The detection of manoeuvring target for space-based radar is a challenging task because of its weak energy and manoeuvring motion. Prolonging the integration time is an effective method to increase signal energy, which can improve the target detection performance. However, with the increase of integration time, the radial velocity, radial acceleration and radial acceleration rate of manoeuvring target will induce linear range walk, quadratic-range curvature, cubic-range curvature and Doppler frequency migration of echo signal, which may degrade the performance of target detection. To solve this problem, a novel method is proposed that implements a parameter separation transform to isolate the acceleration. Then, the velocity and the acceleration rate can be obtained via one-dimensional search after the compensation of linear and cubic-range migration based on Hough transform and third-order Keystone transform. The kernel steps are as follows: (i) the acceleration is isolated by multiplying the range-compressed data in range frequency domain by its timereversed data according to the symmetrical property of azimuth slow time; (ii) the cubic-range curvature is corrected by a third-order Keystone transform. The simulation results demonstrate the effectiveness of the proposed method in estimating radial velocity, radial acceleration and radial acceleration rate of a manoeuvring target, thereby the signal energy can be finely accumulated.

Real-time radial velocity estimation is a key challenge for moving target imaging and location in current single-antenna synthetic aperture radar (SAR)-ground moving target indication systems. Since the conventional methods suffer from ambiguity, complexity realization, or heavy computation load for fast moving target motion estimation, this paper emphasizes the estimation efficiency by simple realization. An efficient Radon transform (RT) estimation is proposed to estimate the radial velocity of fast moving target by utilizing the geometry information, and much more geometry information is exploited to realize clutter cancellation, noise cancellation, and estimation error minimizing in the RT domain, which is not proposed by the others. With only two to four angles used to calculate rather than search for the radial velocity of moving targets, the proposed methods simplify the conventional range and angle (2-D) searching procedure into several time range (1-D) searching procedure efficiently. The theoretical and experimental analysis provides qualitative and quantitative evaluations into the effectiveness of the proposed methods. In the single-antenna SAR system, the proposed methods can estimate the radial velocity of fast moving target efficiently and accurately in high signal to clutter plus noise ratio scenarios.Index Terms-Efficient estimation, geometry information, radial velocity estimation, Radon transform (RT), synthetic aperture radar (SAR)-ground moving target indication (GMTI).

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