Method and device for simultaneously implementing strip mode and wide-area MTI mode for airborne SAR

Abstract

The present disclosure provides a method for airborne SAR to simultaneously realize strip mode and wide-area MTI mode, characterized in that it includes: obtaining working parameters of the strip mode and wide-area MTI mode; executing the strip mode and wide-area MTI mode simultaneously in a divided aperture manner; processing the received echo data of the strip mode and wide-area MTI mode to obtain the strip SAR image and the point information of the moving target, associating the point information of the moving target to form the track information of the moving target; and superimposing the track information to the corresponding position on the strip SAR image, having the ability to simultaneously obtain SAR high-resolution images and ground / sea moving target track information, and being able to mark the moving target track information on the SAR image, being able to improve the accuracy of moving target reconnaissance and monitoring, being able to give full play to the advantages of multi-function radar in all directions and dimensions, and providing efficient situational awareness for radar users. The present disclosure also provides a device for airborne SAR to simultaneously realize the strip mode and wide-area MTI mode.

Description

Technical Field

[0001] The present disclosure relates to the technical field of airborne synthetic aperture radar, and in particular to a method and device for simultaneously realizing a strip mode and a wide-area MTI mode for an airborne dual-channel SAR, which is applicable to a multi-channel radar system with an azimuth ultra-wideband electronically controlled scanning capability. Background Art

[0002] Synthetic Aperture Radar (SAR) is an imaging radar that uses the relative motion between the radar platform and the observed target to coherently process the broadband echo signals received by the radar at different spatial and temporal positions within a certain accumulation time to obtain a two-dimensional image of the target area, thereby helping people analyze and understand the ground object information in the area. Compared with optical imaging, SAR has the advantages of all-day, all-weather and strong penetration, so it is widely used in various fields. SAR imaging has multiple working modes, mainly including strip mode and beam mode. The strip mode works in an oblique side view or a straight side view mode. The illuminated area of ​​the ground is in the shape of a strip. It can obtain continuous images of the target area, provide users with a large amount of valuable observation data, and help users make corresponding decisions.

[0003] As an important application of airborne radar, wide-area moving target indication (MT) has broad application prospects and provides strong technical support for various applications. The wide-area MTI mode can simultaneously obtain Doppler beam sharpening (DBS) low-resolution images and ground / sea moving target trajectory information; wide-area MTI can be applied to guidance, traffic control and environmental monitoring in agriculture, forestry, animal husbandry and fishery: monitoring sections prone to traffic congestion and providing effective diversion strategies, recording and controlling the entry and exit of port ships, locating and tracking fishing boats at sea during storms, etc. Moving target detection and monitoring positioning technology play a key role.

[0004] With the continuous development of electronic information technology, multi-function is also a major development direction of SAR system. At present, SAR system basically has imaging mode and MTI mode, but in use, the radar system can only choose one working mode at the same time, and the observation efficiency is low. At the same time, although the SAR / GMTI mode can obtain SAR images and moving target point track information at the same time, the imaging resolution is low, and it is impossible to observe the moving target multiple times, and it is impossible to form point (flight) track information. Summary of the invention

[0005] The purpose of the present disclosure is to provide a method and device for an airborne dual-channel SAR to simultaneously realize a strip mode and a wide-area MTI mode, and to simultaneously obtain the ability to obtain SAR high-resolution images and ground / sea moving target trajectory information, and to be able to mark the moving target trajectory information on the SAR image, so as to improve the accuracy of moving target reconnaissance and surveillance, and to be able to give full play to the advantages of a multi-function radar in all directions and dimensions, and to provide radar users with efficient situational awareness.

[0006] In order to achieve the above object, an embodiment of the present disclosure provides a method for an airborne SAR to simultaneously implement a stripe mode and a wide-area MTI mode, comprising:

[0007] Get the working parameters of stripe mode and wide area MTI mode;

[0008] executing the stripe mode and the wide-area MTI mode simultaneously in a sub-aperture manner;

[0009] Processing the received echo data of the strip mode and the wide-area MTI mode to obtain a strip SAR image and point track information of a moving target, and associating the point tracks of the moving target to form track information of the moving target; and

[0010] The track information is superimposed on a corresponding position on the strip SAR image.

[0011] According to some embodiments of the present disclosure, obtaining the working parameters of the stripe mode and the wide area MTI mode includes:

[0012] Calculating the working parameters of the strip mode according to a first preset indicator requirement or a first input condition;

[0013] Calculating the operating parameters of the wide area MTI mode according to a second preset indicator requirement or a second input condition;

[0014] Calculating the number of dwell pulses of the wide-area MTI mode according to the requirement of the scanning range of the wide-area MTI mode and the working parameters of the wide-area MTI mode;

[0015] Calculating the revisit time required for scanning one cycle of the wide area MTI mode according to the number of dwell pulses; and

[0016] Determine whether the revisit time meets the requirements for target association tracking. If so, output the working parameters of the strip mode and the working parameters of the wide-area MTI mode. If not, modify the first preset indicator requirement or the first input condition to recalculate the working parameters of the strip mode and the wide-area MTI mode.

[0017] According to some embodiments of the present disclosure, the strip mode and the wide-area MTI mode have the same pulse repetition frequency, and both are the same as the actual transmitted pulse repetition frequency, for implementing simultaneous execution of the strip mode and the wide-area MTI mode in a divided aperture manner; and

[0018] The pulse repetition frequency of the strip mode is greater than or equal to α times the azimuth Doppler bandwidth, wherein the value range of α includes 1.2 to 1.3.

[0019] According to some embodiments of the present disclosure, after determining the value range of the stripe mode pulse repetition frequency, the method further includes:

[0020] Calculating the spatial restriction condition of the wave position in combination with the first preset index requirement or the first input condition and forming a wave position map to ensure that the observation band echo corresponding to the wave position can be received completely and without interference; and

[0021] The signal pulse width and strip mode pulse repetition frequency that satisfy the requirement that the echo interference at the down-machine point does not fall within the receiving window are selected from the wave position diagram.

[0022] According to some embodiments of the present disclosure, the modifying the preset indicator requirement or inputting the condition to recalculate the working parameters of the stripe mode and the wide area MTI mode includes:

[0023] The signal pulse width and strip mode pulse repetition frequency are reselected from the wave position diagram to ensure that the echo interference at the down-plane point does not fall within the receiving window.

[0024] According to some embodiments of the present disclosure, the first preset indicator includes platform flight altitude, flight ground speed, resolution, mapping bandwidth and effective range.

[0025] According to some embodiments of the present disclosure, the operating parameters of the strip mode include: signal bandwidth-narrowband, pulse width, pulse repetition frequency, near-end viewing angle, far-end viewing angle, normal viewing angle, near-end slant range, far-end slant range, sampling start, number of sampling points and azimuth observation angle; and

[0026] The operating parameters of the wide-area MTI mode include: signal bandwidth-wideband, pulse width, pulse repetition frequency, near-end viewing angle, far-end viewing angle, normal viewing angle, near-end slant range, far-end slant range, sampling start, number of sampling points, azimuth scanning range, azimuth scanning step value, number of dwell pulses and revisit time.

[0027] According to some embodiments of the present disclosure, calculating the number of dwell pulses according to the requirement of the scanning range of the wide-area MTI mode and the working parameters of the wide-area MTI mode includes:

[0028] According to the scanning range requirements of the wide-area MTI mode and the pulse width, pulse repetition frequency, near-end viewing angle, far-end viewing angle, normal viewing angle, near-end slant distance, far-end slant distance and sampling start of the wave position selected by the wide-area MTI mode, an appropriate number of dwell pulses is selected so that the effective distance of the wide-area MTI mode is greater than or equal to the far-end slant distance to ensure that the target within the irradiation range meets the detection performance.

[0029] According to some embodiments of the present disclosure, calculating the revisit time required for a wide-area MTI mode scan cycle according to the number of dwell pulses includes:

[0030] The 3dB beamwidth of the antenna in azimuth is

[0031]

[0032] Among them, θ 3dB represents the beam width, λ represents, L a Indicates the antenna length in azimuth;

[0033] With 3dB beam width θ 3dB The half of is the step angle, and the number of beam steps in a single scan is

[0034]

[0035] Among them, N step represents the number of beam steps in a single scan, Ψ represents half of the scan range; and

[0036] The revisit time T required to scan one cycle is calculated as

[0037]

[0038] Where T is the revisit time, n is the number of dwell pulses, and PRF MTI Indicates the pulse repetition frequency of the wide area MTI mode.

[0039] An embodiment of the present disclosure further provides a device for an airborne SAR to simultaneously implement a stripe mode and a wide-area MTI mode, comprising:

[0040] A working parameter acquisition module, used to acquire working parameters of the stripe mode and the wide area MTI mode;

[0041] A radar that simultaneously executes the strip mode and the wide-area MTI mode in a divided-aperture manner;

[0042] a data processing module, processing the received echo data of the strip mode and the wide-area MTI mode to obtain a strip SAR image and point track information of a moving target, and associating the point tracks of the moving target to form the track information of the moving target; and

[0043] Information fusion module, used to superimpose the track information to the corresponding position on the strip SAR image

[0044] Through the above-mentioned embodiments of the present disclosure, after the working parameters of the strip mode and wide-area MTI mode of the airborne SAR are designed by the device for simultaneously realizing the strip mode and the wide-area MTI mode of the airborne SAR, the airborne SAR simultaneously executes the working parameters of the strip mode and the wide-area MTI mode in a divided aperture manner; the echo data working with the strip mode and the wide-area MTI mode parameters are processed respectively, and the ability to simultaneously obtain SAR high-resolution images and trajectory information of ground / sea moving targets, and the moving target trajectory information can be marked on the SAR image, which can improve the accuracy of reconnaissance and monitoring of moving targets, can give full play to the advantages of the multi-function radar in all directions and dimensions, and provide efficient situational awareness for radar users. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 A flowchart schematically shows a method for simultaneously implementing a strip mode and a wide-area MTI mode in an airborne SAR according to an embodiment of the present disclosure;

[0046] Figure 2 A flowchart of working parameter design of a method for simultaneously implementing a strip mode and a wide-area MTI mode in a carrier SAR according to an embodiment of the present disclosure is schematically shown;

[0047] Figure 3 The schematic diagram of the operation of the method for simultaneously implementing the strip mode and the wide-area MTI mode in the carrier SAR of the embodiment of the present disclosure is shown;

[0048] Figure 4 The schematic diagram shows a simulated wave position diagram and a PRF selection range diagram of a specific embodiment of the present disclosure;

[0049] Figure 5 A flowchart of calculating the wide-area MTI mode reentry time according to a specific embodiment of the present disclosure is schematically shown; and

[0050] Figure 6 The figure schematically shows a stripe pattern noise equivalent backscatter coefficient calculated according to a specific embodiment of the present disclosure. DETAILED DESCRIPTION

[0051] In order to make the objectives, technical solutions and advantages of the present disclosure more clearly understood, the present disclosure is further described in detail below in combination with specific embodiments and with reference to the accompanying drawings.

[0052] However, it should be understood that these descriptions are exemplary only and are not intended to limit the scope of the present disclosure. In the following detailed description, for ease of explanation, many specific details are set forth to provide a comprehensive understanding of the embodiments of the present disclosure. However, it is apparent that one or more embodiments may also be implemented without these specific details. In addition, in the following description, the description of the known technology is omitted to avoid unnecessary confusion of the concepts of the present disclosure.

[0053] The terms used herein are only for describing specific embodiments and are not intended to limit the present disclosure. The term "comprising" used herein indicates the existence of features, steps, operations, but does not exclude the existence or addition of one or more other features.

[0054] All terms (including technical and scientific terms) used herein have the meanings commonly understood by those skilled in the art, unless otherwise defined. It should be noted that the terms used herein should be interpreted as having a meaning consistent with the context of this specification, and should not be interpreted in an idealized or overly rigid manner.

[0055] Figure 1 The flowchart of the method for the airborne SAR to simultaneously implement the strip mode and the wide-area MTI mode according to the embodiment of the present disclosure is schematically shown.

[0056] In order to achieve the above objectives, the embodiments of the present disclosure provide a method for airborne SAR to simultaneously implement a strip mode and a wide-area MTI mode, such as Figure 1 As shown, it includes operations S101 to S104.

[0057] According to some embodiments of the present disclosure, operation S101 includes: acquiring operating parameters of the stripe mode and the wide area MTI mode.

[0058] According to some embodiments of the present disclosure, operation S102 includes: operating to simultaneously execute the stripe mode and the wide-area MTI mode in a sub-aperture manner.

[0059] According to some embodiments of the present disclosure, operation S103 includes: processing the received echo data of the strip mode and the wide-area MTI mode to obtain the strip SAR image and the point track information of the moving target, and associating the point track of the moving target to form the track information of the moving target.

[0060] Specifically, different point tracks are classified according to their respective target directions, and point tracks in the same direction are associated to form the track information of the moving target.

[0061] According to some embodiments of the present disclosure, operation S101 includes: superimposing track information to a corresponding position on the strip SAR image.

[0062] Figure 2A flowchart of working parameter design of a method for simultaneously implementing a strip mode and a wide-area MTI mode by a carrier SAR according to an embodiment of the present disclosure is schematically shown.

[0063] According to some embodiments of the present disclosure, as shown in the figure, operation S101 includes sub-operations S201 to S205.

[0064] According to some embodiments of the present disclosure, sub-operation S201 includes: calculating a working parameter of the strip mode according to a first preset indicator requirement or a first input condition.

[0065] According to some embodiments of the present disclosure, sub-operation S202 includes: calculating the working parameters of the wide area MTI mode according to a second preset indicator requirement or a second input condition.

[0066] According to some embodiments of the present disclosure, sub-operation S203 includes: calculating the number of dwell pulses of the wide-area MTI mode according to the requirement of the scanning range of the wide-area MTI mode and the working parameters of the wide-area MTI mode.

[0067] According to some embodiments of the present disclosure, sub-operation S204 includes: calculating a revisit time required for scanning one cycle of the wide area MTI mode according to the number of dwell pulses.

[0068] According to some embodiments of the present disclosure, sub-operation S205 includes: determining whether the revisit time meets the requirement for target association tracking, if so, proceeding to sub-operation S206, if not, returning to sub-operation S201.

[0069] According to some embodiments of the present disclosure, sub-operation S206 includes: outputting operating parameters of the stripe mode and operating parameters of the wide area MTI mode.

[0070] After returning to sub-operation S201, the first preset indicator requirement or the first input condition is modified to recalculate the working parameters of the stripe mode and the wide area MTI mode.

[0071] Figure 3 The working diagram of the method for simultaneously implementing the strip mode and the wide-area MTI mode by the SAR-based embodiment of the present disclosure is schematically shown.

[0072] According to some embodiments of the present disclosure, Figure 3 As shown, the pulse repetition frequencies of the strip mode and the wide-area MTI mode are the same, and are both the same as the pulse repetition frequency of the actual transmission, so as to realize the simultaneous execution of the strip mode and the wide-area MTI mode in a divided aperture manner; and, the pulse repetition frequency of the strip mode is greater than or equal to α times the azimuth Doppler bandwidth, where the value range of α includes 1.2 to 1.3.

[0073] According to some embodiments of the present disclosure, after determining the value range of the strip mode pulse repetition frequency, it also includes: calculating the spatial restriction conditions of the wave position in combination with the first preset indicator requirement or the first input condition and forming a wave position diagram to ensure that the observation band echo corresponding to the wave position can be received completely and without interference; and selecting the signal pulse width and strip mode pulse repetition frequency from the wave position diagram so that the echo interference at the off-board point does not fall within the receiving window.

[0074] According to some embodiments of the present disclosure, modifying preset indicator requirements or input conditions to recalculate the working parameters of the strip mode and wide-area MTI mode includes: reselecting the signal pulse width and strip mode pulse repetition frequency from the wave position diagram so that the echo interference at the down-machine point does not fall within the receiving window.

[0075] According to some embodiments of the present disclosure, the first preset indicator includes platform flight altitude, flight ground speed, resolution, mapping bandwidth and effective range.

[0076] According to some embodiments of the present disclosure, the working parameters of the stripe mode include: signal bandwidth-narrowband, pulse width, pulse repetition frequency, near-end viewing angle, far-end viewing angle, normal viewing angle, near-end slant distance, far-end slant distance, sampling start, number of sampling points and azimuth observation angle; and the working parameters of the wide-area MTI mode include: signal bandwidth-wideband, pulse width, pulse repetition frequency, near-end viewing angle, far-end viewing angle, normal viewing angle, near-end slant distance, far-end slant distance, sampling start, number of sampling points, azimuth scanning range, azimuth scanning step value, number of dwell pulses and revisit time. Among them, in the stripe mode, the azimuth observation angle is fixed and unchanged, and the most commonly used is 0 degrees, that is, working in the positive side view state.

[0077] In this embodiment, the signal bandwidth-narrowband is a narrow bandwidth suitable for a low-resolution strip mode, ensuring that the noise equivalent backscatter coefficient (NEσ0) meets the image signal-to-noise ratio requirement.

[0078] In the selection of bandwidth, the present disclosure designs two signal bandwidths for the stripe mode and the wide-area MTI mode. Assume that the signal bandwidth range of the stripe mode is [f strip,L ,f strip,H ], the signal bandwidth range of the wide-area MTI mode is [f MTI,L ,f MTI,H ], in order to ensure that the signals in the two working modes do not interfere with each other, the bandwidths of the two signals generated by the disclosed design meet f MTI,H <f strip,L .

[0079] According to some embodiments of the present disclosure, calculating the number of dwell pulses according to the scanning range requirements of the wide-area MTI mode and the working parameters of the wide-area MTI mode includes: selecting an appropriate number of dwell pulses according to the scanning range requirements of the wide-area MTI mode and the pulse width, pulse repetition frequency, near-end viewing angle, far-end viewing angle, normal viewing angle, near-end slant distance, far-end slant distance and sampling start of the wave position selected by the wide-area MTI mode, so that the effective distance of the wide-area MTI mode is greater than or equal to the far-end slant distance, so as to ensure that the target within the irradiation range meets the detection performance.

[0080] According to some embodiments of the present disclosure, calculating the revisit time required for a wide-area MTI mode scan cycle according to the number of dwell pulses includes:

[0081] The 3dB beamwidth of the antenna in azimuth is

[0082]

[0083] Among them, θ 3dB represents the beam width, λ represents, L a Indicates the antenna length in azimuth;

[0084] With 3dB beam width θ 3dB The half of is the step angle, and the number of beam steps in a single scan is

[0085]

[0086] Among them, N step represents the number of beam steps in a single scan, Ψ represents half of the scan range; and

[0087] The revisit time T required to scan one cycle is calculated as

[0088]

[0089] Where T is the revisit time, n is the number of dwell pulses, and PRF MTI Indicates the pulse repetition frequency of the wide area MTI mode.

[0090] Figure 5 The flowchart of calculating the wide-area MTI mode re-entry time according to a specific embodiment of the present disclosure is schematically shown.

[0091] According to some embodiments of the present disclosure, it is determined whether the revisit time meets the requirements for target association tracking. If so, the working parameters of the strip mode and the working parameters of the wide-area MTI mode are output. If not, the first preset indicator requirement or the first input condition is modified to recalculate the working parameters of the strip mode and the wide-area MTI mode. Figure 5 As shown, it includes operations S301 to S30.

[0092] According to some embodiments of the present disclosure, operation S301 includes: inputting an azimuth scanning angle and a re-entry time requirement, and inputting a near-end viewing angle, a far-end viewing angle, and a normal viewing angle calculated by operation S202.

[0093] According to some embodiments of the present disclosure, operation S302 includes: initializing the re-entry time to 60 seconds and initializing the PRF to the PRF of operation S201.

[0094] According to some embodiments of the present disclosure, operation S303 includes: determining whether the re-entry time meets the requirement, if so, proceeding to operation S307, if not, proceeding to operation S304.

[0095] According to some embodiments of the present disclosure, operation S304 includes: updating the PRF.

[0096] According to some embodiments of the present disclosure, operation S305 includes: calculating the number of beam steps.

[0097] According to some embodiments of the present disclosure, operation S306 includes: calculating the re-entry time, and returning to operation S303 to re-judge.

[0098] According to some embodiments of the present disclosure, operation S307 includes: outputting a PRF.

[0099] An embodiment of the present disclosure further provides a device for an airborne SAR to simultaneously implement a stripe mode and a wide-area MTI mode, comprising:

[0100] A working parameter acquisition module, used to acquire working parameters of the stripe mode and the wide area MTI mode;

[0101] Radar, which performs both strip mode and wide-area MTI mode in a split-aperture manner;

[0102] A data processing module processes the received echo data of the strip mode and the wide-area MTI mode to obtain the strip SAR image and the point track information of the moving target, and associates the point tracks of the moving target to form the track information of the moving target; and

[0103] The information fusion module is used to superimpose the track information to the corresponding position on the strip SAR image.

[0104] The technical solution of the present disclosure is further illustrated below through a specific embodiment.

[0105] In this embodiment, taking ground reconnaissance and surveillance as an example, the main index requirements and input conditions are as follows:

[0106] Flight altitude: 18000m;

[0107] Flight ground speed: 240m / s;

[0108] Antenna operating bandwidth: 8~12GHz (X band);

[0109] Antenna size: 1500mm (length) × 380mm (height);

[0110] Peak power: 23000W;

[0111] Strip mode resolution: 1m (azimuth) × 1m (distance);

[0112] Wide area MTI mode resolution: 20m;

[0113] Strip mode mapping bandwidth: 20km;

[0114] Wide-area MTI mode mapping bandwidth: 20km;

[0115] Wide-area MTI azimuth scanning range: ±60°;

[0116] Wide-area MTI mode detection of vehicle targets RCS: 10m2; and

[0117] Effective range: 120km.

[0118] Step 1: According to the flight altitude, range, and mapping bandwidth, the strip mode distance mapping area can be determined: near-end slant range 110.1km, far-end slant range 129.9km, near-end viewing angle 80.1°, far-end viewing angle 81.4°, and mapping bandwidth 20km. According to the resolution requirements, the strip mode signal bandwidth can be determined to be 200MHz.

[0119] Determine the value range of PRF. To avoid azimuth ambiguity, the azimuth sampling frequency PRF of the strip mode should be greater than or equal to 1.3 times the azimuth Doppler bandwidth, that is:

[0120]

[0121] In order to prevent range ambiguity, there is another limitation on PRF in the range direction. For side-looking radar,

[0122]

[0123] The present disclosure designs a working form of simultaneously executing the strip mode and the wide-area MTI mode in a divided aperture manner, that is, the PRFs used for strip imaging and the wide-area MTI mode are equal, and the value is the actual transmission PRF. Therefore, the value range of the actual transmission PRF is:

[0124] 737Hz≤PRF system ≤7500Hz

[0125] After determining the selection range of PRF, it is necessary to combine the near-end viewing angle, far-end viewing angle, pulse width and other parameters to determine the spatial restriction conditions of the wave position, that is, the wave position diagram (also called zebra diagram), to ensure that the observation band echo corresponding to the wave position can be received completely and without interference. The wave position diagram is determined by the following restriction conditions: Assuming that the echo is received after passing through i PRFs, the condition that the transmitted pulse does not fall into the echo receiving window is:

[0126]

[0127] Among them, T p is the pulse width, T pt is the pulse protection time, R n , R f are the proximal and distal slant distances, respectively.

[0128] Assuming that the delay time of the echo from the ground under the aircraft is greater than or equal to j PRFs, the following conditions must be met to prevent the echo interference from falling within the receiving window:

[0129]

[0130] Where H is the height of the aircraft relative to the ground.

[0131] According to the above constraints, the appropriate signal pulse width and PRF can be selected from the wave diagram system ,like Figure 4 As shown in the figure, when the pulse width is 100us, the black dotted line is the optional PRF within the observation angle range. In this example, PRF is selected system =900Hz, thus obtaining PRF strip =900Hz,PRF spot =900Hz.

[0132] Calculated by the noise equivalent backscatter coefficient (NESZ) formula:

[0133]

[0134] Where K is the Boltzmann constant (1.38×10- 23 J / K), T0 is the receiver temperature (290K), F n is the receiver noise coefficient, R is the slant range (operating distance) from the carrier to the target, L s is the system loss, P av is the average power of the transmitted signal, G t is the transmitting antenna gain, G r is the receiving antenna gain, ρ g is the ground distance resolution, and V is the aircraft speed.

[0135] Figure 6The figure schematically shows a stripe pattern noise equivalent backscatter coefficient calculated according to a specific embodiment of the present disclosure.

[0136] The noise equivalent backscatter coefficient is better than -38dB, such as Figure 6 The X-band noise equivalent backscatter coefficient is generally required to be better than -20 to -25 dB, and the system design meets the image signal-to-noise ratio requirements.

[0137] Step 2: Based on the flight altitude, range, and mapping bandwidth, the wide-area MTI mode range mapping zone can be determined as follows: near-end slant range 110.1km, far-end slant range 129.9km, near-end viewing angle 80.1°, far-end viewing angle 81.4°, and mapping bandwidth 20km. Based on the resolution requirements, the wide-area MTI mode signal bandwidth can be determined to be 10MHz.

[0138] Step 3: According to the scanning range requirement (±60 degrees) and the pulse width 100us and PRF of the wave position selected in step 2 MTI , near-end viewing angle, far-end viewing angle, normal viewing angle, near-end slant range, far-end slant range and sampling start, select the number of dwell pulses n = 32, and calculate the effective range of the MTI mode by the radar equation:

[0139]

[0140] Among them, P t is the peak transmit power, σ t is the target radar cross-sectional area (RCS), D0 is the detection factor, which is 14dB in this example, and L sys is the system loss (including atmospheric round-trip loss, radome loss, antenna scanning loss, system amplitude and phase error loss, signal processing loss, etc.), and in this example it is taken as 12dB.

[0141] Step 4: Calculate the revisit time T required for the wide-area MTI mode to scan one cycle (±60 degrees).

[0142] The 3dB beamwidth of the antenna in azimuth is:

[0143]

[0144] With 3dB beam width θ 3dB Half of the step angle is the number of beam steps in a single scan. step for:

[0145]

[0146] The revisit time T required to scan one cycle (±ψ degrees) is calculated as:

[0147]

[0148] The wide-area MTI mode detection revisit time of 4.05s meets the requirements for target association tracking, and the design is completed. Output the working parameters of the strip mode and wide-area MTI mode.

[0149] Through the above-mentioned embodiments of the present disclosure, after the working parameters of the strip mode and wide-area MTI mode of the airborne SAR are designed by the device for simultaneously realizing the strip mode and the wide-area MTI mode of the airborne SAR, the airborne SAR simultaneously executes the working parameters of the strip mode and the wide-area MTI mode in a divided aperture manner; the echo data working with the strip mode and the wide-area MTI mode parameters are processed respectively, and the ability to simultaneously obtain SAR high-resolution images and trajectory information of ground / sea moving targets, and the moving target trajectory information can be marked on the SAR image, which can improve the accuracy of reconnaissance and monitoring of moving targets, can give full play to the advantages of the multi-function radar in all directions and dimensions, and provide efficient situational awareness for radar users.

[0150] So far, the embodiments of the present disclosure have been described in detail in conjunction with the accompanying drawings. It should be noted that the implementation methods not shown or described in the drawings or the body of the specification are all forms known to ordinary technicians in the relevant technical field and are not described in detail. In addition, the above definitions of each component are not limited to the various specific structures, shapes or methods mentioned in the embodiments, and ordinary technicians in the field can simply change or replace them.

[0151] It should also be noted that, in the specific embodiments of the present disclosure, unless otherwise indicated, the numerical parameters in the present specification and the appended claims are approximate values ​​and can be changed according to the desired characteristics obtained through the content of the present disclosure. Specifically, all numbers used in the specification and claims to express the size, range conditions, etc. of the composition should be understood to be modified by the term "about" in all cases. In general, the meaning of the expression refers to the change of ±10% in some embodiments, ±5% in some embodiments, ±1% in some embodiments, and ±0.5% in some embodiments by a specific number.

[0152] It will be appreciated by those skilled in the art that the features described in the various embodiments and / or claims of the present disclosure may be combined and / or combined in a variety of ways, even if such combinations and / or combinations are not explicitly described in the present disclosure. In particular, the features described in the various embodiments and / or claims of the present disclosure may be combined and / or combined in a variety of ways without departing from the spirit and teachings of the present disclosure. All of these combinations and / or combinations fall within the scope of the present disclosure.

[0153] The specific embodiments described above further illustrate the purpose, technical solutions and beneficial effects of the present disclosure. It should be understood that the above description is only a specific embodiment of the present disclosure and is not intended to limit the present disclosure. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present disclosure should be included in the protection scope of the present disclosure.

Claims

1. A method for simultaneously implementing strip mode and wide-area MTI mode for airborne SAR, characterized in that: include: Get the working parameters of stripe mode and wide area MTI mode; executing the stripe mode and the wide-area MTI mode simultaneously in a sub-aperture manner; Processing the received echo data of the strip mode and the wide-area MTI mode to obtain a strip SAR image and point track information of a moving target, and associating the point track information of the moving target to form track information of the moving target; as well as superimposing the track information onto a corresponding position on the strip SAR image; The obtaining of the working parameters of the stripe mode and the wide area MTI mode includes: Calculating the working parameters of the strip mode according to a first preset indicator requirement or a first input condition; Calculating the operating parameters of the wide area MTI mode according to a second preset indicator requirement or a second input condition; Calculating the number of dwell pulses of the wide-area MTI mode according to the requirement of the scanning range of the wide-area MTI mode and the working parameters of the wide-area MTI mode; Calculating the revisit time required for scanning one cycle of the wide area MTI mode according to the number of dwell pulses; and Determine whether the revisit time meets the requirement for target association tracking, if so, output the working parameters of the strip mode and the working parameters of the wide-area MTI mode, if not, modify the first preset indicator requirement or the first input condition to recalculate the working parameters of the strip mode and the wide-area MTI mode; The pulse repetition frequencies of the strip mode and the wide-area MTI mode are the same, and are the same as the pulse repetition frequency actually transmitted, so as to realize simultaneous execution of the strip mode and the wide-area MTI mode in a divided-aperture manner; and The pulse repetition frequency of the strip pattern is greater than or equal to the azimuth Doppler bandwidth. times, among which, The value range of includes 1.2~1.3; Determine the value range of PRF. To avoid azimuth ambiguity, the azimuth sampling frequency PRF of the strip mode should be greater than or equal to 1.3 times the azimuth Doppler bandwidth, that is: ； In order to prevent range ambiguity, there is another restriction on PRF in the range direction, which is: ； The working form of the strip mode and wide-area MTI mode is performed simultaneously in a divided aperture manner. The PRFs used for strip imaging and wide-area MTI modes are equal, and the value is the actual transmission PRF; therefore, the value range of the actual transmission PRF is: ； according to The scanning range requirement and the pulse width of the selected wave position are 100us, , near-end viewing angle, far-end viewing angle, normal viewing angle, near-end slant range, far-end slant range and sampling start, select the number of dwell pulses n=32, and calculate the effective range of the MTI mode by the radar equation: ； in, is the peak transmit power, is the pulse width, is the transmit antenna gain, is the receiving antenna gain, represents the wavelength, is the target radar cross-sectional area, n represents the number of dwell pulses, is the Boltzmann constant, is the receiver temperature, is the receiver noise figure, is the detection factor, is the system loss, including atmospheric round-trip loss, radome loss, antenna scanning loss, system amplitude and phase error loss, and signal processing loss.

2. The method according to claim 1, characterized in that After determining the value range of the stripe mode pulse repetition frequency, it also includes: Calculating the spatial restriction condition of the wave position in combination with the first preset index requirement or the first input condition and forming a wave position map to ensure that the observation band echo corresponding to the wave position can be received completely and without interference; and The signal pulse width and strip mode pulse repetition frequency that satisfy the requirement that the echo interference at the down-machine point does not fall within the receiving window are selected from the wave position diagram.

3. The method according to claim 2, characterized in that The modifying of the preset indicator requirement or the input condition to recalculate the working parameters of the strip mode and the wide area MTI mode includes: The signal pulse width and strip mode pulse repetition frequency are reselected from the wave position diagram to ensure that the echo interference at the down-plane point does not fall within the receiving window.

4. The method according to claim 1, characterized in that: The first preset indicators include platform flight altitude, flight ground speed, resolution, mapping bandwidth and effective range.

5. The method according to claim 1, characterized in that The working parameters of the strip mode include: signal bandwidth-narrowband, pulse width, pulse repetition frequency, near-end viewing angle, far-end viewing angle, normal viewing angle, near-end slant range, far-end slant range, sampling start, number of sampling points and azimuth observation angle; and The operating parameters of the wide-area MTI mode include: signal bandwidth-wideband, pulse width, pulse repetition frequency, near-end viewing angle, far-end viewing angle, normal viewing angle, near-end slant range, far-end slant range, sampling start, number of sampling points, azimuth scanning range, azimuth scanning step value, number of dwell pulses and revisit time.

6. The method according to claim 5, characterized in that The calculating the number of dwell pulses according to the requirement of the scanning range of the wide-area MTI mode and the working parameters of the wide-area MTI mode comprises: According to the scanning range requirements of the wide-area MTI mode and the pulse width, pulse repetition frequency, near-end viewing angle, far-end viewing angle, normal viewing angle, near-end slant distance, far-end slant distance and sampling start of the wave position selected by the wide-area MTI mode, an appropriate number of dwell pulses is selected so that the effective distance of the wide-area MTI mode is greater than or equal to the far-end slant distance to ensure that the target within the irradiation range meets the detection performance.

7. The method according to claim 6, characterized in that Calculating the revisit time required for a wide-area MTI mode scan cycle based on the number of dwell pulses includes: The 3dB beamwidth of the antenna in azimuth is in, represents the beam width, represents the wavelength, Indicates the antenna length in azimuth; With 3dB beam width The half of is the step angle, and the number of beam steps in a single scan is in, represents the number of beam steps in a single scan, Ψ represents half of the scan range; and The revisit time required to scan one cycle The calculation is Where T is the revisit time, n is the number of dwell pulses, Indicates the pulse repetition frequency of the wide area MTI mode.

8. A device for implementing the method of any one of claims 1 to 7 for simultaneously implementing a strip mode and a wide-area MTI mode for an airborne SAR, characterized in that: include: A working parameter acquisition module, used to acquire working parameters of the stripe mode and the wide area MTI mode; A radar that simultaneously executes the strip mode and the wide-area MTI mode in a divided-aperture manner; A data processing module processes the received echo data of the strip mode and the wide-area MTI mode to obtain a strip SAR image and point track information of a moving target, and associates the point tracks of the moving target to form the track information of the moving target; as well as The information fusion module is used to superimpose the track information to the corresponding position on the strip SAR image.

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