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

Abstract

The invention discloses an MIMO ATI SAR two-dimensional ocean current measurement system parameter design method based on a genetic algorithm, and the method comprises the steps: building the observation geometry of an MIMO ATI SAR system, and determining a sea surface flow field measurement system index, an interferometric phase expression, and a sea surface two-dimensional velocity vector expression; according to the sea surface two-dimensional velocity vector expression, determining geometric configuration parameters influencing velocity vector errors, and establishing a mathematical relationship between the geometric configuration parameters and the velocity vector errors; determining MIMO ATI SAR system parameters influencing the velocity vector error, and establishing a 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 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; and solving the sea surface two-dimensional velocity vector error objective function based on a genetic algorithm to obtain the optimal geometric configuration parameters of the MIMO ATI SAR system and the optimal parameters of the MIMO ATI SAR system.

Description

Technical Field

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

[0002] Spaceborne synthetic aperture radar (SAR) is one of the fastest-growing and most effective sensors in microwave remote sensing equipment. As an active sensor, spaceborne synthetic aperture radar is not restricted by lighting and climatic conditions and can achieve all-day and all-weather earth observation.

[0003] Observation of ocean surface currents is of great significance for global climate change monitoring, oceanographic research, atmosphere-ocean interaction and its physical and biochemical interaction processes. In the past few decades, a basic database of global flow fields at the mesoscale (10-100km) has been formed through the fusion of satellite-borne altimeters, scatterometers and SAR multi-sensor data. However, there is still a lack of observation methods for sea surface flow field data in the sub-mesoscale range (<10km), and sub-mesoscale ocean movement plays an important role in the transport of carbon dioxide, heat and nutrients.

[0004] In recent years, it has been proven feasible to obtain high-resolution ocean flow fields in the direction of radar line of sight by using space-borne Along-Track Interferometric (ATI) SAR. Space-borne SAR inverts the sea surface flow field mainly through along-track interferometric technology. The average motion velocity of the sea surface scatterers is obtained by using the along-track interferometric phase, and then the wave motion component is taken out to obtain the radial flow field of the sea surface in the direction of radar line of sight. Satellite systems such as the TanDEM-X system and the GF-3 system are equipped with along-track interferometric test modes, and rich experimental data have been obtained, proving the superior performance of along-track interferometric in ocean current inversion. However, along-track interferometric can only obtain one-dimensional flow field data, which lacks practicality.

[0005] The multiple-transmit multiple-receive (MIMO) ATI SAR system consists of a main satellite and at least two auxiliary satellites, where the main satellite is a transmitting satellite with dual antennas set along the track direction to transmit linear frequency modulation signals. The two auxiliary satellites are placed in the front and rear directions of the main satellite, and are single-antenna signal receiving satellites that receive radar echoes reflected by the sea surface from the dual antennas of the main satellite. Thus, the MIMO ATI SAR system forms three baselines to form an interferometric phase, realizing the measurement of the two-dimensional flow field on the sea surface.

[0006] However, the geometric parameters of the main and auxiliary satellites and the radar system parameters involved in the MIMO ATI SAR system have an important impact on the measurement accuracy of the sea surface flow field. The current design method of the SAR system mainly uses image resolution as the design indicator, which is not suitable for the system parameter design of the MIMO ATI SAR sea surface flow field measurement system. Summary of the invention

[0007] In order to solve the above problems existing in the prior art, the present invention provides a parameter design method for a MIMOATI SAR two-dimensional ocean current measurement system based on a genetic algorithm. The technical problem to be solved by the present invention is achieved through the following technical solutions:

[0008] The present invention provides a method for designing parameters of a MIMO ATI SAR two-dimensional ocean current measurement system based on a genetic algorithm, comprising:

[0009] Establish the observation geometry of the MIMO ATI SAR system, determine the sea surface flow field measurement system indicators, interference phase expression and sea surface two-dimensional velocity vector expression;

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

[0011] 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;

[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 two-dimensional velocity vector error objective function of the sea surface is established;

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

[0014] In one embodiment of the present invention, the MIMO ATI SAR system includes: a primary satellite, a first secondary satellite and a second secondary satellite, wherein the primary satellite is a transmitting satellite and is provided with dual antennas along the track direction to transmit linear frequency modulation signals, and 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;

[0015] The sea surface flow field measurement system indicators include: sea surface flow field spatial resolution S s , observation width W g and the velocity accuracy Δv of the sea surface flow field. The geometric configuration parameters affecting the velocity vector error include at least: the primary satellite downward viewing angle θ, the auxiliary satellite oblique viewing angle θ slaveand the primary 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 invention, the interference phase expression includes:

[0017]

[0018] In the formula, 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, λ represents the wavelength, τ represents the time baseline, v cen 、v fore 、v aft Denote the sea surface velocity vector The velocity component of the radar beams of the primary satellite, the first auxiliary satellite and the second auxiliary satellite on the ground projection, θ i ,θ fore ,θ aft 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.

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

[0020] v cen =v gr ;

[0021] v fore =v gr cosρ fore -v az sinρ fore ;

[0022] v aft =v gr cosρ aft +v az sinρ aft

[0023] In the formula, v az 、v gr They represent the azimuth velocity and ground-distance velocity after the convective field velocity is decomposed along the x-axis and y-axis vectors, respectively. The vertical projection of the master 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 master satellite is the z-axis. fore , aft 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, respectively. G z =[1 1 0], Represents the vector from the first auxiliary satellite\the 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 parameter and the velocity vector error comprises:

[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] The main 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 the mathematical relationship between the MIMO ATI SAR system parameters and the velocity vector error comprises:

[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 satellite 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 , 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\the second auxiliary satellite to the satellite observation point, and c represents the propagation speed of electromagnetic waves;

[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] Where, Ω represents the ground two-dimensional resolution direction angle;

[0035] Based on the resolution unit area S g And the spatial resolution S of the sea surface flow field s , calculate the number of multi-views

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

[0037]

[0038] stx 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 the limited range, Δv az represents the azimuth velocity error, Δv ra Indicates the speed error in the range direction.

[0040] In one embodiment of the present invention, the limited range E includes:

[0041] The pulse repetition frequency PRF does not meet the following conditions:

[0042]

[0043]

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

[0045] The maximum value of the pulse repetition frequency PRF Among them, τ far is the scene far-end echo reception time, τ near It is the scene far-end echo reception time.

[0046] In one embodiment of the present invention, 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 , aft The determined matrix H rewrites the two-dimensional sea surface velocity vector expression as follows:

[0048]

[0049] Right now:

[0050]

[0051] In the formula, 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 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, and the average transmitting power of the main satellite R R Indicates the receiving slant distance, 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 transmission 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 velocity vector expression of the sea surface, solving for Δv gr and Δv az .

[0054] In one embodiment of the present invention, the sea surface two-dimensional velocity vector error objective function is solved by using a genetic algorithm as follows:

[0055]

[0056] In the formula, x p_opt 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.

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

[0058] The present invention provides a MIMO ATI SAR two-dimensional ocean current measurement system parameter design method based on a genetic algorithm. Different from the prior art, the method does not take the SAR image resolution as the objective function, but takes the inverted two-dimensional vector velocity accuracy as the sea surface two-dimensional velocity vector error objective function, and obtains the optimal solution, thereby avoiding the repeated weighing of a single system parameter when designing the MIMO ATI SAR system, and fully meets the system parameter design requirements of the MIMO ATI SAR sea surface two-dimensional vector measurement system.

[0059] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0060] Figure 1 It is a flow chart of a parameter design method of a MIMO ATI SAR two-dimensional ocean current measurement system based on a genetic algorithm provided by an embodiment of the present invention;

[0061] Figure 2 is a schematic diagram of a MIMO ATI SAR system provided by an embodiment of the present invention;

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

[0063] Figure 4 is a schematic diagram of ground projection of a beam vector provided by an embodiment of the present invention;

[0064] Figure 5 It is a schematic diagram of the velocity error varying with the signal bandwidth and the synthetic aperture time provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0065] The present invention is further described in detail below with reference to specific embodiments, but the embodiments of the present invention are not limited thereto.

[0066] Figure 1is a flow chart of a method for designing parameters of a MIMO ATI SAR two-dimensional ocean current measurement system based on a genetic algorithm provided by an embodiment of the present invention. Figure 2 Schematic diagram of a MIMO ATI SAR system provided by an embodiment of the present invention. Figures 1-2 As shown, an embodiment of the present invention 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. Establish the observation geometry of the MIMO ATI SAR system, determine the sea surface flow field measurement system indicators, interference phase expression and sea surface two-dimensional velocity vector expression;

[0068] S2. According to the two-dimensional velocity vector expression of the sea surface, determine the geometric configuration parameters that affect the velocity vector error, and establish a mathematical relationship between the geometric configuration parameters and the velocity vector error;

[0069] S3, determining MIMO ATI SAR system parameters that affect 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, a two-dimensional velocity vector error objective function of the sea surface is established;

[0071] S5. Solve the objective function of the two-dimensional velocity vector error of the sea surface based on the genetic algorithm to obtain the 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 includes: a main satellite, a first auxiliary satellite and a second auxiliary satellite. The main satellite is a transmitting satellite, and a dual antenna is provided along the track direction to transmit a linear frequency modulation signal. The first auxiliary satellite and the second auxiliary satellite are respectively located in the front and rear directions of the main satellite, and are single-antenna signal receiving satellites for receiving radar echoes emitted by the main satellite and reflected by the sea surface.

[0073] Optionally, the sea surface flow field measurement system indicators include: sea surface flow field spatial resolution S s , observation width W g As well as the velocity accuracy Δv of the sea surface flow field, the subsequent design needs to meet the spatial resolution S of the sea surface flow field. s and observation width W g Under the premise of optimal design of MIMO ATI SAR system parameters, the minimum sea surface flow field velocity accuracy Δv is obtained.

[0074] The geometric configuration parameters that affect the velocity vector error include at least: the primary satellite down-angle θ, the auxiliary satellite slant angle θ slave and the primary satellite antenna baseline B. The MIMO ATI SAR system parameters that affect the velocity vector error include at least: signal bandwidth and synthetic aperture time.

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

[0076]

[0077] In the formula, represents the interference phase of the primary 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 Denote the sea surface velocity vector The velocity component of the radar beams of the primary satellite, the first auxiliary satellite, and the second auxiliary satellite on the ground projection, θ i ,θ fore ,θ aft 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 phase of the primary satellite, the first auxiliary satellite, and the second auxiliary satellite, respectively. Indicates systematic error.

[0078] The expressions for the two-dimensional velocity vector of the sea surface include:

[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 azimuth velocity and the ground-distance 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 , 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\the 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 beam incident angle of the auxiliary satellite

[0085] S202. 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;

[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 step further includes:

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

[0089]

[0090] Right now:

[0091]

[0092] In the formula, 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 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 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, and the average transmitting power of the main satellite R R Indicates the receiving slant distance, 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 transmission power of the main star, the coherence caused by temporal decoherence t c represents the sea surface coherence time;

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

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

[0096] S301, according to the fuzzy function theory, calculate the ground distance resolution d gr and azimuth resolution d ga :

[0097]

[0098] In the formula, T represents transposition, G ⊥ represents the ground projection matrix, ω T represents the angular velocity vector of the primary satellite 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 , 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\the second auxiliary satellite to the satellite observation point, and c represents the propagation speed of electromagnetic waves;

[0099] S302, based on the ground distance resolution d gr and azimuth resolution d ga , calculate the resolution unit area:

[0100] S g =d gr ·d ga / sin(Ω);

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

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

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

[0104]

[0105] stx 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, Δv ra Indicates the speed error in the range direction.

[0107] Limitation E includes:

[0108] The pulse repetition frequency PRF does not meet the following conditions:

[0109] First, when the transmitter and receiver are separated, only direct wave interference needs to be considered, and the pulse repetition frequency PRF needs to meet the following requirements:

[0110]

[0111] Secondly, the transmission pulse interference also needs to be considered when the intermediate receiving channel and the transmitting channel share the same platform. The restrictions on PRF are:

[0112]

[0113] In addition, to avoid sub-satellite interference, the PRF cannot meet the following requirements:

[0114]

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

[0116] Due to the characteristics of SAR satellites, the useful echo in the observation area should be received within one pulse transmission cycle, that is, the maximum value of the pulse repetition frequency PRF. Among them, τ far is the scene far-end echo reception time, τ near is the scene far-end echo reception 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), θ r Indicates the range beamwidth.

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

[0118]

[0119] In the formula, x p_opt 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.

[0120] The following is a simulation experiment to further illustrate the parameter design method of the MIMO ATI SAR two-dimensional ocean current measurement system based on genetic algorithm provided by the present invention.

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

[0122] Table 1

[0123] Observation width 200km Spatial resolution of sea surface flow 200m Sea surface flow velocity accuracy 3cm

[0124] The optimal geometric configuration parameters and optimal MIMO ATI SAR system parameters designed by 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] To further verify the validity of the results shown in Table 2, the variation trend of velocity error with pulse bandwidth and synthetic aperture time is shown in Figure 5 As shown, 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] It can be seen from the above embodiments that the beneficial effects of the present invention are:

[0129] The present invention provides a MIMO ATI SAR two-dimensional ocean current measurement system parameter design method based on a genetic algorithm. Different from the prior art, the method does not take the SAR image resolution as the objective function, but takes the inverted two-dimensional vector velocity accuracy as the sea surface two-dimensional velocity vector error objective function, and obtains the optimal solution, thereby avoiding the repeated weighing of a single system parameter when designing the MIMO ATI SAR system, and fully meets the system parameter design requirements of the MIMO ATI SAR sea surface two-dimensional vector measurement system.

[0130] In the description of the present invention, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0131] The description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine different embodiments or examples described in this specification.

[0132] The above contents are further detailed descriptions of the present invention in combination with specific preferred embodiments, and it cannot be determined that the specific implementation of the present invention is limited to these descriptions. For ordinary technicians in the technical field to which the present invention belongs, several simple deductions or substitutions can be made without departing from the concept of the present invention, which should be regarded as falling within the protection scope of the present invention.

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, interference phase expression and sea surface two-dimensional velocity vector expression; According to the two-dimensional velocity vector expression of the sea surface, a geometric configuration parameter affecting the velocity vector error is determined, and a mathematical relationship between the geometric configuration parameter and the velocity vector error is established; 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; The two-dimensional sea surface velocity vector error objective function is solved based on a genetic algorithm to obtain optimal geometric configuration parameters and optimal MIMO ATI SAR system parameters of the MIMO ATI SAR system.

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, characterized in that: The MIMO ATI SAR system comprises: a primary satellite, a first secondary satellite and a second secondary satellite, wherein the primary satellite is a transmitting satellite and is provided with dual antennas along the track direction to transmit linear frequency modulation signals, and 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 S s , observation width W g and the velocity accuracy Δv of the sea surface flow field. The geometric configuration parameters affecting the velocity vector error include at least: the primary satellite downward viewing angle θ, the auxiliary satellite oblique viewing angle θ slave and the primary satellite antenna baseline B, the MIMO ATI SAR system parameters affecting the velocity vector error at least include: signal bandwidth and synthetic aperture time.

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, characterized in that: The interference phase expression includes: In the formula, 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, λ represents the wavelength, τ represents the time baseline, v cen 、v fore 、v aft Denote the sea surface velocity vector The velocity component of the radar beams of the primary satellite, the first auxiliary satellite and the second auxiliary satellite on the ground projection, θ i ,θ fore ,θ aft 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.

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 3, characterized in that: The two-dimensional velocity vector expression of the sea surface includes: v cen =v gr ; v fore =v gr cosρ fore -v az sinρ fore ; v aft =v gr cosρ aft +v az sinρ aft In the formula, v az 、v gr They represent the azimuth velocity and ground-distance velocity after the convective field velocity is decomposed along the x-axis and y-axis vectors, respectively. The vertical projection of the master 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 master satellite is the z-axis. fore , aft 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, respectively. G z =[1 1 0], Represents the vector from the first auxiliary satellite\the second auxiliary satellite to the satellite observation point, slave=fore or aft represents the first auxiliary satellite or the second auxiliary satellite.

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 4, characterized in that: The step of establishing a mathematical relationship between the geometric configuration parameters and the velocity vector error comprises: In the xyz coordinate system, the beam incident angle of the auxiliary satellite is 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; The main satellite antenna baseline B = τ·v s , where v s Indicates the satellite speed.

6. The method for designing parameters of a MIMO ATI SAR two-dimensional ocean current measurement system based on a genetic algorithm according to claim 5, characterized in that: 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 d is calculated respectively. gr and azimuth resolution d ga : In the formula, T represents transposition, G ⊥ represents the ground projection matrix, ω T represents the angular velocity vector of the primary satellite 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 , 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\the second auxiliary satellite to the satellite observation point, and c represents the propagation speed of electromagnetic waves; According to the ground distance resolution d gr and the azimuth resolution d ga , calculate the resolution unit area: S g =d gr ·d ga / sin(Ω); Where, Ω represents the ground two-dimensional resolution direction angle; Based on the resolution unit area S g And the spatial resolution S of the sea surface flow field s , calculate the number of multi-views 7. The method for designing parameters of a MIMO ATI SAR two-dimensional ocean current measurement system based on a genetic algorithm according to claim 6, characterized in that: The sea surface two-dimensional velocity vector error objective function is: s.t.x p ∈E; 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, Δvaz represents the azimuth velocity error, Δv ra Indicates the speed error in the range direction.

8. The method for designing parameters of a MIMO ATI SAR two-dimensional ocean current measurement system based on a genetic algorithm according to claim 7, characterized in that: Limitation E includes: The pulse repetition frequency PRF does not meet the following conditions: In the formula, Frac() means taking the decimal part, τ P represents the pulse width, τ RP represents the protection time, L represents the distance between the main star and the first auxiliary star\second auxiliary star; The maximum value of the pulse repetition frequency PRF Among them, τ far is the scene far-end echo reception time, τ near It is the scene far-end echo reception time.

9. The method for designing parameters of a MIMO ATI SAR two-dimensional ocean current measurement system based on a genetic algorithm according to claim 7, characterized in that: Before the step of solving the sea surface two-dimensional velocity vector error objective function, the method further includes: Introduced by θ i ,θ fore ,θ aft and ρ fore , aft The determined matrix H rewrites the two-dimensional sea surface velocity vector expression as follows: Right now: In the formula, 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; 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 MIMO ATISAR 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 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, and the average transmitting power of the main satellite R R Indicates the receiving slant distance, R T Indicates the launch slant distance, L s represents the MIMO ATISAR system loss, k is the Bohr coefficient, P m It is expressed as the average transmission power of the main star, the coherence caused by temporal decoherence t c represents the sea surface coherence time; Based on the standard deviation σ γ and the rewritten two-dimensional velocity vector expression of the sea surface, solving for Δv gr and Δv az .

10. The method for designing parameters of a MIMO ATI SAR two-dimensional ocean current measurement system based on a genetic algorithm according to claim 7, characterized in that: The objective function of the two-dimensional velocity vector error of the sea surface is solved by genetic algorithm as follows: In the formula, x p_opt 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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