Non-parametric-search radar maneuvering target long-term coherent integration method

Abstract

The invention relates to a non-parametric-search radar maneuvering target long-term coherent integration method and belongs to the technical field of radar signal processing. The method includes the steps of firstly, performing Fourier transform on pulse-compressed radar data along distance to obtain distance frequency-interphase slow time two-dimensional data; performing non-uniform sampling order-reducing operation and time coordinate axis scale transform; thirdly, performing distance frequency inverse Fourier transform and non-uniform sampling slow time Fourier transform to allow a maneuvering target to form a peak value in a two-dimensional plane and achieve long-term coherent integration. The method has the advantages that high-order phase signals are reduced to first-order phase signals through one non-uniform sampling order-reducing operation, cross term influence is lowered as compared with a traditional gradual order-reducing method, and parameter estimation precision is increased; parametric search matching calculation is not needed, operation quantity is lowered, and the method is applicable to engineering; distance and high-order Doppler migration can be compensated atthe same time, long-term coherent integration can be achieved, and the maneuvering target detecting ability of a radar in a strong clutter background is increased.

Description

technical field [0001] The invention belongs to the technical field of radar signal processing. More specifically, the invention relates to a non-parametric search long-term coherent accumulation method for radar maneuvering targets, which can be used for detecting and estimating radar maneuvering targets. Background technique [0002] Moving targets with low observability tend to have low signal-to-noise ratio or signal-to-noise / clutter ratio (SNR / SCR) in range and Doppler resolution units, which reduces the detection performance of the radar . In radar signal processing, it is usually possible to extend the accumulation time 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 the radar range resolution and the high-speed movement of the target, the target echo envelope moves a...

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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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