Notch waveform selection method based on target-dependent characteristics

Abstract

The notch waveform selection method based on target correlation characteristics comprises the following steps: selecting a radar waveform according to current parameters of a target, determining a distance R and a speed V of the current target, setting a detection protection speed Vp, obtaining and storing a current aircraft ground speed Vz, judging whether the speed V of the target is greater than the sum of the detection protection speed Vp and the current aircraft ground speed Vz, determining that the target has not entered a notch if the speed V of the target is greater than the sum of the detection protection speed Vp and the current aircraft ground speed Vz, performing normal waveform selection, determining that the target has entered the notch if the speed V of the target is not greater than the sum of the detection protection speed Vp and the current aircraft ground speed Vz, and performing notch waveform selection. Two frames of low-repetition-frequency waveforms are used to irradiate the target, and the target is detected and correlated in a fixed distance range, so that the detection probability of the target is improved and the false alarm rate of the target is reduced.

Description

Technical Field

[0001] This invention belongs to the technical field of radar correlation strategies when targets pass through notches in active phased array radar, and particularly relates to a notch waveform selection method based on target correlation characteristics. Background Technology

[0002] With the large-scale deployment of active phased array radars, the waveform selection strategy of these radars determines several key indicators such as tracking performance and anti-jamming performance. The relative motion between the carrier aircraft and the target aircraft in actual flight changes in real time, requiring the selection of the detection waveform to be adjusted based on the relative distance and speed between the target and the carrier aircraft.

[0003] Maintaining a high target detection probability and low false alarm rate in a strong noise background near the main clutter requires the use of high-energy waveforms and high detection thresholds, but this increases the radar's energy consumption. Yan Chao designed an adaptive waveform selection algorithm to balance this trade-off between target detection and energy consumption. First, waveforms are arranged in ascending order of pulse width. The detection probability is calculated based on the average signal-to-noise ratio returned by each waveform during the next illumination. If a waveform meets the required detection probability, it is selected as the waveform for the next illumination. If none of the waveforms meet the requirement, the last waveform with the longest pulse width is selected, which is the optimal choice provided by the radar (see "Adaptive Waveform Selection for Target Tracking in Phased Array Radar," by Yan Chao). This method has the following drawbacks in waveform selection:

[0004] 1. The signal-to-noise ratio changes in real time during the target's movement, making it difficult to estimate, which may result in a large error in the predicted detection probability.

[0005] 2: When selecting waveforms, only the detection probability is considered, without considering the false alarm probability, resulting in low detection efficiency.

[0006] In view of this, the present invention is hereby proposed. Summary of the Invention

[0007] The purpose of this invention is to provide a notch waveform selection method based on target correlation characteristics, solving the technical problem of low radar detection efficiency in existing methods. The technical solution of this invention has many beneficial effects, as described below:

[0008] A notch waveform selection method based on target correlation characteristics is provided, the method comprising:

[0009] Based on the target's current parameters, select the radar waveform and determine the target's current range R and velocity V;

[0010] Set the detection protection speed Vp, obtain the current ground speed of the carrier aircraft Vz and store it;

[0011] Determine if the target's speed V is greater than the sum of the detection protection speed Vp and the current ground speed Vz of the carrier aircraft. If so, it is determined that the target has not entered the notch, and the normal waveform selection is performed. If not, it is determined that the target has entered the notch, and the notch waveform selection is performed.

[0012] Compared with the prior art, the technical solution provided by the present invention has the following beneficial effects:

[0013] This patent uses two consecutive frames of low repetition rate waveforms to illuminate the target, and detects and correlates the target within a fixed distance range, thereby improving the detection probability of the target and reducing the false alarm rate. Attached Figure Description

[0014] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0015] Figure 1 Schematic diagram of the target passing through the main clutter notch;

[0016] Figure 2 A schematic diagram illustrating the difficulty of detecting the target through the main clutter notch. Detailed Implementation

[0017] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that, in the absence of conflict, the following embodiments and features in the embodiments can be combined with each other. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0018] The notch waveform selection method based on target correlation characteristics of the present invention includes:

[0019] Based on the target's current parameters, select the radar waveform and determine the target's current range R and velocity V;

[0020] Set the detection protection speed Vp, obtain the current ground speed of the carrier aircraft Vz and store it;

[0021] Determine if the target's speed V is greater than the sum of the detection protection speed Vp and the current ground speed Vz of the carrier aircraft. If so, it is determined that the target has not entered the notch, and the normal waveform selection is performed. If not, it is determined that the target has entered the notch, and the notch waveform selection is performed.

[0022] As a specific implementation method provided in this case, if no, it is determined that the target has entered the notch and the notch waveform selection is performed, including: determining whether the target's stable system elevation angle θ is less than -1.5°. If no, the radar selects according to the existing waveform. If yes, it enters the target-related characteristic notch waveform selection. Specifically, a reasonable pulse repetition period (PRI) range is set according to the radar's own characteristics, such as 200us and 600us. The maximum PRI1, which is not in the range blind zone, is calculated based on the target distance and is 600us.

[0023] Based on the target distance, determine whether PRI1±7 and / or PRI1±11 (611us, 589us, 607us and 593us respectively) are within the target distance blind zone. If not, select the largest PRI and set it as PRI2. The blind zone refers to the criterion for whether the radar performs detection during the pulse transmission period. Continuously illuminate the target using the selected PRI1 and PRI2 waveforms, and send the detection values ​​to the target for tracking according to the signal-to-noise ratio.

[0024] Furthermore, the detected values ​​are sent to the target tracking system according to their signal-to-noise ratio, including:

[0025] Constant false alarm rate detection is performed within a distance range of ±500m from the tracking center;

[0026] The detected values ​​are sent to the target tracking system according to their signal-to-noise ratio, and the tracks are correlated, including:

[0027] The target tracking process performs decorrelation processing to obtain the target's correlation parameters, which include at least range, correlation velocity, azimuth, and pitch information.

[0028] The radar correlates the flight path with relevant parameters based on target tracking.

[0029] When the target offsets and maneuvers, its radial velocity decreases to a level comparable to the main clutter velocity (i.e., the difference between the target's radial velocity and the main clutter velocity is less than the minimum detectable velocity), making radar detection (target tracking) difficult. See the detailed motion diagram below. Figure 1 Specifically, during detection, the real-time signal-to-noise ratio decreases when the target is near sidelobe clutter and mainlobe clutter, increasing the difficulty of detection. Additionally, because the radar is in a downward-looking state relative to the target, moving targets such as high-speed trains and cars on the ground will increase the radar's false alarm rate. See the detailed diagram below. Figure 2 .

[0030] Currently, low-repetition-rate (LNR) waveforms (long-period waveforms) are selected for tracking targets within the notch. This results in a lower number of accumulation points, lower target accumulation energy, and a lower echo signal-to-noise ratio. Furthermore, because only one LNR waveform is used, ground-velocity targets cannot be separated, leading to a high false alarm rate during normal detection. To address this issue (existing methods attempt to consider this, but they estimate based on detection probability without considering the false alarm rate, limiting radar detection effectiveness; it's as if real targets are detected, but there are many false targets), this patent uses two consecutive LNR waveforms to illuminate the target, performing detection and correlation within a fixed distance range, thereby improving the target detection probability and reducing the false alarm rate.

[0031] Example

[0032] The first step is for the active phased array radar to enter waveform selection mode, select the corresponding waveform, and then proceed to the second step.

[0033] The second step is to determine the current target's distance as 230km and speed as 300m / s, and then proceed to the third step.

[0034] The third step is to set the target detection protection speed to 20 m / s, record the current ground speed of the carrier aircraft as 290 m / s, and then proceed to the fourth step.

[0035] Fourth step: Determine if the target's speed of 300m / s is greater than 310m / s. Proceed to fifth step.

[0036] Fifth step: When 300m / s < 310m / s, the target has entered the notch. Select the notch waveform and proceed to the sixth step.

[0037] Step 6: Determine if the target's stable pitch angle of -2° is less than -1.5°, then proceed to step 7.

[0038] Step 7: Stabilize the pitch angle -2° < -1.5°, enter the target-related characteristic notch waveform selection, and proceed to step 8.

[0039] Step 8: Set the PRI selection range from 200us to 600us according to the radar characteristics. The maximum range blind zone calculated based on the target's distance and speed is 600us. Then proceed to step 9.

[0040] Step 9: Calculate whether 600±11us and 600±7us are within the distance blind zone, and then proceed to step 10.

[0041] Step 10: Since the waveforms 611us, 589us, 607us, and 593us are not within the distance blind zone, select the largest one, 611us, and proceed to step 11.

[0042] Step 11: Irradiate the target with two waveforms of 600us and 611us in succession, and then proceed to step 12.

[0043] Step 12: Perform constant false alarm rate (CFAR) detection within a distance range of ±500m from the tracking center, and then proceed to step 13.

[0044] Step 13: Send the detection values ​​to the target tracking system according to the signal-to-noise ratio, and proceed to step 14.

[0045] Step fourteen: The target tracking performs decorrelation processing to obtain information such as the target's relevant distance, relevant velocity, azimuth, and pitch, and then proceeds to step fifteen.

[0046] Step 15: Target tracking associates the trajectory with the distance, speed, bearing, and pitch information.

[0047] The advantages are:

[0048] 1. Simultaneously performing two low-repetition-rate measurements on the notch waveform can increase the number of accumulation points and improve the detection energy.

[0049] 2. Two low-repetition-rate detection waveforms are used to perform constant false alarm detection within a certain distance range, reducing computational complexity and keeping the number of false targets controllable.

[0050] 3. Correlate the detection values ​​obtained from two low-repetition-rate detections to obtain the correlation distance and speed, and then perform track association to improve the association success rate.

[0051] The product provided by this invention has been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of this invention. The descriptions of the embodiments above are merely for the purpose of helping to understand the core ideas of this invention. It should be noted that those skilled in the art can make various improvements and modifications to the invention without departing from the principles of the invention, and these improvements and modifications also fall within the protection scope of the invention claims.

Claims

1. A notch waveform selection method based on target correlation characteristics, characterized in that, The methods include: Based on the target's current parameters, select the radar waveform and determine the target's current range R and velocity V; Set the detection protection speed Vp, obtain the current ground speed of the carrier aircraft Vz and store it; Determine if the target's velocity V is greater than the sum of the detection protection velocity Vp and the current ground speed Vz of the carrier aircraft. If so, it is determined that the target has not entered the notch, and normal waveform selection is performed. If not, it is determined that the target has entered the notch, and notch waveform selection is performed. The target's stability system pitch angle is also determined. Is it less than -1.5°? If not, the radar will select based on the existing waveform. If yes, it will enter the target-related characteristic notch waveform selection. The selection of target-related characteristic notch waveforms includes setting a reasonable pulse repetition period (PRI) range based on the radar's own characteristics, and calculating the maximum PRI1 that is not within the range blind zone based on the target distance; determining whether the coprime waveforms PRI1±7 and / or PRI1±11 are within the range blind zone based on the target distance; if not, selecting the largest waveform as PRI2; if so, continuously illuminating the target with the selected PRI1 and PRI2 waveforms, and sending the detected values ​​to the target tracking system according to the signal-to-noise ratio. Sending the detected values ​​to the target tracking system according to the signal-to-noise ratio includes: performing constant false alarm detection within a distance range of ±500m from the tracking center; sending the detected values ​​to the target tracking system according to the signal-to-noise ratio and correlating the flight path, wherein the target tracking system performs decorrelation processing to obtain the target's relevant parameters, which include at least distance, relevant velocity, azimuth, and pitch information; The radar correlates the flight path based on the relevant parameters.

Images