A timing generation method and control system for synthetic aperture radar

Abstract

The present invention discloses a timing generation method and a control system of a synthetic aperture radar, which belongs to the field of synthetic aperture radar imaging technology, and includes the following steps: S1: calculating the angular displacement data of the synthetic aperture radar antenna; S2: calculating the sampling rate within a single scanning cycle of the synthetic aperture radar; S3: calculating the angular displacement difference of the radar antenna rotation each time a pulse signal is emitted; S4: calculating the timing of generating radar actions. In step S1, the calculation formula of the angular displacement data of the radar antenna is the integral curve within the unit rotation time of the radar antenna. The present invention obtains accurate antenna position information in real time, generates a uniform scanning timing for the spatial position according to the acquired position information, and obtains uniform acquisition data according to the timing, thereby effectively reducing the amount of echo data, and omitting the motion compensation part in the calculation process, thereby reducing the requirements for motion compensation.

Description

Technical Field

[0001] The present invention relates to the field of synthetic aperture radar imaging technology, and in particular to a timing generation method of a synthetic aperture radar and a control system thereof. Background Art

[0002] The synthetic aperture radar (SAR) system is an active microwave imaging system with the characteristics of all-day, all-weather, and long-distance imaging. When working in a lower frequency band, it can penetrate vegetation, ground cover and other coverings and detect hidden targets. SAR flies in a straight line at a constant speed, forming a uniform and linear synthetic aperture array flow, which is equivalent to producing an antenna with a large azimuth size, thereby improving the azimuth resolution of the radar. For a fixed target in the imaging scene, in the process of forming the synthetic aperture, the azimuth angle of the target relative to the SAR platform changes continuously, and the Doppler frequency also changes accordingly. With the development of signal processing technology, modern SAR signal processing usually adopts the method of focusing processing, that is, during the synthetic aperture accumulation time, due to the continuous change of the distance from the radar to the target, the envelope offset and nonlinear phase change of the echo signal are caused. By compensating the signal envelope and phase, a well-focused SAR image is obtained.

[0003] SAR not only has important application value in military fields such as wide-area surveillance and battlefield reconnaissance, but has also gradually become an important means in civilian fields such as terrain mapping, environmental monitoring, and disaster assessment.

[0004] With the continuous development of modern radar systems, SAR systems are developing in the direction of multi-functional and multi-mode collaborative work. Generally speaking, the working modes of SAR systems mainly include strip mode, spotlight mode, sliding spotlight mode, and scanning mode. In strip mode, the antenna pointing remains basically unchanged. As the SAR platform moves, a strip imaging area parallel to the track is formed on the ground. Its azimuth resolution depends on the actual size of the radar antenna, and the length of the strip is related to the distance the platform flies along the track. Spotlight mode is a commonly used working mode for high-resolution SAR imaging of small scenes. During the flight of the platform, the radar transmits pulses to the same imaging area by continuously adjusting the antenna beam pointing, forming a very long synthetic aperture, breaking through the limitation of the actual antenna size on the azimuth resolution. The sliding spotlight mode generally controls the moving speed of the antenna irradiation area on the ground to adjust the coherent accumulation time in the azimuth direction, thereby affecting the azimuth resolution of the image. In scanning mode, the antenna performs multiple scans in the range direction within the synthetic aperture time, and obtains a wider range mapping strip of the scene at the expense of the azimuth resolution of the image.

[0005] SAR imaging algorithm theory has also achieved rapid development. Range Migration Algorithm (RMA) is an algorithm for SAR imaging. This method uses Stlot interpolation to correct for range unit migration. It is an accurate and robust SAR imaging algorithm, but the interpolation operation is inefficient, especially in the squint mode. It requires the system to have a very high pulse repetition frequency, which further increases the amount of calculation.

[0006] Due to the influence of atmospheric turbulence, platform vibration and other factors, the SAR motion trajectory changes dramatically. In order to obtain high-resolution SAR images, high-precision motion compensation must be performed. Limited by factors such as platform load and test cost, SAR is generally only equipped with medium or low-precision inertial navigation systems, which are far from meeting the wavelength-level error compensation accuracy requirements required for imaging.

[0007] The SAR radar transmits at a certain pulse repetition frequency (PRF), and then receives the radar echo signal in real time for processing. To obtain high-resolution radar imaging, the radar's PRF can be increased, but the problem is that the amount of echo data increases, which makes back-end processing difficult. Summary of the invention

[0008] The technical problem to be solved by the present invention is: how to solve the problem of difficulty in radar signal processing by reducing the amount of echo data, and provide a timing generation method for synthetic aperture radar, which obtains accurate antenna position information in real time, generates a uniform scanning timing for the spatial position according to the acquired position information, and obtains uniform collection data according to the timing, thereby effectively reducing the amount of echo data, and omitting the motion compensation part in the calculation process, thereby reducing the requirements for motion compensation.

[0009] The present invention solves the above technical problems through the following technical solutions, and the present invention comprises the following steps:

[0010] S1: Calculate the angular displacement data of the synthetic aperture radar antenna

[0011] According to the angular velocity curve of the radar antenna rotation, the angular displacement data of the radar antenna is calculated in real time;

[0012] S2: Calculate the sampling rate within a single scanning cycle of the synthetic aperture radar

[0013] According to the requirements of radar resolution, the sampling rate of radar acquisition is calculated within a scanning cycle, and the number of intervals that need to be collected in a single scanning cycle is obtained. The number of intervals is recorded as N. Multiple mechanical scans can be performed during the operation of the radar, thus forming an intermittent working mode. The intermittent working mode of SAR based on spatial position avoids the radar from being in a long-term working state and reduces the energy consumption of the entire radar.

[0014] S3: Calculate the angular displacement difference of the radar antenna each time a pulse signal is transmitted

[0015] According to the number of intervals to be collected in a single scanning cycle calculated in step S3, the angular displacement difference of the radar antenna rotation each time a pulse signal is transmitted is calculated. The angular displacement difference is recorded as ΔS. The calculation formula of the angular displacement difference is as follows:

[0016] ΔS=S / N

[0017] Among them, S is the total angular displacement of the radar antenna in a single scanning cycle, and N is the number of intervals that need to be collected in a single scanning cycle. The method of generating radar timing in the intermittent working mode reduces the amount of radar echo data and the time of radar signal processing while meeting the resolution of the radar system. The radar echo data collected according to the fixed spatial displacement meets the uniform sampling law, and there is no need to perform motion compensation on the radar echo data. From the perspective of the radar signal processing calculation process, the motion compensation step is omitted, the calculation process is simpler, and the requirements for motion compensation are reduced.

[0018] S4: Calculate the timing of radar action

[0019] The timing of the radar action is generated in real time according to the angular displacement difference ΔS calculated in step S3.

[0020] Furthermore, in step S1, the angular displacement data of the radar antenna is obtained by calculating the integral curve of the radar antenna within a unit rotation time.

[0021] Furthermore, in the step S1, the radar antenna includes three motion states during its rotation, which are acceleration, uniform speed and deceleration in chronological order.

[0022] Furthermore, the acceleration and deceleration processes are both uniform speed change processes.

[0023] Furthermore, the acceleration process, the uniform speed process and the deceleration process constitute a complete scanning cycle.

[0024] Furthermore, the time t1 of the acceleration process is 0.5S, the time t2 of the uniform speed process is 1.5S, the time t3 of the deceleration process is 0.5S, and the time for the radar antenna to rotate in a complete scanning cycle is 2.5S.

[0025] Furthermore, in step S2, the number of intervals to be collected is 368; in step S3, the total angular displacement S of the radar antenna in a single scanning cycle is 120°, and the angular displacement difference of the radar antenna rotation ΔS=120° / 368=0.326°, that is, the radar antenna transmits and receives once every 0.326° rotation.

[0026] The present invention also provides a timing generation control system for a synthetic aperture radar, including a radar antenna unit, a radar servo control unit, a radar signal processing unit, and a radar display and control unit. The radar control system is in an intermittent working mode, and the entire system has a simple workflow, and can realize real-time imaging of any position in space.

[0027] The radar antenna unit is used for directional emission and reception of electromagnetic waves;

[0028] The radar servo control unit is used to control the radar antenna and feed back the position information of the radar antenna to the radar signal processing unit in real time;

[0029] The radar signal processing unit is used to receive the position information of the radar servo control unit in real time, and is controlled by the radar display and control unit to intermittently generate the timing of the entire radar operation and perform real-time imaging;

[0030] The radar display and control unit is used as the center of the entire control system, sending commands to the radar servo control unit to control the radar antenna unit, and at the same time interacting with the radar signal processing unit to intermittently control the timing;

[0031] The radar antenna unit is connected to the radar servo control unit and the radar signal processing unit through a bus, respectively; the radar servo control unit is connected to the radar signal processing unit through a bus, and the radar display and control unit is connected to the radar servo control unit and the radar signal processing unit through a bus.

[0032] Furthermore, the position information of the radar antenna is angle information, direction information, and speed information when the radar antenna rotates.

[0033] Furthermore, the radar servo control unit includes a programmable logic controller, a servo control system and a servo motor. The radar servo control unit monitors the motion working state of the servo motor in real time, completes the control of the radar antenna, and feeds back the position information of the radar antenna to the radar signal processing unit in real time.

[0034] Compared with the prior art, the present invention has the following advantages: the timing generation method and display and control system of the synthetic aperture radar, the SAR based on the spatial position adopts an intermittent working mode to avoid the radar being in a long-term working state, and reduces the energy consumption of the entire radar; the radar timing generation method in the intermittent working mode reduces the data volume of the radar echo and the radar signal processing time while meeting the radar system resolution; the radar echo data collected according to the fixed spatial displacement meets the uniform sampling law, and there is no need to perform motion compensation on the radar echo data. From the perspective of the radar signal processing calculation process, the motion compensation step is omitted, the calculation process is simpler, and the requirement for motion compensation is reduced; the radar control system in the intermittent working mode is adopted, the entire system workflow is simple, and real-time imaging of any position in the space can be achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 It is a schematic diagram of the flow chart of timing generation of synthetic aperture radar in the first embodiment of the present invention;

[0036] Figure 2 Schematic diagram of the angular velocity curve of the radar antenna rotation in the first embodiment of the present invention;

[0037] Figure 3 Schematic diagram of the angular displacement curve of the radar antenna rotation in the first embodiment of the present invention;

[0038] Figure 4 It is a schematic diagram of radar timing generation in the discontinuous working mode in the first embodiment of the present invention;

[0039] Figure 5 A block diagram of a control system for timing generation of a synthetic aperture radar in Embodiment 1 of the present invention;

[0040] Figure 6 It is a rotation schematic diagram of the synthetic aperture radar of the present invention. DETAILED DESCRIPTION

[0041] The following is a detailed description of an embodiment of the present invention. This embodiment is implemented on the premise of the technical solution of the present invention, and a detailed implementation method and a specific operation process are given, but the protection scope of the present invention is not limited to the following embodiment.

[0042] Embodiment 1

[0043] like Figure 1-4As shown, this embodiment provides a technical solution: a timing generation method for a synthetic aperture radar, comprising the following steps:

[0044] S1: Calculate the angular displacement data of the synthetic aperture radar antenna

[0045] According to the angular velocity curve of the radar antenna rotation, the angular displacement data of the radar antenna is calculated in real time;

[0046] S2: Calculate the sampling rate within a single scanning cycle of the synthetic aperture radar

[0047] According to the requirements of radar resolution, the sampling rate of radar acquisition is calculated within a scanning cycle, and the number of intervals that need to be collected in a single scanning cycle is obtained. The number of intervals is recorded as N. Multiple mechanical scans can be performed during the operation of the radar, thus forming an intermittent working mode. The intermittent working mode of SAR based on spatial position avoids the radar from being in a long-term working state and reduces the energy consumption of the entire radar.

[0048] S3: Calculate the angular displacement difference of the radar antenna each time a pulse signal is transmitted

[0049] According to the number of intervals to be collected in a single scanning cycle calculated in step S3, the angular displacement difference of the radar antenna rotation each time a pulse signal is transmitted is calculated. The angular displacement difference is recorded as ΔS. The calculation formula of the angular displacement difference is as follows:

[0050] ΔS=S / N

[0051] Among them, S is the total angular displacement of the radar antenna in a single scanning cycle, and N is the number of intervals that need to be collected in a single scanning cycle. The method of generating radar timing in the intermittent working mode reduces the amount of radar echo data and the time of radar signal processing while meeting the resolution of the radar system. The radar echo data collected according to the fixed spatial displacement meets the uniform sampling law, and there is no need to perform motion compensation on the radar echo data. From the perspective of the radar signal processing calculation process, the motion compensation step is omitted, the calculation process is simpler, and the requirements for motion compensation are reduced.

[0052] S4: Calculate the timing of radar action

[0053] The radar action timing is generated in real time according to the ΔS calculated in step S3. The timing diagram of the radar antenna operation is as follows: Figure 4 shown.

[0054] In step S1, the angular displacement data of the radar antenna is obtained by calculating the integral curve of the radar antenna within a unit rotation time. The schematic diagram of the angular displacement curve of the radar antenna rotation is shown in FIG. Figure 2 shown.

[0055] In step S1, the radar antenna includes three motion states during its rotation, which are acceleration, uniform speed and deceleration in chronological order. Both the acceleration and deceleration processes are uniform speed change processes.

[0056] The schematic diagram of the speed curve of the radar antenna rotation is as follows Figure 2 As shown, the angular velocity of the radar antenna during operation is V, the time of the acceleration process is recorded as t1, the time of the uniform speed process is recorded as t2, and the time of the deceleration process is t3. The acceleration process, the uniform speed process and the deceleration process constitute a complete scanning cycle.

[0057] like Figure 5 As shown, this embodiment also provides a timing generation control system for a synthetic aperture radar, including a radar antenna unit, a radar servo control unit, a radar signal processing unit, and a radar display and control unit. The radar control system is in an intermittent working mode. The entire system has a simple workflow and can achieve real-time imaging of any position in space.

[0058] The radar antenna unit is used for directional emission and reception of electromagnetic waves;

[0059] The radar servo control unit is used to control the radar antenna and feed back the position information of the radar antenna to the radar signal processing unit in real time;

[0060] The radar signal processing unit is used to receive the position information of the radar servo control unit in real time, and is controlled by the radar display and control unit to intermittently generate the timing of the entire radar operation and perform real-time imaging;

[0061] The radar display and control unit is used as the center of the entire control system, sending commands to the radar servo control unit to control the radar antenna unit, and at the same time interacting with the radar signal processing unit to intermittently control the timing;

[0062] The radar antenna unit is connected to the radar servo control unit and the radar signal processing unit through a bus, respectively; the radar servo control unit is connected to the radar signal processing unit through a bus, and the radar display and control unit is connected to the radar servo control unit and the radar signal processing unit through a bus.

[0063] The position information of the radar antenna is the angle information, direction information, and speed information of the radar antenna when it rotates.

[0064] The radar servo control unit includes a programmable logic controller, a servo control system and a servo motor. The radar servo control unit monitors the motion working state of the servo motor in real time, completes the control of the radar antenna, and feeds back the position information of the radar antenna to the radar signal processing unit in real time.

[0065] Embodiment 2

[0066] In this embodiment, the rotation of the radar antenna is divided into acceleration, uniform speed and deceleration processes. The acceleration time is 0.5S, the uniform speed time is 1.5S, the deceleration time is 0.5S, and the antenna rotation time in a complete scanning cycle is 2.5S;

[0067] During the rotation of the radar antenna, the channel encoder feedback obtains the real-time movement speed information of the radar antenna;

[0068] In a complete scanning cycle, the speed of the radar antenna in the uniform speed stage is 60° / S;

[0069] The initial displacement of the radar antenna during operation is 0. After a scanning cycle, the end angular displacement of the radar antenna is 120°. In a scanning cycle, the sampling rate of the radar acquisition is calculated according to the requirements of the radar resolution. The number of intervals that need to be collected in the scanning cycle is 368.

[0070] The calculation formula for the lateral resolution required by the radar is as follows:

[0071] Δx=λ / 4sin(θ / 2), requiring lateral resolution

[0072] To achieve such a lateral resolution of Δx of 5 mm, the wavelength λ is the wavelength of the radar emission, and the end point angular displacement of a scan is required to be 120 degrees; at the same time, the collection interval has the following requirements: the number of intervals to be collected in the scanning cycle is 368

[0073] According to the number of sampling intervals, the angular displacement difference of the radar antenna rotation each time a pulse signal is transmitted is calculated, and the difference is recorded as ΔS. The calculation formula of the difference is: ΔS = 120° / 368 = 0.326°;

[0074] That is, the radar antenna transmits and receives once every 0.326° rotation.

[0075] like Figure 6 As shown, when the SAR performs a scan, the angle of antenna rotation is θ, the angle of antenna rotation during one scan interval is Δθ, the maximum unambiguous distance of SAR radar is R, and the relationship between the antenna rotation angle and the real-time angular displacement is: ΔS = π × Δθ × R / 180, which is actually the relationship between angle and arc length.

[0076] This embodiment also provides a timing generation control system for a synthetic aperture radar, including a radar antenna unit, a radar servo control unit, a radar signal processing unit, and a radar display and control unit;

[0077] The radar antenna unit is connected to the radar servo control unit through a bus, the radar servo control unit is connected to the radar signal processing unit through a bus, the radar antenna unit is connected to the radar signal processing unit through a bus, the radar display and control unit is connected to the radar servo control unit through a bus, and the radar display and control unit is connected to the radar signal processing unit through a bus.

[0078] The radar display and control unit is the control center of the system. When imaging of a certain location is required, the radar display and control unit sends real-time commands to the radar signal processing unit, which works through the radar signal processing unit. The radar signal processing unit feeds back real-time commands to the radar display and control unit, and the radar signal processing unit can start working in real time.

[0079] After receiving the command from the signal processing unit, the radar display and control unit sends real-time commands to the radar servo control unit to control the radar antenna unit. At the same time, the radar servo control unit feeds back the position information to the radar signal processing unit in real time and generates the timing of the intermittent working mode.

[0080] In this embodiment, the radar antenna unit is implemented by a transmitting switch, a receiving switch, a DDS and other modules. The radar antenna unit transmits signals and receives signals through these modules. The radar antenna control unit is composed of a programmable logic controller (PLC), a servo control system and a servo motor, and the rotation angle of the radar antenna is controlled through these modules.

[0081] The radar signal processing unit is implemented by a field programmable gate array (FPGA) and is used for radar timing generation in discontinuous working mode.

[0082] The radar display and control unit consists of a server and a display. The server completes the management and control of the radar antenna control unit and the radar signal processing unit. The display is used to display the radar imaging results at a fixed position in real time.

[0083] In summary, the timing generation method and display and control system of the synthetic aperture radar in the above two groups of embodiments, the SAR based on the spatial position adopts an intermittent working mode to avoid the radar being in a long-term working state, thereby reducing the energy consumption of the entire radar; the radar timing generation method in the intermittent working mode reduces the amount of radar echo data and the radar signal processing time while meeting the radar system resolution; the radar echo data collected according to the fixed spatial displacement meets the uniform sampling law, and there is no need to perform motion compensation on the radar echo data. From the perspective of the radar signal processing calculation process, the motion compensation step is omitted, the calculation process is simpler, and the requirements for motion compensation are reduced; the radar control system in the intermittent working mode is adopted, the entire system workflow is simple, and real-time imaging of any position in the space can be achieved.

[0084] 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 and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for generating a timing sequence of a synthetic aperture radar, characterized in that: The following steps are involved: S1: Calculate the angular displacement data of the synthetic aperture radar antenna, According to the angular velocity curve of the radar antenna rotation, the real-time angular displacement data of the radar antenna is calculated; S2: Calculate the sampling rate within a single scanning cycle of the synthetic aperture radar. According to the radar resolution requirement, the sampling rate of the radar is calculated in one scanning cycle, and the number of intervals that need to be collected in a single scanning cycle is obtained, and the number of intervals is recorded as N; S3: Calculate the angular displacement difference of the radar antenna each time a pulse signal is transmitted. According to the number of intervals to be collected in a single scanning cycle calculated in step S2, the angular displacement difference of the radar antenna rotation each time a pulse signal is transmitted is calculated. The angular displacement difference is recorded as ΔS. The calculation formula of the angular displacement difference is as follows: ΔS=S / N Where S is the total angular displacement of the radar antenna in a single scanning cycle, and N is the number of intervals that need to be collected in a single scanning cycle; S4: Calculate the timing of radar action. The timing of the radar action is generated in real time according to the angular displacement difference ΔS calculated in step S3. The radar performs the actions of transmitting and receiving each time it rotates by the angle of the angular displacement difference, thereby eliminating the motion compensation of the echo data.

2. The timing generation method of synthetic aperture radar according to claim 1, characterized in that: In step S1, the angular displacement data of the radar antenna is obtained by calculating the integral curve of the radar antenna within a unit rotation time.

3. The timing generation method of synthetic aperture radar according to claim 1, characterized in that: In step S1, the radar antenna includes three motion states during its rotation, which are acceleration, uniform speed and deceleration in chronological order.

4. The method for generating a timing sequence of a synthetic aperture radar according to claim 3, characterized in that: The acceleration and deceleration processes are both uniform speed change processes.

5. The timing generation method of synthetic aperture radar according to claim 3, characterized in that: The acceleration process, the uniform speed process and the deceleration process constitute a complete scanning cycle.

6. The method for generating a timing sequence of a synthetic aperture radar according to claim 5, characterized in that: The time t1 of the acceleration process is 0.5S, the time t2 of the uniform speed process is 1.5S, the time t3 of the deceleration process is 0.5S, and the time for the radar antenna to rotate in a complete scanning cycle is 2.5S.

7. The timing generation method of synthetic aperture radar according to claim 1, characterized in that: In step S2, the number of intervals to be collected is 368; in step S3, the total angular displacement S of the radar antenna in a single scanning cycle is 120°, and the angular displacement difference of the radar antenna rotation ΔS=120° / 368=0.326°, that is, the radar antenna transmits and receives once every 0.326° rotation.

8. A timing generation control system for synthetic aperture radar, characterized in that: The method according to any one of claims 1 to 7 is used to control the timing generation of a synthetic aperture radar, including a radar antenna unit, a radar servo control unit, a radar signal processing unit, and a radar display and control unit; The radar antenna unit is connected to the radar servo control unit and the radar signal processing unit through a bus, respectively, and is used for directional transmission and reception of electromagnetic waves; The radar servo control unit is connected to the radar signal processing unit through a bus, and is used to control the radar antenna and feed back the position information of the radar antenna to the radar signal processing unit in real time; The radar signal processing unit is used to receive the position information of the radar servo control unit in real time, and is controlled by the radar display and control unit to intermittently generate the timing of the entire radar operation and perform real-time imaging; The radar display and control unit is connected to the radar servo control unit and the radar signal processing unit through a bus, respectively, and is used to serve as the center of the entire control system, sending commands to the radar servo control unit to control the radar antenna unit, and at the same time interacting with the radar signal processing unit to intermittently control the timing.

9. The timing generation control system of synthetic aperture radar according to claim 8, characterized in that: The position information of the radar antenna is the angle information, direction information, and speed information of the radar antenna when it rotates.

10. The timing generation control system of synthetic aperture radar according to claim 8, characterized in that: The radar servo control unit includes a programmable logic controller, a servo control system and a servo motor. The radar servo control unit monitors the motion working state of the servo motor in real time, completes the control of the radar antenna, and feeds back the position information of the radar antenna to the radar signal processing unit in real time.

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