A long-term coherent accumulation method for radar maneuvering targets based on nonparametric search

Abstract

The invention relates to a long-time coherent accumulation method for radar maneuvering targets for non-parametric search, and belongs to the technical field of radar signal processing. Firstly, Fourier transform is carried out on the radar data after pulse pressure along the range direction to obtain the range frequency-interpulse slow time two-dimensional data; then, the non-uniform sampling reduction operation and scale transformation are carried out; finally, the range frequency is carried out. Inverse Fourier transform, non-uniform sampling slow-time Fourier transform, the maneuvering target will form a peak in the two-dimensional plane to achieve long-term coherent accumulation. The invention reduces the order of the high-order phase signal to the first-order phase signal through only one non-uniform sampling reduction operation, which reduces the influence of the cross term and improves the parameter estimation accuracy compared with the traditional successive order reduction method; no parameter search matching calculation is required. , which reduces the amount of computation and is suitable for engineering applications; it can simultaneously compensate for distance and high-order Doppler walking, achieve long-term coherent accumulation, and improve the detection ability of maneuvering targets under the background of radar strong clutter.

Description

technical field [0001] The invention belongs to the technical field of radar signal processing, and more particularly, the invention relates to a long-term coherent accumulation method for radar maneuvering targets with non-parametric search, which can be used for radar detection and estimation of maneuvering targets. Background technique [0002] Moving targets with low observability tend to have low signal-to-noise / clutter ratio (SNR / SCR) in range and Doppler resolution units, reducing the detection performance of radar . In radar signal processing, the accumulation time can usually be extended to increase the energy of the target and achieve the purpose of improving the signal SNR / SCR. At present, the long-term accumulation of maneuvering targets mainly faces the following two problems: on the one hand, due to the continuous improvement of radar range resolution and the high-speed movement of the target, the target echo envelope moves and bends between different pulse pe...

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Problems solved by technology

[0003] 1) The long-term non-coherent accumulation method based on motion trajectory search, the most typical one is Track-Before-Detection (TBD), through trajectory search methods such as Hough Transform (Hough Transform, HT), the possible The amplitude accumulation of the echo energy of the same trajectory is also called long-term non-coherent accumulation. There is no strict coherent requirement for the system. This method is relatively simple in engineering implementation, but its signal accumulation efficiency and SNR improvement are obviously low Due to the coherent accumulation method, it is not suitable for the detection of weak moving targets in complex environments;

[0004] 2) Segmented long-term accumulation method, that is, a hybrid accumulation method that combines non-coherent and coherent accumulation. Firstly, the distance is divided into segments, and the coherent accumulation between pulses is completed in the segment, and then through distance envelope alignment or Keystone transformation ( KeystoneTransform, KT) method realizes the non-coherent accumulation of echoes, but the accumulation gain of this method is still very limited, and it cannot cope with the complex motion forms of strong clutter background and maneuvering targets

[0005] 3) The step-by-step long-term accumulation method, that is, the second-order KT and envelope interpolation are used to compensate the distance walk, and then, on this basis, the Doppler walk is compensated by transformation, such as phase matching method, fractional Fourier transform (Fractional Fourier Transform, FRFT), Chirplet transform, etc., but the effect of subsequent Doppler walking compensation is affected by the result of distance walking compensation, which is likely to cause target Doppler energy diffusion, and the estimation accuracy of motion parameters is poor

[0006] 4) Long Time Coherent Integration (LTCI) method based on parameter search, such as Radon Fourier Transform (Radon FT, RFT), Radon-FRFT (RFRFT), etc. Motion parameters (initial distance, velocity and acceleration) search range, extract the target observation value located in the distance-slow time two-dimensional plane, and then select the appropriate transformation parameters in the corresponding transformation domain to match and accumulate the observation value, to realize the The long-term coherent accumulation of moving target energy, the main problem of this method is that it needs multi-dimensional parameter search, resulting in a large amount of calculation

[0007] 5) The coherent accumulation method based on correlation and phase difference reduction. Since the echo phase after the pulse pressure of the maneuvering target can be approximated as a polynomial function, the stronger the maneuverability of the target, the higher the polynomial phase. High-order polynomials are reduced to low-order polynomials, and FRFT or FT is used for accumulation to reduce the amount of calculations. However, this method is mostly successive reductions, and each reduction will generate cross terms, which affects the accumulation effect and parameter estimation. precision

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