to the sea surface two-dimensional velocity vector expression, the geometric configuration parameters that influence velocity vector error are determined, and the mathematical relationship between geometric configuration parameters and velocity vector error is established;Determine the MIMO ATI SAR system parameters that influence velocity vector error, establish the mathematical relationship between MIMO ATI SAR system parameters and velocity vector error;Based on the mathematical relationship between geometric configuration parameters and velocity vector error, and the mathematical relationship between MIMO ATI SAR system parameters and velocity vector error, establish the sea surface two-dimensional velocity vector error objective function;Based on genetic algorithm, the sea surface two-dimensional velocity vector error objective function is solved, and the optimal geometric configuration parameters of MIMO ATI SAR system and optimal MIMO ATI SAR system parameters are obtained.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of signal processing, and particularly relates to a MIMO ATI SAR two-dimensional ocean current measurement system parameter design method based on a genetic algorithm. BACKGROUND

[0002] Satellite-borne synthetic aperture radar (SAR) is one of the most rapidly developed and effective sensors in microwave remote sensing devices, and as an active sensor, the satellite-borne synthetic aperture radar is not limited by light and weather conditions, and can realize all-time and all-weather observation of the earth.

[0003] Ocean surface current observation is of great significance to global climate change monitoring, oceanography research, and the study of the interaction between the atmosphere and the ocean and the physical and biochemical interaction process. In the past few decades, through the fusion of multi-sensor data of satellite altimeter, scatterometer and SAR, a global flow field database at the mesoscale (10-100 km) has been formed. However, there is still a lack of observation means for the ocean surface flow field data at the sub-mesoscale range (<10 km), and the sub-mesoscale ocean movement plays an important role in the transportation of carbon dioxide, heat and nutrients.

[0004] In recent years, it has been proven to be feasible to obtain high-resolution radar line-of-sight ocean current field by satellite along-track interferometric (ATI) SAR. The satellite SAR inversion of the ocean surface current field is mainly through along-track interferometric technology, and the average movement speed of the ocean surface scatterer is obtained by using the along-track interferometric phase, and then the wave movement component is removed to obtain the radar line-of-sight direction ocean surface radial flow field. The TanDEM-X system, GF-3 system and other satellite systems are equipped with along-track interferometric test modes, and rich experimental data has been obtained, which proves the superior performance of along-track interferometry in sea current inversion. However, along-track interferometry can only obtain one-dimensional flow field data, which lacks practicality.

[0005] The multi-transmit multi-receive (MIMO) ATI SAR system is composed of a main satellite and at least two auxiliary satellites, wherein the main satellite is a transmitting satellite, and a double antenna is arranged in the along-track direction to be responsible for transmitting a linear frequency modulation signal, and the two auxiliary satellites are respectively placed in the forward and rear directions of the main satellite to be single-antenna signal receiving satellites, and receive the radar echo reflected by the ocean surface after being transmitted by the double antenna of the main satellite. The MIMO ATI SAR system forms three baselines to form an interferometric phase, and realizes the measurement of the two-dimensional flow field of the ocean surface.

[0006] However, the main and auxiliary satellite geometric parameters and radar system parameters involved in the MIMO ATI SAR system have an important influence on the measurement accuracy of the ocean surface flow field, and the current SAR system design method mainly takes image resolution as the design index, and is not suitable for the system parameter design of the MIMO ATI SAR ocean surface flow field measurement system. SUMMARY

[0007] In order to solve the above problems existing in the prior art, the application provides a MIMO ATI SAR two-dimensional ocean current measurement system parameter design method based on a genetic algorithm.

[0008] The application provides a MIMO ATI SAR two-dimensional ocean current measurement system parameter design method based on a genetic algorithm, comprising:

[0009] An observation geometry of a multi-transmitter and multi-receiver in-track interferometric synthetic aperture radar (MIMO ATI SAR) system is established, and a sea surface flow field measurement system index, an interferometric phase expression and a sea surface two-dimensional velocity vector expression are determined;

[0010] According to the sea surface two-dimensional velocity vector expression, geometric configuration parameters affecting the velocity vector error are determined, and a mathematical relationship between the geometric configuration parameters and the velocity vector error is established;

[0011] MIMO ATI SAR system parameters affecting the velocity vector error are determined, and a mathematical relationship between the MIMO ATI SAR system parameters and the velocity vector error is established;

[0012] Based on the mathematical relationship between the geometric configuration parameters and the velocity vector error and the mathematical relationship between the MIMO ATI SAR system parameters and the velocity vector error, a sea surface two-dimensional velocity vector error objective function is established;

[0013] The sea surface two-dimensional velocity vector error objective function is solved based on a genetic algorithm, and optimal geometric configuration parameters and optimal MIMO ATI SAR system parameters of the MIMO ATI SAR system are obtained.

[0014] In an embodiment of the application, the MIMO ATI SAR system comprises a main star, a first auxiliary star and a second auxiliary star, the main star is a transmitting star, and double antennas are arranged in the along-track direction to transmit a linear frequency modulation signal, the first auxiliary star and the second auxiliary star are respectively located in the forward direction and the backward direction of the main star, are single-antenna signal receiving stars, and are used for receiving radar echoes reflected by the sea surface and transmitted by the main star;

[0015] The sea surface flow field measurement system index comprises a sea surface flow field spatial resolution S s , an observation width W g and a sea surface flow field velocity accuracy Δv, and the geometric configuration parameters affecting the velocity vector error at least comprise a main star downward-looking angle θ, an auxiliary star oblique-looking angle θ slaveand a main satellite antenna baseline B, the MIMO ATI SAR system parameters affecting the velocity vector error at least include: signal bandwidth and synthetic aperture time.

[0016] In one embodiment of the present application, the interference phase expression comprises:

[0017]

[0018] wherein, respectively represent the interference phase of the main satellite, the interference phase of the first auxiliary satellite and the interference phase of the second auxiliary satellite, λ represents wavelength, τ represents time baseline, v cen , v fore , v aft respectively represent the sea surface velocity vector on the ground projection of the radar beam of the main satellite, the first auxiliary satellite and the second auxiliary satellite, θ i , θ fore , θ aft respectively represent the beam incidence angle of the main satellite, the first auxiliary satellite and the second auxiliary satellite, respectively represent the random error of the interference phase of the main satellite, the first auxiliary satellite and the second auxiliary satellite, represent system error.

[0019] In one embodiment of the present application, the sea surface two-dimensional velocity vector expression comprises:

[0020] v cen = v gr ;

[0021] v fore = v gr cos ρ fore - v az sin ρ fore ;

[0022] v aft = v gr cos ρ aft + v az sin ρ aft

[0023] wherein, v az , v gr respectively represent the azimuth velocity and the ground range velocity after the vector decomposition of the current field velocity along the x-axis and the y-axis, wherein the vertical projection of the main satellite is the origin of the xyz coordinate system, the direction of the satellite observation point is the y-axis, and the direction of the main satellite is the z-axis, ρ fore , ρ aft respectively represent the angle between the ground projection of the beam vector of the first auxiliary satellite and the y-axis and the angle between the ground projection of the beam vector of the second auxiliary satellite and the y-axis, G z =[1 1 0], Represents the vector from the first auxiliary satellite\second auxiliary satellite to the satellite observation point, slave=fore or aft represents the first auxiliary satellite or the second auxiliary satellite.

[0024] In one embodiment of the present invention, the step of establishing a mathematical relationship between the geometric configuration parameters and the velocity vector error includes:

[0025] In the xyz coordinate system, the beam incident angle of the auxiliary satellite is

[0026] In the xyz coordinate system, determine the coordinates of the primary star [0 0h], the coordinates of the first auxiliary star\the second auxiliary star and the coordinates of the satellite observation point [0h·tanθ0], where h represents the altitude of the host star;

[0027] Primary satellite antenna baseline B = τ·v s , where v s Indicates the satellite speed.

[0028] In one embodiment of the present invention, the step of establishing a mathematical relationship between the MIMO ATI SAR system parameters and the velocity vector error includes:

[0029] According to the fuzzy function theory, the ground distance resolution d is calculated respectively. gr and azimuth resolution d ga :

[0030]

[0031] In the formula, T represents transposition, G ⊥ represents the ground projection matrix, ω T represents the angular velocity vector of the primary star relative to the target, ω R Respectively represent the angular velocity vectors of the first auxiliary satellite and the second auxiliary satellite relative to the target, T s represents the synthetic aperture time, B r represents the signal bandwidth, ξ T ,ξ R Respectively and The unit vector of is the vector from the main star to the satellite observation point, represents the vector from the first auxiliary satellite\second auxiliary satellite to the satellite observation point, and c represents the electromagnetic wave propagation speed;

[0032] According to the ground distance resolution d gr and the azimuth resolution d ga , calculate the resolution unit area:

[0033] S g =d gr ·d ga / sin(Ω);

[0034] In the formula, Ω represents a two-dimensional resolution direction angle of the ground;

[0035] Based on the resolution unit area S g and the sea surface flow field spatial resolution S s , a multi-view number N is calculated

[0036] In an embodiment of the present application, the sea surface two-dimensional velocity vector error objective function is:

[0037]

[0038] s.t.x p ∈E;

[0039] In the formula, the parameter set x p =(θ,θ slave ,B r ,T s ,λ,S s ,W g ) T , E represents a limited range, Δv az represents a azimuthal velocity error, and Δv ra represents a range velocity error.

[0040] In an embodiment of the present application, the limited range E includes:

[0041] The pulse repetition frequency PRF does not satisfy the following condition:

[0042]

[0043]

[0044] In the formula, Frac() represents a decimal part, τ P represents a pulse width, τ RP represents a protection time, and L represents a distance between a main star and a first auxiliary star / second auxiliary star.

[0045] The maximum value of the pulse repetition frequency PRF wherein τ far is a scene far-end echo receiving time, and τ near is a scene far-end echo receiving time.

[0046] In an embodiment of the present application, before the step of solving the sea surface two-dimensional velocity vector error objective function, the method further includes:

[0047] Introduced by θ i ,θ fore ,θ aft and ρ fore , ρ aft The determined matrix H rewrites the two-dimensional sea surface velocity vector expression as follows:

[0048]

[0049] Right now:

[0050]

[0051] Where, represents the random phase error of interference, Δv az , Δv gr They represent the azimuth velocity error and the distance velocity error respectively, represents the calculated systematic error;

[0052] According to the number of multiple views N L calculate Standard deviation Where γ = γ SNR ×γ temp , Residual coherence caused by thermal noise in MIMOATI SAR system Signal-to-noise ratio σ0 represents the sea surface scattering coefficient, the noise equivalent backscattering coefficient T s represents the coherent integration time, T a Indicates the noise temperature, F n Represents the receiver noise figure, G T , G R Represents the antenna gain of the transmitting channel and the receiving channel, and the average transmitting power of the main satellite R R Indicates the receiving slant range, R T Indicates the launch slant distance, L s represents the MIMO ATI SAR system loss, k is the Bohr coefficient, P m It is expressed as the average emission power of the main star, the coherence caused by temporal decoherence t c represents the sea surface coherence time;

[0053] Based on the standard deviation σ γ and the rewritten two-dimensional sea surface velocity vector expression, solve for Δv gr and Δv az .

[0054] In one embodiment of the present application, the genetic algorithm is used to solve the sea surface two-dimensional velocity vector error objective function as follows:

[0055]

[0056] wherein x p_opt represents the optimal parameter set obtained, including the optimal geometric configuration parameters of the ATI SAR system and the optimal MIMO ATI SAR system parameters.

[0057] Compared with the prior art, the present application has the following beneficial effects:

[0058] The present application provides a MIMO ATI SAR two-dimensional ocean current measurement system parameter design method based on a genetic algorithm.

[0059] The present application will be further described in detail below in combination with the accompanying drawings and embodiments. BRIEF DESCRIPTION OF DRAWINGS

[0060] Figure 1 is a flowchart of the MIMO ATI SAR two-dimensional ocean current measurement system parameter design method based on a genetic algorithm provided by the embodiments of the present application;

[0061] Figure 2 is a schematic diagram of the MIMO ATI SAR system provided by the embodiments of the present application;

[0062] Figure 3 is a geometric configuration diagram of the MIMO ATI SAR system provided by the embodiments of the present application;

[0063] Figure 4 is a schematic diagram of the beam vector ground projection provided by the embodiments of the present application;

[0064] Figure 5 is a schematic diagram of the velocity error changing with the signal bandwidth and the synthetic aperture time provided by the embodiments of the present application. DETAILED DESCRIPTION

[0065] The present application will be further described in detail below in combination with the accompanying drawings and embodiments.

[0066] Figure 1is a flowchart of a method for designing parameters of a MIMO ATI SAR two-dimensional ocean current measurement system based on a genetic algorithm provided in an embodiment of the present application, Figure 2 is a schematic diagram of a MIMO ATI SAR system provided in an embodiment of the present application. Figures 1-2 As shown in the figure, the embodiment of the present application provides a method for designing parameters of a MIMO ATI SAR two-dimensional ocean current measurement system based on a genetic algorithm, comprising:

[0067] S1, establishing an observation geometry of a multi-transmitter and multi-receiver in-track interferometric synthetic aperture radar (MIMO ATI SAR) system, determining sea surface current field measurement system indicators, an interferometric phase expression and a sea surface two-dimensional velocity vector expression;

[0068] S2, determining geometric configuration parameters affecting the velocity vector error according to the sea surface two-dimensional velocity vector expression, and establishing a mathematical relationship between the geometric configuration parameters and the velocity vector error;

[0069] S3, determining MIMO ATI SAR system parameters affecting the velocity vector error, and establishing a mathematical relationship between the MIMO ATI SAR system parameters and the velocity vector error;

[0070] S4, based on the mathematical relationship between the geometric configuration parameters and the velocity vector error, and the mathematical relationship between the MIMO ATI SAR system parameters and the velocity vector error, establishing a sea surface two-dimensional velocity vector error objective function;

[0071] S5, solving the sea surface two-dimensional velocity vector error objective function based on a genetic algorithm to obtain optimal geometric configuration parameters and optimal MIMO ATI SAR system parameters of the MIMO ATI SAR system.

[0072] In this embodiment, the MIMO ATI SAR system comprises a main star, a first auxiliary star and a second auxiliary star. The main star is a transmitting star, and has double antennas arranged in the along-track direction to transmit a linear frequency modulation signal. The first auxiliary star and the second auxiliary star are respectively located in the forward direction and the backward direction of the main star, and are single-antenna signal receiving stars for receiving radar echoes reflected by the sea surface and transmitted by the main star.

[0073] Optionally, the sea surface current field measurement system indicators include a sea surface current field spatial resolution S s , an observation width W g and a sea surface current field velocity accuracy Δv. The subsequent design needs to meet the sea surface current field spatial resolution S s and the observation width W g , and through the optimal design of the MIMO ATI SAR system parameters, the minimum sea surface current field velocity accuracy Δv is obtained.

[0074] The geometric configuration parameters affecting the velocity vector error at least include: the main star downward angle θ, the auxiliary star oblique angle θ slave And the main star antenna baseline B, the MIMO ATI SAR system parameters affecting the velocity vector error at least include: signal bandwidth and synthetic aperture time.

[0075] Figure 3 is a geometric configuration diagram of the MIMO ATI SAR system provided by the embodiment of the application, Figure 4 is a schematic diagram of beam vector ground projection. Optionally, the interference phase expression includes:

[0076]

[0077] In the formula, respectively represent the interference phase of the main star, the interference phase of the first auxiliary star and the interference phase of the second auxiliary star, λ represents the wavelength, τ represents the time baseline, v cen , v fore , v aft respectively represent the sea surface velocity vector on the ground projection of the main star, the first auxiliary star and the second auxiliary star radar beam, θ i , θ fore , θ aft respectively represent the beam incidence angle of the main star, the first auxiliary star and the second auxiliary star, respectively represent the random error of the main star, the first auxiliary star and the second auxiliary star interference phase, represent the system error.

[0078] The two-dimensional sea surface velocity vector expression includes:

[0079] v cen = v gr ;

[0080] v fore = v gr cosρ fore -v az sinρ fore ;

[0081] v aft = v gr cosρ aft +v az sinρ aft

[0082] In the formula, v az , v grThey represent the azimuthal velocity and ground-range velocity after the convective field velocity is decomposed along the x-axis and y-axis vectors, respectively. The vertical projection of the main satellite is the origin of the xyz coordinate system, the direction from the origin to the satellite observation point is the y-axis, and the direction from the origin to the main satellite is the z-axis. fore , ρ aft They represent the angles between the projections of the beam vectors of the first auxiliary satellite and the second auxiliary satellite on the ground and the y-axis, G z =[1 1 0], represents the vector from the first auxiliary satellite\second auxiliary satellite to the satellite observation point, slave=fore or aft represents the first auxiliary satellite or the second auxiliary satellite;

[0083] In step S2, the step of establishing a mathematical relationship between the geometric configuration parameters and the velocity vector error includes:

[0084] S201, in the xyz coordinate system, the auxiliary satellite's beam incident angle

[0085] S202. In the xyz coordinate system, determine the coordinates of the primary star [0 0h], the coordinates of the first auxiliary star and the second auxiliary star and the coordinates of the satellite observation point [0h·tanθ0], where h represents the altitude of the host star;

[0086] S203, main satellite antenna baseline B = τ·v s , where v s Indicates the satellite speed.

[0087] Optionally, before the step of solving the sea surface two-dimensional velocity vector error objective function, the method further includes:

[0088] Introduced by θ i ,θ fore ,θ aft and ρ fore , ρ aft The matrix H determined by the sea surface two-dimensional velocity vector expression is rewritten as:

[0089]

[0090] Right now:

[0091]

[0092] Where, represents the random phase error of interference, Δv az , Δv gr They represent the azimuth velocity error and the distance velocity error respectively, represents the calculated systematic error;

[0093] According to the number of multiple views NL Computing the standard deviation of where γ = γ SNR × γ temp , the residual coherence caused by thermal noise of MIMO ATI SAR system signal-to-noise ratio σ0 represents the sea surface scattering coefficient, the noise equivalent backscattering coefficient T s represents the coherent accumulation time, T a represents the noise temperature, F n represents the receiver noise figure, G T , G R respectively represent the antenna gain of the transmitting channel and the receiving channel, the average transmitting power of the primary star R R represents the receiving slant range, R T represents the transmitting slant range, L s represents the loss of MIMO ATI SAR system, k is the Boltzmann constant, P m represents the average transmitting power of the primary star, the coherence caused by temporal decorrelation t c represents the sea surface coherence time;

[0094] Based on the standard deviation σ γ and the rewritten two-dimensional sea surface velocity vector expression, Δv gr and Δv az are solved.

[0095] In step S3, the step of establishing the mathematical relationship between the MIMO ATI SAR system parameters and the velocity vector error includes:

[0096] S301, according to the ambiguity function theory, the ground range resolution d gr and the azimuth resolution d ga are calculated respectively:

[0097]

[0098] In the formula, T represents transposition, G ⊥ represents the ground projection matrix, ω T represents the angular velocity vector of the primary star relative to the target, ω R respectively represent the angular velocity vector of the first auxiliary star\second auxiliary star relative to the target, T s represents the synthetic aperture time, B r represents the signal bandwidth, ξ T , ξ R respectively represent the unit vectors of and ​is a vector from the primary satellite to the satellite observation point, is a vector from the first / second auxiliary satellite to the satellite observation point, and c represents the electromagnetic wave propagation speed;

[0099] S302, according to the ground distance resolution d gr and the azimuth resolution d ga , the resolution unit area S is calculated:

[0100] S g = d gr · d ga / sin(Ω);

[0101] In the formula, Ω represents the ground two-dimensional resolution direction angle;

[0102] S303, based on the resolution unit area S g and the sea surface flow field spatial resolution S s , the number of views N is calculated It should be noted that the number of views N L is a function of the variable primary satellite downward angle θ, auxiliary satellite oblique angle θ sq , signal bandwidth B r , synthetic aperture time T s .

[0103] In this embodiment, the spatial resolution S s and the observation width W are variables, so only the minimum measurement speed error needs to be considered in the parameter optimization process. The sea surface two-dimensional velocity vector error objective function is established as:

[0104]

[0105] s.t.x p ∈E;

[0106] In the formula, the parameter set x p =(θ,θ slave ,B r ,T s ,λ,S s ,W g ) T , E represents the limited range, Δv az represents the azimuth velocity error, and Δv ra represents the range velocity error.

[0107] The limited range E includes:

[0108] The pulse repetition frequency PRF does not satisfy the following condition:

[0109] In the first aspect, only the direct wave interference needs to be considered in the transceiver separation case, and the pulse repetition frequency PRF needs to satisfy:

[0110]

[0111] In the second aspect, the intermediate receiving channel and the transmitting channel are co-platform, and the transmitting pulse interference needs to be considered, and the limitation of PRF is:

[0112]

[0113] In addition, in order to avoid the subsatellite point interference, the PRF cannot satisfy:

[0114]

[0115] In the formula, Frac() represents a decimal part, τ P represents a pulse width, τ RP represents a protection time, and L represents the distance between the main star and the first auxiliary star / second auxiliary star.

[0116] Due to the characteristics of the SAR satellite, the useful echo of the observation area should be received within one pulse transmission period, that is, the maximum value of the pulse repetition frequency PRF is In the formula, τ far is the scene far-end echo receiving time, τ near is the scene far-end echo receiving time. Optionally, the pulse width τ P = 0.15·PRT, τ far = h·tan(θ+θ r / 2), τ near = h·tan(θ-θ r / 2), and θ r represents the distance direction beam width.

[0117] The sea surface two-dimensional velocity vector error objective function solved by using the genetic algorithm is:

[0118]

[0119] In the formula, x p_opt represents an optimal parameter set solved, including optimal geometric configuration parameters of the ATI SAR system and optimal MIMO ATI SAR system parameters.

[0120] The genetic algorithm-based MIMO ATI SAR two-dimensional ocean current measurement system parameter design method provided by the application is further described through simulation experiments.

[0121] The parameters used in the simulation process include: the main star downward angle θ, the auxiliary star oblique angle θ sq , the main star antenna baseline B, the system parameter signal bandwidth B r , and the synthetic aperture time T sand parameters such as wavelength λ, and specific value ranges are: θ∈[15°, 30°], T s ∈[0.3, 1.3s], θ sq ∈[15°, 35°], f c ∈[15GHz, 30GHz] and B r ∈[50MHz, 600MHz], and sea surface flow field measurement system indexes are shown in Table 1:

[0122] Table 1

[0123] Observed swath width 200 km Spatial resolution of the sea surface current field 200m Velocity accuracy of the sea surface current field 3 cm

[0124] Optimal geometric configuration parameters and optimal MIMO ATI SAR system parameters obtained by using the above genetic algorithm-based MIMO ATI SAR two-dimensional ocean current measurement system parameter design method are shown in Table 2:

[0125] Table 2

[0126]

[0127] Further verification of the effectiveness of the results shown in Table 2 is shown in the change trend of the velocity error with the change of the pulse bandwidth and the synthetic aperture time as shown in Figure 5 It can be seen that the velocity error reaches the optimum at the geometric configuration parameters and MIMO ATI SAR system parameters shown in Table 2.

[0128] From the above embodiments, the beneficial effects of the present application are:

[0129] The present application provides a genetic algorithm-based MIMO ATI SAR two-dimensional ocean current measurement system parameter design method, which is different from the prior art. Instead of taking the SAR image resolution as the objective function, the method takes the inversion two-dimensional vector flow velocity accuracy as the sea surface two-dimensional velocity vector error objective function, and obtains the optimal solution, avoiding the repeated trade-off of individual system parameters in the design of the MIMO ATI SAR system, and fully meeting the MIMO ATI SAR sea surface two-dimensional vector measurement system parameter design requirements.

[0130] In the description of the present application, the terms "first", "second" are only for the purpose of description, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of indicated technical features. Therefore, the features defined with "first", "second" can explicitly or implicitly include one or more of the features. In the description of the present application, the meaning of "multiple" is two or more, unless otherwise specifically limited.

[0131] Reference to terms "one embodiment", "some embodiments", "an example", "a specific example", or "some examples" etc., mean that a particular feature, structure, material or characteristic being described is included in at least one embodiment or example of the present application. The appearances of the above-described terms in various places in the specification are not necessarily referring to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics can be combined in any suitable manner in one or more embodiments or examples. Also, the particular features, structures, materials, or characteristics can be combined in any suitable manner in one or more embodiments or examples. Moreover, those skilled in the art will appreciate that the described particular features, structures, materials, or characteristics can be combined in any suitable manner in other combinations of one or more embodiments or examples without necessarily being mutually exclusive.

[0132] The above further describes the present application in detail with reference to specific preferred embodiments. The present application is not limited to these descriptions. Any simple derivations or replacements made by those skilled in the art without departing from the concept of the present application shall be considered as falling within the protection scope of the present application.

Claims

1. A method for designing parameters of a MIMO ATI SAR two-dimensional ocean current measurement system based on a genetic algorithm, characterized in that: include: Establish the observation geometry of the MIMO ATI SAR system, determine the sea surface flow field measurement system indicators, interferometric phase expression, and two-dimensional sea surface velocity vector expression; Determining geometric configuration parameters that affect the velocity vector error based on the two-dimensional sea surface velocity vector expression, and establishing a mathematical relationship between the geometric configuration parameters and the velocity vector error; Determining MIMO ATI SAR system parameters that affect velocity vector error, and establishing a mathematical relationship between the MIMO ATI SAR system parameters and the velocity vector error; Based on the mathematical relationship between the geometric configuration parameters and the velocity vector error, and the mathematical relationship between the MIMO ATI SAR system parameters and the velocity vector error, a two-dimensional velocity vector error objective function of the sea surface is established; Solving the two-dimensional sea surface velocity vector error objective function based on a genetic algorithm to obtain optimal geometric configuration parameters and optimal MIMO ATI SAR system parameters of the MIMO ATI SAR system; The MIMO ATI SAR system includes: a primary satellite, a first secondary satellite, and a second secondary satellite. The primary satellite is a transmitting satellite equipped with dual antennas along the track direction for transmitting linear frequency modulation signals. The first secondary satellite and the second secondary satellite are located in the front and rear directions of the primary satellite, respectively, and are single-antenna signal receiving satellites for receiving radar echoes emitted by the primary satellite and reflected by the sea surface. The sea surface flow field measurement system indicators include: sea surface flow field spatial resolution , observation width and the sea surface flow velocity accuracy The geometric configuration parameters that affect the velocity vector error include at least: the viewing angle under the main satellite , auxiliary star oblique angle and the main satellite antenna baseline , the MIMO ATI SAR system parameters affecting the velocity vector error include at least: signal bandwidth and synthetic aperture time; The interference phase expression includes: ； ； ； Where, 、 、 represent the interference phase of the primary star, the interference phase of the first auxiliary star, and the interference phase of the second auxiliary star, respectively. represents the wavelength, represents the time baseline, 、 、 Represent the sea surface velocity vector velocity components of the radar beams of the primary satellite, the first auxiliary satellite, and the second auxiliary satellite on the ground projections, 、 、 represent the beam incident angles of the primary satellite, the first auxiliary satellite, and the second auxiliary satellite, respectively, 、 、 represent the random errors of the interference phases of the primary star, the first auxiliary star, and the second auxiliary star, respectively, Indicates systematic error; The two-dimensional sea surface velocity vector expression includes: ； ； Where, 、 Respectively represent the velocity of the convection field along axis, The azimuth velocity and the ground-range velocity after the axis vector decomposition, wherein the vertical projection of the main star is The origin of the coordinate system, the direction from the origin to the satellite observation point is Axis, the origin points to the direction of the main star axis, 、 Respectively represent the projection of the first auxiliary satellite and the second auxiliary satellite beam vector on the ground and The angle of the axis, , , Represents the vector from the first auxiliary satellite\second auxiliary satellite to the satellite observation point, Indicates the first auxiliary star or the second auxiliary star; The sea surface two-dimensional velocity vector error objective function is: ； ； In the formula, the parameter set , Indicates a limited range. represents the azimuth velocity error, represents the speed error in the range direction, represents the signal bandwidth, represents the synthetic aperture time; Limited scope include: Pulse repetition frequency The following conditions are not met: ； ； ； ； Where, Indicates taking the decimal part. Indicates the pulse width, Indicates protection time, Indicates the distance between the main star and the first auxiliary star\second auxiliary star, Indicates the propagation speed of electromagnetic waves; Pulse repetition frequency The maximum value ,in, is the scene far-end echo reception time, The near-end echo reception time of the scene.

2. The method for designing parameters of a MIMO ATI SAR two-dimensional ocean current measurement system based on a genetic algorithm according to claim 1, wherein: The step of establishing a mathematical relationship between the geometric configuration parameters and the velocity vector error comprises: In the In the coordinate system, the beam incident angle of the auxiliary satellite ; In the In the coordinate system, determine the coordinates of the main star , coordinates of the first auxiliary star\second auxiliary star and the coordinates of the satellite observation point , represents the altitude of the primary star; Main satellite antenna baseline ,in, Indicates the satellite speed.

3. The method for designing parameters of a MIMO ATI SAR two-dimensional ocean current measurement system based on a genetic algorithm according to claim 2, wherein: The step of establishing a mathematical relationship between the MIMO ATI SAR system parameters and the velocity vector error comprises: According to the fuzzy function theory, the ground distance resolution is calculated respectively and azimuth resolution : ； ； Where, represents transpose, represents the ground projection matrix, represents the angular velocity vector of the primary star relative to the target, Respectively represent the angular velocity vectors of the first auxiliary satellite and the second auxiliary satellite relative to the target, 、 Respectively and The unit vector of is the vector from the main star to the satellite observation point, Represents the vector from the first auxiliary satellite\second auxiliary satellite to the satellite observation point; According to the ground distance resolution and the azimuth resolution , calculate the resolution unit area: ； Where, Indicates the ground two-dimensional resolution direction angle; Based on the resolution unit area And the spatial resolution of the sea surface flow field , calculate the number of multi-views .

4. The method for designing parameters of a MIMO ATI SAR two-dimensional ocean current measurement system based on a genetic algorithm according to claim 1, wherein: Before the step of solving the sea surface two-dimensional velocity vector error objective function, the method further includes: Introduced by 、 、 as well as 、 Decision Matrix , rewrite the two-dimensional sea surface velocity vector expression as: ； Right now: ； Where, represents the interferometric random phase error, represents the interferometric random phase error vector, 、 They represent the azimuth velocity error and the distance velocity error, represents the calculated systematic error; According to the multi-view calculate Standard deviation ,in, , Residual coherence caused by thermal noise in MIMO ATISAR system , signal-to-noise ratio , Represents the sea surface scattering coefficient, noise equivalent backscattering coefficient , represents the coherent integration time, represents the noise temperature, represents the receiver noise figure, 、 Represents the antenna gain of the transmitting channel and the receiving channel, and the average transmitting power of the main satellite , Indicates the receiving slant range, Indicates the launch slant range, Indicates the MIMO ATI SAR system loss, is the Bohr coefficient, It is expressed as the average emission power of the main star, the coherence caused by temporal decoherence , represents the sea surface coherence time; Based on the standard deviation and the rewritten expression of the two-dimensional velocity vector of the sea surface, solve and .

5. The method for designing parameters of a MIMO ATI SAR two-dimensional ocean current measurement system based on a genetic algorithm according to claim 1, wherein: The objective function of the two-dimensional sea surface velocity vector error is solved by genetic algorithm as follows: ； Where, represents the optimal parameter set obtained by solving, including the optimal geometric configuration parameters of the ATI SAR system and the optimal MIMO ATI SAR system parameters.

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