A Spaceborne Pitch-Dimension Frequency-Scanned Beam AMTI Method

Abstract

The present invention discloses a spaceborne pitch-dimensional frequency-scanned beam AMTI method. By introducing time delays into different pitch-dimensional antenna channels of a spaceborne pitch-dimensional frequency-scanned beam AMTI system, the scanning angle of the frequency-scanned beam is greatly increased based on a certain transmit signal bandwidth; range pulse compression is performed on the received echo signals, and then clutter suppression is carried out by utilizing the height-dimensional information difference between ground clutter and airborne moving targets; finally, an airborne moving target can be detected by using a transverse false alarm CFAR detector, and tracking of the airborne moving target is completed in combination with a Kalman filter. The present invention can effectively improve the beam scanning coverage area so as to achieve the effect of wide-area detection of non-cooperative moving targets in the air.

Description

Technical Field

[0001] The present invention belongs to the technical field of spaceborne radar detection, and particularly relates to a spaceborne pitch-dimensional frequency-scanned beam AMTI method. Background Art

[0002] Currently, the wide-area full-course active tracking and surveillance of civil airliners face severe challenges and urgency. All countries urgently need to develop a full-course active tracking, detection and early warning system for civil airliners. The spaceborne pitch-dimensional frequency-scanned beam Air Moving Target Indication (AMTI) early warning radar system can achieve borderless wide-area active tracking and surveillance of civil aircraft such as civil airliners and general aviation aircraft. At the same time, all countries urgently need to develop their own long-range air target early warning systems. The spaceborne pitch-frequency-scanned beam AMTI early warning radar system can achieve long-time, long-distance, wide-area monitoring and early warning of military targets such as long-range missiles, airborne stealth aircraft, and near-space vehicles. The spaceborne pitch-frequency-scanned beam AMTI early warning radar is not restricted by airspace and can detect, track, and early warn air targets at long distances and for long times at any time and any place all day and all weather, having very important civilian value and military research significance.

[0003] For the detection of air moving targets by spaceborne radars, the key problem faced is the radar working mode problem. Due to the non-cooperative characteristics of targets during the detection of air moving targets by spaceborne pitch-dimensional frequency-scanned AMTI radars, directly using existing spaceborne radar detection technologies and working modes will not be able to effectively detect air moving targets over a wide area. Summary of the Invention

[0004] In order to overcome the deficiencies of the prior art, the present invention provides a spaceborne pitch-dimensional frequency-scanned beam AMTI method. By introducing time delays into different pitch-dimensional antenna channels of the spaceborne pitch-dimensional frequency-scanned beam AMTI system, the scanning angle of the frequency-scanned beam is greatly increased on the basis of a certain transmitted signal bandwidth; the received echo signals are subjected to range pulse compression, and then clutter suppression is performed by using the height-dimensional information difference between ground clutter and air moving targets; finally, an air moving target can be detected by using a transverse false alarm CFAR detector, and tracking of the air moving target is completed in combination with a Kalman filter. The present invention can effectively improve the beam scanning coverage area to achieve the effect of wide-area detection of non-cooperative moving targets in the air.

[0005] The technical solution adopted by the present invention to solve its technical problems includes the following steps:

[0006] Step 1: The spaceborne pitch-dimensional frequency-scanned beam AMTI system includes a pitch-dimensional antenna array and an azimuth-dimensional antenna array; the number of array elements of the pitch-dimensional antenna is N r, the number of array elements of the azimuth - dimension antenna array is N a ; The azimuth - dimension antenna array is divided into nan sub - arrays, where nan < N a ; The elevation - dimension antenna array is divided into nrn sub - arrays. It is allowed that a single array element is divided into a sub - array, that is, nrn ≤ N r ;

[0007] Step 2: Introduce a transmission time delay Δt n and phase weighting

[0008] The radar transmits a reference signal as where s0(t) is an arbitrary waveform signal, t is the range fast - time, A is the amplitude of the transmitted signal, and T is the signal time - width; the spectrum corresponding to s0(t) is S0(f r ) and f r is the frequency corresponding to the range fast - time;

[0009] The radar transmitted signal of the nth sub - array is:

[0010] Step 3: The radar transmits a broadband signal during operation to achieve elevation - dimension frequency - phase - controlled positive beam scanning;

[0011] Step 4: According to the time - width of the echo signal, that is, the dwell time of the beam in the scene, set the receiving window width and receiving time to complete the reception of the echo signal;

[0012] Step 5: Perform range pulse compression on the received echo signal. Set the reference signal bandwidth according to the dwell time of the beam in the clutter scene. At the same time, step the carrier frequency of the reference signal within the entire transmitted signal bandwidth, and perform sliding - window matched filtering on the echo signal. Each carrier frequency corresponds to a compression result;

[0013] Step 6: Set the beam scanning speed according to the slant range from the radar to the clutter scene to ensure that the target echo signals on the horizontal line of the entire clutter scene arrive at the radar receiving antenna at the same time;

[0014] Taking zero time delay as a reference, the target time - delay magnitude corresponds to the height position information of the target; for targets with the same height but different horizontal positions, the azimuth direction uses the platform movement and the actual azimuth array to form Doppler resolution ability for position discrimination; for the horizontal position in the range direction, due to the use of the elevation - frequency - scanned pulse signal, the target echo signals at different positions correspond to different center frequencies, and this center frequency corresponds to the elevation angle one - by - one. Use this center frequency to reconstruct and distinguish the horizontal position information in the range direction;

[0015] Step 7: Utilize the height-dimensional information difference between ground clutter and airborne moving targets, and perform clutter suppression based on the clutter range compression result of the spaceborne pitch-frequency scanning beam AMTI radar;

[0016] Step 8: On the basis of the clutter suppression in Step 7, use a transverse false alarm CFAR detector to complete the detection of airborne moving targets; combine a Kalman filter to complete the tracking of airborne moving targets.

[0017] Preferably, the s0(t) is a chirp signal, a non-linear chirp signal, or a coded signal.

[0018] The beneficial effects of the present invention are as follows:

[0019] The present invention overcomes the problems of limited beam coverage area and large amount of echo data when existing spaceborne radars cannot detect non-cooperative moving targets in the air. By introducing time delays in different pitch-dimensional channels, the scanning angle of the frequency scanning beam is greatly increased on the basis of a certain transmitted signal bandwidth, effectively improving the beam scanning coverage area to achieve the effect of wide-area detection of non-cooperative moving targets in the air. Description of the Drawings

[0020] Figure 1 is a schematic diagram of the transmitted and received signals of the present invention.

[0021] Figure 2 is the AMTI processing and tracking result of airborne moving targets in the embodiment of the present invention. Among them, (a)-(i) are the tracking results of airborne moving targets of continuous sub-pulses. Detailed Embodiment

[0022] The present invention will be further described below in conjunction with the drawings and embodiments.

[0023] Aiming at the fact that existing spaceborne radar detection technologies are difficult to effectively detect non-cooperative moving targets in the air, the purpose of the present invention is to propose a spaceborne pitch-dimensional frequency scanning beam AMTI method, which can effectively achieve wide-area detection of non-cooperative moving targets in the air.

[0024] A spaceborne pitch-dimensional frequency scanning beam AMTI method, characterized by comprising the following steps:

[0025] Step 1: The spaceborne pitch-dimensional frequency scanning beam AMTI system consists of a pitch-dimensional antenna array and an azimuthal antenna array. The number of elements in the pitch-dimensional antenna array is N r , and the number of elements in the azimuthal array is N a ; divide the azimuthal antenna array into nan sub-arrays, requiring nan < N a ; the pitch-dimensional antenna array can be divided into nrn sub-arrays, allowing a single element to be divided into a sub-array, that is, nrn ≤ N r .

[0026] Step 2: Introduce a transmission time delay Δt for each sub-array of the pitch-dimensional antenna array n and phase weighting The radar transmits a reference signal where s0(t) can be a chirp signal, or a non-linear chirp signal, or a coded signal, or any other arbitrary waveform signal, t is the range fast time, A is the amplitude of the transmitted signal, and T is the signal time width. The spectrum corresponding to s0(t) is S0(f r ), and f r is the frequency corresponding to the range fast time. The radar transmitted signal of the nth sub-array is:

[0027] Step 3: As Figure 1 shown, during the operation of the radar, by transmitting a broadband signal, pitch-dimensional frequency phased positive beam scanning can be achieved. Combining the time delay Δt n between the pitch-dimensional array elements, the beam scanning range can be effectively extended within a certain scanning frequency range, greatly increasing the detection area for targets. The introduction of phase weighting ensures that the beam scanning area points to the expected detection area. At the same time, combining the detection geometry, by designing the beam scanning area so that the echo signals from different scene areas arrive at the receiving antenna simultaneously, the receiving window time can be greatly shortened, effectively reducing the amount of sampled data.

[0028] Step 4: Since the scene echoes all arrive at the receiving antenna at the same moment, the receiving window width and receiving moment can be set according to the echo signal time width, that is, the dwell time of the beam in the scene, to complete the acquisition of the echo signals.

[0029] Step 5: Perform range pulse compression on the received echo signals, set the reference signal bandwidth according to the dwell time of the beam in the clutter scene, and at the same time step the carrier frequency of the reference signal within the entire transmitted signal bandwidth to complete sliding window matched filtering of the echo signals. Each carrier frequency will correspond to a compression result.

[0030] Step 6: The beam scanning speed is set according to the slant range from the radar to the clutter scene, ensuring that the target echo signals on the horizontal line of the entire clutter scene arrive at the radar receiving antenna at the same time. This means that the targets in the horizontal reference plane of the scene have zero time delay. Usually, there are certain height fluctuations in the clutter scene, causing the clutter and airborne moving targets to deviate from the horizontal reference plane, resulting in the slant range corresponding to the target echo signal being less than the slant range on the horizontal reference plane on the same line of sight. This indicates that the time delay of the targets with a certain height compared to the reference plane is less than zero time delay. Taking zero time delay as a reference, the magnitude of the target time delay corresponds to the height position information of the target. For targets with the same height but different horizontal positions, the azimuth direction can use the platform movement and the actual azimuth array to form Doppler resolution ability for position discrimination. For the horizontal position in the range direction, due to the use of the pitch frequency scanning pulse signal, the target echo signals at different positions correspond to different center frequencies, and this center frequency corresponds to the pitch angle one by one. Use this center frequency to reconstruct and distinguish the horizontal position information in the range direction.

[0031] Step 7: Complete clutter suppression. For airborne moving targets, in addition to showing Doppler characteristics during movement, the biggest difference from ground clutter is that they have a certain height. The height difference between ground clutter and airborne moving targets is at least thousands of meters, or even tens of thousands of meters. Combining the clutter range compression results of the spaceborne pitch frequency scanning beam AMTI radar, the height dimension information difference between ground clutter and airborne moving targets can be effectively utilized for clutter suppression.

[0032] Step 8: On the basis of the clutter suppression in Step 7, use detectors such as constant false alarm rate (CFAR) to complete the detection of airborne moving targets. Combine the Kalman filter to complete the tracking of airborne moving targets. Specific embodiments:

[0034] 1. Simulation parameters

[0035] To verify the effectiveness of the method of the present invention, the simulation parameters in Table 1 are given here.

[0036] Table 1 Simulation data parameters

[0037] Carrier frequency 9.7 GHz Number of elevation channels 16 Pulse repetition frequency 2400 Hz Transmitted signal bandwidth 250 MHz Altitude of airborne moving target 8 km Velocity of airborne moving target 120 m / s

[0038] 2. Simulation content

[0039] Figure 2 It shows the data processing results of the spaceborne pitch dimension frequency scanning beam AMTI for airborne moving targets proposed by the present invention. It can be seen from the figure the AMTI effect of the method of the present invention. Using the method of the present invention can effectively achieve the detection of airborne moving targets.

[0040] In summary, the simulation experiments verify the correctness, effectiveness, and reliability of the present invention.

Claims

1. A spaceborne pitch - dimension frequency - scanned beam AMTI method, characterized in that, It includes the following steps: Step 1: The spaceborne pitch-dimensional frequency scanning beam AMTI system includes a pitch-dimensional antenna array and an azimuth-dimensional antenna array; the number of array elements of the pitch-dimensional antenna is N r , and the number of array elements of the azimuth-dimensional antenna array is N a ; The azimuth-dimensional antenna array is divided into nan sub-arrays, satisfying nan < N a ; The pitch-dimensional antenna array is divided into nrn sub-arrays, allowing a single array element to be divided into a sub-array, that is, satisfying nrn ≤ N r ; Step 2: Introduce a transmission time delay Δt to each sub-array of the pitch-dimensional antenna array n and phase weighting The radar transmitting reference signal is where s0(t) is an arbitrary waveform signal, t is the fast time of range, A is the amplitude of the transmitted signal, and T is the signal time width; the spectrum corresponding to s0(t) is S0(f r ), f r is the frequency corresponding to the fast time of range; The radar emission signal of the nth subarray is as follows: Step 3: The radar emits a broadband signal during operation to achieve frequency phased positive beam scanning in the elevation dimension; Step 4: Set the receiving window width and receiving time according to the time width of the echo signal, i.e., the dwell time of the beam in the scene, to complete the reception of the echo signal; Step 5: Perform range pulse compression on the received echo signal, set the reference signal bandwidth according to the dwell time of the beam in the clutter scene, at the same time step the carrier frequency of the reference signal within the entire transmitted signal bandwidth, and perform sliding window matched filtering on the echo signal. Each carrier frequency corresponds to a compression result; Step 6: Set the beam scanning speed according to the slant range from the radar to the clutter scene to ensure that the target echo signals on the horizontal line of the entire clutter scene reach the radar receiving antenna at the same time; Taking zero time delay as a reference, the target time delay magnitude corresponds to the height position information of the target; for targets with the same height but different horizontal positions, the azimuth uses the platform movement and the actual azimuth array to form Doppler resolution ability for position discrimination; for the horizontal position in the range direction, since the use of the elevation frequency scanning pulse signal makes the target echo signals at different positions correspond to different center frequencies, and this center frequency corresponds to the elevation angle one by one, use this center frequency to reconstruct and distinguish the horizontal position information in the range direction; Step 7: Utilize the height dimension information difference between the ground clutter and the airborne moving target to perform clutter suppression according to the clutter range compression result of the spaceborne elevation frequency scanning beam AMTI radar; Step 8: On the basis of the clutter suppression in Step 7, use a transverse false alarm CFAR detector to complete the detection of airborne moving targets; combine a Kalman filter to complete the tracking of airborne moving targets.

2. The spaceborne pitch - dimension frequency - scanned beam AMTI method according to claim 1, wherein The s0(t) is a linear frequency modulation signal or a non-linear frequency modulation signal or a coded signal.

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