A space-based radar ISAR wave position design method and device for air targets

Abstract

The application relates to a space-based radar ISAR wave position design method and device for an air target, which comprises the following steps: calculating the squint angle, synthetic aperture time, sampling point number, maximum non-blurring distance and blurring number of the space-based radar for observing the air target under each pulse repetition frequency; calculating the echo delay, subsatellite point blurring number and required sampling delay starting moment under each pulse repetition frequency; selecting the pulse repetition frequency; calculating the one-time variable coherent processing interval time under the selected pulse repetition frequency; calculating the sampling starting and azimuth sampling point number of each coherent processing interval, and accumulating the observation time; judging whether the observation time reaches the synthetic aperture time, if not, the cycle is executed; if yes, all wave position designs are completed. The application adaptively completes multi-wave position design, is suitable for the wave position design of the squint wave position observation scene of the front and back, and considers avoiding the subsatellite point echo and the transmission pulse during the wave position design, and the subsatellite point clutter avoidance is completed.

Description

Technical Field

[0001] This invention relates to the field of spaceborne inverse synthetic aperture radar (ISAR) technology, specifically to a method and apparatus for designing ISAR wave positions for airborne targets using space-based radar. Background Technology

[0002] Space-based radar (SBR), with its advantages of global coverage, continuous observation, and independence from national borders and airspace restrictions, plays an increasingly important role in missions such as space situational awareness, aerial target surveillance, and tracking. Inverse Synthetic Aperture Radar (ISAR) imaging technology can generate high-resolution two-dimensional images of non-cooperative moving targets (such as aircraft, missiles, and UAVs), making it a key means of target classification, identification, and intent assessment. However, space-based platforms face significantly different technical challenges when performing ISAR imaging of aerial targets compared to ground-based or airborne ISAR imaging. The design of beam positions (i.e., beam pointing, PRF, and sampling delay) directly determines imaging quality, resource utilization efficiency, and mission success or failure.

[0003] In existing ISAR imaging systems, beamwidth design is typically based on the operating modes of ground-based or airborne radars, primarily focusing on parameters such as target range, azimuth variation, and Doppler bandwidth. However, space-based radar platforms orbit the Earth at extremely high speeds, and their relative motion with aerial targets exhibits complex nonlinear and highly dynamic characteristics. On one hand, the high relative speed between space-based radar and targets, reaching thousands of meters per second, means that targets may cross multiple range gates or Doppler cells during beam dwell time, resulting in severe range-crossing cell movement (MTRC). This leads to a large amount of sampled data, necessitating beamwidth design to balance data volume and echo sampling integrity. Furthermore, space-based radars are limited by onboard energy, computing resources, and data downlink bandwidth, requiring efficient target search, tracking, and imaging mode switching within a limited beamwidth dwell time. This places higher demands on the real-time performance and adaptability of beamwidth design.

[0004] Currently, research on ISAR imaging of airborne targets by space-based radar is still in its early stages. Existing literature mainly focuses on improving the imaging algorithm itself (such as time-frequency analysis, compressed sensing, etc.) or wavefront design methods for observation scenarios such as ground-based ISAR and space-based SAR, lacking a systematic wavefront design process and general method.

[0005] For example, patent application CN118209984A discloses a space-based air-to-air maneuvering target ISAR imaging method and device that jointly detects prior information. It mainly includes: preliminary compensation for target motion during imaging based on target position and Doppler velocity; preliminary SAR imaging of the target; and transformation of the imaged data to the range-pulse domain for envelope alignment and phase correction to obtain accurate ISAR imaging results. However, it lacks a description of the space-based radar ISAR wavefront design method for air-to-air maneuvering targets.

[0006] For example, patent application CN116482678A discloses a method, device, and storage medium for optimizing the wavefront positions of space-based radar for sea surface detection. The method includes: determining a target area and arranging wavefront positions within that area; classifying wavefront positions using a coastline database, extracting and filtering cross-coastal wavefront positions; performing land-sea segmentation on the filtered cross-coastal wavefront positions; filtering the segmented cross-coastal wavefront positions again to obtain the cross-coastal wavefront positions requiring optimization; translating the cross-coastal wavefront positions requiring optimization, performing land-sea segmentation again, and determining the optimal solution based on the maximum intersection of the ocean areas before and after segmentation; and conducting sea-based detection. However, this method targets a sea-based detection scenario, while air-based ISAR wavefront position design inherently requires detection of small, moving scenes. Therefore, this patent is not applicable to air-based ISAR wavefront position design. Summary of the Invention

[0007] This invention provides a method and apparatus for designing ISAR wave positions for airborne targets using space-based radar, in order to solve at least one of the aforementioned technical problems.

[0008] The technical solution of this invention to solve the above-mentioned technical problems is as follows: A method for designing ISAR wave positions for airborne targets by space-based radar, comprising: S1, set the waveform design parameters, maximum time for a single waveform change, protection time and scene width; S2, obtain the current position of the space-based radar, the velocity of the space-based radar, and the position of the air target. Based on the wave position design parameters, the maximum time of the first wave position change, the scene width, the position of the space-based radar, the velocity of the space-based radar, and the position of the air target, calculate the oblique angle, synthetic aperture time, number of sampling points, and pulse repetition frequency selection range for the space-based radar to observe the air target. Within the pulse repetition frequency selection range, traverse multiple pulse repetition frequencies and calculate the maximum unambiguous distance at each pulse repetition frequency. Also, calculate the ambiguity number at each pulse repetition frequency based on the observation time. S3, based on the oblique angle, according to the wave position design parameters, the protection time, the scene width, and the maximum unambiguous distance and number of ambiguities at each pulse repetition frequency, calculate the echo delay and the number of nadir points at each pulse repetition frequency, and calculate the start time of the sampling delay to be avoided at each pulse repetition frequency according to the number of nadir points at each pulse repetition frequency. S4, find the absolute value of the echo delay from all pulse repetition frequencies. A small echo delay is used as the sampling delay, and it is checked whether the start time of the sampling delay to be avoided at the pulse repetition frequency corresponding to the sampling delay meets the preset condition. If not, then let The sampling delay continues until the start time of the sampling delay to be avoided at the pulse repetition frequency corresponding to the sampling delay meets a preset condition. If so, the pulse repetition frequency corresponding to the sampling delay is used as the selected pulse repetition frequency; wherein, The initial value is 1; S5. Based on the synthetic aperture time, the number of sampling points, and the maximum unambiguous distance at the selected pulse repetition frequency, calculate the interval time of one phase coherence processing at the selected pulse repetition frequency. S6. Based on the selected pulse repetition frequency, calculate the sampling start and azimuth sampling point number for each coherent processing interval, and accumulate the observation time. S7, determine whether the observation time has reached the synthetic aperture time. If not, return to S2 and repeat until the observation time reaches the synthetic aperture time. If yes, complete all wave positions design.

[0009] Based on the above-mentioned method for designing ISAR wave positions of airborne targets by space-based radar, the present invention also provides a device for designing ISAR wave positions of airborne targets by space-based radar.

[0010] A space-based radar ISAR beam position design device for airborne targets includes a processor, a memory, and a computer program stored in the memory. When the computer program is executed by the processor, it implements the space-based radar ISAR beam position design method for airborne targets as described above.

[0011] The beneficial effects of this invention are as follows: This invention provides a method and apparatus for ISAR (Infrastructure SAR) beam design for space-based radar targets, applicable to ISAR beam design for space-based radar targets. By dividing the synthetic aperture time into pulse repetition frequencies (PRFs) and the coherent processing interval (CPI) within a single pulse repetition frequency observation, multi-beam design is adaptively achieved, suitable for beam design in both frontal and rearward oblique viewing scenarios. Furthermore, the beam design considers avoiding nadir echoes and transmitted pulses, thus achieving nadir clutter avoidance. This invention is applicable to the acquisition of broadband imaging echo data of space-based radar targets, providing the prerequisite and possibility for space-based airborne ISAR imaging. Attached Figure Description

[0012] Figure 1 This is a flowchart of an ISAR sine wave design method for airborne targets by a space-based radar according to the present invention. Figure 2 A schematic diagram of the geometric model of a space-based ISAR observation scenario of an aerial target; Figure 3 This is a dot matrix layout diagram resembling an airplane shape in the example. Figure 4 The echo 2D plot is a simulation result of the wave position design in the example. Figure 5 This is a structural block diagram of an ISAR (Infrastructure Target Position Design) device for space-based radar targeting airborne targets according to the present invention. Detailed Implementation

[0013] The principles and features of the present invention are described below with reference to the accompanying drawings. The examples given are only for explaining the present invention and are not intended to limit the scope of the present invention.

[0014] like Figure 1 As shown, a method for designing ISAR beam positions for airborne targets using a space-based radar includes: S1, set the waveform design parameters, maximum time for a single waveform change, protection time and scene width; S2, obtain the current position of the space-based radar, the velocity of the space-based radar, and the position of the air target. Based on the wave position design parameters, the maximum time of the first wave position change, the scene width, the position of the space-based radar, the velocity of the space-based radar, and the position of the air target, calculate the oblique angle, synthetic aperture time, number of sampling points, and pulse repetition frequency selection range for the space-based radar to observe the air target. Within the pulse repetition frequency selection range, traverse multiple pulse repetition frequencies and calculate the maximum unambiguous distance at each pulse repetition frequency. Also, calculate the ambiguity number at each pulse repetition frequency based on the observation time. S3, based on the oblique angle, according to the wave position design parameters, the protection time, the scene width, and the maximum unambiguous distance and number of ambiguities at each pulse repetition frequency, calculate the echo delay and the number of nadir points at each pulse repetition frequency, and calculate the start time of the sampling delay to be avoided at each pulse repetition frequency according to the number of nadir points at each pulse repetition frequency. S4, find the absolute value of the echo delay from all pulse repetition frequencies. A small echo delay is used as the sampling delay, and it is checked whether the start time of the sampling delay to be avoided at the pulse repetition frequency corresponding to the sampling delay meets the preset condition. If not, then let The sampling delay continues until the start time of the sampling delay to be avoided at the pulse repetition frequency corresponding to the sampling delay meets a preset condition. If so, the pulse repetition frequency corresponding to the sampling delay is used as the selected pulse repetition frequency; wherein, The initial value is 1; S5. Based on the synthetic aperture time, the number of sampling points, and the maximum unambiguous distance at the selected pulse repetition frequency, calculate the interval time of one phase coherence processing at the selected pulse repetition frequency. S6. Based on the selected pulse repetition frequency, calculate the sampling start and azimuth sampling point number for each coherent processing interval, and accumulate the observation time. S7, determine whether the observation time has reached the synthetic aperture time. If not, return to S2 and repeat until the observation time reaches the synthetic aperture time. If yes, complete all wave positions design.

[0015] In this invention, a space-based radar ISAR (Infrastructure SAR) beam design method for airborne targets is proposed. By dividing the synthetic aperture time into pulse repetition frequencies (PRFs) and the coherent processing interval (CPI) within a single pulse repetition frequency observation, multi-beam design is adaptively achieved. This method is applicable to beam design for both frontal and oblique-looking observation scenarios. Furthermore, the beam design considers avoiding nadir echoes and transmitted pulses, thus achieving nadir clutter avoidance. This invention is applicable to the acquisition of broadband imaging echo data of airborne targets by space-based radar, providing a prerequisite and possibility for space-based airborne ISAR imaging.

[0016] Figure 2 This is the geometric model for ISAR imaging of airborne targets by a space-based radar. The geometric approximation of the observation of airborne targets by the space-based radar is a slant-look clustering model. It should be noted that the airborne target in this embodiment is an aircraft. Since the slant range change introduced by the aircraft's flight within a few seconds is at most on the order of kilometers, the wavefront design can ensure echo acquisition by designing the scene width.

[0017] In S1, the preferred embodiment is as follows: Waveform design parameters include waveform information and azimuth resolution. Waveform information includes signal frequency. , bandwidth of linear frequency modulation signal Pulse width and sampling rate ; Azimuth resolution Set to distance resolution Nearby values ​​are used to match the two-dimensional resolution of the resulting image; where distance resolution is... Determine using the following formula: (1) In the formula, The speed of light in a vacuum. This represents the bandwidth of a linear frequency modulated signal.

[0018] Maximum time of one waveform change (Also known as CPI_Time), will The advantage of setting a large value is that it may reduce the number of waveforms, but the disadvantage is that the migration within a single CPI (correlation interval) is larger, and the sampling pressure in the distance direction is greater. A balance needs to be struck in the design.

[0019] Protection time This is the protection time set for range sampling to prevent range sampling from failing to capture the signal.

[0020] Scene width This refers to the width of the sampled signal. This value ensures that the signal sampling can accommodate a certain scene width and can include slant range changes introduced by the movement of aerial targets.

[0021] In S2, the preferred embodiment is as follows: The position (also known as the satellite position) and velocity (also known as the satellite velocity) of space-based radar are usually calculated by the space-based radar based on navigation information.

[0022] The position of the aerial target is an input parameter, which is derived from the air detection results of the space-based radar (in this embodiment, the aerial target is an aircraft).

[0023] Oblique angle The calculation formula is: (2) In the formula, The vector of the space-based radar velocity. This represents the vector difference between the position of the aerial target and the position of the space-based radar. , The vector representing the position of the aerial target. This is the vector representing the location of the space-based radar; the oblique angle is then calculated. All vectors used are vectors at the initial moment.

[0024] Specifically, when viewed from an oblique angle A value less than 0 indicates that the space-based radar will move away from the aerial target over time; when the angle of view is... A value greater than 0 indicates that the space-based radar will approach the aerial target as time progresses.

[0025] Synthetic pore size time The calculation formula is: (3) In the formula, For wavelength, and .

[0026] Number of sampling points The calculation formula is: (4) In the formula, To round up, This represents the change in migration within the maximum time interval of a single wave phase change, and (5) The pulse repetition frequency selection range (PRF selection range) is set as follows: (6) In the formula, For Doppler bandwidth, and The pulse repetition frequency (PRF) can actually be searched at certain frequency intervals according to the above formula (6).

[0027] The formula for calculating the maximum unambiguous distance at each pulse repetition frequency is as follows: (7) In the formula, The first one selected within the pulse repetition frequency selection range Maximum unambiguous distance at a pulse repetition frequency The first one selected within the pulse repetition frequency selection range The pulse repetition frequency.

[0028] The formula for calculating the ambiguity number corresponding to each pulse repetition frequency is as follows: (8) In the formula, The first one selected within the pulse repetition frequency selection range The ambiguity number at a pulse repetition frequency; For observation time, The initial value is 0, accumulated from the later equation (24).

[0029] In S3, the preferred embodiment is as follows: When the oblique angle When less than 0, echo delay The calculation formula is: (9) When the oblique angle When greater than 0, echo delay The calculation formula is: (10) In the formula, This is for rounding down.

[0030] The formula for calculating the fuzzy number of the under-star point is: (11) In the formula, The first one selected within the pulse repetition frequency selection range Number of nadir points at a pulse repetition frequency This is the vector of the sub-satellite point for space-based radar.

[0031] Sampling delay start time needs to be avoided The calculation formula is: (12) Additionally, based on the starting time of the sampling delay to be avoided The end time of the sampling delay that needs to be avoided can be calculated. Among these, it is necessary to avoid delaying the end time of sampling. The calculation formula is: (13) and The design must avoid sampling delay.

[0032] In S4, the preferred embodiment is as follows: When the oblique angle When the value is less than 0, the preset condition is: (14) When the oblique angle When the value is greater than 0, the default condition is: (15) Specifically, S4 is the step of screening pulse repetition frequencies, and the screened pulse repetition frequencies are defined as the selected pulse repetition frequencies. In this step, if Then the following judgment is made: find the one with the smallest absolute value. ,examine Is it true? If so, then select the one with the smallest absolute value. The corresponding pulse repetition frequency is used as the selected pulse repetition frequency. If not, then exclude the one with the smallest absolute value. The corresponding pulse repetition frequency is then used to find the one with the smallest absolute value. and check Whether it is valid or not, until completion. The choice. If Then the following judgment is made: find the one with the smallest absolute value. ,examine Is it true? If so, then select the one with the smallest absolute value. The corresponding pulse repetition frequency is used as the selected pulse repetition frequency. If not, then exclude the one with the smallest absolute value. The corresponding pulse repetition frequency is then used to find the one with the smallest absolute value. and check Whether it is valid or not, until completion. The choice.

[0033] In S5, the preferred embodiment is as follows: Select the single-phase coherence processing interval at the pulse repetition frequency. The calculation formula is: (16) In the formula, The duration of one pulse repetition frequency. The number of changes in the coherent processing interval, and (17) (18) (19) (20) In the formula, The number of times the pulse repetition frequency needs to be changed. To select the maximum time of migration variation that can be covered by the pulse repetition frequency. To select the maximum unambiguous distance at the pulse repetition frequency.

[0034] In S6, the preferred embodiment is as follows: When the oblique angle When less than 0, sampling begins The calculation formula is: ;(twenty one) When the oblique angle When the value is 0, sampling begins. The calculation formula is: ;(twenty two) In the formula, The coherent processing intervals for each pulse repetition frequency are numbered (starting from 1).

[0035] Number of azimuth sampling points The calculation formula is: .(twenty three) Observation time The cumulative formula is: ;(twenty four) In the formula, For the front The cumulative observation time for each wave position For the front The cumulative observation time for each wavelength; Equation (24) represents an iterative operation, that is, the time for each coherent processing interval is accumulated in this way. This indicates the wave position number; at this point, the wave position design at one pulse repetition frequency has been completed, including wave position design results that may be longer than one coherent processing interval.

[0036] To verify the correctness of the method of this invention, ISAR wavefront design and echo simulation of airborne targets were carried out based on a certain space-based radar system. The initial parameters for wavefront design are shown in Table 1 below: Table 1: Initial parameters for ISAR beam design of a certain space-based radar against airborne targets The simulation target is a lattice of dots resembling an airplane shape, such as... Figure 3 As shown.

[0037] The wave position design results are shown in Table 2 below.

[0038] Table 2: ISAR Wavefront Design Results for a Space-Based Radar Against Air Targets According to the waveform simulation results in Table 2, the results are as follows: Figure 4 As shown, it can be seen that: 1. The aircraft target echo is completely sampled; 2. The coherent processing interval for aircraft target wavefront segmentation does not exceed [a certain value]. 3. The total observation time is 2.728 s, which meets the requirement for azimuth resolution observation of 1 m. This example verifies the correctness of the wave position design method of this invention.

[0039] Based on the above-mentioned method for designing ISAR wave positions of airborne targets by space-based radar, the present invention also provides a device for designing ISAR wave positions of airborne targets by space-based radar.

[0040] like Figure 5 As shown, a space-based radar ISAR beamwidth design device for airborne targets includes a processor, a memory, and a computer program stored in the memory. When the computer program is executed by the processor, it implements the space-based radar ISAR beamwidth design method for airborne targets as described above.

[0041] In one optional embodiment, a space-based radar ISAR beam positioning design device for airborne targets is provided, such as Figure 5 As shown. Figure 5 The illustrated space-based radar ISAR (Infrastructure Targeting and Positioning) device for airborne targets includes a processor and a memory. The processor and memory are connected, for example, via a bus. Optionally, the space-based radar ISAR device for airborne targets may further include a transceiver, which can be used for data interaction between the device and other electronic devices, such as data transmission and / or data reception. It should be noted that in practical applications, the transceiver is not limited to one unit, and the structure of this space-based radar ISAR device for airborne targets does not constitute a limitation on the embodiments of the present invention.

[0042] The processor can be a CPU (Central Processing Unit), a general-purpose processor, a DSP (Digital Signal Processor), an ASIC (Application Specific Integrated Circuit), a PLC (Programmable Logic Controller), a FPGA (Field Programmable Gate Array), or other programmable logic devices, transistor logic devices, hardware components, or any combination thereof. It can implement or execute the various exemplary logic blocks, modules, and circuits described in conjunction with the disclosure of this invention. The processor can also be a combination that implements computational functions, such as a combination of one or more microprocessors, a combination of a DSP and a microprocessor, etc.

[0043] A bus can include a pathway for transmitting information between the aforementioned components. The bus can be a PCI (Peripheral Component Interconnect) bus or an EISA (Extended Industry Standard Architecture) bus, etc. Buses can be categorized as address buses, data buses, control buses, etc. For ease of representation, Figure 5 The bus is represented by a single thick line, but this does not mean that there is only one bus or one type of bus.

[0044] The memory may be ROM (Read Only Memory) or other types of static storage devices capable of storing static information and instructions, RAM (Random Access Memory) or other types of dynamic storage devices capable of storing information and instructions, or EEPROM (Electrically Erasable Programmable Read Only Memory), CD-ROM (Compact Disc Read Only Memory) or other optical disc storage, optical disc storage (including compressed optical discs, laser discs, optical discs, digital universal optical discs, Blu-ray discs, etc.), magnetic disk storage media or other magnetic storage devices, or any other medium capable of carrying or storing desired program code in the form of instructions or data structures and accessible by a computer, but not limited to these.

[0045] The memory stores application code (computer program) that executes the present invention, and its execution is controlled by a processor. The processor executes the application code stored in the memory to implement the content shown in the foregoing method embodiments.

[0046] The space-based radar ISAR beam position design device for airborne targets can also be a terminal device. The terminal device can be any device that can install applications, including at least one of smartphones, tablets, laptops, desktop computers, smart speakers, smartwatches, smart TVs, and smart vehicle devices.

[0047] It should be noted that, Figure 5 The illustrated space-based radar ISAR buoyancy design device for airborne targets is merely an example and should not impose any limitations on the functionality and scope of use of the embodiments of the present invention.

[0048] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for designing ISAR wavefronts for space-based radar targeting airborne targets, characterized in that, include: S1, set the waveform design parameters, maximum time for a single waveform change, protection time and scene width; S2, obtain the current position of the space-based radar, the velocity of the space-based radar, and the position of the air target. Based on the wave position design parameters, the maximum time of the first wave position change, the scene width, the position of the space-based radar, the velocity of the space-based radar, and the position of the air target, calculate the oblique angle, synthetic aperture time, number of sampling points, and pulse repetition frequency selection range for the space-based radar to observe the air target. Within the pulse repetition frequency selection range, traverse multiple pulse repetition frequencies and calculate the maximum unambiguous distance at each pulse repetition frequency. Also, calculate the ambiguity number at each pulse repetition frequency based on the observation time. S3. Based on the oblique angle, according to the wave position design parameters, the protection time, the scene width, and the maximum unambiguous distance and number of ambiguities at each pulse repetition frequency, the echo delay and the number of nadir points at each pulse repetition frequency are calculated accordingly. Based on the number of nadir points at each pulse repetition frequency, the start time of the sampling delay to be avoided at each pulse repetition frequency is calculated accordingly. S4, find the absolute value of the echo delay from all pulse repetition frequencies. A small echo delay is used as the sampling delay, and it is checked whether the start time of the sampling delay to be avoided at the pulse repetition frequency corresponding to the sampling delay meets the preset condition. If not, then let The sampling delay continues until the start time of the sampling delay to be avoided at the pulse repetition frequency corresponding to the sampling delay meets a preset condition. If so, the pulse repetition frequency corresponding to the sampling delay is used as the selected pulse repetition frequency; wherein, The initial value is 1; S5. Based on the synthetic aperture time, the number of sampling points, and the maximum unambiguous distance at the selected pulse repetition frequency, calculate the interval time of one phase coherence processing at the selected pulse repetition frequency. S6. Based on the selected pulse repetition frequency, calculate the sampling start and azimuth sampling point number for each coherent processing interval, and accumulate the observation time. S7, determine whether the observation time has reached the synthetic aperture time. If not, return to S2 and repeat until the observation time reaches the synthetic aperture time. If yes, complete all wave positions design.

2. The ISAR wavefront design method for space-based radar targeting airborne targets according to claim 1, characterized in that, In S1, The waveform design parameters include waveform information and azimuth resolution; wherein, the waveform information includes signal frequency, linear frequency modulated signal bandwidth, pulse width, and sampling rate; the azimuth resolution is set close to the range resolution, and the formula for determining the range resolution is: ； In the formula, The distance resolution is [the specified distance resolution]. The speed of light in a vacuum. The bandwidth of the linear frequency modulated signal is given.

3. The ISAR wavefront design method for space-based radar against airborne targets according to claim 2, characterized in that, In S2, The formula for calculating the oblique angle is: ； In the formula, The oblique angle is... Let be the vector of the velocity of the space-based radar. Let be the vector difference between the position of the aerial target and the position of the space-based radar, and , Let be the vector of the aerial target's position. The vector representing the location of the space-based radar; The formula for calculating the synthesis aperture time is: ； In the formula, The time for synthesizing the aperture; For wavelength, and , The signal frequency; The azimuth resolution; The formula for calculating the number of sampling points is: ； In the formula, The number of sampling points, To round up, The width of the scene. The sampling rate is... The pulse width is... This represents the change in migration within the maximum time interval of a single wave phase change, and , The maximum time for a single waveform change; The pulse repetition frequency selection range is set as follows: ； In the formula, For Doppler bandwidth, and ; The formula for calculating the maximum unambiguous distance is: ； In the formula, The first pulse repetition frequency selected within the range of pulse repetition frequencies Maximum unambiguous distance at a pulse repetition frequency The first pulse repetition frequency selected within the range of pulse repetition frequencies pulse repetition frequency; The formula for calculating the fuzzy number is: ； In the formula, The first pulse repetition frequency selected within the range of pulse repetition frequencies The ambiguity number at a pulse repetition frequency The observation time is, and The initial value is 0.

4. The ISAR wavefront design method for space-based radar against airborne targets according to claim 2, characterized in that, In the S3, When the oblique angle is less than 0, the formula for calculating the echo delay is: ； When the oblique angle is greater than 0, the formula for calculating the echo delay is: ； In the formula, For the echo delay, The first pulse repetition frequency selected within the range of pulse repetition frequencies The ambiguity number at a pulse repetition frequency To round down, The first pulse repetition frequency selected within the range of pulse repetition frequencies Maximum unambiguous distance at a pulse repetition frequency The width of the scene. The pulse width is... For the protection time, The first pulse repetition frequency selected within the range of pulse repetition frequencies The pulse repetition frequency.

5. The ISAR wavefront design method for space-based radar against airborne targets according to claim 2, characterized in that, In the S3, The formula for calculating the fuzzy number of the under-satellite point is as follows: ； In the formula, The first pulse repetition frequency selected within the range of pulse repetition frequencies Number of nadir points at a pulse repetition frequency For space-based radar, the sub-satellite point vector is... The first pulse repetition frequency selected within the range of pulse repetition frequencies Maximum unambiguous distance at a pulse repetition frequency; The formula for calculating the start time of the sampling delay to be avoided is as follows: ； In the formula, The starting time for avoiding sampling delay is mentioned. To round down, The first pulse repetition frequency selected within the range of pulse repetition frequencies The pulse repetition frequency.

6. The ISAR wavefront design method for space-based radar against airborne targets according to claim 2, characterized in that, In S4, When the oblique angle is less than 0, the preset condition is: ； When the oblique angle is greater than 0, the preset condition is: ； In the formula, The starting time for avoiding sampling delay is mentioned. The first pulse repetition frequency selected within the range of pulse repetition frequencies pulse repetition frequency, The pulse width is given.

7. The ISAR wavefront design method for space-based radar against airborne targets according to claim 2, characterized in that, In S5, The formula for calculating the interval time of one phase coherence processing at the selected pulse repetition frequency is as follows: ； In the formula, The selected pulse repetition frequency is used as the interval time for one phase coherence processing. The duration of one pulse repetition frequency. The number of changes in the coherent processing interval, and ； ； ； ； In the formula, To round up, The maximum time for a single waveform change. The time for synthesizing the aperture is [time]. The number of times the pulse repetition frequency needs to be changed. The maximum time of migration variation that can be covered by the selected pulse repetition frequency. To select the maximum unambiguous distance at the selected pulse repetition frequency, The pulse width is... For the protection time, The number of sampling points, The sampling rate is... The oblique angle is... The vector represents the velocity of the space-based radar.

8. The method for designing ISAR wave positions for airborne targets by space-based radar according to claim 2, characterized in that, In S6, When the oblique angle is less than 0, the calculation formula for the sampling start is: ； When the oblique angle is 0, the calculation formula for the sampling start is: ； In the formula, This is the starting point for the sampling. For the protection time, Let be the vector of the velocity of the space-based radar. The oblique angle is... The selected pulse repetition frequency is used as the interval time for one phase coherence processing. Number the coherent processing interval for each pulse repetition frequency. To select the pulse repetition frequency, The number of sampling points, The sampling rate is... The width of the scene.

9. The ISAR wavefront design method for space-based radar against airborne targets according to claim 1, characterized in that, In S6, The formula for calculating the number of azimuth sampling points is: ； In the formula, The number of sampling points in the azimuth direction. The selected pulse repetition frequency is used for one-time phase coherence processing interval. Select the pulse repetition frequency; The cumulative formula for the observation time is: ； In the formula, For the front The cumulative observation time for each wave position For the front The cumulative observation time for each wave position.

10. A device for designing ISAR wave positions for airborne targets using a space-based radar, characterized in that, It includes a processor, a memory, and a computer program stored in the memory, wherein the computer program, when executed by the processor, implements the ISAR buoyancy design method for airborne targets by a space-based radar as described in any one of claims 1 to 9.

Images