Satellite-borne ship monitoring radar detection method and system

Abstract

The invention provides a satellite-borne ship monitoring radar detection method and system. The satellite-borne ship monitoring radar detection method comprises the following steps: setting a sea exploration radar pulse repetition frequency on a zebra map; setting a sea-exploration radar transmitting signal; transmitting a signal and acquiring a sea detection echo according to the setting; calculating a distance fuzzy number set where the main fuzzy energy is located; for distance ambiguity in the distance ambiguity number set, land ambiguity is suppressed; and carrying out effective observation area ship detection on the sea exploration echo after land fuzzy suppression. According to the method, echo signals are noised, the problem of false alarm detection is solved, and the observation performance of the space-based sea surface detection radar is effectively improved; the technical characteristics of range ambiguity suppression are carried out through signal coding and an existing SAR image database, range focusing of an effective observation area is achieved through a matched filter corresponding to the effective observation area, the problem of the high range ambiguity requirement is solved, and a satellite-borne radar system for low-false-alarm ship monitoring is achieved.

Description

Technical Field

[0001] The present invention belongs to the field of spaceborne radar technology, and specifically relates to a spaceborne ship monitoring radar detection method and system, and more specifically to a spaceborne ship monitoring radar system and method based on signal coding and an external SAR image database. Background Art

[0002] Satellite-based ship monitoring technology monitors the location and status of ships in real time, enabling timely detection of potential hazards and preventing accidents. It provides global information on ship movements and helps maintain maritime safety and order. Furthermore, monitoring ship emissions and pollution helps promptly detect and respond to marine pollution incidents. Accurate ship monitoring allows for better management of marine resources, including fisheries. Therefore, satellite-based ship monitoring technology not only improves maritime safety but also plays a significant role in combating illegal activities, protecting the marine environment, and promoting marine resource management.

[0003] The primary means of satellite-based ship monitoring include satellite-based AIS (ship positioning technology), satellite-based SAR (synthetic aperture radar), and detection radar systems. Of these, satellite-based SAR and detection radar offer all-day, all-weather, and wide-area ship detection capabilities, making them powerful means of detecting ships in silence. The core differences between the two lie in their imaging mechanisms and resolution requirements, necessitating different algorithms and system architectures for data processing. Like satellite-based SAR, satellite-based ship detection radar systems face the "minimum antenna area" dilemma for wide-area ocean observations. This prevents the system from balancing radar range and azimuth ambiguity, introducing false ship targets into the effective observation area. Therefore, effectively suppressing ambiguity in satellite-based ship detection radar systems presents a challenging system design challenge.

[0004] Currently, spaceborne radar systems primarily use technologies such as beam position design optimization, phase coding, positive and negative frequency modulation, and digital beamforming to improve range ambiguity. Patent document "A Spaceborne SAR Range Ambiguity Suppression Method Based on Transmitter-Receiver Directional Separation" (CN117233765A) discloses a method for suppressing range ambiguity by separating the transmit and receive patterns from the antenna range direction, reducing the main lobe width, and moving the first ambiguity zone outside the antenna main lobe. This method sacrifices observation width and is therefore unsuitable for wide-area detection by spaceborne ship detection radars.

[0005] The paper "Sub-satellite point and range ambiguity suppression method based on real-time beamforming of spaceborne SAR" (Han Xiaodong, Song Hongjun, Xu Wei, et al. Journal of Electronics and Information Technology, 2013(12):2823-2828.) proposed a sub-satellite point and range ambiguity suppression method, which can suppress the ambiguous signal to the greatest extent without affecting the reception of useful signals. It has a wide range of beam position selection and reduces the difficulty of beam position selection in the design of spaceborne SAR system. However, it requires the system to be a multi-channel system in elevation and pitch directions, and the system complexity is relatively large.

[0006] The patent document "A Real-time Echo Recovery Method for High-Repetition-Frequency Coded Synthetic Aperture Radar" (CN116299461A) discloses that by using a periodic phase-coded sequence to transmit to the ground, a phase-coded steering matrix is constructed, and the echo recovery weight vector is derived through the phase-coded steering matrix to achieve real-time and accurate unambiguous signal recovery in multiple sub-surveying zones. However, it can only be used in SAR imaging systems and requires a high repetition rate.

[0007] The patent "A method for suppressing range ambiguity in spaceborne synthetic aperture radar" (CN112698329A) discloses the use of positive and negative frequency modulation slopes to transmit linear frequency modulation signals, and then compressing the received signals twice to complete two-dimensional focused imaging. This can effectively reduce the interference of target signals in the main ambiguity area and maintain the focusing effect and energy of the targets in the main lobe area. However, the ambiguity in the area that differs from the observation area by an even number of ambiguity numbers is difficult to suppress.

[0008] The patent document "A Method for Suppressing Range Ambiguity in Spaceborne SAR Based on Two-Dimensional Waveform Coding" discloses segmenting the bandwidth of a linear frequency modulation signal and using a particle swarm optimization algorithm to alternately optimize two segmented linear frequency modulation signals. This method generates two orthogonal nonlinear frequency modulation signals with reduced cross-correlation energy, low peak sidelobe ratio, and low integrated sidelobe ratio. This method allows for normal imaging of the echo of the desired scene and suppresses the range ambiguity energy of multiple consecutive orders to varying degrees. However, this method only reduces the range ambiguity to noise, and land ambiguity can lead to reduced ship detection performance at the land-sea interface.

[0009] In general, there is an urgent need for a satellite-based ship monitoring radar detection method and system that can detect and suppress land ambiguity areas, noise the ship echo signals in the distance ambiguity areas, and effectively reduce the false alarm rate of ship detection in the observation area caused by distance ambiguity. Summary of the Invention

[0010] In view of the defects in the prior art, the purpose of the present invention is to provide a satellite-borne ship monitoring radar detection method and system.

[0011] According to the present invention, a detection method for a space-borne ship monitoring radar system is provided, comprising:

[0012] Step S1, setting the sea-penetrating radar to transmit a signal;

[0013] Step S2: Setting the transmission and reception timing of the sea-penetrating radar, including the pulse repetition frequency and the signal transmission-reception window;

[0014] Step S3: transmitting a signal to the sea, and obtaining a radar echo for sea detection according to the transmission and reception timing settings;

[0015] Step S4: Select the range fuzzy number set where the main lobe of the radar range pattern is located to generate a land scattering energy map;

[0016] Step S5: suppressing the land ambiguity of the land scattered energy map for the range ambiguity in the range ambiguity number set;

[0017] Step S6: Detecting ships in the effective observation area on the radar echo after land fuzzy suppression.

[0018] Preferably, the pulse repetition frequency is set according to a functional relationship curve between the incident angle or the ground distance from the sub-satellite point and the pulse repetition frequency, and the original echo of the full antenna main lobe receiving area is received, and the azimuth direction meets the Nyquist sampling requirements.

[0019] The encoding form of the transmission signal is an orthogonal coded pulse sequence, and any two pulses in the sequence are in a time domain orthogonal relationship.

[0020] The pulse sequence transmission form is to perform periodic repeated transmission with the number of pulses in the pulse sequence as a period.

[0021] The pulse sequence length is greater than the difference between the range ambiguity number of the sub-satellite point echo and the range ambiguity number of the echo at the farthest end of the earth plus one.

[0022] Preferably, step S4 includes:

[0023] Step S4.1: Reconstruct the land scattered energy map in the range ambiguity area using the external SAR image database, the transmit and receive timing settings, and the range antenna pattern.

[0024] Step S4.2: Compare the land scattered energy map and select the distance fuzzy number sets containing the top N fuzzy energies by sorting.

[0025] The step S4.1 includes:

[0026] Step S4.1.1: Input satellite position and velocity, pulse repetition frequency, sampling detection, and gate opening and closing times;

[0027] Step S4.1.2: Set the range ambiguity number and use the range-Doppler equation to perform spatial positioning on all azimuth and range ambiguity units;

[0028] Step S4.1.3: Read the ground object scattering intensity map at the located spatial position from the external SAR image database, and construct the land scattering intensity map of the range ambiguity area;

[0029] Step S4.1.4: Use the radar's range antenna pattern to weight the ground object scattering intensity map to obtain the land scattering energy map in the range ambiguity area.

[0030] Preferably, the step S5 includes:

[0031] Step S5.1: Determine the transmitted signal corresponding to the main lobe of the radar range pattern.

[0032] Step S5.2: For the main lobe area of the radar range pattern, the transmitted signal is used as a matched filter to perform range compression on the original echo and perform azimuth focusing processing.

[0033] Step S5.3: Based on the land scattering energy map, suppress the strong points with energy greater than the average energy in the range ambiguity area.

[0034] Step S5.4: Defocus the land scattering energy map in the range ambiguity area after strong point suppression, and perform inverse matching filtering on the transmitted signal to obtain the suppressed radar echo.

[0035] Preferably, the step S6 includes:

[0036] Step S6.1: Determine the transmission signal corresponding to the effective observation area.

[0037] Step S6.2: Use the transmitted signal as a matched filter to perform range compression on the radar echo after land ambiguity suppression, and perform azimuth focusing processing.

[0038] Step S6.3: Detect the selected sea surface area using a constant false alarm detection method to obtain a ship detection result.

[0039] According to the present invention, a detection system for a satellite-borne ship monitoring radar system is provided, comprising:

[0040] Module M1, setting the sea-penetrating radar transmission signal;

[0041] Module M2, setting the transmission and reception timing of the sea-penetrating radar, including the pulse repetition frequency and the signal transmission-reception window;

[0042] Module M3, transmits signals to the sea and obtains radar echoes for sea detection according to the transmit and receive timing settings;

[0043] Module M4, selects the range fuzzy number set where the main lobe of the radar range pattern is located, and generates a land scattering energy map;

[0044] Module M5, suppressing the land ambiguity of the land scattered energy map for the range ambiguity in the range ambiguity number set;

[0045] Module M6: Detect ships in the effective observation area based on the radar echo after land fuzzy suppression.

[0046] Preferably, the pulse repetition frequency is set according to a functional relationship curve between the incident angle or the ground distance from the sub-satellite point and the pulse repetition frequency, and the original echo of the full antenna main lobe receiving area is received, and the azimuth direction meets the Nyquist sampling requirements.

[0047] The encoding form of the transmission signal is an orthogonal coded pulse sequence, and any two pulses in the sequence are in a time domain orthogonal relationship.

[0048] The pulse sequence transmission form is to perform periodic repeated transmission with the number of pulses in the pulse sequence as a period.

[0049] The pulse sequence length is greater than the difference between the range ambiguity number of the sub-satellite point echo and the range ambiguity number of the echo at the farthest end of the earth plus one.

[0050] Preferably, the module M4 includes:

[0051] Module M4.1: Reconstruct the land-scattered energy map in the range ambiguity zone using an external SAR image database, transmit / receive timing settings, and range antenna patterns.

[0052] Module M4.2: Compare the land scattered energy map and select the distance fuzzy number set containing the top N fuzzy energies by sorting.

[0053] The module M4.1 includes:

[0054] Module M4.1.1: Input satellite position and velocity, pulse repetition frequency, sampling detection and gate opening and closing time;

[0055] Module M4.1.2: Set the range ambiguity number and use the range-Doppler equation to perform spatial positioning for all azimuth and range ambiguity units;

[0056] Module M4.1.3: Read the ground object scattering intensity map at the located spatial position from the external SAR image database and construct the land scattering intensity map in the range ambiguity area;

[0057] Module M4.1.4: Use the radar's range antenna pattern to weight the ground scattering intensity map to obtain the land scattering energy map in the range ambiguity area.

[0058] Preferably, the module M5 includes:

[0059] Module M5.1: Determine the transmitted signal corresponding to the main lobe of the radar range pattern.

[0060] Module M5.2: For the main lobe area of the radar range pattern, the transmitted signal is used as a matched filter to perform range compression on the original echo and perform azimuth focusing processing.

[0061] Module M5.3: Based on the land scattered energy map, suppress the strong points with energy greater than the average in the range ambiguity area.

[0062] Module M5.4: Defocus the land scattering energy map in the range ambiguity area after strong point suppression, and use the transmitted signal to perform inverse matched filtering to obtain the suppressed radar echo.

[0063] Preferably, the module M6 includes:

[0064] Module M6.1: Determine the emission signal corresponding to the effective observation area.

[0065] Module M6.2: Use the transmitted signal as a matched filter to perform range compression on the radar echo after land ambiguity suppression and perform azimuth focusing processing.

[0066] Module M6.3: Use the constant false alarm detection method to detect the selected sea surface area and obtain the ship detection results.

[0067] Compared with the prior art, the present invention has the following beneficial effects:

[0068] 1. The present invention reduces the noise of ship echo signals in the range ambiguity zone, thereby solving the problem of false alarm detection caused by range ambiguity in traditional sea surface ship detection radars and effectively improving the observation performance of space-based sea surface detection radars.

[0069] 2. The present invention solves the problem of high distance ambiguity requirement faced by surface ship detection through signal coding and existing SAR image database for distance ambiguity suppression technology, and realizes low false alarm detection of surface ships.

[0070] 3. The present invention utilizes signal coding and existing SAR image database inversion technology to achieve distance focusing of the effective observation area through a matched filter corresponding to the effective observation area, breaking through the problem of high false alarm rate of traditional sea surface ship detection and realizing a low false alarm ship monitoring satellite-borne radar system. BRIEF DESCRIPTION OF THE DRAWINGS

[0071] 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:

[0072] Figure 1 This is a flow chart of the detection method of the spaceborne ship monitoring radar system;

[0073] Figure 2 Schematic diagram of the simulated effective observation area and fuzzy area echo signals;

[0074] Figure 3 This is a schematic diagram of the imaging results of the range fuzzy area;

[0075] Figure 4 This is a schematic diagram of radar detection intensity distribution in the effective observation area before range ambiguity suppression;

[0076] Figure 5 Schematic diagram of radar detection intensity distribution after effective detection and range ambiguity suppression. DETAILED DESCRIPTION

[0077] 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.

[0078] According to the present invention, a detection method for a space-borne ship monitoring radar system includes:

[0079] Step S1: Set the sea-penetrating radar to transmit a signal and receive the original echo in the full antenna main lobe receiving area.

[0080] Step S2: Setting the transmission and reception timing of the sea-penetrating radar.

[0081] Specifically, the transmission and reception timing includes a pulse repetition frequency and a signal transmission-reception window.

[0082] The pulse repetition frequency is set by plotting the functional relationship between the incident angle or the ground distance from the sub-satellite point and the pulse repetition frequency (PRF). That is, on a zebra plot, the pulse repetition frequency of the sea-penetrating radar is set. The set pulse repetition frequency will make the azimuth meet Nyquist sampling and cover the effective observation area, that is:

[0083] PRF>B a

[0084] Where PRF is the pulse repetition frequency, B a is the Doppler bandwidth.

[0085] The signal transmission-reception window is a window in which the time of signal transmission and echo reception do not overlap, and the pulse length superposition reception window length is less than the time of repeated pulse transmission.

[0086] A periodic coded signal pulse sequence is used, that is, the pulse number of the pulse sequence is used as the period for periodic repetition, and any pulses in the coded signal pulse sequence are orthogonal, that is:

[0087] s k (t r )=s k+N (t r )

[0088]

[0089] Among them, s k (t r ) is the kth transmitted pulse, t r is the distance to time, T p is the pulse width, N is the pulse sequence length (repetition period), s n (t r ) is the nth transmitted pulse, s m (t r ) is the mth transmitted pulse in azimuth, and the superscript “*” represents the conjugate operator. Here N should satisfy:

[0090]

[0091] Among them, R far R is the slant distance corresponding to the echo at the farthest end of the earth. nadir is the slant distance from the subsatellite point, c is the speed of light, PRF is the pulse repetition frequency, is the ceiling operator.

[0092] In more preferred embodiments, the signal encoding form is an orthogonal coded pulse sequence, and any two pulses in the sequence are orthogonal in time domain;

[0093] The pulse sequence transmission form is to perform periodic repeated transmission with the number of pulses in the pulse sequence as a period;

[0094] The pulse sequence length must be greater than the difference between the range ambiguity number of the sub-satellite point echo and the range ambiguity number of the echo at the farthest end of the earth plus one.

[0095] Step S3, transmitting signals and recording echoes: Based on the setting of the coded signal pulse sequence and the pulse repetition interval described in step S2, that is, the setting of the transmitting and receiving timing, the sea detection echo is obtained.

[0096] Step S4: Calculating the range fuzzy number set where the main lobe of the radar range pattern is located;

[0097] Specifically, step S4 calculates the range fuzzy number set where the main lobe of the radar range pattern is located, which specifically includes:

[0098] Step S4.1: Reconstruct the land scattering energy map in the range ambiguity region using the external SAR image database, the radar operating timing used in step S3, that is, the coded signal pulse sequence and pulse repetition interval settings, and the range antenna pattern;

[0099] Specifically, the step S4.1 includes:

[0100] Step S4.1.1: Input satellite position and velocity, pulse repetition frequency, sampling detection, gate opening time and closing time;

[0101] Step S4.1.2: Set the range ambiguity number and use the range-Doppler equation to perform spatial positioning on all azimuth and range ambiguity units;

[0102]

[0103] Among them, p t is the target position, p s (t a ),v s (t a ) are the azimuth and time t a The center position and speed of the radar antenna are as follows: c is the speed of light, τ is the gate time of the target, k is the range ambiguity number, PRF is the pulse repetition frequency, λ is the radar wavelength, and f is the target's wavelength. dc is the Doppler center, D DEM Represents an external digital elevation model (DEM) database.

[0104] Step S4.1.3: Read the ground object scattering intensity at the spatial location from the external SAR image database (set to zero if it is water area) and construct the land scattering intensity map of the fuzzy area;

[0105] Step S4.1.4: Use the radar range pattern to weight the ground object scattering intensity map to obtain the fuzzy area land scattering energy map.

[0106] Step S4.2: Compare different land energy maps, and select the distance fuzzy numbers of the top N fuzzy energies by sorting as the distance fuzzy number set.

[0107] Step S5, land ambiguity suppression: for the range ambiguity in the range ambiguity number set determined in step S4, different matched filters are used to perform land ambiguity suppression on the original echo sequence;

[0108] Specifically, for any major range ambiguity area determined in step S4, step S5 specifically includes:

[0109] Step S5.1: Determine the transmission signal corresponding to the main range ambiguity area;

[0110] Step S5.2: For this main range ambiguity area, the transmitted signal is used as a matched filter to perform range compression on the original echo and perform azimuth focusing processing;

[0111] The echo signal received by the radar is expressed as:

[0112]

[0113] Among them, s(t a ,t r ) is the radar echo, s amb,k (t a ,t r ) is the radar echo in the fuzzy area, s obs (t a ,t r ) is the echo in the observation area, t a is the azimuth time, t r is the radar fast time. Assume that the radar echo in the k0th fuzzy area The corresponding transmission signal is Using this signal s(t a ,t r ) for pulse compression

[0114]

[0115] in, is the compressed signal of the echo pulse in the k0 fuzzy region, s' obs,cmp (t a ,t r ) is the compression signal of the echo in the observation area, s' amb,cmp,k (t a ,t r ) is the compressed signal of the echo pulse in the kth fuzzy area, is the kth transmitted pulse, and the superscript “*” represents the conjugate operator.

[0116] By separating the transmit and receive directions of the range antenna pattern, the main lobe beamwidth is narrowed and the fuzzy area is moved out of the main lobe, thereby achieving the purpose of suppressing range ambiguity.

[0117] Step S5.3: Based on the fuzzy area land scattering energy map generated in step S4, suppress the strong points with energy greater than the average energy in the fuzzy area.

[0118] Step S5.4: Defocus the image of the blurred area after the strong point is suppressed, and use the blurred area transmission signal to perform inverse matching filtering to obtain the radar echo after suppressing the strong point in the blurred area.

[0119] Step S6, ship detection in the effective observation area: ship detection processing is performed on the sea-penetrating radar echo after land fuzzy suppression.

[0120] Specifically, step S6 includes:

[0121] Step S6.1: Determine the transmission signal corresponding to the effective observation area;

[0122] Step S6.2: Using the transmitted signal as a matched filter, the radar echo after land ambiguity suppression obtained in step S5.4 is range-compressed and azimuth-focused;

[0123] Step S6.3: Detect the sea surface area using a constant false alarm detection method to obtain a ship detection result.

[0124] The effectiveness of the present invention is verified using simulation data, and the simulation parameters are shown in Table 1.

[0125] Table 1. Simulation parameters of spaceborne sea-penetrating radar system:

[0126]

[0127] Assume that the coded signal adopts the following short offset quadrature waveform:

[0128]

[0129] Among them, K r To modulate the frequency of the transmitted signal, T p is the pulse width, B r is the signal bandwidth, subscript n represents the nth transmitted pulse, j represents the imaginary part, and t represents time.

[0130] by Figure 2 Take the simulation of the effective observation area and the fuzzy area echo signal as an example. Figure 3 For example, the energy difference between the strong point in the fuzzy area and the target is -20dB, and there are 111 near-end fuzzy strong points evenly distributed around the target point. Figure 4 It can be seen that traditional signal coding and processing technology does not suppress the near-end blur, which will cause the noise floor to increase. Figure 5 It can be seen that by adopting periodic coded signals as the transmitting signals of the sea-penetrating radar and using the external SAR image database to detect and suppress the fuzzy land area, the distance focusing of the effective observation area is achieved through the matched filter corresponding to the effective observation area, and the high degree of defocusing of the sea surface ships in the fuzzy observation area is achieved, and the ship echo signals in the distance fuzzy area are noised, which effectively reduces the false alarm rate of ship detection in the observation area caused by distance fuzziness and improves the probability of ship detection in the effective observation area.

[0131] The present invention also provides a satellite-borne ship monitoring radar system detection system, which can be implemented by executing the process steps of the satellite-borne ship monitoring radar system detection method. That is, those skilled in the art can understand the satellite-borne ship monitoring radar system detection method as a preferred implementation of the satellite-borne ship monitoring radar system detection system.

[0132] According to the present invention, a detection system for a satellite-borne ship monitoring radar system is provided, comprising:

[0133] Module M1, set the sea-penetrating radar to transmit signals and receive original echoes;

[0134] Module M2, setting the transmission and reception timing of the sea-penetrating radar, including the pulse repetition frequency and the signal transmission-reception window;

[0135] Module M3, transmits signals to the sea and obtains radar echoes for sea detection according to the transmit and receive timing settings;

[0136] Module M4, selects the range fuzzy number set where the main lobe of the radar range pattern is located, and generates a land scattering energy map;

[0137] Module M5, suppressing the land ambiguity of the land scattered energy map for the range ambiguity in the range ambiguity number set;

[0138] Module M6: Detect ships in the effective observation area based on the radar echo after land fuzzy suppression.

[0139] In more preferred examples, the pulse repetition frequency is set according to a functional relationship curve between the incident angle or the ground distance from the sub-satellite point and the pulse repetition frequency, and the original echo of the full antenna main lobe receiving area is received, and the azimuth direction meets the Nyquist sampling requirements.

[0140] The encoding form of the transmission signal is an orthogonal coded pulse sequence, and any two pulses in the sequence are in a time domain orthogonal relationship.

[0141] The pulse sequence transmission form is to perform periodic repeated transmission with the number of pulses in the pulse sequence as a period.

[0142] The pulse sequence length is greater than the difference between the range ambiguity number of the sub-satellite point echo and the range ambiguity number of the echo at the farthest end of the earth plus one.

[0143] The signal transmission and reception timing in the module M3 is set based on the coded signal pulse sequence and the interval between repeated transmissions of the pulse sequence to obtain radar echoes.

[0144] In more preferred embodiments, the module M4 includes:

[0145] Module M4.1: Reconstruct the land-scattered energy map in the range ambiguity zone using an external SAR image database, transmit / receive timing settings, and range antenna patterns.

[0146] Module M4.2: Compare the land scattered energy map and select the distance fuzzy number set containing the top N fuzzy energies by sorting.

[0147] The module M4.1 includes:

[0148] Module M4.1.1: Input satellite position and velocity, pulse repetition frequency, sampling detection and gate opening and closing time;

[0149] Module M4.1.2: Set the range ambiguity number and use the range-Doppler equation to perform spatial positioning for all azimuth and range ambiguity units;

[0150] Module M4.1.3: Read the ground object scattering intensity map at the located spatial position from the external SAR image database and construct the land scattering intensity map in the range ambiguity area;

[0151] Module M4.1.4: Use the radar's range antenna pattern to weight the ground scattering intensity map to obtain the land scattering energy map in the range ambiguity area.

[0152] In more preferred embodiments, the module M5 includes:

[0153] Module M5.1: Determine the transmitted signal corresponding to the main lobe of the radar range pattern.

[0154] Module M5.2: For the main lobe area of the radar range pattern, the transmitted signal is used as a matched filter to perform range compression on the original echo and perform azimuth focusing processing.

[0155] Module M5.3: Based on the land scattered energy map, suppress the strong points with energy greater than the average in the range ambiguity area.

[0156] Module M5.4: Defocus the land scattering energy map in the range ambiguity area after strong point suppression, and use the transmitted signal to perform inverse matched filtering to obtain the suppressed radar echo.

[0157] In more preferred embodiments, the module M6 includes:

[0158] Module M6.1: Determine the emission signal corresponding to the effective observation area.

[0159] Module M6.2: Use the transmitted signal as a matched filter to perform range compression on the radar echo after land ambiguity suppression and perform azimuth focusing processing.

[0160] Module M6.3: Use the constant false alarm detection method to detect the selected sea surface area and obtain the ship detection results.

[0161] 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.

[0162] 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 detection method for a spaceborne ship monitoring radar system, characterized in that: include: Step S1, setting the sea-penetrating radar to transmit a signal; Step S2: Setting the transmission and reception timing of the sea-penetrating radar, including the pulse repetition frequency and the signal transmission-reception window; Step S3: transmitting a signal to the sea, and obtaining a radar echo for sea detection according to the transmission and reception timing settings; Step S4: selecting a range fuzzy number set where the main lobe of the radar range pattern is located to generate a land scattering energy map; Step S5: suppressing the land ambiguity of the land scattered energy map for the range ambiguity in the range ambiguity number set; Step S6: Detecting ships in the effective observation area on the radar echo after land fuzzy suppression.

2. The detection method of the satellite-borne ship monitoring radar system according to claim 1, characterized in that: The pulse repetition frequency is set according to a functional relationship curve between the incident angle or the ground distance from the sub-satellite point and the pulse repetition frequency, and the original echoes in the full antenna main lobe receiving area are received, and the azimuth direction meets the Nyquist sampling requirements; The encoding form of the transmission signal is an orthogonal coded pulse sequence, and any two pulses in the sequence are in a time domain orthogonal relationship; The pulse sequence transmission form is to perform periodic repeated transmission with the number of pulses in the pulse sequence as a period; The pulse sequence length is greater than the difference between the range ambiguity number of the sub-satellite point echo and the range ambiguity number of the echo at the farthest end of the earth plus one.

3. The detection method of the satellite-borne ship monitoring radar system according to claim 2, characterized in that: The step S4 comprises: Step S4.1: Reconstruct the land scattering energy map in the range ambiguity area using the external SAR image database, the transmit and receive timing settings, and the range antenna pattern; Step S4.2: Compare the land scattered energy map and select the distance fuzzy number set containing the top N fuzzy energies by sorting; The step S4.1 includes: Step S4.1.1: Input satellite position and velocity, pulse repetition frequency, sampling detection, and gate opening and closing times; Step S4.1.2: Set the range ambiguity number and use the range-Doppler equation to perform spatial positioning on all azimuth and range ambiguity units; Step S4.1.3: Read the ground object scattering intensity map at the located spatial position from the external SAR image database, and construct the land scattering intensity map of the range ambiguity area; Step S4.1.4: Use the radar's range antenna pattern to weight the ground object scattering intensity map to obtain the land scattering energy map in the range ambiguity area.

4. The detection method of the satellite-borne ship monitoring radar system according to claim 1, characterized in that: The step S5 includes: Step S5.1: Determine the transmitted signal corresponding to the main lobe of the radar range pattern; Step S5.2: For the main lobe area of the radar range pattern, the transmitted signal is used as a matched filter to perform range compression on the original echo and perform azimuth focusing processing; Step S5.3: Based on the land scattering energy map, suppress the strong points with energy greater than the average energy in the range ambiguity area; Step S5.4: Defocus the land scattering energy map in the range ambiguity area after strong point suppression, and perform inverse matching filtering on the transmitted signal to obtain the suppressed radar echo.

5. The detection method of the satellite-borne ship monitoring radar system according to claim 1, characterized in that: The step S6 includes: Step S6.1: Determine the transmission signal corresponding to the effective observation area; Step S6.2: Using the transmitted signal as a matched filter, the radar echo after land ambiguity suppression is range compressed and azimuth focusing is performed; Step S6.3: Detect the selected sea surface area using a constant false alarm detection method to obtain a ship detection result.

6. A satellite-borne ship monitoring radar system detection system, characterized in that: include: Module M1, setting the sea-penetrating radar transmission signal; Module M2, setting the transmission and reception timing of the sea-penetrating radar, including the pulse repetition frequency and the signal transmission-reception window; Module M3, transmits signals to the sea and obtains radar echoes for sea detection according to the transmit and receive timing settings; Module M4, selects the range fuzzy number set where the main lobe of the radar range pattern is located, and generates a land scattering energy map; Module M5, suppressing the land ambiguity of the land scattered energy map for the range ambiguity in the range ambiguity number set; Module M6: Detect ships in the effective observation area based on the radar echo after land fuzzy suppression.

7. The satellite-borne ship monitoring radar system detection system according to claim 6, characterized in that: The pulse repetition frequency is set according to a functional relationship curve between the incident angle or the ground distance from the sub-satellite point and the pulse repetition frequency, and the original echoes in the full antenna main lobe receiving area are received, and the azimuth direction meets the Nyquist sampling requirements; The encoding form of the transmission signal is an orthogonal coded pulse sequence, and any two pulses in the sequence are in a time domain orthogonal relationship; The pulse sequence transmission form is to perform periodic repeated transmission with the number of pulses in the pulse sequence as a period; The pulse sequence length is greater than the difference between the range ambiguity number of the sub-satellite point echo and the range ambiguity number of the echo at the farthest end of the earth plus one.

8. The satellite-borne ship monitoring radar system detection system according to claim 7, characterized in that: The module M4 includes: Module M4.1: Reconstruct the land-scattered energy map in the range ambiguity zone using an external SAR image database, transmit / receive timing settings, and range antenna patterns. Module M4.2: Compare the land scattered energy map and select the distance fuzzy number set containing the top N fuzzy energies by sorting; The module M4.1 includes: Module M4.1.1: Input satellite position and velocity, pulse repetition frequency, sampling detection and gate opening and closing time; Module M4.1.2: Set the range ambiguity number and use the range-Doppler equation to perform spatial positioning for all azimuth and range ambiguity units; Module M4.1.3: Read the ground object scattering intensity map at the located spatial position from the external SAR image database and construct the land scattering intensity map in the range ambiguity area; Module M4.1.4: Use the radar's range antenna pattern to weight the ground scattering intensity map to obtain the land scattering energy map in the range ambiguity area.

9. The satellite-borne ship monitoring radar system detection system according to claim 6, characterized in that: The module M5 includes: Module M5.1: Determine the transmitted signal corresponding to the main lobe of the radar range pattern; Module M5.2: For the main lobe area of the radar range pattern, the transmitted signal is used as a matched filter to perform range compression on the original echo and perform azimuth focusing processing; Module M5.3: Based on the land scattering energy map, suppress the strong points with energy greater than the average in the range ambiguity area; Module M5.4: Defocus the land scattering energy map in the range ambiguity area after strong point suppression, and use the transmitted signal to perform inverse matched filtering to obtain the suppressed radar echo.

10. The satellite-borne ship monitoring radar system detection system according to claim 6, characterized in that: The module M6 includes: Module M6.1: Determine the emission signal corresponding to the effective observation area; Module M6.2: Uses the transmitted signal as a matched filter to perform range compression on the radar echo after land ambiguity suppression and performs azimuth focusing processing; Module M6.3: Use the constant false alarm detection method to detect the selected sea surface area and obtain the ship detection results.

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