Satellite-borne clutter suppression method and system for sea exploration radar system

Abstract

The invention provides a spaceborne sea detection radar system clutter suppression method and system. The spaceborne sea detection radar system clutter suppression method comprises the steps that S1, sea clutter characteristics of a radar in the detection process are analyzed; s2, modeling the sea clutter based on an analysis result to obtain a sea clutter model; and S3, inhibiting sea clutters by adopting a Doppler channel through the sea clutter model, and optimizing a detection result. According to the method, through a clutter Doppler localization mode, the clutter region block area is reduced to reduce the influence of sea clutter, the process is clear and easy to implement, and the method has a guiding effect on overall designers of a satellite-borne early warning radar system.

Description

Technical Field

[0001] The present invention relates to the technical field of aerospace systems, and in particular to a method and system for suppressing clutter in a spaceborne sea-detection radar system. Background Art

[0002] Compared to airborne / ground-based and airborne early warning radars, spaceborne early warning radars (SWARRs) offer a "higher perspective" and are deployed regardless of national boundaries. They can detect targets over a wider range and at greater distances, providing more time for early warning decisions. This makes them a key development direction for future early warning radars. However, spaceborne early warning radars also face several technical difficulties and challenges. First, the high altitude of spaceborne radars above the ground means that the beam illuminates a wider area on the ground, increasing the amount of clutter entering the radar receiver and significantly impacting target detection. Furthermore, the high orbital velocity of the satellite platforms on which the radars are based causes the radars to exhibit a greater relative motion velocity relative to the clutter sources, resulting in a more severe clutter spectrum expansion, which also negatively impacts target detection.

[0003] When spaceborne early warning radar detects sea surface targets, the target's slow speed causes the Doppler frequency to concentrate near zero frequency. Furthermore, the satellite platform's high-speed motion broadens the mainlobe clutter spectrum. This aliasing of the target's Doppler frequency and the mainlobe clutter spectrum makes it impossible to effectively detect the target from the clutter background in the frequency domain by leveraging its motion characteristics.

[0004] Currently, the conventional approach is to employ the same superclutter detection system as airborne radars. In this case, the target echo competes with all the sea clutter arriving at the radar receiver simultaneously. Therefore, to ensure reliable target detection, the radar system's power-aperture product must be increased, placing stringent demands on the satellite platform. Given limited platform resources, the challenge of effectively suppressing sea clutter and improving the detection performance of spaceborne sea-based early warning radar systems is pressing. Summary of the Invention

[0005] In view of the defects in the prior art, the object of the present invention is to provide a method and system for suppressing clutter in a space-borne sea sounding radar system.

[0006] According to the present invention, a method for suppressing clutter in a spaceborne sea-detection radar system comprises:

[0007] Step S1: Analyze the characteristics of sea clutter during radar detection;

[0008] Step S2: Based on the analysis results, the sea clutter is modeled to obtain a sea clutter model;

[0009] Step S3: Using the sea clutter model, the Doppler channel is used to suppress sea clutter and optimize the detection results.

[0010] Preferably, in step S1:

[0011] Step S1.1: Analyze the spectrum distribution Δf of the radar main lobe clutter;

[0012] Step S1.2: Analyze and obtain the sea clutter backscatter coefficient σ H,V .

[0013] Preferably, the spectrum distribution Δf is expressed as follows:

[0014] Δf=2V / D

[0015] Wherein, V is the velocity of the spaceborne platform relative to the ground, and D is the azimuth length of the radar antenna;

[0016] The sea clutter backscatter coefficient σ H,V , the mathematical expression is:

[0017]

[0018] Among them, α is the ground-grazing angle, SS is the sea state level, f is the operating frequency of the radar, C1, C2, C3, C4, and C5 are a constant, another constant, another constant, a constant, and a constant respectively.

[0019] Preferably, in step S2: the sea clutter size is P c , the mathematical expression is:

[0020]

[0021] Among them, N fold is the radar main lobe clutter ambiguity number, P av is the average radiated power, G t is the radar transmission gain, G r is the radar receiving gain, λ is the wavelength, σ0 is the sea clutter backscatter coefficient, A c is the clutter area, T cpi is the accumulation time, R is the radar range, k is the Boltzmann constant, T0 is the temperature constant, F n is the system noise factor, L s is the system loss;

[0022] Sea clutter clutter area A c , the mathematical expression is:

[0023]

[0024] Among them, α is the angle between the projection of the beam pointing on the ground and the satellite flight direction.

[0025] Preferably, in step S3: the system repetition frequency is designed to be equal to the maximum Doppler of the radar main lobe clutter;

[0026] The repetition frequency design refers to the radar pulse repetition frequency.

[0027] According to the present invention, a clutter suppression system for a spaceborne sea-detection radar system is provided, comprising:

[0028] Module M1: Analyze the characteristics of sea clutter during radar detection;

[0029] Module M2: Based on the analysis results, the sea clutter is modeled to obtain the sea clutter model;

[0030] Module M3: Uses the sea clutter model and Doppler channel to suppress sea clutter and optimize detection results.

[0031] Preferably, in the module M1:

[0032] Module M1.1: Analyze the spectrum distribution Δf of radar mainlobe clutter;

[0033] Module M1.2: Analyze and calculate the sea clutter backscatter coefficient σ H,V .

[0034] Preferably, the spectrum distribution Δf is expressed as follows:

[0035] Δf=2V / D

[0036] Wherein, V is the velocity of the spaceborne platform relative to the ground, and D is the azimuth length of the radar antenna;

[0037] The sea clutter backscatter coefficient σ H,V , the mathematical expression is:

[0038]

[0039] Among them, α is the ground-grazing angle, SS is the sea state level, f is the operating frequency of the radar, C1, C2, C3, C4, and C5 are a constant, another constant, another constant, a constant, and a constant respectively.

[0040] Preferably, in the module M2: the sea clutter size is P c , the mathematical expression is:

[0041]

[0042] Among them, N fold is the radar main lobe clutter ambiguity number, P av is the average radiated power, G t is the radar transmission gain, Gr is the radar receiving gain, λ is the wavelength, σ0 is the sea clutter backscatter coefficient, A c is the clutter area, T cpi is the accumulation time, R is the radar range, k is the Boltzmann constant, T0 is the temperature constant, F n is the system noise factor, L s is the system loss;

[0043] Sea clutter clutter area A c , the mathematical expression is:

[0044]

[0045] Among them, α is the angle between the projection of the beam pointing on the ground and the satellite flight direction.

[0046] Preferably, in the module M3: the system repetition frequency is designed to be equal to the maximum Doppler of the radar main lobe clutter;

[0047] The repetition frequency design refers to the radar pulse repetition frequency.

[0048] Compared with the prior art, the present invention has the following beneficial effects:

[0049] 1. The present invention makes full use of azimuth resolution to disperse clutter on different Doppler channels, suppresses sea clutter, and disperses clutter on different Doppler channels through Doppler localization, thereby reducing the impact of clutter, which is groundbreaking.

[0050] 2. The present invention utilizes the Doppler channel to further segment the clutter in azimuth to reduce the clutter energy intensity, thereby improving the effect of sea surface target detection under a limited power aperture product resource on a satellite.

[0051] 3. The present invention reduces the impact of sea clutter by reducing the area of ​​clutter blocks through clutter Doppler localization. The process is clear and easy to implement, which can provide guidance to the overall designers of spaceborne early warning radar systems. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] Other features, objects and advantages of the present invention will become more apparent upon reading the detailed description of non-limiting embodiments with reference to the following drawings:

[0053] Figure 1 A schematic diagram of the process provided by the present invention;

[0054] Figure 2 A schematic diagram comparing the clutter localization provided by the present invention;

[0055] Figure 3 A schematic diagram of the clutter-to-noise ratio before clutter Doppler localization suppression provided by the present invention;

[0056] Figure 4 This is a schematic diagram of the improvement of the noise-to-noise ratio after the clutter Doppler localization suppression provided by the present invention. DETAILED DESCRIPTION

[0057] The present invention will be described in detail below with reference to specific embodiments. The following examples will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that, for those skilled in the art, several changes and improvements can be made without departing from the scope of the present invention. These all fall within the scope of protection of the present invention.

[0058] Target detection is a process of competing against target energy and sea clutter energy. Given a fixed target energy, the only way to improve detection performance is to reduce the sea clutter energy. Sea clutter energy is determined by its backscatter coefficient and the area of ​​the clutter region. The backscatter coefficient is a physical property and cannot be changed. Therefore, to reduce sea clutter energy, the area of ​​the sea clutter region should be reduced.

[0059] Traditionally, when resources are sufficient, only range resolution is used to eliminate clutter from non-uniform distance units, failing to fully utilize the benefits of azimuth resolution. Thanks to the airborne platform's air detection solution, during sea detection, although the high-speed motion of the satellite platform results in no clear zones for detection, it is possible to fully utilize the Doppler channels to further segment clutter in azimuth, thereby reducing clutter energy intensity. Therefore, as demonstrated in the present invention, clutter should be dispersed across different Doppler channels.

[0060] The present invention proposes for the first time a clutter suppression method for a spaceborne sea detection and early warning radar system, namely, a clutter suppression method for a spaceborne sea detection and early warning radar system, which is innovative. The present invention particularly provides a method of reducing the impact of sea clutter by reducing the area of ​​clutter regions through clutter Doppler localization. The present invention can effectively alleviate the contradiction between the high power aperture product requirement and the limited onboard resources during the design and development of a spaceborne sea detection and early warning radar system, has important theoretical and engineering value, and lays a foundation for the design and engineering development of a spaceborne sea detection and early warning radar system.

[0061] According to the present invention, a method for suppressing clutter in a spaceborne sea-detection radar system comprises:

[0062] Step S1: Analyze the characteristics and influencing factors of sea clutter of the spaceborne sea detection and early warning radar system; that is, analyze the characteristics of sea clutter of the early warning radar;

[0063] Step S2: Modeling sea clutter;

[0064] Step S3: suppressing sea clutter;

[0065] Step S4: Perform simulation analysis on the intensity before and after sea clutter suppression; compare the simulation results to evaluate the sea clutter suppression effect.

[0066] In other words, a clutter suppression method for a spaceborne sea detection and early warning radar system provided by the present invention includes:

[0067] Step S1: Analyze the characteristics of sea clutter during radar detection;

[0068] Step S2: Based on the analysis results, the sea clutter is modeled to obtain a sea clutter model;

[0069] Step S3: Using the sea clutter model, the Doppler channel is used to suppress sea clutter and optimize the detection results.

[0070] Preferably, in step S1:

[0071] Step S1.1: Analyze the spectrum distribution Δf of the radar main lobe clutter;

[0072] Step S1.2: Analyze and obtain the sea clutter backscatter coefficient σ H,V .

[0073] In step S1, the sea clutter characteristics and influencing factors are analyzed, including:

[0074] Step S1.1: Analyze the broadening distribution of the radar main lobe clutter caused by the high-speed moving platform on board. The spectrum distribution of the main lobe clutter is Δf, and the mathematical expression is:

[0075] Δf=2V / D

[0076] Wherein, V is the velocity of the spaceborne platform relative to the ground, and D is the azimuth length of the radar antenna;

[0077] Step S1.2: Analyze the sea clutter characteristics of the spaceborne sea detection and early warning radar, and calculate the sea clutter backscatter coefficient σ H,V , the mathematical expression is:

[0078]

[0079] Where α is the ground-grazing angle, SS is the sea state level, f is the operating frequency of the radar, and C1, C2, C3, C4, and C5 are constants.

[0080] The spectrum distribution of the sea clutter is used to guide the system repetition frequency design and calculate the sea clutter intensity;

[0081] In step S2, based on the backscatter coefficient σ H,V, the sea clutter is modeled, and the size of the sea clutter received by the system at the same time as the target echo is P c , the mathematical expression is:

[0082]

[0083] Among them, N fold is the radar main lobe clutter ambiguity number, P av is the average radiated power, G t is the radar transmission gain, G r is the radar receiving gain, λ is the wavelength, σ0 is the sea clutter backscatter coefficient, A c is the clutter area, T cpi is the accumulation time, R is the radar range, k is the Boltzmann constant, T0 is the temperature constant, F n is the system noise factor, L s is the system loss;

[0084] In step S3, simulation analysis is performed on the sea clutter intensity before and after suppression, including:

[0085] Step S3.1: When no clutter suppression is performed, the area of ​​the sea clutter block received by the system at the same time as the target echo is the clutter area A. c , the mathematical expression is:

[0086]

[0087] Where Δθ 3dB is the azimuth beamwidth of the radar antenna, c is the speed of light, B is the instantaneous working bandwidth of the radar, To wipe the corners;

[0088] Step S3.2: Use the Doppler channel to suppress clutter. At this time, the clutter received by the radar system at the same time as the target echo is localized, and the frequency domain Doppler channel is used to reduce the area behind the sea clutter block, that is, the clutter area A. c ,Specifically, it should also be combined with the pulse dwell time in ,radar system design, because the pulse dwell time determines the granularity in the ,Doppler channel during localization;

[0089] The mathematical expression is:

[0090]

[0091] Where α is the angle between the projection of the beam pointing on the ground and the satellite flight direction;

[0092] To evenly distribute clutter across different Doppler channels, the system repetition rate should be designed to be equal to the maximum Doppler of the radar mainlobe clutter. If the system repetition rate is much higher than the maximum Doppler frequency of the clutter, clutter localization will lose its effectiveness. If the repetition rate is much lower than the maximum Doppler frequency of the clutter, the clutter spectrum will be blurred, significantly reducing the clutter suppression effect.

[0093] The repetition frequency design is a special parameter of system design, namely the radar pulse repetition frequency;

[0094] Specifically, a simulation analysis is performed on the sea clutter intensity before and after suppression to evaluate the sea clutter, and further a simulation analysis is performed on the sea clutter intensity before and after suppression to evaluate the sea clutter suppression effect.

[0095] Specific embodiments of the present invention will be described with reference to examples.

[0096] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments:

[0097] Here we choose the low-orbit X-band spaceborne sea detection and early warning radar to conduct clutter suppression performance evaluation. The satellite orbit altitude of the spaceborne sea detection and early warning radar is about 500km.

[0098] Step 1: The X-band radar system parameters are as follows: average radiated power 2000W, antenna aperture 4m × 1m, antenna polarization mode is HH polarization, system noise figure 2.5dB, operating bandwidth 10MHz, and the sea clutter backscatter model is an empirical model.

[0099] Step 2: Model and analyze the sea clutter according to step S2.

[0100] Step 3: Simulate and analyze the system sea clutter intensity before and after sea clutter suppression. The simulation conditions are shown in Table 1. The simulation results show that the system SNR is 21.3 dB and the target SNR is 13.83 dB.

[0101] Parameter items Value Satellite orbit altitude 500km Radar center frequency 9.6GHz Radar instantaneous operating bandwidth 10MHz Polarization HH Target RCS <![CDATA[ 3000 m 2 ]]> System noise figure 2.5dB System loss 10dB

[0102] Table 1 Simulation input parameters

[0103] like Figure 3 As shown in Figure 2, under the same input conditions, the system detection performance before sea clutter suppression is simulated and analyzed, and the system's SNR is 0.19dB, and the target's SNR is 32.02dB.

[0104] Step 4: If Figure 4 As shown in the figure, under this input condition, the system noise ratio is improved by about 21dB before and after sea clutter localization. It is found that sea clutter can be effectively suppressed by clutter Doppler localization.

[0105] The present invention also provides a system for suppressing clutter of a satellite-borne sea-sounding radar system. The system for suppressing clutter of a satellite-borne sea-sounding radar system can be implemented by executing the process steps of the method for suppressing clutter of a satellite-borne sea-sounding radar system. That is, those skilled in the art can understand the method for suppressing clutter of a satellite-borne sea-sounding radar system as a preferred embodiment of the system for suppressing clutter of a satellite-borne sea-sounding radar system.

[0106] According to the present invention, a clutter suppression system for a spaceborne sea-detection radar system is provided, comprising:

[0107] Module M1: Analyze the characteristics of sea clutter during radar detection;

[0108] Module M2: Based on the analysis results, the sea clutter is modeled to obtain the sea clutter model;

[0109] Module M3: Uses the sea clutter model and Doppler channel to suppress sea clutter and optimize detection results.

[0110] Specifically, in the module M1:

[0111] Module M1.1: Analyze the spectrum distribution Δf of radar mainlobe clutter;

[0112] Module M1.2: Analyze and calculate the sea clutter backscatter coefficient σ H,V .

[0113] Specifically, the spectrum distribution Δf is expressed as follows:

[0114] Δf=2V / D

[0115] Wherein, V is the velocity of the spaceborne platform relative to the ground, and D is the azimuth length of the radar antenna;

[0116] The sea clutter backscatter coefficient σ H,V , the mathematical expression is:

[0117]

[0118] Among them, α is the ground-grazing angle, SS is the sea state level, f is the operating frequency of the radar, C1, C2, C3, C4, and C5 are a constant, another constant, another constant, a constant, and a constant respectively.

[0119] Specifically, in the module M2: the sea clutter size is P c , the mathematical expression is:

[0120]

[0121] Among them, N foldis the radar main lobe clutter ambiguity number, P av is the average radiated power, G t is the radar transmission gain, G r is the radar receiving gain, λ is the wavelength, σ0 is the sea clutter backscatter coefficient, A c is the clutter area, T cpi is the accumulation time, R is the radar range, k is the Boltzmann constant, T0 is the temperature constant, F n is the system noise factor, L s is the system loss;

[0122] Sea clutter clutter area A c , the mathematical expression is:

[0123]

[0124] Among them, α is the angle between the projection of the beam pointing on the ground and the satellite flight direction.

[0125] Specifically, in the module M3: the system repetition frequency is designed to be equal to the maximum Doppler of the radar main lobe clutter;

[0126] The repetition frequency design refers to the radar pulse repetition frequency.

[0127] Those skilled in the art will appreciate that, in addition to implementing the system and its various devices, modules, and units provided by the present invention in purely computer-readable program code, it is entirely possible to implement the same functions of the system and its various devices, modules, and units provided by the present invention in the form of logic gates, switches, application-specific integrated circuits, programmable logic controllers, and embedded microcontrollers by logically programming the method steps. Therefore, the system and its various devices, modules, and units provided by the present invention can be considered a hardware component, and the devices, modules, and units included therein for implementing various functions can also be considered as structures within the hardware component; the devices, modules, and units for implementing various functions can also be considered as both software modules implementing the method and structures within the hardware component.

[0128] The above describes specific embodiments of the present invention. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art may make various changes or modifications within the scope of the claims, which do not affect the essence of the present invention. The embodiments of this application and the features in the embodiments may be combined with each other in any manner unless there is a conflict.

Claims

1. A method for suppressing clutter in a spaceborne sea-detection radar system, characterized in that: include: Step S1: Analyze the characteristics of sea clutter during radar detection; Step S2: Based on the analysis results, the sea clutter is modeled to obtain a sea clutter model; Step S3: Using the sea clutter model, the Doppler channel is used to suppress sea clutter and optimize the detection results.

2. The method for suppressing clutter of a spaceborne sea-detection radar system according to claim 1, characterized in that: In step S1: Step S1.1: Analyze the spectrum distribution Δf of the radar main lobe clutter; Step S1.2: Analyze and obtain the sea clutter backscatter coefficient σ H,V .

3. The method for suppressing clutter of a spaceborne sea-detection radar system according to claim 2, characterized in that: The mathematical expression of the spectrum distribution Δf is: Δf=2V / D Wherein, V is the velocity of the spaceborne platform relative to the ground, and D is the azimuth length of the radar antenna; The sea clutter backscatter coefficient σ H,V , the mathematical expression is: Among them, α is the ground-grazing angle, SS is the sea state level, f is the operating frequency of the radar, C1, C2, C3, C4, and C5 are a constant, another constant, another constant, a constant, and a constant respectively.

4. The method for suppressing clutter of a spaceborne sea-detection radar system according to claim 3, characterized in that: In step S2: the sea clutter size is P c , the mathematical expression is: Among them, N fold is the radar main lobe clutter ambiguity number, P av is the average radiated power, G t is the radar transmission gain, G r is the radar receiving gain, λ is the wavelength, σ0 is the sea clutter backscatter coefficient, A c is the clutter area, T cpi is the accumulation time, R is the radar range, k is the Boltzmann constant, T0 is the temperature constant, F n is the system noise factor, L s is the system loss; Sea clutter clutter area A c , the mathematical expression is: Among them, α is the angle between the projection of the beam pointing on the ground and the satellite flight direction.

5. The method for suppressing clutter of a spaceborne sea-detection radar system according to claim 1, characterized in that: In step S3: the system repetition frequency is designed to be equal to the maximum Doppler of the radar main lobe clutter; The repetition frequency design refers to the radar pulse repetition frequency.

6. A clutter suppression system for a spaceborne sea-detection radar system, characterized in that: include: Module M1: Analyze the characteristics of sea clutter during radar detection; Module M2: Based on the analysis results, the sea clutter is modeled to obtain the sea clutter model; Module M3: Uses the sea clutter model and Doppler channel to suppress sea clutter and optimize detection results.

7. The clutter suppression system for a spaceborne sea-detection radar system according to claim 6, characterized in that: In the module M1: Module M1.1: Analyze the spectrum distribution Δf of radar mainlobe clutter; Module M1.2: Analyze and calculate the sea clutter backscatter coefficient σ H,V .

8. The clutter suppression system for a spaceborne sea-detection radar system according to claim 7, characterized in that: The mathematical expression of the spectrum distribution Δf is: Δf=2V / D Wherein, V is the velocity of the spaceborne platform relative to the ground, and D is the azimuth length of the radar antenna; The sea clutter backscatter coefficient σ H,V , the mathematical expression is: Among them, α is the ground-grazing angle, SS is the sea state level, f is the operating frequency of the radar, C1, C2, C3, C4, and C5 are a constant, another constant, another constant, a constant, and a constant respectively.

9. The clutter suppression system for a spaceborne sea-detection radar system according to claim 8, characterized in that: In the module M2: the sea clutter size is P c , the mathematical expression is: Among them, N fold is the radar main lobe clutter ambiguity number, P av is the average radiated power, G t is the radar transmission gain, G r is the radar receiving gain, λ is the wavelength, σ0 is the sea clutter backscatter coefficient, A c is the clutter area, T cpi is the accumulation time, R is the radar range, k is the Boltzmann constant, T0 is the temperature constant, F n is the system noise factor, L s is the system loss; Sea clutter clutter area A c , the mathematical expression is: Among them, α is the angle between the projection of the beam pointing on the ground and the satellite flight direction.

10. The clutter suppression system for a spaceborne sea-detection radar system according to claim 6, characterized in that: In the module M3: the system repetition frequency is designed to be equal to the maximum Doppler of the radar main lobe clutter; The repetition frequency design refers to the radar pulse repetition frequency.

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