Satellite-borne SAR sliding bunching mode azimuth beam scanning control method and system based on imaging scene adaptive adjustment

Abstract

The invention relates to the technical field of spaceborne synthetic airborne radar imaging, in particular to a spaceborne SAR sliding bunching mode azimuth beam scanning control method and system based on imaging scene adaptive adjustment, and the method comprises the steps: obtaining the thermal noise average signal intensity of a radar receiver in a spaceborne SAR emission silence state; obtaining the current imaging azimuth resolution according to the radar echo signal energy under the current radar azimuth beam pointing and the average signal intensity of the thermal noise of the radar receiver, and adjusting the azimuth beam scanning angular velocity and the next azimuth beam pointing according to the current imaging range resolution, so that the azimuth resolution is matched with the SAR imaging scene target. And the setting of the number of resident pulses in all azimuth angle scanning ranges is completed. According to the method, the azimuth resolution is matched with the high-value target distribution of an imaging scene, the application efficiency of azimuth beam scanning is greatly improved, the requirement of a sliding bunching mode for the radar azimuth beam scanning capability is reduced to a certain extent, and the hardware scale and cost of a spaceborne SAR system are reduced.

Description

Technical Field

[0001] The present invention relates to the field of spaceborne synthetic airborne radar imaging technology, and in particular to a spaceborne SAR sliding spotlight mode azimuth beam scanning control method and system based on imaging scene adaptive adjustment. Background Art

[0002] The dynamic spotlight mode is an important high-resolution imaging mode of spaceborne synthetic aperture radar (SAR). This mode uses azimuth beam scanning to increase the observation time of the target and thus improve the azimuth geometric resolution of the spaceborne SAR. In the conventional sliding spotlight mode of spaceborne SAR, no matter how the imaging scene changes, the radar azimuth beam uses a constant azimuth beam scanning angular velocity to illuminate the imaging area and receive radar echo signals. Obviously, the constant azimuth beam scanning method in the conventional sliding spotlight mode ignores the matching between the azimuth resolution and the radar imaging scene. This azimuth beam scanning method causes the azimuth resolution of some imaging areas to be insufficient, making it difficult to interpret the target well, while the target information in some areas is small and the azimuth resolution is too high, which to a certain extent leads to the waste of the azimuth scanning capability of the spaceborne SAR system. Summary of the invention

[0003] To this end, the present invention provides a method and system for controlling azimuth beam scanning in a sliding spotlight mode of a spaceborne SAR based on adaptive adjustment of imaging scenes, which solves the problem of mismatch between azimuth resolution and imaging scenes under fixed azimuth beam scanning acceleration in the existing conventional spaceborne SAR sliding spotlight mode.

[0004] According to the design scheme provided by the present invention, on the one hand, a method for controlling azimuth beam scanning in a sliding spotlight mode of a spaceborne SAR based on adaptive adjustment of an imaging scene is provided, comprising: Obtain the average signal strength of thermal noise of the radar receiver when the spaceborne SAR radar is transmitting in silent state; The current imaging azimuth resolution is obtained according to the radar echo signal energy under the current radar azimuth beam pointing and the average signal strength of the radar receiver thermal noise. The azimuth beam scanning angular velocity and the next azimuth beam pointing are adjusted according to the current imaging range resolution to match the azimuth resolution with the SAR imaging scene target until the number of dwell pulses in all azimuth angle scanning ranges is set.

[0005] As a method for controlling azimuth beam scanning in a spaceborne SAR sliding spotlight mode based on imaging scene adaptive adjustment of the present invention, further, obtaining the average signal strength of thermal noise of a radar receiver in a spaceborne SAR radar transmitting silent state comprises: Collect and record the receiver thermal noise signal in the spaceborne SAR echo receiving window within multiple pulse repetition periods when the spaceborne SAR radar is transmitting in a silent state; The average signal strength of the radar receiver thermal noise is calculated based on the receiver thermal noise signal strength at each sampling point in the radar echo window of each pulse repetition period, the number of pulses in the thermal noise signal repetition period, and the total number of sampling points in the radar echo receiving window.

[0006] As a spaceborne SAR sliding spotlight mode azimuth beam scanning control method based on imaging scene adaptive adjustment of the present invention, further, according to the radar echo signal energy under the current radar azimuth beam pointing and the average signal strength of the radar receiver thermal noise, the current imaging azimuth resolution is obtained, which includes: Set the initial value of the azimuth beam scanning angular velocity in the sliding spotlight mode; and set the initial value of the azimuth beam pointing angle according to the azimuth beam scanning mode and scanning azimuth of the spaceborne SAR sliding spotlight mode; Determine the number of dwell pulses pointed by the current azimuth beam according to the azimuth beam scanning angular velocity, the minimum beam jump of the phased array antenna and the pulse repetition frequency; The average energy of the radar echo signal under the current azimuth beam direction is obtained according to the radar echo signal at each sampling point of the radar echo window of each pulse repetition period, the number of pulses in the radar echo signal repetition period, and the total number of sampling points in the radar echo receiving window; The current imaging azimuth resolution is obtained based on the average energy of the radar echo signal under the current azimuth beam pointing, the average signal strength of the radar receiver thermal noise, the expected system sensitivity of the SAR satellite, the expected echo signal-to-noise ratio of the SAR satellite and the azimuth reference resolution.

[0007] As a spaceborne SAR sliding spotlight mode azimuth beam scanning control method based on imaging scene adaptive adjustment of the present invention, further, setting the initial value of the azimuth beam scanning angular velocity of the sliding spotlight mode comprises: The initial value of the azimuth beam scanning angular velocity of the sliding beamforming mode is set according to the theoretical resolution broadening coefficient, the moving speed of the spaceborne SAR radar beam in the mapping zone, the effective length of the spaceborne SAR antenna, the azimuth reference resolution, the relative speed between the satellite and the imaging mapping zone, and the shortest distance from the satellite track to the center of the imaging mapping zone.

[0008] As a spaceborne SAR sliding spotlight mode azimuth beam scanning control method based on imaging scene adaptive adjustment of the present invention, further, according to the radar echo signal energy under the current radar azimuth beam pointing and the average signal strength of the radar receiver thermal noise, the current imaging azimuth resolution is obtained, which also includes: A coefficient for adjusting the proportional relationship between resolution and radar echo intensity is set according to the dynamic range of imaging scene intensity; The current imaging azimuth resolution is obtained by combining the proportional relationship coefficient between resolution and radar echo intensity and according to the radar echo signal energy under the current radar azimuth beam pointing and the average signal strength of the radar receiver thermal noise.

[0009] As a spaceborne SAR sliding spotlight mode azimuth beam scanning control method based on imaging scene adaptive adjustment of the present invention, further, adjusting the azimuth beam scanning angular velocity according to the current imaging range resolution includes: The azimuth beam scanning angular velocity is adjusted according to the theoretical resolution broadening coefficient, the moving speed of the spaceborne SAR radar beam in the mapping zone, the effective length of the spaceborne SAR antenna, the current imaging range resolution, the relative speed between the satellite and the imaging mapping zone, and the shortest distance from the satellite track to the center of the imaging mapping zone.

[0010] As a spaceborne SAR sliding spotlight mode azimuth beam scanning control method based on imaging scene adaptive adjustment of the present invention, further, adjusting the next azimuth beam pointing according to the current imaging range resolution includes: The next azimuth beam pointing is adjusted according to the beam jump of the antenna beam scanning.

[0011] On the other hand, the present invention also provides a spaceborne SAR sliding spotlight mode azimuth beam scanning control system based on imaging scene adaptive adjustment, comprising: a thermal noise processing module and a pulse setting module, wherein: The thermal noise processing module is used to obtain the average signal strength of the thermal noise of the radar receiver when the spaceborne SAR radar is transmitting in a silent state; The pulse setting module is used to obtain the current imaging azimuth resolution according to the radar echo signal energy under the current radar azimuth beam pointing and the average signal strength of the radar receiver thermal noise, and adjust the azimuth beam scanning angular velocity and the next azimuth beam pointing according to the current imaging range resolution to match the azimuth resolution with the SAR imaging scene target until the setting of the number of resident pulses within the scanning range of all azimuth angles is completed.

[0012] Beneficial effects of the present invention: 1. The present invention adaptively adjusts the radar azimuth beam scanning angular velocity based on the radar echo signal energy collected by the space-borne SAR system, thereby dynamically adjusting the azimuth resolution of the sliding beam mode, which can match the azimuth resolution with the distribution of high-value targets in the imaging scene, greatly improving the application efficiency of azimuth beam scanning.

[0013] 2. Compared with the conventional sliding beamforming mode with constant azimuth resolution, the present invention can achieve higher azimuth resolution for areas containing a large number of high-value targets by adaptively and dynamically adjusting the azimuth beam scanning angular velocity, while areas without valuable targets only need to meet certain application requirements, and has strong adaptability.

[0014] 3. The present invention can make the azimuth resolution more consistent with the target scene by dynamically and adaptively adjusting the azimuth beam scanning angular velocity, which can not only meet the azimuth resolution requirements of subsequent interpretation and application, but also reduce the requirements of the sliding beam mode on the radar azimuth beam scanning capability to a certain extent, thereby reducing the hardware scale and cost of the spaceborne SAR system, and has good application prospects in spaceborne SAR system imaging. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a schematic diagram of the azimuth beam scanning control process of the spaceborne SAR sliding spotlight mode based on the imaging scene adaptive adjustment in the embodiment; Figure 2 The figure is a schematic diagram of the azimuth beam scanning control algorithm in the embodiment. DETAILED DESCRIPTION

[0016] In order to make the purpose, technical solutions and advantages of the present invention clearer and more understandable, the present invention is further described in detail below in conjunction with the accompanying drawings and technical solutions.

[0017] In view of the mismatch between the azimuth resolution and the imaging scene under the fixed azimuth beam scanning acceleration of the conventional spaceborne SAR sliding spotlight mode, the embodiments of the present invention refer to Figure 1 As shown, a method for controlling azimuth beam scanning in a spaceborne SAR sliding spotlight mode based on adaptive adjustment of imaging scenes is provided, comprising: S101. Acquire the average signal strength of thermal noise of a radar receiver when the spaceborne SAR radar is transmitting in a silent state.

[0018] Specifically, the thermal noise signal of the receiver in the spaceborne SAR echo receiving window within multiple pulse repetition periods when the spaceborne SAR radar is in silent transmission state is collected and recorded; the average signal strength of the radar receiver thermal noise is calculated based on the receiver thermal noise signal strength at each sampling point of the radar echo window in each pulse repetition period, the number of pulses in the thermal noise signal repetition period and the total number of sampling points in the radar echo receiving window.

[0019] By turning off the satellite-borne SAR radar transmitter, the radar is in silent receiving state, receiving and recording N P The noise signal of the pulse repetition period, at this time, the radar receiver thermal noise average signal energy N noise It can be expressed as:

[0020] Where N r Indicates the total number of sampling points in the radar echo receiving window, A noise (n a ,n r ) indicates the nth a The nth pulse repetition period radar echo windowr The signal strength of the receiver thermal noise at each sampling point.

[0021] S102, obtaining the current imaging azimuth resolution according to the radar echo signal energy under the current radar azimuth beam pointing and the average signal strength of the radar receiver thermal noise, adjusting the azimuth beam scanning angular velocity and the next azimuth beam pointing according to the current imaging range resolution, so that the azimuth resolution matches the SAR imaging scene target, until the setting of the number of dwell pulses within the scanning range of all azimuth angles is completed.

[0022] Specifically, the current imaging azimuth resolution is obtained according to the radar echo signal energy under the current radar azimuth beam pointing and the average signal strength of the radar receiver thermal noise, which can be designed to include: Set the initial value of the azimuth beam scanning angular velocity in the sliding spotlight mode; and set the initial value of the azimuth beam pointing angle according to the azimuth beam scanning mode and scanning azimuth of the spaceborne SAR sliding spotlight mode; Determine the number of dwell pulses pointed by the current azimuth beam according to the azimuth beam scanning angular velocity, the minimum beam jump of the phased array antenna and the pulse repetition frequency; The average energy of the radar echo signal under the current azimuth beam direction is obtained according to the radar echo signal at each sampling point of the radar echo window of each pulse repetition period, the number of pulses in the radar echo signal repetition period, and the total number of sampling points in the radar echo receiving window; The current imaging azimuth resolution is obtained based on the average energy of the radar echo signal under the current azimuth beam pointing, the average signal strength of the radar receiver thermal noise, the expected system sensitivity of the SAR satellite, the expected echo signal-to-noise ratio of the SAR satellite and the azimuth reference resolution.

[0023] like Figure 2 The algorithm shown first receives radar input parameters, calculates the average signal strength of thermal noise of the radar receiver based on the input parameters, and cyclically executes the following steps: sets the azimuth beam scanning angular velocity and the initial value of the beam pointing, calculates the radar echo power and azimuth resolution, adjusts the azimuth beam scanning angular velocity and the next beam pointing, until the dynamic pulse dwell book setting is completed under the entire scanning angle range.

[0024] Among them, the initial value of the azimuth beam scanning angular velocity of the sliding beam mode can be set according to the theoretical resolution broadening coefficient, the moving speed of the spaceborne SAR radar beam in the mapping zone, the effective length of the spaceborne SAR antenna, the azimuth reference resolution, the relative speed between the satellite and the imaging mapping zone, and the shortest distance from the satellite track to the center of the imaging mapping zone.

[0025] The initial scanning angular velocity of the azimuth beam in the sliding spotlight mode is mainly determined by the azimuth reference resolution ρ a,ref To determine the azimuth beam scanning angular velocity w r The initial value of can be expressed as:

[0026] Where: k a represents the theoretical resolution broadening coefficient caused by SAR imaging processing, v g Indicates the moving speed of the spaceborne SAR radar beam within the surveying zone, L a represents the effective length of the spaceborne SAR antenna, ρ a,ref Indicates the reference resolution in azimuth, v s represents the relative speed between the satellite and the imaging swath, R c Indicates the shortest distance from the satellite track to the center of the imaging swath.

[0027] The azimuth beam of the spaceborne SAR sliding spotlight mode adopts a scanning method from front to back to increase the synthetic aperture time of the target and thus improve the azimuth resolution of the target. The scanning range of the azimuth beam of the spaceborne SAR sliding spotlight is [-θ scan ,θ scan ], the initial pointing angle of the azimuth beam is determined by the azimuth scanning range in the sliding beamforming mode, where the angle is positive when the beam points in front of the satellite and negative when it points behind the satellite, so the azimuth beam pointing angle θ s The initial value is θ scan .

[0028] According to the set azimuth beam scanning angular velocity w r , to determine the current azimuth beam pointing θ s The number of dwell pulses N q for

[0029] Where round(·) represents rounding operation, q represents the minimum beam jump of the phased array antenna, and PRF represents the pulse repetition frequency.

[0030] The current azimuth beam pointing θ is calculated by the following formula: s The average energy S of the radar echo signal under r

[0031] According to the current statistics, the average energy S of the radar echo signal r , calculate the reasonable orientation resolution ρ of the current scene a , the specific formula can be expressed as:

[0032] Where γ is a constant, which is mainly set according to the dynamic range of imaging scene intensity. This parameter is used to adjust the proportional relationship between resolution and radar echo intensity; NESZ represents the average system sensitivity of the SAR satellite in the mapping band, and SNR represents the echo signal-to-noise ratio expected by the SAR satellite.

[0033] At this time, the azimuth beam scanning angular velocity can be expressed as

[0034] According to the beam jump q of the antenna beam scanning, the next azimuth beam points to θ s It can be expressed as

[0035] Returns the azimuth beam scanning angular velocity w adjusted according to the radar echo power r and azimuth beam pointing θ s Repeat the steps until the number of dwell pulses in the entire azimuth angle scanning range is set.

[0036] Further, based on the above method, an embodiment of the present invention also provides a spaceborne SAR sliding spotlight mode azimuth beam scanning control system based on imaging scene adaptive adjustment, comprising: a thermal noise processing module and a pulse setting module, wherein: The thermal noise processing module is used to obtain the average signal strength of the thermal noise of the radar receiver when the spaceborne SAR radar is transmitting in a silent state; The pulse setting module is used to obtain the current imaging azimuth resolution according to the radar echo signal energy under the current radar azimuth beam pointing and the average signal strength of the radar receiver thermal noise, and adjust the azimuth beam scanning angular velocity and the next azimuth beam pointing according to the current imaging range resolution to match the azimuth resolution with the SAR imaging scene target until the setting of the number of resident pulses within the scanning range of all azimuth angles is completed.

[0037] In the embodiment of this case, when the satellite-borne SAR radar is transmitting in a silent state, the average intensity of the thermal noise signal of the radar receiver is calculated by collecting and recording the thermal noise signal of the receiver in the entire satellite-borne SAR echo receiving window within multiple pulse repetition periods, which is used as an important input for the design of the azimuth beam adaptive scanning in the sliding beam mode. According to the energy of the radar echo signal under the current radar azimuth beam, a mapping relationship between the resolution and the radar echo signal energy is constructed, and the mapping relationship is used to calculate the azimuth resolution suitable for the current imaging. According to the relationship between the azimuth resolution and the azimuth beam scanning angular velocity, the number of dwell pulses under the next azimuth beam is adaptively and dynamically adjusted, so as to achieve the adaptive adjustment of the azimuth beam scanning angular velocity according to the imaging scene, so that the azimuth resolution matches the SAR imaging scene target and meets the application requirements of the SAR imaging scene.

[0038] Unless otherwise specifically stated, the relative steps, numerical expressions and values ​​of the components and steps set forth in these embodiments do not limit the scope of the present invention.

[0039] In this specification, each embodiment is described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the embodiments can be referred to each other. For the system disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant parts can be referred to the method part.

[0040] The units and method steps of each example described in conjunction with the embodiments disclosed herein can be implemented by electronic hardware, computer software, or a combination of the two. In order to clearly illustrate the interchangeability of hardware and software, the composition and steps of each example have been generally described in the above description according to function. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. A person of ordinary skill in the art may use different methods to implement the described functions for each specific application, but such implementation is not considered to be beyond the scope of the present invention.

[0041] Those skilled in the art will appreciate that all or part of the steps in the above method can be completed by instructing related hardware through a program, and the program can be stored in a computer-readable storage medium, such as a read-only memory, a disk or an optical disk. Optionally, all or part of the steps in the above embodiment can also be implemented using one or more integrated circuits, and accordingly, each module / unit in the above embodiment can be implemented in the form of hardware or in the form of software function modules. The present invention is not limited to any specific form of combination of hardware and software.

[0042] Finally, it should be noted that the above-described embodiments are only specific implementations of the present invention, which are used to illustrate the technical solutions of the present invention, rather than to limit them. The protection scope of the present invention is not limited thereto. Although the present invention is described in detail with reference to the above-described embodiments, ordinary technicians in the field should understand that any technician familiar with the technical field can still modify the technical solutions recorded in the above-described embodiments within the technical scope disclosed by the present invention, or can easily think of changes, or make equivalent replacements for some of the technical features therein; and these modifications, changes or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.

Claims

1. A method for controlling azimuth beam scanning in a spaceborne SAR sliding spotlight mode based on adaptive adjustment of imaging scenes, characterized in that: Include: Obtain the average signal strength of thermal noise of the radar receiver when the spaceborne SAR radar is transmitting in silent state; The current imaging azimuth resolution is obtained according to the radar echo signal energy under the current radar azimuth beam pointing and the average signal strength of the radar receiver thermal noise. The azimuth beam scanning angular velocity and the next azimuth beam pointing are adjusted according to the current imaging range resolution to match the azimuth resolution with the SAR imaging scene target until the number of dwell pulses in all azimuth angle scanning ranges is set.

2. The method for controlling azimuth beam scanning in a spaceborne SAR sliding spotlight mode based on adaptive adjustment of imaging scenes according to claim 1, characterized in that: The average signal strength of thermal noise of the radar receiver is obtained when the spaceborne SAR radar is transmitting in a silent state, including: Collect and record the receiver thermal noise signal in the spaceborne SAR echo receiving window within multiple pulse repetition periods when the spaceborne SAR radar is transmitting in a silent state; The average signal strength of the radar receiver thermal noise is calculated based on the receiver thermal noise signal strength at each sampling point in the radar echo window of each pulse repetition period, the number of pulses in the thermal noise signal repetition period, and the total number of sampling points in the radar echo receiving window.

3. The method for controlling azimuth beam scanning in a spaceborne SAR sliding spotlight mode based on adaptive adjustment of imaging scenes according to claim 1, characterized in that: The current imaging azimuth resolution is obtained based on the radar echo signal energy under the current radar azimuth beam pointing and the average signal strength of the radar receiver thermal noise, including: Set the initial value of the azimuth beam scanning angular velocity in the sliding beam mode; And according to the azimuth beam scanning mode and scanning azimuth of the spaceborne SAR sliding spotlight mode, the initial value of the azimuth beam pointing angle is set; Determine the number of dwell pulses pointed by the current azimuth beam according to the azimuth beam scanning angular velocity, the minimum beam jump of the phased array antenna and the pulse repetition frequency; The average energy of the radar echo signal under the current azimuth beam direction is obtained according to the radar echo signal at each sampling point of the radar echo window of each pulse repetition period, the number of pulses in the radar echo signal repetition period, and the total number of sampling points in the radar echo receiving window; The current imaging azimuth resolution is obtained based on the average energy of the radar echo signal under the current azimuth beam pointing, the average signal strength of the radar receiver thermal noise, the expected system sensitivity of the SAR satellite, the expected echo signal-to-noise ratio of the SAR satellite and the azimuth reference resolution.

4. The method for controlling azimuth beam scanning in a spaceborne SAR sliding spotlight mode based on adaptive adjustment of imaging scenes according to claim 3, characterized in that: Set the initial value of the azimuth beam scanning angular velocity in the sliding spotlight mode, including: The initial value of the azimuth beam scanning angular velocity of the sliding beamforming mode is set according to the theoretical resolution broadening coefficient, the moving speed of the spaceborne SAR radar beam in the mapping zone, the effective length of the spaceborne SAR antenna, the azimuth reference resolution, the relative speed between the satellite and the imaging mapping zone, and the shortest distance from the satellite track to the center of the imaging mapping zone.

5. The method for controlling azimuth beam scanning in a spaceborne SAR sliding spotlight mode based on adaptive adjustment of imaging scenes according to claim 1 or 3, characterized in that: The current imaging azimuth resolution is obtained according to the radar echo signal energy under the current radar azimuth beam pointing and the average signal strength of the radar receiver thermal noise, which also includes: A coefficient for adjusting the proportional relationship between resolution and radar echo intensity is set according to the dynamic range of imaging scene intensity; The current imaging azimuth resolution is obtained by combining the proportional relationship coefficient between resolution and radar echo intensity and according to the radar echo signal energy under the current radar azimuth beam pointing and the average signal strength of the radar receiver thermal noise.

6. The method for controlling azimuth beam scanning in a spaceborne SAR sliding spotlight mode based on adaptive adjustment of imaging scenes according to claim 1, characterized in that: Adjust the azimuth beam scanning angular velocity according to the current imaging range resolution, including: The azimuth beam scanning angular velocity is adjusted according to the theoretical resolution broadening coefficient, the moving speed of the spaceborne SAR radar beam in the mapping zone, the effective length of the spaceborne SAR antenna, the current imaging range resolution, the relative speed between the satellite and the imaging mapping zone, and the shortest distance from the satellite track to the center of the imaging mapping zone.

7. The method for controlling azimuth beam scanning in a spaceborne SAR sliding spotlight mode based on imaging scene adaptive adjustment according to claim 1 or 6, characterized in that: Adjust the next azimuth beam pointing according to the current imaging range resolution, including: The next azimuth beam pointing is adjusted according to the beam jump of the antenna beam scanning.

8. A spaceborne SAR sliding spotlight mode azimuth beam scanning control system based on imaging scene adaptive adjustment, characterized in that: Contains: thermal noise processing module and pulse setting module, among which, The thermal noise processing module is used to obtain the average signal strength of the thermal noise of the radar receiver when the spaceborne SAR radar is transmitting in a silent state; The pulse setting module is used to obtain the current imaging azimuth resolution according to the radar echo signal energy under the current radar azimuth beam pointing and the average signal strength of the radar receiver thermal noise, and adjust the azimuth beam scanning angular velocity and the next azimuth beam pointing according to the current imaging range resolution to match the azimuth resolution with the SAR imaging scene target until the setting of the number of resident pulses within the scanning range of all azimuth angles is completed.

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